The Neutral Gas and Ion Mass Spectrometer on the Mars Atmosphere and Volatile Evolution Mission

NASA Technical Reports Server (NTRS)

Mahaffy, Paul R.; Benna, Mehdi; King, Todd; Harpold, Daniel N.; Arvey, Robert; Barciniak, Michael; Bendt, Mirl; Carrigan, Daniel; Errigo, Therese; Holmes, Vincent;

Improved selection criteria for H II regions, based on IRAS sources

NASA Astrophysics Data System (ADS)

Yan, Qing-Zeng; Xu, Ye; Walsh, A. J.; Macquart, J. P.; MacLeod, G. C.; Zhang, Bo; Hancock, P. J.; Chen, Xi; Tang, Zheng-Hong

2018-05-01

We present new criteria for selecting H II regions from the Infrared Astronomical Satellite (IRAS) Point Source Catalogue (PSC), based on an H II region catalogue derived manually from the all-sky Wide-field Infrared Survey Explorer (WISE). The criteria are used to augment the number of H II region candidates in the Milky Way. The criteria are defined by the linear decision boundary of two samples: IRAS point sources associated with known H II regions, which serve as the H II region sample, and IRAS point sources at high Galactic latitudes, which serve as the non-H II region sample. A machine learning classifier, specifically a support vector machine, is used to determine the decision boundary. We investigate all combinations of four IRAS bands and suggest that the optimal criterion is log(F_{60}/F_{12})≥ ( -0.19 × log(F_{100}/F_{25})+ 1.52), with detections at 60 and 100 {μ}m. This selects 3041 H II region candidates from the IRAS PSC. We find that IRAS H II region candidates show evidence of evolution on the two-colour diagram. Merging the WISE H II catalogue with IRAS H II region candidates, we estimate a lower limit of approximately 10 200 for the number of H II regions in the Milky Way.

Dynamical Evolution of the Recent Jet in CH Cyg

NASA Astrophysics Data System (ADS)

Karovska, Margarita

2011-10-01

We propose to carry out Chandra ACIS-S observations combined with HST/WFC3multi-wavelength imaging of the powerful, multi-component jet which was detectedin 2008 in the nearby symbiotic CH Cyg. CH Cyg is a fascinating system containing an evolved giant and a wind-accreting white dwarf, and it is one of the few symbiotics showing jet activity, especially in X-rays. Our goal is to measure the physical characteristics of the individual jet components, from the central source to the region of interaction with the circumbinary environment, reaching to within a few AU from the source of the jet. We will determine the characteristics of the central source, and of the inner and the outer jet, and the dynamical evolution, including precession, and kinematics of the ejecta.

Dynamical Evolution of the Recent Jet in CH Cyg

NASA Astrophysics Data System (ADS)

Karovska, Margarita

2011-09-01

We propose to carry out Chandra ACIS-S observations combined with HST/WFC3 multi-wavelength imaging of the powerful, multi-component jet which was detected in 2008 in the nearby symbiotic CH Cyg. CH Cyg is a fascinating system containing an evolved giant and a wind-accreting white dwarf, and it is one of the few symbiotics showing jet activity, especially in X-rays. Our goal is to measure the physical characteristics of the individual jet components, from the central source to the region of interaction with the circumbinary environment, reaching to within a few AU from the source of the jet. We will determine the characteristics of the central source, and of the inner and the outer jet, and the dynamical evolution, including precession, and kinematics of the ejecta.

Scalar self-force for highly eccentric equatorial orbits in Kerr spacetime

NASA Astrophysics Data System (ADS)

Thornburg, Jonathan; Wardell, Barry

2017-04-01

If a small "particle" of mass μ M (with μ ≪1 ) orbits a black hole of mass M , the leading-order radiation-reaction effect is an O (μ2) "self-force" acting on the particle, with a corresponding O (μ ) "self-acceleration" of the particle away from a geodesic. Such "extreme-mass-ratio inspiral" systems are likely to be important gravitational-wave sources for future space-based gravitational-wave detectors. Here we consider the "toy model" problem of computing the self-force for a scalar-field particle on a bound eccentric orbit in Kerr spacetime. We use the Barack-Golbourn-Vega-Detweiler effective-source regularization with a 4th-order puncture field, followed by an ei m ϕ ("m -mode") Fourier decomposition and a separate time-domain numerical evolution in 2 +1 dimensions for each m . We introduce a finite worldtube that surrounds the particle worldline and define our evolution equations in a piecewise manner so that the effective source is only used within the worldtube. Viewed as a spatial region, the worldtube moves to follow the particle's orbital motion. We use slices of constant Boyer-Lindquist time in the region of the particle's motion, deformed to be asymptotically hyperboloidal and compactified near the horizon and J+ . Our numerical evolution uses Berger-Oliger mesh refinement with 4th-order finite differencing in space and time. Our computational scheme allows computation for highly eccentric orbits and should be generalizable to orbital evolution in the future. Our present implementation is restricted to equatorial geodesic orbits, but this restriction is not fundamental. We present numerical results for a number of test cases with orbital eccentricities as high as 0.98. In some cases we find large oscillations ("wiggles") in the self-force on the outgoing leg of the orbit shortly after periastron passage; these appear to be caused by the passage of the orbit through the strong-field region close to the background Kerr black hole.

Source Regions for the Earth's Magnetic Field During the First Billion Years

NASA Astrophysics Data System (ADS)

Stegman, D. R.; Badro, J.

2018-05-01

Earth's early magnetic field places a severe constraint on the thermal evolution of the mantle and core. We will present how a dynamo in a basal magma ocean can reconcile major outstanding issues with present models.

The Southern HII Region Discovery Survey: Preliminary Results

NASA Astrophysics Data System (ADS)

Shea, Jeanine; Wenger, Trey; Balser, Dana S.; Anderson, Loren D.; Armentrout, William P.; Bania, Thomas M.; Dawson, Joanne; Miller Dickey, John; Jordan, Christopher; McClure-Griffiths, Naomi M.

2017-01-01

HII regions are some of the brightest sources at radio frequencies in the Milky Way and are the sites of massive O and B-type star formation. They have relatively short (< 10 Myr) lifetimes compared to other Galactic objects and therefore reveal information about spiral structure and the chemical evolution of the Galaxy. The HII Region Discovery Surveys (HRDS) discovered about 800 new HII regions in the Galactic longitude range -20 degrees to 270 degrees using primarily the Green Bank Telescope. Candidate HII regions were selected from mid-infrared emission coincident with radio continuum emission, and confirmed as HII regions by the detection of radio recombination lines. Here we discuss the Southern HII Region Discovery Survey (SHRDS), a continuation of the HRDS using the Australia Telescope Compact Array over the Galactic longitude range 230 to 360 degrees. We have reduced and analyzed a small sub-set of the SHRDS sources and discuss preliminary results, including kinematic distances and metallicities.

X-ray Properties and the Environment of Compact Radio Sources.

NASA Astrophysics Data System (ADS)

Siemiginowska, Aneta; Sobolewska, Malgorzata; Guainazzi, Matteo; Hardcastle, Martin; Migliori, Giulia; Ostorero, Luisa; Stawarz, Lukasz

2018-01-01

Compact extragalactic radio sources provide important insights into the initial stages of radio source evolution and probe states of a black hole activity at the time of the formation of the relativistic outflow. Such outflows propagate out to hundreds kpc distances from the origin and impact environment on many scales, and thus influence evolution of structures in the universe. These compact sources show radio features typically observed in large-scale radio galaxies (jets, lobes, hot spots), but contained within the central 1 kpc region of the host galaxy. Compact Symmetric Objects (CSOs, a subclass of GigaHertz Peaked spectrum radio sources) are symmetric and not affected by beaming. Their linear radio size can be translated into a source age if one measures the expansion velocity of the radio structures. Such ages has been measured for a small sample of CSOs. Using the Chandra X-ray Observatory and XMM-Newton we observed a pilot samples of 16 CSOs in X-rays (6 for the first time). Our results show heterogeneous nature of the CSOs X-ray emission indicating a range of AGN luminosities and a complex environment. In particular, we identified four Compton Thick sources with a dense medium (equivalent column > 1e24 cm^-2) capable of disturbing/slowing down the jet and confining the jet to a small region. Thus for the first time we gain the observational evidence in X-ray domain in favor of the hypothesis that in a sub-population of CSOs the radio jets may be confined by the dense X-ray obscuring medium. As a consequence, the kinematic ages of these CSOs may be underestimated.. We discuss the implications of our results on the emission models of CSOs, the earliest stages of the radio source evolution, jet interactions with the ISM, diversity of the environments in which the jets expand, and jet-galaxy co-evolution.Partial support for this work was provided by the NASA grants GO1-12145X, GO4-15099X, NNX10AO60G, NNX17AC23G and XMM AO15 project 78461. This work supported in part by NASA under contract NAS 8-03060 to the Smithsonian Astrophysical Observatory for operation of the Chandra X-ray Center.

A physical model for strain accumulation in the San Francisco Bay region: Stress evolution since 1838

USGS Publications Warehouse

Pollitz, F.; Bakun, W.H.; Nyst, M.

2004-01-01

Understanding of the behavior of plate boundary zones has progressed to the point where reasonably comprehensive physical models can predict their evolution. The San Andreas fault system in the San Francisco Bay region (SFBR) is dominated by a few major faults whose behavior over about one earthquake cycle is fairly well understood. By combining the past history of large ruptures on SFBR faults with a recently proposed physical model of strain accumulation in the SFBR, we derive the evolution of regional stress from 1838 until the present. This effort depends on (1) an existing compilation of the source properties of historic and contemporary SFBR earthquakes based on documented shaking, geodetic data, and seismic data (Bakun, 1999) and (2) a few key parameters of a simple regional viscoelastic coupling model constrained by recent GPS data (Pollitz and Nyst, 2004). Although uncertainties abound in the location, magnitude, and fault geometries of historic ruptures and the physical model relies on gross simplifications, the resulting stress evolution model is sufficiently detailed to provide a useful window into the past stress history. In the framework of Coulomb failure stress, we find that virtually all M ??? 5.8 earthquakes prior to 1906 and M ??? 5.5 earthquakes after 1906 are consistent with stress triggering from previous earthquakes. These events systematically lie in zones of predicted stress concentration elevated 5-10 bars above the regional average. The SFBR is predicted to have emerged from the 1906 "shadow" in about 1980, consistent with the acceleration in regional seismicity at that time. The stress evolution model may be a reliable indicator of the most likely areas to experience M ??? 5.5 shocks in the future.

Identifying open magnetic field regions of the Sun and their heliospheric counterparts

NASA Astrophysics Data System (ADS)

Krista, L. D.; Reinard, A.

2017-12-01

Open magnetic regions on the Sun are either long-lived (coronal holes) or transient (dimmings) in nature. Both phenomena are fundamental to our understanding of the solar behavior as a whole. Coronal holes are the sources of high-speed solar wind streams that cause recurrent geomagnetic storms. Furthermore, the variation of coronal hole properties (area, location, magnetic field strength) over the solar activity cycle is an important marker of the global evolution of the solar magnetic field. Dimming regions, on the other hand, are short-lived coronal holes that often emerge in the wake of solar eruptions. By analyzing their physical properties and their temporal evolution, we aim to understand their connection with their eruptive counterparts (flares and coronal mass ejections) and predict the possibility of a geomagnetic storm. The author developed the Coronal Hole Automated Recognition and Monitoring (CHARM) and the Coronal Dimming Tracker (CoDiT) algorithms. These tools not only identify but track the evolution of open magnetic field regions. CHARM also provides daily coronal hole maps, that are used for forecasts at the NOAA Space Weather Prediction Center. Our goal is to better understand the processes that give rise to eruptive and non-eruptive open field regions and investigate how these regions evolve over time and influence space weather.

Assessment of Emerging Regional Air Quality (AQ) and Greenhouse Gas (GHG) Impacts and Potential Mitigation Strategies in U.S. Energy Sectors

NASA Astrophysics Data System (ADS)

Kinnon, Michael Mac

The current domestic reliance on high-emitting fossil fuels for energy needs is the key driver of U.S. greenhouse gas (GHG) and pollutant emissions driving both climate change and regional air quality (AQ) concerns. Moving forward, emission sources in U.S. energy sectors will be subjected to changes driven by numerous phenomena, including technology evolution, environmental impacts, sustainability goals, and socioeconomic factors. This evolution will directly affect emissions source-related impacts on regional AQ that effective emissions control strategies must account for, including relative source contributions. Though previous studies have evaluated the emissions and AQ impacts of different sectors, technologies and fuels, most previous studies have assessed emissions impacts only without using advanced atmospheric models to accurately account for both spatial and temporal emissions perturbations and atmospheric chemistry and transport. In addition, few previous studies have considered the integration of multiple technologies and fuels in different U.S. regions.. Finally, most studies do not project emissions several decades into the future to assess what sources should be targeted with priority over time. These aspects are critical for understanding how both emissions sources and potential mitigation strategies impact the formation and fate of primary and secondary pollutants, including ground-level ozone and particulate matter concentrations. Therefore, this work utilizes a set of modeling tools to project and then to spatially and temporally resolve emissions as input into a 3-D Eulerian AQ model to assess how sources of emissions contribute to future atmospheric pollutant burdens. Further, analyses of the potential impacts of alternative energy strategies contained in potential mitigation strategies are conducted for priority targets to develop an understanding of how to maximize AQ benefits and avoid unforeseen deleterious tradeoffs between GHG reduction and AQ. Findings include changes in the relative contribution to AQ that elevate the importance of addressing emissions from all sectors and sources including some that may be more difficult to control, including industry, petroleum refineries, and nonlight duty vehicle transportation sources. Additionally, mitigation strategies must consider the full range of life cycle and system effects in order to avoid AQ tradeoffs spatially and temporally.

GUM 48d: AN EVOLVED H II REGION WITH ONGOING STAR FORMATION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Karr, J. L.; Ohashi, N.; Manoj, P.

2009-05-20

High-mass star formation and the evolution of H II regions have a substantial impact on the morphology and star formation history of molecular clouds. The H II region Gum 48d, located in the Centaurus Arm at a distance of 3.5 kpc, is an old, well evolved H II region whose ionizing stars have moved off the main sequence. As such, it represents a phase in the evolution of H II regions that is less well studied than the earlier, more energetic, main-sequence phase. In this paper, we use multiwavelength archive data from a variety of sources to perform a detailedmore » study of this interesting region. Morphologically, Gum 48d displays a ring-like faint H II region associated with diffuse emission from the associated photodissociation region, and is formed from part of a large, massive molecular cloud complex. There is extensive ongoing star formation in the region, at scales ranging from low to high mass, which is consistent with triggered star formation scenarios. We investigate the dynamical history and evolution of this region, and conclude that the original H II region was once larger and more energetic than the faint region currently seen. The proposed history of this molecular cloud complex is one of multiple, linked generations of star formation, over a period of 10 Myr. Gum 48d differs significantly in morphology and star formation from the other H II regions in the molecular cloud; these differences are likely the result of the advanced age of the region, and its different evolutionary status.« less

From dust to light: a study of star formation in NGC2264

NASA Astrophysics Data System (ADS)

Teixeira, P. S.

2008-10-01

The goal of this dissertation is to characterize the star formation history of the young cluster NGC2264 using the unique observational capabilities of the Spitzer Space Telescope. The motivation to conduct this study stems from the fact that most stars are formed within clusters, so the formation and evolution of the latter will effect the stellar mass distribution in the field. Detailed observational studies of young stellar clusters are therefore crucial to provide necessary constraints for theoretical models of cloud and cluster formation and evolution. This study also addresses the evolution of circumstellar disks in NGC2264; empirical knowledge of protoplanetary disk evolution is required for the understanding of how planetary systems such as our own form. The first result obtained from this study was both completely new and unexpected. A dense region within NGC2264 was found to be teeming with bright 24 μm Class I protostars; these sources are embedded within dense submillimeter cores and are spatially distributed along dense filamentary fingers of gas and dust that radially converge on a B-type binary Class I source. This cluster of protostars was baptized the "Spokes cluster" and its analysis provided further insight into the role of thermal support during core formation, collapse and fragmentation. The nearest neighbor projected separation distribution of these Class I sources shows a characteristic spacing that is similar to the Jeans length for the region, indicating that the dusty filaments may have undergone thermal fragmentation. The submillimeter cores of the Spokes cluster were observed at 230GHz using the SubMillimeter Array (SMA) and the resulting high resolution (~1.3") continuum observations revealed a dense grouping of 7 Class 0 sources embedded within a particular core, D-MM1 (~20"x20"). The compact sources have masses ranging between 0.4M and 1.2M, and radii of ~600AU. The mean separation of the Class 0 sources within D-MM1 is considerably smaller than the characteristic spacing between the Class I sources in the larger Spokes cluster and is consistent with hierarchical thermal fragmentation of the dense molecular gas in this region. The results obtained by the study of the Spokes cluster show that the spatial substructuring of a cluster or subcluster is correlated with age, i.e., groupings of very young protostars have clearly more concentrated and substructured spatial distributions. The Spokes cluster could thus be one of several building blocks of NGC2264, and will likely expand and disperse its members through the surrounding region, adding to the rest of NGC2264's stellar population.To further explore this scenario, I identified Pre-Main Sequence (PMS) disk bearing sources in the whole region of NGC2264, as surveyed by InfraRed Array Camera (IRAC) analyzing both their spatial distributions and ages. Of the 1404 sources detected in all four IRAC bands, 116 sources were found to have anemic IRAC disks and 217 sources were found to have thick IRAC disks; the disk fraction was calculated to be 37.5%±6.3% and found to be a function of spectral type, increasing for later type sources. I identified 4 candidate sources with transition disks (disks with inner holes), as well as 6 sources with anemic inner disks and thick outer disks that could be the immediate precursors of transition disks. This is a relevant result for it suggests planet formation may be occurring in the inner disk at very early ages. I found that the spatial distribution of the disk-bearing sources was a function of both disk type and amount of reddening. This spatial analysis enabled the identification of three groups of sources, namely, (i) embedded (AV> 3 magnitudes) sources with thick disks, (ii) unembedded sources with thick disks, and (iii) sources with anemic disks. The first group was found to have a median age of 1 Myr and its spatial distribution is highly concentrated and substructured. The second group, (ii), has a median age of 2 Myr and its spatial distribution is less concentrated and substructured than group (i), but more than the group of sources with anemic disks - the spatial distribution of this third group (age ~ 2 Myr) is not substructured and is more distributed, showing no particular peak or concentration. The star formation history of NGC2264 appears to be as follows: the northern region appears to have undergone the first epoch or episode of star formation, while the second epoch is currently occurring in the center (Spokes cluster) and south (near Allen's source). Status: RO

GCM Simulation of the Large-scale North American Monsoon Including Water Vapor Tracer Diagnostics

NASA Technical Reports Server (NTRS)

Bosilovich, Michael G.; Walker, Gregory; Schubert, Siegfried D.; Sud, Yogesh; Atlas, Robert M. (Technical Monitor)

2001-01-01

The geographic sources of water for the large-scale North American monsoon in a GCM are diagnosed using passive constituent tracers of regional water'sources (Water Vapor Tracers, WVT). The NASA Data Assimilation Office Finite Volume (FV) GCM was used to produce a 10-year simulation (1984 through 1993) including observed sea surface temperature. Regional and global WVT sources were defined to delineate the surface origin of water for precipitation in and around the North American i'vionsoon. The evolution of the mean annual cycle and the interannual variations of the monsoonal circulation will be discussed. Of special concern are the relative contributions of the local source (precipitation recycling) and remote sources of water vapor to the annual cycle and the interannual variation of warm season precipitation. The relationships between soil water, surface evaporation, precipitation and precipitation recycling will be evaluated.

GCM Simulation of the Large-Scale North American Monsoon Including Water Vapor Tracer Diagnostics

NASA Technical Reports Server (NTRS)

Bosilovich, Michael G.; Walker, Gregory; Schubert, Siegfried D.; Sud, Yogesh; Atlas, Robert M. (Technical Monitor)

2002-01-01

The geographic sources of water for the large scale North American monsoon in a GCM (General Circulation Model) are diagnosed using passive constituent tracers of regional water sources (Water Vapor Tracers, WVT). The NASA Data Assimilation Office Finite Volume (FV) GCM was used to produce a 10-year simulation (1984 through 1993) including observed sea surface temperature. Regional and global WVT sources were defined to delineate the surface origin of water for precipitation in and around the North American Monsoon. The evolution of the mean annual cycle and the interannual variations of the monsoonal circulation will be discussed. Of special concern are the relative contributions of the local source (precipitation recycling) and remote sources of water vapor to the annual cycle and the interannual variation of monsoonal precipitation. The relationships between soil water, surface evaporation, precipitation and precipitation recycling will be evaluated.

Patterns of species range evolution in Indo-Pacific reef assemblages reveal the Coral Triangle as a net source of transoceanic diversity.

PubMed

Evans, Sean M; McKenna, Caroline; Simpson, Stephen D; Tournois, Jennifer; Genner, Martin J

2016-06-01

The Coral Triangle in the Indo-Pacific is a region renowned for exceptional marine biodiversity. The area could have acted as a 'centre of origin' where speciation has been prolific or a 'centre of survival' by providing refuge during major environmental shifts such as sea-level changes. The region could also have acted as a 'centre of accumulation' for species with origins outside of the Coral Triangle, owing to it being at a central position between the Indian and Pacific oceans. Here, we investigated support for these hypotheses using population-level DNA sequence-based reconstructions of the range evolution of 45 species (314 populations) of Indo-Pacific reef-associated organisms. Our results show that populations undergoing the most ancient establishment were significantly more likely to be closer to the centre of the Coral Triangle than to peripheral locations. The data are consistent with the Coral Triangle being a net source of coral-reef biodiversity for the Indo-Pacific region, suggesting that the region has acted primarily as a centre of survival, a centre of origin or both. These results provide evidence of how a key location can influence the large-scale distributions of biodiversity over evolutionary timescales. © 2016 The Authors.

Alkali metal and rare earth element evolution of rock-forming minerals from the Gatumba area pegmatites (Rwanda): Quantitative assessment of crystal-melt fractionation in the regional zonation of pegmatite groups

NASA Astrophysics Data System (ADS)

Hulsbosch, Niels; Hertogen, Jan; Dewaele, Stijn; André, Luc; Muchez, Philippe

2014-05-01

This study presents a general model for the evaluation of Rayleigh fractional crystallisation as the principal differentiation mechanism in the formation of regionally zoned common and rare-element pegmatites. The magmatic evolution of these systems from a granitic source is reconstructed by means of alkali element and rare earth element (REE) analyses of rock-forming minerals (feldspars, micas and tourmaline), which represent a whole sequence of regional pegmatite zonation. The Gatumba pegmatite field (Rwanda, Central Africa) is chosen as case study area because of its well-developed regional zonation sequence. The pegmatites are spatially and temporally related to peraluminous G4-granites (986 ± 10 Ma). The regional zonation is developed around a G4-granite and the proximal pegmatites grade outwardly into biotite, two-mica and muscovite pegmatites. Rare-element (Nb-Ta-Sn) pegmatites occur most distal from the granite.

Provenance analysis on detrital zircons from the back-arc Arivechi basin: Implications for the Upper Cretaceous tectonic evolution of northern Sonora and southern Arizona

NASA Astrophysics Data System (ADS)

Rodríguez-Castañeda, José Luis; Ortega-Rivera, Amabel; Roldán-Quintana, Jaime; Espinoza-Maldonado, Inocente Guadalupe

2018-07-01

In the Arivechi region of eastern Sonora, northwestern Mexico, mountainous exposures of Upper Cretaceous rocks that contain monoliths within coarse sedimentary debris are enigmatic, in a province of largely Late Cretaceous continental-margin arc rocks. The rocks sequence in the study area are grouped in two Upper Cretaceous units: the lower Cañada de Tarachi and the younger El Potrero Grande. Detrital zircons collected from three samples of the Cañada de Tarachi and El Potrero Grande units have been analyzed for U-Pb ages to constrain their provenance. These ages constrain the age of the exposed rocks and provide new insights into the geological evolution of eastern Sonora Cretaceous rocks. The detrital zircon age populations determined for the Cañada de Tarachi and El Potrero Grande units contain distinctive Precambrian, Paleozoic, and Mesozoic zircon ages that provide probable source areas which are discussed in detail constraining the tectonic evolution of the region. Comparison of these knew ages with published data suggests that the source terranes, that supplied zircons to the Arivechi basin, correlate with Proterozoic, Paleozoic and Mesozoic domains in southern California and Baja California, northern Sonora, southern Arizona and eastern Chihuahua. The provenance variation is vital to constrain the source of the Cretaceous rocks in eastern Sonora and support a better understanding of the Permo-Triassic Cordilleran Magmatic Arc in the southwestern North America.

Workshop on Mare Volcanism and Basalt Petrogenesis: Astounding Fundamental Concepts (AFC) Developed Over the Last Fifteen Years

NASA Technical Reports Server (NTRS)

Taylor, Lawrence A. (Editor); Longi, John (Editor)

1991-01-01

Papers presented at the workshop on mare volcanism and basalt petrogenesis are compiled. The discussion of recent ideas and concepts within the context of this workshop permitted to catch up on the developments over the last 15 years. The following subject areas were covered: (1) geological setting; (2) magma evolution and source regions; (3) magma source and ascent processes; and (4) history of volcanism.

Lower crustal mush generation and evolution

NASA Astrophysics Data System (ADS)

Karakas, Ozge; Bachmann, Olivier; Dufek, Josef; Wright, Heather; Mangan, Margaret

2016-04-01

Recent seismic, field, and petrologic studies on several active and fossil volcanic settings provide important constraints on the time, volume, and melt fraction of their lower crustal magma bodies. However, these studies provide an incomplete picture of the time and length scales involved during their thermal and compositional evolution. What has been lacking is a thermal model that explains the temporal evolution and state of the lower crustal magma bodies during their growth. Here we use a two-dimensional thermal model and quantify the time and length scales involved in the long-term thermal and compositional evolution of the lower crustal mush regions underlying the Salton Sea Geothermal Field (USA), Mt St Helens (USA), and the Ivrea-Verbano Zone (North Italy). Although a number of seismic, tectonic, petrologic, and field studies explained the tectonic and magmatic evolution of these regions, controversy remains on their lower crustal heat sources, melt fraction, and origin of erupted magmas. Our thermal modeling results suggest that given a geologically reasonable range of basalt fluxes (~10^-3 to 10^-4 km3/yr), a long-lived (>105 yr) crystalline mush is formed in the lower crust. The state of the lower crustal mush is strongly influenced by the magma flux, crustal thickness, and water content of intruded basalt, giving an average melt fraction of <0.2 in thin crust with dry injections (Salton Sea Geothermal Field) and up to 0.4-0.5 in thicker crust with wet injections (Mt St Helens and Ivrea Zone). The melt in the lower crustal mush is mainly evolving through fractional crystallization of basalt with minor crustal assimilation in all regions, in agreement with isotopic studies. Quantification of the lower crustal mush regions is key to understanding the mass and heat balance in the crust, evolution of magma plumbing systems, and geothermal energy exploration.

Characterization of the Spatio-temporal Evolution of the Energy of Recent Tsunamis in Chile and its Connection with the Seismic Source and Geomorphological Conditions

NASA Astrophysics Data System (ADS)

Quiroz, M.; Cienfuegos, R.

2017-12-01

At present, there is good knowledge acquired by the scientific community on characterizing the evolution of tsunami energy at ocean and shelf scales. For instance, the investigations of Rabinovich (2013) and Yamazaki (2011), represent some important advances in this subject. In the present paper we rather focus on tsunami energy evolution, and ultimately its decay, in coastal areas because characteristic time scales of this process has implications for early warning, evacuation initiation, and cancelling. We address the tsunami energy evolution analysis at three different spatial scales, a global scale at the ocean basin level, in particular the Pacific Ocean basin, a regional scale comprising processes that occur at the continental shelf level, and finally a local scale comprising coastal areas or bays. These scales were selected following the motivation to understand how the response is associated with tsunami, and how the energy evolves until it is completely dissipated. Through signal processing methods, such as discrete and wavelets analysis, we analyze time series of recent tsunamigenic events in the main Chilean coastal cities. Based on this analysis, we propose a conceptual model based on the influence of geomorphological variables on the evolution and decay of tsunami energy. This model acts as a filter from the seismic source to the observed response in coastal zones. Finally, we hope to conclude with practical tools that will establish patterns of behavior and scaling of energy evolution through interconnections from seismic source variables and the geomorphological component to understand the response and predict behavior for a given site.

Optimizing laser produced plasmas for efficient extreme ultraviolet and soft X-ray light sources

NASA Astrophysics Data System (ADS)

Sizyuk, Tatyana; Hassanein, Ahmed

2014-08-01

Photon sources produced by laser beams with moderate laser intensities, up to 1014 W/cm2, are being developed for many industrial applications. The performance requirements for high volume manufacture devices necessitate extensive experimental research supported by theoretical plasma analysis and modeling predictions. We simulated laser produced plasma sources currently being developed for several applications such as extreme ultraviolet lithography using 13.5% ± 1% nm bandwidth, possibly beyond extreme ultraviolet lithography using 6.× nm wavelengths, and water-window microscopy utilizing 2.48 nm (La-α) and 2.88 nm (He-α) emission. We comprehensively modeled plasma evolution from solid/liquid tin, gadolinium, and nitrogen targets as three promising materials for the above described sources, respectively. Results of our analysis for plasma characteristics during the entire course of plasma evolution showed the dependence of source conversion efficiency (CE), i.e., laser energy to photons at the desired wavelength, on plasma electron density gradient. Our results showed that utilizing laser intensities which produce hotter plasma than the optimum emission temperatures allows increasing CE for all considered sources that, however, restricted by the reabsorption processes around the main emission region and this restriction is especially actual for the 6.× nm sources.

Properties of transported African mineral dust aerosols in the Mediterranean region

NASA Astrophysics Data System (ADS)

Denjean, Cyrielle; Chevaillier, Servanne; Gaimoz, Cécile; Grand, Noel; Triquet, Sylvain; Zapf, Pascal; Loisil, Rodrigue; Bourrianne, Thierry; Freney, Evelyn; Dupuy, Regis; Sellegri, Karine; Schwarzenbock, Alfons; Torres, Benjamin; Mallet, Marc; Cassola, Federico; Prati, Paolo; Formenti, Paola

2015-04-01

The transport of mineral dust aerosols is a global phenomenon with strong climate implications. Depending on the travel distance over source regions, the atmospheric conditions and the residence time in the atmosphere, various transformation processes (size-selective sedimentation, mixing, condensation of gaseous species, and weathering) can modify the physical and chemical properties of mineral dust, which, in turn, can change the dust's optical properties. The model predictions of the radiative effect by mineral dust still suffer of the lack of certainty of these properties, and their temporal evolution with transport time. Within the frame of the ChArMex project (Chemistry-Aerosol Mediterranean experiment, http://charmex.lsce.ipsl.fr/), one intensive airborne campaign (ADRIMED, Aerosol Direct Radiative Impact in the regional climate in the MEDiterranean region, 06 June - 08 July 2013) has been performed over the Central and Western Mediterranean, one of the two major transport pathways of African mineral dust. In this study we have set up a systematic strategy to determine the optical, physical and optical properties of mineral dust to be compared to an equivalent dataset for dust close to source regions in Africa. This study is based on airborne observations onboard the SAFIRE ATR-42 aircraft, equipped with state of the art in situ instrumentation to measure the particle scattering and backscattering coefficients (nephelometer at 450, 550, and 700 nm), the absorption coefficient (PSAP at 467, 530, and 660 nm), the extinction coefficient (CAPS at 530 nm), the aerosol optical depth (PLASMA at 340 to 1640 nm), the size distribution in the extended range 40 nm - 30 µm by the combination of different particle counters (SMPS, USHAS, FSSP, GRIMM) and the chemical composition obtained by filter sampling. The chemistry and transport model CHIMERE-Dust have been used to classify the air masses according to the dust origin and transport. Case studies of dust transport from known but differing origins (source regions in Tunisia, Algeria, and Mauritania) and at different times after transport, will be presented. Results will be compared to equivalent measurements over source regions interpreted in terms of the evolution of the particle size distribution, chemical composition and optical properties.

Developmental origin of the clavicle, and its implications for the evolution of the neck and the paired appendages in vertebrates.

PubMed

Nagashima, Hiroshi; Sugahara, Fumiaki; Watanabe, Keisuke; Shibata, Masahiro; Chiba, Akina; Sato, Noboru

2016-10-01

In fish, the pectoral appendage is adjacent to the head, but during vertebrate evolution a long neck region emerged via caudal relocation of the pectoral appendage. The pectoral appendage is comprised of endochondral portions, such as the humerus and the scapula, and a dermal portion, such as the clavicle, that contributes to the shoulder girdle. In the search for clues to the mechanism of the caudal relocation of the pectoral appendage, the cell lineage of the rostral lateral plate mesoderm was analyzed in chickens. It was found that, despite the long neck region in chickens, the origin of the clavicle attached to the head mesoderm ranged between 1 and 14 somite levels. Because the pectoral limb bud and the endochondral pectoral appendage developed on 15-20 and 15-24 somite levels, respectively, the clavicle-forming region corresponds to the embryonic neck, which suggests that the relocation would have been executed by the expansion of the source of the clavicle. The rostral portion of the clavicle-forming region overlaps the source of the cucullaris muscle, embraces the pharyngeal arches caudally, and can be experimentally replaced with the head mesoderm to form the cucullaris muscle, which implies that the mesodermal portion could have been the head mesoderm and that the clavicle would have developed at the head/trunk boundary. The link between the head mesoderm and the presumptive clavicle appears to have been the developmental constraint needed to create the evolutionarily conserved musculoskeletal connectivities characterizing the gnathostome neck. In this sense, the dermal girdle of the ganathostomes would represent the wall of the branchial chamber into which the endochondral pectoral appendage appears to have attached since its appearance in evolution. © 2016 Anatomical Society.

Far-infrared observations of a star-forming region in the Corona Australis dark cloud

NASA Technical Reports Server (NTRS)

Cruz-Gonzalez, I.; Mcbreen, B.; Fazio, G. G.

1984-01-01

A high-resolution far-IR (40-250-micron) survey of a 0.9-sq-deg section of the core region of the Corona Australis dark cloud (containing very young stellar objects such as T Tauri stars, Herbig Ae and Be stars, Herbig-Haro objects, and compact H II regions) is presented. Two extended far-IR sources were found, one associated with the Herbig emission-line star R CrA and the other with the irregular emission-line variable star TY CrA. The two sources have substantially more far-IR radiation than could be expected from a blackbody extrapolation of their near-IR fluxes. The total luminosities of these sources are 145 and 58 solar luminosity, respectively, implying that the embedded objects are of intermediate or low mass. The infrared observations of the sources associated with R CrA and TY CrA are consistent with models of the evolution of protostellar envelopes of intermediate mass. However, the TY CrA source appears to have passed the evolutionary stage of expelling most of the hot dust near the central source, yielding an age of about 1 Myr.

Depositional evolution of permo-triassic karoo basins in Tanzania with reference to their economic potential

NASA Astrophysics Data System (ADS)

Kreuser, T.; Wopfner, H.; Kaaya, C. Z.; Markwort, S.; Semkiwa, P. M.; Aslandis, P.

The Karoo basins of Tanzania contain in excess of 3000 m of sediments which were preserved in several NNE-NE striking half grabens or other structural basin conditions. They are all intracratonic basins, most of which filled with terrestrial sediments. In some basins situated nearer the coastal region short marine incursions occurred in the Late Permian. The Ruhuhu Rasin in SW Tanzania provides a typical depositional sequence of a Karoo basin in eastern Africa. Sedimentation commenced with glacigene deposits. These are of Late Carboniferous to Early Permian age and may be equated with other glacial successions in Africa and elsewhere in Gondwana. The glacigene beds are overlain by fluvial-deltaic coal-bearing deposits succeeded by arkoses and continental red beds. A transitionary formation of carbonaceous shales with impure coals gradually develops into thick lacustrine series which are topped by Late Permian bone bearing beds. The Triassic is characterized by a very thick fluvio-deltaic succession of siliciclastics resting with regional unconformity on the Permian. This Early Triassic sequence exhibits well-developed repetitive depositional cycles. Current azimuth measurements indicate fluctuating flow regimes in the Early Permian but relative stable source areas to the west of the basin later on. The depositional evolution of the Ruhuhu Basin is controlled by both tectonic and climatic factors. During basin evolution important energy resources were deposited such as considerable reserves of coal and source rocks of moderate potential for hydrocarbon generation. Uranium enrichment is observed in the Triassic arenaceous series where diagenetic alterations and subsequent cementation processes led to the formation of laumontite. Post Karoo dykes and plugs had only local effect on thermal evolution of potential source rocks. Enrichments of elements, i.e., Nb, Zr, Rb, Cr, and V present additional exploration targets. A comparison with the Karoo basins of the coastal region indicates possible lithological correlation by the application of sequence stratigraphy. No early Permian deposits are exposed in the coastal Karoo basins but their existence within the deeper parts of these basins cannot be ruled out. There, composition of organic matter analysed so far suggests subsidence and heat exposure exceeding post maturity stage.

Structural controls and evolution of gold-, silver-, and REE-bearing copper-cobalt ore deposits, Blackbird district, east-central Idaho: Epigenetic origins

USGS Publications Warehouse

Lund, K.; Tysdal, Russell G.; Evans, Karl V.; Kunk, Michael J.; Pillers, Renee M.

2011-01-01

Textural data at all scales indicate that the host sites for veins and the tectonic evolution of both host rocks and mineral deposits were kinematically linked to Late Cretaceous regional thrust faulting. Heat, fluids, and conduits for generation and circulation of fluids were part of the regional crustal thickening. The faulting also juxtaposed metaevaporite layers in the Mesoproterozoic Yellowjacket Formation over Blackbird district host rocks. We conclude that this facilitated chemical exchange between juxtaposed units resulting in leaching of critical elements (Cl, K, B, Na) from metaevaporites to produce brines, scavenging of metals (Co, Cu, etc) from rocks in the region, and, finally, concentrating metals in the lower-plate ramp structures. Although the ultimate source of the metals remains undetermined, the present Cu-Co ± Au (± Ag ± Ni ± REE) Blackbird ore deposits formed during Late Cretaceous compressional deformation.

Regional magnetic anomaly constraints on continental breakup

DOE Office of Scientific and Technical Information (OSTI.GOV)

von Frese, R.R.B.; Hinze, W.J.; Olivier, R.

1986-01-01

Continental lithosphere magnetic anomalies mapped by the Magsat satellite are related to tectonic features associated with regional compositional variations of the crust and upper mantle and crustal thickness and thermal perturbations. These continental-scale anomaly patterns when corrected for varying observation elevation and the global change in the direction and intensity of the geomagnetic field show remarkable correlation of regional lithospheric magnetic sources across rifted continental margins when plotted on a reconstruction of Pangea. Accordingly, these anomalies provide new and fundamental constraints on the geologic evolution and dynamics of the continents and oceans.

Geochemical evolution of groundwater in the Western Delta region of River Godavari, Andhra Pradesh, India

NASA Astrophysics Data System (ADS)

Nageswara Rao, P. V.; Appa Rao, S.; Subba Rao, N.

2017-05-01

The present study on geochemical evolution of groundwater is taken up to assess the controlling processes of water chemistry in the Western Delta region of the River Godavari (Andhra Pradesh), which is one of the major rice-producing centers in India. The study region is underlain by coarse sand with black clay (buried channels), black silty clay of recent origin (floodplain) and gray/white fine sand of modern beach sediment of marine source (coastal zone), including brown silty clay with fine sand (paleo-beach ridges). Groundwater is mostly brackish and very hard. It is characterized by Na+ > Mg2+ > Ca2+:HCO3 - > Cl- > SO4 2- > NO3 -, Na+ > Mg2+ > Ca2+:Cl- > HCO3 - > SO4 2-, and Mg2+ > Na+ > Ca2+ > or < K+:HCO3 - > Cl- > or > SO4 2- facies. The ionic relations (Ca2+ + Mg2+:HCO3 -, Ca2+ + Mg2+:SO4 2- + HCO3 -, Na+ + K+:TC, Na+ + K+:Cl- + SO4 2-, HCO3 -:TC, HCO3 -:Ca2+ + Mg2+, Na+:Cl- and Na+:Ca2+) indicate that the rock weathering, mineral dissolution, evaporation and ion exchange are the processes to control the aquifer chemistry. Anthropogenic and marine sources are also the supplementary factors for brackish water quality. These observations are further supported by Gibbs mechanisms that control the water chemistry. Thus, the study suggests that the initial quality of groundwater of geogenic origin has been subsequently modified by the influences of anthropogenic and marine sources.

Far-infrared observations of the evolved H II region M16

NASA Technical Reports Server (NTRS)

Mcbreen, B.; Fazio, G. G.; Jaffe, D. T.

1982-01-01

The results of far infrared (FIR) observations of the larger H II region M16, associated with the young open star cluster NGC 6611, are discussed. Three FIR sources detected on an extended ridge of FIR emission within the scanned region are described. The observations confirm that M16 is an H II region in a late stage of evolution. The H II region has expanded and is now extremely density bounded, consisting of an extended region of ionized gas and a series of ionization fronts located at the surrounding molecular cloud boundaries nearest to the exciting OB star cluster. The FIR radiation arises from heated dust at these boundaries.

Tectonic evolution of the Mexico flat slab and patterns of intraslab seismicity.

NASA Astrophysics Data System (ADS)

Moresi, L. N.; Sandiford, D.

2017-12-01

The Cocos plate slab is horizontal for about 250 km beneath the Guerrero region of southern Mexico. Analogous morphologies can spontaneously develop in subduction models, through the presence of a low-viscosity mantle wedge. The Mw 7.1 Puebla earthquake appears to have ruptured the inboard corner of the Mexican flat slab; likely in close proximity to the mantle wedge corner. In addition to the historical seismic record, the Puebla earthquake provides a valuable constraint through which to assess geodynamic models for flat slab evolution. Slab deformation predicted by the "weak wedge" model is consistent with past seismicity in the both the upper plate and slab. Below the flat section, the slab is anomalously warm relative to its depth; the lack of seismicity in the deeper part of the slab fits the global pattern of temperature-controlled slab seismicity. This has implications for understanding the deeper structure of the slab, including the seismic hazard from source regions downdip of the Puebla rupture (epicenters closer to Mexico City). While historical seismicity provides a deformation pattern consistent with the weak wedge model , the Puebla earthquake is somewhat anomalous. The earthquake source mechanism is consistent with stress orientations in our models, however it maps to a region of relatively low deviatoric stress.

X-ray nova MAXI J1828-249. Evolution of the broadband spectrum during its 2013-2014 outburst

NASA Astrophysics Data System (ADS)

Grebenev, S. A.; Prosvetov, A. V.; Burenin, R. A.; Krivonos, R. A.; Mescheryakov, A. V.

2016-02-01

Based on data from the SWIFT, INTEGRAL, MAXI/ISS orbital observatories, and the ground-based RTT-150 telescope, we have investigated the broadband (from the optical to the hard X-ray bands) spectrum of the X-ray nova MAXI J1828-249 and its evolution during the outburst of the source in 2013-2014. The optical and infrared emissions from the nova are shown to be largely determined by the extension of the power-law component responsible for the hard X-ray emission. The contribution from the outer cold regions of the accretion disk, even if the X-ray heating of its surface is taken into account, turns out to be moderate during the source's "high" state (when a soft blackbody emission component is observed in the X-ray spectrum) and is virtually absent during its "low" ("hard") state. This result suggests that much of the optical and infrared emissions from such systems originates in the same region of main energy release where their hard X-ray emission is formed. This can be the Compton or synchro-Compton radiation from a high-temperature plasma in the central accretion disk region puffed up by instabilities, the synchrotron radiation from a hot corona above the disk, or the synchrotron radiation from its relativistic jets.

On the spatial distribution and evolution of ultrafine particles in Barcelona

NASA Astrophysics Data System (ADS)

Dall'Osto, M.; Querol, X.; Alastuey, A.; O'Dowd, C.; Harrison, R. M.; Wenger, J.; Gómez-Moreno, F. J.

2013-01-01

Sources and evolution of ultrafine particles were investigated both horizontally and vertically in the large urban agglomerate of Barcelona, Spain. Within the SAPUSS project (Solving Aerosol Problems by Using Synergistic Strategies), a large number of instruments was deployed simultaneously at different monitoring sites (road, two urban background, regional background, urban tower 150 m a.s.l., urban background tower site 80 m a.s.l.) during a 4 week period in September-October 2010. Particle number concentrations (N>5 nm) are highly correlated with black carbon (BC) at all sites only under strong vehicular traffic influences. By contrast, under cleaner atmospheric conditions (low condensation sink, CS) such correlation diverges towards much higher N/BC ratios at all sites, indicating additional sources of particles including secondary production of freshly nucleated particles. Size-resolved aerosol distributions (N10-500) as well as particle number concentrations (N>5 nm) allow us to identify three types of nucleation and growth events: (1) a regional type event originating in the whole study region and impacting almost simultaneously the urban city of Barcelona and the surrounding urban background area; (2) a regional type event impacting only the regional background area but not the urban agglomerate; (3) an urban type event which originates only within the city centre but whose growth continues while transported away from the city to the regional background. Furthermore, during these clean air days, higher N are found at tower level than at ground level only in the city centre whereas such a difference is not so pronounced at the remote urban background tower. In other words, this study suggests that the column of air above the city ground level possesses the optimal combination between low CS and high vapour source, hence enhancing the concentrations of freshly nucleated particles. By contrast, within stagnant polluted atmospheric conditions, higher N and BC concentrations are always measured at ground level relative to tower level at all sites. Our study suggests that the city centre of Barcelona is a source of non-volatile traffic primary particles (29-39% of N>5 nm), but other sources, including secondary freshly nucleated particles contribute up to 61-71% of particle number (N>5 nm) at all sites. We suggest that organic compounds evaporating from freshly emitted traffic particles are a possible candidate for new particle formation within the city and urban plume.

Sources of stress gradients in electrodeposited Ni MEMS.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hearne, Sean Joseph; Floro, Jerrold Anthony; Dyck, Christopher William

2004-06-01

The ability of future integrated metal-semiconductor micro-systems such as RF MEMS to perform highly complex functions will depend on developing freestanding metal structures that offer improved conductivity and reflectivity over polysilicon structures. For example, metal-based RF MEMS technology could replace the bulky RF system presently used in communications, navigation, and avionics systems. However, stress gradients that induce warpage of active components have prevented the implementation of this technology. Figure 1, is an interference micrograph image of a series of cantilever beams fabricated from electrodeposited Ni. The curvature in the beams was the result of stress gradients intrinsic to the electrodepositionmore » process. To study the sources of the stress in electrodeposition of Ni we have incorporated a wafer curvature based stress sensor, the multibeam optical stress sensor, into an electrodeposition cell. We have determined that there are two regions of stress induced by electrodepositing Ni from a sulfamate-based bath (Fig 2). The stress evolution during the first region, 0-1000{angstrom}, was determined to be dependent only on the substrate material (Au vs. Cu), whereas the stress evolution during the second region, >1000{angstrom}, was highly dependent on the deposition conditions. In this region, the stress varied from +0.5 GPa to -0.5GPa, depending solely on the deposition rate. We examined four likely sources for the compressive intrinsic stress, i.e. reduction in tensile stress, and determined that only the adatom diffusion into grain boundaries model of Sheldon, et al. could account for the observed compressive stress. In the presentation, we shall discuss the compressive stress generation mechanisms considered and the ramifications of these results on fabrication of electrodeposited Ni for MEMS applications.« less

LARGE-SCALE CONTRACTION AND SUBSEQUENT DISRUPTION OF CORONAL LOOPS DURING VARIOUS PHASES OF THE M6.2 FLARE ASSOCIATED WITH THE CONFINED FLUX ROPE ERUPTION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kushwaha, Upendra; Joshi, Bhuwan; Moon, Yong-Jae

We investigate evolutionary phases of an M6.2 flare and the associated confined eruption of a prominence. The pre-flare phase exhibits spectacular large-scale contraction of overlying extreme ultraviolet (EUV) coronal loops during which the loop system was subjected to an altitude decrease of ∼20 Mm (40% of the initial height) for an extended span of ∼30 minutes. This contraction phase is accompanied by sequential EUV brightenings associated with hard X-ray (HXR; up to 25 keV) and microwave (MW) sources from low-lying loops in the core region which together with X-ray spectra indicate strong localized heating in the source region before themore » filament activation. With the onset of the flare’s impulsive phase, we detect HXR and MW sources that exhibit intricate temporal and spatial evolution in relation to the fast rise of the prominence. Following the flare maximum, the filament eruption slowed down and subsequently became confined within the large overlying active region loops. During the confinement process of the erupting prominence, we detect MW emission from the extended coronal region with multiple emission centroids, which likely represent emission from hot blobs of plasma formed after the collapse of the expanding flux rope and entailing prominence material. RHESSI spectroscopy reveals high plasma temperature (∼30 MK) and substantial non-thermal characteristics (δ ∼ 5) during the impulsive phase of the flare. The time evolution of thermal energy exhibits a good correspondence with the variations in cumulative non-thermal energy, which suggests that the energy of accelerated particles is efficiently converted to hot flare plasma, implying an effective validation of the Neupert effect.« less

Accreting, highly magnetized neutron stars at the Eddington limit: a study of the 2016 outburst of SMC X-3

NASA Astrophysics Data System (ADS)

Koliopanos, Filippos; Vasilopoulos, Georgios

2018-06-01

Aims: We study the temporal and spectral characteristics of SMC X-3 during its recent (2016) outburst to probe accretion onto highly magnetized neutron stars (NSs) at the Eddington limit. Methods: We obtained XMM-Newton observations of SMC X-3 and combined them with long-term observations by Swift. We performed a detailed analysis of the temporal and spectral behavior of the source, as well as its short- and long-term evolution. We have also constructed a simple toy-model (based on robust theoretical predictions) in order to gain insight into the complex emission pattern of SMC X-3. Results: We confirm the pulse period of the system that has been derived by previous works and note that the pulse has a complex three-peak shape. We find that the pulsed emission is dominated by hard photons, while at energies below 1 keV, the emission does not pulsate. We furthermore find that the shape of the pulse profile and the short- and long-term evolution of the source light-curve can be explained by invoking a combination of a "fan" and a "polar" beam. The results of our temporal study are supported by our spectroscopic analysis, which reveals a two-component emission, comprised of a hard power law and a soft thermal component. We find that the latter produces the bulk of the non-pulsating emission and is most likely the result of reprocessing the primary hard emission by optically thick material that partly obscures the central source. We also detect strong emission lines from highly ionized metals. The strength of the emission lines strongly depends on the phase. Conclusions: Our findings are in agreement with previous works. The energy and temporal evolution as well as the shape of the pulse profile and the long-term spectra evolution of the source are consistent with the expected emission pattern of the accretion column in the super-critical regime, while the large reprocessing region is consistent with the analysis of previously studied X-ray pulsars observed at high accretion rates. This reprocessing region is consistent with recently proposed theoretical and observational works that suggested that highly magnetized NSs occupy a considerable fraction of ultraluminous X-ray sources.

AGN jet power, formation of X-ray cavities, and FR I/II dichotomy in galaxy clusters

NASA Astrophysics Data System (ADS)

Fujita, Yutaka; Kawakatu, Nozomu; Shlosman, Isaac

2016-04-01

We investigate the ability of jets in active galactic nuclei to break out of the ambient gas with sufficiently large advance velocities. Using observationally estimated jet power, we analyze 28 bright elliptical galaxies in nearby galaxy clusters. Because the gas density profiles in the innermost regions of galaxies have not been resolved so far, we consider two extreme cases for temperature and density profiles. We also follow two types of evolution for the jet cocoons: being driven by the pressure inside the cocoon [Fanaroff-Riley (FR) type I], and being driven by the jet momentum (FR type II). Our main result is that regardless of the assumed form of the density profiles, jets with observed powers of ≲1044 erg s-1 are not powerful enough to evolve as FR II sources. Instead, they evolve as FR I sources and appear to be decelerated below the buoyant velocities of the cocoons when jets were propagating through the central dense regions of the host galaxies. This explains why FR I sources are more frequent than FR II sources in clusters. Furthermore, we predict the sizes of X-ray cavities from the observed jet powers and compare them with the observed ones-they are consistent within a factor of two if the FR I type evolution is realized. Finally, we find that the jets with a power ≳1044 erg s-1 are less affected by the ambient medium, and some of them, but not all, could serve as precursors of the FR II sources.

Spectral classification of selected ISOGAL sources using Himalayan Chandra Telescope

NASA Astrophysics Data System (ADS)

Joshi, U. C.; Ganesh, S.; Baliyan, K. S.; Parthasarathy, M.; Schultheis, M.; Rajpurohit, A.; Simon, G.; Omont, A.

The ISOGAL survey (Omont et al. 1999) is devoted to the observation of selected regions of the Galactic plane in the mid-infrared with ISOCAM. More than 240 fields were observed at 7 and 15 micron wave-bands with ISOCAM at an angular resolution of 6'' which has provided a complete census, in the areas surveyed, of the stars in the late stages (RGB/AGB phases) of stellar evolution. Optical counterparts are detected for some of the ISOGAL sources in the directions where the extinction is relatively lower. We obtained optical spectra of ˜100 such sources with the Himalayan Chandra Telescope (HCT), India and estimated their spectral classes. Optical spectroscopy together with mid-IR data is expected to allow us to obtain the spectral-type vs mass-loss relation which are important parameters to understand the late stages of stellar evolution. In this paper, we present a set of spectra taken in the field FC97 for which ISOGAL survey is complete.

Sources and Fate of DIC in Swedish Streams

NASA Astrophysics Data System (ADS)

Campeau, A.; Wallin, M.; Bishop, K. H.; Giesler, R.; Mörth, C. M.; Venkiteswaran, J. J.

2015-12-01

DIC export by streams and rivers is a major component of the global C cycle. However, many questions remain about the source and fate of aquatic DIC and CO2. Stable carbon isotope δ13C can provide information about the source and evolution of DIC and CO2 along hydrological networks. But the interpretation of δ13C values must be made with caution, since several biogeochemical processes affect the isotopic signal. In this study, we developed a systematic approach resolving these influences when interpreting large-scale patterns in δ13C-DIC and δ13C-CO2 values with regard to the source and fate of C in low order streams. We analyzed δ13C-DIC values in streams from four different regions of Sweden. Taken together they span large gradients in climate, geomorphology and lithology. The source of the DIC pool was predominantly biogenic in three of the regions (δ13C-DICsource = -17.4‰), but not the northernmost, where a clear geogenic input could be identified (δ13C-DICsource =-8.2 ‰). Our results suggest that soil respired CO2 is the main source of stream CO2 (δ13C-CO2source=-22.9‰) in all four regions, yet aquatic processes can also be a contributing component of the DIC pool in streams, with corresponding influence on the δ13C values. Once CO2 was in the stream, degassing was the primary control on its fate. However, there were indications that aquatic biological processes added CO2, (by DOC degradation) in the southernmost region, and that CO2 was removed (by photosynthesis) in the most central region. Correctly interpreted, the carbon stable isotope data can serve as a powerful tool for identifying the source and fate of stream DIC.

Solar cycle evolution of solar wind speed structure between 1973 and 1985 observed with the interplanetary scintillation method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kojima, M.; Kakinuma, T.

1987-07-01

The solar cycle evolution of solar wind speed structure was studied for the years from 1973 to 1985 on a basis of interplanetary scintillation observations using a new method for mapping solar wind speed to the source surface. The major minimum-speed regions are distributed along a neutral line through the whole period of a solar cycle: when solar activity is low, they are distributed on the wavy neutral line along the solar equator; in the active phase they also tend to be distributed along the neutral line, which has a large latitudinal amplitude. The minimum-speed regions tend to be distributedmore » not only along the neutral line but also at low magnetic intensity regions and/or coronal bright regions which do not correspond to the neutral line. As the polar high-speed regions extend equatorward around the minimum phase, the latitudinal gradient of speed increases at the boundaries of the low-speed region, and the width of the low-speed region decreases. One or two years before the minimum of solar activity, two localized minimum-speed regions appear on the neutral line, and their locations are longitudinally separated by 180. copyright American Geophysical Union 1987« less

Optical, physical and chemical properties of transported African mineral dust aerosols in the Mediterranean region

NASA Astrophysics Data System (ADS)

Denjean, Cyrielle; Di Biagio, Claudia; Chevaillier, Servanne; Gaimoz, Cécile; Grand, Noel; Loisil, Rodrigue; Triquet, Sylvain; Zapf, Pascal; Roberts, Greg; Bourrianne, Thierry; Torres, Benjamin; Blarel, Luc; Sellegri, Karine; Freney, Evelyn; Schwarzenbock, Alfons; Ravetta, François; Laurent, Benoit; Mallet, Marc; Formenti, Paola

2014-05-01

The transport of mineral dust aerosols is a global phenomenon with strong climate implications. Depending on the travel distance over source regions, the atmospheric conditions and the residence time in the atmosphere, various transformation processes (size-selective sedimentation, mixing, condensation of gaseous species, and weathering) can modify the physical and chemical properties of mineral dust, which, in turn, can change the dust's optical properties. The model predictions of the radiative effect by mineral dust still suffer of the lack of certainty of these properties, and their temporal evolution with transport time. Within the frame of the ChArMex project (Chemistry-Aerosol Mediterranean experiment, http://charmex.lsce.ipsl.fr/), two intensive airborne campaigns (TRAQA, TRansport and Air QuAlity, 18 June - 11 July 2012, and ADRIMED, Aerosol Direct Radiative Impact in the regional climate in the MEDiterranean region, 06 June - 08 July 2013) have been performed over the Central and Western Mediterranean, one of the two major transport pathways of African mineral dust. In this study we have set up a systematic strategy to determine the optical, physical and optical properties of mineral dust to be compared to an equivalent dataset for dust close to source regions in Africa. This study is based on airborne observations onboard the SAFIRE ATR-42 aircraft, equipped with state of the art in situ instrumentation to measure the particle scattering and backscattering coefficients (nephelometer at 450, 550, and 700 nm), the absorption coefficient (PSAP at 467, 530, and 660 nm), the extinction coefficient (CAPS at 530 nm), the aerosol optical depth (PLASMA at 340 to 1640 nm), the size distribution in the extended range 40 nm - 30 µm by the combination of different particle counters (SMPS, USHAS, FSSP, GRIMM) and the chemical composition obtained by filter sampling. The chemistry and transport model CHIMERE-Dust have been used to classify the air masses according to the dust origin and transport. Case studies of dust transport from known but differing origins (source regions in Tunisia, Algeria, and Mauritania) and at different times after transport, will be presented. Results will be compared to equivalent measurements over source regions interpreted in terms of the evolution of the particle size distribution, chemical composition and optical properties.

Rb-Sr isotopic studies of postorogenic granites from the eastern Arabian Shield, Kingdom of Saudi Arabia

USGS Publications Warehouse

Stuckless, J.S.; Futa, Kiyoto

1987-01-01

Available data indicate that postorogenic granites tend to be older in the southern part of the Arabian Shield. This suggests that plutonism started in the south and progressed to the north. Initial 87Sr/86Sr values also form a regional pattern. These ratios tend to be higher in the eastern part of the Arabian Shield, and suggest one source of continental affinity to the east and one of oceanic affinity to the west. The distribution of initial strontium isotope ratios does not clearly discriminate between the various models for Shield evolution; however, a sedimentary source region of mixed end members seems more compatible with the data pattern than models based on discrete boundaries between unrelated accreted blocks.

Spitzer observations of NGC 2264: the nature of the disk population

NASA Astrophysics Data System (ADS)

Teixeira, P. S.; Lada, C. J.; Marengo, M.; Lada, E. A.

2012-04-01

Aims: NGC 2264 is a young cluster with a rich circumstellar disk population which makes it an ideal target for studying the evolution of stellar clusters. Our goal is to study the star formation history of NGC 2264 and to analyse the primordial disk evolution of its members. Methods: The study presented is based on data obtained with the Infrared Array Camera (IRAC) and the Multiband Imaging Photometer for Spitzer (MIPS) on board the Spitzer Space Telescope, combined with deep near-infrared (NIR) ground-based FLAMINGOS imaging and previously published optical data. Results: We build NIR dust extinction maps of the molecular cloud associated with the cluster, and determine it to have a mass of 2.1 × 103 M⊙ above an AV of 7 mag. Using a differential Ks-band luminosity function (KLF) of the cluster, we estimate the size of the population of NGC 2264, within the area observed by FLAMINGOS, to be 1436 ± 242 members. The star formation efficiency is ≥ ~25%. We identify the disk population and divide it into 3 groups based on their spectral energy distribution slopes from 3.6 μm to 8 μm and on the 24 μm excess emission: (i) optically thick inner disks, (ii) anaemic inner disks, and (iii) disks with inner holes, or transition disks. We analyse the spatial distribution of these sources and find that sources with thick disks segregate into sub-clusterings, whereas sources with anaemic disks do not. Furthermore, sources with anaemic disks are found to be unembedded (i.e., with AV < 3 mag), whereas the clustered sources with thick disks are still embedded within the parental cloud. Conclusions: NGC 2264 has undergone more than one star-forming event, where the anaemic and extincted thick disk population appear to have formed in separate episodes: the sources with anaemic disks are more evolved and have had time to disperse and populate a halo of the cluster. We also find tentative evidence of triggered star-formation in the Fox Fur Nebula. In terms of disk evolution, our findings support the emerging disk evolution paradigm of two distinct evolutionary paths for primordial optically thick disks: a homologous one where the disk emission decreases uniformly at NIR and mid-infrared (MIR) wavelengths, and a radially differential one where the emission from the inner region of the disk decreases more rapidly than from the outer region (forming transition disks).

Detrital zircon U-Pb geochronology and stratigraphy of the Cretaceous Sanjiang Basin in NE China: Provenance record of an abrupt tectonic switch in the mode and nature of the NE Asian continental margin evolution

NASA Astrophysics Data System (ADS)

Zhang, Feng-Qi; Chen, Han-Lin; Batt, Geoffrey E.; Dilek, Yildirim; A, Min-Na; Sun, Ming-Dao; Yang, Shu-Feng; Meng, Qi-An; Zhao, Xue-Qin

2015-12-01

The age spectra obtained from 505 spots of detrital zircon U-Pb ages of five representative sandstone samples from the Sanjiang Basin in NE China point to a significant change in its provenance during the Coniacian-Santonian. The predominant detrital source for the Sanjiang Basin during the early Cretaceous was the Zhangguangcai Range magmatic belt and Jiamusi Block along its western and southern periphery, whereas it changed in the late Cretaceous to its eastern periphery. The timing of these inferred changes in the detrital source regions and drainage patterns nearly coincide with the age of a regional unconformity in and across the basin. The time interval of non-deposition and unconformity development was coeval with a transitional period between an extensional tectonic regime in the early Cretaceous and a contractional deformation episode in the late Cretaceous. The Sanjiang Basin evolved during this time window from a backarc to a foreland basin. The migration of the coastal orogenic belt and the fold and thrust belt development farther inland during the late Cretaceous marked the onset of regional-scale shortening and surface uplift in the upper plate of a flat (or very shallow-dipping) subduction zone. The stratigraphic record, the detrital source and geochronology of the basinal strata, and the internal structure of the Sanjiang Basin present, therefore, an important record of a tectonic switch in the nature of continental margin evolution of Northeast Asia during the late Mesozoic.

The landscape of Titan as witness to its climate evolution

NASA Astrophysics Data System (ADS)

Moore, Jeffrey M.; Howard, Alan D.; Morgan, Alexander M.

2014-09-01

We investigated the range of Titan climate evolution hypotheses regulated by the role, sources, and availability of methane. We analyzed all available image data (principally synthetic aperture radar (SAR)) of Titan's landscape through the T-86 encounter, starting with focused examinations of terrains that carry the markers of climate evolution. Traditional geologic and geomorphic landscape analysis was used to perform morphometric characterization, establish time-stratigraphic relationships, and interpret local and regional geologic process-oriented evolutionary histories. We then assayed the distribution of terrains we identified with respect to both their latitudinal and altimetric occurrence. Our analysis of the terrain types and distributions was used to evaluate and rank the various climate evolution scenarios. We favor progressive hypotheses, which include a relatively brief period in which precipitation was able to affect geomorphic change in low latitudes at scales perceivable in SAR data, with subsequent gradual decline of precipitation intensity coupled with an increasing poleward restriction.

Characteristics of size-segregated carbonaceous aerosols in the Beijing-Tianjin-Hebei region.

PubMed

Guo, Yuhong

2016-07-01

Mass concentrations of organic carbon (OC) and elemental carbon (EC) in size-resolved aerosols were investigated at four sites (three cities and one country) in the Beijing-Tianjin-Hebei region from September 2009 to August 2011. The size distributions of OC and EC presented large evolutions among rural and urban sites, and among four seasons, with highest peaks of OC and EC in fine mode in urban areas during winter. Geometric mean diameters (GMDs) of OC and EC in fine particles at urban sites during winter were lower than those at rural site mainly due to effects of fine particle coagulation and organic compound repartitioning. Fossil fuel emissions were a dominant source of OC and EC in urban areas, while biomass burning was a major source of OC and EC at rural site. Trajectory clustering and CWT analysis showed that regional transport was an important contributor to OC and EC in Beijing.

Geochemical evolution of Cenozoic-Cretaceous magmatism and its relation to tectonic setting, southwestern Idaho, U.S.A

NASA Technical Reports Server (NTRS)

Norman, Marc D.; Leeman, William P.

1989-01-01

The relationships between Cretaceous to Neogene magmatism and the tectonic setting of southwestern and central Idaho are evaluated. An overview of the tectonics and geology of the northwestern U.S. is presented. Major element, trace element, and Sr, Pb, and Nd isotopic data for the region are used to place constraints on magma source characteristics, the manner in which the magmatic sources evolved through time, and the nature of interactions among mantle and crustal domains in response to changing tectonic environment.

Petrology and Physics of Magma Ocean Crystallization

NASA Technical Reports Server (NTRS)

Elkins-Tanton, Linda T.; Parmentier, E. M.; Hess, P. C.

2003-01-01

Early Mars is thought to have been melted significantly by the conversion of kinetic energy to heat during accretion of planetesimals. The processes of solidification of a magma ocean determine initial planetary compositional differentiation and the stability of the resulting mantle density profile. The stability and compositional heterogeneity of the mantle have significance for magmatic source regions, convective instability, and magnetic field generation. Significant progress on the dynamical problem of magma ocean crystallization has been made by a number of workers. The work done under the 2003 MFRP grant further explored the implications of early physical processes on compositional heterogeneity in Mars. Our goals were to connect early physical processes in Mars evolution with the present planet's most ancient observable characteristics, including the early, strong magnetic field, the crustal dichotomy, and the compositional characteristics of the SNC meteorite's source regions as well as their formation as isotopically distinct compositions early in Mars's evolution. We had already established a possible relationship between the major element compositions of SNC meteorite sources and processes of Martian magma ocean crystallization and overturn, and under this grant extended the analysis to the crucial trace element and isotopic SNC signatures. This study then demonstrated the ability to create and end the magnetic field through magma ocean cumulate overturn and subsequent cooling, as well as the feasibility of creating a compositionally- and volumetrically-consistent crustal dichotomy through mode-1 overturn and simultaneous adiabatic melting.

Searching for intermediate groups of galaxies with Suzaku in Bootes field

NASA Astrophysics Data System (ADS)

Tawara, Yuzuru; Mitsuishi, Ikuyuki

2016-07-01

To investigate redshift evolution of groups of galaxies is significant also in terms of galaxy evolution. Recent observational studies show that an AGN fraction and a magnitude gap between the first and the second brightest group galaxies increase in group environments at lower redshifts (Oh et al. 2014 & Gozaliasl et al. 2014). Thus, comprehension for the evolution of the systems will bring us to hints on both morphological evolution of galaxies and galaxy-galaxy interactions. However, observational samples of groups of galaxies at higher redshifts are limited due to its low flux and surface brightness. Thus, we aimed at searching for new samples using both X-ray and optical data. To identify the group systems at higher redshifts, deep optical imaging and spectroscopic data are needed. Bootes field is one of the best regions for this purpose because there are up to 17 bands of data available per source from infrared, optical, UV, and X-ray (e.g., Kenter et al. 2005, Chung et al. 2014). XBootes survey was conducted in 2003 using Chandra (Murray et al. 2005) and X-ray extended sources were detected around intermediate optically-identified groups of galaxies even though Chandra could not reveal their origins due to poor photon statistics. Thus, we conducted X-ray follow-up observations using Suzaku which has low and stable background and thus is optimum for such low surface brightness sources for brightest 6 group candidates with redshifts of 0.15-0.42. Consequently, Suzaku detected excess emissions from all the targets in their images and spectral analysis reveals that 6 sources are originated from group- or poor-cluster-scale halos with temperatures, abundances and luminosities of 1.6-3.0 keV, <0.3 solar and ~1044 erg s-1, respectively. In this conference, we will report on the details of our analysis and results using multiwavelength data such as radio, optical and X-ray to examine the AGN fractions and magnitude gaps in our samples and discuss the redshift evolution.

Emergent Stratification in Solid Tumors Selects for Reduced Cohesion of Tumor Cells: A Multi-Cell, Virtual-Tissue Model of Tumor Evolution Using CompuCell3D.

PubMed

Swat, Maciej H; Thomas, Gilberto L; Shirinifard, Abbas; Clendenon, Sherry G; Glazier, James A

2015-01-01

Tumor cells and structure both evolve due to heritable variation of cell behaviors and selection over periods of weeks to years (somatic evolution). Micro-environmental factors exert selection pressures on tumor-cell behaviors, which influence both the rate and direction of evolution of specific behaviors, especially the development of tumor-cell aggression and resistance to chemotherapies. In this paper, we present, step-by-step, the development of a multi-cell, virtual-tissue model of tumor somatic evolution, simulated using the open-source CompuCell3D modeling environment. Our model includes essential cell behaviors, microenvironmental components and their interactions. Our model provides a platform for exploring selection pressures leading to the evolution of tumor-cell aggression, showing that emergent stratification into regions with different cell survival rates drives the evolution of less cohesive cells with lower levels of cadherins and higher levels of integrins. Such reduced cohesivity is a key hallmark in the progression of many types of solid tumors.

Emergent Stratification in Solid Tumors Selects for Reduced Cohesion of Tumor Cells: A Multi-Cell, Virtual-Tissue Model of Tumor Evolution Using CompuCell3D

PubMed Central

Swat, Maciej H.; Thomas, Gilberto L.; Shirinifard, Abbas; Clendenon, Sherry G.; Glazier, James A.

2015-01-01

Tumor cells and structure both evolve due to heritable variation of cell behaviors and selection over periods of weeks to years (somatic evolution). Micro-environmental factors exert selection pressures on tumor-cell behaviors, which influence both the rate and direction of evolution of specific behaviors, especially the development of tumor-cell aggression and resistance to chemotherapies. In this paper, we present, step-by-step, the development of a multi-cell, virtual-tissue model of tumor somatic evolution, simulated using the open-source CompuCell3D modeling environment. Our model includes essential cell behaviors, microenvironmental components and their interactions. Our model provides a platform for exploring selection pressures leading to the evolution of tumor-cell aggression, showing that emergent stratification into regions with different cell survival rates drives the evolution of less cohesive cells with lower levels of cadherins and higher levels of integrins. Such reduced cohesivity is a key hallmark in the progression of many types of solid tumors. PMID:26083246

The Planck Catalogue of Galactic Cold Clumps : Looking at the early stages of star-formation

NASA Astrophysics Data System (ADS)

Montier, Ludovic

2015-08-01

The Planck satellite has provided an unprecedented view of the submm sky, allowing us to search for the dust emission of Galactic cold sources. Combining Planck-HFI all-sky maps in the high frequency channels with the IRAS map at 100um, we built the Planck catalogue of Galactic Cold Clumps (PGCC, Planck 2015 results XXVIII 2015), counting 13188 sources distributed over the whole sky, and following mainly the Galactic structures at low and intermediate latitudes. This is the first all-sky catalogue of Galactic cold sources obtained with a single instrument at this resolution and sensitivity, which opens a new window on star-formation processes in our Galaxy.I will briefly describe the colour detection method used to extract the Galactic cold sources, i.e., the Cold Core Colour Detection Tool (CoCoCoDeT, Montier et al. 2010), and its application to the Planck data. I will discuss the statistical distribution of the properties of the PGCC sources (in terms of dust temperature, distance, mass, density and luminosity), which illustrates that the PGCC catalogue spans a large variety of environments and objects, from molecular clouds to cold cores, and covers various stages of evolution. The Planck catalogue is a very powerful tool to study the formation and the evolution of prestellar objects and star-forming regions.I will finally present an overview of the Herschel Key Program Galactic Cold Cores (PI. M.Juvela), which allowed us to follow-up about 350 Planck Galactic Cold Clumps, in various stages of evolution and environments. With this program, the nature and the composition of the 5' Planck sources have been revealed at a sub-arcmin resolution, showing very different configurations, such as starless cold cores or multiple Young Stellar objects still embedded in their cold envelope.

Chemical Composition of Asian Continental Outflow over the Western Pacific: Results from Transport and Chemical Evolution over the Pacific (TRACE-P)

NASA Technical Reports Server (NTRS)

Russo, R. S.; Talbot, R. W.; Dibb, J. E.; Scheuer, E.; Seid, G.; Jordan, C. E.; Fuelberg, H. E.; Sachse, G. W.; Avery, M. A.; Vay, S. A.

2003-01-01

We characterize the chemical composition of Asian continental outflow observed during the NASA Transport and Chemical Evolution over the Pacific (TRACE-P) mission during February-April 2001 in the western Pacific using data collected on the NASA DC-8 aircraft. A significant anthropogenic impact was present in the free troposphere and as far east as 150degE longitude reflecting rapid uplift and transport of continental emissions. Five-day backward trajectories were utilized to identify five principal Asian source regions of outflow: central, coastal, north-northwest(NNW), southeast (SE), and west-southwest (WSW). The maximum mixing ratios for several species, such as CO, C2Cl4, CH3Cl, and hydrocarbons, were more than a factor of 2 larger in the boundary layer of the central and coastal regions due to industrial activity in East Asia. CO was well correlated with C2H2, C2H6, C2Cl4, and CH3Cl at low altitudes in these two regions (r(sup 2) approx. 0.77-0.97). The NNW, WSW, and SE regions were impacted by anthropogenic sources above the boundary layer presumably due to the longer transport distances of air masses to the western Pacific. Frontal and convective lifting of continental emissions was most likely responsible for the high altitude outflow in these three regions. Photochemical processing was influential in each source region resulting in enhanced mixing ratios of O3, PAN, HNO3, H2O2, and CH3OOH. The air masses encountered in all five regions were composed of a complex mixture of photcrchemically aged air with more recent emissions mixed into the outflow as indicated by enhanced hydrocarbon ratios (C2H2/CO greater than or equal to 3 and C3H8/C2H6 greater than or equal to 0.2). Combustion, industrial activities, and the burning of biofuels and biomass all contributed to the chemical composition of air masses from each source region as demonstrated by the H6, SO2, and C2Cl4 were compared for the TRACE-P and PEM-West B missions. In the more northern regions, O3, CO, and SO2 were higher at low altitudes during TRACE-P. In general, mixing ratios were fairly similar between the two missions in the southern regions. A comparison between CO/CO2, CO/CH4, C2H6/C3H8, NO(x)/SO2, and NO(y)/(SO2 + nss-SO4) ratios for the five source regions and for the 2000 Asian emissions summary showed vay close agreement indicating that Asian emissions were well represented by the TRACE-P data and tbe emissions inventory.

Molecular Diagnostics of the Interstellar Medium and Star Forming Regions

NASA Astrophysics Data System (ADS)

Hartquist, T. W.; Dalgarno, A.

1996-03-01

Selected examples of the use of observationally inferred molecular level populations and chemical compositions in the diagnosis of interstellar sources and processes important in them (and in other diffuse astrophysical sources) are given. The sources considered include the interclump medium of a giant molecular cloud, dark cores which are the progenitors of star formation, material responding to recent star formation and which may form further stars, and stellar ejecta (including those of supernovae) about to merge with the interstellar medium. The measurement of the microwave background, mixing of material between different nuclear burning zones in evolved stars and turbulent boundary layers (which are present in and influence the structures and evolution of all diffuse astrophysical sources) are treated.

Detectability of Arctic methane sources at six sites performing continuous atmospheric measurements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thonat, Thibaud; Saunois, Marielle; Bousquet, Philippe

Understanding the recent evolution of methane emissions in the Arctic is necessary to interpret the global methane cycle. Emissions are affected by significant uncertainties and are sensitive to climate change, leading to potential feedbacks. A polar version of the CHIMERE chemistry-transport model is used to simulate the evolution of tropospheric methane in the Arctic during 2012, including all known regional anthropogenic and natural sources, in particular freshwater emissions which are often overlooked in methane modelling. CHIMERE simulations are compared to atmospheric continuous observations at six measurement sites in the Arctic region. In winter, the Arctic is dominated by anthropogenic emissions;more » emissions from continental seepages and oceans, including from the East Siberian Arctic Shelf, can contribute significantly in more limited areas. In summer, emissions from wetland and freshwater sources dominate across the whole region. The model is able to reproduce the seasonality and synoptic variations of methane measured at the different sites. We find that all methane sources significantly affect the measurements at all stations at least at the synoptic scale, except for biomass burning. In particular, freshwater systems play a decisive part in summer, representing on average between 11 and 26 % of the simulated Arctic methane signal at the sites. This indicates the relevance of continuous observations to gain a mechanistic understanding of Arctic methane sources. Sensitivity tests reveal that the choice of the land-surface model used to prescribe wetland emissions can be critical in correctly representing methane mixing ratios. The closest agreement with the observations is reached when using the two wetland models which have emissions peaking in August–September, while all others reach their maximum in June–July. Such phasing provides an interesting constraint on wetland models which still have large uncertainties at present. Also testing different freshwater emission inventories leads to large differences in modelled methane. Attempts to include methane sinks (OH oxidation and soil uptake) reduced the model bias relative to observed atmospheric methane. Here, the study illustrates how multiple sources, having different spatiotemporal dynamics and magnitudes, jointly influence the overall Arctic methane budget, and highlights ways towards further improved assessments.« less

Detectability of Arctic methane sources at six sites performing continuous atmospheric measurements

DOE PAGES

Thonat, Thibaud; Saunois, Marielle; Bousquet, Philippe; ...

2017-07-11

Understanding the recent evolution of methane emissions in the Arctic is necessary to interpret the global methane cycle. Emissions are affected by significant uncertainties and are sensitive to climate change, leading to potential feedbacks. A polar version of the CHIMERE chemistry-transport model is used to simulate the evolution of tropospheric methane in the Arctic during 2012, including all known regional anthropogenic and natural sources, in particular freshwater emissions which are often overlooked in methane modelling. CHIMERE simulations are compared to atmospheric continuous observations at six measurement sites in the Arctic region. In winter, the Arctic is dominated by anthropogenic emissions;more » emissions from continental seepages and oceans, including from the East Siberian Arctic Shelf, can contribute significantly in more limited areas. In summer, emissions from wetland and freshwater sources dominate across the whole region. The model is able to reproduce the seasonality and synoptic variations of methane measured at the different sites. We find that all methane sources significantly affect the measurements at all stations at least at the synoptic scale, except for biomass burning. In particular, freshwater systems play a decisive part in summer, representing on average between 11 and 26 % of the simulated Arctic methane signal at the sites. This indicates the relevance of continuous observations to gain a mechanistic understanding of Arctic methane sources. Sensitivity tests reveal that the choice of the land-surface model used to prescribe wetland emissions can be critical in correctly representing methane mixing ratios. The closest agreement with the observations is reached when using the two wetland models which have emissions peaking in August–September, while all others reach their maximum in June–July. Such phasing provides an interesting constraint on wetland models which still have large uncertainties at present. Also testing different freshwater emission inventories leads to large differences in modelled methane. Attempts to include methane sinks (OH oxidation and soil uptake) reduced the model bias relative to observed atmospheric methane. Here, the study illustrates how multiple sources, having different spatiotemporal dynamics and magnitudes, jointly influence the overall Arctic methane budget, and highlights ways towards further improved assessments.« less

Detectability of Arctic methane sources at six sites performing continuous atmospheric measurements

NASA Astrophysics Data System (ADS)

Thonat, Thibaud; Saunois, Marielle; Bousquet, Philippe; Pison, Isabelle; Tan, Zeli; Zhuang, Qianlai; Crill, Patrick M.; Thornton, Brett F.; Bastviken, David; Dlugokencky, Ed J.; Zimov, Nikita; Laurila, Tuomas; Hatakka, Juha; Hermansen, Ove; Worthy, Doug E. J.

2017-07-01

Understanding the recent evolution of methane emissions in the Arctic is necessary to interpret the global methane cycle. Emissions are affected by significant uncertainties and are sensitive to climate change, leading to potential feedbacks. A polar version of the CHIMERE chemistry-transport model is used to simulate the evolution of tropospheric methane in the Arctic during 2012, including all known regional anthropogenic and natural sources, in particular freshwater emissions which are often overlooked in methane modelling. CHIMERE simulations are compared to atmospheric continuous observations at six measurement sites in the Arctic region. In winter, the Arctic is dominated by anthropogenic emissions; emissions from continental seepages and oceans, including from the East Siberian Arctic Shelf, can contribute significantly in more limited areas. In summer, emissions from wetland and freshwater sources dominate across the whole region. The model is able to reproduce the seasonality and synoptic variations of methane measured at the different sites. We find that all methane sources significantly affect the measurements at all stations at least at the synoptic scale, except for biomass burning. In particular, freshwater systems play a decisive part in summer, representing on average between 11 and 26 % of the simulated Arctic methane signal at the sites. This indicates the relevance of continuous observations to gain a mechanistic understanding of Arctic methane sources. Sensitivity tests reveal that the choice of the land-surface model used to prescribe wetland emissions can be critical in correctly representing methane mixing ratios. The closest agreement with the observations is reached when using the two wetland models which have emissions peaking in August-September, while all others reach their maximum in June-July. Such phasing provides an interesting constraint on wetland models which still have large uncertainties at present. Also testing different freshwater emission inventories leads to large differences in modelled methane. Attempts to include methane sinks (OH oxidation and soil uptake) reduced the model bias relative to observed atmospheric methane. The study illustrates how multiple sources, having different spatiotemporal dynamics and magnitudes, jointly influence the overall Arctic methane budget, and highlights ways towards further improved assessments.

The 2016 M7.8 Kaikōura earthquake revealed by multiple seismic wavefield simulations: slow rupture propagation on a geometrically complex fault network

NASA Astrophysics Data System (ADS)

Kaneko, Y.; Francois-Holden, C.; Hamling, I. J.; D'Anastasio, E.; Fry, B.

2017-12-01

The 2016 M7.8 Kaikōura (New Zealand) earthquake generated ground motions over 1g across a 200-km long region, resulted in multiple onshore and offshore fault ruptures, a profusion of triggered landslides, and a regional tsunami. Here we examine the rupture evolution during the Kaikōura earthquake multiple kinematic modelling methods based on local strong-motion and high-rate GPS data. Our kinematic models constrained by near-source data capture, in detail, a complex pattern of slowly (Vr < 2km/s) propagating rupture from the south to north, with over half of the moment release occurring in the northern source region, mostly on the Kekerengu fault, 60 seconds after the origin time. Interestingly, both models indicate rupture re-activation on the Kekerengu fault with the time separation of 11 seconds. We further conclude that most near-source waveforms can be explained by slip on the crustal faults, with little (<8%) or no contribution from the subduction interface.

TEMPORAL VARIABILITY FROM THE TWO-COMPONENT ADVECTIVE FLOW SOLUTION AND ITS OBSERVATIONAL EVIDENCE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dutta, Broja G.; Chakrabarti, Sandip K.

2016-09-10

In the propagating oscillatory shock model, the oscillation of the post-shock region, i.e., the Compton cloud, causes the observed low-frequency quasi-periodic oscillations (QPOs). The evolution of QPO frequency is explained by the systematic variation of the Compton cloud size, i.e., the steady radial movement of the shock front, which is triggered by the cooling of the post-shock region. Thus, analysis of the energy-dependent temporal properties in different variability timescales can diagnose the dynamics and geometry of accretion flows around black holes. We study these properties for the high-inclination black hole source XTE J1550-564 during its 1998 outburst and the low-inclinationmore » black hole source GX 339-4 during its 2006–07 outburst using RXTE /PCA data, and we find that they can satisfactorily explain the time lags associated with the QPOs from these systems. We find a smooth decrease of the time lag as a function of time in the rising phase of both sources. In the declining phase, the time lag increases with time. We find a systematic evolution of QPO frequency and hard lags in these outbursts. In XTE J1550-564, the lag changes from hard to soft (i.e., from a positive to a negative value) at a crossing frequency (ν {sub c}) of ∼3.4 Hz. We present possible mechanisms to explain the lag behavior of high and low-inclination sources within the framework of a single two-component advective flow model.« less

Continental magnetic anomaly constraints on continental reconstruction

NASA Technical Reports Server (NTRS)

Vonfrese, R. R. B.; Hinze, W. J.; Olivier, R.; Bentley, C. R.

1985-01-01

Crustal magnetic anomalies mapped by the MAGSAT satellite for North and South America, Europe, Africa, India, Australia and Antarctica and adjacent marine areas were adjusted to a common elevation of 400 km and differentially reduced to the radial pole of intensity 60,000 nT. These radially polarized anomalies are normalized for differential inclination, declination and intensity effects of the geomagnetic field, so that in principle they directly reflected the geometric and magnetic polarization attributes of sources which include regional petrologic variations of the crust and upper mantle, and crustal thickness and thermal perturbations. Continental anomalies demonstrate remarkably detailed correlation of regional magnetic sources across rifted margins when plotted on a reconstruction of Pangea. Accordingly, they suggest further fundamental constraints on the geologic evolution of the continents and their reconstructions.

Closing the Seasonal Ocean Surface Temperature Balance in the Eastern Tropical Oceans from Remote Sensing and Model Reanalyses

NASA Technical Reports Server (NTRS)

Roberts, J. Brent; Clayson, C. A.

2012-01-01

Residual forcing necessary to close the MLTB on seasonal time scales are largest in regions of strongest surface heat flux forcing. Identifying the dominant source of error - surface heat flux error, mixed layer depth estimation, ocean dynamical forcing - remains a challenge in the eastern tropical oceans where ocean processes are very active. Improved sub-surface observations are necessary to better constrain errors. 1. Mixed layer depth evolution is critical to the seasonal evolution of mixed layer temperatures. It determines the inertia of the mixed layer, and scales the sensitivity of the MLTB to errors in surface heat flux and ocean dynamical forcing. This role produces timing impacts for errors in SST prediction. 2. Errors in the MLTB are larger than the historical 10Wm-2 target accuracy. In some regions, a larger accuracy can be tolerated if the goal is to resolve the seasonal SST cycle.

Crustal evolution inferred from Apollo magnetic measurements

NASA Technical Reports Server (NTRS)

Dyal, P.; Daily, W. D.; Vanyan, L. L.

1978-01-01

Magnetic field and solar wind plasma density measurements were analyzed to determine the scale size characteristics of remanent fields at the Apollo 12, 15, and 16 landing sites. Theoretical model calculations of the field-plasma interaction, involving diffusion of the remanent field into the solar plasma, were compared to the data. The information provided by all these experiments shows that remanent fields over most of the lunar surface are characterized by spatial variations as small as a few kilometers. Large regions (50 to 100 km) of the lunar crust were probably uniformly magnetized during early crustal evolution. Bombardment and subsequent gardening of the upper layers of these magnetized regions left randomly oriented, smaller scale (5 to 10 km) magnetic sources close to the surface. The larger scale size fields of magnitude approximately 0.1 gammas are measured by the orbiting subsatellite experiments and the small scale sized remanent fields of magnitude approximately 100 gammas are measured by the surface experiments.

Early Precambrian crustal evolution of south India

NASA Technical Reports Server (NTRS)

Srinivasan, R.

1986-01-01

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

VLA OH Zeeman Observations of the NGC 6334 Complex Source A

NASA Astrophysics Data System (ADS)

Mayo, E. A.; Sarma, A. P.; Troland, T. H.; Abel, N. P.

2004-12-01

We present a detailed analysis of the NGC 6334 complex source A, a compact continuum source in the SW region of the complex. Our intent is to determine the significance of the magnetic field in the support of the surrounding molecular cloud against gravitational collapse. We have performed OH 1665 and 1667 MHz observations taken with the Very Large Array in the BnA configuration and combined these data with the lower resolution CnB data of Sarma et al. (2000). These observations reveal magnetic fields with values of the order of 350 μ G toward source A, with maximum fields reaching 500 μ G. We have also theoretically modeled the molecular cloud surrounding source A using Cloudy, with the constraints to the model based on observation. This model provides significant information on the density of H2 through the cloud and also the relative density of H2 to OH which is important to our analysis of the region. We will combine the knowledge gained through the Cloudy modeling with Virial estimates to determine the significance of the magnetic field to the dynamics and evolution of source A.

Young Cluster Berkeley 59: Properties, Evolution, and Star Formation

NASA Astrophysics Data System (ADS)

Panwar, Neelam; Pandey, A. K.; Samal, Manash R.; Battinelli, Paolo; Ogura, K.; Ojha, D. K.; Chen, W. P.; Singh, H. P.

2018-01-01

Berkeley 59 is a nearby (∼1 kpc) young cluster associated with the Sh2-171 H II region. We present deep optical observations of the central ∼2.5 × 2.5 pc2 area of the cluster, obtained with the 3.58 m Telescopio Nazionale Galileo. The V/(V–I) color–magnitude diagram manifests a clear pre-main-sequence (PMS) population down to ∼0.2 M ⊙. Using the near-infrared and optical colors of the low-mass PMS members, we derive a global extinction of A V = 4 mag and a mean age of ∼1.8 Myr, respectively, for the cluster. We constructed the initial mass function and found that its global slopes in the mass ranges of 0.2–28 M ⊙ and 0.2–1.5 M ⊙ are ‑1.33 and ‑1.23, respectively, in good agreement with the Salpeter value in the solar neighborhood. We looked for the radial variation of the mass function and found that the slope is flatter in the inner region than in the outer region, indicating mass segregation. The dynamical status of the cluster suggests that the mass segregation is likely primordial. The age distribution of the PMS sources reveals that the younger sources appear to concentrate close to the inner region compared to the outer region of the cluster, a phenomenon possibly linked to the time evolution of star-forming clouds. Within the observed area, we derive a total mass of ∼103 M ⊙ for the cluster. Comparing the properties of Berkeley 59 with other young clusters, we suggest it resembles more closely the Trapezium cluster.

ATLASGAL: Chemical evolution of star forming clumps

NASA Astrophysics Data System (ADS)

Figura, Charles C.; Urquhart, James S.; Wyrowski, Friedrich

2017-01-01

Although massive stars are few in number, they impact their host molecular clouds, clusters, and galaxies in profound ways, playing a vital role in regulating star formation in their host galaxy. Understanding the formation of these massive stars is critical to understanding this evolution, but their rapid early development causes them to reach the main sequence while still shrouded in their natal molecular cloud. Many studies have investigated these regions in a targeted manner, but a full understanding necessitates a broader view at all stages of formation across many star forming regions.We have used mid-infrared continuum surveys to guide selection of a statistically large sample of massive dust clumps from the 10,000 such clumps identified in the ATLASGAL Compact Source Catalogue (CSC), ensuring that all stages of the evolutionary process are included. A final sample of 600 fourth-quadrant sources within 1 degree of the Galactic plane were observed with the Mopra telescope with an 8 GHz bandwidth between 85.2 and 93.4 GHz.We present an overview of our results. We have identified over 30 molecular lines, seven of which with detected hyperfine structure, as well as several mm-radio recombination line transitions. Source velocities indicate that these regions trace the Crux-Scutum, Norma, and Carina Sagitarius arms. We have performed an analysis of linewidth and line intensity ratios, correlating these with star formation stages as identified by IR brightness at the 70 and 24 μm bands, and present several molecular pairs whose linewidth and intensity might serve as significant tracers of the evolutionary stage of star formation. We comment on the results of PCA analysis of the measured parameters for the overall population and the star formation stage subgroups with an eye toward characterising early stellar development through molecular line observations.

Magnetic fields in multiple bright-rimmed clouds in different directions of H II region IC 1396

NASA Astrophysics Data System (ADS)

Soam, Archana; Maheswar, G.; Lee, Chang Won; Neha, S.; Kim, Kee-Tae

2018-06-01

Bright-rimmed clouds (BRCs) form on the edges of H II regions affected by high-energy radiation from a central ionizing source. The UV radiation from the ionizing source results in compression and ionization, causing either cloud disruption or further star formation. In this work, we present R-band polarization measurements towards four BRCs, namely IC 1396A, BRC 37, BRC 38 and BRC 39, located in different directions in the H II region, Sh2-131, in order to map the magnetic field (B-field) in the plane of the sky. These BRCs are illuminated by the O star HD 206267 and present a range of projected on-sky geometries. This provides an opportunity to gain an understanding of the magnetized evolution of BRCs. The B-field geometries of the clouds deduced from the polarization data, after correction for foreground contamination by the interstellar medium, are seen to be connected to the ambient B-fields on large scales. They seem to play an important role in shaping the clouds IC 1396A and BRC 37. BRCs 38 and 39 show a broader and snubber head morphology, possibly because the B-fields are aligned with incoming radiation, as revealed in the simulations. A good general agreement is noted on comparing our observational results with the simulations, supporting the importance of B-fields in BRC evolution. This work is the first step towards systematic mapping the B-fields morphology in multiple BRCs in an expanding H II region, extending our previous work.

Variations in the Iron Mineralogy of a Loess Section in Tajikistan During the Mid-Pleistocene and Late Pleistocene: Implications for the Climatic Evolution in Central Asia

NASA Astrophysics Data System (ADS)

Jia, Jia; Lu, Hao; Wang, Youjun; Xia, Dunsheng

2018-04-01

The loess sequences in Tajikistan are an important archive of information about the development of climate and atmospheric circulation in central Asia during the Pleistocene. Here we present the results of an iron mineralogical study of a loess sequence in Tajikistan to reconstruct paleoclimate evolution during the mid-Pleistocene and late Pleistocene. The record indicates that interglacial intervals were relatively humid and glacials were dry. We propose a shift in the character of the interglacial climate of the region to more humid after beginning of MIS 9; however, temperature was relatively stable. The location and intensity of Westerlies have a close link with Asian Summer Monsoon (ASM) circulations. From the beginning of MIS 9, there was a southward movement of the Westerlies circulation, which corresponded to a retreat of the Indian Summer Monsoon (ISM). A similar relationship also existed between the East Asian Summer Monsoon (EASM) circulation and the Westerlies, which is evidenced by the formation of the most weakly developed soil unit in the EASM-dominated regions during MIS 9, in contrast with the formation of the most strongly developed soil unit in the Westerlies-dominated regions. As conditions in the areas of loess deposition became more humid, the sedimentary basins which are the dust source areas became progressively more arid. The aridification of the source areas may be the result of increased Northern Hemisphere ice volume and accelerated high mountains and/or plateaus uplift in the surrounding regions.

Multi-scale constraints of sediment source to sink systems in frontier basins: a forward stratigraphic modeling case study of the Levant region

NASA Astrophysics Data System (ADS)

Hawie, Nicolas; Deschamps, Remy; Granjeon, Didier; Nader, Fadi-Henri; Gorini, Christian; Müller, Carla; Montadert, Lucien; Baudin, François

2015-04-01

Recent scientific work underlined the presence of a thick Cenozoic infill in the Levant Basin reaching up to 12 km. Interestingly; restricted sedimentation was observed along the Levant margin in the Cenozoic. Since the Late Eocene successive regional geodynamic events affecting Afro-Arabia and Eurasia (collision and strike slip deformation)induced fast marginal uplifts. The initiation of local and long-lived regional drainage systems in the Oligo-Miocene period (e.g. Lebanon versus Nile) provoked a change in the depositional pattern along the Levant margin and basin. A shift from carbonate dominated environments into clastic rich systems has been observed. Through this communication we explore the importance of multi-scale constraints (i.e.,seismic, well and field data) in the quantification of the subsidence history, sediment transport and deposition of a Middle-Upper Miocene "multi-source" to sink system along the northernLevant frontier region. We prove through a comprehensive forward stratigraphic modeling workflow that the contribution to the infill of the northern Levant Basin (offshore Lebanon) is split in between proximal and more distal clastic sources as well as in situ carbonate/hemipelagic deposition. In a wider perspective this work falls under the umbrella of multi-disciplinary source to sink studies that investigate the impact of geodynamic events on basin/margin architectural evolutions, consequent sedimentary infill and thus on petroleum systems assessment.

Long-range transport of black carbon to the Pacific Ocean and its dependence on aging timescale

NASA Astrophysics Data System (ADS)

Zhang, J.; Liu, J.; Tao, S.; Ban-Weiss, G. A.

2015-06-01

Improving the ability of global models to predict concentrations of black carbon (BC) over the Pacific Ocean is essential to evaluate the impact of BC on marine climate. In this study, we tag BC tracers from 13 source regions around the globe in a global chemical transport model MOZART-4. Numerous sensitivity simulations are carried out varying the aging timescale of BC emitted from each source region. The aging timescale for each source region is optimized by minimizing errors in vertical profiles of BC mass mixing ratios between simulations and HIAPER Pole-to-Pole Observations (HIPPO). For most HIPPO deployments, in the Northern Hemisphere, optimized aging timescales are less than half a day for BC emitted from tropical and mid-latitude source regions, and about 1 week for BC emitted from high latitude regions in all seasons except summer. We find that East Asian emissions contribute most to the BC loading over the North Pacific, while South American, African and Australian emissions dominate BC loadings over the South Pacific. Dominant source regions contributing to BC loadings in other parts of the globe are also assessed. The lifetime of BC originating from East Asia (i.e., the world's largest BC emitter) is found to be only 2.2 days, much shorter than the global average lifetime of 4.9 days, making East Asia's contribution to global burden only 36 % of BC from the second largest emitter, Africa. Thus, evaluating only relative emission rates without accounting for differences in aging timescales and deposition rates is not predictive of the contribution of a given source region to climate impacts. Our simulations indicate that lifetime of BC increases nearly linearly with aging timescale for all source regions. When aging rate is fast, the lifetime of BC is largely determined by factors that control local deposition rates (e.g. precipitation). The sensitivity of lifetime to aging timescale depends strongly on the initial hygroscopicity of freshly emitted BC. Our findings suggest that the aging timescale of BC varies significantly by region and season, and can strongly influence the contribution of source regions to BC burdens around the globe. Improving parameterizations of the aging process for BC is important for enhancing the predictive skill of air quality and climate models. Future observations that investigate the evolution of hygroscopicity of BC as it ages from different source regions to the remote atmosphere are urgently needed.

Long-range transport of black carbon to the Pacific Ocean and its dependence on aging timescale

NASA Astrophysics Data System (ADS)

Zhang, J.; Liu, J.; Tao, S.; Ban-Weiss, G. A.

2015-10-01

Improving the ability of global models to predict concentrations of black carbon (BC) over the Pacific Ocean is essential to evaluate the impact of BC on marine climate. In this study, we tag BC tracers from 13 source regions around the globe in a global chemical transport model, Model for Ozone and Related Chemical Tracers, version 4 (MOZART-4). Numerous sensitivity simulations are carried out varying the aging timescale of BC emitted from each source region. The aging timescale for each source region is optimized by minimizing errors in vertical profiles of BC mass mixing ratios between simulations and HIAPER Pole-to-Pole Observations (HIPPO). For most HIPPO deployments, in the Northern Hemisphere, optimized aging timescales are less than half a day for BC emitted from tropical and midlatitude source regions and about 1 week for BC emitted from high-latitude regions in all seasons except summer. We find that East Asian emissions contribute most to the BC loading over the North Pacific, while South American, African and Australian emissions dominate BC loadings over the South Pacific. Dominant source regions contributing to BC loadings in other parts of the globe are also assessed. The lifetime of BC originating from East Asia (i.e., the world's largest BC emitter) is found to be only 2.2 days, much shorter than the global average lifetime of 4.9 days, making the contribution from East Asia to the global BC burden only 36 % of that from the second largest emitter, Africa. Thus, evaluating only relative emission rates without accounting for differences in aging timescales and deposition rates is not predictive of the contribution of a given source region to climate impacts. Our simulations indicate that the lifetime of BC increases nearly linearly with aging timescale for all source regions. When the aging rate is fast, the lifetime of BC is largely determined by factors that control local deposition rates (e.g., precipitation). The sensitivity of lifetime to aging timescale depends strongly on the initial hygroscopicity of freshly emitted BC. Our findings suggest that the aging timescale of BC varies significantly by region and season and can strongly influence the contribution of source regions to BC burdens around the globe. Therefore, improving parameterizations of the aging process for BC is important for enhancing the predictive skill of global models. Future observations that investigate the evolution of the hygroscopicity of BC as it ages from different source regions to the remote atmosphere are urgently needed.

3-Helium in Obscure H II Regions

NASA Astrophysics Data System (ADS)

Bania, T. M.; Rood, R. T.; Balser, D. S.

1999-05-01

The light isotope of helium, (3) He, can serve as a probe of cosmology, the evolution of low mass stars, and the chemical evolution of the Galaxy. Its abundance can be determined via measurements of the 3.46 cm hyperfine transition of (3) He(+) . Potentially observable sources of ionized gas include H ii regions and planetary nebulae. The selection of (3) He targets is counter-intuitive because the (3) He(+) hyperfine line strength is proportional to the source density, while one usually thinks of H ii regions in terms of radio continuum or recombination line strength both of which depend on the square of the density. The (3) He(+) line strength depends on the (3) He(+) abundance ratio and a number of other factors: $ TL(A}({) (3) He(+)) ~ frac {N((3) He(+)}{N() H(+)}) frac {({TC(A}}D)({1/2)) Te(1/4) (theta_obs (2) - theta_beam (2})({3/4}}{Delta {v}({)) (3) He(+)) [ln(5.717 x 10(-3}Te({3/2})]^{1/2)) theta_obs } where T_L^A and Delta v are the antenna temperature and FWHM of the ^3He^+ line, D is the nebular distance, T_C^A and theta_obs are the antenna temperature and observed FWHM angular size of the continuum emission, theta_beam is the telescope's FWHM beam, and Te is the nebular electron temperature. For H {sc ii} regions much larger than the telescope beam we can select targets using the criterion: TLA(^3He^+)\\sim\\sqrt{TCA D\\theta_obs}. This is the case since we can neglect the weak dependence on T_e and because we do not know either ^3He^{+}/H^+ or Delta v. Thus big, distant H ii regions could be potential ^3He^+ targets even if their continuum emission is weak. Armed with this knowledge we included H ii regions like S209 in our early observing list along with more famous sources like W43. Still we did not have the temerity to push this reasoning to the limit. We have now found, however, that this selection criterion is valid for even the wimpiest known H ii regions. Here we report on the detection of ^3He^+$ emission in 8 distant, low density H ii regions.

UV and X-ray Evolution of AR12230 as Observed with IRIS and FOXSI-II

NASA Astrophysics Data System (ADS)

Ryan, Daniel; Christe, Steven; Glesener, Lindsay; Vievering, Julie; Krucker, Sam; Ishikawa, Shin-Nosuke

2017-08-01

We present a multi-spectral and spatio-temporal analysis of AR12230 using both UV and X-ray spectroscopic imaging obtained as part of a coordinated observing campaign on 11 December 2014. The campaign involved IRIS (Interface Region Imaging Spectrometer) -- which provides both UV imaging and slit spectrograph observations of optically thick chromospheric and transition region emission -- and FOXSI-II (Focusing Optics X-ray Solar Imager) -- the second in a series of sounding rocket flights which combines grazing incidence direct focusing optics to produce solar X-ray spectroscopic imaging in the range 4-15keV. The active region exhibits a prolonged compact brightening in the IRIS 1330 A and 1400 A slit-jaw channels near the center of the active region throughout the duration of the observations. In the early phase of the observations FOXSI-II shows an X-ray source approximately 20x20 arcsec centered at the same location. The X-ray spectra show the presence of hot (~8 MK) thermal plasma and is suggestive of the presence of non-thermal electrons.. Later, two additional transient, spatially extended, simultaneous brightenings are observed, one of which was captured by the IRIS slit spectrograph. We combine these observations to explore the evolution and topology of the active region. Hydrodynamic modeling of the chromosphere is used to place a limit on the amount of non-thermal electrons required to produce the observed UV emission. This result is then compared to the limit inferred from the FOXSI-II X-ray spectra. Thus, we explore the role of non-thermal electrons and hydrodynamics in the energization and evolution of plasma in active regions.

Tropopause inversion layer formation and stratosphere-troposphere exchange during idealized baroclinic wave life cycle experiments

NASA Astrophysics Data System (ADS)

Kunkel, Daniel; Wirth, Volkmar; Hoor, Peter

2014-05-01

Recent simulations of baroclinic wave life cycles revealed that the tropopause inversion layer (TIL), commonly situated just above the thermal tropopause, is evident in such experiments and emerges after the onset of wave breaking. Furthermore, bidirectional stratosphere-troposphere exchange (STE) occurs during this non-linear stage of the wave evolution and might be affected by the appearance of the TIL. We study the evolution and the impact of the TIL on STE by using the COSMO model in an idealized mid-latitude channel geometry configuration without physical sub-grid scale parameterizations. We initialize the model with a geostrophically balanced upper level jet stream which is disturbed by an anomaly of potential vorticity to trigger the evolution of the baroclinic waves. Moreover, we use passive tracers of tropospheric or stratospheric origin to identify regions of potential STE. Our results show that the static stability is low in regions of stratosphere to troposphere exchange (STT), while it is high in regions dominated by exchange in the opposite direction (TST). Furthermore, inertia gravity waves, originating from regions with strong ageostrophic wind components, modulate the static stability as well as the vertical shear of the horizontal wind near and above the tropopause. While propagating away from their source, the inertia gravity waves lead to large values of the squared Brunt Vaisala frequency in regions which are simultaneously characterized by low bulk Richardson numbers. Thus, these regions are statically stable and turbulent at the same time and might be crucial for TST, thereby explaining tropospheric mixing ratio changes of e.g. CO across the tropopause which commonly change from tropospheric to stratospheric values a few hundred meters above the local thermal tropopause.

X-ray diving in the center of Sh2-129: looking for the driving source of Ou4

NASA Astrophysics Data System (ADS)

Grosso, Nicolas

2012-10-01

The outflow phenomenon is associated both with the early and the last phase of the stellar evolution. Recently, a unique bipolar outflow with an angular size of 1.2 degrees was discovered in the blister HII region Sh2-129. Ou4, nicknamed "The Giant Squid", is to our knowledge the bipolar outflow with the largest angular size ever found. We propose joint XMM-Newton/EPIC (35 ks) and Chandra/HRC-I (16 ks) observations to look for the driving source of Ou4 and to clarify the nature of this object.

An Extremely Rich Group Of Starbursts And Agns At A Z=3.1 Proto-Cluster Core

NASA Astrophysics Data System (ADS)

Umehata, Hideki

2017-06-01

The environment where galaxies inhabit is expected to play a critical role in shaping their evolution. Galaxies and nuclei in the dense environment at high redshift (i.e., proto-clusters) provide a good laboratory to investigate the accelerated, most extreme evolution of galaxies at a given epoch. Using ALMA band 3 and band 6, we mapped a 2'x3' region within the node at the junction of the 50 Mpc-scale filamentary three-dimensional structure traced by Lyman-alpha emitters (LAEs) in this field. We obtained 18 robustly detected 1.1mm sources (here after submillimeter galaxies, SMGs) with a signal-to-noise ratio (SNR) >5. We also detected CO(3-2) line from 8 SMGs, which in general shows relatively extended structure. Totally 12 ALMA SMGs have spectroscopic redshifts of z=3.09 and six of them host a X-ray luminous active galactic nuclei (AGN). We also find that multiple z=3.09 ALMA SMGs contribute to two AzTEC sources, supporting that interaction may be responsible for a significant fraction of multiplicity in single-dish sources. Our results suggest that the vigorous star formation activity and the growth of super massive black holes (SMBHs) occurred simultaneously in the densest regions at z 3, which is likely to correspond to the most active historical phase of the massive galaxy population found in the core of the clusters in the present universe.

The Evolution of Open Magnetic Flux Driven by Photospheric Dynamics

NASA Technical Reports Server (NTRS)

Linker, Jon A.; Lionello, Roberto; Mikic, Zoran; Titov, Viacheslav S.; Antiochos, Spiro K.

2010-01-01

The coronal magnetic field is of paramount importance in solar and heliospheric physics. Two profoundly different views of the coronal magnetic field have emerged. In quasi-steady models, the predominant source of open magnetic field is in coronal holes. In contrast, in the interchange model, the open magnetic flux is conserved, and the coronal magnetic field can only respond to the photospheric evolution via interchange reconnection. In this view the open magnetic flux diffuses through the closed, streamer belt fields, and substantial open flux is present in the streamer belt during solar minimum. However, Antiochos and co-workers, in the form of a conjecture, argued that truly isolated open flux cannot exist in a configuration with one heliospheric current sheet (HCS) - it will connect via narrow corridors to the polar coronal hole of the same polarity. This contradicts the requirements of the interchange model. We have performed an MHD simulation of the solar corona up to 20R solar to test both the interchange model and the Antiochos conjecture. We use a synoptic map for Carrington Rotation 1913 as the boundary condition for the model, with two small bipoles introduced into the region where a positive polarity extended coronal hole forms. We introduce flows at the photospheric boundary surface to see if open flux associated with the bipoles can be moved into the closed-field region. Interchange reconnection does occur in response to these motions. However, we find that the open magnetic flux cannot be simply injected into closed-field regions - the flux eventually closes down and disconnected flux is created. Flux either opens or closes, as required, to maintain topologically distinct open and closed field regions, with no indiscriminate mixing of the two. The early evolution conforms to the Antiochos conjecture in that a narrow corridor of open flux connects the portion of the coronal hole that is nearly detached by one of the bipoles. In the later evolution, a detached coronal hole forms, in apparent violation of the Antiochos conjecture. Further investigation reveals that this detached coronal hole is actually linked to the extended coronal hole by a separatrix footprint on the photosphere of zero width. Therefore, the essential idea of the conjecture is preserved, if we modify it to state that coronal holes in the same polarity region are always linked, either by finite width corridors or separatrix footprints. The implications of these results for interchange reconnection and the sources of the slow solar wind are briefly discussed.

The XMM-SERVS Survey: first results in the 5 deg^2 XMM-LSS region

NASA Astrophysics Data System (ADS)

Chen, Chien-Ting; Brandt, William; Luo, Bin; X-SERVS team

2018-01-01

We present an X-ray source catalog obtained with XMM-Newton in the XMM-LSS region as part of the X-SERVS survey (XMM-SERVS-LSS), which aims to expand the parameter space of current X-ray surveys with medium-deep X-ray observations in multiple large fields with superb multiwavelength coverage. Within the 5 deg$^2$ XMM-SERVS-LSS field, we combine the 1.3 Ms XMM observations allocated at XMM AO-15 with archival data, and identified 5218 X-ray sources of which 2400 are new sources. We reach $1.2\\times10^{-15}$ erg s$^{-1} cm$^{-1}$ for 50\\% of the area, which is comparable to the XMM-COSMOS survey but with 2.5 times more sources. We also present multiwavelength identifications, basic photometric properties, and spectroscopic redshifts obtained from the literature. These data, combined with the existing data from COSMOS, will enable a wide range of science on AGN evolution, including studying SMBH growth across the full range of cosmic environments and minimizing cosmic variance.

Dispersion Measure Variation of Repeating Fast Radio Burst Sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Yuan-Pei; Zhang, Bing, E-mail: yypspore@gmail.com, E-mail: zhang@physics.unlv.edu

The repeating fast radio burst (FRB) 121102 was recently localized in a dwarf galaxy at a cosmological distance. The dispersion measure (DM) derived for each burst from FRB 121102 so far has not shown significant evolution, even though an apparent increase was recently seen with newly detected VLA bursts. It is expected that more repeating FRB sources may be detected in the future. In this work, we investigate a list of possible astrophysical processes that might cause DM variation of a particular FRB source. The processes include (1) cosmological scale effects such as Hubble expansion and large-scale structure fluctuations; (2)more » FRB local effects such as gas density fluctuation, expansion of a supernova remnant (SNR), a pulsar wind nebula, and an H ii region; and (3) the propagation effect due to plasma lensing. We find that the DM variations contributed by the large-scale structure are extremely small, and any observable DM variation is likely caused by the plasma local to the FRB source. In addition to mechanisms that decrease DM over time, we suggest that an FRB source in an expanding SNR around a nearly neutral ambient medium during the deceleration (Sedov–Taylor and snowplow) phases or in a growing H ii region can increase DM. Some effects (e.g., an FRB source moving in an H ii region or plasma lensing) can produce either positive or negative DM variations. Future observations of DM variations of FRB 121102 and other repeating FRB sources can provide important clues regarding the physical origin of these sources.« less

Assessing the evolution of oases in arid regions by reconstructing their historic spatio-temporal distribution: a case study of the Heihe River Basin, China

NASA Astrophysics Data System (ADS)

Xie, Yaowen; Wang, Guisheng; Wang, Xueqiang; Fan, Peilei

2017-12-01

Oasis evolution, one of the most obvious surface processes in arid regions, affects various aspects of the regional environment, such as hydrological processes, ecological conditions, and microclimates. In this paper, the historical spatio-temporal evolution of the cultivated oases in the Heihe River Basin, the second largest inland watershed in the northwest of China, was assessed using multidisciplinary methods and data from multiple sources, including historical literature, ancient sites, maps and remotely sensed images. The findings show that cultivated oases were first developed on a large scale during the Han Dynasty (121 BC-220) and then gradually decreased in extent from the Six Dynasties period (220-581) to the Sui-Tang period (581-907), reaching a minimum in the Song-Yuan period (960-1368). An abrupt revival occurred during the Ming Dynasty (1368-1644) and continued through the Qing Dynasty (1644-1911), and during the period of the Republic of China (1912-1949), oasis development reached its greatest peak of the entire historical period. The oasis areas during seven major historical periods, i.e., Han, Six Dynasties, Sui-Tang, Song-Yuan, Ming, Qing, and Republic of China, are estimated to have been 1703 km2, 1115 km2, 629 km2, 614 km2, 964 km2, 1205 km2, and 1917 km2, respectively. The spatial distribution generally exhibited a continuous sprawl process, with the center of the oases moving gradually from the downstream region to the middle and even upstream regions. The oases along the main river remained stable during most periods, whereas those close to the terminal reaches were subject to frequent variations and even abandonment. Socio-economic factors were the main forces driving the evolution of cultivated oases in the area; among them, political and societal stability, national defense, agricultural policy, population, and technological progress were the most important.

Application of differential evolution algorithm on self-potential data.

PubMed

Li, Xiangtao; Yin, Minghao

2012-01-01

Differential evolution (DE) is a population based evolutionary algorithm widely used for solving multidimensional global optimization problems over continuous spaces, and has been successfully used to solve several kinds of problems. In this paper, differential evolution is used for quantitative interpretation of self-potential data in geophysics. Six parameters are estimated including the electrical dipole moment, the depth of the source, the distance from the origin, the polarization angle and the regional coefficients. This study considers three kinds of data from Turkey: noise-free data, contaminated synthetic data, and Field example. The differential evolution and the corresponding model parameters are constructed as regards the number of the generations. Then, we show the vibration of the parameters at the vicinity of the low misfit area. Moreover, we show how the frequency distribution of each parameter is related to the number of the DE iteration. Experimental results show the DE can be used for solving the quantitative interpretation of self-potential data efficiently compared with previous methods.

Application of Differential Evolution Algorithm on Self-Potential Data

PubMed Central

Li, Xiangtao; Yin, Minghao

2012-01-01

Differential evolution (DE) is a population based evolutionary algorithm widely used for solving multidimensional global optimization problems over continuous spaces, and has been successfully used to solve several kinds of problems. In this paper, differential evolution is used for quantitative interpretation of self-potential data in geophysics. Six parameters are estimated including the electrical dipole moment, the depth of the source, the distance from the origin, the polarization angle and the regional coefficients. This study considers three kinds of data from Turkey: noise-free data, contaminated synthetic data, and Field example. The differential evolution and the corresponding model parameters are constructed as regards the number of the generations. Then, we show the vibration of the parameters at the vicinity of the low misfit area. Moreover, we show how the frequency distribution of each parameter is related to the number of the DE iteration. Experimental results show the DE can be used for solving the quantitative interpretation of self-potential data efficiently compared with previous methods. PMID:23240004

The 2016 Kaikōura Earthquake Revealed by Kinematic Source Inversion and Seismic Wavefield Simulations: Slow Rupture Propagation on a Geometrically Complex Crustal Fault Network

NASA Astrophysics Data System (ADS)

Holden, C.; Kaneko, Y.; D'Anastasio, E.; Benites, R.; Fry, B.; Hamling, I. J.

2017-11-01

The 2016 Kaikōura (New Zealand) earthquake generated large ground motions and resulted in multiple onshore and offshore fault ruptures, a profusion of triggered landslides, and a regional tsunami. Here we examine the rupture evolution using two kinematic modeling techniques based on analysis of local strong-motion and high-rate GPS data. Our kinematic models capture a complex pattern of slowly (Vr < 2 km/s) propagating rupture from south to north, with over half of the moment release occurring in the northern source region, mostly on the Kekerengu fault, 60 s after the origin time. Both models indicate rupture reactivation on the Kekerengu fault with the time separation of 11 s between the start of the original failure and start of the subsequent one. We further conclude that most near-source waveforms can be explained by slip on the crustal faults, with little (<8%) or no contribution from the subduction interface.

GLOBAL ENERGETICS OF SOLAR FLARES. IV. CORONAL MASS EJECTION ENERGETICS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aschwanden, Markus J., E-mail: aschwanden@lmsal.com

2016-11-01

This study entails the fourth part of a global flare energetics project, in which the mass m {sub cme}, kinetic energy E {sub kin}, and the gravitational potential energy E {sub grav} of coronal mass ejections (CMEs) is measured in 399 M and X-class flare events observed during the first 3.5 years of the Solar Dynamics Observatory (SDO) mission, using a new method based on the EUV dimming effect. EUV dimming is modeled in terms of a radial adiabatic expansion process, which is fitted to the observed evolution of the total emission measure of the CME source region. The modelmore » derives the evolution of the mean electron density, the emission measure, the bulk plasma expansion velocity, the mass, and the energy in the CME source region. The EUV dimming method is truly complementary to the Thomson scattering method in white light, which probes the CME evolution in the heliosphere at r ≳ 2 R {sub ⊙}, while the EUV dimming method tracks the CME launch in the corona. We compare the CME parameters obtained in white light with the LASCO/C2 coronagraph with those obtained from EUV dimming with the Atmospheric Imaging Assembly onboard the SDO for all identical events in both data sets. We investigate correlations between CME parameters, the relative timing with flare parameters, frequency occurrence distributions, and the energy partition between magnetic, thermal, nonthermal, and CME energies. CME energies are found to be systematically lower than the dissipated magnetic energies, which is consistent with a magnetic origin of CMEs.« less

Probing Protoplanetary Disks: From Birth to Planets

NASA Astrophysics Data System (ADS)

Cox, Erin Guilfoil

2018-01-01

Disks are very important in the evolution of protostars and their subsequent planets. How early disks can form has implications for early planet formation. In the youngest protostars (i.e., Class 0 sources) magnetic fields can control disk growth. When the field is parallel to the collapsing core’s rotation axis, infalling material loses angular momentum and disks form in later stages. Sub-/millimeter polarization continuum observations of Class 0 sources at ~1000 au resolution support this idea. However, in the inner (~100 au), denser regions, it is unknown if the polarization only traces aligned dust grains. Recent theoretical studies have shown that self-scattering of thermal emission in the disk may contribute significantly to the polarization. Determining the scattering contribution in these sources is important to disentangle the magnetic field. At older times (the Class II phase), the disk structure can both act as a modulator and signpost of planet formation, if there is enough of a mass reservoir. In my dissertation talk, I will present results that bear on disk evolution at both young and late ages. I will present 8 mm polarization results of two Class 0 protostars (IRAS 4A and IC348 MMS) from the VLA at ~50 au resolution. The inferred magnetic field of IRAS 4A has a circular morphology, reminiscent of material being dragged into a rotating structure. I will show results from SOFIA polarization data of the area surrounding IRAS 4A at ~4000 au. I will also present ALMA 850 micron polarization data of ten protostars in the Perseus Molecular Cloud. Most of these sources show very ordered patterns and low (~0.5%) polarization in their inner regions, while having very disordered patterns and high polarization patterns in their extended emission that may suggest different mechanisms in the inner/outer regions. Finally, I will present results from our ALMA dust continuum survey of protoplanetary disks in Rho Ophiuchus; we measured both the sizes and fluxes of 49 pre main-sequence stellar systems and detected either gaps or cavities in ~6 of these sources. Combined, these results build upon how early protoplanetary disks can form around young protostars and thus how early planets can begin to form.

Characteristics of Individual Eruptive Events on the Lunar Western Limb and Farside: Implications for Magma Ascent and Eruption Mechanisms

NASA Astrophysics Data System (ADS)

Yingst, R. A.; Head, J. W., III

1996-03-01

The connection between lunar magma source regions and the location and emplacement conditions of volcanic surface features remains unclear, both conceptually and quantitatively with respect to our understanding of transport mechanisms. Investigation of these issues requires use of surface feature characteristics to reconstruct the conditions of transport and eruption, so that thermal evolution models may be tested. Specifically, mare deposits are asymmetrically distributed over the lunar surface, with the nearside displaying the vast majority of surface basalts. Apollo and recent Clementine data have confirmed a dichotomy between the nearside and the farside with respect to crustal thickness. This implies a possible relationship between the efficiency of magma transport and the amount of crust through which magma must pass. It has been suggested that mare emplacement has been controlled by propagation of dikes driven by the overpressurization of diapir-like source regions stalled below the cooling lunar highland crust. Thus, regions of thinner crust would be expected to allow a greater number of dikes to reach the surface under the same source region conditions, than areas with thicker crust. Recent analyses of the characteristics of lava ponds in the South Pole/Aitken and Orientale/Mendel-Rydberg basins based on Clementine, Lunar Orbiter and Zond data have provided evidence that supports this theory.

A unified framework for modelling sediment fate from source to sink and its interactions with reef systems over geological times.

PubMed

Salles, Tristan; Ding, Xuesong; Webster, Jody M; Vila-Concejo, Ana; Brocard, Gilles; Pall, Jodie

2018-03-27

Understanding the effects of climatic variability on sediment dynamics is hindered by limited ability of current models to simulate long-term evolution of sediment transfer from source to sink and associated morphological changes. We present a new approach based on a reduced-complexity model which computes over geological time: sediment transport from landmasses to coasts, reworking of marine sediments by longshore currents, and development of coral reef systems. Our framework links together the main sedimentary processes driving mixed siliciclastic-carbonate system dynamics. It offers a methodology for objective and quantitative sediment fate estimations over regional and millennial time-scales. A simulation of the Holocene evolution of the Great Barrier Reef shows: (1) how high sediment loads from catchments erosion prevented coral growth during the early transgression phase and favoured sediment gravity-flows in the deepest parts of the northern region basin floor (prior to 8 ka before present (BP)); (2) how the fine balance between climate, sea-level, and margin physiography enabled coral reefs to thrive under limited shelf sedimentation rates after ~6 ka BP; and, (3) how since 3 ka BP, with the decrease of accommodation space, reduced of vertical growth led to the lateral extension of reefs consistent with available observational data.

The dehydration, rehydration and tectonic setting of greenstone belts in a portion of the northern Kaapvaal Craton, South Africa

NASA Technical Reports Server (NTRS)

Vanreenen, D. D.; Barton, J. M., Jr.; Roering, C.; Vanschalkwyk, J. C.; Smit, C. A.; Debeer, J. D.; Stettler, E. H.

1986-01-01

High-grade gneiss terranes and low-grade granite-greenstone terranes are well known in several Archaean domains. The geological relationship between these different crustal regions, however, is still controversial. One school of thought favors fundamental genetic differences between high-grade and low-grade terranes while others argue for a depth-controlled crustal evolution. The detailed examination of well-exposed Archaean terranes at different metamorphic grades, therefore, is not only an important source of information about the crustal levels exposed, but also is critical to the understanding of the possible tectonic and metamorphic evolution of greenstone belts with time. Three South African greenstone belts are compared.

Sr isotopic composition of Afar volcanics and its implication for mantle evolution

NASA Astrophysics Data System (ADS)

Barberi, F.; Civetta, L.; Varet, J.

1980-10-01

Investigations of Rb-Sr systematics of basalts from the Afar depression (Ethiopia) indicate the presence of a heterogeneous mantle source region. The Sr isotopic compositions of the basalts from the Afar axial and transverse ranges identify source regions which are enriched in LIL elements and radiogenic Sr (axial ranges) and others which are relatively depleted (transverse ranges). Sr isotopic composition of basalts from the Red Sea, Gulf of Aden and Gulf of Tadjoura, which range from 0.70300 to 0.70340 are also reported and compared with the more radiogenic Afar region, which is characterized by 87Sr/ 86Sr ranging from 0.70328 to 0.70410. Available geochemical and isotopic data suggest that a relation exists between magma composition and the advancement of the rifting process through progressive lithosphere attenuation leading to continental break-up. However, the petrogenetic process is not simple and probably implies a vertically zoned mantle beneath the Afar region. Sr isotopic evidence suggests that the vertically zoned mantle is more radiogenic and enriched in LIL elements in its upper part.

Cenozoic erosion of the Transantarctic Mountains: A source-to-sink thermochronological study

NASA Astrophysics Data System (ADS)

Zattin, M.; Pace, D.; Andreucci, B.; Rossetti, F.; Talarico, F. M.

2014-09-01

The formation of the Transantarctic Mountains (TAM) is strictly related to the evolution of the West Antarctic Rift system, but the timing of their exhumation is still not fully assessed. In this work, we provide new apatite fission-track data collected on the region between the Royal Society Range and the Britannia Range. Cooling ages are late Eocene-Oligocene in the center of the region but they get older both northwards and southwards. We infer that exhumation was strictly controlled by TAM-parallel fault strands that were active after the Oligocene. The Royal Society Range and the Britannia Range represent transition zones corresponding to transverse structures, probably inherited from early basement crustal discontinuities and reactivated as transfer regions during rift propagation. The exhumation of the investigated region has been then modeled and predicted thermochronological ages have been compared with detrital data from the Miocene sedimentary succession drilled in the Victoria Land Basin. Results indicate that this sector of the TAM is the most probable candidate for the source of sediments and that during the Neogene 3 km (but up to 5 km) of rocks was exhumed.

Sixty-Five Million Years of Change in Temperature and Topography Explain Evolutionary History in Eastern North American Plethodontid Salamanders.

PubMed

Barnes, Richard; Clark, Adam Thomas

2017-07-01

For many taxa and systems, species richness peaks at midelevations. One potential explanation for this pattern is that large-scale changes in climate and geography have, over evolutionary time, selected for traits that are favored under conditions found in contemporary midelevation regions. To test this hypothesis, we use records of historical temperature and topographic changes over the past 65 Myr to construct a general simulation model of plethodontid salamander evolution in eastern North America. We then explore possible mechanisms constraining species to midelevation bands by using the model to predict plethodontid evolutionary history and contemporary geographic distributions. Our results show that models that incorporate both temperature and topographic changes are better able to predict these patterns, suggesting that both processes may have played an important role in driving plethodontid evolution in the region. Additionally, our model (whose annotated source code is included as a supplement) represents a proof of concept to encourage future work that takes advantage of recent advances in computing power to combine models of ecology, evolution, and earth history to better explain the abundance and distribution of species over time.

Identifying ultrahigh-energy cosmic-ray accelerators with future ultrahigh-energy neutrino detectors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fang, Ke; Miller, M. Coleman; Kotera, Kumiko

2016-12-01

The detection of ultrahigh-energy (UHE) neutrino sources would contribute significantly to solving the decades-old mystery of the origin of the highest-energy cosmic rays. We investigate the ability of a future UHE neutrino detector to identify the brightest neutrino point sources, by exploring the parameter space of the total number of observed events and the angular resolution of the detector. The favored parameter region can be translated to requirements for the effective area, sky coverage and angular resolution of future detectors, for a given source number density and evolution history. Moreover, by studying the typical distance to sources that are expectedmore » to emit more than one event for a given diffuse neutrino flux, we find that a significant fraction of the identifiable UHE neutrino sources may be located in the nearby Universe if the source number density is above ∼10{sup −6} Mpc{sup −3}. If sources are powerful and rare enough, as predicted in blazar scenarios, they can first be detected at distant locations. Our result also suggests that if UHE cosmic-ray accelerators are neither beamed nor transients, it will be possible to associate the detected UHE neutrino sources with nearby UHE cosmic-ray and gamma-ray sources, and that they may also be observed using other messengers, including ones with limited horizons such as TeV gamma rays, UHE gamma rays and cosmic rays. We find that for a ∼>5σ detection of UHE neutrino sources with a uniform density, n {sub s} {sub ∼}10{sup −7}−10{sup −5} Mpc{sup −3}, at least ∼100−1000 events and sub-degree angular resolution are needed, and the results depend on the source evolution model.« less

Identifying ultrahigh-energy cosmic-ray accelerators with future ultrahigh-energy neutrino detectors

NASA Astrophysics Data System (ADS)

Fang, Ke; Kotera, Kumiko; Miller, M. Coleman; Murase, Kohta; Oikonomou, Foteini

2016-12-01

The detection of ultrahigh-energy (UHE) neutrino sources would contribute significantly to solving the decades-old mystery of the origin of the highest-energy cosmic rays. We investigate the ability of a future UHE neutrino detector to identify the brightest neutrino point sources, by exploring the parameter space of the total number of observed events and the angular resolution of the detector. The favored parameter region can be translated to requirements for the effective area, sky coverage and angular resolution of future detectors, for a given source number density and evolution history. Moreover, by studying the typical distance to sources that are expected to emit more than one event for a given diffuse neutrino flux, we find that a significant fraction of the identifiable UHE neutrino sources may be located in the nearby Universe if the source number density is above ~10-6 Mpc-3. If sources are powerful and rare enough, as predicted in blazar scenarios, they can first be detected at distant locations. Our result also suggests that if UHE cosmic-ray accelerators are neither beamed nor transients, it will be possible to associate the detected UHE neutrino sources with nearby UHE cosmic-ray and gamma-ray sources, and that they may also be observed using other messengers, including ones with limited horizons such as TeV gamma rays, UHE gamma rays and cosmic rays. We find that for a gtrsim5σ detection of UHE neutrino sources with a uniform density, ns~10-7-10-5 Mpc-3, at least ~100-1000 events and sub-degree angular resolution are needed, and the results depend on the source evolution model.

Complex interactions between diapirs and 4-D subduction driven mantle wedge circulation.

NASA Astrophysics Data System (ADS)

Sylvia, R. T.; Kincaid, C. R.

2015-12-01

Analogue laboratory experiments generate 4-D flow of mantle wedge fluid and capture the evolution of buoyant mesoscale diapirs. The mantle is modeled with viscous glucose syrup with an Arrhenius type temperature dependent viscosity. To characterize diapir evolution we experiment with a variety of fluids injected from multiple point sources. Diapirs interact with kinematically induced flow fields forced by subducting plate motions replicating a range of styles observed in dynamic subduction models (e.g., rollback, steepening, gaps). Data is collected using high definition timelapse photography and quantified using image velocimetry techniques. While many studies assume direct vertical connections between the volcanic arc and the deeper mantle source region, our experiments demonstrate the difficulty of creating near vertical conduits. Results highlight extreme curvature of diapir rise paths. Trench-normal deflection occurs as diapirs are advected downward away from the trench before ascending into wedge apex directed return flow. Trench parallel deflections up to 75% of trench length are seen in all cases, exacerbated by complex geometry and rollback motion. Interdiapir interaction is also important; upwellings with similar trajectory coalesce and rapidly accelerate. Moreover, we observe a new mode of interaction whereby recycled diapir material is drawn down along the slab surface and then initiates rapid fluid migration updip along the slab-wedge interface. Variability in trajectory and residence time leads to complex petrologic inferences. Material from disparate source regions can surface at the same location, mix in the wedge, or become fully entrained in creeping flow adding heterogeneity to the mantle. Active diapirism or any other vertical fluid flux mechanism employing rheological weakening lowers viscosity in the recycling mantle wedge affecting both solid and fluid flow characteristics. Many interesting and insightful results have been presented based upon 2-D, steady-state thermal and flow regimes. We reiterate the importance of 4-D time evolution in subduction models. Analogue experiments allow added feedbacks and complexity improving intuition and providing insight for further investigation.

An ALMA Survey of Protoplanetary Disks in the σ Orionis Cluster

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ansdell, M.; Williams, J. P.; Marel, N. van der

2017-05-01

The σ  Orionis cluster is important for studying protoplanetary disk evolution, as its intermediate age (∼3–5 Myr) is comparable to the median disk lifetime. We use ALMA to conduct a high-sensitivity survey of dust and gas in 92 protoplanetary disks around σ  Orionis members with M {sub *} ≳ 0.1  M {sub ⊙}. Our observations cover the 1.33 mm continuum and several CO J  = 2–1 lines: out of 92 sources, we detect 37 in the millimeter continuum and 6 in {sup 12}CO, 3 in {sup 13}CO, and none in C{sup 18}O. Using the continuum emission to estimate dust mass, we find only 11more » disks with M {sub dust} ≳ 10  M {sub ⊕}, indicating that after only a few Myr of evolution most disks lack sufficient dust to form giant planet cores. Stacking the individually undetected continuum sources limits their average dust mass to 5×  lower than that of the faintest detected disk, supporting theoretical models that indicate rapid dissipation once disk clearing begins. Comparing the protoplanetary disk population in σ  Orionis to those of other star-forming regions supports the steady decline in average dust mass and the steepening of the M {sub dust}– M {sub *} relation with age; studying these evolutionary trends can inform the relative importance of different disk processes during key eras of planet formation. External photoevaporation from the central O9 star is influencing disk evolution throughout the region: dust masses clearly decline with decreasing separation from the photoionizing source, and the handful of CO detections exist at projected separations of >1.5 pc. Collectively, our findings indicate that giant planet formation is inherently rare and/or well underway by a few Myr of age.« less

Development of High-Resolution Dynamic Dust Source Function - A Case Study with a Strong Dust Storm in a Regional Model

NASA Technical Reports Server (NTRS)

Kim, Dongchul; Chin, Mian; Kemp, Eric M.; Tao, Zhining; Peters-Lidard, Christa D.; Ginoux, Paul

2017-01-01

A high-resolution dynamic dust source has been developed in the NASA Unified-Weather Research and Forecasting (NU-WRF) model to improve the existing coarse static dust source. In the new dust source map, topographic depression is in 1-km resolution and surface bareness is derived using the Normalized Difference Vegetation Index (NDVI) data from Moderate Resolution Imaging Spectroradiometer (MODIS). The new dust source better resolves the complex topographic distribution over the Western United States where its magnitude is higher than the existing, coarser resolution static source. A case study is conducted with an extreme dust storm that occurred in Phoenix, Arizona in 0203 UTC July 6, 2011. The NU-WRF model with the new high-resolution dynamic dust source is able to successfully capture the dust storm, which was not achieved with the old source identification. However the case study also reveals several challenges in reproducing the time evolution of the short-lived, extreme dust storm events.

Development of High-Resolution Dynamic Dust Source Function -A Case Study with a Strong Dust Storm in a Regional Model

PubMed Central

Kim, Dongchul; Chin, Mian; Kemp, Eric M.; Tao, Zhining; Peters-Lidard, Christa D.; Ginoux, Paul

2018-01-01

A high-resolution dynamic dust source has been developed in the NASA Unified-Weather Research and Forecasting (NU-WRF) model to improve the existing coarse static dust source. In the new dust source map, topographic depression is in 1-km resolution and surface bareness is derived using the Normalized Difference Vegetation Index (NDVI) data from Moderate Resolution Imaging Spectroradiometer (MODIS). The new dust source better resolves the complex topographic distribution over the Western United States where its magnitude is higher than the existing, coarser resolution static source. A case study is conducted with an extreme dust storm that occurred in Phoenix, Arizona in 02-03 UTC July 6, 2011. The NU-WRF model with the new high-resolution dynamic dust source is able to successfully capture the dust storm, which was not achieved with the old source identification. However the case study also reveals several challenges in reproducing the time evolution of the short-lived, extreme dust storm events. PMID:29632432

Development of High-Resolution Dynamic Dust Source Function -A Case Study with a Strong Dust Storm in a Regional Model.

PubMed

Kim, Dongchul; Chin, Mian; Kemp, Eric M; Tao, Zhining; Peters-Lidard, Christa D; Ginoux, Paul

2017-06-01

A high-resolution dynamic dust source has been developed in the NASA Unified-Weather Research and Forecasting (NU-WRF) model to improve the existing coarse static dust source. In the new dust source map, topographic depression is in 1-km resolution and surface bareness is derived using the Normalized Difference Vegetation Index (NDVI) data from Moderate Resolution Imaging Spectroradiometer (MODIS). The new dust source better resolves the complex topographic distribution over the Western United States where its magnitude is higher than the existing, coarser resolution static source. A case study is conducted with an extreme dust storm that occurred in Phoenix, Arizona in 02-03 UTC July 6, 2011. The NU-WRF model with the new high-resolution dynamic dust source is able to successfully capture the dust storm, which was not achieved with the old source identification. However the case study also reveals several challenges in reproducing the time evolution of the short-lived, extreme dust storm events.

Evolution of anthropogenic emissions at the global and regional scale during the past three decades

NASA Astrophysics Data System (ADS)

Granier, C.; Bessagnet, B. B.; Bond, T. C.; D'Angiola, A.; Denier van der Gon, H.; Frost, G. J.; Heil, A.; Kaiser, J.; Kinne, S. A.; Klimont, Z.; Kloster, S.; Lamarque, J.; Liousse, C.; Masui, T.; Meleux, F.; Mieville, A.; Ohara, T.; Raut, J.; Riahi, K.; Schultz, M. G.; Smith, S.; Thomson, A. M.; van Aardenne, J.; van der Werf, G.; van Vuuren, D.

2010-12-01

The knowledge of the distributions of surface emissions of gases and aerosols is essential for an accurate modeling and analysis of the distribution and evolution of the concentration of gaseous and particulate chemical species. The quantification of surface fluxes by source of origin is furthermore central to the assessment of effects and the development of control measures. Over the past few years, different ranges of emission fluxes have been proposed by several studies, which have provided emissions at different spatial and temporal scales. We have compared the emissions of several chemical compounds, i.e. carbon monoxide, nitrogen oxides, sulfur dioxide and black carbon, as provided by global and regional emissions inventories in different regions of the world for the past thirty years. The presentation will focus on the United States, Europe and China. Significant differences between the datasets providing emissions in these regions have been identified, reaching for example 60% and 35% for anthropogenic emissions of carbon monoxide and nitrogen oxides in both regions, respectively. We will assess the current uncertainties on surface emissions and their recent trends. This analysis is often hindered because of differences in base years and in species considered in the different datasets. Current work aiming at compiling comparable metrics for such species for the analysis of regional and global emission datasets will be discussed.

Basin evolution and structural reconstruction of northeastern Morocco and northwestern Algeria

DOE Office of Scientific and Technical Information (OSTI.GOV)

Scott, S.

1995-08-01

The high plateau region of Morocco and northwestern Algeria contains a Permo-Triassic rift basin with over 8,000 meters of Paleozoic, Mesozoic and Tertiary sediments. The area exhibits many similarities to the prolific Triassic basins of neighboring Algeria. Previous impediments to exploration in the high plateau area focused on the inability to seismically image sub-salt, pre-Jurassic block faulted structures and the perceived lack of adequate source rocks. This study combined seismic and basin modelling techniques to decipher the pre-salt structures, interpret basin evolution, and access source rock potential. Large structural and stratigraphic features can now be discerned where Permo-Triassic block faultedmore » structures are overlain by thick Triassic-Jurassic mobile evaporate seals and sourced by underlying Paleozoic shales. Contrary to the last published reports, over 20 years ago, oil and gas generation appears to have been continuous in the Carboniferous since 350 ma. Migration directly from the Carboniferous shales to Triassic conglomerates is envisaged with adequate seals provided by the overlying Triassic-Jurassic evaporate sequence. An earlier rapid pulse of oil and gas generation between 300-340 ma from the Silurian source rocks was probably too early to have resulted in hydrocarbon accumulation in the primary Triassic targets but if reservoir is present in the Carboniferous section, then those strata may have been sourced by the Silurian shales.« less

Effects of mining activities on evolution of water chemistry in coal-bearing aquifers in karst region of Midwestern Guizhou, China: evidences from δ13C of dissolved inorganic carbon and δ34S of sulfate.

PubMed

Li, Qingguang; Wu, Pan; Zha, Xuefang; Li, Xuexian; Wu, Linna; Gu, Shangyi

2018-04-24

The generation of acid mine drainage (AMD) may accelerate watershed erosion and promote the migration of heavy metals, then threaten local ecosystems such as aquatic life and even human health. Previous studies have focused primarily on influence of AMD in surface environment. In order to reveal the acidizing processes in karst high-sulfur coalfield in Southwest China, this study, by contrast, focused on the hydrogeochemical evolution process and acidification mechanism of mine water in Zhijin coalfield, western Guizhou Province. The oxidation of pyrite and other sulfides induced strong acidification of mine water according to the water chemical analysis. As a result, a series of geochemical processes such as dissolution of carbonates and silicates, hydrolysis of metal ions, and degassing of CO 2 complicated water chemical evolution. The dissolution of silicates controlled the chemical composition of mine water, but more carbonates might be dissolved during the acidification of mine water. The sources of sulfate are quite different in water samples collected from the two selected mine. According to sulfur isotope analysis, the dissolution of gypsum is the primary source of sulfate in samples from Hongfa mine, whereas sulfide oxidation contributed a large amount of sulfate to the mine water in Fenghuangshan mine. The dissolution of carbonates should be an important source of DIC in mine water and CO 2 originating from organic mineralization might also have a certain contribution. This study elucidated the groundwater chemical evolution processes in high-sulfur coal-bearing strata and provided a foundation for further study of carbonates erosion and carbon emission during acidification of mine water.

Lunar and Planetary Science XXXV: Ancient Mars Water and Landforms

NASA Technical Reports Server (NTRS)

2004-01-01

Titles in this section include: 1) Giant Lowland Polygons: Relics of an Ancient Martian Ocean? 2) Lake Shorelines: Earth Analogs for Hypothesized Martian Coastal Features; 3) Complex Evolution of Paleolacustrine Systems on Mars: An Example from the Holden Crater; 4) Geomorphology and Hydraulics of Ma'adim Vallis, Mars, During a Noachian/Hesperian Boundary Paleoflood; 5) Geologic Evolution of Dao Vallis, Mars; 6) Advances in Reconstructing the Geologic History of the Chryse Region Outflow Channels on Mars; 7) Ravi Vallis, Mars - Paleoflood Origin and Genesis of Secondary Chaos Zones; 8) Walla Walla Vallis and Wallula Crater: Two Recently Discovered Martian Features Record Aqueous History; 9) Tharsis Recharge: a Source of Groundwater for Martian Outflow Channels; 10) Factors Controlling Water Volumes and Release Rates in Martian Outflow Channels; 11) Significance of Confined Cavernous Systems for Outflow Channel Water Sources, Reactivation Mechanisms and Chaos Formation; 12) Systematic Differences in Topography of Martian and Terrestrial Drainage Basins; 13) Waves on Seas of Mars and Titan: Wind-Tunnel Experiments on Wind-Wave Generation in Extraterrestrial Atmospheres.

Landscape scale prediction of earthquake-induced landsliding based on seismological and geomorphological parameters.

NASA Astrophysics Data System (ADS)

Marc, O.; Hovius, N.; Meunier, P.; Rault, C.

2017-12-01

In tectonically active areas, earthquakes are an important trigger of landslides with significant impact on hillslopes and river evolutions. However, detailed prediction of landslides locations and properties for a given earthquakes remain difficult.In contrast we propose, landscape scale, analytical prediction of bulk coseismic landsliding, that is total landslide area and volume (Marc et al., 2016a) as well as the regional area within which most landslide must distribute (Marc et al., 2017). The prediction is based on a limited number of seismological (seismic moment, source depth) and geomorphological (landscape steepness, threshold acceleration) parameters, and therefore could be implemented in landscape evolution model aiming at engaging with erosion dynamics at the scale of the seismic cycle. To assess the model we have compiled and normalized estimates of total landslide volume, total landslide area and regional area affected by landslides for 40, 17 and 83 earthquakes, respectively. We have found that low landscape steepness systematically leads to overprediction of the total area and volume of landslides. When this effect is accounted for, the model is able to predict within a factor of 2 the landslide areas and associated volumes for about 70% of the cases in our databases. The prediction of regional area affected do not require a calibration for the landscape steepness and gives a prediction within a factor of 2 for 60% of the database. For 7 out of 10 comprehensive inventories we show that our prediction compares well with the smallest region around the fault containing 95% of the total landslide area. This is a significant improvement on a previously published empirical expression based only on earthquake moment.Some of the outliers seems related to exceptional rock mass strength in the epicentral area or shaking duration and other seismic source complexities ignored by the model. Applications include prediction on the mass balance of earthquakes and this model predicts that only earthquakes generated on a narrow range of fault sizes may cause more erosion than uplift (Marc et al., 2016b), while very large earthquakes are expected to always build topography. The model could also be used to physically calibrate hillslope erosion or perturbations to river network within landscape evolution model.

Hubble Space Telescope Hx Imaging of Star-forming Galaxies at z approximately equal to 1-1.5: Evolution in the Size and Luminosity of Giant H II Regions

NASA Technical Reports Server (NTRS)

Livermore, R. C.; Jones, T.; Richard, J.; Bower, R. G.; Ellis, R. S.; Swinbank, A. M.; Rigby, J. R.; Smail, Ian; Arribas, S.; Rodriguez-Zaurin, J.;

Formation and evolution of a metasomatized lithospheric root at the motionless Antarctic plate: the case of East Island, Crozet Archipelago (Indian Ocean)

NASA Astrophysics Data System (ADS)

Meyzen, Christine; Marzoli, Andrea; Bellieni, Giuliano; Levresse, Gilles

2016-04-01

Sitting atop the nearly stagnant Antarctic plate (ca. 6.46 mm/yr), the Crozet archipelago midway between Madagascar and Antarctica constitutes a region of unusually shallow (1543-1756 m below sea level) and thickened oceanic crust (10-16.5 km), high geoid height, and deep low-velocity zone, which may reflect the surface expression of a mantle plume. Here, we present new major and trace element data for Quaternary sub-aerial alkali basalts from East Island, the easterly and oldest island (ca. 9 Ma) of the Crozet archipelago. Crystallization at uppermost mantle depth and phenocryst accumulation have strongly affected their parental magma compositions. Their trace element patterns show a large negative K anomaly relative to Ta-La, moderate depletions in Rb and Ba with respect to Th-U, and heavy rare earth element (HREE) depletions relative to light REE. These characteristics allow limits to be placed upon the composition and mineralogy of their mantle source. The average trace element spectrum of East Island basalts can be matched by melting of about 2 % of a garnet-phlogopite-bearing peridotite source. The stability field of phlogopite restricts melting depth to lithospheric levels. The modelled source composition requires a multistage evolution, where the mantle has been depleted by melt extraction before having been metasomatized by alkali-rich plume melts. The depleted mantle component may be sourced by residual mantle plume remnants stagnated at the melting locus due to a weak lateral flow velocity inside the melting regime, whose accumulation progressively edifies a depleted lithospheric root above the plume core. Low-degree alkali-rich melts are likely derived from the plume source. Such a mantle source evolution may be general to both terrestrial and extraterrestrial environments where the lateral component velocity of the mantle flow field is extremely slow.

Holocene Depositional History of the Southern New Jersey Barrier and Backbarrier Regions

DTIC Science & Technology

1990-02-01

1954) that the continental shelf is a source for beach sediment. 25. Biederman (1962) and Charlesworth (1968) compared sediments along- shore and...perpendicular to the coast in a number of barrier and backbarrier environments. Biederman (1962) found that mean grain size decreased from north to south...Geology and Stratigraphic Preser- vation Potential and Evolution of Delaware’s Barrier Systems," Marine Geology. Vol 63, pp 235-262. Biederman , E. W

EUV laser produced and induced plasmas for nanolithography

NASA Astrophysics Data System (ADS)

Sizyuk, Tatyana; Hassanein, Ahmed

2017-10-01

EUV produced plasma sources are being extensively studied for the development of new technology for computer chips production. Challenging tasks include optimization of EUV source efficiency, producing powerful source in 2 percentage bandwidth around 13.5 nm for high volume manufacture (HVM), and increasing the lifetime of collecting optics. Mass-limited targets, such as small droplet, allow to reduce contamination of chamber environment and mirror surface damage. However, reducing droplet size limits EUV power output. Our analysis showed the requirement for the target parameters and chamber conditions to achieve 500 W EUV output for HVM. The HEIGHTS package was used for the simulations of laser produced plasma evolution starting from laser interaction with solid target, development and expansion of vapor/plasma plume with accurate optical data calculation, especially in narrow EUV region. Detailed 3D modeling of mix environment including evolution and interplay of plasma produced by lasers from Sn target and plasma produced by in-band and out-of-band EUV radiation in ambient gas, used for the collecting optics protection and cleaning, allowed predicting conditions in entire LPP system. Effect of these conditions on EUV photon absorption and collection was analyzed. This work is supported by the National Science Foundation, PIRE project.

Astrochemical evolution along star formation: Overview of the IRAM Large Program ASAI

NASA Astrophysics Data System (ADS)

Lefloch, Bertrand; Bachiller, R.; Ceccarelli, C.; Cernicharo, J.; Codella, C.; Fuente, A.; Kahane, C.; López-Sepulcre, A.; Tafalla, M.; Vastel, C.; Caux, E.; González-García, M.; Bianchi, E.; Gómez-Ruiz, A.; Holdship, J.; Mendoza, E.; Ospina-Zamudio, J.; Podio, L.; Quénard, D.; Roueff, E.; Sakai, N.; Viti, S.; Yamamoto, S.; Yoshida, K.; Favre, C.; Monfredini, T.; Quitián-Lara, H. M.; Marcelino, N.; Roberty, H. Boechat; Cabrit, S.

2018-04-01

Evidence is mounting that the small bodies of our Solar System, such as comets and asteroids, have at least partially inherited their chemical composition from the first phases of the Solar System formation. It then appears that the molecular complexity of these small bodies is most likely related to the earliest stages of star formation. It is therefore important to characterize and to understand how the chemical evolution changes with solar-type protostellar evolution. We present here the Large Program "Astrochemical Surveys At IRAM" (ASAI). Its goal is to carry out unbiased millimeter line surveys between 80 and 272 GHz of a sample of ten template sources, which fully cover the first stages of the formation process of solar-type stars, from prestellar cores to the late protostellar phase. In this article, we present an overview of the surveys and results obtained from the analysis of the 3 mm band observations. The number of detected main isotopic species barely varies with the evolutionary stage and is found to be very similar to that of massive star-forming regions. The molecular content in O- and C- bearing species allows us to define two chemical classes of envelopes, whose composition is dominated by either a) a rich content in O-rich complex organic molecules, associated with hot corino sources, or b) a rich content in hydrocarbons, typical of Warm Carbon Chain Chemistry sources. Overall, a high chemical richness is found to be present already in the initial phases of solar-type star formation.

Strong coronal channelling and interplanetary evolution of a solar storm up to Earth and Mars

PubMed Central

Möstl, Christian; Rollett, Tanja; Frahm, Rudy A.; Liu, Ying D.; Long, David M.; Colaninno, Robin C.; Reiss, Martin A.; Temmer, Manuela; Farrugia, Charles J.; Posner, Arik; Dumbović, Mateja; Janvier, Miho; Démoulin, Pascal; Boakes, Peter; Devos, Andy; Kraaikamp, Emil; Mays, Mona L.; Vršnak, Bojan

2015-01-01

The severe geomagnetic effects of solar storms or coronal mass ejections (CMEs) are to a large degree determined by their propagation direction with respect to Earth. There is a lack of understanding of the processes that determine their non-radial propagation. Here we present a synthesis of data from seven different space missions of a fast CME, which originated in an active region near the disk centre and, hence, a significant geomagnetic impact was forecasted. However, the CME is demonstrated to be channelled during eruption into a direction +37±10° (longitude) away from its source region, leading only to minimal geomagnetic effects. In situ observations near Earth and Mars confirm the channelled CME motion, and are consistent with an ellipse shape of the CME-driven shock provided by the new Ellipse Evolution model, presented here. The results enhance our understanding of CME propagation and shape, which can help to improve space weather forecasts. PMID:26011032

Comparing Temporally-Separated Solar Wind Structures at 1 AU (STEREO A and OMNI)

NASA Astrophysics Data System (ADS)

Galvin, A. B.; Farrugia, C. J.; Jian, L. K.

2017-12-01

One may use the longitudinal coverage of different spacecraft assets, or the same asset over sequential Carrington Rotations, to study the solar wind behavior from long-lived structures (coronal holes, active regions), or occasionally observe the extent of transient structures (Farrugia et al., 2011). This is of interest as the evolution of the extent and persistence of interplanetary coronal mass ejections (ICMEs) and of stream interaction regions (SIRs) have implications for space weather forecasting. One challenge is that one must be aware of the temporal evolution of the structure on the Sun and the affect of `sampling' different solar sources due to different solar latitudes of the in-situ spacecraft observations. Here we look at case studies of recent event time intervals during 2015-2017 where solar wind emanating from long-lived coronal-hole structures are observed both at STEREO A and at near-Earth assets (OMNI2). The observations are taken at similar solar latitudes and longitudes but temporally separated by several days or weeks.

The Evolution of Hydrocarbon Compounds in Saturn's Stratosphere During the 2010 Northern Storm

NASA Astrophysics Data System (ADS)

Hesman, B. E.; Bjoraker, G. L.; Achterberg, R. K.; Sada, P. V.; Jennings, D. E.; Lunsford, A. W.; Sinclair, J.; Romani, P. N.; Boyle, R.; Fletcher, L. N.; Irwin, P.

2013-12-01

The massive eruption at 40N (planetographic latitude) in December 2010 has produced significant and long-lived changes in temperature and species abundances in Saturn's northern hemisphere (Hesman et al. 2012a, Fletcher et al. 2012). The northern storm region has been observed on many occasions between January 2011 and June of 2012 by Cassini's Composite Infrared Spectrometer (CIRS). In this time period, temperatures in regions referred to as 'beacons' (warm regions in the stratosphere at certain longitudes in the storm latitude) became significantly warmer than pre-storm values of 140K. In this period hydrocarbon emission greatly increased; however, this increased emission could not be attributed due to the temperature changes alone for many of these species (Hesman et al. 2012b, Bjoraker et al 2012). The unique nature of the stratospheric beacons also resulted in the detection of ethylene (C2H4) using CIRS. These beacon regions have also led to the identification of rare hydrocarbon species such as C4H2 and C3H4 in the stratosphere. These species are all expected from photochemical processes in the stratosphere, however high temperatures, unusual chemistry, or dynamics are enhancing these species. The exact cause of these enhancements is still under investigation. Ground-based observations were performed using the high-resolution spectrometer Celeste in May 2011 to confirm the CIRS detection of C2H4 and to study its spectral signatures at higher spectral resolution. In order to follow the evolution of its emission further observations were performed in July 2011 and March 2012. These observations are being used in conjunction with the CIRS observations to investigate the source of the approximately 100-fold increase of ethylene in the stratospheric beacon. The time evolution of hydrocarbon emission from C2H2, C2H4, C2H6, C3H4, and C4H2 in Saturn's Northern Storm beacon regions will be discussed. References: Bjoraker, G., B.E. Hesman, R.K. Achterberg, P.N. Romani. 2012, 'The Evolution of Hydrocarbons in Saturn's Northern Storm Region,' AAS DPS Conference, Vol. 44, #403.05. Fletcher, L.N. et al. 2012, 'The Origin and Evolution of Saturn's 2011-2012 Stratospheric Vortex,' Icarus, 221, 560-586. Hesman, B.E. et al. 2012a, 'Elusive Ethylene Detected in Saturn's Northern Storm Region,' The Astrophysical Journal, 760, 24-30. Hesman, B.E. et al. 2012b, 'Ethylene Emission in the Aftermath of Saturn's 2010 Northern Storm,' AAS DPS Conference, Vol. 44, #403.06.

Antibody mimetics: promising complementary agents to animal-sourced antibodies.

PubMed

Baloch, Abdul Rasheed; Baloch, Abdul Wahid; Sutton, Brian J; Zhang, Xiaoying

2016-01-01

Despite their wide use as therapeutic, diagnostic and detection agents, the limitations of polyclonal and monoclonal antibodies have inspired scientists to design the next generation biomedical agents, so-called antibody mimetics that offer many advantages over conventional antibodies. Antibody mimetics can be constructed by protein-directed evolution or fusion of complementarity-determining regions through intervening framework regions. Substantial progress in exploiting human, butterfly (Pieris brassicae) and bacterial systems to design and select mimetics using display technologies has been made in the past 10 years, and one of these mimetics [Kalbitor® (Dyax)] has made its way to market. Many challenges lie ahead to develop mimetics for various biomedical applications, especially those for which conventional antibodies are ineffective, and this review describes the current characteristics, construction and applications of antibody mimetics compared to animal-sourced antibodies. The possible limitations of mimetics and future perspectives are also discussed.

Quasi-static three-dimensional magnetic field evolution in solar active region NOAA 11166 associated with an X1.5 flare

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vemareddy, P.; Wiegelmann, T., E-mail: vema@prl.res.in, E-mail: wiegelmann@mps.mpg.de

We study the quasi-static evolution of coronal magnetic fields constructed from the non-linear force-free field (NLFFF) approximation aiming to understand the relation between the magnetic field topology and ribbon emission during an X1.5 flare in active region (AR) NOAA 11166. The flare with a quasi-elliptical and two remote ribbons occurred on 2011 March 9 at 23:13 UT over a positive flux region surrounded by negative flux at the center of the bipolar AR. Our analysis of the coronal magnetic structure with potential and NLFFF solutions unveiled the existence of a single magnetic null point associated with a fan-spine topology andmore » is co-spatial with the hard X-ray source. The footpoints of the fan separatrix surface agree with the inner edge of the quasi-elliptical ribbon and the outer spine is linked to one of the remote ribbons. During the evolution, the slow footpoint motions stressed the field lines along the polarity inversion line and caused electric current layers in the corona around the fan separatrix surface. These current layers trigger magnetic reconnection as a consequence of dissipating currents, which are visible as cusp-shaped structures at lower heights. The reconnection process reorganized the magnetic field topology whose signatures are observed at the separatrices/quasi-separatrix layer structure in both the photosphere and the corona during the pre-to-post flare evolution. In agreement with previous numerical studies, our results suggest that the line-tied footpoint motions perturb the fan-spine system and cause null point reconnection, which eventually causes the flare emission at the footpoints of the field lines.« less

Martian Igneous Geochemistry: The Nature of the Martian Mantle

NASA Technical Reports Server (NTRS)

Mittlefehldt, D. W.; Elkins-Tanton, L. T.; Peng, Z. X.; Herrin, J. S.

2012-01-01

Mafic igneous rocks probe the interiors of their parent objects, reflecting the compositions and mineralogies of their source regions, and the magmatic processes that engendered them. Incompatible trace element contents of mafic igneous rocks are widely used to constrain the petrologic evolution of planets. We focus on incompatible element ratios of martian meteorites to constrain the petrologic evolution of Mars in the context of magma ocean/cumulate overturn models [1]. Most martian meteorites contain some cumulus grains, but regardless, their incompatible element ratios are close to those of their parent magmas. Martian meteorites form two main petrologic/ age groupings; a 1.3 Ga group composed of clinopyroxenites (nakhlites) and dunites (chassignites), and a <1 Ga group composed of basalts and lherzolites (shergottites).

Testing the Accuracy of Data-driven MHD Simulations of Active Region Evolution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Leake, James E.; Linton, Mark G.; Schuck, Peter W., E-mail: james.e.leake@nasa.gov

Models for the evolution of the solar coronal magnetic field are vital for understanding solar activity, yet the best measurements of the magnetic field lie at the photosphere, necessitating the development of coronal models which are “data-driven” at the photosphere. We present an investigation to determine the feasibility and accuracy of such methods. Our validation framework uses a simulation of active region (AR) formation, modeling the emergence of magnetic flux from the convection zone to the corona, as a ground-truth data set, to supply both the photospheric information and to perform the validation of the data-driven method. We focus ourmore » investigation on how the accuracy of the data-driven model depends on the temporal frequency of the driving data. The Helioseismic and Magnetic Imager on NASA’s Solar Dynamics Observatory produces full-disk vector magnetic field measurements at a 12-minute cadence. Using our framework we show that ARs that emerge over 25 hr can be modeled by the data-driving method with only ∼1% error in the free magnetic energy, assuming the photospheric information is specified every 12 minutes. However, for rapidly evolving features, under-sampling of the dynamics at this cadence leads to a strobe effect, generating large electric currents and incorrect coronal morphology and energies. We derive a sampling condition for the driving cadence based on the evolution of these small-scale features, and show that higher-cadence driving can lead to acceptable errors. Future work will investigate the source of errors associated with deriving plasma variables from the photospheric magnetograms as well as other sources of errors, such as reduced resolution, instrument bias, and noise.« less

Tectonostratigraphic history of the Neogene Maimará basin, Northwest Argentina

NASA Astrophysics Data System (ADS)

Galli, Claudia I.; Coira, Beatriz L.; Alonso, Ricardo N.; Iglesia Llanos, María P.; Prezzi, Claudia B.; Kay, Suzanne Mahlburg

2016-12-01

This paper presents the tectonostratigraphic evolution of the Maimará Basin and explores the relationship between the clastic sediments and pyroclastic deposits in the basin and the evolution of the adjacent orogeny and magmatic arc. The sedimentary facies in this part of the basin include, in ascending order, an ephemeral fluvial system, a deep braided fluvial system and a medial to distal ephemeral fluvial system. We interpret that Maimará Formation accumulated in a basin that has developed two stages of accumulation. Stage 1 extended from 7 to 6.4 Ma and included accelerated tectonic uplift in the source areas, and it corresponds to the ephemeral fluvial system deposits. Stage 2, which extended from 6.4 to 4.8 Ma, corresponds to a tectonically quiescent period and included the development of the deep braided fluvial system deposits. The contact between the Maimará and Tilcara formations is always characterized by a regional unconformity and, in the study area, also shows pronounced erosion. Rare earth element and other chemical characteristics of the tuff intervals in the Maimará Formation fall into two distinct groups suggesting the tuffs were erupted from two distinct late Miocene source regions. The first and most abundant group has characteristics that best match tuffs erupted from the Guacha, Pacana and Pastos Grandes calderas, which are located 200 and 230 km west of the study area at 22º-23º30‧S latitude. The members the second group are chemically most similar to the Merihuaca Ignimbrite from the Cerro Galán caldera 290 km south-southwest of the studied section. The distinctive geochemical characteristics are excellent tools to reconstruct the stratigraphic evolution of the Neogene Maimará basin from 6.4 to 4.8 Ma.

Zonal asymmetric evolution of aerosol optical depth in the subtropics of northern hemisphere in boreal spring and its association with the thermal forcing of Tibetan Plateau

NASA Astrophysics Data System (ADS)

Liu, B.; Jin, Q.; He, J.

2017-12-01

More than 70% population living in the subtropics of the northern hemisphere are exposed to the serious air pollution. In the present, the zonal asymmetric evolution of the 550-nm aerosol optical depth (AOD) over this region has been observed between the East Asian (EA) and the East North American (ENA) continent from boreal winter to summer. The peak of AOD emerges in April over the EA and decreases evidently till June, meanwhile the AOD is still increasing over the ENA, although the low-level southerly is prevailing over the two areas. The diagnosis suggests that such zonal asymmetry is ascribed to the distinct feedback between general circulation and atmospheric heat source (AHS) in situ. The condensation heating becomes dominant in the AHS over the East Asia in April, along with the low-level southerly and the upper-tropospheric northerly, implicating the formation of summertime circulation pattern. Afterwards, the deep convection and the ventilation with strong ascending is generated to reduce the AOD over the EA. Whereas the similar configuration between circulation and AHS takes place over the ENA in June. Furthermore, the possible reason for the different evolution of atmospheric heating source between East Asia and East North America has been discussed.

Self-shielding of hydrogen in the IGM during the epoch of reionization

NASA Astrophysics Data System (ADS)

Chardin, Jonathan; Kulkarni, Girish; Haehnelt, Martin G.

2018-04-01

We investigate self-shielding of intergalactic hydrogen against ionizing radiation in radiative transfer simulations of cosmic reionization carefully calibrated with Lyα forest data. While self-shielded regions manifest as Lyman-limit systems in the post-reionization Universe, here we focus on their evolution during reionization (redshifts z = 6-10). At these redshifts, the spatial distribution of hydrogen-ionizing radiation is highly inhomogeneous, and some regions of the Universe are still neutral. After masking the neutral regions and ionizing sources in the simulation, we find that the hydrogen photoionization rate depends on the local hydrogen density in a manner very similar to that in the post-reionization Universe. The characteristic physical hydrogen density above which self-shielding becomes important at these redshifts is about nH ˜ 3 × 10-3 cm-3, or ˜20 times the mean hydrogen density, reflecting the fact that during reionization photoionization rates are typically low enough that the filaments in the cosmic web are often self-shielded. The value of the typical self-shielding density decreases by a factor of 3 between redshifts z = 3 and 10, and follows the evolution of the average photoionization rate in ionized regions in a simple fashion. We provide a simple parameterization of the photoionization rate as a function of density in self-shielded regions during the epoch of reionization.

Self-shielding of hydrogen in the IGM during the epoch of reionization

NASA Astrophysics Data System (ADS)

Chardin, Jonathan; Kulkarni, Girish; Haehnelt, Martin G.

2018-07-01

We investigate self-shielding of intergalactic hydrogen against ionizing radiation in radiative transfer simulations of cosmic reionization carefully calibrated with Lyα forest data. While self-shielded regions manifest as Lyman limit systems in the post-reionization Universe, here we focus on their evolution during reionization (redshifts z = 6-10). At these redshifts, the spatial distribution of hydrogen-ionizing radiation is highly inhomogeneous, and some regions of the Universe are still neutral. After masking the neutral regions and ionizing sources in the simulation, we find that the hydrogen photoionization rate depends on the local hydrogen density in a manner very similar to that in the post-reionization Universe. The characteristic physical hydrogen density above which self-shielding becomes important at these redshifts is about nH ˜ 3 × 10-3 cm-3, or ˜20 times the mean hydrogen density, reflecting the fact that during reionization photoionization rates are typically low enough that the filaments in the cosmic web are often self-shielded. The value of the typical self-shielding density decreases by a factor of 3 between redshifts z = 3 and 10, and follows the evolution of the average photoionization rate in ionized regions in a simple fashion. We provide a simple parametrization of the photoionization rate as a function of density in self-shielded regions during the epoch of reionization.

The Evolution of Open Magnetic Flux Driven by Photospheric Dynamics

NASA Astrophysics Data System (ADS)

Linker, Jon A.; Lionello, Roberto; Mikić, Zoran; Titov, Viacheslav S.; Antiochos, Spiro K.

2011-04-01

The coronal magnetic field is of paramount importance in solar and heliospheric physics. Two profoundly different views of the coronal magnetic field have emerged. In quasi-steady models, the predominant source of open magnetic field is in coronal holes. In contrast, in the interchange model, the open magnetic flux is conserved, and the coronal magnetic field can only respond to the photospheric evolution via interchange reconnection. In this view, the open magnetic flux diffuses through the closed, streamer belt fields, and substantial open flux is present in the streamer belt during solar minimum. However, Antiochos and coworkers, in the form of a conjecture, argued that truly isolated open flux cannot exist in a configuration with one heliospheric current sheet—it will connect via narrow corridors to the polar coronal hole of the same polarity. This contradicts the requirements of the interchange model. We have performed an MHD simulation of the solar corona up to 20 R sun to test both the interchange model and the Antiochos conjecture. We use a synoptic map for Carrington rotation 1913 as the boundary condition for the model, with two small bipoles introduced into the region where a positive polarity extended coronal hole forms. We introduce flows at the photospheric boundary surface to see if open flux associated with the bipoles can be moved into the closed-field region. Interchange reconnection does occur in response to these motions. However, we find that the open magnetic flux cannot be simply injected into closed-field regions—the flux eventually closes down and disconnected flux is created. Flux either opens or closes, as required, to maintain topologically distinct open- and closed-field regions, with no indiscriminate mixing of the two. The early evolution conforms to the Antiochos conjecture in that a narrow corridor of open flux connects the portion of the coronal hole that is nearly detached by one of the bipoles. In the later evolution, a detached coronal hole forms, in apparent violation of the Antiochos conjecture. Further investigation reveals that this detached coronal hole is actually linked to the extended coronal hole by a separatrix footprint on the photosphere of zero width. Therefore, the essential idea of the conjecture is preserved, if we modify it to state that coronal holes in the same polarity region are always linked, either by finite width corridors or separatrix footprints. The implications of these results for interchange reconnection and the sources of the slow solar wind are briefly discussed.

Revision of Hopewellian trading patterns in Midwestern North America based on mineralogical sourcing

USGS Publications Warehouse

Hughes, R.E.; Berres, T.E.; Moore, D.M.; Farnsworth, K.B.

1998-01-01

Traditional exchange models purport that all Hopewell-style platform pipes of flint clay were quarried and crafted in southern Ohio by Native Americans from a local kaolinitic flint clay, and that those found in the Havana Hopewell region of western Illinois were transported from southern Ohio along an Ohio River trade network. However, the results of this study show that berthierine-rich flint clay from northwestern Illinois was the only source for pipestone artifacts of the Havana Hopewell region. We base this on (1) X-ray diffraction analysis of quickly made smears, (2) spatiotemporal distribution of artifacts in the Sterling-Rock Falls, Illinois area, and (3) petrographic, X-ray fluorescence, Mo??ssbauer, and SEM/EDX analyses. This understanding of the source of this material made it possible to visually identify the source of large numbers of curated artifacts as having been made of material from the Sterling-Rock Falls area. This discovery has implications for understanding cultural and material exchange among Hopewellian societies. Also, it is the first report of berthierine flint clay and of flint clay that formed before the evolution of terrestrial plants. ?? 1998 John Wiley & Sons, Inc.

Accelerating pathway evolution by increasing the gene dosage of chromosomal segments.

PubMed

Tumen-Velasquez, Melissa; Johnson, Christopher W; Ahmed, Alaa; Dominick, Graham; Fulk, Emily M; Khanna, Payal; Lee, Sarah A; Schmidt, Alicia L; Linger, Jeffrey G; Eiteman, Mark A; Beckham, Gregg T; Neidle, Ellen L

2018-06-18

Experimental evolution is a critical tool in many disciplines, including metabolic engineering and synthetic biology. However, current methods rely on the chance occurrence of a key step that can dramatically accelerate evolution in natural systems, namely increased gene dosage. Our studies sought to induce the targeted amplification of chromosomal segments to facilitate rapid evolution. Since increased gene dosage confers novel phenotypes and genetic redundancy, we developed a method, Evolution by Amplification and Synthetic Biology (EASy), to create tandem arrays of chromosomal regions. In Acinetobacter baylyi , EASy was demonstrated on an important bioenergy problem, the catabolism of lignin-derived aromatic compounds. The initial focus on guaiacol (2-methoxyphenol), a common lignin degradation product, led to the discovery of Amycolatopsis genes ( gcoAB ) encoding a cytochrome P450 enzyme that converts guaiacol to catechol. However, chromosomal integration of gcoAB in Pseudomonas putida or A. baylyi did not enable guaiacol to be used as the sole carbon source despite catechol being a growth substrate. In ∼1,000 generations, EASy yielded alleles that in single chromosomal copy confer growth on guaiacol. Different variants emerged, including fusions between GcoA and CatA (catechol 1,2-dioxygenase). This study illustrates the power of harnessing chromosomal gene amplification to accelerate the evolution of desirable traits.

Parallel Evolution of Genes and Languages in the Caucasus Region

PubMed Central

Balanovsky, Oleg; Dibirova, Khadizhat; Dybo, Anna; Mudrak, Oleg; Frolova, Svetlana; Pocheshkhova, Elvira; Haber, Marc; Platt, Daniel; Schurr, Theodore; Haak, Wolfgang; Kuznetsova, Marina; Radzhabov, Magomed; Balaganskaya, Olga; Romanov, Alexey; Zakharova, Tatiana; Soria Hernanz, David F.; Zalloua, Pierre; Koshel, Sergey; Ruhlen, Merritt; Renfrew, Colin; Wells, R. Spencer; Tyler-Smith, Chris; Balanovska, Elena

2012-01-01

We analyzed 40 SNP and 19 STR Y-chromosomal markers in a large sample of 1,525 indigenous individuals from 14 populations in the Caucasus and 254 additional individuals representing potential source populations. We also employed a lexicostatistical approach to reconstruct the history of the languages of the North Caucasian family spoken by the Caucasus populations. We found a different major haplogroup to be prevalent in each of four sets of populations that occupy distinct geographic regions and belong to different linguistic branches. The haplogroup frequencies correlated with geography and, even more strongly, with language. Within haplogroups, a number of haplotype clusters were shown to be specific to individual populations and languages. The data suggested a direct origin of Caucasus male lineages from the Near East, followed by high levels of isolation, differentiation and genetic drift in situ. Comparison of genetic and linguistic reconstructions covering the last few millennia showed striking correspondences between the topology and dates of the respective gene and language trees, and with documented historical events. Overall, in the Caucasus region, unmatched levels of gene-language co-evolution occurred within geographically isolated populations, probably due to its mountainous terrain. PMID:21571925

Structure, stratigraphy and petroleum geology of the south east Nam Con Son Basin, offshore Vietnam

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fraser, A.J.; Matthews, S.J.; Lowe, S.

1996-12-31

Recent exploration of the south east Nam Con Son Basin, offshore Vietnam, by BP in alliance with Statoil has involved acquisition of new seismic and well data. These new data have allowed re-evaluation of the tectono-stratigraphic development and petroleum geology, and have provided additional constraints on the regional tectonic evolution. The offshore Vietnamese basins have evolved in response to the complex relative motions of Indochina, Peninsular Malaysia, Borneo and the South China Sea during the Cenozoic. On the regional scale these motions have been accommodated by strike-slip fault development, rifting and contraction. In the Nam Con Son Basin these motionsmore » have interacted in different ways from the Palaeogene to recent. Two rifting episodes are recognized; a Palaeogene phase dominated by E-W trending extensional faults, and a Miocene phase dominated by N-S to NE-SW trending faults. The structural evolution is complicated by a pulse of mild contraction during the Middle Miocene. The sedimentary fill of the basin evolves from continental fluvio-lacustrine in the Palaeogene through to fully marine following the second phase of rifting in the Miocene. This pulsed structural and stratigraphic evolution has resulted in basinwide deposition of source, reservoir and seal facies, and produced a variety of potential trapping styles. This paper describes the hydrocarbon habitat of the south east Nam Con Son Basin within the context of the regional tectono-stratigraphic model.« less

Structure, stratigraphy and petroleum geology of the south east Nam Con Son Basin, offshore Vietnam

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fraser, A.J.; Matthews, S.J.; Lowe, S.

1996-01-01

Recent exploration of the south east Nam Con Son Basin, offshore Vietnam, by BP in alliance with Statoil has involved acquisition of new seismic and well data. These new data have allowed re-evaluation of the tectono-stratigraphic development and petroleum geology, and have provided additional constraints on the regional tectonic evolution. The offshore Vietnamese basins have evolved in response to the complex relative motions of Indochina, Peninsular Malaysia, Borneo and the South China Sea during the Cenozoic. On the regional scale these motions have been accommodated by strike-slip fault development, rifting and contraction. In the Nam Con Son Basin these motionsmore » have interacted in different ways from the Palaeogene to recent. Two rifting episodes are recognized; a Palaeogene phase dominated by E-W trending extensional faults, and a Miocene phase dominated by N-S to NE-SW trending faults. The structural evolution is complicated by a pulse of mild contraction during the Middle Miocene. The sedimentary fill of the basin evolves from continental fluvio-lacustrine in the Palaeogene through to fully marine following the second phase of rifting in the Miocene. This pulsed structural and stratigraphic evolution has resulted in basinwide deposition of source, reservoir and seal facies, and produced a variety of potential trapping styles. This paper describes the hydrocarbon habitat of the south east Nam Con Son Basin within the context of the regional tectono-stratigraphic model.« less

Connecting crustal seismicity and earthquake-driven stress evolution in Southern California

USGS Publications Warehouse

Pollitz, Fred; Cattania, Camilla

2017-01-01

Tectonic stress in the crust evolves during a seismic cycle, with slow stress accumulation over interseismic periods, episodic stress steps at the time of earthquakes, and transient stress readjustment during a postseismic period that may last months to years. Static stress transfer to surrounding faults has been well documented to alter regional seismicity rates over both short and long time scales. While static stress transfer is instantaneous and long lived, postseismic stress transfer driven by viscoelastic relaxation of the ductile lower crust and mantle leads to additional, slowly varying stress perturbations. Both processes may be tested by comparing a decade-long record of regional seismicity to predicted time-dependent seismicity rates based on a stress evolution model that includes viscoelastic stress transfer. Here we explore crustal stress evolution arising from the seismic cycle in Southern California from 1981 to 2014 using five M≥6.5 source quakes: the M7.3 1992 Landers, M6.5 1992 Big Bear, M6.7 1994 Big Bear, M7.1 1999 Hector Mine, and M7.2 2010 El Mayor-Cucapah earthquakes. We relate the stress readjustment in the surrounding crust generated by each quake to regional seismicity using rate-and-state friction theory. Using a log likelihood approach, we quantify the potential to trigger seismicity of both static and viscoelastic stress transfer, finding that both processes have systematically shaped the spatial pattern of Southern California seismicity since 1992.

On the spatial distribution and evolution of ultrafine aerosols in urban air

NASA Astrophysics Data System (ADS)

Dall'Osto, M.; Querol, X.; Alastuey, A.; O'Dowd, C.; Harrison, R. M.; Wenger, J.; Gómez-Moreno, F. J.

2012-07-01

Sources and evolution of ultrafine particles (<0.1 μ m diameter) were investigated both horizontally and vertically in the large urban agglomerate of Barcelona, Spain. Within the SAPUSS project (Solving Aerosol Problems by Using Synergistic Strategies), a large number of instruments was deployed simultaneously at different monitoring sites (road, two urban background, regional background, urban tower 150 μa.s.l., urban background tower site 80 m a.s.l.) during a 4 week period in September-October 2010. Particle number concentrations (N>5nm) are highly correlated with black carbon (BC) at all sites only under strong vehicular traffic influences. By contrast, under clean atmospheric conditions (low condensation sinks, CS) such correlation diverges towards much higher N/BC ratios at all sites, indicating additional sources of particles including secondary production of freshly nucleated particles. This is also evident in the urban background annual mean diurnal trend of N/BC, showing a midday peak in all seasons. Size-resolved aerosol distributions (N10-500) as well as particle number concentrations (N>5nm) allow us to identify two types of nucleation and growth events: a regional type event originating in the whole study region and impacting almost simultaneously the urban city of Barcelona and the surrounding background area; and an urban type which originates only within the city centre but whose growth continues while transported away from the city to the regional background. Furthermore, during these clean air days, higher N are found at tower level than at ground level only in the city centre whereas such a difference is not so pronounced at the remote urban background tower. In other words, this study suggests that the column of air above the city ground level possesses the best compromise between low CS and high vapour source, hence enhancing the concentrations of freshly nucleated particles. By contrast, within stagnant polluted atmospheric conditions, higher N and BC concentrations are always measured at ground level relative to tower level at all sites. Our study suggests that the city centre is a source of both non-volatile traffic primary (29-39%) and secondary freshly nucleated particles (up to 61-71%) at all sites. We suggest that organic compounds evaporating from freshly emitted traffic particles are a possible candidate for new particle formation within the city and urban plume.

Case study of dust event sources from the Gobi and Taklamakan deserts: An investigation of the horizontal evolution and topographical effect using numerical modeling and remote sensing.

PubMed

Fan, Jin; Yue, Xiaoying; Sun, Qinghua; Wang, Shigong

2017-06-01

A severe dust event occurred from April 23 to April 27, 2014, in East Asia. A state-of-the-art online atmospheric chemistry model, WRF/Chem, was combined with a dust model, GOCART, to better understand the entire process of this event. The natural color images and aerosol optical depth (AOD) over the dust source region are derived from datasets of moderate resolution imaging spectroradiometer (MODIS) loaded on a NASA Aqua satellite to trace the dust variation and to verify the model results. Several meteorological conditions, such as pressure, temperature, wind vectors and relative humidity, are used to analyze meteorological dynamic. The results suggest that the dust emission occurred only on April 23 and 24, although this event lasted for 5days. The Gobi Desert was the main source for this event, and the Taklamakan Desert played no important role. This study also suggested that the landform of the source region could remarkably interfere with a dust event. The Tarim Basin has a topographical effect as a "dust reservoir" and can store unsettled dust, which can be released again as a second source, making a dust event longer and heavier. Copyright © 2016. Published by Elsevier B.V.

High-resolution DEMs for High-mountain Asia: A systematic, region-wide assessment of geodetic glacier mass balance and dynamics

NASA Astrophysics Data System (ADS)

Shean, D. E.; Arendt, A. A.; Osmanoglu, B.; Montesano, P.

2017-12-01

High Mountain Asia (HMA) constitutes the largest glacierized region outside of the Earth's polar regions. Although available observations are limited, long-term records indicate sustained regional glacier mass loss since 1850, with increased loss in recent decades. Recent satellite data (e.g., GRACE, ICESat-1) show spatially variable glacier mass balance, with significant mass loss in the Himalaya and Hindu Kush and slight mass gain in the Karakoram. We generated 4000 high-resolution digital elevation models (DEMs) from sub-meter commercial stereo imagery (DigitalGlobe WorldView/GeoEye) acquired over glaciers in High-mountain Asia from 2002-present (mostly 2013-present). We produced a regional 8-m DEM mosaic for 2015 and estimated 15-year geodetic mass balance for 40000 glaciers larger than 0.1 km2. We are combining with other regional DEM sources to systematically document the spatiotemporal evolution of glacier mass balance for the entire HMA region. We also generated monthly to interannual DEM and velocity time series for high-priority sites distributed across the region, with >15-20 DEMs available for some locations from 2010-present. These records document glacier dynamics, seasonal snow accumulation/redistribution, and processes that affect glacier mass balance (e.g., ice-cliff retreat, debris cover evolution). These efforts will provide basin-scale assessments of snow/ice melt runoff contributions for model cal/val and downstream water resources applications. We will continue processing all archived and newly available commercial stereo imagery for HMA, and will release all DEMs through the HiMAT DAAC.

Evolution of lower hybrid turbulence in the ionosphere

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ganguli, G.; Crabtree, C.; Mithaiwala, M.

2015-11-15

Three-dimensional evolution of the lower hybrid turbulence driven by a spatially localized ion ring beam perpendicular to the ambient magnetic field in space plasmas is analyzed. It is shown that the quasi-linear saturation model breaks down when the nonlinear rate of scattering by thermal electron is larger than linear damping rates, which can occur even for low wave amplitudes. The evolution is found to be essentially a three-dimensional phenomenon, which cannot be accurately explained by two-dimensional simulations. An important feature missed in previous studies of this phenomenon is the nonlinear conversion of electrostatic lower hybrid waves into electromagnetic whistler andmore » magnetosonic waves and the consequent energy loss due to radiation from the source region. This can result in unique low-amplitude saturation with extended saturation time. It is shown that when the nonlinear effects are considered the net energy that can be permanently extracted from the ring beam is larger. The results are applied to anticipate the outcome of a planned experiment that will seed lower hybrid turbulence in the ionosphere and monitor its evolution.« less

Emission and propagation of Saturn kilometric radiation: Magnetoionic modes, beaming pattern, and polarization state

NASA Astrophysics Data System (ADS)

Lamy, L.; Cecconi, B.; Zarka, P.; Canu, P.; Schippers, P.; Kurth, W. S.; Mutel, R. L.; Gurnett, D. A.; Menietti, D.; Louarn, P.

2011-04-01

The Cassini mission crossed the source region of the Saturn kilometric radiation (SKR) on 17 October 2008. On this occasion, the Radio and Plasma Wave Science (RPWS) experiment detected both local and distant radio sources, while plasma parameters were measured in situ by the magnetometer and the Cassini Plasma Spectrometer. A goniopolarimetric inversion was applied to RPWS three-antenna electric measurements to determine the wave vector k and the complete state of polarization of detected waves. We identify broadband extraordinary (X) mode as well as narrowband ordinary (O) mode SKR at low frequencies. Within the source region, SKR is emitted just above the X mode cutoff frequency in a hot plasma, with a typical electron-to-wave energy conversion efficiency of ˜1% (2% peak). The knowledge of the k vector is then used to derive the locus of SKR sources in the kronian magnetosphere, which shows X and O components emanating from the same regions. We also compute the associated beaming angle at the source θ‧ = (k, -B) either from (1) in situ measurements or a model of the magnetic field vector (for local to distant sources) or (2) polarization measurements (for local sources). Obtained results, similar for both modes, suggest quasi-perpendicular emission for local sources, whereas the beaming pattern of distant sources appears as a hollow cone with a frequency-dependent constant aperture angle: θ‧ = 75° ± 15° below 300 kHz, decreasing at higher frequencies to reach θ‧ (1000 kHz) = 50° ± 25°. Finally, we investigate quantitatively the SKR polarization state, observed to be strongly elliptical at the source, and quasi-purely circular for sources located beyond approximately two kronian radii. We show that conditions of weak mode coupling are achieved along the raypath, under which the magnetoionic theory satisfactorily describes the evolution of the observed polarization. These results are analyzed comparatively with the auroral kilometric radiation at Earth.

Sources Of Evolution Of The Japan Air Self Defense Force’s Strategy

DTIC Science & Technology

2016-12-01

has built an air defense operation based air power .2 However, some argue that it is difficult to call JASDF’s strategy defensive when analyzing...offensively. He asserted that air power should continue the offensive operations because the enemy is overwhelmed with psychological nervousness by just...naval activities in the East China Sea when the JASDF fails to maintain the air superiority capability balance in the region. In fact, while the most of

Implications of convection in the Moon and the terrestrial planets

NASA Technical Reports Server (NTRS)

Turcotte, Donald L.

1987-01-01

The early thermal and chemical evolution of the Moon is discussed. The rubidium-strontium, neodymium-samarium, and uranium-thorium-lead systems were studied. The relation of source region heterogeneity to the mixing associated with mantle convection is considered. Work on the application of fractal concepts to planetary geology and geophysics is also discussed. The fractal concept was applied to fragmentation, including the frequency-size distribution of meteorites, asteroids and particulate matter produced by impacts.

Effect of inhomogeneities on high precision measurements of cosmological distances

NASA Astrophysics Data System (ADS)

Peel, Austin; Troxel, M. A.; Ishak, Mustapha

2014-12-01

We study effects of inhomogeneities on distance measures in an exact relativistic Swiss-cheese model of the Universe, focusing on the distance modulus. The model has Λ CDM background dynamics, and the "holes" are nonsymmetric structures described by the Szekeres metric. The Szekeres exact solution of Einstein's equations, which is inhomogeneous and anisotropic, allows us to capture potentially relevant effects on light propagation due to nontrivial evolution of structures in an exact framework. Light beams traversing a single Szekeres structure in different ways can experience either magnification or demagnification, depending on the particular path. Consistent with expectations, we find a shift in the distance modulus μ to distant sources due to demagnification when the light beam travels primarily through the void regions of our model. Conversely, beams are magnified when they propagate mainly through the overdense regions of the structures, and we explore a small additional effect due to time evolution of the structures. We then study the probability distributions of Δ μ =μΛ CDM-μSC for sources at different redshifts in various Swiss-cheese constructions, where the light beams travel through a large number of randomly oriented Szekeres holes with random impact parameters. We find for Δ μ the dispersions 0.004 ≤σΔ μ≤0.008 mag for sources with redshifts 1.0 ≤z ≤1.5 , which are smaller than the intrinsic dispersion of, for example, magnitudes of type Ia supernovae. The shapes of the distributions we obtain for our Swiss-cheese constructions are peculiar in the sense that they are not consistently skewed toward the demagnification side, as they are in analyses of lensing in cosmological simulations. Depending on the source redshift, the distributions for our models can be skewed to either the demagnification or the magnification side, reflecting a limitation of these constructions. This could be the result of requiring the continuity of Einstein's equations throughout the overall spacetime patchwork, which imposes the condition that compensating overdense shells must accompany the underdense void regions in the holes. The possibility to explore other uses of these constructions that could circumvent this limitation and lead to different statistics remains open.

SDSS IV MaNGA: Dependence of Global and Spatially Resolved SFR–M ∗ Relations on Galaxy Properties

NASA Astrophysics Data System (ADS)

Pan, Hsi-An; Lin, Lihwai; Hsieh, Bau-Ching; Sánchez, Sebastián F.; Ibarra-Medel, Héctor; Boquien, Médéric; Lacerna, Ivan; Argudo-Fernández, Maria; Bizyaev, Dmitry; Cano-Díaz, Mariana; Drory, Niv; Gao, Yang; Masters, Karen; Pan, Kaike; Tabor, Martha; Tissera, Patricia; Xiao, Ting

2018-02-01

The galaxy integrated Hα star formation rate–stellar mass relation, or SFR(global)–M *(global) relation, is crucial for understanding star formation history and evolution of galaxies. However, many studies have dealt with SFR using unresolved measurements, which makes it difficult to separate out the contamination from other ionizing sources, such as active galactic nuclei and evolved stars. Using the integral field spectroscopic observations from SDSS-IV MaNGA, we spatially disentangle the contribution from different Hα powering sources for ∼1000 galaxies. We find that, when including regions dominated by all ionizing sources in galaxies, the spatially resolved relation between Hα surface density (ΣHα (all)) and stellar mass surface density (Σ*(all)) progressively turns over at the high Σ*(all) end for increasing M *(global) and/or bulge dominance (bulge-to-total light ratio, B/T). This in turn leads to the flattening of the integrated Hα(global)–M *(global) relation in the literature. By contrast, there is no noticeable flattening in both integrated Hα(H II)–M *(H II) and spatially resolved ΣHα (H II)–Σ*(H II) relations when only regions where star formation dominates the ionization are considered. In other words, the flattening can be attributed to the increasing regions powered by non-star-formation sources, which generally have lower ionizing ability than star formation. An analysis of the fractional contribution of non-star-formation sources to total Hα luminosity of a galaxy suggests a decreasing role of star formation as an ionizing source toward high-mass, high-B/T galaxies and bulge regions. This result indicates that the appearance of the galaxy integrated SFR–M * relation critically depends on their global properties (M *(global) and B/T) and relative abundances of various ionizing sources within the galaxies.

Exploring the engines of molecular outflows

NASA Astrophysics Data System (ADS)

Testi, Leonardo

1995-03-01

Water vapour masers and CO outflows are well known to be associated with the youngest phases of evolution of massive stellar objects. Nevertheless, up to now there is a lack of high resolution multiwavelength study of the regions containing these objects. Using the VLA, the CSO and the TIRGO equipped with the new Near-Infrared (NIR) camera ARNICA, we have begun a systematic study of water maser/CO outflow regions. These new high resolution and high sensitivity data have proved to be very useful in probing the star formation activity and the connection between infrared and radio sources. Here we report the results obtained in a preliminary sub- sample of objects. The NIR data showed that both the maser spots and the large- scale outflows tend to be associated to the most embedded and probably younger sources of the infrared clusters. Infrared emission lines observed with narrow band filters show the presence of jet-like structures in most of the sources observed. Water masers, jet-like and Herbig-Haro-like infrared structures, and CO outflows enable to probe ejection phenomena at all spacial scales ranging from 0.01 to 1 parsec.

Extreme star formation in the Milky Way: luminosity distributions of young stellar objects in W49A and W51

NASA Astrophysics Data System (ADS)

Eden, D. J.; Moore, T. J. T.; Urquhart, J. S.; Elia, D.; Plume, R.; König, C.; Baldeschi, A.; Schisano, E.; Rigby, A. J.; Morgan, L. K.; Thompson, M. A.

2018-07-01

We have compared the star-formation properties of the W49A and W51 regions by using far-infrared data from the Herschel infrared Galactic Plane Survey (Hi-GAL) and 850-μm observations from the James Clerk Maxwell Telescope (JCMT) to obtain luminosities and masses, respectively, of associated compact sources. The former are infrared luminosities from the catalogue of Elia et al., while the latter are from the JCMT Plane survey source catalogue as well as measurements from new data. The clump-mass distributions of the two regions are found to be consistent with each other, as are the clump-formation efficiency and star-formation efficiency analogues. However, the frequency distributions of the luminosities of the young stellar objects are significantly different. While the luminosity distribution in W51 is consistent with Galaxy-wide samples, that of W49A is top heavy. The differences are not dramatic and are concentrated in the central regions of W49A. However, they suggest that physical conditions there, which are comparable in part to those in extragalactic starbursts, are significantly affecting the star-formation properties or evolution of the dense clumps in the region.

Extreme star formation in the Milky Way: Luminosity distributions of young stellar objects in W49A and W51

NASA Astrophysics Data System (ADS)

Eden, D. J.; Moore, T. J. T.; Urquhart, J. S.; Elia, D.; Plume, R.; König, C.; Baldeschi, A.; Schisano, E.; Rigby, A. J.; Morgan, L. K.; Thompson, M. A.

2018-03-01

We have compared the star-formation properties of the W49A and W51 regions by using far-infrared data from the Herschel infrared Galactic Plane Survey (Hi-GAL) and 850-μm observations from the James Clerk Maxwell Telescope (JCMT) to obtain luminosities and masses, respectively, of associated compact sources. The former are infrared luminosities from the catalogue of Elia et al. (2017), while the latter are from the JCMT Plane survey source catalogue as well as measurements from new data. The clump-mass distributions of the two regions are found to be consistent with each other, as are the clump-formation efficiency and star-formation efficiency analogues. However, the frequency distributions of the luminosities of the young stellar objects are significantly different. While the luminosity distribution in W51 is consistent with Galaxy-wide samples, that of W49A is top-heavy. The differences are not dramatic, and are concentrated in the central regions of W49A. However, they suggest that physical conditions there, which are comparable in part to those in extragalactic starbursts, are significantly affecting the star-formation properties or evolution of the dense clumps in the region.

Smoothed particle hydrodynamic simulations of expanding HII regions

NASA Astrophysics Data System (ADS)

Bisbas, Thomas G.

2009-09-01

This thesis deals with numerical simulations of expanding ionized regions, known as HII regions. We implement a new three dimensional algorithm in Smoothed Particle Hydrodynamics for including the dynamical effects of the interaction between ionizing radiation and the interstellar medium. This interaction plays a crucial role in star formation at all epochs. We study the influence of ionizing radiation in spherically symmetric clouds. In particular, we study the spherically symmetric expansion of an HII region inside a uniform-density, non-self-gravitating cloud. We examine the ability of our algorithm to reproduce the known theoretical solution and we find that the agreement is very good. We also study the spherically symmetric expansion inside a uniform-density, self-gravitating cloud. We propose a new differential equation of motion for the expanding shell that includes the effects of gravity. Comparing its numerical solution with the simulations, we find that the equation predicts the position of the shell accurately. We also study the expansion of an off-centre HII region inside a uniform-density, non- self-gravitating cloud. This results in an evolution known as the rocket effect, where the ionizing radiation pushes and accelerates the cloud away from the exciting star leading to its dispersal. During this evolution, cometary knots appear as a result of Rayleigh-Taylor and Vishniac instabilities. The knots are composed of a dense head with a conic tail behind them, a structure that points towards the ionizing source. Our simulations show that these knots are very reminiscent of the observed structures in planetary nebula, such as in the Helix nebula. The last part of this thesis is dedicated to the study of cores ionized by an exciting source which is placed outside and far away from them. The evolution of these cores is known as radiation driven compression (or implosion). We perform simulations and compare our findings with results of other workers and we find that they agree very well. Using stable Bonnor-Ebert spheres, we extend our study to modelling triggered star formation within these cores as they are overrun and compressed by the incident ionizing flux. We construct a parameter space diagram and we map regions where star formation is expected to be observed. All the above results indicate that the algorithm presented in this thesis works well for treating the propagation of ionizing radiation. This new algorithm provides the means to explore and evaluate the role of ionizing radiation in regulating the efficiency and statistics of star formation.

An Integrated Geophysical and Tectonic Study of the Structure and Evolution of the Crust in the Snake River Plain Region, Pacific Northwest

NASA Astrophysics Data System (ADS)

Keller, G. R.; Khatiwada, M.

2016-12-01

The Snake River Plain region in the Pacific Northwest of North America has been the target of a number of recent studies that have revealed further complexities in its structure and tectonic evolution. Based on surface morphology and Late Cenozoic volcanic activity, the Snake River Plain consists of an eastern and western arm (ESRP and WSRP) that are similar in many respects but also quite different in other respects. Thus, its origin, evolution, structural complexities, the role of extension and magmatism in its formation, and the tectonic drivers are still subjects of debate. Numerous seismic studies have specifically focused on the structure of the ESRP and Yellowstone area. However, crustal-scale studies of the WSRP are limited. We added new gravity data to the existing coverage in the WSRP region and undertook a regional, integrated analysis approach that included magnetic, seismic reflection and refraction profiling, receiver function results, geological and geospatial data, and interpreted well logs. Our integrated geophysical modeling focused on the structure of the WSRP. We generated two crustal models across it at locations where the most existing geophysical and geological constraints were available. We observed both differences and similarities in the structure of the WSRP and ESRP. Although, the shallow crustal structures are different, a mid-crustal mafic intrusion is a major source of the high gravity anomaly values. Within the context of recent studies in the surrounding region, the intersection of the two arms of the Snake River Plain emerges as a major element of a complex tectonic intersection that includes the High Lava Plains of eastern Oregon, the Northern Nevada Rift, a southwestern extension of the ESRP into northern Nevada, as well as, faulting and volcanism extending northwestward to connect with the Columbia River Basalts region.

Probing the Evolution of Massive Young Stellar Objects using Weak Class II 6.7GHz Methanol Maser Emission

NASA Astrophysics Data System (ADS)

Ludwig, Bethany Ann; Cunningham, Nichol

2017-01-01

We present results from an investigation of class II 6.7GHz methanol masers towards four Massive Young Stellar Objects (MYSOs). The sources, selected from the Red MSX Source (RMS) Survey (Lumsden et al. 2013), were previously understood to be non-detections for class II methanol maser emission in the methanol multi-beam (MMB) Survey (Caswell et al. 2010.) Class II methanol masers are a well-known sign post of massive star forming regions and may be utilized to probe their relatively poorly understood formation. It is possible that these non-detections are simply weak masers that are potentially associated with a younger evolutionary phase of MYSOs as hypothesized by Olmi et al. (2014). The sources were chosen to sample various stages of evolution, having similar 21 to 8 micron flux ratios and bolometric luminosities as other MYSOs with previous class II methanol maser detections. We observed all 4 MYSOs with ATCA (~2" resolution) at 10 times deeper sensitivity than previously obtained with the MMB survey and have a spectral resolution of 0.087kms^-1 . The raw data is reduced using the program Miriad (Sault, R. J., et al., 1995) and deconvolutioned using the program CASA (McMullin, J. P., et al. 2007.) We determine one of the four observed MYSOs is harboring a weak class II methanol maser. We discuss the possibility of sensitivity limitations on the remaining sources as well as environmental and evolutionary differences between the sources.

A Survey of Distant Clusters of Galaxies Selected by X-Rays

NASA Technical Reports Server (NTRS)

McNamara, Brian

1997-01-01

I will discuss the results of a new survey of X-ray selected, distant clusters of galaxies that has been undertaken by our group at.CfA (Vikhlinin, McNamara, Forman, Jones). We have analyzed the inner 17.5 arcminute region of roughly 650 ROSAT PSPC images of high latitude fields to compile a complete, flux-limited sample of clusters with a mean flux limit roughly 20 times more sensitive than the Einstein Medium Sensitivity Survey. The goal of our survey, which presently contains 233 extended X-ray sources, is to study cluster evolution over cosmological timescales. We have obtained optical images for nearly all of the faintest sources using the 1.2 m telescope of the Fred L. Whipple Observatory, and when including POSS images of the brighter sources, we have nearly completed the identification of all of the extended sources. Roughly 80% of the sources were identified as clusters of galaxies. We have measured redshifts for 42 clusters using the MMT, and including additional measurements from the literature, roughly 70 clusters in our catalog have spectroscopic redshifts. Using CCD photometry and spectroscopic redshifts, we have determined a magnitude-redshift relation which will allow redshifts of the remaining clusters in our sample to be determined photometrically to within a delta z over z of roughly ten percent. I will discuss the Log(N)-Log(S) relation for our sample and compare it to other determinations. In addition, I will discuss the evolution of core radii of clusters.

Region Evolution eXplorer - A tool for discovering evolution trends in ontology regions.

PubMed

Christen, Victor; Hartung, Michael; Groß, Anika

2015-01-01

A large number of life science ontologies has been developed to support different application scenarios such as gene annotation or functional analysis. The continuous accumulation of new insights and knowledge affects specific portions in ontologies and thus leads to their adaptation. Therefore, it is valuable to study which ontology parts have been extensively modified or remained unchanged. Users can monitor the evolution of an ontology to improve its further development or apply the knowledge in their applications. Here we present REX (Region Evolution eXplorer) a web-based system for exploring the evolution of ontology parts (regions). REX provides an analysis platform for currently about 1,000 versions of 16 well-known life science ontologies. Interactive workflows allow an explorative analysis of changing ontology regions and can be used to study evolution trends for long-term periods. REX is a web application providing an interactive and user-friendly interface to identify (un)stable regions in large life science ontologies. It is available at http://www.izbi.de/rex.

Neofunctionalization of Duplicated P450 Genes Drives the Evolution of Insecticide Resistance in the Brown Planthopper.

PubMed

Zimmer, Christoph T; Garrood, William T; Singh, Kumar Saurabh; Randall, Emma; Lueke, Bettina; Gutbrod, Oliver; Matthiesen, Svend; Kohler, Maxie; Nauen, Ralf; Davies, T G Emyr; Bass, Chris

2018-01-22

Gene duplication is a major source of genetic variation that has been shown to underpin the evolution of a wide range of adaptive traits [1, 2]. For example, duplication or amplification of genes encoding detoxification enzymes has been shown to play an important role in the evolution of insecticide resistance [3-5]. In this context, gene duplication performs an adaptive function as a result of its effects on gene dosage and not as a source of functional novelty [3, 6-8]. Here, we show that duplication and neofunctionalization of a cytochrome P450, CYP6ER1, led to the evolution of insecticide resistance in the brown planthopper. Considerable genetic variation was observed in the coding sequence of CYP6ER1 in populations of brown planthopper collected from across Asia, but just two sequence variants are highly overexpressed in resistant strains and metabolize imidacloprid. Both variants are characterized by profound amino-acid alterations in substrate recognition sites, and the introduction of these mutations into a susceptible P450 sequence is sufficient to confer resistance. CYP6ER1 is duplicated in resistant strains with individuals carrying paralogs with and without the gain-of-function mutations. Despite numerical parity in the genome, the susceptible and mutant copies exhibit marked asymmetry in their expression with the resistant paralogs overexpressed. In the primary resistance-conferring CYP6ER1 variant, this results from an extended region of novel sequence upstream of the gene that provides enhanced expression. Our findings illustrate the versatility of gene duplication in providing opportunities for functional and regulatory innovation during the evolution of an adaptive trait. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

A very deep IRAS survey - Constraints on the evolution of starburst galaxies

NASA Astrophysics Data System (ADS)

Hacking, Perry; Condon, J. J.; Houck, J. R.

1987-05-01

Counts of sources (primarily starburst galaxies) from a deep 60 microns IRAS survey published by Hacking and Houck (1987) are compared with four evolutionary models. The counts below 100 mJy are higher than expected if no evolution has taken place out to a redshift of approximately 0.2. Redshift measurements of the survey sources should be able to distinguish between luminosity-evolution and density-evolution models and detect as little as a 20 percent brightening or increase in density of infrared sources per billion years ago (H/0/ = 100 km/s per Mpc). Starburst galaxies cannot account for the reported 100 microns background without extreme evolution at high redshifts.

Long-Term Observation of Small and Medium-Scale Gravity Waves over the Brazilian Equatorial Region

NASA Astrophysics Data System (ADS)

Essien, Patrick; Buriti, Ricardo; Wrasse, Cristiano M.; Medeiros, Amauri; Paulino, Igo; Takahashi, Hisao; Campos, Jose Andre

2016-07-01

This paper reports the long term observations of small and medium-scale gravity waves over Brazilian equatorial region. Coordinated optical and radio measurements were made from OLAP at Sao Joao do Cariri (7.400S, 36.500W) to investigate the occurrences and properties and to characterize the regional mesospheric gravity wave field. All-sky imager measurements were made from the site. for almost 11 consecutive years (September 2000 to November 2010). Most of the waves propagated were characterized as small-scale gravity. The characteristics of the two waves events agreed well with previous gravity wave studies from Brazil and other sites. However, significant differences in the wave propagation headings indicate dissimilar source regions. The observed medium-scale gravity wave events constitute an important new dataset to study their mesospheric properties at equatorial latitudes. These data exhibited similar propagation headings to the short period events, suggesting they originated from the same source regions. It was also observed that some of the medium-scale were capable of propagating into the lower thermosphere where they may have acted directly as seeds for the Rayleigh-Taylor instability development. The wave events were primarily generated by meteorological processes since there was no correlation between the evolution of the wave events and solar cycle F10.7.

Two Outbreak Sources of Influenza A (H7N9) Viruses Have Been Established in China.

PubMed

Wang, Dayan; Yang, Lei; Zhu, Wenfei; Zhang, Ye; Zou, Shumei; Bo, Hong; Gao, Rongbao; Dong, Jie; Huang, Weijuan; Guo, Junfeng; Li, Zi; Zhao, Xiang; Li, Xiaodan; Xin, Li; Zhou, Jianfang; Chen, Tao; Dong, Libo; Wei, Hejiang; Li, Xiyan; Liu, Liqi; Tang, Jing; Lan, Yu; Yang, Jing; Shu, Yuelong

2016-06-15

Due to enzootic infections in poultry and persistent human infections in China, influenza A (H7N9) virus has remained a public health threat. The Yangtze River Delta region, which is located in eastern China, is well recognized as the original source for H7N9 outbreaks. Based on the evolutionary analysis of H7N9 viruses from all three outbreak waves since 2013, we identified the Pearl River Delta region as an additional H7N9 outbreak source. H7N9 viruses are repeatedly introduced from these two sources to the other areas, and the persistent circulation of H7N9 viruses occurs in poultry, causing continuous outbreak waves. Poultry movements may contribute to the geographic expansion of the virus. In addition, the AnH1 genotype, which was predominant during wave 1, was replaced by JS537, JS18828, and AnH1887 genotypes during waves 2 and 3. The establishment of a new source and the continuous evolution of the virus hamper the elimination of H7N9 viruses, thus posing a long-term threat of H7N9 infection in humans. Therefore, both surveillance of H7N9 viruses in humans and poultry and supervision of poultry movements should be strengthened. Since its occurrence in humans in eastern China in spring 2013, the avian H7N9 viruses have been demonstrating the continuing pandemic threat posed by the current influenza ecosystem in China. As the viruses are silently circulated in poultry, with potentially severe outcomes in humans, H7N9 virus activity in humans in China is very important to understand. In this study, we identified a newly emerged H7N9 outbreak source in the Pearl River Delta region. Both sources in the Yangtze River Delta region and the Pearl River Delta region have been established and found to be responsible for the H7N9 outbreaks in mainland China. Copyright © 2016, American Society for Microbiology. All Rights Reserved.

Two Outbreak Sources of Influenza A (H7N9) Viruses Have Been Established in China

PubMed Central

Wang, Dayan; Yang, Lei; Zhu, Wenfei; Zhang, Ye; Zou, Shumei; Bo, Hong; Gao, Rongbao; Dong, Jie; Huang, Weijuan; Guo, Junfeng; Li, Zi; Zhao, Xiang; Li, Xiaodan; Xin, Li; Zhou, Jianfang; Chen, Tao; Dong, Libo; Wei, Hejiang; Li, Xiyan; Liu, Liqi; Tang, Jing; Lan, Yu; Yang, Jing

2016-01-01

ABSTRACT Due to enzootic infections in poultry and persistent human infections in China, influenza A (H7N9) virus has remained a public health threat. The Yangtze River Delta region, which is located in eastern China, is well recognized as the original source for H7N9 outbreaks. Based on the evolutionary analysis of H7N9 viruses from all three outbreak waves since 2013, we identified the Pearl River Delta region as an additional H7N9 outbreak source. H7N9 viruses are repeatedly introduced from these two sources to the other areas, and the persistent circulation of H7N9 viruses occurs in poultry, causing continuous outbreak waves. Poultry movements may contribute to the geographic expansion of the virus. In addition, the AnH1 genotype, which was predominant during wave 1, was replaced by JS537, JS18828, and AnH1887 genotypes during waves 2 and 3. The establishment of a new source and the continuous evolution of the virus hamper the elimination of H7N9 viruses, thus posing a long-term threat of H7N9 infection in humans. Therefore, both surveillance of H7N9 viruses in humans and poultry and supervision of poultry movements should be strengthened. IMPORTANCE Since its occurrence in humans in eastern China in spring 2013, the avian H7N9 viruses have been demonstrating the continuing pandemic threat posed by the current influenza ecosystem in China. As the viruses are silently circulated in poultry, with potentially severe outcomes in humans, H7N9 virus activity in humans in China is very important to understand. In this study, we identified a newly emerged H7N9 outbreak source in the Pearl River Delta region. Both sources in the Yangtze River Delta region and the Pearl River Delta region have been established and found to be responsible for the H7N9 outbreaks in mainland China. PMID:27030268

Utility of aeromagnetic studies for mapping of potentially active faults in two forearc basins: Puget Sound, Washington, and Cook Inlet, Alaska

USGS Publications Warehouse

Saltus, R.W.; Blakely, R.J.; Haeussler, Peter J.; Wells, R.E.

2005-01-01

High-resolution aeromagnetic surveys over forearc basins can detect faults and folds in weakly magnetized sediments, thus providing geologic constraints on tectonic evolution and improved understanding of seismic hazards in convergent-margin settings. Puget Sound, Washington, and Cook Inlet, Alaska, provide two case histories. In each lowland region, shallow-source magnetic anomalies are related to active folds and/or faults. Mapping these structures is critical for understanding seismic hazards that face the urban regions of Seattle, Washington, and Anchorage, Alaska. Similarities in aeromagnetic anomaly patterns and magnetic stratigraphy between the two regions suggest that we can expect the aeromagnetic method to yield useful structural information that may contribute to earth-hazard and energy resource investigations in other forearc basins.

High-expanding cortical regions in human development and evolution are related to higher intellectual abilities.

PubMed

Fjell, Anders M; Westlye, Lars T; Amlien, Inge; Tamnes, Christian K; Grydeland, Håkon; Engvig, Andreas; Espeseth, Thomas; Reinvang, Ivar; Lundervold, Astri J; Lundervold, Arvid; Walhovd, Kristine B

2015-01-01

Cortical surface area has tremendously expanded during human evolution, and similar patterns of cortical expansion have been observed during childhood development. An intriguing hypothesis is that the high-expanding cortical regions also show the strongest correlations with intellectual function in humans. However, we do not know how the regional distribution of correlations between intellectual function and cortical area maps onto expansion in development and evolution. Here, in a sample of 1048 participants, we show that regions in which cortical area correlates with visuospatial reasoning abilities are generally high expanding in both development and evolution. Several regions in the frontal cortex, especially the anterior cingulate, showed high expansion in both development and evolution. The area of these regions was related to intellectual functions in humans. Low-expanding areas were not related to cognitive scores. These findings suggest that cortical regions involved in higher intellectual functions have expanded the most during development and evolution. The radial unit hypothesis provides a common framework for interpretation of the findings in the context of evolution and prenatal development, while additional cellular mechanisms, such as synaptogenesis, gliogenesis, dendritic arborization, and intracortical myelination, likely impact area expansion in later childhood. © The Author 2013. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Astrochemical evolution along star formation: overview of the IRAM Large Program ASAI

NASA Astrophysics Data System (ADS)

Lefloch, Bertrand; Bachiller, R.; Ceccarelli, C.; Cernicharo, J.; Codella, C.; Fuente, A.; Kahane, C.; López-Sepulcre, A.; Tafalla, M.; Vastel, C.; Caux, E.; González-García, M.; Bianchi, E.; Gómez-Ruiz, A.; Holdship, J.; Mendoza, E.; Ospina-Zamudio, J.; Podio, L.; Quénard, D.; Roueff, E.; Sakai, N.; Viti, S.; Yamamoto, S.; Yoshida, K.; Favre, C.; Monfredini, T.; Quitián-Lara, H. M.; Marcelino, N.; Boechat-Roberty, H. M.; Cabrit, S.

2018-07-01

Evidence is mounting that the small bodies of our Solar system, such as comets and asteroids, have at least partially inherited their chemical composition from the first phases of the Solar system formation. It then appears that the molecular complexity of these small bodies is most likely related to the earliest stages of star formation. It is therefore important to characterize and to understand how the chemical evolution changes with solar-type protostellar evolution. We present here the Large Program `Astrochemical Surveys At IRAM' (ASAI). Its goal is to carry out unbiased millimetre line surveys between 80 and 272 GHz of a sample of 10 template sources, which fully cover the first stages of the formation process of solar-type stars, from pre-stellar cores to the late protostellar phase. In this paper, we present an overview of the surveys and results obtained from the analysis of the 3 mm band observations. The number of detected main isotopic species barely varies with the evolutionary stage and is found to be very similar to that of massive star-forming regions. The molecular content in O- and C-bearing species allows us to define two chemical classes of envelopes, whose composition is dominated by either (a) a rich content in O-rich complex organic molecules, associated with hot corino sources, or (b) a rich content in hydrocarbons, typical of warm carbon-chain chemistry sources. Overall, a high chemical richness is found to be present already in the initial phases of solar-type star formation.

The Observed Evolution of the Black-Hole-Host Mass Relation to z~3.5

NASA Astrophysics Data System (ADS)

Trakhtenbrot, Benny; Urry, C. Megan; Civano, Francesca M.; Rosario, David J.; Elvis, Martin; Schawinski, Kevin; Suh, Hyewon; Bongiorno, Angela; Simmons, Brooke; Marchesi, Stefano

2016-01-01

We present our Keck/MOSFIRE project to probe basic black hole and host galaxy properties in a sample of faint Active Galactic Nuclei (AGN) at z~2.1-3.7, selected through the extensive X-ray Chandra coverage of the COSMOS field. Compared with previous studies of unobscured AGN at these high redshifts, our sources have lower AGN luminosities, corresponding to significantly higher number densities, of order ˜10-6-10-5 Mpc-3. The new K-band data covers the spectral region surrounding the broad Hbeta or Halpha emission lines, and enables the estimation of black hole masses (MBH) and accretion rates (in terms of L/LEdd). The lower AGN luminosities also allow for robust determinations of the host galaxies stellar masses, therefore enabling us to trace the evolution of the BH-to-stellar mass ratio (MBH/M*) to z~3.5. Compared with the rarer, higher-luminosity quasars targeted in previous studies, we find that the 12 AGN in our sample have lower MBH (~5x108 Msun), but similar accretion rates (L/LEdd~0.1-0.5). The BH-to-stellar mass ratio, MBH/M*, has a large scatter, with several sources reaching extremely high ratios of MBH/M* ~ 10% - higher by at least an order of magnitude than what is observed in the local Universe. The typical mass ratio for our sample is consistent with a trend of MBH/M* ~ (1+z)2. I will highlight some intriguing sources in the sample, and will briefly discuss the implications of our findings to the co-evolution of SMBHs and their host galaxies.

Segmental Duplications in Euchromatic Regions of Human Chromosome 5: A Source of Evolutionary Instability and Transcriptional Innovation

PubMed Central

Courseaux, Anouk; Richard, Florence; Grosgeorge, Josiane; Ortola, Christine; Viale, Agnes; Turc-Carel, Claude; Dutrillaux, Bernard; Gaudray, Patrick; Nahon, Jean-Louis

2003-01-01

Recent analyses of the structure of pericentromeric and subtelomeric regions have revealed that these particular regions of human chromosomes are often composed of blocks of duplicated genomic segments that have been associated with rapid evolutionary turnover among the genomes of closely related primates. In the present study, we show that euchromatic regions of human chromosome 5—5p14, 5p13, 5q13, 5q15–5q21—also display such an accumulation of segmental duplications. The structure, organization and evolution of those primate-specific sequences were studied in detail by combining in silico and comparative FISH analyses on human, chimpanzee, gorilla, orangutang, macaca, and capuchin chromosomes. Our results lend support to a two-step model of transposition duplication in the euchromatic regions, with a founder insertional event at the time of divergence between Platyrrhini and Catarrhini (25–35 million years ago) and an apparent burst of inter- and intrachromosomal duplications in the Hominidae lineage. Furthermore, phylogenetic analysis suggests that the chronology and, likely, molecular mechanisms, differ regarding the region of primary insertion—euchromatic versus pericentromeric regions. Lastly, we show that as their counterparts located near the heterochromatic region, the euchromatic segmental duplications have consistently reshaped their region of insertion during primate evolution, creating putative mosaic genes, and they are obvious candidates for causing ectopic rearrangements that have contributed to evolutionary/genomic instability. [Supplemental material is available online at www.genome.org. The following individuals kindly provided reagents, samples, or unpublished information as indicated in the paper: D. Le Paslier, A. McKenzie, J. Melki, C. Sargent, J. Scharf and S. Selig.] PMID:12618367

Star-Forming Regions in Orion as a Dust Evolution Laboratory

NASA Astrophysics Data System (ADS)

Wiebe, D.; Murga, M.; Sivkova, E.

2017-06-01

Star-forming regions (SFR) represent a convenient opportunity to study various processes related both to dust growth and to dust destruction. While extragalactic SFRs allow considering these processes in a wide range of metallicities, UV field intensities, etc., the Orion star-forming complex opens up a possibility to observe dust evolution with an unprecedented angular resolution. We review various observations related to dust evolution in some most prominent Orion regions, paying special attention to organic dust evolution, and introduce a new model of organic dust evolution.

Characterization of Asian Dust Properties Near Source Region During ACE-Asia

NASA Technical Reports Server (NTRS)

Tsay, Si-Chee; Hsu, N. Christina; King, Michael D.; Kaufman, Yoram J.; Herman, Jay R.

2004-01-01

Asian dust typically originates in desert areas far from polluted urban regions. During transport, dust layers can interact with anthropogenic sulfate and soot aerosols from heavily polluted urban areas. Added to the complex effects of clouds and natural marine aerosols, dust particles reaching the marine environment can have drastically different properties than those from the source. Thus, understanding the unique temporal and spatial variations of Asian aerosols is of special importance in regional-to-global climate issues such as radiative forcing, the hydrological cycle, and primary biological productivity in the mid-Pacific Ocean. During ACE-Asia campaign, we have acquired ground- based (temporal) and satellite (spatial) measurements to infer aerosol physical/optical/radiative properties, column precipitable water amount, and surface reflectivity over this region. The inclusion of flux measurements permits the determination of aerosol radiative flux in addition to measurements of loading and optical depth. At the time of the Terra/MODIS, SeaWiFS, TOMS and other satellite overpasses, these ground-based observations can provide valuable data to compare with satellite retrievals over land. In this paper, we will demonstrate new capability of the Deep Blue algorithm to track the evolution of the Asian dust storm from sources to sinks. Although there are large areas often covered by clouds in the dust season in East Asia, this algorithm is able to distinguish heavy dust from clouds over the entire regions. Examination of the retrieved daily maps of dust plumes over East Asia clearly identifies the sources contributing to the dust loading in the atmosphe. We have compared the satellite retrieved aerosol optical thickness to the ground-based measurements and obtained a reasonable agreement between these two. Our results also indicate that there is a large difference in the retrieved value of spectral single scattering albedo of windblown dust between different sources in East Asia.

Spectral Index Properties of millijansky Radio Sources in ATLAS

NASA Astrophysics Data System (ADS)

Randall, Kate; Hopkins, A. M.; Norris, R. P.; Zinn, P.; Middelberg, E.; Mao, M. Y.; Sharp, R. G.

2012-01-01

At the faintest radio flux densities (S1.4GHz < 10 milliJansky (mJy)), the spectral index properties of radio sources are not well constrained. The bright radio source population (S1.4GHz > 10 mJy) is well studied and is predominantly comprised of AGN. At fainter flux densities, particularly into the microJansky regime, star-forming galaxies begin to dominate the radio source population. Understanding these faint radio source populations is essential for understanding galaxy evolution, and the link between AGN and star formation. Conflicting results have recently arisen regarding whether there is a flattening of the average spectral index between a low radio frequency (325 or 610 MHz) and 1.4 GHz at these faint flux densities. To explore this issue, we have investigated the spectral index properties of a new catalogue of 843 MHz radio sources in the ELAIS-S1 (the European Large Area ISO Survey - South 1 Region) field. Our results support previous work showing a tendency towards flatter radio spectra at fainter flux densities. This catalogue is cross-matched to the Australia Telescope Large Area Survey (ATLAS), the widest deep radio survey to date at 1.4 GHz, with complementary 2.3 GHz, optical and infrared Spitzer Wide-area Infra-Red Extragalactic data. The variation of spectral index properties have been explored as a function of redshift, luminosity and flux density. [These new measurements have been used to identify a population of faint Compact Steep Spectrum sources, thought to be one of the earliest stages of the AGN life-cycle. Exploring this population will aid us in understanding the evolution of AGN as a whole.

Volatile element chemistry of selected lunar, meteoritic, and terrestrial samples

NASA Technical Reports Server (NTRS)

Simoneit, B. R.; Christiansen, P. C.; Burlingame, A. L.

1973-01-01

Using vacuum pyrolysis and high resolution mass spectrometry, a study is made of the gas release patterns of representative lunar samples, meteorites, terrestrial samples, and synthetic samples doped with various sources of carbon and nitrogen. The pyrolytic gas evolution patterns were intercorrelated, allowing an assessment of the possible sources of the volatilizable material in the lunar samples to be made. Lightly surface adsorbed species and more strongly chemisorbed species are released from ambient to 300 C and from 300 to 500 C, respectively. The low-temperature volatiles (less than 500 C) derived from various chondrites correlate well with the gas evolution patterns of volatile-rich samples, as for example 74220 and 61221. Solar wind entrapped species and molecules derived from reactions probably in the grain surfaces are evolved from about 500 to 700 C, respectively. Solar wind implanted C, N, and S species are generated from 750 to 1150 C, probably by reaction with the mineral matrix during the annealing process. Possible indigenous and/or refractory carbide, nitride, and sulfide C, N, and S are released in the region from 1200 C to fusion.

A STATE-DEPENDENT INFLUENCE OF TYPE I BURSTS ON THE ACCRETION IN 4U 1608-52?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ji, Long; Zhang, Shu; Chen, YuPeng

2014-08-20

We investigated the possible feedback of type I bursts on the accretion process during the spectral evolution of the atoll source 4U 1608-52. By fitting the burst spectrum with a blackbody and an adjustable, persistent spectral component, we found that the latter is significantly state-dependent. In the banana state, the persistent flux increases along the burst evolution, while in the island state this trend holds only when the bursts are less luminous and start to reverse at higher burst luminosities. We speculate that, by taking into account both the Poynting-Robertson drag and radiation pressure, these phenomena may arise from the interactionsmore » between the radiation field of the type I burst and the inner region of the accretion disk.« less

Genome sequence analysis of the model grass Brachypodium distachyon: insights into grass genome evolution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schulman, Al

2009-08-09

Three subfamilies of grasses, the Erhardtoideae (rice), the Panicoideae (maize, sorghum, sugar cane and millet), and the Pooideae (wheat, barley and cool season forage grasses) provide the basis of human nutrition and are poised to become major sources of renewable energy. Here we describe the complete genome sequence of the wild grass Brachypodium distachyon (Brachypodium), the first member of the Pooideae subfamily to be completely sequenced. Comparison of the Brachypodium, rice and sorghum genomes reveals a precise sequence- based history of genome evolution across a broad diversity of the grass family and identifies nested insertions of whole chromosomes into centromericmore » regions as a predominant mechanism driving chromosome evolution in the grasses. The relatively compact genome of Brachypodium is maintained by a balance of retroelement replication and loss. The complete genome sequence of Brachypodium, coupled to its exceptional promise as a model system for grass research, will support the development of new energy and food crops« less

Homology of the reptilian coracoid and a reappraisal of the evolution and development of the amniote pectoral apparatus

PubMed Central

Vickaryous, Matthew K; Hall, Brian K

2006-01-01

As in monotreme mammals, the pectoral apparatus of basal (fossil) amniotes includes two coracoid elements, the procoracoid and metacoracoid. Among extant reptiles the metacoracoid has long been assumed lost; this notion is herein challenged. A comprehensive review of data from numerous sources, including the fossil record, experimental embryology, genetic manipulations and an analysis of morphology at the level cell condensations, supports the conclusion that the metacoracoid gives rise to the majority of the reptilian coracoid. By contrast, the reptilian procoracoid remains as a rudiment that is incorporated as a process of the (meta)coracoid and/or the glenoid region of the scapula early during development, prior to skeletogenesis. Application of this integrated approach corroborates and enhances previous work describing the evolution of the pectoral apparatus in mammals. A revised scenario of amniote coracoid evolution is presented emphasizing the importance of considering cell condensations when evaluating the homology of a skeletal complex. PMID:16533312

Density and persistence analyze on the spreading models multi-regions multi-patchs

NASA Astrophysics Data System (ADS)

Hariyanto, Hanafi, Lukman; Wahyudi, Suhud

2017-08-01

The spread of the virus is widespread in some countries and even can reach some continents. This ever happened in the pandemic H1N1 virus outbreak in 2005 which covers 3 continents, as well as the H5N1 virus that hits several regions in Indonesia. If the virus spreads to the region as a source of the spread, the outbreak will occur due to the movement of infected individuals or vector that moves freely in other regions. The focus of this paper is to analyze the characteristics of the sub-population density, as well as the persistence of individuals moving on the path that connecting two areas of its distribution through mathematical models constructed by the spread of the virus in the three regions. The analysis results showed that the movement of individual sub-population exposure to all of the tracks or individual transfer on another track are having transition due to the genetic evolution of the virus and that causes potential outbreaks in the wider regions.

Implications for air quality and the impact of financial and economic crisis in South Spain: Geochemical evolution of atmospheric aerosol in the ceramic region of Bailén

NASA Astrophysics Data System (ADS)

Sánchez de la Campa, A. M.; de la Rosa, J. D.

2014-12-01

A temporal series study of atmospheric aerosol was performed over the last ten years (2003-2012) in an urban background monitoring station with ceramic industrial influence, in Bailén, SE Spain. Temporal trends of major and minor chemical components of PM10 for a long term data series were investigated, showing that PM10 concentrations have been steadily decreasing over almost a decade, with a statistical significance. Measurements indicate a reduction of elements and components related to the industrial activity of brick-ceramic production (V, Cd, Rb, La, Cr, Ni, As, Pb and SO42-). Conversely, Cu levels define an increasing trend from the beginning of the study period but with the highest step trend since 2011-2012, coinciding with the beginning of the financial and economic crisis in 2008. A similar time evolution pattern of Cu and OC, EC, and K levels may be a tracer of domestic local combustion source, and a new biomass burning source has been identified. Chemical composition of olive tree logs suggest as the combustion of wood with high concentration of Cu can imply an increase of Cu concentration in the atmospheric particles compared with other sources such as traffic.

Upper Miocene-Pliocene provenance evolution of the Central Canyon in northwestern South China Sea

NASA Astrophysics Data System (ADS)

Cui, Yuchi; Shao, Lei; Qiao, Peijun; Pei, Jianxiang; Zhang, Daojun; Tran, Huyen

2018-06-01

Provenance studies of the Central Canyon, Qiongdongnan Basin has provided significant insights into paleographic and sedimentology research of the South China Sea (SCS). A suite of geochemical approaches mainly including rare earth elemental (REE) analysis and detrital zircon U-Pb dating has been systematically applied to the "source-to-sink" system involving our upper Miocene-Pliocene Central Canyon sediments and surrounding potential source areas. Based on samples tracing the entire course of the Central Canyon, REE distribution patterns indicate that the western channel was generally characterized by positive Eu anomalies in larger proportion, in contrast to the dominance of negative values of its eastern side during late Miocene-Pliocene. Additionally, for the whole canyon and farther regions of Qiongdongnan Basin, the number of samples bearing negative Eu anomalies tended to increase within younger geological strata. On the other hand, U-Pb geochronology results suggest a wide Proterozoic to Mesozoic age range with peak complexity in Yanshanian, Indosinian, Caledonian and Jinningian periods. However in detail, age combination of most western samples displayed older-age signatures than the eastern. To make it more evidently, western boreholes of the Central Canyon are mainly characterized with confined Indosinian and Caledonian clusters which show great comparability with mafic-to-ultramafic source of Kontum Massif of Central Vietnam, while eastern samples largely bear with distinguishable Yanshanian and Indosinian peaks which more resemble with Hainan Island. Based on geochemistry and geochronology analyses, two significant suppliers and sedimentary infilling processes are generated: (1) the Indosinian collision orogenic belt in central-northern Vietnam, Indochina has ever played significant role in Central Canyon sedimentary evolution, (2) Hainan Island once as a typical provenance restricted within eastern Central Canyon, has been enlarging its influence into the whole channel, even into the farther western regions of Qiongdongnan Basin.

Lithofacies control in detrital zircon provenance studies: Insights from the Cretaceous Methow basin, southern Canadian Cordillera

USGS Publications Warehouse

DeGraaff-Surpless, K.; Mahoney, J.B.; Wooden, J.L.; McWilliams, M.O.

2003-01-01

High-frequency sampling for detrital zircon analysis can provide a detailed record of fine-scale basin evolution by revealing the temporal and spatial variability of detrital zircon ages within clastic sedimentary successions. This investigation employed detailed sampling of two sedimentary successions in the Methow/Methow-Tyaughton basin of the southern Canadian Cordillera to characterize the heterogeneity of detrital zircon signatures within single lithofacies and assess the applicability of detrital zircon analysis in distinguishing fine-scale provenance changes not apparent in lithologic analysis of the strata. The Methow/Methow-Tyaughton basin contains two distinct stratigraphic sequences of middle Albian to Santonian clastic sedimentary rocks: submarine-fan deposits of the Harts Pass Formation/Jackass Mountain Group and fluvial deposits of the Winthrop Formation. Although both stratigraphic sequences displayed consistent ranges in detrital zircon ages on a broad scale, detailed sampling within each succession revealed heterogeneity in the detrital zircon age distributions that was systematic and predictable in the turbidite succession but unpredictable in the fluvial succession. These results suggest that a high-density sampling approach permits interpretation of finescale changes within a lithologically uniform turbiditic sedimentary succession, but heterogeneity within fluvial systems may be too large and unpredictable to permit accurate fine-scale characterization of the evolution of source regions. The robust composite detrital zircon age signature developed for these two successions permits comparison of the Methow/Methow-Tyaughton basin age signature with known plutonic source-rock ages from major plutonic belts throughout the Cretaceous North American margin. The Methow/Methow-Tyaughton basin detrital zircon age signature matches best with source regions in the southern Canadian Cordillera, requiring that the basin developed in close proximity to the southern Canadian Cordillera and providing evidence against large-scale dextral translation of the Methow terrane.

Very deep IRAS survey - constraints on the evolution of starburst galaxies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hacking, P.; Houck, J.R.; Condon, J.J.

1987-05-01

Counts of sources (primarily starburst galaxies) from a deep 60 microns IRAS survey published by Hacking and Houck (1987) are compared with four evolutionary models. The counts below 100 mJy are higher than expected if no evolution has taken place out to a redshift of approximately 0.2. Redshift measurements of the survey sources should be able to distinguish between luminosity-evolution and density-evolution models and detect as little as a 20 percent brightening or increase in density of infrared sources per billion years ago (H/0/ = 100 km/s per Mpc). Starburst galaxies cannot account for the reported 100 microns background withoutmore » extreme evolution at high redshifts. 21 references.« less

Interactive coupling of regional climate and sulfate aerosol models over eastern Asia

NASA Astrophysics Data System (ADS)

Qian, Yun; Giorgi, Filippo

1999-03-01

The NCAR regional climate model (RegCM) is interactively coupled to a simple radiatively active sulfate aerosol model over eastern Asia. Both direct and indirect aerosol effects are represented. The coupled model system is tested for two simulation periods, November 1994 and July 1995, with aerosol sources representative of present-day anthropogenic sulfur emissions. The model sensitivity to the intensity of the aerosol source is also studied. The main conclusions from our work are as follows: (1) The aerosol distribution and cycling processes show substantial regional spatial variability, and temporal variability varying on a range of scales, from the diurnal scale of boundary layer and cumulus cloud evolution to the 3-10 day scale of synoptic scale events and the interseasonal scale of general circulation features; (2) both direct and indirect aerosol forcings have regional effects on surface climate; (3) the regional climate response to the aerosol forcing is highly nonlinear, especially during the summer, due to the interactions with cloud and precipitation processes; (4) in our simulations the role of the aerosol indirect effects is dominant over that of direct effects; (5) aerosol-induced feedback processes can affect the aerosol burdens at the subregional scale. This work constitutes the first step in a long term research project aimed at coupling a hierarchy of chemistry/aerosol models to the RegCM over the eastern Asia region.

Two protostar candidates in the bright-rimmed dark cloud LDN 1206

NASA Technical Reports Server (NTRS)

Ressler, Michael E.; Shure, Mark

1991-01-01

The discovery of several near IR objects associated with two IRAS point sources in the LDN 1206 region is reported. IRAS 22272 + 6358A is probably a 'protostar' which is seen only in scattered light at near-IR wavelengths because of heavy obscuration by an almost edge-on circumstellar disk. In contrast, IRAS 22272 + 6358B is directly visible at these wavelengths and is perhaps an object which lies between protostars and T-Tauri stars in its evolution. Both direct and polarimetric K-band images of the region are presented, as well as spectral energy distributions constructed from J, H, K, L, L-prime, and M data and published far-IR and mm data.

The 26 December 2001 Solar Event Responsible for GLE63. I. Observations of a Major Long-Duration Flare with the Siberian Solar Radio Telescope

NASA Astrophysics Data System (ADS)

Grechnev, V. V.; Kochanov, A. A.

2016-12-01

Ground level enhancements (GLEs) of cosmic-ray intensity occur, on average, once a year. Because they are rare, studying the solar sources of GLEs is especially important to approach understanding their origin. The SOL2001-12-26 eruptive-flare event responsible for GLE63 seems to be challenging in some aspects. Deficient observations limited our understanding of it. Analysis of additional observations found for this event provided new results that shed light on the flare configuration and evolution. This article addresses the observations of this flare with the Siberian Solar Radio Telescope (SSRT). Taking advantage of its instrumental characteristics, we analyze the detailed SSRT observations of a major long-duration flare at 5.7 GHz without cleaning the images. The analysis confirms that the source of GLE63 was associated with an event in active region 9742 that comprised two flares. The first flare (04:30 - 05:03 UT) reached a GOES importance of about M1.6. Two microwave sources were observed, whose brightness temperatures at 5.7 GHz exceeded 10 MK. The main flare, up to an importance of M7.1, started at 05:04 UT and occurred in strong magnetic fields. The observed microwave sources reached a brightness temperature of about 250 MK. They were not static. After appearing on the weaker-field periphery of the active region, the microwave sources moved toward each other nearly along the magnetic neutral line, approaching the stronger-field core of the active region, and then moved away from the neutral line like expanding ribbons. These motions rule out an association of the non-thermal microwave sources with a single flaring loop.

Simultaneous Solar Maximum Mission and Very Large Array (VLA) observations of solar active regions

NASA Technical Reports Server (NTRS)

Lang, K. R.

1985-01-01

Simultaneous observations of solar active regions with the Solar Maximum Mission (SMM) Satellite and the Very Large Array (VLA) have been obtained and analyzed. Combined results enhance the scientific return for beyond that expeted from using either SMM or VLA alone. A total of two weeks of simultaneous SMM/VLA data were obtained. The multiple wavelength VLA observations were used to determine the temperature and magnetic structure at different heights within coronal loops. These data are compared with simultaneous SMM observations. Several papers on the subject are in progress. They include VLA observations of compact, transient sources in the transition region; simultaneous SMM/VLA observations of the coronal loops in one active region and the evolution of another one; and sampling of the coronal plasma using thermal cyclotron lines (magnetic field - VLA) and soft X ray spectral lines (electron density and electron temperaure-SMM).

Report of the panel on geopotential fields: Magnetic field, section 9

NASA Technical Reports Server (NTRS)

Achache, Jose J.; Backus, George E.; Benton, Edward R.; Harrison, Christopher G. A.; Langel, Robert A.

1991-01-01

The objective of the NASA Geodynamics program for magnetic field measurements is to study the physical state, processes and evolution of the Earth and its environment via interpretation of measurements of the near Earth magnetic field in conjunction with other geophysical data. The fields measured derive from sources in the core, the lithosphere, the ionosphere, and the magnetosphere. Panel recommendations include initiation of multi-decade long continuous scalar and vector measurements of the Earth's magnetic field by launching a five year satellite mission to measure the field to about 1 nT accuracy, improvement of our resolution of the lithographic component of the field by developing a low altitude satellite mission, and support of theoretical studies and continuing analysis of data to better understand the source physics and improve the modeling capabilities for different source regions.

Possible consequences of absence of "Jupiters" in planetary systems.

PubMed

Wetherill, G W

1994-01-01

The formation of the gas giant planets Jupiter and Saturn probably required the growth of massive approximately 15 Earth-mass cores on a time scale shorter than the approximately 10(7) time scale for removal of nebular gas. Relatively minor variations in nebular parameters could preclude the growth of full-size gas giants even in systems in which the terrestrial planet region is similar to our own. Systems containing "failed Jupiters," resembling Uranus and Neptune in their failure to capture much nebular gas, would be expected to contain more densely populated cometary source regions. They will also eject a smaller number of comets into interstellar space. If systems of this kind were the norm, observation of hyperbolic comets would be unexpected. Monte Carlo calculations of the orbital evolution of region of such systems (the Kuiper belt) indicate that throughout Earth history the cometary impact flux in their terrestrial planet regions would be approximately 1000 times greater than in our Solar System. It may be speculated that this could frustrate the evolution of organisms that observe and seek to understand their planetary system. For this reason our observation of these planets in our Solar System may tell us nothing about the probability of similar gas giants occurring in other planetary systems. This situation can be corrected by observation of an unbiased sample of planetary systems.

Protostellar accretion traced with chemistry. High-resolution C18O and continuum observations towards deeply embedded protostars in Perseus

NASA Astrophysics Data System (ADS)

Frimann, Søren; Jørgensen, Jes K.; Dunham, Michael M.; Bourke, Tyler L.; Kristensen, Lars E.; Offner, Stella S. R.; Stephens, Ian W.; Tobin, John J.; Vorobyov, Eduard I.

2017-06-01

Context. Understanding how accretion proceeds is a key question of star formation, with important implications for both the physical and chemical evolution of young stellar objects. In particular, very little is known about the accretion variability in the earliest stages of star formation. Aims: Our aim is to characterise protostellar accretion histories towards individual sources by utilising sublimation and freeze-out chemistry of CO. Methods: A sample of 24 embedded protostars are observed with the Submillimeter Array (SMA) in context of the large program "Mass Assembly of Stellar Systems and their Evolution with the SMA" (MASSES). The size of the C18O-emitting region, where CO has sublimated into the gas-phase, is measured towards each source and compared to the expected size of the region given the current luminosity. The SMA observations also include 1.3 mm continuum data, which are used to investigate whether or not a link can be established between accretion bursts and massive circumstellar disks. Results: Depending on the adopted sublimation temperature of the CO ice, between 20% and 50% of the sources in the sample show extended C18O emission indicating that the gas was warm enough in the past that CO sublimated and is currently in the process of refreezing; something which we attribute to a recent accretion burst. Given the fraction of sources with extended C18O emission, we estimate an average interval between bursts of 20 000-50 000 yr, which is consistent with previous estimates. No clear link can be established between the presence of circumstellar disks and accretion bursts, however the three closest known binaries in the sample (projected separations <20 AU) all show evidence of a past accretion burst, indicating that close binary interactions may also play a role in inducing accretion variability.

Convection Constraints and Current Sheet Thinning During the Substorm Growth Phase

NASA Astrophysics Data System (ADS)

Otto, A.; Hsieh, M.

2012-12-01

A typical property during the growth phase of geomagnetic substorms is the thinning of the near-Earth current sheet, most pronounced in the region between 6 and 15 RE. We propose that the cause for this current sheet thinning is convection from the midnight tail region to the dayside to replenish magnetospheric magnetic flux that is eroded at the dayside as a result of dayside reconnection. Slow (adiabatic) convection from the near-Earth tail region toward the dayside must conserve the entropy on magnetic field lines. This constraint prohibits a source of magnetic flux from a region further out in the magnetotail. Thus the near-Earth tail region is increasingly depleted of magnetic flux (the Erickson and Wolf [1980] problem) with entropy matching that of flux tubes that are eroded on the dayside. It is proposed that the magnetic flux depletion in the near-Earth tail forces the formation of thin current layers. The process is illustrated and examined by three-dimensional meso-scale MHD simulations. It is shown that the simulations yield a time scale, location, and other general characteristics of the current sheet evolution consistent with observations during the substorm growth phase. The developing thin current sheet is easily destabilized and can undergo localized reconnection events. We present properties of the thinning current sheet, the associated entropy evolution, examples of localized reconnection onset and we discuss the dependence of this process on external parameters such the global reconnection rate.

The formation and evolution of earth-mass dark matter microhalos and their impact on indirect probes of dark matter

NASA Astrophysics Data System (ADS)

Ishiyama, Tomoaki

2013-07-01

Earth-mass dark matter microhalos with a size of ~100 AU are the first structures formed in the universe, if the dark matter of the universe is made of neutralinos. We report the results of ultra-high-resolution cosmological N-body simulations of the formation and evolution of these microhalos. We found that microhalos have the central density cusps of the form ρ ∝ r-1.5, much steeper than the cusps of larger dark halos. The central regions of these microhalos survive the encounters with stars except in the very inner region of the galaxy down to the radius of a few hundreds parsecs from the galactic center. The annihilation signals from the nearest microhalos are observed as gamma-ray point sources (radius less than 1'), with unusually large proper motions of ~0.2 deg per year. Their surface brightnesses are ~10% of that of the galactic center. Their signal-to-noise ratios might be better if they are far from the galactic plane.

The definition, recognition, and interpretation of convergent evolution, and two new measures for quantifying and assessing the significance of convergence.

PubMed

Stayton, C Tristan

2015-08-01

Convergent evolution is an important phenomenon in the history of life. Despite this, there is no common definition of convergence used by biologists. Instead, several conceptually different definitions are employed. The primary dichotomy is between pattern-based definitions, where independently evolved similarity is sufficient for convergence, and process-based definitions, where convergence requires a certain process to produce this similarity. The unacknowledged diversity of definitions can lead to problems in evolutionary research. Process-based definitions may bias researchers away from studying or recognizing other sources of independently evolved similarity, or lead researchers to interpret convergent patterns as necessarily caused by a given process. Thus, pattern-based definitions are recommended. Existing measures of convergence are reviewed, and two new measures are developed. Both are pattern based and conceptually minimal, quantifying nothing but independently evolved similarity. One quantifies the amount of phenotypic distance between two lineages that is closed by subsequent evolution; the other simply counts the number of lineages entering a region of phenotypic space. The behavior of these measures is explored in simulations; both show acceptable Type I and Type II error. The study of convergent evolution will be facilitated if researchers are explicit about working definitions of convergence and adopt a standard toolbox of convergence measures. © 2015 The Author(s). Evolution © 2015 The Society for the Study of Evolution.

Quantifying terrestrial ecosystem carbon dynamics in the Jinsha watershed, Upper Yangtze, China from 1975 to 2000

USGS Publications Warehouse

Zhao, Shuqing; Liu, Shuguang; Yin, Runsheng; Li, Zhengpeng; Deng, Yulin; Tan, Kun; Deng, Xiangzheng; Rothstein, David; Qi, Jiaguo

2010-01-01

Quantifying the spatial and temporal dynamics of carbon stocks in terrestrial ecosystems and carbon fluxes between the terrestrial biosphere and the atmosphere is critical to our understanding of regional patterns of carbon budgets. Here we use the General Ensemble biogeochemical Modeling System to simulate the terrestrial ecosystem carbon dynamics in the Jinsha watershed of China’s upper Yangtze basin from 1975 to 2000, based on unique combinations of spatial and temporal dynamics of major driving forces, such as climate, soil properties, nitrogen deposition, and land use and land cover changes. Our analysis demonstrates that the Jinsha watershed ecosystems acted as a carbon sink during the period of 1975–2000, with an average rate of 0.36 Mg/ha/yr, primarily resulting from regional climate variation and local land use and land cover change. Vegetation biomass accumulation accounted for 90.6% of the sink, while soil organic carbon loss before 1992 led to a lower net gain of carbon in the watershed, and after that soils became a small sink. Ecosystem carbon sink/source patterns showed a high degree of spatial heterogeneity. Carbon sinks were associated with forest areas without disturbances, whereas carbon sources were primarily caused by stand-replacing disturbances. It is critical to adequately represent the detailed fast-changing dynamics of land use activities in regional biogeochemical models to determine the spatial and temporal evolution of regional carbon sink/source patterns.

Renewable Energy Sources in Formation of South Urals Modern Urban Systems

NASA Astrophysics Data System (ADS)

Khudyakov, A. Ju; Shabiev, S. G.

2017-11-01

The article considers the vital problems of renewable energy sources using by the example of the South Urals as a part of a general energy system of the Russian Federation, makes a forecast and gives recommendations on the application of specific technologies: solar energy, wind energy, deep heat energy and geothermal energy. It also considers the influence of the climatology on selection of the development pattern for the alternative energy industry. The article contains an example of wind energy used as a driver of the Karabash company town development in the Chelyabinsk region. The development of the economic energy sector is extremely important for the Russian Federation, both from the point of view of strategic security and from the point of view of integration into a modern development on the principles of Sustainable Development. To provide a full understanding of the role of alternative energy in the energy sector of the country, the article presents the materials illustrating the regional potential in terms of alternative energy sources use. This article is a part of the global research on the settlement system evolution in the South Urals. The authors studied the historical, geographical, demographic, economic characteristics of the region. Finally, a forecast for development at the regional level was made. Some of the aforementioned results were obtained due to the testing research in the learning process of the students from the South Ural State University (national research university).

Studying the laws of software evolution in a long-lived FLOSS project.

PubMed

Gonzalez-Barahona, Jesus M; Robles, Gregorio; Herraiz, Israel; Ortega, Felipe

2014-07-01

Some free, open-source software projects have been around for quite a long time, the longest living ones dating from the early 1980s. For some of them, detailed information about their evolution is available in source code management systems tracking all their code changes for periods of more than 15 years. This paper examines in detail the evolution of one of such projects, glibc, with the main aim of understanding how it evolved and how it matched Lehman's laws of software evolution. As a result, we have developed a methodology for studying the evolution of such long-lived projects based on the information in their source code management repository, described in detail several aspects of the history of glibc, including some activity and size metrics, and found how some of the laws of software evolution may not hold in this case. © 2013 The Authors. Journal of Software: Evolution and Process published by John Wiley & Sons Ltd.

Studying the laws of software evolution in a long-lived FLOSS project

PubMed Central

Gonzalez-Barahona, Jesus M; Robles, Gregorio; Herraiz, Israel; Ortega, Felipe

2014-01-01

Some free, open-source software projects have been around for quite a long time, the longest living ones dating from the early 1980s. For some of them, detailed information about their evolution is available in source code management systems tracking all their code changes for periods of more than 15 years. This paper examines in detail the evolution of one of such projects, glibc, with the main aim of understanding how it evolved and how it matched Lehman's laws of software evolution. As a result, we have developed a methodology for studying the evolution of such long-lived projects based on the information in their source code management repository, described in detail several aspects of the history of glibc, including some activity and size metrics, and found how some of the laws of software evolution may not hold in this case. © 2013 The Authors. Journal of Software: Evolution and Process published by John Wiley & Sons Ltd. PMID:25893093

Distant and Regional Atmospheric Circulation Influences Governing Integrated Water Vapor Transport and the Occurrence of Extreme Precipitation Events

NASA Astrophysics Data System (ADS)

Bosart, L. F.; Papin, P. P.; Bentley, A. M.

2017-12-01

This presentation will show how the evolution of the large-scale and regional-scale atmospheric circulation contributes to the occurrence of extreme precipitation events (EPEs). An EPE requires that tropospheric moisture flux convergence (MFC) and the associated removal of hydrometeors be balanced by moisture replenishment via integrated (water) vapor transport (IVT) to continuously replenish condensed moisture. Moisture source regions may be distant or regional. Distant moisture sources may require the interaction of lower- and upper-level jet streams with a pre-existing mobile atmospheric disturbance to produce sufficient lift to condense moisture. Pre-existing regional moisture sources may require frontal lifting the presence of MFC to condense moisture. In cases of long-range IVT, such as moisture from a western North Pacific typhoon being drawn poleward along an atmospheric river (AR) toward the west coast of North America, moisture may be transported 1000s of kilometers along a low-level jet before a combination of dynamic and orographic lift results in an EPE. Alternatively, in the case of a typical summer warm and humid air mass over the continental United States, unused moisture may exist for several days in this air mass before sufficient MFC associated with a thermally direct mesoscale frontal circulation can concentrate and condense the moisture. In this case, there may be no long-range IVT via ARs. Instead, the atmospheric circulations may evolve to produce sustained MFC associated with mesoscale frontal circulations, especially in the presence of complex terrain, to produce an EPE. During this presentation, examples of EPEs associated with long-range IVT and distant MFC versus EPEs associated with regional MFC and mesoscale frontal circulations will be illustrated.

Rapid rate of control-region evolution in Pacific butterflyfishes (Chaetodontidae).

PubMed

McMillan, W O; Palumbi, S R

1997-11-01

Sequence differences in the tRNA-proline (tRNApro) end of the mitochondrial control-region of three species of Pacific butterflyfishes accumulated 33-43 times more rapidly than did changes within the mitochondrial cytochrome b gene (cytb). Rapid evolution in this region was accompanied by strong transition/transversion bias and large variation in the probability of a DNA substitution among sites. These substitution constraints placed an absolute ceiling on the magnitude of sequence divergence that could be detected between individuals. This divergence "ceiling" was reached rapidly and led to a decay in the relative rate of control-region/cytb b evolution. A high rate of evolution in this section of the control-region of butterflyfishes stands in marked contrast to the patterns reported in some other fish lineages. Although the mechanism underlying rate variation remains unclear, all taxa with rapid evolution in the 5'-end of the control-region showed extreme transition biases. By contrast, in taxa with slower control-region evolution, transitions accumulated at nearly the same rate as transversions. More information is needed to understand the relationship between nucleotide bias and the rate of evolution in the 5'-end of the control-region. Despite strong constraints on sequence change, phylogenetic information was preserved in the group of recently differentiated species and supported the clustering of sequences into three major mtDNA groupings. Within these groups, very similar control-region sequences were widely distributed across the Pacific Ocean and were shared between recognized species, indicating a lack of mitochondrial sequence monophyly among species.

Combining controlled-source seismology and receiver function information to derive 3-D Moho topography for Italy

NASA Astrophysics Data System (ADS)

Spada, M.; Bianchi, I.; Kissling, E.; Agostinetti, N. Piana; Wiemer, S.

2013-08-01

The accurate definition of 3-D crustal structures and, in primis, the Moho depth, are the most important requirement for seismological, geophysical and geodynamic modelling in complex tectonic regions. In such areas, like the Mediterranean region, various active and passive seismic experiments are performed, locally reveal information on Moho depth, average and gradient crustal Vp velocity and average Vp/Vs velocity ratios. Until now, the most reliable information on crustal structures stems from controlled-source seismology experiments. In most parts of the Alpine region, a relatively large number of controlled-source seismology information are available though the overall coverage in the central Mediterranean area is still sparse due to high costs of such experiments. Thus, results from other seismic methodologies, such as local earthquake tomography, receiver functions and ambient noise tomography can be used to complement the controlled-source seismology information to increase coverage and thus the quality of 3-D crustal models. In this paper, we introduce a methodology to directly combine controlled-source seismology and receiver functions information relying on the strengths of each method and in relation to quantitative uncertainty estimates for all data to derive a well resolved Moho map for Italy. To obtain a homogeneous elaboration of controlled-source seismology and receiver functions results, we introduce a new classification/weighting scheme based on uncertainty assessment for receiver functions data. In order to tune the receiver functions information quality, we compare local receiver functions Moho depths and uncertainties with a recently derived well-resolved local earthquake tomography-derived Moho map and with controlled-source seismology information. We find an excellent correlation in the Moho information obtained by these three methodologies in Italy. In the final step, we interpolate the controlled-source seismology and receiver functions information to derive the map of Moho topography in Italy and surrounding regions. Our results show high-frequency undulation in the Moho topography of three different Moho interfaces, the European, the Adriatic-Ionian, and the Liguria-Corsica-Sardinia-Tyrrhenia, reflecting the complexity of geodynamical evolution.

Coupled Source-to-Sink and Geodynamic Modeling of Extensional Basins: A Case Study of the Gulf of Corinth, Greece.

NASA Astrophysics Data System (ADS)

Smithells, R. A.

2015-12-01

Many studies investigate rift evolution with geodynamic models, giving insight into the architecture and morphology of extensional basins. Recent advances in modeling allow better temporal and spatial resolution in surface processes when coupled with geodynamic processes, allowing modeling the interactions between sediment erosion and deposition with rift development. Here we use a combination of dynamic forward modeling and landscape evolution models to determine feedback and interaction of sediment erosion and deposition with rift development and fault localization. The Gulf of Corinth is an ideal basin to study the effect of surface processes on rifting because it can be considered a closed system for sediment erosion and deposition. It is a young rift, not affected by subsequent overprinting and there is a large amount of data from offshore seismic surveys and onshore fieldwork to constrain its evolution. We reconstruct paleo topography of the catchment area by removing the effects of fault activity and sediment erosion. The reconstructed topography is used to model different scenarios for landscape evolution and the results determine the relative importance of regional and fault related uplift and subsidence on the drainage evolution in the Gulf of Corinth. The landscape models are also used to constrain source area and total amount of sediment eroded from the catchment area. The eroded onshore volume and the amount of sediment deposited offshore are compared in order to reconstruct the source-to-sink balance for the Gulf of Corinth. Our results constrain the evolution of the catchment area and timings of drainage reversals that occurred in the fluvial systems of the Gulf of Corinth. Coupled forward tectonic-surface process modeling is used to investigate feedback between rift formation and the surface processes and to determine its role in developing asymmetry and fault migration in an extensional setting. In this study we investigate the effect of a mature sediment routing system on rift development. Our models show that migrating fault activity may be triggered by migration of sediment deposition filling the accommodation space provided by the associated half grabens. The asymmetric development of the rift can be explained by the preferred erosion and deposition of the southern flank of the Gulf of Corinth.

How Dry was too Dry? Evaluating the Impact of Climatic Stress on Prehistoric Human Populations in southern Ethiopia.

NASA Astrophysics Data System (ADS)

Foerster, V. E.; Asrat, A.; Cohen, A. S.; Junginger, A.; Lamb, H. F.; Schaebitz, F.; Trauth, M. H.; Vogelsang, R.

2016-12-01

What role did abrupt climate shifts play in human evolution and the dispersal of Homo sapiens within and beyond the African continent? How did gradual climatic transitions on the other hand affect cultural and technological innovations in the source region of modern humans? In order to evaluate the effect of environmental instability on human evolution, with their cultural and technological innovations, and with their expansion out of Africa, it is essential to understand how the east African climate switches from dry to wet and back to dry. Determining the timespan of both long-term transitions and climate flickers eventually provides the much needed environmental information how much time early humans had to react (evolution, migration, adaption) to the profound changes in their living environment. As a contribution to providing an environmental context to these central questions on human-climate interaction, the Hominin Sites and Paleolakes Drilling Project (HSPDP) has successfully completed coring five fluvio-lacustrine archives of climate change during the last 3.5 Ma in East Africa. The five high-priority areas in Ethiopia and Kenya are located in close proximity to key paleoanthropological sites covering various steps in evolution. Here we present a comparison between the youngest part of our continuous climate reconstruction (temporal resolution of up to 3 years) from the Chew Bahir site in southern Ethiopia and the available archaeological record of human presence in the source region of modern humans for the past 20 ka. The results contribute to test hypotheses on the impact of climatic stress on migration, the role of human decision-making and environmental thresholds (Foerster et al., 2015, 2016). Furthermore, we match key technological innovations in the area with the profound environmental changes during the highly debated mid-Holocene wet-dry transition. Finally, we give a first overview over possible phases of climatic stress during the last >500 ka in the first homeland of modern humans, as a time interval that comprises the transition into the Middle Stone Age as well as the origin and dispersal of Homo sapiens.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vernet, R.

The Bas Congo basin extends from Gabon to Angola and is a prolific oil province where both pre-salt and post salt sources and reservoirs have been found. In the northern part of the basin referred to as the Congo coastal basin, the proven petroleum system is more specific: mature source rocks are found only in pre-salt series whereas by contrast 99 % proven hydrocarbon reserves am located in post-salt traps. Such a system is controlled by the following factors: Source rocks are mostly organic rich shales deposited in a restricted environment developed in a rift prior to the Atlantic Oceanmore » opening; Migration from pre-salt sources to post-salt traps is finalized by local discontinuities of the regional salt layer acting otherwise as a tight seal; Post-salt reservoirs are either carbonates or sands desposited in the evolutive shelf margin developped during Upper Cretaceous; Geometric traps are linked to salt tectonics (mostly turtle-shaped structures); Regional shaly seals are related to transgressive shales best developped during high rise sea level time interval. Stratigraphically, the age of hydrocarbon fields trends are younger and younger from West to East: lower Albian in Nkossa, Upper Albian and lower Cenomanian in Likouala, Yanga, Sendji, Upper Cenomanian in Tchibouela, Turonian in Tchendo, Turanian and Senonian in Emeraude.« less

Aerosol Mapping From Space: Strengths, Limitations, and Applications

NASA Technical Reports Server (NTRS)

Kahn, Ralph

2010-01-01

The aerosol data products from the NASA Earth Observing System's MISR and MODIS instruments provide significant advances in regional and global aerosol optical depth (AOD) mapping, aerosol type measurement, and source plume characterization from space. These products have been and are being used for many applications, ranging from regional air quality assessment, to aerosol air mass type identification and evolution, to wildfire smoke injection height and aerosol transport model validation. However, retrieval uncertainties and coverage gaps still limit the quantitative constraints these satellite data place on some important questions, such as global-scale long-term trends and direct aerosol radiative forcing. Major advances in these areas seem to require a different paradigm, involving the integration of satellite with suborbital data and with models. This presentation will briefly summarize where we stand, and what incremental improvements we can expect, with the current MISR and MODIS aerosol products, and will then elaborate on some initial steps aimed at the necessary integration of satellite data with data from other sources and with chemical transport models.

Evolution of the Large Scale Circulation, Cloud Structure and Regional Water Cycle Associated with the South China Sea Monsoon During May-June, 1998

NASA Technical Reports Server (NTRS)

Lau, William K.-M.; Li, Xiao-Fan

2001-01-01

In this paper, changes in the large-scale circulation, cloud structures and regional water cycle associated with the evolution of the South China Sea (SCS) monsoon in May-June 1998 were investigated using data from the Tropical Rainfall Measuring Mission (TRMM) and field data from the South China Sea Monsoon Experiment (SCSMEX). Results showed that both tropical and extratropical processes strongly influenced the onset and evolution of the SCS monsoon. Prior to the onset of the SCS monsoon, enhanced convective activities associated with the Madden and Julian Oscillation were detected over the Indian Ocean, and the SCS was under the influence of the West Pacific Anticyclone (WPA) with prevailing low level easterlies and suppressed convection. Establishment of low-level westerlies across Indo-China, following the development of a Bay of Bengal depression played an important role in building up convective available potential energy over the SCS. The onset of SCS monsoon appeared to be triggered by the equatorward penetration of extratropical frontal system, which was established over the coastal region of southern China and Taiwan in early May. Convective activities over the SCS were found to vary inversely with those over the Yangtze River Valley (YRV). Analysis of TRMM microwave and precipitation radar data revealed that during the onset phase, convection over the northern SCS consisted of squall-type rain cell embedded in meso-scale complexes similar to extratropical systems. The radar Z-factor intensity indicated that SCS clouds possessed a bimodal distribution, with a pronounced signal (less than 30dBz) at a height of 2-3 km, and another one (less than 25 dBz) at the 8-10 km level, separated by a well-defined melting level indicated by a bright band at around 5-km level. The stratiform-to-convective cloud ratio was approximately 1:1 in the pre-onset phase, but increased to 5:1 in the active phase. Regional water budget calculations indicated that during the active phase, the SCS was a strong sink (E-P much less than 0) of atmospheric moisture, with the primary source of moisture coming from regions further west over Indo-China and the eastern Indian Ocean. Before onset and during the break, the SCS was a moisture source (E-P greater than ) to the overlying atmosphere. In particular, the SCS provided the bulk of moisture to the torrential rain over the YRV in mid-June 1998.

Methods and Systems for Measurement and Estimation of Normalized Contrast in Infrared Thermography

NASA Technical Reports Server (NTRS)

Koshti, Ajay M. (Inventor)

2017-01-01

Methods and systems for converting an image contrast evolution of an object to a temperature contrast evolution and vice versa are disclosed, including methods for assessing an emissivity of the object; calculating an afterglow heat flux evolution; calculating a measurement region of interest temperature change; calculating a reference region of interest temperature change; calculating a reflection temperature change; calculating the image contrast evolution or the temperature contrast evolution; and converting the image contrast evolution to the temperature contrast evolution or vice versa, respectively.

Methods and Systems for Measurement and Estimation of Normalized Contrast in Infrared Thermography

NASA Technical Reports Server (NTRS)

Koshti, Ajay M. (Inventor)

2015-01-01

Methods and systems for converting an image contrast evolution of an object to a temperature contrast evolution and vice versa are disclosed, including methods for assessing an emissivity of the object; calculating an afterglow heat flux evolution; calculating a measurement region of interest temperature change; calculating a reference region of interest temperature change; calculating a reflection temperature change; calculating the image contrast evolution or the temperature contrast evolution; and converting the image contrast evolution to the temperature contrast evolution or vice versa, respectively.

Deformation of allochthonous salt and evolution of related salt-structural systems, eastern Louisiana Gulf Coast

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schuster, D.C.

1996-12-31

Salt tectonics in the northern Gulf of Mexico involves both vertical diapirism and lateral silling or flow of salt into wings and tablets (sheets). Combinations of these two modes of salt deformation, concurrent with sediment loading and salt evacuation, have produced complex structures in the coastal and offshore region of southeastern Louisiana, a prolific oil and gas province. Many large growth faults and salt domes in the study area root into intra-Tertiary salt welds that were formerly occupied by allochthonous salt tablets. Two end-member structural systems involving evacuation of former tabular salt are recognized: roho systems and stepped counter-regional systems.more » Both end-member systems share a similar multi-staged evolution, including (1) initial formation of a south-leaning salt dome or wall sourced from the Jurassic salt level; (2) progressive development into a semi-tabular allochthonous salt body; and (3) subsequent loading, evacuation, and displacement of the tabular salt into secondary domes. In both systems, it is not uncommon to find salt displaced as much as 16-24 km south of its autochthonous source, connected by a horizontal salt weld to an updip, deflated counter-regional feeder. Although both end-member structural systems may originate before loading of allochthonous salt having grossly similar geometry, their final structural configurations after loading and salt withdrawal are distinctly different. Roho systems are characterized by large-displacement, listric, south-dipping growth faults that sole into intra-Tertiary salt welds marked by high-amplitude reflections continuous with residual salt masses. Salt from the former salt tablets has been loaded and squeezed laterally and downdip. Stepped counter-regional systems, in contrast, comprise large salt domes and adjacent large-displacement, north-dipping growth faults that sole into intra-Tertiary salt welds before stepping down again farther north.« less

Microearthquake sequences along the Irpinia normal fault system in Southern Apennines, Italy

NASA Astrophysics Data System (ADS)

Orefice, Antonella; Festa, Gaetano; Alfredo Stabile, Tony; Vassallo, Maurizio; Zollo, Aldo

2013-04-01

Microearthquakes reflect a continuous readjustment of tectonic structures, such as faults, under the action of local and regional stress fields. Low magnitude seismicity in the vicinity of active fault zones may reveal insights into the mechanics of the fault systems during the inter-seismic period and shine a light on the role of fluids and other physical parameters in promoting or disfavoring the nucleation of larger size events in the same area. Here we analyzed several earthquake sequences concentrated in very limited regions along the 1980 Irpinia earthquake fault zone (Southern Italy), a complex system characterized by normal stress regime, monitored by the dense, multi-component, high dynamic range seismic network ISNet (Irpinia Seismic Network). On a specific single sequence, the May 2008 Laviano swarm, we performed accurate absolute and relative locations and estimated source parameters and scaling laws that were compared with standard stress-drops computed for the area. Additionally, from EGF deconvolution, we computed a slip model for the mainshock and investigated the space-time evolution of the events in the sequence to reveal possible interactions among earthquakes. Through the massive analysis of cross-correlation based on the master event scanning of the continuous recording, we also reconstructed the catalog of repeated earthquakes and recognized several co-located sequences. For these events, we analyzed the statistical properties, location and source parameters and their space-time evolution with the aim of inferring the processes that control the occurrence and the size of microearthquakes in a swarm.

TEMPORAL EVOLUTION OF MULTIPLE EVAPORATING RIBBON SOURCES IN A SOLAR FLARE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Graham, D. R.; Cauzzi, G., E-mail: dgraham@arcetri.astro.it

2015-07-10

We present new results from the Interface Region Imaging Spectrograph (IRIS) showing the dynamic evolution of chromospheric evaporation and condensation in a flare ribbon, with the highest temporal and spatial resolution to date. IRIS observed the entire impulsive phase of the X-class flare SOL2014-09-10T17:45 using a 9.4 s cadence “sit-and-stare” mode. As the ribbon brightened successively at new positions along the slit, a unique impulsive phase evolution was observed for many tens of individual pixels in both coronal and chromospheric lines. Each activation of a new footpoint displays the same initial coronal upflows of up to ∼300 km s{sup −1}more » and chromospheric downflows up to 40 km s{sup −1}. Although the coronal flows can be delayed by over 1 minute with respect to those in the chromosphere, the temporal evolution of flows is strikingly similar between all pixels and consistent with predictions from hydrodynamic flare models. Given the large sample of independent footpoints, we conclude that each flaring pixel can be considered a prototypical, “elementary” flare kernel.« less

Regional magnetic anomaly constraints on continental rifting

NASA Technical Reports Server (NTRS)

Vonfrese, R. R. B.; Hinze, W. J.; Olivier, R.; Bentley, C. R.

1985-01-01

Radially polarized MAGSAT anomalies of North and South America, Europe, Africa, India, Australia and Antarctica demonstrate remarkably detailed correlation of regional magnetic lithospheric sources across rifted margins when plotted on a reconstruction of Pangea. These major magnetic features apparently preserve their integrity until a superimposed metamorphoric event alters the magnitude and pattern of the anomalies. The longevity of continental scale magnetic anomalies contrasts markedly with that of regional gravity anomalies which tend to reflect predominantly isostatic adjustments associated with neo-tectonism. First observed as a result of NASA's magnetic satellite programs, these anomalies provide new and fundamental constraints on the geologic evolution and dynamics of the continents and oceans. Accordingly, satellite magnetic observations provide a further tool for investigating continental drift to compliment other lines of evidence in paleoclimatology, paleontology, paleomagnetism, and studies of the radiometric ages and geometric fit of the continents.

Background field removal using a region adaptive kernel for quantitative susceptibility mapping of human brain

NASA Astrophysics Data System (ADS)

Fang, Jinsheng; Bao, Lijun; Li, Xu; van Zijl, Peter C. M.; Chen, Zhong

2017-08-01

Background field removal is an important MR phase preprocessing step for quantitative susceptibility mapping (QSM). It separates the local field induced by tissue magnetic susceptibility sources from the background field generated by sources outside a region of interest, e.g. brain, such as air-tissue interface. In the vicinity of air-tissue boundary, e.g. skull and paranasal sinuses, where large susceptibility variations exist, present background field removal methods are usually insufficient and these regions often need to be excluded by brain mask erosion at the expense of losing information of local field and thus susceptibility measures in these regions. In this paper, we propose an extension to the variable-kernel sophisticated harmonic artifact reduction for phase data (V-SHARP) background field removal method using a region adaptive kernel (R-SHARP), in which a scalable spherical Gaussian kernel (SGK) is employed with its kernel radius and weights adjustable according to an energy "functional" reflecting the magnitude of field variation. Such an energy functional is defined in terms of a contour and two fitting functions incorporating regularization terms, from which a curve evolution model in level set formation is derived for energy minimization. We utilize it to detect regions of with a large field gradient caused by strong susceptibility variation. In such regions, the SGK will have a small radius and high weight at the sphere center in a manner adaptive to the voxel energy of the field perturbation. Using the proposed method, the background field generated from external sources can be effectively removed to get a more accurate estimation of the local field and thus of the QSM dipole inversion to map local tissue susceptibility sources. Numerical simulation, phantom and in vivo human brain data demonstrate improved performance of R-SHARP compared to V-SHARP and RESHARP (regularization enabled SHARP) methods, even when the whole paranasal sinus regions are preserved in the brain mask. Shadow artifacts due to strong susceptibility variations in the derived QSM maps could also be largely eliminated using the R-SHARP method, leading to more accurate QSM reconstruction.

Background field removal using a region adaptive kernel for quantitative susceptibility mapping of human brain.

PubMed

Fang, Jinsheng; Bao, Lijun; Li, Xu; van Zijl, Peter C M; Chen, Zhong

2017-08-01

Background field removal is an important MR phase preprocessing step for quantitative susceptibility mapping (QSM). It separates the local field induced by tissue magnetic susceptibility sources from the background field generated by sources outside a region of interest, e.g. brain, such as air-tissue interface. In the vicinity of air-tissue boundary, e.g. skull and paranasal sinuses, where large susceptibility variations exist, present background field removal methods are usually insufficient and these regions often need to be excluded by brain mask erosion at the expense of losing information of local field and thus susceptibility measures in these regions. In this paper, we propose an extension to the variable-kernel sophisticated harmonic artifact reduction for phase data (V-SHARP) background field removal method using a region adaptive kernel (R-SHARP), in which a scalable spherical Gaussian kernel (SGK) is employed with its kernel radius and weights adjustable according to an energy "functional" reflecting the magnitude of field variation. Such an energy functional is defined in terms of a contour and two fitting functions incorporating regularization terms, from which a curve evolution model in level set formation is derived for energy minimization. We utilize it to detect regions of with a large field gradient caused by strong susceptibility variation. In such regions, the SGK will have a small radius and high weight at the sphere center in a manner adaptive to the voxel energy of the field perturbation. Using the proposed method, the background field generated from external sources can be effectively removed to get a more accurate estimation of the local field and thus of the QSM dipole inversion to map local tissue susceptibility sources. Numerical simulation, phantom and in vivo human brain data demonstrate improved performance of R-SHARP compared to V-SHARP and RESHARP (regularization enabled SHARP) methods, even when the whole paranasal sinus regions are preserved in the brain mask. Shadow artifacts due to strong susceptibility variations in the derived QSM maps could also be largely eliminated using the R-SHARP method, leading to more accurate QSM reconstruction. Copyright © 2017. Published by Elsevier Inc.

ngVLA Key Science Goal 2: Probing the Initial Conditions for Planetary Systems and Life with Astrochemistry

NASA Astrophysics Data System (ADS)

McGuire, Brett; ngVLA Science Working Group 1

2018-01-01

One of the most challenging aspects in understanding the origin and evolution of planets and planetary systems is tracing the influence of chemistry on the physical evolution of a system from a molecular cloud to a solar system. Existing facilities have already shown the stunning degree of molecular complexity present in these systems. The unique combination of sensitivity and spatial resolution offered by the ngVLA will permit the observation of both highly complex and very low-abundance chemical species that are exquisitely sensitive to the physical conditions and evolutionary history of their sources, which are out of reach of current observatories. In turn, by understanding the chemical evolution of these complex molecules, unprecedentedly detailed astrophysical insight can be gleaned from these astrochemical observations.This poster will overview a number of key science goals in astrochemistry which will be enabled by the ngVLA, including:1) imaging of the deepest, densest regions in protoplanetary disks and unveiling the physical history through isotopic ratios2) probing the ammonia snow line in these disks, thought to be the only viable tracer of the water snowline3) observations of the molecular content of giant planet atmospheres4) detections of new, complex molecules, potentially including the simplest amino acids and sugars5) tracing the origin of chiral excess in star-forming regions

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.

An investigation of coronal active region loop structures using AS&E rocket X-ray images

NASA Technical Reports Server (NTRS)

Webb, D. F.

1983-01-01

Simultaneous high spatial resolution observations at 6 cm in soft X-rays, in photospheric magnetograms, and in optical filtergrams were used to compare the most intense sources of centimetric emission in two active regions to coronal loops, sunspots, chromospheric structures, and photospheric magnetic fields. Results show that the majority of the bright microwave components are not associated with sunspots or X-ray emission. A nonthermal mechanism appears necessary to explain the brightest microwave components, discrete regions of continuous particle acceleration may be common in active regions. Studies of the plasma parameters of selected loops imply that the radio emission is consistent with gyro-resonance absorption at the third and fourth harmonic, at least from part of each loop. Results are presented for: (1) X-ray and microwave observations of active regions; (2) comparison of coronal holes observed in soft X-rays and Hel 10830 A spectrosheliograms; and (3) the reappearance of polar coronal holes and the evolution of the solar magnetic field.

Successive Two-sided Loop Jets Caused by Magnetic Reconnection between Two Adjacent Filamentary Threads

NASA Astrophysics Data System (ADS)

Tian, Zhanjun; Liu, Yu; Shen, Yuandeng; Elmhamdi, Abouazza; Su, Jiangtao; Liu, Ying D.; Kordi, Ayman. S.

2017-08-01

We present observational analysis of two successive two-sided loop jets observed by the ground-based New Vacuum Solar Telescope and the space-borne Solar Dynamics Observatory. The two successive two-sided loop jets manifested similar evolution processes and both were associated with the interaction of two small-scale adjacent filamentary threads, magnetic emerging, and cancellation processes at the jet’s source region. High temporal and high spatial resolution observations reveal that the two adjacent ends of the two filamentary threads are rooted in opposite magnetic polarities within the source region. The two threads approached each other, and then an obvious brightening patch is observed at the interaction position. Subsequently, a pair of hot plasma ejections are observed heading in opposite directions along the paths of the two filamentary threads at a typical speed for two-sided loop jets of the order 150 km s-1. Close to the end of the second jet, we report the formation of a bright hot loop structure at the source region, which suggests the formation of new loops during the interaction. Based on the observational results, we propose that the observed two-sided loop jets are caused by magnetic reconnection between the two adjacent filamentary threads, largely different from the previous scenario that a two-sided loop jet is generated by magnetic reconnection between an emerging bipole and the overlying horizontal magnetic fields.

Intermittent tremor migrations beneath Guerrero, Mexico, and implications for fault healing within the slow slip zone

NASA Astrophysics Data System (ADS)

Peng, Yajun; Rubin, Allan M.

2017-01-01

Slow slip events exhibit significant complexity in slip evolution and variations in recurrence intervals. Behavior that varies systematically with recurrence interval is likely to reflect different extents of fault healing between these events. Here we use high-resolution tremor catalogs beneath Guerrero, Mexico, to investigate the mechanics of slow slip. We observe complex tremor propagation styles, including rapid tremor migrations propagating either along the main tremor front or backward, reminiscent of those in northern Cascadia. We also find many migrations that originate well behind the front and repeatedly occupy the same source region during a tremor episode, similar to those previously reported from Shikoku, Japan. These migrations could be driven by slow slip in the surrounding regions, with recurrence intervals possibly modulated by tides. The propagation speed of these migrations decreases systematically with time since the previous migration over the same source area. Tremor amplitudes seem consistent with changes in the propagation speeds being controlled primarily by changes in the slip speeds. One interpretation is that the high propagation speeds and inferred high slip speeds during the migrations with short recurrence intervals are caused by incomplete healing within the host rock adjacent to the shear zone, which could lead to high permeability and reduced dilatant strengthening of the fault gouge. Similar processes may operate in other slow slip source regions such as Cascadia.

On the evolution of clustering of 24-μm-selected galaxies

NASA Astrophysics Data System (ADS)

Magliocchetti, M.; Cirasuolo, M.; McLure, R. J.; Dunlop, J. S.; Almaini, O.; Foucaud, S.; de Zotti, G.; Simpson, C.; Sekiguchi, K.

2008-01-01

This paper investigates the clustering properties of a complete sample of 1041 24-μm-selected sources brighter than F24μm = 400μJy in the overlapping region between the Spitzer Wide-Area Infrared Extragalactic (SWIRE) and UKIRT Infrared Deep Sky Survey (UKIDSS) Ultra Deep Survey (UDS) surveys. With the help of photometric redshift determinations we have concentrated on the two interval ranges z = [0.6-1.2] (low-z sample) and z >= 1.6 (high-z sample) as it is in these regions were we expect the mid-infrared (IR) population to be dominated by intense dust-enshrouded activity such as star formation and black hole accretion. Investigations of the angular correlation function produce an amplitude A ~ 0.010 for the high-z sample and A ~ 0.0055 for the low-z one. The corresponding correlation lengths are r0 = 15.9+2.9-3.4 and 8.5+1.5-1.8Mpc, showing that the high-z population is more strongly clustered. Comparisons with physical models for the formation and evolution of large-scale structure reveal that the high-z sources are exclusively associated with very massive (M >~ 1013Msolar) haloes, comparable to those which locally host groups-to-clusters of galaxies and are very common within such (rare) structures. Conversely, lower z galaxies are found to reside in smaller haloes (Mmin ~ 1012Msolar) and to be very rare in such systems. On the other hand, mid-IR photometry shows that the low-z and high-z samples include similar objects and probe a similar mixture of active galactic nucleus (AGN) and star-forming galaxies. While recent studies have determined a strong evolution of the 24-μm luminosity function between z ~ 2 and 0, they cannot provide information on the physical nature of such an evolution. Our clustering results instead indicate that this is due to the presence of different populations of objects inhabiting different structures, as active systems at z <~ 1.5 are found to be exclusively associated with low-mass galaxies, while very massive sources appear to have concluded their active phase before this epoch. Finally, we note that the small-scale clustering data seem to require steep (ρ ~ r-3) profiles for the distribution of galaxies within their haloes. This is suggestive of close encounters and/or mergers which could strongly favour both AGN and star formation activity.

Star formation towards the Galactic H II region RCW 120. Herschel observations of compact sources

NASA Astrophysics Data System (ADS)

Figueira, M.; Zavagno, A.; Deharveng, L.; Russeil, D.; Anderson, L. D.; Men'shchikov, A.; Schneider, N.; Hill, T.; Motte, F.; Mège, P.; LeLeu, G.; Roussel, H.; Bernard, J.-P.; Traficante, A.; Paradis, D.; Tigé, J.; André, P.; Bontemps, S.; Abergel, A.

2017-04-01

Context. The expansion of H II regions can trigger the formation of stars. An overdensity of young stellar objects is observed at the edges of H II regions but the mechanisms that give rise to this phenomenon are not clearly identified. Moreover, it is difficult to establish a causal link between H II -region expansion and the star formation observed at the edges of these regions. A clear age gradient observed in the spatial distribution of young sources in the surrounding might be a strong argument in favor of triggering. Aims: We aim to characterize the star formation observed at the edges of H II regions by studying the properties of young stars that form there. We aim to detect young sources, derive their properties and their evolution stage in order to discuss the possible causal link between the first-generation massive stars that form the H II region and the young sources observed at their edges. Methods: We have observed the Galactic H II region RCW 120 with Herschel PACS and SPIRE photometers at 70, 100, 160, 250, 350 and 500 μm. We produced temperature and H2 column density maps and use the getsources algorithm to detect compact sources and measure their fluxes at Herschel wavelengths. We have complemented these fluxes with existing infrared data. Fitting their spectral energy distributions with a modified blackbody model, we derived their envelope dust temperature and envelope mass. We computed their bolometric luminosities and discuss their evolutionary stages. Results: The overall temperatures of the region (without background subtraction) range from 15 K to 24 K. The warmest regions are observed towards the ionized gas. The coldest regions are observed outside the ionized gas and follow the emission of the cold material previously detected at 870 μm and 1.3 mm. The H2 column density map reveals the distribution of the cold medium to be organized in filaments and highly structured. Column densities range from 7 × 1021 cm-2 up to 9 × 1023 cm-2 without background subtraction. The cold regions observed outside the ionized gas are the densest and host star formation when the column density exceeds 2 × 1022 cm-2. The most reliable 35 compact sources are discussed. Using existing CO data and morphological arguments we show that these sources are likely to be associated with the RCW 120 region. These sources' volume densities range from 2 × 105 cm-3 to 108 cm-3. Five sources have envelope masses larger than 50 M⊙ and are all observed in high column density regions (>7 × 1022 cm-2). We find that the evolutionary stage of the sources primarily depends on the density of their hosting condensation and is not correlated with the distance to the ionizing star. Conclusions: The Herschel data, with their unique sampling of the far infrared domain, have allowed us to characterize the properties of compact sources observed towards RCW 120 for the first time. We have also been able to determine the envelope temperature, envelope mass and evolutionary stage of these sources. Using these properties we have shown that the density of the condensations that host star formation is a key parameter of the star-formation history, irrespective of their projected distance to the ionizing stars. Table A.1 is also available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/600/A93Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

Molecular epidemiology and phylogenetic analysis of human papillomavirus infection in women with cervical lesions and cancer from the coastal region of Ecuador.

PubMed

Bedoya-Pilozo, Cesar H; Medina Magües, Lex G; Espinosa-García, Maylen; Sánchez, Martha; Parrales Valdiviezo, Johanna V; Molina, Denisse; Ibarra, María A; Quimis-Ponce, María; España, Karool; Párraga Macias, Karla E; Cajas Flores, Nancy V; Orlando, Solon A; Robalino Penaherrera, Jorge A; Chedraui, Peter; Escobar, Saul; Loja Chango, Rita D; Ramirez-Morán, Cecibel; Espinoza-Caicedo, Jasson; Sánchez-Giler, Sunny; Limia, Celia M; Alemán, Yoan; Soto, Yudira; Kouri, Vivian; Culasso, Andrés C A; Badano, Inés

The aim of the present study was to gather information regarding the molecular epidemiology of Human papillomavirus (HPV) and related risk factors in a group of women with low- and high-grade cervical lesions and cancer from the coastal region of Ecuador. In addition, we studied the evolution of HPV variants from the most prevalent types and provided a temporal framework for their emergence, which may help to trace the source of dissemination within the region. We analyzed 166 samples, including 57 CIN1, 95 CIN2/3 and 14 cancer cases. HPV detection and typing was done by PCR-sequencing (MY09/MY11). HPV variants and estimation of the time to most recent common ancestor (tMRCA) was assessed through phylogeny and coalescence analysis. HPV DNA was found in 54.4% of CIN1, 74.7% of CIN2/3 and 78.6% of cancer samples. HPV16 (38.9%) and HPV58 (19.5%) were the most prevalent types. Risk factors for the development of cervical lesions/cancer were the following: three or more pregnancies (OR=4.3), HPV infection (OR=3.7 for high-risk types; OR=3.5 for HPV16), among others. With regard to HPV evolution, HPV16 isolates belonged to lineages A (69%) and D (31%) whereas HPV58 isolates belonged only to lineage A. The period of emergence of HPV16 was in association with human populations (tMRCA=91052 years for HPV16A and 27000 years for HPV16D), whereas HPV58A preceded Homo sapiens evolution (322257 years). This study provides novel data on HPV epidemiology and evolution in Ecuador, which will be fundamental in the vaccine era. Copyright © 2017 Asociación Argentina de Microbiología. Publicado por Elsevier España, S.L.U. All rights reserved.

Transport Mechanisms Governing initial Leading-Edge Vortex Development on a Pitching Wing

NASA Astrophysics Data System (ADS)

Wabick, Kevin; Berdon, Randall; Buchholz, James; Johnson, Kyle; Thurow, Brian

2017-11-01

The formation and evolution of Leading Edge Vortices (LEVs) are ubiquitous in natural fliers and maneuvering wings, and have a profound impact on aerodynamic loads. The formation of an LEV is experimentally investigated on a pitching flat-plate wing of aspect-ratio 2, and dimensionless pitch rates of k = Ωc / 2 U of 0.1, 0.2, and 0.5, at a Reynolds number of 104. The sources and sinks of vorticity that contribute to the growth and evolution of the LEV are investigated at spanwise regions of interest, and their relative balance is compared to other wing kinematics, and the case of a two-dimensional pitching wing. This work is supported by the Air Force Office of Scientific Research (Grant Number FA9550-16-1-0107, Dr. Douglas Smith, program manager).

The evolution of volcanism, tectonics, and volatiles on Mars - An overview of recent progress

NASA Technical Reports Server (NTRS)

Zimbelman, James R.; Solomon, Sean C.; Sharpton, Virgil L.

1991-01-01

Significant results of the 'Mars: Evolution of Volcanism, Tectonics, and Volatiles' (MEVTV) project are presented. The data for the project are based on geological mapping from the Viking images, petrologic and chemical analyses of SNC meteorites, and both mapping and temporal grouping of major fault systems. The origin of the planet's crustal dichotomy is examined in detail, the kinematics and formation of wrinkle ridges are discussed, and some new theories are set forth. Because the SNC meteorites vary petrologically and isotopically, the sources of the parental Martian magma are heterogeneous. Transcurrent faulting coupled with the extensional strains that form Valles Marineris suggest early horizontal movement of lithospheric blocks. A theory which connects the formation of the crustal dichotomy to the Tharsis region associates the horizontal motions with plate tectonics that generated a new lithosphere.

Optical design for CETUS: a wide-field 1.5m aperture UV payload being studied for a NASA probe class mission study

NASA Astrophysics Data System (ADS)

Woodruff, Robert A.; Hull, Tony; Heap, Sara R.; Danchi, William; Kendrick, Stephen E.; Purves, Lloyd

2017-09-01

We are developing a NASA Headquarters selected Probe-class mission concept called the Cosmic Evolution Through UV Spectroscopy (CETUS) mission, which includes a 1.5-m aperture diameter large field-of-view (FOV) telescope optimized for UV imaging, multi-object spectroscopy, and point-source spectroscopy. The optical system includes a Three Mirror Anastigmatic (TMA) telescope that simultaneously feeds three separate scientific instruments: the near-UV (NUV) Multi-Object Spectrograph (MOS) with a next-generation Micro-Shutter Array (MSA); the two-channel camera covering the far-UV (FUV) and NUV spectrum; and the point-source spectrograph covering the FUV and NUV region with selectable R 40,000 echelle modes and R 2,000 first order modes. The optical system includes fine guidance sensors, wavefront sensing, and spectral and flat-field in-flight calibration sources. This paper will describe the current optical design of CETUS.

Optical design for CETUS: a wide-field 1.5m aperture UV payload being studied for a NASA probe class mission study

NASA Astrophysics Data System (ADS)

Woodruff, Robert; Robert Woodruff, Goddard Space Flight Center, Kendrick Optical Consulting

2018-01-01

We are developing a NASA Headquarters selected Probe-class mission concept called the Cosmic Evolution Through UV Spectroscopy (CETUS) mission, which includes a 1.5-m aperture diameter large field-of-view (FOV) telescope optimized for UV imaging, multi-object spectroscopy, and point-source spectroscopy. The optical system includes a Three Mirror Anastigmatic (TMA) telescope that simultaneously feeds three separate scientific instruments: the near-UV (NUV) Multi-Object Spectrograph (MOS) with a next-generation Micro-Shutter Array (MSA); the two-channel camera covering the far-UV (FUV) and NUV spectrum; and the point-source spectrograph covering the FUV and NUV region with selectable R~ 40,000 echelle modes and R~ 2,000 first order modes. The optical system includes fine guidance sensors, wavefront sensing, and spectral and flat-field in-flight calibration sources. This paper will describe the current optical design of CETUS.

Herschel observations of the Galactic H II region RCW 79

NASA Astrophysics Data System (ADS)

Liu, Hong-Li; Figueira, Miguel; Zavagno, Annie; Hill, Tracey; Schneider, Nicola; Men'shchikov, Alexander; Russeil, Delphine; Motte, Frédérique; Tigé, Jérémy; Deharveng, Lise; Anderson, Loren D.; Li, Jin-Zeng; Wu, Yuefang; Yuan, Jing-Hua; Huang, Maohai

2017-06-01

Context. Triggered star formation around H II regions could be an important process. The Galactic H II region RCW 79 is a prototypical object for triggered high-mass star formation. Aims: We aim to obtain a census of the young stellar population observed at the edges of the H II region and to determine the properties of the young sources in order to characterize the star formation processes that take place at the edges of this ionized region. Methods: We take advantage of Herschel data from the surveys HOBYS, "Evolution of Interstellar Dust", and Hi-Gal to extract compact sources. We use the algorithm getsources. We complement the Herschel data with archival 2MASS, Spitzer, and WISE data to determine the physical parameters of the sources (e.g., envelope mass, dust temperature, and luminosity) by fitting the spectral energy distribution. Results: We created the dust temperature and column density maps along with the column density probability distribution function (PDF) for the entire RCW 79 region. We obtained a sample of 50 compact sources in this region, 96% of which are situated in the ionization-compressed layer of cold and dense gas that is characterized by the column density PDF with a double-peaked lognormal distribution. The 50 sources have sizes of 0.1-0.4 pc with a typical value of 0.2 pc, temperatures of 11-26 K, envelope masses of 6-760 M⊙, densities of 0.1-44 × 105 cm-3, and luminosities of 19-12 712 L⊙. The sources are classified into 16 class 0, 19 intermediate, and 15 class I objects. Their distribution follows the evolutionary tracks in the diagram of bolometric luminosity versus envelope mass (Lbol-Menv) well. A mass threshold of 140 M⊙, determined from the Lbol-Menv diagram, yields 12 candidate massive dense cores that may form high-mass stars. The core formation efficiency (CFE) for the 8 massive condensations shows an increasing trend of the CFE with density. This suggests that the denser the condensation, the higher the fraction of its mass transformation into dense cores, as previously observed in other high-mass star-forming regions. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.Final reduced data and maps used in the paper (FITS format) are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/602/A95

Distances, Kinematics, And Structure Of The Orion Complex

NASA Astrophysics Data System (ADS)

Kounkel, Marina; Hartmann, Lee

2018-01-01

I present an analysis of the structure and kinematics of the Orion Molecular Cloud Complex in an effort to better characterize the dynamical state of the closest region of ongoing massive star formation. I measured stellar parallax and proper motions with <5% uncertainty using radio VLBI observations of non-thermally-emitting sources located in various star forming regions within the Orion Complex. This includes the first direct distance measurements for sources that are located outside of the Orion Nebula. I identified a number of binary systems in the VLBI dataset and fitted their orbital motion, which allows for the direct measurement of the masses of the individual components. Additionally, I have identified several stars that have been ejected from the Orion Nebula due to strong gravitational interactions with the most massive members. I complemented the parallax and proper motion measurements with the observations of optical radial velocities of the stars toward the Orion Complex, probing the histories of both dynamic evolution and star formation in the region, providing a 6-dimensional model of the Complex. These observations can serve as a baseline for comparison of the upcoming results from the Gaia space telescope

A global geochemical model for the evolution of the mantle

NASA Technical Reports Server (NTRS)

Anderson, D. L.

1979-01-01

It is proposed that the upper mantle transition region, 220 to 670 km, is composed of eclogite which has been derived from primitive mantle by about 20 percent partial melting and that this is the source and sink of oceanic crust. The remainder of the upper mantle is garnet peridotite which is the source of continental basalts and hotspot magmas. This region is enriched in incompatible elements by hydrous and CO2 rich metasomatic fluids which have depleted the underlying layers in the L.I.L. elements and L.R.E.E. The volatiles make this a low-velocity, high attenuation, low viscosity region. The eclogite layer is internally heated and its controls the convection pattern in the upper mantle. Plate tectonics is intermittent. The continental thermal anomaly at a depth of 150-220 km triggers kimberlite and carbonatite activity, alkali and flood basalt volcanism, vertical tectonics and continental breakup. Hot spots remain active after the continents leave and build the oceanic islands. Mantle plumes rise from a depth of about 220 km. Midocean ridge basalts rise from the depleted layer below this depth. Material from this layer can also be displaced upwards by subducted oceanic lithosphere to form back-arc basins.

Characterisation of the properties of a negative hydrogen ion beam by several beam diagnostic techniques

NASA Astrophysics Data System (ADS)

Maurizio, R.; Fantz, U.; Bonomo, F.; Serianni, G.

2016-06-01

The beam properties of the BATMAN negative ion source, which is the prototype of one module of the source for the ITER neutral beam injection system, are characterised by means of three diagnostic techniques: beam emission spectroscopy (BES), the experimental calorimeter mini-STRIKE and a copper calorimeter. The main beam parameters—beam divergence, homogeneity and top-bottom asymmetries—are studied in different operational scenarios: with different magnetic filter field setups, source settings and with different gases (hydrogen or deuterium). Among all dependences, the influence of the magnetic field configuration on the beam and the evolution of the beam features during some conditioning days are investigated in detail. Data show that the stronger the filter field in the beam region, the higher the beam top-bottom asymmetry—likely a v× B effect. During the conditioning of the source, such vertical beam asymmetry increases as well, suggesting an inhomogeneous H -production at the first grid of the extraction system.

Combining measurements and modelling to quantify the contribution of atmospheric fallout, local industry and road traffic to PAH stocks in contrasting catchments.

PubMed

Gateuille, David; Evrard, Olivier; Lefevre, Irène; Moreau-Guigon, Elodie; Alliot, Fabrice; Chevreuil, Marc; Mouchel, Jean-Marie

2014-06-01

Various sources supply PAHs that accumulate in soils. The methodology we developed provided an evaluation of the contribution of local sources (road traffic, local industries) versus remote sources (long range atmospheric transport, fallout and gaseous exchanges) to PAH stocks in two contrasting subcatchments (46-614 km²) of the Seine River basin (France). Soil samples (n = 336) were analysed to investigate the spatial pattern of soil contamination across the catchments and an original combination with radionuclide measurements provided new insights into the evolution of the contamination with depth. Relationships between PAH concentrations and the distance to the potential sources were modelled. Despite both subcatchments are mainly rural, roadside areas appeared to concentrate 20% of the contamination inside the catchment while a local industry was found to be responsible for up to 30% of the stocks. Those results have important implications for understanding and controlling PAH contamination in rural areas of early-industrialized regions. Copyright © 2014 Elsevier Ltd. All rights reserved.

K-Rich Basaltic Sources beneath Ultraslow Spreading Central Lena Trough in the Arctic Ocean

NASA Astrophysics Data System (ADS)

Ling, X.; Snow, J. E.; Li, Y.

2016-12-01

Magma sources fundamentally influence accretion processes at ultraslow spreading ridges. Potassium enriched Mid-Ocean Ridge Basalt (K-MORB) was dredged from the central Lena Trough (CLT) in the Arctic Ocean (Nauret et al., 2011). Its geochemical signatures indicate a heterogeneous mantle source with probable garnet present under low pressure. To explore the basaltic mantle sources beneath the study area, multiple models are carried out predicting melting sources and melting P-T conditions in this study. P-T conditions are estimated by the experimental derived thermobarometer from Hoang and Flower (1998). Batch melting model and major element model (AlphaMELTs) are used to calculate the heterogeneous mantle sources. The modeling suggests phlogopite is the dominant H2O-K bearing mineral in the magma source. 5% partial melting of phlogopite and amphibole mixing with depleted mantle (DM) melt is consistent with the incompatible element pattern of CLT basalt. P-T estimation shows 1198-1212oC/4-7kbar as the possible melting condition for CLT basalt. Whereas the chemical composition of north Lena Trough (NLT) basalt is similar to N-MORB, and the P-T estimation corresponds to 1300oC normal mantle adiabat. The CLT basalt bulk composition is of mixture of 40% of the K-MORB endmember and an N-MORB-like endmember similar to NLT basalt. Therefore the binary mixing of the two endmembers exists in the CLT region. This kind of mixing infers to the tectonic evolution of the region, which is simultaneous to the Arctic Ocean opening.

Reconstructing the Historical Series of Plant Functional Types in the Three-River Headwaters Region in China

NASA Astrophysics Data System (ADS)

Mao, X.; Li, T.

2016-12-01

This study uses a physiological biome model to reconstruct the 5910 years historical plant functional type series based on the mechanisms about how environmental constraints affect plant growths. The study area is the Three-Rivers Source Headwaters Region (TRHR) in the south of Qinghai Province of China, which is the source area of the Yangtse River, Yellow River, and Lantsang River, with mean altitude above 4000 meters. The environmental constraints we use are temperature and precipitation. Our results demonstrate that there are only three kinds of biomes existing in this area in the history: the Cool Grass/Shrub, Tundra, and Semidesert. The evolutions of biomes are ruled by two basic patterns. The first is the precipitation driving interconversion of the Semidesert and Tundra and the conversion from the Cool Grass/Shrub to the Semidesert. The second is the temperature driving interconversion of the Tundra and Cool Grass/Shrub. The conversion from the Semidesert to the Cool Grass/Shrub can be generated by the permutations of the first process and the second process. The frequency of the first mode is far higher than the second one, which means that precipitation plays a more active role in the biome evolutions while the temperature makes a long and stable influence on these processes. In the spatial and temporal plant type series generated above, we find that the proportion of the area covered by high quality plants (the Cool Grass/Shrub and Tundra) in around 600 AD is higher than most of other periods in the history, which may led to the rise of the Tibetan Empire. The proportion above, however, decreased sharply in around 1600 AD, which was caused by the Little Ice Age. From this research, we can find the influences of major climatic events on the plant distribution, and understand the interaction or co-evolution of climates and plants more clearly. This study will help us protect our environment more scientifically and with a clearer direction.

Modelling urban δ13C variations in the Greater Toronto Area

NASA Astrophysics Data System (ADS)

Pugliese, S.; Vogel, F. R.; Murphy, J. G.; Worthy, D. E. J.; Zhang, J.; Zheng, Q.; Moran, M. D.

2015-12-01

Even in urbanized regions, carbon dioxide (CO2) emissions are derived from a variety of biogenic and anthropogenic sources and are influenced by atmospheric transport across borders. As policies are introduced to reduce the emission of CO2, there is a need for independent verification of emissions reporting. In this work, we aim to use carbon isotope (13CO2 and 12CO2) simulations in combination with atmospheric measurements to distinguish between CO2 sources in the Greater Toronto Area (GTA), Canada. This is being done by developing an urban δ13C framework based on existing CO2 emission data and forward modelling using a chemistry transport model, CHIMERE. The framework is designed to use region specific δ13C signatures of the dominant CO2 sources together with a CO2 inventory at a fine spatial and temporal resolution; the product is compared against highly accurate 13CO2 and 12CO2 ambient data. The strength of this framework is its potential to estimate both locally produced and regionally transported CO­2. Locally, anthropogenic CO­2 in urban areas is often derived from natural gas combustion (for heating) and gasoline/diesel combustion (for transportation); the isotopic signatures of these processes are significantly different (approximately d13CVPDB = -40 ‰ and -26 ‰ respectively) and can be used to infer their relative contributions. Furthermore, the contribution of transported CO2 can also be estimated as nearby regions often rely on other sources of heating (e.g. coal combustion), which has a very different signature (approximately d13CVPDB = -23 ‰). We present an analysis of the GTA in contrast to Paris, France where atmospheric observations are also available and 13CO2 has been studied. Utilizing our δ13C framework and differences in sectoral isotopic signatures, we quantify the relative contribution of CO2 sources on the overall measured concentration and assess the ability of this framework as a tool for tracing the evolution of sector-specific emissions.

Spectral Characteristics of Young Stars Associated with the Sh2-296 Nebula

NASA Astrophysics Data System (ADS)

Fernandes, Beatriz; Gregorio-Hetem, Jane

Aiming to contribute to the understanding of star formation and evolution in the Canis Major (CMa R1) Molecular Clouds Complex, we analyze the spectral characteristics of a population of young stars associated with the arc-shaped nebula Sh2-296. Our XMM/Newton observations detected 109 X-ray sources in the region and optical spectroscopy was performed with Gemini telescope for 85 optical counterparts. We identified and characterized 51 objects that present features typically found in young objects, such as Hα emission and strong absorption on the Li I line.

The Helioseismic and Magnetic Imager (HMI) Investigation for the Solar Dynamics Observatory (SDO)

NASA Technical Reports Server (NTRS)

Scherrer, Philip Hanby; Schou, Jesper; Bush, R. I.; Kosovichev, A. G.; Bogart, R. S.; Hoeksema, J. T.; Liu, Y.; Duvall, T. L., Jr.; Zhao, J.; Title, A. M.;

The Role of Small-Scale Processes in Solar Active Region Decay

NASA Astrophysics Data System (ADS)

Meyer, Karen; Mackay, Duncan

2017-08-01

Active regions are locations of intense magnetic activity on the Sun, whose evolution can result in highly energetic eruptive phenomena such as solar flares and coronal mass ejections (CMEs). Therefore, fast and accurate simulation of their evolution and decay is essential in the prediction of Space Weather events. In this talk we present initial results from our new model for the photospheric evolution of active region magnetic fields. Observations show that small-scale processes appear to play a role in the dispersal and decay of solar active regions, for example through cancellation at the boundary of sunspot outflows and erosion of flux by surrounding convective cells. Our active region model is coupled to our existing model for the evolution of small-scale photospheric magnetic features. Focusing first on the active region decay phase, we consider the evolution of its magnetic field due to both large-scale (e.g. differential rotation) and small-scale processes, such as its interaction with surrounding small-scale magnetic features and convective flows.This project is funded by The Carnegie Trust for the Universities of Scotland, through their Research Incentives Grant scheme.

L'Evolution des Galaxies Infrarouges: des observations cosmologiques avec ISO à une modélisation de l'infrarouge moyen au submillimétrique

NASA Astrophysics Data System (ADS)

Dole, H.

2000-10-01

This thesis deals with the analysis of the FIRBACK deep survey performed in the far infrared at 170 microns with the Infrared Space Observatory, whose aim is the study of the galaxies contributing to the Cosmic Infrared Background, and with the modellisation of galaxy evolution in the mid-infrared to submillimeter range. The FIRBACK survey covers 3.89 square degrees in 3 high galactic latitude and low foreground emission fields (2 of which are in the northern sky). I first present the techniques of reduction, processing and calibration of the ISOPHOT cosmological data. I show that there is a good agreement between PHOT and DIRBE on extended emission, thanks to the derivation of the PHOT footprint. Final maps are created, and the survey is confusion limited at (sigma = 45 mJy). I present then the techniques of source extraction and the simulations for photometry needed to build the final catalog of 106 sources between 180 mJy (4 sigma) and 2.4 Jy. The complementary catalog is made of 90 sources between 135 and 180 mJy. Galaxy counts show a large excess with respect to local counts or models (with and without evolution), only compatible with strong evolution scenarios. The Cosmic Infrared Background (CIB) is resolved at 4% at 170 microns. The identifications of the sources at other wavelengths suggest that most of the sources are local, but a non negligible part lies above redshift 1. I have developped a phenomenological model of galaxy evolution in order to constrain galaxy evolution in the infrared and to have a better understanding of what the FIRBACK sources are. Using the local Luminosity Function (LF), and template spectra of starburst galaxies, it is possible to constrain the evolution of the LF using all the available data: deep source counts at 15, 170 and 850 microns and the CIB spectrum. I show that galaxy evolution is dominated by a high infrared luminosity population, peaking at 2.0 1011 solar luminosities. Redshift distributions are in agreement with available observations. Predictions are possible with our model for the forthcoming space missions such as SIRTF, Planck and FIRST.

What can hafnium isotope ratios arrays tell us about orogenic processes? An insight into geodynamic processes operating in the Alpine/Mediterranean region

NASA Astrophysics Data System (ADS)

Henderson, B.; Murphy, J.; Collins, W. J.; Hand, M. P.

2013-12-01

Over the last decade, technological advances in laser-ablation sampling techniques have resulted in an increase in the number of combined U-Pb-Hf zircon isotope studies used to investigate crustal evolution on a local, regional and global scale. Hafnium isotope arrays over large time scales (>500 myr) have been interpreted to track evolving plate tectonic configurations, and the geological outputs associated with changing plate boundaries. We use the Alpine-Mediterranean region as an example of how hafnium isotope arrays record the geodynamic processes associated with the complex geological evolution of a region. The geology of Alpine-Mediterranean region preserves a complex, semi-continuous tectonic history that extends from the Neoproterozoic to the present day. Major components of the Variscan and Alpine orogens are microcontinental ribbons derived from the northern Gondwanan margin, which were transferred to the Eurasian plate during the opening and closing of the Rheic and Paleo-Tethys Oceans. Convergence of the Eurasian and African plates commenced in the Mid-Late Cretaceous, following the destruction of the Alpine-Tethys Ocean during the terminal breakup of Pangea. In general, convergence occurred slowly and is characterised by northward accretion of Gondwanan fragments, interspersed with subduction of African lithosphere and intermittent roll-back events. A consequence of this geodynamic scenario was periods of granite-dominated magmatism in an arc-backarc setting. New Hf isotope data from the peri-Gondwanan terranes (Iberia, Meguma and Avalonia) and a compilation of existing Phanerozoic data from the Alpine-Mediterranean region, indicate ~500 myr (Cambrian-Recent) of reworking of peri-Gondwanan crust. The eHf array follows a typical crustal evolution pattern (Lu/Hf=0.015) and is considered to reflect reworking of juvenile peri-Gondwanan (Neoproterozoic) crust variably mixed with an older (~1.8-2.0 Ga) source component, probably Eburnian crust from the West Africa Craton. The Phanerozoic Hf isotopic data from Variscan and Alpine Europe suggest that slow translation of continental fragments from one continent to another produces a characteristic, long-term crustal reworking eHf array, which strongly contrasts with the Hf array defined by Phanerozoic circum-Pacific orogens.

X-ray Binaries in the Central Region of M31

NASA Astrophysics Data System (ADS)

Trudolyubov, Sergey P.; Priedhorsky, W. C.; Cordova, F. A.

2006-09-01

We present the results of the systematic survey of X-ray sources in the central region of M31 using the data of XMM-Newton observations. The spectral properties and variability of 124 bright X-ray sources were studied in detail. We found that more than 80% of sources observed in two or more observations show significant variability on the time scales of days to years. At least 50% of the sources in our sample are spectrally variable. The fraction of variable sources in our survey is much higher than previously reported from Chandra survey of M31, and is remarkably close to the fraction of variable sources found in M31 globular cluster X-ray source population. We present spectral distribution of M31 X-ray sources, based on the spectral fitting with a power law model. The distribution of spectral photon index has two main peaks at 1.8 and 2.3, and shows clear evolution with source luminosity. Based on the similarity of the properties of M31 X-ray sources and their Galactic counterparts, we expect most of X-ray sources in our sample to be accreting binary systems with neutron star and black hole primaries. Combining the results of X-ray analysis (X-ray spectra, hardness-luminosity diagrams and variability) with available data at other wavelengths, we explore the possibility of distinguishing between bright neutron star and black hole binary systems, and identify 7% and 25% of sources in our sample as a probable black hole and neutron star candidates. Finally, we compare the M31 X-ray source population to the source populations of normal galaxies of different morphological type. Support for this work was provided through NASA Grant NAG5-12390. Part of this work was done during a summer workshop ``Revealing Black Holes'' at the Aspen Center for Physics, S. T. is grateful to the Center for their hospitality.

Favorable genomic environments for cis-regulatory evolution: A novel theoretical framework.

PubMed

Maeso, Ignacio; Tena, Juan J

2016-09-01

Cis-regulatory changes are arguably the primary evolutionary source of animal morphological diversity. With the recent explosion of genome-wide comparisons of the cis-regulatory content in different animal species is now possible to infer general principles underlying enhancer evolution. However, these studies have also revealed numerous discrepancies and paradoxes, suggesting that the mechanistic causes and modes of cis-regulatory evolution are still not well understood and are probably much more complex than generally appreciated. Here, we argue that the mutational mechanisms and genomic regions generating new regulatory activities must comply with the constraints imposed by the molecular properties of cis-regulatory elements (CREs) and the organizational features of long-range chromatin interactions. Accordingly, we propose a new integrative evolutionary framework for cis-regulatory evolution based on two major premises for the origin of novel enhancer activity: (i) an accessible chromatin environment and (ii) compatibility with the 3D structure and interactions of pre-existing CREs. Mechanisms and DNA sequences not fulfilling these premises, will be less likely to have a measurable impact on gene expression and as such, will have a minor contribution to the evolution of gene regulation. Finally, we discuss current comparative cis-regulatory data under the light of this new evolutionary model, and propose that the two most prominent mechanisms for the evolution of cis-regulatory changes are the overprinting of ancestral CREs and the exaptation of transposable elements. Copyright © 2015 Elsevier Ltd. All rights reserved.

A MULTIWAVELENGTH STUDY OF STAR FORMATION IN THE VICINITY OF GALACTIC H II REGION Sh 2-100

DOE Office of Scientific and Technical Information (OSTI.GOV)

Samal, M. R.; Pandey, A. K.; Sagar, R.

We present multiwavelength investigation of morphology, physical-environment, stellar contents, and star formation activity in the vicinity of star-forming region Sh 2-100. It is found that the Sh 2-100 region contains seven H II regions of ultracompact and compact nature. The present estimation of distance for three H II regions, along with the kinematic distance for others, suggests that all of them belong to the same molecular cloud complex. Using near-infrared photometry, we identified the most probable ionizing sources of six H II regions. Their approximate photometric spectral type estimates suggest that they are massive early-B to mid-O zero-age-main-sequence stars andmore » agree well with radio continuum observations at 1280 MHz, for sources whose emissions are optically thin at this frequency. The morphology of the complex shows a non-uniform distribution of warm and hot dust, well mixed with the ionized gas, which correlates well with the variation of average visual extinction ({approx}4.2-97 mag) across the region. We estimated the physical parameters of ionized gas with the help of radio continuum observations. We detected an optically visible compact nebula located to the south of the 850 {mu}m emission associated with one of the H II regions and the diagnostic of the optical emission line ratios gives electron density and electron temperature of {approx}0.67 x 10{sup 3} cm{sup -3} and {approx}10{sup 4} K, respectively. The physical parameters suggest that all the H II regions are in different stages of evolution, which correlate well with the probable ages in the range {approx}0.01-2 Myr of the ionizing sources. The spatial distribution of infrared excess stars, selected from near-infrared and Infrared Array Camera color-color diagrams, correlates well with the association of gas and dust. The positions of infrared excess stars, ultracompact and compact H II regions at the periphery of an H I shell, possibly created by a WR star, indicate that star formation in Sh 2-100 region might have been induced by an expanding H I shell.« less

Design and Analysis of an Isokinetic Sampling Probe for Submicron Particle Measurements at High Altitude

NASA Technical Reports Server (NTRS)

Heath, Christopher M.

2012-01-01

An isokinetic dilution probe has been designed with the aid of computational fluid dynamics to sample sub-micron particles emitted from aviation combustion sources. The intended operational range includes standard day atmospheric conditions up to 40,000-ft. With dry nitrogen as the diluent, the probe is intended to minimize losses from particle microphysics and transport while rapidly quenching chemical kinetics. Initial results indicate that the Mach number ratio of the aerosol sample and dilution streams in the mixing region is an important factor for successful operation. Flow rate through the probe tip was found to be highly sensitive to the static pressure at the probe exit. Particle losses through the system were estimated to be on the order of 50% with minimal change in the overall particle size distribution apparent. Following design refinement, experimental testing and validation will be conducted in the Particle Aerosol Laboratory, a research facility located at the NASA Glenn Research Center to study the evolution of aviation emissions at lower stratospheric conditions. Particle size distributions and number densities from various combustion sources will be used to better understand particle-phase microphysics, plume chemistry, evolution to cirrus, and environmental impacts of aviation.

Evolution and Spatiotemporal Dynamics of Enterovirus A71 Subgenogroups in Vietnam.

PubMed

Thao, Nguyen Thi Thanh; Donato, Celeste; Trang, Vu Thi Huyen; Kien, Nguyen Trung; Trang, Ph M Mai Thuy; Khanh, Tran Quoc; Nguyet, Dang Thi; Sessions, October M; Cuong, Hoang Quoc; Lan, Phan Trong; Huong, Vu Thi Que; van Doorn, H Rogier; Vijaykrishna, Dhanasekaran

2017-12-12

Enterovirus A71 (EV-A71) is the major cause of severe hand, foot, and mouth disease and viral encephalitis in children across the Asia-Pacific region, including in Vietnam, which has experienced a high burden of disease in recent years. Multiple subgenogroups (C1, C4, C5, and B5) concurrently circulate in the region with a large variation in epidemic severity. The relative differences in their evolution and epidemiology were examined within Vietnam and globally. A total of 752 VP1 gene sequences were analyzed (413 generated in this study combined with 339 obtained from GenBank), collected from patients in 36 provinces in Vietnam during 2003-2013, along with epidemiological metadata. Globally representative VP1 gene datasets of subgenogroups were used to coestimate time-resolved phylogenies and relative genetic diversity to infer virus origins and regional transmission network. Despite frequent virus migration between countries, the highest genetic diversity of individual subgenogroups was maintained independently for several years in specific Asian countries representing genogroup-specific sources of EV-A71 diversity. This study highlights a persistent transmission network of EV-A71, with specific Asian countries seeding other countries in the region and beyond, emphasizing the need for improved EV-A71 surveillance and detailed genetic and antigenic characterization. © The Author 2017. Published by Oxford University Press for the Infectious Diseases Society of America. All rights reserved. For permissions, e-mail: journals.permissions@oup.com.

Impacts of the Detection of Cassiopeia A Point Source.

PubMed

Umeda; Nomoto; Tsuruta; Mineshige

2000-05-10

Very recently the Chandra first light observation discovered a point-like source in the Cassiopeia A supernova remnant. This detection was subsequently confirmed by the analyses of the archival data from both ROSAT and Einstein observations. Here we compare the results from these observations with the scenarios involving both black holes (BHs) and neutron stars (NSs). If this point source is a BH, we offer as a promising model a disk-corona type model with a low accretion rate in which a soft photon source at approximately 0.1 keV is Comptonized by higher energy electrons in the corona. If it is an NS, the dominant radiation observed by Chandra most likely originates from smaller, hotter regions of the stellar surface, but we argue that it is still worthwhile to compare the cooler component from the rest of the surface with cooling theories. We emphasize that the detection of this point source itself should potentially provide enormous impacts on the theories of supernova explosion, progenitor scenario, compact remnant formation, accretion to compact objects, and NS thermal evolution.

Chemical characterization and source apportionment of fine particulate matter in Yangzhou, China, using offline aerosol mass spectrometry

NASA Astrophysics Data System (ADS)

Li, L.; Ge, X.; Xu, J.; Ye, Z.

2016-12-01

In recent years, Aerodyne Aerosol Mass Spectrometer (AMS) has been widely used for online and real-time monitoring of fine aerosol particles all over the world. However, due to the high cost and complex maintenance, the AMS was typically deployed for short-term intense field measurements, limiting its ability in elucidating the long-term behaviors and dominant sources of regional fine particles (PM2.5). In this study, we collected daily PM2.5 filter samples across a relatively long period (November 2015 to April 2016, in total >100 samples) using a high-volume sampler, in urban Yangzhou - a city in the Yangtze River Delta region, China. These samples were analyzed by using a suite of analytical techniques, for the water-soluble inorganic ions (WSIs), organic carbon (OC), elemental carbon (EC), water-soluble organic carbon (WSOC) and total nitrogen (TN), trace metal elements, etc. More importantly, an Aerodyne soot particle aerosol mass spectrometer (SP-AMS) was for the first time introduced for the offline characterization of the PM2.5 samples collected in this region. In particular, Positive matrix factorization was conducted on the SP-AMS determined water-soluble fraction of organic aerosols (WSOA), and three distinct sources were separated, including a primary OA (POA), a less oxygenated OA (LOOA), and a more oxygenated OA (MOOA). Chemical characteristics and evolution processes of these OA subcomponents were further discussed. Our results are useful for the air pollution management in the YRD region, and the technique developed can be applied elsewhere as well.

Neogene evolution of the North New Guinea basin, Papua New Guinea: New constraints from seismic and subsidence analysis and implications for hydrocarbon exploration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cullen, A.B.; Pigott, J.D.

1990-06-01

The present-day North New Guinea basin is a Plio-Pleistocene successor basin that formed subsequent to accretion of the Finisterre volcanic arc to the Australian Plate. The Ramu, Sepik, and Piore infrabasins formed in a forearc setting relative to the continental Maramuni magmatic arc. The evolution of these infrabasins was strongly influenced by accretion of the composite Torricelli-Prince Alexander terrane to the Australian Plate. Regional reflection seismic data and tectonic subsidence-subsidence rate calculations for seven wells drilled in the North New Guinea basin reveal a complex history. The timing and magnitude of subsidence and changes in subsidence rates differ between eachmore » of the Miocene infrabasins. A diachronous middle to late Miocene unconformity generally truncates infrabasin sequences. The Nopan No. 1 in the Sepik basin, however, has a complete middle Miocene to Pleistocene sedimentary record. This well records late Miocene negative subsidence rates documenting that the Nopan anticline grew as erosion occurred elsewhere in the region. This circumstance suggests that the major, sequence-bounding unconformity results from regional uplift and deformation, rather than changes in global sea level. The Plio-Pleistocene evolution of the North New Guinea basin has two profound implications regarding hydrocarbon exploration. First, the late Pliocene structural inversion of parts of the basin hinders stratigraphic and facies correlation inferred from the present setting. The recognition of basin inversion is particularly important in the Piore basin for predicting the distribution of potential reservoir facies in the Miocene carbonates. Second, the subsidence data suggest that although potential source rocks may be thermally within the oil window, these rocks may not have had sufficient time to mature owing to their recent burial.« less

New insights into the outflows from R Aquarii

NASA Astrophysics Data System (ADS)

Liimets, T.; Corradi, R. L. M.; Jones, D.; Verro, K.; Santander-García, M.; Kolka, I.; Sidonio, M.; Kankare, E.; Kankare, J.; Pursimo, T.; Wilson, P. A.

2018-05-01

Context. The source R Aquarii is a symbiotic binary surrounded by a large and complex nebula with a prominent curved jet. It is one of the closest known symbiotic systems, and therefore offers a unique opportunity to study the central regions of these systems and the formation and evolution of astrophysical jets. Aims: We aim to study the evolution of the central jet and outer nebula of R Aqr, taking advantage of a long term monitoring campaign of optical imaging, as well as of high-resolution integral field spectroscopy. Methods: Narrow-band images acquired over a period of more than 21 yr were compared in order to study the expansion and evolution of all components of the R Aqr nebula. The magnification method was used to derive the kinematic ages of the features that appear to expand radially. Integral field spectroscopy of the [O III] 5007 Å emission is used to study the velocity structure of the central regions of the jet. Results: New extended features, further out than the previously known hourglass nebula, are detected. The kinematic distance to R Aqr is calculated to be 178 pc using the expansion of the large hourglass nebula. This nebula of R Aqr is found to be roughly 650 yr old, while the inner regions have ages ranging from 125 to 290 yr. The outer nebula is found to be well described by a ballistic expansion, while for most components of the jet strong deviations from such behaviour are found. We find that the northern jet is mostly red-shifted while its southern part is blue-shifted, apparently at odds with findings from previous studies but almost certainly a consequence of the complex nature of the jet and variations in ionisation and illumination between observations.

Geochemistry of Martian Meteorites and the Petrologic Evolution of Mars

NASA Technical Reports Server (NTRS)

Mittlefehldt, D. W.

2002-01-01

Mafic igneous rocks serve as probes of the interiors of their parent bodies - the compositions of the magmas contain an imprint of the source region composition and mineralogy, the melting and crystallization processes, and mixing and assimilation. Although complicated by their multifarious history, it is possible to constrain the petrologic evolution of an igneous province through compositional study of the rocks. Incompatible trace elements provide one means of doing this. I will use incompatible element ratios of martian meteorites to constrain the early petrologic evolution of Mars. Incompatible elements are strongly partitioned into the melt phase during igneous processes. The degree of incompatibility will differ depending on the mineral phases in equilibrium with the melt. Most martian meteorites contain some cumulus grains, but nevertheless, incompatible element ratios of bulk meteorites will be close to those of their parent magmas. ALH 84001 is an exception, and it will not be discussed. The martian meteorites will be considered in two groups; a 1.3 Ga group composed of the clinopyroxenites and dunite, and a younger group composed of all others.

The evolution of an ancient technology

PubMed Central

2017-01-01

We investigate pattern and process in the transmission of traditional weaving cultures in East and Southeast Asia. Our investigation covers a range of scales, from the experiences of individual weavers (‘micro’) to the broad-scale patterns of loom technologies across the region (‘macro’). Using published sources, we build an empirical model of cultural transmission (encompassing individual weavers, the household and the community), focussing on where cultural information resides and how it is replicated and how transmission errors are detected and eliminated. We compare this model with macro-level outcomes in the form of a new dataset of weaving loom technologies across a broad area of East and Southeast Asia. The lineages of technologies that we have uncovered display evidence for branching, hybridization (reticulation), stasis in some lineages, rapid change in others and the coexistence of both simple and complex forms. There are some striking parallels with biological evolution and information theory. There is sufficient detail and resolution in our findings to enable us to begin to critique theoretical models and assumptions that have been produced during the last few decades to describe the evolution of culture. PMID:28573032

The evolution of an ancient technology.

PubMed

Buckley, Christopher D; Boudot, Eric

2017-05-01

We investigate pattern and process in the transmission of traditional weaving cultures in East and Southeast Asia. Our investigation covers a range of scales, from the experiences of individual weavers ('micro') to the broad-scale patterns of loom technologies across the region ('macro'). Using published sources, we build an empirical model of cultural transmission (encompassing individual weavers, the household and the community), focussing on where cultural information resides and how it is replicated and how transmission errors are detected and eliminated. We compare this model with macro-level outcomes in the form of a new dataset of weaving loom technologies across a broad area of East and Southeast Asia. The lineages of technologies that we have uncovered display evidence for branching, hybridization (reticulation), stasis in some lineages, rapid change in others and the coexistence of both simple and complex forms. There are some striking parallels with biological evolution and information theory. There is sufficient detail and resolution in our findings to enable us to begin to critique theoretical models and assumptions that have been produced during the last few decades to describe the evolution of culture.

Post-rift magmatic evolution of the eastern North American “passive-aggressive” margin

USGS Publications Warehouse

Mazza, Sarah E.; Gazel, Esteban; Johnson, Elizabeth A.; Bizmis, Michael; McAleer, Ryan J.; Biryol, C. Berk

2017-01-01

Understanding the evolution of passive margins requires knowledge of temporal and chemical constraints on magmatism following the transition from supercontinent to rifting, to post-rifting evolution. The Eastern North American Margin (ENAM) is an ideal study location as several magmatic pulses occurred in the 200 My following rifting. In particular, the Virginia-West Virginia region of the ENAM has experienced two postrift magmatic pulses at ∼152 Ma and 47 Ma, and thus provides a unique opportunity to study the long-term magmatic evolution of passive margins. Here we present a comprehensive set of geochemical data that includes new 40Ar/39Ar ages, major and trace-element compositions, and analysis of radiogenic isotopes to further constrain their magmatic history. The Late Jurassic volcanics are bimodal, from basanites to phonolites, while the Eocene volcanics range from picrobasalt to rhyolite. Modeling suggests that the felsic volcanics from both the Late Jurassic and Eocene events are consistent with fractional crystallization. Sr-Nd-Pb systematics for the Late Jurassic event suggests HIMU and EMII components in the magma source that we interpret as upper mantle components rather than crustal interaction. Lithospheric delamination is the best hypothesis for magmatism in Virginia/West Virginia, due to tectonic instabilities that are remnant from the long-term evolution of this margin, resulting in a “passive-aggressive” margin that records multiple magmatic events long after rifting ended.

Moment-tensor inversion for offshore earthquakes east of Taiwan and their implications to regional collision

NASA Astrophysics Data System (ADS)

Kao, Honn; Jian, Pei-Ru; Ma, Kuo-Fong; Huang, Bor-Shouh; Liu, Chun-Chi

Reliable determination of source parameters for offshore earthquakes east of Taiwan with mb<5.5 was a difficult task because of the poor azimuthal coverage by local network and the lack of signals at teleseismic distances. We take advantage of the recently established “Broadband Array in Taiwan for Seismology” (BATS) to invert seismic moment tensors for 7 such events occurred in 1996. To cope with different patterns of background noise and unknown structural details, we utilize variable frequency bands in the inversion and adapt a two-step procedure to select best velocity models for individual epicenter-station paths. Our results are consistent with the overall patterns of regional collision and indicate that the resulting compressive stress has caused significant intraplate deformation within the Philippine Sea plate. Simulation of the region's geological evolution and orogenic processes should take this factor into account and allow the Philippine Sea plate to deform internally.

Sgr A* as Source of the Positrons Observed in the Galactic Center Region

NASA Astrophysics Data System (ADS)

Jean, Pierre; Guessoum, Nidhal; Ferrière, Katia

2017-01-01

We explore the possibility that a substantial fraction of the positrons observed to annihilate in the central region of our Galaxy come from the supermassive black hole Sgr A* that lies at the center. This idea was proposed by several authors, but the propagation of the emitted positrons into the bulge and beyond remained a serious problem for models of the origin of GC positrons. We assume models of positron production with different energies. The propagation of positrons from their production site is followed in detail with Monte-Carlo simulations, taking into account the physical conditions of the propagation regions as well as various physical interactions. Using the known physics of positron annihilation in astrophysical environments, we calculate the properties of the annihilation emission (time evolution and spatial distribution) for the different models under consideration. We present the results of these simulations and the conclusions/constraints that can be inferred from them.

Late Mesozoic-Cenozoic intraplate magmatism in Central Asia and its relation with mantle diapirism: Evidence from the South Khangai volcanic region, Mongolia

NASA Astrophysics Data System (ADS)

Yarmolyuk, Vladimir V.; Kudryashova, Ekaterina A.; Kozlovsky, Alexander M.; Lebedev, Vladimir A.; Savatenkov, Valery M.

2015-11-01

The South Khangai volcanic region (SKVR) comprises fields of Late Mesozoic-Cenozoic volcanic rocks scattered over southern and central Mongolia. Evolution of the region from the Late Jurassic to the Late Cenozoic includes 13 successive igneous episodes that are more or less evenly distributed in time. Major patterns in the distribution of different-aged volcanic complexes were controlled by a systematic temporal migration of volcanic centers over the region. The total length of their trajectory exceeds 1600 km. Principle characteristics of local magmatism are determined. The composition of igneous rocks varies from basanites to rhyolites (predominantly, high-K rocks), with geochemistry close to that of OIB. The rock composition, however, underwent transformations in the Mesozoic-Cenozoic. Rejuvenation of mafic rocks is accompanied by decrease in the contents of HREE and increase of Nb and Ta. According to isotope data, the SKVR magmatic melts were derived from three isotope sources that differed in the Sr, Nd, and Pb isotopic compositions and successively alternated in time. In the Early Cretaceous, the predominant source composition was controlled by interaction of the EMII- and PREMA-type mantle materials. The PREMA-type mantle material dominated quantitatively in the Late Cretaceous and initial Early Cenozoic. From the latest Early Cenozoic to Late Cenozoic, the magma source also contained the EMI-type material along with the PREMA-type. The structural fabric, rock composition, major evolutionary pattern, and inner structure of SKVR generally comply with the criteria used to distinguish the mantle plume-related regions. Analogous features can be seen in other regions of recent volcanism in Central Asia (South Baikal, Udokan, Vitim, and Tok Stanovik). The structural autonomy of these regions suggests that distribution of the Late Mesozoic-Cenozoic volcanism in Central Asia was controlled by a group of relatively small hot finger-type mantle plumes associated with the common hot mantle field of Central Asia.

Large-Scale Aspects and Temporal Evolution of Pulsating Aurora

NASA Technical Reports Server (NTRS)

Jones, S. L.; Lessard, M. R.; Rychert, K.; Spanswick, E.; Donovan, E.

2010-01-01

Pulsating aurora is a common phenomenon generally believed to occur mainly in the aftermath of a, substorm, where dim long-period pulsating patches appear. The study determines the temporal and spatial evolution of pulsating events using two THEN IIIS ASI stations, at Gillam (66.18 mlat, 332.78 mlon, magnetic midnight at 0634 UT) and Fort Smith, (67.38 mlat, 306.64 mlon, magnetic midnight at, 0806 UT) along roughly the same invariant latitude. Parameters have been calculated from a database of 74 pulsating aurora events from 119 days of good optical data within the period from September 2007 through March 2008 as identified with the Gillam camera. It is shown that the source region of pulsating aurora drifts or expands eastward, away from magnetic midnight, for pre-midnight onsets and that the spatial evolution is more complicated for post midnight onsets, which has implications for the source mechanism. The most probable duration of a pulsating aurora event is roughly 1.5 hours while the distribution of possible event durations includes many long (several hours) events. This may suggest that pulsating aurora is not strictly a substorm recovery phase phenomenon but rather a persistent, long-lived phenomenon that may be temporarily disrupted by auroral substorms. Observations from the Gillam station show that in fact, pulsating aurora is quite common with the occurrence rate increasing to around 60% for morning hours, with 6910 of pulsating aurora onsets occurring after substorm breakup.

New Insights into Tectonics of the Saint Elias, Alaska, Region Based on Local Seismicity and Tomography

NASA Astrophysics Data System (ADS)

Ruppert, N. A.; Zabelina, I.; Freymueller, J. T.

2013-12-01

Saint Elias Mountains in southern Alaska are manifestation of ongoing tectonic processes that include collision of the Yakutat block with and subduction of the Yakutat block and Pacific plate under the North American plate. Interaction of these tectonic blocks and plates is complex and not well understood. In 2005 and 2006 a network of 22 broadband seismic sites was installed in the region as part of the SainT Elias TEctonics and Erosion Project (STEEP), a five-year multi-disciplinary study that addressed evolution of the highest coastal mountain range on Earth. High quality seismic data provides unique insights into earthquake occurrence and velocity structure of the region. Local earthquake data recorded between 2005 and 2010 became a foundation for detailed study of seismotectonic features and crustal velocities. The highest concentration of seismicity follows the Chugach-St.Elias fault, a major on land tectonic structure in the region. This fault is also delineated in tomographic images as a distinct contrast between lower velocities to the south and higher velocities to the north. The low-velocity region corresponds to the rapidly-uplifted and exhumed sediments on the south side of the range. Earthquake source parameters indicate high degree of compression and undertrusting processes along the coastal area, consistent with multiple thrust structures mapped from geological studies in the region. Tomographic inversion reveals velocity anomalies that correlate with sedimentary basins, volcanic features and subducting Yakutat block. We will present precise earthquake locations and source parameters recorded with the STEEP and regional seismic network along with the results of P- and S-wave tomographic inversion.

Amazonia is the primary source of Neotropical biodiversity.

PubMed

Antonelli, Alexandre; Zizka, Alexander; Carvalho, Fernanda Antunes; Scharn, Ruud; Bacon, Christine D; Silvestro, Daniele; Condamine, Fabien L

2018-05-14

The American tropics (the Neotropics) are the most species-rich realm on Earth, and for centuries, scientists have attempted to understand the origins and evolution of their biodiversity. It is now clear that different regions and taxonomic groups have responded differently to geological and climatic changes. However, we still lack a basic understanding of how Neotropical biodiversity was assembled over evolutionary timescales. Here we infer the timing and origin of the living biota in all major Neotropical regions by performing a cross-taxonomic biogeographic analysis based on 4,450 species from six major clades across the tree of life (angiosperms, birds, ferns, frogs, mammals, and squamates), and integrate >1.3 million species occurrences with large-scale phylogenies. We report an unprecedented level of biotic interchange among all Neotropical regions, totaling 4,525 dispersal events. About half of these events involved transitions between major environmental types, with a predominant directionality from forested to open biomes. For all taxonomic groups surveyed here, Amazonia is the primary source of Neotropical diversity, providing >2,800 lineages to other regions. Most of these dispersal events were to Mesoamerica (∼1,500 lineages), followed by dispersals into open regions of northern South America and the Cerrado and Chaco biomes. Biotic interchange has taken place for >60 million years and generally increased toward the present. The total amount of time lineages spend in a region appears to be the strongest predictor of migration events. These results demonstrate the complex origin of tropical ecosystems and the key role of biotic interchange for the assembly of regional biotas. Copyright © 2018 the Author(s). Published by PNAS.

Amazonia is the primary source of Neotropical biodiversity

PubMed Central

2018-01-01

The American tropics (the Neotropics) are the most species-rich realm on Earth, and for centuries, scientists have attempted to understand the origins and evolution of their biodiversity. It is now clear that different regions and taxonomic groups have responded differently to geological and climatic changes. However, we still lack a basic understanding of how Neotropical biodiversity was assembled over evolutionary timescales. Here we infer the timing and origin of the living biota in all major Neotropical regions by performing a cross-taxonomic biogeographic analysis based on 4,450 species from six major clades across the tree of life (angiosperms, birds, ferns, frogs, mammals, and squamates), and integrate >1.3 million species occurrences with large-scale phylogenies. We report an unprecedented level of biotic interchange among all Neotropical regions, totaling 4,525 dispersal events. About half of these events involved transitions between major environmental types, with a predominant directionality from forested to open biomes. For all taxonomic groups surveyed here, Amazonia is the primary source of Neotropical diversity, providing >2,800 lineages to other regions. Most of these dispersal events were to Mesoamerica (∼1,500 lineages), followed by dispersals into open regions of northern South America and the Cerrado and Chaco biomes. Biotic interchange has taken place for >60 million years and generally increased toward the present. The total amount of time lineages spend in a region appears to be the strongest predictor of migration events. These results demonstrate the complex origin of tropical ecosystems and the key role of biotic interchange for the assembly of regional biotas. PMID:29760058

Sources and Sinks: A Stochastic Model of Evolution in Heterogeneous Environments

NASA Astrophysics Data System (ADS)

Hermsen, Rutger; Hwa, Terence

2010-12-01

We study evolution driven by spatial heterogeneity in a stochastic model of source-sink ecologies. A sink is a habitat where mortality exceeds reproduction so that a local population persists only due to immigration from a source. Immigrants can, however, adapt to conditions in the sink by mutation. To characterize the adaptation rate, we derive expressions for the first arrival time of adapted mutants. The joint effects of migration, mutation, birth, and death result in two distinct parameter regimes. These results may pertain to the rapid evolution of drug-resistant pathogens and insects.

SOURCE REGIONS OF THE INTERPLANETARY MAGNETIC FIELD AND VARIABILITY IN HEAVY-ION ELEMENTAL COMPOSITION IN GRADUAL SOLAR ENERGETIC PARTICLE EVENTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ko, Yuan-Kuen; Wang, Yi-Ming; Tylka, Allan J.

Gradual solar energetic particle (SEP) events are those in which ions are accelerated to their observed energies by interactions with a shock driven by a fast coronal mass ejection (CME). Previous studies have shown that much of the observed event-to-event variability can be understood in terms of shock speed and evolution in the shock-normal angle. However, an equally important factor, particularly for the elemental composition, is the origin of the suprathermal seed particles upon which the shock acts. To tackle this issue, we (1) use observed solar-wind speed, magnetograms, and the potential-field source-surface model to map the Sun-L1 interplanetary magneticmore » field (IMF) line back to its source region on the Sun at the time of the SEP observations and (2) then look for a correlation between SEP composition (as measured by Wind and Advanced Composition Explorer at ∼2-30 MeV nucleon{sup –1}) and characteristics of the identified IMF source regions. The study is based on 24 SEP events, identified as a statistically significant increase in ∼20 MeV protons and occurring in 1998 and 2003-2006, when the rate of newly emergent solar magnetic flux and CMEs was lower than in solar-maximum years, and the field-line tracing is therefore more likely to be successful. We find that the gradual SEP Fe/O is correlated with the field strength at the IMF source, with the largest enhancements occurring when the footpoint field is strong due to the nearby presence of an active region (AR). In these cases, other elemental ratios show a strong charge-to-mass (q/M) ordering (at least on average), similar to that found in impulsive events. Such results lead us to suggest that magnetic reconnection in footpoint regions near ARs bias the heavy-ion composition of suprathermal seed ions by processes qualitatively similar to those that produce larger heavy-ion enhancements in impulsive SEP events. To address potential technical concerns about our analysis, we also discuss efforts to exclude impulsive SEP events from our event sample.« less

Sources of non-fossil-fuel emissions in carbonaceous aerosols during early winter in Chinese cities

NASA Astrophysics Data System (ADS)

Liu, Di; Li, Jun; Cheng, Zhineng; Zhong, Guangcai; Zhu, Sanyuan; Ding, Ping; Shen, Chengde; Tian, Chongguo; Chen, Yingjun; Zhi, Guorui; Zhang, Gan

2017-09-01

China experiences frequent and severe haze outbreaks from the beginning of winter. Carbonaceous aerosols are regarded as an essential factor in controlling the formation and evolution of haze episodes. To elucidate the carbon sources of air pollution, source apportionment was conducted using radiocarbon (14C) and unique molecular organic tracers. Daily 24 h PM2. 5 samples were collected continuously from October 2013 to November 2013 in 10 Chinese cities. The 14C results indicated that non-fossil-fuel (NF) emissions were predominant in total carbon (TC; average = 65 ± 7 %). Approximately half of the EC was derived primarily from biomass burning (BB) (average = 46 ± 11 %), while over half of the organic carbon (OC) fraction comprised NF (average = 68 ± 7 %). On average, the largest contributor to TC was NF-derived secondary OC (SOCnf), which accounted for 46 ± 7 % of TC, followed by SOC derived from fossil fuels (FF) (SOCf; 16 ± 3 %), BB-derived primary OC (POCbb; 13 ± 5 %), POC derived from FF (POCf; 12 ± 3 %), EC derived from FF (ECf; 7 ± 2 %) and EC derived from BB (ECbb; 6 ± 2 %). The regional background carbonaceous aerosol composition was characterized by NF sources; POCs played a major role in northern China, while SOCs contributed more in other regions. However, during haze episodes, there were no dramatic changes in the carbon source or composition in the cities under study, but the contribution of POC from both FF and NF increased significantly.

Geology and hydrocarbon potential in the state of Qatar, Arabian Gulf

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alsharhan, A.S.; Nairn, A.E.M.

The state of Qatar is situated in the southern Arabian Gulf and covers an area of 12,000 km{sup 2}. It is formed by a large, broad anticline, which is part of the regional south-southwest-north-northeast-trending Qatar-South Fars arch. The arch separates the two Infracambrian salt basins. The Dukhan field was the first discovery, made in 1939, in the Upper Jurassic limestones. Since then, a series of discoveries have been made so that Qatar has become one of the leading OPEC oil states. Hydrocarbon accumulations are widely dispersed throughout the stratigraphic column from upper Paleozoic to Cretaceous producing strata. The most prolificmore » reservoirs are the Permian and Mesozoic shelf carbonate sequences. Minor clastic reservoirs occur in the Albian and Paleozoic sequences. Seals, mainly anhydrite and shale. occur both intraformationally and regionally. Several stratigraphic intervals contain source rocks or potential source rocks. The Silurian shales arc the most likely source of the hydrocarbon stored in the upper Paleozoic clastics and carbonates. The upper Oxfordian-middle Kimmeridgian rocks formed in the extensive starved basin during the Mesozoic period of sea level rise. Total organic carbon ranges between 1 and 6%, with the sulfur content approximately 9%. The source material consists of sapropelic liptodetrinite and algae. The geological background of the sedimentary facies through geologic time, stratigraphy, and structural evolution which control source, and the subsequent timing and migration of large-scale hydrocarbon generation are presented in detail.« less

Evolution of power sources for implantable cardioverter defibrillators

NASA Astrophysics Data System (ADS)

Crespi, Ann M.; Somdahl, Sonja K.; Schmidt, Craig L.; Skarstad, Paul M.

The evolution of seven generations of power sources for implantable cardioverter defibrillators (ICD) is presented. The packaging efficiency of the power sources has steadily increased, resulting in smaller, lighter batteries while maintaining the required electrical characteristics. The main areas for improvement were reduction of headspace volume, reduction of separator volume, and a change from a two-cell battery to a single cell.

Gene network polymorphism is the raw material of natural selection: the selfish gene network hypothesis.

PubMed

Boldogköi, Zsolt

2004-09-01

Population genetics, the mathematical theory of modern evolutionary biology, defines evolution as the alteration of the frequency of distinct gene variants (alleles) differing in fitness over the time. The major problem with this view is that in gene and protein sequences we can find little evidence concerning the molecular basis of phenotypic variance, especially those that would confer adaptive benefit to the bearers. Some novel data, however, suggest that a large amount of genetic variation exists in the regulatory region of genes within populations. In addition, comparison of homologous DNA sequences of various species shows that evolution appears to depend more strongly on gene expression than on the genes themselves. Furthermore, it has been demonstrated in several systems that genes form functional networks, whose products exhibit interrelated expression profiles. Finally, it has been found that regulatory circuits of development behave as evolutionary units. These data demonstrate that our view of evolution calls for a new synthesis. In this article I propose a novel concept, termed the selfish gene network hypothesis, which is based on an overall consideration of the above findings. The major statements of this hypothesis are as follows. (1) Instead of individual genes, gene networks (GNs) are responsible for the determination of traits and behaviors. (2) The primary source of microevolution is the intraspecific polymorphism in GNs and not the allelic variation in either the coding or the regulatory sequences of individual genes. (3) GN polymorphism is generated by the variation in the regulatory regions of the component genes and not by the variance in their coding sequences. (4) Evolution proceeds through continuous restructuring of the composition of GNs rather than fixing of specific alleles or GN variants.

Regional seismic stratigraphy and controls on the Quaternary evolution of the Cape Hatteras region of the Atlantic passive margin, USA

USGS Publications Warehouse

Mallinson, D.J.; Culver, S.J.; Riggs, S.R.; Thieler, E.R.; Foster, D.; Wehmiller, J.; Farrell, K.M.; Pierson, J.

2010-01-01

Seismic and core data, combined with amino acid racemization and strontium-isotope age data, enable the definition of the Quaternary stratigraphic framework and recognition of geologic controls on the development of the modern coastal system of North Carolina, U.S.A. Seven regionally continuous high amplitude reflections are defined which bound six seismic stratigraphic units consisting of multiple regionally discontinuous depositional sequences and parasequence sets, and enable an understanding of the evolution of this margin. Data reveal the progressive eastward progradation and aggradation of the Quaternary shelf. The early Pleistocene inner shelf occurs at a depth of ca. 20-40 m beneath the western part of the modern estuarine system (Pamlico Sound). A mid- to outer shelf lowstand terrace (also early Pleistocene) with shelf sand ridge deposits comprising parasequence sets within a transgressive systems tract, occurs at a deeper level (ca. 45-70 m) beneath the modern barrier island system (the Outer Banks) and northern Pamlico Sound. Seismic and foraminiferal paleoenvironmental data from cores indicate the occurrence of lowstand strandplain shoreline deposits on the early to middle Pleistocene shelf. Middle to late Pleistocene deposits occur above a prominent unconformity and marine flooding surface that truncates underlying units, and contain numerous filled fluvial valleys that are incised into the early and middle Pleistocene deposits. The stratigraphic framework suggests margin progradation and aggradation modified by an increase in the magnitude of sea-level fluctuations during the middle to late Pleistocene, expressed as falling stage, lowstand, transgressive and highstand systems tracts. Thick stratigraphic sequences occur within the middle Pleistocene section, suggesting the occurrence of high capacity fluvial point sources debouching into the area from the west and north. Furthermore, the antecedent topography plays a significant role in the evolution of the geomorphology and stratigraphy of this marginal system. ?? 2009 Elsevier B.V.

Memoryless control of boundary concentrations of diffusing particles.

PubMed

Singer, A; Schuss, Z; Nadler, B; Eisenberg, R S

2004-12-01

Flux between regions of different concentration occurs in nearly every device involving diffusion, whether an electrochemical cell, a bipolar transistor, or a protein channel in a biological membrane. Diffusion theory has calculated that flux since the time of Fick (1855), and the flux has been known to arise from the stochastic behavior of Brownian trajectories since the time of Einstein (1905), yet the mathematical description of the behavior of trajectories corresponding to different types of boundaries is not complete. We consider the trajectories of noninteracting particles diffusing in a finite region connecting two baths of fixed concentrations. Inside the region, the trajectories of diffusing particles are governed by the Langevin equation. To maintain average concentrations at the boundaries of the region at their values in the baths, a control mechanism is needed to set the boundary dynamics of the trajectories. Different control mechanisms are used in Langevin and Brownian simulations of such systems. We analyze models of controllers and derive equations for the time evolution and spatial distribution of particles inside the domain. Our analysis shows a distinct difference between the time evolution and the steady state concentrations. While the time evolution of the density is governed by an integral operator, the spatial distribution is governed by the familiar Fokker-Planck operator. The boundary conditions for the time dependent density depend on the model of the controller; however, this dependence disappears in the steady state, if the controller is of a renewal type. Renewal-type controllers, however, produce spurious boundary layers that can be catastrophic in simulations of charged particles, because even a tiny net charge can have global effects. The design of a nonrenewal controller that maintains concentrations of noninteracting particles without creating spurious boundary layers at the interface requires the solution of the time-dependent Fokker-Planck equation with absorption of outgoing trajectories and a source of ingoing trajectories on the boundary (the so called albedo problem).

Atmospheric methane over Siberia: measurements from the 2014 YAK-AEROSIB aircraft campaign

NASA Astrophysics Data System (ADS)

Paris, Jean-Daniel; Pisso, Ignacio; Ancellet, Gérard; Law, Kathy; Arshinov, Mikhail Yu.; Belan, Boris D.; Nédélec, Philippe; Myhre, Cathrine Lund

2017-04-01

The YAK-AEROSIB program collects high-precision in-situ measurements of the vertical distribution of CO2, CH4, CO, O3, black carbon and ultrafine particles distribution in the Siberian troposphere, as well as other parameters including aerosol lidar profiles, on a pan-Siberian aircraft transect. Recent efforts aim at better understanding the respective role of CH4 emission processes in driving its large scale atmospheric variability over the region. The October 2014 YAK-AEROSIB/MOCA campaign from Novosibirsk to Salekhard and over the Kara sea and the Yamal peninsula sampled air masses affected by local, regional and remote pollution. We analyse the contribution of local anthropogenic sources to measured CH4 enhancements, in relation to atmospheric mixing and transport conditions. Our analysis also attempts to detect CH4 signal from sources of methane in the Siberian shelf and the Arctic ocean during low level flight legs over the Kara sea using the airborne measurements and a Lagrangian model coupled to potential CH4 hydrate and geological sources. The measured CH4 concentrations do not contradict a potential source upstream of our measurements, but the interpretation is challenging due to a very low CH4 signal. The challenging question of the methane budget and its evolution in Siberia leads to a need for new approaches. A new generation of airborne measurements, more flexible, is now needed.

The GALEX Catalog of UV Sources in the Magellanic Clouds

NASA Astrophysics Data System (ADS)

Thilker, David A.; Bianchi, L.; Simons, R.

2014-01-01

The Galaxy Evolution Explorer (GALEX) has performed unprecedented imaging surveys of the Magellanic Clouds (MC) and their surrounding areas including the Magellanic Bridge (MB) in near-UV (NUV, 1771-2831 Å) and far-UV (FUV, 1344-1786 Å) bands at 5″ resolution. Substantially more area was covered in the NUV than FUV, particularly in the bright central regions, because of the GALEX FUV detector failure. The 5σ depth of the NUV imaging varies between 20.8 and 22.7 (ABmag). Such imaging provides the first sensitive view of the entire content of hot stars in the Magellanic System, revealing the presence of young populations even in sites with extremely low star-formation rate surface density like the MB, owing to high sensitivity of the UV data to hot stars and the dark sky at these wavelengths. Crowding limits the quality of source detection and photometry from the standard mission pipeline processing. Therefore, we performed custom PSF-fitting photometry of the GALEX data in the MC survey region (<15° from the LMC, <10° from the SMC). After merging multiple detections of sources in overlapping images, the resulting catalog we have produced contains many million unique NUV point sources. This poster provides a first look at the GALEX MC survey and highlights some of the science investigations that the catalog and imaging dataset will make possible.

Mitochondrial introgression suggests extensive ancestral hybridization events among Saccharomyces species.

PubMed

Peris, David; Arias, Armando; Orlić, Sandi; Belloch, Carmela; Pérez-Través, Laura; Querol, Amparo; Barrio, Eladio

2017-03-01

Horizontal gene transfer (HGT) in eukaryotic plastids and mitochondrial genomes is common, and plays an important role in organism evolution. In yeasts, recent mitochondrial HGT has been suggested between S. cerevisiae and S. paradoxus. However, few strains have been explored given the lack of accurate mitochondrial genome annotations. Mitochondrial genome sequences are important to understand how frequent these introgressions occur, and their role in cytonuclear incompatibilities and fitness. Indeed, most of the Bateson-Dobzhansky-Muller genetic incompatibilities described in yeasts are driven by cytonuclear incompatibilities. We herein explored the mitochondrial inheritance of several worldwide distributed wild Saccharomyces species and their hybrids isolated from different sources and geographic origins. We demonstrated the existence of several recombination points in mitochondrial region COX2-ORF1, likely mediated by either the activity of the protein encoded by the ORF1 (F-SceIII) gene, a free-standing homing endonuclease, or mostly facilitated by A+T tandem repeats and regions of integration of GC clusters. These introgressions were shown to occur among strains of the same species and among strains of different species, which suggests a complex model of Saccharomyces evolution that involves several ancestral hybridization events in wild environments. Copyright © 2017 Elsevier Inc. All rights reserved.

Exploring equivalence domain in nonlinear inverse problems using Covariance Matrix Adaption Evolution Strategy (CMAES) and random sampling

NASA Astrophysics Data System (ADS)

Grayver, Alexander V.; Kuvshinov, Alexey V.

2016-05-01

This paper presents a methodology to sample equivalence domain (ED) in nonlinear partial differential equation (PDE)-constrained inverse problems. For this purpose, we first applied state-of-the-art stochastic optimization algorithm called Covariance Matrix Adaptation Evolution Strategy (CMAES) to identify low-misfit regions of the model space. These regions were then randomly sampled to create an ensemble of equivalent models and quantify uncertainty. CMAES is aimed at exploring model space globally and is robust on very ill-conditioned problems. We show that the number of iterations required to converge grows at a moderate rate with respect to number of unknowns and the algorithm is embarrassingly parallel. We formulated the problem by using the generalized Gaussian distribution. This enabled us to seamlessly use arbitrary norms for residual and regularization terms. We show that various regularization norms facilitate studying different classes of equivalent solutions. We further show how performance of the standard Metropolis-Hastings Markov chain Monte Carlo algorithm can be substantially improved by using information CMAES provides. This methodology was tested by using individual and joint inversions of magneotelluric, controlled-source electromagnetic (EM) and global EM induction data.

Crustal evolution inferred from Apollo magnetic measurements

NASA Technical Reports Server (NTRS)

Dyal, P.; Daily, W. D.; Vanian, L. L.

1978-01-01

The topology of lunar remanent fields is investigated by analyzing simultaneous magnetometer and solar wind spectrometer data. The diffusion model proposed by Vanyan (1977) to describe the field-plasma interaction at the lunar surface is extended to describe the interaction with fields characterized by two scale lengths, and the extended model is compared with data from three Apollo landing sites (Apollo 12, 15 and 16) with crustal fields of differing intensity and topology. Local remanent field properties from this analysis are compared with high spatial resolution magnetic maps obtained from the electron reflection experiment. It is concluded that remanent fields over most of the lunar surface are characterized by spatial variations as small as a few kilometers. Large regions (50 to 100 km) of the lunar crust were probably uniformly magnetized early in the evolution of the crust. Smaller scale (5 to 10 km) magnetic sources close to the surface were left by bombardment and subsequent gardening of the upper layers of these magnetized regions. The small scale sized remanent fields of about 100 gammas are measured by surface experiments, whereas the larger scale sized fields of about 0.1 gammas are measured by the orbiting subsatellite experiments.

Operation of a high impedance applied-B extraction ion diode on the SABRE positive polarity linear induction accelerator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hanson, D.L.; Cuneo, M.E.; McKay, P.F.

We present results from initial experiments with a high impedance applied-B extraction diode on the SABRE ten stage linear induction accelerator (6.7 MV, 300 kA). We have demonstrated efficient coupling of power from the accelerator through an extended MITL (Magnetically Insulated Transmission Line) into a high intensity ion beam. Both MITL electron flow in the diode region and ion diode behavior, including ion source turn-on, virtual cathode formation and evolution, enhancement delay, and ion coupling efficiency, are strongly influenced by the geometry of the diode insulating magnetic field. For our present diode electrode geometry, electrons from the diode feed stronglymore » influence the evolution of the virtual cathode. Both experimental data and particle-in-cell numerical simulations show that uniform insulation of these feed electrons is required for uniform ion emission and efficient diode operation.« less

Trends of atmospheric circulation during singular hot days in Europe

NASA Astrophysics Data System (ADS)

Jézéquel, Aglaé; Cattiaux, Julien; Naveau, Philippe; Radanovics, Sabine; Ribes, Aurélien; Vautard, Robert; Vrac, Mathieu; Yiou, Pascal

2018-05-01

The influence of climate change on mid-latitudes atmospheric circulation is still very uncertain. The large internal variability makes it difficult to extract any statistically significant signal regarding the evolution of the circulation. Here we propose a methodology to calculate dynamical trends tailored to the circulation of specific days by computing the evolution of the distances between the circulation of the day of interest and the other days of the time series. We compute these dynamical trends for two case studies of the hottest days recorded in two different European regions (corresponding to the heat-waves of summer 2003 and 2010). We use the NCEP reanalysis dataset, an ensemble of CMIP5 models, and a large ensemble of a single model (CESM), in order to account for different sources of uncertainty. While we find a positive trend for most models for 2003, we cannot conclude for 2010 since the models disagree on the trend estimates.

PM sources in a highly industrialised area in the process of implementing PM abatement technology. Quantification and evolution.

PubMed

Cruz Minguillón, María; Querol, Xavier; Alastuey, Andrés; Monfort, Eliseo; Vicente Miró, José

2007-10-01

Principal component analysis (PCA) coupled with a multilinear regression analysis (MLRA) was applied to PM(10) speciation data series (2002-2005) from four sampling sites in a highly industrialised area (ceramic production) in the process of implementing emission abatement technology. Five common factors with similar chemical profiles were identified at all the sites: mineral, regional background (influenced by the industrial estate located on the coast: an oil refinery and a power plant), sea spray, industrial 1 (manufacture and use of glaze components, including frit fusion) and road traffic. The contribution of the regional background differs slightly from site to site. The mineral factor, attributed to the sum of several sources (mainly the ceramic industry, but also with minor contributions from soil resuspension and African dust outbreaks) contributes between 9 and 11 microg m(-3) at all the sites. Source industrial 1 entails an increase in PM(10) levels between 4 and 5 microg m(-3) at the urban sites and 2 microg m(-3) at the suburban background site. However, after 2004, this source contributed less than 2 microg m(-3) at most sites, whereas the remaining sources did not show an upward or downward trend along the study period. This gradual decrease in the contribution of source industrial 1 coincides with the implementation of PM abatement technology in the frit fusion kilns of the area. This relationship enables us to assess the efficiency of the implementation of environmental technologies in terms of their impact on air quality.

Connecting Coronal Mass Ejections to Their Solar Active Region Sources: Combining Results from the HELCATS and FLARECAST Projects

NASA Astrophysics Data System (ADS)

Murray, Sophie A.; Guerra, Jordan A.; Zucca, Pietro; Park, Sung-Hong; Carley, Eoin P.; Gallagher, Peter T.; Vilmer, Nicole; Bothmer, Volker

2018-04-01

Coronal mass ejections (CMEs) and other solar eruptive phenomena can be physically linked by combining data from a multitude of ground-based and space-based instruments alongside models; however, this can be challenging for automated operational systems. The EU Framework Package 7 HELCATS project provides catalogues of CME observations and properties from the Heliospheric Imagers on board the two NASA/STEREO spacecraft in order to track the evolution of CMEs in the inner heliosphere. From the main HICAT catalogue of over 2,000 CME detections, an automated algorithm has been developed to connect the CMEs observed by STEREO to any corresponding solar flares and active-region (AR) sources on the solar surface. CME kinematic properties, such as speed and angular width, are compared with AR magnetic field properties, such as magnetic flux, area, and neutral line characteristics. The resulting LOWCAT catalogue is also compared to the extensive AR property database created by the EU Horizon 2020 FLARECAST project, which provides more complex magnetic field parameters derived from vector magnetograms. Initial statistical analysis has been undertaken on the new data to provide insight into the link between flare and CME events, and characteristics of eruptive ARs. Warning thresholds determined from analysis of the evolution of these parameters is shown to be a useful output for operational space weather purposes. Parameters of particular interest for further analysis include total unsigned flux, vertical current, and current helicity. The automated method developed to create the LOWCAT catalogue may also be useful for future efforts to develop operational CME forecasting.

Impact of increasing antarctic glacial freshwater release on regional sea-ice cover in the Southern Ocean

NASA Astrophysics Data System (ADS)

Merino, Nacho; Jourdain, Nicolas C.; Le Sommer, Julien; Goosse, Hugues; Mathiot, Pierre; Durand, Gael

2018-01-01

The sensitivity of Antarctic sea-ice to increasing glacial freshwater release into the Southern Ocean is studied in a series of 31-year ocean/sea-ice/iceberg model simulations. Glaciological estimates of ice-shelf melting and iceberg calving are used to better constrain the spatial distribution and magnitude of freshwater forcing around Antarctica. Two scenarios of glacial freshwater forcing have been designed to account for a decadal perturbation in glacial freshwater release to the Southern Ocean. For the first time, this perturbation explicitly takes into consideration the spatial distribution of changes in the volume of Antarctic ice shelves, which is found to be a key component of changes in freshwater release. In addition, glacial freshwater-induced changes in sea ice are compared to typical changes induced by the decadal evolution of atmospheric states. Our results show that, in general, the increase in glacial freshwater release increases Antarctic sea ice extent. But the response is opposite in some regions like the coastal Amundsen Sea, implying that distinct physical mechanisms are involved in the response. We also show that changes in freshwater forcing may induce large changes in sea-ice thickness, explaining about one half of the total change due to the combination of atmospheric and freshwater changes. The regional contrasts in our results suggest a need for improving the representation of freshwater sources and their evolution in climate models.

Rapid radiation and dispersal out of the Qinghai-Tibetan Plateau of an alpine plant lineage Rhodiola (Crassulaceae).

PubMed

Zhang, Jian-Qiang; Meng, Shi-Yong; Allen, Geraldine A; Wen, Jun; Rao, Guang-Yuan

2014-08-01

Rhodiola L. (Crassulaceae) is a mid-sized plant genus consisting of about 70 species, with most species distributed on the Qinghai-Tibetan Plateau (QTP) and the adjacent areas, and several species in north-east Asia, Europe, and North America. This study explored the origin and diversification history of Rhodiola and tested the biogeographic relationships between the QTP and other regions of the Northern Hemisphere. We sequenced the nuclear ribosomal internal transcribed spacers and eight plastid DNA fragments representing 55 species of Rhodiola, and reconstructed phylogenetic relationships with maximum parsimony, maximum likelihood and Bayesian inference. Several instances of incongruence between the nuclear and the plastid data sets were revealed, which can best be explained by reticulate evolution. Species of Rhodiola and Pseudosedum form a well-supported clade sister to Phedimus. Dating analysis suggested that the origin and diversification times of this group are largely correlated with the extensive uplifts of the Qinghai-Tibetan Plateau. Ancestral state reconstruction supports the hypothesis that Rhodiola originated on the QTP, and then dispersed to other regions of the Northern Hemisphere. Our findings highlight the importance of the uplifts of the Qinghai-Tibetan Plateau in promoting species diversification and the possible role of reticulate evolution in the diversification process. Our results also suggest the biogeographic significance of QTP as the source area in alpine plant evolution in the Northern Hemisphere. Copyright © 2014 Elsevier Inc. All rights reserved.

RECONNECTION PROPERTIES OF LARGE-SCALE CURRENT SHEETS DURING CORONAL MASS EJECTION ERUPTIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lynch, B. J.; Kazachenko, M. D.; Edmondson, J. K.

2016-07-20

We present a detailed analysis of the properties of magnetic reconnection at large-scale current sheets (CSs) in a high cadence version of the Lynch and Edmondson 2.5D MHD simulation of sympathetic magnetic breakout eruptions from a pseudostreamer source region. We examine the resistive tearing and break-up of the three main CSs into chains of X- and O-type null points and follow the dynamics of magnetic island growth, their merging, transit, and ejection with the reconnection exhaust. For each CS, we quantify the evolution of the length-to-width aspect ratio (up to ∼100:1), Lundquist number (∼10{sup 3}), and reconnection rate (inflow-to-outflow ratiosmore » reaching ∼0.40). We examine the statistical and spectral properties of the fluctuations in the CSs resulting from the plasmoid instability, including the distribution of magnetic island area, mass, and flux content. We show that the temporal evolution of the spectral index of the reconnection-generated magnetic energy density fluctuations appear to reflect global properties of the CS evolution. Our results are in excellent agreement with recent, high-resolution reconnection-in-a-box simulations even though our CSs’ formation, growth, and dynamics are intrinsically coupled to the global evolution of sequential sympathetic coronal mass ejection eruptions.« less

The low-recombining pericentromeric region of barley restricts gene diversity and evolution but not gene expression

PubMed Central

Baker, Katie; Bayer, Micha; Cook, Nicola; Dreißig, Steven; Dhillon, Taniya; Russell, Joanne; Hedley, Pete E; Morris, Jenny; Ramsay, Luke; Colas, Isabelle; Waugh, Robbie; Steffenson, Brian; Milne, Iain; Stephen, Gordon; Marshall, David; Flavell, Andrew J

2014-01-01

The low-recombining pericentromeric region of the barley genome contains roughly a quarter of the genes of the species, embedded in low-recombining DNA that is rich in repeats and repressive chromatin signatures. We have investigated the effects of pericentromeric region residency upon the expression, diversity and evolution of these genes. We observe no significant difference in average transcript level or developmental RNA specificity between the barley pericentromeric region and the rest of the genome. In contrast, all of the evolutionary parameters studied here show evidence of compromised gene evolution in this region. First, genes within the pericentromeric region of wild barley show reduced diversity and significantly weakened purifying selection compared with the rest of the genome. Second, gene duplicates (ohnolog pairs) derived from the cereal whole-genome duplication event ca. 60MYa have been completely eliminated from the barley pericentromeric region. Third, local gene duplication in the pericentromeric region is reduced by 29% relative to the rest of the genome. Thus, the pericentromeric region of barley is a permissive environment for gene expression but has restricted gene evolution in a sizeable fraction of barley's genes. PMID:24947331

Petrogenesis of Mare Basalts, Mg-Rich Suites and SNC Parent Magmas

NASA Technical Reports Server (NTRS)

Hess, Paul C.

2004-01-01

The successful models for the internal evolution of the Moon must consider the volume, distribution, timing, composition and, ultimately, the petrogenesis of mare basaltic volcanism. Indeed, given the paucity of geophysical data, the internal state of the Moon in the past can be gleaned only be unraveling the petrogenesis of the various igneous products on the Moon and, particularly, the mare basalts. most useful in constraining the depth and composition of their source region [Delano, 1980] despite having undergone a certain degree of shallow level olivine crystallization.The bulk of the lunar volcanic glass suite can be modeled as the partial melting products of an olivine + orthopyroxene source region deep within the lunar mantle. Ti02 contents vary from 0.2 wt % -1 7.0wt [Shearer and Papike, 1993]. Values that extreme would seem to require a Ti- bearing phase such as ilmenite in the source of the high-Ti (but not in the VLT source) because a source region of primitive LMO olivine and orthopyroxene, even when melted in small degrees cannot account for the observed range of Ti02 compositions. The picritic glasses are undersaturated with respect to ilmenite at all pressures investigated therefore ilmenite must have been consumed during melting, leaving an ilmenite free residue and an undersaturated melt [Delano, 1980, Longhi, 1992, Elkins et al, 2000 among others]. Multi- saturation pressures for the glasses potentially represent the last depths at which the liquids equilibrated with a harzburgite residue before ascending to the surface. These occur at great depths within the lunar mantle. Because the liquids have suffered some amount of crystal fractionation, this is at best a minimum depth. If the melts are mixtures, then it is only an average depth of melting. Multisaturation, nevertheless, is still a strong constraint on source mineralogy, revealing that the generation of the lunar basalts was dominated by melting of olivine and orthopyroxene.

Analysis of Earthquake Source Spectra in Salton Trough

NASA Astrophysics Data System (ADS)

Chen, X.; Shearer, P. M.

2009-12-01

Previous studies of the source spectra of small earthquakes in southern California show that average Brune-type stress drops vary among different regions, with particularly low stress drops observed in the Salton Trough (Shearer et al., 2006). The Salton Trough marks the southern end of the San Andreas Fault and is prone to earthquake swarms, some of which are driven by aseismic creep events (Lohman and McGuire, 2007). In order to learn the stress state and understand the physical mechanisms of swarms and slow slip events, we analyze the source spectra of earthquakes in this region. We obtain Southern California Seismic Network (SCSN) waveforms for earthquakes from 1977 to 2009 archived at the Southern California Earthquake Center (SCEC) data center, which includes over 17,000 events. After resampling the data to a uniform 100 Hz sample rate, we compute spectra for both signal and noise windows for each seismogram, and select traces with a P-wave signal-to-noise ratio greater than 5 between 5 Hz and 15 Hz. Using selected displacement spectra, we isolate the source spectra from station terms and path effects using an empirical Green’s function approach. From the corrected source spectra, we compute corner frequencies and estimate moments and stress drops. Finally we analyze spatial and temporal variations in stress drop in the Salton Trough and compare them with studies of swarms and creep events to assess the evolution of faulting and stress in the region. References: Lohman, R. B., and J. J. McGuire (2007), Earthquake swarms driven by aseismic creep in the Salton Trough, California, J. Geophys. Res., 112, B04405, doi:10.1029/2006JB004596 Shearer, P. M., G. A. Prieto, and E. Hauksson (2006), Comprehensive analysis of earthquake source spectra in southern California, J. Geophys. Res., 111, B06303, doi:10.1029/2005JB003979.

Isotopic and Hydrogeochemical Assessment of Groundwater quality of Punjab and Haryana, India.

NASA Astrophysics Data System (ADS)

Jyoti, V.; Douglas, E. M.; Hannigan, R.; Schaaf, C.; Moore, J.

2016-12-01

Punjab and Haryana lie in the semi-arid region of northwestern India and are characterized by a limited access to freshwater resources and an increasing dependence on groundwater resources to meet human demand, resulting in overexploitation. The objectives of the present study was to characterize groundwater recharge sources using stable isotopes of (δ2H) and (δ18O) and to trace geochemical evolution of groundwater using rare earth elements (REEs). Samples were collected from 30 different locations including shallow domestic handpumps, deep irrigation wells, surface water and rainwater. Samples were analyzed for stable isotopes of (δ2H) and (δ18O) using Isotope Ratio Mass Spectrometry (IRMS) and trace elements using Inductively Coupled Plasma Mass Spectrometry (ICPMS) at University of Massachusetts Boston. Precipitation, surface water and irrigation return flow were identified as the primary sources of recharge to groundwater. Sustainability of recharge sources is highly dependent on the glacier-fed rivers from the Himalayas that are already experiencing impacts from climate change. Geochemistry of REEs revealed geochemically evolved groundwater system with carbonate subsurface weathering as major hydrological processes. Enhanced dissolution of carbonates in the future can be a serious issue with extremely hard groundwater leaving scaly deposits inside pipes and wells. This would not only worsen the groundwater quality but would impose financial implications on the groundwater users in the community. If irrigated culture is to survive as an economically viable and environmentally sustainable activity in the region, groundwater management activities have to be planned at the regional scale.

Successive Two-sided Loop Jets Caused by Magnetic Reconnection between Two Adjacent Filamentary Threads

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tian, Zhanjun; Liu, Yu; Shen, Yuandeng

We present observational analysis of two successive two-sided loop jets observed by the ground-based New Vacuum Solar Telescope and the space-borne Solar Dynamics Observatory . The two successive two-sided loop jets manifested similar evolution processes and both were associated with the interaction of two small-scale adjacent filamentary threads, magnetic emerging, and cancellation processes at the jet’s source region. High temporal and high spatial resolution observations reveal that the two adjacent ends of the two filamentary threads are rooted in opposite magnetic polarities within the source region. The two threads approached each other, and then an obvious brightening patch is observedmore » at the interaction position. Subsequently, a pair of hot plasma ejections are observed heading in opposite directions along the paths of the two filamentary threads at a typical speed for two-sided loop jets of the order 150 km s{sup −1}. Close to the end of the second jet, we report the formation of a bright hot loop structure at the source region, which suggests the formation of new loops during the interaction. Based on the observational results, we propose that the observed two-sided loop jets are caused by magnetic reconnection between the two adjacent filamentary threads, largely different from the previous scenario that a two-sided loop jet is generated by magnetic reconnection between an emerging bipole and the overlying horizontal magnetic fields.« less

Source Regions of the Interplanetary Magnetic Field and Variability in Heavy-Ion Elemental Composition in Gradual Solar Energetic Particle Events

NASA Technical Reports Server (NTRS)

Ko, Yuan-Kuen; Tylka, Allan J.; Ng, Chee K.; Wang, Yi-Ming; Dietrich, William F.

2013-01-01

Gradual solar energetic particle (SEP) events are those in which ions are accelerated to their observed energies by interactions with a shock driven by a fast coronal mass-ejection (CME). Previous studies have shown that much of the observed event-to-event variability can be understood in terms of shock speed and evolution in the shock-normal angle. But an equally important factor, particularly for the elemental composition, is the origin of the suprathermal seed particles upon which the shock acts. To tackle this issue, we (1) use observed solar-wind speed, magnetograms, and the PFSS model to map the Sun-L1 interplanetary magnetic field (IMF) line back to its source region on the Sun at the time of the SEP observations; and (2) then look for correlation between SEP composition (as measured by Wind and ACE at approx. 2-30 MeV/nucleon) and characteristics of the identified IMF-source regions. The study is based on 24 SEP events, identified as a statistically-significant increase in approx. 20 MeV protons and occurring in 1998 and 2003-2006, when the rate of newly-emergent solar magnetic flux and CMEs was lower than in solar-maximum years and the field-line tracing is therefore more likely to be successful. We find that the gradual SEP Fe/O is correlated with the field strength at the IMF-source, with the largest enhancements occurring when the footpoint field is strong, due to the nearby presence of an active region. In these cases, other elemental ratios show a strong charge-to-mass (q/M) ordering, at least on average, similar to that found in impulsive events. These results lead us to suggest that magnetic reconnection in footpoint regions near active regions bias the heavy-ion composition of suprathermal seed ions by processes qualitatively similar to those that produce larger heavy-ion enhancements in impulsive SEP events. To address potential technical concerns about our analysis, we also discuss efforts to exclude impulsive SEP events from our event sample.

Source Regions of the Interplanetary Magnetic Field and Variability in Heavy-Ion Elemental Composition in Gradual Solar Energetic Particle Events (Invited)

NASA Astrophysics Data System (ADS)

Tylka, A. J.; Ko, Y.; Ng, C. K.; Wang, Y.; Dietrich, W. F.

2013-12-01

Gradual solar energetic particle (SEP) events are those in which ions are accelerated to their observed energies by interactions with a shock driven by a fast coronal mass-ejection (CME). Previous studies have shown that much of the observed event-to-event variability can be understood in terms of shock speed and evolution in the shock-normal angle. But an equally important factor, particularly for the elemental composition, is the origin of the suprathermal seed particles upon which the shock acts. To tackle this issue, we (1) use observed solar-wind speed, magnetograms, and the PFSS model to map the Sun-L1 interplanetary magnetic field (IMF) line back to its source region on the Sun at the time of the SEP observations; and (2) then look for correlation between SEP composition (as measured by Wind and ACE at ~2-30 MeV/nucleon) and characteristics of the identified IMF-source regions. The study is based on 24 SEP events, identified as a statistically-significant increase in ~20 MeV protons and occurring in 1998 and 2003-2006, when the rate of newly-emergent solar magnetic flux and CMEs was lower than in solar-maximum years and the field-line tracing is therefore more likely to be successful. We find that the gradual SEP Fe/O is correlated with the field strength at the IMF-source, with the largest enhancements occurring when the footpoint field is strong, due to the nearby presence of an active region. In these cases, other elemental ratios show a strong charge-to-mass (q/M) ordering, at least on average, similar to that found in impulsive events. These results lead us to suggest that magnetic reconnection in footpoint regions near active regions bias the heavy-ion composition of suprathermal seed ions by processes qualitatively similar to those that produce larger heavy-ion enhancements in impulsive SEP events. To address potential technical concerns about our analysis, we also discuss efforts to exclude impulsive SEP events from our event sample.

The Galactic Magnetic Field as Viewed from the VLA

NASA Astrophysics Data System (ADS)

van Eck, Cameron; Brown, Jo-Anne

2009-05-01

Interstellar magnetic fields play critical roles in many astrophysical processes. Yet despite their importance, our knowledge about magnetic fields in our Galaxy remains limited. For the field within the Milky Way much of what we do know comes from radio astronomy, through observations of polarization and Faraday rotation measures (RMs) of extragalactic sources and pulsars. A high angular density of RM measurements in several critical areas of the Galaxy is needed to clarify the Galactic magnetic field structure. Understanding the overall structure of the magnetic field will subsequently help us determine the origin and evolution of the field. In an effort to determine the overall structure of the field, Sun et al. (2008) produced 3 models of the Galactic magnetic field based on RM measurements available at the time. These models made distinct predictions for RMs in a region of the inner Galaxy at low Galactic latitude. Using observations made with the Very Large Array (VLA), we have determined RMs for sources in this critical region. In this talk we will present the results of our study and show how the RMs strongly support the ASS+RING model.

Characteristics of sources and sinks of momentum in a turbulent boundary layer

NASA Astrophysics Data System (ADS)

Fiscaletti, D.; Ganapathisubramani, B.

2018-05-01

In turbulent boundary layers, the wall-normal gradient of the Reynolds shear stress identifies momentum sources and sinks (T =∂ [-u v ]/∂ y ). These motions can be physically interpreted in two ways: (1) as contributors to the turbulence term balancing the mean momentum equation, and (2) as regions of strong local interaction between velocity and vorticity fluctuations. In this paper, the space-time evolution of momentum sources and sinks is investigated in a turbulent boundary layer at the Reynolds number (Reτ) = 2700, with time-resolved planar particle image velocimetry in a plane along the streamwise and wall-normal directions. Wave number-frequency power spectra of T fluctuations reveal that the wave velocities of momentum sources and sinks tend to match the local streamwise velocity in proximity to the wall. However, as the distance from the wall increases, the wave velocities of the T events are slightly lower than the local streamwise velocities of the flow, which is also confirmed from the tracking in time of the intense momentum sources and sinks. This evidences that momentum sources and sinks are preferentially located in low-momentum regions of the flow. The spectral content of the T fluctuations is maximum at the wall, but it decreases monotonically as the distance from the wall grows. The relative spectral contributions of the different wavelengths remains unaltered at varying wall-normal locations. From autocorrelation coefficient maps, the characteristic streamwise and wall-normal extents of the T motions are respectively 60 and 40 wall units, independent of the wall distance. Both statistics and instantaneous visualizations show that momentum sources and sinks have a preferential tendency to be organized in positive-negative pairs in the wall-normal direction.

Water in star-forming regions with Herschel (WISH). II. Evolution of 557 GHz 110-101 emission in low-mass protostars

NASA Astrophysics Data System (ADS)

Kristensen, L. E.; van Dishoeck, E. F.; Bergin, E. A.; Visser, R.; Yıldız, U. A.; San Jose-Garcia, I.; Jørgensen, J. K.; Herczeg, G. J.; Johnstone, D.; Wampfler, S. F.; Benz, A. O.; Bruderer, S.; Cabrit, S.; Caselli, P.; Doty, S. D.; Harsono, D.; Herpin, F.; Hogerheijde, M. R.; Karska, A.; van Kempen, T. A.; Liseau, R.; Nisini, B.; Tafalla, M.; van der Tak, F.; Wyrowski, F.

2012-06-01

Context. Water is a key tracer of dynamics and chemistry in low-mass star-forming regions, but spectrally resolved observations have so far been limited in sensitivity and angular resolution, and only data from the brightest low-mass protostars have been published. Aims: The first systematic survey of spectrally resolved water emission in 29 low-mass (L < 40 L⊙) protostellar objects is presented. The sources cover a range of luminosities and evolutionary states. The aim is to characterise the line profiles to distinguish physical components in the beam and examine how water emission changes with protostellar evolution. Methods: H2O was observed in the ground-state 110-101 transition at 557 GHz (Eup/kB ~ 60 K) as single-point observations with the Heterodyne Instrument for the Far-Infrared (HIFI) on Herschel in 29 deeply embedded Class 0 and I low-mass protostars. Complementary far-IR and sub-mm continuum data (including PACS data from our programme) are used to constrain the spectral energy distribution (SED) of each source. H2O intensities are compared to inferred envelope properties, e.g., mass and density, outflow properties and CO 3-2 emission. Results: H2O emission is detected in all objects except one (TMC1A). The line profiles are complex and consist of several kinematic components tracing different physical regions in each system. In particular, the profiles are typically dominated by a broad Gaussian emission feature, indicating that the bulk of the water emission arises in outflows, not in the quiescent envelope. Several sources show multiple shock components appearing in either emission or absorption, thus constraining the internal geometry of the system. Furthermore, the components include inverse P-Cygni profiles in seven sources (six Class 0, one Class I) indicative of infalling envelopes, and regular P-Cygni profiles in four sources (three Class I, one Class 0) indicative of expanding envelopes. Molecular "bullets" moving at ≳50 km s-1 with respect to the source are detected in four Class 0 sources; three of these sources were not known to harbour bullets previously. In the outflow, the H2O/CO abundance ratio as a function of velocity is nearly the same for all line wings, increasing from 10-3 at low velocities (<5 km s-1) to ≳10-1 at high velocities (>10 km s-1). The water abundance in the outer cold envelope is low, ≳10-10. The different H2O profile components show a clear evolutionary trend: in the younger Class 0 sources the emission is dominated by outflow components originating inside an infalling envelope. When large-scale infall diminishes during the Class I phase, the outflow weakens and H2O emission all but disappears. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.Appendices are available in electronic form at http://www.aanda.org

Some Characteristics of Current Star Formation in the 30 Doradus Nebula Revealed by HST/NICMOS

NASA Astrophysics Data System (ADS)

Walborn, Nolan R.; Barbá, Rodolfo H.; Brandner, Wolfgang; Rubio, Mónica; Grebel, Eva K.; Probst, Ronald G.

1999-01-01

The extensive ``second generation'' of star formation within the 30 Doradus Nebula, evidently triggered by the R136 central cluster around its periphery, has been imaged with the Near-Infrared Camera and Multi-Object Spectrometer (NICMOS) on the Hubble Space Telescope. Many new IR sources, including multiple systems, clusters, and nebular structures, are found in these images. Six of the NICMOS fields are described here, in comparison with the WFPC2 images of the same fields. Knots 1-3 of Walborn & Blades (early O stars embedded in dense nebular knots) are all found to be compact multiple systems. Knot 1 is shown to reside at the top of a massive dust pillar oriented directly toward R136, whose summit has just been removed, exposing the newborn stellar system. Knots 1 and 3 are also near the brightest IR sources in the region, while parsec-scale jet structures are discovered in association with Knots 2 and 3. The Knot 2 structures consist of detached, nonstellar IR sources aligned on either side of the stellar system, which are interpreted as impact points of a highly collimated, possibly rotating bipolar jet on the surrounding dark clouds; the H_2O maser found by Whiteoak et al. is also in this field. These outflows from young massive stars in 30 Dor are the first extragalactic examples of the phenomenon. In the field of the pillars south of R136, recently discussed in comparison with the M16 pillars by Scowen et al., a new luminous stellar IR source has been discovered. These results establish the 30 Doradus Nebula as a prime region in which to investigate the formation and very early evolution of massive stars and multiple systems. The theme of triggered formation within the heads of extensive dust pillars oriented toward R136 is strong. In addition, these results provide further insights into the global structure and evolution of 30 Doradus, which are significant in view of its status as the best resolved extragalactic starburst. This paper is dedicated to W. W. Morgan, who taught me the power of morphology to uncover new phenomena in astronomy.-N. R. W.

CURRENT SHEET THINNING AND ENTROPY CONSTRAINTS DURING THE SUBSTORM GROWTH PHASE

NASA Astrophysics Data System (ADS)

Otto, A.; Hall, F., IV

2009-12-01

A typical property during the growth phase of geomagnetic substorms is the thinning of the near-Earth current sheet, most pronounced in the region between 6 and 15 R_E. We propose that the cause for the current sheet thinning is convection from the midnight tail region to the dayside to replenish magnetospheric magnetic flux which is eroded at the dayside as a result of dayside reconnection. Adiabatic convection from the near-Earth tail region toward the dayside must conserve the entropy on magnetic field lines. This constraint prohibits a source of the magnetic flux from a region further out in the magnetotail. Thus the near-Earth tail region is increasingly depleted of magnetic flux (the Erickson and Wolf [1980] problem) with entropy matching that of flux tubes that are eroded on the dayside. It is proposed that the magnetic flux depletion in the near-Earth tail forces the formation of thin current layers. The process is documented by three-dimensional MHD simulations. It is shown that the simulations yield a time scale, location, and other general characteristics of the current sheet evolution during the substorm growth phase.

U-Pb Detrital Zircon Ages from Sarawak: Changes in Provenance Reflecting the Tectonic Evolution of Southeast Asia

NASA Astrophysics Data System (ADS)

Breitfeld, H. T.; Galin, T.; Hall, R.

2014-12-01

Sarawak is located on the northern edge of Sundaland in NW Borneo. Five sedimentary basins are distinguished with ages from Triassic to Cenozoic. New light mineral, heavy mineral and U-Pb detrital zircon ages show differences in provenance reflecting the tectonic evolution of the region. The oldest clastic sediments are Triassic of the Sadong-Kuching Basin and were sourced by a Carnian to Norian volcanic arc and erosion of Cathaysian rocks containing zircons of Paleoproterozoic age. Sandstones of the Upper Jurassic to Cretaceous Bau-Pedawan Basin have distinctive zircon populations indicating a major change of tectonic setting, including initiation of subduction below present-day West Sarawak in the Late Jurassic. A wide range of inherited zircon ages indicates various Cathaysian fragments as major source areas and the arrival of the SW Borneo Block following subduction beneath the Schwaner Mountains in the early Late Cretaceous. After collision of the SW Borneo Block and the microcontinental fragments with Sundaland in the early Late Cretaceous, deep marine sedimentation (Pedawan Formation) ceased, and there was uplift forming the regional Pedawan-Kayan unconformity. Two episodes of extension were responsible for basin development on land from the latest Cretaceous onwards, probably in a strike-slip setting. The first episode formed the Kayan Basin in the Latest Cretaceous (Maastrichtian) to Early Paleocene, and the second formed the Ketungau Basin and the Penrissen Sandstone in the Middle to Late Eocene. Zircons indicate nearby volcanic activity throughout the Early Cenozoic in NW Borneo. Inherited zircon ages indicate an alternation between Borneo and Tin Belt source rocks. A large deep marine basin, the Rajang Basin, formed north of the Lupar Line fault. Zircons from sediments of the Rajang Basin indicate they are of similar age and provenance as the contemporaneous terrestrial sediments to the south suggesting a narrow steep continental Sundaland margin at the position of the Lupar Line.

Surface and Lightning Sources of Nitrogen Oxides over the United States: Magnitudes, Chemical Evolution, and Outflow

NASA Technical Reports Server (NTRS)

Hudman, Rynda C.; Jacob, Daniel J.; Turquety, Solene; Leinbensperger, E. M.; Murray, L. T.; Wu, Samuel; Gilliland, A. B.; Avery, Melody A.; Bertram, Timothy H.; Brune, W. H.;

Reactive Nitrogen in Asian Continental Outflow over the Western Pacific: Results from the NASA Transport and Chemical Evolution over the Pacific (TRACE-P)Airborne Mission

NASA Technical Reports Server (NTRS)

Talbot, R.; Dibb, J.; Scheuer, E.; Seid, G.; Russo, R.; Sandholm, S.; Tan, D.; Blake, D.; Blake, N.; Singh, H.

2003-01-01

We present here results for reactive nitrogen species measured aboard the NASA DC-8 aircraft during the Transport and Chemical Evolution over the Pacific TRACE-P) mission. The large-scale distributions total reactive nitrogen (NO(sub y,sum) = NO + NO2 + HNO3 + PAN + C(sub 1)-C(sub 5) alkyl nitrates) and O3 and CO were better defined in the boundary layer with significant degradation of the relationships as altitude increased. Typically, NO(sub y,sum) was enhanced over background levels of approx.260 pptv by 20-to-30-fold. The ratio C2H2/CO had values of 1-4 at altitudes up to 10 km and as far eastward as 150degE, implying significant vertical mixing of air parcels followed by rapid advection across the Pacific. Analysis air parcels originating from five principal Asian source regions showed that HNO3 and PAN dominated NO(sub y,sum). Correlations of NO(sub y,sum) with C2Cl4 (urban tracer) were not well defined in any of the source regions, and they were only slightly better with CH3Cl (biomass tracer). Air parcels over the western Pacific contained a complex mixture of emission sources that are not easily resolvable as shown by analysis of the Shanghai mega-city plume. It contained an intricate mixture of pollution emissions and exhibited the highest mixing ratios of NO(sub y,sum) species observed during TRACE-P. Comparison of tropospheric chemistry between the earlier PEM-West B mission and the recent TRACE-P data showed that in the boundary layer significant increases in the mixing ratios of NO(sub y,sum)species have occurred, but the middle and upper troposphere seems to have been affected minimally by increasing emissions on the Asian continent over the last 7 years.

Geography and Similarity of Regional Cuisines in China

PubMed Central

Zhu, Yu-Xiao; Huang, Junming; Zhang, Zi-Ke; Zhang, Qian-Ming; Zhou, Tao; Ahn, Yong-Yeol

2013-01-01

Food occupies a central position in every culture and it is therefore of great interest to understand the evolution of food culture. The advent of the World Wide Web and online recipe repositories have begun to provide unprecedented opportunities for data-driven, quantitative study of food culture. Here we harness an online database documenting recipes from various Chinese regional cuisines and investigate the similarity of regional cuisines in terms of geography and climate. We find that geographical proximity, rather than climate proximity, is a crucial factor that determines the similarity of regional cuisines. We develop a model of regional cuisine evolution that provides helpful clues for understanding the evolution of cuisines and cultures. PMID:24260166

Geography and similarity of regional cuisines in China.

PubMed

Zhu, Yu-Xiao; Huang, Junming; Zhang, Zi-Ke; Zhang, Qian-Ming; Zhou, Tao; Ahn, Yong-Yeol

2013-01-01

Food occupies a central position in every culture and it is therefore of great interest to understand the evolution of food culture. The advent of the World Wide Web and online recipe repositories have begun to provide unprecedented opportunities for data-driven, quantitative study of food culture. Here we harness an online database documenting recipes from various Chinese regional cuisines and investigate the similarity of regional cuisines in terms of geography and climate. We find that geographical proximity, rather than climate proximity, is a crucial factor that determines the similarity of regional cuisines. We develop a model of regional cuisine evolution that provides helpful clues for understanding the evolution of cuisines and cultures.

A balloon-borne 102-cm telescope for far-infrared astronomy

NASA Technical Reports Server (NTRS)

Fazio, Giovanni G.

1990-01-01

In the early 1970's, the Smithsonian Astrophysical Observatory and the University of Arizona engaged in a cooperative program to develop a balloon-borne 102-cm telescope capable of carrying out far infrared (40 to 250 micron) observations of astronomical interest above the earth's atmosphere. Since 1972, the telescope has flown and successfully recovered a total of nineteen times. Thirteen of the flights produced high-quality astronomical data, resulting in more than 92.5 hours of photometric and spectroscopic observations of numerous objects, such as H 2 regions, dark clouds, molecular clouds, a planetary nebula, a galaxy, the galactic center, the planets, and an asteroid. From the launch site in Palestine, Texas, sources as far south as -50 degrees declination were observed. The balloon-borne telescope was one of the most sensitive instruments ever used for observation in the far infrared region of the spectrum. It was most productive in producing high resolution maps of large areas (typically square degrees) centered on known H 2 regions, molecular clouds, and dark cloud complexes. In many cases, these scans produced the first far infrared maps of these regions, and many new sources were discovered. The results have led to a better understanding of the distribution of gas and dust in these regions, the evolution of H 2 regions, and the processes of star formation in giant molecular clouds. The following topics are presented: (1) the focal plane instrumentation; (2) the history and flight record; (3) scientific results and publications; (4) eduational aspects; and (5) future planes.

The role of the insula in intuitive expert bug detection in computer code: an fMRI study.

PubMed

Castelhano, Joao; Duarte, Isabel C; Ferreira, Carlos; Duraes, Joao; Madeira, Henrique; Castelo-Branco, Miguel

2018-05-09

Software programming is a complex and relatively recent human activity, involving the integration of mathematical, recursive thinking and language processing. The neural correlates of this recent human activity are still poorly understood. Error monitoring during this type of task, requiring the integration of language, logical symbol manipulation and other mathematical skills, is particularly challenging. We therefore aimed to investigate the neural correlates of decision-making during source code understanding and mental manipulation in professional participants with high expertise. The present fMRI study directly addressed error monitoring during source code comprehension, expert bug detection and decision-making. We used C code, which triggers the same sort of processing irrespective of the native language of the programmer. We discovered a distinct role for the insula in bug monitoring and detection and a novel connectivity pattern that goes beyond the expected activation pattern evoked by source code understanding in semantic language and mathematical processing regions. Importantly, insula activity levels were critically related to the quality of error detection, involving intuition, as signalled by reported initial bug suspicion, prior to final decision and bug detection. Activity in this salience network (SN) region evoked by bug suspicion was predictive of bug detection precision, suggesting that it encodes the quality of the behavioral evidence. Connectivity analysis provided evidence for top-down circuit "reutilization" stemming from anterior cingulate cortex (BA32), a core region in the SN that evolved for complex error monitoring such as required for this type of recent human activity. Cingulate (BA32) and anterolateral (BA10) frontal regions causally modulated decision processes in the insula, which in turn was related to activity of math processing regions in early parietal cortex. In other words, earlier brain regions used during evolution for other functions seem to be reutilized in a top-down manner for a new complex function, in an analogous manner as described for other cultural creations such as reading and literacy.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tatsumi, Yoshiyuki; Kimura, Nobukazu; Itaya, Tetsumaru

K-Ar dates and chemical compositions of basalts in the Gregory Rift, Kenya, demonstrate marked secular variation of lava chemistry. Two magmatic cycles characterized by incompatible element relative depletion are recognized; both occurring immediately after the peak of basaltic volcanism and coeval with both trachyte/phonolite volcanism and domal uplift of the region. These cycles may be attributed to increasing degree of partial melting of mantle source material in association with thinning of the lithosphere by thermal erosion through contact with hot upwelling asthenospheric mantle. Cyclic variation in asthenosphere upwelling may be considered an important controlling process in the evolution of themore » Gregory Rift.« less

Photochemical fractionation of O-16 in the space medium modeled by resonance excitation of CO by H-Lyman alpha

NASA Technical Reports Server (NTRS)

Arrhenius, G.; Corrigan, M. J.; Fitzgerald, R. W.

1988-01-01

Analyses of meteorite matter, the present structure of the solar system, and the evolution of matter in stellar systems are used to provide inferences concerning the formation of primordial matter in the solar system. Results indicate that molecular excitation processes similar to those observed today in circumstellar regions and dark interstellar clouds were operating in the early solar nebula. It is suggested that resonance excitation of broad isotopic bands by strong UV line sources may have resulted in the anomalous isotopic compositions noted in meteorites.

Numerical Simulation of the Anomalous Transport of High-Energy Cosmic Rays in Galactic Superbubble

NASA Technical Reports Server (NTRS)

Barghouty, A. F.; Price, E. M.; MeWaldt, R. A.

2013-01-01

A continuous-time random-walk (CTRW) model to simulate the transport and acceleration of high-energy cosmic rays in galactic superbubbles has recently been put forward (Barghouty & Schnee 2102). The new model has been developed to simulate and highlight signatures of anomalous transport on particles' evolution and their spectra in a multi-shock, collective acceleration context. The superbubble is idealized as a heterogeneous region of particle sources and sinks bounded by a random surface. This work concentrates on the effects of the bubble's assumed astrophysical characteristics (cf. geometry and roughness) on the particles' spectra.

On disk-planet interactions and orbital eccentricities

NASA Technical Reports Server (NTRS)

Ward, William R.

1988-01-01

While Lindblad resonances both within and without a perturber's orbit excite its eccentricity, the present study of the eccentricity evolution due to the density wave interaction between a planetesimal and a Keplerian disk notes that coronation resonances in these regions lose their eccentricity damping effectiveness if the object is embedded in a continuous disk without a gap. Attention is given to another class of Lindblad resonances which, under these conditions, operates on disk material coorbiting with the perturber; these resonances thereby become the most important source of eccentricity damping. A model problem indicates that eccentricity ultimately undergoes decay.

On the atmospheric photochemistry of nitric acid

NASA Technical Reports Server (NTRS)

Austin, J.; Garcia, R. R.; Russell, J. M., III; Solomon, S.; Tuck, A. F.

1986-01-01

Measurements of the temporal and spatial variations in HNO3, particularly those from the Nimbus 7 limb IR monitor of the stratosphere (LIMS) satellite experiment, are compared to both a two-dimensional chemical/dynamical model and to chemistry/parcel trajectory analyses. Significant discrepancies are found between the observed and modeled variations in the winter season, especially in the polar night region. The study of the evolution of HNO3 suggests that an important source exists for this species in the high-latitude winter stratosphere that is not included in presently accepted photochemical schemes. Possible reactions to account for this discrepancy are explored.

Particulate Matter Pollution and its Regional Transport in the Mid-Atlantic States

NASA Astrophysics Data System (ADS)

He, H.; Goldberg, D. L.; Hembeck, L.; Canty, T. P.; Vinciguerra, T.; Ring, A.; Salawitch, R. J.; Dickerson, R. R.

2015-12-01

Particulate matter (PM) causes negative effects on human health, impair visibility in scenic areas, and affect regional/global climate. PM can be formed through chemical changes of precursors, including biogenic VOCs and anthropogenic SO2 and NOx often from fossil fuel combustion. In the past decades, PM pollution in the US has improved substantially. However, some areas in the Mid-Atlantic States are still designated as 'moderate' nonattainment by EPA. We utilize datasets obtained during the NASA 2011 DISCOVER-AQ campaign to characterize the composition and distribution of summertime PM pollution in the Mid-Atlantic States. Aircraft measurements and OMI satellite retrieval of major anthropogenic precursors (NO2 and SO2) are analyzed to investigate the regional transport of PM precursors from upwind sources. We compare PM concentration and chemical composition observed during the field campaign to CMAQ simulations with the latest EPA emission inventory. Specifically, we focus on the secondary organic aerosol (SOA) chemistry in CMAQ simulations using various biogenic VOCs estimates from the MEGAN and BEIS models. Airborne PM observations including PILS measurements from DISCOVER-AQ campaign and OMI retrievals of HCHO are also used to validate and improve the representation of SOA chemistry and PM pollution within CMAQ. The comparison reveals the source and evolution of PM pollution in the Mid-Atlantic States.

Parallel Tracks as Quasi-steady States for the Magnetic Boundary Layers in Neutron-star Low-mass X-Ray Binaries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Erkut, M. Hakan; Çatmabacak, Onur, E-mail: mherkut@gmail.com

The neutron stars in low-mass X-ray binaries (LMXBs) are usually thought to be weakly magnetized objects accreting matter from their low-mass companions in the form of a disk. Albeit weak compared to those in young neutron-star systems, the neutron-star magnetospheres in LMXBs can play an important role in determining the correlations between spectral and temporal properties. Parallel tracks appearing in the kilohertz (kHz) quasi-periodic oscillation (QPO) frequency versus X-ray flux plane can be used as a tool to study the magnetosphere–disk interaction in neutron-star LMXBs. For dynamically important weak fields, the formation of a non-Keplerian magnetic boundary layer at themore » innermost disk truncated near the surface of the neutron star is highly likely. Such a boundary region may harbor oscillatory modes of frequencies in the kHz range. We generate parallel tracks using the boundary region model of kHz QPOs. We also present the direct application of our model to the reproduction of the observed parallel tracks of individual sources such as 4U 1608–52, 4U 1636–53, and Aql X-1. We reveal how the radial width of the boundary layer must vary in the long-term flux evolution of each source to regenerate the parallel tracks. The run of the radial width looks similar for different sources and can be fitted by a generic model function describing the average steady behavior of the boundary region over the long term. The parallel tracks then correspond to the possible quasi-steady states the source can occupy around the average trend.« less

Superwind evolution: the young starburst-driven wind galaxy NGC 2782

NASA Astrophysics Data System (ADS)

Bravo-Guerrero, Jimena; Stevens, Ian R.

2017-06-01

We present results from a 30-ks Chandra observation of the important starburst galaxy NGC 2782, covering the 0.3-10 keV energy band. We find evidence of a superwind of small extent, which is likely in an early stage of development. We find a total of 27 X-ray point sources within a region of radius 2D25 of the galaxy centre and that are likely associated with the galaxy. Of these, 13 are ultraluminous X-ray point sources (ULXs; LX ≥ 1039 erg s- 1) and a number have likely counterparts. The X-ray luminosities of the ULX candidates are 1.2-3.9 × 1039 erg s- 1. NGC 2782 seems to have an unusually large number of ULXs. Central diffuse X-ray emission extending to ˜3 kpc from the nuclear region has been detected. We also find an X-ray structure to the south of the nucleus, coincident with Hα filaments and with a 5-GHz radio source. We interpret this as a blow-out region of a forming superwind. This X-ray bubble has a total luminosity (0.3-10 keV) of 5 × 1039 erg s-1 (around 15 per cent of the total luminosity of the extended emission), and an inferred wind mass of 1.5 × 106 M⊙ . We also discuss the nature of the central X-ray source in NGC 2782, and conclude that it is likely a low-luminosity active galactic nucleus, with a total X-ray luminosity of LX = 6 × 1040 erg s-1, with strong Fe line emission at 6.4 keV.

Parallel Tracks as Quasi-steady States for the Magnetic Boundary Layers in Neutron-star Low-mass X-Ray Binaries

NASA Astrophysics Data System (ADS)

Erkut, M. Hakan; Çatmabacak, Onur

2017-11-01

The neutron stars in low-mass X-ray binaries (LMXBs) are usually thought to be weakly magnetized objects accreting matter from their low-mass companions in the form of a disk. Albeit weak compared to those in young neutron-star systems, the neutron-star magnetospheres in LMXBs can play an important role in determining the correlations between spectral and temporal properties. Parallel tracks appearing in the kilohertz (kHz) quasi-periodic oscillation (QPO) frequency versus X-ray flux plane can be used as a tool to study the magnetosphere-disk interaction in neutron-star LMXBs. For dynamically important weak fields, the formation of a non-Keplerian magnetic boundary layer at the innermost disk truncated near the surface of the neutron star is highly likely. Such a boundary region may harbor oscillatory modes of frequencies in the kHz range. We generate parallel tracks using the boundary region model of kHz QPOs. We also present the direct application of our model to the reproduction of the observed parallel tracks of individual sources such as 4U 1608-52, 4U 1636-53, and Aql X-1. We reveal how the radial width of the boundary layer must vary in the long-term flux evolution of each source to regenerate the parallel tracks. The run of the radial width looks similar for different sources and can be fitted by a generic model function describing the average steady behavior of the boundary region over the long term. The parallel tracks then correspond to the possible quasi-steady states the source can occupy around the average trend.

Influence of regional-scale anthropogenic emissions on CO2 distributions over the western North Pacific

NASA Astrophysics Data System (ADS)

Vay, S. A.; Woo, J.-H.; Anderson, B. E.; Thornhill, K. L.; Blake, D. R.; Westberg, D. J.; Kiley, C. M.; Avery, M. A.; Sachse, G. W.; Streets, D. G.; Tsutsumi, Y.; Nolf, S. R.

2003-10-01

We report here airborne measurements of atmospheric CO2 over the western North Pacific during the March-April 2001 Transport and Chemical Evolution over the Pacific (TRACE-P) mission. The CO2 spatial distributions were notably influenced by cyclogenesis-triggered transport of regionally polluted continental air masses. Examination of the CO2 to C2H2/CO ratio indicated rapid outflow of combustion-related emissions in the free troposphere below 8 km. Although the highest CO2 mixing ratios were measured within the Pacific Rim region, enhancements were also observed further east over the open ocean at locations far removed from surface sources. Near the Asian continent, discrete plumes encountered within the planetary boundary layer contained up to 393 ppmv of CO2. Coincident enhancements in the mixing ratios of C2Cl4, C2H2, and C2H4 measured concurrently revealed combustion and industrial sources. To elucidate the source distributions of CO2, an emissions database for Asia was examined in conjunction with the chemistry and 5-day backward trajectories that revealed the WNW/W sector of northeast Asia was a major contributor to these pollution events. Comparisons of NOAA/CMDL and JMA surface data with measurements obtained aloft showed a strong latitudinal gradient that peaked between 35° and 40°N. We estimated a net CO2 flux from the Asian continent of approximately 13.93 Tg C day-1 for late winter/early spring with the majority of the export (79%) occurring in the lower free troposphere (2-8 km). The apportionment of the flux between anthropogenic and biospheric sources was estimated at 6.37 Tg C day-1 and 7.56 Tg C day-1, respectively.

Supporting Source Code Comprehension during Software Evolution and Maintenance

ERIC Educational Resources Information Center

Alhindawi, Nouh

2013-01-01

This dissertation addresses the problems of program comprehension to support the evolution of large-scale software systems. The research concerns how software engineers locate features and concepts along with categorizing changes within very large bodies of source code along with their versioned histories. More specifically, advanced Information…

Estimation of the Past and Future Infrastructure Damage Due the Permafrost Evolution Processes

NASA Astrophysics Data System (ADS)

Sergeev, D. O.; Chesnokova, I. V.; Morozova, A. V.

2015-12-01

The geocryological processes such as thermokarst, frost heaving and fracturing, icing, thermal erosion are the source of immediate danger for the structures. The economic losses during the construction procedures in the permafrost area are linked also with the other geological processes that have the specific character in cold regions. These processes are swamping, desertification, deflation, flooding, mudflows and landslides. Linear transport structures are most vulnerable component of regional and national economy. Because the high length the transport structures have to cross the landscapes with different permafrost conditions that have the different reaction to climate change. The climate warming is favorable for thermokarst and the frost heaving is linked with climate cooling. In result the structure falls in the circumstances that are not predicted in the construction project. Local engineering problems of structure exploitation lead to global risks of sustainable development of regions. Authors developed the database of geocryological damage cases for the last twelve years at the Russian territory. Spatial data have the attributive table that was filled by the published information from various permafrost conference proceedings. The preliminary GIS-analysis of gathered data showed the widespread territorial distribution of the cases of negative consequences of geocryological processes activity. The information about maximum effect from geocryological processes was validated by detailed field investigation along the railways in Yamal and Transbaicalia Regions. Authors expect the expanding of database by similar data from other sectors of Arctic. It is important for analyzing the regional, time and industrial tendencies of geocryological risk evolution. Obtained information could be used in insurance procedures and in information systems of decisions support in different management levels. The investigation was completed with financial support by Russian Foundation of Basic Research (Project #13-05-00462).

The Evolution of Transition Region Loops Using IRIS and AIA

NASA Technical Reports Server (NTRS)

Winebarger, Amy R.; DePontieu, Bart

2014-01-01

Over the past 50 years, the model for the structure of the solar transition region has evolved from a simple transition layer between the cooler chromosphere to the hotter corona to a complex and diverse region that is dominated by complete loops that never reach coronal temperatures. The IRIS slitjaw images show many complete transition region loops. Several of the "coronal" channels in the SDO AIA instrument include contributions from weak transition region lines. In this work, we combine slitjaw images from IRIS with these channels to determine the evolution of the loops. We develop a simple model for the temperature and density evolution of the loops that can explain the simultaneous observations. Finally, we estimate the percentage of AIA emission that originates in the transition region.

Constructive neutral evolution: exploring evolutionary theory's curious disconnect.

PubMed

Stoltzfus, Arlin

2012-10-13

Constructive neutral evolution (CNE) suggests that neutral evolution may follow a stepwise path to extravagance. Whether or not CNE is common, the mere possibility raises provocative questions about causation: in classical neo-Darwinian thinking, selection is the sole source of creativity and direction, the only force that can cause trends or build complex features. However, much of contemporary evolutionary genetics departs from the conception of evolution underlying neo-Darwinism, resulting in a widening gap between what formal models allow, and what the prevailing view of the causes of evolution suggests. In particular, a mutationist conception of evolution as a 2-step origin-fixation process has been a source of theoretical innovation for 40 years, appearing not only in the Neutral Theory, but also in recent breakthroughs in modeling adaptation (the "mutational landscape" model), and in practical software for sequence analysis. In this conception, mutation is not a source of raw materials, but an agent that introduces novelty, while selection is not an agent that shapes features, but a stochastic sieve. This view, which now lays claim to important theoretical, experimental, and practical results, demands our attention. CNE provides a way to explore its most significant implications about the role of variation in evolution. Alex Kondrashov, Eugene Koonin and Johann Peter Gogarten reviewed this article.

Constructive neutral evolution: exploring evolutionary theory’s curious disconnect

PubMed Central

2012-01-01

Abstract Constructive neutral evolution (CNE) suggests that neutral evolution may follow a stepwise path to extravagance. Whether or not CNE is common, the mere possibility raises provocative questions about causation: in classical neo-Darwinian thinking, selection is the sole source of creativity and direction, the only force that can cause trends or build complex features. However, much of contemporary evolutionary genetics departs from the conception of evolution underlying neo-Darwinism, resulting in a widening gap between what formal models allow, and what the prevailing view of the causes of evolution suggests. In particular, a mutationist conception of evolution as a 2-step origin-fixation process has been a source of theoretical innovation for 40 years, appearing not only in the Neutral Theory, but also in recent breakthroughs in modeling adaptation (the “mutational landscape” model), and in practical software for sequence analysis. In this conception, mutation is not a source of raw materials, but an agent that introduces novelty, while selection is not an agent that shapes features, but a stochastic sieve. This view, which now lays claim to important theoretical, experimental, and practical results, demands our attention. CNE provides a way to explore its most significant implications about the role of variation in evolution. Reviewers Alex Kondrashov, Eugene Koonin and Johann Peter Gogarten reviewed this article. PMID:23062217

Social evolution in the Hallstatt--La Tène period.

PubMed

Smrcka, Václav

2009-01-01

On the archaeological finds, written reports and in the composition of the bone tissue, we can suppose that social evolution in Hallstatt--La Tène period proceeded through the three following stages. In the Early Iron Age (Hallstatt period) with funerary furnishings of barrows, seldom, also, of burial grounds, we can distinguish only two groups: a ruler and his court with women and servants. Elements of nomadic and pastoral traditions can be distinguished in the ruling stratum. The second class of people living in bondage has agricultural features. At this first stage of social evolution (approximately between the 7th and the 5th centuries B.C.), in the period of princes, we can distinguish only two social groups--the king (prince) with his court on one side and peasants on the other side. This social stratification determines access to land and, at the same time, ownership of mobile wealth--cattle. The elite accumulates wealth coming also from other sources, for example, in an eponymic locality it mines salt and controls its distribution, other elites of the Hallstatt society control key points of trade, in the first place the trade in amber, being the trade proper provided by foreign merchants. In an archaeological context there appear the settlements of the elite of the refugium. The second social stage with military democracy (in the 4th and the 3rd centuries B.C.) is characterised by several factors: 1st Cheaper weapons, due to their manufacture using products with ensured sources of raw material, 2nd overproduction of foodstuffs, 3rd increase of population. Access to the sources has a larger spectrum, this is why the social stratification of the structured unevenness in this period is taking the form of a pyramid. This social pyramid is confirmed by written reports and also appears in the funerary furnishings. Not only are the ruler and his "court" put in the graves, but also all the members of the clan. We suppose that the new social group of priests, who gained a high social prestige both in wartime and in peacetime, took part in this change of mentality and opinions. Due to the rich admission of the dietary elements Sr and Zn, we suppose that it could be garniture 600 in the burial grounds that represents this group. From the result it can be deduced at 5% significance level (p = 0.0519) that also the relations between the garnitures within the social stratification differ consistently with the region. When strontium content in social groups was statistically tested regardless of the region, differences are found at the 5% level of significance (p = 0.0402) between the group II (males with weapons, females with anklets and with 2 bracelets, 54 skeletons with mean content of 198 microg Sr/g of bone) and group IV (males without funerary furniture, children and exceptions, 31 skeletons with mean content of 154.9 microg Sr/g of bone). Also at statistical testing of lead content, regardless of the region, there are differences at the 5% level of significance between group II (48 skeletons with mean content 1.5 microg Pb/g of bone) and group IV (27 skeletons with mean content 0.47 microg Pb/g of bone). Regardless of region there is an apparent difference in consumption of the vegetal component of diet (strontium) and social marker (lead) between the richest elite group II and group IV covering the persons living in bondage on the level of slaves. The third phase of social evolution of the urban type is characterised by the evolution of oppida. Production is fully concentrated here. An oppidum is a market place formed by agricultural villages. Due to the change of the funerary rite towards cremation and the absence of burial grounds, the social structure can only be judged in a mediated manner by means of written reports. A large number of smaller tribal "kingdoms" are concentrated into several larger ones, comprising even several tribes, such as, for example at the king of the Boeotians and of the Taurisks Kritasir in Pannonia and Norik [1]. In these three phases, social evolution lasted for 6 to 7 centuries and headed towards the state system. It was interrupted by the migrations of the Celts and by external pressure from the Romans and the Germans.

Source attribution using FLEXPART and carbon monoxide emission inventories for the IAGOS In-situ Observation database

NASA Astrophysics Data System (ADS)

Fontaine, Alain; Sauvage, Bastien; Pétetin, Hervé; Auby, Antoine; Boulanger, Damien; Thouret, Valerie

2016-04-01

Since 1994, the IAGOS program (In-Service Aircraft for a Global Observing System http://www.iagos.org) and its predecessor MOZAIC has produced in-situ measurements of the atmospheric composition during more than 46000 commercial aircraft flights. In order to help analyzing these observations and further understanding the processes driving their evolution, we developed a modelling tool SOFT-IO quantifying their source/receptor link. We improved the methodology used by Stohl et al. (2003), based on the FLEXPART plume dispersion model, to simulate the contributions of anthropogenic and biomass burning emissions from the ECCAD database (http://eccad.aeris-data.fr) to the measured carbon monoxide mixing ratio along each IAGOS flight. Thanks to automated processes, contributions are simulated for the last 20 days before observation, separating individual contributions from the different source regions. The main goal is to supply add-value products to the IAGOS database showing pollutants geographical origin and emission type. Using this information, it may be possible to link trends in the atmospheric composition to changes in the transport pathways and to the evolution of emissions. This tool could be used for statistical validation as well as for inter-comparisons of emission inventories using large amounts of data, as Lagrangian models are able to bring the global scale emissions down to a smaller scale, where they can be directly compared to the in-situ observations from the IAGOS database.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ewing, J.I.; Meyer, R.P.

The Rivera Ocean Seismic Experiment (ROSE) was designed as a combined sea and land seismic program to utilize both explosive and earthquakes to study a number of features of the structure and evolution of a mid-ocean ridge, a major oceanic fracture zone, and the transition region between ocean and continent. The primary region selected for the experiment included the Rivera Fracture Zone, the crest and eastern flank of the East Pacific north of the Rivera and adjacent areas of Baja California and mainland Mexico. The experiment included: (1) study of the East Pacific Rise south of the Orozco Fracture Zonemore » primarily using ocean bottom recording and explosive sources. (2) a seismicity program at the Orozco, and (3) a land-based program of recording natural events along the coastal region of Mexico. A considerable amount of useful data was obtained in each of the three subprograms. In the marine parts of the experiment we were able to address a variety of problems including structure and evolution of young oceanic crust and mantle, structure and dynamics of the East Pacific Rise, seismicity of the Orozco Fracture Zone, and partitioning of energy transmission between the ocean volume and the crust/lithosphere. On land, the fortuitous occurrence of the Petatlan M7.6 earthquake of March 14, 1979, permitted the acquisition of an excellent data set of foreshocks and aftershocks of this large event, which provide new insight into the filling of a major seismic gap in the region. This overview describes the scientific rationale and the design of the experiments, along with some general results.« less

IODP workshop: developing scientific drilling proposals for the Argentina Passive Volcanic Continental Margin (APVCM) - basin evolution, deep biosphere, hydrates, sediment dynamics and ocean evolution

NASA Astrophysics Data System (ADS)

Flood, Roger D.; Violante, Roberto A.; Gorgas, Thomas; Schwarz, Ernesto; Grützner, Jens; Uenzelmann-Neben, Gabriele; Hernández-Molina, F. Javier; Biddle, Jennifer; St-Onge, Guillaume; Workshop Participants, Apvcm

2017-05-01

The Argentine margin contains important sedimentological, paleontological and chemical records of regional and local tectonic evolution, sea level, climate evolution and ocean circulation since the opening of the South Atlantic in the Late Jurassic-Early Cretaceous as well as the present-day results of post-depositional chemical and biological alteration. Despite its important location, which underlies the exchange of southern- and northern-sourced water masses, the Argentine margin has not been investigated in detail using scientific drilling techniques, perhaps because the margin has the reputation of being erosional. However, a number of papers published since 2009 have reported new high-resolution and/or multichannel seismic surveys, often combined with multi-beam bathymetric data, which show the common occurrence of layered sediments and prominent sediment drifts on the Argentine and adjacent Uruguayan margins. There has also been significant progress in studying the climatic records in surficial and near-surface sediments recovered in sediment cores from the Argentine margin. Encouraged by these recent results, our 3.5-day IODP (International Ocean Discovery Program) workshop in Buenos Aires (8-11 September 2015) focused on opportunities for scientific drilling on the Atlantic margin of Argentina, which lies beneath a key portion of the global ocean conveyor belt of thermohaline circulation. Significant opportunities exist to study the tectonic evolution, paleoceanography and stratigraphy, sedimentology, and biosphere and geochemistry of this margin.

Controls on subglacial patterns and depositional environments in western Ireland

NASA Astrophysics Data System (ADS)

Knight, J.

2009-12-01

In western Ireland, Late Devensian ice flow dynamics and resultant patterns of landforms and sediments reflect the interplay between internal (glaciological) forcing and external forcing by rapid climate changes centred on the adjacent Atlantic Ocean. This interplay can be best demonstrated where ice from climatically-sensitive mountain source regions flowed into surrounding lowlands, such as the Connemara region of west County Galway, western Ireland. Here, a semi-independent ice cap was present over the Twelve Bens mountains, and interacted with ice from the much larger regional ice sheet from central Ireland. Landform and sediment patterns in the flat lowland region (c. 100 km2 below 30 m asl) to the south of the Twelve Bens reflect elements of this ice interaction. In detail, landform and sediment distributions here are highly complex with marked spatial differences in patterns of sediment availability. Across much of the region, sculpted bedrock forms (whaleback and bedrock drumlin ridges, roches mountonnées, striae) reflect subglacial abrasion across the underlying igneous and metamorphic bedrock that forms a relatively flat and lake-dominated landscape. Glacigenic sediments are found only at or around ice-retreat margins, and within isolated bedrock valleys. Here, diamicton drumlins are relatively uncommon but yet must represent depositional conditions that are not reflected elsewhere in this ice sheet sector where subglacial sediments are generally absent. This paper explores the interrelationship between local and regional ice flows through their impact on spatial patterns of glacial landforms and sediments. The paper presents field data on the characteristics of bedrock forms (erosional) and diamicton drumlins (depositional). Subglacial sediments are described from drumlin outcrops at key sites around Connemara, which helps in the understanding of the evolution of the subglacial environment in response to ice interactions from different source regions.

Evolution Under Environmental Stress at Macro- and Microscales

PubMed Central

Nevo, Eviatar

2011-01-01

Environmental stress has played a major role in the evolution of living organisms (Hoffman AA, Parsons PA. 1991. Evolutionary genetics and environmental stress. Oxford: Oxford University Press; Parsons PA. 2005. Environments and evolution: interactions between stress, resource inadequacy, and energetic efficiency. Biol Rev Camb Philos Soc. 80:589–610). This is reflected by the massive and background extinctions in evolutionary time (Nevo E. 1995a. Evolution and extinction. Encyclopedia of Environmental Biology. New York: Academic Press, Inc. 1:717–745). The interaction between organism and environment is central in evolution. Extinction ensues when organisms fail to change and adapt to the constantly altering abiotic and biotic stressful environmental changes as documented in the fossil record. Extreme environmental stress causes extinction but also leads to evolutionary change and the origination of new species adapted to new environments. I will discuss a few of these global, regional, and local stresses based primarily on my own research programs. These examples will include the 1) global regional and local experiment of subterranean mammals; 2) regional experiment of fungal life in the Dead Sea; 3) evolution of wild cereals; 4) “Evolution Canyon”; 5) human brain evolution, and 6) global warming. PMID:21979157

Evolution under environmental stress at macro- and microscales.

PubMed

Nevo, Eviatar

2011-01-01

Environmental stress has played a major role in the evolution of living organisms (Hoffman AA, Parsons PA. 1991. Evolutionary genetics and environmental stress. Oxford: Oxford University Press; Parsons PA. 2005. Environments and evolution: interactions between stress, resource inadequacy, and energetic efficiency. Biol Rev Camb Philos Soc. 80:589-610). This is reflected by the massive and background extinctions in evolutionary time (Nevo E. 1995a. Evolution and extinction. Encyclopedia of Environmental Biology. New York: Academic Press, Inc. 1:717-745). The interaction between organism and environment is central in evolution. Extinction ensues when organisms fail to change and adapt to the constantly altering abiotic and biotic stressful environmental changes as documented in the fossil record. Extreme environmental stress causes extinction but also leads to evolutionary change and the origination of new species adapted to new environments. I will discuss a few of these global, regional, and local stresses based primarily on my own research programs. These examples will include the 1) global regional and local experiment of subterranean mammals; 2) regional experiment of fungal life in the Dead Sea; 3) evolution of wild cereals; 4) "Evolution Canyon"; 5) human brain evolution, and 6) global warming.

On-line thermal dependence study of the main solar cell electrical photoconversion parameters using low thermal emission lamps.

PubMed

Gallardo, J J; Navas, J; Alcántara, R; Fernández-Lorenzo, C; Aguilar, T; Martín-Calleja, J

2012-06-01

This paper presents a non-conventional methodology and an instrumental system to measure the effect of temperature on the photovoltaic properties of solar cells. The system enables the direct measurement of the evolution of open-circuit voltage and short-circuit current intensity in relation to a continuously decreasing temperature. The system uses a high-intensity white light-emitting diode light source with low emissions of radiation in the infrared region of the electromagnetic spectrum, resulting in a reduced heating of the photovoltaic devices by the irradiation source itself. To check the goodness of the system and the methodology designed, several measurements were performed with monocrystalline silicon solar cells, dye-sensitized solar cells, and thin-film amorphous silicon solar cells, showing similar tendencies to those reported in the literature.

The size of coronal hard X-ray sources in solar flares: How big are they?

NASA Astrophysics Data System (ADS)

Effenberger, F.; Krucker, S.; Rubio da Costa, F.

2017-12-01

Coronal hard X-ray sources are considered to be one of the key signatures of non-thermal particle acceleration and heating during the energy release in solar flares. In some cases, X-ray observations reveal multiple components spatially located near and above the loop top and even further up in the corona. Here, we combine a detailed RHESSI imaging analysis of near-limb solar flares with occulted footpoints and a multi-wavelength study of the flare loop evolution in SDO/AIA. We connect our findings to different current sheet formation and magnetic break-out scenarios and relate it to particle acceleration theory. We find that the upper and usually fainter emission regions can be underestimated in their size due to the majority of flux originating from the lower loops.

Benefits of rotational ground motions for planetary seismology

NASA Astrophysics Data System (ADS)

Donner, S.; Joshi, R.; Hadziioannou, C.; Nunn, C.; van Driel, M.; Schmelzbach, C.; Wassermann, J. M.; Igel, H.

2017-12-01

Exploring the internal structure of planetary objects is fundamental to understand the evolution of our solar system. In contrast to Earth, planetary seismology is hampered by the limited number of stations available, often just a single one. Classic seismology is based on the measurement of three components of translational ground motion. Its methods are mainly developed for a larger number of available stations. Therefore, the application of classical seismological methods to other planets is very limited. Here, we show that the additional measurement of three components of rotational ground motion could substantially improve the situation. From sparse or single station networks measuring translational and rotational ground motions it is possible to obtain additional information on structure and source. This includes direct information on local subsurface seismic velocities, separation of seismic phases, propagation direction of seismic energy, crustal scattering properties, as well as moment tensor source parameters for regional sources. The potential of this methodology will be highlighted through synthetic forward and inverse modeling experiments.

Spectral evolution in young active galactic nuclei

NASA Technical Reports Server (NTRS)

Boldt, E.; Leiter, D.

1986-01-01

The spectral evolution of AGNs is discussed within the context of a scenario where the cosmic X-ray background (CXB) is dominated by these sources. Attention is draqwn to the fact that the individually observed AGN X-ray spectra are significantly steeper than that of the CXB. The remarkably flat spectrum thereby required for the 'as-yet' unresolved sources of the residual CXB is interpreted as an observational constraint on an earlier stage of AGN evolution. Assuming black hole disk accretion, a picture emerges where young AGNs are compact Eddington limited thermal X-ray sources and where canonical AGNs represent later stages in which they have become appreciably less compact, exhibiting the importance of nonthermal disk-dynamo processes.

The Formation and Gravitational-wave Detection of Massive Stellar Black Hole Binaries

NASA Astrophysics Data System (ADS)

Belczynski, Krzysztof; Buonanno, Alessandra; Cantiello, Matteo; Fryer, Chris L.; Holz, Daniel E.; Mandel, Ilya; Miller, M. Coleman; Walczak, Marek

2014-07-01

If binaries consisting of two ~100 M ⊙ black holes exist, they would serve as extraordinarily powerful gravitational-wave sources, detectable to redshifts of z ~ 2 with the advanced LIGO/Virgo ground-based detectors. Large uncertainties about the evolution of massive stars preclude definitive rate predictions for mergers of these massive black holes. We show that rates as high as hundreds of detections per year, or as low as no detections whatsoever, are both possible. It was thought that the only way to produce these massive binaries was via dynamical interactions in dense stellar systems. This view has been challenged by the recent discovery of several >~ 150 M ⊙ stars in the R136 region of the Large Magellanic Cloud. Current models predict that when stars of this mass leave the main sequence, their expansion is insufficient to allow common envelope evolution to efficiently reduce the orbital separation. The resulting black hole-black hole binary remains too wide to be able to coalesce within a Hubble time. If this assessment is correct, isolated very massive binaries do not evolve to be gravitational-wave sources. However, other formation channels exist. For example, the high multiplicity of massive stars, and their common formation in relatively dense stellar associations, opens up dynamical channels for massive black hole mergers (e.g., via Kozai cycles or repeated binary-single interactions). We identify key physical factors that shape the population of very massive black hole-black hole binaries. Advanced gravitational-wave detectors will provide important constraints on the formation and evolution of very massive stars.

Evolution of Proton and Alpha Particle Velocities through the Solar Cycle

NASA Astrophysics Data System (ADS)

Ďurovcová, T.; Šafránková, J.; Němeček, Z.; Richardson, J. D.

2017-12-01

Relative properties of solar wind protons and α particles are often used as indicators of a source region on the solar surface, and analysis of their evolution along the solar wind path tests our understanding of physics of multicomponent magnetized plasma. The paper deals with the comprehensive analysis of the difference between proton and α particle bulk velocities at 1 au with a special emphasis on interplanetary coronal mass ejections (ICMEs). A comparison of about 20 years of Wind observations at 1 au with Helios measurements closer to the Sun (0.3-0.7 au) generally confirms the present knowledge that (1) the differential speed between both species increases with the proton speed; (2) the differential speed is lower than the local Alfvén speed; (3) α particles are faster than protons near the Sun, and this difference decreases with the increasing distance. However, we found a much larger portion of observations with protons faster than α particles in Wind than in Helios data and attributed this effect to a preferential acceleration of the protons in the solar wind. A distinct population characterized by a very small differential velocity and nearly equal proton and α particle temperatures that is frequently observed around the maximum of solar activity was attributed to ICMEs. Since this population does not exhibit any evolution with increasing collisional age, we suggest that, by contrast to the solar wind from other sources, ICMEs are born in an equilibrium state and gradually lose this equilibrium due to interactions with the ambient solar wind.

Investigating the source of near-relativistic and relativistic electrons in Earth's inner radiation belt

DOE PAGES

Turner, Drew Lawson; O'Brien, T. P.; Fennell, J. F.; ...

2017-01-30

Using observations from NASA's Van Allen Probes, we study the role of sudden particle enhancements at low L shells (SPELLS) as a source of inner radiation belt electrons. SPELLS events are characterized by electron intensity enhancements of approximately an order of magnitude or more in less than 1 day at L < 3. During quiet and average geomagnetic conditions, the phase space density radial distributions for fixed first and second adiabatic invariants are peaked at 2 < L < 3 for electrons ranging in energy from ~50 keV to ~1 MeV, indicating that slow inward radial diffusion is not themore » dominant source of inner belt electrons under quiet/average conditions. During SPELLS events, the evolution of electron distributions reveals an enhancement of phase space density that can exceed 3 orders of magnitude in the slot region and continues into the inner radiation belt, which is evidence that these events are an important—and potentially dominant—source of inner belt electrons. Electron fluxes from September 2012 through February 2016 reveal that SPELLS occur frequently (~2.5/month at 200 keV), but the number of observed events decreases exponentially with increasing electron energy for ≥100 keV. After SPELLS events, the slot region reforms due to slow energy-dependent decay over several day time scales, consistent with losses due to interactions with plasmaspheric hiss. Altogether, these results indicate that the peaked phase space density distributions in the inner electron radiation belt result from an “on/off,” geomagnetic-activity-dependent source from higher radial distances.« less

The ultraviolet view of the Magellanic Clouds from GALEX: A first look at the LMC source catalog

NASA Astrophysics Data System (ADS)

Simons, Raymond; Thilker, David; Bianchi, Luciana; Wyder, Ted

2014-03-01

The Galaxy Evolution Exporer (GALEX) has performed unprecedented imaging surveys of the Magellanic Clouds (MC) and their surrounding areas including the Magellanic Bridge (MB) in near-UV (NUV, 1771-2831 Å) and far-UV (FUV, 1344-1786 Å) bands at 5″ resolution. Substantially more area was covered in the NUV than FUV, particularly in the bright central regions, because of the GALEX FUV detector failure. The 5σ depth of the NUV imaging varies between 20.8 and 22.7 (ABmag). Such imaging provides the first sensitive view of the entire content of hot stars in the Magellanic System, revealing the presence of young populations even in sites with extremely low star-formation rate surface density like the MB, owing to high sensitivity of the UV data to hot stars and the dark sky at these wavelengths. The density of UV sources is quite high in many areas of the LMC and SMC. Crowding limits the quality of source detection and photometry from the standard mission pipeline processing. We performed custom-photometry of the GALEX data in the MC survey region (<15° from the LMC, <10° from the SMC). After merging multiple detections of sources in overlapping images, the resulting catalog we have produced for the LMC contains nearly six million unique NUV point sources within 15° and is briefly presented herein. This paper provides a first look at the GALEX MC survey and highlights some of the science investigations that the entire catalog and imaging dataset will make possible.

Investigating the source of near-relativistic and relativistic electrons in Earth's inner radiation belt

DOE Office of Scientific and Technical Information (OSTI.GOV)

Turner, Drew Lawson; O'Brien, T. P.; Fennell, J. F.

Using observations from NASA's Van Allen Probes, we study the role of sudden particle enhancements at low L shells (SPELLS) as a source of inner radiation belt electrons. SPELLS events are characterized by electron intensity enhancements of approximately an order of magnitude or more in less than 1 day at L < 3. During quiet and average geomagnetic conditions, the phase space density radial distributions for fixed first and second adiabatic invariants are peaked at 2 < L < 3 for electrons ranging in energy from ~50 keV to ~1 MeV, indicating that slow inward radial diffusion is not themore » dominant source of inner belt electrons under quiet/average conditions. During SPELLS events, the evolution of electron distributions reveals an enhancement of phase space density that can exceed 3 orders of magnitude in the slot region and continues into the inner radiation belt, which is evidence that these events are an important—and potentially dominant—source of inner belt electrons. Electron fluxes from September 2012 through February 2016 reveal that SPELLS occur frequently (~2.5/month at 200 keV), but the number of observed events decreases exponentially with increasing electron energy for ≥100 keV. After SPELLS events, the slot region reforms due to slow energy-dependent decay over several day time scales, consistent with losses due to interactions with plasmaspheric hiss. Altogether, these results indicate that the peaked phase space density distributions in the inner electron radiation belt result from an “on/off,” geomagnetic-activity-dependent source from higher radial distances.« less

Limits on transverse momentum dependent evolution from semi-inclusive deep inelastic scattering at moderate Q

NASA Astrophysics Data System (ADS)

Aidala, C. A.; Field, B.; Gamberg, L. P.; Rogers, T. C.

2014-05-01

In the QCD evolution of transverse momentum dependent parton distribution and fragmentation functions, the Collins-Soper evolution kernel includes both a perturbative short-distance contribution and a large-distance nonperturbative, but strongly universal, contribution. In the past, global fits, based mainly on larger Q Drell-Yan-like processes, have found substantial contributions from nonperturbative regions in the Collins-Soper evolution kernel. In this article, we investigate semi-inclusive deep inelastic scattering measurements in the region of relatively small Q, of the order of a few GeV, where sensitivity to nonperturbative transverse momentum dependence may become more important or even dominate the evolution. Using recently available deep inelastic scattering data from the COMPASS experiment, we provide estimates of the regions of coordinate space that dominate in transverse momentum dependent (TMD) processes when the hard scale is of the order of only a few GeV. We find that distance scales that are much larger than those commonly probed in large Q measurements become important, suggesting that the details of nonperturbative effects in TMD evolution are especially significant in the region of intermediate Q. We highlight the strongly universal nature of the nonperturbative component of evolution and its potential to be tightly constrained by fits from a wide variety of observables that include both large and moderate Q. On this basis, we recommend detailed treatments of the nonperturbative component of the Collins-Soper evolution kernel for future TMD studies.

H i Absorption in the Steep-Spectrum Superluminal Quasar 3C 216.

PubMed

Pihlström; Vermeulen; Taylor; Conway

1999-11-01

The search for H i absorption in strong compact steep-spectrum sources is a natural way to probe the neutral gas contents in young radio sources. In turn, this may provide information about the evolution of powerful radio sources. The recently improved capabilities of the Westerbork Synthesis Radio Telescope have made it possible to detect a 0.31% (19 mJy) deep neutral atomic hydrogen absorption line associated with the steep-spectrum superluminal quasar 3C 216. The redshift (z=0.67) of the source shifts the frequency of the 21 cm line down to the ultra-high-frequency (UHF) band (850 MHz). The exact location of the H i-absorbing gas remains to be determined by spectral line VLBI observations at 850 MHz. We cannot exclude that the gas might be extended on galactic scales, but we think it is more likely to be located in the central kiloparsec. Constraints from the lack of X-ray absorption probably rule out obscuration of the core region, and we argue that the most plausible site for the H i absorption is in the jet-cloud interaction observed in this source.

The Chandra X-Ray Observatory: Progress Report and Highlights

NASA Technical Reports Server (NTRS)

Weisskopf, Martin C.

2012-01-01

Over the past 13 years, the Chandra X-ray Observatory's ability to provide high resolution X-ray images and spectra have established it as one of the most versatile and powerful tools for astrophysical research in the 21st century. Chandra explores the hot, high-energy regions of the universe, observing X-ray sources with fluxes spanning more than 10 orders of magnitude, from the X-ray brightest, Sco X-1, to the faintest sources in the Chandra Deep Field South survey. Thanks to its continuing operational life, the Chandra mission now also provides a long observing baseline which, in and of itself, is opening new research opportunities. Observations in the past few years alone have deepened our understanding of the co-evolution of supermassive black holes and galaxies, the details of black hole accretion, the nature of dark energy and dark matter, the details of supernovae and their progenitors, the interiors of neutron stars, the evolution of massive stars, and the high-energy environment of protoplanetary nebulae and the interaction of an exo-planet with its star. Here we update the technical status, highlight some of the scientific results, and very briefly discuss future prospects. We fully expect that the Observatory will continue to provide outstanding scientific results for many years to come.

Probing the Active Galactic Nuclei using optical spectroscopy

NASA Astrophysics Data System (ADS)

Vivek, M.

Variability studies offer one of the best tools for understanding the physical conditions present in regions close to the central engine in an AGN. We probed the various properties of AGN through time variability studies of spectral lines in the optical wavelengths using the 2m telescope in IUCAA Girawali observatory. The absorption line variability studies are mainly concentrated in understanding the nature of outflows in quasars. Quasar outflows have a huge impact on the evolution of central supermassive blackholes, their host galaxies and the surrounding intergalactic medium. Studying the variability in these Broad Absorption Lines (BALs) can help us understand the structure, evolution, and basic physical properties of these outflows. We conducted a repeated Low ionization BAL monitoring program with 27 LoBALs (Low Ionization BALs) at z 0.3-2.1 covering timescales from 3.22 to 7.69 years in the quasar rest frame. We see a variety of phenomena, including some BALs that either appeared or disappeared completely and some BALs which do not vary over the observation period. In one case, the excited fine structure lines have changed dramatically. One source shows signatures of radiative acceleration. Here, we present the results from this program. Emission line studies are concentrated in understanding the peculiar characteristics of a dual-AGN source SDSS J092712.64+294344.0.

Tracing the Early Development of Harmful Algal Blooms on the West Florida Shelf with the Aid of Lagrangian Coherent Structures

PubMed Central

Olascoaga, M. J.; Beron-Vera, F. J.; Brand, L. E.; Koçak, H.

2008-01-01

Several theories have been proposed to explain the development of harmful algal blooms (HABs) produced by the toxic dinoflagellate Karenia brevis on the West Florida Shelf. However, because the early stages of HAB development are usually not detected, these theories have been so far very difficult to verify. In this paper we employ simulated Lagrangian coherent structures (LCSs) to trace potential early locations of the development of a HAB in late 2004 before it was transported to a region where it could be detected by satellite imagery. The LCSs, which are extracted from surface ocean currents produced by a data-assimilative HYCOM (HYbrid-Coordinate Ocean Model) simulation, constitute material fluid barriers that demarcate potential pathways for HAB evolution. Using a simplified population dynamics model we infer the factors that could possibly lead to the development of the HAB in question. The population dynamics model determines nitrogen in two components, nutrients and phytoplankton, which are assumed to be passively advected by surface ocean currents produced by the above HYCOM simulation. Two nutrient sources are inferred for the HAB whose evolution is found to be strongly tied to the simulated LCSs. These nutrient sources are found to be located nearshore and possibly due to land runoff. PMID:19137076

AzTEC 1.1 mm OBSERVATIONS OF THE MBM12 MOLECULAR CLOUD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, M. J.; Kim, S.; Youn, S.

2012-02-10

We present 1.1 mm observations of the dust continuum emission from the MBM12 high-latitude molecular cloud observed with the Astronomical Thermal Emission Camera (AzTEC) mounted on the James Clerk Maxwell Telescope on Mauna Kea, Hawaii. We surveyed 6.34 deg{sup 2} centered on MBM12, making this the largest area that has ever been surveyed in this region with submillimeter and millimeter telescopes. Eight secure individual sources were detected with a signal-to-noise ratio of over 4.4. These eight AzTEC sources can be considered to be real astronomical objects compared to the other candidates based on calculations of the false detection rate. Themore » distribution of the detected 1.1 mm sources or compact 1.1 mm peaks is spatially anti-correlated with that of the 100 {mu}m emission and the {sup 12}CO emission. We detected the 1.1 mm dust continuum emitting sources associated with two classical T Tauri stars, LkH{alpha}262 and LkH{alpha}264. Observations of spectral energy distributions (SEDs) indicate that LkH{alpha}262 is likely to be Class II (pre-main-sequence star), but there are also indications that it could be a late Class I (protostar). A flared disk and a bipolar cavity in the models of Class I sources lead to more complicated SEDs. From the present AzTEC observations of the MBM12 region, it appears that other sources detected with AzTEC are likely to be extragalactic and located behind MBM12. Some of these have radio counterparts and their star formation rates are derived from a fit of the SEDs to the photometric evolution of galaxies in which the effects of a dusty interstellar medium have been included.« less

Organic aerosols over Indo-Gangetic Plain: Sources, distributions and climatic implications

NASA Astrophysics Data System (ADS)

Singh, Nandita; Mhawish, Alaa; Deboudt, Karine; Singh, R. S.; Banerjee, Tirthankar

2017-05-01

Organic aerosol (OA) constitutes a dominant fraction of airborne particulates over Indo-Gangetic Plain (IGP) especially during post-monsoon and winter. Its exposure has been associated with adverse health effects while there are evidences of its interference with Earth's radiation balance and cloud condensation (CC), resulting possible alteration of hydrological cycle. Therefore, presence and effects of OA directly link it with food security and thereby, sustainability issues. In these contexts, atmospheric chemistry involving formation, volatility and aging of primary OA (POA) and secondary OA (SOA) have been reviewed with specific reference to IGP. Systematic reviews on science of OA sources, evolution and climate perturbations are presented with databases collected from 82 publications available throughout IGP till 2016. Both gaseous and aqueous phase chemical reactions were studied in terms of their potential to form SOA. Efforts were made to recognize the regional variation of OA, its chemical constituents and sources throughout IGP and inferences were made on its possible impacts on regional air quality. Mass fractions of OA to airborne particulate showed spatial variation likewise in Lahore (37 and 44% in fine and coarse fractions, respectively), Patiala (28 and 37%), Delhi (25 and 38%), Kanpur (24 and 30%), Kolkata (11 and 21%) and Dhaka. Source apportionment studies indicate biomass burning, coal combustion and vehicular emissions as predominant OA sources. However, sources represent considerable seasonal variations with dominance of gasoline and diesel emissions during summer and coal and biomass based emissions during winter and post-monsoon. Crop residue burning over upper-IGP was also frequently held responsible for massive OA emission, mostly characterized by its hygroscopic nature, thus having potential to act as CC nuclei. Conclusively, climatic implication of particulate bound OA has been discussed in terms of its interaction with radiation balance.

Patterns of Song across Natural and Anthropogenic Soundscapes Suggest That White-Crowned Sparrows Minimize Acoustic Masking and Maximize Signal Content.

PubMed

Derryberry, Elizabeth P; Danner, Raymond M; Danner, Julie E; Derryberry, Graham E; Phillips, Jennifer N; Lipshutz, Sara E; Gentry, Katherine; Luther, David A

2016-01-01

Soundscapes pose both evolutionarily recent and long-standing sources of selection on acoustic communication. We currently know more about the impact of evolutionarily recent human-generated noise on communication than we do about how natural sounds such as pounding surf have shaped communication signals over evolutionary time. Based on signal detection theory, we hypothesized that acoustic phenotypes will vary with both anthropogenic and natural background noise levels and that similar mechanisms of cultural evolution and/or behavioral flexibility may underlie this variation. We studied song characteristics of white-crowned sparrows (Zonotrichia leucophrys nuttalli) across a noise gradient that includes both anthropogenic and natural sources of noise in San Francisco and Marin counties, California, USA. Both anthropogenic and natural soundscapes contain high amplitude low frequency noise (traffic or surf, respectively), so we predicted that birds would produce songs with higher minimum frequencies in areas with higher amplitude background noise to avoid auditory masking. We also anticipated that song minimum frequencies would be higher than the projected lower frequency limit of hearing based on site-specific masking profiles. Background noise was a strong predictor of song minimum frequency, both within a local noise gradient of three urban sites with the same song dialect and cultural evolutionary history, and across the regional noise gradient, which encompasses 11 urban and rural sites, several dialects, and several anthropogenic and natural sources of noise. Among rural sites alone, background noise tended to predict song minimum frequency, indicating that urban sites were not solely responsible for driving the regional pattern. These findings support the hypothesis that songs vary with local and regional soundscapes regardless of the source of noise. Song minimum frequency from five core study sites was also higher than the lower frequency limit of hearing at each site, further supporting the hypothesis that songs vary to transmit through noise in local soundscapes. Minimum frequencies leveled off at noisier sites, suggesting that minimum frequencies are constrained to an upper limit, possibly to retain the information content of wider bandwidths. We found evidence that site noise was a better predictor of song minimum frequency than territory noise in both anthropogenic and natural soundscapes, suggesting that cultural evolution rather than immediate behavioral flexibility is responsible for local song variation. Taken together, these results indicate that soundscapes shape song phenotype across both evolutionarily recent and long-standing soundscapes.

Patterns of Song across Natural and Anthropogenic Soundscapes Suggest That White-Crowned Sparrows Minimize Acoustic Masking and Maximize Signal Content

PubMed Central

Derryberry, Graham E.; Phillips, Jennifer N.; Lipshutz, Sara E.; Gentry, Katherine; Luther, David A.

2016-01-01

Soundscapes pose both evolutionarily recent and long-standing sources of selection on acoustic communication. We currently know more about the impact of evolutionarily recent human-generated noise on communication than we do about how natural sounds such as pounding surf have shaped communication signals over evolutionary time. Based on signal detection theory, we hypothesized that acoustic phenotypes will vary with both anthropogenic and natural background noise levels and that similar mechanisms of cultural evolution and/or behavioral flexibility may underlie this variation. We studied song characteristics of white-crowned sparrows (Zonotrichia leucophrys nuttalli) across a noise gradient that includes both anthropogenic and natural sources of noise in San Francisco and Marin counties, California, USA. Both anthropogenic and natural soundscapes contain high amplitude low frequency noise (traffic or surf, respectively), so we predicted that birds would produce songs with higher minimum frequencies in areas with higher amplitude background noise to avoid auditory masking. We also anticipated that song minimum frequencies would be higher than the projected lower frequency limit of hearing based on site-specific masking profiles. Background noise was a strong predictor of song minimum frequency, both within a local noise gradient of three urban sites with the same song dialect and cultural evolutionary history, and across the regional noise gradient, which encompasses 11 urban and rural sites, several dialects, and several anthropogenic and natural sources of noise. Among rural sites alone, background noise tended to predict song minimum frequency, indicating that urban sites were not solely responsible for driving the regional pattern. These findings support the hypothesis that songs vary with local and regional soundscapes regardless of the source of noise. Song minimum frequency from five core study sites was also higher than the lower frequency limit of hearing at each site, further supporting the hypothesis that songs vary to transmit through noise in local soundscapes. Minimum frequencies leveled off at noisier sites, suggesting that minimum frequencies are constrained to an upper limit, possibly to retain the information content of wider bandwidths. We found evidence that site noise was a better predictor of song minimum frequency than territory noise in both anthropogenic and natural soundscapes, suggesting that cultural evolution rather than immediate behavioral flexibility is responsible for local song variation. Taken together, these results indicate that soundscapes shape song phenotype across both evolutionarily recent and long-standing soundscapes. PMID:27128443

Study on relationship between evolution of regional gravity field and seismic hazard

NASA Astrophysics Data System (ADS)

Li, W.; Xu, C.; Shen, C.

2017-12-01

The lack of anomalous signal is a big issue for the study of geophysics using historical geodesy observations, which is a relatively new area of earth gravimetry application in seismology. Hence the use of the gravity anomaly (GA) derived from either a global geopotential model (GGM) or a regional gravity reanalysis (Ground Gravity Survey, GGS) becomes an important alternative solution. In this study, the GGS at 186 points for the period of 2010 2014 in the Sichuan-Yunnan region (SYR) stations are analyzed. To study the temporal and spatial distribution characteristics of regional gravity filed (RGF) and its evolution mechanism. Taking the geological and geophysical data as constraints. From the GGM expanded up to degree 360, GA were obtained after gravity reduction, especially removing the reference field. The dynamically evolutional characteristics of gravity field are closely relative to fault activity. The gravity changes with time about 5 years at LongMenShan fault (LMSF) have a slop of -12.83±2.9 μGal/a, indicating that LMSF has an uplift. To test the signal extraction algorithm in some geodynamic processes, GA from the SYR were inverted and it was also imposed as a priori information. Fortunately, some significant gravity variation have been detected at some stations in the thrust fault before and after four earthquakes, in which typical anomalies (earthquake precursor, EP) were positive GA variation near the epicenter and the occurrence of a high-gravity-gradient zone across the epicenter prior to the Lushan earthquake (Ms 7.0). The repeated observation results during about 5 years indicate that no significant gravity changes related to other geodynamical events were observed in most observation epochs. In addition, the mechanism of gravity changes at Lushan was also explored. We calculated the gravity change rates based on the model of Songpan-Ganze block (SGB) to Sichuan basin (SCB). And the changes is in good agreement with observed one, indicating that present gravity changes at Lushan were caused by SGB to SCB. The results and understanding are of great significance for further study of tectonic characteristics in this region, and the GGS-derived anomalies has the potential to be used as a reliable source of EP on a regional scale for seismic, or a favorable basis for seismic hazards.

Modelling the role of magmatic intrusions in the post-breakup thermal evolution of Volcanic Passive Margins

NASA Astrophysics Data System (ADS)

Peace, Alexander; McCaffrey, Ken; Imber, Jonny; van Hunen, Jeroen; Hobbs, Richard; Gerdes, Keith

2013-04-01

Passive margins are produced by continental breakup and subsequent seafloor spreading, leaving a transition from continental to oceanic crust. Magmatism is associated with many passive margins and produces diagnostic criteria that include 1) abundant breakup related magmatism resulting in a thick igneous crust, 2) a high velocity zone in the lower crust and 3) seaward dipping reflectors (SDRs) in seismic studies. These Volcanic Passive Margins (VPMs) represent around 75% of the Atlantic passive margins, but beyond this high level description, these magma-rich settings remain poorly understood and present numerous challenges to petroleum exploration. In VPMs the extent to which the volume, timing, location and emplacement history of magma has played a role in controlling heat flow and thermal evolution during margin development remains poorly constrained. Reasons for this include; 1) paucity of direct heat flow and thermal gradient measurements at adequate depth ranges across the margins, 2) poor onshore exposure 3) highly eroded flood basalts and 4) poor seismic imaging beneath thick offshore basalt sequences. As a result, accurately modelling the thermal history of the basins located on VPMs is challenging, despite the obvious importance for determining the maturation history of potential source rocks in these settings. Magmatism appears to have affected the thermal history of the Vøring Basin on the Norwegian VPM, in contrast the effects on the Faeroe-Shetland Basin was minimal. The more localised effects in the Faeroe-Shetland Basin compared to Vøring Basin may be explained by the fact that the main reservoir sandstones appear to be synchronous with thermal uplift along the basin margin and pulsed volcanism, indicating that the bulk of the magmatism occurred at the basin extremities in the Faeroe-Shetland Basin, where its effect on source maturation was lessened. Our hypothesis is that source maturation occurs as a result of regional temperature and pressure increases, and the effects of even a large singular magmatic event are small beyond the immediate vicinity, therefore quantifying cumulative regional heat flow is of utmost importance. The apparently complex relationships between source rock maturation and magmatism are not limited to the north-east Atlantic margins. Other VPMs of interest include the regions between West Greenland and Eastern Canada (Labrador Sea, Davis Strait and Baffin Bay), East Greenland, NW Australia, Western India and segments of the Western African and Eastern South American margins. This project utilises 1D numerical modelling of magmatic intrusions into a sedimentary column to gain an understanding into the thermal influence of post-breakup magmatic activity on source rock maturation in representative VPMs. Considerations include the timing, periodicity of intrusions, thickness, spacing and background heat in the basin.

Recent Advances in Subsurface Imaging and Monitoring with Active Sources in China

NASA Astrophysics Data System (ADS)

Wang, B.; Chen, Y.; Wang, W.; Yang, W.

2017-12-01

Imaging high-resolution crustal structures and monitoring their temporal changes with active sources is essential to our understanding of regional tectonics and seismic hazards. In the past decades, great efforts has been made in China to looking for an ideal artificial seismic source to study continental crustal structures. After a mountain of field experiments, we developed permanent and portable seismic airgun sources for inland seismotectonic studies. Here we introduce several applications of using airgun source to imaging local crustal structures and monitoring velocity changes associated with natural and anthropogenic loadings. During Oct. 10th-20th, 2015, we carried out a crustal structure exploration experiment by firing portable airgun source along the Yangtze River in Anhui Province of eastern China. About 5000 shots were fired along 300km long section of the river. More than 2000 portable short period seismometers or geophones were deployed during the experiment. About 3000 of 5000 shots were fired at 20 fixed sites roughly evenly distributed along the river, and the rest shots were fired in the walkway. Seismic signal radiated by airgun source can be tracked to 350km. 2D/3D near surface and crustal velocity structure along the Yangtze River and adjacent region were inverted from airgun seismic records. Inverted velocity show well consistence with previous images and geological structure. The high resolution structural image provides a better understanding on regional geologic features and distribution of mineral resources. In the past five years, three Fixed Aigun Signal Transmitting Stations (FASTS) were built in western China. Those FASTS generate seismic signals with high repeatability, which can be tracked to the distance 1300 km. The highly reproducible signals are used to monitor the subtle subsurface changes. Observed diurnal and semi-diurnal velocity changes 10-4 are supposed to be results of barometrical and tidal loading. Suspicious velocity changes prior to several moderate earthquakes are detected around. Seismic velocity measured around the Hutubi underground gas storage show clear correlation with the gas pressure. Those results shed some light on the short term evolution of the shallow to low crust, which may boost our understanding the mechanism of local seismic hazards.

Analysis of surface deformation during the eruptive process of El Hierro Island (Canary Islands, Spain): Detection, Evolution and Forecasting.

NASA Astrophysics Data System (ADS)

Berrocoso, M.; Fernandez-Ros, A.; Prates, G.; Martin, M.; Hurtado, R.; Pereda, J.; Garcia, M. J.; Garcia-Cañada, L.; Ortiz, R.; Garcia, A.

2012-04-01

The surface deformation has been an essential parameter for the onset and evolution of the eruptive process of the island of El Hierro (October 2011) as well as for forecasting changes in seismic and volcanic activity during the crisis period. From GNSS-GPS observations the reactivation is early detected by analizing the change in the deformation of the El Hierro Island regional geodynamics. It is found that the surface deformation changes are detected before the occurrence of seismic activity using the station FRON (GRAFCAN). The evolution of the process has been studied by the analysis of time series of topocentric coordinates and the variation of the distance between stations on the island of El Hierro (GRAFCAN station;IGN network; and UCA-CSIC points) and LPAL-IGS station on the island of La Palma. In this work the main methodologies and their results are shown: •The location (and its changes) of the litospheric pressure source obtained by applying the Mogi model. •Kalman filtering technique for high frequency time series, used to make the forecasts issued for volcanic emergency management. •Correlations between deformation of the different GPS stations and their relationship with seismovolcanic settings.

Global carbon monoxide cycle: Modeling and data analysis

NASA Astrophysics Data System (ADS)

Arellano, Avelino F., Jr.

The overarching goal of this dissertation is to develop robust, spatially and temporally resolved CO sources, using global chemical transport modeling, CO measurements from Climate Monitoring and Diagnostic Laboratory (CMDL) and Measurement of Pollution In The Troposphere (MOPITT), under the framework of Bayesian synthesis inversion. To rigorously quantify the CO sources, I conducted five sets of inverse analyses, with each set investigating specific methodological and scientific issues. The first two inverse analyses separately explored two different CO observations to estimate CO sources by region and sector. Under a range of scenarios relating to inverse methodology and data quality issues, top-down estimates using CMDL CO surface and MOPITT CO remote-sensed measurements show consistent results particularly on a significantly large fossil fuel/biofuel (FFBF) emission in East Asia than present bottom-up estimates. The robustness of this estimate is strongly supported by forward and inverse modeling studies in the region particularly from TRansport and Chemical Evolution over the Pacific (TRACE-P) campaign. The use of high-resolution measurement for the first time in CO inversion also draws attention to a methodology issue that the range of estimates from the scenarios is larger than posterior uncertainties, suggesting that estimate uncertainties may be underestimated. My analyses highlight the utility of top-down approach to provide additional constraints on present global estimates by also pointing to other discrepancies including apparent underestimation of FFBF from Africa/Latin America and biomass burning (BIOM) sources in Africa, southeast Asia and north-Latin America, indicating inconsistencies on our current understanding of fuel use and land-use patterns in these regions. Inverse analysis using MOPITT is extended to determine the extent of MOPITT information and estimate monthly regional CO sources. A major finding, which is consistent with other atmospheric observations but differ with satellite area-burned observations, is a significant overestimation in southern Africa for June/July relative to satellite-and-model-constrained BIOM emissions of CO. Sensitivity inverse analyses on observation error covariance and structure, and sequential inversion using NOAA CMDL to fully exploit available information, confirm the robustness of the estimates and further recognize the limitations of the approach, implying the need to further improve the methodology and to reconcile discrepancies.

A Model for the Thermal and Chemical Evolution of the Moon's Interior: Implications for the Onset of Mare Volcanism

NASA Technical Reports Server (NTRS)

Hess, Paul C.; Parmentier, E. M.

1995-01-01

Crystallization of the lunar magma ocean creates a chemically stratified Moon consisting of an anorthositic crust and magma ocean cumulates overlying the primitive lunar interior. Within the magma ocean cumulates the last liquids to crystallize form dense, ilmenite-rich cumulates that contain high concentrations of incompatible radioactive elements. The underlying olivine-orthopyroxene cumulates are also stratified with later crystallized, denser, more Fe-rich compositions at the top. This paper explores the chemical and thermal consequences of an internal evolution model accounting for the possible role of these sources of chemical buoyancy. Rayleigh-Taylor instability causes the dense ilmenite-rich cumulate layer and underlying Fe-rich cumulates to sink toward the center of the Moon, forming a dense lunar core. After this overturn, radioactive heating within the ilmenite-rich cumulate core heats the overlying mantle, causing it to melt. In this model, the source region for high-TiO2 mare basalts is a convectively mixed layer above the core-mantle boundary which would contain small and variable amounts of admixed ilmenite and KREEP. This deep high-pressure melting, as required for mare basalts, occurs after a reasonable time interval to explain the onset of mare basalt volcanism if the content of radioactive elements in the core and the chemical density gradients above the core are sufficiently high but within a range of values that might have been present in the Moon. Regardless of details implied by particular model parameters, gravitational overturn driven by the high density of magma ocean Fe-rich cumulates should concentrate high-TiO2 mare basalt sources, and probably a significant fraction of radioactive heating, toward the center of the Moon. This will have important implications for both the thermal evolution of the Moon and for mare basalt genesis.

Evolution of vehicle exhaust particles in the atmosphere.

PubMed

Canagaratna, Manjula R; Onasch, Timothy B; Wood, Ezra C; Herndon, Scott C; Jayne, John T; Cross, Eben S; Miake-Lye, Richard C; Kolb, Charles E; Worsnop, Douglas R

2010-10-01

Aerosol mass spectrometer (AMS) measurements are used to characterize the evolution of exhaust particulate matter (PM) properties near and downwind of vehicle sources. The AMS provides time-resolved chemically speciated mass loadings and mass-weighted size distributions of nonrefractory PM smaller than 1 microm (NRPM1). Source measurements of aircraft PM show that black carbon particles inhibit nucleation by serving as condensation sinks for the volatile and semi-volatile exhaust gases. Real-world source measurements of ground vehicle PM are obtained by deploying an AMS aboard a mobile laboratory. Characteristic features of the exhaust PM chemical composition and size distribution are discussed. PM mass and number concentrations are used with above-background gas-phase carbon dioxide (CO2) concentrations to calculate on-road emission factors for individual vehicles. Highly variable ratios between particle number and mass concentrations are observed for individual vehicles. NRPM1 mass emission factors measured for on-road diesel vehicles are approximately 50% lower than those from dynamometer studies. Factor analysis of AMS data (FA-AMS) is applied for the first time to map variations in exhaust PM mass downwind of a highway. In this study, above-background vehicle PM concentrations are highest close to the highway and decrease by a factor of 2 by 200 m away from the highway. Comparison with the gas-phase CO2 concentrations indicates that these vehicle PM mass gradients are largely driven by dilution. Secondary aerosol species do not show a similar gradient in absolute mass concentrations; thus, their relative contribution to total ambient PM mass concentrations increases as a function of distance from the highway. FA-AMS of single particle and ensemble data at an urban receptor site shows that condensation of these secondary aerosol species onto vehicle exhaust particles results in spatial and temporal evolution of the size and composition of vehicle exhaust PM on urban and regional scales.

Air quality in the megacity of São Paulo: Evolution over the last 30 years and future perspectives

NASA Astrophysics Data System (ADS)

Andrade, Maria de Fatima; Kumar, Prashant; de Freitas, Edmilson Dias; Ynoue, Rita Yuri; Martins, Jorge; Martins, Leila D.; Nogueira, Thiago; Perez-Martinez, Pedro; de Miranda, Regina Maura; Albuquerque, Taciana; Gonçalves, Fabio Luiz Teixeira; Oyama, Beatriz; Zhang, Yang

2017-06-01

We present a comprehensive review of published results from the last 30 years regarding the sources and atmospheric characteristics of particles and ozone in the Metropolitan Area of São Paulo (MASP). During the last 30 years, many efforts have been made to describe the emissions sources and to analyse the primary and secondary formation of pollutants under a process of increasing urbanisation in the metropolitan area. From the occurrence of frequent violations of air quality standards in the 1970s and 1980s (due to the uncontrolled air pollution sources) to a substantial decrease in the concentrations of the primary pollutants, many regulations have been imposed and enforced, although those concentrations do not yet conform to the World Health Organization guidelines. The greatest challenge currently faced by the São Paulo State Environmental Protection Agency and the local community is controlling secondary pollutants such as ozone and fine particles. Understanding the formation of these secondary pollutants, by experimental or modelling approaches, requires the description of the atmospheric chemical processes driven by biofuel, ethanol and biodiesel emissions. Exposure to air pollution is the cause of many injuries to human health, according to many studies performed not only in the region but also worldwide, and affects susceptible populations such as children and the elderly. The MASP is the biggest megacity in the Southern Hemisphere, and its specifics are important for other urban areas that are facing the challenge of intensive growth that puts pressure on natural resources and worsens the living conditions in urban areas. This text discusses how imposing regulations on air quality and emission sources, mainly related to the transportation sector, has affected the evolution of pollutant concentrations in the MASP.

TRACING THE REVERBERATION LAG IN THE HARD STATE OF BLACK HOLE X-RAY BINARIES

DOE Office of Scientific and Technical Information (OSTI.GOV)

De Marco, B.; Ponti, G.; Nandra, K.

2015-11-20

We report results obtained from a systematic analysis of X-ray lags in a sample of black hole X-ray binaries, with the aim of assessing the presence of reverberation lags and studying their evolution during outburst. We used XMM-Newton and simultaneous Rossi X-ray Timing Explorer (RXTE) observations to obtain broadband energy coverage of both the disk and the hard X-ray Comptonization components. In most cases the detection of reverberation lags is hampered by low levels of variability-power signal-to-noise ratio (typically when the source is in a soft state) and/or short exposure times. The most detailed study was possible for GX 339-4more » in the hard state, which allowed us to characterize the evolution of X-ray lags as a function of luminosity in a single source. Over all the sampled frequencies (∼0.05–9 Hz), we observe the hard lags intrinsic to the power-law component, already well known from previous RXTE studies. The XMM-Newton soft X-ray response allows us to detail the disk variability. At low frequencies (long timescales) the disk component always leads the power-law component. On the other hand, a soft reverberation lag (ascribable to thermal reprocessing) is always detected at high frequencies (short timescales). The intrinsic amplitude of the reverberation lag decreases as the source luminosity and the disk fraction increase. This suggests that the distance between the X-ray source and the region of the optically thick disk where reprocessing occurs gradually decreases as GX 339-4 rises in luminosity through the hard state, possibly as a consequence of reduced disk truncation.« less

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

PubMed Central

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

2014-01-01

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

Paleoclimatic and Paleoceanographic Holocene Sedimentary Records in the Gulf of California - Eastern Pacific Ocean Interhemispheric Connections

NASA Astrophysics Data System (ADS)

Perez-Cruz, L.; Urrutia-Fucugauchi, J.

2009-05-01

Initial results of a study on the distribution, thickness and stratigraphy of the sedimentary sequences in the Gulf of California are presented. The Gulf is an elongated narrow young oceanic basin bordered by the Baja California peninsula and mainland Mexico. The Gulf extends over 1200 km across the Tropic of Cancer from the tropical to the temperate zones, surrounded by arid and semi-arid regions, including the Sonora-Mojave Desert. Paleoceanographic conditions are dominated by water exchange at the Gulf mouth and water masses changes along the Gulf. Tectonic basins reach down in excess of 3000 m depths and get shallower to the north. Here we focus on the Holocene sediment sequences in the southern sector, which contains several marginal and central anoxic basins that constitute rich archives of paleoclimatic and paleoenvironmental evolution for the past 3.6 Ma. In the mouth area, main sources of sediments are silicic volcanic and intrusive rocks in the Baja peninsula and mainland, including Los Cabos and Puerto Vallarta batholiths. Fine-grained eolian dusts, pluvial and biogenic sediments are present in the sediment cores in the Gulf basins such as La Paz, Alfonso, Carmen, Pescadero and Guaymas basins. Turbiditic currents and tephra deposits also occur in the cores. Paleoclimatic records show the influences of regional processes, including the ENSO and PDO signals marked by drought and increased precipitation phases. Relative distribution and thickness of sediments at the mouth of the Gulf correlate with bathymetry and location with respect to spreading center, transform faults and margins of the peninsula and mainland Mexico. Rock magnetic core scans and mineralogy at few locations are available, which allow inferences on sediment sources, transport and deposition processes, diagenesis, paleoceanographic and paleoclimatic evolution for the Holocene.

Temporal evolution of solar wind ion composition and their source coronal holes during the declining phase of cycle 23. I. Low-latitude extension of polar coronal holes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ko, Yuan-Kuen; Wang, Yi-Ming; Muglach, Karin

2014-06-01

We analyzed 27 solar wind (SW) intervals during the declining phase of cycle 23, whose source coronal holes (CHs) can be unambiguously identified and are associated with one of the polar CHs. We found that the SW ions have a temporal trend of decreasing ionization state, and such a trend is different between the slow and fast SW. The photospheric magnetic field, both inside and at the outside boundary of the CH, also exhibits a trend of decrease with time. However, EUV line emissions from different layers of the atmosphere exhibit different temporal trends. The coronal emission inside the CHmore » generally increases toward the CH boundary as the underlying field increases in strength and becomes less unipolar. In contrast, this relationship is not seen in the coronal emission averaged over the entire CH. For C and O SW ions that freeze-in at lower altitude, stronger correlation between their ionization states and field strength (both signed and unsigned) appears in the slow SW, while for Fe ions that freeze-in at higher altitude, stronger correlation appears in the fast SW. Such correlations are seen both inside the CH and at its boundary region. On the other hand, the coronal electron temperature correlates well with the SW ion composition only in the boundary region. Our analyses, although not able to determine the likely footpoint locations of the SW of different speeds, raise many outstanding questions for how the SW is heated and accelerated in response to the long-term evolution of the solar magnetic field.« less

Quantification of surface emissions: An historical perspective from GEIA

NASA Astrophysics Data System (ADS)

Granier, C.; Denier Van Der Gon, H.; Doumbia, E. H. T.; Frost, G. J.; Guenther, A. B.; Hassler, B.; Janssens-Maenhout, G. G. A.; Lasslop, G.; Melamed, M. L.; Middleton, P.; Sindelarova, K.; Tarrason, L.; van Marle, M.; W Kaiser, J.; van der Werf, G.

2015-12-01

Assessments of the composition of the atmosphere and its evolution require accurate knowledge of the surface emissions of atmospheric compounds. The first community development of global surface emissions started in 1990, when GEIA was established as a component of the International Global Atmospheric Chemistry (IGAC) project. At that time, GEIA meant "Global Emissions Inventory Activity". Since its inception, GEIA has brought together people to understand emissions from anthropogenic, biomass burning and natural sources. The first goal of GEIA was to establish a "best" inventory for the base year 1985 at 1x1 degree resolution. Since then many inventories have been developed by various groups at the global and regional scale at different temporal and spatial resolutions. GEIA, which now means the "Global Emissions Initiative", has evolved into assessing, harmonizing and distributing emissions datasets. We will review the main achievements of GEIA, and show how the development and evaluation of surface emissions has evolved during the last 25 years. We will discuss the use of surface, in-situ and remote sensing observations to evaluate and improve the quantification of emissions. We will highlight the main uncertainties currently limiting emissions datasets, such as the spatial and temporal evolution of emissions at different resolutions, the quantification of emerging emission sources (such as oil/gas extraction and distribution, biofuels, etc.), the speciation of the emissions of volatile organic compounds and of particulate matter, the capacity building necessary for organizing the development of regional emissions across the world, emissions from shipping, etc. We will present the ECCAD (Emissions of Atmospheric Compounds and Compilation of Ancillary Data) database, developed as part of GEIA to facilitate the access and evaluation of emission inventories.

Gains and Losses of Transcription Factor Binding Sites in Saccharomyces cerevisiae and Saccharomyces paradoxus.

PubMed

Schaefke, Bernhard; Wang, Tzi-Yuan; Wang, Chuen-Yi; Li, Wen-Hsiung

2015-07-27

Gene expression evolution occurs through changes in cis- or trans-regulatory elements or both. Interactions between transcription factors (TFs) and their binding sites (TFBSs) constitute one of the most important points where these two regulatory components intersect. In this study, we investigated the evolution of TFBSs in the promoter regions of different Saccharomyces strains and species. We divided the promoter of a gene into the proximal region and the distal region, which are defined, respectively, as the 200-bp region upstream of the transcription starting site and as the 200-bp region upstream of the proximal region. We found that the predicted TFBSs in the proximal promoter regions tend to be evolutionarily more conserved than those in the distal promoter regions. Additionally, Saccharomyces cerevisiae strains used in the fermentation of alcoholic drinks have experienced more TFBS losses than gains compared with strains from other environments (wild strains, laboratory strains, and clinical strains). We also showed that differences in TFBSs correlate with the cis component of gene expression evolution between species (comparing S. cerevisiae and its sister species Saccharomyces paradoxus) and within species (comparing two closely related S. cerevisiae strains). © The Author(s) 2015. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.

Different evolutionary patterns of SNPs between domains and unassigned regions in human protein-coding sequences.

PubMed

Pang, Erli; Wu, Xiaomei; Lin, Kui

2016-06-01

Protein evolution plays an important role in the evolution of each genome. Because of their functional nature, in general, most of their parts or sites are differently constrained selectively, particularly by purifying selection. Most previous studies on protein evolution considered individual proteins in their entirety or compared protein-coding sequences with non-coding sequences. Less attention has been paid to the evolution of different parts within each protein of a given genome. To this end, based on PfamA annotation of all human proteins, each protein sequence can be split into two parts: domains or unassigned regions. Using this rationale, single nucleotide polymorphisms (SNPs) in protein-coding sequences from the 1000 Genomes Project were mapped according to two classifications: SNPs occurring within protein domains and those within unassigned regions. With these classifications, we found: the density of synonymous SNPs within domains is significantly greater than that of synonymous SNPs within unassigned regions; however, the density of non-synonymous SNPs shows the opposite pattern. We also found there are signatures of purifying selection on both the domain and unassigned regions. Furthermore, the selective strength on domains is significantly greater than that on unassigned regions. In addition, among all of the human protein sequences, there are 117 PfamA domains in which no SNPs are found. Our results highlight an important aspect of protein domains and may contribute to our understanding of protein evolution.

Observational aspects of outbursting black hole sources: Evolution of spectro-temporal features and X-ray variability

NASA Astrophysics Data System (ADS)

Sreehari, H.; Nandi, Anuj; Radhika, D.; Iyer, Nirmal; Mandal, Samir

2018-02-01

We report on our attempt to understand the outbursting profile of Galactic Black Hole sources, keeping in mind the evolution of temporal and spectral features during the outburst. We present results of evolution of quasi-periodic oscillations, spectral states and possible connection with jet ejections during the outburst phase. Further, we attempt to connect the observed X-ray variabilities (i.e., `class'/`structured' variabilities, similar to GRS 1915+105) with spectral states of black hole sources. Towards these studies, we consider three black hole sources that have undergone single (XTE J1859+226), a few (IGR J17091-3624) and many (GX 339-4) outbursts since the start of RXTE era. Finally, we model the broadband energy spectra (3-150 keV) of different spectral states using RXTE and NuSTAR observations. Results are discussed in the context of two-component advective flow model, while constraining the mass of the three black hole sources.

Evolution of Extragalactic Radio Sources and Quasar/Galaxy Unification

NASA Astrophysics Data System (ADS)

Onah, C. I.; Ubachukwu, A. A.; Odo, F. C.; Onuchukwu, C. C.

2018-04-01

We use a large sample of radio sources to investigate the effects of evolution, luminosity selection and radio source orientation in explaining the apparent deviation of observed angular size - redshift (θ - z) relation of extragalactic radio sources (EGRSs) from the standard model. We have fitted the observed θ - z data with standard cosmological models based on a flat universe (Ω0 = 1). The size evolution of EGRSs has been described as luminosity, temporal and orientation-dependent in the form DP,z,Φ ≍ P±q(1 + z)-m sinΦ, with q=0.3, Φ=59°, m=-0.26 for radio galaxies and q=-0.5, Φ=33°, m=3.1 for radio quasars respectively. Critical points of luminosity, logPcrit=26.33 WHz-1 and logDc=2.51 kpc (316.23 kpc) of the present sample of radio sources were also observed. All the results were found to be consistent with the popular quasar/galaxy unification scheme.

Western Disturbances: A review

NASA Astrophysics Data System (ADS)

Dimri, A. P.; Niyogi, D.; Barros, A. P.; Ridley, J.; Mohanty, U. C.; Yasunari, T.; Sikka, D. R.

2015-06-01

Cyclonic storms associated with the midlatitude Subtropical Westerly Jet (SWJ), referred to as Western Disturbances (WDs), play a critical role in the meteorology of the Indian subcontinent. WDs embedded in the southward propagating SWJ produce extreme precipitation over northern India and are further enhanced over the Himalayas due to orographic land-atmosphere interactions. During December, January, and February, WD snowfall is the dominant precipitation input to establish and sustain regional snowpack, replenishing regional water resources. Spring melt is the major source of runoff to northern Indian rivers and can be linked to important hydrologic processes from aquifer recharge to flashfloods. Understanding the dynamical structure, evolution-decay, and interaction of WDs with the Himalayas is therefore necessary to improve knowledge which has wide ranging socioeconomic implications beyond short-term disaster response including cold season agricultural activities, management of water resources, and development of vulnerability-adaptive measures. In addition, WD wintertime precipitation provides critical mass input to existing glaciers and modulates the albedo characteristics of the Himalayas and Tibetan Plateau, affecting large-scale circulation and the onset of the succeeding Indian Summer Monsoon. Assessing the impacts of climate variability and change on the Indian subcontinent requires fundamental understanding of the dynamics of WDs. In particular, projected changes in the structure of the SWJ will influence evolution-decay processes of the WDs and impact Himalayan regional water availability. This review synthesizes past research on WDs with a perspective to provide a comprehensive assessment of the state of knowledge to assist both researchers and policymakers, and context for future research.

Multivariate study of trace element distribution in the geological record of Roñanzas Peat Bog (Asturias, N. Spain). Paleoenvironmental evolution and human activities over the last 8000 calyr BP.

PubMed

Gallego, José Luis R; Ortiz, José E; Sierra, Carlos; Torres, Trinidad; Llamas, J F

2013-06-01

Trace element concentrations in the Roñanzas peat bog record reveal a contribution of natural processes but the influence of anthropogenic factors predominates in the last two millenniums, particularly aerosol deposition linked to mining and industrial activities in northern Spain. We observed that the Roñanzas record can be considered a preserved environment, suitable to search for local (<50 km), regional (50-150 km) and/or long-distance human activity fingerprinting, specifically that related to the deposition of heavy metals such as Pb, Zn and Hg. We also carried out a multivariate statistical study in order to clarify the geochemical behavior of trace and major elements. Our study design represents a novel approach to assign natural vs. human contributions in peatlands. Therefore, synergies obtained by the simultaneous study of multivariate statistics and enrichment factors allow robust conclusions about paleoenvironmental evolution and human activities. Anthropogenic influence has also been reported in similar records in other parts of Europe, thereby suggesting large-scale sources for atmospheric pollution. However, here we revealed remarkable particularities, such as the association of Cd, Zn and Pb, mainly linked to regional and local factors (mining and more recently the metallurgical industry), whereas we propose that the occurrence of Hg is associated with a combination of regional factors and global atmospheric pollution. Copyright © 2013 Elsevier B.V. All rights reserved.

Exposed bright features on the comet 67P/Churyumov-Gerasimenko: distribution and evolution

NASA Astrophysics Data System (ADS)

Deshapriya, J. D. P.; Barucci, M. A.; Fornasier, S.; Hasselmann, P. H.; Feller, C.; Sierks, H.; Lucchetti, A.; Pajola, M.; Oklay, N.; Mottola, S.; Masoumzadeh, N.; Tubiana, C.; Güttler, C.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; Bertaux, J.-L.; Bertini, I.; Bodewits, D.; Boudreault, S.; Cremonese, G.; Da Deppo, V.; Davidsson, B. J. R.; Debei, S.; Cecco, M. De; Deller, J.; Fulle, M.; Groussin, O.; Gutierrez, P. J.; Hoang, H. V.; Hviid, S. F.; Ip, W.; Jorda, L.; Keller, H. U.; Knollenberg, J.; Kramm, R.; Kührt, E.; Küppers, M.; Lara, L.; Lazzarin, M.; Lopez Moreno, J. J.; Marzari, F.; Naletto, G.; Preusker, F.; Shi, X.; Thomas, N.; Vincent, J.-B.

2018-05-01

Context. Since its arrival at the comet 67P/Churyumov-Gerasimenko in August 2014, the Rosetta spacecraft followed the comet as it went past the perihelion and beyond until September 2016. During this time there were many scientific instruments operating on board Rosetta to study the comet and its evolution in unprecedented detail. In this context, our study focusses on the distribution and evolution of exposed bright features that have been observed by OSIRIS, which is the scientific imaging instrument aboard Rosetta. Aims: We envisage investigating various morphologies of exposed bright features and the mechanisms that triggered their appearance. Methods: We co-registered multi-filter observations of OSIRIS images that are available in reflectance. The Lommel-Seeliger disk function was used to correct for the illumination conditions and the resulting colour cubes were used to perform spectrophotometric analyses on regions of interest. Results: We present a catalogue of 57 exposed bright features observed on the nucleus of the comet, all of which are attributed to the presence of H2O ice on the comet. Furthermore, we categorise these patches under four different morphologies and present geometric albedos for each category. Conclusions: Although the nucleus of 67P/Churyumov-Gerasimenko appears to be dark in general, there are localised H2O ice sources on the comet. Cometary activity escalates towards the perihelion passage and reveals such volatile ices. We propose that isolated H2O ice patches found in smooth terrains in regions, such as Imhotep, Bes, and Hapi, result from frost as an aftermath of the cessation of the diurnal water cycle on the comet as it recedes from perihelion. Upon the comet's return to perihelion, such patches are revealed when sublimation-driven erosion removes the thin dust layers that got deposited earlier. More powerful activity sources such as cometary outbursts are capable of revealing much fresher, less contaminated H2O ice that is preserved with consolidated cometary material, as observed on exposed patches resting on boulders. This is corroborated by our albedo calculations that attribute higher albedos for bright features with formations related to outbursts.

The Effectiveness of an Online Curriculum on High School Students' Understanding of Biological Evolution

ERIC Educational Resources Information Center

Marsteller, Robert B.; Bodzin, Alec M.

2015-01-01

An online curriculum about biological evolution was designed to promote increased student content knowledge and evidentiary reasoning. A feasibility study was conducted with 77 rural high school biology students who learned with the online biological evolution unit. Data sources included the Biological Evolution Assessment Measure (BEAM), an…

Student Acquisition of Biological Evolution-Related Misconceptions: The Role of Public High School Introductory Biology Teachers

ERIC Educational Resources Information Center

Yates, Tony Brett

2011-01-01

In order to eliminate student misconceptions concerning biological evolution, it is important to identify their sources. The purposes of this study were to: (a) identify biological evolution-related misconceptions held by Oklahoma public high school Biology I teachers; (b) identify biological evolution-related misconceptions held by Oklahoma…

Two Types of Long-duration Quasi-static Evolution of Solar Filaments

NASA Astrophysics Data System (ADS)

Xing, C.; Li, H. C.; Jiang, B.; Cheng, X.; Ding, M. D.

2018-04-01

In this Letter, we investigate the long-duration quasi-static evolution of 12 pre-eruptive filaments (four active region (AR) and eight quiescent filaments), mainly focusing on the evolution of the filament height in 3D and the decay index of the background magnetic field. The filament height in 3D is derived through two-perspective observations of Solar Dynamics Observatory (SDO) and Solar TErrestrial RElations Observatory (STEREO). The coronal magnetic field is reconstructed using the potential field source surface model. A new finding is that the filaments we studied show two types of long-duration evolution: one type comprises a long-duration static phase and a short, slow rise phase with a duration of less than 12 hr and a speed of 0.1–0.7 km s‑1, while the other one only presents a slow rise phase but with an extremely long duration of more than 60 hr and a smaller speed of 0.01–0.2 km s‑1. At the moment approaching the eruption, the decay index of the background magnetic field at the filament height is similar for both AR and quiescent filaments. The average value and upper limit are ∼0.9 and ∼1.4, close to the critical index of torus instability. Moreover, the filament height and background magnetic field strength are also found to be linearly and exponentially related with the filament length, respectively.

The Himalaya-Bengal Fan source to sink system - new insights by correlation of re-processed seismic data and IODP Expedition 354 results

NASA Astrophysics Data System (ADS)

Bergmann, Fenna; Schwenk, Tilmann; Spiess, Volkard; France-Lanord, Christian

2016-04-01

The Bengal Fan, hosted in the northern Indian Ocean, is the largest submarine fan on Earth. Fan evolution started in the Early Eocene as a direct response to the collision of India with the Asian continent in Middle Paleocene times. Subsequently the Himalayan plateau uplift was initiated. Thereby generated interactions with the regional climate caused the evolution of the Indian monsoonal system. Drained by the rivers Ganges and Brahmaputra, ~ 80% of eroded Himalayan sediments are deposited in the Bengal Fan. Hence, the Fan provides the most complete record of the Himalayan history and is well suited to investigate the direct link between the tectonic uplift and the climate evolution of the region. Sediments are transported onto the deep sea fan by turbidity currents building up chan-nel-levee systems. These channel-levee systems are the main architectural elements of the Bengal Fan and are suspected to have their onset in Late Miocene times. Frequent channel avulsion on the upper fan led to the abandonment of old channels and formation of new channel-levee systems or even channel-reoccupation. This complex erosional/depositional system involves lateral depocenter migration, probably on millennial timescales. Conse-quently, investigations of the Himalaya as sediment source begins with a comprehensive understanding of transport, deposition and modification within the Bengal Fan sediment sink. In February/March 2015 the IODP Expedition 354 drilled at 7 sites along a ~320 km long E-W transect at 8° N. Aiming at the recovery of pre-fan deposits and deposits of the Pliocene and Upper Miocene Fan evolution, three deep sites (900 - 1200 mbsf) were realized. These where complemented by four shallow sites (200-300 mbsf) for a detailed study of the depos-its of the last 1-2 million years, including the latest known channel activities (Holocene times). Several channel-levee systems and inter-channel deposits were drilled, active at different times of Fan evolution. To connect the sites of the drilling transect by means of seismo-stratigraphic analysis a large seismo-acoustic dataset gathered during cruises SO93 (1994), SO125/126 (1997) and SO188 (2006), all carried out in cooperation between the University of Bremen and the BGR, Hannover, is available. The dataset contains multichannel seismic data acquired with differ-ent seismic sources (GI-Gun/Watergun) to achieve differing subbottom penetration/resolution ratios. Although most of the pre-site survey data were already processed, major improve-ment could be gained by thoroughly (re) processing using new processing techniques and software developments. First processing results show significantly enhanced S/N ratio, reso-lution and reflector coherency. Full processing of the Watergun data was conducted for the first time. This high vertical resolution data has so far never been investigated and comple-ments the database, especially for a more detailed study of the upper few hundred meters of Bengal Fan deposits. First examinations of the watergun data in combination with drilling results proved them to be beneficial for the crucial borehole - seismic correlation and the investigations of the internal levee architecture, especially for the latest active channel-levee system.

Self-gravity, Resonances, and Orbital Diffusion in Stellar Disks

NASA Astrophysics Data System (ADS)

Fouvry, Jean-Baptiste; Binney, James; Pichon, Christophe

2015-06-01

Fluctuations in a stellar system's gravitational field cause the orbits of stars to evolve. The resulting evolution of the system can be computed with the orbit-averaged Fokker-Planck equation once the diffusion tensor is known. We present the formalism that enables one to compute the diffusion tensor from a given source of noise in the gravitational field when the system's dynamical response to that noise is included. In the case of a cool stellar disk we are able to reduce the computation of the diffusion tensor to a one-dimensional integral. We implement this formula for a tapered Mestel disk that is exposed to shot noise and find that we are able to explain analytically the principal features of a numerical simulation of such a disk. In particular the formation of narrow ridges of enhanced density in action space is recovered. As the disk's value of Toomre's Q is reduced and the disk becomes more responsive, there is a transition from a regime of heating in the inner regions of the disk through the inner Lindblad resonance to one of radial migration of near-circular orbits via the corotation resonance in the intermediate regions of the disk. The formalism developed here provides the ideal framework in which to study the long-term evolution of all kinds of stellar disks.

Kuiper Belt Objects of different sizes and average densities: thermal evolution scenarios and modern structure of matter

NASA Astrophysics Data System (ADS)

Shchuko, O. B.; Shchuko, S. D.; Kartashov, D.; Orosei, R.

2012-04-01

Thermal evolution of accretion-formed Kuiper Belt Objects (KBOs) with modern sizes from 200 to 2000 km and average densities from 1100 to 3200 kg/m3 has been studied by mathematical simulation methods. The values range of physical parameters of the accretion material and ultimate radionuclide content, securing KBO existence at present, have been found. The solid dust material of protosolar cloud fringe regions and fine-fractured H2O condensate in the form of amorphous ice are considered to have been the building matter for these objects. This material was represented by small dust particles of different chemical and mineralogical composition, embedded with radionuclides 238U, 235U, 232Th, 40K providing the sources of radiogenic heat. H2O condensate secured the presence of amorphous ice in the forming body's matter. Radiogenic heat leads to H2O phase transitions which define a body's interior matter differentiation. The radionuclide content at the initial time of the body formation determined the dynamically changing degree of the interior matter differentiation at different KBO depths for the whole period from the initial up to the present time. For the models of the celestial objects considered, the dynamically changing boundaries of spherically symmetric regions with different degree of matter differentiation have been determined.

A STATISTICAL STUDY OF FLARE PRODUCTIVITY ASSOCIATED WITH SUNSPOT PROPERTIES IN DIFFERENT MAGNETIC TYPES OF ACTIVE REGIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Ya-Hui; Hsieh, Min-Shiu; Yu, Hsiu-Shan

It is often believed that intense flares preferentially originate from the large-size active regions (ARs) with strong magnetic fields and complex magnetic configurations. This work investigates the dependence of flare activity on the AR properties and clarifies the influence of AR magnetic parameters on the flare productivity, based on two data sets of daily sunspot and flare information as well as the GOES soft X-ray measurements and HMI vector magnetograms. By considering the evolution of magnetic complexity, we find that flare behaviors are quite different in the short- and long-lived complex ARs and the ARs with more complex magnetic configurationsmore » are likely to host more impulsive and intense flares. Furthermore, we investigate several magnetic quantities and perform the two-sample Kolmogorov–Smirnov test to examine the similarity/difference between two populations in different types of ARs. Our results demonstrate that the total source field strength on the photosphere has a good correlation with the flare activity in complex ARs. It is noted that intense flares tend to occur at the regions of strong source field in combination with an intermediate field-weighted shear angle. This result implies that the magnetic free energy provided by a complex AR could be high enough to trigger a flare eruption even with a moderate magnetic shear on the photosphere. We thus suggest that the magnetic free energy represented by the source field rather than the photospheric magnetic complexity is a better quantity to characterize the flare productivity of an AR, especially for the occurrence of intense flares.« less

Microseisms Generated by Super Typhoon Megi in the Western Pacific Ocean

NASA Astrophysics Data System (ADS)

Lin, Jianmin; Lin, Jian; Xu, Min

2017-12-01

Microseisms generated by the super typhoon Megi (13-24 October 2010) were detected on both land-based and island-based seismic stations. We applied temporal frequency spectrum analysis to investigate the temporal evolution of the microseisms. When Megi was over the deep basins of the Philippine Sea, only weak microseisms with short-period double frequency (SPDF, ˜0.20-0.40 Hz) were observed. However, after Megi traveled into the shallower waters of the South China Sea, microseisms with both long-period double frequency (LPDF, ˜0.12-0.20 Hz) and SPDF were recorded. The excitation source regions of the microseisms were analyzed using seismic waveform records and synthetic modeling in frequency domain. Results reveal that part of the LPDF microseisms were excited in coastal source regions, while the intensity of both LPDF and SPDF microseisms correlated well with the distance from seismic stations to the typhoon center. Synthetic computations of equivalent surface pressure and corresponding microseisms show that the wave-to-wave interaction induced by coastal reflection has primary effects on microseismic frequency band of ˜0.10-0.20 Hz. The coastal generation of the dispersive LPDF microseisms is also supported by the observation of ocean swells induced by Megi through the images of C-band ENVISAT-ASAR satellite during its migration process. Two source regions of the microseisms during the life span of Megi are finally distinguished: One was mainly located in the left-rear quadrant of the typhoon center that generated both LPDF and SPDF microseisms at shallow seas, while the other one was near the coasts that generated mostly LPDF microseisms.

Relationship between Famatinian Arc Magmatism and Recent Mafic Volcanism in Northwest Argentina: Implications for Lithospheric Composition and Evolution Beneath the Puna Plateau

NASA Astrophysics Data System (ADS)

Drew, S.; Schoenbohm, L.; Ducea, M.

2008-12-01

The tectonic and magmatic evolution of the Puna Plateau (NW Argentina) has generated much debate over the past two decades. This study focuses on the young (< 7 Ma), mafic magmatism that led to the creation of monogenetic and simple polygenetic volcanoes throughout the plateau. These volcanics provide a means to evaluate the recent petro-tectonic development of the plateau and, in combination with Ordovician intrusive rocks, determine the isotopic composition and long term evolution of the sub-continental lithospheric mantle (SCLM) beneath the Andean back-arc domain. Here we present new whole rock major and trace element data and isotopic values for volcanic samples collected from the Antofagasta and Pasto Ventura basins in the southern Puna Plateau. Major element chemistry shows most of our samples are basalt, trachybasalt, basaltic andesite and basaltic trachyandesites, some with < 50.0 wt% SiO2 and > 8.0 wt% MgO, which is indicative of a strong mantle component. The more primitive lavas likely have a sub-crustal origin and experienced minimal interaction with overlying crust during transport to the surface. Two of our samples with low wt% MgO, a silicic andesite and a dacite, indicate an extensive crustal component and possibly a lower crust origin for evolved magmas. All samples have light trace element enrichment compared to NMORB and elevated abundances of LIL and LRE elements compared to HFS and HRE elements, indicating the magmas originated from a metasomatized source region. The samples also have variable (low and high) Nb, Ta and Ti negative anomalies, which are interpreted to be a signature of the source region. Our samples do not have a lithospheric delamination (~OIB) trace element signature as proposed by previous workers in support of a delamination model. Additionally, the samples have isotopic values (e.g. 87Sr/86Sr >0.7055 and ɛNd <0) that are not comparable to depleted asthenosphere. It is impossible for asthenospheric magma to obtain these isotopic values through crustal assimilation or AFC processes while maintaining a basalt major element composition and high Ni and Cr concentrations. Therefore, we propose the mafic magmas are sourced from a SCLM that, in accord with the LIL and LRE element concentrations, has been metasomatized during dehydration and possibly melting of a subducting oceanic plate. The young volcanics have isotopic values nearly identical to those of Early Ordovician Famatinian gabbros and norites. We suggest the most primitive Puna volcanic and Famatinian samples originated from the same SCLM source region. This implies at least a thin portion of the SCLM has remained intact beneath NW Argentina for the last ~485 million years. Resultantly, the SCLM was likely thinned to its present thickness sometime between the Early Ordovician and the Late Miocene. Thinning may have occurred by long term mantle wedge processes. Steady shortening and thickening of the continental crust and gradual removal of the SCLM by convection is envisioned here. The occurrence of discrete, intermittent delamination events is not favored because removal and then regeneration of the SCLM would not have allowed for preservation of the Famatinian isotopic signature.

Current Sheet Thinning Associated with Dayside Reconnection

NASA Astrophysics Data System (ADS)

Hsieh, M.; Otto, A.; Ma, X.

2011-12-01

The thinning of the near-Earth current sheet during the growth phase is of critical importance to understand geomagnetic substorms and the conditions that lead to the onset of the expansion phase. We have proposed that convection from the midnight tail region to the dayside as the cause for this current sheet thinning. Adiabatic convection from the near-Earth tail region toward the dayside must conserve the entropy on magnetic field lines. This constraint prohibits a source of the magnetic flux from a region further out in the magnetotail. Thus the near-Earth tail region is increasingly depleted of magnetic flux (the Erickson and Wolf [1980] problem) with entropy matching that of flux tubes that are eroded on the dayside. The process is examined by three-dimensional MHD simulations. The properties of the current sheet thinning are determined as a function of the magnitude of convection toward the dayside and the lobe boundary conditions. It is shown that the model yields a time scale, location, and other general characteristics of the current sheet evolution consistent with observations during the substorm growth phase.

Exploration gaps exist in Nigeria`s prolific delta

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thomas, D.

The Niger delta region of the Republic of Nigeria is Africa`s largest oil producing area. It is clear that Nigeria will continue to contribute significantly to world petroleum production well into the 21st century: with increases in recoverable oil reserves in the Niger delta onshore and offshore; the promising potential of the Niger delta deepwater region; and a lesser but not insignificant contribution from the unexplored onshore Benue trough, part of the mid-African rift system, which has already proved to hold substantial oil reserves in the Doba basin of neighboring Chad. This is the first of five parts on Nigeria`smore » oil and gas potential. The later articles deal with Niger delta oil reserves and production, Niger delta gas reserves, the delta`s deepwater region, and the Benue trough and onshore cretaceous rift basins. This article deals with the geologic setting of the Niger delta-Benue trough region, the synrift deposits, marine sedimentation, margin evolution, geologic strata and reservoirs, reservoir character, structure and traps, hydrocarbon types, geotemperatures, and source rock quality.« less

Genome structure drives patterns of gene family evolution in ciliates, a case study using Chilodonella uncinata (Protista, Ciliophora, Phyllopharyngea).

PubMed

Gao, Feng; Song, Weibo; Katz, Laura A

2014-08-01

In most lineages, diversity among gene family members results from gene duplication followed by sequence divergence. Because of the genome rearrangements during the development of somatic nuclei, gene family evolution in ciliates involves more complex processes. Previous work on the ciliate Chilodonella uncinata revealed that macronuclear β-tubulin gene family members are generated by alternative processing, in which germline regions are alternatively used in multiple macronuclear chromosomes. To further study genome evolution in this ciliate, we analyzed its transcriptome and found that (1) alternative processing is extensive among gene families; and (2) such gene families are likely to be C. uncinata specific. We characterized additional macronuclear and micronuclear copies of one candidate alternatively processed gene family-a protein kinase domain containing protein (PKc)-from two C. uncinata strains. Analysis of the PKc sequences reveals that (1) multiple PKc gene family members in the macronucleus share some identical regions flanked by divergent regions; and (2) the shared identical regions are processed from a single micronuclear chromosome. We discuss analogous processes in lineages across the eukaryotic tree of life to provide further insights on the impact of genome structure on gene family evolution in eukaryotes. © 2014 The Author(s). Evolution © 2014 The Society for the Study of Evolution.

Atmospheric nuclei in the Pacific midtroposphere: Their nature, concentration, and evolution

NASA Technical Reports Server (NTRS)

Clarke, Antony D.

1993-01-01

An extensive flight series was carried out during May-June 1990 in the remote North and South Pacific free tropospheric aboard the NASA DC-8. Condensation nuclei counters and optical particle counters provided information on aerosol particles with diameters between 0.003 and 7.0 micrometers. Vertical profiles revealed aerosol layers to be a common feature of the free troposphere. Regions with highest aerosol mass tended to have the highest concentrations of surface-derived nuclei but the lowest concentrations of total nuclei. Regions with lowest aerosol mass tended to have the highest concentrations of the smaller 'ultrafine' condensation nuclei with diameters below 0.02 mircometers. Horizontal transects totaling over 35,000 km at about 9 to 10-km altitude exhibited variability of approximately 3 orders of magnitude in both aerosol mass and number concentrations over spatial scales ranging from 1 to 1000 km. At these altitudes an approximate inverse relationship between ultrafine concentrations and the surface area of the larger aerosol was evident. Regions having lowest aerosol mass were characterized by aerosol thermal volatility, indicative of a predominately sulfuric acid composition, and by very high concentrations of ultrafine nuclei, indicative of recent homogeneous nucleation. These conditions were frequently observed but were conspicuously evident above cloud over the intertropical convergence zone. The clean, free troposphere appears to be a significant source region for new tropospheric nuclei. A simplified model of the lifetime, coagulation, and cycling of these nuclei suggests that they constitute a source of cloud condensation nuclei in the lower troposphere.

Regional and temporal variability of melts during a Cordilleran magma pulse: Age and chemical evolution of the jurassic arc, eastern mojave desert, California

USGS Publications Warehouse

Barth, A.P.; Wooden, J.L.; Miller, David; Howard, Keith A.; Fox, Lydia; Schermer, Elizabeth R.; Jacobson, C.E.

2017-01-01

Intrusive rock sequences in the central and eastern Mojave Desert segment of the Jurassic Cordilleran arc of the western United States record regional and temporal variations in magmas generated during the second prominent pulse of Mesozoic continental arc magmatism. U/Pb zircon ages provide temporal control for describing variations in rock and zircon geochemistry that reflect differences in magma source components. These source signatures are discernible through mixing and fractionation processes associated with magma ascent and emplacement. The oldest well-dated Jurassic rocks defining initiation of the Jurassic pulse are a 183 Ma monzodiorite and a 181 Ma ignimbrite. Early to Middle Jurassic intrusive rocks comprising the main stage of magmatism include two high-K calc-alkalic groups: to the north, the deformed 183–172 Ma Fort Irwin sequence and contemporaneous rocks in the Granite and Clipper Mountains, and to the south, the 167–164 Ma Bullion sequence. A Late Jurassic suite of shoshonitic, alkali-calcic intrusive rocks, the Bristol Mountains sequence, ranges in age from 164 to 161 Ma and was emplaced as the pulse began to wane. Whole-rock and zircon trace-element geochemistry defines a compositionally coherent Jurassic arc with regional and secular variations in melt compositions. The arc evolved through the magma pulse by progressively greater input of old cratonic crust and lithospheric mantle into the arc magma system, synchronous with progressive regional crustal thickening.

Precipitation Recycling in the NASA GEOS Data Assimilation System

NASA Technical Reports Server (NTRS)

Bosilovich, Michael G.; Schubert, Siegfried; Molod, Andrea; Takacs, Lawrence L.

1999-01-01

Analysis of precipitation recycling can improve the understanding of regional hydrologic anomalies, especially their evolution and maintenance. Diagnostic models of the recycling of precipitation and are applied to 15 years of the NASA Goddard Earth Observing System (GEOS) Data Assimilation System (DAS). Recycled precipitation is defined as the fraction of precipitation within a given region that originated as surface evaporation from the same region. The focus of the present work is on the interannual variability of the central United States hydrologic cycle and precipitation recycling. The extreme years of 1988 (drought) and 1993 (flood) are compared with the 15 year base period mean annual cycle. The results indicate that recycling ratio (the amount of precipitation with a local source relative to the total precipitation) is greater in 1988 than both the base period mean and the 1993 season (with 1993 recycling ratio less than the mean). On the other hand, both the summers of 1988 and 1993 show less total recycled precipitation than the mean. The results also show that precipitation recycling may have been more important in the spring of 1993, when the region was primed for flooding, than the summer, when the sever flooding occurred. The diagnostic approaches to precipitation recycling suffer from some weaknesses. Numerical simulations and assimilation using passive tracers have the potential to provide more accurate calculations of precipitation recycling and the remote sources of water. This ability is being incorporated into the latest GEOS data assimilation system, and some preliminary results will be presented.

Relationships between subduction and extension in the Aegean region: evidence from granite plutons of the Biga Peninsula, NW Turkey

NASA Astrophysics Data System (ADS)

Black, K. N.; Catlos, E. J.; Oyman, T.; Demirbilek, M.

2012-04-01

The Biga Peninsula is a tectonically complex region in western Turkey characterized by Tethyan sutures overprinted by extensional grabens, active fault strands of the North Anatolian Shear Zone, and numerous granitoid plutons. Two end-member models for the initiation of extension in the Biga region have been proposed, both of which focus on the role of igneous assemblages. The first model involves the emplacement of a hot mantle plume that thins and weakens crust and isostatic doming drives extension. The second has regional tensional stresses as the driving force, and magmatism is a consequence of decompression. Here we focus on understanding the timing and geochemical evolution of three granitoid plutons located in and just south of the Biga Peninsula to understand which end-member model could be applicable to the Aegean region. The Kestanbolu pluton is located north of the proposed Vardar Suture Zone, whereas the Eybek and Kozak plutons are north of the Izmir-Ankara Suture Zone. These sutures may mark regions of the closure of branches of the NeoTethyan Ocean. To better understand their sources and tectonic evolution, we acquired geochemical and geochronological data, and cathodoluminescence (CL) images of the rocks. Previously reported ages of the plutons range from Late Eocene to Middle Miocene. Here we acquired in situ (in thin section) ion microprobe U-Pb ages of zircon grains found in a range of textural relationships. Ages from the Kozak pluton range from 37.8±5.4 Ma to 10.3±2.4 Ma (238U/206Pb, ±1σ) with two ages from a single grain of 287±26 Ma and 257±18 Ma. We also found Oligocene to Late Miocene zircon grains in the Kestanbolu pluton, whereas zircons from the Eybek pluton range from 34.3±4.8 Ma to 21.2±1.7 Ma. Samples collected from the Kozak and Eybek plutons are magnesian, calc-alkalic, and metaluminous, whereas the Kestanbolu rocks are magnesian, alkali-calcic, and metaluminous with one ferroan sample and one peraluminous sample. Trace element data suggest the Kozak and Kestanbolu plutons have a volcanic arc source, whereas the Eybek pluton is syn-collisional. CL imagery documents a complex history of these granites including magma mixing, multiple episodes of brittle deformation, and fluid alteration. Microveins, microcracks, and myrmekite textures are present, indicating brittle deformation and fluid alteration. Plagioclase grains display a range of compositional zoning and some show distinctly cracked cores that are evidence of magma mixing. The Kozak, Eybek and Kestanbolu plutons may be sourced from the melting of the subducting Mediterranean oceanic crust with a contribution from the overlying Eurasian continental crust. These granites intruded into the Vardar and/or Izmir-Ankara Sutures, entraining the Permian zircon grain. The Oligocene zircon ages are consistent with magmatism propagating from north to south in the Aegean region, whereas the Late Miocene results are consistent with ongoing extension throughout the region at this time. In this scenario, slowing subduction along the Hellenic arc led to the formation of extensional structures that provided space for the accommodation of these magma bodies.

Increasing virulence, but not infectivity, associated with serially emergent virus strains of a fish rhabdovirus

USGS Publications Warehouse

Breyta, Rachel; McKenney, Douglas; Tesfaye, Tarin; Ono, Kotaro; Kurath, Gael

2016-01-01

Surveillance and genetic typing of field isolates of a fish rhabdovirus, infectious hematopoietic necrosis virus (IHNV), has identified four dominant viral genotypes that were involved in serial viral emergence and displacement events in steelhead trout (Oncorhynchus mykiss) in western North America. To investigate drivers of these landscape-scale events, IHNV isolates designated 007, 111, 110, and 139, representing the four relevant genotypes, were compared for virulence and infectivity in controlled laboratory challenge studies in five relevant steelhead trout populations. Viral virulence was assessed as mortality using lethal dose estimates (LD50), survival kinetics, and proportional hazards analysis. A pattern of increasing virulence for isolates 007, 111, and 110 was consistent in all five host populations tested, and correlated with serial emergence and displacements in the virus-endemic lower Columbia River source region during 1980–2013. The fourth isolate, 139, did not have higher virulence than the previous isolate 110. However, the mG139M genotype displayed a conditional displacement phenotype in that it displaced type mG110M in coastal Washington, but not in the lower Columbia River region, indicating that factors other than evolution of higher viral virulence were involved in some displacement events. Viral infectivity, measured as infectious dose (ID50), did not correlate consistently with virulence or with viral emergence, and showed a narrow range of variation relative to the variation observed in virulence. Comparison among the five steelhead trout populations confirmed variation in resistance to IHNV, but correlations with previous history of virus exposure or with sites of viral emergence varied between IHNV source and sink regions. Overall, this study indicated increasing viral virulence over time as a potential driver for emergence and displacement events in the endemic Lower Columbia River source region where these IHNV genotypes originated, but not in adjacent sink regions.

Finding High Quality Young Star Candidates in Ceph C using X-ray, Optical, and IR data

NASA Astrophysics Data System (ADS)

Orr, Laura; Rebull, Luisa M.; Johnson, Milton; Miller, Alexandra; Aragon Orozco, Anthony; Bakhaj, Benjamin; Bakshian, Jacquelyn; Chiffelle, Elizabeth; DeLint, Arie; Gerber, Stefan; Mader, Jared; Marengo, Amelia; McAdams, Jesse; Montufar, Cassandra; Orr, Quinton; San Emeterio, Lis; Stern, Eliyah; Weisserman, Drew

2017-01-01

We looked for new candidate young stars within the star forming region of Ceph OB3, more specifically in a region of this molecular cloud called Ceph C. While this region lies in the galactic plane and is included in several large surveys, Ceph C has not been well studied in the past and few young stellar objects (YSOs) have been identified there. The YSOVAR team (Rebull et al. 2014) has time-series monitoring data of this region, and in order to understand the diversity of the light curves, it is crucial to understand which objects in the field of view are likely YSOs, and which are foreground/background objects. The goal of our study is to identify candidate YSO sources as well as support the greater understanding of the variety, evolution, and variability of young stars. Our search for young stars includes data in X-ray, optical, and IR. Data points used are from Chandra, SDSS, IPHAS, 2MASS, Spitzer IRAC and MIPS, and WISE, giving us data over many orders of magnitude, 0.001 to 25 microns (0.36 to 25 microns without the X-rays). The catalogs were merged across all available wavelengths. Each source was inspected in all available images to insure good matches and quality of data across wavelengths and to eliminate poor candidates, those with contamination or confusion, and non-YSO objects. Spectral energy distributions (SEDs) for each candidate YSO were constructed and compared to images for greater assessment and reliable YSO identification. Color-color and color-magnitude diagrams have been created for the sources in this region and are used in conjunction with images, SEDs, X-ray, IR excess, and variability properties to identify candidate YSOs. Support provided for this work by the NASA/IPAC Teacher Archive Research Program (NITARP), which receives funding from the NASA ADP program.

Evaluation of Ice sheet evolution and coastline changes from 1960s in Amery Ice Shelf using multi-source remote sensing images

NASA Astrophysics Data System (ADS)

Qiao, G.; Ye, W.; Scaioni, M.; Liu, S.; Feng, T.; Liu, Y.; Tong, X.; Li, R.

2013-12-01

Global change is one of the major challenges that all the nations are commonly facing, and the Antarctica ice sheet changes have been playing a critical role in the global change research field during the past years. Long time-series of ice sheet observations in Antarctica would contribute to the quantitative evaluation and precise prediction of the effects on global change induced by the ice sheet, of which the remote sensing technology would make critical contributions. As the biggest ice shelf and one of the dominant drainage systems in East Antarctic, the Amery Ice Shelf has been making significant contributions to the mass balance of the Antarctic. Study of Amery Ice shelf changes would advance the understanding of Antarctic ice shelf evolution as well as the overall mass balance. At the same time, as one of the important indicators of Antarctica ice sheet characteristics, coastlines that can be detected from remote sensing imagery can help reveal the nature of the changes of ice sheet evolution. Most of the scientific research on Antarctica with satellite remote sensing dated from 1970s after LANDSAT satellite was brought into operation. It was the declassification of the cold war satellite reconnaissance photographs in 1995, known as Declassified Intelligence Satellite Photograph (DISP) that provided a direct overall view of the Antarctica ice-sheet's configuration in 1960s, greatly extending the time span of Antarctica surface observations. This paper will present the evaluation of ice-sheet evolution and coastline changes in Amery Ice Shelf from 1960s, by using multi-source remote sensing images including the DISP images and the modern optical satellite images. The DISP images scanned from negatives were first interior-oriented with the associated parameters, and then bundle block adjustment technology was employed based on the tie points and control points, to derive the mosaic image of the research region. Experimental results of coastlines generated from DISP images and that from ASTER images were analyzed, and the changes and evolution of Amery ice shelf were then evaluated, following by the discussion of the possible drives.

Calibration of an estuarine sediment transport model to sediment fluxes as an intermediate step for simulation of geomorphic evolution

USGS Publications Warehouse

Ganju, N.K.; Schoellhamer, D.H.

2009-01-01

Modeling geomorphic evolution in estuaries is necessary to model the fate of legacy contaminants in the bed sediment and the effect of climate change, watershed alterations, sea level rise, construction projects, and restoration efforts. Coupled hydrodynamic and sediment transport models used for this purpose typically are calibrated to water level, currents, and/or suspended-sediment concentrations. However, small errors in these tidal-timescale models can accumulate to cause major errors in geomorphic evolution, which may not be obvious. Here we present an intermediate step towards simulating decadal-timescale geomorphic change: calibration to estimated sediment fluxes (mass/time) at two cross-sections within an estuary. Accurate representation of sediment fluxes gives confidence in representation of sediment supply to and from the estuary during those periods. Several years of sediment flux data are available for the landward and seaward boundaries of Suisun Bay, California, the landward-most embayment of San Francisco Bay. Sediment flux observations suggest that episodic freshwater flows export sediment from Suisun Bay, while gravitational circulation during the dry season imports sediment from seaward sources. The Regional Oceanic Modeling System (ROMS), a three-dimensional coupled hydrodynamic/sediment transport model, was adapted for Suisun Bay, for the purposes of hindcasting 19th and 20th century bathymetric change, and simulating geomorphic response to sea level rise and climatic variability in the 21st century. The sediment transport parameters were calibrated using the sediment flux data from 1997 (a relatively wet year) and 2004 (a relatively dry year). The remaining years of data (1998, 2002, 2003) were used for validation. The model represents the inter-annual and annual sediment flux variability, while net sediment import/export is accurately modeled for three of the five years. The use of sediment flux data for calibrating an estuarine geomorphic model guarantees that modeled geomorphic evolution will not exceed the actual supply of sediment from the watershed and seaward sources during the calibration period. Decadal trends in sediment supply (and therefore fluxes) can accumulate to alter decadal geomorphic change. Therefore, simulations of future geomorphic evolution are bolstered by this intermediate calibration step.

Morphology and Evolution of Sublimation Pits on Pluto

NASA Astrophysics Data System (ADS)

Abu-Hashmeh, N.; Conrad, J. W.; Nimmo, F.; Moore, J. M.; Stern, A.; Olkin, C.; Weaver, H. A., Jr.; Ennico Smith, K.; Young, L. A.

2017-12-01

Pluto's Sputnik Planitia region hosts a geologically young surface of nitrogen ice that exhibits striking pitted terrain (Moore et al., Science 351, 2016). These pits are most likely formed by sublimation due to incident sunlight, similar to the southern polar cap of Mars (Byrne and Ingersoll, Science 299, 2003); however, their evolution over time has resulted in unique morphological characteristics. Motivated by this, we used the high-resolution mosaic strips captured by New Horizons' Long Range Reconnaissance Imager (LORRI) to map sublimation pits in the southernmost region of Sputnik Planitia. Statistical data shows pit orientations appearing North-South dominant; their morphology also indicates extensional evolution along the major axis caused by further sublimation and contact-coalescence processes. Qualitative analysis of the region yielded indications of an evolutionary path for individual pits that coalesce into each other and exhibit an elongated end-stage. Additionally, densely-pitted regions generally appear to correlate with regions containing longer pits, implying that coalescence may be an important process for elongation. We also model the evolution geometry through competing effects of diffusion (viscous relaxation) and retreat (sublimation) (Buhler and Ingersoll, LPSC Abstract #1746, 2017). The model demonstrates single-pit and coalescing-pit evolutions that influence overall length, as well as a potential ability for the pit center to move in space while the pit morphology evolves.

Parasitism drives host genome evolution: Insights from the Pasteuria ramosa-Daphnia magna system.

PubMed

Bourgeois, Yann; Roulin, Anne C; Müller, Kristina; Ebert, Dieter

2017-04-01

Because parasitism is thought to play a major role in shaping host genomes, it has been predicted that genomic regions associated with resistance to parasites should stand out in genome scans, revealing signals of selection above the genomic background. To test whether parasitism is indeed such a major factor in host evolution and to better understand host-parasite interaction at the molecular level, we studied genome-wide polymorphisms in 97 genotypes of the planktonic crustacean Daphnia magna originating from three localities across Europe. Daphnia magna is known to coevolve with the bacterial pathogen Pasteuria ramosa for which host genotypes (clonal lines) are either resistant or susceptible. Using association mapping, we identified two genomic regions involved in resistance to P. ramosa, one of which was already known from a previous QTL analysis. We then performed a naïve genome scan to test for signatures of positive selection and found that the two regions identified with the association mapping further stood out as outliers. Several other regions with evidence for selection were also found, but no link between these regions and phenotypic variation could be established. Our results are consistent with the hypothesis that parasitism is driving host genome evolution. © 2017 The Author(s). Evolution © 2017 The Society for the Study of Evolution.

New Measurement for Correlation of Co-evolution Relationship of Subsequences in Protein.

PubMed

Gao, Hongyun; Yu, Xiaoqing; Dou, Yongchao; Wang, Jun

2015-12-01

Many computational tools have been developed to measure the protein residues co-evolution. Most of them only focus on co-evolution for pairwise residues in a protein sequence. However, number of residues participate in co-evolution might be multiple. And some co-evolved residues are clustered in several distinct regions in primary structure. Therefore, the co-evolution among the adjacent residues and the correlation between the distinct regions offer insights into function and evolution of the protein and residues. Subsequence is used to represent the adjacent multiple residues in one distinct region. In the paper, co-evolution relationship in each subsequence is represented by mutual information matrix (MIM). Then, Pearson's correlation coefficient: R value is developed to measure the similarity correlation of two MIMs. MSAs from Catalytic Data Base (Catalytic Site Atlas, CSA) are used for testing. R value characterizes a specific class of residues. In contrast to individual pairwise co-evolved residues, adjacent residues without high individual MI values are found since the co-evolved relationship among them is similar to that among another set of adjacent residues. These subsequences possess some flexibility in the composition of side chains, such as the catalyzed environment.

A Parent-Offspring Trade-Off Limits the Evolution of an Ontogenetic Niche Shift.

PubMed

Ten Brink, Hanna; de Roos, André M

2017-07-01

Many free-living animal species, including the majority of fish, insects, and amphibians, change their food and habitat during their life. Even though these ontogenetic changes in niche are common, it is not well understood which ecological conditions have favored the evolution of these shifts. Using an adaptive dynamics approach, we show that it is evolutionarily advantageous to switch to an alternative food source in the course of ontogeny when this results in a higher intake rate for the switching consumers. Individuals are, however, not able to specialize on this new food source when this negatively affects the performance early in life on the original food source. Selection on these early life stages is so strong that in species with a complete diet shift, evolution results in large juveniles and adults that are maladapted to the alternative food source while their offspring are specialized on the original food source when young. These outcomes suggest strong selection to decouple the different life stages, such that they can maximize their performance on different food sources independently from each other. Metamorphosis could be a way to decouple the different life stages and therefore evolve in species that feed on multiple food sources during their life.

Dark stars: a review.

PubMed

Freese, Katherine; Rindler-Daller, Tanja; Spolyar, Douglas; Valluri, Monica

2016-06-01

Dark stars are stellar objects made (almost entirely) of hydrogen and helium, but powered by the heat from dark matter annihilation, rather than by fusion. They are in hydrostatic and thermal equilibrium, but with an unusual power source. Weakly interacting massive particles (WIMPs), among the best candidates for dark matter, can be their own antimatter and can annihilate inside the star, thereby providing a heat source. Although dark matter constitutes only [Formula: see text]0.1% of the stellar mass, this amount is sufficient to power the star for millions to billions of years. Thus, the first phase of stellar evolution in the history of the Universe may have been dark stars. We review how dark stars come into existence, how they grow as long as dark matter fuel persists, and their stellar structure and evolution. The studies were done in two different ways, first assuming polytropic interiors and more recently using the MESA stellar evolution code; the basic results are the same. Dark stars are giant, puffy (∼10 AU) and cool (surface temperatures  ∼10 000 K) objects. We follow the evolution of dark stars from their inception at  ∼[Formula: see text] as they accrete mass from their surroundings to become supermassive stars, some even reaching masses  >[Formula: see text] and luminosities  >[Formula: see text], making them detectable with the upcoming James Webb Space Telescope. Once the dark matter runs out and the dark star dies, it may collapse to a black hole; thus dark stars may provide seeds for the supermassive black holes observed throughout the Universe and at early times. Other sites for dark star formation may exist in the Universe today in regions of high dark matter density such as the centers of galaxies. The current review briefly discusses dark stars existing today, but focuses on the early generation of dark stars.

Dark stars: a review

NASA Astrophysics Data System (ADS)

Freese, Katherine; Rindler-Daller, Tanja; Spolyar, Douglas; Valluri, Monica

2016-06-01

Dark stars are stellar objects made (almost entirely) of hydrogen and helium, but powered by the heat from dark matter annihilation, rather than by fusion. They are in hydrostatic and thermal equilibrium, but with an unusual power source. Weakly interacting massive particles (WIMPs), among the best candidates for dark matter, can be their own antimatter and can annihilate inside the star, thereby providing a heat source. Although dark matter constitutes only ≲ 0.1% of the stellar mass, this amount is sufficient to power the star for millions to billions of years. Thus, the first phase of stellar evolution in the history of the Universe may have been dark stars. We review how dark stars come into existence, how they grow as long as dark matter fuel persists, and their stellar structure and evolution. The studies were done in two different ways, first assuming polytropic interiors and more recently using the MESA stellar evolution code; the basic results are the same. Dark stars are giant, puffy (˜10 AU) and cool (surface temperatures  ˜10 000 K) objects. We follow the evolution of dark stars from their inception at  ˜1{{M}⊙} as they accrete mass from their surroundings to become supermassive stars, some even reaching masses  >{{10}6}{{M}⊙} and luminosities  >{{10}10}{{L}⊙} , making them detectable with the upcoming James Webb Space Telescope. Once the dark matter runs out and the dark star dies, it may collapse to a black hole; thus dark stars may provide seeds for the supermassive black holes observed throughout the Universe and at early times. Other sites for dark star formation may exist in the Universe today in regions of high dark matter density such as the centers of galaxies. The current review briefly discusses dark stars existing today, but focuses on the early generation of dark stars.

PROBING DYNAMICS OF ELECTRON ACCELERATION WITH RADIO AND X-RAY SPECTROSCOPY, IMAGING, AND TIMING IN THE 2002 APRIL 11 SOLAR FLARE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fleishman, Gregory D.; Nita, Gelu M.; Gary, Dale E.

Based on detailed analysis of radio and X-ray observations of a flare on 2002 April 11 augmented by realistic three-dimensional modeling, we have identified a radio emission component produced directly at the flare acceleration region. This acceleration region radio component has distinctly different (1) spectrum, (2) light curves, (3) spatial location, and, thus, (4) physical parameters from those of the separately identified trapped or precipitating electron components. To derive evolution of physical parameters of the radio sources we apply forward fitting of the radio spectrum time sequence with the gyrosynchrotron source function with five to six free parameters. At themore » stage when the contribution from the acceleration region dominates the radio spectrum, the X-ray- and radio-derived electron energy spectral indices agree well with each other. During this time the maximum energy of the accelerated electron spectrum displays a monotonic increase with time from {approx}300 keV to {approx}2 MeV over roughly one minute duration indicative of an acceleration process in the form of growth of the power-law tail; the fast electron residence time in the acceleration region is about 2-4 s, which is much longer than the time of flight and so requires a strong diffusion mode there to inhibit free-streaming propagation. The acceleration region has a relatively strong magnetic field, B {approx} 120 G, and a low thermal density, n{sub e} {approx}< 2 Multiplication-Sign 10{sup 9} cm{sup -3}. These acceleration region properties are consistent with a stochastic acceleration mechanism.« less

Iteration expansion and regional evolution: phylogeography of Dendrobium officinale and four related taxa in southern China

PubMed Central

Hou, Beiwei; Luo, Jing; Zhang, Yusi; Niu, Zhitao; Xue, Qingyun; Ding, Xiaoyu

2017-01-01

The genus Dendrobium was used as a case study to elucidate the evolutionary history of Orchidaceae in the Sino-Japanese Floristic Region (SJFR) and Southeast Asia region. These evolutionary histories remain largely unknown, including the temporal and spatial distribution of the evolutionary events. The present study used nuclear and plastid DNA to determine the phylogeography of Dendrobium officinale and four closely related taxa. Plastid DNA haplotype and nuclear data were shown to be discordant, suggesting reticulate evolution drove the species’ diversification. Rapid radiation and genetic drift appeared to drive the evolution of D. tosaense and D. flexicaule, whereas introgression or hybridization might have been involved in the evolution of D. scoriarum and D. shixingense. The phylogeographical structure of D. officinale revealed that core natural distribution regions might have served as its glacial refuges. In recent years, human disturbances caused its artificial migration and population extinction. The five taxa may have originated from the Nanling Mountains and the Yungui Plateau and then migrated northward or eastward. After the initial iteration expansion, D. officinale populations appeared to experience the regional evolutionary patterns in different regions and follow the sequential or rapid decline in gene exchange. PMID:28262789

Chapter 19: The age of scarplike landforms from diffusion-equation analysis

USGS Publications Warehouse

Hanks, Thomas C.

2000-01-01

The purpose of this paper is to review developments in the quantitative modeling of fault-scarp geomorphology, principally those since 1980. These developments utilize diffusionequation mathematics, in several different forms, as the basic model of fault-scarp evolution. Because solutions to the general diffusion equation evolve with time, as we expect faultscarp morphology to evolve with time, the model solutions carry information about the age of the structure and thus its time of formation; hence the inclusion of this paper in this volume. The evolution of fault-scarp morphology holds a small but special place in the much larger class of problems in landform evolution. In general, landform evolution means the evolution of topography as a function of both space and time. It is the outcome of the competition among those tectonic processes that make topography, erosive processes that destroy topography, and depositional processes that redistribute topography. Deposition and erosion can always be coupled through conservation-of-mass relations, but in general deposition occurs at great distance from the source region of detritus. Moreover, erosion is an inherently rough process whereas deposition is inherently smooth, as is evident from even casual inspection of shaded-relief, digital-elevation maps (e.g., Thelin and Pike, 1990; Simpson and Anders, 1992) and the current fascination with fractal representations oferoding terrains (e.g., Huang and Turcotte, 1989; Newman and Turcotte, 1990). Nevertheless, large-scale landform-evolution modeling, now a computationally intensive, advanced numerical exercise, is generating ever more realistic landforms (e.g., Willgoose and others, 1991a,b; Kooi and Beaumont, 1994; Tucker and Slingerland, 1994), although many of the rate coefficients remain poorly prescribed

Cosmic Rays as a Factor of Biosphere Evolution

NASA Astrophysics Data System (ADS)

Miroshnichenko, L. I.

2014-11-01

There are no doubts that the Earth's space environment in the past inevitably exerted direct and/or indirect influence [1--4] on the conditions of terrestrial life and biospheric evolution. Well-known cosmic factors are usually streams of cosmic dust and gas, comets and asteroids, cosmic rays (energetic particles of galactic and/or solar origin), interplanetary plasma (solar wind), and electromagnetic radiation of different energies, wavelengths, or frequencies. Of great interest are radiation conditions and their variations, especially in the remote past (over the geological time scales). The Sun, the most important and indispensable condition for the existence of the Earth's biosphere, is also a potential source of dangerous emissions. In continuation of (and in addition to) our review paper [3], below we summarize the observational data and results of theoretical works that have been carried out and/or published mainly after 2012. These studies are actually in the frontier region between the Astrobiology and Space Weather. Our main attention is paid to cosmic rays (CR) of galactic and solar origin (GCR and SCR, respectively).

The evolution of the moon and the terrestrial planets

NASA Technical Reports Server (NTRS)

Toksoez, M. N.; Johnston, D. H.

1974-01-01

The thermal evolutions of the Moon, Mars, Venus and Mercury are calculated theoretically starting from cosmochemical condensation models. An assortment of geological, geochemical and geophysical data are used to constrain both the present day temperatures and the thermal histories of the planets' interiors. Such data imply that the planets were heated during or shortly after formation and that all the terrestrial planets started their differentiations early in their history. The moon, smallest in size, is characterized as a differentiated body with a crust, a thick solid mantle and an interior region which may be partially molten. Mars, intermediate in size, is assumed to have differentiated an Fe-FeS core. Venus is characterized as a planet not unlike the earth in many respects. Core formation has occurred probably during the first billion years after the formation. Mercury, which probably has a large core, may have a 500 km thick solid lithosphere and a partially molten core if it is assumed that some heat sources exist in the core.

The Evolution of Holistic Processing of Faces

PubMed Central

Burke, Darren; Sulikowski, Danielle

2013-01-01

In this paper we examine the holistic processing of faces from an evolutionary perspective, clarifying what such an approach entails, and evaluating the extent to which the evidence currently available permits any strong conclusions. While it seems clear that the holistic processing of faces depends on mechanisms evolved to perform that task, our review of the comparative literature reveals that there is currently insufficient evidence (or sometimes insufficiently compelling evidence) to decide when in our evolutionary past such processing may have arisen. It is also difficult to assess what kinds of selection pressures may have led to evolution of such a mechanism, or even what kinds of information holistic processing may have originally evolved to extract, given that many sources of socially relevant face-based information other than identity depend on integrating information across different regions of the face – judgments of expression, behavioral intent, attractiveness, sex, age, etc. We suggest some directions for future research that would help to answer these important questions. PMID:23382721

Emplacement ages, geochemical and Sr-Nd-Hf isotopic characterization of Mesozoic to early Cenozoic granitoids of the Sikhote-Alin Orogenic Belt, Russian Far East: Crustal growth and regional tectonic evolution

NASA Astrophysics Data System (ADS)

Jahn, Bor-ming; Valui, Galina; Kruk, Nikolai; Gonevchuk, V.; Usuki, Masako; Wu, Jeremy T. J.

2015-11-01

The Sikhote-Alin Range of the Russian Far East is an important accretionary orogen of the Western Pacific Orogenic Belt. In order to study the formation and tectonic evolution of the orogen, we performed zircon U-Pb dating, as well as geochemical and Sr-Nd-Hf isotopic analyses on 24 granitoid samples from various massifs in the Primorye and Khabarovsk regions. The zircon dating revealed that the granitoids were emplaced from 131 to 56 Ma (Cretaceous to Paleogene). In the Primorye Region, granitoids in the coastal Sikhote-Alin intruded the Cretaceous Taukha Accretionary Terrane from ca. 90 to 56 Ma, whereas those along the Central Sikhote-Alin Fault zone intruded the Jurassic Samarka Accretionary Terrane during ca. 110-75 Ma. The "oldest" monzogranite (131 Ma) was emplaced in the Lermontovka area of the NW Primorye Region. Granitoid massifs along the Central Sikhote-Alin Fault zone in the Khabarovsk Region formed from 109 to 58 Ma. Thus, the most important tectonothermal events in the Sikhote-Alin orogen took place in the Cretaceous. Geochemical analysis indicates that most samples are I-type granitoids. They have initial 87Sr/86Sr ratios ranging from 0.7040 to 0.7083, and initial Nd isotopic ratios, expressed as εNd(t) values, from +3.0 to -5.0 (mostly 0 to -5). The data suggest that the granitoid magmas were generated by partial melting of sources with mixed lithologies, including the subducted accretionary complex ± hidden Paleozoic-Proterozoic basement rocks. Based on whole-rock Nd isotopic data, we estimated variable proportions (36-77%) of juvenile component (=mantle-derived basaltic rocks) in the generation of the granitic magmas. Furthermore, zircon Hf isotopic data (εHf(t) = 0 to +15) indicate that the zircon grains crystallized from melts of mixed sources and that crustal assimilation occurred during magmatic differentiation. The quasi-continuous magmatism in the Sikhote-Alin orogen suggests that the Paleo-Pacific plate subduction was very active in the Late Cretaceous. The apparently regular progression of granitic intrusion ages from 80 to 56 Ma in the Taukha Terrane may reflect oblique underflow of the Paleo-Pacific plate beneath the Eurasian continental margin. Subduction was not only manifested by granitic intrusion, but also by abundant silicic volcanism. The Late Cretaceous Paleo-Pacific plate motion probably changed from parallel or sub-parallel to oblique relative to the continental margin of the Sikhote-Alin, leading to the change of magmatic source region and geochemical characteristics of the derived igneous rocks. Late Cretaceous rapid sea-floor spreading at ca. 100 Ma induced highly active subduction and led to voluminous magmatism in the entire Circum-Pacific realm. Finally, the present age and isotopic study lends support to the hypothesis of geologic and tectonic correlation between Sikhote-Alin and SW Japan.

Volcanism-Climate Interactions

NASA Technical Reports Server (NTRS)

Walter, Louis S. (Editor); Desilva, Shanaka (Editor)

1991-01-01

The range of disciplines in the study of volcanism-climate interactions includes paleoclimate, volcanology, petrology, tectonics, cloud physics and chemistry, and climate and radiation modeling. Questions encountered in understanding the interactions include: the source and evolution of sulfur and sulfur-gaseous species in magmas; their entrainment in volcanic plumes and injection into the stratosphere; their dissipation rates; and their radiative effects. Other issues include modeling and measuring regional and global effects of such large, dense clouds. A broad-range plan of research designed to answer these questions was defined. The plan includes observations of volcanoes, rocks, trees, and ice cores, as well as satellite and aircraft observations of erupting volcanoes and resulting lumes and clouds.

Particle simulation of electromagnetic emissions from electrostatic instability driven by an electron ring beam on the density gradient

NASA Astrophysics Data System (ADS)

Horký, Miroslav; Omura, Yoshiharu; Santolík, Ondřej

2018-04-01

This paper presents the wave mode conversion between electrostatic and electromagnetic waves on the plasma density gradient. We use 2-D electromagnetic code KEMPO2 implemented with the generation of density gradient to simulate such a conversion process. In the dense region, we use ring beam instability to generate electron Bernstein waves and we study the temporal evolution of wave spectra, velocity distributions, Poynting flux, and electric and magnetic energies to observe the wave mode conversion. Such a conversion process can be a source of electromagnetic emissions which are routinely measured by spacecraft on the plasmapause density gradient.

The Herschel ATLAS: Evolution of the 250 Micrometer Luminosity Function Out to z = 0.5

NASA Technical Reports Server (NTRS)

Dye, S.; Dunne, L.; Eales, S.; Smith, D. J. B.; Amblard, A.; Auld, R.; Baes, M.; Baldry, I. K.; Bamford, S.; Blain, A. W.;

Remotely Distinguishing and Mapping Endogenic Water on the Moon

NASA Technical Reports Server (NTRS)

Klima, Rachel L.; Petro, Noah E.

2017-01-01

Water and/or hydroxyl detected remotely on the lunar surface originates from several sources: (i) comets and other exogenous debris; (ii) solar wind implantation; (iii) the lunar interior. While each of these sources is interesting in its own right, distinguishing among them is critical for testing hypotheses for the origin and evolution of the Moon and our Solar System. Existing spacecraft observations are not of high enough spectral resolution to uniquely characterize the bonding energies of the hydroxyl molecules that have been detected. Nevertheless, the spatial distribution and associations of H, OH- or H2O with specific lunar lithologies provide some insight into the origin of lunar hydrous materials. The global distribution of OH-/H2O as detected using infrared spectroscopic measurements from orbit is here examined, with particular focus on regional geological features that exhibit OH-/H2O absorption band strengths that differ from their immediate surroundings.

The High Energy X-ray Spectrum of 4U1700-37 Observed from OSO-8

NASA Technical Reports Server (NTRS)

Dolan, J. F.; Coe, M. J.; Crannell, C. J.; Dennis, B. R.; Frost, K. J.; Maurer, G. S.; Orwig, L. E.

1979-01-01

The most intense hard X-ray source in the confused region in Scorpius is identified as 4U1700-37. The 3.4-day modulation is seen above 20 keV with the intensity during eclipse being consistent with zero flux. The photon-number spectrum from 20 to 150 keV is well represented by a single power law with a photo-number spectral index of -2.77 + or - 0.35 or by a thermal bremsstrahlung spectrum with kT = 27 96.8-min X-ray modulation previously reported at lower energies. Despite the difficulties in reconciling both the lack of periodic modulation in the emitted X-radiation and the orbital dynamics of the system with theories of the evolution and physical properties of neutron stars, the observed properties of 4U1700-37 are all consistent with the source being a spherically accreting neutron star rather than a black hole.

Relating stress models of magma emplacement to volcano-tectonic earthquakes

NASA Astrophysics Data System (ADS)

Vargas-Bracamontes, D.; Neuberg, J.

2007-12-01

Among the various types of seismic signals linked to volcanic processes, volcano-tectonic earthquakes are probably the earliest precursors of volcanic eruptions. Understanding their relationship with magma emplacement can provide insight into the mechanisms of magma transport at depth and assist in the ultimate goal of forecasting eruptions. Volcano-tectonic events have been observed to occur on faults that experience increases in Coulomb stress changes as the result of magma intrusions. To simulate stress changes associated with magmatic injections, we test different models of volcanic sources in an elastic half-space. For each source model, we look at several aspects that influence the stress conditions of the magmatic system such as the regional tectonic setting, the effect of varying the elastic parameters of the media, the evolution of the magma with time, as well as the volume and rheology of the ascending magma.

Variations in Gas and Water Pulses at an Arctic Seep: Fluid Sources and Methane Transport

NASA Astrophysics Data System (ADS)

Hong, W.-L.; Torres, M. E.; Portnov, A.; Waage, M.; Haley, B.; Lepland, A.

2018-05-01

Methane fluxes into the oceans are largely dependent on the methane phase as it migrates upward through the sediments. Here we document decoupled methane transport by gaseous and aqueous phases in Storfjordrenna (offshore Svalbard) and propose a three-stage evolution model for active seepage in the region where gas hydrates are present in the shallow subsurface. In a preactive seepage stage, solute diffusion is the primary transport mechanism for methane in the dissolved phase. Fluids containing dissolved methane have high 87Sr/86Sr ratios due to silicate weathering in the microbial methanogenesis zone. During the active seepage stage, migration of gaseous methane results in near-seafloor gas hydrate formation and vigorous seafloor gas discharge with a thermogenic fingerprint. In the postactive seepage stage, the high concentration of dissolved lithium points to the contribution of a deeper-sourced aqueous fluid, which we postulate advects upward following cessation of gas discharge.

What can the programming language Rust do for astrophysics?

NASA Astrophysics Data System (ADS)

Blanco-Cuaresma, Sergi; Bolmont, Emeline

2017-06-01

The astrophysics community uses different tools for computational tasks such as complex systems simulations, radiative transfer calculations or big data. Programming languages like Fortran, C or C++ are commonly present in these tools and, generally, the language choice was made based on the need for performance. However, this comes at a cost: safety. For instance, a common source of error is the access to invalid memory regions, which produces random execution behaviors and affects the scientific interpretation of the results. In 2015, Mozilla Research released the first stable version of a new programming language named Rust. Many features make this new language attractive for the scientific community, it is open source and it guarantees memory safety while offering zero-cost abstraction. We explore the advantages and drawbacks of Rust for astrophysics by re-implementing the fundamental parts of Mercury-T, a Fortran code that simulates the dynamical and tidal evolution of multi-planet systems.

Wide-Field Infrared Survey Explorer Observations of the Evolution of Massive Star-Forming Regions

NASA Technical Reports Server (NTRS)

Koenig, X. P.; Leisawitz, D. T.; Benford, D. J.; Rebull, L. M.; Padgett, D. L.; Assef, R. J.

2011-01-01

We present the results of a mid-infrared survey of 11 outer Galaxy massive star-forming regions and 3 open clusters with data from the Wide-field Infrared Survey Explorer (WISE). Using a newly developed photometric scheme to identify young stellar objects and exclude extragalactic contamination, we have studied the distribution of young stars within each region. These data tend to support the hypothesis that latter generations may be triggered by the interaction of winds and radiation from the first burst of massive star formation with the molecular cloud material leftover from that earlier generation of stars.We dub this process the "fireworks hypothesis" since star formation by this mechanism would proceed rapidly and resemble a burst of fireworks.We have also analyzed small cutout WISE images of the structures around the edges of these massive star-forming regions. We observe large (1-3 pc size) pillar and trunk-like structures of diffuse emission nebulosity tracing excited polycyclic aromatic hydrocarbon molecules and small dust grains at the perimeter of the massive star-forming regions. These structures contain small clusters of emerging Class I and Class II sources, but some are forming only a single to a few new stars.

Wide-Field Infrared Survey Explorer Observations of the Evolution of Massive Star-Forming Regions

NASA Technical Reports Server (NTRS)

Koenig, X. P.; Leisawitz, D. T.; Benford, D. J.; Rebull, L. M.; Padgett, D. L.; Asslef, R. J.

2012-01-01

We present the results of a mid-infrared survey of II outer Galaxy massive star-forming regions and 3 open clusters with data from the Wide-field Infrared Survey Explorer (WISE). Using a newly developed photometric scheme to identify young stellar objects and exclude extragalactic contamination, we have studied the distribution of young stars within each region. These data tend to support the hypothesis that latter generations may be triggered by the interaction of winds and radiation from the first burst of massive star formation with the molecular cloud material leftover from that earlier generation of stars. We dub this process the "fireworks hypothesis" since star formation by this mechanism would proceed rapidly and resemble a burst of fireworks. We have also analyzed small cutout WISE images of the structures around the edges of these massive star-forming regions. We observe large (1-3 pc size) pillar and trunk-like structures of diffuse emission nebulosity tracing excited polycyclic aromatic hydrocarbon molecules and small dust grains at the perimeter of the massive star-forming regions. These structures contain small clusters of emerging Class I and Class II sources, but some are forming only a single to a few new stars.

Regional health inequalities: changes observed in Brazil from 2000-2016.

PubMed

Albuquerque, Mariana Vercesi de; Viana, Ana Luiza d'Ávila; Lima, Luciana Dias de; Ferreira, Maria Paula; Fusaro, Edgard Rodrigues; Iozzi, Fabíola Lana

2017-04-01

Advances in reducing poverty and inequalities in the 2000s had a paradoxical effect in Brazil. This article examines how socioeconomic transformations, and the complexity of health services, are expressed in the regions established for planning purposes and the inter-governmental management of the Brazilian Unified Health System. An effort was made to identify and explain differences in the compositions of the 438 existing health regions and their spatial distribution by comparing situations observed in 2016 with those in 2000. Factor analysis and grouping techniques were used to construct a typology in the two years of the series, which was based on a diverse set of secondary data sources. It was found that there was an evolution in terms of income levels and service provision within the health regions, with a significant improvement in the socioeconomic conditions of the population. These results suggest that there was a positive impact from the combination of strategies related to social, economic and regional policies for the promotion of development, which generated more widespread well-being within the affected areas. However, limitations remain regarding the policies implemented for the universalization of the health system.

Evidence of spectrally broad Gravity Wave packet propagation and dispersion in the mesopause region observed by the Na lidar and Mesospheric Temperature Mapper above Logan, Utah

NASA Astrophysics Data System (ADS)

Yuan, T.; Heale, C. J.; Snively, J. B.

2016-12-01

Utilizing observations from the Na lidar at Utah State University and the nearby Mesospheric Temperature Mapper (MTM) at Bear Lake Observatory (BLO) [41.9°N, 111.4°W], we investigate a unique case of vertical dispersion for a spectrally broad gravity wave packet in the mesopause region over Logan, Utah (41.7°N, 111.8°W) that occurred on September 2nd, 2011, to study the waves' evolution as a packet propagates upward. The lidar observed temperature perturbation was dominated by close to a 1-hour modulation at 100 km during the early hours, but gradually evolved into a 1.5-hour modulation during the second half of the night. The vertical wavelength also decreased simultaneously, while the vertical group and phase velocities of the packet apparently slowed, as it was approaching a critical level during the second half of the night. A two-dimensional numerical model is utilized to simulate the observed GW processes, finding that the location of the lidar relative to the source can strongly influence which portion of the spectrum can be observed at a particular location relative to a source.

Evidence of correlated evolution and adaptive differentiation of stem and leaf functional traits in the herbaceous genus, Helianthus.

PubMed

Pilote, Alex J; Donovan, Lisa A

2016-12-01

Patterns of plant stem traits are expected to align with a "fast-slow" plant economic spectrum across taxa. Although broad patterns support such tradeoffs in field studies, tests of hypothesized correlated trait evolution and adaptive differentiation are more robust when taxa relatedness and environment are taken into consideration. Here we test for correlated evolution of stem and leaf traits and their adaptive differentiation across environments in the herbaceous genus, Helianthus. Stem and leaf traits of 14 species of Helianthus (28 populations) were assessed in a common garden greenhouse study. Phylogenetically independent contrasts were used to test for evidence of correlated evolution of stem hydraulic and biomechanical properties, correlated evolution of stem and leaf traits, and adaptive differentiation associated with source habitat environments. Among stem traits, there was evidence for correlated evolution of some hydraulic and biomechanical properties, supporting an expected tradeoff between stem theoretical hydraulic efficiency and resistance to bending stress. Population differentiation for suites of stem and leaf traits was found to be consistent with a "fast-slow" resource-use axis for traits related to water transport and use. Associations of population traits with source habitat characteristics supported repeated evolution of a resource-acquisitive "drought-escape" strategy in arid environments. This study provides evidence of correlated evolution of stem and leaf traits consistent with the fast-slow spectrum of trait combinations related to water transport and use along the stem-to-leaf pathway. Correlations of traits with source habitat characteristics further indicate that the correlated evolution is associated, at least in part, with adaptive differentiation of Helianthus populations among native habitats differing in climate. © 2016 Botanical Society of America.

Regional Aerosol Optical Properties and Radiative Impact of the Extreme Smoke Event in the European Arctic in Spring 2006

NASA Technical Reports Server (NTRS)

Lund Myhre, C.; Toledano, C.; Myhre, G.; Stebel, K.; Yttri, K.; Aaltonen, V.; Johnsrud, M.; Frioud, M.; Cachorro, V.; deFrutos, A.;

Galaxy evolution at high-redshift: Millimeter-wavelength surveys with the AzTEC camera

NASA Astrophysics Data System (ADS)

Scott, Kimberly S.

Galaxies detected by their thermal dust emission at submillimeter (submm) and millimeter (mm) wavelengths comprise a population of massive, intensely star-forming systems in the early Universe. These "submm/mm- galaxies", or SMGs, likely represent an important phase in the assembly and/or evolution of massive galaxies and are thought to be the progenitors of massive elliptical galaxies. While their projected number density as a function of source brightness provides key constraints on models of galaxy evolution, SMG surveys carried out over the past twelve years with the first generation of submm/mm-wavelength cameras have not imaged a large enough area to sufficient depths to provide the statistical power needed to discriminate between competing galaxy evolution scenarios. In this dissertation, we present the results from SMG surveys carried out over the past four years using the new sensitive mm-wavelength camera AzTEC. With the improved mapping speed of the AzTEC camera combined with dedicated telescope time devoted to deep, large-area extragalactic surveys, we have tripled both the area surveyed towards blank- fields (that is, regions with no known galaxy over-densities) at submm/mm wavelengths and the total number of detected SMGs. Here, we describe the properties and performance of the AzTEC instrument while operating on the James Clerk Maxwell Telescope (JCMT) and the Atacama Submillimeter Telescope Experiment (ASTE). We then present the results from two of the blank-field regions imaged with AzTEC: the JCMT/COSMOS field, which we discovered is over- dense in the number of very bright SMGs, and the ASTE survey of the Great Observatories Origins Deep-South field, which represents one of the deepest surveys ever carried out at submm/mm wavelengths. Finally, we combine the results from all of the blank-fields imaged with AzTEC while operating on the JCMT and the ASTE to calculate the most accurate measurements to date of the SMG number counts.

Mitochondrial genome evolution in the Saccharomyces sensu stricto complex.

PubMed

Ruan, Jiangxing; Cheng, Jian; Zhang, Tongcun; Jiang, Huifeng

2017-01-01

Exploring the evolutionary patterns of mitochondrial genomes is important for our understanding of the Saccharomyces sensu stricto (SSS) group, which is a model system for genomic evolution and ecological analysis. In this study, we first obtained the complete mitochondrial sequences of two important species, Saccharomyces mikatae and Saccharomyces kudriavzevii. We then compared the mitochondrial genomes in the SSS group with those of close relatives, and found that the non-coding regions evolved rapidly, including dramatic expansion of intergenic regions, fast evolution of introns and almost 20-fold higher rearrangement rates than those of the nuclear genomes. However, the coding regions, and especially the protein-coding genes, are more conserved than those in the nuclear genomes of the SSS group. The different evolutionary patterns of coding and non-coding regions in the mitochondrial and nuclear genomes may be related to the origin of the aerobic fermentation lifestyle in this group. Our analysis thus provides novel insights into the evolution of mitochondrial genomes.

Basin analysis of North Sea viking graben: new techniques in an old basin

DOE Office of Scientific and Technical Information (OSTI.GOV)

Iliffe, J.E.; Cao, S.; Lerche, I.

1987-05-01

Rapid sedimentation rates from the Upper Cretaceous to Tertiary in the North Sea require that burial history modeling account for overpressuring. Use of a quantitative fluid flow/compaction model, along with the inversion of thermal indicators to obtain independent estimates of paleoheat flu, can greatly enhance their knowledge of a basin's evolution and hydrocarbon potential. First they assess the modeling sensitivity to the quality of data and variation of other input parameters. Then application to 16 wells with vitrinite data in the Viking graben north of 59/sup 0/ latitude and to pseudo-wells derived from deep seismic profiling of BIRPA greatly enhancesmore » the study of regional variations. A Tissot generation model is run on all the wells for each potential source rock. The resulting amounts of oil and gas generated are contoured to produce a regional oil and gas provenance map for each source rock. The model results are compared and tested against the known producing fields. Finally, by restoration of the two-dimensional seismic reflection profiles, the temporal variations of basement subsidence and paleoheat flow are related to the tectonic zoning of the region and to the extensional history. The combined structural, thermal, and depositional information available due to technological progress in both modeling and deep seismic profiling allows a better understanding of previously proposed models of extension.« less

Population genomic analyses reveal a history of range expansion and trait evolution across the native and invaded range of yellow starthistle (Centaurea solstitialis)

PubMed Central

BARKER, BRITTANY S.; ANDONIAN, KRIKOR; SWOPE, SARAH M.; LUSTER, DOUGLAS G.; DLUGOSCH, KATRINA M.

2017-01-01

Identifying sources of genetic variation and reconstructing invasion routes for non-native introduced species is central to understanding the circumstances under which they may evolve increased invasiveness. In this study, we used genome-wide single nucleotide polymorphisms to study the colonization history of Centaurea solstitialis in its native range in Eurasia and invasions into the Americas. We leveraged this information to pinpoint key evolutionary shifts in plant size, a focal trait associated with invasiveness in this species. Our analyses revealed clear population genomic structure of potential source populations in Eurasia, including deep differentiation of a lineage found in the southern Apennine and Balkan Peninsulas and divergence among populations in Asia, eastern Europe, and western Europe. We found strongest support for an evolutionary scenario in which western European populations were derived from an ancient admixture event between populations from eastern Europe and Asia, and subsequently served as the main genetic ‘bridgehead’ for introductions to the Americas. Introductions to California appear to be from a single source region, and multiple, independent introductions of divergent genotypes likely occurred into the Pacific Northwest. Plant size has evolved significantly at three points during range expansion, including a large size increase in the lineage responsible for the aggressive invasion of California’s interior. These results reveal a long history of colonization, admixture, and trait evolution in C. solstitialis, and suggest routes for improving evidence-based management decisions for one of the most ecologically and economically damaging invasive species in the western United States. PMID:28029713

Studying the Formation and Evolution of Eruptive Solar Magnetic Flux Ropes

NASA Astrophysics Data System (ADS)

Linton, M.

2017-12-01

Solar magnetic eruptions are dramatic sources of solar activity, and dangerous sources of space weather hazards. Many of these eruptions take the form of magnetic flux ropes, i.e., magnetic fieldlines wrapping around a core magnetic flux tube. Investigating the processes which form these flux ropes both prior to and during eruption, and investigating their evolution after eruption, can give us a critical window into understanding the sources of and processes involved in these eruptions. This presentation will discuss modeling and observational investigations into these various phases of flux rope formation, eruption, and evolution, and will discuss how these different explorations can be used to develop a more complete picture of erupting flux rope dynamics. This work is funded by the NASA Living with a Star program.

Tracking Oxidation During Transport of Trace Gases in Air from the Northern to Southern Hemisphere

NASA Astrophysics Data System (ADS)

Montzka, S. A.; Moore, F. L.; Atlas, E. L.; Parrish, D. D.; Miller, B. R.; Sweeney, C.; McKain, K.; Hall, B. D.; Siso, C.; Crotwell, M.; Hintsa, E. J.; Elkins, J. W.; Blake, D. R.; Barletta, B.; Meinardi, S.; Claxton, T.; Hossaini, R.

2017-12-01

Trace gas mole fractions contain the imprint of recent influences on an air mass such as sources, transport, and oxidation. Covariations among the many gases measured from flasks during ATom and HIPPO, and from the ongoing NOAA cooperative air sampling program enable recent influences to be identified from a wide range of sources including industrial activity, biomass burning, emissions from wetlands, and uptake by terrestrial ecosystems. In this work we explore the evolution of trace gas concentrations owing to atmospheric oxidation as air masses pass through the tropics, the atmospheric region with the highest concentrations of the hydroxyl radical. Variations in C2-C5 hydrocarbon concentrations downwind of source regions provide a measure of photochemical ageing in an air mass since emission, but they become less useful when tracking photochemical ageing as air is transported from the NH into the SH owing to their low mixing ratios, lifetimes that are very short relative to transport times, non-industrial sources in the tropics (e.g., biomass burning), and southern hemispheric sources. Instead, we consider a range of trace gases and trace gas pairs that provide a measure of photochemical processing as air transits the tropics. To be useful in this analysis, these trace gases would have lifetimes comparable to interhemispheric transport times, emissions arising from only the NH at constant relative magnitudes, and concentrations sufficient to allow precise and accurate measurements in both hemispheres. Some anthropogenically-emitted chlorinated hydrocarbons meet these requirements and have been measured during ATom, HIPPO, and from NOAA's ongoing surface sampling efforts. Consideration of these results and their implications for tracking photochemical processing in air as it is transported across the tropics will be presented.

Sr-Nd-Hf isotopic fingerprinting of transatlantic dust derived from North Africa

NASA Astrophysics Data System (ADS)

Zhao, Wancang; Balsam, William; Williams, Earle; Long, Xiaoyong; Ji, Junfeng

2018-03-01

Long-range transport of African dust plays an important role in understanding dust-climate relationships including dust source areas, dust pathways and associated atmospheric and/or oceanic processes. Clay-sized Sr-Nd-Hf isotopic compositions can be used as geochemical fingerprints to constrain dust provenance and the pathways of long-range transported mineral dust. We investigated the clay-sized Sr-Nd-Hf isotopic composition of surface samples along four transects bordering the Sahara Desert. The transects are from Mali, Niger/Benin/Togo, Egypt and Morocco. Our results show that the Mali transect on the West African Craton (WAC) produces lower εNd (εNd-mean = -16.38) and εHf (εHf-mean = -9.59) values than the other three transects. The Egyptian transect exhibits the lowest 87Sr/86Sr ratios (87Sr/86Srmean = 0.709842), the highest εHf (εHf-mean = -0.34) and εNd values of the four transects. Comparison of the clay-sized Sr-Nd-Hf isotopic values from our North African samples to transatlantic African dust collected in Barbados demonstrates that the dust's provenance is primarily the western Sahel and Sahara as well as the central Sahel. Summer emission dust is derived mainly from the western Sahel and Sahara regions. The source of transatlantic dust in spring and autumn is more varied than in the summer and includes dust not only from western areas, but also south central areas. Comparison of the Sr-Nd-Hf isotopic fingerprints between the source and sink of transatlantic dust also suggests that a northwestward shift in dust source occurs from the winter, through the spring and into the summer. The isotopic data we develop here provide another tool for discriminating changes in dust archives resulting from paleoenvironmental evolution of source regions.

Methane emissions from pan-Arctic lakes during the 21st century: An analysis with process-based models of lake evolution and biogeochemistry

NASA Astrophysics Data System (ADS)

Tan, Zeli; Zhuang, Qianlai

2015-12-01

The importance of methane emissions from pan-Arctic lakes in the global carbon cycle has been suggested by recent studies. These studies indicated that climate change influences this methane source mainly in two ways: the warming of lake sediments and the evolution of thermokarst lakes. Few studies have been conducted to quantify the two impacts together in a unified modeling framework. Here we adapt a region-specific lake evolution model to the pan-Arctic scale and couple it with a lake methane biogeochemical model to quantify the change of this freshwater methane source in the 21st century. Our simulations show that the extent of thaw lakes will increase throughout the 21st century in the northern lowlands of the pan-Arctic where the reworking of epigenetic ice in drained lake basins will continue. The projected methane emissions by 2100 are 28.3 ± 4.5 Tg CH4 yr-1 under a low warming scenario (Representative Concentration Pathways (RCPs) 2.6) and 32.7 ± 5.2 Tg CH4 yr-1 under a high warming scenario (RCP 8.5), which are about 2.5 and 2.9 times the simulated present-day emissions. Most of the emitted methane originates from nonpermafrost carbon stock. For permafrost carbon, the methanogenesis will mineralize a cumulative amount of 3.4 ± 0.8 Pg C under RCP 2.6 and 3.9 ± 0.9 Pg C under RCP 8.5 from 2006 to 2099. The projected emissions could increase atmospheric methane concentrations by 55.0-69.3 ppb. This study further indicates that the warming of lake sediments dominates the increase of methane emissions from pan-Arctic lakes in the future.

Change of PAHs with evolution of paddy soils from prehistoric to present over the last six millennia in the Yangtze River Delta region, China.

PubMed

Zhang, Jin; Cornelia, Mueller-Niggemann; Wang, Minyan; Cao, Zhihong; Luo, Xiping; Wong, Minghung; Chen, Wei

2013-04-01

To evaluate the influence of hydroponics management on soil organic components with evolution of paddy soil over the last six millennia, PAHs, as a biomarker, as well as total organic carbon content were used to explore changes of paddy soil organic carbon in two entirely buried ancient paddy soil profiles. The results showed that hydroponics management can cause organic carbon deposition in rice paddy. The changing of total PAH concentrations was not always in accordance with the changing of total organic carbon contents in layers of the buried ancient paddy soils. The PAHs in 6280 BP prehistoric paddy soil layer was 3-ring>5-ring>4-ring>6-ring, while in layers of the present paddy soil and the prehistoric upland were 3-ring>4-ring>5-ring>6-ring. The contribution of phenanthrene to total PAHs in two profiles and the increasing ratio of phenanthrene to alkylated PAHs from parent material/6280 BP prehistoric upland to 6280 BP paddy suggested substantial increase of the anthropogenic influence of hydroponics management on rice paddy soil. And in view of the (14)C age and bioremains in the two profiles, it was only possible for PAHs to be derived from hydroponics management with evolution of the paddy soils form the Neolithic age. Cadalene could be used as an indicator for biological sources of PAHs released by rice plant residues, and benzo[g,h,i]fluoranthene and benzo[g,h,i]perylene for pyrogenic sources released by field vegetation fires. Crown Copyright © 2013. Published by Elsevier B.V. All rights reserved.

The formation and gravitational-wave detection of massive stellar black hole binaries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Belczynski, Krzysztof; Walczak, Marek; Buonanno, Alessandra

2014-07-10

If binaries consisting of two ∼100 M{sub ☉} black holes exist, they would serve as extraordinarily powerful gravitational-wave sources, detectable to redshifts of z ∼ 2 with the advanced LIGO/Virgo ground-based detectors. Large uncertainties about the evolution of massive stars preclude definitive rate predictions for mergers of these massive black holes. We show that rates as high as hundreds of detections per year, or as low as no detections whatsoever, are both possible. It was thought that the only way to produce these massive binaries was via dynamical interactions in dense stellar systems. This view has been challenged by themore » recent discovery of several ≳ 150 M{sub ☉} stars in the R136 region of the Large Magellanic Cloud. Current models predict that when stars of this mass leave the main sequence, their expansion is insufficient to allow common envelope evolution to efficiently reduce the orbital separation. The resulting black hole-black hole binary remains too wide to be able to coalesce within a Hubble time. If this assessment is correct, isolated very massive binaries do not evolve to be gravitational-wave sources. However, other formation channels exist. For example, the high multiplicity of massive stars, and their common formation in relatively dense stellar associations, opens up dynamical channels for massive black hole mergers (e.g., via Kozai cycles or repeated binary-single interactions). We identify key physical factors that shape the population of very massive black hole-black hole binaries. Advanced gravitational-wave detectors will provide important constraints on the formation and evolution of very massive stars.« less

Proterozoic crustal evolution of the Eucla basement, Australia: Implications for destruction of oceanic crust during emergence of Nuna

NASA Astrophysics Data System (ADS)

Kirkland, C. L.; Smithies, R. H.; Spaggiari, C. V.; Wingate, M. T. D.; Quentin de Gromard, R.; Clark, C.; Gardiner, N. J.; Belousova, E. A.

2017-05-01

The crystalline basement beneath the Cretaceous to Cenozoic Bight and Eucla Basins, in Western Australia has received comparatively little attention even though it lies on the eastern margin of one of the most mineral resource endowed regions on the planet. This basement is characterized by a complex geological evolution spanning c. 2 billion years, but paucity of outcrop and younger basin cover present a daunting challenge to understand the basement geology. In this work the composition of the unexposed Proterozoic crystalline basement to the Bight and Eucla Basins is investigated through zircon Hf isotopes and whole rock geochemistry from new drillcore samples. This region includes two geophysically defined basement entities: The Madura Province, containing: 1) c. 1478 Ma Sleeper Camp Formation, which has variable isotopic signatures including evolved values interpreted to reflect reworking of rare slivers of hyperextended Archean crust, 2) 1415-1389 Ma Haig Cave Supersuite, with mantle-like isotope values interpreted as melting of subduction-modified N-MORB source, and 3) 1181-1125 Ma Moodini Supersuite, with juvenile isotopic signatures interpreted to reflect mixed mafic lower-crustal and asthenospheric melts produced at the base of thinned crust. The Coompana Province, to the east of the Madura Province, has three major magmatic components: 1) c. 1610 Ma Toolgana Supersuite, with chemical and isotopic characteristics of primitive arc rock, 2) c. 1490 Ma Undawidgi Supersuite, with juvenile isotope values consistent with extensional processes involving asthenospheric input and 3) 1192-1140 Ma Moodini Supersuite, with strong isotopic similarity to Moodini Supersuite rocks in the Madura Province. This new isotopic and geochemical data shows that the Madura and Coompana regions together represent a huge tract of predominantly juvenile material. Magma sources recognised, include; 1) depleted mantle, producing MORB-like crust at c. 1950 Ma, but also contributing to younger magmatism; 2) recycled c. 1950 Ma crust reworked in primitive arcs and in intra-plate settings and; 3) minor evolved material representing fragments of hyperextended continent. The observed isotopic evolution pattern is comparable to that of other central Australian Proterozoic provinces, including the Musgrave Province, the northern margin of the Gawler Craton, and components within the Rudall Province. Linking these isotopic signatures defines the Mirning Ocean, and its subducted and underplated equivalents. In a global context we suggest c. 1950 Ma crust production reflects the onset of ordered oceanic spreading centres, which swept juvenile crustal fragments into Nuna.

The Role of Hydrogen Sulfide in Evolution and the Evolution of Hydrogen Sulfide in Metabolism and Signaling.

PubMed

Olson, Kenneth R; Straub, Karl D

2016-01-01

The chemical versatility of sulfur and its abundance in the prebiotic Earth as reduced sulfide (H2S) implicate this molecule in the origin of life 3.8 billion years ago and also as a major source of energy in the first seven-eighths of evolution. The tremendous increase in ambient oxygen ∼ 600 million years ago brought an end to H2S as an energy source, and H2S-dependent animals either became extinct, retreated to isolated sulfide niches, or adapted. The first 3 billion years of molecular tinkering were not lost, however, and much of this biochemical armamentarium easily adapted to an oxic environment where it contributes to metabolism and signaling even in humans. This review examines the role of H2S in evolution and the evolution of H2S metabolism and signaling. ©2016 Int. Union Physiol. Sci./Am. Physiol. Soc.

Virgo Intergalactic Globulars from the Sloan Survey

NASA Astrophysics Data System (ADS)

Gregg, Michael; West, Michael

2017-07-01

We have identified a new sample of Virgo intergalactic globular clusters (IGCs) and ultra compact dwarfs (UCDs) which have been serendipitously observed to date in Sloan Survey spectroscopy. There are 23 new objects with secure redshifts, all relatively red point sources with reliable velocities placing them at Virgo distances. They are spread widely across Virgo, significantly extending the spatial distribution of Virgo IGCs and UCDs to regions outside the well-studied M87 core region. The new sample are generally fainter, bluer, and probably more metal poor on average than the more centrally located, previously known objects. This systematic change carries information about the formation and continued evolution by accretion of the Virgo cluster, indicating a transition to less massive and less luminous objects being tidally disrupted in the outskirts now and in the recent past, compared to conditions in the inner cluster at early epochs.

UCLA IGPP Space Plasma Simulation Group

NASA Technical Reports Server (NTRS)

1998-01-01

During the past 10 years the UCLA IGPP Space Plasma Simulation Group has pursued its theoretical effort to develop a Mission Oriented Theory (MOT) for the International Solar Terrestrial Physics (ISTP) program. This effort has been based on a combination of approaches: analytical theory, large scale kinetic (LSK) calculations, global magnetohydrodynamic (MHD) simulations and self-consistent plasma kinetic (SCK) simulations. These models have been used to formulate a global interpretation of local measurements made by the ISTP spacecraft. The regions of applications of the MOT cover most of the magnetosphere: the solar wind, the low- and high-latitude magnetospheric boundary, the near-Earth and distant magnetotail, and the auroral region. Most recent investigations include: plasma processes in the electron foreshock, response of the magnetospheric cusp, particle entry in the magnetosphere, sources of observed distribution functions in the magnetotail, transport of oxygen ions, self-consistent evolution of the magnetotail, substorm studies, effects of explosive reconnection, and auroral acceleration simulations.

Origin of the positron excess in cosmic rays.

PubMed

Blasi, Pasquale

2009-07-31

We show that the positron excess measured by the PAMELA experiment in the region between 10 and 100 GeV may well be a natural consequence of the standard scenario for the origin of Galactic cosmic rays. The "excess" arises because of positrons created as secondary products of hadronic interactions inside the sources, but the crucial physical ingredient which leads to a natural explanation of the positron flux is the fact that the secondary production takes place in the same region where cosmic rays are being accelerated. Therefore secondary positrons (and electrons) participate in the acceleration process and turn out to have a very flat spectrum, which is responsible, after propagation in the Galaxy, for the observed positron excess. This effect cannot be avoided though its strength depends on the values of the environmental parameters during the late stages of evolution of supernova remnants.

Molecular evolution and the latitudinal biodiversity gradient.

PubMed

Dowle, E J; Morgan-Richards, M; Trewick, S A

2013-06-01

Species density is higher in the tropics (low latitude) than in temperate regions (high latitude) resulting in a latitudinal biodiversity gradient (LBG). The LBG must be generated by differential rates of speciation and/or extinction and/or immigration among regions, but the role of each of these processes is still unclear. Recent studies examining differences in rates of molecular evolution have inferred a direct link between rate of molecular evolution and rate of speciation, and postulated these as important drivers of the LBG. Here we review the molecular genetic evidence and examine the factors that might be responsible for differences in rates of molecular evolution. Critical to this is the directionality of the relationship between speciation rates and rates of molecular evolution.

Radio outbursts in extragalactic sources

NASA Astrophysics Data System (ADS)

Kinzel, Wayne Morris

Three aspects of the flux density variability of extragalactic radio sources were examined: millimeter wavelength short timescale variability, the spectral evolution of outbursts, and whether the outbursts are periodically spaced. Observations of extragalactic radio sources were conducted using the Five College Radio Astronomy Observatory between January and June 1985 at 88.2 GHz and during June and July 1985 at 40.0 GHz. Many of the sources exhibited significant flux density variations during the observing span. In addition, the most rapid variations observed were comparable with those reported in previous works. Two sources, 0355+50 and OJ287, both exhibited outbursts whose rise and fall timescales were less than a month. An anomalous flux density dropout was observed in 3C446 and was interpreted as an occultation event. Data at five frequencies between 2.7 and 89.6 GHz from the Dent-Balonek monitoring program were used to investigate the spectral evolution of eight outbursts. Outburst profile fitting was used to deconvolve the individual outbursts from one another at each frequency. The fit profiles were used to generate multiple epoch spectra to investigate the evolution of the outbursts. A phase residual minimization method was used to examine four sources for periodic behavior.

Radioactivity as a significant energy source in prebiotic synthesis.

PubMed

Garzón, L; Garzón, M L

2001-01-01

Radioactivity in the continental crust (due mainly to the isotopes 238U, 235U, 232Th and 40K), as a energy source for chemical evolution in the early Archean (between 3.5 and approximately 4 Ga bp), is reviewed. The most important radioactive source in the continental crust is due to the production and accumulation of radioactive gases within the crust voids (porosity). The study of such mechanism has allowed us to reach a deeper understanding about the nature of the radioactive source and to describe its behavior, particularly with regard to prebiotic chemical evolution. An effective total energy of 3 x 10(18) Ja-1 has been obtained for a depth of 1 km, 4 Ga ago. If a depth of 30 km is taken, the obtained value is almost equal to the UV solar energy radiation (lambda < 150 nm). Within the voids the radioactive source of the continental crust played a relevant role in prebiotic synthesis. In uranium deposits of the same age, the role of radioactivity must have been even more relevant in favoring chemical evolution.

A New Diagnostic Diagram of Ionization Sources for High-redshift Emission Line Galaxies

NASA Astrophysics Data System (ADS)

Zhang, Kai; Hao, Lei

2018-04-01

We propose a new diagram, the kinematics–excitation (KEx) diagram, which uses the [O III] λ5007/Hβ line ratio and the [O III] λ5007 emission line width (σ [O III]) to diagnose the ionization source and physical properties of active galactic nuclei (AGNs) and star-forming galaxies (SFGs). The KEx diagram is a suitable tool to classify emission line galaxies at intermediate redshift because it uses only the [O III] λ5007 and Hβ emission lines. We use the main galaxy sample of SDSS DR7 and the Baldwin‑Phillips‑Terlevich (BPT) diagnostic to calibrate the diagram at low redshift. The diagram can be divided into three regions: the KEx-AGN region, which consists mainly of pure AGNs, the KEx-composite region, which is dominated by composite galaxies, and the KEx-SFG region, which contains mostly SFGs. LINERs strongly overlap with the composite and AGN regions. AGNs are separated from SFGs in this diagram mainly because they preferentially reside in luminous and massive galaxies and have higher [O III]/Hβ than SFGs. The separation between AGNs and SFGs is even cleaner thanks to the additional 0.15/0.12 dex offset in σ [O III] at fixed luminosity/stellar mass. We apply the KEx diagram to 7866 galaxies at 0.3 < z < 1 in the DEEP2 Galaxy Redshift Survey, and compare it to an independent X-ray classification scheme using Chandra observations. X-ray AGNs are mostly located in the KEx-AGN region, while X-ray SFGs are mostly located in the KEx-SFG region. Almost all Type 1 AGNs lie in the KEx-AGN region. These tests support the reliability of this classification diagram for emission line galaxies at intermediate redshift. At z ∼ 2, the demarcation line between SFGs and AGNs is shifted by ∼0.3 dex toward higher values of σ [O III] due to evolution effects.

The evolution of sex chromosomes in organisms with separate haploid sexes.

PubMed

Immler, Simone; Otto, Sarah Perin

2015-03-01

The evolution of dimorphic sex chromosomes is driven largely by the evolution of reduced recombination and the subsequent accumulation of deleterious mutations. Although these processes are increasingly well understood in diploid organisms, the evolution of dimorphic sex chromosomes in haploid organisms (U/V) has been virtually unstudied theoretically. We analyze a model to investigate the evolution of linkage between fitness loci and the sex-determining region in U/V species. In a second step, we test how prone nonrecombining regions are to degeneration due to accumulation of deleterious mutations. Our modeling predicts that the decay of recombination on the sex chromosomes and the addition of strata via fusions will be just as much a part of the evolution of haploid sex chromosomes as in diploid sex chromosome systems. Reduced recombination is broadly favored, as long as there is some fitness difference between haploid males and females. The degeneration of the sex-determining region due to the accumulation of deleterious mutations is expected to be slower in haploid organisms because of the absence of masking. Nevertheless, balancing selection often drives greater differentiation between the U/V sex chromosomes than in X/Y and Z/W systems. We summarize empirical evidence for haploid sex chromosome evolution and discuss our predictions in light of these findings. © 2015 The Author(s).

Characteristics and sources of submicron aerosols above the urban canopy (260 m) in Beijing, China, during the 2014 APEC summit

NASA Astrophysics Data System (ADS)

Chen, C.; Sun, Y. L.; Xu, W. Q.; Du, W.; Zhou, L. B.; Han, T. T.; Wang, Q. Q.; Fu, P. Q.; Wang, Z. F.; Gao, Z. Q.; Zhang, Q.; Worsnop, D. R.

2015-11-01

The megacity of Beijing has experienced frequent severe fine particle pollution during the last decade. Although the sources and formation mechanisms of aerosol particles have been extensively investigated on the basis of ground measurements, real-time characterization of aerosol particle composition and sources above the urban canopy in Beijing is rare. In this study, we conducted real-time measurements of non-refractory submicron aerosol (NR-PM1) composition at 260 m at the Beijing 325 m meteorological tower (BMT) from 10 October to 12 November 2014, by using an aerosol chemical speciation monitor (ACSM) along with synchronous measurements of size-resolved NR-PM1 composition near ground level using a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS). The NR-PM1 composition above the urban canopy was dominated by organics (46 %), followed by nitrate (27 %) and sulfate (13 %). The high contribution of nitrate and high NO3- / SO42- mass ratios illustrates an important role of nitrate in particulate matter (PM) pollution during the study period. The organic aerosol (OA) was mainly composed of secondary OA (SOA), accounting for 61 % on an average. Different from that measured at the ground site, primary OA (POA) correlated moderately with SOA, likely suggesting a high contribution from regional transport above the urban canopy. The Asia-Pacific Economic Cooperation (APEC) summit with strict emission controls provides a unique opportunity to study the impacts of emission controls on aerosol chemistry. All aerosol species were shown to have significant decreases of 40-80 % during APEC from those measured before APEC, suggesting that emission controls over regional scales substantially reduced PM levels. However, the bulk aerosol composition was relatively similar before and during APEC as a result of synergetic controls of aerosol precursors. In addition to emission controls, the routine circulations of mountain-valley breezes were also found to play an important role in alleviating PM levels and achieving the "APEC blue" effect. The evolution of vertical differences between 260 m and the ground level was also investigated. Our results show complex vertical differences during the formation and evolution of severe haze episodes that are closely related to aerosol sources and boundary-layer dynamics.

Characteristics and sources of submicron aerosols above the urban canopy (260 m) in Beijing, China during 2014 APEC summit

NASA Astrophysics Data System (ADS)

Chen, C.; Sun, Y. L.; Xu, W. Q.; Du, W.; Zhou, L. B.; Han, T. T.; Wang, Q. Q.; Fu, P. Q.; Wang, Z. F.; Gao, Z. Q.; Zhang, Q.; Worsnop, D. R.

2015-08-01

The megacity of Beijing has experienced frequent severe fine particle pollution during the last decade. Although the sources and formation mechanisms of aerosol particles have been extensively investigated on the basis of ground measurements, real-time characterization of aerosol particle composition and sources above the urban canopy in Beijing is rare. In this study, we conducted real-time measurements of non-refractory submicron aerosol (NR-PM1) composition at 260 m at the 325 m Beijing Meteorological Tower (BMT) from 10 October to 12 November 2014, by using an aerosol chemical speciation monitor (ACSM) along with synchronous measurements of size-resolved NR-PM1 composition at near ground level using a High-Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS). The NR-PM1 composition above the urban canopy was dominated by organics (46 %), followed by nitrate (27 %) and sulfate (13 %). The high contribution of nitrate and high NO3-/SO42- mass ratios illustrate an important role of nitrate in particulate matter (PM) pollution during the study period. The organic aerosol (OA) was mainly composed by secondary OA (SOA), accounting for 61 % on an average. Different from that measured at the ground site, primary OA (POA) correlated moderately with SOA, likely suggesting a high contribution from regional transport above the urban canopy. The Asia-Pacific Economic Cooperation (APEC) summit with strict emission controls provides a unique opportunity to study the impacts of emission controls on aerosol chemistry. All aerosol species were shown to have significant decreases of 40-80 % during APEC from those measured before APEC, suggesting that emission controls over regional scales substantially reduced PM levels. However, the bulk aerosol composition was relatively similar before and during APEC as a result of synergetic controls of aerosol precursors such as SO2, NOx, and volatile organic compounds (VOCs). In addition to emission controls, the routine circulations of mountain-valley breezes were also found to play an important role in alleviating PM levels and achieving the "APEC blue" effect. The evolution of vertical differences between 260 m and the ground level was also investigated. Our results show complex vertical differences during the formation and evolution of severe haze episodes that are closely related to aerosol sources and boundary layer dynamics.

The Cosmological Evolution of Radio Sources with CENSORS

NASA Technical Reports Server (NTRS)

Brookes, Mairi; Best, Philip; Peacock, John; Dunlop, James; Rottgering, Huub

2006-01-01

The CENSORS survey, selected from the NVSS, has been followed up using EIS, K-band imaging and spectroscopic observations to produce a radio sample capable of probing the source density in the regime: z greater than 2.5. With a current spectroscopic completeness of 62%, CENSORS has been used in direct modeling of RLF evolution and in V/V(sub max) tests. There is evidence for a shallow decline in number density of source in the luminosity range 10(sup 26) - 10(sup 27)WHz(sup -1) at 1.4GHz.

Simultaneous Survey of Water and Class I Methanol Masers toward Red MSX Sources

NASA Astrophysics Data System (ADS)

Kim, Chang-Hee; Kim, Kee-Tae; Park, Yong-Sun

2018-06-01

We report simultaneous single-dish surveys of 22 GHz H2O and 44 and 95 GHz class I CH3OH masers toward 299 Red Midcourse Space Experiment Sources in the protostellar stage. The detection rates are 45% at 22 GHz, 28% at 44 GHz, and 23% at 95 GHz. There are 15, 53, and 51 new discoveries at 22, 44, and 95 GHz, respectively. We detect high-velocity (>30 km s‑1) features in 27 H2O maser sources. The 95 GHz maser emission is detected only in 44 GHz maser sources. The two transitions show strong correlations in the peak velocity, peak flux density, and isotropic maser luminosity, indicating that they are likely generated in the same sites by the same mechanisms. The 44 GHz masers have much narrower distributions than 22 GHz masers in the relative peak velocity and velocity range, while 6.7 GHz class II CH3OH masers have distributions intermediate between the two. The maser luminosity significantly correlates with the parental clump mass, while it correlates well with the bolometric luminosity of the central protostar only when data of the low-mass regime from the literature are added. Comparison with the results of previous maser surveys toward massive star-forming regions suggests that the detection rates of 22 and 44 GHz masers tend to increase as the central objects evolve. This is contrary to the trends found in low- and intermediate-mass star-forming regions. Thus, the occurrence of both masers might depend on the surrounding environments as well as on the evolution of the central object.

ALMA deep field in SSA22: Survey design and source catalog of a 20 arcmin2 survey at 1.1 mm

NASA Astrophysics Data System (ADS)

Umehata, Hideki; Hatsukade, Bunyo; Smail, Ian; Alexander, David M.; Ivison, Rob J.; Matsuda, Yuichi; Tamura, Yoichi; Kohno, Kotaro; Kato, Yuta; Hayatsu, Natsuki H.; Kubo, Mariko; Ikarashi, Soh

2018-06-01

To search for dust-obscured star-formation activity in the early Universe, it is essential to obtain a deep and wide submillimeter/millimeter map. The advent of the Atacama Large Millimeter/submillimeter Array (ALMA) has enabled us to obtain such maps with sufficiently high spatial resolution to be free from source confusion. We present a new 1.1 mm-wave map obtained by ALMA in the SSA22 field. The field contains a remarkable proto-cluster at z = 3.09; therefore, it is an ideal region to investigate the role of a large-scale cosmic web on dust-obscured star formation. The typical 1σ depth of our map is 73 μJy beam-1 with a {0^{^''.}5} resolution. Combining the present survey with earlier, archived observations, we map an area of 20 arcmin2 (71 comoving Mpc2 at z = 3.09). Within the combined survey area we have detected 35 sources at a signal-to-noise ratio (S/N) >5, with flux densities of S1.1mm = 0.43-5.6 mJy, equivalent to star-formation rates of ≳100-1000 M⊙ yr-1 at z = 3.09, for a Chabrier initial mass function: 17 sources out of 35 are new detections. The cumulative number counts show an excess by a factor of three to five compared to blank fields. The excess suggests enhanced, dust-enshrouded star-formation activity in the proto-cluster on a 10 comoving Mpc scale, indicating accelerated galaxy evolution in this overdense region.

Subduction, erosion and the sediment record: Insights from Miocene sediments, Hengchun Peninsula, Taiwan

NASA Astrophysics Data System (ADS)

Kirstein, Linda; Carter, Andrew; Chen, Yue-Gau

2010-05-01

Detrital sedimentary records include vast archives of material that have been removed from developing tectonically active regions. These archives have been used to investigate challenging questions on continental deformation, exhumation and palaeodrainage using a variety of different techniques including heavy minerals, fission-track dating and palaeocurrent reconstructions. The Hengchun Peninsula of southern Taiwan and offshore Hengchun Ridge form a present day accretionary prism, with accretionary wedge growth occurring both by frontal accretion, with sediments from the continental margin scraped up into the accretionary wedge and by underplating. Miocene sediments in Hengchun include foreland basin deposits, deep marine turbidites and forearc basin deposits. As a result the detrital sediments record details of accretionary prism growth associated with continued Luzon arc-continent collision. Diametrically opposite palaeocurrents are preserved in the Miocene sandstones of the Hengchun Peninsula, southern Taiwan. Controversial explanations include an exotic source terrane to the south and/or 180 ° rotation of a depositional basin. We document the tecto-thermal evolution of the Miocene sediment source(s) using a double dating approach. U-Pb grain ages range from Miocene to Archaean, while zircon fission-tracks record thermal cooling primarily in the Cretaceous with minor peaks in the Miocene, Triassic, Jurassic and Permian. The primary source of the Miocene sediments at the centre of the controversy was similar. Palaeocurrent data are influenced by local basin geometry and submarine topography and suggest that sediment deposition in the Miocene was strongly controlled by incipient subduction, associated structural trends and submarine topography. A similar control on deposition in the modern Taiwan collision zone is apparent in the offshore region today.

Sand fairway mapping as a tool for tectonic restoration in orogenic belts

NASA Astrophysics Data System (ADS)

Butler, Rob

2016-04-01

The interplay between regional subsidence mechanisms and local deformation associated with individual fold-thrust structures is commonly investigated in neotectonic subaerial systems using tectonic geomorphology. Taking these approaches back into the early evolution of mountain belts is difficult as much of the key evidence is lost through erosion. The challenge is to develop appropriate tools for investigating these early stages of orogenesis. However, many such systems developed under water. In these settings the connections between regional and local tectonics are manifest in complex bathymetry. Turbidity currents flowing between and across these structures will interact with their substrate and thus their deposits, tied to stratigraphic ages, can chart tectonic evolution. Understanding the depositional processes of the turbidity currents provides substantial further insight on confining seabed geometry and thus can establish significant control on the evolution of bathymetric gradients and continuity through basins. However, reading these records commonly demands working in structurally deformed terrains that hitherto have discouraged sedimentological study. This is now changing. Sand fairway mapping provides a key approach. Fairway maps chart connectivity between basins and hence their relative elevation through time. Larger-scale tectonic reconstructions may be tested by linking fairway maps to sand composition and other provenance data. More detailed turbidite sedimentology provides substantial further insight. In confined turbidite systems, it is the coarser sand component that accumulates in the deeper basin with fines fractionated onto the flanks. Flow bypass, evidenced by abrupt breaks in grading within individual event beds, can be used to predict sand fraction distribution down fairways. Integrating sedimentology into fairway maps can chart syntectonic slope evolution and thus provide high resolution tools equivalent to those in subaerial tectonic geomorphology. The stratigraphic records are preserved in many parts of the Alpine-Mediterranean region. Examples are drawn from the Eo-Oligocene of the western Alps and the early Miocene of the Maghreb-Apennine system to illustrate how turbidite sedimentology, linked to studies of basin structure, can inform understanding of tectonic processes on regional and local scales. In both examples, sediment was delivered across deforming basin arrays containing contractional structures, sourced from beyond the immediate orogenic segments. The depositional systems show that multiple structures were active in parallel, rather than develop in any particular sequence. Both systems show that significant deformation occurs, emerging to the syn-orogenic surface ahead of the main orogenic wedge. The cycling of uplift and subsidence of "massifs" can be significantly more complex that the histories resolved from thermochronological data alone.

Multiscale Spatial Modeling of Human Exposure from Local Sources to Global Intake.

PubMed

Wannaz, Cedric; Fantke, Peter; Jolliet, Olivier

2018-01-16

Exposure studies, used in human health risk and impact assessments of chemicals, are largely performed locally or regionally. It is usually not known how global impacts resulting from exposure to point source emissions compare to local impacts. To address this problem, we introduce Pangea, an innovative multiscale, spatial multimedia fate and exposure assessment model. We study local to global population exposure associated with emissions from 126 point sources matching locations of waste-to-energy plants across France. Results for three chemicals with distinct physicochemical properties are expressed as the evolution of the population intake fraction through inhalation and ingestion as a function of the distance from sources. For substances with atmospheric half-lives longer than a week, less than 20% of the global population intake through inhalation (median of 126 emission scenarios) can occur within a 100 km radius from the source. This suggests that, by neglecting distant low-level exposure, local assessments might only account for fractions of global cumulative intakes. We also study ∼10 000 emission locations covering France more densely to determine per chemical and exposure route which locations minimize global intakes. Maps of global intake fractions associated with each emission location show clear patterns associated with population and agriculture production densities.

Long Term Temporal and Spectral Evolution of Point Sources in Nearby Elliptical Galaxies

NASA Astrophysics Data System (ADS)

Durmus, D.; Guver, T.; Hudaverdi, M.; Sert, H.; Balman, Solen

2016-06-01

We present the results of an archival study of all the point sources detected in the lines of sight of the elliptical galaxies NGC 4472, NGC 4552, NGC 4649, M32, Maffei 1, NGC 3379, IC 1101, M87, NGC 4477, NGC 4621, and NGC 5128, with both the Chandra and XMM-Newton observatories. Specifically, we studied the temporal and spectral evolution of these point sources over the course of the observations of the galaxies, mostly covering the 2000 - 2015 period. In this poster we present the first results of this study, which allows us to further constrain the X-ray source population in nearby elliptical galaxies and also better understand the nature of individual point sources.

Evolution of aerosol vertical distribution during particulate pollution events in Shanghai

NASA Astrophysics Data System (ADS)

Zhang, Yunwei; Zhang, Qun; Leng, Chunpeng; Zhang, Deqin; Cheng, Tiantao; Tao, Jun; Zhang, Renjian; He, Qianshan

2015-06-01

A set of micro pulse lidar (MPL) systems operating at 532 nm was used for ground-based observation of aerosols in Shanghai in 2011. Three typical particulate pollution events (e.g., haze) were examined to determine the evolution of aerosol vertical distribution and the planetary boundary layer (PBL) during these pollution episodes. The aerosol vertical extinction coefficient (VEC) at any given measured altitude was prominently larger during haze periods than that before or after the associated event. Aerosols originating from various source regions exerted forcing to some extent on aerosol loading and vertical layering, leading to different aerosol vertical distribution structures. Aerosol VECs were always maximized near the surface owing to the potential influence of local pollutant emissions. Several peaks in aerosol VECs were found at altitudes above 1 km during the dust- and bioburning-influenced haze events. Aerosol VECs decreased with increasing altitude during the local-polluted haze event, with a single maximum in the surface atmosphere. PM2.5 increased slowly while PBL and visibility decreased gradually in the early stages of haze events; subsequently, PM2.5 accumulated and was exacerbated until serious pollution bursts occurred in the middle and later stages. The results reveal that aerosols from different sources impact aerosol vertical distributions in the atmosphere and that the relationship between PBL and pollutant loadings may play an important role in the formation of pollution.

The Mojave River from sink to source: The 2018 Desert Symposium Field Trip Road Log

USGS Publications Warehouse

Miller, David; Reynolds, R.E.; Groover, Krishangi D.; Buesch, David C.; Brown, H. J.; Cromwell, Geoffrey; Densmore-Judy, Jill; Garcia, A.L.; Hughson, D.; Knott, J.R.; Lovich, Jeffrey E.

2018-01-01

The Mojave River evolved over the past few million years by “fill and spill” from upper basins near its source in the Transverse Ranges to lower basins. Each newly “spilled into” basin in the series? sustained a long-lived lake but gradually filled with Mojave River sediment, leading to spill to a yet lower elevation? basin. The Mojave River currently terminates at Silver Lake, near Baker, CA, but previously overflowed this terminus onward to Lake Manly in Death Valley during the last glacial cycle. The river’s origin and evolution are intricately interwoven with tectonic, climatic, and geomorphic processes through time, beginning with San Andreas fault interactions that created a mountain range across a former externally draining river. We will see and discuss the Mojave River’s predecessor streams and basins, its evolution as it lengthened to reach the central Mojave Desert, local and regional tectonic controls, groundwater flow, flood history, and support of isolated perennial stream reaches that host endemic species. In association with these subjects are supporting studies such as paleoclimate records, location and timing for groundwater and wetlands in the central Mojave Desert, and effects of modern water usage. The trip introduces new findings for the groundwater basin of Hinkley Valley, including an ongoing remediation project that provides a wealth of information on past and present river flow and associated development of the groundwater system.

Simulating the transport and chemical evolution of biomass burning pollutants originating from Southeast Asia during 7-SEAS/2010 Dongsha experiment

NASA Astrophysics Data System (ADS)

Chuang, Ming-Tung; Fu, Joshua S.; Lin, Neng-Huei; Lee, Chung-Te; Gao, Yang; Wang, Sheng-Hsiang; Sheu, Guey-Rong; Hsiao, Ta-Chih; Wang, Jia-Lin; Yen, Ming-Cheng; Lin, Tang-Huang; Thongboonchoo, Narisara; Chen, Wei-Chen

2015-07-01

This study aimed to simulate the transport of biomass burning (BB) aerosol originating from Southeast Asia (SEA) during the Dongsha Experiment conducted from March 2010 to April 2010. Transport pathways were reanalyzed and steering flow in the mid-latitude areas and anticyclones in low-latitude areas were found to control the transport of BB plume after it was injected to a high atmosphere. For the 12 simulated and observed events at Mt. Lulin (2862 m MSL; 23°28‧07″ N, 120°52‧25″ E), the 72 h backward trajectories were all tracked back to southern China and northern Indochina, which were the locations of the largest BB fire activities in SEA. Chemical evolutions of BB pollutants along the moving trajectories showed that organic matter was always the dominant component in PM2.5, consistent with the observations at both near-source regions and Mt. Lulin. For nitrogen species, nearly all NOx molecules oxidized into HNO3, NO3-, PAN, and PANX in fires or near fires. The synchronic consumption of NOx, SO2, and NH3 explained the production of the major components of inorganic salts. In the moving BB plume, sulfate concentration increased with decreased nitrate concentration. Ratios of ammonium to PM2.5 and elemental carbon to PM2.5 remained nearly constant because additional sources were lacking.

Magnetic Evolution Linked to the Interrelated Activity Complexes Involving Transequatorial Coronal Holes

NASA Astrophysics Data System (ADS)

Gutiérrez, Heidy; Taliashvili, Lela; Lazarian, Alexandre

2018-06-01

We studied a magnetic evolution linked to a cadence of interrelated activities developed in a large solar region during Carrington rotations, CRs 2119 - 2121, based on multi-wavelength and multi-spacecraft observations. Three coronal holes (CHs), two transequatorial and one isolated, eight filaments and some active regions were distributed closely in the region. Every of these filaments partial and/or complete eruption was linked to a Coronal Mass Ejection (CME) or coronal jet. We found different types of interrelated activities: eruptions of three pairs of interrelated filaments close to a CH and eruptions of two filaments close to the active region and CH. Some indicators of the magnetic reconnection were observed frequently during the pre- as well as post-filament eruptions. Additionally, post-filament eruption and/or post-CME processes show their implication in the evolution of nearby CHs and newly formed transient CHs or dimming regions, including a new CH formation. We discussed the small- and large-scale magnetic reconfigurations associated with these interrelated activity complexes, the ones involving long-lived transequatorial CHs, and their possible implication in the evolution of the global solar magnetic field, especially with the starting processes of quadruple configuration and polarity reversal of the solar cycle 24.

Multi-locus phylogeny of dolphins in the subfamily Lissodelphininae: character synergy improves phylogenetic resolution

PubMed Central

Harlin-Cognato, April D; Honeycutt, Rodney L

2006-01-01

Background Dolphins of the genus Lagenorhynchus are anti-tropically distributed in temperate to cool waters. Phylogenetic analyses of cytochrome b sequences have suggested that the genus is polyphyletic; however, many relationships were poorly resolved. In this study, we present a combined-analysis phylogenetic hypothesis for Lagenorhynchus and members of the subfamily Lissodelphininae, which is derived from two nuclear and two mitochondrial data sets and the addition of 34 individuals representing 9 species. In addition, we characterize with parsimony and Bayesian analyses the phylogenetic utility and interaction of characters with statistical measures, including the utility of highly consistent (non-homoplasious) characters as a conservative measure of phylogenetic robustness. We also explore the effects of removing sources of character conflict on phylogenetic resolution. Results Overall, our study provides strong support for the monophyly of the subfamily Lissodelphininae and the polyphyly of the genus Lagenorhynchus. In addition, the simultaneous parsimony analysis resolved and/or improved resolution for 12 nodes including: (1) L. albirostris, L. acutus; (2) L. obscurus and L. obliquidens; and (3) L. cruciger and L. australis. In addition, the Bayesian analysis supported the monophyly of the Cephalorhynchus, and resolved ambiguities regarding the relationship of L. australis/L. cruciger to other members of the genus Lagenorhynchus. The frequency of highly consistent characters varied among data partitions, but the rate of evolution was consistent within data partitions. Although the control region was the greatest source of character conflict, removal of this data partition impeded phylogenetic resolution. Conclusion The simultaneous analysis approach produced a more robust phylogenetic hypothesis for Lagenorhynchus than previous studies, thus supporting a phylogenetic approach employing multiple data partitions that vary in overall rate of evolution. Even in cases where there was apparent conflict among characters, our data suggest a synergistic interaction in the simultaneous analysis, and speak against a priori exclusion of data because of potential conflicts, primarily because phylogenetic results can be less robust. For example, the removal of the control region, the putative source of character conflict, produced spurious results with inconsistencies among and within topologies from parsimony and Bayesian analyses. PMID:17078887

Lithosphere-Atmosphere coupling: Spectral element modeling of the evolution of acoustic waves in the atmosphere from an underground source.

NASA Astrophysics Data System (ADS)

Averbuch, Gil; Price, Colin

2015-04-01

Lithosphere-Atmosphere coupling: Spectral element modeling of the evolution of acoustic waves in the atmosphere from an underground source. G. Averbuch, C. Price Department of Geosciences, Tel Aviv University, Israel Infrasound is one of the four Comprehensive Nuclear-Test Ban Treaty technologies for monitoring nuclear explosions. This technology measures the acoustic waves generated by the explosions followed by their propagation through the atmosphere. There are also natural phenomena that can act as an infrasound sources like sprites, volcanic eruptions and earthquakes. The infrasound waves generated from theses phenomena can also be detected by the infrasound arrays. In order to study the behavior of these waves, i.e. the physics of wave propagation in the atmosphere, their evolution and their trajectories, numerical methods are required. This presentation will deal with the evolution of acoustic waves generated by underground sources (earthquakes and underground explosions). A 2D Spectral elements formulation for lithosphere-atmosphere coupling will be presented. The formulation includes the elastic wave equation for the seismic waves and the momentum, mass and state equations for the acoustic waves in a moving stratified atmosphere. The coupling of the two media is made by boundary conditions that ensures the continuity of traction and velocity (displacement) in the normal component to the interface. This work has several objectives. The first is to study the evolution of acoustic waves in the atmosphere from an underground source. The second is to derive transmission coefficients for the energy flux with respect to the seismic magnitude and earth density. The third will be the generation of seismic waves from acoustic waves in the atmosphere. Is it possible?

Malagasy Genetic Ancestry Comes from an Historical Malay Trading Post in Southeast Borneo.

PubMed

Brucato, Nicolas; Kusuma, Pradiptajati; Cox, Murray P; Pierron, Denis; Purnomo, Gludhug A; Adelaar, Alexander; Kivisild, Toomas; Letellier, Thierry; Sudoyo, Herawati; Ricaut, François-Xavier

2016-09-01

Malagasy genetic diversity results from an exceptional protoglobalization process that took place over a thousand years ago across the Indian Ocean. Previous efforts to locate the Asian origin of Malagasy highlighted Borneo broadly as a potential source, but so far no firm source populations were identified. Here, we have generated genome-wide data from two Southeast Borneo populations, the Banjar and the Ngaju, together with published data from populations across the Indian Ocean region. We find strong support for an origin of the Asian ancestry of Malagasy among the Banjar. This group emerged from the long-standing presence of a Malay Empire trading post in Southeast Borneo, which favored admixture between the Malay and an autochthonous Borneo group, the Ma'anyan. Reconciling genetic, historical, and linguistic data, we show that the Banjar, in Malay-led voyages, were the most probable Asian source among the analyzed groups in the founding of the Malagasy gene pool. © The Author 2016. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.

Probing the infrared counterparts of diffuse far-ultraviolet sources in the Galaxy

NASA Astrophysics Data System (ADS)

Saikia, Gautam; Shalima, P.; Gogoi, Rupjyoti; Pathak, Amit

2017-12-01

Recent availability of high quality infrared (IR) data for diffuse regions in the Galaxy and external galaxies have added to our understanding of interstellar dust. A comparison of ultraviolet (UV) and IR observations may be used to estimate absorption, scattering and thermal emission from interstellar dust. In this paper, we report IR and UV observations for selective diffuse sources in the Galaxy. Using archival mid-infrared (MIR) and far-infrared (FIR) observations from Spitzer Space Telescope, we look for counterparts of diffuse far-ultraviolet (FUV) sources observed by the Voyager, Far Ultraviolet Spectroscopic Explorer (FUSE) and Galaxy Evolution Explorer (GALEX) telescopes in the Galaxy. IR emission features at 8 μm are generally attributed to Polycyclic Aromatic Hydrocarbon (PAH) molecules, while emission at 24 μm are attributed to Very Small Grains (VSGs). The data presented here is unique and our study tries to establish a relation between various dust populations. By studying the FUV-IR correlations separately at low and high latitude locations, we have identified the grain component responsible for the diffuse FUV emission.

ATLASGAL - towards a complete sample of massive star forming clumps

NASA Astrophysics Data System (ADS)

Urquhart, J. S.; Moore, T. J. T.; Csengeri, T.; Wyrowski, F.; Schuller, F.; Hoare, M. G.; Lumsden, S. L.; Mottram, J. C.; Thompson, M. A.; Menten, K. M.; Walmsley, C. M.; Bronfman, L.; Pfalzner, S.; König, C.; Wienen, M.

2014-09-01

By matching infrared-selected, massive young stellar objects (MYSOs) and compact H II regions in the Red MSX Source survey to massive clumps found in the submillimetre ATLASGAL (APEX Telescope Large Area Survey of the Galaxy) survey, we have identified ˜1000 embedded young massive stars between 280° < ℓ < 350° and 10° < ℓ < 60° with | b | < 1.5°. Combined with an existing sample of radio-selected methanol masers and compact H II regions, the result is a catalogue of ˜1700 massive stars embedded within ˜1300 clumps located across the inner Galaxy, containing three observationally distinct subsamples, methanol-maser, MYSO and H II-region associations, covering the most important tracers of massive star formation, thought to represent key stages of evolution. We find that massive star formation is strongly correlated with the regions of highest column density in spherical, centrally condensed clumps. We find no significant differences between the three samples in clump structure or the relative location of the embedded stars, which suggests that the structure of a clump is set before the onset of star formation, and changes little as the embedded object evolves towards the main sequence. There is a strong linear correlation between clump mass and bolometric luminosity, with the most massive stars forming in the most massive clumps. We find that the MYSO and H II-region subsamples are likely to cover a similar range of evolutionary stages and that the majority are near the end of their main accretion phase. We find few infrared-bright MYSOs associated with the most massive clumps, probably due to very short pre-main-sequence lifetimes in the most luminous sources.

Geochemistry of Cretaceous granites from Mianning in the Panxi region, Sichuan Province, southwestern China: Implications for their generation

NASA Astrophysics Data System (ADS)

Xu, Cheng; Huang, Zhilong; Qi, Liang; Fu, Pingqing; Liu, Congqiang; Li, Endong; Guan, Tao

2007-03-01

The Cretaceous granites of Mianning, located in the northern Panxi region, were emplaced after collision of the Tibetan Plateau and Yangtze Block. These granites have very high K 2O + Na 2O, Ga, Zr, Nb, Y, REE (except Eu), and very low MgO, CaO, P 2O 5, and Sr contents relative to M-, I- or S-type granites. Based on the chemical discrimination criteria of Whalen et al . [Whalen, J.B., Currie, K.L., Chappell, B.W., 1987. A-type granites: geochemical characteristics, distribution and petrogenesis. Contributions to Mineralogy and Petrology 95, 407-419], most of them are A-type granites. Moreover, the granites plot in the range of post-collision granites and belong to the A2 type. Elevated initial Sr isotopic ratios (>0.72) suggest their derivation dominantly from a crustal source. These features are consistent with granite formation in a post-orogenic setting, such as after subduction or collision between of the Tibetan Plateau and Yangtze Block. In addition, the granites are characterized by low abundances of Ba, Sr, P, Ti, and Eu, positive correlation between Ba and Eu anomalies, and negative correlation between Rb and K/Rb. Plots of Rb vs. Sr suggest that fractional crystallization affected the final compositions of these granites after melting from a dominantly crustal source. From the late Proterozoic to late Mesozoic, the crustal composition, compared to that of the mantle, appears to have increased in the Panxi region. While the mantle component played an important part in the generation of Cretaceous granites in southeastern China, its influence was relatively minor in the Panxi region. Thus, there was a significant difference in mantle evolution between southeastern China and the Panxi region, which led to different metallogenic processes.

On the multiday haze in the Asian continental outflow: the important role of synoptic conditions combined with regional and local sources

NASA Astrophysics Data System (ADS)

Seo, Jihoon; Kim, Jin Young; Youn, Daeok; Lee, Ji Yi; Kim, Hwajin; Lim, Yong Bin; Kim, Yumi; Cher Jin, Hyoun

2017-08-01

The air quality of the megacities in populated and industrialized regions like East Asia is affected by both local and regional emission sources. The combined effect of regional transport and local emissions on multiday haze was investigated through a synthetic analysis of PM2. 5 sampled at both an urban site in Seoul, South Korea and an upwind background site on Deokjeok Island over the Yellow Sea during a severe multiday haze episode in late February 2014. Inorganic components and carbonaceous species of daily PM2. 5 samples were measured, and gaseous pollutants, local meteorological factors, and synoptic meteorological conditions were also determined. A dominance of fine-mode particles (PM2. 5 / PM10 ˜ 0.8), a large secondary inorganic fraction (76 %), high OC / EC (> 7), and highly oxidized aerosols (oxygen-to-carbon ratio of ˜ 0.6 and organic-mass-to-carbon ratio of ˜ 1.9) under relatively warm, humid, and stagnant conditions characterize the multiday haze episode in Seoul; however, the early and late stages of the episode show different chemical compositions of PM2. 5. High concentrations of sulfate in both Seoul and the upwind background in the early stage suggest a significant regional influence on the onset of the multiday haze. At the same time, high concentrations of nitrate and organic compounds in Seoul, which are local and highly correlated with meteorological factors, suggest the contribution of local emissions and secondary formation under stagnant meteorological conditions to the haze. A slow eastward-moving high-pressure system from southern China to the East China Sea induces the regional transport of aerosols and potential gaseous precursors for secondary aerosols from the North China Plain in the early stage but provides stagnant conditions conducive to the accumulation and the local formation of aerosols in the late stage. A blocking ridge over Alaska that developed during the episode hinders the zonal propagation of synoptic-scale systems and extends the haze period to several days. This study provides chemical insights into haze development sequentially by regional transport and local sources, and shows that the synoptic condition plays an important role in the dynamical evolution of long-lasting haze in the Asian continental outflow region.

Mutagens and carcinogens - Occurrence and role during chemical and biological evolution

NASA Technical Reports Server (NTRS)

Giner-Sorolla, A.; Oro, J.

1981-01-01

The roles of mutagenic and carcinogenic substances in early biologic evolution is examined, along with terrestrial and extraterrestrial sources of mutagens and carcinogens. UV solar radiation is noted to have served to stimulate prebiotic life while also causing harmful effects in plants and animals. Aromatic compounds have been found in meteorites, and comprise leukemogens, polycyclic hydrocarbons, and nitrasamine precursors. Other mutagenic sources are volcanoes, and the beginning of evolution with mutagenic substances is complicated by the appearance of malignancies due to the presence of carcinogens. The atmosphere of the Precambrian period contained both mutagens and early carcinogens and, combined with volcanic activity discharges, formed an atmospheric chemical background analogous to the background ionizing radiation. Carcinogenesis is concluded to be intrinsic to nature, having initiated evolution and, eventually, cancer cells.

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

PubMed Central

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

2016-01-01

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

Microstructure Evolution and Selective Corrosion Resistance in Underwater Multi-pass 2101 Duplex Stainless Steel Welding Joints

NASA Astrophysics Data System (ADS)

Hu, Yu; Shi, Yonghua; Shen, Xiaoqin; Wang, Zhongmin

2018-05-01

A recently developed promising material, 2101 lean duplex stainless steel, represents an alternative to 304 austenite stainless steel. In this work, multi-pass 2101 weld joints were fabricated using the flux-cored arc welding method in a hyperbaric chamber. The pressure varied from 0 to 0.75 MPa. The evolution of the welding process and microstructure was investigated. γ 2 formation in the reheated zones of the WM and HAZ was not uniform. The closer the reheated zone is to the subsequent heat source, the greater the γ 2 formation in the reheated zone. Sufficient primary austenite transformation inhibited Cr2N precipitation and the subsequent intragranular γ 2 formation in the reheated weld passes of the 0.45 MPa weld metal. The localized corrosion resistance of each zone of the 0.45 MPa DSS joint was measured using non-destructive double-loop electrochemical potentiokinetic reactivation tests. The localized corrosion was induced by γ 2 and Cr2N. The root region of the 0.45 MPa weld metal underwent two subsequent welding thermal cycles, which induced increased γ 2 formation and lower resistance to corrosion because of the decreased pitting resistance value of γ 2. The correlation between microstructure evolution and the distribution of selective corrosion was determined.

Dynamics and early post-tsunami evolution of floating marine debris near Fukushima Daiichi

NASA Astrophysics Data System (ADS)

Matthews, John Philip; Ostrovsky, Lev; Yoshikawa, Yutaka; Komori, Satoru; Tamura, Hitoshi

2017-08-01

The devastating tsunami triggered by the Tōhoku-Oki earthquake of 11 March 2011 caused a crisis at the Fukushima Daiichi nuclear power station where it overtopped the seawall defences. On retreating, the tsunami carried loose debris and wreckage seaward and marshalled buoyant material into extensive plumes. Widespread concern over the fate of these and numerous other Tōhoku tsunami depositions prompted attempts to simulate debris dispersion throughout the wider Pacific. However, the effects of locally perturbed wind and wave fields, active Langmuir circulation and current-induced attrition determine a complex and poorly understood morphology for large floating agglomerations. Here we show that the early post-tsunami evolution of marine-debris plumes near Fukushima Daiichi was also shaped by near-surface wind modifications that took place above relatively calm (lower surface roughness) waters covered by surface films derived from oil and other contaminants. High-spatial-resolution satellite tracking reveals faster-than-expected floating-debris motions and invigorated plume evolution within these regions, while numerical modelling of turbulent air flow over the low-drag, film-covered surface predicts typically metre-per-second wind strengthening at centimetric heights, sufficient to explain the observed debris-speed increases. Wind restructuring probably stimulates the dispersion of flotsam from both biological and anthropogenic sources throughout a global ocean of highly variable surface roughness.

The Evolution of Pristine Gas: Implications for Milky Way Halo Stars

NASA Astrophysics Data System (ADS)

Sarmento, Richard J.; Scannapieco, Evan; Pan, Liubin

2016-06-01

We implement a new subgrid model for turbulent mixing to accurately follow the cosmological evolution of the first stars, the mixing of their supernova ejecta and the impact on the chemical composition of the Galactic Halo. Using the cosmological adaptive mesh refinement code RAMSES, we implement a model for the pollution of pristine gas as described in Pan et al. (2013). This allows us to account for the fraction of Z < Zcrit stars formed throughout the simulation volume, even in regions in which the average metallicity is well above Zcrit. Further, as a result of modeling the pristine fraction of gas, we also improve our modeling of the metallicity of the polluted fraction, fpol, of both the gas and stars.Additionally, we track the evolution of the “primordial metals” generated by Pop III supernovae. These metals are taken up by second-generation stars and are likely to lead to unique abundance signatures characteristic of carbon enhanced, metal poor (CEMP) stars. As an illustrative example, we associate primordial metals with abundance ratios used by Keller at al (2014) to explain the source of metals in the star SMSS J031300.36- 670839.3, finding good agreement with the observed [Fe/H], [C/H], [O/H] and [Mg/Ca] ratios in CEMP Milky Way (MW) halo stars.

Wave-Kinetic Simulations of the Nonlinear Generation of Electromagnetic VLF Waves through Velocity Ring Instabilities

NASA Astrophysics Data System (ADS)

Ganguli, G.; Crabtree, C. E.; Rudakov, L.; Mithaiwala, M.

2014-12-01

Velocity ring instabilities are a common naturally occuring magnetospheric phenomenon that can also be generated by man made ionospheric experiments. These instabilities are known to generate lower-hybrid waves, which generally cannot propagte out of the source region. However, nonlinear wave physics can convert these linearly driven electrostatic lower-hybrid waves into electromagnetic waves that can escape the source region. These nonlinearly generated waves can be an important source of VLF turbulence that controls the trapped electron lifetime in the radiation belts. We develop numerical solutions to the wave-kinetic equation in a periodic box including the effects of nonlinear (NL) scattering (nonlinear Landau damping) of Lower-hybrid waves giving the evolution of the wave-spectra in wavenumber space. Simultaneously we solve the particle diffusion equation of both the background plasma particles and the ring ions, due to both linear and nonlinear Landau resonances. At initial times for cold ring ions, an electrostatic beam mode is excited, while the kinetic mode is stable. As the instability progresses the ring ions heat, the beam mode is stabilized, and the kinetic mode destabilizes. When the amplitude of the waves becomes sufficient the lower-hybrid waves are scattered (by either nearly unmagnetized ions or magnetized electrons) into electromagnetic magnetosonic waves [Ganguli et al 2010]. The effect of NL scattering is to limit the amplitude of the waves, slowing down the quasilinear relaxation time and ultimately allowing more energy from the ring to be liberated into waves [Mithaiwala et al. 2011]. The effects of convection out of the instability region are modeled, additionally limiting the amplitude of the waves, allowing further energy to be liberated from the ring [Scales et al., 2012]. Results are compared to recent 3D PIC simulations [Winske and Duaghton 2012].

Evaluation of New and Proposed Organic Aerosol Sources and Mechanisms using the Aerosol Modeling Testbed. MILAGRO, CARES, CalNex, BEACHON, and GVAX

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hodzic, Alma; Jimenez, Jose L.

2015-04-09

This work investigated the formation and evolution of organic aerosols (OA) arising from anthropogenic and biogenic sources in a framework that combined state-of-the-science process and regional modeling, and their evaluation against advanced and emerging field measurements. Although OA are the dominant constituents of submicron particles, our understanding of their atmospheric lifecycle is limited, and current models fail to describe the observed amounts and properties of chemically formed secondary organic aerosols (SOA), leaving large uncertainties on the effects of SOA on climate. Our work has provided novel modeling constraints on sources, formation, aging and removal of SOA by investigating in particularmore » (i) the contribution of trash burning emissions to OA levels in a megacity, (ii) the contribution of glyoxal to SOA formation in aqueous particles in California during CARES/CalNex and over the continental U.S., (iii) SOA formation and regional growth over a pine forest in Colorado and its sensitivity to anthropogenic NOx levels during BEACHON, and the sensitivity of SOA to (iv) the sunlight exposure during its atmospheric lifetime, and to (v) changes in solubility and removal of organic vapors in the urban plume (MILAGRO, Mexico City), and over the continental U.S.. We have also developed a parameterization of water solubility for condensable organic gases produced from major anthropogenic and biogenic precursors based on explicit chemical modeling, and made it available to the wider community. This work used for the first time constraints from the explicit model GECKO-A to improve SOA representation in 3D regional models such as WRF-Chem.« less

The circum-Chryse region as a possible example of a hydrologic cycle on Mars: Geologic observations and theoretical evaluation

NASA Technical Reports Server (NTRS)

Moore, Jeffrey M.; Clow, Gary D.; Davis, Wanda L.; Gulick, Virginia C.; Janke, David R.; Mckay, Christopher P.; Stoker, Carol R.; Zent, Aaron P.

1995-01-01

The transection and superposition relationships among channels, chaos, surface materials units, and other features in the circum-Chryse region of Mars were used to evaluate relative age relationships and evolution of flood events. Channels and chaos in contact (with one another) were treated as single discrete flood-carved systems. Some outflow channel systems form networks and are inferred to have been created by multiple flood events. Within some outflow channel networks, several separate individual channel systems can be traced to a specific chaos which acted as flood-source area to that specific flood channel. Individual flood-carved systems were related to widespread materials units or other surface features that served as stratigraphic horizons. Chryse outflow channels are inferred to have formed over most of the perceivable history of Mars. Outflow channels are inferred to become younger with increasing proximity to the Chryse basin. The relationship of subsequent outflow channel sources to the sources of earlier floods is inferred to disfavor episodic flooding due to the progresssive tapping of a juvenile near-surface water supply. Instead, we propose the circum-Chryse region as a candidate site of past hydrological recycling. The discharge rates necessary to carve the circum-Chryse outflow channels would have inevitably formed temporary standing bodies of H2O on the Martian surface where the flood-waters stagnated and pooled (the Chryse basin is topographically enclosed). These observations and inferences have led us to formulate and evaluate two hypotheses. Our numerical evaluations indicate that of these two hypotheses formulated, the groundwater seep cycle seems by far the more viable. Further observations from forthcoming missions may permit the determination of which mechanisms may have operated to recycle the Chryse flood-waters.

Dominant factors in controlling marine gas pools in South China

USGS Publications Warehouse

Xu, S.; Watney, W.L.

2007-01-01

In marine strata from Sinian to Middle Triassic in South China, there develop four sets of regional and six sets of local source rocks, and ten sets of reservoir rocks. The occurrence of four main formation periods in association with five main reconstruction periods, results in a secondary origin for the most marine gas pools in South China. To improve the understanding of marine gas pools in South China with severely deformed geological background, the dominant control factors are discussed in this paper. The fluid sources, including the gas cracked from crude oil, the gas dissolved in water, the gas of inorganic origin, hydrocarbons generated during the second phase, and the mixed pool fluid source, were the most significant control factors of the types and the development stage of pools. The period of the pool formation and the reconstruction controlled the pool evolution and the distribution on a regional scale. Owing to the multiple periods of the pool formation and the reconstruction, the distribution of marine gas pools was complex both in space and in time, and the gas in the pools is heterogeneous. Pool elements, such as preservation conditions, traps and migration paths, and reservoir rocks and facies, also served as important control factors to marine gas pools in South China. Especially, the preservation conditions played a key role in maintaining marine oil and gas accumulations on a regional or local scale. According to several dominant control factors of a pool, the pool-controlling model can be constructed. As an example, the pool-controlling model of Sinian gas pool in Weiyuan gas field in Sichuan basin was summed up. ?? Higher Education Press and Springer-Verlag 2007.

IceAge: Chemical Evolution of Ices during Star Formation

NASA Astrophysics Data System (ADS)

McClure, Melissa; Bailey, J.; Beck, T.; Boogert, A.; Brown, W.; Caselli, P.; Chiar, J.; Egami, E.; Fraser, H.; Garrod, R.; Gordon, K.; Ioppolo, S.; Jimenez-Serra, I.; Jorgensen, J.; Kristensen, L.; Linnartz, H.; McCoustra, M.; Murillo, N.; Noble, J.; Oberg, K.; Palumbo, M.; Pendleton, Y.; Pontoppidan, K.; Van Dishoeck, E.; Viti, S.

2017-11-01

Icy grain mantles are the main reservoir for volatile elements in star-forming regions across the Universe, as well as the formation site of pre-biotic complex organic molecules (COMs) seen in our Solar System. We propose to trace the evolution of pristine and complex ice chemistry in a representative low-mass star-forming region through observations of a: pre-stellar core, Class 0 protostar, Class I protostar, and protoplanetary disk. Comparing high spectral resolution (R 1500-3000) and sensitivity (S/N 100-300) observations from 3 to 15 um to template spectra, we will map the spatial distribution of ices down to 20-50 AU in these targets to identify when, and at what visual extinction, the formation of each ice species begins. Such high-resolution spectra will allow us to search for new COMs, as well as distinguish between different ice morphologies,thermal histories, and mixing environments. The analysis of these data will result in science products beneficial to Cycle 2 proposers. A newly updated public laboratory ice database will provide feature identifications for all of the expected ices, while a chemical model fit to the observed ice abundances will be released publically as a grid, with varied metallicity and UV fields to simulate other environments. We will create improved algorithms to extract NIRCAM WFSS spectra in crowded fields with extended sources as well as optimize the defringing of MIRI LRS spectra in order to recover broad spectral features. We anticipate that these resources will be particularly useful for astrochemistry and spectroscopy of fainter, extended targets like star forming regions of the SMC/LMC or more distant galaxies.

Patterns and processes of drainage network evolution on Mars

NASA Astrophysics Data System (ADS)

Stucky de Quay, G.; Roberts, G. G.

2017-12-01

Large, complex drainage networks exist on the surface of Mars. These drainage patterns suggest that base level change, fluvial erosion, and deposition of sedimentary rock have played important roles in determining the shape of Martian topography. On Earth, base-level change plays the most important role in determining shapes of river profiles at wavelengths greater than a few kilometers. Wavelet transforms of Martian drainage patterns indicate that the same is true for most Martian drainage. For example, rivers in the Warrego Valles system have large convex-upward elevation profiles, with broad knickzones spanning more than 100 kilometers in length and few kilometers in height. More than 90% of the spectra power of rivers in this system resides at wavelengths greater than 10 kilometers. We examine the source of this long wavelength spectra power by jointly inverting suites of Martian river profiles for damped spatio-temporal histories of base-level change. Drainage networks were extracted from the High Resolution Stereo Camera (HRSC) topographic dataset using flow-routing algorithms. Calculated uplift rate histories indicate that regional uplift at wavelengths greater than 100 kilometers play an important role in determining the history of landscape evolution in Warrego Valles. In other regions (e.g. Holden and Eberswalde craters) joint inversion of families of rivers draining craters helps to constrain values of erosional parameters in a simplified version of the stream power erosional model. Integration of calculated incision rates suggest that we can perform a simple mass balance between eroded and deposited rock in regions where both depositional and erosional landforms exist.

Evidence for Precursors of the Coronal Hole Jets in Solar Bright Points

NASA Astrophysics Data System (ADS)

Bagashvili, Salome R.; Shergelashvili, Bidzina M.; Japaridze, Darejan R.; Kukhianidze, Vasil; Poedts, Stefaan; Zaqarashvili, Teimuraz V.; Khodachenko, Maxim L.; De Causmaecker, Patrick

2018-03-01

A set of 23 observations of coronal jet events that occurred in coronal bright points has been analyzed. The focus was on the temporal evolution of the mean brightness before and during coronal jet events. In the absolute majority of the cases either single or recurrent coronal jets (CJs) were preceded by slight precursor disturbances observed in the mean intensity curves. The key conclusion is that we were able to detect quasi-periodical oscillations with characteristic periods from sub-minute up to 3–4 minute values in the bright point brightness that precedes the jets. Our basic claim is that along with the conventionally accepted scenario of bright-point evolution through new magnetic flux emergence and its reconnection with the initial structure of the bright point and the coronal hole, certain magnetohydrodynamic (MHD) oscillatory and wavelike motions can be excited and these can take an important place in the observed dynamics. These quasi-oscillatory phenomena might play the role of links between different epochs of the coronal jet ignition and evolution. They can be an indication of the MHD wave excitation processes due to the system entropy variations, density variations, or shear flows. It is very likely a sharp outflow velocity transverse gradients at the edges between the open and closed field line regions. We suppose that magnetic reconnections can be the source of MHD waves due to impulsive generation or rapid temperature variations, and shear flow driven nonmodel MHD wave evolution (self-heating and/or overreflection mechanisms).

An overview of the MILAGRO 2006 Campaign: Mexico City emissions and their transport and transformation

NASA Astrophysics Data System (ADS)

Molina, L. T.; Madronich, S.; Gaffney, J. S.; Apel, E.; de Foy, B.; Fast, J.; Ferrare, R.; Herndon, S.; Jimenez, J. L.; Lamb, B.; Osornio-Vargas, A. R.; Russell, P.; Schauer, J. J.; Stevens, P. S.; Volkamer, R.; Zavala, M.

2010-09-01

MILAGRO (Megacity Initiative: Local And Global Research Observations) is an international collaborative project to examine the behavior and the export of atmospheric emissions from a megacity. The Mexico City Metropolitan Area (MCMA) - one of the world's largest megacities and North America's most populous city - was selected as the case study to characterize the sources, concentrations, transport, and transformation processes of the gases and fine particles emitted to the MCMA atmosphere and to evaluate the regional and global impacts of these emissions. The findings of this study are relevant to the evolution and impacts of pollution from many other megacities. The measurement phase consisted of a month-long series of carefully coordinated observations of the chemistry and physics of the atmosphere in and near Mexico City during March 2006, using a wide range of instruments at ground sites, on aircraft and satellites, and enlisting over 450 scientists from 150 institutions in 30 countries. Three ground supersites were set up to examine the evolution of the primary emitted gases and fine particles. Additional platforms in or near Mexico City included mobile vans containing scientific laboratories and mobile and stationary upward-looking lidars. Seven instrumented research aircraft provided information about the atmosphere over a large region and at various altitudes. Satellite-based instruments peered down into the atmosphere, providing even larger geographical coverage. The overall campaign was complemented by meteorological forecasting and numerical simulations, satellite observations and surface networks. Together, these research observations have provided the most comprehensive characterization of the MCMA's urban and regional atmospheric composition and chemistry that will take years to analyze and evaluate fully. In this paper we review over 120 papers resulting from the MILAGRO/INTEX-B Campaign that have been published or submitted, as well as relevant papers from the earlier MCMA-2003 Campaign, with the aim of providing a road map for the scientific community interested in understanding the emissions from a megacity such as the MCMA and their impacts on air quality and climate. This paper describes the measurements performed during MILAGRO and the results obtained on MCMA's atmospheric meteorology and dynamics, emissions of gases and fine particles, sources and concentrations of volatile organic compounds, urban and regional photochemistry, ambient particulate matter, aerosol radiative properties, urban plume characterization, and health studies. A summary of key findings from the field study is presented.

Rhyolitic tephra record of the Gona region, southern Afar Rift, Ethiopia: Characteristics correlation and chronology

NASA Astrophysics Data System (ADS)

Dunbar, N. W.; Brown, F. H.; Levin, N. E.; McIntosh, W. C.; Rogers, M.; Semaw, S.; Simpson, S. W.; Stinchcomb, G. E.

2016-12-01

The Gona region, on the western flank of the southern Afar Rift, in Ethiopia, contains a rich and complex tephra record that provides insight into structural evolution of the region and chronological controls on the local record of human evolution. Despite lack of source volcanoes in the Gona region, thick (up to 80 cm), fine-grained (20-500 µm), fresh, pure, glassy distal tephra layers, which are discontinuous and appear to have undergone significant secondary thickening shortly after deposition, are present in sediments deposited in the last two million years. Altered tephra are present in older sediments. New data are consistent with those reported by Quade et al. (2008), showing that tephra from Gona are typically rhyolitic, consistent with derivation from large, but distant volcanic eruptions. Significant geochemical variation is observed between different tephra layers, particularly with respect to FeO (ranging between 2 and 7.5 wt.% in different rhyolitic tephra), Ca, Mn, and Cl. Elements Na and K are variable, consistent with alkali mobility during glass hydration. Although some tephra layers contain feldspar and are thus datable using the 40Ar/39Ar, others are not directly datable, so must be geochemically linked to dated source eruptions. A unit of particular focus is the widespread marker tuff known locally as the Boolihinan tuff, which is associated with significant hominin fossils and artifacts. This locally aphyric unit, which consists of highly expanded rhyolitic glass, exhibits some geochemical variability, particularly with respect to SiO2 (74-78 wt.%), but yields a robust compositions with respect to Fe, Ca, Mn, and Cl. The Boolihinan tuff was previously tentatively correlated to a 1.6 Ma tephra found in DSDP core DEM-4-1. However, we suggest here a more robust correlation to two samples of an unwelded ignimbrite with 40Ar/39Ar ages of 1.281±0.061 and 1.253±0.041 (27-01 and 27-05 of Morgan et al., 2012) from the Melka Kunture area, which is over 300 km from the Gona field area. The Boolihinan tuff is interpreted to be the ashfall equivalent of the unwelded ignimbrite. This correlation provides a chronological marker which in turn provides improved age constraints to the fossils and artifacts at Gona that are found in association with this tephra.

A time dependent approach to model X-ray and γ-ray light curves of Mrk 421 observed during the flare in February 2010

NASA Astrophysics Data System (ADS)

Singh, K. K.; Sahayanathan, S.; Sinha, A.; Bhatt, N.; Tickoo, A. K.; Yadav, K. K.; Rannot, R. C.; Chandra, P.; Venugopal, K.; Marandi, P.; Kumar, N.; Goyal, H. C.; Goyal, A.; Agarwal, N. K.; Kothari, M.; Chanchalani, K.; Dhar, V. K.; Chouhan, N.; Bhat, C. K.; Koul, M. K.; Koul, R.

2017-07-01

Strong X-ray and γ-ray flares have been detected in February 2010 from the high synchrotron peaked blazar Mrk 421 (z = 0.031). With the motivation of understanding the physics involved in this flaring activity, we study the variability of the source in X-ray and γ-ray energy bands during the period February 10-23, 2010 (MJD 55237-55250). We use near simultaneous X-ray data collected by MAXI, Swift-XRT and γ-ray data collected by Fermi-LAT and TACTIC along with the optical V-band observations by SPOLat Steward Observatory. We observe that the variation in the one day averaged flux from the source during the flare is characterized by fast rise and slow decay. Besides, the TeV γ-ray flux shows a strong correlation with the X-ray flux, suggesting the former to be an outcome of synchrotron self Compton emission process. To model the observed X-ray and γ-ray light curves, we numerically solve the kinetic equation describing the evolution of particle distribution in the emission region. The injection of particle distribution into the emission region, from the putative acceleration region, is assumed to be a time dependent power law. The synchrotron and synchrotron self Compton emission from the evolving particle distribution in the emission region are used to reproduce the X-ray and γ-ray flares successfully. Our study suggests that the flaring activity of Mrk 421 can be an outcome of an efficient acceleration process associated with the increase in underlying non-thermal particle distribution.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lugaz, N.; Shibata, K.; Downs, C.

We present a numerical investigation of the coronal evolution of a coronal mass ejection (CME) on 2005 August 22 using a three-dimensional thermodynamic magnetohydrodynamic model, the space weather modeling framework. The source region of the eruption was anemone active region (AR) 10798, which emerged inside a coronal hole. We validate our modeled corona by producing synthetic extreme-ultraviolet (EUV) images, which we compare to EIT images. We initiate the CME with an out-of-equilibrium flux rope with an orientation and chirality chosen in agreement with observations of an H{alpha} filament. During the eruption, one footpoint of the flux rope reconnects with streamermore » magnetic field lines and with open field lines from the adjacent coronal hole. It yields an eruption which has a mix of closed and open twisted field lines due to interchange reconnection and only one footpoint line-tied to the source region. Even with the large-scale reconnection, we find no evidence of strong rotation of the CME as it propagates. We study the CME deflection and find that the effect of the Lorentz force is a deflection of the CME by about 3{sup 0} R{sup -1}{sub sun} toward the east during the first 30 minutes of the propagation. We also produce coronagraphic and EUV images of the CME, which we compare with real images, identifying a dimming region associated with the reconnection process. We discuss the implication of our results for the arrival at Earth of CMEs originating from the limb and for models to explain the presence of open field lines in magnetic clouds.« less

Features of Microwave Radiation and Magnetographic Characteristics of Solar Active Region NOAA 12242 Before the X1.8 Flare on December 20, 2014

NASA Astrophysics Data System (ADS)

Abramov-Maximov, V. E.; Borovik, V. N.; Opeikina, L. V.; Tlatov, A. G.; Yasnov, L. V.

2017-12-01

This paper continues the cycle of authors' works on the detection of precursors of large flares (M5 and higher classes) in active regions (ARs) of the Sun by their microwave radiation and magnetographic characteristics. Generalization of the detected precursors of strong flares can be used to develop methods for their prediction. This paper presents an analysis of the development of NOAA AR 12242, in which an X1.8 flare occurred on December 20, 2014. The analysis is based on regular multiazimuth and multiwavelength observations with the RATAN-600 radio telescope in the range 1.65-10 cm with intensity and circular polarization analysis and data from the Solar Dynamics Observatory (SDO). It was found that a new component appeared in the AR microwave radiation two days before the X-flare. It became dominant in the AR the day before the flare and significantly decreased after the flare. The use of multiazimuth observations from RATAN-600 and observations at 1.76 cm from the Nobeyama Radioheliograph made it possible to identify the radio source that appeared before the X-flare with the site of the closest convergence of opposite polarity fields near the neutral line in the AR. It was established that the X-flare occurred 20 h after the total gradient of the magnetic field of the entire region calculated from SDO/HMI data reached its maximum value. Analysis of the evolution of the microwave source that appeared before the X-flare in AR 12242 and comparison of its parameters with the parameters of other components of the AR microwave radiation showed that the new source can be classified as neutral line associated sources (NLSs), which were repeatedly detected by the RATAN-600 and other radio telescopes 1-3 days before the large flares.

Identifying sources of acidity and spatial distribution of acid sulfate soils in the Anglesea River catchment, southern Australia

NASA Astrophysics Data System (ADS)

Wong, Vanessa; Yau, Chin; Kennedy, David

2015-04-01

Globally, coastal and estuarine floodplains are frequently underlain by sulfidic sediments. When exposed to oxygen, sulfidic sediments oxidise to form acid sulfate soils, adversely impacting on floodplain health and adjacent aquatic ecoystems. In eastern Australia, our understanding of the formation of these coastal and estuarine floodplains, and hence, spatial distribution of acid sulfate soils, is relatively well established. These soils have largely formed as a result of sedimentation of coastal river valleys approximately 6000 years BP when sea levels were one to two metres higher. However, our understanding of the evolution of estuarine systems and acid sulfate soil formation, and hence, distribution, in southern Australia remains limited. The Anglesea River, in southern Australia, is subjected to frequent episodes of poor water quality and low pH resulting in closure of the river and, in extreme cases, large fish kill events. This region is heavily reliant on tourism and host to a number of iconic features, including the Great Ocean Road and Twelve Apostles. Poor water quality has been linked to acid leakage from mining activities and Tertiary-aged coal seams, peat swamps and acid sulfate soils in the region. However, our understanding of the sources of acidity and distribution of acid sulfate soils in this region remains poor. In this study, four sites on the Anglesea River floodplain were sampled, representative of the main vegetation communities. Peat swamps and intertidal marshes were both significant sources of acidity on the floodplain in the lower catchment. However, acid neutralising capacity provided by carbonate sands suggests that there are additional sources of acidity higher in the catchment. This pilot study has highlighted the complexity in the links between the floodplain, upper catchment and waterways with further research required to understand these links for targeted acid management strategies.

U-Pb zircon geochronology of the Paleogene - Neogene volcanism in the NW Anatolia: Its implications for the Late Mesozoic-Cenozoic geodynamic evolution of the Aegean

NASA Astrophysics Data System (ADS)

Ersoy, E. Yalçın; Akal, Cüneyt; Genç, Ş. Can; Candan, Osman; Palmer, Martin R.; Prelević, Dejan; Uysal, İbrahim; Mertz-Kraus, Regina

2017-10-01

The northern Aegean region was shaped by subduction, obduction, collision, and post-collisional extension processes. Two areas in this region, the Rhodope-Thrace-Biga Peninsula to the west and Armutlu-Almacık-Nallıhan (the Central Sakarya) to the east, are characterized by extensive Eocene to Miocene post-collisional magmatic associations. We suggest that comparison of the Cenozoic magmatic events of these two regions may provide insights into the Late Mesozoic to Cenozoic tectonic evolution of the Aegean. With this aim, we present an improved Cenozoic stratigraphy of the Biga Peninsula derived from a new comprehensive set of U-Pb zircon age data obtained from the Eocene to Miocene volcanic units in the region. The compiled radiometric age data show that calc-alkaline volcanic activity occurred at 43-15 Ma in the Biga Peninsula, 43-17 Ma in the Rhodope and Thrace regions, and 53-38 Ma in the Armutlu-Almacık-Nallıhan region, which are slightly overlapping. We discuss the possible cause for the distinct Cenozoic geodynamic evolution of the eastern and western parts of the region, and propose that the Rhodope, Thrace and Biga regions in the north Aegean share the same Late Mesozoic to Cenozoic geodynamic evolution, which is consistent with continuous subduction, crustal accretion, southwestward trench migration and accompanying extension; all preceded by the Late Cretaceous - Paleocene collision along the Vardar suture zone. In contrast, the Armutlu-Almacık-Nallıhan region was shaped by slab break-off and related processes following the Late Cretaceous - Paleocene collision along the İzmir-Ankara suture zone. The eastern and western parts of the region are presently separated by a northeast-southwest trending transfer zone that was likely originally present as a transform fault in the subducted Tethys oceanic crust, and demonstrates that the regional geodynamic evolution can be strongly influenced by the geographical distribution of geologic features on the subducting plate.

Soil HONO Emissions and Its Potential Impact on the Atmospheric Chemistry and Nitrogen Cycle

NASA Astrophysics Data System (ADS)

Su, H.; Chen, C.; Zhang, Q.; Poeschl, U.; Cheng, Y.

2014-12-01

Hydroxyl radicals (OH) are a key species in atmospheric photochemistry. In the lower atmosphere, up to ~30% of the primary OH radical production is attributed to the photolysis of nitrous acid (HONO), and field observations suggest a large missing source of HONO. The dominant sources of N(III) in soil, however, are biological nitrification and denitrification processes, which produce nitrite ions from ammonium (by nitrifying microbes) as well as from nitrate (by denitrifying microbes). We show that soil nitrite can release HONO and explain the reported strength and diurnal variation of the missing source. The HONO emissions rates are estimated to be comparable to that of nitric oxide (NO) and could be an important source of atmospheric reactive nitrogen. Fertilized soils appear to be particularly strong sources of HONO. Thus, agricultural activities and land-use changes may strongly influence the oxidizing capacity of the atmosphere. A new HONO-DNDC model was developed to simulate the evolution of HONO emissions in agriculture ecosystems. Because of the widespread occurrence of nitrite-producing microbes and increasing N and acid deposition, the release of HONO from soil may also be important in natural environments, including forests and boreal regions. Reference: Su, H. et al., Soil Nitrite as a Source of Atmospheric HONO and OH Radicals, Science, 333, 1616-1618, 10.1126/science.1207687, 2011.

Historical evolution of sources identification by means of Receptor Modeling in the Metropolitan Area of São Paulo, Brazil.

NASA Astrophysics Data System (ADS)

Miranda, R. M.; Andrade, M. D. F.; Marien, Y., Sr.

2017-12-01

The atmospheric aerosols sources have been identified in Sao Paulo since the 80´s with the use of receptor models. The Metropolitan Area of São Paulo (MASP) is a megacity with a population of 21 million, corresponding to more than 11% of the total population of Brazil. The first results for the identification of sources of particles were obtained with the application of Absolute Principal Component Analysis, Factor Analysis and Chemical Mass Balance. More recently the Positive Matrix Factorization has been used in combination with the other receptor models. With the improvement of the aerosol composition analytical determination (more elements and better resolution) the source identification has became more accurate. But, in spite of that, the main sources are the same for fine particles: vehicular emission, secondary formation and biomass burning. The large amount of biofuels used in the MASP makes this region an important example of the atmospheric chemistry of fossil fuel and biofuel emissions. The 7 million vehicles can run on gasohol, ethanol (95% ethanol + 5% gasoline) and biodiesel (mostly for trucks and buses). We have considered the Black Carbon as the tracer for diesel engines and biomass burning, being this last source associated not only with burning of sugar cane plantation and forest fires, but also with wood and charcoal used in restaurant and domestic cooking and residues burning. The responsibility of the vehicular emission to the fine particles has been maintained in approximately 50% of the mass. The soil resuspension was associated with 8% of the fine particles origin. We are presenting the data obtained from experiments performed from 1983 to 2014, not continuously and mainly performed in the winter time. It is a long period of data that is going to be considered. The previous results obtained with the application of PCA were compared to that obtained with PMF applied to the historical data collected at MASP, showing the evolution of the participation of mobile and biomass burning.

The Evolution of Compact Binary Star Systems.

PubMed

Postnov, Konstantin A; Yungelson, Lev R

2006-01-01

We review the formation and evolution of compact binary stars consisting of white dwarfs (WDs), neutron stars (NSs), and black holes (BHs). Binary NSs and BHs are thought to be the primary astrophysical sources of gravitational waves (GWs) within the frequency band of ground-based detectors, while compact binaries of WDs are important sources of GWs at lower frequencies to be covered by space interferometers (LISA). Major uncertainties in the current understanding of properties of NSs and BHs most relevant to the GW studies are discussed, including the treatment of the natal kicks which compact stellar remnants acquire during the core collapse of massive stars and the common envelope phase of binary evolution. We discuss the coalescence rates of binary NSs and BHs and prospects for their detections, the formation and evolution of binary WDs and their observational manifestations. Special attention is given to AM CVn-stars - compact binaries in which the Roche lobe is filled by another WD or a low-mass partially degenerate helium-star, as these stars are thought to be the best LISA verification binary GW sources.

The missing links of neutron star evolution in the eROSITA all-sky X-ray survey

NASA Astrophysics Data System (ADS)

Pires, A. M.

2017-12-01

The observational manifestation of a neutron star is strongly connected with the properties of its magnetic field. During the star’s lifetime, the field strength and its changes dominate the thermo-rotational evolution and the source phenomenology across the electromagnetic spectrum. Signatures of magnetic field evolution are best traced among elusive groups of X-ray emitting isolated neutron stars (INSs), which are mostly quiet in the radio and γ-ray wavelengths. It is thus important to investigate and survey INSs in X-rays in the hope of discovering peculiar sources and the long-sought missing links that will help us to advance our understanding of neutron star evolution. The Extended Röntgen Survey with an Imaging Telescope Array (eROSITA), the primary instrument on the forthcoming Spectrum-RG mission, will scan the X-ray sky with unprecedented sensitivity and resolution. The survey has thus the unique potential to unveil the X-ray faint end of the neutron star population and probe sources that cannot be assessed by standard pulsar surveys.

Global EDGAR v4.1 emissions of air pollutants: analysis of impacts of emissions abatement in industry and road transport on regional and global scale

NASA Astrophysics Data System (ADS)

Janssens-Maenhout, G.; Olivier, J. G.; Doering, U. M.; van Aardenne, J.; Monni, S.; Pagliari, V.; Peters, J. A.

2010-12-01

The new version v4.1 of the Emission Database for Global Atmospheric Research (EDGAR) compiled by JRC and PBL provides independent estimates of the global anthropogenic emissions and emission trends of precursors of tropospheric ozone (CO, NMVOC, NOx) and acidifying substances (NOx, NH3, SO2) for the period 1970-2005. All emissions are detailed at country level consistently using the same technology-based methodology, combining activity data (international statistics) from publicly available sources and to the extent possible emission factors as recommended by the EMEP/EEA air pollutant emission inventory guidebook. By using high resolution global grid maps per source category of area sources and point sources, we also compiled datasets with annual emissions on a 0.1x0.1 degree grid, as input for atmospheric models. We provide full and up-to-date inventories per country, also for developing countries. Moreover, the time series back in time to 1970 provides for the trends in official national inventories a historic perspective. As part of our objective to contribute to more reliable inventories by providing a reference emissions database for emission scenarios, inventory comparisons and for atmospheric modellers, we strive to transparently document all data sources used and assumptions made where data was missing, in particular for assumptions made on the shares of technologies where relevant. Technology mixes per country or region were taken from other data sources (such as the Platts database) or estimated using other sources or countries as proxy. The evolution in the adoption of technologies world-wide over the 35 years covered by EDGAR v4.1 will be illustrated for the power industry and the road transport sectors, in particular for Europe and the US. Similarly the regional and global impacts of implemented control measures and end-of pipe abatements will be illustrated by the examples of - NOx and SO2 end-of pipe abatements being implemented since the late eighties for power plants in Europe, and since 2000 appearing in the economically emerging countries such as China; - EURO3 control measures, a European standard for passenger cars, which now reached the age of being exported to African and Latin-American countries. An outlook will be given on the current readiness of Europe to meet the challenging goals of the National Emission Ceilings directive.

Titan Polar Landscape Evolution

NASA Technical Reports Server (NTRS)

Moore, Jeffrey M.

2016-01-01

With the ongoing Cassini-era observations and studies of Titan it is clear that the intensity and distribution of surface processes (particularly fluvial erosion by methane and Aeolian transport) has changed through time. Currently however, alternate hypotheses substantially differ among specific scenarios with respect to the effects of atmospheric evolution, seasonal changes, and endogenic processes. We have studied the evolution of Titan's polar region through a combination of analysis of imaging, elevation data, and geomorphic mapping, spatially explicit simulations of landform evolution, and quantitative comparison of the simulated landscapes with corresponding Titan morphology. We have quantitatively evaluated alternate scenarios for the landform evolution of Titan's polar terrain. The investigations have been guided by recent geomorphic mapping and topographic characterization of the polar regions that are used to frame hypotheses of process interactions, which have been evaluated using simulation modeling. Topographic information about Titan's polar region is be based on SAR-Topography and altimetry archived on PDS, SAR-based stereo radar-grammetry, radar-sounding lake depth measurements, and superposition relationships between geomorphologic map units, which we will use to create a generalized topographic map.

Automated Identification of Coronal Holes from Synoptic EUV Maps

NASA Astrophysics Data System (ADS)

Hamada, Amr; Asikainen, Timo; Virtanen, Ilpo; Mursula, Kalevi

2018-04-01

Coronal holes (CHs) are regions of open magnetic field lines in the solar corona and the source of the fast solar wind. Understanding the evolution of coronal holes is critical for solar magnetism as well as for accurate space weather forecasts. We study the extreme ultraviolet (EUV) synoptic maps at three wavelengths (195 Å/193 Å, 171 Å and 304 Å) measured by the Solar and Heliospheric Observatory/Extreme Ultraviolet Imaging Telescope (SOHO/EIT) and the Solar Dynamics Observatory/Atmospheric Imaging Assembly (SDO/AIA) instruments. The two datasets are first homogenized by scaling the SDO/AIA data to the SOHO/EIT level by means of histogram equalization. We then develop a novel automated method to identify CHs from these homogenized maps by determining the intensity threshold of CH regions separately for each synoptic map. This is done by identifying the best location and size of an image segment, which optimally contains portions of coronal holes and the surrounding quiet Sun allowing us to detect the momentary intensity threshold. Our method is thus able to adjust itself to the changing scale size of coronal holes and to temporally varying intensities. To make full use of the information in the three wavelengths we construct a composite CH distribution, which is more robust than distributions based on one wavelength. Using the composite CH dataset we discuss the temporal evolution of CHs during the Solar Cycles 23 and 24.

Late Pliocene establishment of exorheic drainage in the northeastern Tibetan Plateau as evidenced by the Wuquan Formation in the Lanzhou Basin

NASA Astrophysics Data System (ADS)

Guo, Benhong; Liu, Shanpin; Peng, Tingjiang; Ma, Zhenhua; Feng, Zhantao; Li, Meng; Li, Xiaomiao; Li, Jijun; Song, Chunhui; Zhao, Zhijun; Pan, Baotian; Stockli, Daniel F.; Nie, Junsheng

2018-02-01

The fluvial archives in the upper-reach Yellow River basins provide important information about drainage history of the northeastern Tibetan Plateau (TP) associated with geomorphologic evolution and climate change. However, the Pliocene fluvial strata within this region have not been studied in detail, hence limiting the understanding of the late Cenozoic development of regional fluvial systems. In this paper, we present the results of a study of the geochronology, sedimentology, and provenance of the fluvial sequence of the Wuquan Formation in the Lanzhou Basin in the northeastern TP. Magnetostratigraphic and cosmogenic nuclide burial ages indicate that the Wuquan Formation was deposited during 3.6-2.2 Ma. Furthermore, sedimentary facies, gravel composition, paleocurrent data, and detrital zircon Usbnd Pb age spectra reveal that the fluvial sequence resembles the terraces of the Yellow River in terms of source area, flow direction, and depositional environment. Our results indicate that a paleo-drainage system flowing out of the northeastern TP was established by ca. 3.6 Ma and that the upstream parts of the Yellow River must have developed subsequently from this paleo-drainage system. The late Pliocene drainage system fits well with the dramatic uplift of the northeastern TP, an intensified Asian summer monsoon, and global increase in erosion rates, which may reflect interactions between geomorphic evolution, tectonic deformation, and climate change.

Star Formation in the Central Regions of Galaxies

NASA Astrophysics Data System (ADS)

Tsai, Mengchun

2015-08-01

The galactic central region connects the galactic nucleus to the host galaxy. If the central black hole co-evolved with the host galaxies, there should be some evidence left in the central region. We use the environmental properties in the central regions such as star-forming activity, stellar population and molecular abundance to figure out a possible scenario of the evolution of galaxies. In this thesis at first we investigated the properties of the central regions in the host galaxies of active and normal galaxies. We used radio emission around the nuclei of the host galaxies to represent activity of active galactic nuclei (AGNs), and used infrared ray (IR) emission to represent the star-forming activity and stellar population of the host galaxies. We determined that active galaxies have higher stellar masses (SMs) within the central kiloparsec radius than normal galaxies do independent of the Hubble types of the host galaxies; but both active and normal galaxies exhibit similar specific star formation rates (SSFRs). We also discovered that certain AGNs exhibit substantial inner stellar structures in the IR images; most of the AGNs with inner structures are Seyferts, whereas only a few LINERs exhibit inner structures. We note that the AGNs with inner structures show a positive correlation between the radio activity of the AGNs and the SFRs of the host galaxies, but the sources without inner structures show a negative correlation between the radio power and the SFRs. These results might be explained with a scenario of starburst-AGN evolution. In this scenario, AGN activities are triggered following a nuclear starburst; during the evolution, AGN activities are accompanied by SF activity in the inner regions of the host galaxies; at the final stage of the evolution, the AGNs might transform into LINERs, exhibiting weak SF activity in the central regions of the host galaxies. For further investigation about the inner structure, we choose the most nearby and luminous Seyfert galaxy with inner structure as an example. In this thesis, we present CO(3-2) interferometric observations of the central region of the Seyfert 2 galaxy NGC1068 using the Submillimeter Array, together with CO(1-0) data taken with the Owens Valley Radio Observatory Millimeter Array. Both the CO(3-2) and CO(1-0) emission lines are mainly distributed within ~5 arcsec of the nucleus and along the spiral arms, but the intensity distributions show differences; the CO(3-2) map peaks in the nucleus, while the CO(1-0) emission is mainly located along the spiral arms. The CO(3-2)/CO(1-0) ratio is about 3.1 in the nucleus, which is four times as large as the average line ratio in the spiral arms, suggesting that the molecular gas there must be affected by the radiation arising from the AGN. On the other hand, the line ratios in the spiral arms vary over a wide range from 0.24 to 2.34 with a average value around 0.75, which is similar to the line ratios of star-formation regions, indicating that the molecular gas is affected by star formation. Besides, we see a tight correlation between CO(3-2)/(1-0) ratios in the spiral arms and star formation rate surface densities derived from Spitzer 8 micron dust flux densities. We also compare the CO(3-2)/(1-0) ratio and the star formation rate at different positions within the spiral arms; both are found to decrease as the radius from the nucleus increases.

Provenance from zircon U-Pb age distributions in crustally contaminated granitoids

NASA Astrophysics Data System (ADS)

Bahlburg, Heinrich; Berndt, Jasper

2016-05-01

The basement of sedimentary basins is often entirely covered by a potentially multi-stage basin fill and therefore removed from direct observation and sampling. Melts intruding through the basin stratigraphy at a subsequent stage in the geological evolution of a region may assimilate significant volumes of country rocks. This component may be preserved in the intrusive body either as xenoliths or it may be reflected only by the age spectrum of incorporated zircons. Here we present the case of an Ordovician calc-alkaline intrusive belt in NW Argentina named the "Faja Eruptiva de la Puna Oriental" (Faja Eruptiva), which in the course of intrusion sampled the unexposed and unknown basement of the Ordovician basin in this region, and parts of the basin stratigraphy. We present new LA-ICP-MS U-Pb ages on zircons from 9 granodiorites and granites of the Faja Eruptiva. The main part of the Faja Eruptiva intruded c. 445 Ma in the Late Ordovician. The zircon ages obtained from the intrusive rocks have a large spread between 2683.5 ± 21.6 and 440.0 ± 4.9 Ma and reflect the underlying crust and may be interpreted in several ways. The inherited zircons may have been derived from the oldest known unit in the region, the thick siliciclastic turbidite successions of the upper Neoproterozoic-lower Cambrian Puncoviscana Formation, which is inferred to represent the basement of the NW Argentina. The basement to the Puncoviscana Formation is not known. Alternatively, the inherited zircons may reflect the geochronological structure of the entire unexposed Early Paleozoic crust underlying this region of which the Puncoviscana Formation was only one component. This crust likely contained rocks pertaining to and detritus derived from earlier orogenic cycles of the southwestern Amazonia craton, including sources of Early Meso- and Paleoproterozoic age. Detritus derived, in turn, from the Faja Eruptiva intrusive belt reflects the origin of the granitoids as well as the inherited geochronological and isotope geochemical structure of either the basement and/or distant sources having supplied material to the basement rocks. If unrecognized, sediment formed from such granitoid sources may erroneously be used to infer the exposure of, and direct detrital contributions from, a variety of older source rocks in fact not directly involved in the studied source-sink system.

The Herschel Deconfusion Project: Constraining the Cosmic Evolution of Dust in Galaxies Using the Deepest Available Data

NASA Astrophysics Data System (ADS)

Ferguson, Henry

With the end of the Herschel mission and no immediate successor at far-infrared wavelengths, it is imperative to extract as much information as possible from the existing data. The difference between the theoretical noise limit and the confusion limit suggests that significant improvements can be made with a more sophisticated treatment of source confusion. This is possible because we have a lot of information about the Herschel deep fields from other wavelengths. The project will use existing already-reduced data from Herschel's deepest observations, which targeted the CANDELS. These data have a wealth of observations from Hubble, Spitzer, Chandra and many other telescopes. The main work will be to develop and employ a new Bayesian technique that incorporates spectral-energy-distribution priors to constrain the range of likely far-infrared fluxes for each source that is detected by Hubble. The far-IR images are then segmented and the regions which are likely to suffer the most confusion are simultaneously fit, using the (broad) constraints on the likely farIR fluxes as a Bayesian prior. The first pass of photometry will yield reliable photometry for sources at least a factor of two fainter than existing catalogs. Subsequent passes can yield full probability distributions for the ensemble Far-IR SEDs of much fainter sources (overcoming some of the limitations of stacking in image space). We will used the improved and deeper FIR photometry to address two "crises" in reconciling galaxy evolution models with high-z galaxy observations: (1) the surprisingly young ages of most bright Lyman-break galaxies at redshift z=3 and (2) the surprisingly high star-formation rates and dust masses high-redshift sub-mm and FIR-selected galaxies. The former could potentially be explained if many of the descendants of UVbright galaxies at z=4 have too much dust by z=3 to be included in Lyman-break samples. The latter problem could be resolved if the fluxes of many FIR and sub-mm selected galaxies are affected by blending. The project will employ state-of-the art semi-analytical models for galaxy evolution, both for guidance in developing flexible Bayesian priors, and for guidance on the interpretation of the results. As part of the work we plan to further test and improve the treatment of dust in these models.

Aspirations and Expectations: Comparing Scientist and Teacher Views as a Source of Ideas for Teaching Evolution

ERIC Educational Resources Information Center

Weiss, Matthias; Dreesmann, Daniel C.

2014-01-01

Biological evolution still lacks representation in school, especially below high school level. In order to find new implications that could help achieve significant improvement in teaching evolution, twelve expert interviews with both renowned researchers and experienced science teachers were conducted. Results of the comparison between the…

Evolution of brain region volumes during artificial selection for relative brain size.

PubMed

Kotrschal, Alexander; Zeng, Hong-Li; van der Bijl, Wouter; Öhman-Mägi, Caroline; Kotrschal, Kurt; Pelckmans, Kristiaan; Kolm, Niclas

2017-12-01

The vertebrate brain shows an extremely conserved layout across taxa. Still, the relative sizes of separate brain regions vary markedly between species. One interesting pattern is that larger brains seem associated with increased relative sizes only of certain brain regions, for instance telencephalon and cerebellum. Till now, the evolutionary association between separate brain regions and overall brain size is based on comparative evidence and remains experimentally untested. Here, we test the evolutionary response of brain regions to directional selection on brain size in guppies (Poecilia reticulata) selected for large and small relative brain size. In these animals, artificial selection led to a fast response in relative brain size, while body size remained unchanged. We use microcomputer tomography to investigate how the volumes of 11 main brain regions respond to selection for larger versus smaller brains. We found no differences in relative brain region volumes between large- and small-brained animals and only minor sex-specific variation. Also, selection did not change allometric scaling between brain and brain region sizes. Our results suggest that brain regions respond similarly to strong directional selection on relative brain size, which indicates that brain anatomy variation in contemporary species most likely stem from direct selection on key regions. © 2017 The Author(s). Evolution © 2017 The Society for the Study of Evolution.

Gains and Losses of Transcription Factor Binding Sites in Saccharomyces cerevisiae and Saccharomyces paradoxus

PubMed Central

Schaefke, Bernhard; Wang, Tzi-Yuan; Wang, Chuen-Yi; Li, Wen-Hsiung

2015-01-01

Gene expression evolution occurs through changes in cis- or trans-regulatory elements or both. Interactions between transcription factors (TFs) and their binding sites (TFBSs) constitute one of the most important points where these two regulatory components intersect. In this study, we investigated the evolution of TFBSs in the promoter regions of different Saccharomyces strains and species. We divided the promoter of a gene into the proximal region and the distal region, which are defined, respectively, as the 200-bp region upstream of the transcription starting site and as the 200-bp region upstream of the proximal region. We found that the predicted TFBSs in the proximal promoter regions tend to be evolutionarily more conserved than those in the distal promoter regions. Additionally, Saccharomyces cerevisiae strains used in the fermentation of alcoholic drinks have experienced more TFBS losses than gains compared with strains from other environments (wild strains, laboratory strains, and clinical strains). We also showed that differences in TFBSs correlate with the cis component of gene expression evolution between species (comparing S. cerevisiae and its sister species Saccharomyces paradoxus) and within species (comparing two closely related S. cerevisiae strains). PMID:26220934

Monitoring an air pollution episode in Shenzhen by combining MODIS satellite images and the HYSPLIT model

NASA Astrophysics Data System (ADS)

Li, Lili; Liu, Yihong; Wang, Yunpeng

2017-07-01

Urban air pollution is influenced not only by local emission sources including industry and vehicles, but also greatly by regional atmospheric pollutant transportation from the surrounding areas, especially in developed city clusters, like the Pearl River Delta (PRD). Taking an air pollution episode in Shenzhen as an example, this paper investigates the occurrence and evolution of the pollution episode and identifies the transport pathways of air pollutants in Shenzhen by combining MODIS satellite images and HYSPLIT back trajectory analysis. Results show that this pollution episode is mainly caused by the local emission of pollutants in PRD and oceanic air masses under specific weather conditions.

The Evolution of Human Genetic and Phenotypic Variation in Africa

PubMed Central

Campbell, Michael C.

2010-01-01

Africa is the birthplace of modern humans, and is the source of the geographic expansion of ancestral populations into other regions of the world. Indigenous Africans are characterized by high levels of genetic diversity within and between populations. The pattern of genetic variation in these populations has been shaped by demographic events occurring over the last 200,000 years. The dramatic variation in climate, diet, and exposure to infectious disease across the continent has also resulted in novel genetic and phenotypic adaptations in extant Africans. This review summarizes some recent advances in our understanding of the demographic history and selective pressures that have influenced levels and patterns of diversity in African populations. PMID:20178763

Modeling plasma loudspeakers.

PubMed

Béquin, Ph; Castor, K; Herzog, Ph; Montembault, V

2007-04-01

This paper deals with the acoustic modeling and measurement of a needle-to-grid plasma loudspeaker using a negative Corona discharge. In the first part, we summarize the model described in previous papers, where the electrode gap is divided into a charged particle production region near the needle and a drift region which occupies most of the inter-electrode gap. In each region, interactions between charged and neutral particles in the ionized gas lead to a perturbation of the surrounding air, and thus generate an acoustic field. In each region, viewed as a separate acoustic source, an acoustical model requiring only a few parameters is proposed. In the second part of the paper, an experimental setup is presented for measuring acoustic pressures and directivities. This setup was developed and used to study the evolution of the parameters with physical properties, such as the geometrical and electrical configuration and the needle material. In the last part of this paper, a study on the electroacoustic efficiency of the plasma loudspeaker is described, and differences with respect to the design parameters are analyzed. Although this work is mainly aimed at understanding transduction phenomena, it may be found useful for the development of an audio loudspeaker.

Comparison of Orbital Parameters for GEO Debris Predicted by LEGEND and Observed by MODEST: Can Sources of Orbital Debris be Identified?

NASA Technical Reports Server (NTRS)

Barker, Edwin S.; Matney, M. J.; Liou, J.-C.; Abercromby, K. J.; Rodriquez, H. M.; Seitzer, P.

2006-01-01

Since 2002 the National Aeronautics and Space Administration (NASA) has carried out an optical survey of the debris environment in the geosynchronous Earth-orbit (GEO) region with the Michigan Orbital Debris Survey Telescope (MODEST) in Chile. The survey coverage has been similar for 4 of the 5 years allowing us to follow the orbital evolution of Correlated Targets (CTs), both controlled and un-controlled objects, and Un-Correlated Targets (UCTs). Under gravitational perturbations the distributions of uncontrolled objects, both CTs and UCTs, in GEO orbits will evolve in predictable patterns, particularly evident in the inclination and right ascension of the ascending node (RAAN) distributions. There are several clusters (others have used a "cloud" nomenclature) in observed distributions that show evolution from year to year in their inclination and ascending node elements. However, when MODEST is in survey mode (field-of-view approx.1.3deg) it provides only short 5-8 minute orbital arcs which can only be fit under the assumption of a circular orbit approximation (ACO) to determine the orbital parameters. These ACO elements are useful only in a statistical sense as dedicated observing runs would be required to obtain sufficient orbital coverage to determine a set of accurate orbital elements and then to follow their evolution. Identification of the source(s) for these "clusters of UCTs" would be advantageous to the overall definition of the GEO orbital debris environment. This paper will set out to determine if the ACO elements can be used to in a statistical sense to identify the source of the "clustering of UCTs" roughly centered on an inclination of 12deg and a RAAN of 345deg. The breakup of the Titan 3C-4 transtage on February 21, 1992 has been modeled using NASA s LEGEND (LEO-to-GEO Environment Debris) code to generate a GEO debris cloud. Breakup fragments are created based on the NASA Standard Breakup Model (including fragment size, area-to-mass (A/M), and delta-V distributions). Once fragments are created, they are propagated forward in time with a subroutine GEOPROP. Perturbations included in GEOPROP are those due to solar/lunar gravity, radiation pressure, and major geopotential terms. The question to be addressed: are the UCTs detected by MODEST in this inclination/RAAN region related to the Titan 3C-4 breakup? Discussion will include the observational biases in attempting to detect a specific, uncontrolled target during given observing session. These restrictions include: (1) the length of the observing session which is 8 hours or less at any given date or declination; (2) the assumption of ACO elements for detected object when the breakup model predicts debris with non-zero eccentricities; (3) the size and illumination or brightness of the debris predicted by the model and the telescope/sky limiting magnitude.

Detrital and volcanic zircon U-Pb ages from southern Mendoza (Argentina): An insight on the source regions in the northern part of the Neuquén Basin

NASA Astrophysics Data System (ADS)

Naipauer, Maximiliano; Tapia, Felipe; Mescua, José; Farías, Marcelo; Pimentel, Marcio M.; Ramos, Victor A.

2015-12-01

The infill of the Neuquén Basin recorded the Meso-Cenozoic geological and tectonic evolution of the southern Central Andes being an excellent site to investigate how the pattern of detrital zircon ages varies trough time. In this work we analyze the U-Pb (LA-MC-ICP-MS) zircon ages from sedimentary and volcanic rocks related to synrift and retroarc stages of the northern part of the Neuquén Basin. These data define the crystallization age of the synrift volcanism at 223 ± 2 Ma (Cerro Negro Andesite) and the maximum depositional age of the original synrift sediments at ca. 204 Ma (El Freno Formation). Two different pulses of rifting could be recognized according to the absolute ages, the oldest developed during the Norian and the younger during the Rhaetian-Sinemurian. The source regions of the El Freno Formation show that the Choiyoi magmatic province was the main source rock of sediment supply. An important amount of detrital zircons with Triassic ages was identified and interpreted as a source area related to the synrift magmatism. The maximum depositional age calculated for the Tordillo Formation in the Atuel-La Valenciana depocenter is at ca. 149 Ma; as well as in other places of the Neuquén Basin, the U-Pb ages calculated in the Late Jurassic Tordillo Formation do not agree with the absolute age of the Kimmeridgian-Tithonian boundary (ca. 152 Ma). The main source region of sediment in the Tordillo Formation was the Andean magmatic arc. Basement regions were also present with age peaks at the Carboniferous, Neoproterozoic, and Mesoproterozoic; these regions were probably located to the east in the San Rafael Block. The pattern of zircon ages summarized for the Late Jurassic Tordillo and Lagunillas formations were interpreted as a record of the magmatic activity during the Triassic and Jurassic in the southern Central Andes. A waning of the magmatism is inferred to have happened during the Triassic. The evident lack of ages observed around ca. 200 Ma suggests cessation of the synrift magmatism. The later increase in magmatic activity during the Early Jurassic is attributed to the onset of Andean subduction, with maximum peaks at ca. 191 and 179 Ma. The trough at ca. 165 Ma and the later increase in the Late Jurassic could be explained by changes in the relative convergence rate in the Andean subduction regime, or by the shift to a more mafic composition of the magmatism with minor zircon fertility.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Juneau, Stéphanie; Bournaud, Frédéric; Daddi, Emanuele

Emission line diagnostic diagrams probing the ionization sources in galaxies, such as the Baldwin-Phillips-Terlevich (BPT) diagram, have been used extensively to distinguish active galactic nuclei (AGN) from purely star-forming galaxies. However, they remain poorly understood at higher redshifts. We shed light on this issue with an empirical approach based on a z ∼ 0 reference sample built from ∼300,000 Sloan Digital Sky Survey galaxies, from which we mimic selection effects due to typical emission line detection limits at higher redshift. We combine this low-redshift reference sample with a simple prescription for luminosity evolution of the global galaxy population to predictmore » the loci of high-redshift galaxies on the BPT and Mass-Excitation (MEx) diagnostic diagrams. The predicted bivariate distributions agree remarkably well with direct observations of galaxies out to z ∼ 1.5, including the observed stellar mass-metallicity (MZ) relation evolution. As a result, we infer that high-redshift star-forming galaxies are consistent with having normal interstellar medium (ISM) properties out to z ∼ 1.5, after accounting for selection effects and line luminosity evolution. Namely, their optical line ratios and gas-phase metallicities are comparable to that of low-redshift galaxies with equivalent emission-line luminosities. In contrast, AGN narrow-line regions may show a shift toward lower metallicities at higher redshift. While a physical evolution of the ISM conditions is not ruled out for purely star-forming galaxies and may be more important starting at z ≳ 2, we find that reliably quantifying this evolution is hindered by selections effects. The recipes provided here may serve as a basis for future studies toward this goal. Code to predict the loci of galaxies on the BPT and MEx diagnostic diagrams and the MZ relation as a function of emission line luminosity limits is made publicly available.« less

Analysis of the evolution of precipitation in the Haihe river basin of China under changing environment

NASA Astrophysics Data System (ADS)

Ding, Xiangyi; Liu, Jiahong; Gong, Jiaguo

2018-02-01

Precipitation is one of the important factors of water cycle and main sources of regional water resources. It is of great significance to analyze the evolution of precipitation under changing environment for identifying the evolution law of water resources, thus can provide a scientific reference for the sustainable utilization of water resources and the formulation of related policies and measures. Generally, analysis of the evolution of precipitation consists of three levels: analysis the observed precipitation change based on measured data, explore the possible factors responsible for the precipitation change, and estimate the change trend of precipitation under changing environment. As the political and cultural centre of China, the climatic conditions in the Haihe river basin have greatly changed in recent decades. This study analyses the evolution of precipitation in the basin under changing environment based on observed meteorological data, GCMs and statistical methods. Firstly, based on the observed precipitation data during 1961-2000 at 26 meteorological stations in the basin, the actual precipitation change in the basin is analyzed. Secondly, the observed precipitation change in the basin is attributed using the fingerprint-based attribution method, and the causes of the observed precipitation change is identified. Finally, the change trend of precipitation in the basin under climate change in the future is predicted based on GCMs and a statistical downscaling model. The results indicate that: 1) during 1961-2000, the precipitation in the basin showed a decreasing trend, and the possible mutation time was 1965; 2) natural variability may be the factor responsible for the observed precipitation change in the basin; 3) under climate change in the future, precipitation in the basin will slightly increase by 4.8% comparing with the average, and the extremes will not vary significantly.

Assessing rockfall susceptibility in steep and overhanging slopes using three-dimensional analysis of failure mechanisms

USGS Publications Warehouse

Matasci, Battista; Stock, Greg M.; Jaboyedoff, Michael; Carrea, Dario; Collins, Brian D.; Guérin, Antoine; Matasci, G.; Ravanel, L.

2018-01-01

Rockfalls strongly influence the evolution of steep rocky landscapes and represent a significant hazard in mountainous areas. Defining the most probable future rockfall source areas is of primary importance for both geomorphological investigations and hazard assessment. Thus, a need exists to understand which areas of a steep cliff are more likely to be affected by a rockfall. An important analytical gap exists between regional rockfall susceptibility studies and block-specific geomechanical calculations. Here we present methods for quantifying rockfall susceptibility at the cliff scale, which is suitable for sub-regional hazard assessment (hundreds to thousands of square meters). Our methods use three-dimensional point clouds acquired by terrestrial laser scanning to quantify the fracture patterns and compute failure mechanisms for planar, wedge, and toppling failures on vertical and overhanging rock walls. As a part of this work, we developed a rockfall susceptibility index for each type of failure mechanism according to the interaction between the discontinuities and the local cliff orientation. The susceptibility for slope parallel exfoliation-type failures, which are generally hard to identify, is partly captured by planar and toppling susceptibility indexes. We tested the methods for detecting the most susceptible rockfall source areas on two famously steep landscapes, Yosemite Valley (California, USA) and the Drus in the Mont-Blanc massif (France). Our rockfall susceptibility models show good correspondence with active rockfall sources. The methods offer new tools for investigating rockfall hazard and improving our understanding of rockfall processes.

The JCMT Transient Survey: Data Reduction and Calibration Methods

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mairs, Steve; Lane, James; Johnstone, Doug

Though there has been a significant amount of work investigating the early stages of low-mass star formation in recent years, the evolution of the mass assembly rate onto the central protostar remains largely unconstrained. Examining in depth the variation in this rate is critical to understanding the physics of star formation. Instabilities in the outer and inner circumstellar disk can lead to episodic outbursts. Observing these brightness variations at infrared or submillimeter wavelengths constrains the current accretion models. The JCMT Transient Survey is a three-year project dedicated to studying the continuum variability of deeply embedded protostars in eight nearby star-formingmore » regions at a one-month cadence. We use the SCUBA-2 instrument to simultaneously observe these regions at wavelengths of 450 and 850 μ m. In this paper, we present the data reduction techniques, image alignment procedures, and relative flux calibration methods for 850 μ m data. We compare the properties and locations of bright, compact emission sources fitted with Gaussians over time. Doing so, we achieve a spatial alignment of better than 1″ between the repeated observations and an uncertainty of 2%–3% in the relative peak brightness of significant, localized emission. This combination of imaging performance is unprecedented in ground-based, single-dish submillimeter observations. Finally, we identify a few sources that show possible and confirmed brightness variations. These sources will be closely monitored and presented in further detail in additional studies throughout the duration of the survey.« less

Sky Quality Meter measurements in a colour-changing world

NASA Astrophysics Data System (ADS)

Sánchez de Miguel, A.; Aubé, M.; Zamorano, J.; Kocifaj, M.; Roby, J.; Tapia, C.

2017-05-01

The Sky Quality Meter (SQM) has become the most common device used to track the evolution of the brightness of the sky from polluted regions to first-class astronomical observatories. A vast database of SQM measurements already exists for many places in the world. Unfortunately, the SQM operates over a wide spectral band and its spectral response interacts with the sky's spectrum in a complex manner. This is why the optical signals are difficult to interpret when the data are recorded in regions with different sources of artificial light. The brightness of the night sky is linked in a complex way to ground-based light emissions, while taking into account atmospheric-induced optical distortion as well as spectral transformation from the underlying ground surfaces. While the spectral modulation of the sky's radiance has been recognized, it still remains poorly characterized and quantified. The impact of the SQM's spectral characteristics on sky-brightness measurements is analysed here for different light sources, including low- and high-pressure sodium lamps, PC-amber and white LEDs, metal halide and mercury lamps. We show that a routine conversion of radiance to magnitude is difficult, or rather impossible, because the average wavelength depends on actual atmospheric and environment conditions, the spectrum of the source and device-specific properties. We correlate SQM readings with both the Johnson astronomical photometry bands and the human system of visual perception, assuming different lighting technologies. These findings have direct implications for the processing of SQM data and for their improvement and/or remediation.

On the mid-infrared variability of candidate eruptive variables (exors): A comparison between Spitzer and WISE data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Antoniucci, S.; Giannini, T.; Li Causi, G.

2014-02-10

Aiming to statistically study the variability in the mid-IR of young stellar objects, we have compared the 3.6, 4.5, and 24 μm Spitzer fluxes of 1478 sources belonging to the C2D (Cores to Disks) legacy program with the WISE fluxes at 3.4, 4.6, and 22 μm. From this comparison, we have selected a robust sample of 34 variable sources. Their variations were classified per spectral Class (according to the widely accepted scheme of Class I/flat/II/III protostars), and per star forming region. On average, the number of variable sources decreases with increasing Class and is definitely higher in Perseus and Ophiuchusmore » than in Chamaeleon and Lupus. According to the paradigm Class ≡ Evolution, the photometric variability can be considered to be a feature more pronounced in less evolved protostars, and, as such, related to accretion processes. Moreover, our statistical findings agree with the current knowledge of star formation activity in different regions. The 34 selected variables were further investigated for similarities with known young eruptive variables, namely the EXors. In particular, we analyzed (1) the shape of the spectral energy distribution, (2) the IR excess over the stellar photosphere, (3) magnitude versus color variations, and (4) output parameters of model fitting. This first systematic search for EXors ends up with 11 bona fide candidates that can be considered as suitable targets for monitoring or future investigations.« less

Evolution of ribonuclease in relation to polypeptide folding mechanisms.

NASA Technical Reports Server (NTRS)

Barnard, E. A.; Cohen, M. S.; Gold, M. H.; Kim, J.-K.

1972-01-01

Comparisons of the N-terminal region of pancreatic RNAase in seven species are presented, taking into account cow, bison, deer, rat, pig, kangaroo, and turtle. The available limited evidence on hypervariable regions indicates that there is still an evolutionary constraint on them. It is proposed that there is a selection pressure acting on all regions of a protein sequence in evolution. Mutations that tend to obstruct the folding process can lead to various intensities of selection pressure.

ANATOMY OF DEPLETED INTERPLANETARY CORONAL MASS EJECTIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kocher, M.; Lepri, S. T.; Landi, E.

We report a subset of interplanetary coronal mass ejections (ICMEs) containing distinct periods of anomalous heavy-ion charge state composition and peculiar ion thermal properties measured by ACE /SWICS from 1998 to 2011. We label them “depleted ICMEs,” identified by the presence of intervals where C{sup 6+}/C{sup 5+} and O{sup 7+}/O{sup 6+} depart from the direct correlation expected after their freeze-in heights. These anomalous intervals within the depleted ICMEs are referred to as “Depletion Regions.” We find that a depleted ICME would be indistinguishable from all other ICMEs in the absence of the Depletion Region, which has the defining property ofmore » significantly low abundances of fully charged species of helium, carbon, oxygen, and nitrogen. Similar anomalies in the slow solar wind were discussed by Zhao et al. We explore two possibilities for the source of the Depletion Region associated with magnetic reconnection in the tail of a CME, using CME simulations of the evolution of two Earth-bound CMEs described by Manchester et al.« less

The Distance to the Heliospheric VLF Emission Region

NASA Technical Reports Server (NTRS)

McNutt, R. L., Jr.; Lazarus, A. J.; Belcher, J. W.; Lyon, J.; Goodrich, C. C.; Kulkarni, R.

1995-01-01

Two major episodes of heliospheric VLF emissions near 3 kHz have been observed by the Voyager spacecraft in 1983-1984 and 1992-1993. This higher-frequency component is apparently triggered by solar wind transients with sufficiently large spatial extents and energies to continue to propagate as shocks in the heliosheath. Entrainment of previously unshocked material and changed flow conditions in the heliosheath both tend to slow the shock propagation. The shock evolution is not self-similar. Rather, it is intermediate to two blast-wave similarity solutions in the moving solar wind frame. In one solution the shock moves as time to the 2/3 power and in the other as time to the 4/5 power. Using these models, the shock/Forbush decrease observed at Voyager 2 in September, 1991 and the turn-on of the 1992 emission is consistent with an emission region distance of approx. 130 AU (assuming no additional slowing of the shock in the heliosheath). If the termination shock was at approx. 70 AU when the transient shock collided with it, the true distance to the source region was probably closer to approx. 115 AU.

The distance to the heliospheric VLF emission region

NASA Technical Reports Server (NTRS)

Mcnutt, R. L., Jr.; Lazarus, A. J.; Belcher, J. W.; Lyon, J.; Goodrich, C. C.; Kulkarni, R.

1995-01-01

Two major episodes of heliospheric VLF emissions near 3 kHz have been observed by the Voyager spacecraft in 1983/84 and 1992/3. This higher-frequency component is apparently triggered by solar wind transients with sufficiently large spatial extents and energies to continue to propagate as shocks in the heliosheath. Entrainment of previously unshocked material and changed flow conditions in the heliosheath both tend to slow the shock propagation. The shock evolution is not self-similar. Rather, it is intermediate to two blast-wave similarity solutions in the moving solar wind frame. In one solution the shock moves as time to the 2/3 power and in the other as time to the 4/5 power. Using these models, the shock/Forbush decrease observed at Voyager 2 in September, 1991 and the turn-on of the 1992 emission is consistent with an emission region distance of approximately 130 AU (assuming no additional slowing of the shock in the heliosheath). If the termination shock was at approximately 70 AU when the transient shock collided with it, the true distance to the source region was probably closer to approximately 115 AU.

Geochemistry of Intra-Transform Lavas from the Galápagos Transform Fault

NASA Astrophysics Data System (ADS)

Morrow, T. A.; Mittelstaedt, E. L.; Harpp, K. S.

2013-12-01

The Galápagos plume has profoundly affected the development and evolution of the nearby (<250 km) Galápagos Transform Fault (GTF), a ~100km right-stepping offset in the Galápagos Spreading Center (GSC). The GTF can be divided into two sections that represent different stages of transform evolution: the northern section exhibits fully developed transform fault morphology, whereas the southern section is young, and deformation is more diffuse. Both segments are faulted extensively and include numerous small (<0.5km3) monogenetic volcanic cones, though volcanic activity is more common in the south. To examine the composition of the mantle source and melting conditions responsible for the intra-transform lavas, as well as the influence of the plume on GTF evolution, we present major element, trace element, and radiogenic isotope analysis of samples collected during SON0158, EWI0004, and MV1007 cruises. Radiogenic isotope ratio variations in the Galápagos Archipelago require four distinct mantle reservoirs across the region: PLUME, DM, FLO, and WD. We find that Galápagos Transform lavas are chemically distinct from nearby GSC lavas and neighboring seamounts. They have radiogenic isotopic compositions that lie on a mixing line between DM and PLUME, with little to no contribution from any other mantle reservoirs despite their geographic proximity to WD-influenced lavas erupted along the GSC and at nearby (<50km away) seamounts. Within the transform, lavas from the northern section are more enriched in radiogenic isotopes than lavas sampled in the southern section. Transform lavas are anomalously depleted in incompatible trace elements (ITEs) relative to GSC lavas, suggesting unique melting conditions within the transform. Isotopic variability along the transform axis indicates that mantle sources and/or melting mechanisms vary between the northern and southern sections, which may relate to their distances from the plume or the two-stage development and evolution of the Galápagos Transform Fault. We present a melting model that reproduces GTF lava chemistry from a mixture of two partial melts of PLUME and DM. We assume that the DM source has an ITE composition similar to the depleted upper mantle, melting is purely fractional, and lavas do not fractionate during ascent. Solutions were achieved using a Metropolis algorithm and constrained by observed GTF lava chemistry. Model results predict that GTF lavas are produced by a mixture of a ~3%×1% partial melt of the PLUME source and a ~5%×4% partial melt of the DM source. Our model predicts that a larger proportion of PLUME melts contribute to GTF lavas than DM melts. Absence of the WD component and relatively low concentrations of ITEs may indicate that lavas in the GTF are produced from a source that has already undergone partial melting and is being re-melted beneath the TF. Re-melting may be caused by extension across the GTF, or development of the southern section of the GTF via the ~1Ma ridge jump.

Parameter identifiability and regional calibration for reservoir inflow prediction

NASA Astrophysics Data System (ADS)

Kolberg, Sjur; Engeland, Kolbjørn; Tøfte, Lena S.; Bruland, Oddbjørn

2013-04-01

The large hydropower producer Statkraft is currently testing regional, distributed models for operational reservoir inflow prediction. The need for simultaneous forecasts and consistent updating in a large number of catchments supports the shift from catchment-oriented to regional models. Low-quality naturalized inflow series in the reservoir catchments further encourages the use of donor catchments and regional simulation for calibration purposes. MCMC based parameter estimation (the Dream algorithm; Vrugt et al, 2009) is adapted to regional parameter estimation, and implemented within the open source ENKI framework. The likelihood is based on the concept of effectively independent number of observations, spatially as well as in time. Marginal and conditional (around an optimum) parameter distributions for each catchment may be extracted, even though the MCMC algorithm itself is guided only by the regional likelihood surface. Early results indicate that the average performance loss associated with regional calibration (difference in Nash-Sutcliffe R2 between regionally and locally optimal parameters) is in the range of 0.06. The importance of the seasonal snow storage and melt in Norwegian mountain catchments probably contributes to the high degree of similarity among catchments. The evaluation continues for several regions, focusing on posterior parameter uncertainty and identifiability. Vrugt, J. A., C. J. F. ter Braak, C. G. H. Diks, B. A. Robinson, J. M. Hyman and D. Higdon: Accelerating Markov Chain Monte Carlo Simulation by Differential Evolution with Self-Adaptive Randomized Subspace Sampling. Int. J. of nonlinear sciences and numerical simulation 10, 3, 273-290, 2009.

Identifying the regional-scale groundwater-surface water interaction on the Sanjiang Plain, Northeast China.

PubMed

Wang, Xihua; Zhang, Guangxin; Xu, Y Jun; Sun, Guangzhi

2015-11-01

Assessment on the interaction between groundwater and surface water (GW-SW) can generate information that is critical to regional water resource management, especially for regions that are highly dependent on groundwater resources for irrigation. This study investigated such interaction on China's Sanjiang Plain (10.9 × 10(4) km(2)) and produced results to assist sustainable regional water management for intensive agricultural activities. Methods of hierarchical cluster analysis (HCA), principal component analysis (PCA), and statistical analysis were used in this study. One hundred two water samplings (60 from shallow groundwater, 7 from deep groundwater, and 35 from surface water) were collected and grouped into three clusters and seven sub-clusters during the analyses. The PCA analysis identified four principal components of the interaction, which explained 85.9% variance of total database, attributed to the dissolution and evolution of gypsum, feldspar, and other natural minerals in the region that was affected by anthropic and geological (sedimentary rock mineral) activities. The analyses showed that surface water in the upper region of the Sanjiang Plain gained water from local shallow groundwater, indicating that the surface water in the upper region was relatively more resilient to withdrawal for usage, whereas in the middle region, there was only a weak interaction between shallow groundwater and surface water. In the lower region of the Sanjiang Plain, surface water lost water to shallow groundwater, indicating that the groundwater was vulnerable to pollution by pesticides and fertilizers from terrestrial sources.

A Global Catalogue of Large SO2 Sources and Emissions Derived from the Ozone Monitoring Instrument

NASA Technical Reports Server (NTRS)

Fioletov, Vitali E.; McLinden, Chris A.; Krotkov, Nickolay; Li, Can; Joiner, Joanna; Theys, Nicolas; Carn, Simon; Moran, Mike D.

2016-01-01

Sulfur dioxide (SO2) measurements from the Ozone Monitoring Instrument (OMI) satellite sensor processed with the new principal component analysis (PCA) algorithm were used to detect large point emission sources or clusters of sources. The total of 491 continuously emitting point sources releasing from about 30 kt yr(exp -1) to more than 4000 kt yr(exp -1) of SO2 per year have been identified and grouped by country and by primary source origin: volcanoes (76 sources); power plants (297); smelters (53); and sources related to the oil and gas industry (65). The sources were identified using different methods, including through OMI measurements themselves applied to a new emission detection algorithm, and their evolution during the 2005- 2014 period was traced by estimating annual emissions from each source. For volcanic sources, the study focused on continuous degassing, and emissions from explosive eruptions were excluded. Emissions from degassing volcanic sources were measured, many for the first time, and collectively they account for about 30% of total SO2 emissions estimated from OMI measurements, but that fraction has increased in recent years given that cumulative global emissions from power plants and smelters are declining while emissions from oil and gas industry remained nearly constant. Anthropogenic emissions from the USA declined by 80% over the 2005-2014 period as did emissions from western and central Europe, whereas emissions from India nearly doubled, and emissions from other large SO2-emitting regions (South Africa, Russia, Mexico, and the Middle East) remained fairly constant. In total, OMI-based estimates account for about a half of total reported anthropogenic SO2 emissions; the remaining half is likely related to sources emitting less than 30 kt yr(exp -1) and not detected by OMI.

Lunar volatiles: a clue for understanding the evolution of the Moon and a resource to its exploration

NASA Astrophysics Data System (ADS)

Gerasimov, Mikhail

Introduction: The discovery of noticeable hydrogen concentration (believed to be in the form of water) in the polar regions was among the most exciting recent events in the exploration of the Moon. Concentration of water in polar regolith was estimated at a level of 4-6 wt.% [1,2]. Such high concentration of water in polar regolith on volatiles depleted Moon is probably a result of migration of water molecules from its hot equatorial latitudes to cold traps of the northern and southern polar regions. These depositions of volatiles on one hand contain important information on the evolution of the Moon and on the other hand their utilization can be a bases for the future human exploration. The question about diversity and source of the volatiles is still open. Sources of lunar volatiles: Three main possible sources of the Lunar polar volatiles are: Degassing of the interior. Endogenous source of volatiles is provided by degassing of heated interior of planetary bodies. In this case chemical composition of released gases reflects thermodynamic equilibrium of gases over typical magmas at temperatures around 1000°C. The composition of such gas mixtures is characterized by domination of H2O, CO2, and SO2 over other H, C, and S containing components. CO/CO2 ratio here is typically far below 0.1 level. Hydrocarbons are mainly aromatic hydrocarbons, alkanes, and cycloalkanes. Sulfur containing gases are mainly SO2, H2S, and Sx. Isotopic ratios of volatile elements should be the same as for the bulk Moon. Interaction of solar wind protons with surface rocks. Energetic solar wind protons with the absence of an atmospheric shield can react with oxygen of surface rocks and produce water molecules as end product. Such a mechanism provides a source of mainly water on the Moon with solar hydrogen isotopes and Moon rocks oxygen isotopes. Degassing of impacting meteorites and comets. Volatiles of impacting meteorites and comets are released into transient atmosphere. It was shown experimentally [3] that the forming gases are qualitatively similar for various rocky materials including meteorites of different classes. Such gas mixtures have the following characteristics: the CO/CO2 ratio is ³1, hydrocarbons are presented mainly by alkenes and PAHs, sulfur containing gases are presented by SO2, CS2, H2S, and COS in decreasing sequence, production of HCN, and noticeable release of water. Isotopic composition of volatile elements reflects the projectile to target proportion of their source. Gas-analytic package (GAP) of the Lunar-Resource mission: It is very important to investigate all the inventory of polar volatiles as well as isotopic composition of volatile elements to understand the real source of lunar volatiles and to evaluate their validity as a resource for the Moon exploration. The GAP is aimed on comprehensive investigation of the inventory of volatiles in the regolith of polar regions. It consists of three instruments: 1) Thermal Analyzer; 2) Gas Chromatograph with Tunable Diode Laser Absorption Spectrometer for isotopic measurements of H, O, and C in evolved gases; and 3) Neutral Gas Mass-Spectrometer. References: [1] Mitrofanov, I. G. et al. 2010. Science 330: 483-486. [2] Colaprete, A. et al. 2010. Science 330: 463-468. [3] Gerasimov, M.V. 2002. Geological Society of America Special Paper 356: 705-716. Acknowledgements: This work was supported by P-22 Program of the RAS.

Differential Accumulation of Retroelements and Diversification of NB-LRR Disease Resistance Genes in Duplicated Regions Following Polyploidy in the Ancestor of Soybean

USDA-ARS?s Scientific Manuscript database

The genomes of most flowering plants have undergone polyploidization at some point in their evolution. How such polyploidization events have impacted the subsequent evolution of genome structure is poorly understood. We sequenced two homoeologous regions in soybean (Glycine max), which underwent a...