WorldWideScience

Sample records for chemical evolution traced

  1. Atmospheric Transport During the Transport and Chemical Evolution over the Pacific TRACE-P Experiment

    Science.gov (United States)

    Fuelberg, Henry E.; Kiley, C. M.; Hannan, J. R.; Westberg, D. J.; Avery, M. A.; Newell, R. E.

    2003-01-01

    Atmospheric transport over the Pacific Basin is described during NASA's Transport and Chemical Evolution Over the Pacific Experiment (TRACE-P) that was conducted between February - April 2001. The mission included extensive chemical sampling from two aircraft based primarily in Hong Kong and Yokota Air Base, Japan. Meteorological conditions during TRACE-P changed rapidly due to the seasonal winter/spring transition and the decay of prolonged ENSO cold phase (La Nina) conditions. To document these changes, TRACE-P was divided into two halves, and mean flow patterns during each half are presented and discussed. Important circulation features are the semi-permanent Siberian anticyclone and transient middle latitude cyclones that form near eastern Asia and then move eastward over the northern Pacific. Five-day backward trajectories from the various flight tracks show that air sampled by the aircraft had been transported from a variety of locations. Some parcels remained over the tropical western North Pacific during the entire period, while other important origins were Southeast Asia, Africa, and central Asia. Patterns of satellite-derived precipitation and lightning are described. TRACE-P occurs during a neutral to weak La Nina period of relatively cold sea surface temperatures in the tropical Pacific. Compared to climatology, the TRACE-P period exhibits deep convection located west of its typical position; however, tropospheric flow patterns do not exhibit a strong La Nina signal. Circulation patterns during TRACE-P are found to be generally similar to those during NASA's PEM WEST-B mission that occurred in the same region during February - March 1994.

  2. Transport and Chemical Evolution over the Pacific (TRACE-P) aircraft mission: Design, execution, and first results

    OpenAIRE

    Jacob, Daniel James; Crawford, James; Kleb, Mary; Connors, VIckie; Bendura, Richard; Raper, James; Sachse, Glen; Gille, John; Emmons, Louisa; Heald, Colette

    2003-01-01

    The NASA Transport and Chemical Evolution over the Pacific (TRACE-P) aircraft mission was conducted in February–April 2001 over the NW Pacific (1) to characterize the Asian chemical outflow and relate it quantitatively to its sources and (2) to determine its chemical evolution. It used two aircraft, a DC-8 and a P-3B, operating out of Hong Kong and Yokota Air Force Base (near Tokyo), with secondary sites in Hawaii, Wake Island, Guam, Okinawa, and Midway. The aircraft carried instrumentation f...

  3. Modelling the chemical evolution

    OpenAIRE

    Hensler, Gerhard; Recchi, Simone

    2010-01-01

    Advanced observational facilities allow to trace back the chemical evolution of the Universe, on the one hand, from local objects of different ages and, secondly, by direct observations of redshifted objects. The chemical enrichment serves as one of the cornerstones of cosmological evolution. In order to understand this chemical evolution in morphologically different astrophysical objects models are constructed based on analytical descriptions or numerical methods. For the comparison of their...

  4. Transport and Chemical Evolution over the Pacific (TRACE-P)Aircraft Mission: Design, Execution, and First Results

    Science.gov (United States)

    Jacob, Daniel J.; Crawford, James H.; Kleb, Mary M.; Connors, Vickie S.; Bendura, Richard J.; Raper, James L.; Sachse, Glen W.; Gille, John C.; Emmons, Louisa; Heald, Colette L.

    2003-01-01

    The NASA Transport and Chemical Evolution over the Pacific (TRACE-P) aircraft mission was conducted in February-April 2001 over the NW Pacific (1) to characterize the Asian chemical outflow and relate it quantitatively to its sources and (2) to determine its chemical evolution. It used two aircraft, a DC-8 and a P-3B, operating out of Hong Kong and Yokota Air Force Base (near Tokyo), with secondary sites in Hawaii, Wake Island, Guam, Okinawa, and Midway. The aircraft carried instrumentation for measurements of long-lived greenhouse gases, ozone and its precursors, aerosols and their precursors, related species, and chemical tracers. Five chemical transport models (CTMs) were used for chemical forecasting. Customized bottom-up emission inventories for East Asia were generated prior to the mission to support chemical forecasting and to serve as a priori for evaluation with the aircraft data. Validation flights were conducted for the Measurements Of Pollution In The Troposphere (MOPITT) satellite instrument and revealed little bias (6 plus or minus 2%) in the MOPITT measurements of CO columns. A major event of transpacific Asian pollution was characterized through combined analysis of TRACE-P and MOPITT data. The TRACE-P observations showed that cold fronts sweeping across East Asia and the associated warm conveyor belts (WCBs) are the dominant pathway for Asian outflow to the Pacific in spring. The WCBs lift both anthropogenic and biomass burning (SE Asia) effluents to the free troposphere, resulting in complex chemical signatures. The TRACE-P data are in general consistent with a priori emission inventories, lending confidence in our ability to quantify Asian emissions from socioeconomic data and emission factors. However, the residential combustion source in rural China was found to be much larger than the a priori, and there were also unexplained chemical enhancements (HCN, CH3Cl, OCS, alkylnitrates) in Chinese urban plumes. The Asian source of CCl4 was found to

  5. THE GALACTIC STRUCTURE AND CHEMICAL EVOLUTION TRACED BY THE POPULATION OF PLANETARY NEBULAE

    International Nuclear Information System (INIS)

    Planetary nebulae (PNe) derive from the evolution of ∼1-8 Msun mass stars, corresponding to a wide range of progenitor ages, and thus are essential probes of the chemical evolution of galaxies, and indispensable to constrain the results from chemical models. We use an extended and homogeneous data set of Galactic PNe to study the metallicity gradients and the Galactic structure and evolution. The most up-to-date abundances, distances (calibrated with Magellanic Cloud PNe), and other parameters have been employed, together with a novel homogeneous morphological classification, to characterize the different PN populations. We confirm that morphological classes have a strong correlation with Peimbert's type PN, and also with their distribution on the Galactic landscape. We studied the α-element distribution within the Galactic disk, and found that the best selected disk population (i.e., excluding bulge and halo component), together with the most reliable PN distance scale yields to a radial oxygen gradient of Δlog(O/H)/ΔRG = -0.023 ± 0.006 dex kpc-1 for the whole disk sample, and of Δlog(O/H)/ΔRG = -0.035 ± 0.024, -0.023 ± 0.005, and -0.011 ± 0.013 dex kpc-1, respectively for Type I, II, and III PNe, i.e., for high-, intermediate-, and low-mass progenitors. Neon gradients for the same PN types confirm the trend. Accurate statistical analysis shows moderately high uncertainties in the slopes, but also confirms the trend of steeper gradient for PNe with more massive progenitors, indicating a possible steepening with time of the Galactic disk metallicity gradient for what the α-elements are concerned. We found that the metallicity gradients are almost independent on the distance scale model used, as long as these scales are equally well calibrated with the Magellanic Clouds. The PN metallicity gradients presented here are consistent with the local metallicity distribution; furthermore, oxygen gradients determined with young and intermediate age PNe show good

  6. CHEMICAL EVOLUTION

    Energy Technology Data Exchange (ETDEWEB)

    Calvin, Melvin

    1965-06-01

    How did life come to be on the surface of the earth? Darwin himself recognized that his basic idea of evolution by variation and natural selection must be a continuous process extending backward in time through that period in which the first living things arose and into the period of 'Chemical Evolution' which preceded it. We are approaching the examination of these events by two routes. One is to seek for evidence in the ancient rocks of the earth which were laid down prior to that time in which organisms capable of leaving their skeletons in the rocks to be fossilized were in existence. This period is sometime prior to approximately 600 million years ago. The earth is believed to have taken its present form approximately 4700 million years ago. We have found in rocks whose age is about 1000 million years certain organic molecules which are closely related to the green pigment of plants, chlorophyll. This seems to establish that green plants were already fluorishing prior to that time. We have now found in rocks of still greater age, namely, 2500 million years, the same kinds of molecules mentioned above which can be attributed to the presence of living organisms. If these molecules are as old as the rocks, we have thus shortened the time available for the generation of the complex biosynthetic sequences which give rise to these specific hydrocarbons (polyisoprenoids) to less than 2000 million years.

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

    Science.gov (United States)

    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

  8. Compendium of NASA Data Base for the Global Tropospheric Experiment's Transport and Chemical Evolution Over the Pacific (TRACE-P). Volume 1; DC-8

    Science.gov (United States)

    Kleb, Mary M.; Scott, A. Donald, Jr.

    2003-01-01

    This report provides a compendium of NASA aircraft data that are available from NASA's Global Tropospheric Experiment's (GTE) Transport and Chemical Evolution over the Pacific (TRACE-P) Mission. The broad goal of TRACE-P was to characterize the transit and evolution of the Asian outflow over the western Pacific. Conducted from February 24 through April 10, 2001, TRACE-P integrated airborne, satellite- and ground-based observations, as well as forecasts from aerosol and chemistry models. The format of this compendium utilizes data plots (time series) of selected data acquired aboard the NASA/Dryden DC-8 (vol. 1) and NASA/Wallops P-3B (vol. 2) aircraft during TRACE-P. The purpose of this document is to provide a representation of aircraft data that are available in archived format via NASA Langley s Distributed Active Archive Center (DAAC) and through the GTE Project Office archive. The data format is not intended to support original research/analyses, but to assist the reader in identifying data that are of interest.

  9. Compendium of NASA Data Base for the Global Tropospheric Experiment's Transport and Chemical Evolution Over the Pacific (TRACE-P). Volume 2; P-3B

    Science.gov (United States)

    Kleb, Mary M.; Scott, A. Donald, Jr.

    2003-01-01

    This report provides a compendium of NASA aircraft data that are available from NASA's Global Tropospheric Experiment's (GTE) Transport and Chemical Evolution over the Pacific (TRACE-P) Mission. The broad goal of TRACE-P was to characterize the transit and evolution of the Asian outflow over the western Pacific. Conducted from February 24 through April 10, 2001, TRACE-P integrated airborne, satellite- and ground based observations, as well as forecasts from aerosol and chemistry models. The format of this compendium utilizes data plots (time series) of selected data acquired aboard the NASA/Dryden DC-8 (vol. 1) and NASA/Wallops P-3B (vol. 2) aircraft during TRACE-P. The purpose of this document is to provide a representation of aircraft data that are available in archived format via NASA Langley's Distributed Active Archive Center (DAAC) and through the GTE Project Office archive. The data format is not intended to support original research/analyses, but to assist the reader in identifying data that are of interest.

  10. Models of Chemical Evolution

    OpenAIRE

    Matteucci, Francesca

    2003-01-01

    The basic principles underlying galactic chemical evolution and the most important results of chemical evolution models are discussed. In particular, the chemical evolution of the Milky Way galaxy, for which we possess the majority of observational constraints, is described. Then, it is shown how different star formation histories influence the chemical evolution of galaxies of different morphological type. Finally, the role of abundances and abundance ratios as cosmic clocks is emphasized an...

  11. Chemical evolution and life

    OpenAIRE

    Malaterre Christophe

    2015-01-01

    In research on the origins of life, the concept of “chemical evolution” aims at explaining the transition from non-living matter to living matter. There is however strong disagreement when it comes to defining this concept more precisely, and in particular with reference to a chemical form of Darwinian evolution: for some, chemical evolution is nothing but Darwinian evolution applied to chemical systems before life appeared; yet, for others, it is the type of evolution that happened before na...

  12. Tracing chemical evolution over the extent of the Milky Way's disk with apogee red clump stars

    International Nuclear Information System (INIS)

    We employ the first two years of data from the near-infrared, high-resolution SDSS-III/APOGEE spectroscopic survey to investigate the distribution of metallicity and α-element abundances of stars over a large part of the Milky Way disk. Using a sample of ≈10, 000 kinematically unbiased red-clump stars with ∼5% distance accuracy as tracers, the [α/Fe] versus [Fe/H] distribution of this sample exhibits a bimodality in [α/Fe] at intermediate metallicities, –0.9 < [Fe/H] <–0.2, but at higher metallicities ([Fe/H] ∼+0.2) the two sequences smoothly merge. We investigate the effects of the APOGEE selection function and volume filling fraction and find that these have little qualitative impact on the α-element abundance patterns. The described abundance pattern is found throughout the range 5 < R < 11 kpc and 0 < |Z| < 2 kpc across the Galaxy. The [α/Fe] trend of the high-α sequence is surprisingly constant throughout the Galaxy, with little variation from region to region (∼10%). Using simple galactic chemical evolution models, we derive an average star-formation efficiency (SFE) in the high-α sequence of ∼4.5 × 10–10 yr–1, which is quite close to the nearly constant value found in molecular-gas-dominated regions of nearby spirals. This result suggests that the early evolution of the Milky Way disk was characterized by stars that shared a similar star-formation history and were formed in a well-mixed, turbulent, and molecular-dominated ISM with a gas consumption timescale (SFE–1) of ∼2 Gyr. Finally, while the two α-element sequences in the inner Galaxy can be explained by a single chemical evolutionary track, this cannot hold in the outer Galaxy, requiring, instead, a mix of two or more populations with distinct enrichment histories.

  13. Tracing chemical evolution over the extent of the Milky Way's disk with apogee red clump stars

    Energy Technology Data Exchange (ETDEWEB)

    Nidever, David L. [Department of Astronomy, University of Michigan, Ann Arbor, MI 48104 (United States); Bovy, Jo [Institute for Advanced Study, Einstein Drive, Princeton, NJ 08540 (United States); Bird, Jonathan C. [Physics and Astronomy Department, Vanderbilt University, 1807 Station B, Nashville, TN 37235 (United States); Andrews, Brett H.; Johnson, Jennifer A.; Weinberg, David H. [Department of Astronomy and the Center for Cosmology and Astro-Particle Physics, The Ohio State University, Columbus, OH 43210 (United States); Hayden, Michael; Holtzman, Jon; Feuillet, Diane [New Mexico State University, Las Cruces, NM 88003 (United States); Majewski, Steven R.; García Pérez, Ana E. [Department of Astronomy, University of Virginia, Charlottesville, VA, 22904 (United States); Smith, Verne [National Optical Astronomy Observatory, Tucson, AZ 85719 (United States); Robin, Annie C.; Sobeck, Jennifer [Institut Utinam, CNRS UMR 6213, OSU THETA, Université de Franche-Comté, 41bis avenue de l' Observatoire, F-25000 Besançon (France); Cunha, Katia [Observatorio Nacional, Rio de Janeiro (Brazil); Allende Prieto, Carlos [Instituto de Astrofsica de Canarias, E-38205 La Laguna, Tenerife (Spain); Zasowski, Gail [Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218 (United States); Schiavon, Ricardo P. [Astrophysics Research Institute, IC2, Liverpool Science Park, Liverpool John Moores University, 146 Brownlow Hill, Liverpool, L3 5RF (United Kingdom); Schneider, Donald P. [Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802 (United States); Shetrone, Matthew, E-mail: dnidever@umich.edu [University of Texas at Austin, McDonald Observatory, 32 Fowlkes Road, McDonald Observatory, TX 79734-3005 (United States); and others

    2014-11-20

    We employ the first two years of data from the near-infrared, high-resolution SDSS-III/APOGEE spectroscopic survey to investigate the distribution of metallicity and α-element abundances of stars over a large part of the Milky Way disk. Using a sample of ≈10, 000 kinematically unbiased red-clump stars with ∼5% distance accuracy as tracers, the [α/Fe] versus [Fe/H] distribution of this sample exhibits a bimodality in [α/Fe] at intermediate metallicities, –0.9 < [Fe/H] <–0.2, but at higher metallicities ([Fe/H] ∼+0.2) the two sequences smoothly merge. We investigate the effects of the APOGEE selection function and volume filling fraction and find that these have little qualitative impact on the α-element abundance patterns. The described abundance pattern is found throughout the range 5 < R < 11 kpc and 0 < |Z| < 2 kpc across the Galaxy. The [α/Fe] trend of the high-α sequence is surprisingly constant throughout the Galaxy, with little variation from region to region (∼10%). Using simple galactic chemical evolution models, we derive an average star-formation efficiency (SFE) in the high-α sequence of ∼4.5 × 10{sup –10} yr{sup –1}, which is quite close to the nearly constant value found in molecular-gas-dominated regions of nearby spirals. This result suggests that the early evolution of the Milky Way disk was characterized by stars that shared a similar star-formation history and were formed in a well-mixed, turbulent, and molecular-dominated ISM with a gas consumption timescale (SFE{sup –1}) of ∼2 Gyr. Finally, while the two α-element sequences in the inner Galaxy can be explained by a single chemical evolutionary track, this cannot hold in the outer Galaxy, requiring, instead, a mix of two or more populations with distinct enrichment histories.

  14. Chemical evolution of galaxies

    CERN Document Server

    Matteucci, Francesca

    2012-01-01

    The term “chemical evolution of galaxies” refers to the evolution of abundances of chemical species in galaxies, which is due to nuclear processes occurring in stars and to gas flows into and out of galaxies. This book deals with the chemical evolution of galaxies of all morphological types (ellipticals, spirals and irregulars) and stresses the importance of the star formation histories in determining the properties of stellar populations in different galaxies. The topic is approached in a didactical and logical manner via galaxy evolution models which are compared with observational results obtained in the last two decades: The reader is given an introduction to the concept of chemical abundances and learns about the main stellar populations in our Galaxy as well as about the classification of galaxy types and their main observables. In the core of the book, the construction and solution of chemical evolution models are discussed in detail, followed by descriptions and interpretations of observations of ...

  15. 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

    Science.gov (United States)

    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.

  16. Chemical evolution and life

    Directory of Open Access Journals (Sweden)

    Malaterre Christophe

    2015-01-01

    Full Text Available In research on the origins of life, the concept of “chemical evolution” aims at explaining the transition from non-living matter to living matter. There is however strong disagreement when it comes to defining this concept more precisely, and in particular with reference to a chemical form of Darwinian evolution: for some, chemical evolution is nothing but Darwinian evolution applied to chemical systems before life appeared; yet, for others, it is the type of evolution that happened before natural selection took place, the latter being the birthmark of living systems. In this contribution, I review the arguments defended by each side and show how both views presuppose a dichotomous definition of “life”.

  17. Chemical evolution of galaxies

    International Nuclear Information System (INIS)

    Initial conditions are probably set by results of Big Bang nucleosynthesis (BBNS) without intervening complications affecting the composition of visible matter so that extrapolation of observed abundances to BBNS products seems fairly secure. Primordial helium and deuterium abundances deduced in this way place upper and lower limits on baryonic density implying that both baryonic and non-baryonic dark matter exist and predicting no more than 3 neutrino flavours as recently confirmed in accelerator experiments. The validity of simple galactic chemical evolution models assumed in extrapolating back to the Big Bang is examined in the light of the frequency distribution of iron or oxygen abundances in the Galactic halo, bulge and disk. (orig.)

  18. Chemical Evolution in Omega Centauri

    OpenAIRE

    Smith, Verne V.

    2003-01-01

    The globular cluster Omega Centauri displays evidence of a complex star formation history and peculiar internal chemical evolution, setting it apart from essentially all other globular clusters of the Milky Way. In this review we discuss the nature of the chemical evolution that has occurred within Omega Cen and attempt to construct a simple scenario to explain its chemistry.

  19. Chemical Evolution of Protostellar Matter

    Science.gov (United States)

    Langer, William D.; vanDishoeck, Ewine F.; Bergin, Edwin A.; Blake, Geoffrey A.; Tielens, Alexander G. G. M.; Velusamy, Thangasamy; Whittet, Douglas C. B.

    2000-01-01

    We review the chemical processes that are important in the evolution from a molecular cloud core to a protostellar disk. These cover both gas phase and gas grain interactions. The current observational and theoretical state of this field are discussed.

  20. Introduction to Galactic Chemical Evolution

    CERN Document Server

    Matteucci, Francesca

    2016-01-01

    In this lecture I will introduce the concept of galactic chemical evolution, namely the study of how and where the chemical elements formed and how they were distributed in the stars and gas in galaxies. The main ingredients to build models of galactic chemical evolution will be described. They include: initial conditions, star formation history, stellar nucleosynthesis and gas flows in and out of galaxies. Then some simple analytical models and their solutions will be discussed together with the main criticisms associated to them. The yield per stellar generation will be defined and the hypothesis of instantaneous recycling approximation will be critically discussed. Detailed numerical models of chemical evolution of galaxies of different morphological type, able to follow the time evolution of the abundances of single elements, will be discussed and their predictions will be compared to observational data. The comparisons will include stellar abundances as well as interstellar medium ones, measured in galax...

  1. Stellar Yields and Chemical Evolution

    OpenAIRE

    Gibson, Brad K.

    1997-01-01

    Several speakers at IAU Symposium #187 (Cosmic Chemical Evolution) alluded to the zeroth-order agreement between Type II supernovae (SNe) stellar yield compilations, as predicted by the models of those most responsible for driving progress in the field - i.e., Arnett (1991,1996); Maeder (1992); Woosley & Weaver (1995); Langer & Henkel (1995); Thielemann et al. (1996). It is important though for those entering (or indeed, already involved in!) the chemical evolution field to be cognizant of th...

  2. Topics on Galactic Chemical Evolution

    OpenAIRE

    Prantzos, Nikos

    2011-01-01

    I discuss three different topics in Galactic chemical evolution:the "puzzling" absence of any observational signature of secondary elements ; the building of the Galactic halo in the framework of hierarchical galaxy formation, as evidenced from its metallicity distribution ; and the potentially important role that radial migration may play in the evolution of galactic disks, according to recent studies.

  3. Concrete Chemical Evolution

    International Nuclear Information System (INIS)

    The objectives of this analysis are to discuss and evaluate testing results that were performed for the M andO by the Pennsylvania State University (PSU) to evaluate the potential long-term evolution of organic admixtures in cementitious materials at elevated temperatures. The testing was designed to help provide a basis for a determination by the Performance Assessment group (PA) of the long-term acceptability and longevity of cementitious materials for repository use. The main purpose of the testing was to assess the evolution of gases (especially CO2) from hydrated cement paste at elevated temperatures and to determine the impact on alkalinity, i.e., the pH value of cement paste pore solution. This information in turn can be used as scoping information to determine if further tests of this nature are needed to support PA. As part of this discussion and evaluation of the PSU results, an assessment of alkalinity in a ''cementitious repository'' and an evaluation of organic materials are presented

  4. Concrete Chemical Evolution

    Energy Technology Data Exchange (ETDEWEB)

    D.H. Tang

    1998-07-31

    The objectives of this analysis are to discuss and evaluate testing results that were performed for the M&O by the Pennsylvania State University (PSU) to evaluate the potential long-term evolution of organic admixtures in cementitious materials at elevated temperatures. The testing was designed to help provide a basis for a determination by the Performance Assessment group (PA) of the long-term acceptability and longevity of cementitious materials for repository use. The main purpose of the testing was to assess the evolution of gases (especially CO{sub 2}) from hydrated cement paste at elevated temperatures and to determine the impact on alkalinity, i.e., the pH value of cement paste pore solution. This information in turn can be used as scoping information to determine if further tests of this nature are needed to support PA. As part of this discussion and evaluation of the PSU results, an assessment of alkalinity in a ''cementitious repository'' and an evaluation of organic materials are presented.

  5. Chemical evolution in space

    Science.gov (United States)

    Greenberg, J. M.

    1984-01-01

    Most of the complex molecules in interstellar space ar probably contained in small, frozen interstellar dust grains which are about as old as the earth and have been photochemically converted into large organic molecules. These molecules' maximum molecular weight is limited only by the approximately 0.1-micron grain size. Their evolution leads from cool, evolved stellar atmospheres' formation of seedlings to destruction through incorporation into the material of new stars. Organic dust constitutes about 0.1 percent of the total mass of the Milky Way, far outweighing any estimates of total planetary mass in the Galaxy. Because comets may be virtually pure, aggregated interstellar dust, they offer a source of interstellar organic material for detailed study.

  6. Galaxy formation and chemical evolution

    OpenAIRE

    2014-01-01

    The manner the galaxy accretes matter along with the star formation rates at different epochs, influence the evolution of the stable isotopic inventories of the galaxy. A detailed analysis is presented here to study the dependence of the galactic chemical evolution on the accretion scenario of the galaxy along with the star formation rate during the early accretionary phase of the galactic thick disk and thin disk. Our results indicate that a rapid early accretion of the galaxy during the for...

  7. Characteristics and Influence of Biosmoke on the Fine-Particle Ionic Composition Measured in Asian Outflow during the Transport and Chemical Evolution Over the Pacific (TRACE-P) Experiment

    Science.gov (United States)

    Ma, Y.; Weber, R. J.; Lee, Y.-N.; Orsini, D. A.; Maxwell-Meier, K.; Thornton, D. C.; Bandy, A. R.; Clarke, A. D.; Blake, D. R.; Sachse, G. W.

    2003-01-01

    We investigate the sources, prevalence, and fine-particle inorganic composition of biosmoke over the western Pacific Ocean between 24 February and 10 April 2001. The analysis is based on highly time-resolved airborne measurements of gaseous and fine- particle inorganic chemical composition made during the NASA Transport and Chemical Evolution over the Pacific (TRACE-P) experiment. At latitudes below approximately 25 deg. N, relatively pure biomass burning plumes of enhanced fine-particle potassium, nitrate, ammonium, light-absorbing aerosols, and CO concentrations were observed in plumes that back trajectories and satellite fire map data suggest originated from biomass burning in southeast Asia. Fine-particle water-soluble potassium (K+) is confirmed to be a unique biosmoke tracer, and its prevalence throughout the experiment indicates that approximately 20% of the TRACE-P Asian outflow plumes were influenced, to some extent, by biomass or biofuel burning emissions. At latitudes above 25 deg. N, highly mixed urban/industrial and biosmoke plumes, indicated by SO(sup 2, sub 4) and K+, were observed in 5 out of 53 plumes. Most plumes were found in the Yellow Sea and generally were associated with much higher fine-particle loadings than plumes lacking a biosmoke influence. The air mass back trajectories of these mixed plumes generally pass through the latitude range of between 34 deg. and 40 deg. N on the eastern China coast, a region that includes the large urban centers of Beijing and Tianjin. A lack of biomass burning emissions based on fire maps and high correlations between K+ and pollution tracers (e.g., S(sup 2, sub 4) suggest biofuel sources. Ratios of fine-particle potassium to sulfate are used to provide an estimate of relative contributions of biosmoke emissions to the mixed Asian plumes. The ratio is highly correlated with fine-particle volume (r(sup 2) = 0.85) and predicts that for the most polluted plume encounter in TRACE-P, approximately 60% of the

  8. Chemical evolution of molecular clouds

    Science.gov (United States)

    Prasad, Sheo S.; Tarafdar, Sankar P.; Villere, Karen R.; Huntress, Wesley T., Jr.

    1987-01-01

    The principles behind the coupled chemical-dynamical evolution of molecular clouds are described. Particular attention is given to current problems involving the simplest species (i.e., C. CO, O2, and H2) in quiescent clouds. The results of a comparison made between the molecular abundances in the Orion ridge and the hot core (Blake, 1986) are presented.

  9. Introduction to Galactic Chemical Evolution

    Science.gov (United States)

    Matteucci, Francesca

    2016-04-01

    In this lecture I will introduce the concept of galactic chemical evolution, namely the study of how and where the chemical elements formed and how they were distributed in the stars and gas in galaxies. The main ingredients to build models of galactic chemical evolution will be described. They include: initial conditions, star formation history, stellar nucleosynthesis and gas flows in and out of galaxies. Then some simple analytical models and their solutions will be discussed together with the main criticisms associated to them. The yield per stellar generation will be defined and the hypothesis of instantaneous recycling approximation will be critically discussed. Detailed numerical models of chemical evolution of galaxies of different morphological type, able to follow the time evolution of the abundances of single elements, will be discussed and their predictions will be compared to observational data. The comparisons will include stellar abundances as well as interstellar medium ones, measured in galaxies. I will show how, from these comparisons, one can derive important constraints on stellar nucleosynthesis and galaxy formation mechanisms. Most of the concepts described in this lecture can be found in the monograph by Matteucci (2012).

  10. Chemical Evolution of the Galaxy

    OpenAIRE

    Tosi, M.

    1994-01-01

    Standard models for the chemical evolution of the Galaxy are reviewed with particular emphasis on the history of the abundance gradients in the disk. The effects on the disk structure and metallicity of gas accretion are discussed, showing that a significant fraction of the current disk mass has been accreted in the last Gyrs and that the chemical abundances of the infalling gas can be non primordial but should not exceed 0.3 Z(sun). The distributions with time and with galactocentric distanc...

  11. Evolution of associative learning in chemical networks.

    Directory of Open Access Journals (Sweden)

    Simon McGregor

    Full Text Available Organisms that can learn about their environment and modify their behaviour appropriately during their lifetime are more likely to survive and reproduce than organisms that do not. While associative learning - the ability to detect correlated features of the environment - has been studied extensively in nervous systems, where the underlying mechanisms are reasonably well understood, mechanisms within single cells that could allow associative learning have received little attention. Here, using in silico evolution of chemical networks, we show that there exists a diversity of remarkably simple and plausible chemical solutions to the associative learning problem, the simplest of which uses only one core chemical reaction. We then asked to what extent a linear combination of chemical concentrations in the network could approximate the ideal Bayesian posterior of an environment given the stimulus history so far? This Bayesian analysis revealed the 'memory traces' of the chemical network. The implication of this paper is that there is little reason to believe that a lack of suitable phenotypic variation would prevent associative learning from evolving in cell signalling, metabolic, gene regulatory, or a mixture of these networks in cells.

  12. The Chemical Evolution of Phosphorus

    CERN Document Server

    Jacobson, Heather R; Frebel, Anna; Roederer, Ian U; Cescutti, Gabriele; Matteucci, Francesca

    2014-01-01

    Phosphorus is one of the few remaining light elements for which little is known about its nucleosynthetic origin and chemical evolution, given the lack of optical absorption lines in the spectra of long-lived FGK-type stars. We have identified a P I doublet in the near-ultraviolet (2135/2136 A) that is measurable in stars of low metallicity. Using archival Hubble Space Telescope-STIS spectra, we have measured P abundances in 13 stars spanning -3.3 <= [Fe/H] <= -0.2, and obtained an upper limit for a star with [Fe/H] ~ -3.8. Combined with the only other sample of P abundances in solar-type stars in the literature, which spans a range of -1 <= [Fe/H] <= +0.2, we compare the stellar data to chemical evolution models. Our results support previous indications that massive-star P yields may need to be increased by a factor of a few to match stellar data at all metallicities. Our results also show that hypernovae were important contributors to the P production in the early universe. As P is one of the ke...

  13. Measurements of HNO3, SO2 High Resolution Aerosol SO4 (sup 2-), and Selected Aerosol Species Aboard the NASA DC-8 Aircraft: During the Transport and Chemical Evolution Over the Pacific Airborne Mission (TRACE-P)

    Science.gov (United States)

    Talbot, Robert W.; Dibb, Jack E.

    2004-01-01

    The UNH investigation during TRACE-P provided measurements of selected acidic gases and aerosol species aboard the NASA DC-8 research aircraft. Our investigation focused on measuring HNO3, SO2, and fine (less than 2 microns) aerosol SO4(sup 2-) with two minute time resolution in near-real-time. We also quantified mixing ratios of aerosol ionic species, and aerosol (210)Pb and (7)Be collected onto bulk filters at better than 10 minute resolution. This suite of measurements contributed extensively to achieving the principal objectives of TRACE-P. In the context of the full data set collected by experimental teams on the DC-8, our observations provide a solid basis for assessing decadal changes in the chemical composition and source strength of Asian continental outflow. This region of the Pacific should be impacted profoundly by Asian emissions at this time with significant degradation of air quality over the next few decades. Atmospheric measurements in the western Pacific region will provide a valuable time series to help quantify the impact of Asian anthropogenic activities. Our data also provide important insight into the chemical and physical processes transforming Asian outflow during transport over the Pacific, particularly uptake and reactions of soluble gases on aerosol particles. In addition, the TRACE-P data set provide strong constraints for assessing and improving the chemical fields simulated by chemical transport models.

  14. Evolution of chemical abundances in Seyfert galaxies

    OpenAIRE

    Ballero, S. K.; Matteucci, F; Ciotti, L.; Calura, F; P. Padovani

    2007-01-01

    We computed the chemical evolution of spiral bulges hosting Seyfert nuclei, based on updated chemical and spectro-photometrical evolution models for the bulge of our Galaxy, made predictions about other quantities measured in Seyferts, and modeled the photometry of local bulges. The chemical evolution model contains detailed calculations of the Galactic potential and of the feedback from the central supermassive black hole, and the spectro-photometric model covers a wide range of stellar ages...

  15. Entanglement Entropy Evolution under Double-trace Deformation

    CERN Document Server

    Song, Yushu

    2016-01-01

    In this paper, we study the bulk entanglement entropy evolution in conical BTZ black bole background using the heat kernel method. This is motivated by exploring the new examples where quantum corrections of entanglement entropy give the leading contribution. We find that in the large black hole limit the bulk entanglement entropy decreases under the double-trace deformation which is consistent with the holographic $c$ theorem and in the small black hole limit the bulk entanglement entropy increases under the double-trace deformation.

  16. Chemical Sensing for Buried Landmines - Fundamental Processes Influencing Trace Chemical Detection

    Energy Technology Data Exchange (ETDEWEB)

    PHELAN, JAMES M.

    2002-05-01

    Mine detection dogs have a demonstrated capability to locate hidden objects by trace chemical detection. Because of this capability, demining activities frequently employ mine detection dogs to locate individual buried landmines or for area reduction. The conditions appropriate for use of mine detection dogs are only beginning to emerge through diligent research that combines dog selection/training, the environmental conditions that impact landmine signature chemical vapors, and vapor sensing performance capability and reliability. This report seeks to address the fundamental soil-chemical interactions, driven by local weather history, that influence the availability of chemical for trace chemical detection. The processes evaluated include: landmine chemical emissions to the soil, chemical distribution in soils, chemical degradation in soils, and weather and chemical transport in soils. Simulation modeling is presented as a method to evaluate the complex interdependencies among these various processes and to establish conditions appropriate for trace chemical detection. Results from chemical analyses on soil samples obtained adjacent to landmines are presented and demonstrate the ultra-trace nature of these residues. Lastly, initial measurements of the vapor sensing performance of mine detection dogs demonstrates the extreme sensitivity of dogs in sensing landmine signature chemicals; however, reliability at these ultra-trace vapor concentrations still needs to be determined. Through this compilation, additional work is suggested that will fill in data gaps to improve the utility of trace chemical detection.

  17. The Chemical Evolution of Helium

    CERN Document Server

    Balser, D S

    2006-01-01

    We report on measurements of the 4He abundance toward the outer Galaxy HII region S206 with the NRAO Green Bank telescope. Observations of hydrogen and helium radio recombination lines between 8-10 GHz were made toward the peak radio continuum position in S206. We derive 4He/H = 0.08459 +/- 0.00088 (random) +/- 0.0010 (known systematic), 20% lower than optical recombination line results. It is difficult to reconcile the large discrepancy between the optical and radio values even when accounting for temperature, density, and ionization structure or for optical extinction by dust. Using only M17 and S206 we determine dY/dZ = 1.41 +/- 0.62 in the Galaxy, consistent with standard chemical evolution models. High helium abundances in the old stellar population of elliptical galaxies can help explain the increase in UV emission with shorter wavelength between 2000 and 1200 Angstrom, called the UV-upturn or UVX. Our lower values of dY/dZ are consistent with a normal helium abundance at higher metallicity and suggest ...

  18. Entanglement Entropy Evolution under Double-trace Deformation

    OpenAIRE

    Song, Yushu

    2016-01-01

    In this paper, we study the bulk entanglement entropy evolution in conical BTZ black bole background using the heat kernel method. This is motivated by exploring the new examples where quantum corrections of entanglement entropy give the leading contribution. We find that in the large black hole limit the bulk entanglement entropy decreases under the double-trace deformation which is consistent with the holographic $c$ theorem and in the small black hole limit the bulk entanglement entropy in...

  19. Titan's temporal evolution in stratospheric trace gases near the poles

    Science.gov (United States)

    Coustenis, Athena; Jennings, Donald E.; Achterberg, Richard K.; Bampasidis, Georgios; Lavvas, Panayiotis; Nixon, Conor A.; Teanby, Nicholas A.; Anderson, Carrie M.; Cottini, Valeria; Flasar, F. Michael

    2016-05-01

    We analyze spectra acquired by the Cassini/Composite Infrared Spectrometer (CIRS) at high resolution from October 2010 until September 2014 in nadir mode. Up until mid 2012, Titan's Northern atmosphere exhibited the enriched chemical content found since the Voyager days (November 1980), with a peak around the Northern Spring Equinox (NSE) in 2009. Since then, we have observed the appearance at Titan's south pole of several trace species for the first time, such as HC3N and C6H6, observed only at high northern latitudes before equinox. We investigate here latitudes poleward of 50°S and 50°N from 2010 (after the Southern Autumnal Equinox) until 2014. For some of the most abundant and longest-lived hydrocarbons (C2H2, C2H6 and C3H8) and CO2, the evolution in the past 4 years at a given latitude is not very significant within error bars especially until mid-2013. In more recent dates, these molecules show a trend for increase in the south. This trend is dramatically more pronounced for the other trace species, especially in 2013-2014, and at 70°S relative to 50°S. These two regions then demonstrate that they are subject to different dynamical processes in and out of the polar vortex region. For most species, we find higher abundances at 50°N compared to 50°S, with the exception of C3H8, CO2, C6H6 and HC3N, which arrive at similar mixing ratios after mid-2013. While the 70°N data show generally no change with a trend rather to a small decrease for most species within 2014, the 70°S results indicate a strong enhancement in trace stratospheric gases after 2012. The 663 cm-1 HC3N and the C6H6 674 cm-1 emission bands appeared in late 2011/early 2012 in the south polar regions and have since then exhibited a dramatic increase in their abundances. At 70°S HC3N, HCN and C6H6 have increased by 3 orders of magnitude over the past 3-4 years while other molecules, including C2H4, C3H4 and C4H2, have increased less sharply (by 1-2 orders of magnitude). This is a strong

  20. Chemical evolution in hierarchical scenarios

    OpenAIRE

    Tissera P.B.

    2012-01-01

    We studied the chemical properties of Milky-Way mass galaxies. We found common global chemical patterns with particularities which reflect their different assembly histories in a hierarchical scenario. We carried out a comprehensively analysis of the dynamical components (central spheroid, disc, inner and outer haloes) and their chemical properties.

  1. Molybdenite Mineral Evolution: A Study Of Trace Elements Through Time

    Science.gov (United States)

    McMillan, M. M.; Downs, R. T.; Stein, H. J.; Zimmerman, A.; Beitscher, B. A.; Sverjensky, D. A.; Papineau, D.; Armstrong, J. T.; Hazen, R. M.

    2010-12-01

    Mineral evolution explores changes through time in Earth’s near-surface mineralogy, including diversity of species, relative abundances of species, and compositional ranges of major, minor and trace elements. Such studies elucidate the co-evolution of the geosphere and biosphere. Accordingly, we investigated trace and minor elements in molybdenite (MoS2) with known ages from 3 billion years to recent. Molybdenite, the commonest mineral of Mo, may prove to be a useful case study as a consequence of its presence in Earth’s early history, the effects of oxidation on Mo mobility, and the possible role of Mo mineral coevolution with biology via its role in the nitrogen fixation enzyme nitrogenase. We employed ICPMS, SEM and electron microprobe analyses to detect trace and minor elements. We detected significant amounts of Mn and Cu (~100 ppm) and greater amounts of Fe, W, and Re (to ~4000 ppm). Molybdenites commonly contain micro inclusions, resulting in local concentrations in otherwise homogeneous samples. Inhomogeneities in Fe, Zn and Sn concentrations, for example, point to the presence of pyrite, sphalerite and cassiterite inclusions, respectively. Analyses examined as a function of time reveal that samples containing significant concentrations (>200 ppm, compared to average values < 100 ppm) of W and Re formed primarily within the last billion years. These trends may reflect changes in the mobility of W and Re in oxic hydrothermal fluids at shallow crustal conditions following the Great Oxidation Event.

  2. Reconstructing the cosmic evolution of the chemical elements

    CERN Document Server

    Frebel, Anna

    2014-01-01

    The chemical elements are created in nuclear fusion processes in the hot and dense cores of stars. The energy generated through nucleosynthesis allows stars to shine for billions of years. When these stars explode as massive supernovae, the newly made elements are expelled, chemically enriching the surrounding regions. Subsequent generations of stars are formed from gas that is slightly more element enriched than that from which previous stars formed. This chemical evolution can be traced back to its beginning soon after the Big Bang by studying the oldest and most metal-poor stars still observable in the Milky Way today. Through chemical analysis, they provide the only available tool for gaining information about the nature of the short-lived first stars and their supernova explosions more than thirteen billion years ago. These events set in motion the transformation of the pristine universe into a rich cosmos of chemically diverse planets, stars, and galaxies.

  3. A chemical evolution model for galaxy clusters

    OpenAIRE

    Portinari, L.; A. Moretti(Fermilab, Batavia, IL, USA); Chiosi, C.

    2001-01-01

    We develop a toy-model for the chemical evolution of the intracluster medium, polluted by the galactic winds from elliptical galaxies. The model follows the "galaxy formation history" of cluster galaxies, constrained by the observed luminosity function.

  4. Chemical Evolution models of Local Group galaxies

    OpenAIRE

    Tosi., M

    2003-01-01

    Status quo and perspectives of standard chemical evolution models of Local Group galaxies are summarized, discussing what we have learnt from them, what we know we have not learnt yet, and what I think we will learn in the near future. It is described how Galactic chemical evolution models have helped showing that: i) stringent constraints on primordial nucleosynthesis can be derived from the observed Galactic abundances of the light elements, ii) the Milky Way has been accreting external gas...

  5. Galactic chemical evolution: the observational side

    OpenAIRE

    McWilliam, Andrew

    2010-01-01

    In this review I outline some ideas in chemical evolution, necessary for understanding the evolution of galaxies from measured elemental abundance ratios. I then discuss abundance results from studies of Local Group dwarf galaxies and the globular cluster Omega Cen. I present a qualitative scenario of prolonged chemical enrichment in a leaky box that can explain the observed abundance ratios in these systems. Space limitations prevent a comprehensive review of this vast field, so I have restr...

  6. Evolution of a short pulse using ray tracing

    International Nuclear Information System (INIS)

    In a recent paper (Cairns and Fuchs 2010 Nucl. Fusion 80 095001) we have shown how the asymptotic method of stationary phase can be used to find the radiation pattern from an antenna in the far field region. The novel feature of this work is that it describes how to obtain the wave amplitude and phase in complex geometries where an explicit solution in terms of a phase integral is not available. Instead the necessary information is obtained from ray-tracing methods. Here we show how this method can be adapted to give the evolution of a short pulse in a plasma with arbitrary space and time dependence. Again the exact wave form of the pulse, including phase information, can be obtained from ray tracing. This provides a computationally simple way of calculating the behaviour of a short pulse that may be useful in studying some problems in laser–plasma interactions.

  7. Some Chemical Group Separations of Radioactive Trace Elements

    International Nuclear Information System (INIS)

    As a pretreatment for gamma spectrometric analysis methods have been developed for the chemical separation of traces of P, Sc, Ge, As, Se, Br, Zr, Nb, Ru, Ag, Cd, Sn, Sb, I, Hf, Ta, Re, Os, Au and Hg into 9 different groups. By combining the present methods with already existing chemical group separation methods for traces of Na, K, Ca, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Rb, Sr, Mo, In, Fe, Cs, Ba, L.a, the rare earths, W and Ir, a complete separation scheme comprising 15 groups of elements has been worked out. The chemical 15-group separation method has been advantageously used in gamma spectrometric routine analysis of biological materials

  8. The potential for chemical evolution on Titan

    Science.gov (United States)

    Beauchamp, P. M.; Lunine, J. I.; Welch, C.

    2002-01-01

    Sampling of organics to determine oxygen content, extent of acetylene polymerization, existence of chiral molecules and enantiomeric excesses, and searches for specific polymer products, would be of interest in assessing how organic chemistry evolves toward biochemistry. Such efforts would require fairly sophisticated chemical analyses from landed missions. This paper examines this chemistry and the potential instruments that could distinguish chemical evolution.

  9. The chemical evolution of the solar neighbourhood

    OpenAIRE

    Vanbeveren, D.; De Donder, E.

    2002-01-01

    Recent models of galactic chemical evolution account for updated evolutionary models of massive stars (with special emphasis on stellar winds) and for the effects of intermediate mass and massive binaries. The results are summarised. We also present a critical discussion on possible effects of stellar rotation on overall galactic chemical evolutionary simulations.

  10. Climate-chemical interactions and greenhouse effects of trace gases

    Science.gov (United States)

    Shi, Guang-Yu; Fan, Xiao-Biao

    1994-01-01

    A completely coupled one-dimensional radiative-convective (RC) and photochemical-diffusion (PC) model has been developed recently and used to study the climate-chemical interactions. The importance of radiative-chemical interactions within the troposphere and stratosphere has been examined in some detail. We find that increases of radiatively and/or chemically active trace gases such as CO2, CH4 and N2O have both the direct effects and the indirect effects on climate change by changing the atmospheric O3 profile through their interaction with chemical processes in the atmosphere. It is also found that the climatic effect of ozone depends strongly on its vertical distribution throughout the troposphere and stratosphere, as well on its column amount in the atmosphere.

  11. Comets - Chemistry and chemical evolution

    Science.gov (United States)

    Donn, B.

    1982-01-01

    Research on the chemical composition and conditions in comets and their possible role in the origin of life on earth is surveyed. The inorganic and organic compounds and ions indicated in the ultraviolet and visible spectra of comets are noted, and evidence for the existence of at least a small proportion of complex organic molecules in comets is presented. It is then pointed out that while cometary material could have reached the earth and provided volatile elements from which biochemical compounds could have formed, it is unlikely that a cometary nucleus could have withstood the temperatures and pressures necessary to sustain an environment in which life could have originated.

  12. Isotopic anomalies - Chemical memory of Galactic evolution

    Science.gov (United States)

    Clayton, Donald D.

    1988-01-01

    New mechanisms for the chemical memory of isotopic anomalies are proposed which are based on the temporal change during the chemical evolution of the Galaxy of the isotopic composition of the mean ejecta from stars. Because of the differing temporal evolution of primary and secondary products of nucleosynthesis, the isotopic composition of the bulk interstellar medium changes approximately linearly with time, and thus any dust component having an age different from that of average dust will be isotopically anomalous. Special attention is given to C, O, Mg, Si, and isotopically heavy average-stellar condensates of SiC.

  13. Radiation-induced chemical evolution of biomolecules

    International Nuclear Information System (INIS)

    Chemical evolution in glycilglycine (Gly2) films irradiated with 146 nm vacuum ultraviolet light was studied. It is found that quantum efficiency of chemical evolution from Gly2 to glycilglycilglycine (Gly3) is smaller than that to glycilglycilglycilglycine (Gly4) due to the multiple step of reaction. Furthermore, we have carried out measurement of soft X-ray natural circular dichroism spectra for serine and alanine films in the energy region of oxygen 1s transition and we report the splitting of 1s→π* transitions.

  14. Chemical evolution of the early Martian hydrosphere

    Science.gov (United States)

    Schaefer, M. W.

    1990-01-01

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

  15. Chemical Evolution in Hierarchical Clustering Scenarios

    OpenAIRE

    Tissera, Patricia B.; Scannapieco, Cecilia

    2003-01-01

    We present first results of an implementation of chemical evolution in a cosmological hydrodynamical code, focusing the analysis on the effects of cooling baryons according to their metallicity. We found that simulations with primordial cooling can underestimate the star formation rate from $z < 3$ and by up to $\\approx 20 %$. We constructed simulated spectra by combining the star formation and chemical history of galactic systems with spectra synthesis models and assess the impact of chemica...

  16. Galactic chemical evolution hydrogen through zinc

    CERN Document Server

    Timmes, F X; Timmes, F X; Woosley, S E

    1994-01-01

    Using the output from a grid of 60 Type II supernova models (Woosley \\& Weaver 1994) of varying mass (11 \\ltaprx M/M\\sun \\ltaprx 40) and metallicity (0, 10^{-4}, 0.01, 0.1, and 1 Z\\sol), the chemical evolution of 76 stable isotopes, from hydrogen to zinc, is calculated. The chemical evolution calculation employs a simple dynamical model for the Galaxy (infall with a 4 billion year e-folding time scale onto a exponential disk and 1/r^2 bulge), and standard evolution parameters, such as a Salpeter initial mass function and a quadratic Schmidt star formation rate. The theoretical results are compared in detail with observed stellar abundances in stars with metallicities in the range -3.0 \\ltaprx [Fe/H] \\ltaprx 0.0 dex. While our discussion focuses on the solar neighborhood where there are the most observations, the supernovae rates, an intrinsically Galactic quantity, are also discussed.

  17. Evolution of chemical abundances in Seyfert galaxies

    CERN Document Server

    Ballero, S K; Ciotti, L; Calura, F; Padovani, P

    2007-01-01

    We computed the chemical evolution of spiral bulges hosting Seyfert nuclei, based on updated chemical and spectro-photometrical evolution models for the bulge of our Galaxy, made predictions about other quantities measured in Seyferts, and modeled the photometry of local bulges. The chemical evolution model contains detailed calculations of the Galactic potential and of the feedback from the central supermassive black hole, and the spectro-photometric model covers a wide range of stellar ages and metallicities. We followed the evolution of bulges in the mass range 10^9 - 10^{11} Msun by scaling the star formation efficiency and the bulge scalelength as in the inverse-wind scenario for elliptical galaxies, and considering an Eddington limited accretion onto the central supermassive black hole. We successfully reproduced the observed black hole-host bulge mass relation. The observed nuclear bolometric luminosity is reproduced only at high redshift or for the most massive bulges; in the other cases, at z = 0 a r...

  18. The Chemical Evolution of Dynamically Hot Galaxies

    Directory of Open Access Journals (Sweden)

    Michael G. Richer

    2001-01-01

    Full Text Available We investigate the chemical properties of M32, the bulges of M31 and the Milky Way, and the dwarf spheroidal galaxies NGC 205, NGC 185, Sagittarius, and Fornax using oxygen abundances for their planetary nebulae. Our principal result is that the mean stellar oxygen abundances correlate very well with thei r mean velocity dispersions, implying that the balance between energy input from type II supernovae and the gravitational potential controls chemical evolution in bulges, ellipticals, and dwarf spheroidals. It appears that chemical evolution ceases once supernovae have injected sufficient energy that a galacti c wind develops. All of the galaxies follow a single relation between oxygen abundance and luminosity, but the dwarf spheroidals have systematically higher [O/Fe] ratios than the other galaxies. Consequently, dynamically hot galaxies do not share a common star formation history nor need to a common chemical evolution, despite attaining similar mean stellar oxygen abundances when formin g similar masses. The oxygen abundances support previous indications that stars in higher luminosity ellipticals and bulges were formed on a shorter time scale than their counterparts in less luminous systems.

  19. Chemical evolution in spiral and irregular galaxies

    Science.gov (United States)

    Torres-Peimbert, S.

    1986-01-01

    A brief review of models of chemical evolution of the interstellar medium in our galaxy and other galaxies is presented. These models predict the time variation and radial dependence of chemical composition in the gas as function of the input parameters; initial mass function, stellar birth rate, chemical composition of mass lost by stars during their evolution (yields), and the existence of large scale mass flows, like infall from the halo, outflow to the intergalactic medium or radial flows within a galaxy. At present there is a considerable wealth of observational data on the composition of HII regions in spiral and irregular galaxies to constrain the models. Comparisons are made between theory and the observed physical conditions. In particular, studies of helium, carbon, nitrogen and oxygen abundances are reviewed. In many molecular clouds the information we have on the amount of H2 is derived from the observed CO column density, and a standard CO/H2 ratio derived for the solar neighborhood. Chemical evolution models and the observed variations in O/H and N/O values, point out the need to include these results in a CO/H2 relation that should be, at least, a function of the O/H ratio. This aspect is also discussed.

  20. Chemical Evolution of the Juvenile Universe

    CERN Document Server

    Wasserburg, G J

    2009-01-01

    Only massive stars contribute to the chemical evolution of the juvenile universe corresponding to [Fe/H]-0.32. Recent observations show that there are stars with [Sr/Fe]<-2 and [Fe/H]<-3. This proves that the two-component model is not correct and that a third component is necessary to explain the observations. This leads to a simple three-component model including low-mass and normal SNe II and hypernovae (HNe), which gives a good description of essentially all the data for stars with [Fe/H]<-1.5. We conclude that HNe are more important than normal SNe II in the chemical evolution of the low-A elements, in sharp distinction to earlier models. (Abridged)

  1. Chemical evolution: A solar system perspective

    Science.gov (United States)

    Oro, J.

    1989-01-01

    During the last three decades major advances were made in the understanding of the formation of carbon compounds in the universe and of the occurrence of processes of chemical evolution in the solar system and beyond. This was made possible by the development of new astronomical techniques and by the exploration of the solar system by means of properly instrumented spacecraft. Some of the major findings made as a result of these observations are summarized.

  2. Tracing back the evolution of the candidate LBV HD168625

    CERN Document Server

    Mahy, L; Royer, P; Waelkens, C

    2016-01-01

    Aims. We obtained Herschel/PACS imaging and spectroscopic observations of the nebula surrounding the candidate LBV HD168625. By combining these data with optical spectra of the star, we want to constrain the abundances in the nebula and in the star and compare them to trace back its evolution. Methods. We use CMFGEN to determine the fundamental parameters and the CNO abundances of the central star whilst the abundances of the nebula are derived from the emission lines present in the Herschel/PACS spectrum. Result. The FIR images show a nebula composed of an elliptical ring/torus of ejecta with a ESE-WNW axis and of a second perpendicular bipolar structure composed of empty caps/rings. We detect equatorial shells composed of dust and ionized material with different sizes when observed at different wavelengths, and bipolar caps more of less separated from the central star in H$\\alpha$ and mid-IR images. This complex global structure seems to show 2 different inclinations: 40{\\deg} for the equatorial torus and 6...

  3. Multiphase chemical evolution in elliptical galaxies

    CERN Document Server

    Fujita, Y; Okoshi, K

    1996-01-01

    The recent {\\em ASCA} results show that the iron abundance of the X-ray gas of elliptical galaxies is less than the solar abundance (Z_{\\sun}). The observed low iron abundance is inconsistent with the predictions of the previous chemical evolution models. In order to solve this problem, we present a simple model of chemical evolution for elliptical galaxies after the galactic wind period under the assumption that the gases ejected from stars do not mix with the circumferential gas. The ejected gas components evolve separately according to their birth time and origin. We have investigated their evolution qualitatively. The gas components originated from supernova remnant shells cool and drop out of the hot gas faster than the other components because of their high density and metal abundance. As a result, supernovae cannot heat the whole gas of the elliptical galaxies effectively, in contrary to the previous results. If the metal abundance of mass-loss gas is not uniform, the mass-loss gas with higher abundanc...

  4. Inhomogeneous chemical evolution of the Galactic disk

    Science.gov (United States)

    Malinie, Guy; Hartmann, Dieter H.; Clayton, Donald D.; Mathews, Grant J.

    1993-01-01

    We present analytical models for inhomogeneous chemical evolution (ICE) of systems in which the star formation history resembles a series of bursts, localized in space and/or time, with intermittent periods of remixing. The additional parameter of this model is the metallicity increment of bursting subsystems, but this parameter is constrained by the spread in the age-metallicity relation. We apply this model to the solar annulus in the Galactic disk and show that ICE models yield an improved fit to the observed shape of the stellar abundance distribution function (ADF). The G-dwarf problem can be alleviated with ICE models, but infall of metal poor gas and/or some preenrichment of the disk during the epoch of protogalactic evolution is still required to explain the paucity of low-metallicity dwarfs. ICE models also suggest an explanation of the reduced frequency of metal-rich G-dwarfs relative to the predictions of the simple model. It does not seem likely that chemical evolution of the solar annulus proceeded in a medium that was well-mixed at all times.

  5. Galacti chemical evolution: Hygrogen through zinc

    Science.gov (United States)

    Timmes, F. X.; Woosley, S. E.; Weaver, Thomas A.

    1995-01-01

    Using the output from a grid of 60 Type II supernova models (Woosley & Weaver 1995) of varying mass (11 approx. less than (M/solar mass) approx. less than 40) and metallicity (0, 10(exp -4), 0.01, and 1 solar metallicity), the chemical evolution of 76 stable isotopes, from hydrogen to zinc, is calculated. The chemical evolution calculation employs a simple dynamical model for the Galaxy (infall with a 4 Gyr e-folding timescale onto a exponential dsk and 1/r(exp 2) bulge), and standard evolution parameters, such as a Salpeter initial mass function and a quadratic Schmidt star formation rate. The theoretical results are compared in detail with observed stellar abundances in stars with metallicities in the range -3.0 approx. less than (Fe/H) approx. less than 0.0 dex. While our discussion focuses on the solar neighborhood where there are the most observations, the supernova rates, an intrinsically Galactic quality, are also discussed.

  6. Thermal and Chemical Evolution of Collapsing Filaments

    CERN Document Server

    Gray, William J

    2013-01-01

    Intergalactic filaments form the foundation of the cosmic web that connect galaxies together, and provide an important reservoir of gas for galaxy growth and accretion. Here we present very high resolution two-dimensional simulations of the thermal and chemical evolution of such filaments, making use of a 32 species chemistry network that tracks the evolution of key molecules formed from hydrogen, oxygen, and carbon. We study the evolution of filaments over a wide range of parameters including the initial density, initial temperature, strength of the dissociating UV background, and metallicity. In low-redshift, $Z \\approx 0.1 Z_\\odot $ filaments, the evolution is determined completely by the initial cooling time. If this is sufficiently short, the center of the filament always collapses to form dense, cold core containing a substantial fraction of molecules. In high-redshift, $Z=10^{-3} Z_\\odot$ filaments, the collapse proceeds much more slowly. This is due mostly to the lower initial temperatures, which lead...

  7. Equilibrium and Sudden Events in Chemical Evolution

    CERN Document Server

    Weinberg, David H; Freudenburg, Jenna

    2016-01-01

    We present new analytic solutions for one-zone (fully mixed) chemical evolution models and explore their implications. In contrast to existing analytic models, we incorporate a realistic delay time distribution for Type Ia supernovae (SNIa) and can therefore track the separate evolution of $\\alpha$-elements produced by core collapse supernovae (CCSNe) and iron peak elements synthesized in both CCSNe and SNIa. In generic cases, $\\alpha$ and iron abundances evolve to an equilibrium at which element production is balanced by metal consumption and gas dilution, instead of continuing to increase over time. The equilibrium absolute abundances depend principally on supernova yields and the outflow mass loading parameter $\\eta$, while the equilibrium abundance ratio [$\\alpha$/Fe] depends mainly on yields and secondarily on star formation history. A stellar population can be metal-poor either because it has not yet evolved to equilibrium or because high outflow efficiency makes the equilibrium abundance itself low. Sy...

  8. Chemical evolution of primitive solar system bodies

    Science.gov (United States)

    Oro, J.; Mills, T.

    1989-01-01

    Observations on organic molecules and compounds containing biogenic elements in the interstellar medium and in the primitive bodies of the solar system are reviewed. The discovery of phosphorus molecular species in dense interstellar clouds, the existence of organic ions in the dust and gas phase of the comas of Comet Halley, and the presence of presolar, deuterium-hydrogen ratios in the amino acids of carbonaceous chondrites are discussed. The relationships between comets, dark asteroids, and carbonaceous chondrites are examined. Also, consideration is given to the chemical evolution of Titan, the primitive earth, and early Mars.

  9. Chemical Evolution Models of Local dSph Galaxies

    CERN Document Server

    Carigi, L; Gilmore, G; Carigi, Leticia; Hernandez, Xavier; Gilmore, Gerard

    2002-01-01

    We calculate chemical evolution models for 4 dwarf spheroidal satellites of the Milky Way (Carina, Ursa Minor, Leo I and Leo II) for which reliable non-parametric star formation histories have been derived. In this way, the independently obtained star formation histories are used to constrain the evolution of the systems we are treating. This allows us to obtain robust inferences on the history of such crucial parameters of galactic evolution as gas infall, gas outflows and global metallicities for these systems. We can then trace the metallicity and abundance ratios of the stars formed, the gas present at any time within the systems and the details of gas ejection, of relevance to enrichment of the galaxies environment. We find that galaxies showing one single burst of star formation (Ursa Minor and Leo II) require a dark halo slightly larger that the current estimates for their tidal radii, or the presence of a metal rich selective wind, which might carry away much of the energy output of their supernovae b...

  10. Chemical Evolution of Blue Compact Galaxies

    Institute of Scientific and Technical Information of China (English)

    Fei Shi; Xu Kong; Fu-Zhen Cheng

    2006-01-01

    Based on a sample of 72 Blue Compact Galaxies (BCGs) observed with the 2.16 m telescope of the National Astronomical Observatories, Chinese Academy of Sciences (NAOC) and about 4000 strong emission line galaxies from the Sloan Digital Sky Survey,we analyzed their chemical evolution history using the revised chemical evolution model of Larsen et al. Our sample covers a much larger metallicity range (7.2<12+log(O/H) <9.0). We found that, in order to reproduce the observed abundance pattern and gas fraction over the whole metallicity range, a relatively continuous star formation history is needed for high metallicity galaxies, while assuming a series of instantaneous bursts with long quiescent periods (some Gyrs) for low metallicity galaxies. Model calculations also show that only the closed-box model is capable of reproducing the observational data over the whole metallicity range. Models that consider the ordinary winds and/or inflow can only fit the observations in the low metallicity range, and a model with enriched wind cannot fit the data in the whole metallicity range. This implies that the current adopted simple wind and inflow models are not applicable to massive galaxies, where the underlying physics of galactic winds or inflow could be more complicated.

  11. Uncertainties in Galactic Chemical Evolution Models

    Science.gov (United States)

    Côté, Benoit; Ritter, Christian; O’Shea, Brian W.; Herwig, Falk; Pignatari, Marco; Jones, Samuel; Fryer, Chris L.

    2016-06-01

    We use a simple one-zone galactic chemical evolution model to quantify the uncertainties generated by the input parameters in numerical predictions for a galaxy with properties similar to those of the Milky Way. We compiled several studies from the literature to gather the current constraints for our simulations regarding the typical value and uncertainty of the following seven basic parameters: the lower and upper mass limits of the stellar initial mass function (IMF), the slope of the high-mass end of the stellar IMF, the slope of the delay-time distribution function of Type Ia supernovae (SNe Ia), the number of SNe Ia per M ⊙ formed, the total stellar mass formed, and the final mass of gas. We derived a probability distribution function to express the range of likely values for every parameter, which were then included in a Monte Carlo code to run several hundred simulations with randomly selected input parameters. This approach enables us to analyze the predicted chemical evolution of 16 elements in a statistical manner by identifying the most probable solutions, along with their 68% and 95% confidence levels. Our results show that the overall uncertainties are shaped by several input parameters that individually contribute at different metallicities, and thus at different galactic ages. The level of uncertainty then depends on the metallicity and is different from one element to another. Among the seven input parameters considered in this work, the slope of the IMF and the number of SNe Ia are currently the two main sources of uncertainty. The thicknesses of the uncertainty bands bounded by the 68% and 95% confidence levels are generally within 0.3 and 0.6 dex, respectively. When looking at the evolution of individual elements as a function of galactic age instead of metallicity, those same thicknesses range from 0.1 to 0.6 dex for the 68% confidence levels and from 0.3 to 1.0 dex for the 95% confidence levels. The uncertainty in our chemical evolution model

  12. Xenia: A Probe of Cosmic Chemical Evolution

    Science.gov (United States)

    Kouveliotou, Chryssa; Piro, L.

    2008-01-01

    Xenia is a concept study for a medium-size astrophysical cosmology mission addressing the Cosmic Origins key objective of NASA's Science Plan. The fundamental goal of this objective is to understand the formation and evolution of structures on various scales from the early Universe to the present time (stars, galaxies and the cosmic web). Xenia will use X-and y-ray monitoring and wide field X-ray imaging and high-resolution spectroscopy to collect essential information from three major tracers of these cosmic structures: the Warm Hot Intergalactic Medium (WHIM), Galaxy Clusters and Gamma Ray Bursts (GRBs). Our goal is to trace the chemo-dynamical history of the ubiquitous warm hot diffuse baryon component in the Universe residing in cosmic filaments and clusters of galaxies up to its formation epoch (at z =0-2) and to map star formation and galaxy metal enrichment into the re-ionization era beyond z 6. The concept of Xenia (Greek for "hospitality") evolved in parallel with the Explorer of Diffuse Emission and GRB Explosions (EDGE), a mission proposed by a multinational collaboration to the ESA Cosmic Vision 2015. Xenia incorporates the European and Japanese collaborators into a U.S. led mission that builds on the scientific objectives and technological readiness of EDGE.

  13. AGB stars and the chemical evolution of galaxies

    OpenAIRE

    Tosi, Monica

    2007-01-01

    Asymptotic Giant Branch (AGB) stars are important players in the chemical evolution modelling of galaxies, because they are major producers of several chemical elements and excellent tracers of the structure and of the star formation activity of their parent galaxies. A few examples on the importance of AGB stars are presented in this review, together with a number of open problems affecting chemical evolution model predictions related to the element enrichment by AGB stars: the evolution of ...

  14. The Chemical Evolution of Titan's Atmosphere

    Science.gov (United States)

    Kaiser, Ralf I.

    2010-11-01

    Astrochemistry or Astrochemical Dynamics presents a newly emerging, interdisciplinary and innovative field comprising scientists in chemistry, physics, biology, astronomy, and planetary chemistry. The prime directive of Astrochemical Dynamics is to understand the origin and chemical evolution of the interstellar medium and of our Solar System. Here, the arrival of the Cassini-Huygens probe at Saturn's moon Titan - the only Solar System body besides Earth and Venus with a solid surface and thick atmosphere - in 2004 opened up a new chapter in the history of Solar System exploration. Titan's most prominent optically visible features are the aerosol-based haze layers, which give Titan its orange-brownish color. However, the underlying chemical processes, which initiate the haze formation, have been the least understood to date. This talk reviews recent laboratory studies on the role of polyacetylenes (polyynes) and (hetero)aromatic molecules like the phenyl radical, benzene, and pyridine in the formation of Titan's organic haze layers utilizing crossed molecular beam experiments. Those investigations provide key concepts on the formation mechanisms of unsaturated hydrocarbon molecules - in particular polyynes and aromatic compounds - together with their hydrogen deficient precursors from the "bottom up" in the atmosphere of Saturn's moon Titan. A brief outline to future research directions tackling also the heterogeneous chemistry on Titan and in hydrocarbon-rich atmospheres in the outer Solar System in general will also be presented.

  15. Chemical Evolution of Presolar Organics in Astromaterials

    Science.gov (United States)

    Nakamura-Messenger, K.; Clemett, S. J.; Messenger, Scott; Keller, L. P.

    2010-01-01

    Sub-micron, hollow organic globules reported from several carbonaceous chondrites, interplanetary dust particles, and comet Wild-2 samples returned by NASA?s Stardust mission are enriched in N-15/N-14 and D/H compared with terrestrial materials and the parent materials [1-4]. These anomalies are ascribed to the preservation of presolar cold molecular cloud material from where H, C, and N isotopic constraints point to chemical fractionation near 10 K [5]. An origin well beyond the planet forming region and their survival in meteorites suggests submicrometer organic globules were once prevalent throughout the solar nebula. The survival of the membrane structures indicates primitive meteorites and cometary dust particles would have delivered these organic precursors to the early Earth as well as other planets and satellites. The physical, chemical, and isotopic properties of the organic globules varies to its meteorite types and its lithologies. For example, organic globules in the Tagish Lake meteorite are always embedded in fined grained (poorly crystallized) saponite, and hardly encapsulated in coarse grained serpentine, even though saponite and serpentine are both main components of phyllosilicate matrix of the Tagish Lake meteorite. The organic globules are commonly observed in the carbonate-poor lithology but not in the carbonate-rich one. In Tagish Lake, isolated single globules are common, but in the Bells (CM2) meteorite, globules are mostly aggregated. We will review the evolutions of the organic globules from its birth to alteration in the parent bodies in terms of its own physical and chemical properties as well as its associated minerals.

  16. Natural evidence for chemical and early biological evolution

    Science.gov (United States)

    Kvenvolden, K. A.

    1974-01-01

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

  17. Tennessee to Texas: Tracing the Evolution Controversy in Public Education

    Science.gov (United States)

    Armenta, Tony; Lane, Kenneth E.

    2010-01-01

    Darwin's Theory of Evolution has stirred controversy since its inception. Public schools in the United States, pressed by special interest groups on both sides of the controversy, have struggled with how best to teach the theory, if at all. Court cases have dealt with whether states can ban the teaching of evolutionary theory, whether Creationism…

  18. Chemical Evolution of the Juvenile Universe

    Science.gov (United States)

    Wasserburg, G. J.; Qian, Y.-Z.

    2009-09-01

    Models of average Galactic chemical abundances are in good general agreement with observations for [Fe/H] > -1.5, but there are gross discrepancies at lower metallicities. Only massive stars contribute to the chemical evolution of the `juvenile universe' corresponding to [Fe/H] SN II contributions. Both low-mass (~8-11 Msolar) and normal (~12-25 Msolar) SNe II produce neutron stars, which have intense neutrino-driven winds in their nascent stages. These winds produce elements such as Sr, Y and Zr through charged-particle reactions (CPR). Such elements are often called the `light r-process elements', but are considered here as products of CPR and not the r process. The observed absence of production of the low-A elements (Na through Zn including Fe) when the true r-process elements (Ba and above) are produced requires that only low-mass SNe II be the site if the r process occurs in SNe II. Normal SNe II produce the CPR elements in addition to the low-A elements. This results in a two-component model that is quantitatively successful in explaining the abundances of all elements relative to hydrogen for -3 = -0.32. Recent observations show that there are stars with [Sr/Fe] <~ -2 and [Fe/H] < -3. This proves that the two-component model is not correct and that a third component is necessary to explain the observations. The production of CPR elements associated with the formation of neutron stars requires that the third component must be massive stars ending as black holes. It is concluded that stars of ~25-50 Msolar (possibly up to ~100 Msolar) are the appropriate candidates. These produce hypernovae (HNe) that have very high Fe yields and are observed today. Stars of ~140-260 Msolar are completely disrupted upon explosion. However, they produce an abundance pattern greatly deficient in elements of odd atomic numbers, which is not observed, and therefore they are not considered as a source here. Using a Salpeter initial mass function, it is shown that HNe are a source

  19. Galaxy evolution: the effect of dark matter on the chemical evolution of ellipticals and galaxy clusters

    OpenAIRE

    Matteucci, F.; Gibson, B. K.

    1996-01-01

    In this paper we discuss the chemical evolution of elliptical galaxies and its consequences on the evolution of the intracluster medium (ICM). We use chemical evolution models taking into account dark matter halos and compare the results with previous models where dark matter was not considered. In particular, we examine the evolution of the abundances of some relevant heavy elements such as oxygen, magnesium and iron and conclude that models including dark matter halos and an initial mass fu...

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

    Science.gov (United States)

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

    1998-01-01

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

  1. Applications of a versatile technique for trace analysis: atmospheric pressure negative chemical ionization.

    OpenAIRE

    Thomson, B A; Davidson, W R; Lovett, A M

    1980-01-01

    The ability to use ambient air as a carrier and reagent gas in an atmospheric pressure chemical ionization source allows instantaneous air analysis to be combined with hypersensitivity toward a wide variety of compounds. The TAGA (Trace Atmospheric Gas Analyser) is an instrument which is designed to use both positive and negative atmospheric pressure chemical ionization (APCI) for trace gas analysis; this paper describes several applications of negative APCI which demonstrates that the techni...

  2. Recent advances in chemical engineering. Tracers and tracing methods

    International Nuclear Information System (INIS)

    The first congress on 'tracers and tracing methods' has taken place in Nancy in November 1998. It has been a successful national event with more than 100 participants and 65 presentations. The applications of radiotracers in different industries have been studied. The target participants were the researchers, engineers and technologists of various industrial and research sectors

  3. Galaxy Formation and Chemical Evolution in Hierarchical Hydrodynamical Simulations

    OpenAIRE

    Cora, S. A.; Mosconi, M. B.; P. B. Tissera; Lambas, D. G.

    2000-01-01

    We report first results of an implementation of a chemical model in a cosmological code, based on the Smoothed Particle Hydrodynamics (SPH) technique. We show that chemical SPH simulations are a promising tool to provide clues for the understanding of the chemical properties of galaxies in relation to their formation and evolution in a cosmological framework.

  4. Tracing monotreme venom evolution in the genomics era.

    Science.gov (United States)

    Whittington, Camilla M; Belov, Katherine

    2014-04-01

    The monotremes (platypuses and echidnas) represent one of only four extant venomous mammalian lineages. Until recently, monotreme venom was poorly understood. However, the availability of the platypus genome and increasingly sophisticated genomic tools has allowed us to characterize platypus toxins, and provides a means of reconstructing the evolutionary history of monotreme venom. Here we review the physiology of platypus and echidna crural (venom) systems as well as pharmacological and genomic studies of monotreme toxins. Further, we synthesize current ideas about the evolution of the venom system, which in the platypus is likely to have been retained from a venomous ancestor, whilst being lost in the echidnas. We also outline several research directions and outstanding questions that would be productive to address in future research. An improved characterization of mammalian venoms will not only yield new toxins with potential therapeutic uses, but will also aid in our understanding of the way that this unusual trait evolves. PMID:24699339

  5. Tracing Monotreme Venom Evolution in the Genomics Era

    Directory of Open Access Journals (Sweden)

    Camilla M. Whittington

    2014-04-01

    Full Text Available The monotremes (platypuses and echidnas represent one of only four extant venomous mammalian lineages. Until recently, monotreme venom was poorly understood. However, the availability of the platypus genome and increasingly sophisticated genomic tools has allowed us to characterize platypus toxins, and provides a means of reconstructing the evolutionary history of monotreme venom. Here we review the physiology of platypus and echidna crural (venom systems as well as pharmacological and genomic studies of monotreme toxins. Further, we synthesize current ideas about the evolution of the venom system, which in the platypus is likely to have been retained from a venomous ancestor, whilst being lost in the echidnas. We also outline several research directions and outstanding questions that would be productive to address in future research. An improved characterization of mammalian venoms will not only yield new toxins with potential therapeutic uses, but will also aid in our understanding of the way that this unusual trait evolves.

  6. Chemical effects of ionizing radiation and sonic energy in the context of chemical evolution

    International Nuclear Information System (INIS)

    Ionizing radiation and sonic energy are considered as sources for chemical evolution processes. These sources have still a modest place in the interdisciplinary approach for the prebiological synthesis of organic compounds. Studies in Radiation Chemistry and Sonochemistry can provide a deeper insight into the chemical processes that may have importance for prebiotic chemistry. The present work concerns the analysis of some chemical reactions induced by ionizing radiation or cavitation in aqueous media that may be relevant to chemical evolution studies. (author)

  7. Conference on chemical evolution and the origin of life

    International Nuclear Information System (INIS)

    This report contains 19 summaries of papers presented at the Conference on Chemical Evolution and the Origin of Life held at the International Centre for Theoretical Physics. A separate indexing is provided for each summary

  8. On the transition period from chemical to biological evolution

    International Nuclear Information System (INIS)

    We discuss the consequences of the hypothesis that biological evolution was contemporary with an important event in chemical evolution, namely, the induction of a small chiral bias by the electroweak neutral interaction, amplified by the Salam enhancement factor, which we discuss in terms of familiar crystallographic terms. (author). 18 refs, 3 tabs

  9. Chemical evolution and the preservation of organic compounds on Mars

    Science.gov (United States)

    Kanavarioti, Anastassia; Mancinelli, Rocco L.

    1989-01-01

    Several lines of evidence suggest that the environment on early Mars and early Earth were very similar. Since life is abundant on Earth, it seems likely that conditions on early Earth were conducive to chemical evolution and the origin of life. The similarity between early Mars and early Earth encourages the hypothesis that chemical evolution might have also occurred on Mars, but that decreasing temperatures and the loss of its atmosphere brought the evolution to a halt. The possibility of finding on Mars remnants of organic material dating back to this early clement period is addressed.

  10. Stellar nucleosynthesis and chemical evolution of the solar neighborhood

    Science.gov (United States)

    Clayton, Donald D.

    1988-01-01

    Current theoretical models of nucleosynthesis (N) in stars are reviewed, with an emphasis on their implications for Galactic chemical evolution. Topics addressed include the Galactic population II red giants and early N; N in the big bang; star formation, stellar evolution, and the ejection of thermonuclearly evolved debris; the chemical evolution of an idealized disk galaxy; analytical solutions for a closed-box model with continuous infall; and nuclear burning processes and yields. Consideration is given to shell N in massive stars, N related to degenerate cores, and the types of observational data used to constrain N models. Extensive diagrams, graphs, and tables of numerical data are provided.

  11. Calculating Chemical Evolution on the Web

    Science.gov (United States)

    Meyer, B. S.; Denny, J. E.; Clayton, D. D.

    2001-01-01

    We have constructed an interactive web site that may be of interest to cosmochemists seeking to understand the evolution of isotopes in the Galaxy. The URL is http://photon.phys.clemson.edu/gce.html. Additional information is contained in the original extended abstract.

  12. Evolution of exocrine chemical defense in leaf beetles (Coleoptera: Chrysomelidae)

    OpenAIRE

    Pasteels, Jacques M.; Rowell-Rahier, Martine; Braekman, J.C.; Daloze, D.; Duffey, S.

    2009-01-01

    In this review we speculate on possible scenarios for the evolution of the very high diversity in chemical compounds liberated by exocrine glands of adults Chrysomelidae. Shift in host plant affinities and subsequent adaptation of the beetles to the plant toxins strongly influence the nature of the beetles' chemical defense.

  13. Chemical evolution of Elliptical Galaxies and the ICM

    OpenAIRE

    Pipino, Antonio; Matteucci, Francesca

    2002-01-01

    We present a new model for the chemical evolution of elliptical galaxies taking into account SN feedback, detailed nucleosynthesis and galactic winds. We discuss the effect of galactic winds on the chemical enrichment of the ICM and compute the energy per particle injected by the galaxies into the ICM.

  14. The possible role of soluble salts in chemical evolution

    Science.gov (United States)

    Lahav, N.; Chang, S.

    1982-01-01

    A model for a prebiotic environment in which concentration, condensation, and chemical evolution of biomolecules could have occurred is proposed. The principal reactions expected of proteins, nucleic acids, lipids, and some of their precursors in this environment are discussed. The model is based on the concept of a fluctuating system in which hydration and dehydration processes occur in a cyclic manner, with allowance for high concentrations of soluble salts, such as chlorides and sulfates. It is concluded that the proposed prebiotic environment with its dynamical characteristics is a plausible model for the chemical evolution from biomonomers through random oligomers toward self-replicating chemical systems.

  15. Molecular Evolution and Functional Divergence of Trace Amine–Associated Receptors

    OpenAIRE

    Eyun, Seong-il; Moriyama, Hideaki; Hoffmann, Federico G.; Moriyama, Etsuko N.

    2016-01-01

    Trace amine-associated receptors (TAARs) are a member of the G-protein-coupled receptor superfamily and are known to be expressed in olfactory sensory neurons. A limited number of molecular evolutionary studies have been done for TAARs so far. To elucidate how lineage-specific evolution contributed to their functional divergence, we examined 30 metazoan genomes. In total, 493 TAAR gene candidates (including 84 pseudogenes) were identified from 26 vertebrate genomes. TAARs were not identified ...

  16. Modelling the Fate of Ionizable Trace Organic Chemicals from Consumption to Food Crops

    DEFF Research Database (Denmark)

    Polesel, Fabio; Plósz, Benedek G.; Trapp, Stefan

    In this study, we developed and applied a simulation tool to comprehensively predict the fate of three ionizable trace chemicals (triclosan—TCS, furosemide—FUR, ciprofloxacin—CIP) from human consumption/excretion up to the accumulation in wheat, following application of sewage sludge or irrigation...... with river water. Highest translocation to wheat (4.3 μg kgDW-1 in grain) was calculated for FUR, being more significant with irrigation (>45% of emission to soil) than with sludge application (<30%). The simulation tool presented here can be used for estimating human exposure to trace chemicals via...

  17. Interaction of chemical species with biological regulation of the metabolism of essential trace elements

    Energy Technology Data Exchange (ETDEWEB)

    Windisch, W. [Center of Life and Food Sciences, Technische Univ. Muenchen, Freising (Germany)

    2002-02-01

    Variations in the chemical speciation of dietary trace elements can result in the provision of different amounts of these micronutrients to the organism and might thus induce interactions with trace-element metabolism. The chemical species of Zn, Fe, Cu, and Mn can interact with other components of the diet even before reaching the site of absorption, e.g. by formation of poorly soluble complexes with phytic acid. This might considerably modify the amount of metabolically available trace elements; differences between absorptive capacity per se toward dietary species seems to be less important. Homeostasis usually limits the quantities of Zn, Fe, Cu, and Mn transported from the gut into the organism, and differences between dietary species are largely eliminated at this step. There is no homeostatic control of absorption of Se and I, and organisms seem to be passively exposed to influx of these micronutrients irrespective of dietary speciation. Inside the organism the trace elements are usually converted into a metabolically recognizable form, channeled into their biological functions, or submitted to homeostatically controlled excretion. Some dietary species can, however, be absorbed as intact compounds. As long as the respective quantities of trace elements are not released from their carriers, they are not recognized properly by trace element metabolism and might induce tissue accumulation, irrespective of homeostatic control. (orig.)

  18. Chemical Ionization Mass Spectrometry-Based Measurements of HO2 and RO2 During TRACE-P

    Science.gov (United States)

    Cantrell, Christopher A.; Eisele, Fred L.

    2004-01-01

    The Transport and Chemical Evolution over the Pacific (TRACE-P) mission extends NASA's Global Tropospheric Experiment (GTE) series of campaigns. TRACE-P was an aircraft-based campaign that was part of a larger ground-based and aircraft-based program (APARE) under the auspices of the International Global Atmospheric Chemistry (IGAC) program. TRACE-P was designed to (1) determine the chemical composition of Asian outflow over the western Pacific, and to (2) determine the chemical evolution of the Asian outflow. These objectives were addressed through a variety of observations and numerical modeling exercises. In particular, the goals included sampling strategies that would improve understanding of the budgets of odd hydrogen species (OH and HO2), budgets of NOx (NO, NO2, and their reservoirs), and impacts of oxidants produced in the outflow on air quality in the United States. The NASA DC-8 and P-3B aircraft were deployed in the March and April, 2001 out of primary bases of operation in Hong Kong and Yokota Air Base in Japan. These two aircraft have complementary capabilities which allow high altitude and long range impacts, as well as low altitude, local impacts to be assessed. In order to quantify the composition and evolution of Asian outflow, it is important to quantify as many species as possible including photochemically active species (e.g. NO2, CH2O, O3, acetone, etc.), sources species (VOCs, CO, NOx, SO2, aerosols), reactive intermediates including free radicals (OH, HO2, RO2, and their reservoirs), and end products (nitric acid, sulfuric acid, secondary aerosols, etc.). The more complete the measurement suite, the more tightly constrained the numerical modeling can be (within the uncertainties of the measurements). The numerical models range in sophistication from simple steady state box models (as employed in this study) to multi-dimensional chemical transport models. Data were collected on approximately 20 flights of the DC-8 and 21 flights of the P-3B

  19. Trace element distribution in different chemical fractions of False Bay sediments

    International Nuclear Information System (INIS)

    Trace metals in the aquatic environment are generally concentrated on solid geochemical phases which eventually become incorporated into estuarine and marine sediments. The mechanism of trace metal concentration is believed to be adsorption on various geochemical phases, such as hydrous metal oxides, clays and organic matter. Metals in estuarine sediments can thus be expected to be partitioned between different phases, depending on the concentration of the phase and the strength of the adsorption bond. The bioavailability of sediment-bound metals to deposit-feeding organisms will depend on trace metal partitioning and the kinetics of biological metal uptake from each geochemical phase. The major objective of this study was to establish an analytical procedure involving sequential chemical extractions for the partitioning of particulate trace metals in sediment samples, collected from False Bay. Eight metals were examined, i.e. Cd, Cu, Cr, Fe, Mn, Ni, Pb and Zn. X-ray diffraction was also used in the study

  20. Evolution of nuclear chemical industry in France

    International Nuclear Information System (INIS)

    The present characteristics can be summarized in one word: expansion. Impelled by the CEA, but also by such organisations as the Electricite de France and the Merchant Marine, the French nuclear effort for the years 1957-1961 reaches about 600 thousand millions francs; over half this sum will be spent by chemical industry on research, pilot installations, construction of plants and delivery. The aim is to work efficiently, quickly and profitably. This is achieved through close collaboration between the big state organisations and private industry. It is chiefly along the following lines that this large scale effort is carried on: - thorough chemical treatment of increasing tonnages of ores from the French Union, with the aim of producing pure, plentiful and cheap uranium. - careful preparation of nuclear fuels, economical and perfectly adapted to the various types of reactor in operation or under construction. - Further treatment of irradiated fuels to extract the plutonium completely, as well as the uranium and certain fission products. industrial manufacture of material of nuclear purity or corrosion resistant required by the technology of energy producing or research reactors. - Supply to the many foreign or French users of isotopes and radioactive tracers required by medicine, industry and agriculture in ever-increasing numbers. - Meticulous chemical treatment of gaseous or liquid effluent in strictly controlled stations in order that reactors and their annexes will be perfectly safe to use. This account shows the great extent of the effort laid out by a young, energetic chemical industry in full swing. Having made sure of its techniques and set up numerous installations it is fully in a position to confront the French atomic programme. In addition it is able and anxious to associate with the developments of foreign atomic industry, especially EURATOM and Eurochemic. (author)

  1. The Impact of Modeling Assumptions in Galactic Chemical Evolution Models

    CERN Document Server

    Côté, Benoit; Ritter, Christian; Herwig, Falk; Venn, Kim A

    2016-01-01

    We use the OMEGA galactic chemical evolution code to investigate how the assumptions used for the treatment of galactic inflows and outflows impact numerical predictions. The goal is to determine how our capacity to reproduce the chemical evolution trends of a galaxy is affected by the choice of implementation used to include those physical processes. In pursuit of this goal, we experiment with three different prescriptions for galactic inflows and outflows and use OMEGA within a Markov Chain Monte Carlo code to recover the set of input parameters that best reproduces the chemical evolution of nine elements in the dwarf spheroidal galaxy Sculptor. Despite their different degrees of intended physical realism, we found that all three prescriptions can reproduce in an almost identical way the stellar abundance trends observed in Sculptor. While the three models have the same capacity to fit the data, the best values recovered for the parameters controlling the number of Type Ia supernovae and the strength of gal...

  2. Surface enhanced Raman spectroscopy detection of trace chemicals in inhomogeneous fluid mixtures

    OpenAIRE

    Tiainen, Laura

    2015-01-01

    Detecting trace chemicals in heterogeneous fluid mixtures has a variety of possible applications for example in food industry. The drivers of this development have not only been build on consumer awareness but have also been emphasized by decision makers at the EU level. The current laboratory methods are laborious, expensive and slow, which challenges their application in milk quality control especially in terms of qualitatively detecting such chemical residues an melamine. More studied are ...

  3. The Bologna Open Clusters Chemical Evolution project (in short: BOCCE)

    OpenAIRE

    Bragaglia, Angela

    2007-01-01

    I present here our project, the Bologna Open Clusters Chemical Evolution (BOCCE) project, aimed at using Open Clusters as tracers of the disk properties and their evolution with time. We are collecting and homogeneously analyzing data, both photometric and spectroscopic, on a large sample of open clusters, representative of the old cluster population, and I show here results obtained on a subset of our clusters.

  4. Close Pairs as Probes of the Galaxy's Chemical Evolution

    CERN Document Server

    Vanbeveren, D; Vanbeveren, Dany; Donder, Erwin De

    2006-01-01

    Understanding the galaxy in which we live is one of the great intellectual challenges facing modern science. With the advent of high quality observational data, the chemical evolution modeling of our galaxy has been the subject of numerous studies in the last years. However, all these studies have one missing element which is the evolution of close binaries. Reason: their evolution is very complex and single stars only perhaps can do the job. (Un)Fortunately at present we know that a significant fraction of the observed intermediate mass and massive stars are members of a binary or multiple system and that certain objects can only be formed through binary evolution. Therefore galactic studies that do not account for close binaries may be far from realistic. We implemented a detailed binary population in a galactic chemical evolutionary model. Notice that this is not something simple like replacing chemical yields. Here we discuss three topics: the effect of binaries on the evolution of 14N, the evolution of t...

  5. Chemical Evolution of Irregular and Blue Compact Galaxies

    OpenAIRE

    L. Carigi; Colin, P.; Peimbert, M.; Sarmiento, A

    1994-01-01

    We discuss the chemical evolution of metal poor galaxies and conclude that their oxygen deficiency is not due to: the production of black holes by massive stars or a varying slope of the Initial Mass Function, IMF, at the high-mass end. A varying IMF at the low-mass end alone or in combination with: (a) an outflow of oxygen-rich material, (b) an outflow of well-mixed material, and (c) the presence of dark matter that does not participate in the chemical evolution process, is needed to explain...

  6. Galactic chemical evolution: Carbon through Zinc

    CERN Document Server

    Kobayashi, C; Nomoto, K; Tominaga, N; Ohkubo, T

    2006-01-01

    We calculate the evolution of heavy element abundances from C to Zn in the solar neighborhood adopting our new nucleosynthesis yields. Our yields are calculated for wide ranges of metallicity (Z=0-Z_\\odot) and the explosion energy (normal supernovae and hypernovae), based on the light curve and spectra fitting of individual supernovae. The elemental abundance ratios are in good agreement with observations. Among the alpha-elements, O, Mg, Si, S, and Ca show a plateau at [Fe/H] < -1, while Ti is underabundant overall. The observed abundance of Zn ([Zn/Fe] ~ 0) can be explained only by the high energy explosion models, which requires a large contribution of hypernovae. The observed decrease in the odd-Z elements (Na, Al, and Cu) toward low [Fe/H] is reproduced by the metallicity effect on nucleosynthesis. The iron-peak elements (Cr, Mn, Co, and Ni) are consistent with the observed mean values at -2.5 < [Fe/H] < -1$, and the observed trend at the lower metallicity can be explained by the energy effect. ...

  7. Evolution of trace gases and particles emitted by a chaparral fire in California

    Directory of Open Access Journals (Sweden)

    C. E. Wold

    2012-02-01

    Full Text Available Biomass burning (BB is a major global source of trace gases and particles. Accurately representing the production and evolution of these emissions is an important goal for atmospheric chemical transport models. We measured a suite of gases and aerosols emitted from an 81 hectare prescribed fire in chaparral fuels on the central coast of California, US on 17 November 2009. We also measured physical and chemical changes that occurred in the isolated downwind plume in the first ~4 h after emission. The measurements were carried out onboard a Twin Otter aircraft outfitted with an airborne Fourier transform infrared spectrometer (AFTIR, aerosol mass spectrometer (AMS, single particle soot photometer (SP2, nephelometer, LiCor CO2 analyzer, a chemiluminescence ozone instrument, and a wing-mounted meteorological probe. Our measurements included: CO2; CO; NOx; NH3; non-methane organic compounds; organic aerosol (OA; inorganic aerosol (nitrate, ammonium, sulfate, and chloride; aerosol light scattering; refractory black carbon (rBC; and ambient temperature, relative humidity, barometric pressure, and three-dimensional wind velocity. The molar ratio of excess O3 to excess CO in the plume (ΔO3/ΔCO increased from −5.13 (±1.13 × 10−3 to 10.2 (±2.16 × 10−2 in ~4.5 h following smoke emission. Excess acetic and formic acid (normalized to excess CO increased by factors of 1.73 ± 0.43 and 7.34 ± 3.03 (respectively over the same time since emission. Based on the rapid decay of C2H4 we infer an in-plume average OH concentration of 5.27 (±0.97 × 106 molec cm−3, consistent with previous studies showing elevated OH concentrations in biomass burning plumes. Ammonium, nitrate, and sulfate all increased over the course of 4 h. The observed ammonium increase was a factor of 3.90 ± 2.93 in about 4 h, but accounted for just ~36

  8. Evolution of trace gases and particles emitted by a chaparral fire in California

    Directory of Open Access Journals (Sweden)

    S. K. Akagi

    2011-08-01

    Full Text Available Biomass burning (BB is a major global source of trace gases and particles. Accurately representing the production and evolution of these emissions is an important goal for atmospheric chemical transport models. We measured a suite of gases and aerosols emitted from an 81 ha prescribed fire in chaparral fuels on the central coast of California, US on 17 November 2009. We also measured post-emission chemical changes in the isolated downwind plume for ~4 h of smoke aging. The measurements were carried out on board a Twin Otter aircraft outfitted with an airborne Fourier transform infrared spectrometer (AFTIR, aerosol mass spectrometer (AMS, single particle soot photometer (SP2, nephelometer, LiCor CO2 analyzer, a chemiluminescence ozone instrument, and a wing-mounted meteorological probe. Our measurements included: CO2; CO; NOx; NH3; non-methane organic compounds; organic aerosol (OA; inorganic aerosol (nitrate, ammonium, sulfate, and chloride; aerosol light scattering; refractory black carbon (rBC; and ambient temperature, relative humidity, barometric pressure, and three-dimensional wind velocity. The molar ratio of excess O3 to excess CO in the plume (ΔO3/ΔCO increased from −0.005 to 0.102 in 4.5 h. Excess acetic and formic acid (normalized to excess CO increased by factors of 1.7 ± 0.4 and 7.3 ± 3.0 (respectively over the same aging period. Based on the rapid decay of C2H4 we infer an in-plume average OH concentration of 5.3 (±1.0 × 106 molecules cm−3, consistent with previous studies showing elevated OH concentrations in biomass burning plumes. Ammonium, nitrate, and sulfate all increased with plume aging. The observed ammonium increase was a factor of 3.9 ± 2.6 in about 4 h, but accounted for just ~36 % of the gaseous ammonia lost on a molar basis. Some of the gas phase NH3 loss may have been due to condensation

  9. Carbon Monoxide Isotopes: On the Trail of Galactic Chemical Evolution

    Science.gov (United States)

    Langer, W.

    1995-01-01

    From the early days of the discovery of radio emission from carbon monoxide it was realized that it offered unusual potential for under- standing the chemical evolution of the Galaxy and external galaxies through measurements of molecular isotopes. These results bear on stellar nucleosynthesis, star formation, and gases in the interstellar medium. Progress in isotopic radio measurements will be reviewed.

  10. Oxygen abundances and the chemical evolution of spiral galaxies

    OpenAIRE

    Tosi., M; Angeles I. Díaz

    1983-01-01

    This is an electronic version of an article published in Memorie della Società Astronomica Italiana. Tosi, M. and A. I. Díaz. Oxygen abundances and the chemical evolution of spiral galaxies. Memorie della Società Astronomica Italiana 54, 4 (1983): 889-890

  11. Signatures of Chemical Evolution in Protostellar Nebulae

    Science.gov (United States)

    Nuth, Joseph A., III; Johnson, Natasha

    2011-01-01

    A decade ago observers began to take serious notice of the presence of crystalline silicate grains in the dust flowing away from some comets. While crystallinity had been seen in such objects previously, starting with the recognitions by Campins and Ryan (1990) that the 10 micron feature of Comet Halley resembled that of the mineral forsterite, most such observations were either ignored or dismissed as no path to explain such crystalline grains was available in the literature. When it was first suggested that an outward flow must be present to carry annealed silicate grains from the innermost regions of the Solar Nebula out to the regions where comets could form (Nuth, 1999; 2001) this suggestion was also dismissed because no such transport mechanism was known at the time. Since then not only have new models of nebular dynamics demonstrated the reality of long distance outward transport (Ciesla, 2007; 2008; 2009) but examination of older models (Boss, 2004) showed that such transport had been present but had gone unrecognized for many years. The most unassailable evidence for outward nebular transport came with the return of the Stardust samples from Comet Wild2, a Kuiper-belt comet that contained micron-scale grains of high temperature minerals resembling the Calcium-Aluminum Inclusions found in primitive meteorites (Zolensky et aI., 2006) that formed at T > 1400K. Now that outward transport in protostellar nebulae has been firmly established, a re-examination of its consequences for nebular gas is in order that takes into account both the factors that regulate both the outward flow as well as those that likely control the chemical composition of the gas. Laboratory studies of surface catalyzed reactions suggest that a trend toward more highly reduced carbon and nitrogen compounds in the gas phase should be correlated with a general increase in the crystallinity of the dust (Nuth et aI., 2000), but is such a trend actually observable? Unlike the Fischer-Tropsch or

  12. Chemical Evolution of Dwarf Spheroidal and Blue Compact Galaxies

    CERN Document Server

    Lanfranchi, G A; Lanfranchi, Gustavo A.; Matteucci, Francesca

    2003-01-01

    We studied the chemical evolution of Dwarf Spheroidal (dSph) and Blue Compact Galaxies (BCGs) by means of comparison between the predictions of chemical evolution models and several observed abundance ratios. Detailed models with up to date nucleosynthesis taking into account the role played by supernovae of different types (II, Ia) were developed for both types of galaxies allowing us to follow the evolution of several chemical elements. The models are specified by the prescriptions of the star formation (SF) and galactic wind efficiencies chosen to reproduce the main features of these galaxies. We also investigated a possible connection in the evolution of dSph and BCGs and compared the predictions of the models to the abundance ratios observed in Damped Lyman alpha Systems (DLAs). The main conclusions are: i) the observed distribution of [alpha/Fe] vs. [Fe/H] in dSph is mainly a result of the SF rate coupled with the wind efficiency; ii) a low SF efficiency and a high wind efficiency are required to reprod...

  13. Wet precipitation scavenging of soluble atmospheric trace gases due to chemical absorption in inhomogeneous atmosphere

    Science.gov (United States)

    Elperin, Tov; Fominykh, Andrew; Krasovitov, Boris

    2016-04-01

    We analyze the effects of irreversible chemical reactions of the first and higher orders and aqueous-phase dissociation reactions on the rate of trace gas scavenging by rain in the atmosphere with non-uniform concentration and temperature. We employ an one-dimensional model of precipitation scavenging of chemically active soluble gaseous pollutants that is valid for small gradients of temperature and concentration in the atmosphere. It is demonstrated that transient altitudinal distribution of concentration under the influence of rain is determined by the partial hyperbolic differential equation of the first order. Scavenging coefficients are calculated for wet removal of chlorine, nitrogen dioxide and sulfur dioxide for the exponential and linear initial altitudinal distributions of trace gases concentration in the atmosphere and linear and uniform altitudinal temperature distributions. Theoretical predictions of the dependence of the magnitude of the scavenging coefficient on rain intensity for sulfur dioxide are in a good agreement with the available atmospheric measurements.

  14. From consumption to harvest: Environmental fate prediction of excreted ionizable trace organic chemicals

    DEFF Research Database (Denmark)

    Polesel, Fabio; Plósz, Benedek G.; Trapp, Stefan

    2015-01-01

    with freshwater or reclaimed wastewater. Recent research has shown the tendency for these substances to accumulate in food crops. In this study, we developed and applied a simulation tool to predict the fate of three ionizable trace chemicals (triclosan-TCS, furosemide-FUR, ciprofloxacin-CIP) from human...... the relative translocation of FUR to plant (45.3%-48.9% of emission to soil), as compared to sludge application (21.9%-27.6%). A comparison with peer-reviewed literature showed that model predictions were close to experimental data for elimination in WWTP, concentrations in sewage and sludge...... and bioconcentration factors (BCFs) in plant tissues, which showed however a large variability. The simulation tool presented here can thus be useful for priority setting and for the estimation of human exposure to trace chemicals via intake of food crops....

  15. Inversion of long-lived trace gas emissions using combined Eulerian and Lagrangian chemical transport models

    OpenAIRE

    Rigby, M.; A. J. Manning; R. G. Prinn

    2011-01-01

    We present a method for estimating emissions of long-lived trace gases from a sparse global network of high-frequency observatories, using both a global Eulerian chemical transport model and Lagrangian particle dispersion model. Emissions are derived in a single step after determining sensitivities of the observations to initial conditions, the high-resolution emissions field close to observation points, and larger regions further from the measurements. This method has the several advantages ...

  16. Chemical Evolution of the Galactic Disk and Bulge

    OpenAIRE

    Wyse, Rosemary F. G.

    1994-01-01

    Invited Review at IAU Symp 164 on Stellar Populations. The Milky Way Galaxy offers a unique opportunity for testing theories of galaxy formation and evolution. The study of the spatial distribution, kinematics and chemical abundances of stars in the Milky Way Galaxy allows one to address specific questions pertinent to this meeting such as When was the Galaxy assembled? Is this an ongoing process? What was the merging history of the Milky Way?

  17. The impact of chemical evolution on the observable properties of stellar populations

    OpenAIRE

    Tosi., M

    2000-01-01

    The major effects of the chemical evolution of galaxies on the characteristics of their stellar populations are reviewed. A few examples of how the observed stellar properties derived from colour--magnitude diagrams can constrain chemical evolution models are given.

  18. Oparin's coacervates as an important milestone in chemical evolution

    Science.gov (United States)

    Kolb, Vera M.

    2015-09-01

    Although Oparin's coacervate model for the origin of life by chemical evolution is almost 100 years old, it is still valid. However, the structure of his originally proposed coacervate is not considered prebiotic, based on some recent developments in prebiotic chemistry. We have remedied this deficiency of the Oparin's model, by substituting his coacervate with a prebiotically feasible one. Oparin's coacervates are aqueous structures, but have a boundary with the rest of the aqueous medium. They exhibit properties of self-replication, and provide a path to a primitive metabolism, via chemical competition and thus a primitive selection. Thus, coacervates are good models for proto-cells. We review here some salient points of Oparin's model and address also some philosophical views on the beginning of natural selection in primitive chemical systems.

  19. The role of OH in the chemical evolution of protoplanetary disks II. Gas-rich environments

    CERN Document Server

    Molano, Germán Chaparro

    2012-01-01

    Context. We present a method for including gas extinction of cosmic-ray-generated UV photons in chemical models of the midplane of protoplanetary disks, focusing on its implications on ice formation and chemical evolution. Aims. Our goal is to improve on chemical models by treating cosmic rays, the main source of ionization in the midplane of the disk, in a way that is consistent with current knowledge of the gas and grain environment present in those regions. We trace the effects of cosmic rays by identifying the main chemical reaction channels and also the main contributors to the gas opacity to cosmic-ray-induced UV photons. This information is crucial in implementing gas opacities for cosmic-ray-induced reactions in full 2D protoplanetary disk models. Methods. We considered time-dependent chemical models within the range 1-10 AU in the midplane of a T Tauri disk. The extinction of cosmic-ray-induced UV photons by gaseous species was included in the calculation of photorates at each timestep. We integrated...

  20. Tracing the evolution of oblitacythereis through a sudden event of oceanic proportions

    Energy Technology Data Exchange (ETDEWEB)

    Benson, R.H.

    1985-01-01

    The ostracod genus Oblitacythereis is characteristic of the upper bathyal sediments of Neogene age in the region of the Mediterranean, just outside of the Straits of Gibraltar in the Atlantic and on the Walvis Ridge. Its evolution can be traced from a Tethyan ancestry of its carapace sculpture through 1) changes in structurally-important cell division in the histological pattern forming the reticulation of the carapace, and 2) modification of positions in the pore conuli of the epidermal nervous system. This study examines the changes that take place near Gibraltar at the time of the formation of the Mediterranean after the Messinian Salinity Crisis and compares these changes with other similar histories of deeper - and shallower - water ostracod genera.

  1. Trace element modelling of magma evolution in the Fongen-Hyllingen Intrusion, Trondheim region, Norway

    International Nuclear Information System (INIS)

    The trace element evolution of the Fongen-Hyllingen Intrusion has been studied on the basis of ICPMS analyses of 21 whole rocks and 12 plagioclase separates. Emphasis has been placed on Stage IV of the intrusion that crystallized essentially after magma addition had ceased. Whereas the compositions of minerals and rocks in Stage IV exhibit strong normal fractionation trends, crustal contamination is evident in a wide range of incompatible element ratios that should be relatively constant if simple fractional crystallization prevailed. Crustal contamination in Stage IV is confirmed by isotopic studies. The distribution of incompatible elements in Stage IV can be successfully explained by AFC modelling. Olivine compositions and isotopic ratios in the most primitive cumulates together with the slight LREE-enrichment in their coexisting melts suggest that the FHI parental magma was subjected to at least olivine fractionation during ascent to the magma chamber. This resulted in a decrease in the Mg-number of the melt without changing its isotopic ratio and incompatible trace element ratios. The slight enrichment in LREE and relatively low Zr/Y ratios in the melt coexisting with the most primitive cumulates imply that the FHI primary melt was derived from garnet-free mantle. The relative abundance of incompatible elements in the most primitive calculated melts, geochemically similar to low-Ti continental flood basalts, suggest that a subcontinental mantle source was most probable for the parental melt for FHI. (author)

  2. Evaluation of Predicted and Observed Data on Biotransformation of Twenty-Nine Trace Organic Chemicals

    KAUST Repository

    Bertolini, Maria

    2011-07-01

    Trace organic chemicals present in household products, pesticides, pharmaceuticals and personal care products may have adverse ecotoxicological effects once they are released to the environment. These chemicals are usually transported with the sewage to wastewater treatment facilities, where they might be attenuated depending on the degree of treatment applied prior to discharge to receiving streams. This study evaluates the removal performance of 29 trace organic compounds during two different activated sludge treatment systems. Predominant attenuation processes such as biotransformation and sorption for the target compounds were identified. Biotransformation rate constants determined in this study were used to assess removal of compounds from other treatment plants with similar operational conditions, using data gathered from the literature. The commercial software Catalogic was applied to predict environmental fate of chemicals. The software program consisted of four models able to simulate molecular transformations and to generate degradation trees. In order to assess the accuracy of this program in predicting biotransformation, one biodegradation model is used to contrast predicted degradation pathway with metabolic pathways reported in the literature. The predicted outcome was correct for more than 40 percent of the 29 targeted substances, while 38 percent of the chemicals exhibited some degree of lower agreement between predicted and observed pathways. Percent removal data determined for the two treatment facilities was compared with transformation probability output from Catalogic. About 80 percent of the 29 compounds exhibited a good correlation between probability of transformation of the parent compound and percent removal data from the two treatment plants (R2 = 0.82 and 0.9). Based upon findings for 29 trace organic chemicals regarding removal during activated sludge treatment, attacked fragments present in their structures, predicted data from

  3. Inhomogeneous Chemical Evolution of the Galaxy in the Solar Neighbourhood

    Indian Academy of Sciences (India)

    S. Sahijpal

    2013-12-01

    -body numerical simulations of an inhomogeneous Galactic Chemical Evolution (GCE) of the solar neighbourhood with a high temporal resolution are presented. The solar annular ring is divided into distinct spatial grids of area ∼ 1–2 kpc2. Each grid evolves distinctly in terms of star formation and nucleosynthetic yields from numerous generations of stars. The evolution of the galaxy is simulated by considering discrete episodes of star formation. Subsequent to the evolution of the simulated stars within each grid the stellar nucleosynthetic yields are homogenized within the grid rather than the traditionally adopted criteria of homogenizing over the entire solar annular ring. This provides a natural mechanism of generating heterogeneities in the elemental abundance distribution of stars. A complex chemical evolutionary history is inferred that registers episodes of time-dependent contributions from SN II+Ib/c with respect to SN Ia. It was observed that heterogeneities can remerge even after episodes of large scale homogenizations on scales larger than the grid size. However, a comparison of the deduced heterogeneities with the observed scatter in the elemental abundances of the dwarf stars suggest only a partial match, specifically, for [Fe/H] > -0.5. The deduced heterogeneities in the case of carbon, oxygen, magnesium, silicon, sulphur, calcium and titanium can explain the observed heterogeneities for [Fe/H] < -0.5. It may not be possible to explain the entire observed spread exclusively on the basis of the inhomogeneous GCE.

  4. Comet impacts and chemical evolution on the bombarded earth

    Science.gov (United States)

    Oberbeck, Verne R.; Aggarwal, Hans

    1992-01-01

    Amino acids yields for previously published shock tube experiments are used with minimum Cretaceous-Tertiary (K/T) impactor mass and comet composition to predict AIB amino acid K/T boundary sediment column density. The inferred initial concentration of all amino acids in the K/T sea and in similar primordial seas just after 10 km comet impacts would have been at least 10 exp -7 M. However, sinks for amino acids must also be considered in calculating amino acid concentrations after comet impacts and in assessing the contribution of comets to the origin of life. The changing concentration of cometary amino acids due to ultraviolet light is compared with the equilibrium concentration of amino acids produced in the sea from corona discharge in the atmosphere, deposition in water, and degradation by ultraviolet light. Comets could have been more important than endogenous agents for initial evolution of amino acids. Sites favorable for chemical evolution of amino acids are examined, and it is concluded that chemical evolution could have occurred at or above the surface even during periods of intense bombardment of earth before 3.8 billion years ago.

  5. The chemical evolution of Manganese in different stellar systems

    CERN Document Server

    Cescutti, G; Lanfranchi, G A; McWilliam, A

    2008-01-01

    Aims. To model the chemical evolution of manganese relative to iron in three different stellar systems: the solar neighbourhood, the Galactic bulge and the Sagittarius dwarf spheroidal galaxy, and compare our results with the recent and homogeneous observational data. Methods. We adopt three chemical evolution models well able to reproduce the main properties of the solar vicinity, the galactic Bulge and the Sagittarius dwarf spheroidal. Then, we compare different stellar yields in order to identify the best set to match the observational data in these systems. Results. We compute the evolution of manganese in the three systems and we find that in order to reproduce simultaneously the [Mn/Fe] versus [Fe/H] in the Galactic bulge, the solar neighbourhood and Sagittarius, the type Ia SN Mn yield must be metallicity-dependent. Conclusions. We conclude that the different histories of star formation in the three systems are not enough to reproduce the different behaviour of the [Mn/Fe] ratio, unlike the situation f...

  6. Tracing the Evolution of High-redshift Galaxies Using Stellar Abundances

    Science.gov (United States)

    Crosby, Brian D.; O'Shea, Brian W.; Beers, Timothy C.; Tumlinson, Jason

    2016-03-01

    This paper presents the first results from a model for chemical evolution that can be applied to N-body cosmological simulations and quantitatively compared to measured stellar abundances from large astronomical surveys. This model convolves the chemical yield sets from a range of stellar nucleosynthesis calculations (including asymptotic giant branch stars, Type Ia and II supernovae, and stellar wind models) with a user-specified stellar initial mass function (IMF) and metallicity to calculate the time-dependent chemical evolution model for a “simple stellar population” (SSP) of uniform metallicity and formation time. These SSP models are combined with a semianalytic model for galaxy formation and evolution that uses merger trees from N-body cosmological simulations to track several α- and iron-peak elements for the stellar and multiphase interstellar medium components of several thousand galaxies in the early (z ≥ 6) universe. The simulated galaxy population is then quantitatively compared to two complementary data sets of abundances in the Milky Way stellar halo and is capable of reproducing many of the observed abundance trends. The observed abundance ratio distributions are best reproduced with a Chabrier IMF, a chemically enriched star formation efficiency of 0.2, and a redshift of reionization of 7. Many abundances are qualitatively well matched by our model, but our model consistently overpredicts the carbon-enhanced fraction of stars at low metallicities, likely owing to incomplete coverage of Population III stellar yields and supernova models and the lack of dust as a component of our model.

  7. Advanced Nanoporous Materials for Micro-Gravimetric Sensing to Trace-Level Bio/Chemical Molecules

    Directory of Open Access Journals (Sweden)

    Pengcheng Xu

    2014-10-01

    Full Text Available Functionalized nanoporous materials have been developed recently as bio/chemical sensing materials. Due to the huge specific surface of the nano-materials for molecular adsorption, high hopes have been placed on gravimetric detection with micro/nano resonant cantilevers for ultra-sensitive sensing of low-concentration bio/chemical substances. In order to enhance selectivity of the gravimetric resonant sensors to the target molecules, it is crucial to modify specific groups onto the pore-surface of the nano-materials. By loading the nanoporous sensing material onto the desired region of the mass-type transducers like resonant cantilevers, the micro-gravimetric bio/chemical sensors can be formed. Recently, such micro-gravimetric bio/chemical sensors have been successfully applied for rapid or on-the-spot detection of various bio/chemical molecules at the trace-concentration level. The applicable nanoporous sensing materials include mesoporous silica, zeolite, nanoporous graphene oxide (GO and so on. This review article focuses on the recent achievements in design, preparation, functionalization and characterization of advanced nanoporous sensing materials for micro-gravimetric bio/chemical sensing.

  8. Modelling the Fate of Xenobiotic Trace Chemicals via Wastewater Treatment and Agricultural Resource Reuse

    OpenAIRE

    Polesel, Fabio; Plósz, Benedek G.; Trapp, Stefan; Andersen, Henrik Rasmus

    2016-01-01

    Som et resultat af menneskelige aktiviteter er lægemidler og biocider allestedsnærværende i miljøet på sporstofniveau. Store mængder af disse stoffer, også kendt som miljøfremmede stoffer (på Engelsk XTCs: Xenobiotic Trace Chemicals), frigives dagligt fra: (i) husholdninger og sundhedsfaciliteter, som følge af indtagelse og bortskaffelse; (ii) dyrehold og tilsvarende faciliteter, som følge af dyrs indtagelse; og (iii) industrianlæg. En betydelig del af disse udledninger når frem til kommunale...

  9. Tuning the performance of a natural treatment process using metagenomics for improved trace organic chemical attenuation

    KAUST Repository

    Drewes, Jorg

    2014-02-01

    By utilizing high-throughput sequencing and metagenomics, this study revealed how the microbial community characteristics including composition, diversity, as well as functional genes in managed aquifer recharge (MAR) systems can be tuned to enhance removal of trace organic chemicals of emerging concern (CECs). Increasing the humic content of the primary substrate resulted in higher microbial diversity. Lower concentrations and a higher humic content of the primary substrate promoted the attenuation of biodegradable CECs in laboratory and field MAR systems. Metagenomic results indicated that the metabolic capabilities of xenobiotic biodegradation were significantly promoted for the microbiome under carbon-starving conditions. © IWA Publishing 2014.

  10. The role of cometary particle coalescence in chemical evolution

    Science.gov (United States)

    Oberbeck, V. R.; Mckay, C. P.; Carle, G. C.; Valentin, J. R.; Scattergood, T. W.

    1989-01-01

    Important prebiotic organic compounds might have been transported to earth in dust or produced in vapor clouds resulting from atmospheric explosions or impacts of comets. These compounds coalesced in the upper atmosphere with particles ejected from craters formed by impacts of large objects. Coalescence during exposure to UV radiation concentrated organic monomers and enhanced formation of oligomers. Continuing coalescence added material to the growing particles and shielded prebiotic compounds from prolonged UV radiation. These particles settled into the lower atmosphere where they were scavenged by rain. Aqueous chemistry and evaporation of raindrops containing monomers in high temperature regions near the earth's surface also promoted continued formation of oligomers. Finally, these oligomers were deposited in the oceans where continued prebiotic evolution led to the most primitive cell. Results of present studies suggest that prebiotic chemical evolution may be an inevitable consequence of impacting comets during the late accretion of planets anywhere in the universe if oceans remained on those planetary surfaces.

  11. From chemical reactions to evolution: Emergence of species

    Science.gov (United States)

    Carletti, T.; Fanelli, D.

    2007-01-01

    The Chemoton model constitutes a minimalistic description of a protocell unit. The original formulation assumes three coupled chemical networks, representing a proto-metabolism, a template duplication and the membrane growth. An improved version is here proposed that explicitly incorporates the effects of the volume changes, due to the membrane growth. A stochastic mechanism is also introduced that mimics a stochastic source of error in the template duplication process. Numerical simulations are performed to monitor the time evolution of a family of protocells, under the chemoton hypothesis. An open-ended Darwinian evolution under the pressure of the environment is reproduced thus allowing to conclude that differentiation into species is an emergent property of the model.

  12. A paradigm-based evolution of chemical engineering

    Institute of Scientific and Technical Information of China (English)

    Alexandru Woinaroschy

    2016-01-01

    A short presentation of chemical engineering evolution, as guided by its paradigms, is exposed. The first paradigm–unit operations–has emerged as a necessity of systematization due to the explosion of chemical industrial applica-tions at the end of 19th century. The birth in the late 1950s of the second paradigm–transport phenomena–was the consequence of the need for a deep, scientific knowledge of the phenomena that explain what happens inside of unit operations. In the second part of 20th century, the importance of chemical product properties and qualities has become essential y in the market fights. Accordingly, it was required with additional and even new fundamen-tal approaches, and product engineering was recognized as the third paradigm. Nowadays chemical industry, as a huge materials and energy consumer, and with a strong ecological impact, couldn't remain outside of sustainability requirements. The basics of the fourth paradigm–sustainable chemical engineering–are now formulated.

  13. Constraints on chemical evolution models from QSOALS abundances

    Science.gov (United States)

    Lauroesch, J. T.

    1993-01-01

    Models of the formation and early chemical evolution of our Galaxy are guided and constrained by our knowledge of abundances in globular cluster stars and halo field stars. The abundance patterns identified in halo and disk stars should be discernible in absorption lines of gas clouds in forming galaxies which are accidentally lying in front of background QSO's. Conversely, the ensemble of QSO absorption line systems (QSOALS) at each redshift may suggest a detailed model for the formation of our Galaxy that is testable using abundance patterns in halo stars.

  14. Galactic chemical evolution and nucleocosmochronology - Standard model with terminated infall

    Science.gov (United States)

    Clayton, D. D.

    1984-01-01

    Some exactly soluble families of models for the chemical evolution of the Galaxy are presented. The parameters considered include gas mass, the age-metallicity relation, the star mass vs. metallicity, the age distribution, and the mean age of dwarfs. A short BASIC program for calculating these parameters is given. The calculation of metallicity gradients, nuclear cosmochronology, and extinct radioactivities is addressed. An especially simple, mathematically linear model is recommended as a standard model of galaxies with truncated infall due to its internal consistency and compact display of the physical effects of the parameters.

  15. Chemical evolution of the Earth: Equilibrium or disequilibrium process?

    Science.gov (United States)

    Sato, M.

    1985-01-01

    To explain the apparent chemical incompatibility of the Earth's core and mantle or the disequilibrium process, various core forming mechanisms have been proposed, i.e., rapid disequilibrium sinking of molten iron, an oxidized core or protocore materials, and meteorite contamination of the upper mantle after separation from the core. Adopting concepts used in steady state thermodynamics, a method is devised for evaluating how elements should distribute stable in the Earth's interior for the present gradients of temperature, pressure, and gravitational acceleration. Thermochemical modeling gives useful insights into the nature of chemical evolution of the Earth without overly speculative assumptions. Further work must be done to reconcile siderophile elements, rare gases, and possible light elements in the outer core.

  16. Tabletop imaging of structural evolutions in chemical reactions

    CERN Document Server

    Ibrahim, Heide; Beaulieu, Samuel; Schmidt, Bruno E; Thiré, Nicolas; Bisson, Éric; Hebeisen, Christoph T; Wanie, Vincent; Giguére, Mathieu; Kieffer, Jean-Claude; Sanderson, Joseph; Schuurman, Michael S; Légaré, François

    2014-01-01

    The introduction of femto-chemistry has made it a primary goal to follow the nuclear and electronic evolution of a molecule in time and space as it undergoes a chemical reaction. Using Coulomb Explosion Imaging we have shot the first high-resolution molecular movie of a to and fro isomerization process in the acetylene cation. So far, this kind of phenomenon could only be observed using VUV light from a Free Electron Laser [Phys. Rev. Lett. 105, 263002 (2010)]. Here we show that 266 nm ultrashort laser pulses are capable of initiating rich dynamics through multiphoton ionization. With our generally applicable tabletop approach that can be used for other small organic molecules, we have investigated two basic chemical reactions simultaneously: proton migration and C=C bond-breaking, triggered by multiphoton ionization. The experimental results are in excellent agreement with the timescales and relaxation pathways predicted by new and definitively quantitative ab initio trajectory simulations.

  17. Chemical differentiation in a prestellar core traces non-uniform illumination

    CERN Document Server

    Spezzano, Silvia; Caselli, Paola; Harju, Jorma; Brünken, Sandra

    2016-01-01

    Dense cloud cores present chemical differentiation due to the different distribution of C-bearing and N-bearing molecules, the latter being less affected by freeze-out onto dust grains. In this letter we show that two C-bearing molecules, CH$_3$OH and $c$-C$_3$H$_2$, present a strikingly different (complementary) morphology while showing the same kinematics toward the prestellar core L1544. After comparing their distribution with large scale H$_2$ column density N(H$_2$) map from the Herschel satellite, we find that these two molecules trace different environmental conditions in the surrounding of L1544: the $c$-C$_3$H$_2$ distribution peaks close to the southern part of the core, where the surrounding molecular cloud has a N(H$_2$) sharp edge, while CH$_3$OH mainly traces the northern part of the core, where N(H$_2$) presents a shallower tail. We conclude that this is evidence of chemical differentiation driven by different amount of illumination from the interstellar radiation field: in the South, photochem...

  18. Applying surrogates and indicators to assess removal efficiency of trace organic chemicals during chemical oxidation of wastewaters.

    Science.gov (United States)

    Dickenson, Eric R V; Drewes, Jörg E; Sedlak, David L; Wert, Eric C; Snyder, Shane A

    2009-08-15

    To respond to concerns associated with wastewater-derived contaminants water utilities are looking for new approaches for monitoring trace organic chemicals in conventional and advanced water treatment processes. This study examines the use of a combination of surrogate parameters and indicator compounds tailored to monitor the removal efficiency of advanced oxidation processes employed by treatment plants engaged in indirect potable water reuse programs. Potential surrogate parameters and indicator compounds, identified by reviewing previous publications and classified by their structural properties, were tested in pilot- and full-scale treatment systems. Dilantin, DEET, meprobamate, and iopromide are good indicators to assess optimized oxidation conditions while ozonating tertiary-treated wastewaters. UVA reduction, ozone byproduct formation, such as simple organic acids, and ozone exposure correlated with "sweet spot" compounds, where ozone exposure correlated with trace organic removal across five tertiary-treated wastewaters. Findings indicate that the proposed framework can serve as a conservative monitoring approach for advanced oxidation processes as well as other indirect potable reuse processes to ensure proper removal of identified and unidentified wastewater-derived organic contaminants, to detect failures in system performance, and is protective of public health. PMID:19746720

  19. PNe as observational constraints in chemical evolution models for NGC 6822

    OpenAIRE

    Hernández-Martínez, L.; L. Carigi; Peña, M. (Marian); M. Peimbert

    2011-01-01

    Chemical evolution models are useful for understanding the formation and evolution of stars and galaxies. Model predictions will be more robust as more observational constraints are used. We present chemical evolution models for the dwarf irregular galaxy NGC 6822 using chemical abundances of old and young Planetary Nebulae (PNe) and \\ion{H}{ii} regions as observational constraints. Two sets of chemical abundances, one derived from collisionally excited lines (CELs) and one, from recombinatio...

  20. The gas-ice chemical interplay during cloud evolution

    CERN Document Server

    Hocuk, S

    2014-01-01

    During the evolution of diffuse clouds to molecular clouds, gas-phase molecules freeze out on surfaces of small dust particles to form ices. On dust surfaces, water is the main constituent of the icy mantle in which a complex chemistry is taking place. We aim to study the formation pathways and the composition of the ices throughout the evolution of diffuse clouds. For this purpose, we use time-dependent rate equations to calculate the molecular abundances in both gas phase and on solid surfaces (onto dust grains). We fully consider the gas-dust interplay by including the details of freeze-out, chemical and thermal desorption, as well as the most important photo-processes on grain surfaces. The difference in binding energies of chemical species on bare and icy surfaces is also incorporated into our equations. Using the numerical code FLASH, we perform a hydrodynamical simulation of a gravitationally bound diffuse cloud and follow its contraction. We find that while the dust grains are still bare, water format...

  1. A Chemical Evolution Model for the Fornax Dwarf Spheroidal Galaxy

    Directory of Open Access Journals (Sweden)

    Yuan Zhen

    2016-01-01

    Full Text Available Fornax is the brightest Milky Way (MW dwarf spheroidal galaxy and its star formation history (SFH has been derived from observations. We estimate the time evolution of its gas mass and net inflow and outflow rates from the SFH usinga simple star formation law that relates the star formation rate to the gas mass. We present a chemical evolution model on a 2D mass grid with supernovae (SNe as sources of metal enrichment. We find that a key parameter controlling the enrichment is the mass Mx of the gas to mix with the ejecta from each SN. The choice of Mx depends on the evolution of SN remnants and on the global gas dynamics. It differs between the two types of SNe involved and between the periods before and after Fornax became an MW satellite at time t = tsat. Our results indicate that due to the global gas outflow at t > tsat, part of the ejecta from each SN may directly escape from Fornax. Sample results from our model are presented and compared with data.

  2. A Chemical Evolution Model for the Fornax Dwarf Spheroidal Galaxy

    CERN Document Server

    Yuan, Zhen; Jing, Y P

    2015-01-01

    Fornax is the brightest Milky Way (MW) dwarf spheroidal galaxy and its star formation history (SFH) has been derived from observations. We estimate the time evolution of its gas mass and net inflow and outflow rates from the SFH using a simple star formation law that relates the star formation rate to the gas mass. We present a chemical evolution model on a 2D mass grid with supernovae (SNe) as sources of metal enrichment. We find that a key parameter controlling the enrichment is the mass M_x of the gas to mix with the ejecta from each SN. The choice of M_x depends on the evolution of SN remnants and on the global gas dynamics. It differs between the two types of SNe involved and between the periods before and after Fornax became an MW satellite at time t = t_sat . Our results indicate that due to the global gas outflow at t > t_sat , part of the ejecta from each SN may directly escape from Fornax. Sample results from our model are presented and compared with data.

  3. Secondary metallicity in analytic models of chemical evolution of galaxies

    Science.gov (United States)

    Clayton, D. D.; Pantelaki, I.

    1986-01-01

    Analytic models of the chemical evolution of galactic regions that grow in mass owing to the continuous infall of matter are characterized, emphasizing the solutions for secondary nuclei (defined as those nuclei whose stellar yields are proportional to the abundance of a primary seed nucleus) in the families of models described by Clayton (1984 and 1985). Wide variations in time dependence of both primary and secondary nuclei as well as in the ratio of secondary to primary are displayed by these model families, confirming again the usefulness of these families as interpretive guides if galaxies do in fact evolve with substantial infall. Additionally, analytic solutions are presented for two other possible interesting systems: the evolution of abundances if the primary metallicity in the infall is increasing in time, and the evolution of abundances if the primary yield changes linearly with time owing to continuous changes in the stellar mass function, the opacity, or other astrophysical agents. Finally, test evaluations of the instantaneous recycling approximation on which these analytic models rely are presented.

  4. Tracing chemical genealogy through the archives of the institute of organic chemistry at the University of Zurich

    OpenAIRE

    Finney, N

    2008-01-01

    Aspects of the history of chemists and chemistry in the Institute of Organic Chemistry at the University of Zurich are traced through chemical genealogy and retained samples from the chemical archives. The work of three OCI faculty members (Werner, Karrer and Eugster) who completed their graduate studies in the Institute is highlighted.

  5. Contrasting the chemical evolution of the Milky Way and Andromeda galaxies

    OpenAIRE

    Renda, Agostino; Kawata, Daisuke; Fenner, Yeshe; Gibson, Brad K.

    2004-01-01

    The chemical evolution history of a galaxy hides clues about how it formed and has been changing through time. We have studied the chemical evolution history of the Milky Way (MW) and Andromeda (M31) to find which are common features in the chemical evolution of disc galaxies as well as which are galaxy-dependent. We use a semi-analytic multi-zone chemical evolution model. Such models have succeeded in explaining the mean trends of the observed chemical properties in these two Local Group spi...

  6. Molecular Evolution and Functional Divergence of Trace Amine–Associated Receptors

    Science.gov (United States)

    Eyun, Seong-il; Moriyama, Hideaki; Hoffmann, Federico G.; Moriyama, Etsuko N.

    2016-01-01

    Trace amine-associated receptors (TAARs) are a member of the G-protein-coupled receptor superfamily and are known to be expressed in olfactory sensory neurons. A limited number of molecular evolutionary studies have been done for TAARs so far. To elucidate how lineage-specific evolution contributed to their functional divergence, we examined 30 metazoan genomes. In total, 493 TAAR gene candidates (including 84 pseudogenes) were identified from 26 vertebrate genomes. TAARs were not identified from non-vertebrate genomes. An ancestral-type TAAR-like gene appeared to have emerged in lamprey. We found four therian-specific TAAR subfamilies (one eutherian-specific and three metatherian-specific) in addition to previously known nine subfamilies. Many species-specific TAAR gene duplications and losses contributed to a large variation of TAAR gene numbers among mammals, ranging from 0 in dolphin to 26 in flying fox. TAARs are classified into two groups based on binding preferences for primary or tertiary amines as well as their sequence similarities. Primary amine-detecting TAARs (TAAR1-4) have emerged earlier, generally have single-copy orthologs (very few duplication or loss), and have evolved under strong functional constraints. In contrast, tertiary amine-detecting TAARs (TAAR5-9) have emerged more recently and the majority of them experienced higher rates of gene duplications. Protein members that belong to the tertiary amine-detecting TAAR group also showed the patterns of positive selection especially in the area surrounding the ligand-binding pocket, which could have affected ligand-binding activities and specificities. Expansions of the tertiary amine-detecting TAAR gene family may have played important roles in terrestrial adaptations of therian mammals. Molecular evolution of the TAAR gene family appears to be governed by a complex, species-specific, interplay between environmental and evolutionary factors. PMID:26963722

  7. Molecular Evolution and Functional Divergence of Trace Amine-Associated Receptors.

    Science.gov (United States)

    Eyun, Seong-Il; Moriyama, Hideaki; Hoffmann, Federico G; Moriyama, Etsuko N

    2016-01-01

    Trace amine-associated receptors (TAARs) are a member of the G-protein-coupled receptor superfamily and are known to be expressed in olfactory sensory neurons. A limited number of molecular evolutionary studies have been done for TAARs so far. To elucidate how lineage-specific evolution contributed to their functional divergence, we examined 30 metazoan genomes. In total, 493 TAAR gene candidates (including 84 pseudogenes) were identified from 26 vertebrate genomes. TAARs were not identified from non-vertebrate genomes. An ancestral-type TAAR-like gene appeared to have emerged in lamprey. We found four therian-specific TAAR subfamilies (one eutherian-specific and three metatherian-specific) in addition to previously known nine subfamilies. Many species-specific TAAR gene duplications and losses contributed to a large variation of TAAR gene numbers among mammals, ranging from 0 in dolphin to 26 in flying fox. TAARs are classified into two groups based on binding preferences for primary or tertiary amines as well as their sequence similarities. Primary amine-detecting TAARs (TAAR1-4) have emerged earlier, generally have single-copy orthologs (very few duplication or loss), and have evolved under strong functional constraints. In contrast, tertiary amine-detecting TAARs (TAAR5-9) have emerged more recently and the majority of them experienced higher rates of gene duplications. Protein members that belong to the tertiary amine-detecting TAAR group also showed the patterns of positive selection especially in the area surrounding the ligand-binding pocket, which could have affected ligand-binding activities and specificities. Expansions of the tertiary amine-detecting TAAR gene family may have played important roles in terrestrial adaptations of therian mammals. Molecular evolution of the TAAR gene family appears to be governed by a complex, species-specific, interplay between environmental and evolutionary factors. PMID:26963722

  8. Molecular Evolution and Functional Divergence of Trace Amine-Associated Receptors.

    Directory of Open Access Journals (Sweden)

    Seong-Il Eyun

    Full Text Available Trace amine-associated receptors (TAARs are a member of the G-protein-coupled receptor superfamily and are known to be expressed in olfactory sensory neurons. A limited number of molecular evolutionary studies have been done for TAARs so far. To elucidate how lineage-specific evolution contributed to their functional divergence, we examined 30 metazoan genomes. In total, 493 TAAR gene candidates (including 84 pseudogenes were identified from 26 vertebrate genomes. TAARs were not identified from non-vertebrate genomes. An ancestral-type TAAR-like gene appeared to have emerged in lamprey. We found four therian-specific TAAR subfamilies (one eutherian-specific and three metatherian-specific in addition to previously known nine subfamilies. Many species-specific TAAR gene duplications and losses contributed to a large variation of TAAR gene numbers among mammals, ranging from 0 in dolphin to 26 in flying fox. TAARs are classified into two groups based on binding preferences for primary or tertiary amines as well as their sequence similarities. Primary amine-detecting TAARs (TAAR1-4 have emerged earlier, generally have single-copy orthologs (very few duplication or loss, and have evolved under strong functional constraints. In contrast, tertiary amine-detecting TAARs (TAAR5-9 have emerged more recently and the majority of them experienced higher rates of gene duplications. Protein members that belong to the tertiary amine-detecting TAAR group also showed the patterns of positive selection especially in the area surrounding the ligand-binding pocket, which could have affected ligand-binding activities and specificities. Expansions of the tertiary amine-detecting TAAR gene family may have played important roles in terrestrial adaptations of therian mammals. Molecular evolution of the TAAR gene family appears to be governed by a complex, species-specific, interplay between environmental and evolutionary factors.

  9. Modeling the chemical evolution of a collapsing prestellar core in two spatial dimensions

    CERN Document Server

    van Weeren, R J; Hogerheijde, M R

    2009-01-01

    The physical conditions in a collapsing cloud can be traced by observations of molecular lines. To correctly interpret these observations the abundance distributions of the observed species need to be derived. The chemistry in a collapsing molecular cloud is not in a steady state as the density and temperature evolve. We therefore need to follow chemical reactions, both in the gas phase and on dust grains, as well as gas-grain interactions, to predict the abundance distributions. Our aim is to model the abundances of molecules, in the gas phase and on grain mantles in the form of ice, from prestellar core collapse to disk formation. We use a 2-dimensional hydrodynamical simulation as a physical model from which we take the density, temperature, and the flow of the gas. Trace particles, moving along with the gas, are used to follow the chemistry during prestellar core collapse and disk formation. The evolution of the abundances and the composition of ices on grain mantles were compared to observations. We also...

  10. Planetary Nebulae as Probes of the Chemical Evolution of Dynamically Hot Systems

    OpenAIRE

    Michael G. Richer; McCall, Marshall L.

    2004-01-01

    The measurement of chemical abundances in planetary nebulae in nearby galaxies is now relatively straightforward. The challenge is to use these chemical abundances to infer the chemical evolution of their host galaxies. At this point, our understanding of chemical evolution based upon planetary nebulae in galaxies without star formation is strongly coupled to our understanding of the relationship between the chemical abundances in stars and planetary nebulae in the Milky Way bulge. Supposing ...

  11. Geophysical and geochemical tracing of fault-zone slip and seal mechanisms through diagenetic evolution

    Science.gov (United States)

    Matonti, Christophe; Guglielmi, Yves; Viseur, Sophie; Leonide, Phlippe; Floquet, Marc; Garambois, Stéphane

    2015-04-01

    Fault and fractures properties are responsible of a large part of the fluid transfer properties at all scales, especially in tight rocks. Fault reactivations increase the complexity of the fault zone structure and cause slip reactivation on previously formed fractures. Multiple fracture reactivations can deeply modify the initial fracture properties all along the rocks diagenetic history, leading to alternate periods of fractures sealing and seismic instability. For instance, each slip step may be associated with cementation/dissolution that can be traced through combined geophysical and geochemical analyses. To that end, we studied a polyphased fault-zone outcropping on a quarry presenting a very smooth surface due to diamond wire saw exploitation of rock blocks. The quarry is composed of carbonates displaying non-porous inner-platform rudist facies of Late Cenomanian. Inside the fault zone, the rock is affected by two en-échelon fracture clusters, the first one being simply formed in mode 1 and cemented, the second one being polyphased (multiple reactivations, cementation and karstification phases). We performed a detailed structural and diagenetical characterization (fractures, karsts and stylolites digitalization on Gocad software; thin section and plug porosity), along with geochemical analyses of carbon and oxygen isotopes ratios on fracture fillings/cements and geophysical measurements at two scales. First, 1298 ultrasonic P-wave velocity measurements using a piezoelectric source were performed on a rock block (2.4x1.5x1.1m parallelepiped sampled in the fault zone border), along a vertical cross section. Then, more than 200 seismic measurements using hammer source across the decameter scale outcrop. Source and receivers were precisely located using a LIDAR 3D model of the fault-zone outcrop. First key results from ultrasonic measurements show that the fracture diagenetical/temporal evolution induces an anisotropic Vp variation regarding the dip angle of the

  12. Experimental study on trace chemical contaminant generation rates of human metabolism in spacecraft crew module

    Science.gov (United States)

    Lihua, Guo; Xinxing, He; Guoxin, Xu; Xin, Qi

    2012-12-01

    Trace chemical contaminants generated by human metabolism is a major source of contamination in spacecraft crew module. In this research, types and generation rates of pollutants from human metabolism were determined in the Chinese diets. Expired air, skin gas, and sweat of 20 subjects were analyzed at different exercise states in a simulated module. The exercise states were designed according to the basic activities in the orbit of astronauts. Qualitative and quantitative analyses of contaminants generated by human metabolic were performed with gas chromatography/mass spectrometry, gas chromatography and UV spectrophotometer. Sixteen chemical compounds from metabolic sources were found. With the increase in physical load, the concentrations of chemical compounds from human skin and expired air correspondingly increased. The species and the offgassing rates of pollutants from human metabolism are different among the Chinese, Americans and the Russians due to differences in ethnicity and dietary customs. This research provides data to aid in the design, development and operation of China's long duration space mission.

  13. Tracing origins of complex pharmaceutical preparations using surface desorption atmospheric pressure chemical ionization mass spectrometry.

    Science.gov (United States)

    Zhang, Xinglei; Jia, Bin; Huang, Keke; Hu, Bin; Chen, Rong; Chen, Huanwen

    2010-10-01

    A novel strategy to trace the origins of commercial pharmaceutical products has been developed based on the direct chemical profiling of the pharmaceutical products by surface desorption atmospheric pressure chemical ionization mass spectrometry (DAPCI-MS). Besides the unambiguous identification of active drug components, various compounds present in the matrixes are simultaneously detected without sample pretreatment, providing valuable information for drug quality control and origin differentiation. Four sources of commercial amoxicillin products made by different manufacturers have been successfully differentiated. This strategy has been extended to secerning six sources of Liuwei Dihuang Teapills, which are herbal medicine preparations with extremely complex matrixes. The photolysis status of chemical drug products and the inferior natural herd medicine products prepared with different processes (e.g., extra heating) were also screened using the method reported here. The limit of detection achieved in the MS/MS experiments was estimated to be 1 ng/g for amoxicillin inside the capsule product. Our experimental data demonstrate that DAPCI-MS is a useful tool for rapid pharmaceutical analysis, showing promising perspectives for tracking the entire pharmaceutical supply chain to prevent counterfeit intrusions. PMID:20809628

  14. Chemical evolution of two-component galaxies. II

    International Nuclear Information System (INIS)

    In order to confirm and refine the results obtained in a previous paper the chemical evolution of two-component (spheroid + disk) galaxies is derived rejecting the instantaneous recycling approximation, by means of numerical computations, accounting for (i) the collapse phase of the gas, assumed to be uniform in density and composition, and (ii) a birth-rate stellar function. Computations are performed relatively to the solar neighbourhood and to model galaxies which closely resemble the real morphological sequence: in both cases, numerical results are compared with analytical ones. The numerical models of this paper constitute a first-order approximation, while higher order approximations could be made by rejecting the hypothesis of uniform density and composition, and making use of detailed dynamical models. (Auth.)

  15. Chemical evolution. XL - Clay-mediated oxidation of diaminomaleonitrile

    Science.gov (United States)

    Ferris, J. P.; Hagan, W. J., Jr.; Alwis, K. W.; Mccrea, J.

    1982-01-01

    The inhibition of the oligomerization of HCN by montmorillonite clays is shown to be caused by oxidation of diaminomaleonitrile (DAMN) by ferric ion in the clay lattice, with ferrous ion and oxalic acid the reaction products. It is demonstrated that diiminosuccinonitrile is the initial reaction product and is rapidly hydrolized to oxalic acid and HCN. The same oxidative transformations are effected by ferric ion bound to Dowex 50, ferric ion in solution, and Ni(NH3)6(2+). The rate of reaction of DAMN indicates no catalytic role for the clay in the oxidation of DAMN, and little reaction of the latter was observed with montmorillonite in which the bulk of the iron was in the divalent state. The possible significance of these redox reactions to chemical evolution is discussed.

  16. Analytic models of the chemical evolution of galaxies

    Science.gov (United States)

    Clayton, Donald D.

    1986-01-01

    Techniques are described for constructing analytic models of the chemical evolution of galaxies subject to infall of metal-poor material onto a maturing disk. A class of linear models is discussed which takes the star-formation rate within a defined region to be proportional to the mass of interstellar gas within that region, and the instantaneous recycling approximation is adopted. The solutions are obtained by approximately matching the infall rate to parametrized familiies of functions for which the equations are exactly soluble. The masses, the primary and secondary metallicities, and the gas concentrations of radioactive chronometers can all then be analytically expressed. Surveys of galactic abundances in location and in time can be compared to the parameter spaces of the analytic representations.

  17. Galactic chemical evolution and nucleocosmochronology - Analytic quadratic models

    Science.gov (United States)

    Clayton, D. D.

    1985-01-01

    Quadratic models of the chemical evolution of the Galaxy for a star formation rate proportional to the square of the gas mass are studied. The search for analytic solutions to the gas mass and star mass for time-dependent rates of gaseous infall onto the disk is examined. The quadratic models are compared to models having linear star formation rates. The mass, metallicity, number of stars, and U-235/U-238 isotopic ratio for the models which are subjected to the same infall rate, the same initial disk mass, and the same final gas fraction are compared. The results of the comparison indicate that: (1) the average dwarf age is greater in the quadratic model, (2) the metallicity grows initially faster in the quadratic model, (3) the quadratic model has a smaller percentage of low-Z dwarfs, and (4) the U-235/U-238 isotopic ratio indicates a younger quadratic model.

  18. AGB yields and Galactic Chemical Evolution: last updated

    Science.gov (United States)

    Bisterzo, S.; Travaglio, C.; Wiescher, M.; Gallino, R.; Köppeler, F.; Straniero, O.; Cristallo, S.; Imbriani, G.; Görres, J.; deBoer, R. J.

    2016-01-01

    We study the s-process abundances at the epoch of the Solar-system formation as the outcome of nucleosynthesis occurring in AGB stars of various masses and metallicities. The calculations have been performed with the Galactic chemical evolution (GCE) model presented by [1, 2]. With respect to previous works, we used updated solar meteoritic abundances, a neutron capture cross section network that includes the most recent measurements, and we implemented the s-process yields with an extended range of AGB initial masses. The new set of AGB yields includes a new evaluation of the 22Ne(α, n)25Mg rate, which takes into account the most recent experimental information.

  19. New chemical evolution analytical solutions including environment effects

    CERN Document Server

    Spitoni, E

    2015-01-01

    In the last years, more and more interest has been devoted to analytical solutions, including inflow and outflow, to study the metallicity enrichment in galaxies. In this framework, we assume a star formation rate which follows a linear Schmidt law, and we present new analytical solutions for the evolution of the metallicity (Z) in galaxies. In particular, we take into account environmental effects including primordial and enriched gas infall, outflow, different star formation efficiencies, and galactic fountains. The enriched infall is included to take into account galaxy-galaxy interactions. Our main results can be summarized as: i) when a linear Schmidt law of star formation is assumed, the resulting time evolution of the metallicity Z is the same either for a closed-box model or for an outflow model. ii) The mass-metallicity relation for galaxies which suffer a chemically enriched infall, originating from another evolved galaxy with no pre-enriched gas, is shifted down in parallel at lower Z values, if co...

  20. Dynamical and chemical evolution of the thin disc

    CERN Document Server

    Just, Andreas

    2015-01-01

    Our detailed analytic local disc model (JJ-model) quantifies the interrelation between kinematic properties (e.g. velocity dispersions and asymmetric drift), spatial parameters (scale-lengths and vertical density profiles), and properties of stellar sub-populations (age and abundance distributions). Any consistent radial extension of the disc evolution model should predict specific features in the different distribution functions and in their correlations. Large spectroscopic surveys (SEGUE, RAVE, APOGEE, Gaia-ESO) allow significant constraints on the long-term evolution of the thin disc. We discuss the qualitative difference of correlations (like the alpha-enhancement as function of metallicity) and distribution functions (e.g. in [Mg/H] or [Fe/H]) for the construction of a disc model. In the framework of the JJ-model we build a local chemical enrichment model and show that significant vertical gradients for main sequence and red clump stars are expected in the thin disc. A Jeans analysis of the asymmetric d...

  1. Cosmic chemical evolution with intermediate mass pop III stars

    International Nuclear Information System (INIS)

    We explore the consequences of an early population of intermediate mass stars (IMS) in the 2 – 8 Msun range on cosmic chemical evolution. We discuss the implications of this population as it pertains to several cosmological and astrophysical observables. Some very metal-poor galactic stars show large enhancements of carbon, typical of the C-rich ejecta of IMS; moreover, halo star carbon and oxygen abundances show a scatter, which imply a wide range of star-formation and nucleosynthetic histories contributed to the first generations of stars. Also, recent analyses of the He abundance in metal-poor extragalactic H II regions suggest an elevated primitive abundance of Helium, Yp ≅ 0.256 by mass, higher than the predicted result from big bang nucleosynthesis assuming the baryon density determined by WMAP, Yp ≅ 0.249. This offset suggests a prompt initial enrichment of He in early metal-poor structures, and IMS Pop III stars are again good candidates. We also discuss the effect of these Pop III stars on global cosmic evolution for example the reionization of the Universe. We conclude that if IMS are to be associated with some Population III stars, their relevance is limited to low mass structures involving a little fraction of the total baryon content of the Universe typical at redshift 10 [1].

  2. Chemical Properties of Starburst Galaxies Near and Far: Clues to Galaxy Evolution

    OpenAIRE

    Contini, T.; Treyer, M. -A.; Mouhcine, M.; Sullivan, M.; Ellis, R. S.,

    2001-01-01

    The determination of chemical abundances in star-forming galaxies and the study of their evolution on cosmological timescales are powerful tools for understanding galaxy formation and evolution. This contribution presents the latest results in this domain. We show that detailed studies of chemical abundances in UV-selected, HII and starburst nucleus galaxies, together with the development of new chemical evolution models, put strong constraints on the evolutionary stage of these objects in te...

  3. Modelling the spectro-photometric and chemical evolution of Low Surface Brightness spiral galaxies

    OpenAIRE

    Hoek, L. B. van den; de Blok, W J G

    1995-01-01

    We investigate the star formation history and chemical evolution of Low Surface Brightness (LSB) spiral galaxies by means of their observed spectro-photometric and chemical properties. We present preliminary results for Johnson-Cousins UBVRI magnitudes and stellar [O/H] abundance ratios using a galactic chemical evolution model incorporating a detailed metallicity dependent set of stellar input data covering all relevant stages of stellar evolution. Comparison of our model results with observ...

  4. Chemical differentiation in a prestellar core traces non-uniform illumination

    Science.gov (United States)

    Spezzano, S.; Bizzocchi, L.; Caselli, P.; Harju, J.; Brünken, S.

    2016-08-01

    Dense cloud cores present chemical differentiation because C- and N-bearing molecules are distributed differently, the latter being less affected by freeze-out onto dust grains. In this letter we show that two C-bearing molecules, CH3OH and c-C3H2, present a strikingly different (complementary) morphology while showing the same kinematics towards the prestellar core L1544. After comparing their distribution with the large-scale H2 column density N(H2) map from the Herschel satellite, we find that these two molecules trace different environmental conditions in the surrounding of L1544: the c-C3H2 distribution peaks close to the southern part of the core, where the surrounding molecular cloud has an N(H2) sharp edge, while CH3OH mainly traces the northern part of the core, where N(H2) presents a shallower tail. We conclude that this is evidence of chemical differentiation driven by different amounts of illumination from the interstellar radiation field: in the south, photochemistry maintains more C atoms in the gas phase, allowing carbon-chain (such as c-C3H2) production; in the north, C is mainly locked in CO, and methanol traces the zone where CO starts to freeze out significantly. During the process of cloud contraction, different gas and ice compositions are thus expected to mix towards the central regions of the core, where a potential solar-type system will form. An alternative view on carbon-chain chemistry in star-forming regions is also provided. Based on observations carried out with the IRAM 30 m Telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain).The reduced data 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/592/L11

  5. Intercomparisons of Airborne Measurements of Aerosol Ionic Chemical Composition during TRACE-P and ACE-Asia

    Science.gov (United States)

    Ma, Y.; Weber, R. J.; Maxwell-Meier, K.; Orsini, D. A.; Lee, Y.-N.; Huebert, B. J.; Howell, S. G.; Bertram, T.; Talbot, R. W.

    2003-01-01

    As part of the two field studies, Transport and Chemical Evolution over the Pacific (TRACE-P), and the Asian Aerosol Characterization Experiment (ACEAsia), the inorganic chemical composition of tropospheric aerosols was measured over the western Pacific from three separate aircraft using various methods. Comparisons are made between the rapid online techniques of the Particle Into Liquid Sampler (PILS) for measurement of a suite of fine particle ionic compounds and a mist chamber (MC/IC) measurement of fine sulfate, and the longer time-integrated filter and multi-orifice impactor (MOI) measurements. Comparisons between identical PILS on two separate aircraft flying in formation showed that they were highly correlated (e.g., sulfate r(sup 2) of 0.95), but were systematically different by 10 +/- 5% (linear regression slope and 95% confidence bounds), and had generally higher concentrations on the aircraft with a low turbulence inlet and shorter inlet-to-instrument transmission tubing. Comparisons of PILS and mist chamber measurements of fine sulfate on two different aircraft during formation flying had an 3 of 0.78 and a relative difference of 39% +/- 5%. MOI ionic data integrated to the PILS upper measurement size of 1.3 pm sampling from separate inlets on the same aircraft showed that for sulfate, PILS and MOI were within 14% +/- 6% and correlated with an r(sup 2) of 0.87. Most ionic compounds were within f 30%, which is in the range of differences reported between PILS and integrated samplers from ground-based comparisons. In many cases, direct intercomparison between the various instruments is difficult due to differences in upper-size detection limits. However, for this study, the results suggest that the fine particle mass composition measured from aircraft agree to within 30-40%.

  6. Modelling the chemical evolution in galaxies with KROME

    CERN Document Server

    Bovino, Stefano; Capelo, Pedro R; Schleicher, Dominik R G; Banerjee, R

    2015-01-01

    In this paper we present and test chemical models for three-dimensional hydrodynamical simulations of galaxy evolution. The microphysics is modelled by employing the public chemistry package KROME and the chemical networks have been tested to work in a wide range of densities and temperatures. We describe a simple H/He network following the formation of H2, and a more sophisticated network which includes metals. Photochemistry, thermal processes, and different prescriptions for the H2 catalysis on dust are presented and tested within a simple one-zone framework. We explore the effect of changing some of the key parameters such as metallicity, radiation and non-equilibrium versus equilibrium metal cooling approximations on the transition between the different gas phases. We find that employing an accurate treatment of the dust-related processes induces a faster HI-H2 transition. In addition, we show when the equilibrium assumption for metal cooling holds, and how a non-equilibrium approach affects the thermal ...

  7. Modeling the chemical evolution of nitrogen oxides near roadways

    Science.gov (United States)

    Wang, Yan Jason; DenBleyker, Allison; McDonald-Buller, Elena; Allen, David; Zhang, K. Max

    2011-01-01

    The chemical evolution of nitrogen dioxide (NO 2) and nitrogen monoxide (NO) in the vicinity of roadways is numerically investigated using a computational fluid dynamics model, CFD-VIT-RIT and a Gaussian-based model, CALINE4. CFD-VIT-RIT couples a standard k- ɛ turbulence model for turbulent mixing and the Finite-Rate model for chemical reactions. CALINE4 employs a discrete parcel method, assuming that chemical reactions are independent of the dilution process. The modeling results are compared to the field measurement data collected near two roadways in Austin, Texas, State Highway 71 (SH-71) and Farm to Market Road 973 (FM-973), under parallel and perpendicular wind conditions during the summer of 2007. In addition to ozone (O 3), other oxidants and reactive species including hydroperoxyl radical (HO 2), organic peroxyl radical (RO 2), formaldehyde (HCHO) and acetaldehyde (CH 3CHO) are considered in the transformation from NO to NO 2. CFD-VIT-RIT is shown to be capable of predicting both NO x and NO 2 profiles downwind. CALINE4 is able to capture the NO x profiles, but underpredicts NO 2 concentrations under high wind velocity. Our study suggests that the initial NO 2/NO x ratios have to be carefully selected based on traffic conditions in order to assess NO 2 concentrations near roadways. The commonly assumed NO 2/NO x ratio by volume of 5% may not be suitable for most roadways, especially those with a high fraction of heavy-duty truck traffic. In addition, high O 3 concentrations and high traffic volumes would lead to the peak NO 2 concentration occurring near roadways with elevated concentrations persistent over a long distance downwind.

  8. Chemical evolution of giant molecular clouds in simulations of galaxies

    Science.gov (United States)

    Richings, Alexander J.; Schaye, Joop

    2016-08-01

    We present an analysis of Giant Molecular Clouds (GMCs) within hydrodynamic simulations of isolated, low-mass (M* ~ 10^9 M_sol) disc galaxies. We study the evolution of molecular abundances and the implications for CO emission and the X_CO conversion factor in individual clouds. We define clouds either as regions above a density threshold n_H,min = 10 cm^-3, or using an observationally motivated CO intensity threshold of 0.25 K km s^-1. Our simulations include a non-equilibrium chemical model with 157 species, including 20 molecules. We also investigate the effects of resolution and pressure floors (i.e. Jeans limiters). We find cloud lifetimes up to ~40 Myr, with a median of 13 Myr, in agreement with observations. At one tenth solar metallicity, young clouds (<10-15 Myr) are underabundant in H2 and CO compared to chemical equilibrium, by factors of ~3 and 1-2 orders of magnitude, respectively. At solar metallicity, GMCs reach chemical equilibrium faster (within ~1 Myr). We also compute CO emission from individual clouds. The mean CO intensity, I_CO, is strongly suppressed at low dust extinction, A_v, and possibly saturates towards high A_v, in agreement with observations. The I_CO - A_v relation shifts towards higher A_v for higher metallicities and, to a lesser extent, for stronger UV radiation. At one tenth solar metallicity, CO emission is weaker in young clouds (<10-15 Myr), consistent with the underabundance of CO. Consequently, X_CO decreases by an order of magnitude from 0 to 15 Myr, albeit with a large scatter.

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

    Science.gov (United States)

    Oro, J.; Lazcano, A.

    1991-01-01

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

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

    Science.gov (United States)

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

    1986-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1986-05-01

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

  12. Chemical speciation of trace metals emitted from Indonesian peat fires for health risk assessment

    Science.gov (United States)

    Betha, Raghu; Pradani, Maharani; Lestari, Puji; Joshi, Umid Man; Reid, Jeffrey S.; Balasubramanian, Rajasekhar

    2013-03-01

    Regional smoke-induced haze in Southeast Asia, caused by uncontrolled forest and peat fires in Indonesia, is of major environmental and health concern. In this study, we estimated carcinogenic and non-carcinogenic health risk due to exposure to fine particles (PM2.5) as emitted from peat fires at Kalimantan, Indonesia. For the health risk analysis, chemical speciation (exchangeable, reducible, oxidizable, and residual fractions) of 12 trace metals (Al, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Ti, V and Zn) in PM2.5 was studied. Results indicate that Al, Fe and Ti together accounted for a major fraction of total metal concentrations (~ 83%) in PM2.5 emissions in the immediate vicinity of peat fires. Chemical speciation reveals that a major proportion of most of the metals, with the exception of Cr, Mn, Fe, Ni and Cd, was present in the residual fraction. The exchangeable fraction of metals, which represents their bioavailability, could play a major role in inducing human health effects of PM2.5. This fraction contained carcinogenic metals such as Cd (39.2 ng m- 3) and Ni (249.3 ng m- 3) that exceeded their WHO guideline values by several factors. Health risk estimates suggest that exposure to PM2.5 emissions in the vicinity of peat fires poses serious health threats.

  13. Learning to Rapidly Re-Contact the Lost Plume in Chemical Plume Tracing

    Directory of Open Access Journals (Sweden)

    Meng-Li Cao

    2015-03-01

    Full Text Available Maintaining contact between the robot and plume is significant in chemical plume tracing (CPT. In the time immediately following the loss of chemical detection during the process of CPT, Track-Out activities bias the robot heading relative to the upwind direction, expecting to rapidly re-contact the plume. To determine the bias angle used in the Track-Out activity, we propose an online instance-based reinforcement learning method, namely virtual trail following (VTF. In VTF, action-value is generalized from recently stored instances of successful Track-Out activities. We also propose a collaborative VTF (cVTF method, in which multiple robots store their own instances, and learn from the stored instances, in the same database. The proposed VTF and cVTF methods are compared with biased upwind surge (BUS method, in which all Track-Out activities utilize an offline optimized universal bias angle, in an indoor environment with three different airflow fields. With respect to our experimental conditions, VTF and cVTF show stronger adaptability to different airflow environments than BUS, and furthermore, cVTF yields higher success rates and time-efficiencies than VTF.

  14. Detection and monitoring of toxic chemical at ultra trace level by utilizing doped nanomaterial.

    Directory of Open Access Journals (Sweden)

    Sher Bahadar Khan

    Full Text Available Composite nanoparticles were synthesized by eco-friendly hydrothermal process and characterized by different spectroscopic techniques. All the spectroscopic techniques suggested the synthesis of well crystalline optically active composite nanoparticles with average diameter of ∼ 30 nm. The synthesized nanoparticles were applied for the development of chemical sensor which was fabricated by coating the nanoparticles on silver electrode for the recognition of phthalimide using simple I-V technique. The developed sensor exhibited high sensitivity (1.7361 µA.mM(-1.cm(-2, lower detection limit (8.0 µM and long range of detection (77.0 µM to 0.38 M. Further the resistances of composite nanoparticles based sensor was found to be 2.7 MΩ which change from 2.7 to 1.7 with change in phthalimide concentration. The major advantages of the designed sensor over existing sensors are its simple technique, low cost, lower detection limit, high sensitivity and long range of detection. It can detect phthalimide even at trace level and sense over wide range of concentrations. Therefore the composite nanoparticals would be a better choice for the fabrication of phthalimide chemical sensor and would be time and cost substituted implement for environmental safety.

  15. Cyril Ponnamperuma Memorial. Trieste conference on chemical evolution, 4: Physics of the origin and evolution of life. Summaries

    International Nuclear Information System (INIS)

    The document includes 19 summaries of papers presented at the Trieste Conference on Chemical Evolution, 4: Physics of the Origin and Evolution of Life (Cyril Ponnamperuma Memorial), Miramare, Trieste, 4-8 September 1995. The abstracts have been indexed individually. 3 refs, 1 fig

  16. High sensitivity detection and characterization of the chemical state of trace element contamination on silicon wafers

    International Nuclear Information System (INIS)

    Increasing the speed and complexity of semiconductor integrated circuits requires advanced processes that put extreme constraints on the level of metal contamination allowed on the surfaces of silicon wafers. Such contamination degrades the performance of the ultrathin SiO2 gate dielectrics that form the heart of the individual transistors. Ultimately, reliability and yield are reduced to levels that must be improved before new processes can be put into production. It should be noted that much of this metal contamination occurs during the wet chemical etching and rinsing steps required for the manufacture of integrated circuits and industry is actively developing new processes that have already brought the metal contamination to levels beyond the measurement capabilities of conventional analytical techniques. The measurement of these extremely low contamination levels has required the use of synchrotron radiation total reflection X-ray fluorescence (SR-TXRF) where sensitivities 100 times better than conventional techniques have been achieved. This has resulted in minimum detection limits for transition metals of 8 x 107 atoms/cm2. SR-TXRF studies of the amount of metal contamination deposited on a silicon surface as a function of pH and oxygen content of the etching solutions have provided insights into the mechanisms of metal deposition from solutions containing trace amounts of metals ranging from parts per trillion to parts per billion. Furthermore, by using XANES to understand the chemical state of the metal atmos after deposition, it has been possible to develop chemical models for the deposition processes. Examples will be provided for copper deposition from ultra pure water and acidic solutions. (author)

  17. On the detectability of trace chemical species in the martian atmosphere using gas correlation filter radiometry

    Science.gov (United States)

    Sinclair, J. A.; Irwin, P. G. J.; Calcutt, S. B.; Wilson, E. L.

    2015-11-01

    The martian atmosphere is host to many trace gases including water (H2O) and its isotopologues, methane (CH4) and potentially sulphur dioxide (SO2), nitrous oxide (N2O) and further organic compounds, which would serve as indirect tracers of geological, chemical and biological processes on Mars. With exception of the recent detection of CH4 by Curiosity, previous detections of these species have been unsuccessful or considered tentative due to the low concentrations of these species in the atmosphere (∼10-9 partial pressures), limited spectral resolving power and/or signal-to-noise and the challenge of discriminating between telluric and martian features when observing from the Earth. In this study, we present radiative transfer simulations of an alternative method for detection of trace gas species - the gas correlation radiometry method. Two potential observing scenarios were explored where a gas correlation filter radiometer (GCFR) instrument: (1) performs nadir and/or limb sounding of the martian atmosphere in the thermal infrared (200-2000 cm-1 from an orbiting spacecraft or (2) performs solar occultation measurements in the near-infrared (2000-5000 cm-1) from a lander on the martian surface. In both scenarios, simulations of a narrowband filter radiometer (without gas correlation) were also generated to serve as a comparison. From a spacecraft, we find that a gas correlation filter radiometer, in comparison to a filter radiometer (FR), offers a greater discrimination between temperature and dust, a greater discrimination between H2O and HDO, and would allow detection of N2O and CH3OH at concentrations of ∼10 ppbv and ∼2 ppbv, respectively, which are lower than previously-derived upper limits. However, the lowest retrievable concentration of SO2 (approximately 2 ppbv) is comparable with previous upper limits and CH4 is only detectable at concentrations of approximately 10 ppbv, which is an order of magnitude higher than the concentration recently measured

  18. Chemical evolution of multicomponent aerosol particles during evaporation

    Science.gov (United States)

    Zardini, Alessandro; Riipinen, Ilona; Pagels, Joakim; Eriksson, Axel; Worsnop, Douglas; Switieckli, Erik; Kulmala, Markku; Bilde, Merete

    2010-05-01

    Atmospheric aerosol particles have an important but not well quantified effect on climate and human health. Despite the efforts made in the last decades, the formation and evolution of aerosol particles in the atmosphere is still not fully understood. The uncertainty is partly due to the complex chemical composition of the particles which comprise inorganic and organic compounds. Many organics (like dicarboxylic acids) can be present both in the gas and in the condensed phase due to their low vapor pressure. Clearly, an understanding of this partition is crucial to address any other issue in atmospheric physics and chemistry. Moreover, many organics are water soluble, and their influence on the properties of aqueous solution droplets is still poorly characterized. The solid and sub-cooled liquid state vapor pressures of some organic compounds have been previously determined by measuring the evaporation rate of single-compound crystals [1-3] or binary aqueous droplets [4-6]. In this work, we deploy the HTDMA technique (Hygroscopicity Tandem Differential Mobility Analyzer) coupled with a 3.5m laminar flow-tube and an Aerosol Mass Spectrometer (AMS) for determining the chemical evolution during evaporation of ternary droplets made of one dicarboxylic acid (succinic acid, commonly found in atmospheric samples) and one inorganic compound (sodium chloride or ammonium sulfate) in different mixing ratios, in equilibrium with water vapor at a fixed relative humidity. In addition, we investigate the evaporation of multicomponent droplets and crystals made of three organic species (dicarboxylic acids and sugars), of which one or two are semi-volatile. 1. Bilde M. and Pandis, S.N.: Evaporation Rates and Vapor Pressures of Individual Aerosol Species Formed in the Atmospheric Oxidation of alpha- and beta-Pinene. Environmental Science and Technology, 35, 2001. 2. Bilde M., et al.: Even-Odd Alternation of Evaporation Rates and Vapor Pressures of C3-C9 Dicarboxylic Acid Aerosols

  19. Use of external cavity quantum cascade laser compliance voltage in real-time trace gas sensing of multiple chemicals

    Energy Technology Data Exchange (ETDEWEB)

    Phillips, Mark C.; Taubman, Matthew S.; Kriesel, Jason M.

    2015-02-08

    We describe a prototype trace gas sensor designed for real-time detection of multiple chemicals. The sensor uses an external cavity quantum cascade laser (ECQCL) swept over its tuning range of 940-1075 cm-1 (9.30-10.7 µm) at a 10 Hz repetition rate.

  20. Extragalactic Planetary Nebulae: tracers of the chemical evolution of nearby galaxies

    OpenAIRE

    Magrini, Laura; Stanghellini, Letizia; Goncalves, Denise R.

    2011-01-01

    The study of the chemical composition of Planetary Nebulae in external galaxies is of paramount importance in the fields of stellar evolution and of the chemical enrichment history of galaxies. In the last years a number of spectroscopic studies with 6-8m-class telescopes have been devoted to this subject improving our knowledge of, among other, the time-evolution of the radial metallicity gradient in disk galaxies, the chemical evolution of dwarf galaxies, and the stellar evolution at low me...

  1. CHEMICAL EVOLUTION AND THE GALACTIC HABITABLE ZONE OF M31

    Directory of Open Access Journals (Sweden)

    Leticia Carigi

    2013-01-01

    Full Text Available We have computed the Galactic Habitable Zones (GHZs of the Andromeda galaxy (M31 based on the probability of terrestrial planet formation, which depends on the metallicity (Z of the interstellar medium, and the number of stars formed per unit surface area. The GHZ was obtained from a chemical evolution model built to reproduce a metallicity gradient in the galactic disk, [O/H](r=−0.015 dex kpc−1 × r(kpc + 0.44 dex. If we assume that Earth-like planets form with a probability law that follows the Z distribution shown by stars with detected planets, the most probable GHZ per pc2 is located between 3 and 7 kpc for planets with ages between 6 and 7 Gyr. However, the highest number of stars with habitable planets is located in a ring between 12 and 14 kpc with a mean age of 7 Gyr. 11% and 6.5% of the all formed stars in M31 may have planets capable of hosting basic and complex life, respectively.

  2. Chemical evolution of giant molecular clouds in simulations of galaxies

    CERN Document Server

    Richings, Alexander J

    2016-01-01

    We present an analysis of Giant Molecular Clouds (GMCs) identified in hydrodynamic simulations of isolated, low-mass (M* ~ 10^9 M_sol) disc galaxies, with a particular focus on the evolution of molecular abundances and the implications for CO emission and the X_CO conversion factor in individual clouds. We define clouds either as regions above a density threshold n_H,min = 10 cm^-3, or using an observationally motivated velocity-integrated CO line intensity threshold of 0.25 K km s^-1. Our simulations include a non-equilibrium treatment for the chemistry of 157 species, including 20 molecules. We use a suite of runs to carefully investigate the effects of numerical resolution and pressure floors (i.e. Jeans mass limiters). We find cloud lifetimes up to ~40 Myr, with a median of 13 Myr, in agreement with observations. At ten per cent solar metallicity, young clouds (<10-15 Myr) tend to be underabundant in H2 and CO compared to chemical equilibrium, by factors of ~3 and 1-2 orders of magnitude, respectively....

  3. Galactic chemical evolution of heavy elements from Barium to Europium

    CERN Document Server

    Travaglio, C; Gallino, R; Busso, M; Ferrini, F; Straniero, O

    1999-01-01

    We follow the chemical evolution of the Galaxy for elements from Ba to Eu, using an evolutionary model suitable to reproduce a large set of Galactic (local and non local) and extragalactic constraints. Input stellar yields for neutron-rich nuclei have been separated into their s-process and r-process components. The production of s-process elements in thermally pulsing asymptotic giant branch stars of low mass proceeds from the combined operation of two neutron sources: the dominant reaction 13C(alpha,n)16O, which releases neutrons in radiative conditions during the interpulse phase, and the reaction 22Ne(alpha,n)25Mg, marginally activated during thermal instabilities. The resulting s-process distribution is strongly dependent on the stellar metallicity. For the standard model discussed in this paper, it shows a sharp production of the Ba-peak elements around Z = Z_sun/4. Concerning the r-process yields, we assume that the production of r-nuclei is a primary process occurring in stars near the lowest mass lim...

  4. The Galactic Habitable Zone I. Galactic Chemical Evolution

    CERN Document Server

    González, G; Ward, P; Gonzalez, Guillermo; Brownlee, Donald; Ward, Peter

    2001-01-01

    We propose the concept of a "Galactic Habitable Zone" (GHZ). Analogous to the Circumstellar Habitable Zone (CHZ), the GHZ is that region in the Milky Way where an Earth-like planet can retain liquid water on its surface and provide a long-term habitat for animal-like aerobic life. In this paper we examine the dependence of the GHZ on Galactic chemical evolution. The single most important factor is likely the dependence of terrestrial planet mass on the metallicity of its birth cloud. We estimate, very approximately, that a metallicity at least half that of the Sun is required to build a habitable terrestrial planet. The mass of a terrestrial planet has important consequences for interior heat loss, volatile inventory, and loss of atmosphere. A key issue is the production of planets that sustain plate tectonics, a critical recycling process that provides feedback to stabilize atmospheric temperatures on planets with oceans and atmospheres. Due to the more recent decline from the early intense star formation ac...

  5. The Chemical Evolution of Globular Clusters - II. Metals and Fluorine

    CERN Document Server

    Sanchez-Blazquez, Patricia; Gibson, Brad K; Karakas, Amanda I; Pilkington, Kate; Calura, Francesco

    2011-01-01

    In the first paper in this series, we proposed a new framework in which to model the chemical evolution of globular clusters. This model, is predicated upon the assumption that clusters form within an interstellar medium enriched locally by the ejecta of a single Type Ia supernova and varying numbers of asymptotic giant branch stars, superimposed on an ambient medium pre-enriched by low-metallicity Type II supernovae. Paper I was concerned with the application of this model to the observed abundances of several reactive elements and so-called non-metals for three classical intermediate-metallicity clusters, with the hallmark of the work being the successful recovery of many of their well-known elemental and isotopic abundance anomalies. Here, we expand upon our initial analysis by (a) applying the model to a much broader range of metallicities (from the factor of three explored in Paper I, to now, a factor of ~50; i.e., essentially, the full range of Galactic globular cluster abundances, and (b) incorporating...

  6. Inflow, Outflow, Yields, and Stellar Population Mixing in Chemical Evolution Models

    OpenAIRE

    Brett H. Andrews(Department of Astronomy, Ohio State University, 140 West 18th Avenue, Columbus, OH 43210, USA); Weinberg, David H.; Schönrich, Ralph; Johnson, Jennifer A.

    2016-01-01

    Chemical evolution models are powerful tools for interpreting stellar abundance surveys and understanding galaxy evolution. However, their predictions depend heavily on the treatment of inflow, outflow, star formation efficiency (SFE), the IMF, the SNIa delay time distribution, stellar yields, and mixing of stellar populations. Using flexCE, a new, flexible one-zone chemical evolution code, we investigate the effects of individual parameters and the trade-offs between them. Two of the most im...

  7. THE LONG-TERM EVOLUTION OF THE GALACTIC DISK TRACED BY DISSOLVING STAR CLUSTERS

    International Nuclear Information System (INIS)

    The Galactic disk retains vast amount of information about how it came to be and how it evolved over cosmic time. However, we know very little about the secular processes associated with disk evolution. One major uncertainty is the extent to which stars migrate radially through the disk, thereby washing out signatures of their past (e.g., birth sites). Recent theoretical work finds that such 'blurring' of the disk can be important if spiral arms are transient phenomena. Here we describe an experiment to determine the importance of diffusion from the Solar circle with cosmic time. Consider a star cluster that has been placed into a differentially rotating, stellar fluid. We show that all clusters up to ∼104 Msun in mass, and a significant fraction of those up to ∼105 Msun, are expected to be chemically homogeneous, and that clusters of this size can be assigned a unique 'chemical tag' by measuring the abundances of ∼<10 independent element groups, with better age and orbit determinations allowing fewer abundance measurements. The star cluster therefore acts like a 'tracer dye', and the present-day distribution of its stars provides a strong constraint on the rate of radial diffusion or migration in the Galactic disk. A star cluster of particular interest for this application is the 'Solar family' - the stars that were born with the Sun. If we were able to identify a significant fraction of these, we could determine whether the Sun was born at its present radius or much further in. We show all-sky projections for the Solar family under different dynamical scenarios and identify the most advantageous fields on the sky for the experiment. Sellwood and Binney have argued for strong radial transport driven by transient spiral perturbations: in principle, we could measure the strength of this migration directly. In searching for the Solar family, we would also identify many thousands of other chemically homogeneous groups, providing a wealth of additional

  8. Trace metals of an acid mine drainage stream using a chemical model (WATEQ) and sediment analysis

    International Nuclear Information System (INIS)

    The high metal contents common to the discharge of acid-mine drainage (AMD) from mines and mine spoils is an environmental concern to both government and industry. This paper reports the results of investigation of the behavior of metals in an AMD system at a former surface coal mine in Tuscarawas County, Oh. AMD discharges from seeps travels, in respective order through a laminar flow stream; a Typha-dominated wetland; a turbulent flow stream; and a sediment retention pond. Dissolved metals (Fe, Mn, Zn, Cr, Cd, Cu, and Al) major and minor components, and other parameters (pH, dissolved oxygen and Eh) were measured in the AMD water at each sample location. A chemical mineral equilibrium model (WATEQ) was used to predict the minerals which should precipitate at each site. Results suggest that the seeps are supersaturated and should be precipitating hematite, goethite and magnetite (iron oxides), and siderite (iron carbonate), whereas water of the other downstream sites were at or below equilibrium conditions for these minerals. The hydrogeochemistry of the AMD was further studied using sequential chemical attacks on the precipitate sediment surface coatings, in order to determine metal concentrations in the exchangeable, carbonate, Fe-Mn oxyhydroxide, and oxidizable fractions. The carbonate and exchangeable fractions of the precipitate are dominated by Ca and Fe, as well as Mg in the carbonate fraction. The Fe-Mn oxyhydroxide fraction contained Fe, Al, Mn, Mg, and trace metals, and also contained the greatest concentration of total elements in the system. The Fe-Mn oxyhydroxide is therefore, the major sink for metals of this AMD system. The decrease in the concentration of metals in the sediment precipitates in the downstream locations, is consistent with WATEQ and water analysis results

  9. Effect of temperature on removal of trace organic chemicals in managed aquifer recharge systems

    KAUST Repository

    Alidina, Mazahirali

    2015-03-01

    This study was undertaken to investigate whether changes in temperature experienced in MAR systems affect attenuation of trace organic chemicals (TOrCs). A set of laboratory-scale soil columns were placed in a temperature-controlled environmental chamber and operated at five different temperature set-points (30, 20, 10, 8 and 4. °C) covering the range of typical groundwater temperatures in cold, moderate and arid climate regions. Removal of bulk organic carbon both in the infiltration zone as well as during deeper infiltration was independent of temperature. Of the 22 TOrCs investigated, only six chemicals exhibited changes in attenuation as a function of temperature. Attenuation of four of the compounds (diclofenac, gemfibrozil, ketoprofen and naproxen) decreased as the temperature was reduced from 30. °C to 4. °C, likely due to decreased microbial activity at lower temperatures. As the temperature was decreased, however, attenuation of oxybenzone and trimethoprim were noted to increase. This increased attenuation was likely due to more efficient sorption at lower temperatures, though possible changes in the microbial composition as the temperature decreased may also have contributed to this change. Changes in rate constants of attenuation (. ka) for the biotransformed TOrCs with temperature suggested the existence of a critical temperature at 10. °C for three of the four TOrCs, where significant changes to rates of attenuation occurred. Results from this study indicated that for most TOrCs, changes in temperature do not impact their attenuation. Thus, seasonal changes in temperature are not considered to be a major concern for attenuation of most TOrCs in MAR systems.

  10. Removal of trace organic chemicals and performance of a novel hybrid ultrafiltration-osmotic membrane bioreactor.

    Science.gov (United States)

    Holloway, Ryan W; Regnery, Julia; Nghiem, Long D; Cath, Tzahi Y

    2014-09-16

    A hybrid ultrafiltration-osmotic membrane bioreactor (UFO-MBR) was investigated for over 35 days for nutrient and trace organic chemical (TOrC) removal from municipal wastewater. The UFO-MBR system uses both ultrafiltration (UF) and forward osmosis (FO) membranes in parallel to simultaneously extract clean water from an activated sludge reactor for nonpotable (or environmental discharge) and potable reuse, respectively. In the FO stream, water is drawn by osmosis from activated sludge through an FO membrane into a draw solution (DS), which becomes diluted during the process. A reverse osmosis (RO) system is then used to reconcentrate the diluted DS and produce clean water suitable for direct potable reuse. The UF membrane extracts water, dissolved salts, and some nutrients from the system to prevent their accumulation in the activated sludge of the osmotic MBR. The UF permeate can be used for nonpotable reuse purposes (e.g., irrigation and toilet flushing). Results from UFO-MBR investigation illustrated that the chemical oxygen demand, total nitrogen, and total phosphorus removals were greater than 99%, 82%, and 99%, respectively. Twenty TOrCs were detected in the municipal wastewater that was used as feed to the UFO-MBR system. Among these 20 TOrCs, 15 were removed by the hybrid UFO-MBR system to below the detection limit. High FO membrane rejection was observed for all ionic and nonionic hydrophilic TOrCs and lower rejection was observed for nonionic hydrophobic TOrCs. With the exceptions of bisphenol A and DEET, all TOrCs that were detected in the DS were well rejected by the RO membrane. Overall, the UFO-MBR can operate sustainably and has the potential to be utilized for direct potable reuse applications. PMID:25113310

  11. Combined utilization of DGTs and bioindicators to trace chemical contamination threats on coastal ecosystems

    OpenAIRE

    Richir, Jonathan; Luy, Nicolas; Serpe, Pierre; Lefèbvre, Lucie; Deraikem, Alexandre; Lepoint, Gilles; Biondo, Renzo; Gobert, Sylvie

    2011-01-01

    Trace metal monitoring in marine organisms and their living habitats permit to trace chronic or acute contaminations of marine ecosystems due to human activities. While dissolved trace metal concentrations give us an overall and punctual view over biota contamination status, bioindicator species put their bioavailable and possible toxic fraction in an obvious. However, difficulties mainly inherent to metal measurements in seawater lead field ecotoxicologists to study marine pollution essentia...

  12. A simple and general method for solving detailed chemical evolution with delayed production of iron and other chemical elements

    CERN Document Server

    Vincenzo, Fiorenzo; Spitoni, Emanuele

    2016-01-01

    In this Letter, we present a new theoretical method for solving the chemical evolution of galaxies, by assuming the instantaneous recycling approximation for chemical elements restored by massive stars and the Delay Time Distribution formalism for the delayed chemical enrichment by Type Ia Supernovae. The galaxy gas mass assembly history, together with the assumed stellar yields and initial mass function, represent the starting point of this method. We derive a very simple and general equation which closely relates the Laplace transforms of the galaxy gas accretion and star formation history, which can be used to simplify the problem of retrieving these quantities in most of current galaxy evolution models. We find that - once the galaxy star formation history has been reconstructed from our assumptions - the differential equation for the evolution of the chemical element $X$ can be suitably solved with classical methods. We apply our model to reproduce the $[\\text{O/Fe}]$ and $[\\text{Si/Fe}]$ vs. $[\\text{Fe/...

  13. A simple and general method for solving detailed chemical evolution with delayed production of iron and other chemical elements

    OpenAIRE

    Vincenzo, Fiorenzo; Matteucci, Francesca; Spitoni, Emanuele

    2016-01-01

    In this Letter, we present a new theoretical method for solving the chemical evolution of galaxies, by assuming the instantaneous recycling approximation for chemical elements restored by massive stars and the Delay Time Distribution formalism for the delayed chemical enrichment by Type Ia Supernovae. The galaxy gas mass assembly history, together with the assumed stellar yields and initial mass function, represent the starting point of this method. We derive a very simple and general equatio...

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

    CERN Document Server

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

    2016-01-01

    We present the metallicity distribution of a sample of 471 RR Lyrae (RRL) stars in the Sculptor dSph, obtained from the $I$-band Period-Luminosity relation. It is the first time that the early chemical evolution of a dwarf galaxy is characterized in such a detailed and quantitative way, using photometric data alone. We find a broad metallicity distribution (FWHM=0.8 dex) that is peaked at [Fe/H]$\\simeq$-1.90 dex, in excellent agreement with literature values obtained from spectroscopic data. Moreover, we are able to directly trace the metallicity gradient out to a radius of $\\sim$55 arcmin. We find that in the outer regions (r$>\\sim$32 arcmin) the slope of the metallicity gradient from the RRLs (-0.025 dex arcmin$^{-1}$) is comparable to the literature values based on red giant (RG) stars. However, in the central part of Sculptor we do not observe the latter gradients. This suggests that there is a more metal-rich and/or younger population in Sculptor that does not produce RRLs. This scenario is strengthened ...

  15. Chemical weathering of granitic rocks: an experimental approach and Pb-Li isotope tracing

    International Nuclear Information System (INIS)

    In order to characterize water-rock interactions in granite, we performed laboratory experiments and Pb-Li isotope tracing. The aim of the present work is to better constrain the processes of water-rock interactions, both in terms of source and extent of weathering, by measuring major and trace elements, as well as Pb and Li isotope signatures. (authors)

  16. The chemical evolution of galaxies causing damped Ly$\\alpha$ absorption

    OpenAIRE

    Lindner, Ulrich; Alvensleben, Uta Fritze - v.; Fricke, Klaus J.

    1997-01-01

    We have compiled all available data on chemical abundances in damped Lyman alpha absorption systems for comparison with results from our combined chemical and spectrophotometric galaxy evolution models. Preliminary results from chemically consistent calculations are in agreement with observations of damped Ly$\\alpha$ systems.

  17. Chemical evolution of formation waters in the Palm Valley gas field, Northern Territory

    International Nuclear Information System (INIS)

    The chemical composition and evolution of formation waters associated with gas production in the Palm Valley field, Northern Territory, has important implications for reservoir management, saline water disposal, and gas reserve calculations. Historically, the occurrence of saline formation water in gas fields has been the subject of considerable debate. A better understanding of the origin, chemical evolution and movement of the formation water at Palm Valley has important implications for future reservoir management, disposal of highly saline water and accurate gas reserves estimation. Major and trace element abundance data suggest that a significant component of the highly saline water from Palm Valley has characteristics that may have been derived from a modified evaporated seawater source such as an evaporite horizon. The most dilute waters probably represent condensate and the variation in the chemistry of the intermediate waters suggests they were derived from a mixture of the condensate with the highly saline brine. The chemical and isotopic results raise several interrelated questions; the ultimate source of the high salinity and the distribution of apparently mixed compositions. In this context several key observation are highlighted. Strontium concentrations are extremely high in the brines; although broadly similar in their chemistry, the saline fluids are neither homogeneous nor well mixed; the 87Sr/86Sr ratios in the brines are higher than the signatures preserved in the evaporitic Bitter Springs Formation, and all other conceivably marine-related evaporites (Strauss, 1993); the 87Sr/86Sr ratios in the brines are lower than those measured from groundmass carbonates in the host rocks, and that the87Sr/86Sr ratios of the brines are similar, but still somewhat higher than those measured in vein carbonates from the reservoir. It is concluded that the high salinity brine entered the reservoir during the Devonian uplift and was subsequently displaced by the

  18. Biotransformation of trace organic chemicals during groundwater recharge: How useful are first-order rate constants?

    KAUST Repository

    Regnery, J.

    2015-05-29

    This study developed relationships between the attenuation of emerging trace organic chemicals (TOrC) during managed aquifer recharge (MAR) as a function of retention time, system characteristics, and operating conditions using controlled laboratory-scale soil column experiments simulating MAR. The results revealed that MAR performance in terms of TOrC attenuation is primarily determined by key environmental parameters (i.e. redox, primary substrate). Soil columns with suboxic and anoxic conditions performed poorly (i.e. less than 30% attenuation of moderately degradable TOrC) in comparison to oxic conditions (on average between 70-100% attenuation for the same compounds) within a residence time of three days. Given this dependency on redox conditions, it was investigated if key parameter-dependent rate constants are more suitable for contaminant transport modeling to properly capture the dynamic TOrC attenuation under field-scale conditions. Laboratory-derived first-order removal kinetics were determined for 19 TOrC under three different redox conditions and rate constants were applied to MAR field data. Our findings suggest that simplified first-order rate constants will most likely not provide any meaningful results if the target compounds exhibit redox dependent biotransformation behavior or if the intention is to exactly capture the decline in concentration over time and distance at field-scale MAR. However, if the intention is to calculate the percent removal after an extended time period and subsurface travel distance, simplified first-order rate constants seem to be sufficient to provide a first estimate on TOrC attenuation during MAR.

  19. Inversion of long-lived trace gas emissions using combined Eulerian and Lagrangian chemical transport models

    Directory of Open Access Journals (Sweden)

    M. Rigby

    2011-05-01

    Full Text Available We present a method for estimating emissions of long-lived trace gases from a sparse global network of high-frequency observatories, using both a global Eulerian chemical transport model and Lagrangian particle dispersion model. Emissions are derived in a single step after determining sensitivities of the observations to initial conditions, the high-resolution emissions field close to observation points, and larger regions further from the measurements. This method has the several advantages over inversions using one type of model alone, in that: high-resolution simulations can be carried out in limited domains close to the measurement sites, with lower resolution being used further from them; the influence of errors due to aggregation of emissions close to the measurement sites can be minimized; assumptions about boundary conditions to the Lagrangian model do not need to be made, since the entire emissions field is estimated; any combination of appropriate models can be used, with no code modification. Because the sensitivity to the entire emissions field is derived, the estimation can be carried out using traditional statistical methods without the need for multiple steps in the inversion. We demonstrate the utility of this approach by determining global SF6 emissions using measurements from the Advanced Global Atmospheric Gases Experiment (AGAGE between 2007 and 2009. The global total and large-scale patterns of the derived emissions agree well with previous studies, whilst allowing emissions to be determined at higher resolution than has previously been possible, and improving the agreement between the modeled and observed mole fractions at some sites.

  20. Inversion of long-lived trace gas emissions using combined Eulerian and Lagrangian chemical transport models

    Directory of Open Access Journals (Sweden)

    M. Rigby

    2011-09-01

    Full Text Available We present a method for estimating emissions of long-lived trace gases from a sparse global network of high-frequency observatories, using both a global Eulerian chemical transport model and Lagrangian particle dispersion model. Emissions are derived in a single step after determining sensitivities of the observations to initial conditions, the high-resolution emissions field close to observation points, and larger regions further from the measurements. This method has the several advantages over inversions using one type of model alone, in that: high-resolution simulations can be carried out in limited domains close to the measurement sites, with lower resolution being used further from them; the influence of errors due to aggregation of emissions close to the measurement sites can be minimized; assumptions about boundary conditions to the Lagrangian model do not need to be made, since the entire emissions field is estimated; any combination of appropriate models can be used, with no code modification. Because the sensitivity to the entire emissions field is derived, the estimation can be carried out using traditional statistical methods without the need for multiple steps in the inversion. We demonstrate the utility of this approach by determining global SF6 emissions using measurements from the Advanced Global Atmospheric Gases Experiment (AGAGE between 2007 and 2009. The global total and large-scale patterns of the derived emissions agree well with previous studies, whilst allowing emissions to be determined at higher resolution than has previously been possible, and improving the agreement between the modeled and observed mole fractions at some sites.

  1. The occurrence of emerging trace organic chemicals in wastewater effluents in Saudi Arabia

    KAUST Repository

    Alidina, Mazahirali

    2014-04-01

    Emerging trace organic chemicals (TOrCs) released into the environment via discharge of wastewater effluents have been detected in rivers and lakes worldwide, raising concerns due to their potential persistence, toxicity and bioaccumulation. This study provides the first reconnaissance of TOrC occurrence in wastewater effluents within Saudi Arabia. Four wastewater treatment plants (WWTPs 1-4) located in Western Saudi Arabia were sampled hourly over twelve-hour periods, for a total of six sampling events. All samples were analyzed for a wide range of TOrC encompassing pharmaceuticals, personal care products and household chemicals. Treatment and capacities of the plants varied from non-nitrifying to full biological nutrient removal providing a representative cross section of different types of plants operational within the country. A comparison of TOrC occurrence in effluents in Saudi Arabia with respective effluent qualities in the United States revealed similar levels for most TOrC. Overall, the occurrence of TOrC was higher at two of the plants. The higher TOrC concentrations at WWTP 1 are likely due to the non-nitrifying biological treatment process. The unique TOrC occurrence observed in the WWTP 3 effluent was unlike any other plant and was attributed to the influence of a large number of international visitors in its sewershed. The occurrence of TOrC in this plant was not expected to be representative of the occurrence elsewhere in the country. Bimodal diurnal variation expected for a range of TOrC was not observed, though some hourly variation in TOrC loading was noted for WWTP 3. Since water reclamation and reuse have received increasing interest in Saudi Arabia within the last few years, results from this study provide a good foundation in deciding whether advanced treatment is necessary to attenuate TOrC deemed to be of concern in effluents, or if natural treatment such as managed aquifer recharge provides sufficient protection to public health. © 2014

  2. Chemical Evolution of Interstellar Dust into Planetary Materials

    Science.gov (United States)

    Fomenkova, M. N.; Chang, S.; DeVincenzi, Donald L. (Technical Monitor)

    1995-01-01

    Comets are believed to retain some interstellar materials, stored in fairly pristine conditions since-their formation. The composition and properties of cometary dust grains should reflect those of grains in the outer part of the protosolar nebula which, at least in part, were inherited from the presolar molecular cloud. However, infrared emission features in comets differ from their interstellar counterparts. These differences imply processing of interstellar material on its way to incorporation in comets, but C and N appear to be retained. Overall dust evolution from the interstellar medium (ISM) to planetary materials is accompanied by an increase in proportion of complex organics and a decrease in pure carbon phases. The composition of cometary dust grains was measured in situ during fly-by missions to comet Halley in 1986. The mass spectra of about 5000 cometary dust grains with masses of 5 x 10(exp -17) - 5 x 10(exp -12) g provide data about the presence and relative abundances of the major elements H, C, N, O,Na, Mg, Al, Si, S, Cl, K, Ca, Ti, Cr, Fe, Ni. The bulk abundances of major rock-forming elements integrated over all spectra were found to be solar within a factor of 2, while the volatile elements H, C, N, O in dust are depleted in respect to their total cosmic abundances. The abundances of C and N in comet dust are much closer to interstellar than to meteoritic and are higher than those of dust in the diffuse ISM. In dense molecular clouds dust grains are covered by icy mantles, the average composition of which is estimated to be H:C:N:O = 96:14:1:34. Up to 40% of elemental C and O may be sequestered in mantles. If we use this upper limit to add H, C, N and O as icy mantle material to the abundances residing in dust in the diffuse ISM, then the resulting values for H. C, and N match cometary abundances. Thus, ice mantles undergoing chemical evolution on grains in the dense ISM appear to have been transformed into less volatile and more complex organic

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

    Science.gov (United States)

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

    1991-01-01

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

  4. Domains of States of Chemical Systems: Le Chatelier Response, Structure of the Domains and Evolution

    OpenAIRE

    Zilbergleyt, B.

    2005-01-01

    The paper investigates influence of the Le Chatelier response on the chemical system behavior under stress, the shape of its domains of states in terms of static and dynamic bifurcation diagrams, and the system proneness to evolution. The usage of maps in thermodynamics of chemical systems is discussed. Thermodynamics of chemical triggers, designed in similarity with laser, is described. Results of this work are important in context of new model of chemical equilibrium.

  5. The origin of nitrogen and the chemical evolution of spiral galaxies

    OpenAIRE

    Angeles I. Díaz; Tosi, M.

    1986-01-01

    This is an electronic version of an article published in Astronomy and Astrophysics. Diaz, A.I. and M. Tosi. The origin of nitrogen and the chemical evolution of spiral galaxies. Astronomy and Astrophysics 158 (1986): 60-66

  6. An Empirical Study on Evolution of the Connectivity for VANETs Based on Taxi GPS Traces

    OpenAIRE

    Huifang Feng; Youji Xu

    2016-01-01

    Network connectivity is a fundamental requirement for intervehicle communication and services in VANETs. The fast movement of the vehicles results in rapid changes in network topology generating dynamic variation in network connectivity, which causes dynamic variation in network connectivity. In this paper, we analyze the evolution of the VANETs connectivity based on the realistic data collected by the GPS devices installed on taxis in Shanghai. The study of the evolution characteristics show...

  7. Modelling the chemical evolution of star forming filaments

    CERN Document Server

    Seifried, D

    2015-01-01

    We present simulations of star forming filaments incorporating - to our knowledge - the largest chemical network used to date on-the-fly in a 3D-MHD simulation. The network contains 37 chemical species and about 300 selected reaction rates. For this we use the newly developed package KROME (Grassi et al. 2014). Our results demonstrate the feasibility of using such a complex chemical network in 3D-MHD simulations on modern supercomputers. We perform simulations with different strengths of the interstellar radiation field and the cosmic ray ionisation rate and find chemical and physical results in accordance with observations and other recent numerical work.

  8. Chemical Evolution of the Stellar and Gaseous Components of Galaxies in Hydrodynamical Cosmological Simulations

    OpenAIRE

    Cora, S. A.; P. B. Tissera; Lambas, D. G.; Mosconi, M. B.

    2000-01-01

    We present preliminary results on the effects of mergers on the chemical properties of galactic objects in hierarchical clustering scenarios. We adopt a hydrodynamical chemical code that allows to describe the coupled evolution of dark matter and baryons within a cosmological context. We found that disk-like and spheroid-like objects have distinctive metallicity patterns that may be the result of different evolution.

  9. The role of impacting processes in the chemical evolution of the atmosphere of primordial Earth

    Science.gov (United States)

    Mukhin, Lev M.; Gerasimov, M. V.

    1991-01-01

    The role of impacting processes in the chemical evolution of the atmosphere of primordial Earth is discussed. The following subject areas are covered: (1) Earth's initial atmosphere; (2) continuous degassing; (3) impact processes and the Earth's protoatmosphere; and (4) the evolution of an impact-generated atmosphere.

  10. Optimizing Managed Aquifer Recharge (MAR) Systems for Removal of Trace Organic Chemicals (TOrCs)

    KAUST Repository

    Alidina, Mazahirali

    2014-06-01

    Managed aquifer recharge (MAR) is a low-energy subsurface water treatment system with the potential of being an important component of sustainable water reuse schemes. Alongside common wastewater contaminants, MAR systems have been shown to attenuate a range of trace organic chemicals (TOrCs). Despite several factors being possibly important for TOrC attenuation, many have not been investigated in depth. This research effort investigated three factors affecting attenuation of the moderately degradable TOrCs: primary substrate, adaptation of the microbial community to presence of TOrCs, and groundwater temperature. The overall goal was to optimize TOrC attenuation using different MAR configurations considering how these factors affect TOrC attenuation. The primary substrate composition and concentration significantly impacted attenuation of the moderately degradable TOrCs. Lower primary substrate concentrations and more refractory carbon generally resulted in better TOrC transformation, a more diverse microbial community in the infiltration zone and more diverse capabilities for TOrC degradation. The enzyme group cytochrome P450 may be important for TOrC transformation since its genes were more abundant under carbon-starving primary substrate conditions. Adaptation of the microbial community by pre-exposure to TOrCs was not required in order to degrade them. However, adaptation to the primary substrate was necessary for TOrC biotransformation due to its effect on the microbial community. Attenuation of most TOrCs was unaffected by changes in temperature. Some moderately degradable TOrCs, however, were better attenuated at higher temperatures likely due to increased microbial activity. Others were better degraded at lower temperatures likely due to favorable sorption conditions. In the context of applying MAR systems to potential water reuse schemes within Saudi Arabia, a reconnaissance study of TOrC occurrence in treated wastewater effluents was undertaken. Most of

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

    Science.gov (United States)

    Liffman, Kurt; Clayton, Donald D.

    1989-01-01

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

  12. Function of a landscape lake in the reduction of biotoxicity related to trace organic chemicals from reclaimed water.

    Science.gov (United States)

    Ma, Xiaoyan Y; Wang, Xiaochang C; Wang, Donghong; Ngo, Huu Hao; Zhang, Qiuya; Wang, Yongkun; Dai, Dinan

    2016-11-15

    The storage of water in a landscape lake can act as a buffer zone between reclaimed water production and reuse, but there is still uncertainty about the variation of water quality and toxic effects during the open-storage process. In this study, long-term sample collection, chemical analyses and biotoxicity assessments were conducted on reclaimed water before and after open storage in a landscape lake. The organic contents, in terms of chemical oxygen demand and total organic carbon, were found to be slightly higher in the lake water than that in the reclaimed water, but substantial reduction of the total concentration of 52 trace organic chemicals was obtained and microorganism toxicity, phytotoxicity, aquatic vertebrate toxicity and genotoxicity, were significantly weakened after open storage. Furthermore, the total risk quotient (RQTotal) decreased from 5.12 (potential ecological risk level) in the reclaimed water to 0.18 (negligible ecological risk level) in the lake water. The removal of chlorpyrifos, dichlorphos and tetracycline was identified as the main reason for biotoxicity reduction after open storage. The seminatural environment of the landscape lake would have provided a favorable condition for the decay of toxic trace organic chemicals so that the stored water turned to be safer for further reuse. PMID:27475464

  13. Agricultural fires in the southeastern U.S. during SEAC4RS: Emissions of trace gases and particles and evolution of ozone, reactive nitrogen, and organic aerosol

    Science.gov (United States)

    Liu, Xiaoxi; Zhang, Y.; Huey, L. G.; Yokelson, R. J.; Wang, Y.; Jimenez, J. L.; Campuzano-Jost, P.; Beyersdorf, A. J.; Blake, D. R.; Choi, Y.; St. Clair, J. M.; Crounse, J. D.; Day, D. A.; Diskin, G. S.; Fried, A.; Hall, S. R.; Hanisco, T. F.; King, L. E.; Meinardi, S.; Mikoviny, T.; Palm, B. B.; Peischl, J.; Perring, A. E.; Pollack, I. B.; Ryerson, T. B.; Sachse, G.; Schwarz, J. P.; Simpson, I. J.; Tanner, D. J.; Thornhill, K. L.; Ullmann, K.; Weber, R. J.; Wennberg, P. O.; Wisthaler, A.; Wolfe, G. M.; Ziemba, L. D.

    2016-06-01

    Emissions from 15 agricultural fires in the southeastern U.S. were measured from the NASA DC-8 research aircraft during the summer 2013 Studies of Emissions and Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys (SEAC4RS) campaign. This study reports a detailed set of emission factors (EFs) for 25 trace gases and 6 fine particle species. The chemical evolution of the primary emissions in seven plumes was examined in detail for ~1.2 h. A Lagrangian plume cross-section model was used to simulate the evolution of ozone (O3), reactive nitrogen species, and organic aerosol (OA). Observed EFs are generally consistent with previous measurements of crop residue burning, but the fires studied here emitted high amounts of SO2 and fine particles, especially primary OA and chloride. Filter-based measurements of aerosol light absorption implied that brown carbon (BrC) was ubiquitous in the plumes. In aged plumes, rapid production of O3, peroxyacetyl nitrate (PAN), and nitrate was observed with ΔO3/ΔCO, ΔPAN/ΔNOy, and Δnitrate/ΔNOy reaching ~0.1, ~0.3, and ~0.3. For five selected cases, the model reasonably simulated O3 formation but underestimated PAN formation. No significant evolution of OA mass or BrC absorption was observed. However, a consistent increase in oxygen-to-carbon (O/C) ratios of OA indicated that OA oxidation in the agricultural fire plumes was much faster than in urban and forest fire plumes. Finally, total annual SO2, NOx, and CO emissions from agricultural fires in Arkansas, Louisiana, Mississippi, and Missouri were estimated (within a factor of ~2) to be equivalent to ~2% SO2 from coal combustion and ~1% NOx and ~9% CO from mobile sources.

  14. Tracing the temporal evolution of clusters in a financial stock market

    CERN Document Server

    Arratia, Argimiro

    2011-01-01

    We propose a methodology for clustering financial time series of stocks' returns, and a graphical set-up to quantify and visualise the evolution of these clusters through time. The proposed graphical representation allows for the application of well known algorithms for solving classical combinatorial graph problems, which can be interpreted as problems relevant to portfolio design and investment strategies. We illustrate this graph representation of the evolution of clusters in time and its use on real data from the Madrid Stock Exchange market.

  15. On radial gas flows, the Galactic Bar and chemical evolution in the Galactic Disc

    OpenAIRE

    Portinari, L.; Chiosi, C.

    2000-01-01

    We develop a numerical chemical model allowing for radial flows of gas, with the aim to analyse the possible role of gas flows in the chemical evolution of the Galactic Disc. The dynamical effects of the Galactic Bar on the radial gas profile of the Disc are especially addressed.

  16. Using a scalar parameter to trace dislocation evolution in atomistic modeling

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Jinbo [ORNL; Zhang, Z F [Shenyang National Laboratory for Materials Science; Osetskiy, Yury N [ORNL; Stoller, Roger E [ORNL

    2015-01-01

    A scalar gamma-parameter is proposed from the Nye tensor. Its maximum value occurs along a dislocation line, either straight or curved, when the coordinate system is purposely chosen. This parameter can be easily obtained from the Nye tensor calculated at each atom in atomistic modeling. Using the gamma-parameter, a fully automated approach is developed to determine core atoms and the Burgers vectors of dislocations simultaneously. The approach is validated by revealing the smallest dislocation loop and by tracing the whole formation process of complicated dislocation networks on the fly.

  17. Modelling the chemical evolution of molecular clouds as a function of metallicity

    CERN Document Server

    Penteado, Em M; Rocha-Pinto, H J

    2014-01-01

    The Galaxy is in continuous elemental evolution. Since new elements produced by dying stars are delivered to the interstellar medium, the formation of new enerations of stars and planetary systems is influenced by this metal enrichment. We aim to study the role of the metallicity on the gas phase chemistry of the interstellar medium. Using a system of coupled-ordinary differential equations to model the chemical reactions, we simulate the evolution of the abundance of molecules in the gas phase for different initial interstellar elemental compositions. These varying initial elemental compositions consider the change in the "elemental abundances" predicted by a self-consistent model of the elemental evolution of the Galaxy. As far as we are aware, this is the first attempt to combine elemental evolution of the Galaxy and chemical evolution of molecular clouds. The metallicity was found to have a strong effect on the overall gas phase composition. With decreasing metallicity, the number of long carbon chains wa...

  18. Characterising the Removal of Trace Organic Chemicals in Wastewater - Are we using the Right Tools?

    DEFF Research Database (Denmark)

    Plósz, Benedek G.; Polesel, Fabio

    Hypothesis tests posed on trace organics fate and removal in wastewater are often answered using approaches that can introduce significant bias in observations made on the system. Using non-representative sampling approaches in sewer and wastewater treatment plant studies is an example (Ort et al...

  19. Spinel from Apollo 12 Olivine Mare Basalts: Chemical Systematics of Selected Major, Minor, and Trace Elements

    Science.gov (United States)

    Papike, J. J.; Karner, J. M.; Shearer, C. K.; Spilde, M. N.

    2002-01-01

    Spinels from Apollo 12 Olivine basalts have been studied by Electron and Ion microprobe techniques. The zoning trends of major, minor and trace elements provide new insights into the conditions under which planetary basalts form. Additional information is contained in the original extended abstract.

  20. Evolution of the stratospheric temperature and chemical composition over one Titanian year

    Energy Technology Data Exchange (ETDEWEB)

    Coustenis, Athena; Bampasidis, G.; Vinatier, S. [Laboratoire d' Etudes Spatiales et d' Instrumentation en Astrophysique (LESIA), Observatoire de Paris, CNRS, UPMC Univ. Paris 06, Univ. Paris-Diderot, 5, place Jules Janssen, F-92195 Meudon Cedex (France); Achterberg, R. K.; Jennings, D. E.; Nixon, C. A.; Flasar, F. M.; Carlson, R. C.; Romani, P. N.; Guandique, E. A. [NASA/Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Lavvas, P. [GSMA, Université Reims Champagne-Ardenne, F-51687 Reims Cedex 2 (France); Teanby, N. A. [School of Earth Sciences, University of Bristol, Bristol BS8 1RJ (United Kingdom); Orton, G. [MS 183-501, Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Stamogiorgos, S., E-mail: athena.coustenis@obspm.fr [Faculty of Physics, National and Kapodistrian University of Athens, Panepistimioupolis, GR 15783 Zographos, Athens (Greece)

    2013-12-20

    Since the Voyager 1 (V1) flyby in 1980, Titan's exploration from space and the ground has been ongoing for more than a full revolution of Saturn around the Sun (one Titanian year or 29.5 Earth years had elapsed in 2010 May). In this study, we search for temporal variations affecting Titan's atmospheric thermal and chemical structure within that year. We process Cassini/CIRS data taken during the Titan flybys from 2006-2013 and find a rather uneventful equatorial evolution. Conversely, at northern latitudes, we found enhanced abundances around the period of the northern spring equinox in mid-2009, which subsequently decreased (from 2010 to 2012), returning to values similar to those found in the V1 epoch, one Titanian year before. In the southern latitudes, since 2012, we see a trend for an increase of several trace gases (C{sub 4}H{sub 2}, C{sub 3}H{sub 4}, and HCN), indicative of a seasonal atmospheric reversal setting in. When we compare the CIRS 2010 and the 1980 V1/IRIS spectra (reanalyzed here), we find limited inter-annual variations. A return to the 1980 stratospheric temperatures and abundances is generally achieved from 50°N to 50°S, indicative of the solar radiation being the dominating energy source at 10 AU, as for the Earth, as predicted by general circulation and photochemical models. Exceptions concern the most complex hydrocarbons (C{sub 4}H{sub 2} and C{sub 3}H{sub 4}). We also consider data from ground-based and Earth-orbiting observatories (such as from the Infrared Space Observatory, revisited here) and discuss possible atmospheric composition trends during a Titanian year.

  1. Evolution of the stratospheric temperature and chemical composition over one Titanian year

    International Nuclear Information System (INIS)

    Since the Voyager 1 (V1) flyby in 1980, Titan's exploration from space and the ground has been ongoing for more than a full revolution of Saturn around the Sun (one Titanian year or 29.5 Earth years had elapsed in 2010 May). In this study, we search for temporal variations affecting Titan's atmospheric thermal and chemical structure within that year. We process Cassini/CIRS data taken during the Titan flybys from 2006-2013 and find a rather uneventful equatorial evolution. Conversely, at northern latitudes, we found enhanced abundances around the period of the northern spring equinox in mid-2009, which subsequently decreased (from 2010 to 2012), returning to values similar to those found in the V1 epoch, one Titanian year before. In the southern latitudes, since 2012, we see a trend for an increase of several trace gases (C4H2, C3H4, and HCN), indicative of a seasonal atmospheric reversal setting in. When we compare the CIRS 2010 and the 1980 V1/IRIS spectra (reanalyzed here), we find limited inter-annual variations. A return to the 1980 stratospheric temperatures and abundances is generally achieved from 50°N to 50°S, indicative of the solar radiation being the dominating energy source at 10 AU, as for the Earth, as predicted by general circulation and photochemical models. Exceptions concern the most complex hydrocarbons (C4H2 and C3H4). We also consider data from ground-based and Earth-orbiting observatories (such as from the Infrared Space Observatory, revisited here) and discuss possible atmospheric composition trends during a Titanian year.

  2. Geochemical modelling of groundwater evolution using chemical equilibrium codes

    International Nuclear Information System (INIS)

    Geochemical equilibrium codes are a modern tool in studying interaction between groundwater and solid phases. The most common used programs and application subjects are shortly presented in this article. The main emphasis is laid on the approach method of using calculated results in evaluating groundwater evolution in hydrogeological system. At present in geochemical equilibrium modelling also kinetic as well as hydrologic constrains along a flow path are taken into consideration

  3. Nonlinear Front Evolution of Hydrodynamic Chemical Waves in Vertical Cylinders

    OpenAIRE

    Wilder, J. W.; Vasquez, D.A.; Edwards, Boyd F.

    1997-01-01

    The nonlinear stability of three-dimensional reaction-diffusion fronts in vertical cylinders is considered using the viscous hydrodynamic fluid equations in the limit of infinite thermal diffusivity. A nonlinear front evolution equation is presented and used to examine the transition from nonaxisymmetric to axisymmetric convection observed in experiments performed in cylinders. Comparisons with experiments show excellent agreement in both the shape and speed of the front.

  4. The Role of Sexual Selection in the Evolution of Chemical Signals in Insects

    OpenAIRE

    Sandra Steiger; Johannes Stökl

    2014-01-01

    Chemical communication is the most ancient and widespread form of communication. Yet we are only beginning to grasp the complexity of chemical signals and the role they play in sexual selection. Focusing on insects, we review here the recent progress in the field of olfactory-based sexual selection. We will show that there is mounting empirical evidence that sexual selection affects the evolution of chemical traits, but form and strength of selection differ between species. Studies indicate t...

  5. Structural and functional evolution of the trace amine-associated receptors TAAR3, TAAR4 and TAAR5 in primates.

    Directory of Open Access Journals (Sweden)

    Claudia Stäubert

    Full Text Available The family of trace amine-associated receptors (TAAR comprises 9 mammalian TAAR subtypes, with intact gene and pseudogene numbers differing considerably even between closely related species. To date the best characterized subtype is TAAR1, which activates the G(s protein/adenylyl cyclase pathway upon stimulation by trace amines and psychoactive substances like MDMA or LSD. Recently, chemosensory function involving recognition of volatile amines was proposed for murine TAAR3, TAAR4 and TAAR5. Humans can smell volatile amines despite carrying open reading frame (ORF disruptions in TAAR3 and TAAR4. Therefore, we set out to study the functional and structural evolution of these genes with a special focus on primates. Functional analyses showed that ligands activating the murine TAAR3, TAAR4 and TAAR5 do not activate intact primate and mammalian orthologs, although they evolve under purifying selection and hence must be functional. We also find little evidence for positive selection that could explain the functional differences between mouse and other mammals. Our findings rather suggest that the previously identified volatile amine TAAR3-5 agonists reflect the high agonist promiscuity of TAAR, and that the ligands driving purifying selection of these TAAR in mouse and other mammals still await discovery. More generally, our study points out how analyses in an evolutionary context can help to interpret functional data generated in single species.

  6. Chromosome evolution in Solanum traced by cross-species BAC-FISH.

    Science.gov (United States)

    Szinay, Dóra; Wijnker, Erik; van den Berg, Ronald; Visser, Richard G F; de Jong, Hans; Bai, Yuling

    2012-08-01

    Chromosomal rearrangements are relatively rare evolutionary events and can be used as markers to study karyotype evolution. This research aims to use such rearrangements to study chromosome evolution in Solanum. Chromosomal rearrangements between Solanum crops and several related wild species were investigated using tomato and potato bacterial artificial chromosomes (BACs) in a multicolour fluorescent in situ hybridization (FISH). The BACs selected are evenly distributed over seven chromosomal arms containing inversions described in previous studies. The presence/absence of these inversions among the studied Solanum species were determined and the order of the BAC-FISH signals was used to construct phylogenetic trees.Compared with earlier studies, data from this study provide support for the current grouping of species into different sections within Solanum; however, there are a few notable exceptions, such as the tree positions of S. etuberosum (closer to the tomato group than to the potato group) and S. lycopersicoides (sister to S. pennellii). These apparent contradictions might be explained by interspecific hybridization events and/or incomplete lineage sorting. This cross-species BAC painting technique provides unique information on genome organization, evolution and phylogenetic relationships in a wide variety of species. Such information is very helpful for introgressive breeding. PMID:22686400

  7. Chemical evolution of circumstellar matter around young stellar objects

    Science.gov (United States)

    van Dishoeck, E. F.; Blake, G. A.

    1995-01-01

    Recent observational studies of the chemical composition of circumstellar matter around both high- and low-mass young stellar objects are reviewed. The molecular abundances are found to be a strong function of evolutionary state, but not of system mass or luminosity. The data are discussed with reference to recent theoretical models.

  8. Chemical Evolution and the Galactic Habitable Zone of M31

    NARCIS (Netherlands)

    Carigi, Leticia; Garcia-Rojas, Jorge; Meneses-Goytia, Sofia

    2013-01-01

    We have computed the Galactic Habitable Zones (GHZs) of the Andromeda galaxy (M31) based on the probability of terrestrial planet formation, which depends on the metallicity (Z) of the interstellar medium, and the number of stars formed per unit surface area. The GHZ was obtained from a chemical evo

  9. Influence of Population III stars on cosmic chemical evolution

    OpenAIRE

    Rollinde, E.; Vangioni, E.; Maurin, D.; Olive, K. A.; Daigne, F.; Silk, J.; Vincent, F.

    2008-01-01

    New observations from the Hubble ultra deep field suggest that the star formation rate at z>7 drops off faster than previously thought. Using a newly determined star formation rate for the normal mode of Population II/I stars (PopII/I), including this new constraint, we compute the Thomson scattering optical depth and find a result that is marginally consistent with WMAP5 results. We also reconsider the role of Population III stars (PopIII) in light of cosmological and stellar evolution const...

  10. Galactic chemical evolution - Z versus ln(1/mu) relationship

    International Nuclear Information System (INIS)

    The ways in which a radial abundance gradient in a disk galaxy may be interpreted are reexamined, asking how metallicity Z depends upon gas mass fraction mu in analytic models characterized by a temporally varying history of metal-poor infall. Six different such models are studied, and it is shown that the metallicity versus gas fraction relationship is well approximated by an expression which is the analog of the Z = y ln(1/mu) relation for closed evolution. The approximation appears valid when the infall rate is nonneglible, but not so great that it dominates the gas budget. 13 references

  11. Galactic chemical evolution - Z versus ln(1/mu) relationship

    Science.gov (United States)

    Clayton, Donald D.

    1987-01-01

    The ways in which a radial abundance gradient in a disk galaxy may be interpreted are reexamined, asking how metallicity Z depends upon gas mass fraction mu in analytic models characterized by a temporally varying history of metal-poor infall. Six different such models are studied, and it is shown that the metallicity versus gas fraction relationship is well approximated by an expression which is the analog of the Z = y ln(1/mu) relation for closed evolution. The approximation appears valid when the infall rate is nonneglible, but not so great that it dominates the gas budget.

  12. Chemical Evolution of Mn in Three Dwarf Spheroidal Galaxies

    Indian Academy of Sciences (India)

    Men-Quan Liu; Jie Zhang

    2014-09-01

    Based on an improved model, more reasonable nucleosyn-thesis and explosion rate of SNeIa and CCSNe, we studied Mn evolution for three local dwarf spheroidal galaxies (dSphs), considering the detailed SNe yield and explosion rates for different types of progenitors. The results can explain the main observation ofMn abundance for tens stars in those dSphs, and give some constraints to the nucleosynthesis and explosion ratio of different types of supernovae and Star Formation Rates (SFR) in those dSphs.

  13. Characterising the Removal of Trace Organic Chemicals in Wastewater - Are we using the Right Tools?

    OpenAIRE

    Plósz, Benedek G.; Polesel, Fabio

    2015-01-01

    Hypothesis tests posed on trace organics fate and removal in wastewater are often answered using approaches that can introduce significant bias in observations made on the system. Using non-representative sampling approaches in sewer and wastewater treatment plant studies is an example (Ort et al., 2010). This study provides a critical discussion of processes and methodologies used in laboratory- and full-scale wastewater experimental studies, and offers potential solutions to observed pitfal...

  14. Biorefine: Recovery of nutrients and metallic trace elements from different wastes by chemical and biochemical processes

    OpenAIRE

    Tarayre, Cédric; Fischer, Christophe; De Clercq, Lies; Michels, Evi; Meers, Erik; Buysse, Jeroen; Delvigne, Frank; Thonart, Philippe

    2014-01-01

    At present, most waste processing operations are not oriented towards the valorization of valuable reusable components such as nitrogen, phosphorus, potassium and even Metallic Trace Elements (MTEs). Currently, sewage sludge, for example is usually used as a fertilizer in agriculture, in energy production or in the field of construction. Ashes originating from sludge incineration contain heavy metals and minerals in large quantities. Manure is mainly used in agriculture, although considerable...

  15. Validation and quality assurance applied to goat milk chemical composition: minerals and trace elements measurements

    OpenAIRE

    Trancoso, Inês; Roseiro, Luísa; Martins, António P. L.; Trancoso, Maria Ascensão

    2009-01-01

    In the present study, quality assurance programmes were implemented to validate and control the analytical methodologies used for the characterization of minerals and trace elements in goat milk from Portuguese breeds. With the exception of chloride that was determined by potentiometric titration, all the other elements were determined by spectroscopic techniques after different sample decomposition: P was measured by ultraviolet-visible molecular absorption spectrometry, Ca, Fe, K, Mg, Mn, N...

  16. Differing courses of genetic evolution of Bradyrhizobium inoculants as revealed by long-term molecular tracing in Acacia mangium plantations.

    Science.gov (United States)

    Perrineau, M M; Le Roux, C; Galiana, A; Faye, A; Duponnois, R; Goh, D; Prin, Y; Béna, G

    2014-09-01

    Introducing nitrogen-fixing bacteria as an inoculum in association with legume crops is a common practice in agriculture. However, the question of the evolution of these introduced microorganisms remains crucial, both in terms of microbial ecology and agronomy. We explored this question by analyzing the genetic and symbiotic evolution of two Bradyrhizobium strains inoculated on Acacia mangium in Malaysia and Senegal 15 and 5 years, respectively, after their introduction. Based on typing of several loci, we showed that these two strains, although closely related and originally sampled in Australia, evolved differently. One strain was recovered in soil with the same five loci as the original isolate, whereas the symbiotic cluster of the other strain was detected with no trace of the three housekeeping genes of the original inoculum. Moreover, the nitrogen fixation efficiency was variable among these isolates (either recombinant or not), with significantly high, low, or similar efficiencies compared to the two original strains and no significant difference between recombinant and nonrecombinant isolates. These data suggested that 15 years after their introduction, nitrogen-fixing bacteria remain in the soil but that closely related inoculant strains may not evolve in the same way, either genetically or symbiotically. In a context of increasing agronomical use of microbial inoculants (for biological control, nitrogen fixation, or plant growth promotion), this result feeds the debate on the consequences associated with such practices. PMID:25002434

  17. Upper Troposphere/Lower Stratosphere (UTLS) Trace Gas Evolution in Recent Satellite Datasets: Relationships to Stratospheric and Upper Tropospheric Jets

    Science.gov (United States)

    Manney, G. L.; Hegglin, M. I.; Daffer, W. H.; Santee, M. L.; Bernath, P. F.; Boone, C. D.; Gille, J. C.; Kinnison, D.; Krueger, K.; Livesey, N. J.; Minschwaner, K.; Nardi, B.; Pawson, S.; Walker, K. A.

    2008-12-01

    A method has been developed for categorizing the location and characteristics of upper tropospheric jets and of the lower reaches of the stratospheric polar night jet (PNJ) that extend into the upper troposphere/lower stratosphere (UTLS). This method is applied to define the position, width and dynamical characteristics (e.g., windspeed/direction, potential vorticity, temperature, static stability, etc) of the primary subtropical jet (STJ) core, as well as similar information on multiple jets in the extratropical (ET) UTLS. The PNJ in the UTLS is characterized at each level by its position, width, and dynamical characteristics. Jet characteristics during quasi-isentropic stratosphere-troposphere exchange (STE) events and seasonal evolution of jet structure are investigated in Goddard Earth Observing System Version 5 (GEOS-5) and other meteorological analyses. Satellite trace gas measurements from several current instruments, including the Aura Microwave Limb Sounder (MLS), Atmospheric Chemistry Experiment-Fourier Transform Spectrometer (ACE-FTS) and the Aura High Resolution Dynamics Limb Sounder (HIRDLS), are studied to further our understanding of the seasonal evolution of the ET tropopause layer in relation to the STJ and the tropopause.

  18. Structural evolution during the reduction of chemically derived graphene oxide.

    Science.gov (United States)

    Bagri, Akbar; Mattevi, Cecilia; Acik, Muge; Chabal, Yves J; Chhowalla, Manish; Shenoy, Vivek B

    2010-07-01

    The excellent electrical, optical and mechanical properties of graphene have driven the search to find methods for its large-scale production, but established procedures (such as mechanical exfoliation or chemical vapour deposition) are not ideal for the manufacture of processable graphene sheets. An alternative method is the reduction of graphene oxide, a material that shares the same atomically thin structural framework as graphene, but bears oxygen-containing functional groups. Here we use molecular dynamics simulations to study the atomistic structure of progressively reduced graphene oxide. The chemical changes of oxygen-containing functional groups on the annealing of graphene oxide are elucidated and the simulations reveal the formation of highly stable carbonyl and ether groups that hinder its complete reduction to graphene. The calculations are supported by infrared and X-ray photoelectron spectroscopy measurements. Finally, more effective reduction treatments to improve the reduction of graphene oxide are proposed. PMID:20571578

  19. The Chemical and Dynamical Evolution of Isolated Dwarf Galaxies

    OpenAIRE

    Pilkington, K.; Gibson, B. K.; Calura, F; Stinson, G.S.; Brook, C. B.; Brooks, A.

    2011-01-01

    Using a suite of simulations (Governato et al. 2010) which successfully produce bulgeless (dwarf) disk galaxies, we provide an analysis of their associated cold interstellar media (ISM) and stellar chemical abundance patterns. A preliminary comparison with observations is undertaken, in order to assess whether the properties of the cold gas and chemistry of the stellar components are recovered successfully. To this end, we have extracted the radial and vertical gas density profiles, neutral h...

  20. Chemical evolution on the giant planets and Titan

    Science.gov (United States)

    Caldwell, J.; Owen, T.

    1984-01-01

    The atmospheres of Jupiter, Saturn, Neptune and Uranus, and Titan are characterized chemically in a review of recent observational and theoretical investigations. Compositions are indicated in tables, and special emphasis is given to the formation of HCN on Jupiter, the differentiation of polar and equatorial zones in the Jovian atmosphere, the mechanisms responsible for the color of the Great Red Spot, and the possible origin of the N2-dominated atmosphere of Titan.

  1. Trace determination of cobalt ion by using malic acid-malonic acid double substrate oscillating chemical system

    Institute of Scientific and Technical Information of China (English)

    Jie Wang; Wu Yang; Jie Ren; Miao Guo; Xiao Dong Chen; Wen Bin Wang; Jin Zhang Gao

    2008-01-01

    A novel kinetic method for determination of trace amounts of cobalt ion was proposed and validated. The method is based on adding malic acid into classical Belousov-Zhabotinskii (B-Z) oscillating chemical system to form a double substrate one. The results showed that when the concentration of cobalt ion was in the range of 5.27× 10-8 to 5.37×10-12mol L-1 the change of the oscillating period was directly proportional to the negative logarithm of cobalt ion concentration. The sensitivity and precision of the developed method were quite satisfactory. The limit of detection was down to 5.20 x 10-13 mol L-1 which was a highest sensitivity found for determination of metal ions using oscillating chemical reaction so far. Some factors influencing the determination were also examined. The method has been successfully used to determine cobalt ion in vitamin B12 injection.

  2. Physico-Chemical parameters and trace-metals concentration in effluents from various industries in vicinity of Lahore

    International Nuclear Information System (INIS)

    Increasing problem of pollution has become serious in almost all big cities of Pakistan. The industrial effluents (Liquid waste) discharged by different industries are drained into streams/nallahs, which ultimately join the waterways (streams, lakes, rivers or sea). The effluent samples from five industries, like Tanneries, Chemicals, Pharmaceuticals, Fertilizers and metal/electroplating, working in Lahore, Sheikhupura and Kalashahkaku were selected for analysis. The parameters, like Temperature, pH, conductivity, hardness, alkalinity, total dissolved solids, chemical oxygen demands, phosphate, nitrate, nitrite, major cations (Na, K, Ca, Mg) and heavy/trace metals, were studied. The results were compared with National environmental Quality standards (NEQS). It was further observed that when effluents of industries join fresh water of stream, lakes or rivers, this causes severe water-pollution and damages the flora and fauna. Suggestions for effective control of water-pollution are also given. (author)

  3. Chemical Evolution in the Interstellar Medium: From Astrochemistry to Astrobiology

    Science.gov (United States)

    Allamandola, Louis J.

    2009-01-01

    Great strides have been made in our understanding of interstellar material thanks to advances in infrared astronomy and laboratory astrophysics. Ionized polycyclic aromatic hydrocarbons (PAHs), shockingly large molecules by earlier astrochemical standards, are widespread and very abundant throughout much of the Universe. In cold molecular clouds, the birthplace of planets and stars, interstellar molecules freeze onto dust and ice particles forming mixed molecular ices dominated by simple species such as water, methanol, ammonia, and carbon monoxide. Within these clouds, and especially in the vicinity of star and planet forming regions, these ices and PAHs are processed by ultraviolet light and cosmic rays forming hundreds of far more complex species, some of biogenic interest. Eventually, these are delivered to primordial planets by comets and meteorites. Astrochemical evolution, highlights of this field from a chemist's perspective, and the astronomer's infrared toolbox will be reviewed.

  4. Chemical kinetic pathways for the emission of trace by-products in combustion processes

    International Nuclear Information System (INIS)

    A collorbative research program has been initiated to study the emissions of a wide variety of chemical species from stationary combustion systems. These product species have been included in Clean Air act legislation and their emissions must be rigidly controlled, but there is a need for a much better understanding of the physical and chemical mechanisms that produce and consume them. We are using physical and chemical mechanisms that produce and consume them. We are using numerical modeling techniques to study the chemical reactions and fluid mechanical factors that occur in industrial burners. We are examining systems including premixed and diffusion flames, and stirred and plug flow reactors in these modeling studies to establish the major factors leading to emissions of these chemicals

  5. The Chemical Evolution of the Universe I High Column Density Absorbers

    CERN Document Server

    Mathlin, G P; Churches, D K; Edmunds, M G

    2000-01-01

    We construct a simple, robust model of the chemical evolution of galaxies from high to low redshift, and apply it to published observations of damped Lyman-alpha quasar absorption line systems (DLAs). The elementary model assumes quiescent star formation and isolated galaxies (no interactions, mergers or gas flows). We consider the influence of dust and chemical gradients in the galaxies, and hence explore the selection effects in quasar surveys. We fit individual DLA systems to predict some observable properties of the absorbing galaxies, and also indicate the expected redshift behaviour of chemical element ratios involving nucleosynthetic time delays. Despite its simplicity, our `monolithic collapse' model gives a good account of the distribution and evolution of the metallicity and column density of DLAs, and of the evolution of the global star formation rate and gas density below redshifts z 3. However, from the comparison of DLA observations with our model, it is clear that star formation rates at higher...

  6. Tracing chemical evolution over the extent of the Milky Way's Disk with APOGEE Red Clump Stars

    CERN Document Server

    Nidever, David L; Bird, Jonathan C; Andrews, Brett H; Hayden, Michael; Holtzman, Jon; Majewski, Steven R; Smith, Verne; Robin, Annie C; Perez, Ana E Garcia; Cunha, Katia; Prieto, Carlos Allende; Zasowski, Gail; Schiavon, Ricardo P; Johnson, Jennifer A; Weinberg, David H; Feuillet, Diane; Schneider, Donald P; Shetrone, Matthew; Sobeck, Jennifer; Garcia-Hernandez, D A; Zamora, O; Rix, Hans-Walter; Beers, Timothy C; Wilson, John C; O'Connell, Robert W; Minchev, Ivan; Chiappini, Cristina; Anders, Friedrich; Bizyaev, Dmitry; Brewington, Howard; Ebelke, Garrett; Frinchaboy, Peter M; Ge, Jian; Kinemuchi, Karen; Malanushenko, Elena; Malanushenko, Viktor; Marchante, Moses; Meszaros, Szabolcs; Oravetz, Daniel; Pan, Kaike; Simmons, Audrey; Skrutskie, Michael F

    2014-01-01

    We employ the first two years of data from the near-infrared, high-resolution SDSS-III/APOGEE spectroscopic survey to investigate the distribution of metallicity and alpha-element abundances of stars over a large part of the Milky Way disk. Using a sample of ~10,000 kinematically-unbiased red-clump stars with ~5% distance accuracy as tracers, the [alpha/Fe] vs. [Fe/H] distribution of this sample exhibits a bimodality in [alpha/Fe] at intermediate metallicities, -0.9<[Fe/H]<-0.2, but at higher metallicities ([Fe/H]=+0.2) the two sequences smoothly merge. We investigate the effects of the APOGEE selection function and volume filling fraction and find that these have little qualitative impact on the alpha-element abundance patterns. The described abundance pattern is found throughout the range 5

  7. Chemical evolution of the HC3N and N2H+ molecules in dense cores of the Vela C giant molecular cloud complex

    CERN Document Server

    Ohashi, Satoshi; Fujii, Kosuke; Sanhueza, Patricio; Luong, Quang Nguyen; Choi, Minho; Hirota, Tomoya; Mizuno, Norikazu

    2015-01-01

    We have observed the HC3N (J=10-9) and N2H+ (J=1-0) lines toward the Vela C molecular clouds with the Mopra 22 m telescope to study chemical characteristics of dense cores. The intensity distributions of these molecules are similar to each other at an angular resolution of 53", corresponding to 0.19 pc suggesting that these molecules trace the same dense cores. We identified 25 local peaks in the velocity-integrated intensity maps of the HC3N and/or N2H+ emission. Assuming LTE conditions, we calculated the column densities of these molecules and found a tendency that N2H+/HC3N abundance ratio seems to be low in starless regions while it seems to be high in star-forming regions, similar to the tendencies in the NH3/CCS, NH3/HC3N, and N2H+/CCS abundance ratios found in previous studies of dark clouds and the Orion A GMC. We suggest that carbon chain molecules, including HC3N, may trace chemically young molecular gas and N-bearing molecules, such as N2H+, may trace later stages of chemical evolution in the Vela ...

  8. The isotopic and chemical evolution of Mount St. Helens

    Science.gov (United States)

    Halliday, A.N.; Fallick, A.E.; Dickin, A.P.; Mackenzie, A.B.; Stephens, W.E.; Hildreth, W.

    1983-01-01

    Isotopic and major and trace element analysis of nine samples of eruptive products spanning the history of the Mt. St. Helens volcano suggest three different episodes; (1) 40,000-2500 years ago: eruptions of dacite with ??{lunate}Nd = +5, ??{lunate}Sr = -10, variable ??18O, 206Pb/204Pb ??? 18.76, Ca/Sr ??? 60, Rb/Ba ??? 0.1, La/Yb ??? 18, (2) 2500-1000 years ago: eruptions of basalt, andesite and dacite with ??{lunate}Nd = +4 to +8, ??{lunate}Sr = -7 to -22, variable ??18O (thought to represent melting of differing mantle-crust reservoirs), 206Pb/204Pb = 18.81-18.87, variable Ca/Sr, Rb/Ba, La/Yb and high Zr, (3) 1000 years ago to present day: eruptions of andesite and dacite with ??{lunate}Nd = +6, ??{lunate}Sr = -13, ??18O ???6???, variable 206Pb/204Pb, Ca/Sr ??? 77, Rb/Ba = 0.1, La/Yb ??? 11. None of the products exhibit Eu anomalies and all are LREE enriched. There is a strong correlation between 87Sr/86Sr and differentiation indices. These data are interpreted in terms of a mantle heat source melting young crust bearing zircon and garnet, but not feldspar, followed by intrusion of this crustal reservoir by mantle-derived magma which caused further crustal melting and contaminated the crustal magma system with mafic components. Since 1000 years ago all the eruptions have been from the same reservoir which has displayed a much more gradual re-equilibration of Pb isotopic compositions than other components suggesting that Pb is being transported via a fluid phase. The Nd and Sr isotopic compositions lie along the mantle array and suggest that the mantle underneath Mt. St. Helens is not as depleted as MORB sources. There is no indication of seawater involvement in the source region. ?? 1983.

  9. Magnesium isotopes as a probe of the Milky Way chemical evolution

    OpenAIRE

    Thygesen, Anders Overaa

    2015-01-01

    The study of elemental abundance ratios from spectroscopy of stars has for a long time been used to investigate the structure and the chemical evolution history of the Milky Way. However, even with the ever-increasing number of stars with detailed abundances, many details about the Milky Way evolution are still not understood. While elemental abundance measurements already provide a lot of information, nucleosynthesis models predict not only bulk abundances of an element, but also its isotopi...

  10. Chemical and sewage sludge co-incineration in a full-scale MSW incinerator: toxic trace element mass balance.

    Science.gov (United States)

    Biganzoli, Laura; Grosso, Mario; Giugliano, Michele; Campolunghi, Manuel

    2012-10-01

    Co-incineration of sludges with MSW is a quite common practice in Europe. This paper illustrates a case of co-incineration of both sewage sludges and chemical sludges, the latter obtained from drinking water production, in a waste-to-energy (WTE) plant located in northern Italy and equipped with a grate furnace, and compares the toxic trace elements mass balance with and without the co-incineration of sludges. The results show that co-incineration of sewage and chemical sludges does not result in an increase of toxic trace elements the total release in environment, with the exception of arsenic, whose total release increases from 1 mg t(fuel) (-1) during standard operation to 3 mg t(fuel) (-1) when sludges are co-incinerated. The increase of arsenic release is, however, attributable to the sole bottom ashes, where its concentration is five times higher during sludge co-incineration. No variation is observed for arsenic release at the stack. This fact is a further guarantee that the co-incineration of sludges, when performed in a state-of-the-art WTE plant, does not have negative effects on the atmospheric environment. PMID:22584266

  11. Recent advances in chemical evolution and the origins of life

    Science.gov (United States)

    Oro, John; Lazcano, Antonio

    1992-01-01

    Consideration is given to the ideas of Oparin and Haldane who independently suggested more than 60 years ago that the first forms of life were anaerobic, heterotrophic bacteria that emerged as the result of a long period of chemical abiotic synthesis of organic compounds. It is suggested that at least some requirements for life are met in the Galaxy due to the cosmic abundance of carbon, nitrogen, oxygen, and other biogenic elements; the existence of extraterrestrial organic compounds; and the processes of stellar and interstellar planetary formation.

  12. Chemical evolution of the solar nebula: A new model

    Science.gov (United States)

    Trivedi, B. M. P.

    1984-01-01

    The common notion of a hot solar nebula from which meteoritic minerals condensed is not supported by theories of star formation. A model is developed which can give the same sequence of condensation without recourse to hot solar nebula. In this model, the solar nebula was formed from the matter ejected by the Sun during its T Tauri phase and the chemical condensation took place in this outflowing matter. Isotopic anomalies and the unique minerals found in meteorites may be explained by this model.

  13. Chemical modelling of trace elements in pore water from PFBC residues containing ammonia

    International Nuclear Information System (INIS)

    Ammonia is added to the PFBC process with the purpose to reduce the emissions of NOx in the stack gases. The design of the system for cleaning the stack gases will lead to an increased adsorption of ammonia and an accumulation of soluble ammonium salts in the cyclone ash from PFBC processes. This can be an environmental problem since the amounts will increase over the coming years and there will be a need to dispose the residues. When infiltrating rainwater penetrates the disposed residues ammonia and ammonium salts result in a contamination of the pore water with ammonia in the disposed residues. This entail the solubility of several trace elements in the residues that form soluble complexes with ammonia will increase and cause an increased contamination of groundwater and surface water. In this study the increased solubilities is calculated for the trace elements cadmium, cobalt, copper, mercury, nickel, silver and zinc in the residues using thermodynamical data. The calculations have been performed with probable solid phases of the trace elements at oxidizing and reducing conditions as a function of pH and at varying concentration of ammonia in the pore water. The thermodynamic calculations have been performed with the geochemical code EQ3NR. The results from the calculations show that as a concentration of 17 mg NH3/l in the pore water of the residues increases the solubilities for copper and silver. If the concentration of ammonia increases to 170 mg NH3/l will the solubilities increase also for cadmium, nickel and zinc. (12 refs., 39 figs.)

  14. Tracing the fate of carbon and the atmospheric evolution of Mars

    CERN Document Server

    Hu, Renyu; Ehlmann, Bethany L; Yung, Yuk L

    2015-01-01

    The climate of Mars likely evolved from a warmer, wetter early state to the cold, arid current state. However, no solutions for this evolution have previously been found to satisfy the observed geological features and isotopic measurements of the atmosphere. Here we show that a family of solutions exist, invoking no missing reservoirs or loss processes. Escape of carbon via CO photodissociation and sputtering enriches heavy carbon (13C) in the Martian atmosphere, partially compensated by moderate carbonate precipitation. The current atmospheric 13C/12C and rock and soil carbonate measurements indicate an early atmosphere with a surface pressure <1 bar. Only scenarios with large amounts of carbonate formation in open lakes permit higher values up to 1.8 bar. The evolutionary scenarios are fully testable with data from the MAVEN mission and further studies of the isotopic composition of carbonate in the Martian rock record through time.

  15. Tracing the evolution of the light-harvesting antennae in chlorophyll a/b-containing organisms.

    Science.gov (United States)

    Koziol, Adam G; Borza, Tudor; Ishida, Ken-Ichiro; Keeling, Patrick; Lee, Robert W; Durnford, Dion G

    2007-04-01

    The light-harvesting complexes (LHCs) of land plants and green algae have essential roles in light capture and photoprotection. Though the functional diversity of the individual LHC proteins are well described in many land plants, the extent of this family in the majority of green algal groups is unknown. To examine the evolution of the chlorophyll a/b antennae system and to infer its ancestral state, we initiated several expressed sequence tag projects from a taxonomically broad range of chlorophyll a/b-containing protists. This included representatives from the Ulvophyceae (Acetabularia acetabulum), the Mesostigmatophyceae (Mesostigma viride), and the Prasinophyceae (Micromonas sp.), as well as one representative from each of the Euglenozoa (Euglena gracilis) and Chlorarachniophyta (Bigelowiella natans), whose plastids evolved secondarily from a green alga. It is clear that the core antenna system was well developed prior to green algal diversification and likely consisted of the CP29 (Lhcb4) and CP26 (Lhcb5) proteins associated with photosystem II plus a photosystem I antenna composed of proteins encoded by at least Lhca3 and two green algal-specific proteins encoded by the Lhca2 and 9 genes. In organisms containing secondary plastids, we found no evidence for orthologs to the plant/algal antennae with the exception of CP29. We also identified PsbS homologs in the Ulvophyceae and the Prasinophyceae, indicating that this distinctive protein appeared prior to green algal diversification. This analysis provides a snapshot of the antenna systems in diverse green algae, and allows us to infer the changing complexity of the antenna system during green algal evolution. PMID:17307901

  16. Rheological, structural and chemical evolution of bitumen under gamma irradiation

    International Nuclear Information System (INIS)

    Bitumen derived from crude oil by fractional distillation has been used in the nuclear industry as a radioactive waste encapsulation matrix. When subjected to α, β and γ self-irradiation, this organic matrix undergoes radiolysis, generating hydrogen bubbles and modifying the physical and chemical properties of the material. In this paper, the effects of irradiation on bitumen materials, especially in terms of its physical, chemical, structural and rheological properties, were characterized at radiation doses ranging from 1 to 7 MGy. An increase in the shear viscosity and melt yield stress was observed with increasing doses. Similarly, the elastic and viscous moduli (G' and G'') increase with the dose, with a more pronounced increase for G' that reflects enhanced elasticity arising from radiation-induced cross-linking. In addition, a low-frequency plateau is observed for G', reflecting pseudo-solid behavior and leading to an increase of the complex viscosity. This behavior is due to increased interactions between asphaltene particles, and to aromatization of the bitumen by γ-radiations. Cross-linking of bitumen enhances its strength, as confirmed by various techniques (modulated DSC, DTA/TGA, SEC, FTIR and XRD). (authors)

  17. Chemical Evolution of Strongly Interacting Quark-Gluon Plasma

    International Nuclear Information System (INIS)

    At very initial stage of relativistic heavy ion collisions a wave of quark-gluon matter is produced from the break-up of the strong color electric field and then thermalizes at a short time scale (~1 fm/c). However, the quark-gluon plasma (QGP) system is far out of chemical equilibrium, especially for the heavy quarks which are supposed to reach chemical equilibrium much late. In this paper a continuing quark production picture for strongly interacting QGP system is derived, using the quark number susceptibilities and the equation of state; both of them are from the results calculated by the Wuppertal-Budapest lattice QCD collaboration. We find that the densities of light quarks increase by 75% from the temperature T=400 MeV to T=150 MeV, while the density of strange quark annihilates by 18% in the temperature region. We also offer a discussion on how this late production of quarks affects the final charge-charge correlations

  18. Tracing the cosmic metal evolution in the low-redshift intergalactic medium

    Energy Technology Data Exchange (ETDEWEB)

    Michael Shull, J. [Also at Institute of Astronomy, University of Cambridge, Cambridge CB3 OHA, UK. (United Kingdom); Danforth, Charles W.; Tilton, Evan M., E-mail: michael.shull@colorado.edu, E-mail: danforth@colorado.edu, E-mail: evan.tilton@colorado.edu [CASA, Department of Astrophysical and Planetary Sciences, University of Colorado, Boulder, CO 80309 (United States)

    2014-11-20

    Using the Cosmic Origins Spectrograph aboard the Hubble Space Telescope, we measured the abundances of six ions (C III, C IV, Si III, Si IV, N V, and O VI) in the low-redshift (z ≤ 0.4) intergalactic medium (IGM). Both C IV and Si IV have increased in abundance by a factor of ∼10 from z ≈ 5.5 to the present. We derive ion mass densities, ρ{sub ion} ≡ Ω{sub ion}ρ{sub cr}, with Ω{sub ion} expressed relative to the closure density. Our models of mass-abundance ratios, (Si III/Si IV) =0.67{sub −0.19}{sup +0.35}, (C III/C IV) =0.70{sub −0.20}{sup +0.43}, and (Ω{sub C} {sub III}+Ω{sub C} {sub IV})/(Ω{sub Si} {sub III}+Ω{sub Si} {sub IV})=4.9{sub −1.1}{sup +2.2}, are consistent with the photoionization parameter log U = –1.5 ± 0.4, hydrogen photoionization rate Γ{sub H} = (8 ± 2) × 10{sup –14} s{sup –1} at z < 0.4, and specific intensity I {sub 0} = (3 ± 1) × 10{sup –23} erg cm{sup –2} s{sup –1} Hz{sup –1} sr{sup –1} at the Lyman limit. Consistent ionization corrections for C and Si are scaled to an ionizing photon flux Φ{sub 0} = 10{sup 4} cm{sup –2} s{sup –1}, baryon overdensity Δ {sub b} ≈ 200 ± 50, and ''alpha-enhancement'' (Si/C enhanced to three times its solar ratio). We compare these metal abundances to the expected IGM enrichment and abundances in higher photoionized states of carbon (C V) and silicon (Si V, Si VI, and Si VII). Our ionization modeling infers IGM metal densities of (5.4 ± 0.5) × 10{sup 5} M {sub ☉} Mpc{sup –3} in the photoionized Lyα forest traced by the C and Si ions and (9.1 ± 0.6) × 10{sup 5} M {sub ☉} Mpc{sup –3} in hotter gas traced by O VI. Combining both phases, the heavy elements in the IGM have mass density ρ {sub Z} = (1.5 ± 0.8) × 10{sup 6} M {sub ☉} Mpc{sup –3} or Ω {sub Z} ≈ 10{sup –5}. This represents 10% ± 5% of the metals produced by (6 ± 2) × 10{sup 8} M {sub ☉} Mpc{sup –3} of integrated star formation with yield y{sub m} = 0

  19. Star Formation History and Chemical Evolution of the Sextans Dwarf Spheroidal Galaxy

    OpenAIRE

    Lee, Myung Gyoon; Yuk, In-Soo; Park, Hong Soo; Harris, Jason; Zaritsky, Dennis

    2009-01-01

    We present the star formation history and chemical evolution of the Sextans dSph dwarf galaxy as a function of galactocentric distance. We derive these from the $VI$ photometry of stars in the $42' \\times 28'$ field using the SMART model developed by Yuk & Lee (2007, ApJ, 668, 876) and adopting a closed-box model for chemical evolution. For the adopted age of Sextans 15 Gyr, we find that $>$84% of the stars formed prior to 11 Gyr ago, significant star formation extends from 15 to 11 Gyr ago (...

  20. The isotopic and chemical evolution of planets: Mars as a missing link

    Science.gov (United States)

    Depaolo, D. J.

    1988-01-01

    The study of planetary bodies has advanced to a stage where it is possible to contemplate general models for the chemical and physical evolution of planetary interiors, which might be referred to as UMPES (Unified Models of Planetary Evolution and Structure). UMPES would be able to predict the internal evolution and structure of a planet given certain input parameters such as mass, distance from the sun, and a time scale for accretion. Such models are highly dependent on natural observations because the basic material properties of planetary interiors, and the processes that take place during the evolution of planets are imperfectly understood. The idea of UMPES was particularly unrealistic when the only information available was from the earth. However, advances have been made in the understanding of the general aspects of planetary evolution now that there is geochemical and petrological data available for the moon and for meteorites.

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

    Science.gov (United States)

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

    1982-01-01

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

  2. The age of the Galactic disk - Inflow, chemical evolution, astration, and radioactivity

    Science.gov (United States)

    Clayton, Donald D.

    1989-01-01

    Theoretical models of Galactic evolution and observational data on the age of the Galaxy are compared, with a focus on recent results. Topics addressed include the infall of material and its effects on the age-metallicity relation, the distribution of metallicity, the present gas fraction and metallicity, and the age spectrum of interstellar nuclei; the chemical evolution of the solar neighborhood; the key results of nuclear cosmochronology; and astration effects on Galactic age. It is found that both nuclear cosmochronology and detailed stellar and Galactic evolution models tend to support an age of 12-16 Gyr.

  3. Ultra-Trace Chemical Sensing with Long-Wave Infrared Cavity-Enhanced Spectroscopic Sensors

    Energy Technology Data Exchange (ETDEWEB)

    Taubman, Matthew S.; Myers, Tanya L.; Cannon, Bret D.; Williams, Richard M.; Schultz, John F.

    2003-02-20

    The infrared sensors task of Pacific Northwest National Laboratory's (PNNL's) Remote Spectroscopy Project (Task B of Project PL211) is focused on the science and technology of remote and in-situ spectroscopic chemical sensors for detecting proliferation and coun-tering terrorism. Missions to be addressed by remote chemical sensor development in-clude detecting proliferation of nuclear or chemical weapons, and providing warning of terrorist use of chemical weapons. Missions to be addressed by in-situ chemical sensor development include countering terrorism by screening luggage, personnel, and shipping containers for explosives, firearms, narcotics, chemical weapons, or chemical weapons residues, and mapping contaminated areas. The science and technology is also relevant to chemical weapons defense, air operations support, monitoring emissions from chemi-cal weapons destruction or industrial activities, law enforcement, medical diagnostics, and other applications. Sensors for most of these missions will require extreme chemical sensitivity and selectiv-ity because the signature chemicals of importance are expected to be present in low con-centrations or have low vapor pressures, and the ambient air is likely to contain pollutants or other chemicals with interfering spectra. Cavity-enhanced chemical sensors (CES) that draw air samples into optical cavities for laser-based interrogation of their chemical content promise real-time, in-situ chemical detection with extreme sensitivity to specified target molecules and superb immunity to spectral interference and other sources of noise. PNNL is developing CES based on quantum cascade (QC) lasers that operate in the mid-wave infrared (MWIR - 3 to 5 microns) and long-wave infrared (LWIR - 8 to 14 mi-crons), and CES based on telecommunications lasers operating in the short-wave infrared (SWIR - 1 to 2 microns). All three spectral regions are promising because smaller mo-lecular absorption cross sections in the SWIR

  4. Trace the evolution of organic matter in interplanetary objects using residue analogues

    Science.gov (United States)

    Danger, G.; Fresneau, A.; Abou Mrad, N.; de Marcellus, P.; Orthous-Daunay, F. R.; Modica, P.; Vuitton, V.; Duvernay, F.; Flandinet, L.; Le Sergeant d'Hendecourt, L.; Thissen, R.; Chiavassa, T.

    2015-10-01

    This contribution focuses on one aspect of our work, which is related to the analysis of refractory residues formed from the UV irradiation and the subsequent warming-up to room temperature of astrophysical ice analogs, the RAHIIA project. The understanding of the chemical composition of these refractory residues, commonly called "yellow stuff", as well as the possible pathways to their formation in astrophysical environments, is an important step to establish what kind of organic matter could be available within interplanetary objects such as comets or asteroids, part of which end up as preserved meteorites on telluric planets.

  5. A Physically Based Coupled Chemical and Physical Weathering Model for Simulating Soilscape Evolution

    Science.gov (United States)

    Willgoose, G. R.; Welivitiya, D.; Hancock, G. R.

    2015-12-01

    A critical missing link in existing landscape evolution models is a dynamic soil evolution models where soils co-evolve with the landform. Work by the authors over the last decade has demonstrated a computationally manageable model for soil profile evolution (soilscape evolution) based on physical weathering. For chemical weathering it is clear that full geochemistry models such as CrunchFlow and PHREEQC are too computationally intensive to be couplable to existing soilscape and landscape evolution models. This paper presents a simplification of CrunchFlow chemistry and physics that makes the task feasible, and generalises it for hillslope geomorphology applications. Results from this simplified model will be compared with field data for soil pedogenesis. Other researchers have previously proposed a number of very simple weathering functions (e.g. exponential, humped, reverse exponential) as conceptual models of the in-profile weathering process. The paper will show that all of these functions are possible for specific combinations of in-soil environmental, geochemical and geologic conditions, and the presentation will outline the key variables controlling which of these conceptual models can be realistic models of in-profile processes and under what conditions. The presentation will finish by discussing the coupling of this model with a physical weathering model, and will show sample results from our SSSPAM soilscape evolution model to illustrate the implications of including chemical weathering in the soilscape evolution model.

  6. Lighting up stars in chemical evolution models: the CMD of Sculptor

    Science.gov (United States)

    Vincenzo, F.; Matteucci, F.; de Boer, T. J. L.; Cignoni, M.; Tosi, M.

    2016-08-01

    We present a novel approach to draw the synthetic color-magnitude diagram of galaxies, which can provide - in principle - a deeper insight in the interpretation and understanding of current observations. In particular, we `light up' the stars of chemical evolution models, according to their initial mass, metallicity and age, to eventually understand how the assumed underlying galaxy formation and evolution scenario affects the final configuration of the synthetic CMD. In this way, we obtain a new set of observational constraints for chemical evolution models beyond the usual photospheric chemical abundances. The strength of our method resides in the very fine grid of metallicities and ages of the assumed database of stellar isochrones. In this work, we apply our photo-chemical model to reproduce the observed CMD of the Sculptor dSph and find that we can reproduce the main features of the observed CMD. The main discrepancies are found at fainter magnitudes in the main sequence turn-off and sub-giant branch, where the observed CMD extends towards bluer colors than the synthetic one; we suggest that this is a signature of metal-poor stellar populations in the data, which cannot be captured by our assumed one-zone chemical evolution model.

  7. Plant chemical defence allocation constrains evolution of local range.

    Science.gov (United States)

    Siemens, David H; Haugen, Riston; Matzner, Steven; Vanasma, Nicholas

    2009-12-01

    Many species of plants in the wild are distributed spatially in patches, the boundaries of which may occur and change because of a complicated interplay between myriad environmental stressors and limitations of, or constraints on, plant coping mechanisms. By examining genetic variation and co-variation among marker-inferred inbred lines and sib-families of an upland wild mustard species within and just a few meters across a natural patch boundary, we show that the evolution of tolerance to the stressful environment outside the patch may be constrained by allocation to glucosinolate compounds (GS) that are defensive against generalist insect herbivores. Several potential stressors were associated with the patch boundary, but carbon isotope ratios indicated that sib-families with smaller stomatal apertures maintained performance better in response to late season dry conditions, suggesting that drought was an important stressor. The presence of GS may help explain the characteristic patchy distribution of mustards, a relatively diverse and important plant family. This result challenges one end of the continuum of the long-standing Plant Apparency hypothesis, which essentially states the opposite causation, that low molecular weight toxins like GS are evolutionary responses of patchy distributions and correlated life-history traits. PMID:19863716

  8. Antimicrobial activity, phyto chemical profile and trace minerals of black mulberry (morus nigra l.) fresh juice

    International Nuclear Information System (INIS)

    In the present work, the fresh juice of black mulberry (Morus nigra) was tested for antimicrobial activity against various pathogenic microorganisms. Total antioxidant contents, total phenolic contents, total anthocyanins, trace minerals, total acid contents, total solids and ascorbic acid content were also evaluated. The results showed good antimicrobial activity both for Gram- positive and Gram-negative bacteria, with highest zones of inhibition for Bacillus spizizenii (19.68 mm, Gram-positive) and Pseudomonas aeruginosa (19.87 mm, Gram-negative). The black mulberry juice was rich in ascorbic acid (23.45 mg/100 g), had low overall acid content (1.60 %) and had 19% total soluble solids. The average total anthocyanins and total phenolic contents of black mulberry juice were 769 mu g/g of cyanidin 3-glucoside equivalent (Cy 3-gly) per gram and 2050 mu g of gallic acid equivalent (GAE) per gram of fresh juice. The average antioxidant activity (Trolox equivalent, TE) of fresh juice was 14.00 mu mol/g according to a FRAP assay and 20.10 mu mol/g according to a DPPH assay. The fresh juice was also rich in a variety of trace minerals. (author)

  9. Asian dust storm observed at a rural mountain site in southern China: chemical evolution and heterogeneous photochemistry

    Directory of Open Access Journals (Sweden)

    W. Nie

    2012-12-01

    Full Text Available Heterogeneous processes on dust particles are important for understanding the chemistry and radiative balance of the atmosphere. This paper investigates an intense Asian dust storm episode observed at Mount Heng (1269 m a.s.l. in southern China on 24–26 April 2009. A set of aerosol and trace gas data collected during the study was analyzed to investigate their chemical evolution and heterogeneous photochemistry as the dust traveled to southern China. Results show that the mineral dust arriving at Mt. Heng experienced significant modifications during transport, with large enrichments in secondary species (sulfate, nitrate, and ammonium compared with the dust composition collected at an upwind mountain top site (Mount Hua. A photochemical age "clock" (−Log10(NOx/NOy was employed to quantify the atmospheric processing time. The result indicates an obvious increase in the abundance of secondary water-soluble ions in dust particles with the air mass atmospheric processing time. Based on the observations, a 4-stage evolution process is proposed for carbonate-containing Asian dust, starting from fresh dust to particles coated with hydrophilic and acidic materials. Daytime-enhanced nitrite formation on the dust particles was also observed, which indicates the recent laboratory result of the TiO2 photocatalysis of NO2 as a potential source of nitrite and nitrous acid.

  10. Asian dust storm observed at a rural mountain site in Southern China: chemical evolution and heterogeneous photochemistry

    Directory of Open Access Journals (Sweden)

    W. Nie

    2012-08-01

    Full Text Available Heterogeneous processes on dust particles are important for understanding the chemistry and radiative balance of the atmosphere. This paper investigates an intense Asian dust storm episode observed at Mount Heng (1250 m a.s.l. in Southern China on 24–26 April 2009. A set of aerosol and trace gas data collected during the study was analyzed to investigate their chemical evolution and heterogeneous photochemistry as the dust traveled to Southern China. Results show that the mineral dust arriving at Mt. Heng experienced significant modifications during transport, with large enrichments in secondary species (sulfate, nitrate, and ammonium compared with the dust composition collected at an upwind mountain top site (Mount Hua. A photochemical age "clock" (−log10(NOx/NOy was employed to quantify the atmospheric processing time. The result indicates an obvious increase in the abundance of secondary water-soluble ions in dust particles with the air mass' photochemical age. Based on the observations, a 4-stage evolution process is proposed for carbonate-rich Asian dust, starting from fresh dust to particles coated with hydrophilic and acidic materials. Daytime-enhanced nitrite formation on the dust particles was also observed, which indicates the recent laboratory result of the TiO2 photocatalysis of NO2 as a potential source of nitrite and nitrous acid.

  11. CYANAMIDE: A POSSIBLE KEY COMPOUND IN CHEMICAL EVOLUTION

    Energy Technology Data Exchange (ETDEWEB)

    Steinman, Gary; Lemmon, Richard M.; Calvin, Melvin

    1964-05-01

    The prebiotic synthesis of phosphorus-containing compounds--such as nucleotides and polynucleotides--would require both a geologically plausible source of the element and pathways for its incorporation into chemical systems on the primitive Earth. The mineral apatite, which is the only significant source of phosphate on Earth, has long been thought to be problematical in this respect due to its low solubility and reactivity. However, in the last decade or so, at least two pathways have been demonstrated which would circumvent these perceived problems. In addition, recent results would seem to suggest an additional, extraterrestrial source of reactive phosphorus. It appears that the 'phosphorus problem' is no longer the stumbling block which it was once thought to be.

  12. Natural Pyrrhotite as a Catalyst in Prebiotic Chemical Evolution

    Directory of Open Access Journals (Sweden)

    César Menor-Salván

    2013-08-01

    Full Text Available The idea of an autotrophic organism as the first living being on Earth leads to the hypothesis of a protometabolic, complex chemical system. In one of the main hypotheses, the first metabolic systems emerged from the interaction between sulfide minerals and/or soluble iron-sulfide complexes and fluids rich in inorganic precursors, which are reduced and derived from crustal or mantle activity. Within this context, the possible catalytic role of pyrrhotite, one of the most abundant sulfide minerals, in biomimetic redox and carbon fixation reactions was studied. Our results showed that pyrrhotite, under simulated hydrothermal conditions, could catalyze the pyruvate synthesis from lactate and that a dynamic system formed by coupling iron metal and iron-sulfur species in an electrochemical cell could promote carbon fixation from thioacetate esters.

  13. Natural pyrrhotite as a catalyst in prebiotic chemical evolution.

    Science.gov (United States)

    de Aldecoa, Alejandra López Ibáñez; Roldán, Francisco Velasco; Menor-Salván, César

    2013-01-01

    The idea of an autotrophic organism as the first living being on Earth leads to the hypothesis of a protometabolic, complex chemical system. In one of the main hypotheses, the first metabolic systems emerged from the interaction between sulfide minerals and/or soluble iron-sulfide complexes and fluids rich in inorganic precursors, which are reduced and derived from crustal or mantle activity. Within this context, the possible catalytic role of pyrrhotite, one of the most abundant sulfide minerals, in biomimetic redox and carbon fixation reactions was studied. Our results showed that pyrrhotite, under simulated hydrothermal conditions, could catalyze the pyruvate synthesis from lactate and that a dynamic system formed by coupling iron metal and iron-sulfur species in an electrochemical cell could promote carbon fixation from thioacetate esters. PMID:25369819

  14. THE CHEMICAL EVOLUTION OF THE URSA MINOR DWARF SPHEROIDAL GALAXY

    International Nuclear Information System (INIS)

    We present an abundance analysis based on high-resolution spectra of 10 stars selected to span the full range in metallicity in the Ursa Minor (UMi) dwarf spheroidal (dSph) galaxy. We find that [Fe/H] for the sample stars ranges from -1.35 to -3.10 dex. Combining our sample with previously published work for a total of 16 luminous UMi giants, we establish the trends of abundance ratios [X/Fe] as functions of [Fe/H] for 15 elements. In key cases, particularly for the α-elements, these trends resemble those for stars in the outer part of the Galactic halo, especially at the lowest metallicities probed. The neutron-capture elements show an r-process distribution over the full range of Fe metallicity reached in this dSph galaxy. This suggests that the duration of star formation in the UMi dSph was shorter than in other dSph galaxies. The derived ages for a larger sample of UMi stars with more uncertain metallicities also suggest a population dominated by uniformly old (∼13 Gyr) stars, with a hint of an age-metallicity relationship. Upon comparing our results for UMi, our earlier work in Draco, and published studies of more metal-rich dSph Galactic satellites, there appears to be a pattern of moving from a chemical inventory for dSph giants with [Fe/H] ∼ - 1.5 dex leads to a chemical inventory wildly discrepant from that of any component of the Milky Way. We note the presence of two UMi giants with [Fe/H] <-3.0 dex in our sample and reaffirm that the inner Galactic halo could have been formed by early accretion of Galactic satellite galaxies and dissolution of young globular clusters, while the outer halo could have formed from those satellite galaxies that accreted somewhat later.

  15. Losing track of the time: the chemical clock of prestellar core evolution in hydrodynamic simulation

    Science.gov (United States)

    Szucs, L.; Glover, S.; Caselli, P.

    2016-05-01

    The ortho:para ratio of H2D+ is a proposed observational indicator of prestellar core ages, and thus a possible tool to determine the typical star formation time scale. The conversion of the measured ratio to an age estimate requires modelling of the chemical evolution. Such models usually consider static, one zone models of physical conditions. The relevant chemical time scales, however, are comparable to the dynamic time scale, therefore the history of gas might affect the ratio. To investigate the significance of gas dynamics and history on the spin-state ratio, we analyse prestellar cores formed in various environment in a hydrodynamic simulation. The fully time dependent, spatially resolved chemical evolution of the cores are computed using a state-of-art ortho:para and deuteration chemical network. The true ages are compared to the once indicated by the ortho:para ratio.

  16. Chemical evolution of rapidly recharging groundwaters in shield environments

    International Nuclear Information System (INIS)

    This report describes results of a multidisciplinary study of the geochemical and microbiological evolution of groundwaters that are recharged into two overburden/surface-bedrock environments in the Underground Research Laboratory (URL) lease area, Lac du Bonnet, Manitoba. Sampling of groundwaters in overburden and shallow bedrock piezometers in the East Swamp area and in packer-isolated bedrock borehole zones in the main shaft of the URL facility was performed during consecutive winter, spring, summer and fall seasons over a one-year period in 1995/1996. The purpose of this study was to investigate and compare the hydrochemical, isotopic and microbiological responses to seasonal variations in the groundwater flow regime in the upper ∼200 m of granitic bedrock and overburden sediments in the URL lease area. The study showed that small amounts of oxygenated, 18O-depleted spring-melt water penetrated the bedrock at the URL, to depths of ∼200 m, under the influence of the pronounced water-table drawdown surrounding the URL. The travel times of recharge to this depth were less than two months. A similar pulse was not seen in the outcrop recharge area of the East Swamp where only natural gradients exist. No significant seasonal variations in groundwater chemistry were observed in either environment. Variations in 3 H content between borehole zones indicates mixing between deeper (older) groundwater and shallow (recent) recharge. Concentrations of dissolved organic carbon (DOC) showed seasonal variations in groundwaters at both study areas whereas only a limited seasonal relationship was seen in micro-organism concentrations. However, the general observation that micro-organism content is highest in groundwaters containing high levels of DOC and dissolved 02, and lower concentrations are found in low-DOC and O2-deficient groundwaters, indicates that microbially mediated oxidation of DOC may be occurring to cause the trend towards reducing conditions along the flow

  17. Life from the stars?. [extraterrestrial sources contributing to chemical evolution on Earth

    Science.gov (United States)

    Pendleton, Yvonne J.; Cruikshank, Dale P.

    1994-01-01

    Scientists are now seriously considering the possibility that organic matter from interstellar space could have influenced, or even spurred, the origin of life on Earth. Various aspects of chemical evolution are discussed along with possible extraterrestrial sources responsible for contributing to Earth's life-producing, chemical composition. Specific topics covered include the following: interstellar matter, molecular clouds, asteroid dust, organic molecules in our solar system, interplanetary dust and comets, meteoritic composition, and organic-rich solar-system bodies.

  18. Effect of water treatment additives on lime softening residual trace chemical composition--implications for disposal and reuse.

    Science.gov (United States)

    Cheng, Weizhi; Roessler, Justin; Blaisi, Nawaf I; Townsend, Timothy G

    2014-12-01

    Drinking water treatment residues (WTR) offer potential benefits when recycled through land application. The current guidance in Florida, US allows for unrestricted land application of lime softening WTR; alum and ferric WTR require additional evaluation of total and leachable concentrations of select trace metals prior to land application. In some cases a mixed WTR is produced when lime softening is accompanied by the addition of a coagulant or other treatment chemical; applicability of the current guidance is unclear. The objective of this research was to characterize the total and leachable chemical content of WTR from Florida facilities that utilize multiple treatment chemicals. Lime and mixed lime WTR samples were collected from 18 water treatment facilities in Florida. Total and leachable concentrations of the WTR were measured. To assess the potential for disposal of mixed WTR as clean fill below the water table, leaching tests were conducted at multiple liquid to solid ratios and under reducing conditions. The results were compared to risk-based soil and groundwater contamination thresholds. Total metal concentrations of WTR were found to be below Florida soil contaminant thresholds with Fe found in the highest abundance at a concentration of 3600 mg/kg-dry. Aluminum was the only element that exceeded the Florida groundwater contaminant thresholds using SPLP (95% UCL = 0.23 mg/L; risk threshold = 0.2 mg/L). Tests under reducing conditions showed elevated concentrations of Fe and Mn, ranging from 1 to 3 orders of magnitude higher than SPLP leachates. Mixed lime WTR concentrations (total and leachable) were lower than the ferric and alum WTR concentrations, supporting that mixed WTR are appropriately represented as lime WTR. Testing of WTR under reducing conditions demonstrated the potential for release of certain trace metals (Fe, Al, Mn) above applicable regulatory thresholds; additional evaluation is needed to assess management options where

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

    CERN Document Server

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

    2014-01-01

    Understanding the chemical evolution of young (high-mass) star-forming regions is a central topic in star formation research. Chemistry is employed as a unique tool 1) to investigate the underlying physical processes and 2) to characterize the evolution of the chemical composition. We observed a sample of 59 high-mass star-forming regions at different evolutionary stages varying from the early starless phase of infrared dark clouds to high-mass protostellar objects to hot molecular cores and, finally, ultra-compact HII regions at 1mm and 3mm with the IRAM 30m telescope. We determined their large-scale chemical abundances and found that the chemical composition evolves along with the evolutionary stages. On average, the molecular abundances increase with time. We modeled the chemical evolution, using a 1D physical model where density and temperature vary from stage to stage coupled with an advanced gas-grain chemical model and derived the best-fit chi^2 values of all relevant parameters. A satisfying overall a...

  20. Chemical evolution of local galaxies in a hierarchical model

    CERN Document Server

    Calura, Francesco

    2009-01-01

    We investigate the chemical properties of local galaxies within a cosmological framework in the hierarchical picture of galaxy formation. To this aim, we use a hierarchical semi-analytic model which includes the contribution from (i) low and intermediate mass stars, (ii) type Ia Supernovae (SNe) and (iii) massive stars. - Abridged - We compare our predictions with available observations in the Milky Way (MW), in local dwarf galaxies and in local ellipticals. For Milky-Way-like galaxies, we can successfully reproduce the [O-Fe] vs [Fe/H] relation observed in disc stars and the stellar metallicity distribution (SMD). For dwarf galaxies, the stellar metallicity vs mass relation is reproduced by assuming that a substantial fraction of the heavy elements is lost through metal-enhanced outflows and a type Ia SN realization probability lower than the one of MW-like galaxies. - Abridged - In ellipticals, the observations indicate higher [alpha/Fe] values in larger galaxies. - Abridged - Our results computed with a st...

  1. Outgassing and chemical evolution of C/2012 S1 (ISON)

    Science.gov (United States)

    Dello Russo, Neil; Vervack, Ronald J.; Kawakita, Hideyo; Cochran, Anita; McKay, Adam J.; Harris, Walter M.; Weaver, Harold A.; Lisse, Carey M.; DiSanti, Michael A.; Kobayashi, Hitomi; Biver, Nicolas; Bockelée-Morvan, Dominique; Crovisier, Jacques; Opitom, Cyrielle; Jehin, Emmanuel

    2015-11-01

    Volatile production rates, relative abundances, rotational temperatures, and spatial distributions in the coma were measured in C/2012 S1 (ISON) using long-slit high-dispersion (λ/Δλ ~ 25,000) infrared spectroscopy as part of a worldwide observing campaign. Spectra were obtained on UT 2013 October 26 and 28 with NIRSPEC at the W. M. Keck Observatory, and UT 2013 November 19 and 20 with CSHELL at the NASA IRTF. H2O was detected on all dates, with production rates increasing by about a factor of 40 between October 26 (Rh = 1.12 AU) and November 20 (Rh = 0.43 AU). Short-term variability of H2O was also seen as the production rate increased by nearly a factor of two during observations obtained over a period of about six hours on November 19. C2H6, CH3OH and CH4 abundances were slightly depleted relative to H2O in ISON compared to mean values for comets measured at infrared wavelengths. On the November dates, C2H2, HCN and OCS abundances relative to H2O appear to be close to the range of mean values, whereas H2CO and NH3 were significantly enhanced. We will compare derived chemical abundances in ISON to other comets measured with infrared spectroscopy.

  2. Radiation-chemical degradation of traces of trichloroethylene and perchloroethylene in drinking water

    International Nuclear Information System (INIS)

    The degradation caused by gamma irradiation of traces of trichloroethylene and perchloroethylene in certain water samples has been investigated over a wide range of concentrations. In general, the degradation is the slower, the higher the concentration of organic and inorganic substances (especially of nitrates) dissolved in the respective water. For pollutant concentrations up to about 500 ppb and for drinking water with rather low nitrate content (some ppm) the degradation follows a first-order rate law. For higher concentrations of pollutants or/and nitrates a much more complex behaviour is observed. In general, perchloroethylene is degraded slower than trichloroethylene. During degradation, organic chlorine is converted quantitatively to chloride ions. Unfortunately, as a side reaction nitrate is partially reduced to nitrite. Except for that, first rough estimates resulted in costs which seem to render such a process economically quite attractive. (orig.)

  3. Modeling Transcient Trace Data

    OpenAIRE

    Mathur, Anup; Abrams, Marc

    1996-01-01

    This paper introduces a novel technique to construct an empirical workload model fitting time-varying (transient) trace data. The trace can be a categorical or numerical time-series. We model the trace as a Piecewise Independent stochastic process. To estimate the parameters for our model we first build a Rate Evolution Graph from the trace data. Piecewise linear regression is then used to construct a joint time-dependent probablity mass function for the trace data. Two methods are propo...

  4. Influence of chemical trace additives on the future ageing of the UA1 central detector

    International Nuclear Information System (INIS)

    A number of systematic tests investigating the effect of various chemical additives on the ageing of prototypes of the UA1 Central Detector have been performed. In addition to the classical substances of water, ethanol and isopropanol emphasis is also put upon more uncommon chemicals, usually required as doping seeds for UV laser calibration. Chamber lifetime can be strongly influenced by them, depending on their concentration. Evidence is presented that proper choice and dosage can lead to a significant extension of normal wire chamber lifetime. (orig.)

  5. Temporal evolution of pollution by trace metals and plants analysis in Apipucos reservoir, Recife, PE, Brazil

    International Nuclear Information System (INIS)

    Water and sediments may reflect the current quality of an aquatic system and the historical behavior of certain hydrological and chemical parameters. Analysis of metals in sediment profiles are used to determine anomalies in their concentrations, as well as sources of pollution. This study was performed in Apipucos Reservoir in the city of Recife, Brazil. Samples of water, plants and sediments were collected in the study area and their metals content (extract by adding acids) were determined a fast sequential atomic absorption spectrometer (SpectrAA-220FS/VARIAN). The 210Pb activity concentration in each sediment layer was determined through the beta counting of 210Bi after lead precipitation as lead chromate. The results showed the metals' behavior in sediments: iron and manganese concentrations in sediments increase proportionately with the ages of the sediments. In general, cobalt, copper and zinc were also their concentrations increased over the years. These same elements in water are similar from the blank samples, however the roots of 'Eichhornia crassipes' assimilated higher concentrations of metals than the stems and leaves of this species. (author)

  6. The Temperature Structure in Ionized Nebulae and the Chemical Evolution of Galaxies

    OpenAIRE

    2002-01-01

    A few results that indicate the presence of temperature variations in gaseous nebulae are reviewed. The evidence is based on: a) temperatures derived from different methods, and b) on comparisons of abundances predicted by models of galactic chemical evolution with abundances derived from observations.

  7. Impact constraints on the environment for chemical evolution and the continuity of life

    Science.gov (United States)

    Oberbeck, Verne R.; Fogleman, Guy

    1990-01-01

    The moon and the earth were bombarded heavily by planetesimals and asteroids that were capable of interfering with chemical evolution and the origin of life. This paper explores the frequency of giant terrestrial impacts able to stop prebiotic chemistry in the probable regions of chemical evolution. The limited time available between impacts disruptive to prebiotic chemistry at the time of the oldest evidence of life suggests the need for a rapid process for chemical evolution of life. On the other hand, rapid chemical evolution in cloud systems and lakes or other shallow evaporating water bodies would have been possible because reactants could have been concentrated and polymerized rapidly in this environment. Thus life probably could have originated near the surface between frequent surface-sterilizing impacts. There may not have been continuity of life depending on sunlight because there is evidence that life, existing as early as 3.8 Gyr ago, may have been destroyed by giant impacts. The first such organisms on earth were probably not the ancestors of present life.

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

    Science.gov (United States)

    Gill, Elizabeth Deas

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

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

    Science.gov (United States)

    1990-01-01

    The current state is reviewed of the study of chemical evolution and planetary biology and the probable future is discussed of the field, at least for the near term. To this end, the report lists the goals and objectives of future research and makes detailed, comprehensive recommendations for accomplishing them, emphasizing those issues that were inadequately discussed in earlier Space Studies Board reports.

  10. Lighting up stars in chemical evolution models: the CMD of Sculptor

    Science.gov (United States)

    Vincenzo, F.; Matteucci, F.; de Boer, T. J. L.; Cignoni, M.; Tosi, M.

    2016-08-01

    We present a novel approach to draw the synthetic colour-magnitude diagram (CMD) of galaxies, which can provide - in principle - a deeper insight in the interpretation and understanding of current observations. In particular, we `light up' the stars of chemical evolution models, according to their initial mass, metallicity and age, to eventually understand how the assumed underlying galaxy formation and evolution scenario affects the final configuration of the synthetic CMD. In this way, we obtain a new set of observational constraints for chemical evolution models beyond the usual photospheric chemical abundances. The strength of our method resides in the very fine grid of metallicities and ages of the assumed data base of stellar isochrones. In this work, we apply our photochemical model to reproduce the observed CMD of the Sculptor dSph and find that we can reproduce the main features of the observed CMD. The main discrepancies are found at fainter magnitudes in the main sequence turn-off and sub-giant branch, where the observed CMD extends towards bluer colours than the synthetic one; we suggest that this is a signature of metal-poor stellar populations in the data, which cannot be captured by our assumed one-zone chemical evolution model.

  11. Chemical evolution of spiral galaxies: models with star formation proportional to molecular hydrogen

    OpenAIRE

    Tosi, M.; Angeles I. Díaz

    1990-01-01

    This is an electronic version of an article published in Monthly Notices of the Royal Astronomical Society. Tosi, M., Díaz, A.I. Chemical evolution of spiral galaxies: models with star formation proportional to molecular hydrogen. Monthly Notices of the Royal Astronomical Society 246 (1990): 616-623

  12. Chemical evolution of deep groundwaters in granites, information acquired from natural systems

    International Nuclear Information System (INIS)

    A research program has been carried out for five years, concerning a major aspect of deep radioactive waste disposals: groundwaters in the host-rock. The following items have been examined: the exact composition of confined waters, excluding those which are found in highly conductive (even deep) fractures; evolution path from surface waters to confined waters; possible influence of the repository on the composition of groundwaters; possible influence of groundwaters on the elements which could escape the repository (major elements, trace elements, radioactive elements). The following methodology is used: groundwater sampling and analysis, identification of the major phenomena controlling element concentration in groundwaters, modelling, modelling validation. (author). 11 refs., 4 figs., 3 tabs

  13. Chemical and luminosity evolution, and counts of galaxies in a merger model

    Science.gov (United States)

    Colin, P.; Schramm, D. N.

    1993-01-01

    A merger model is applied to the chemical and luminosity evolution of galaxies. Two aspects are focused on. The first is the problem of abundance ratios as a function of metallicity. The second is related to the luminosity evolution of galaxies. In relation to the former, we calculate the evolution of several chemical elements exploring a broad space of possible star formation rates, including those derived using phenomenological arguments from a multiple merger galaxy formation scenario. We are able to reproduce the observed plateau in the ratio of the abundances of oxygen to iron versus metallicity as a direct consequence of one of the merging SFR used; we have utilized a standard Type II supernovae nucleosynthesis scenario coupled with a reasonable binary model for Type Ia supernovae and its consequent nucleosynthetic yields. Following the consequent luminosity effects in a straightforward way enables the estimation of the evolution of bolometric luminosity. We have used our recently developed code for photometric evolution of galaxies to make a preliminary computation of the number-magnitude relationship, assuming a standard picture of galaxy evolution, in the B and K bands.

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

    Science.gov (United States)

    Devincenzi, D. L.

    1983-01-01

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

  15. Magmatic evolution of a volcano studied by 230Th-238U disequilibrium and trace elements systematics: the Etna case

    International Nuclear Information System (INIS)

    Age determinations of several lava flows from Etna through 230Th-238U disequilibrium (internal isochrons) yield a precise chronology of the volcano's history for the last 200,000 years, and emphasize the main episodes in the formation of this huge complex strato-volcano. Study of (230Th/232Th)0 initial ratios of lavas together with their trace-element compositions yields a consistent model of magmatic evolution implying the existence, for 200,000 years, of a deep reservoir of alkalic magma periodically mixed with magmas of tholeiitic affinity. These short periods of mixing appear to be related to the formation of the large calderas of Etna. In addition to these processes affecting the deep reservoir, fractional crystallization also occurred in more superficial levels of the volcanic edifice, thereby yielding several series of differentiation of relatively short duration. As for its geochemistry, Etna's volcanism is of oceanic type but with its own characteristics and in a peculiar geodynamic context, at the edge of the African Plate. (author)

  16. About evolution of alive orgamisms in conditions of radioactive and chemical stress (biophysical aspect)

    International Nuclear Information System (INIS)

    The problems of evolution of living organisms in conditions of radioactive and chemical stress are considered. Tendencies of development of the world community are evidence of global anthropogenic influence increase on biosphere, which is caused by many components, the main of them being radiation contamination and chemical pollution. The possible mechanisms of new species appearance are discussed on molecular level taking into account mutagenic factors caused by radiation and chemical stress. The quantum field hypothesis on the basis of Landau-Ginzburg equation of molecular mechanisms of mutations connected with new species appearance is presented.(A.A.D.)

  17. Dynamically- and chemically-induced grain boundary migration in quartz: microstructures, crystallographic fabrics, and trace element contents

    Science.gov (United States)

    Nachlas, Will; Thomas, Jay

    2016-04-01

    Grain boundary migration (GBM) is a common mechanism by which quartz recrystallizes in the Earth. In the most basic sense, GBM occurs as atoms exchange structural positions across a planar defect. Reconstitution of grains via GBM imparts a new crystallographic orientation, but its effect on the geochemistry of recrystallized grains remains uncertain and depends on the kinetic and thermodynamic properties of the moving grain boundary. Two of the dominant driving forces for GBM are lattice strain energy, controlled by the applied stress field, and chemical potential energy, controlled by differences in mineral stability. We present observations from static and dynamic recrystallization experiments showing evidence for GBM in response to both of these driving forces. In static recrystallization experiments, quartz recrystallized in response to local variations in trace-level Ti concentrations, whereas in dynamic recrystallization experiments, quartz recrystallized during dislocation creep in response to the imposed differential stress. Each case produced recrystallized quartz exhibiting diagnostic microstructures, crystallographic fabrics, and trace element contents that can be used to infer the mechanisms of quartz recrystallization and the pressure-temperature conditions at which recrystallization occurred.

  18. Modelling the Fate of Xenobiotic Trace Chemicals via Wastewater Treatment and Agricultural Resource Reuse

    DEFF Research Database (Denmark)

    Polesel, Fabio

    XTCs are in fact multispecies chemicals, being present in neutral and/or ionized form in wastewater. We demonstrated that pH conditions and, to a lesser extent, iron salt dosing for chemical phosphorus removal can significantly affect solid-liquid partitioning of the zwitterionic antibiotic...... in the European Union. The tool combined was specifically addressed for fate prediction of ionizable XTCs (the biocide triclosan, the diuretic furosemide and the antibiotic ciprofloxacin). Furosemide was found rather persistent to wastewater treatment (removal efficiency ≤ 40%) and to further undergo...... indicate the need of deepening investigations of XTC fate in agricultural systems. Accumulation in food crops may result in indirect human exposure to XTCs via dietary intake, which can be eventually estimated using model predictions. The presented simulation tool can thus be used for pre-screening and...

  19. ALMA-resolved salt emission traces the chemical footprint and inner wind morphology of VY CMa

    CERN Document Server

    Decin, L; Millar, T J; Baudry, A; De Beck, E; Homan, W; Smith, N; Van de Sande, M; Walsh, C

    2016-01-01

    (abreviated) We aim to study the inner-wind structure (R<250 Rstar) of the well-known red supergiant VY CMa. We analyse high spatial resolution (~0".24x0".13) ALMA Science Verification (SV) data in band 7 in which four thermal emission lines of gaseous sodium chloride (NaCl) are present at high signal-to-noise ratio. For the first time, the NaCl emission in the inner wind region of VY CMa is spatially resolved. The ALMA observations reveal the contribution of up to four different spatial regions. The NaCl emission pattern is different compared to the dust continuum and TiO2 emission already analysed from the ALMA SV data. The emission can be reconciled with an axisymmetric geometry, where the lower density polar/rotation axis has a position angle of ~50 degrees measured from north to east. However, this picture can not capture the full morphological diversity, and discrete mass ejection events need to be invoked to explain localized higher-density regions. The velocity traced by the gaseous NaCl line profi...

  20. Occurrence and fate of emerging trace organic chemicals in wastewater plants in Chennai, India.

    Science.gov (United States)

    Anumol, Tarun; Vijayanandan, Arya; Park, Minkyu; Philip, Ligy; Snyder, Shane A

    2016-01-01

    The presence of pharmaceuticals, hormones, pesticides and industrial contaminants collectively termed as trace organic compounds (TOrCs) in wastewater has been well-documented in USA, Europe, China and other regions. However, data from India, the second most populous country in the world is severely lacking. This study investigated the occurrence and concentrations of twenty-two indicator TOrCs at three wastewater treatment plants (WWTPs) in South India serving diverse communities across three sampling campaigns. Samples were collected after each WWTP treatment unit and removal efficiencies for TOrCs were determined. Eleven TOrCs were detected in every sample from every location at all sites, while only five TOrCs were detected consistently in effluent samples. Caffeine was present at greatest concentration in the influent of all three plants with average concentrations ranging between 56 and 65μg/L. In contrast, the x-ray contrast media pharmaceutical, iohexol, was the highest detected compound on average in the effluent at all three WWTPs (2.1-8.7μg/L). TOrCs were not completely removed in the WWTPs with removal efficiencies being compound specific and most of the attenuation being attributed to the biological treatment processes. Caffeine and triclocarban were well removed (>80%), while other compounds were poorly removed (acesulfame, sucralose, iohexol) or maybe even formed (carbamazepine) within the WWTPs. The effluent composition of the 22 TOrCs were similar within the three WWTPs but quite different to those seen in the US, indicating the importance of region-specific monitoring. Diurnal trends indicated that variability is compound specific but trended within certain classes of compounds (artificial sweeteners, and pharmaceuticals). The data collected on TOrCs from this study can be used as a baseline to identify potential remediation and regulatory strategies in this understudied region of India. PMID:27054837

  1. A new sampler for collecting separate dry and wet atmospheric depositions of trace organic chemicals

    Science.gov (United States)

    Waite, Don T.; Cessna, Allan J.; Gurprasad, Narine P.; Banner, James

    Studies conducted in Saskatchewan and elsewhere have demonstrated the atmospheric transport of agricultural pesticides and other organic contaminants and their deposition into aquatic ecosystems. To date these studies have focused on ambient concentrations in the atmosphere and in wet precipitation. To measure the dry deposition of organic chemicals, a new sampler was designed which uses a moving sheet of water to passively trap dry particles and gasses. The moving sheet of water drains into a reservoir and, during recirculation through the sampler, is passed through an XAD-2 resin column which adsorbs the trapped organic contaminants. All surfaces which contact the process water are stainless steel or Teflon. Chemicals collected can be related to airborne materials depositing into aquatic ecosystems. The sampler has received a United States patent (number 5,413,003 - 9 May 1996) with the Canadian patent pending. XAD-2 resin adsorption efficiencies for 10 or 50 μg fortifications of ten pesticides ranged from 76% for atrazine (2-chloro-4-ethylamino-6-isopropylamino- S-triazine) to 110% for triallate [ S-(2,3,3-trichloro-2-phenyl)bis(1-methylethyl)carbamothioate], dicamba (2-methoxy-3,6-dichlorobenzoic acid) and toxaphene (chlorinated camphene mixture). Field testing using duplicate samplers showed good reproducibility and amounts trapped were consistent with those from high volume and bulk pan samplers located on the same site. Average atmospheric dry deposition rates of three chemicals, collected for 5 weeks in May and June, were: dicamba, 69 ng m -2 da -1; 2,4-D (2,4-dichlorophenoxyacetic acid), 276 ng m -2 da -1: and, γ-HCH ( γ-1, 2, 3, 4, 5, 6-hexachlorocyclohexane), 327 ng m -2 da -1.

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

    Science.gov (United States)

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

    1990-01-01

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

  3. Measuring the Effect of Fuel Chemical Structure on Particulate and Gaseous Emissions using Isotope Tracing

    International Nuclear Information System (INIS)

    Using accelerator mass spectrometry (AMS), a technique initially developed for radiocarbon dating and recently applied to internal combustion engines, carbon atoms within specific fuel molecules can be labeled and followed in particulate or gaseous emissions. In addition to examining the effect of fuel chemical structure on emissions, the specific source of carbon for PM can be identified if an isotope label exists in the appropriate fuel source. Existing work has focused on diesel engines, but the samples (soot collected on quartz filters or combustion gases captured in bombs or bags) are readily collected from large industrial combustors as well

  4. Characterization and evolution of dissolved organic matter in acidic forest soil and its impact on the mobility of major and trace elements (case of the Strengbach watershed)

    Science.gov (United States)

    Gangloff, Sophie; Stille, Peter; Pierret, Marie-Claire; Weber, Tiphaine; Chabaux, François

    2014-04-01

    Dissolved Organic Carbon (DOC) plays an important role in the behavior of major and trace elements in the soil and influences their transfer from soil to soil solution. The first objective of this study is to characterize different organic functional groups for the Water Extractable Organic Carbon (WEOC) fractions of a forest soil as well as their evolution with depth. The second objective is to clarify the influence of these organic functional groups on the migration of the trace elements in WEOC fractions compared to those in the soil solution obtained by lysimeter plates. All experiments have been performed on an acidic forest soil profile (five depths in the first meter) of the experimental spruce parcel in the Stengbach catchment. The Infra-red spectra of the freeze-dried WEOC fractions show a modification of the molecular structure with depth, i.e. a decrease of the polar compounds such as polysaccharides and an increase of the less polar hydro-carbon functional groups with a maximum value of the aromaticity at 30 cm depth. A Hierarchical Ascending Classification (HAC) of the evolution of Water Extractable Chemical Elements (WECE) with the evolution of the organic functional groups in the organic matter (OM) enriched soil compartments permits recognition of relationships between trace element behavior and the organic functional group variations. More specifically, Pb is preferentially bound to the carboxylic acid function of DOC mainly present in the upper soil compartment and rare earth elements (REE) show similar behavior to Fe, V and Cr with a good affinity to carboxy-phenolic and phenolic groups of DOC. The experimental results show that heavy REE compared to light REE are preferentially bound to the aromatic functional group. This different behavior fractionates the REE pattern of soil solutions at 30 cm depth due to the here observed aromaticity enrichment of DOC. These different affinities for the organic functional groups of the DOC explain some

  5. Chemical spots and their dynamical evolution on HgMn stars

    OpenAIRE

    Korhonen, Heidi; Hubrig, Swetlana; Briquet, Maryline; González, Federico; Savanov, Igor

    2010-01-01

    Our recent studies of late B-type stars with HgMn peculiarity revealed for the first time the presence of fast dynamical evolution of chemical spots on their surfaces. These observations suggest a hitherto unknown physical process operating in the stars with radiative outer envelopes. Furthermore, we have also discovered existence of magnetic fields on these stars that have up to now been thought to be non-magnetic. Here we will discuss the dynamical spot evolution on HD 11753 and our new res...

  6. Irradiated solutions of citric acid in the context of chemical evolution

    International Nuclear Information System (INIS)

    The radiolysis of citric acid in an aqueous solution and its connection with chemical evolution has been investigated. The importance of this compound which, probably had a double role during the evolutive period, first as a precursor in the synthesis of some pyrimidines and second as metabolic intermediary in the carboxilic acids cycle. The decomposition of the citric acid, the identification of the products obtained from the radiolysis and the distributions of these products were investigated with relation to the different doses used. (author) 9 refs.; 1 fig

  7. Chemical spots and their dynamical evolution on HgMn stars

    CERN Document Server

    Korhonen, Heidi; Briquet, Maryline; Gonzalez, Federico; Savanov, Igor

    2010-01-01

    Our recent studies of late B-type stars with HgMn peculiarity revealed for the first time the presence of fast dynamical evolution of chemical spots on their surfaces. These observations suggest a hitherto unknown physical process operating in the stars with radiative outer envelopes. Furthermore, we have also discovered existence of magnetic fields on these stars that have up to now been thought to be non-magnetic. Here we will discuss the dynamical spot evolution on HD 11753 and our new results on magnetic fields on AR Aur.

  8. Limited Influence of Oxygen on the Evolution of Chemical Diversity in Metabolic Networks

    Directory of Open Access Journals (Sweden)

    Kazuhiro Takemoto

    2013-10-01

    Full Text Available Oxygen is thought to promote species and biomolecule diversity. Previous studies have suggested that oxygen expands metabolic networks by acquiring metabolites with different chemical properties (higher hydrophobicity, for example. However, such conclusions are typically based on biased evaluation, and are therefore non-conclusive. Thus, we re-investigated the effect of oxygen on metabolic evolution using a phylogenetic comparative method and metadata analysis to reduce the bias as much as possible. Notably, we found no difference in metabolic network expansion between aerobes and anaerobes when evaluating phylogenetic relationships. Furthermore, we showed that previous studies have overestimated or underestimated the degrees of differences in the chemical properties (e.g., hydrophobicity between oxic and anoxic metabolites in metabolic networks of unicellular organisms; however, such overestimation was not observed when considering the metabolic networks of multicellular organisms. These findings indicate that the contribution of oxygen to increased chemical diversity in metabolic networks is lower than previously thought; rather, phylogenetic signals and cell-cell communication result in increased chemical diversity. However, this conclusion does not contradict the effect of oxygen on metabolic evolution; instead, it provides a deeper understanding of how oxygen contributes to metabolic evolution despite several limitations in data analysis methods.

  9. Towards an Integrated Model of Earth's Thermo-Chemical Evolution and Plate Tectonics

    Science.gov (United States)

    Tackley, P. J.; Xie, S.

    2001-05-01

    It has long been a challenge for geodynamicists, who have typically modeled homogeneous mantles, to explain the geochemical evidence for the existence of several distinct chemical reservoirs, in terms of a dynamically and chemically self-consistent model. While the mixing behavior of generalized tracers has received much attention in the modeling community, a recent trend has been towards mantle convection models that track the evolution of specific chemical species, both major and minor, and can thus be related to geochemical observations. However, obtaining realistic chemical evolution in such models is dependent on their having a reasonable representation of plate tectonic behavior since the recycling of oceanic crust and complementary depleted residuum is a key process in Earth that other terrestrial planets may lack. In general, this has required inserting plate motions by hand in models. In recent years, however, we have learned how to perform numerical simulations of mantle convection in which plate tectonic behavior is introduced self-consistently through plastic yielding of the lithosphere. In this presentation, models of mantle convection that combine a treatment of geochemical evolution with self-consistently generated plate tectonics, will be presented. Preliminary results indicate that the system can self-consistently evolve regions which have a HIMU-like signature as well as regions with a high He3/He4 ratio.

  10. Lighting up stars in chemical evolution models: the CMD of Sculptor

    CERN Document Server

    Vincenzo, Fiorenzo; de Boer, Thomas J L; Cignoni, Michele; Tosi, Monica

    2016-01-01

    We present a novel approach to draw the synthetic color-magnitude diagram of galaxies, which can provide - in principle - a deeper insight in the interpretation and understanding of current observations. In particular, we `light up' the stars of chemical evolution models, according to their initial mass, metallicity and age, to eventually understand how the assumed underlying galaxy formation and evolution scenario affects the final configuration of the synthetic CMD. In this way, we obtain a new set of observational constraints for chemical evolution models beyond the usual photospheric chemical abundances. The strength of our method resides in the very fine grid of metallicities and ages of the assumed database of stellar isochrones. In this work, we apply our photo-chemical model to reproduce the observed CMD of the Sculptor dSph and find that we can reproduce the main features of the observed CMD. The main discrepancies are found at fainter magnitudes in the main sequence turn-off and sub-giant branch, wh...

  11. An Ultra-Trace Analysis Technique for SF6 Using Gas Chromatography with Negative Ion Chemical Ionization Mass Spectrometry.

    Science.gov (United States)

    Jong, Edmund C; Macek, Paul V; Perera, Inoka E; Luxbacher, Kray D; McNair, Harold M

    2015-07-01

    Sulfur hexafluoride (SF6) is widely used as a tracer gas because of its detectability at low concentrations. This attribute of SF6 allows the quantification of both small-scale flows, such as leakage, and large-scale flows, such as atmospheric currents. SF6's high detection sensitivity also facilitates greater usage efficiency and lower operating cost for tracer deployments by reducing quantity requirements. The detectability of SF6 is produced by its high molecular electronegativity. This property provides a high potential for negative ion formation through electron capture thus naturally translating to selective detection using negative ion chemical ionization mass spectrometry (NCI-MS). This paper investigates the potential of using gas chromatography (GC) with NCI-MS for the detection of SF6. The experimental parameters for an ultra-trace SF6 detection method utilizing minimal customizations of the analytical instrument are detailed. A method for the detection of parts per trillion (ppt) level concentrations of SF6 for the purpose of underground ventilation tracer gas analysis was successfully developed in this study. The method utilized a Shimadzu gas chromatography with negative ion chemical ionization mass spectrometry system equipped with an Agilent J&W HP-porous layer open tubular column coated with an alumina oxide (Al2O3) S column. The method detection limit (MDL) analysis as defined by the Environmental Protection Agency of the tracer data showed the method MDL to be 5.2 ppt. PMID:25452581

  12. High sensitivity detection and characterization of the chemical state of trace element contamination on silicon wafers

    CERN Document Server

    Pianetta, Piero A; Baur, K; Brennan, S; Homma, T; Kubo, N

    2003-01-01

    Increasing the speed and complexity of semiconductor integrated circuits requires advanced processes that put extreme constraints on the level of metal contamination allowed on the surfaces of silicon wafers. Such contamination degrades the performance of the ultrathin SiO sub 2 gate dielectrics that form the heart of the individual transistors. Ultimately, reliability and yield are reduced to levels that must be improved before new processes can be put into production. It should be noted that much of this metal contamination occurs during the wet chemical etching and rinsing steps required for the manufacture of integrated circuits and industry is actively developing new processes that have already brought the metal contamination to levels beyond the measurement capabilities of conventional analytical techniques. The measurement of these extremely low contamination levels has required the use of synchrotron radiation total reflection X-ray fluorescence (SR-TXRF) where sensitivities 100 times better than conv...

  13. Trans-Pacific transport and evolution of aerosols and trace gases from Asia during the INTEX-B field campaign

    Directory of Open Access Journals (Sweden)

    B. Adhikary

    2009-08-01

    Full Text Available The Sulfur Transport and dEposition Model (STEM developed at the University of Iowa is applied to the analysis of observations obtained during the Intercontinental Chemical Transport Experiment-Phase B (INTEX-B, conducted over the Pacific Ocean during the 2006 North American spring season. This paper reports on the model performance of meteorological parameters, trace gases, aerosols and photolysis rate (J-values predictions with the NASA DC-8 and NSF/NCAR C-130 airborne measurements along with observations from three surface sites Mt. Bachelor, Trinidad Head and Kathmandu, Nepal. In general the model shows appreciable skill in predicting many of the important aspects of the observed distributions. The major meteorological parameters driving long range transport are accurately predicted by the WRF simulations used in this study. Furthermore, the STEM model predicts aerosols and trace gases concentrations within a standard deviation of most of the observed mean values. The results also point towards areas where model improvements are needed; e.g., the STEM model underestimates CO (15% for the DC8 and 6% for the C-130, whereas it overpredicts PAN (by a factor of two for both aircraft. The errors in the model calculations are attributed to uncertainty in emissions estimates and uncertainty in the top and lateral boundary conditions. Results from a series of sensitivity simulations examining the impact of the growth of emissions in Asia from 2000 to 2006, the importance of biomass burning, the effect of using boundary conditions from different global models, and the role of heterogeneous chemistry on the predictions are also presented. The impacts of heterogeneous reactions at specific times during dust transport episodes can be significant, and in the presence of dust both sulfate and nitrate aerosol production is increased and gas phase nitric acid levels are reduced appreciably (~50%. The aging of the air masses during the long range

  14. Application of chemical fractionation for monitoring some trace elements in street and industrial dust from Wadmedani, Sudan

    International Nuclear Information System (INIS)

    This study monitors some trace elements concentration in street and industrial dust from Wad Medani city, Gezira State in central Sudan. A total of 20 samples of dust were collected from crowded and non-crowded streets, material processing workshop and a tannery. Samples were treated by sequential chemical extraction in five fractions, which termed as exchangeable fraction, carbonate fraction, Fe-Mn oxides fraction, organic matter fraction and residual fraction. The same samples were digested by wet method. The obtained solutions were analyzed for Cr, Fe, Ni, Cu, Zn, and Pb content using Atomic Absorption Spectrometer (AAS) and for Na and K content using Flame Emission Spectrometer (FES). X-Ray Fluorescence Spectrometer (XRF) was used to determine the total content of Na, K, Cr, Fe, Ni, Cu, Zn and Pb in the bulk sample. Results of total content, which obtained by AAS, FES and XRF spectrometry, were compared with each other and with total content for the fractionated samples. Certified reference materials from IAEA were analyzed to make sure of the data obtained. The ranges of concentrations obtained are 113-3900 μg/g for Cr, 0.3-110.4 mg/g for Fe, 27-500 μg/g for Ni, 34.7-4390 μ/g for Cu, 62-1320 μg/g for Zn and 40-1250 μg/g for Pb dry weight. The obtained results were analyzed statistically using multivariate methods that include Correlation Matrices, Principal Component Analysis (PCA) and cluster analysis. The concentrations of trace elements in street and industrial dust of Wad Medani were compared with those values in literature. It has been observed that the dust from street and industrial area of wad Medani is slightly affected by anthropogenic sources.(Author)

  15. Trace Elements and Physico-Chemical Quality of the Well Waters in Mahitsy, Province of Antananarivo, Madagascar

    International Nuclear Information System (INIS)

    The proposed study area of Mahitsy is located in the province of Antananarivo. Only 14.38% of the population in the rural zone has access to safe drinking water. Most of human population use wells or springs as the main source of drinking water. Wells are generally less than 20 meters deep and they are not properly sealed. Well waters investigated in January 2004 have a very large range of trace constituent and chemical composition in the zone of interest. Manganese concentrations range is 8μg.L-1-1115 μg.L-1 and concentrations of barium vary in the range of 55μg.L-1- 4967 μg.L-1. 67% of monitored well waters are of manganese concentration higher than 50μg.L-1 and 44% contain barium with a concentration higher than 700μg.L-1. Total dissolved solids vary between 8 mg.L-1 and 881 mg.L-1 and well water pHs are acidic (4.28 - 5.94). Nitrate concentrations monitored in Mahitsy groundwaters show that, 54% of the well water samples exceed 50 mg.L-1(WHO guidelines value) and 84% exceed 13.5 mg.L-1 (indicative value of human activities). The nitrate content ranges from 4 to 489 mg.L-1. Groundwater nitrate correlates positively with chloride and potassium. That would suggest that the high content of nitrate may result from the septic tank, the cesspool and the animal wastes storage, located next to the well. However, people draw water from groundwater for domestic purposes, as the water infrastructure remains undeveloped in the studied area. The measurement of trace constituents are performed using Total Relflection X-ray Fluorescence (TXRF) analytical method and the major ions are determined by Ion Chromatograph (IC) system.

  16. Plant absorption of trace elements in sludge amended soils and correlation with soil chemical speciation

    Energy Technology Data Exchange (ETDEWEB)

    Torri, Silvana, E-mail: torri@agro.uba.ar [Catedra de Fertilidad y Fertilizantes, Facultad de Agronomia, UBA, Avda San Martin 4453, Buenos Aires (C1417 DSE) (Argentina); Lavado, Raul [Catedra de Fertilidad y Fertilizantes, Facultad de Agronomia, UBA, Avda San Martin 4453, Buenos Aires (C1417 DSE) (Argentina)

    2009-07-30

    The aim of the present study was to investigate the relationship between Lolium perenne L. uptake of Cd, Cu, Pb, and Zn in sludge amended soils and soil availability of these elements assessed by soil sequential extraction. A greenhouse experiment was set with three representative soils of the Pampas Region, Argentina, amended with sewage sludge and sewage sludge enriched with its own incinerated ash. After the stabilization period of 60 days, half of the pots were sampled for soil analysis; the rest of the pots were sown with L. perenne and harvested 8, 12, 16 and 20 weeks after sowing, by cutting just above the soil surface. Cadmium and Pb concentrations in aerial tissues of L. perenne were below detection limits, in good agreement with the soil fractionation study. Copper and Zn concentration in the first harvest were significantly higher in the coarse textured soil compared to the fine textured soil, in contrast with soil chemical speciation. In the third harvest, there was a positive correlation between Cu and Zn concentration in aerial biomass and soil fractions usually considered of low availability. We conclude that the most available fractions obtained by soil sequential extraction did not provide the best indicator of Cu and Zn availability to L. perenne.

  17. Application of INAA to reveal the chemical evolution of selected volcanic eruptiva from Santorini, Greece

    International Nuclear Information System (INIS)

    The pumiceous products of the large-scale explosive eruptions at Santorini show a high grade of similarity in their optical appearance as well as in their chemical composition. The demand for a clear classification of these eruption products was raised from archaeological research, where pumice can be interpreted as a 'post-eruption' time marker. Elements that underwent significant changes because of geochemical processes and that could be indicative for a distinction of pumice produced by the five major explosive eruptions were looked for. INAA of 25 elements allows a clear classification and contributes new information to the chemical evolution of Santorini volcano. (author)

  18. The chemical evolution of a travertine-depositing stream: geochemical processes and mass transfer reactions

    Science.gov (United States)

    Lorah, M.M.; Herman, J.S.

    1988-01-01

    Focuses on quantiatively defining the chemical changes occurring in Falling Spring Creek, a travertine-depositing stream located in Alleghany County, Virgina. The processes of CO2 outgassing and calcite precipitation or dissolution control the chemical evolution of the stream. Physical evidence for calcite precipitation exists in the travertine deposits which are first observed immediately above the waterfall and extend for at least 1.0 km below the falls. Net calcite precipitation occurs at all times of the year but is greatest during low-flow conditions in the summer and early fall. -from Authors

  19. The mineralogic evolution of the Martian surface through time: Implications from chemical reaction path modeling studies

    Science.gov (United States)

    Plumlee, G. S.; Ridley, W. I.; Debraal, J. D.; Reed, M. H.

    1993-01-01

    Chemical reaction path calculations were used to model the minerals that might have formed at or near the Martian surface as a result of volcano or meteorite impact driven hydrothermal systems; weathering at the Martian surface during an early warm, wet climate; and near-zero or sub-zero C brine-regolith reactions in the current cold climate. Although the chemical reaction path calculations carried out do not define the exact mineralogical evolution of the Martian surface over time, they do place valuable geochemical constraints on the types of minerals that formed from an aqueous phase under various surficial and geochemically complex conditions.

  20. Simulating the evolution of the chemical composition of the 1988/89 winter vortex

    Science.gov (United States)

    Jones, R. L.; Mckenna, D. S.; Poole, L. R.; Solomon, S.

    1990-01-01

    During the 1988/89 Airborne Arctic Stratospheric Expedition (AASE) observations of the chemical composition and aerosol characteristics of the winter vortex were obtained from a NASA ER-2 aircraft. In this paper we present interpretations of observations obtained on three ER-2 flights using a Lagrangian coupled photochemical-microphysical model. It is argued that observations obtained on Jaunary 16 and 19, and February 10, represent different stages of the chemical evolution of the vortex, from the early stages of chlorine release, the onset of denitrification and the intensively processed state.

  1. The Chemical Evolution of Narrow Emission Line Galaxies: the Key to their Formation Processes

    CERN Document Server

    Torres-Papaqui, J P; Ortega-Minakata, R A

    2011-01-01

    Using the largest sample of narrow emission line galaxies available so far, we show that their spectral characteristics are correlated with different physical parameters, like the chemical abundances, the morphologies, the masses of the bulge and the mean stellar age of the stellar populations of the host galaxies. It suggests that the spectral variations observed in standard spectroscopic diagnostic diagrams are not due solely to variations of ionization parameters or structures but reflect also the chemical evolution of the galaxies, which in turn can be explained by different galaxy formation processes.

  2. The possible roles of water in the prebiotic chemical evolution of DNA.

    Science.gov (United States)

    Cui, Shuxun

    2010-09-21

    There is no doubt that water is pivotal to life. Yet, as the emergence of life is still a big challenge in science, the detailed involvement of water in that process is not well recognized. Following the clues provided by recent single-molecule studies on DNA, we attempt to elucidate the possible roles of water in the prebiotic chemical evolution. Water has long been recognized as an important reactant in the Miller-Urey experiment and then as the only solvent of the primitive soup. Besides that, water also played a vital role in the prebiotic chemical evolution: water is the important criterion in the combinatorial library screening for self-assembling macromolecules. With this notion, the uniformity of biochemistry for all terrestrial life may be explained. A possible roadmap from the inorganic world to the origin of life is also discussed. PMID:20577681

  3. Mutagens and carcinogens - Occurrence and role during chemical and biological evolution

    Science.gov (United States)

    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.

  4. 化工生产装置保温伴热要素分析%Analysts of The Factors of Heat Preservation & Heat Tracing of Chemical Production

    Institute of Scientific and Technical Information of China (English)

    杜锴

    2015-01-01

    化工生产装置的保温与伴热对生产的平稳运行有着至关重要的作用和意义。各生产装置中对保温伴热的需求主要受气候、环境温度、介质的物理特性、装置的操作指标、系统的反应条件等因素影响。从决定装置的保温需求要素、决定装置伴热措施要素与实施、保温伴热所需的设备和材料等方面入手,对影响化工生产装置保温伴热因素进行了深入的分析,为化工生产装置的保温伴热拓宽思路。%Heat preservation and heat tracing of chemical production plant, has a great effect on stable of operation of pro-duction.The request of heat preservation and heat tracing of every chemical production plant, is mainly influenced by the following reasons:climate, the temperature of the environment, physical properties of the medium, operating index of the device, the reaction condition of the system, etc.The thesis start with the crucial factors of the heat preservation request of the plant, the elements and the implementation of the decision device with the heat tracing, the equipment and materials of heat preservation and heat tracing, make a detailed analysis of the factors of heat preservation and heat tracing of chemical production, broaden ideas of heat tracing of chemical production.

  5. Inhomogeneous chemical evolution of the galactic disk: evidence for sequential stellar enrichment

    OpenAIRE

    Hoek, van den, L.B.; Jong, de, Franciska

    1997-01-01

    We investigate the origin of the abundance variations observed among similarly aged F and G dwarfs in the local Galactic disk. We present arguments in support of combined infall of metal-deficient gas and sequential enrichment by successive stellar generations in the local Galactic disk ISM. We show that galactic chemical evolution models which take into account these processes simultaneously are consistent with both the observed abundance variations among similarly aged dwarfs in the solar n...

  6. The Chemical Evolution of Galaxies: The Stellar Mass-Metallicity Relation

    CERN Document Server

    Hartwick, F D A

    2016-01-01

    The predictions of the multiple burst accretion model of chemical evolution are compared to the observations of the stellar masses and metallicities of star-forming galaxies. With the addition of one parameter, the model can account for the observations of the star-forming galaxies if the observations of the galaxies are identified with the star bursting behaviour of the model. This consistency with the model holds only if galaxy downsizing is assumed to occur.

  7. Inhomogeneous halo collapse and early Galactic chemical evolution - Globular cluster metallicities

    Science.gov (United States)

    Malinie, G.; Hartmann, D. H.; Mathews, G. J.

    1991-01-01

    A new solution to the observed Galactic globular cluster metallicity distribution is proposed by considering inhomogeneous collapse of a centrally condensed proto-Galaxy. In contrast to the standard one-zone model, it is shown that, for inhomogeneous models, the metallicity distribution can be reproduced without the need to decrease the nucleosynthetic yield for metal-poor stars. Chemical evolution in free fall is calculated analytically. A hybrid hydroparticle code is developed to study the effect of supernova induced pressure.

  8. Chemical and biological evolution of (U-14C)phenol sorbed on activated carbon

    International Nuclear Information System (INIS)

    Methods describing the chemical and biological evolution of (U-14C)phenol adsorbed on activated carbon are given with or without the use of bacteria. Without bacteria, the (U-14C)phenol initially adsorbed is not removed from the carbon after adding a solution of unlabelled phenol through the column for eight days. With bacteria, the (U-14C)phenol initially present, is removed (60-70%) from activated carbon with a solution containing unlabelled phenol, nitrogen and phosphorus. (author)

  9. A new galactic chemical evolution model with dust: results for dwarf irregular galaxies and DLA systems

    CERN Document Server

    Gioannini, Lorenzo; Vladilo, Giovanni; Calura, Francesco

    2016-01-01

    We present a galactic chemical evolution model which adopts updated prescriptions for all the main processes governing the dust cycle. We follow in detail the evolution of the abundances of several chemical species (C, O, S, Si, Fe and Zn) in the gas and dust of a typical dwarf irregular galaxy. The dwarf irregular galaxy is assumed to evolve with a low but continuous level of star formation and experience galactic winds triggered by supernova explosions. We predict the evolution of the gas to dust ratio in such a galaxy and discuss critically the main processes involving dust, such as dust production by AGB stars and Type II SNe, destruction and accretion (gas condensation in clouds). We then apply our model to Damped Lyman-Alpha systems which are believed to be dwarf irregulars, as witnessed by their abundance patterns. Our main conclusions are: i) we can reproduce the observed gas to dust ratio in dwarf galaxies. ii) We find that the process of dust accretion plays a fundamental role in the evolution of du...

  10. Different-sized dust grains and the chemical evolution of protostellar objects

    Science.gov (United States)

    Kochina, O. V.; Wiebe, D. S.

    2014-04-01

    Results of modeling the chemical evolution of protostellar objects are presented. The models take into account the existence of different dust populations with distinct grain sizes, total mass fractions, and temperatures. In addition to "classical" dust grains, the models include an entirely different second dust population, with dust grain sizes of 30 Å and a higher temperature. Two chemical-evolution models are compared, one taking into account only classical dust and the other including both dust populations. The influence of a complex dust composition on the general evolution of the molecular contents of prestellar cores and the abundances of a number of chemical species is studied. At early evolutionary stages, differences are mainly determined by the modification changes in the photoprocesses' balance due to efficient UV absorption by the second population of dust grains and in collisional reactions with the dust grains. At late stages, distinctions between the models are also determined by the increasing dominance of additional reaction channels. The species that respond to the presence of small grains in different ways are separated into different groups. Allowing for the presence of small grains makes it possible to significantly lower the water abundance in the gas phase.

  11. Galactic chemical abundance evolution in the solar neighborhood up to the Iron peak

    CERN Document Server

    Alibes, A; Canal, R; Alibes, Andreu; Labay, Javier; Canal, Ramon

    2000-01-01

    We have developed a detailed standard chemical evolution model to study the evolution of all the chemical elements up to the iron peak in the solar vicinity. We consider that the Galaxy was formed through two episodes of exponentially decreasing infall, out of extragalactic gas. In a first infall episode, with a duration of $\\sim$ 1 Gyr, the halo and the thick disk were assembled out of primordial gas, while the thin disk formed in a second episode of infall of slightly enriched extragalactic gas, with much longer timescale. The model nicely reproduces the main observational constraints of the solar neighborhood, and the calculated elemental abundances at the time of the solar birth are in excellent agreement with the solar abundances. By the inclusion of metallicity dependent yields for the whole range of stellar masses we follow the evolution of 76 isotopes of all the chemical elements between hydrogen and zinc. Those results are confronted with a large and recent body of observational data, and we discuss ...

  12. The effects of stimulated star formation on the evolution of the galaxy. III - The chemical evolution of nonlinear systems

    Science.gov (United States)

    Shore, Steven N.; Ferrini, Federico; Palla, Francesco

    1987-01-01

    The evolution of models for star formation in galaxies with disk and halo components is discussed. Two phases for the halo (gas and stars) and three for the disk (including clouds) are used in these calculations. The star-formation history is followed using nonlinear phase-coupling models which completely determine the populations of the phases as a function of time. It is shown that for a wide range of parameters, including the effects of both spontaneous and stimulated star formation and mass exchange between the spatial components of the system, the observed chemical history of the galaxy can easily be obtained. The most sensitive parameter in the detailed metallicity and star-formation history for the system is the rate of return of gas to the diffuse phase upon stellar death.

  13. Effects of stimulated star formation on the evolution of the Galaxy. III. The chemical evolution of nonlinear systems

    International Nuclear Information System (INIS)

    The evolution of models for star formation in galaxies with disk and halo components is discussed. Two phases for the halo (gas and stars) and three for the disk (including clouds) are used in these calculations. The star-formation history is followed using nonlinear phase-coupling models which completely determine the populations of the phases as a function of time. It is shown that for a wide range of parameters, including the effects of both spontaneous and stimulated star formation and mass exchange between the spatial components of the system, the observed chemical history of the galaxy can easily be obtained. The most sensitive parameter in the detailed metallicity and star-formation history for the system is the rate of return of gas to the diffuse phase upon stellar death. 36 references

  14. The role of magma mixing in the evolution of high-K calc-alkaline granitoid suites: in situ trace element and Sr-Nd-Hf isotope constraints

    Science.gov (United States)

    Laurent, Oscar; Zeh, Armin; Gerdes, Axel; Slaby, Ewa; Villaros, Arnaud

    2015-04-01

    The so-called "I-type", high-K calc-alkaline granitoids are often considered as "hybrid" in origin, i.e. involving both mantle and crustal components in their petrogenesis. The interactions between both components either take place (1) at mantle levels (i.e. enriched mantle source); (2) at emplacement levels (i.e. crustal contamination and/or magma mixing with crustal melts) or (3) both. Magma mixing is, in particular, frequently invoked to explain the compositional range of high-K calc-alkaline granitoid suites, especially phases of intermediate composition (SiO2 = 60-65 wt.%) such as quartz-diorites or granodiorites. We investigated the role of magma mixing in the origin of such rocks using elemental and isotope (Sr-Nd-Hf) chemistry of magmatic minerals (plagioclase, zircon, apatite, titanite, epidote), measured in situ by LA-(MC-)ICPMS, allowing a much greater spatial resolution than classical whole-rock geochemistry. We focused on a suite of late-Archaean (2.69 Ga-old) high-K, calc-alkaline granitoids from the Pietersburg block, northern Kaapvaal Craton (South Africa): the Mashashane, Matlala, Matok and Moletsi plutons. Those plutons range from diorites to monzogranites, emplaced at different crustal levels but all within a relatively short time span and showing evidence for interactions (mingling), both at the outcrop and mineral scale. Hf isotope data on zircon confirm that all rocks are cogenetic (identical ɛHf(t)), but trace element and Sr isotopes in plagioclase point to the involvement of several components in their petrogenesis, at different stages of the magma evolution. The most mafic rocks (diorites) derive from the interaction, at mantle levels, between depleted peridotite and a sedimentary component of quartzofeldspathic nature. The mineral chemistry of more felsic rocks can be explained by (1) differentiation from the diorite magmas through Amp + Plag fractionation; (2) interactions with magmas derived from melting of local crust (tonalites

  15. The chemical evolution of the Galactic Bulge seen through micro-lensing events

    Directory of Open Access Journals (Sweden)

    Lucatello S.

    2012-02-01

    Full Text Available Galactic bulges are central to understanding galaxy formation and evolution. Here we report on recent studies using micro-lensing events to obtain spectra of high resolution and moderately high signal-to-noise ratios of dwarf stars in the Galactic bulge. Normally this is not feasible for the faint turn-off stars in the Galactic bulge, but micro-lensing offers this possibility. Elemental abundance trends in the Galactic bulge as traced by dwarf stars are very similar to those seen for dwarf stars in the solar neighbourhood. We discuss the implications of the ages and metallicity distribution function derived for the micro-lensed dwarf stars in the Galactic bulge.

  16. Seasonal variations in fate and removal of trace organic chemical contaminants while operating a full-scale membrane bioreactor.

    Science.gov (United States)

    Trinh, Trang; van den Akker, Ben; Coleman, Heather M; Stuetz, Richard M; Drewes, Jörg E; Le-Clech, Pierre; Khan, Stuart J

    2016-04-15

    Trace organic chemical (TrOC) contaminants are of concern for finished water from water recycling schemes because of their potential adverse environmental and public health effects. Understanding the impacts of seasonal variations on fate and removal of TrOCs is important for proper operation, risk assessment and management of treatment systems for water recycling such as membrane bioreactors (MBRs). Accordingly, this study investigated the fate and removal of a wide range of TrOCs through a full-scale MBR plant during summer and winter seasons. TrOCs included 12 steroidal hormones, 3 xeno-estrogens, 2 pesticides and 23 pharmaceuticals and personal care products. Seasonal differences in the mechanisms responsible for removing some of the TrOCs were evident. In particular the contribution of biotransformation and biomass adsorption to the overall removal of estrone, bisphenol A, 17β-estradiol and triclosan were consistently different between the two seasons. Substantially higher percentage removal via biotransformation was observed during the summer sampling period, which compensated for a reduction in removal attributed to biomass adsorption. The opposite was observed during winter, where the contribution of biotransformation to the overall removal of these TrOCs had decreased, which was offset by an improvement in biomass adsorption. The exact mechanisms responsible for this shift are unknown, however are likely to be temperature related as warmer temperatures can lower sorption efficiency, yet enhance biotransformation of these TrOCs. PMID:26815294

  17. Investigation of Chemical and Physical Changes to Bioapatite During Fossilization Using Trace Element Geochemistry, Infrared Spectroscopy and Stable Isotopes

    Science.gov (United States)

    Suarez, C. A.; Kohn, M. J.

    2013-12-01

    Bioapatite in the form of vertebrate bone can be used for a wide variety of paleo-proxies, from determination of ancient diet to the isotopic composition of meteoric water. Bioapatite alteration during diagenesis is a constant barrier to the use of fossil bone as a paleo-proxy. To elucidate the physical and chemical alteration of bone apatite during fossilization, we analyzed an assortment of fossil bones of different ages for trace elements, using LA-ICP-MS, stable isotopes, and reflected IR spectroscopy. One set of fossil bones from the Pleistocene of Idaho show a diffusion recrystallization profile, however, rare earth element (REE) profiles indicate diffusion adsorption. This suggests that REE diffusion is controlled by changing (namely decreasing) boundary conditions (i.e. decreasing concentration of REE in surrounding pore fluids). Reflected IR analysis along this concentration profile reveal that areas high in U have lost type A carbonate from the crystal structure in addition to water and organics. Stable isotopic analysis of carbon and oxygen will determine what, if any, change in the isotopic composition of the carbonate component of apatite has occurred do to the diffusion and recrystallization process. Analysis of much older bone from the Cretaceous of China reveal shallow REE and U concentration profiles and very uniform reflected IR spectra with a significant loss of type A carbonate throughout the entire bone cortex. Analysis of stable isotopes through the bone cortex will be compared to the stable isotopes collected from the Pleistocene of Idaho.

  18. Development of a predictive framework to assess the removal of trace organic chemicals by anaerobic membrane bioreactor.

    Science.gov (United States)

    Wijekoon, Kaushalya C; McDonald, James A; Khan, Stuart J; Hai, Faisal I; Price, William E; Nghiem, Long D

    2015-01-01

    This study aims to develop a predictive framework to assess the removal and fate of trace organic chemicals (TrOCs) during wastewater treatment by anaerobic membrane bioreactor (AnMBR). The fate of 27 TrOCs in both the liquid and sludge phases during AnMBR treatment was systematically investigated. The results demonstrate a relationship between hydrophobicity and specific molecular features of TrOCs and their removal efficiency. These molecular features include the presence of electron withdrawing groups (EWGs) or donating groups (EDGs), especially those containing nitrogen and sulphur. All seven hydrophobic contaminants were well removed (>70%) by AnMBR treatment. Most hydrophilic TrOCs containing EDGs were also well removed (>70%). In contrast, hydrophilic TrOCs containing EWGs were mostly poorly removed and could accumulate in the sludge phase. The removal of several nitrogen/sulphur bearing TrOCs (e.g., linuron and caffeine) by AnMBR was higher than that by aerobic treatment, possibly due to nitrogen or sulphur reducing bacteria. PMID:25918032

  19. The Role of Dissolved Organic Carbon and Preadaptation in the Biotransformation of Trace Organic Chemicals during Aquifer Recharge and Recovery

    KAUST Repository

    Ouf, Mohamed

    2012-05-01

    Aquifer recharge and recovery (ARR) is a low-cost and environmentally-friendly treatment technology which uses conventionally treated wastewater effluent for groundwater recharge and subsequent recovery for agricultural, industrial or drinking water uses. This study investigated the effect of different dissolved organic carbon (DOC) composition in wastewater effluent on the fate of trace organic chemicals (TOrCs) during ARR. Four biologically active columns were setup receiving synthetic wastewater effluent with varying DOC compositions. The difference in DOC composition triggered variations in the microbial community’s diversity and hence its ability to degrade TOrCs. It was found that the presence of protein-like DOC enhances the removal of DOC in comparison with the presence of humic-like DOC. On the other hand, the presence of humic-like DOC, which is more difficult to degrade, improved the removal of several degradable TOrCs. Other column experiments were also carried out to investigate the role of previous and continuous exposure to TOrCs in their removal. The use of soil pre-exposed to low concentrations of TOrCs and DOC provided better removal of both DOC and TOrCs. The findings of this study suggest that the presence of more humic-like DOC in the effluent enhances the biotransformation of TOrCs during ARR. In addition, long exposure to both DOC and TOrCs increases the degree of their removal over time

  20. Chemical evolution of protoplanetary disks - the effects of viscous accretion, turbulent mixing and disk winds

    CERN Document Server

    Heinzeller, Dominikus; Walsh, Catherine; Millar, Tom J

    2011-01-01

    We calculate the chemical evolution of protoplanetary disks considering radial viscous accretion, vertical turbulent mixing and vertical disk winds. We study the effects on the disk chemical structure when different models for the formation of molecular hydrogen on dust grains are adopted. Our gas-phase chemistry is extracted from the UMIST Database for Astrochemistry (Rate06) to which we have added detailed gas-grain interactions. We use our chemical model results to generate synthetic near- and mid-infrared LTE line emission spectra and compare these with recent Spitzer observations. Our results show that if H2 formation on warm grains is taken into consideration, the H2O and OH abundances in the disk surface increase significantly. We find the radial accretion flow strongly influences the molecular abundances, with those in the cold midplane layers particularly affected. On the other hand, we show that diffusive turbulent mixing affects the disk chemistry in the warm molecular layers, influencing the line ...

  1. Chemical Pollution and Evolution of Massive Starbursts: Cleaning up the Environment in Star-Forming Galaxies

    Science.gov (United States)

    Kobulnicky, C.

    1996-12-01

    I present the results of a research program seeking to characterize the impact of massive star-clusters on the chemical and dynamical evolution of metal-poor, irregular and blue compact galaxies. The evolution of high mass stars is thought to contribute the bulk of heavy element enrichment in the interstellar medium, especially alpha -process elements like O, Si, etc. Yet, in actively star-forming galaxies, localized chemical inhomogeneities are seldom observed. Spatially-resolved optical and ultraviolet spectroscopy from the Hubble Space Telescope and ground-based observatories is used to search for chemical enrichment in the vicinity of young star clusters in nearby galaxies. VLA aperture synthesis maps are used to examine the neutral hydrogen content, dynamics, and local environment of the sample galaxies. Despite the spread in evolutionary state of the starbursts determined by the EW of Balmer emission lines and the radio continuum spectral index, few instances of localized enrichment are found. In light of these data, the ``instantaneous enrichment'' scenario for extragalactic HII regions appears less probable than one which operates on long timescales and global spatial scales. The results are consistent with the idea that starburst driven winds expel freshly synthesized metals in a hot 10(6) K phase into the halos of galaxies where they cool, condense into globules, and mix homogeneously with the rest of the galaxy on long (dynamical) timescales. The C/O and N/O ratios of the galaxies are used as new tools for measuring the recent star formation history. Implications for chemical evolution of galaxies both locally and cosmologically are developed.

  2. ALMA-resolved salt emission traces the chemical footprint and inner wind morphology of VY Canis Majoris

    Science.gov (United States)

    Decin, L.; Richards, A. M. S.; Millar, T. J.; Baudry, A.; De Beck, E.; Homan, W.; Smith, N.; Van de Sande, M.; Walsh, C.

    2016-07-01

    Context. At the end of their lives, most stars lose a significant amount of mass through a stellar wind. The specific physical and chemical circumstances that lead to the onset of the stellar wind for cool luminous stars are not yet understood. Complex geometrical morphologies in the circumstellar envelopes prove that various dynamical and chemical processes are interlocked and that their relative contributions are not easy to disentangle. Aims: We aim to study the inner-wind structure (Rdensity structure in the inner envelope and to examine the chemical interaction between gas and dust species. Methods: We analyse high spatial resolution (~0.̋24×0.̋13) ALMA science verification (SV) data in band 7, in which four thermal emission lines of gaseous sodium chloride (NaCl) are present at high signal-to-noise ratio. Results: For the first time, the NaCl emission in the inner wind region of VY CMa is spatially resolved. The ALMA observations reveal the contribution of up to four different spatial regions. The NaCl emission pattern is different compared to the dust continuum and TiO2 emission already analysed from the ALMA SV data. The emission can be reconciled with an axisymmetric geometry, where the lower density polar/rotation axis has a position angle of ~50° measured from north to east. However, this picture cannot capture the full morphological diversity, and discrete mass ejection events need to be invoked to explain localized higher-density regions. The velocity traced by the gaseous NaCl line profiles is significantly lower than the average wind terminal velocity, and much slower than some of the fastest mass ejections, signalling a wide range of characteristic speeds for the mass loss. Gaseous NaCl is detected far beyond the main dust condensation region. Realising the refractory nature of this metal halide, this hints at a chemical process that prevents all NaCl from condensing onto dust grains. We show that in the case of the ratio of the surface binding

  3. Speciation of trace elements in biological samples by nuclear analytical and related techniques coupled with chemical and biochemical separation

    International Nuclear Information System (INIS)

    In the past, most analytical problems relating to biological systems were addressed by measuring the total concentrations of elements. Now there is increasing interest of the importance of their chemical forms, in which an element is present in biological systems, e.g., the oxidation state, the binding state with macromolecules, or even the molecular structure. The biological effects of chromium, which is classified as an essential nutrient, are dependent upon its oxidation. state. In general, trivalent chromium is biochemically active, whereas hexavalent chromium is considered to be toxic. Mercury is one of serious environmental persistent pollutants. However, organic forms of mercury are known to possess much higher toxicity than inorganic mercury. Therefore, information on speciation is critically required in order to better understanding of their bioavailability, metabolism, transformation, and toxicity in vivo. Recently, chemical speciation of selenium, mercury, copper, zinc, iron, and so on, has been investigated by INAA, ICP-MS, XRF, EXAFS and related techniques combined with chemical and biochemical separation (extraction, chromatography, gel electrophoresis, etc.). INAA, XRF, and ICP-MS have superior advantages in aspect of multielemental analysis with high accuracy and sensitivity, which render the possibility of analyzing various elements of interest simultaneously. These offline or online techniques have been flexibly applied to different biological matrixes, such as human hair, serum, urine, various tissues and organs in our researches. In addition, EXAFS provides structural information about the moiety of metal centers up to a distance of approximately 4-5 Anstrom. For instance, hepatocellular carcinoma (HCC) is one of the most common cancers worldwide. Imbalance of elements, such as Se, Zn, Fe, Cu, Cd, Ca, etc., has been found in the whole blood or serum of patients with HCC. We found that the profiles of Se, Cd, Fe, Zn and Cu-containing proteins

  4. Beverton-Holt discrete pest management models with pulsed chemical control and evolution of pesticide resistance

    Science.gov (United States)

    Liang, Juhua; Tang, Sanyi; Cheke, Robert A.

    2016-07-01

    Pest resistance to pesticides is usually managed by switching between different types of pesticides. The optimal switching time, which depends on the dynamics of the pest population and on the evolution of the pesticide resistance, is critical. Here we address how the dynamic complexity of the pest population, the development of resistance and the spraying frequency of pulsed chemical control affect optimal switching strategies given different control aims. To do this, we developed novel discrete pest population growth models with both impulsive chemical control and the evolution of pesticide resistance. Strong and weak threshold conditions which guarantee the extinction of the pest population, based on the threshold values of the analytical formula for the optimal switching time, were derived. Further, we addressed switching strategies in the light of chosen economic injury levels. Moreover, the effects of the complex dynamical behaviour of the pest population on the pesticide switching times were also studied. The pesticide application period, the evolution of pesticide resistance and the dynamic complexity of the pest population may result in complex outbreak patterns, with consequent effects on the pesticide switching strategies.

  5. Inflow, Outflow, Yields, and Stellar Population Mixing in Chemical Evolution Models

    CERN Document Server

    Andrews, Brett H; Schönrich, Ralph; Johnson, Jennifer A

    2016-01-01

    Chemical evolution models are powerful tools for interpreting stellar abundance surveys and understanding galaxy evolution. However, their predictions depend heavily on the treatment of inflow, outflow, star formation efficiency (SFE), the IMF, the SNIa delay time distribution, stellar yields, and mixing of stellar populations. Using flexCE, a new, flexible one-zone chemical evolution code, we investigate the effects of individual parameters and the trade-offs between them. Two of the most important parameters are the SFE and outflow mass-loading parameter, which shift the knee in [O/Fe]-[Fe/H] and the equilibrium abundances, respectively. One-zone models with simple star formation histories follow narrow tracks in [O/Fe]-[Fe/H] that do not match the observed bimodality in this plane. A mix of one-zone models with variations in their inflow timescales and outflow mass-loading parameters, as motivated by the inside-out galaxy formation scenario with radial mixing, reproduces the high- and low-alpha sequences b...

  6. Time Evolution of Thermo-Mechanically and Chemically Coupled Magma Chambers

    Science.gov (United States)

    Ozimek, C.; Karlstrom, L.; Erickson, B. A.

    2015-12-01

    Complexity in the volcanic eruption cycle reflects time variation both of magma inputs to the crustal plumbing system and of crustal melt storage zones (magma chambers). These data include timing and volumes of eruptions, as well as erupted compositions. Thus models must take into account the coupled nature of physical attributes. Here we combine a thermo-mechanical model for magma chamber growth and pressurization with a chemical model for evolving chamber compositions, in the limit of rapid mixing, to study controls on eruption cycles and compositions through time. We solve for the mechanical evolution of a 1D magma chamber containing melt, crystals and bubbles, in a thermally evolving and viscoelastic crust. This pressure and temperature evolution constrains the input values of a chemical box model (Lee et al., 2013) that accounts for recharge, eruption, assimilation and fractional crystallization (REAFC) within the chamber. We plan to study the influence of melt supply, input composition, and chamber depth eruptive fluxes and compositions. Ultimately we will explore multiple chambers coupled by elastic-walled dikes. We expect that this framework will facilitate self-consistent inversion of long-term eruptive histories in terms of magma transport physics. Lee, C.-T. A., Lee, T.-C., Wu, C.-T., 2013. Modeling the compositional evolution of recharging, evacuating, and fractionating (REFC) magma chambers: Implications for differentiationof arc magmas. Geochemica Cosmochimica Acta, http://dx.doi.org/10.1016/j.gca.2013.08.009.

  7. Conference on chemical evolution and the origin of life: Self-organization of the macromolecules of life

    International Nuclear Information System (INIS)

    The formation of biomolecules was a necessary step in the evolution of life on earth. This interdisciplinary conference emphasized the role of replication in processes of self-organization of biological macromolecules. The present document contains abstracts of the 26 contributions to the conference on chemical evolution. The individual contributions have been indexed separately for the database

  8. Temporal evolution of the chemical structure during the pattern transfer by ion-beam sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Ha, N.-B.; Jeong, S.; Yu, S.; Ihm, H.-I.; Kim, J.-S.

    2015-01-01

    Highlights: • Chemical analyses of the individual nano structures simultaneously with the investigation of their morphological evolution were performed. • Degradation of the transferred pattern starts before the overlayer is fully removed. • The chemical analysis reveals the severe reduction of the sputter yield of the material forming the overlayer near the interface due to the compound formation, requesting caution in the practice of the pattern transfer. - Abstract: Ru films patterned by ion-beam sputtering (IBS) serve as sacrificial masks for the transfer of the patterns to Si(1 0 0) and metallic glass substrates by continued IBS. Under the same sputter condition, however, both bare substrates remain featureless. Chemical analyses of the individual nano structures simultaneously with the investigation of their morphological evolution reveal that the pattern transfer, despite its apparent success, suffers from premature degradation before the mask is fully removed by IBS. Moreover, the residue of the mask or Ru atoms stubbornly remains near the surface, resulting in unintended doping or alloying of both patterned substrates.

  9. Temporal evolution of the chemical structure during the pattern transfer by ion-beam sputtering

    International Nuclear Information System (INIS)

    Highlights: • Chemical analyses of the individual nano structures simultaneously with the investigation of their morphological evolution were performed. • Degradation of the transferred pattern starts before the overlayer is fully removed. • The chemical analysis reveals the severe reduction of the sputter yield of the material forming the overlayer near the interface due to the compound formation, requesting caution in the practice of the pattern transfer. - Abstract: Ru films patterned by ion-beam sputtering (IBS) serve as sacrificial masks for the transfer of the patterns to Si(1 0 0) and metallic glass substrates by continued IBS. Under the same sputter condition, however, both bare substrates remain featureless. Chemical analyses of the individual nano structures simultaneously with the investigation of their morphological evolution reveal that the pattern transfer, despite its apparent success, suffers from premature degradation before the mask is fully removed by IBS. Moreover, the residue of the mask or Ru atoms stubbornly remains near the surface, resulting in unintended doping or alloying of both patterned substrates

  10. Planet signatures and effect of the chemical evolution of the Galactic thin-disk stars

    CERN Document Server

    Spina, Lorenzo; Ramírez, Ivan

    2016-01-01

    Context: Studies based on high-precision abundance determinations revealed that chemical patterns of solar twins are characterised by the correlation between the differential abundances relative to the Sun and the condensation temperatures (Tc) of the elements. It has been suggested that the origin of this relation is related to the chemical evolution of the Galactic disk, but other processes, associated with the presence of planets around stars, might also be involved. Aims: We analyse HIRES spectra of 14 solar twins and the Sun to provide new insights on the mechanisms that can determine the relation between [X/H] and Tc. Methods: Our spectroscopic analysis produced stellar parameters (Teff, log g, [Fe/H], and $\\xi$), ages, masses, and abundances of 22 elements (C, O, Na, Mg, Al, Si, S, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sr, Y, and Ba). We used these determinations to place new constraints on the chemical evolution of the Galactic disk and to verify whether this process alone can explain the diff...

  11. Surfactant-controlled damage evolution during chemical mechanical planarization of nanoporous films

    International Nuclear Information System (INIS)

    The integration of nanoporous organosilicate thin films involving chemical mechanical planarization (CMP) is a significant challenge due the evolution of defects in the films during CMP in the form of cracking and delamination. This study shows that small changes in CMP electrolyte chemistry and surfactant additions can have dramatic effects on crack growth rates in the films. Crack growth rates were sensitive to the type of electrolyte and decreased in the presence of electrolytes that caused crack tip blunting. Growth rates were also sensitive to nonionic surfactant additions where molecular structure and weight were demonstrated to be important variables. An optimized blend of surfactants and electrolytes can significantly retard defect evolution due to molecular bridging. Surfactant self-assembly and resulting molecular bridging were characterized by in situ atomic force microscopy and used to quantify the molecular bridging observed.

  12. EXTREMELY METAL-POOR STARS AND A HIERARCHICAL CHEMICAL EVOLUTION MODEL

    International Nuclear Information System (INIS)

    Early phases of the chemical evolution of the Galaxy and formation history of extremely metal-poor (EMP) stars are investigated using hierarchical galaxy formation models. We build a merger tree of the Galaxy according to the extended Press-Schechter theory. We follow the chemical evolution along the tree and compare the model results to the metallicity distribution function and abundance ratio distribution of the Milky Way halo. We adopt three different initial mass functions (IMFs). In a previous study, we argued that the typical mass, Mmd, of EMP stars should be high, Mmd ∼ 10 Msun, based on studies of binary origin carbon-rich EMP stars. In this study, we show that only the high-mass IMF can explain an observed small number of EMP stars. For relative element abundances, the high-mass IMF and the Salpeter IMF predict similar distributions. We also investigate dependence on nucleosynthetic yields of supernovae (SNe). The theoretical SN yields by Kobayashi et al. and Chieffi and Limongi show reasonable agreement with observations for α-elements. Our model predicts a significant scatter of element abundances at [Fe/H] < -3. We adopted the stellar yields derived in the work of Francois et al., which produce the best agreement between the observational data and the one-zone chemical evolution model. Their yields well reproduce a trend of the averaged abundances of EMP stars but predict much larger scatter than do the observations. The model with hypernovae predicts Zn abundance, in agreement with the observations, but other models predict lower [Zn/Fe]. Ejecta from the hypernovae with large explosion energy is mixed in large mass and decreases the scatter of the element abundances.

  13. Role of primary substrate composition and concentration on attenuation of trace organic chemicals in managed aquifer recharge systems

    KAUST Repository

    Alidina, Mazahirali

    2014-11-01

    This study was undertaken to investigate the role of primary substrate composition and concentration on the attenuation of biodegradable emerging trace organic chemicals (TOrCs) in simulated managed aquifer recharge (MAR) systems. Four sets of soil columns were established in the laboratory, each receiving synthetic feed solutions comprising different ratios and concentrations of peptone-yeast and humic acid as the primary substrate to investigate the effect on removal of six TOrCs (atenolol, caffeine, diclofenac, gemfibrozil, primidone, and trimethoprim). Based on abiotic control experiments, adsorption was not identified as a significant attenuation mechanism for primidone, gemfibrozil and diclofenac. Caffeine, atenolol and trimethoprim displayed initial adsorptive losses, however, adsorption coefficients derived from batch tests confirmed that adsorption was limited and in the long-term experiment, biodegradation was the dominant attenuation process. Within a travel time of 16h, caffeine - an easily degradable compound exhibited removal exceeding 75% regardless of composition or concentration of the primary substrate. Primidone - a poorly degradable compound, showed no removal in any column regardless of the nature of the primary substrate. The composition and concentration of the primary substrate, however, had an effect on attenuation of moderately degradable TOrCs, such as atenolol, gemfibrozil and diclofenac, with the primary substrate composition seeming to have a larger impact on TOrC attenuation than its concentration. When the primary substrate consisted mainly of refractory substrate (humic acid), higher removal of the moderately degradable TOrCs was observed. The microbial communities in the columns receiving more refractory carbon, were noted to be more diverse and hence likely able to express a wider range of enzymes, which were more suitable for TOrC transformation. The effect of the primary substrate on microbial community composition, diversity

  14. Lithospheric evolution of the Northern Arabian Shield: Chemical and isotopic evidence from basalts, xenoliths and granites

    Science.gov (United States)

    Stein, M.

    1988-01-01

    The evolution of the upper-mantle and the lower-crust (the conteinental lithosphere), is the area of Israel and Sinai was studied, using the chemical composition and the Nd-Sr isotopic systematics from mantle and crustal nodules, their host basalts, and granites. The magmatism and the metasomatism making the lithosphere are related to uprise of mantle diapirs in the uppermost mantle of the area. These diapirs heated the base of the lithosphere, eroded, and replaced it with new hot material. It caused a domal uplift of the lithosphere (and the crust). The doming resulted in tensional stresses that in turn might develop transport channels for the basalt.

  15. The Star Formation & Chemical Evolution History of the Fornax Dwarf Spheroidal Galaxy

    CERN Document Server

    de Boer, T J L; Hill, V; Saha, A; Olszewski, E W; Mateo, M; Starkenburg, E; Battaglia, G; Walker, M G

    2012-01-01

    We present deep photometry in the B,V and I filters from CTIO/MOSAIC for about 270.000 stars in the Fornax dwarf Spheroidal galaxy, out to a radius of r_ell\\sim0.8 degrees. By combining the accurately calibrated photometry with the spectroscopic metallicity distributions of individual Red Giant Branch stars we obtain the detailed star formation and chemical evolution history of Fornax. Fornax is dominated by intermediate age (1-10 Gyr) stellar populations, but also includes ancient (10-14 Gyr), and young (-1.5 dex, with a clear trend in age.

  16. Probing the Mass Assembly and Chemical Evolution of High-z Galaxies with MASSIV

    CERN Document Server

    Contini, T; Queyrel, J; Vergani, D; Tasca, L; Amram, P; Garilli, B; Kissler-Patig, M; Fèvre, O Le; Moultaka, J; Paioro, L; Tresse, L; Bournaud, F; Perez-Montero, E

    2011-01-01

    Understanding the different mechanisms of galaxy assembly at various cosmic epochs is a key issue for galaxy evolution and formation models. We present MASSIV (Mass Assembly Survey with SINFONI in VVDS) in this context, an on-going survey with VLT/SINFONI aiming to probe the kinematics and chemical abundances of a unique sample of 84 star-forming galaxies selected in the redshift range z ~ 1-2. This large sample, spanning a wide range of stellar masses, is unique at these high redshifts and statistically representative of the overall galaxy population. In this paper, we give an overview of the MASSIV survey and then focus on the spatially-resolved chemical properties of high-z galaxies and their implication on the process of galaxy assembly.

  17. Structural Evolution of SiC Films During Plasma-Assisted Chemical Vapour Deposition

    International Nuclear Information System (INIS)

    Evolution of chemical bonding configurations for the films deposited from hexamethyldisiloxane (HMDSO) diluted with H2 during plasma assisted chemical vapour deposition is investigated. In the experiment a small amount of CH4 was added to adjust the plasma environment and modify the structure of the deposited films. The measurements of Raman spectroscopy and X-ray diffraction (XRD) revealed the production of 6H-SiC embedded in the amorphous matrix without the input of CH4. As CH4 was introduced into the deposition reaction, the transition of 6H-SiC to cubic SiC in the films took place, and also the film surfaces changed from a structure of ellipsoids to cauliflower-like shapes. With a further increase of CH4 in the flow ratio, the obtained films varied from Si-C bonding dominant to a sp2/sp3 carbon-rich composition. (low temperature plasma)

  18. The partition behavior and the chemical speciation of selected trace elements in a typical coal sample during pyrolysis / Tivo Bafana Hlatshwayo

    OpenAIRE

    Hlatshwayo, Tivo Bafana

    2008-01-01

    Sasol is by far the world's leading company in upgrading of low-grade coal into high value chemicals and fuels. Such plants also utilise fine particles or pulverised coal in the combustion process to generate steam and electricity for their processes. Certain trace elements released from coal during utilisation may be of environmental concern. From the literature findings it appears that the elements of interest are mercury, arsenic and selenium due to their potential health hazard and as...

  19. Estimated total emissions of trace gases from the Canberra wildfires of 2003: a new method using satellite measurements of aerosol optical depth and the MOZART chemical transport model

    OpenAIRE

    Paton-Walsh, C.; L. K. Emmons; S. R. Wilson

    2010-01-01

    In this paper we describe a new method for estimating trace gas emissions from large vegetation fires using measurements of aerosol optical depth from the MODIS instruments onboard NASA's Terra and Aqua satellites, combined with the atmospheric chemical transport model MOZART. The model allows for an estimate of double counting of enhanced levels of aerosol optical depth in consecutive satellite overpasses. Using this method we infer an estimated total emission of 10±3 Tg of c...

  20. Estimated total emissions of trace gases from the Canberra Wildfires of 2003: a new method using satellite measurements of aerosol optical depth & the MOZART chemical transport model

    OpenAIRE

    Paton-Walsh, C.; L. K. Emmons; S. R. Wilson

    2010-01-01

    In this paper we describe a new method for estimating trace gas emissions from large vegetation fires using satellite measurements of aerosol optical depth (AOD) at 550 nm, combined with an atmospheric chemical transport model. The method uses a threshold value to screen out normal levels of AOD that may be caused by raised dust, sea salt aerosols or diffuse smoke transported from distant fires. Using this method we infer an estimated total emission of 15±5 Tg of carbon monoxide, 0...

  1. Chemical versus temporal controls on the evolution of tholeiitic and calc-alkaline magmas at two volcanoes in the Alaska-Aleutian arc

    Science.gov (United States)

    George, R.; Turner, S.; Hawkesworth, C.; Bacon, C.R.; Nye, C.; Stelling, P.; Dreher, S.

    2004-01-01

    The Alaska-Aleutian island arc is well known for erupting both tholeiitic and calc-alkaline magmas. To investigate the relative roles of chemical and temporal controls in generating these contrasting liquid lines of descent we have undertaken a detailed study of tholeiitic lavas from Akutan volcano in the oceanic A1eutian arc and calc-alkaline products from Aniakchak volcano on the continental A1askan Peninsula. The differences do not appear to be linked to parental magma composition. The Akutan lavas can be explained by closed-system magmatic evolution, whereas curvilinear trace element trends and a large range in 87 Sr/86 Sr isotope ratios in the Aniakchak data appear to require the combined effects of fractional crystallization, assimilation and magma mixing. Both magmatic suites preserve a similar range in 226 Ra-230 Th disequilibria, which suggests that the time scale of crustal residence of magmas beneath both these volcanoes was similar, and of the order of several thousand years. This is consistent with numerical estimates of the time scales for crystallization caused by cooling in convecting crustal magma chambers. During that time interval the tholeiitic Akutan magmas underwent restricted, closed-system, compositional evolution. In contrast, the calc-alkaline magmas beneath Aniakchak volcano underwent significant open-system compositional evolution. Combining these results with data from other studies we suggest that differentiation is faster in calc-alkaline and potassic magma series than in tholeiitic series, owing to a combination of greater extents of assimilation, magma mixing and cooling.

  2. Molybdenum and technetium cycle in the environment. Physical chemical evolution and mobility in soils and plants

    International Nuclear Information System (INIS)

    Molybdenum 99 and technetium 99 from liquid discharges of base nuclear installations (reactors, reprocessing plants, UF6 treatment, etc.) can reach the environment via irrigation waters and atmospheric deposits. The contribution to the soil by irrigation results in a physical-chemical transformation, the results of which, in the case of technetium 99, could be volatilization via microbes. The changes in the physical-chemical forms of technetium in different soils reveals the preponderant effect of the initial amount deposited. The determination of the rate of technetium and molybdenum assimilation shows a certain similarity in behaviour; yet the localization of these isotopes is not the same. The transfer of molybdenum and technetium via the root system is different in its intensity; this is mainly due to different physical-chemical forms. Finally, each isotope has an optimum assimilation threshold and a toxicity threshold. The study of the physical-chemical evolution and the mobility in the soil-plant-water table system of these two isotopes shows a new aspect with respect to certain transfer channels to the human being

  3. Functional evolution of the trace amine associated receptors in mammals and the loss of TAAR1 in dogs

    Directory of Open Access Journals (Sweden)

    Westmoreland Susan V

    2010-02-01

    Full Text Available Abstract Background The trace amine associated receptor family is a diverse array of GPCRs that arose before the first vertebrates walked on land. Trace amine associated receptor 1 (TAAR1 is a wide spectrum aminergic receptor that acts as a modulator in brain monoaminergic systems. Other trace amine associated receptors appear to relate to environmental perception and show a birth-and-death pattern in mammals similar to olfactory receptors. Results Across mammals, avians, and amphibians, the TAAR1 gene is intact and appears to be under strong purifying selection based on rates of amino acid fixation compared to neutral mutations. We have found that in dogs it has become a pseudogene. Our analyses using a comparative genetics approach revealed that the pseudogenization event predated the emergence of the Canini tribe rather than being coincident with canine domestication. By assessing the effects of the TAAR1 agonist β-phenylethylamine on [3H]dopamine uptake in canine striatal synaptosomes and comparing the degree and pattern of uptake inhibition to that seen in other mammals, including TAAR1 knockout mice, wild type mice and rhesus monkey, we found that the TAAR1 pseudogenization event resulted in an uncompensated loss of function. Conclusion The gene family has seen expansions among certain mammals, notably rodents, and reductions in others, including primates. By placing the trace amine associated receptors in an evolutionary context we can better understand their function and their potential associations with behavior and neurological disease.

  4. Analysis of the chemical evolution of the Galactic disk via dynamical simulations of the open cluster system

    OpenAIRE

    Tecce, T. E.; Pellizza, L. J.; Piatti, A. E.

    2006-01-01

    For several decades now, open clusters have been used to study the structure and chemical evolution of the disk of our Galaxy. Due to the fact that their ages and metallicities can be determined with relatively good precision, and since they can be observed even at great distances, they are excellent tracers of the variations in the abundance of heavy chemical elements with age and position in the Galactic disk. In the present work we analyze the star formation history and the chemical evolut...

  5. a Baseline Study of Physico-Chemical Parameters and Trace Metals in Waters of Manakudy, South-West Coast of India

    Science.gov (United States)

    Subramanian, M.; Muthumanikkam, J.

    2013-05-01

    The transport of trace metals from the land to ocean has a number of different routes and efficiencies. The sources of toxic elements into the rivers to be debouched into the sea through estuaries are either weathered naturally from the soils and rocks or introduced anthropogenically from point or non-point sources, in labile form or in particulate form. However, recent studies indicate that the transport of trace elements to the aquatic environment is much more complex than what has been thought. The chemistry and ecology of an estuarine system are entirely different from the fluvial as well as the marine system. Estuarine environment is characterized by a constantly changing mixture of salt and freshwater. In the present study area Manakudy estuary is situated about 8 kilometres north west of Kanyakumari (Latitude N 08 05 21.8 and Longitude E 077 29 03.7). To gain a better understanding of the geochemical behavior of physico-chemical parameters and trace elements in the estuary and to examine variations in associated chemical changes, 20 water samples were collected throughout the Manakudy estuary, a minor river in south-western India. These samples, collected in typical dry season during 2012, were analyzed for physico-chemical parameters, dissolved major and trace elements. Our results show that dissolved Na, Mg, Ca and Cl behave conservatively along the salinity gradient. The concentration of nutrients is normal and they are due to the higher organic activity in soils as well as faster rates of chemical weathering reaction in the source region. The concentration of major ions is due to tidal influence and it increases with salinity and the nutrients do behave non-conservatively due to biogenic removal. The conservative behaviour of the trace metals with salinity has been strongly affected by the introduction of these metals by external sources. Even though the trace metals in the contaminated water have been removed and incorporated in sediments due to

  6. Chemical evolution and the galactic habitable zone of M31 (the Andromeda Galaxy)

    CERN Document Server

    Carigi, L; Garcia-Rojas, J

    2012-01-01

    We have computed the Galactic Habitable Zones (GHZs) of the Andromeda galaxy (M31) based mainly, but not exclusively, on the probability of terrestrial planet formation, which depends on the metallicity (Z) of the interstellar medium. The GHZ was therefore obtained from a chemical evolution model built to reproduce a precise metallicity gradient in the galactic disk, [O/H](r) $ = -0.015 \\pm 0.003 dex kpc^{-1} x r(kpc) + 0.44 \\pm 0.04 dex $. This gradient is the most probable when intrinsic scatter is present in the observational data. The chemical evolution model predicted a higher star formation history in both the halo and disk components of M31 and a less efficient inside-out galactic formation, compared to those of the Milky Way. If we assumed that Earth-like planets form with a probability law that follows the Z distribution shown by stars with detected planets, the most probable GHZ with basic life is located between 6 and 17 kpc on planets with ages between 4.5 and 1 Gy, and the most probable GHZ with ...

  7. Mass and Metallicity Requirement in Stellar Models for Galactic Chemical Evolution Applications

    CERN Document Server

    Côté, Benoit; Heger, Alexander; Ritter, Christian; O'Shea, Brian W; Herwig, Falk; Travaglio, Claudia; Bisterzo, Sara

    2016-01-01

    We used a one-zone chemical evolution model to address the question of how many metallicities and massive stars are required in grids of stellar models for galactic chemical evolution applications. We used a set of yields that includes seven masses between 13 and 30 Msun, 15 metallicities between 0 and 0.03 in mass fraction, and different remnant mass prescriptions. We ran several simulations where we sampled subsets of stellar models to explore the impact of different grid resolutions. Stellar yields from low- and intermediate-mass stars and from Type Ia supernovae have been included in our simulations, but with a fixed grid resolution. We compared our results with the stellar abundances observed in the Milky Way for O, Na, Mg, Si, S, K, Ca, Ti, and Mn. Our results suggest that the range of metallicity considered is more important than the number of metallicities within that range, which only affects our numerical predictions by about 0.1 dex. We found that our predictions at [Fe/H] < -2 are very sensitiv...

  8. Extremely Metal-Poor Stars and a Hierarchical Chemical Evolution Model

    CERN Document Server

    Komiya, Yutaka

    2011-01-01

    Early phases of the chemical evolution and formation history of extremely metal poor (EMP) stars are investigated using hierarchical galaxy formation models. We build a merger tree of the Galaxy according to the extended Press-Schechter theory. We follow the chemical evolution along the tree, and compare the model results to the metallicity distribution function (MDF) and abundance ratio distribution of the Milky Way halo. We adopt three different initial mass functions (IMFs). In a previous studies, we argue that typical mass of EMP stars should be high-mass(~10Msun) based on studies of binary origin carbon-rich EMP stars. In this study, we show that only the high-mass IMF can explain a observed small number of EMP stars. For relative element abundances, the high-mass IMF and the Salpeter IMF predict similar distributions. We also investigate dependence on nucleosynthetic yields of supernovae (SNe). The theoretical SN yields by Kobayashi et al.(2006) and Chieffi & Limonge (2004) show reasonable agreement...

  9. Surface reconstruction and chemical evolution of stoichiometric layered cathode materials for lithium-ion batteries.

    Science.gov (United States)

    Lin, Feng; Markus, Isaac M; Nordlund, Dennis; Weng, Tsu-Chien; Asta, Mark D; Xin, Huolin L; Doeff, Marca M

    2014-01-01

    The present study sheds light on the long-standing challenges associated with high-voltage operation of LiNi(x)Mn(x)Co(1-2x)O2 cathode materials for lithium-ion batteries. Using correlated ensemble-averaged high-throughput X-ray absorption spectroscopy and spatially resolved electron microscopy and spectroscopy, here we report structural reconstruction (formation of a surface reduced layer, to transition) and chemical evolution (formation of a surface reaction layer) at the surface of LiNi(x)Mn(x)Co(1-2x)O2 particles. These are primarily responsible for the prevailing capacity fading and impedance buildup under high-voltage cycling conditions, as well as the first-cycle coulombic inefficiency. It was found that the surface reconstruction exhibits a strong anisotropic characteristic, which predominantly occurs along lithium diffusion channels. Furthermore, the surface reaction layer is composed of lithium fluoride embedded in a complex organic matrix. This work sets a refined example for the study of surface reconstruction and chemical evolution in battery materials using combined diagnostic tools at complementary length scales. PMID:24670975

  10. Chemical evolution of volatile organic compounds in the outflow of the Mexico City Metropolitan area

    Directory of Open Access Journals (Sweden)

    E. C. Apel

    2010-03-01

    Full Text Available The volatile organic compound (VOC distribution in the Mexico City Metropolitan Area (MCMA and its evolution as it is uplifted and transported out of the MCMA basin was studied during the 2006 MILAGRO/MIRAGE-Mex field campaign. The results show that in the morning hours in the city center, the VOC distribution is dominated by non-methane hydrocarbons (NMHCs but with a substantial contribution from oxygenated volatile organic compounds (OVOCs, predominantly from primary emissions. Alkanes account for a large part of the NMHC distribution in terms of mixing ratios. In terms of reactivity, NMHCs also dominate overall, especially in the morning hours. However, in the afternoon, as the boundary layer lifts and air is mixed and aged within the basin, the distribution changes as secondary products are formed. The WRF-Chem (Weather Research and Forecasting with Chemistry model and MOZART (Model for Ozone and Related chemical Tracers were able to approximate the observed MCMA daytime patterns and absolute values of the VOC OH reactivity. The MOZART model is also in agreement with observations showing that NMHCs dominate the reactivity distribution except in the afternoon hours. The WRF-Chem and MOZART models showed higher reactivity than the experimental data during the nighttime cycle, perhaps indicating problems with the modeled nighttime boundary layer height.

    A northeast transport event was studied in which air originating in the MCMA was intercepted aloft with the Department of Energy (DOE G1 on 18 March and downwind with the National Center for Atmospheric Research (NCAR C130 one day later on 19 March. A number of identical species measured aboard each aircraft gave insight into the chemical evolution of the plume as it aged and was transported as far as 1000 km downwind; ozone was shown to be photochemically produced in the plume. The WRF-Chem and MOZART models were used to examine the spatial extent and temporal evolution of the plume

  11. A simple multistage closed-(box+reservoir model of chemical evolution

    Directory of Open Access Journals (Sweden)

    Caimmi R.

    2011-01-01

    Full Text Available Simple closed-box (CB models of chemical evolution are extended on two respects, namely (i simple closed-(box+reservoir (CBR models allowing gas outflow from the box into the reservoir (Hartwick 1976 or gas inflow into the box from the reservoir (Caimmi 2007 with rate proportional to the star formation rate, and (ii simple multistage closed-(box+reservoir (MCBR models allowing different stages of evolution characterized by different inflow or outflow rates. The theoretical differential oxygen abundance distribution (TDOD predicted by the model maintains close to a continuous broken straight line. An application is made where a fictitious sample is built up from two distinct samples of halo stars and taken as representative of the inner Galactic halo. The related empirical differential oxygen abundance distribution (EDOD is represented, to an acceptable extent, as a continuous broken line for two viable [O/H]-[Fe/H] empirical relations. The slopes and the intercepts of the regression lines are determined, and then used as input parameters to MCBR models. Within the errors (-+σ, regression line slopes correspond to a large inflow during the earlier stage of evolution and to low or moderate outflow during the subsequent stages. A possible inner halo - outer (metal-poor bulge connection is also briefly discussed. Quantitative results cannot be considered for applications to the inner Galactic halo, unless selection effects and disk contamination are removed from halo samples, and discrepancies between different oxygen abundance determination methods are explained.

  12. Challenge for real-time and real-space resolved spectroscopy of surface chemical reactions. Aiming at trace of irreversible and inhomogeneous reactions

    International Nuclear Information System (INIS)

    A novel experimental technique, time-resolved wavelength-dispersive soft X-ray imaging spectroscopy, is proposed in order to achieve real-time and real-space resolved spectroscopy for the observation of irreversible and inhomogeneous surface chemical reactions. By combining the wavelength-dispersed soft X rays, in which the X-ray wavelength (photon energy) changes as a function of position on the sample, with the photoelectron emission microscope, the soft X-ray absorption spectra are separately obtained at different positions on the sample without scanning the X-ray monochromator. Therefore, the real-time resolved measurement of site-selective soft X-ray absorption spectroscopy is realized in one event without repeating the chemical reaction. It is expected that the spatial distribution of different chemical species is traced during the surface chemical reaction, which is essential to understand the reaction mechanism. (author)

  13. Chemical bioimaging for the subcellular localization of trace elements by high contrast TEM, TEM/X-EDS, and NanoSIMS.

    Science.gov (United States)

    Penen, Florent; Malherbe, Julien; Isaure, Marie-Pierre; Dobritzsch, Dirk; Bertalan, Ivo; Gontier, Etienne; Le Coustumer, Philippe; Schaumlöffel, Dirk

    2016-09-01

    Chemical bioimaging offers an important contribution to the investigation of biochemical functions, biosorption and bioaccumulation processes of trace elements via their localization at the cellular and even at the subcellular level. This paper describes the combined use of high contrast transmission electron microscopy (HC-TEM), energy dispersive X-ray spectroscopy (X-EDS), and nano secondary ion mass spectrometry (NanoSIMS) applied to a model organism, the unicellular green algae Chlamydomonas reinhardtii. HC-TEM providing a lateral resolution of 1nm was used for imaging the ultrastructure of algae cells which have diameters of 5-10μm. TEM coupled to X-EDS (TEM/X-EDS) combined textural (morphology and size) analysis with detection of Ca, P, K, Mg, Fe, and Zn in selected subcellular granules using an X-EDS probe size of approx. 1μm. However, instrumental sensitivity was at the limit for trace element detection. NanoSIMS allowed chemical imaging of macro and trace elements with subcellular resolution (element mapping). Ca, Mg, and P as well as the trace elements Fe, Cu, and Zn present at basal levels were detected in pyrenoids, contractile vacuoles, and granules. Some metals were even localized in small vesicles of about 200nm size. Sensitive subcellular localization of trace metals was possible by the application of a recently developed RF plasma oxygen primary ion source on NanoSIMS which has shown good improvements in terms of lateral resolution (below 50nm), sensitivity, and stability. Furthermore correlative single cell imaging was developed combining the advantages of TEM and NanoSIMS. An advanced sample preparation protocol provided adjacent ultramicrotome sections for parallel TEM and NanoSIMS analyses of the same cell. Thus, the C. reinhardtii cellular ultrastructure could be directly related to the spatial distribution of metals in different cell organelles such as vacuoles and chloroplast. PMID:27288221

  14. Sr isotope evolution during chemical weathering of granites -- impact of relative weathering rates of minerals

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The Sr isotopic systematics in the weathering profiles of biotite granite and granite porphyry in southern Jiangxi Province were investigated. The results showed that during the chemical weathering of granites, remarked fractionation occurred between Rb and Sr. During the early stages of chemical weathering of granites, the released Sr/Si and Sr/Ca ratios are larger than those of the parent rocks, and the leaching rate of Sr is higher than those of Si, Ca, K, Rb, etc. Dynamic variations in relative weathering rates of the main Sr-contributing minerals led to fluctuation with time in 87Sr/86Sr ratios of inherent and released Sr in the weathering crust of granite. Successive weathering of biotite, plagioclase and K-feldspar made 87Sr/86Sr ratios in the weathering residues show such a fluctuation trend as to decrease first, increase, and then decrease again till they maintain stable. This work further indicates that when Sr isotopes are used to trace biogeochemical processes on both the catchment and global scales, one must seriously take account of the prefer-ential release of Sr from dissolving solid phase and the fluctuation of 87Sr/86Sr ratios caused by the variations of relative weathering rates of Sr-contributing minerals.

  15. Synoptic and chemical evolution of the Antarctic vortex in winter and spring, 1987

    Science.gov (United States)

    Tuck, A. F.

    1988-01-01

    The dynamical evolution of the vortex at least up to 50 mb is dominated by synoptic scales in the troposphere. In particular, there is a clear response when poleward extension of tropospheric anticyclones from latitudes of 40 and 50 S to 70 and 80 S occurs. This response is evident in isentropic potential vorticity maps, TOMS ozone fields and SAM II polar stratospheric clouds. An important feature of the high latitude Southern Hemisphere lower stratosphere is a transition at potential temperatures in the 390 to 400 K range. This transition, the vortopause, is clearly marked in aircraft profiles of O3, H2O, N2O and ClO at latitudes 68 to 72 S near the Antarctic peninsula, and also cross-sections of potential vorticity and potential temperature; above it, the isopleths are more closely spaced than below it. The aircraft measurements of H2O, O3, NO sub y, N2O, ClO, and whole air data are examined in material coordinates, theta and P sub theta, backed up by trajectory analysis. The evolution of the chemical mixing ratios is examined in these coordinates as a function of time from mid-August to late September. Conclusions are drawn about the rates of change and their causes. The meteorological and aircraft data are examined for evidence of the following kinds of motion with respect to the vortex: ingress of air aloft, subsidence, peeling off of air to lower latitudes, and folding of the vortopause. Conclusions are presented regarding the evidence for a chemical sink of ozone above and below theta = 400 K, and whether the vortex has a mass flow through it, or if the chemical sink operates on a fixed mass of air. Implications for mid-latitudes are briefly considered in the light of the conclusions.

  16. Chemical, physical, and optical evolution of biomass burning aerosols: a case study

    Directory of Open Access Journals (Sweden)

    G. Adler

    2010-10-01

    Full Text Available In-situ chemical composition measurements of ambient aerosols have been used for characterizing the evolution of submicron aerosols from a large anthropogenic biomass burning (BB event in Israel. A high resolution Time of Flight Aerosol Mass Spectrometer (Hi-RES-TOF-AMS was used to follow the chemical evolution of BB aerosols during a night-long, extensive nationwide wood burning event and during the following day. While extensive BB is not common in this region, burning of agricultural waste is a common practice. The aging process of the BB aerosols was followed through their chemical, physical and optical properties. Mass spectrometric analysis of the aerosol organic component showed that aerosol aging is characterized by shifting from less oxidized fresh BB aerosols to more oxidized aerosols. Evidence for aerosol aging during the day following the BB event was indicated by an increase in the organic mass, its oxidation state, the total aerosol concentration, and a shift in the modal particle diameter. The effective broadband refractive index (EBRI was derived using a white light optical particle counter (WELAS. The average EBRI for a mixed population of aerosols dominated by open fires was m=1.53(±0.03+0.07i(±0.03, during the smoldering phase of the fires we found the EBRI to be m=1.54(±0.01+0.04i(±0.01 compared to m=1.49(±0.01+0.02i(±0.01 of the aged aerosols during the following day. This change indicates a decrease in the overall aerosol absorption and scattering. Elevated levels of particulate Polycyclic Aromatic Hydrocarbons (PAHs were detected during the entire event, which suggest possible implications for human health during such extensive event.

  17. Chemical, physical, and optical evolution of biomass burning aerosols: a case study

    Science.gov (United States)

    Adler, G.; Flores, J. M.; Abo Riziq, A.; Borrmann, S.; Rudich, Y.

    2011-02-01

    In-situ chemical composition measurements of ambient aerosols have been used for characterizing the evolution of submicron aerosols from a large anthropogenic biomass burning (BB) event in Israel. A high resolution Time of Flight Aerosol Mass Spectrometer (HR-RES-TOF-AMS) was used to follow the chemical evolution of BB aerosols during a night-long, extensive nationwide wood burning event and during the following day. While these types of extensive BB events are not common in this region, burning of agricultural waste is a common practice. The aging process of the BB aerosols was followed through their chemical, physical and optical properties. Mass spectrometric analysis of the aerosol organic component showed that aerosol aging is characterized by shifting from less oxidized fresh BB aerosols to more oxidized aerosols. Evidence for aerosol aging during the day following the BB event was indicated by an increase in the organic mass, its oxidation state, the total aerosol concentration, and a shift in the modal particle diameter. The effective broadband refractive index (EBRI) was derived using a white light optical particle counter (WELAS). The average EBRI for a mixed population of aerosols dominated by open fires was m = 1.53(±0.03) + 0.07i(±0.03), during the smoldering phase of the fires we found the EBRI to be m = 1.54(±0.01) + 0.04i(±0.01) compared to m = 1.49(±0.01) + 0.02i(±0.01) of the aged aerosols during the following day. This change indicates a decrease in the overall aerosol absorption and scattering. Elevated levels of particulate Polycyclic Aromatic Hydrocarbons (PAHs) were detected during the entire event, which suggest possible implications for human health during such extensive event.

  18. Chemical, physical, and optical evolution of biomass burning aerosols: a case study

    Directory of Open Access Journals (Sweden)

    G. Adler

    2011-02-01

    Full Text Available In-situ chemical composition measurements of ambient aerosols have been used for characterizing the evolution of submicron aerosols from a large anthropogenic biomass burning (BB event in Israel. A high resolution Time of Flight Aerosol Mass Spectrometer (HR-RES-TOF-AMS was used to follow the chemical evolution of BB aerosols during a night-long, extensive nationwide wood burning event and during the following day. While these types of extensive BB events are not common in this region, burning of agricultural waste is a common practice. The aging process of the BB aerosols was followed through their chemical, physical and optical properties. Mass spectrometric analysis of the aerosol organic component showed that aerosol aging is characterized by shifting from less oxidized fresh BB aerosols to more oxidized aerosols. Evidence for aerosol aging during the day following the BB event was indicated by an increase in the organic mass, its oxidation state, the total aerosol concentration, and a shift in the modal particle diameter. The effective broadband refractive index (EBRI was derived using a white light optical particle counter (WELAS. The average EBRI for a mixed population of aerosols dominated by open fires was m = 1.53(±0.03 + 0.07i(±0.03, during the smoldering phase of the fires we found the EBRI to be m = 1.54(±0.01 + 0.04i(±0.01 compared to m = 1.49(±0.01 + 0.02i(±0.01 of the aged aerosols during the following day. This change indicates a decrease in the overall aerosol absorption and scattering. Elevated levels of particulate Polycyclic Aromatic Hydrocarbons (PAHs were detected during the entire event, which suggest possible implications for human health during such extensive event.

  19. Investigating the role for adaptation of the microbial community to transform trace organic chemicals during managed aquifer recharge

    KAUST Repository

    Alidina, Mazahirali

    2014-06-01

    This study was undertaken to investigate whether adaptation by pre-exposure to trace organic chemicals (TOrCs) was necessary for microbial transformation during managed aquifer recharge (MAR). Two pairs of laboratory-scale soil columns, each receiving a different primary substrate, were utilized to simulate the dominant bulk organic carbon present in MAR systems receiving wastewater effluent of varying quality and having undergone different degrees of pre-treatment, as well as organic carbon prevalent at different stages of subsurface travel. Each pair of columns consisted of duplicate set-ups receiving the same feed solution with only one pre-exposed to a suite of eight TOrCs for approximately ten months. Following the pre-exposure period, a spiking experiment was conducted in which the non-exposed columns also received the same suite of TOrCs. TOrC attenuation was quantified for the pre- and non-exposed columns of each pair during the spiking experiment. The microbial community structure and function of these systems were characterized by pyrosequencing of 16S rRNA gene and metagenomics, respectively. Biotransformation rather than sorption was identified as the dominant removal mechanism for almost all the TOrCs (except triclocarban). Similar removal efficiencies were observed between pre-exposed and non-exposed columns for most TOrCs. No obvious differences in microbial community structure were revealed between pre- and non-exposed columns. Using metagenomics, biotransformation capacity potentials of the microbial community present were also similar between pre- and non-exposed columns of each pair. Overall, the pre-exposure of MAR systems to TOrCs at ng/L levels did not affect their attenuation and had no obvious influence on the resulting microbial community structure and function. Thus, other factors such as bioavailability of the primary substrate play a greater role regarding biotransformation of TOrCs. These results indicate that MAR systems adapted to a

  20. Investigating the role for adaptation of the microbial community to transform trace organic chemicals during managed aquifer recharge.

    Science.gov (United States)

    Alidina, Mazahirali; Li, Dong; Drewes, Jörg E

    2014-06-01

    This study was undertaken to investigate whether adaptation by pre-exposure to trace organic chemicals (TOrCs) was necessary for microbial transformation during managed aquifer recharge (MAR). Two pairs of laboratory-scale soil columns, each receiving a different primary substrate, were utilized to simulate the dominant bulk organic carbon present in MAR systems receiving wastewater effluent of varying quality and having undergone different degrees of pre-treatment, as well as organic carbon prevalent at different stages of subsurface travel. Each pair of columns consisted of duplicate set-ups receiving the same feed solution with only one pre-exposed to a suite of eight TOrCs for approximately ten months. Following the pre-exposure period, a spiking experiment was conducted in which the non-exposed columns also received the same suite of TOrCs. TOrC attenuation was quantified for the pre- and non-exposed columns of each pair during the spiking experiment. The microbial community structure and function of these systems were characterized by pyrosequencing of 16S rRNA gene and metagenomics, respectively. Biotransformation rather than sorption was identified as the dominant removal mechanism for almost all the TOrCs (except triclocarban). Similar removal efficiencies were observed between pre-exposed and non-exposed columns for most TOrCs. No obvious differences in microbial community structure were revealed between pre- and non-exposed columns. Using metagenomics, biotransformation capacity potentials of the microbial community present were also similar between pre- and non-exposed columns of each pair. Overall, the pre-exposure of MAR systems to TOrCs at ng/L levels did not affect their attenuation and had no obvious influence on the resulting microbial community structure and function. Thus, other factors such as bioavailability of the primary substrate play a greater role regarding biotransformation of TOrCs. These results indicate that MAR systems adapted to a

  1. The Dynamical and Chemical Evolution of Dwarf Spheroidal Galaxies with GEAR

    CERN Document Server

    Revaz, Yves

    2011-01-01

    We present a fully parallel chemo-dynamical Tree/SPH code, GEAR, which allows to perform high resolution simulations with detailed chemical diagnostics. Starting from the public version of Gadget-2, we included the complex treatment of the baryon physics: gas cooling, star formation law, chemical evolution and supernovae feedback. We qualified the performances of GEAR with the case of dSph galaxies. GEAR conserves the total energy budget of the systems to better than 5% over 14Gyr and proved excellent convergence of the results with numerical resolution. We showed that models of dSphs in a static Euclidean space, where the expansion of the universe is neglected are valid. In addition, we tackled some of the existing open questions in the field, like the stellar mass fraction of dSphs and its link with the predicted dark matter halo mass function, the effect of the supernova feedback, the spatial distribution of the stellar populations, and the origin of the diversity in star formation histories and chemical a...

  2. The Composition of the Sagittarius Dwarf Spheroidal Galaxy and Implications for Nucleosynthesis and Chemical Evolution

    CERN Document Server

    McWilliam, A; William, Andrew Mc; Smecker-Hane, Tammy A.

    2004-01-01

    We outline the results of a study of the chemical composition of 14 stars in the Sagittarius dwarf spheroidal galaxy (Sgr dSph). For the Sgr dSph stars with [Fe/H]>-1 the abundances are highly unusual, showing a striking enhancement in heavy s-process elements, increasing with [Fe/H], deficiencies of the alpha- elements (O, Si, Ca, and Ti), deficiencies of Al and Na, and deficiencies of the iron-peak elements Mn and Cu. Our abundances suggest that the composition of the metal-rich Sgr dSph stars is dominated by the ejecta of an old, metal-poor population, including products of AGB stars and type Ia supernovae (SN). We suggest two scenarios to explain the observations: Prolonged chemical evolution in a galaxy experiencing significant mass-loss, and chemical enrichment with episodic bursts of star formation. The Galactic globular cluster Omega Cen, and the Fornax dwarf galaxy show similar abundance patterns, which suggests that those systems evolved similar to the Sgr dSph.

  3. Chemical evolution of volatile organic compounds in the outflow of the Mexico City Metropolitan area

    Energy Technology Data Exchange (ETDEWEB)

    Apel, E.; Springston, S.; Karl, T.; Emmons, L.; Flocke, F.; Hills, A. J.; Madronich, S.; Lee-Taylor, J.; Fried, A.; Weibring, P.; Walega, J.; Richter, D., Tie, X.; Mauldin, L.; Campos, T.; Sive, B.; Kleinman, L.; Springston, S., Zaveri, R.; deGouw, J.; Zheng, J.; Zhang, R.; Rudolph, J.; Junkermann, W.; Riemer, D. D.

    2009-11-01

    The volatile organic compound (VOC) distribution in the Mexico City Metropolitan Area (MCMA) and its evolution as it is uplifted and transported out of the MCMA basin was studied during the 2006 MILAGRO/MIRAGE-Mex field campaign. The results show that in the morning hours in the city center, the VOC distribution is dominated by non-methane hydrocarbons (NMHCs) but with a substantial contribution from oxygenated volatile organic compounds (OVOCs), predominantly from primary emissions. Alkanes account for a large part of the NMHC distribution in terms of mixing ratios. In terms of reactivity, NMHCs also dominate overall, especially in the morning hours. However, in the afternoon, as the boundary layer lifts and air is mixed and aged within the basin, the distribution changes as secondary products are formed. The WRF-Chem (Weather Research and Forecasting with Chemistry) model and MOZART (Model for Ozone and Related chemical Tracers) were able to reproduce the general features of the daytime cycle of the VOC OH reactivity distribution showing that NMHCs dominate the distribution except in the afternoon hours and that the VOC OH reactivity peaks in the early morning due to high morning emissions from the city into a shallow boundary layer. The WRF-Chem and MOZART models showed higher reactivity than the experimental data during the nighttime cycle, perhaps indicating problems with the modeled nighttime boundary layer height. In addition, a plume was studied in which air was advected out of the MCMA and intercepted downwind with the DOE G1 on 18 March and the NCAR C130 one day later on 19 March. A number of identical species measured aboard each aircraft gave insight into the chemical evolution of the plume as it aged and was transported as far as 1000 km downwind. Ozone and many OVOCs were photochemically produced in the plume. The WRF-Chem and MOZART models were used to examine the spatial and temporal extent of the 19 March plume and to help interpret the OH

  4. Chemical evolution of volatile organic compounds in the outflow of the Mexico City Metropolitan area

    Energy Technology Data Exchange (ETDEWEB)

    Apel, Eric; Emmons, L.; Karl, Thomas G.; Flocke, Frank M.; Hills, A. J.; Madronich, Sasha; Lee-Taylor, J.; Fried, Alan; Weibring, P.; Walega, J.; Richter, Dirk; Tie, X.; Mauldin, L.; Campos, Teresa; Weinheimer, Andrew J.; Knapp, David; Sive, B.; Kleinman, Lawrence I.; Springston, S.; Zaveri, Rahul A.; Ortega, John V.; Voss, Paul B.; Blake, D. R.; Baker, Angela K.; Warneke, Carsten; Welsh-Bon, Daniel; de Gouw, Joost A.; Zheng, J.; Zhang, Renyi; Rudolph, Jochen; Junkermann, W.; Riemer, D.

    2010-01-01

    The volatile organic compound (VOC) distribution in the Mexico City Metropolitan Area (MCMA) and its evolution as it is uplifted and transported out of the MCMA basin was studied during the 2006 MILAGRO/MIRAGE-Mex field campaign. The results show that in the morning hours in the city center, the VOC distribution is dominated by non-methane hydrocarbons (NMHCs) but with a substantial contribution from oxygenated volatile organic compounds (OVOCs), predominantly from primary emissions. Alkanes account for a large part of the NMHC distribution in terms of mixing ratios. In terms of reactivity, NMHCs also dominate overall, especially in the morning hours. However, in the afternoon, as the boundary layer lifts and air is mixed and aged within the basin, the distribution changes as secondary products are formed. The WRF-Chem (Weather Research and Forecasting with Chemistry) model and MOZART (Model for Ozone and Related chemical Tracers) were able to reproduce the general features of the daytime cycle of the VOC OH reactivity distribution showing that NMHCs dominate the distribution except in the afternoon hours and that the VOC OH reactivity peaks in the early morning due to high morning emissions from the city into a shallow boundary layer. The WRF-Chem and MOZART models showed higher reactivity than the experimental data during the nighttime cycle, perhaps indicating problems with the modeled nighttime boundary layer height. In addition, a plume was studied in which air was advected out of the MCMA and intercepted downwind with the DOE G1 on March 18 and the NCAR C130 one day later on March 19. A number of identical species measured aboard each aircraft gave insight into the chemical evolution of the plume as it aged and was transported as far as 1000 km downwind. Ozone and many OVOCs were photochemically produced in the plume. The WRF-Chem and MOZART models were used to examine the spatial and temporal extent of the March 19 plume and to help interpret the OH

  5. Chemical evolution of volatile organic compounds in the outflow of the Mexico City Metropolitan area

    Directory of Open Access Journals (Sweden)

    W. Junkermann

    2009-11-01

    Full Text Available The volatile organic compound (VOC distribution in the Mexico City Metropolitan Area (MCMA and its evolution as it is uplifted and transported out of the MCMA basin was studied during the 2006 MILAGRO/MIRAGE-Mex field campaign. The results show that in the morning hours in the city center, the VOC distribution is dominated by non-methane hydrocarbons (NMHCs but with a substantial contribution from oxygenated volatile organic compounds (OVOCs, predominantly from primary emissions. Alkanes account for a large part of the NMHC distribution in terms of mixing ratios. In terms of reactivity, NMHCs also dominate overall, especially in the morning hours. However, in the afternoon, as the boundary layer lifts and air is mixed and aged within the basin, the distribution changes as secondary products are formed. The WRF-Chem (Weather Research and Forecasting with Chemistry model and MOZART (Model for Ozone and Related chemical Tracers were able to reproduce the general features of the daytime cycle of the VOC OH reactivity distribution showing that NMHCs dominate the distribution except in the afternoon hours and that the VOC OH reactivity peaks in the early morning due to high morning emissions from the city into a shallow boundary layer. The WRF-Chem and MOZART models showed higher reactivity than the experimental data during the nighttime cycle, perhaps indicating problems with the modeled nighttime boundary layer height. In addition, a plume was studied in which air was advected out of the MCMA and intercepted downwind with the DOE G1 on 18~March and the NCAR C130 one day later on 19~March. A number of identical species measured aboard each aircraft gave insight into the chemical evolution of the plume as it aged and was transported as far as 1000 km downwind. Ozone and many OVOCs were photochemically produced in the plume. The WRF-Chem and MOZART models were used to examine the spatial and temporal extent of the 19~March plume and to help interpret

  6. The use of neutron activation analysis for particle size fractionation and chemical characterization of trace elements in urban air particulate matter

    International Nuclear Information System (INIS)

    The concentration of more than 25 trace elements have been determined in total air particulate matter and in the size segregated fractions from the urban area of Pavia (North Italy). The PM10 fraction was also collected and analyzed. A study of the solubility in water and in physiological solution of the trace elements contained in the PM10 was also carried out. The resulting solutions were further submitted to column chromatography using Chelex 100 to perform a preliminary chemical characterization. INAA was used as the main analytical technique. ET-AAS was used for all Pb and Cd measurements and, in some cases, for the analysis of V, Mn, Cu and Ni. (author)

  7. Evolution of Autocatalytic Sets in Computational Models of Chemical Reaction Networks

    Science.gov (United States)

    Hordijk, Wim

    2016-06-01

    Several computational models of chemical reaction networks have been presented in the literature in the past, showing the appearance and (potential) evolution of autocatalytic sets. However, the notion of autocatalytic sets has been defined differently in different modeling contexts, each one having some shortcoming or limitation. Here, we review four such models and definitions, and then formally describe and analyze them in the context of a mathematical framework for studying autocatalytic sets known as RAF theory. The main results are that: (1) RAF theory can capture the various previous definitions of autocatalytic sets and is therefore more complete and general, (2) the formal framework can be used to efficiently detect and analyze autocatalytic sets in all of these different computational models, (3) autocatalytic (RAF) sets are indeed likely to appear and evolve in such models, and (4) this could have important implications for a possible metabolism-first scenario for the origin of life.

  8. On the origin and chemical evolution of ground water at the Olkiluoto site

    International Nuclear Information System (INIS)

    The knowledge on the quality of Olkiluoto groundwater and its chemical interactions have been based on the data gathered during the sampling in 1980-1992. In addition to the data gained during the preliminary investigation phase, data has also been obtained from the bedrock investigations for the final repository for low- and intermediate-level reactor waste at Olkiluoto. The deep boreholes at the investigation site, were equipped with multipackers in 1991-1992. During the present investigation programme, the areal coverage was significantly improved by the new data on the groundwater samples from the deep multipackered boreholes. Furthermore, the analysis programme was extended in respect to former one to include more analyses, especially of isotopes and gaseous species. The currently available data gives new insight into the areal picture and the quality of the groundwater, and thus requires the specifying of the previous geochemical interpretations of the origin and the evolution of the groundwater at Olkiluoto. (37 refs.)

  9. Simple Chemical Solution Deposition of Co₃O₄ Thin Film Electrocatalyst for Oxygen Evolution Reaction.

    Science.gov (United States)

    Jeon, Hyo Sang; Jee, Michael Shincheon; Kim, Haeri; Ahn, Su Jin; Hwang, Yun Jeong; Min, Byoung Koun

    2015-11-11

    Oxygen evolution reaction (OER) is the key reaction in electrochemical processes, such as water splitting, metal-air batteries, and solar fuel production. Herein, we developed a facile chemical solution deposition method to prepare a highly active Co3O4 thin film electrode for OER, showing a low overpotential of 377 mV at 10 mA/cm(2) with good stability. An optimal loading of ethyl cellulose additive in a precursor solution was found to be essential for the morphology control and thus its electrocatalytic activity. Our results also show that the distribution of Co3O4 nanoparticle catalysts on the substrate is crucial in enhancing the inherent OER catalytic performance. PMID:26489005

  10. Prebiotic coordination chemistry: The potential role of transition-metal complexes in the chemical evolution

    Science.gov (United States)

    Beck, M.

    1979-01-01

    In approaching the extremely involved and complex problem of the origin of life, consideration of the coordination chemistry appeared not only as a possibility but as a necessity. The first model experiments appear to be promising because of prebiotic-type synthesis by means of transition-metal complexes. It is especially significant that in some instances various types of vitally important substances (nucleic bases, amino acids) are formed simultaneously. There is ground to hope that systematic studies in this field will clarify the role of transition-metal complexes in the organizatorial phase of chemical evolution. It is obvious that researchers working in the fields of the chemistry of cyano and carbonyl complexes, and of the catalytic effect of transition-metal complexes are best suited to study these aspects of the attractive and interesting problem of the origin of life.

  11. Evolution of Autocatalytic Sets in Computational Models of Chemical Reaction Networks.

    Science.gov (United States)

    Hordijk, Wim

    2016-06-01

    Several computational models of chemical reaction networks have been presented in the literature in the past, showing the appearance and (potential) evolution of autocatalytic sets. However, the notion of autocatalytic sets has been defined differently in different modeling contexts, each one having some shortcoming or limitation. Here, we review four such models and definitions, and then formally describe and analyze them in the context of a mathematical framework for studying autocatalytic sets known as RAF theory. The main results are that: (1) RAF theory can capture the various previous definitions of autocatalytic sets and is therefore more complete and general, (2) the formal framework can be used to efficiently detect and analyze autocatalytic sets in all of these different computational models, (3) autocatalytic (RAF) sets are indeed likely to appear and evolve in such models, and (4) this could have important implications for a possible metabolism-first scenario for the origin of life. PMID:26499126

  12. Chemical Evolution of Strongly Magnetized Quark Core in a Newborn Neutron Star

    CERN Document Server

    Ghosh, T K; Ghosh, Tanusri; Chakrabarty, Somenath

    2001-01-01

    The chemical evolution of nascent quark matter core in a newborn compact neutron star is studied in presence of a strong magnetic field. The effective rate of strange quark production in degenerate quark matter core in presence of strong magnetic fields is obtained. The investigations show that in presence of strong magnetic fields a quark matter core becomes energetically unstable and hence a deconfinement transition to quark matter at the centre of a compact neutron star under such circumstances is not possible. The critical strength of magnetic field at the central core to make the system energetically unstable with respect to dense nuclear matter is found to be $\\sim 4.4\\times 10^{13}$G. This is the typical strength at which the Landau levels for electrons are populated. The other possible phase transitions at such high density and ultra strong magnetic field environment are discussed.

  13. Merging binary black holes formed through chemically homogeneous evolution in short-period stellar binaries

    Science.gov (United States)

    Mandel, Ilya; de Mink, Selma E.

    2016-05-01

    We explore a newly proposed channel to create binary black holes of stellar origin. This scenario applies to massive, tight binaries where mixing induced by rotation and tides transports the products of hydrogen burning throughout the stellar envelopes. This slowly enriches the entire star with helium, preventing the build-up of an internal chemical gradient. The stars remain compact as they evolve nearly chemically homogeneously, eventually forming two black holes, which we estimate typically merge 4-11 Gyr after formation. Like other proposed channels, this evolutionary pathway suffers from significant theoretical uncertainties, but could be constrained in the near future by data from advanced ground-based gravitational-wave detectors. We perform Monte Carlo simulations of the expected merger rate over cosmic time to explore the implications and uncertainties. Our default model for this channel yields a local binary black hole merger rate of about 10 Gpc-3 yr-1 at redshift z = 0, peaking at twice this rate at z = 0.5. This means that this channel is competitive, in terms of expected rates, with the conventional formation scenarios that involve a common-envelope phase during isolated binary evolution or dynamical interaction in a dense cluster. The events from this channel may be distinguished by the preference for nearly equal-mass components and high masses, with typical total masses between 50 and 110 M⊙. Unlike the conventional isolated binary evolution scenario that involves shrinkage of the orbit during a common-envelope phase, short time delays are unlikely for this channel, implying that we do not expect mergers at high redshift.

  14. Radiation-induced chemical evolution of glycine to (Gly)2, (Gly)3, and (Gly)4

    International Nuclear Information System (INIS)

    Recently amino acids were detected from some meteorites. Since these amino acids were found after hydrolysis, some oligopeptides were possibly formed in space. A simulation experiment of chemical evolution from Glycine (Gly) to Glycylglycine ((Gly)2) was reported by Kaneko et al. In this work, we irradiated (Gly)2 with 8 eV vacuum ultraviolet photons or with 530 eV soft X-ray photons and examined absolute values of quantum yield of radiation-induced chemical evolution from Gly2 to Glycylglycylglycine ((Gly)3) and Glycylglycylglycylglycine ((Gly)4). Thin films of (Gly)2 were prepared on quartz plate or CuBe plate with a vacuum evaporation technique. These samples were irradiated by 8 eV photons from a Xe2* excimer lamp or by 530 eV soft X-ray photons at SPring-8 Synchrotron Radiation Facility. Irradiated samples were analyzed with a high performance liquid chromatography HPLC. Decomposition of (Gly)2 and production of Gly, (Gly)3 and (Gly)4 were observed. Quantum yield Y was defined to be N = Y N0, where N is the number of produced or decomposed molecule, and N0 is the number of (Gly)2 molecules excited by photons. Obtained results by 8 eV irradiation were summarized in Table 1. The similar magnitude of decomposition of (Gly)2 may show that yield of the primary breaking reaction upon photo-excitation is of similar magnitude. It should be noted that (Gly)3 and (Gly)4 was produced by irradiation with the yield of 10-4 without any catalysis. For soft X-ray irradiation, yield of Gly was tentatively determined to be about 40. This largervalue than that for 8 eV irradiation may originate from large energy of incident soft X-ray photons just like a result reported by Simakov et al. We will discuss in detail at the conference. (authors)

  15. Evolution of limestone fracture permeability under coupled thermal, hydrologi-cal, mechanical, and chemical conditions

    Institute of Scientific and Technical Information of China (English)

    李凤滨; 盛金昌; 詹美礼; 徐力猛; 吴强; 贾春兰

    2014-01-01

    The effect of temperature on the rock fracture permeability is a very important factor in the prediction of the permeability of enhanced geothermal systems and in reservoir engineering. In this study, the flow-through experiments were conducted on a single limestone fracture at different temperatures of 25oC, 40oC and 60oC, and with differential pressures of 0.3 MPa and 0.4 MPa. The experimental results suggest a complex temporal evolution of the fracture aperture. The aperture increases considerably with increasing temperature and reduces gradually to a steady value at a stable temperature. The results of three short-term experiments (QT-1, QT-2, QT-3) indicate an exponential relationship between the permeability and the temperature change ratio (DT/T ) , which provides a further evidence that the rising temperature increases the aperture. It is shown that the changing temperature has its influence on two possible accounts:the chemical dissolution and the pressure dissolution. These two processes have opposite impacts on the fracture permeability. The chemical dissolution increases the permeability with a rising temperature while the pressure disso-lution reduces the permeability with a stable temperature. These make a very complex picture of the permeability evolution. Our results show that the fracture permeability reduces 39.2%when the temperature increases by 15oC (during the 25oC-40 C interval) and 42.6% when the temperature increases by 20oC (during the 40oC-60oC interval). It can be concluded that the permeability decreases to a greater extent for larger increases in temperature.

  16. Chemical differentiation, thermal evolution, and catastrophic overturn on Venus: Predictions and geologic observations

    Science.gov (United States)

    Head, James W.; Parmentier, E. M.; Hess, P. C.

    1993-01-01

    Observations from Magellan show that: (1) the surface of Venus is generally geologically young, (2) there is no evidence for widespread recent crustal spreading or subduction, (3) the crater population permits the hypothesis that the surface is in production, and (4) relatively few impact craters appear to be embayed by volcanic deposits suggesting that the volcanic flux has drastically decreased as a function of time. These observations have led to consideration of hypotheses suggesting that the geological history of Venus may have changed dramatically as a function of time due to general thermal evolution, and/or thermal and chemical evolution of a depleted mantle layer, perhaps punctuated by catastrophic overturn of upper layers or episodic plate tectonics. We have previously examined the geological implications of some of these models, and here we review the predictions associated with two periods of Venus history. Stationary thick lithosphere and depleted mantle layer, and development of regional to global development of regional to global instabilities, and compare these predictions to the geological characteristics of Venus revealed by Magellan.

  17. From stellar to planetary composition: Galactic chemical evolution of Mg/Si mineralogical ratio

    CERN Document Server

    Adibekyan, V; Figueira, P; Dorn, C; Sousa, S G; Delgado-Mena, E; Israelian, G; Hakobyan, A A; Mordasini, C

    2015-01-01

    The main goal of this work is to study element ratios that are important for the formation of planets of different masses. We study potential correlations between the existence of planetary companions and the relative elemental abundances of their host stars. We use a large sample of FGK-type dwarf stars for which precise Mg, Si, and Fe abundances have been derived using HARPS high-resolution and high-quality data. A first analysis of the data suggests that low-mass planet host stars show higher [Mg/Si] ratios, while giant planet hosts present [Mg/Si] that is lower than field stars. However, we found that the [Mg/Si] ratio significantly depends on metallicity through Galactic chemical evolution. After removing the Galactic evolution trend only the difference in the [Mg/Si] elemental ratio between low-mass planet hosts and non-hosts was present in a significant way. These results suggests that low-mass planets are more prevalent around stars with high [Mg/Si]. Our results demonstrate the importance of Galactic...

  18. Isotopic and geochemical studies of fluid-rock interactions and the chemical evolution of the oceans

    Energy Technology Data Exchange (ETDEWEB)

    Derry, L.A.

    1989-01-01

    The isotopic compositions of Sr and Nd, and the abundances of rare earth elements (REE) are used to study various types of fluid-rock interactions in the Earth's crust. The isotopic compositions of Sr and Nd and REE patterns in marine chemical sediments of Precambrian age are used to estimate the relative importance of continental weathering versus submarine hydrothermal activity in determining the chemical mass balance of the Precambrian oceans. Major and trace element abundances and Sr and Nd isotopes are used to quantify the degree of interaction of a carbonatite fluid-magmatic system with felsic crust, and to constrain the isotopic characteristics of the mantle source region. The isotopic composition of Sr is reported from a well characterized sequence of Upper Proterozoic carbonates from Svalbard and east Greenland. A simple model of carbonate recycling and isotopic mass balance calculations illustrate that sedimentary recycling can have a strong influence on Sr in the oceans. REE patterns from Precambrian banded iron formations (BIFs) are very similar to modern metalliferous sediments, and imply that the overall REE pattern of Precambrian seawater was similar to today. The mantle-like {var epsilon}{sub Nd} values and positive Eu anomalies imply that the source of the REE in the BIFs was submarine hydrothermal activity. The implications of a large hydrothermal flux of reduced Fe on the redox controls of the Precambrian atmosphere are explored, and a testable hypothesis is developed. The mass balance of Eu in the oceans is affected by preferential scavenging at hydrothermal sites. Data from the Cherry Hill, CA mineralizing system imply a complex plumbing system and a long residence time for the water. Isotopic data from the Fen alkaline complex, Norway, define mixing trends between mantle derived magmas or magmatic fluids and old crust.

  19. Isotopic Constraints on the Chemical Evolution of Geothermal Fluids, Long Valley, CA

    Energy Technology Data Exchange (ETDEWEB)

    Brown, Shaun; Kennedy, Burton; DePaolo, Donald; Evans, William

    2008-08-01

    A spatial survey of the chemical and isotopic composition of fluids from the Long Valley hydrothermal system was conducted. Starting at the presumed hydrothermal upwelling zone in the west moat of the caldera, samples were collected from the Casa Diablo geothermal field and a series of monitoring wells defining a nearly linear, ~;;14 km long, west-to-east trend along the proposed fluid flow path (Sorey et al., 1991). Samples were analyzed for the isotopes of water, Sr, Ca, and noble gases, the concentrations of major cations and anions and total CO2. Our data confirm earlier models in which the variations in water isotopes along the flow path reflect mixing of a single hydrothermal fluid with local groundwater. Variations in Sr data are poorly constrained and reflect fluid mixing, multiple fluid-pathways or water-rock exchange along the flow path as suggested by Goff et al. (1991). Correlated variations among total CO2, noble gases and the concentration and isotopic composition of Ca suggest progressive fluid degassing (loss of CO2, noble gases) driving calcite precipitation as the fluid flows west-to-east across the caldera. This is the first evidence that Ca isotopes may trace and provide definitive evidence of calcite precipitation along fluid flow paths in geothermal systems.

  20. Chemical speciation and human health risk of trace metals in urban street dusts from a metropolitan city, Nanjing, SE China

    International Nuclear Information System (INIS)

    The modified BCR (the European Community Bureau of Reference) sequential extraction procedure was applied for partitioning and evaluating the mobility, availability and persistence of trace metals (Al, Cd, Co, Cr, Cu, Ni, Pb, Sr, V and Zn) in urban street dusts collected from different areas of Nanjing, China. The mobility sequence based on the sum of the BCR sequential extraction stages was: Sr (91.65%) > Pb (79.16%) > Zn (74.26%) > Cu (68.53%) > Co (45.98%) > Al (40.01%) ≈ V (38.45%) ≈ Ni (37.88%) > Cr (29.35%) > Cd (22.68%). Almost every trace metal had its highest total concentrations in the industrial area, except for Sr which had its highest concentration in the commercial area. Contamination factors (Cf), risk assessment code (RAC) and enrichment factor (Ef) were then calculated to further assess the environmental risk and provide a preliminary estimate of the main sources of trace metals in street dusts. Non-carcinogenic effects and carcinogenic effects due to exposure to urban street dusts were assessed for both children and adults. For non-carcinogenic effects, ingestion was the main route of exposure to street dusts for these metals, followed by dermal contact and inhalation. Hazard index values for all studied metals were lower than the safe level of 1, and Pb exhibited the highest risk value (0.125) in the case of children. The carcinogenic risk for Cd, Co, Cr and Ni were all below the acceptable level (−6). - Highlights: • This study assesses a comprehensive environmental risk of urban trace metal pollution. • This study evaluates human health risk combined with the speciation of trace metals. • This study points the critical contaminated metals that need to be paid special attention. • This study supplies useful information and reference on the application of BCR SPE method

  1. A NEW CHEMICAL EVOLUTION MODEL FOR DWARF SPHEROIDAL GALAXIES BASED ON OBSERVED LONG STAR FORMATION HISTORIES

    International Nuclear Information System (INIS)

    We present a new chemical evolution model for dwarf spheroidal galaxies (dSphs) in the local universe. Our main aim is to explain both their observed star formation histories and metallicity distribution functions simultaneously. Applying our new model for the four local dSphs, that is, Fornax, Sculptor, Leo II, and Sextans, we find that our new model reproduces the observed chemical properties of the dSphs consistently. Our results show that the dSphs have evolved with both a low star formation efficiency and a large gas outflow efficiency compared with the Milky Way, as suggested by previous works. Comparing the observed [α/Fe]-[Fe/H] relation of the dSphs with the model predictions, we find that our model favors a longer onset time of Type Ia supernovae (i.e., 0.5 Gyr) than that suggested in previous studies (i.e., 0.1 Gyr). We discuss the origin of this discrepancy in detail

  2. Chemical and Phase Evolution of Amorphous Molybdenum Sulfide Catalysts for Electrochemical Hydrogen Production.

    Science.gov (United States)

    Lee, Sang Chul; Benck, Jesse D; Tsai, Charlie; Park, Joonsuk; Koh, Ai Leen; Abild-Pedersen, Frank; Jaramillo, Thomas F; Sinclair, Robert

    2016-01-26

    Amorphous MoSx is a highly active, earth-abundant catalyst for the electrochemical hydrogen evolution reaction. Previous studies have revealed that this material initially has a composition of MoS3, but after electrochemical activation, the surface is reduced to form an active phase resembling MoS2 in composition and chemical state. However, structural changes in the MoSx catalyst and the mechanism of the activation process remain poorly understood. In this study, we employ transmission electron microscopy (TEM) to image amorphous MoSx catalysts activated under two hydrogen-rich conditions: ex situ in an electrochemical cell and in situ in an environmental TEM. For the first time, we directly observe the formation of crystalline domains in the MoSx catalyst after both activation procedures as well as spatially localized changes in the chemical state detected via electron energy loss spectroscopy. Using density functional theory calculations, we investigate the mechanisms for this phase transformation and find that the presence of hydrogen is critical for enabling the restructuring process. Our results suggest that the surface of the amorphous MoSx catalyst is dynamic: while the initial catalyst activation forms the primary active surface of amorphous MoS2, continued transformation to the crystalline phase during electrochemical operation could contribute to catalyst deactivation. These results have important implications for the application of this highly active electrocatalyst for sustainable H2 generation. PMID:26624225

  3. Life in the light: nucleic acid photoproperties as a legacy of chemical evolution.

    Science.gov (United States)

    Beckstead, Ashley A; Zhang, Yuyuan; de Vries, Mattanjah S; Kohler, Bern

    2016-09-21

    Photophysical investigations of the canonical nucleobases that make up DNA and RNA during the past 15 years have revealed that excited states formed by the absorption of UV radiation decay with subpicosecond lifetimes (i.e., inventories on the early Earth before the emergence of life and the subsequent development of a protective ozone shield. Here, we review the general physical and chemical principles that underlie the photostability, or "UV hardiness", of modern nucleic acids and discuss the possible implications of these findings for prebiotic chemical evolution. In RNA and DNA strands, much longer-lived excited states are observed, which at first glance appear to increase the risk of photochemistry. It is proposed that the dramatically different photoproperties that emerge from assemblies of photostable building blocks may explain the transition from a world of molecular survival to a world in which energy-rich excited electronic states were eventually tamed for biological purposes such as energy transduction, signaling, and repair of the genetic machinery. PMID:27539809

  4. Chemically modified nucleic acid aptamers for in vitro selections: evolving evolution.

    Science.gov (United States)

    Kusser, W

    2000-03-01

    Combinatorial library selections through the systematic evolution of ligands by exponential enrichment (SELEX) technique identify so-called nucleic acid aptamers that bind with high-affinity and specificity to a wide range of selected molecules. However, the modest chemical functionality of nucleic acids poses some limits on their versatility as binders and catalysts, and, furthermore, the sensitivity of pure RNA- and DNA-based aptamers to nucleases restricts their use as therapeutic and diagnostic agents. Here we review synthetic chemistries for modifying nucleotides that have been developed to enhance the affinity of aptamers for targets and to increase their stability in biological fluids. Implementation of in vitro selections with modified nucleotides promises to be an elegant technique for the creation of ligands with novel physical and chemical properties and is anticipated to have a significant impact on biotechnology, diagnostics and drug development. The current molecular designs and applications of modified nucleotides for in vitro selections are reviewed, along with a discussion of future developments expected to further the utility of this approach in both practical and theoretical terms. PMID:10943570

  5. Evolution of the quaternary magmatic system, Mineral Mountains, Utah: Interpretations from chemical and experimental modeling

    Energy Technology Data Exchange (ETDEWEB)

    Nash, W.P.; Crecraft, H.R.

    1982-09-01

    The evolution of silicic magmas in the upper crust is characterized by the establishment of chemical and thermal gradients in the upper portion of magma chambers. The chemical changes observed in rhyolite magmas erupted over a period of 300,000 years in the Mineral Mountains are similar to those recorded at Twin Peaks, Utah, and in the spatially zoned Bishop Tuff from Long Valley, California. Chemical and fluid dynamic models indicate that cooling of a silicic magma body from the top and sides can result in the formation of a roof zone above a convecting region which is chemically and thermally stratified, as well as highly fractionated and water rich. Crystallization experiments have been performed with sodium carbonate solutions as an analog to crystallization in magmatic systems. Top and side cooling of a homogeneous sodium carbonate solution results in crystallization along the top and sides and upward convection of sodium carbonate-depleted fluid. A stably stratified roof zone, which is increasingly water rich and cooler upwards, develops over a thermally and chemically homogeneous convecting region. Crystallization at the top ultimately ceases, and continued upward convection of water-rich fluid causes a slight undersaturation adjacent to the roof despite cooler temperatures. By analogy, crystallization at the margins of a magma chamber and buoyant rise of the fractionated boundary layer into the roof zone can account for the chemical evolution of the magma system at the Mineral Mountains. To produce compositionally stratified silicic magmas requires thermal input to a silicic system via mafic magmas. The small volume, phenocryst-poor rhyolite magma which persisted for at least 300,000 years in the Mineral Mountains requires the presence of a continued thermal input from a mafic magma source. The presence of silicic lavas signifies that there is a substantial thermal anomaly both in the crust and upper mantle. The production of silicic lavas requires (1) the

  6. Analyzing the Distribution and Chemical Evolution of Major Nitrogen Carriers within Protoplanetary Disks

    Science.gov (United States)

    Pegues, Jamila; Oberg, Karin

    2016-01-01

    Nitrogen is an important component in many of the world's known organic and inorganic compounds, and its presence is crucial for the existence and survival of life as we know it on Earth today. And yet, in comparison to the total amount of nitrogen available, nitrogen exists as a depleted resource throughout the Solar System, with Earth and unearthed meteorites featuring nitrogen levels depleted from 1 to 5 orders of magnitude relative to the Sun. Additionally, comets have been discovered that contain depleted levels of N2 in comparison to CO, despite the similar binding strengths of both N2 and CO to ices, with ices functioning as the main component in comets.Mechanisms that are likely to play a major part in the distribution of nitrogen throughout the Solar System, and other extra-solar systems, are condensation fronts, such as snowlines and snowsurfaces. Here, condensation fronts refer to the locations at which 50% of a given volatile is contained in gaseous form, while the other 50% is contained within grain form. During formation, astronomical bodies will accumulate different chemical compositions, depending upon where they form with respect to the locations of the condensation fronts within the system. In addition, a system's initial chemistry, as well as how that chemistry evolves, will ultimately alter how the volatiles in the system are distributed over time.Thus, the locations of these condensation fronts, coupled with a protoplanetary disk's initial chemistry and chemical evolution, are mechanisms that affect the eventual distribution and evolution of the disk's volatiles. In this project, we characterize and interpret these mechanisms within disk models. We vary the disk's time dependence and initial chemical conditions, and then analyze the effects of those variations upon the main carriers of nitrogen in both gaseous and grain form. From observed patterns and characteristics of these varied models, we evolve our understanding of curious nitrogen

  7. The star formation and chemical evolution history of the Fornax dwarf spheroidal galaxy

    Science.gov (United States)

    de Boer, T. J. L.; Tolstoy, E.; Hill, V.; Saha, A.; Olszewski, E. W.; Mateo, M.; Starkenburg, E.; Battaglia, G.; Walker, M. G.

    2012-08-01

    We present deep photometry in the B, V and I filters from CTIO/MOSAIC for about 270 000 stars in the Fornax dwarf spheroidal galaxy, out to a radius of rell ≈ 0.8 degrees. By combining the accurately calibrated photometry with the spectroscopic metallicity distributions of individual red giant branch stars we obtain the detailed star formation and chemical evolution history of Fornax. Fornax is dominated by intermediate age (1-10 Gyr) stellar populations, but also includes ancient (10-14 Gyr), and young (≤1 Gyr) stars. We show that Fornax displays a radial age gradient, with younger, more metal-rich populations dominating the central region. This confirms results from previous works. Within an elliptical radius of 0.8 degrees, or 1.9 kpc from the centre, a total mass in stars of 4.3 × 107 M⊙ was formed, from the earliest times until 250 Myr ago. Using the detailed star formation history, age estimates are determined for individual stars on the upper RGB, for which spectroscopic abundances are available, giving an age-metallicity relation of the Fornax dSph from individual stars. This shows that the average metallicity of Fornax went up rapidly from [Fe/H] ≤ -2.5 dex to [Fe/H] = -1.5 dex between 8-12 Gyr ago, after which a more gradual enrichment resulted in a narrow, well-defined sequence which reaches [Fe/H] ≈ -0.8 dex, ≈3 Gyr ago. These ages also allow us to measure the build-up of chemical elements as a function of time, and thus determine detailed timescales for the evolution of individual chemical elements. A rapid decrease in [Mg/Fe] is seen for the stars with [Fe/H] ≥ -1.5 dex, with a clear trend in age. Table 1 is only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/544/A73

  8. The dynamical and chemical evolution of dwarf spheroidal galaxies with GEAR

    Science.gov (United States)

    Revaz, Y.; Jablonka, P.

    2012-02-01

    We present the fully parallel chemo-dynamical Tree/SPH code GEAR, which allows us to perform high resolution simulations with detailed chemical diagnostics. Starting from the public version of Gadget-2, we included the complex treatment of the baryon physics: gas cooling, star formation law, chemical evolution, and supernova feedback. We qualified the performances of GEAR in the case of dwarf spheroidal galaxies (dSphs) galaxies. Our code GEAR conserves the total energy budget of the systems to better than 5% over 14 Gyr and provides an excellent convergence of the results with numerical resolution. We showed that models of dSphs in a static Euclidean space, where the expansion of the universe is neglected are valid. In addition, we tackled some existing open questions in the field, such as the stellar mass fraction of dSphs and its link to the predicted dark matter halo mass function, the effect of supernova feedback, the spatial distribution of the stellar populations, and the origin of the diversity in star formation histories and chemical abundance patterns. Strong supernova-driven winds seem incompatible with the observed metallicities and luminosities. Despite newly formed stars being preferentially found in the galaxy central parts, turbulent motions in the gas can quickly erase any metallicity gradient. The diversity in properties of dSph are related to a range of total masses, as well as a range of dispersion in the central densities, which is also seen in the halos emerging from a ΛCDM cosmogony. Appendices A and B are available in electronic form at http://www.aanda.org

  9. Marine and terrestrial herbivores display convergent chemical ecology despite 400 million years of independent evolution.

    Science.gov (United States)

    Rasher, Douglas B; Stout, E Paige; Engel, Sebastian; Shearer, Tonya L; Kubanek, Julia; Hay, Mark E

    2015-09-29

    Chemical cues regulate key ecological interactions in marine and terrestrial ecosystems. They are particularly important in terrestrial plant-herbivore interactions, where they mediate both herbivore foraging and plant defense. Although well described for terrestrial interactions, the identity and ecological importance of herbivore foraging cues in marine ecosystems remain unknown. Here we show that the specialist gastropod Elysia tuca hunts its seaweed prey, Halimeda incrassata, by tracking 4-hydroxybenzoic acid to find vegetative prey and the defensive metabolite halimedatetraacetate to find reproductive prey. Foraging cues were predicted to be polar compounds but instead were nonpolar secondary metabolites similar to those used by specialist terrestrial insects. Tracking halimedatetraacetate enables Elysia to increase in abundance by 12- to 18-fold on reproductive Halimeda, despite reproduction in Halimeda being rare and lasting for only ∼36 h. Elysia swarm to reproductive Halimeda where they consume the alga's gametes, which are resource rich but are chemically defended from most consumers. Elysia sequester functional chloroplasts and halimedatetraacetate from Halimeda to become photosynthetic and chemically defended. Feeding by Elysia suppresses the growth of vegetative Halimeda by ∼50%. Halimeda responds by dropping branches occupied by Elysia, apparently to prevent fungal infection associated with Elysia feeding. Elysia is remarkably similar to some terrestrial insects, not only in its hunting strategy, but also its feeding method, defense tactics, and effects on prey behavior and performance. Such striking parallels indicate that specialist herbivores in marine and terrestrial systems can evolve convergent ecological strategies despite 400 million years of independent evolution in vastly different habitats. PMID:26324909

  10. Setting the volatile composition of (exo)planet-building material. Does chemical evolution in disk midplanes matter?

    CERN Document Server

    Eistrup, Christian; van Dishoeck, Ewine F

    2016-01-01

    [Abridged] Chemical evolution in the protoplanetary disk midplane can modify the composition of ices and gases. We have investigated if and how chemical evolution affects the abundances and distributions of key volatile species in the midplane of a protoplanetary disk in the 0.2-30 AU range. A full chemical network including gas-phase, gas-grain interactions and grain-surface chemistry is used to evolve chemistry in time, for 1 Myr. Great diversity is observed in the relative abundance ratios of the main considered species: H2O, CO, CO2, CH4, O2, NH3 and N2. The choice of ionisation level, the choice of initial abundances, as well as the extent of chemical reaction types included are all factors that affect the chemical evolution. The only exception is the inheritance scenario with a low ionisation level, which results in negligible changes compared with the initial abundances, regardless of whether grain-surface chemistry is included. The chemical processing changes the C/O ratios for gas and ice significant...

  11. Measurements of trace gases that may indicate or influence the tropospheric oxidising capacityusing a chemical ionisation mass spectrometer (CIMS)

    OpenAIRE

    Bannan, Thomas James

    2015-01-01

    The oxidation of primary emitted species such as volatile organic compounds (VOCs) acts as a source of ozone and therefore has detrimental effects on air quality and climate. In order to understand at what rate oxidation is occurring in the troposphere, i.e. the oxidation capacity, an understanding of the contributors to oxidation and possible markers of oxidation are imperative. Formic acid, a ubiquitous trace gas, which contributes significantly to the acidity of precipitation, could, becau...

  12. Progress in microbial activity and chemical properties of a trace element polluted soil under assisted natural remediation

    OpenAIRE

    Pérez de Mora, Alfredo; Burgos, Pilar; Cabrera, Francisco, (S.I.) (1724-1799); Madejón, Engracia

    2012-01-01

    In this work, we studied the temporal dynamics of several microbiological properties in a trace element polluted soil under the influence of various amendments and/or a plant cover during a 30 month-period. The experiment was carried out in containers filled with ca. 150 kg of contaminated soil. Seven treatments were established: four organic (leonardite LEO, litter LIT, municipal waste compost MWC and biosolid compost BC) and one inorganic (sugarbeet lime SL), where the gra...

  13. From the Beginning: The "Journal of Chemical Education" and Secondary School Chemistry

    Science.gov (United States)

    Lagowski, Joseph J.

    2014-01-01

    The people, events, and issues that were involved in the beginning and the evolution of the "Journal of Chemical Education" and the Division of Chemical Education (DivCHED) are traced and discussed. The constitution of the American Chemical Society incorporates the roots of chemical education as an area of interest to the Society. Both…

  14. Radial metallicity gradients in spiral galaxies from H II regions and planetary nebulae: probing galactic chemical evolution

    Science.gov (United States)

    Stanghellini, Letizia

    2015-08-01

    Radial metallicity gradients, typically observed in spiral galaxies, are excellent constraints for chemical evolution models. The contemporary studies of the two stellar populations, whose progenitors have formed at different times, yield to the chemical and time constraining of the models. In this context, planetary nebula and HII region analysis proved to be ideal two-epochs test populations. We present an assortment of galaxies whose oxygen abundances have been determined both with weak- and strong-line methods, and whose radial metallicity gradients and their evolution in time have disclosed very interesting correlations with the galaxy characteristics. New results from our Gemini/GMOS observations, and a review of the best literature data, set the stage for a better understanding of spiral galaxy evolution.

  15. Enhancing the detection sensitivity of trace analysis of pharmaceutical genotoxic impurities by chemical derivatization and coordination ion spray-mass spectrometry.

    Science.gov (United States)

    Bai, Lin; Sun, Mingjiang; An, Jianguo; Liu, David Q; Chen, Ted K; Kord, Alireza S

    2010-01-15

    Many pharmaceutical genotoxic impurities are neutral molecules. Trace level analysis of these neutral analytes is hampered by their poor ionization efficiency in mass spectrometry (MS). Two analytical approaches including chemical derivatization and coordination ion spray-MS were developed to enhance neutral analyte detection sensitivity. The chemical derivatization approach converts analytes into highly ionizable or permanently charged derivatives, which become readily detectable by MS. The coordination ion spray-MS method, on the other hand, improves ionization by forming neutral-ion adducts with metal ions such as Na(+), K(+), or NH(4)(+) which are introduced into the electrospray ionization source. Both approaches have been proven to be able to enhance the detection sensitivity of neutral pharmaceuticals dramatically. This article demonstrates the successful applications of the two approaches in the analysis of four pharmaceutical genotoxic impurities identified in a single drug development program, of which two are non-volatile alkyl chlorides and the other two are epoxides. PMID:19954782

  16. Improvement in the chemical separation and determination of uncertainties for bulk analysis of Pu isotopes at ultra-trace levels by using MC-ICP-MS

    International Nuclear Information System (INIS)

    Improved bulk analysis based on extraction chromatography and systematic evaluations of uncertainties of plutonium isotopes at ultra-trace levels in environmental swipe samples are presented. In the modified method based on a single column system using UTEVA resin for MC-ICP-MS, hydrogen peroxide was introduced to obtain pure plutonium isotopes from chemical separation by removing excess organic-based reducing reagents. We confirmed that hydrogen peroxide effectively decomposed the reducing reagents characterized by UV-Vis absorption spectroscopy and the peak fluctuations were significantly reduced. To examine the reliability of analytical performance, we systematically evaluated the combined uncertainties during the overall chemical procedures using simulated samples containing Pu reference materials. (author)

  17. Harmony search algorithm with differential evolution based control parameter co-evolution and its application in chemical process dynamic optimization

    Institute of Scientific and Technical Information of China (English)

    范勤勤; 王循华; 颜学峰

    2015-01-01

    A modified harmony search algorithm with co-evolutional control parameters (DEHS), applied through differential evolution optimization, is proposed. In DEHS, two control parameters, i.e., harmony memory considering rate and pitch adjusting rate, are encoded as a symbiotic individual of an original individual (i.e., harmony vector). Harmony search operators are applied to evolving the original population. DE is applied to co-evolving the symbiotic population based on feedback information from the original population. Thus, with the evolution of the original population in DEHS, the symbiotic population is dynamically and self-adaptively adjusted, and real-time optimum control parameters are obtained. The proposed DEHS algorithm has been applied to various benchmark functions and two typical dynamic optimization problems. The experimental results show that the performance of the proposed algorithm is better than that of other HS variants. Satisfactory results are obtained in the application.

  18. Evolution of the Stratospheric Temperature and Chemical Composition over One Titanian Year

    Science.gov (United States)

    Coustenis, Athena; Bampasidis,G.; Achterberg, R. K.; Lavvas, P.; Jennings, D. E.; Nixon, C. A.; Teanby, N. A.; Vinatier, S.; Flasar, F. M.; Carlson, R. C.; Orton, G.; Romani, P. N.; Guandique, E. A.; Stamogiorgos, S.

    2013-01-01

    Since the Voyager 1 (V1) flyby in 1980, Titans exploration from space and the ground has been ongoing for more than a full revolution of Saturn around the Sun (one Titan year or 29.5 Earth years was completed in May 2010). In this study we search for temporal variations affecting Titans atmospheric thermal and chemical structure within that year. We process Cassini CIRS data taken during the Titan flybys from 2006-2013 and compare them to the 1980 V1IRIS spectra (re-analyzed here). We also consider data from Earth-based and -orbiting observatories (such as from the ISO, re-visited). When we compare the CIRS 2010 and the IRIS data we find limited inter-annual variations, below the 25 or35 levels for the lower and middle, or the high latitudes, respectively. A return to the 1980 stratospheric temperatures and abundances is generally achieved from 50degN to 50degS, indicative of the solar radiation being the dominating energy source at 10 AU, as for the Earth, as predicted by GCM and photochemical models. However, some exceptions exist among the most complex hydrocarbons (C4H2 and C3H4), especially in the North. In the Southern latitudes, since 2012, we see a trend for an increase of several trace gases, possibly indicative of a seasonal atmospheric reversal. At the Northern latitudes we found enhanced abundances around the period of the northern spring equinox in mid-2009 (as in Bampasidis et al. 2012), which subsequently decreased (from 2010-2012) returning to values similar to those found in the V1 epoch a Titanian year before.

  19. Chemical evolution of groundwater in a drainage basin of Holocene age, east-central Alberta, Canada

    Science.gov (United States)

    Wallick, E. I.

    1981-12-01

    Chemical evolution of groundwater in a small drainage basin of glacial origin (10,250 yr. B.P., based on radiocarbon age dating of gyttja from a closed saline lake in the basin) was studied in order to understand the generation of salts in surface-mined areas on the interior plains of Alberta. The basin was considered to be a natural analogue of a surface-disturbed area because of the large volumes of rock that had been redistributed by glaciers with the resulting change in topography and drainage. The distributions of hydraulic head, total dissolved solids (TDS), and environmental isotopes essentially reflect the superimposition of groundwater flow systems associated with the post-glacial topography upon a regional bedrock flow system of older but undertermined age. In the glacial drift aquifers and aquitards (sands and till), the groundwater composition was typically Ca-Mg-bicarbonate type at depths less than 30 m, but at depths of 30-100 m, the composition was Na-bicarbonate-sulfate type. In the deeper bedrock aquifers (> 100 m), Nabicarbonate-sulfate and Na-bicarbonate-chloride types were present. TDS was as low as 400 mg/l in the shallow drift aquifer, generally constant at ˜1000 mg/l in the deep drift and shallow bedrock aquifer, and over 1700 mg/l in the deep bedrock aquifer system. Chemical evolution of groundwater in the area appears to be dominated by two depth zones having different types of water-rock interaction. In the shallow drift zone, the dissolution of soil CO 2 in infiltrating groundwater, oxidation of organic carbon, sulfur and pyrite result in the formation of carbonic and sulfuric acids that attack carbonate and silicate minerals. On the basis of X-ray diffraction analysis, these minerals were calcite, dolomite, plagioclase feldspar, and smectite clays. However, in the deep regional bedrock aquifer, conditions are reducing (presence of methane), groundwater is alkaline (pH 8.6-10.3), and the Na-bicarbonate-chloride composition of groundwater

  20. Chemical evolution during the process of proto-star formation by considering a two dimensional hydrodynamic model

    CERN Document Server

    Das, Ankan; Chakrabarti, Sandip K; Chakrabarti, Sonali

    2013-01-01

    Chemical composition of a molecular cloud is highly sensitive to the physical properties of the cloud. In order to obtain the chemical composition around a star forming region, we carry out a two dimensional hydrodynamical simulation of the collapsing phase of a proto-star. A total variation diminishing scheme (TVD) is used to solve the set of equations governing hydrodynamics. This hydrodynamic code is capable of mimicking evolution of the physical properties during the formation of a proto-star. We couple our reasonably large gas-grain chemical network to study the chemical evolution during the collapsing phase of a proto-star. To have a realistic estimate of the abundances of bio-molecules in the interstellar medium, we include the recently calculated rate coefficients for the formation of several interstellar bio-molecules into our gas phase network. Chemical evolution is studied in detail by keeping grain at the constant temperature throughout the simulation as well as by using the temperature variation ...

  1. The Heating of Mid-Infrared Dust in the Nearby Galaxy M33: A Testbed for Tracing Galaxy Evolution

    CERN Document Server

    Calapa, M; Draine, B T; Boquien, M; Kramer, C; Xilouris, M; Verley, S; Braine, J; Relaño-Pastor, M; van der Werf, P; Israel, F; Hermelo, I; Albrecht, M

    2014-01-01

    Because the 8 {\\mu}m polycyclic aromatic hydrocarbon (PAH) emission has been found to correlate with other well-known star formation tracers, it has widely been used as a star formation rate (SFR) tracer. There are, however, studies that challenge the accuracy and reliability of the 8 {\\mu}m emission as a SFR tracer. Our study, part of the Herschel M33 Extended Survey (HERM33ES) open time key program, aims at addressing this issue by analyzing the infrared emission from the nearby spiral galaxy M33 at the high spatial scale of 75 pc. Combining data from the Herschel Space Observatory and the Spitzer Space Telescope we find that the 8 {\\mu}m emission is better correlated with the 250 {\\mu}m emission, which traces cold interstellar gas, than with the 24 {\\mu}m emission. The L(8)/L(24) ratio is highly depressed in 24 {\\mu}m luminous regions, which correlate with known HII regions. We also compare our results with the dust emission models by Draine & Li (2007). We confirm that the depression of 8 {\\mu}m PAH e...

  2. Chemical Identification of Archaeological Obsidian from Lagartero, Chiapas, Mexico, Using Main and Trace Elements Determined by PIXE. Chapter 10

    International Nuclear Information System (INIS)

    Proton induced X ray emission (proton PIXE) analysis has been used for determination of minor and trace element concentrations of archaeological obsidian samples, which were collected at the site at Lagartero, Chiapas, Mexico. Samples of Mexican and Guatemalan sources were also analysed. Statistical treatments such as principal component analyses were applied to the data set. Obsidians from Lagartero were identified as coming from the Guatemalan sources of Ixtepeque and El Chayal, with one sample from Ucareo/Zinapecuaro, Mexico. These results indicate that there was contact between the population of Lagartero and other Mayans or Mesoamericans. (author)

  3. Temperature evolution of the band gap in BiFeO3 traced by resonant Raman scattering

    Science.gov (United States)

    Weber, Mads Christof; Guennou, Mael; Toulouse, Constance; Cazayous, Maximilien; Gillet, Yannick; Gonze, Xavier; Kreisel, Jens

    2016-03-01

    Knowledge of the electronic band structure of multiferroic oxides, crucial for the understanding and tuning of photoinduced effects, remains very limited even in the model and thoroughly studied BiFeO3. Here, we investigate the electronic band structure of BiFeO3 using Raman scattering with twelve different excitation wavelengths ranging from the blue to the near infrared. We show that resonant Raman signatures can be assigned to direct and indirect electronic transitions, as well as in-gap electronic levels, most likely associated with oxygen vacancies. Their temperature evolution establishes that the remarkable and intriguing variation of the optical band gap can be related to the shrinking of an indirect electronic band gap, while the energies for direct electronic transitions remains nearly temperature independent.

  4. Ultrafaint dwarfs—star formation and chemical evolution in the smallest galaxies

    International Nuclear Information System (INIS)

    In earlier work, we showed that a dark matter halo with a virial mass of 107 M ☉ can retain a major part of its baryons in the face of the pre-ionization phase and supernova (SN) explosion from a 25 M ☉ star. Here, we expand on the results of that work, investigating the star formation and chemical evolution of the system beyond the first SN. In a galaxy with a mass M vir = 107 M ☉, sufficient gas is retained by the potential for a second period of star formation to occur. The impact of a central explosion is found to be much stronger than that of an off-center explosion both in blowing out the gas and in enriching it, as in the off-center case most of the SN energy and metals escape into the intergalactic medium. We model the star formation and metallicity, given the assumption that stars form for 100, 200, 400, and 600 Myr, and discuss the results in the context of recent observations of very low-mass galaxies. We show that we can account for most features of the observed relationship between [α/Fe] and [Fe/H] in ultra-faint dwarf galaxies with the assumption that the systems formed at a low mass, rather than being remnants of much larger systems.

  5. Ultrafaint dwarfs—star formation and chemical evolution in the smallest galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Webster, David; Bland-Hawthorn, Joss [Sydney Institute for Astronomy, School of Physics, University of Sydney, NSW 2006 (Australia); Sutherland, Ralph, E-mail: d.webster@physics.usyd.edu.au [Research School of Astronomy and Astrophysics, Australian National University, Cotter Road, Weston, ACT 2611 (Australia)

    2014-11-20

    In earlier work, we showed that a dark matter halo with a virial mass of 10{sup 7} M {sub ☉} can retain a major part of its baryons in the face of the pre-ionization phase and supernova (SN) explosion from a 25 M {sub ☉} star. Here, we expand on the results of that work, investigating the star formation and chemical evolution of the system beyond the first SN. In a galaxy with a mass M {sub vir} = 10{sup 7} M {sub ☉}, sufficient gas is retained by the potential for a second period of star formation to occur. The impact of a central explosion is found to be much stronger than that of an off-center explosion both in blowing out the gas and in enriching it, as in the off-center case most of the SN energy and metals escape into the intergalactic medium. We model the star formation and metallicity, given the assumption that stars form for 100, 200, 400, and 600 Myr, and discuss the results in the context of recent observations of very low-mass galaxies. We show that we can account for most features of the observed relationship between [α/Fe] and [Fe/H] in ultra-faint dwarf galaxies with the assumption that the systems formed at a low mass, rather than being remnants of much larger systems.

  6. Microstructure and chemical bond evolution of diamond-like carbon films machined by femtosecond laser

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jing; Wang, Chunhui [Science and Technology on Thermostructure Composite Materials Laboratory, Northwestern Polytechnical University, Xi’an 710072 (China); Liu, Yongsheng, E-mail: yongshengliu@nwpu.edu.cn [Science and Technology on Thermostructure Composite Materials Laboratory, Northwestern Polytechnical University, Xi’an 710072 (China); Cheng, Laifei [Science and Technology on Thermostructure Composite Materials Laboratory, Northwestern Polytechnical University, Xi’an 710072 (China); Li, Weinan [State Key Laboratory of Transient Optics and Photonics, Xi’an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi’an 10068 (China); Zhang, Qing [Science and Technology on Thermostructure Composite Materials Laboratory, Northwestern Polytechnical University, Xi’an 710072 (China); Yang, Xiaojun [State Key Laboratory of Transient Optics and Photonics, Xi’an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi’an 10068 (China)

    2015-06-15

    Highlights: • The machining depth was essentially proportional to the laser power. • The well patterned microgrooves and ripple structures with nanoparticles were formed distinctly in the channels. And the number of nanoparticles increased with the processing power as well. • It revealed a conversion from amorphous carbon to nanocrystalline graphite after laser treated with increasing laser power. • It showed that a great decrease of sp{sup 3}/sp{sup 2} after laser treatment. - Abstract: Femtosecond laser is of great interest for machining high melting point and hardness materials such as diamond-like carbon, SiC ceramic, et al. In present work, the microstructural and chemical bond evolution of diamond-like carbon films were investigated using electron microscopy and spectroscopy techniques after machined by diverse femtosecond laser power in air. The results showed the machining depth was essentially proportional to the laser power. The well patterned microgrooves and ripple structures with nanoparticles were formed distinctly in the channels. Considering the D and G Raman band parameters on the laser irradiation, it revealed a conversion from amorphous carbon to nanocrystalline graphite after laser treated with increasing laser power. X-ray photoelectron spectroscopy analysis showed a great decrease of sp{sup 3}/sp{sup 2} after laser treatment.

  7. Bimodal chemical evolution of the Galactic disk and the Barium abundance of Cepheids

    CERN Document Server

    Lepine, Jacques R D; Barros, Douglas A; Junqueira, Thiago C; Scarano, Sergio

    2013-01-01

    In order to understand the Barium abundance distribution in the Galactic disk based on Cepheids, one must first be aware of important effects of the corotation resonance, situated a little beyond the solar orbit. The thin disk of the Galaxy is divided in two regions that are separated by a barrier situated at that radius. Since the gas cannot get across that barrier, the chemical evolution is independent on the two sides of it. The barrier is caused by the opposite directions of flows of gas, on the two sides, in addition to a Cassini-like ring void of HI (caused itself by the flows). A step in the metallicity gradient developed at corotation, due to the difference in the average star formation rate on the two sides, and to this lack of communication between them. In connection with this, a proof that the spiral arms of our Galaxy are long-lived (a few billion years) is the existence of this step. When one studies the abundance gradients by means of stars which span a range of ages, like the Cepheids, one has...

  8. Microstructure and chemical bond evolution of diamond-like carbon films machined by femtosecond laser

    International Nuclear Information System (INIS)

    Highlights: • The machining depth was essentially proportional to the laser power. • The well patterned microgrooves and ripple structures with nanoparticles were formed distinctly in the channels. And the number of nanoparticles increased with the processing power as well. • It revealed a conversion from amorphous carbon to nanocrystalline graphite after laser treated with increasing laser power. • It showed that a great decrease of sp3/sp2 after laser treatment. - Abstract: Femtosecond laser is of great interest for machining high melting point and hardness materials such as diamond-like carbon, SiC ceramic, et al. In present work, the microstructural and chemical bond evolution of diamond-like carbon films were investigated using electron microscopy and spectroscopy techniques after machined by diverse femtosecond laser power in air. The results showed the machining depth was essentially proportional to the laser power. The well patterned microgrooves and ripple structures with nanoparticles were formed distinctly in the channels. Considering the D and G Raman band parameters on the laser irradiation, it revealed a conversion from amorphous carbon to nanocrystalline graphite after laser treated with increasing laser power. X-ray photoelectron spectroscopy analysis showed a great decrease of sp3/sp2 after laser treatment

  9. Chemical abundances in low surface brightness galaxies: Implications for their evolution

    Science.gov (United States)

    Mcgaugh, S. S.; Bothun, G. D.

    1993-01-01

    Low Surface Brightness (LSB) galaxies are an important but often neglected part of the galaxy content of the universe. Their importance stems both from the selection effects which cause them to be under-represented in galaxy catalogs, and from what they can tell us about the physical processes of galaxy evolution that has resulted in something other than the traditional Hubble sequence of spirals. An important constraint for any evolutionary model is the present day chemical abundances of LSB disks. Towards this end, spectra for a sample of 75 H 2 regions distributed in 20 LSB disks galaxies were obtained. Structurally, this sample is defined as having B(0) fainter than 23.0 mag arcsec(sup -2) and scale lengths that cluster either around 3 kpc or 10 kpc. In fact, structurally, these galaxies are very similar to the high surface brightness spirals which define the Hubble sequence. Thus, our sample galaxies are not dwarf galaxies but instead have masses comparable to or in excess of the Milky Way. The basic results from these observations are summarized.

  10. The Role of the IGIMF in the chemical evolution of the solar neighbourhood

    CERN Document Server

    Calura, Francesco; Matteucci, Francesca; Kroupa, Pavel

    2011-01-01

    The integrated galactic initial mass function (IGIMF) is computed from the combination of the stellar initial mass function (IMF) and the embedded cluster mass function, described by a power law with index beta. The result of the combination is a time-varying IMF which depends on the star formation rate. We applied the IGIMF formalism to a chemical evolution model for the solar neighbourhood and compared the results obtained by assuming three possible values for beta with the ones obtained by means of a standard, well-tested, constant IMF. In general, a lower absolute value of beta implies a flatter IGIMF, hence a larger number of massive stars, higher Type Ia and II supernova rates, higher mass ejection rates and higher [alpha/Fe] values at a given metallicity. Our suggested fiducial value for beta is 2, since with this value we can account for most of the local observables. We discuss our results in a broader perspective, with some implications regarding the possible universality of the IMF and the importan...

  11. Structural and morphological evolution of gallium nitride nanorods grown by chemical beam epitaxy

    International Nuclear Information System (INIS)

    The morphological and structural evolution is presented for GaN nanorods grown by chemical beam epitaxy on (0001) Al2O3 substrates. Their structural and optical properties are investigated by x-ray diffraction, scanning and transmission electron microscopy, and temperature-dependent photoluminescence measurements. While increasing the growth temperature and the flow rate of radio-frequency nitrogen radical, the three-dimensional growth mode will be enhanced to form one-dimensional nanostructures. The high density of well-aligned nanorods with a diameter of 30-50 nm formed uniformly over the entire sapphire substrate. The x-ray diffraction patterns and transmission electron microscopic images indicate that the self-assembled GaN nanorods are a pure single crystal and preferentially oriented in the c-axis direction. Particularly, the ''S-shape'' behavior with localization of ∼10 meV observed in the temperature-dependent photoluminescence might be ascribed to the fluctuation in crystallographic defects and composition.

  12. The Influence of Environment on the Chemical Evolution in Low-mass Galaxies

    CERN Document Server

    Liu, Yiqing; Peng, Eric

    2016-01-01

    The mean alpha-to-iron abundance ratio ([$\\alpha$/Fe]) of galaxies is sensitive to the chemical evolution processes at early time, and it is an indicator of star formation timescale ($\\tau_{{\\rm SF}}$). Although the physical reason remains ambiguous, there is a tight relation between [$\\alpha$/Fe] and stellar velocity dispersion ($\\sigma$) among massive early-type galaxies (ETGs). However, no work has shown convincing results as to how this relation behaves at low masses. We assemble 15 data sets from the literature and build a large sample that includes 192 nearby low-mass ($18<\\sigma<80$~\\kms) ETGs. We find that the [$\\alpha$/Fe]-$\\sigma$ relation generally holds for low-mass ETGs, except in extreme environments. Specifically, in normal galaxy cluster environments, the [$\\alpha$/Fe]-$\\sigma$ relation and its intrinsic scatter are, within uncertainties, similar for low-mass and high-mass ETGs. However, in the most massive relaxed galaxy cluster in our sample, the zero point of the relation is higher an...

  13. Evolution of microbiological and physico-chemical quality of pasteurized milk

    Directory of Open Access Journals (Sweden)

    Natalia Gonzaga

    2015-11-01

    Full Text Available Milk quality is defined, among other parameters, by a reduced number of spoilage microorganisms, low somatic cell count and the absence of pathogens and chemical waste. Several studies conducted in different regions of the country have emphasized the high percentage of samples not complying with the standard. The purpose of this study was to evaluate the evolution of microbiological and physicochemical quality of pasteurized milk produced in the State of Paraná over 7 years. A total of 457 samples of pasteurized milk were analyzed, 104 samples in 2008, 269 samples in 2011 and 84 samples in 2014. The samples were subjected to physicochemical analysis of cryoscopy and enzyme search for alkaline phosphatase and peroxidase. Regarding microbiological tests, coliform counts were performed at 30°C and 45°C and count plate pattern. In the laboratory, physicochemical analysis were performed according to the Normative 68 and microbiological as normative instruction 62, both of the Brazilian Ministry of Agriculture, Livestock and Food Supply. The results showed that over the years the microbiological quality of milk decreased, with an increase of non-standard samples. For enzymes alkaline phosphatase, peroxidase, the pasteurization temperature has been observed over time and the overheating of the milk was more frequent in 2011. Fraud by addition of water in milk has either decreased or become more sophisticated, making its detection difficult.

  14. Structural and morphological evolution of gallium nitride nanorods grown by chemical beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Kuo, Shou-Yi; Lai, Fang-I; Chen, Wei-Chun; Hsiao, Chien-Nan; Lin, Woei-Tyng [Department of Electronic Engineering, Chang Gung University, Taiwan, Green Technology Research Center, Chang Gung University, 259 Wen-Hwa 1st Road, Kwei-Shan, Tao-Yuan 333, Taiwan (China); Department of Electrical Engineering, Yuan-Ze University, Taiwan, 135, Far-East Rd., Chung-Li, Taoyuan, Tao-Yuan, 320, Taiwan (China); Instrument Technology Research Center, National Applied Research Laboratories, Taiwan, 20 R and D Road VI, Hsinchu Science Park, Hsinchu 300, Taiwan (China); Department of Electrical Engineering, Yuan-Ze University, Taiwan, 135, Far-East Road, Chung-Li, Taoyuan, Tao-Yuan, 320, Taiwan (China)

    2009-07-15

    The morphological and structural evolution is presented for GaN nanorods grown by chemical beam epitaxy on (0001) Al{sub 2}O{sub 3} substrates. Their structural and optical properties are investigated by x-ray diffraction, scanning and transmission electron microscopy, and temperature-dependent photoluminescence measurements. While increasing the growth temperature and the flow rate of radio-frequency nitrogen radical, the three-dimensional growth mode will be enhanced to form one-dimensional nanostructures. The high density of well-aligned nanorods with a diameter of 30-50 nm formed uniformly over the entire sapphire substrate. The x-ray diffraction patterns and transmission electron microscopic images indicate that the self-assembled GaN nanorods are a pure single crystal and preferentially oriented in the c-axis direction. Particularly, the ''S-shape'' behavior with localization of {approx}10 meV observed in the temperature-dependent photoluminescence might be ascribed to the fluctuation in crystallographic defects and composition.

  15. Recharge in northern clime calcareous sandy soils: soil water chemical and carbon-14 evolution

    International Nuclear Information System (INIS)

    Chemical analyses were performed on soil water extracted from two cores taken from a sandy calcareous soil near Delhi, Ontario. Calcite saturation is attained within the unsaturated zone over short distances and short periods of time, whereas dolomite undersaturation persists to the groundwater table. The progressive dissolution of dolomite by soil water, within the unsaturated zone, after calcite saturation is reached results in calcite supersaturation. Deposition of iron and manganese oxyhydroxide phases occurs at the carbonate leached/unleached zone boundary. This is a result of soil water neutralization due to carbonate dissolution during infiltration but may also reflect the increased rate of oxidation of dissolved ferrous and manganous ions at higher pH's. The role of bacteria in this process has not been investigated. The depth of the carbonate leached/unleached zone boundary in a calcareous soil has important implications for 14C groundwater dating. The depth of this interface at the study site (= approximately 2 m) does not appear to limit 14C diffusion from the root zone to the depth at which carbonate dissolution occurs. Thus, soil water achieves open system isotopic equilibrium with the soil CO2 gas phase. It is calculated that in soils with similar physical properties to the study soil but with depths of leaching of 5 m or more, complete 14C isotopic equilibration of soil water with soil gas would not occur. Soil water, under these conditions would recharge to the groundwater exhibiting some degree of closed system 14C isotopic evolution. (author)

  16. Evolution and chemical and dynamical effects of high-mass stars

    CERN Document Server

    Meynet, Georges; Georgy, Cyril; Pignatari, Marco; Hirschi, Raphael; Ekstrom, Sylvia; Maeder, Andre

    2008-01-01

    We review general characteristics of massive stars, present the main observable constraints that stellar models should reproduce. We discuss the impact of massive star nucleosynthesis on the early phases of the chemical evolution of the Milky Way (MW). We show that rotating models can account for the important primary nitrogen production needed at low metallicity. Interestingly such rotating models can also better account for other features as the variation with the metallicity of the C/O ratio. Damped Lyman Alpha (DLA) systems present similar characteristics as the halo of the MW for what concern the N/O and C/O ratios. Although in DLAs, the star formation history might be quite different from that of the halo, in these systems also, rotating stars (both massive and intermediate) probably play an important role for explaining these features. The production of primary nitrogen is accompanied by an overproduction of other elements as $^{13}$C, $^{22}$Ne and s-process elements. We show also how the observed var...

  17. Evolution of spectral behavior and chemical composition in the tree canopy of a dehesa ecosystem

    Directory of Open Access Journals (Sweden)

    R. González-Cascón

    2016-06-01

    Full Text Available In the context of the BIOSPEC and FLUXPEC projects (http://www.lineas.cchs.csic.es/fluxpec/, spectral and biophysical variables measurements at leaf level have been conducted in the tree canopy of a holm oak dehesa (Quercus ilex ecosystem during four vegetative periods. Measurements of bi-conical reflectance factor of intact leaf (ASD Fieldspec 3® spectroradiometer, specific leaf mass (SLM, leaf water content (LWC, nutrient (N, P, K, Ca, Mg, Mn, Fe, and Zn and chlorophyll concentration were performed. The spectral measurements have been related with the biophysical variables by stepwise and partial least squares regression analyses. These analyses allowed to identify the spectral bands and regions that best explain the evolution of the biophysical variables and to estimate the nutrient contents during the leaf maturation process. Statistically significant estimates of the majority of the variables studied were obtained. Wavelengths that had the highest contributions explaining the chemical composition of the forest canopy were located in spectral regions of the red edge, the green visible region, and the shortwave infrared.

  18. Observational approach to the chemical evolution of high-mass binaries

    CERN Document Server

    Pavlovski, K; Tamajo, E; Kolbas, V

    2010-01-01

    The complexity of composite spectra of close binaries makes the study of the individual stellar spectra extremely difficult. For this reason there exists very little information on the chemical composition of high-mass stars in close binaries, despite its importance for understanding the evolution of massive stars and close binary systems. A way around this problem exists: spectral disentangling allows a time-series of composite spectra to be decomposed into their individual components whilst preserving the total signal-to-noise ratio in the input spectra. Here we present the results of our ongoing project to obtain the atmospheric parameters of high-mass components in binary and multiple systems using spectral disentangling. So far, we have performed detailed abundance studies for 14 stars in eight eclipsing binary systems. Of these, V380 Cyg, V621 Per and V453 Cyg are the most informative as their primary components are evolved either close to or beyond the TAMS. Contrary to theoretical predictions of rotat...

  19. Oxygen Gas Abundances at z~1.4: Implications for the Chemical Evolution History of Galaxies

    CERN Document Server

    Maier, C; Carollo, C M; Meisenheimer, K; Hippelein, H; Stockton, A

    2006-01-01

    The 1chemical evolution models are used to relate t...

  20. Introducing Graduate Students to the Chemical Information Landscape: The Ongoing Evolution of a Graduate-Level Chemical Information Course

    Science.gov (United States)

    Currano, Judith N.

    2016-01-01

    The University of Pennsylvania's doctoral chemistry curriculum has included a required course in chemical information since 1995. Twenty years later, the course has evolved from a loosely associated series of workshops on information resources to a holistic examination of the chemical literature and its place in the general research process. The…

  1. Chemical evolution of the Galactic bulge as traced by microlensed dwarf and subgiant stars. IV. Two bulge populations

    CERN Document Server

    Bensby, T; Meléndez, J; Gould, A; Feltzing, S; Asplund, M; Johnson, J A; Lucatello, S; Yee, J C; Ramírez, I; Cohen, J G; Thompson, I; Gal-Yam, A; Sumi, T; Bond, I A

    2011-01-01

    [ABRIDGED] Based on high-resolution (R~42000 to 48000) and high signal-to-noise (S/N~50 to 150) spectra obtained with UVES/VLT, we present detailed elemental abundances (O, Na, Mg, Al, Si, Ca, Ti, Cr, Fe, Ni, Zn, Y, and Ba) and stellar ages for 26 microlensed dwarf and subgiant stars in the Galactic bulge. The analysis is based on equivalent width measurements and standard 1-D LTE MARCS model stellar atmospheres. We also present NLTE Li abundances based on line synthesis of the 7Li line at 670.8 nm. We show that the bulge metallicity distribution (MDF) is double-peaked; one peak at [Fe/H]= -0.6 and one at [Fe/H]=+0.3, and with a dearth of stars around solar metallicity. This is in contrast to the MDF derived from red giants in Baade's window, which peaks at this exact value. A simple significance test shows that it is extremely unlikely to have such a gap in the microlensed dwarf star MDF if the dwarf stars are drawn from the giant star MDF. To resolve this issue we discuss several possibilities, but we can n...

  2. Tourmaline as a recorder of magmatic-hydrothermal evolution: an in situ major and trace element analysis of tourmaline from the Qitianling batholith, South China

    Science.gov (United States)

    Yang, Shui-Yuan; Jiang, Shao-Yong; Zhao, Kui-Dong; Dai, Bao-Zhang; Yang, Tao

    2015-12-01

    Four types of tourmaline in the Qitianling granitic batholith, South China, were identified in this study: euhedral disseminated tourmaline (DT type) in the early stage of granite consolidation; typical interstitial nodular tourmaline (NT type) formed late in the crystallization history; radial tourmaline veinlet (RT type) and vein tourmaline (VT type) of hydrothermal origin. We performed major and trace element analysis by in situ electron microprobe and laser ablation inductively coupled plasma mass spectrometry on these four tourmaline types. Compositionally, these tourmalines fall into the alkali group and schorl-dravite solid solution series. There is clear correlation between trace and major elements in VT-type tourmalines, likely related to co-variations of these elements in the hydrothermal fluid from which the tourmaline precipitated. Tourmaline from granites displays low REE abundances and negative LREE trends, positive Eu anomalies, and HREE below or close to their detection limits. The DT-type tourmalines show a positive Eu anomaly, which is probably due to a preferential incorporation of Eu2+ over Eu3+. REE depletion in NT-type tourmalines may reflect co-crystallization of REE-rich minerals. The positive Eu anomaly in NT-type tourmalines is due to late-stage release of Eu2+ caused by tourmaline replacement of early feldspar. Vein tourmalines (RT and VT type) display similar slopes from La to Nd, without an Eu anomaly. The chondrite-normalized REE patterns in tourmalines from veins display a concave upward-shaped, MREE-depleted pattern, with minimum values at Ho increasing steadily to Lu, and may reflect the REE characteristics of the precipitated medium. HREE enrichment in hydrothermal fluid can be attributed to the formation of REE-fluoride complexes during the internal fluid evolution.

  3. THE TWO-PHASE FORMATION HISTORY OF SPIRAL GALAXIES TRACED BY THE COSMIC EVOLUTION OF THE BAR FRACTION

    International Nuclear Information System (INIS)

    We study the evolution of galactic bars and the link with disk and spheroid formation in a sample of zoom-in cosmological simulations. Our simulation sample focuses on galaxies with present-day stellar masses in the 1010-1011 M☉ range, in field and loose group environments, with a broad variety of mass growth histories. In our models, bars are almost absent from the progenitors of present-day spirals at z > 1.5, and they remain rare and generally too weak to be observable down to z ≈ 1. After this characteristic epoch, the fractions of observable and strong bars rise rapidly, bars being present in 80% of spiral galaxies and easily observable in two thirds of these at z ≤ 0.5. This is quantitatively consistent with the redshift evolution of the observed bar fraction, although the latter is presently known up to z ≈ 0.8 because of band-shifting and resolution effects. Our models hence predict that the decrease in the bar fraction with increasing redshift should continue with a fraction of observable bars not larger than 10%-15% in disk galaxies at z > 1. Our models also predict later bar formation in lower-mass galaxies, in agreement with existing data. We find that the characteristic epoch of bar formation, namely redshift z ≈ 0.8-1 in the studied mass range, corresponds to the epoch at which today's spirals acquire their disk-dominated morphology. At higher redshift, disks tend to be rapidly destroyed by mergers and gravitational instabilities and rarely develop significant bars. We hence suggest that the bar formation epoch corresponds to the transition between an early 'violent' phase of spiral galaxy formation at z ≥ 1 and a late 'secular' phase at z ≤ 0.8. In the secular phase, the presence of bars substantially contributes to the growth of the (pseudo-)bulge, but the bulge mass budget remains statistically dominated by the contribution of mergers, interactions, and disk instabilities at high redshift. Early bars at z > 1 are often short

  4. The heating of mid-infrared dust in the nearby galaxy M33: A testbed for tracing galaxy evolution

    International Nuclear Information System (INIS)

    Infrared emission is an invaluable tool for quantifying star formation in galaxies. Because the 8 μm polycyclic aromatic hydrocarbon (PAH) emission has been found to correlate with other well-known star formation tracers, it has widely been used as a star formation rate (SFR) tracer. There are, however, studies that challenge the accuracy and reliability of the 8 μm emission as a SFR tracer. Our study, part of the Herschel (Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA) M33 Extended Survey (HERM33ES) open time key program, aims at addressing this issue by analyzing the infrared emission from the nearby spiral galaxy M33 at the high spatial scale of ∼75 pc. Combining data from the Herschel Space Observatory and the Spitzer Space Telescope, we find that the 8 μm emission is better correlated with the 250 μm emission, which traces cold interstellar gas, than with the 24 μm emission. Furthermore, the L(8)/L(250) ratio is more tightly correlated with the 3.6 μm emission, a tracer of evolved stellar populations and stellar mass, than with a combination of Hα and 24 μm emission, a tracer of SFR. The L(8)/L(24) ratio is highly depressed in 24 μm luminous regions, which correlate with known H II regions. We also compare our results with the dust emission models by Draine and Li. We confirm that the depression of 8 μm PAH emission near star-forming regions is higher than what is predicted by models; this is possibly an effect of increased stellar radiation from young stars destroying the dust grains responsible for the 8 μm emission as already suggested by other authors. We find that the majority of the 8 μm emission is fully consistent with heating by the diffuse interstellar medium, similar to what recently determined for the dust emission in M31 by Draine et al. We also find that the fraction of 8 μm emission associated with the diffuse

  5. Evolution of near-field physico-chemical characteristics of the SFR repository

    International Nuclear Information System (INIS)

    The evaluation of the post-closure performance of the SFR repository needs to consider time dependent evolution of the repository environment. Time-dependent reaction of near-field barriers (cement, steel, bentonite) with saturating groundwater will lead to the development of hyper alkaline repository pore fluids, chemically reducing conditions, and ultimately, the generation of gas through anaerobic corrosion of metals. Cement and concrete will act as chemical conditioning agents to minimise metal corrosion and ultimately, maximise radioelement sorption. The chemical and physical evolution of cement and concrete through reaction with ambient groundwater will thus affect sorption processes through changes in pH, complexing ligands, and solid surface properties. It is desirable that these changes be incorporated into the safety assessment. The sorption behaviour of radionuclides in cementitious systems has been reviewed in detail. The available evidence from experimental work carried out on the influence of organic materials on the sorption behaviour of radionuclides, indicates that most organic degradation products will not affect sorption significantly at the concentrations expected in a cementitious repository. The notable exception to this conclusion involves the degradation products of cellulose and, in particular, polycarboxylic acids represented by iso-saccharinic acid (ISA). Results using ISA indicate a significant reduction in sorption of Pu, by several orders of magnitude, for an ISA concentration of about 10-3 M. More recent data indicate that the negative effect is not as great, though still significant. Therefore, some scoping calculations are advisable to determine how realistic an ISA concentration of about 10-3 M would be for the SFR repository and to estimate concentrations of other relevant organic compounds, in particular EDTA, for comparison. Scoping calculations relevant to the longevity of hyper alkaline pore fluid conditions at SFR have been

  6. Tracing the evolution of active galactic nuclei host galaxies over the last 9 Gyr of cosmic time

    International Nuclear Information System (INIS)

    We present the results of a combined galaxy population analysis for the host galaxies of active galactic nuclei (AGN) identified at 0 < z < 1.4 within the Sloan Digital Sky Survey, Boötes, and DEEP2 surveys. We identified AGN in a uniform and unbiased manner at X-ray, infrared, and radio wavelengths. Supermassive black holes undergoing radiatively efficient accretion (detected as X-ray and/or infrared AGN) appear to be hosted in a separate and distinct galaxy population than AGN undergoing powerful mechanically dominated accretion (radio AGN). Consistent with some previous studies, radiatively efficient AGN appear to be preferentially hosted in modest star-forming galaxies, with little dependence on AGN or galaxy luminosity. AGN exhibiting radio-emitting jets due to mechanically dominated accretion are almost exclusively observed in massive, passive galaxies. Crucially, we now provide strong evidence that the observed host-galaxy trends are independent of redshift. In particular, these different accretion-mode AGN have remained as separate galaxy populations throughout the last 9 Gyr. Furthermore, it appears that galaxies hosting AGN have evolved along the same path as galaxies that are not hosting AGN with little evidence for distinctly separate evolution.

  7. Tracing the evolution of active galactic nuclei host galaxies over the last 9 Gyr of cosmic time

    Energy Technology Data Exchange (ETDEWEB)

    Goulding, A. D.; Forman, W. R.; Jones, C.; Murray, S. S.; Paggi, A.; Ashby, M. L. N.; Huang, J.-S.; Kraft, R.; Willner, S. P. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Hickox, R. C. [Department of Physics and Astronomy, Dartmouth College, Hanover, NH 03755 (United States); Coil, A. L. [Department of Physics, Center for Astrophysics and Space Sciences, University of California at San Diego, 9500 Gilman Drive, La Jolla, San Diego, CA 92093 (United States); Cooper, M. C. [Center for Galaxy Evolution, Department of Physics and Astronomy, University of California, Irvine, 4129 Frederick Reines Hall, Irvine, CA 92697 (United States); Newman, J. A. [Department of Physics and Astronomy, University of Pittsburgh, 3941 O' Hara Street, Pittsburgh, PA 15260 (United States); Weiner, B. J., E-mail: agoulding@cfa.harvard.edu [Steward Observatory, 933 North Cherry Street, University of Arizona, Tucson, AZ 85721 (United States)

    2014-03-01

    We present the results of a combined galaxy population analysis for the host galaxies of active galactic nuclei (AGN) identified at 0 < z < 1.4 within the Sloan Digital Sky Survey, Boötes, and DEEP2 surveys. We identified AGN in a uniform and unbiased manner at X-ray, infrared, and radio wavelengths. Supermassive black holes undergoing radiatively efficient accretion (detected as X-ray and/or infrared AGN) appear to be hosted in a separate and distinct galaxy population than AGN undergoing powerful mechanically dominated accretion (radio AGN). Consistent with some previous studies, radiatively efficient AGN appear to be preferentially hosted in modest star-forming galaxies, with little dependence on AGN or galaxy luminosity. AGN exhibiting radio-emitting jets due to mechanically dominated accretion are almost exclusively observed in massive, passive galaxies. Crucially, we now provide strong evidence that the observed host-galaxy trends are independent of redshift. In particular, these different accretion-mode AGN have remained as separate galaxy populations throughout the last 9 Gyr. Furthermore, it appears that galaxies hosting AGN have evolved along the same path as galaxies that are not hosting AGN with little evidence for distinctly separate evolution.

  8. Traces of co-evolution in high z X-ray selected and submm-luminous QSOs

    CERN Document Server

    Khan-Ali, A; Page, M J; Stevens, J A; Mateos, S; Symeonidis, M; Orjales, J M Cao

    2014-01-01

    We present a detailed study of a X -ray selected sample of 5 submillimeter bright QSOs at $z\\sim2$, where the highest rates of star formation (SF) and further growth of black holes (BH) occur. Therefore, this sample is a great laboratory to investigate the co-evolution of star formation and AGN. We present here the analysis of the spectral energy distributions (SED) of the 5 QSOS, including new data from Herschel PACS and SPIRE. Both AGN components (direct and reprocessed) and like Star Formation (SF) are needed to model its SED. From the SED and their UV-optical spectra we have estimated the mass of the black hole ($M_{BH} = 10^9 - 10^{10} M_{SUN}$) and bolometric luminosities of AGN ($L_{BOL} = (0.8-20) \\times 10^{13} L_{SUN}$). These objects show very high luminosities in the far infrared range (at the H/ULIRG levels) and very high rates of SF (SFR = 400-1400 $M_{SUN}$/y). Known their current SFR and their BH masses, we deduce that their host galaxies must be already very massive, or would not have time to...

  9. Reconstruction of mid-crustal pluton assembly and evolution using trace elements in augite: Sausfjellet pluton, Bindal batholith, north-central Norway.

    Science.gov (United States)

    Coint, Nolwenn; Barnes, Calvin; Yoshinobu, Aaron; Prestvik, Tore; Barnes, Melanie

    2013-04-01

    The Sausfjellet pluton is a 445 Ma gabbroic to monzonitic body of 7 Km in diameter emplaced in two stages at ~700 MPa pressure. Stage 1 is a coarse pyroxene hornblende gabbro. Stage 2 intrudes a steep contact between marbles on the east and pelitic migmatites on the west. Stage 2 displays a gradational transition from hornblende biotite two-pyroxene diorite to hornblende biotite three-pyroxene quartz monzonite. This transition is accompanied by a decrease in the An content of normally-zoned plagioclase from An61 to An27. Much of the pluton consists of cumulate rocks, as illustrated by the presence of anorthosite and pyroxene-rich layers. In the western part of the intrusion, hosted by metapelitic rocks, incompatible element concentrations and bulk-rock ^18O increase to levels that cannot be explained by fractional crystallization. These increases were originally explained by AFC processes, but because of the cumulative nature of the rocks, it is difficult to assess magmatic processes using bulk rock compositions. Therefore, we analyzed trace element contents and core-to-rim zoning in augite as a proxy to track changes in melt composition. Augite is normally zoned, with lower incompatible element abundances in the cores than in the rims, consistent with evolution of the melt by fractional crystallization. However, instead of plotting along a single differentiation trend, augite compositions define two trends, which is inconsistent with a closed system. The most mafic rocks define a trend with lower REE contents and smaller (negative) Eu anomalies compared to those from the more evolved part of the pluton, although the two trends overlap in Zr content. The two trends correspond to the central, more mafic zone that intrudes marble and the western, more evolved zone that intrudes metapelites. The trend associated with the western zone consists of the same samples that show bulk-rock ^18O enrichment, and is best explained as resulting from assimilation of the host

  10. Chesapeake Bay earth science study: interstitial water chemistry-chemical zonation, tributaries study, and trace metals. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Hill, J.M.; Blakeslee, P.J.; Conkwright, R.D.; McKeon, G.

    1982-11-01

    The sediments of the Chesapeake Bay constitute a large reservoir of chemical species derived from natural and anthropogenic sources. The behavior of these materials in the estuary is determined by the physiochemical sedimentary environments in which they are found. Three major environments are identified, from the interstitial water chemistry as Northern Bay, Middle Bay, and Southern Bay. The chemical sedimentary environments of five tributaries to the main Bay were sampled for interstitial water. The data indicate the concentration of the metals are greater than coastal seawater and river water, and comparable to concentrations found in municipal waste.

  11. Detection of trace levels of triclopyr using capillary gas chromatography-electron-capture negative-ion chemical ionization mass spectrometry.

    Science.gov (United States)

    Begley, P; Foulger, B E

    1988-04-01

    Triclopyr, after esterification, is shown to be a suitable candidate for detection by gas chromatography-electron-capture negative-ion chemical ionization mass spectrometry forming a characteristic carboxylate anion which offers a high detection sensitivity. A detection limit of 70 fg reaching the ionizer is indicated. Low backgrounds and an absence of chemical interferences are shown for vegetation extracts, using a simple method of extraction and derivatisation. A similar behaviour is demonstrated for 2,4-D and 2,4,5-T. PMID:3379116

  12. Seawater-like trace element signatures (REE + Y) of Eoarchaean chemical sedimentary rocks from southern West Greenland, and their corruption during high-grade metamorphism

    Science.gov (United States)

    Friend, C. R. L.; Nutman, A. P.; Bennett, V. C.; Norman, M. D.

    2008-02-01

    Modern chemical sediments display a distinctive rare earth element + yttrium (REE + Y) pattern involving depleted LREE, positive La/La*SN, Eu/Eu*SN, and YSN anomalies (SN = shale normalised) that is related to precipitation from circumneutral to high pH waters with solution complexation of the REEs dominated by carbonate ions. This is often interpreted as reflecting precipitation from surface waters (usually marine). The oldest broadly accepted chemical sediments are c. 3,700 Ma amphibolite facies banded iron-formation (BIF) units in the Isua supracrustal belt, Greenland. Isua BIFs, including the BIF international reference material IF-G are generally considered to be seawater precipitates, and display these REE + Y patterns (Bolhar et al. in Earth Planet Sci Lett 222:43 60, 2004). Greenland Eoarchaean BIF metamorphosed up to granulite facies from several localities in the vicinity of Akilia (island), display REE + Y patterns identical to Isua BIF, consistent with an origin by chemical sedimentation from seawater and a paucity of clastic input. Furthermore, the much-debated magnetite-bearing siliceous unit of “earliest life” rocks (sample G91/26) from Akilia has the same REE + Y pattern. This suggests that sample G91/26 is also a chemical sediment, contrary to previous assertions (Bolhar et al. in Earth Planet Sci Lett 222:43 60, 2004), and including suggestions that the Akilia unit containing G91/26 consists entirely of silica-penetrated, metasomatised, mafic rock (Fedo and Whitehouse 2002a). Integration of our trace element data with those of Bolhar et al. (Earth Planet Sci Lett 222:43 60, 2004) demonstrates that Eoarchaean siliceous rocks in Greenland, with ages from 3.6 to 3.85 Ga, have diverse trace element signatures. There are now geographically-dispersed, widespread examples with Isua BIF-like REE + Y signatures, that are interpreted as chemically unaltered, albeit metamorphosed, chemical sediments. Other samples retain remnants of LREE depletion but

  13. Seasonal and spatial variation of trace elements in multi-size airborne particulate matters of Beijing, China: Mass concentration, enrichment characteristics, source apportionment, chemical speciation and bioavailability

    Science.gov (United States)

    Gao, Jiajia; Tian, Hezhong; Cheng, Ke; Lu, Long; Wang, Yuxuan; Wu, Ye; Zhu, Chuanyong; Liu, Kaiyun; Zhou, Junrui; Liu, Xingang; Chen, Jing; Hao, Jiming

    2014-12-01

    The seasonal and spatial variation characteristics of 19 elements (Al, As, Be, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, S, Sb, Se, Zn) in TSP/PM10/PM2.5 samples were investigated, which were collected from April 2011 to January 2012 simultaneously at an urban downtown site, a traffic roadside site, a suburban site, and a rural site in Beijing. The elevated concentrations of several toxic trace elements (As, Cd, Mn, Ni, Pb, etc.) in particles revealed that the contamination of toxic elements in Beijing could not be neglected. Positive matrix factorization method (PMF) was applied for source apportionment of trace elements in PM, and three factors (crust related sources, combustion sources, and traffic and steel industrial related sources) were identified. Furthermore, the chemical speciation and bioavailability of various elements were identified by applying European Community Bureau of Reference (BCR) procedure. Our results showed that eight toxic elements (As, Cd, Cr, Cu, Ni, Pb, Sb and Zn) exhibited higher mobility in PM2.5 than in PM10. Notably, elements of As, Cd, Pb and Zn were presented with higher mobility than the other elements, and these elements were lightly to release into the environment and easily available to human body. Additionally, As, Cd, Pb and Zn also accounted for higher percentages in the bound to mobile fractions at the central urban areas of Beijing. Therefore, special concerns should be paid to these toxic trace elements which had relatively high mobility in fine particles, when planning and implementing the comprehensive air pollution mitigation policies in Beijing.

  14. Evolution of near-field physico-chemical characteristics of the SFR repository

    Energy Technology Data Exchange (ETDEWEB)

    Savage, D. [Quintessa Ltd., Nottingham (United Kingdom); Stenhouse, M. [Monitor Scientific LLC, Denver, CO (United States); Benbow, S. [Quintessa Ltd., Henley-on-Thames (United Kingdom)

    2000-08-01

    The evaluation of the post-closure performance of the SFR repository needs to consider time dependent evolution of the repository environment. Time-dependent reaction of near-field barriers (cement, steel, bentonite) with saturating groundwater will lead to the development of hyper alkaline repository pore fluids, chemically reducing conditions, and ultimately, the generation of gas through anaerobic corrosion of metals. Cement and concrete will act as chemical conditioning agents to minimise metal corrosion and ultimately, maximise radioelement sorption. The chemical and physical evolution of cement and concrete through reaction with ambient groundwater will thus affect sorption processes through changes in pH, complexing ligands, and solid surface properties. It is desirable that these changes be incorporated into the safety assessment. The sorption behaviour of radionuclides in cementitious systems has been reviewed in detail. The available evidence from experimental work carried out on the influence of organic materials on the sorption behaviour of radionuclides, indicates that most organic degradation products will not affect sorption significantly at the concentrations expected in a cementitious repository. The notable exception to this conclusion involves the degradation products of cellulose and, in particular, polycarboxylic acids represented by iso-saccharinic acid (ISA). Results using ISA indicate a significant reduction in sorption of Pu, by several orders of magnitude, for an ISA concentration of about 10{sup -3} M. More recent data indicate that the negative effect is not as great, though still significant. Therefore, some scoping calculations are advisable to determine how realistic an ISA concentration of about 10{sup -3} M would be for the SFR repository and to estimate concentrations of other relevant organic compounds, in particular EDTA, for comparison. Scoping calculations relevant to the longevity of hyper alkaline pore fluid conditions at SFR

  15. Chemical portioning and speciation of some trace elements in soil and street dust from Khartoum state, Sudan

    International Nuclear Information System (INIS)

    In this study, surface soil and street dust samples were collected from Khartoum State, from areas exposed to industrial and traffic emission and from areas expected to be free from elemental emission to serve as control. Samples were digested using wet digestion method to determine the total concentration of Na, K, Cr, Mn, Fe, Cu, Zn and Pb using Atomic Absorption spectrophotometer (Aas), X-Ray fluorescence and flame photometer. Also samples were chemically fractionated using chemical specification method, and the solutions analyzed using Aas to determine the chemical form of the elements. Quality assurance of the data was achieved through the analysis of certified reference material. The range of the total concentration for Na, K, Mn, Fe, Cu, Zn and Pb are 400-5175, 220-4690, 0.07-315.25, 20-250, 2050.8-46000, 0.5-2305, 4.5-280, 9.5-6200 mg/kg respectively. results obtained agree with expected emission profile as inferred from the emitting source locations. Distribution of elements from emitting source locations and control samples in different chemical fractions was carried out, and the findings reinforced by enrichment factors calculations as well by the results obtained by statistical multi-variate analysis methods such as principle compared with previous literature.(Author)

  16. Development of electrochemical sensors for trace detection of explosives and for the detection of chemical warfare agents

    Science.gov (United States)

    Berger, T.; Ziegler, H.; Krausa, Michael

    2000-08-01

    A huge number of chemical sensors are based on electrochemical measurement methods. Particularly amperometric sensorsystems are employed for the fast detection of pollutants in industry and environment as well as for analytic systems in the medical diagnosis. The large number of different applications of electrochemical sensors is based on the high sensitivity of electrochemical methods and on the wide of possibilities to enhance the selectivity by variation of electrochemical and chemical parameters. Besides this, electrochemical sensorsystems are frequently simple to operate, transportable and cheap. Up to now the electrochemical method of cyclic voltammetry is used only seldom for sensors. Clearly the efficiency of cyclic voltammetry can be seen at the sensorsystem for the detection of nitro- and aminotoluenes in solids and waters as presented here. The potentiodynamic sensors system can be employed for the fast and easy risk estimation of contaminated areas. Because of the high sensitivity of electrochemical methods the detection of chemical substances with a low vapor pressure is possible also. The vapor pressure of TNT at room temperature is 7 ppb for instances. With a special electrochemical set-up we were able to measure TNT approximately 10 cm above a TNT-sample. In addition we were able to estimate TNT in the gaseous phase approximately 10 cm above a real plastic mine. Therefore it seems to be possible to develop an electrochemical mien detection. Moreover, we present that the electrochemical detection of RDX, HMX and chemical warfare agents is also possible.

  17. The evolution of plant chemical defence - new roles for hydroxynitrile glucosides in Lotus japonicus

    DEFF Research Database (Denmark)

    Knudsen, Camilla

    function and evolution. Further, it contributes to our understanding of the formation and role of biosynthetic gene clusters in plant chemical defence. The bifurcation in hydroxynitrile glucoside biosynthesis and catabolism observed in Lotus japonicus makes it a very suitable model system to study the......Plants are sessile organisms well-known to produce a vast array of chemical compounds of which many are used in chemical defence against herbivores and pathogens. The biosynthesis of these plant chemical defence compounds poses a considerable risk of self-toxicity for the plant itself. Several...... types of adaptations enable plants to avoid the potential lethal effects of their own defence compounds. These adaptations include detoxification and stabilization by glycosylation and the genomic clustering of biosynthetic pathway genes. These two types are the main focus of this PhD thesis on...

  18. Chemical Characteristics and Geochemical Evolution of Groundwater in the North China Plain

    Science.gov (United States)

    Zhan, Yanhong; Teng, Yanguo; Zuo, Rui

    2015-04-01

    components in shallow groundwater had significantly increased since 1970s. Concentration of bicarbonate ion in shallow groundwater from Zone I had a maximum increase rate of 7.8 (mg/L)/year during 1995 and 2000. In deep groundwater from Zone I to Zone III, the increase rate was basically less than 0.7 (mg/L)/year and 0.4 (mg/L)/year, respectively. The main components in deep groundwater from Zone II showed great increases during 1985 and 1995, being 9.5 (mg/L)/year of chloride ion and 1.8 (mg/L)/year of magnesium ion. However, pollutant discharged by human activities and over-exploitation of deep groundwater which caused groundwater levels sharply declining and the dynamic and chemical conditions of groundwater changing, may attribute to the increases of major components in shallow groundwater and deep groundwater of Zone II. Key words: The North China Plain, Characteristic, temporal; evolution; water-rock interaction

  19. Mercury's thermo-chemical evolution from numerical models constrained by Messenger observations

    Science.gov (United States)

    Tosi, N.; Breuer, D.; Plesa, A. C.; Wagner, F.; Laneuville, M.

    2012-04-01

    The Messenger spacecraft, in orbit around Mercury for almost one year, has been delivering a great deal of new information that is changing dramatically our understanding of the solar system's innermost planet. Tracking data of the Radio Science experiment yielded improved estimates of the first coefficients of the gravity field that permit to determine the normalized polar moment of inertia of the planet (C/MR2) and the ratio of the moment of inertia of the mantle to that of the whole planet (Cm/C). These two parameters provide a strong constraint on the internal mass distribution and, in particular, on the core mass fraction. With C/MR2 = 0.353 and Cm/C = 0.452 [1], interior structure models predict a core radius as large as 2000 km [2], leaving room for a silicate mantle shell with a thickness of only ~ 400 km, a value significantly smaller than that of 600 km usually assumed in parametrized [3] as well as in numerical models of Mercury's mantle dynamics and evolution [4]. Furthermore, the Gamma-Ray Spectrometer measured the surface abundance of radioactive elements, revealing, besides uranium and thorium, the presence of potassium. The latter, being moderately volatile, rules out traditional formation scenarios from highly refractory materials, favoring instead a composition not much dissimilar from a chondritic model. Considering a 400 km thick mantle, we carry out a large series of 2D and 3D numerical simulations of the thermo-chemical evolution of Mercury's mantle. We model in a self-consistent way the formation of crust through partial melting using Lagrangian tracers to account for the partitioning of radioactive heat sources between mantle and crust and variations of thermal conductivity. Assuming the relative surface abundance of radiogenic elements observed by Messenger to be representative of the bulk mantle composition, we attempt at constraining the degree to which uranium, thorium and potassium are concentrated in the silicate mantle through a broad

  20. A Multimedia Fate Model to Support Chemical Management in China: A Case Study for Selected Trace Organics.

    Science.gov (United States)

    Zhu, Ying; Price, Oliver R; Kilgallon, John; Rendal, Cecilie; Tao, Shu; Jones, Kevin C; Sweetman, Andrew J

    2016-07-01

    SESAMe v3.3, a spatially explicit multimedia fate model for China, is a tool suggested to support quantitative risk assessment for national scale chemical management. The key advantage over the previous version SESAMe v3.0 is consideration of spatially varied environmental pH. We evaluate the model performance using estimates of emission from total industry usage of three UV filters (benzophenone-3, octocrylene, and octyl methoxycinnamate) and three antimicrobials (triclosan, triclocarban, and climbazole). The model generally performs well for the six case study chemicals as shown by the comparison between predictions and measurements. The importance of accounting for chemical ionization is demonstrated with the fate and partitioning of both triclosan and climbazole sensitivity to environmental pH. The model predicts ionizable chemicals (triclosan, climbazole, benzophenone-3) to primarily partition into soils at steady state, despite hypothetically only being released to freshwaters, as a result of agricultural irrigation by freshwater. However, further model calibration is needed when more field data becomes available for soils and sediments and for larger areas of water. As an example, accounting for the effect of pH in the environmental risk assessment of triclosan, limited freshwater areas (0.03% or ca. 55 km(2)) in mainland China are modeled to exceed its conservative environmental no-effect threshold. SESAMe v3.3 can be used to support the development of chemical risk assessment methodologies with the spatial aspects of the model providing a guide to the identification regions of interest in which to focus monitoring campaigns or develop a refined risk assessment. PMID:27280340

  1. Chemical Evolution in Sersic 159-03 Observed with Xmm-Newton

    Energy Technology Data Exchange (ETDEWEB)

    de Plaa, Jelle; Werner, N.; Bykov, A.M.; Kaastra, J.S.; Mendez, M.; Vink, J.; Bleeker, J.A.M.; Bonamente, M.; Peterson, J.R.; /SRON, Utrecht /Utrecht, Astron. Inst.

    2006-03-10

    Using a new long X-ray observation of the cluster of galaxies Sersic 159-03 with XMM-Newton, we derive radial temperature and abundance profiles using single- and multi-temperature models. The fits to the EPIC and RGS spectra prefer multi-temperature models especially in the core. The radial profiles of oxygen and iron measured with EPIC/RGS and the line profiles in RGS suggest that there is a dip in the O/Fe ratio in the centre of the cluster compared to its immediate surroundings. A possible explanation for the large scale metallicity distribution is that SNIa and SNII products are released in the ICM through ram-pressure stripping of in-falling galaxies. This causes a peaked metallicity distribution. In addition, SNIa in the central cD galaxy enrich mainly the centre of the cluster with iron. This excess of SNIa products is consistent with the low O/Fe ratio we detect in the centre of the cluster. We fit the abundances we obtain with yields from SNIa, SNII and Population-III stars to derive the clusters chemical evolution. We find that the measured abundance pattern does not require a Population-III star contribution. The relative contribution of the number of SNIa with respect to the total number of SNe which enrich the ICM is about 25-50%. Furthermore, we discuss the possible presence of a non-thermal component in the EPIC spectra. A potential source of this non-thermal emission can be inverse-Compton scattering between Cosmic Microwave Background (CMB) photons and relativistic electrons, which are accelerated in bow shocks associated with ram-pressure stripping of in-falling galaxies.

  2. Evolution of chemical-physical parameters and rheological characteristics of Sarda and Maltese goat dry hams

    Directory of Open Access Journals (Sweden)

    Rina Mazzette

    2012-10-01

    Full Text Available In Sardinia, goat farming is a very important resource. Sarda and Maltese breed are reared mainly for milk production and for suckling kids meat, while meat from adult goats is undervalued. The use of adult goat meat to obtain ripened ham will contribute to safeguard the Sardinian goat supply chain. The aim of the present study was to characterize Sarda and Maltese goat dry ham in order to evaluate the quality of autochthonous goat breed meat. Chemical-physical characteristics were determined dur-ing the production stages, while the rheological and colour parameters and the composition of the goat ham were determined at the end of ripening. The pH evolution during processing were similar to other cured meat products, e.g. sheep hams, even though the values were high, especially in the products from Sarda breed. The aw value regularly decreased during processing. Colour parameters (L*, a*, b* in the hams from Maltese goat breed were significantly (P<0.05 higher than in those from Sarda. The Sarda goat ham showed a significantly lower percentage of moisture (42% vs 52%, an higher protein content (44.35% vs 34.19%, while no differences were pointed out in the total fat content. Among the ham rheological properties, hardness parameters showed higher levels (13850.22±7589.92 vs 11073.99±6481.31, respectively in Sarda and Maltese hams in comparison to similar products from pork and sheep, while adhesiveness value was lower. The results show that the quality parameters of goat ripened hams are affected mainly by the charac-teristics of the goat meat, in relation on the breed and the breeding system, and, less, by the traditional technology.

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

    Science.gov (United States)

    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.; Cohen, Ronald C.; Dibb, Jack E.; Flocke, F. M.; Fried, Alan; Holloway, J.; Neuman, J. A.; Orville, R.; Perring, Anne; Ren, Xinrong; Ryerson, T. B.; Sachse, Glen W.; Singh, H. B.; Swanson, Aaron; Wooldridge, Paul J.

    2007-01-01

    We use observations from two aircraft during the International Consortium for Atmospheric Research on Transport and Transformation (ICARTT) campaign over the eastern United States and North Atlantic during summer 2004, interpreted with a global 3-D model of tropospheric chemistry (GEOS-Chem) to test current understanding of the regional sources, chemical evolution, and export of nitrogen oxides. The boundary layer NO(x) data provide top-down verification of a 50% decrease in power plant and industry NO(x) emissions over the eastern United States between 1999 and 2004. Observed 8-12 8 km NO(x) concentrations in ICARTT were 0.55 +/- 36 ppbv, much larger than in previous United States aircraft campaigns (ELCHEM, SUCCESS, SONEX). We show that regional lightning was the dominant source of this NO(x) and increased upper tropospheric ozone by 10 ppbv. Simulating the ICARTT upper tropospheric NO(x) observations with GEOS-Chem require a factor of 4 increase in the model NO(x) yield per flash (to 500 mol/flash). Observed OH concentrations were a factor of 2 lower than can be explained from current photochemical models, and if correct would imply a broader lightning influence in the upper troposphere than presently thought.An NO(y)-CO correlation analysis of the fraction f of North American NO(x) emissions vented to the free troposphere as NO(y) (sum of NO(x) and its oxidation products PAN and HNO3) s shows observed f=16+/-10 percent and modeled f=14 +/- 8 percent, consistent with previous studies. Export to the lower free troposphere is mostly HNO3 but at higher altitudes is mostly PAN. The model successfully simulates NO(y) export efficiency and speciation, supporting previous model estimates of a large U.S. contribution to tropospheric ozone through NO(x) and PAN export.

  4. The structural evolution and diffusion during the chemical transformation from cobalt to cobalt phosphide nanoparticles

    KAUST Repository

    Ha, Don-Hyung

    2011-01-01

    We report the structural evolution and the diffusion processes which occur during the phase transformation of nanoparticles (NPs), ε-Co to Co 2P to CoP, from a reaction with tri-n-octylphosphine (TOP). Extended X-ray absorption fine structure (EXAFS) investigations were used to elucidate the changes in the local structure of cobalt atoms which occur as the chemical transformation progresses. The lack of long-range order, spread in interatomic distances, and overall increase in mean-square disorder compared with bulk structure reveal the decrease in the NP\\'s structural order compared with bulk structure, which contributes to their deviation from bulk-like behavior. Results from EXAFS show both the Co2P and CoP phases contain excess Co. Results from EXAFS, transmission electron microscopy, X-ray diffraction, and density functional theory calculations reveal that the inward diffusion of phosphorus is more favorable at the beginning of the transformation from ε-Co to Co2P by forming an amorphous Co-P shell, while retaining a crystalline cobalt core. When the major phase of the sample turns to Co 2P, the diffusion processes reverse and cobalt atom out-diffusion is favored, leaving a hollow void, characteristic of the nanoscale Kirkendall effect. For the transformation from Co2P to CoP theory predicts an outward diffusion of cobalt while the anion lattice remains intact. In real samples, however, the Co-rich nanoparticles continue Kirkendall hollowing. Knowledge about the transformation method and structural properties provides a means to tailor the synthesis and composition of the NPs to facilitate their use in applications. © 2011 The Royal Society of Chemistry.

  5. CHEMICAL EVOLUTION IN HIGH-MASS STAR-FORMING REGIONS: RESULTS FROM THE MALT90 SURVEY

    International Nuclear Information System (INIS)

    The chemical changes of high-mass star-forming regions provide a potential method for classifying their evolutionary stages and, ultimately, ages. In this study, we search for correlations between molecular abundances and the evolutionary stages of dense molecular clumps associated with high-mass star formation. We use the molecular line maps from Year 1 of the Millimetre Astronomy Legacy Team 90 GHz (MALT90) Survey. The survey mapped several hundred individual star-forming clumps chosen from the ATLASGAL survey to span the complete range of evolution, from prestellar to protostellar to H II regions. The evolutionary stage of each clump is classified using the Spitzer GLIMPSE/MIPSGAL mid-IR surveys. Where possible, we determine the dust temperatures and H2 column densities for each clump from Herschel/Hi-GAL continuum data. From MALT90 data, we measure the integrated intensities of the N2H+, HCO+, HCN and HNC (1-0) lines, and derive the column densities and abundances of N2H+ and HCO+. The Herschel dust temperatures increase as a function of the IR-based Spitzer evolutionary classification scheme, with the youngest clumps being the coldest, which gives confidence that this classification method provides a reliable way to assign evolutionary stages to clumps. Both N2H+ and HCO+ abundances increase as a function of evolutionary stage, whereas the N2H+ (1-0) to HCO+ (1-0) integrated intensity ratios show no discernable trend. The HCN (1-0) to HNC(1-0) integrated intensity ratios show marginal evidence of an increase as the clumps evolve

  6. The galactic habitable zone of the Milky Way and M31 from chemical evolution models with gas radial flows

    CERN Document Server

    Spitoni, E; Sozzetti, A

    2014-01-01

    The galactic habitable zone is defined as the region with sufficient abundance of heavy elements to form planetary systems in which Earth-like planets could be born and might be capable of sustaining life, after surviving to close supernova explosion events. Galactic chemical evolution models can be useful for studying the galactic habitable zones in different systems. We apply detailed chemical evolution models including radial gas flows to study the galactic habitable zones in our Galaxy and M31. We compare the results to the relative galactic habitable zones found with "classical" (independent ring) models, where no gas inflows were included. For both the Milky Way and Andromeda, the main effect of the gas radial inflows is to enhance the number of stars hosting a habitable planet with respect to the "classical" model results, in the region of maximum probability for this occurrence, relative to the classical model results. These results are obtained by taking into account the supernova destruction process...

  7. The distribution of mercury and other trace elements in the bones of two human individuals from medieval Denmark – the chemical life history hypothesis

    DEFF Research Database (Denmark)

    Rasmussen, Kaare Lund; Skytte, Lilian; Pilekær, Christian;

    2013-01-01

    Excavating human skeletons is the closest archaeologists can get to the people who lived in the past. Once excavated the bones are often analysed chemically in order to yield as much information as possible. Most archaeometric analyses performed on samples of human skeletal remains have been...... individuals can be clearly distinguished by Principal Component Analysis of all the measured trace elements.Our data support a previously published hypothesis that the elemental ratios Sr/Ca, Ba/Ca and Mg/Ca are indicative of provenance. Aluminium, Fe and Mn can be attributed to various forms of diagenesis......, while Hg is not present in sufficiently large amounts in the surrounding soil to allow diagenesis to explain the high Hg values in the trabecular tissue. Instead we propose that Hg must originate from decomposed soft tissue....

  8. Trace element behavior and P-T-t evolution during partial melting of exhumed eclogite in the North Qaidam UHPM belt (NW China): Implications for adakite genesis

    Science.gov (United States)

    Zhang, Guibin; Niu, Yaoling; Song, Shuguang; Zhang, Lifei; Tian, Zuolin; Christy, Andrew G.; Han, Lei

    2015-06-01

    We have studied trace element behavior and timing of decompression melting of UHP rocks during exhumation recorded in the magmatic products, i.e., the melt phase (leucosomes), cumulate (garnetite) and residue (amphibolitized eclogite) from a single outcrop in the south Dulan area, North Qaidam UHPM belt, NW China. Two distinct episodes of partial melting are recognized. First, Grt-free tonalitic-trondhjemitic leucosome melts with higher silica crystallized at 424.0 ± 2.7 Ma. Garnets grew in the leucosome melt but fractionated out to form garnetite cumulates along with Ti-rich phases (rutile and titanite), strengthening the adakitic signature of the leucosome. Later Grt-bearing leucosome melts with an age of 412.4 ± 2.9 Ma cross-cut boudins and layers of amphibolitized eclogite. Geochemical investigation of bulk-rocks and in situ minerals verifies the genetic relationship between the amphibolitized eclogite and the tonalitic-trondhjemitic melts. Zircons from the amphibolitized eclogite have older (> 700 Ma) protolith ages, with subsequent eclogite-facies metamorphism, retrograde granulite-facies overprinting and partial melting. Phase modeling and Zr-in-rutile thermometry calculations in combination with zircon geochronology reveal the evolution P-T-t path for the exhumation and the partial melting of the deeply subducted continental crust at the North Qaidam subduction zone in the Early Paleozoic.

  9. Current state and temporal evolution of the chemical composition of atmospheric depositions in forest areas of the CONECOFOR network

    OpenAIRE

    Marchetto A; Arisci S.; Tartari GA; Balestrini R; Tait D

    2014-01-01

    Current state and temporal evolution of the chemical composition of atmospheric depositions in forest areas of the CONECOFOR network. Since 1997, atmospheric deposition was sampled and analyzed in the permanent plots of the Italian network for the evaluation of forest health (CONECOFOR), under the coordination of the Italian Forest Service. This paper presents the results of the activity carried out in 2009, when the EU-funded LIFE+ “FutMon” project allowed to extend the sampling network to 2...

  10. Chemical durability of alkali-borosilicate glasses studied by analytical SEM, IBA, isotopic-tracing and SIMS

    International Nuclear Information System (INIS)

    Simple and complex alkali-borosilicate glasses were submitted to aqueous corrosion at room temperature, 60 and 90 deg. C in solutions with pH ranging between 0 and 12. Analytical scanning electron microscopy (SEM), ion beam analysis (IBA) techniques, isotopic tracing and secondary ion mass-depth profiling (SIMS) have been used to investigate the variations of the surface composition of glass. In acidic medium, the glass surface is generally covered by a thick hydrated silica layer, mobile elements like Li, Na and B and transition elements (Fe, Zr, Mo, etc.) are strongly depleted. Near pH 7, relative enrichments of aluminium, iron and rare earths are shown together with strong Li, Na and B depletions. In basic medium, the glass surface exhibits relative enrichments of the major part of transition metals (from Cr to U) whereas mobile elements seem to be kept close to their nominal concentration level at the glass surface and Si is severely impoverished. Hydrogen incorporated at the glass surface after leaching is much more immobile in neutral and basic media than in acid medium

  11. Trace Hydrophobic Organic Chemicals Present in Pennsylvania Groundwater are Correlated with Geogenic Brines rather than Hydraulic Fracturing Active Zones

    Science.gov (United States)

    Drollette, B.; Shregglman, K.; D'Ambro, E.; Elsner, M.; Warner, N. R.; O'Connor, M.; Karatum, O.; Vengosh, A.; Jackson, R. B.; Darrah, T.; Plata, D.

    2014-12-01

    Recent studies demonstrated that deep Marcellus shale brines migrate into shallow groundwater aquifers, presumably via fractures in the subsurface that exist independent of any gas extraction activities. However, whereas many inorganic species are conservative tracers, hydrophobic organic compounds are both sorptive and reactive, and geogenic organic chemicals may not survive transport from deep shales to the subsurface. Here, 40 shallow groundwater samples from private wells in Northeastern Pennsylvania were analyzed for volatile organic compounds (VOCs) and gasoline range organic compounds (GRO), and 17 were analyzed for VOCs, GRO, and diesel range organic compounds (DRO). BTEX compounds (i.e., benzene, toluene, ethylbenzene, and xylenes) were detected in 6 of 40 samples at concentrations orders of magnitude below EPA maximum contaminant levels (e.g., detected in 10 of 40 samples at concentrations as high as 8.8 ± 0.4 ppb and did not correlate with distance to the nearest hydraulic fracturing well (p = 0.24) nor in active fracturing zones, which we defined as sample locations less than 1 km from a well (p = 0.60). However, GRO was strongly correlated (p = 0.004) with shallow groundwater with Marcellus Shale inorganic chemical character, as delineated by inorganic chemical analysis. DRO was detected in all 17 samples up to 158 ± 4 ppb and did not spatially correlate with distance to the nearest hydraulic fracturing well (p = 0.74), nor active zones (p = 0.61). Similar to GRO, DRO did correlate with shallow groundwater containing Marcellus Shale character with moderate significance (p = 0.08). These results indicate that: (a) hydrophobic organic chemicals can survive transport from the deep subsurface to shallow groundwaters, and (b) transport of these compounds is not detectably enhanced by hydraulic fracturing activities in Northeastern PA as of the 2012-2014 summers.

  12. Chemical versus Enzymatic Digestion of Contaminated Estuarine Sediment: Relative Importance of Iron and Manganese Oxides in Controlling Trace Metal Bioavailability

    Science.gov (United States)

    Turner, A.; Olsen, Y. S.

    2000-12-01

    Chemical and enzymatic reagents have been employed to determine available concentrations of Fe, Mn, Cu and Zn in contaminated estuarine sediment. Gastric and intestinal enzymes (pepsin, pH 2, and trypsin, pH 7·6, respectively) removed significantly more metal than was water-soluble or exchangeable (by seawater or ammonium acetate), while gastro-intestinal fluid of the demersal teleost, Pleuronectes platessa L. (plaice), employed to operationally define a bioavailable fraction of contaminants, generally solubilized more metal than the model enzymes. Manganese was considerably more available than Fe under these conditions and it is suggested that the principal mechanism of contaminant release is via surface complexation and reductive solubilization of Mn oxides, a process which is enhanced under conditions of low pH. Of the chemical reagents tested, acetic acid best represents the fraction of Mn (as well as Cu and Zn) which is available under gastro-intestinal conditions, suggesting that the reducing tendency of acetate is similar to that of the ligands encountered in the natural digestive environment. Although the precise enzymatic and non-enzymatic composition of plaice gastro-intestinal fluid may be different to that encountered in more representative, filter-feeding or burrowing organisms, a general implication of this study is that contaminants associated with Mn oxides are significantly more bioavailable than those associated with Fe oxides, and that contaminant bioavailability may be largely dictated by the oxidic composition of contaminated sediment.

  13. Multiple magma evolution and ore-forming processes of the Hongge layered intrusion, SW China: Insights from Sr-Nd isotopes, trace elements and platinum-group elements

    Science.gov (United States)

    Liao, Mingyang; Tao, Yan; Song, Xieyan; Li, Yubang; Xiong, Feng

    2015-12-01

    The Hongge layered intrusion (259 Ma), which is located in the inner zone of the Emeishan large igneous province (ELIP), is one of the most typical Fe-Ti-V ore deposits in the Pan-Xi area. Mafic-ultramafic layered intrusions of the ELIP have attracted a lot of attention lately because these intrusions host world class Fe-Ti-V oxide deposits plus interesting Cu-Ni-(PGE) mineralization which may have economic potential. This paper, reports new whole-rock major and trace element compositions, PGE abundances and Sr-Nd isotopic data for selected cumulate rocks and basalts. We use these data to investigate the nature of parental magmas and the controls on its evolution from the source mantle en route to the surface involving the Hongge ore-bearing intrusion. Two abrupt changes in Mt/Ilm and trace element ratios such as Ba/Th with depths in the Hongge layered intrusion indicate that this intrusion formed by at least two pluses of relatively primitive magma. The whole rock Sr-Nd isotopic data of basaltic and intrusive rocks plot in the region of Emeishan low-Ti basalts and the compositions of residual liquid (at ∼1260 °C and 1155 °C) calculated by MELTS are similar to our actual high-Ti (BFQ-2) and low-Ti (BC-1) basltic samples, indicate they are co-magmatic rather than derivation from a distinct source. Total PGE abundances in the Hongge samples are extremely low, ranging from 0.5 to 10 ppb. Sulfide-bearing rocks in the Hongge intrusion and the nearby coeval Banfangqing and Baicao basalts have similar mantle-like Pd/Pt ratios (2-6) and extremely high Cu/Pd ratios (3 × 104 to 4 × 105), indicating that sulfide segregation took place at depth prior to emplacement at Hongge and eruption in this region. Sulfide saturation in the Hongge magma may have resulted from such crustal contamination event. Crystallization of silicate minerals under the anhydrous magma, magma hydration plus Fe-Ti enrichments in the parental magma are three critical factors for the formation of Fe

  14. Evolution and prospects of Spanish chemical sector. An overview from its Industrial Observatory; Evolucion y perspectivas del sector quimico espanol. Vision desde su observatorio industrial

    Energy Technology Data Exchange (ETDEWEB)

    Collado Bravo, J.; Sanchez Sanchez, F.

    2012-07-01

    The Industrial Observatory of the Chemical Sector was created in 2005 in order to follow the evolution of the Spanish chemical sector and to improve the competitiveness of the chemical companies operating in Spain. For this sector and its evolution over the years, know their main problems and the actions can be undertaken to solve or minimize them and, ultimately, learn how improve its competitiveness, the Industrial Observatory of the Chemical Sector is a good source of information. This article analyzes the Spanish chemical sector and its evolution in the period 2003-2010 using the field and the data produced within the Observatory, and then to state, through competitive factors discussed in it, what are the main measures proposed to improve the chemical sector. (Author)

  15. Multi-element trace determinations in pure alkaline earth fluoride powders by high-resolution ICP-MS using wet-chemical sample preparation and laser ablation

    Energy Technology Data Exchange (ETDEWEB)

    Tibi, Markus; Heumann, Klaus G. [Institute of Inorganic Chemistry and Analytical Chemistry, Johannes Gutenberg-University Mainz, Duesbergweg 10-14, 55099, Mainz (Germany)

    2003-09-01

    Four alternative analytical procedures for the determination of ten important trace impurities (Mg, Cr, Fe, Cu, Zn, Sr, Zr, Cd, Ba, and Pb) in pure alkaline earth fluoride powders were applied using high-resolution inductively coupled plasma mass spectrometry (ICP-MS). Two procedures are based on a wet-chemical microwave digestion with boric acid and quantification by the standard addition technique and isotope dilution mass spectrometry (IDMS), respectively. In addition, analyses are also performed by laser ablation as a direct solid sampling technique applying matrix-matched external calibration as well as isotope dilution of the powdered sample. For most elements good agreement between the different methods is found. Detection limits for laser ablation vary between 0.05 ng g{sup -1} for Zr and 20 ng g{sup -1} for Mg. They are about one to two orders of magnitude lower than those of the wet-chemical procedures, which is mainly due to the high dilution factor during the sample preparation step. Advantages and restrictions of the different analytical procedures are discussed with respect to their routine applicability. Due to its relatively high accuracy, low detection limits, and time-efficiency LA-ICP-IDMS is the preferred choice if no standard reference materials are available. (orig.)

  16. 生命之树与进化模式:导言%Tracing Patterns of Evolution through the Tree of Life: Introduction

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    @@ One and half centuries ago, Charles Darwin (1859) presented overwhelming evidence and argued that all life on the earth shared common descent, and "from so simple a beginning endless forms most beautiful and most wonderful have been, and are being evolved". Ernst Haeckel (1886) and several of his contemporaries attempted to trace the pattern of descent among all extant and extinct forms in what Darwin referred to as "the great Tree of Life". Ever since then, systematists and evolutionary biologists have been exploring morphological, cytogenetic, chemical, developmental and molecular characters, and actively developing theories and methods to infer phylogenetic relationships among organisms from these characters. This endeavor has been especially stimulated by the rise of molecular biology and the emergence of computer science over the past 50 years. At the beginning of the 21st century, we are presented with an unprecedented opportunity to reconstruct the entire Tree of Life, and further, to study evolutionary processes and mechanisms in the context of a robust phylogenetic framework.

  17. Tracing sources of nitrate in groundwater by using hydro-chemical and isotopic methods: Beirut region and its suburbs

    International Nuclear Information System (INIS)

    Analyses of hydrochemical and stable isotopes of 2H and 18O were conducted on groundwater samples collected in Beirut city and its suburbs and tapped in a limestone aquifer. The analyses were done to document the chemical and isotopic characters of the natural groundwater and to determine its origin. Hydrochemical data are classified on the basis of dominant anions. Mineral groundwater quality was found affected by different pollution sources in the southern suburb of Beirut. Isotopic analyses delineate two major groups of groundwater. The first group is directly influenced by direct recharge into the aquifer from precipitation. The second group, showing elevated mineral characteristics, is influenced by a secondary evaporation process reflecting an isotopic enrichment in groundwater. δ15N investigation of the isotopically enriched samples determines the origin of nitrate pollution from either infiltration of animal waste or septic systems to groundwater. (author)

  18. Seasonal Evolution of the Rhizosphere Effect on Major and Trace Elements in Soil Solutions of Norway Spruce ( Picea abies Karst) and Beech ( Quercus sessiliflora Smith) in an Acidic Forest Soil

    OpenAIRE

    Christophe Calvaruso; Christelle Collignon; Antoine Kies; Marie-Pierre Turpault

    2014-01-01

    In low-nutrient ecosystems such as forests developed on acidic soil, the main limiting factor for plant growth is the availability of soil nutrients. The aim of this study was to investigate in a temperate forest: 1) the influence of the rhizosphere processes on the availability of nutrients and trace elements during one year period and 2) the seasonal evolution of this rhizosphere effect. Bulk soil and rhizosphere were collected in organo-mineral and mineral horizons of an acidic soil during...

  19. Equilibrium constraints on buffer erosion based on the chemistry and chemical evolution of glacial meltwaters

    International Nuclear Information System (INIS)

    Document available in extended abstract form only. Colloidal montmorillonite sols could form if the bentonite buffer in a KBS-3 repository for spent nuclear fuel should expand into a fracture and come into contact with dilute glacial meltwaters that have migrated to repository depths from the surface of a warm-based ice sheet. Transport of the sols away from deposition holes in flowing groundwater could conceivably result in significant erosional mass losses of the buffer, thus compromising one or more safety functions assigned to this key engineered barrier. Equilibrium constraints on sol formation were considered in the present study based on observations characterizing the chemistry of sub-glacial meltwaters and the possible chemical evolution of such solutions as they migrate through repository host rocks at Forsmark. Montmorillonite sols are stable under two general limiting conditions: 1) if the concentrations of divalent cations in the colloidal system are below a threshold 'critical coagulation concentration' (CCC) consistent with DLVO theory and the Shulze-Hardy rule, or 2) if monovalent cations occupy a significant fraction of ion-exchange sites. Regarding the first condition, the CCC for Ca2+, the dominant divalent cation in many Swedish groundwaters, is approximately 1 mM. Regarding the second condition, a limited number of experimental studies indicate that montmorillonite sols become unstable, forming gels, if the equivalent fraction, X, of Ca2+ on exchange sites ≥ 0.9. This behaviour results from the effects of ion-ion correlations, which are not accounted for in DLVO theory and which strongly increase the net attraction between colloidal particles having high surface charge and divalent counterions in the electrical double layer. Mass-action constraints for the reaction Ca2+(solution) + 2Na+(montmorillonite) = 2Na+(solution) + Ca2+(montmorillonite) assuming that 1) exchange sites are occupied predominantly by Na+ and/or Ca2+ and 2) the

  20. Tropical troposphere to stratosphere transport of carbon monoxide and long-lived trace species in the Chemical Lagrangian Model of the Stratosphere (CLaMS

    Directory of Open Access Journals (Sweden)

    R. Pommrich

    2014-08-01

    Full Text Available Variations in the mixing ratio of trace gases of tropospheric origin entering the stratosphere in the tropics are of interest for assessing both troposphere to stratosphere transport fluxes in the tropics and the impact of these transport fluxes on the composition of the tropical lower stratosphere. Anomaly patterns of carbon monoxide (CO and long-lived tracers in the lower tropical stratosphere allow conclusions about the rate and the variability of tropical upwelling to be drawn. Here, we present a simplified chemistry scheme for the Chemical Lagrangian Model of the Stratosphere (CLaMS for the simulation, at comparatively low numerical cost, of CO, ozone, and long-lived trace substances (CH4, N2O, CCl3F (CFC-11, CCl2F2 (CFC-12, and CO2 in the lower tropical stratosphere. For the long-lived trace substances, the boundary conditions at the surface are prescribed based on ground-based measurements in the lowest model level. The boundary condition for CO in the free troposphere is deduced from MOPITT measurements (at ≈ 700–200 hPa. Due to the lack of a specific representation of mixing and convective uplift in the troposphere in this model version, enhanced CO values, in particular those resulting from convective outflow are underestimated. However, in the tropical tropopause layer and the lower tropical stratosphere, there is relatively good agreement of simulated CO with in-situ measurements (with the exception of the TROCCINOX campaign, where CO in the simulation is biased low ≈ 10–20 ppbv. Further, the model results are of sufficient quality to describe large scale anomaly patterns of CO in the lower stratosphere. In particular, the zonally averaged tropical CO anomaly patterns (the so called "tape recorder" patterns simulated by this model version of CLaMS are in good agreement with observations. The simulations show a too rapid upwelling compared to observations as a consequence of the overestimated vertical velocities in

  1. Clues to the chemical evolution of agpaitic magmas from compositional zoning in kakortokite-hosted eudialyte, Ilímaussaq Complex, South Greenland

    Science.gov (United States)

    Borst, A. M.; Smit, M. A.; Waight, T. E.; Nielsen, T. F. D.; Friis, H.

    2014-12-01

    This study addresses the petrological and geochemical variations of eudialyte and related phases in kakortokites from the ~1.16 Ga Ilímaussaq Complex, S Greenland. The kakortokites form a suite of rhythmically layered agpaitic nepheline syenites, highly enriched in REE, Zr, Nb, Ta (HFSE) and halogens (F, Cl). Instead of containing common HFSE-phases such as zircon or titanite, agpaitic rocks exhibit complex Na-Zr-Ti-silicates, e.g. eudialyte and rinkite. To gain further insight in the crystallisation parameters and layering forming processes in agpaitic systems, we performed major and trace-element analyses on cumulus eudialyte. The data reveal complex compositional zoning patterns, including hour-glass sector-zoning, sub-μm scale oscillatory zoning and core-rim relationships. The latter were explored to identify subtle trends in the chemical evolution and in-situ fractionation of the liquids from which they crystallised. Most crystals exhibit a general rimward increase in REE concentrations (1.0-1.3 wt% Ce203 and 0.5-0.7 wt% La2O3), which is consistent with REE enrichment in the fractionating bulk magma. Similarly, Ba contents significantly increase towards the rims (300-900 ppm), while Cl (1.0-1.6 wt%), Rb (7-20 ppm) and Pb (60-160 ppm) decrease. In few cases, crystals exhibit partial rims with relatively low REE contents (~0.5 wt% RE2O3), which is in contrast with the general core-rim trend in the euhedral cores. These particular eudialyte segments are tentatively interpreted as crystallites from inter-cumulate melt, which underwent a chemical evolution distinctly different from that of the bulk magma. The decrease in REE contents may reflect the introduction of new REE-phases at the inter-cumulus stage, such as rinkite-group minerals, which contain ~20 wt% RE2O3 and occur interstitial to the major cumulus minerals feldspar, nepheline, arfvedsonite and eudialyte. Hour-glass sector zoning in the euhedral eudialyte cores involves small variations (< 0.1 wt%) in

  2. Chemical and isotopic analysis of hydrocarbon traces degassed out of Callovo-Oxfordian argilites from Bure (France): methodology and results

    International Nuclear Information System (INIS)

    Isotopic mass spectrometry online with gas chromatography (GC-C-IRMS) allows the measurement of the carbon isotopic ratios of hydrocarbon gases (C1 to C4) after complete combustion to CO2. The method also permits to measure proportions of the different hydrocarbon gases and CO2. Such data provide valuable information about the source and genesis of a gas sample, as well as the post-formation physicochemical processes which might affect it in the geological environment. In particular, it is possible to distinguish hydrocarbon gases of bacterial or thermogenic origin based on the proportion of methane and the carbon isotope ratio as measured by GC-C-IRMS. However, if the relative concentrations of carbon molecules are very small (from 1 ppm to 1000 ppm), the isotopic information cannot be obtained directly with GC-C-IRMS. An additional step allowing the pre-concentration of hydrocarbons must be introduced in the analytical procedure. Indeed, in order to obtain an adequate accuracy, several operating conditions are of prime importance: sufficient signal intensity, good quality peak shape, low signal/noise ratio. We present here a pre-concentration system based on the removal of major gas compounds (N2, O2, Ar, etc...) and trapping of carbon molecules. The purified carbon molecules are released in an inert carrier gas, focussed through a tiny capillary, and introduced in the chromatograph for separation, combustion of each compound and final analysis in the mass spectrometer. This technique provides the chemical concentration in the initial gas and the carbon isotope composition of each individual carbon molecular compound. Its high sensitivity allows measurement of isotopic ratios for concentrations as low as 1 ppm of methane, 0,5 ppm of ethane and 0,3 ppm of propane, for bulk gas samples of 10 cc in standard conditions. Total analytical uncertainty on δ13C measurements is ± 1 0/00 or better. The results of a first application of this technique to the Callovo

  3. Determination of Methylmercury Traces in Biological Matrix: Chemical Extraction and Nuclear Quantification with the Neutron Activation Analysis Technique

    International Nuclear Information System (INIS)

    Mercury is present in the environment as a result of the human and natural activities.The total amount of Hg present in the biosphere has been incremented three times since the industrial era, and now it is affecting in a global sense all the ecosystem.One of the main entrance of Hg in the human diet is the consumption of fish and other marine creatures.Most of the ingested Hg is mono methylmercury (MeHg), which is one of the most toxic forms in which this element could be found because it crosses membranes.Since the toxicity levels are low, the determination of concentrations of total Hg and Me Hg require very careful sampling, sample conditioning and analytical procedures to prevent either losses or contamination, or the degradation of the Hg species.In this work, we implemented a chemical Me Hg extraction procedure, using a ionic exchange resin, with three different types of fish tissue: muscle, liver and hepato pancreas.After Me Hg extraction, the determination and quantification was made by Instrumental Neutron Activation Analysis, by measuring the 197 Au, y el 203 Tl deexcitation s, created through the radioactive decay of the isotopes 197 Hg y 203 Hg.The influence of several parameters on the overall extraction process, such as velocity of passage through the ionic exchange column and the acid concentration used in the extraction was evaluated.Regarding the INAA determinations, a choice was made for the irradiation, decay and counting times, neutron and gamma doses, and the counting geometry The detection limit found for this technique (dry weight) is 140 pg MeHg/g. The Hg contents of the muscle samples were measured with the 279 keV emission of the product of the 202 Hg(n,g)203 Hg reaction, with a recovery of (100 ± 13)%. Liver and Hepato pancreas samples were measured with the 77 keV gamma emission of the 197 Hg, checking this result with the 67 y 69 keV X emissions from the same isotope.The liver samples needed an extra vacuum filtering process during

  4. Present state and chemical evolution of the atmospheres of Titan, Triton, and Pluto

    International Nuclear Information System (INIS)

    An evaluation is made of the current understanding of the atmospheres of Titan, Triton, and Pluto, as well as of theoretical models for their origin and evolution. All three atmospheres contain methane, while Titan, and probably Triton, have nitrogen. The primary driver in the evolution of the Titan atmosphere has been the irreversible photolysis of methane. If a surface reservoir of liquid methane exists to resupply the atmosphere, it is subject to enrichment in ethane due to the long-term photolysis of methane. The key issue in the origin and early evolution of Titan's atmosphere is the source of molecular nitrogen; two schemes for the conversion of ammonia to nitrogen have been considered

  5. Present state and chemical evolution of the atmospheres of Titan, Triton, and Pluto

    Science.gov (United States)

    Lunine, J. I.; Atreya, S. K.; Pollack, J. B.

    1989-01-01

    An evaluation is made of the current understanding of the atmospheres of Titan, Triton, and Pluto, as well as of theoretical models for their origin and evolution. All three atmospheres contain methane, while Titan, and probably Triton, have nitrogen. The primary driver in the evolution of the Titan atmosphere has been the irreversible photolysis of methane. If a surface reservoir of liquid methane exists to resupply the atmosphere, it is subject to enrichment in ethane due to the long-term photolysis of methane. The key issue in the origin and early evolution of Titan's atmosphere is the source of molecular nitrogen; two schemes for the conversion of ammonia to nitrogen have been considered.

  6. Chemical fertilizers as a source of (238)U, (40)K, (226)Ra, (222)Rn, and trace metal pollutant of the environment in Saudi Arabia.

    Science.gov (United States)

    Alshahri, Fatimh; Alqahtani, Muna

    2015-06-01

    The specific activities of (238)U, (226)Ra, (40)K, and (222)Rn in chemical fertilizers were measured using gamma ray spectrometer and Cr-39 detector. In this study, 21 chemical fertilizers were collected from Eastern Saudi Arabian markets. The specific activities of (238)U ranged from 23 ± 0.5 to 3900 ± 195 Bq kg(-1); (226)Ra ranged from 5.60 ± 2.80 to 392 ± 18 Bq kg(-1); and (40)K ranged from 18.4 ± 3 to 16,476 ± 820 Bq kg(-1). The radon concentrations and the radon exhalation rates were found to vary from 3.20 ± 1.20 to 1532 ± 160 Bq m(-3) and from 1.60 to 774 mBq m(-2) h(-1), respectively. Radium equivalent activities (Raeq) were calculated for the analyzed samples to assess the radiation hazards arising due to the use of these chemical fertilizers in the agriculture soil. The Raeq for six local samples (nitrogen, phosphorous, and potassium (NPK) and single superphosphate (SSP)) and one imported sample (Sulfate of Potash (SOP)) were greater than the acceptable value 370 Bq kg(-1). The total air absorbed doses rates in air 1 m above the ground (D) were calculated for all samples. All samples, except one imported granule sample diammonium phosphate (DAP), were higher than the estimated average global terrestrial radiation of 55 nGy h(-1). The highest annual effective dose was in triple super phosphate (TSP) fertilizers (2.1 mSv y(-1)). The results show that the local TSP, imported SOP, and local NPK (sample 13) fertilizers were unacceptable for use as fertilizers in agricultural soil. Furthermore, the toxic elements and trace metals (Pb, Cd, Cr, Co, Ni, Hg, and As) were determined using atomic absorption spectrometer. The concentrations of chromium in chemical fertilizers were higher than the global values. PMID:25532871

  7. Factors controlling the chemical composition of colloidal and dissolved fractions in soil solutions and the mobility of trace elements in soils

    Science.gov (United States)

    Gangloff, Sophie; Stille, Peter; Schmitt, Anne-Désirée; Chabaux, François

    2016-09-01

    The objectives of this study were to determine the processes and physico-chemical conditions that affect the composition of the soil solutions of a forest soil and to elucidate their impact on the transport of major and trace elements through the colloidal (0.2 μm to 5 kDa) and dissolved (soil. All experiments were performed with soil solutions obtained using lysimeter plates situated on an experimental spruce parcel of the Strengbach catchment (Northeastern France). The surface samples filtered at 0.2 μm facilitated the examination of the influence of litter decomposition on the chemical composition of the upper soil solutions. The impact of the soils biogeochemical conditions (pH, moisture, temperature, oxic or anoxic conditions) on litter decomposition was also examined. More particularly, the increase in NH4+ and NO2- compounds in some of the soil solutions points to denitrification processes in an anoxic environment. Thus, under anoxic conditions, the soil solution is enriched in Ca, P, Mn and Zn, whereas under oxic conditions it is enriched in Al and Fe. The physico-chemical conditions are more seasonally dependent in the upper soil horizons than in the deeper ones and have an impact on the variability of the chemical composition of the soil solutions. The colloidal and dissolved fractions of the soil solutions were obtained by tangential flow ultra-filtration. The experimental results reveal that nutrients, such as NO3- and P, are primarily in the dissolved fraction and consequently bioavailable; secondary minerals may be dissolved and/or precipitate in the colloidal fraction, such as pyromorphite (Pb5(PO4)3(OH, Cl, F)). The results further indicate that microbial activity influences the composition of the colloidal and dissolved fractions, and possibly enriches the colloidal fraction in Ca, Mn and P, diminishes the concentrations of Pb, V, Cr and Fe in the dissolved fraction, and changes the structure of organic carbon (OC). These results are important

  8. The physical and chemical evolution of protostellar disks. The growth of protostellar disks: Progress to date

    Science.gov (United States)

    Stahler, Steven W.

    1993-01-01

    This study constitutes one part of our multi-disciplinary approach to the evolution of planet-forming disks. The goal is to establish the disks' thermal and mechanical properties as they grow by the infall of their parent interstellar clouds. Thus far, significant advances toward establishing the evolving surface density of such disks was made.

  9. Directed Evolution Strategies for Enantiocomplementary Haloalkane Dehalogenases : From Chemical Waste to Enantiopure Building Blocks

    NARCIS (Netherlands)

    van Leeuwen, Jan G. E.; Wijma, Hein J.; Floor, Robert J.; van der Laan, Jan-Metske; Janssen, Dick B.

    2012-01-01

    We used directed evolution to obtain enantiocomplementary haloalkane dehalogenase variants that convert the toxic waste compound 1,2,3-trichloropropane (TCP) into highly enantioenriched (R)- or (S)-2,3-dichloropropan-1-ol, which can easily be converted into optically active epichlorohydrinsattractiv

  10. Estimated total emissions of trace gases from the Canberra Wildfires of 2003: a new method using satellite measurements of aerosol optical depth & the MOZART chemical transport model

    Directory of Open Access Journals (Sweden)

    C. Paton-Walsh

    2010-06-01

    Full Text Available In this paper we describe a new method for estimating trace gas emissions from large vegetation fires using satellite measurements of aerosol optical depth (AOD at 550 nm, combined with an atmospheric chemical transport model. The method uses a threshold value to screen out normal levels of AOD that may be caused by raised dust, sea salt aerosols or diffuse smoke transported from distant fires. Using this method we infer an estimated total emission of 15±5 Tg of carbon monoxide, 0.05±0.02 Tg of hydrogen cyanide, 0.11±0.03 Tg of ammonia, 0.25±0.07 Tg of formaldehyde, 0.03±0.01 of acetylene, 0.10±0.03 Tg of ethylene, 0.03±0.01 Tg of ethane, 0.21±0.06 Tg of formic acid and 0.28±0.09 Tg of methanol released to the atmosphere from the Canberra fires of 2003. An assessment of the uncertainties in the new method is made and we show that our estimate agrees (within expected uncertainties with estimates made using current conventional methods of multiplying together factors for the area burned, fuel load, the combustion efficiency and the emission factor for carbon monoxide. A simpler estimate derived directly from the satellite AOD measurements is also shown to be in agreement with conventional estimates, suggesting that the method may, under certain meteorological conditions, be applied without the complication of using a chemical transport model. The new method is suitable for estimating emissions from distinct large fire episodes and although it has some significant uncertainties, these are largely independent of the uncertainties inherent in conventional techniques. Thus we conclude that the new method is a useful additional tool for characterising emissions from vegetation fires.

  11. Chemical evolution of bentonite buffer in a KBS-3 type spent fuel repository from thermal to post glacial phase

    International Nuclear Information System (INIS)

    Document available in extended abstract form only. The very long-term interaction between the bentonite buffer and ground waters present in a KBS-3 spent fuel repository has not been studied systematically, although this evolution is the base scenario in safety-case studies. In long-term safety considerations one must take into account all successive disturbances a bentonite buffer may have experienced (even short-term ones), as the effects of these are often irreversible. The interaction starts soon after the installation of bentonite blocks, when water is intruding into a deposition hole. The initially partially dry compacted bentonite starts to saturate and swell under the temperature gradient resulting from the heat formed by decaying radionuclides inside a copper canister. However, heat formation will decrease with time and bentonite will achieve full saturation after about one thousand years. The groundwater composition is estimated to change during the first 100,000 years from saline to extremely dilute, the latter likely encountered during the post-glacial phase. The bentonite is in contact with groundwater through a water-conducting fracture and possibly through excavation damaged and spalling zones formed around the deposition hole. An interesting question is the extent to which this coupling can slow down chemical changes in bentonite. Another important process affecting the evolution is the chemical alteration of the primary minerals in bentonite (i.e. montmorillonite and the accessory minerals). Swelling and other mechanical phenomena are important during the saturation of the buffer, but implementing these to our reactive transport models is beyond the scope of this paper. The implementing remains, however, the final aim. In this work, 2D reactive transport (TOUGHREACT v. 1.0) and some 3D COMSOL Multiphysics (COMSOL 2008) model calculations have been carried out on the chemical evolution of bentonite buffer from the operational phase of the repository

  12. Quantification of trace fatty acid methyl esters in diesel fuel by using multidimensional gas chromatography with electron and chemical ionization mass spectrometry.

    Science.gov (United States)

    Webster, R L; Rawson, P M; Evans, D J; Marriott, P J

    2016-07-01

    Measurement of contamination of marine and naval diesel fuels (arising from product mixing or adulteration) with biodiesel or fatty acid methyl esters can be problematic, especially at very low levels. A suitable solution for this task for trace amounts of individual fatty acid methyl esters with resolution and quantification can be achieved by using a multidimensional gas chromatographic approach with electron and chemical ionization mass spectrometric detection. A unique column set comprising a 100 m methyl-siloxane nonpolar first dimension column and high-temperature ionic liquid column in the second dimension enabled identification of individual fatty acid methyl esters at below the lowest concentrations required to be reported in a diesel fuel matrix. Detection limits for individual fatty acid methyl esters compounds ranged from 0.5 to 5.0 mg/L, with excellent linearity up to 5000 mg/L and repeatability of the method from 1.3 to 3.2%. The method was applied to the analysis of diesel fuel samples with suspected biodiesel contamination. Contamination at 568 mg/L was calculated for an unknown sample and interpretation of the results permitted the determination of a likely source of the contamination. PMID:27159197

  13. Vertical exchange and chemical conversion of trace elements over topographically complex terrain; Vertikaler Austausch und chemische Umwandlung von Spurenstoffen ueber topographisch gegliedertem Gelaende

    Energy Technology Data Exchange (ETDEWEB)

    Kuntze, K.

    2001-10-01

    The influence of topography on the vertical exchange of trace elements was investigated with the aid of a numeric simulation model. It is a couopled 3D model consisting of the mesoscale model KAMM and the dispersion model DRAIS, extended by the gaseous phase mechanism of the RADM model. This way, both meteorological and chemical processes can be analyzed in a preselected time and spatial resolution. The simulations were validated by a comparison with measurements made during the TRACT campaign. Satisfactory agreement between the two was established. [German] In der vorliegenden Arbeit wurde der Einfluss der Topographie auf den vertikalen Austausch von Spurenstoffen mit Hilfe eines numerischen Simulationsmodells untersucht. Bei dem Simulationsmodell handelt es sich um ein dreidimensionales gekoppeltes Modell, welches aus dem mesoskaligen Modell KAMM und dem um den Gasphasenmechanismus des RADM-Modells erweiterten Ausbreitungsmodell DRAIS besteht. Mit diesem Modellsystem war es moeglich, sowohl meterologische als auch chemische Prozesse in einer vorher gewaehlten zeitlichen und raeumlichen Aufloesung zu betrachten. Um die Qualitaet der Simulation und damit deren Verwendbarkeit fuer die Untersuchungen festzustellen, wurde ein Vergleich mit Messungen durchgefuehrt. Dazu wurden berechnete meterologische und chemische Groessen mit den waehrend der Feldmesskampagne TRACT gemessenen Groessen verglichen. Der Vergleich der simulierten Groessen sowohl mit Radiosondenaufstiegen als auch mit Zeitreihen und Flugzeugmessungen lieferte eine gute Uebereinstimmung. (orig.)

  14. Role of primary substrate composition on microbial community structure and function and trace organic chemical attenuation in managed aquifer recharge systems

    KAUST Repository

    Li, Dong

    2014-03-26

    This study was performed to reveal the microbial community characteristics in simulated managed aquifer recharge (MAR), a natural water treatment system, under different concentrations and compositions of biodegradable dissolved organic carbon (BDOC) and further link these to the biotransformation of emerging trace organic chemicals (TOrCs). Two pairs of soil-column setups were established in the laboratory receiving synthetic feed solutions composed of different peptone/humic acid ratios and concentrations. Higher BDOC concentration resulted in lower microbial community diversity and higher relative abundance of Betaproteobacteria. Decreasing the peptone/humic acid ratio resulted in higher diversity of the community and higher relative abundances of Firmicutes, Planctomycetes, and Actinobacteria. The metabolic capabilities of microbiome involved in xenobiotics biodegradation were significantly promoted under lower BDOC concentration and higher humic acid content. Cytochrome P450 genes were also more abundant under these primary substrate conditions. Lower peptone/humic acid ratios also promoted the attenuation of most TOrCs. These results suggest that the primary substrate characterized by a more refractory character could increase the relative abundances of Firmicutes, Planctomycetes, and Actinobacteria, as well as associated cytochrome P450 genes, all of which should play important roles in the biotransformation of TOrCs in this natural treatment system. © 2014 Springer-Verlag.

  15. Rationale and Methods for Archival Sampling and Analysis of Atmospheric Trace Chemical Contaminants On Board Mir and Recommendations for the International Space Station

    Science.gov (United States)

    Perry, J. L.; James, J. T.; Cole, H. E.; Limero, T. F.; Beck, S. W.

    1997-01-01

    Collection and analysis of spacecraft cabin air samples are necessary to assess the cabin air quality with respect to crew health. Both toxicology and engineering disciplines work together to achieve an acceptably clean cabin atmosphere. Toxicology is concerned with limiting the risk to crew health from chemical sources, setting exposure limits, and analyzing air samples to determine how well these limits are met. Engineering provides the means for minimizing the contribution of the various contaminant generating sources by providing active contamination control equipment on board spacecraft and adhering to a rigorous material selection and control program during the design and construction of the spacecraft. A review of the rationale and objectives for sampling spacecraft cabin atmospheres is provided. The presently-available sampling equipment and methods are reviewed along with the analytical chemistry methods employed to determine trace contaminant concentrations. These methods are compared and assessed with respect to actual cabin air quality monitoring needs. Recommendations are presented with respect to the basic sampling program necessary to ensure an acceptably clean spacecraft cabin atmosphere. Also, rationale and recommendations for expanding the scope of the basic monitoring program are discussed.

  16. A Model for the Thermal and Chemical Evolution of the Moon's Interior: Implications for the Onset of Mare Volcanism

    Science.gov (United States)

    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.

  17. Quantitative chemical tagging, stellar ages and the chemo-dynamical evolution of the Galactic disc

    CERN Document Server

    Mitschang, A W; Zucker, D B; Anguiano, B; Bensby, T; Feltzing, S

    2013-01-01

    The early science results from the new generation of high-resolution stellar spectroscopic surveys, such as GALAH and the Gaia-ESO survey, will represent major milestones in the quest to chemically tag the Galaxy. Yet this technique to reconstruct dispersed coeval stellar groups has remained largely untested until recently. We build on previous work that developed an empirical chemical tagging probability function, which describes the likelihood that two field stars are conatal, that is, they were formed in the same cluster environment. In this work we perform the first ever blind chemical tagging experiment, i.e., tagging stars with no known or otherwise discernable associations, on a sample of 714 disc field stars with a number of high quality high resolution homogeneous metal abundance measurements. We present evidence that chemical tagging of field stars does identify coeval groups of stars, yet these groups may not represent distinct formation sites, e.g. as in dissolved open clusters, as previously thou...

  18. Reduced biological control and enhanced chemical pest management in the evolution of fungus farming in ants

    DEFF Research Database (Denmark)

    Fernández-Marín, Hermógenes; Zimmerman, Jess K; Nash, David R;

    2009-01-01

    To combat disease, most fungus-growing ants (Attini) use antibiotics from mutualistic bacteria (Pseudonocardia) that are cultured on the ants' exoskeletons and chemical cocktails from exocrine glands, especially the metapleural glands (MG). Previous work has hypothesized that (i) Pseudonocardia a...... reliance on mutualistic Pseudonocardia are correlated with larger colony size among attine genera, raising questions about the efficacy of managing disease in large societies with chemical cocktails versus bacterial antimicrobial metabolites....

  19. Nuclear traces in glass

    International Nuclear Information System (INIS)

    The charged particles produce, in dielectric materials, physical and chemical effects which make evident the damaged zone along the trajectory of the particle. This damaged zone is known as the latent trace. The latent traces can be enlarged by an etching of the detector material. This treatment attacks preferently the zones of the material where the charged particles have penetrated, producing concavities which can be observed through a low magnification optical microscope. These concavities are known as developed traces. In this work we describe the glass characteristics as a detector of the fission fragments traces. In the first chapter we present a summary of the existing basic theories to explain the formation of traces in solids. In the second chapter we describe the etching method used for the traces development. In the following chapters we determine some chatacteristics of the traces formed on the glass, such as: the development optimum time; the diameter variation of the traces and their density according to the temperature variation of the detector; the glass response to a radiation more penetrating than that of the fission fragments; the distribution of the developed traces and the existing relation between this ditribution and the fission fragments of 252Cf energies. The method which has been used is simple and cheap and can be utilized in laboratories whose resources are limited. The commercial glass which has been employed allows the registration of the fission fragments and subsequently the realization of experiments which involve the counting of the traces as well as the identification of particles. (author)

  20. Chemical evolution, petrogenesis, and regional chemical correlations of the flood basalt sequence in the central Deccan Traps, India

    Indian Academy of Sciences (India)

    Leone Melluso; Mario Barbieri; Luigi Beccaluva

    2004-12-01

    The lava sequence of the central-western Deccan Traps (from Jalgaon towards Mumbai) is formed by basalts and basaltic andesites having a significant variation in TiO2 (from 1.2 to 3.3 wt%), Zr (from 84 to 253 ppm), Nb (from 5 to 16 ppm) and Ba (from 63 to 407 ppm), at MgO ranging from 10 to 4.2 wt%. Most of these basalts follow a liquid line of descent dominated by low pressure fractionation of clinopyroxene, plagioclase and olivine, starting from the most mafic compositions, in a temperature range from 1220° to 1125°C. These rocks resemble those belonging to the lowermost formations of the Deccan Traps in the Western Ghats (Jawhar, Igatpuri and Thakurvadi) as well as those of the Poladpur formation. Samples analyzed for 87Sr/86Sr give a range of initial ratios from 0.70558 to 0.70621. A group of flows of the Dhule area has low TiO2 (1.2–1.5 wt%) and Zr (84–105 ppm) at moderate MgO (5.2–6.2 wt%), matching the composition of low-Ti basalts of Gujarat, low-Ti dykes of the Tapti swarm and Toranmal basalts, just north of the study area. This allows chemical correlations between the lavas of central Deccan, the Tapti dykes and the northwestern outcrops. The mildly enriched high field strength element contents of the samples with TiO2 < 1.5 wt% make them products of mantle sources broadly similar to those which generated the Ambenali basalts, but their high La/Nb and Ba/Nb, negative Nb anomalies in the mantle normalized diagrams, and relatively high 87Sr/86Sr, make evident a crustal input with crustally derived materials at less differentiated stages than those represented in this sample set, or even within the sub-Indian lithospheric mantle.