The next generation of galaxy evolution models: A symbiosis of stellar populations and chemical abundances

Science.gov (United States)

Kotulla, Ralf

2012-10-01

Over its lifespan Hubble has invested significant effort into detailed observations of galaxies both in the local and distant universe. To extract the physical information from the observed {spectro-}photometry requires detailed and accurate models. Stellar population synthesis models are frequently used to obtain stellar masses, star formation rate, galaxy ages and star formation histories. Chemical evolution models offer another valuable and complementary approach to gain insight into many of the same aspects, yet these two methods have rarely been used in combination.Our proposed next generation of galaxy evolution models will help us improve our understanding of how galaxies form and evolve. Building on GALEV evolutionary synthesis models we incorporate state-of-the-art input physics for stellar evolution of binaries and rotating stars as well as new spectral libraries well matched to the modern observational capabilities. Our improved chemical evolution model allows us to self-consistently trace abundances of individual elements, fully accounting for the increasing initial abundances of successive stellar generations. GALEV will support variable Initial Mass Functions {IMF}, enabling us to test recent observational findings of a non-universal IMF by predicting chemical properties and integrated spectra in an integrated and consistent manner.HST is the perfect instrument for testing this approach. Its wide wavelength coverage from UV to NIR enables precise SED fitting, and with its spatial resolution we can compare the inferred chemical evolution to studies of star clusters and resolved stellar populations in nearby galaxies.

Evolution of trace elements in the planetary boundary layer in southern China: Effects of dust storms and aerosol-cloud interactions

Science.gov (United States)

Li, Tao; Wang, Yan; Zhou, Jie; Wang, Tao; Ding, Aijun; Nie, Wei; Xue, Likun; Wang, Xinfeng; Wang, Wenxing

2017-03-01

Aerosols and cloud water were analyzed at a mountaintop in the planetary boundary layer in southern China during March-May 2009, when two Asian dust storms occurred, to investigate the effects of aerosol-cloud interactions (ACIs) on chemical evolution of atmospheric trace elements. Fe, Al, and Zn predominated in both coarse and fine aerosols, followed by high concentrations of toxic Pb, As, and Cd. Most of these aerosol trace elements, which were affected by dust storms, exhibited various increases in concentrations but consistent decreases in solubility. Zn, Fe, Al, and Pb were the most abundant trace elements in cloud water. The trace element concentrations exhibited logarithmic inverse relationships with the cloud liquid water content and were found highly pH dependent with minimum concentrations at the threshold of pH 5.0. The calculation of Visual MINTEQ model showed that 80.7-96.3% of Fe(II), Zn(II), Pb(II), and Cu(II) existed in divalent free ions, while 71.7% of Fe(III) and 71.5% of Al(III) were complexed by oxalate and fluoride, respectively. ACIs could markedly change the speciation distributions of trace elements in cloud water by pH modification. The in-cloud scavenging of aerosol trace elements likely reached a peak after the first 2-3 h of cloud processing, with scavenging ratios between 0.12 for Cr and 0.57 for Pb. The increases of the trace element solubility (4-33%) were determined in both in-cloud aerosols and postcloud aerosols. These results indicated the significant importance of aerosol-cloud interactions to the evolution of trace elements during the first several cloud condensation/evaporation cycles.

Atmospheric reaction systems as null-models to identify structural traces of evolution in metabolism.

Directory of Open Access Journals (Sweden)

Petter Holme

Full Text Available The metabolism is the motor behind the biological complexity of an organism. One problem of characterizing its large-scale structure is that it is hard to know what to compare it to. All chemical reaction systems are shaped by the same physics that gives molecules their stability and affinity to react. These fundamental factors cannot be captured by standard null-models based on randomization. The unique property of organismal metabolism is that it is controlled, to some extent, by an enzymatic machinery that is subject to evolution. In this paper, we explore the possibility that reaction systems of planetary atmospheres can serve as a null-model against which we can define metabolic structure and trace the influence of evolution. We find that the two types of data can be distinguished by their respective degree distributions. This is especially clear when looking at the degree distribution of the reaction network (of reaction connected to each other if they involve the same molecular species. For the Earth's atmospheric network and the human metabolic network, we look into more detail for an underlying explanation of this deviation. However, we cannot pinpoint a single cause of the difference, rather there are several concurrent factors. By examining quantities relating to the modular-functional organization of the metabolism, we confirm that metabolic networks have a more complex modular organization than the atmospheric networks, but not much more. We interpret the more variegated modular arrangement of metabolism as a trace of evolved functionality. On the other hand, it is quite remarkable how similar the structures of these two types of networks are, which emphasizes that the constraints from the chemical properties of the molecules has a larger influence in shaping the reaction system than does natural selection.

Influence of trace aromatics on the chemical growth mechanisms of Titan aerosol analogues

Science.gov (United States)

Gautier, Thomas; Sebree, Joshua A.; Li, Xiang; Pinnick, Veronica T.; Grubisic, Andrej; Loeffler, Mark J.; Getty, Stephanie A.; Trainer, Melissa G.; Brinckerhoff, William B.

2017-06-01

The chemical structure and formation pathways of Titan aerosols remain largely unknown. In this work, we studied the effect of trace aromatics on the chemical composition and formation pathways of laboratory analogues of Titan's organic aerosols. The aerosol analogues were produced using four different trace aromatic molecules, comprised of one or two aromatic rings, each with or without a nitrogen heteroatom. Samples were then analyzed by laser desorption/ionization Mass Spectrometry (LDMS), revealing a high variability in the sample composition depending on the trace aromatic used. Our work reveals that the final chemical structure of the aerosols depends strongly on the number of aromatic rings in the trace molecule, leading either to a polymeric or to a random co-polymeric growth of the sample. These different chemical structures can affect the physical properties of the aerosol. Future analysis of Titan's aerosols using better resolution could potentially determine whether either of the growth hypotheses are preferred.

A stochastic approach to chemical evolution

International Nuclear Information System (INIS)

Copi, C.J.

1997-01-01

Observations of elemental abundances in the Galaxy have repeatedly shown an intrinsic scatter as a function of time and metallicity. The standard approach to chemical evolution does not attempt to address this scatter in abundances since only the mean evolution is followed. In this work, the scatter is addressed via a stochastic approach to solving chemical evolution models. Three simple chemical evolution scenarios are studied using this stochastic approach: a closed box model, an infall model, and an outflow model. These models are solved for the solar neighborhood in a Monte Carlo fashion. The evolutionary history of one particular region is determined randomly based on the star formation rate and the initial mass function. Following the evolution in an ensemble of such regions leads to the predicted spread in abundances expected, based solely on different evolutionary histories of otherwise identical regions. In this work, 13 isotopes are followed, including the light elements, the CNO elements, a few α-elements, and iron. It is found that the predicted spread in abundances for a 10 5 M circle-dot region is in good agreement with observations for the α-elements. For CN, the agreement is not as good, perhaps indicating the need for more physics input for low-mass stellar evolution. Similarly for the light elements, the predicted scatter is quite small, which is in contradiction to the observations of 3 He in HII regions. The models are tuned for the solar neighborhood so that good agreement with HII regions is not expected. This has important implications for low-mass stellar evolution and on using chemical evolution to determine the primordial light-element abundances in order to test big bang nucleosynthesis. copyright 1997 The American Astronomical Society

Using Star Clusters as Tracers of Star Formation and Chemical Evolution: The Chemical Enrichment History of the Large Magellanic Cloud

Science.gov (United States)

Chilingarian, Igor V.; Asa’d, Randa

2018-05-01

The star formation (SFH) and chemical enrichment (CEH) histories of Local Group galaxies are traditionally studied by analyzing their resolved stellar populations in a form of color–magnitude diagrams obtained with the Hubble Space Telescope. Star clusters can be studied in integrated light using ground-based telescopes to much larger distances. They represent snapshots of the chemical evolution of their host galaxy at different ages. Here we present a simple theoretical framework for the chemical evolution based on the instantaneous recycling approximation (IRA) model. We infer a CEH from an SFH and vice versa using observational data. We also present a more advanced model for the evolution of individual chemical elements that takes into account the contribution of supernovae type Ia. We demonstrate that ages, iron, and α-element abundances of 15 star clusters derived from the fitting of their integrated optical spectra reliably trace the CEH of the Large Magellanic Cloud obtained from resolved stellar populations in the age range 40 Myr age–metallicity relation. Moreover, the present-day total gas mass of the LMC estimated by the IRA model (6.2× {10}8 {M}ȯ ) matches within uncertainties the observed H I mass corrected for the presence of molecular gas (5.8+/- 0.5× {10}8 {M}ȯ ). We briefly discuss how our approach can be used to study SFHs of galaxies as distant as 10 Mpc at the level of detail that is currently available only in a handful of nearby Milky Way satellites. .

Investigating Planetesimal Evolution by Experiments with Fe-Ni Metallic Melts: Light Element Composition Effects on Trace Element Partitioning Behavior

Science.gov (United States)

Chabot, N. L.

2017-12-01

As planetesimals were heated up in the early Solar System, the formation of Fe-Ni metallic melts was a common occurrence. During planetesimal differentiation, the denser Fe-Ni metallic melts separated from the less dense silicate components, though some meteorites suggest that their parent bodies only experienced partial differentiation. If the Fe-Ni metallic melts did form a central metallic core, the core eventually crystallized to a solid, some of which we sample as iron meteorites. In all of these planetesimal evolution processes, the composition of the Fe-Ni metallic melt influenced the process and the resulting trace element chemical signatures. In particular, the metallic melt's "light element" composition, those elements present in the metallic melt in a significant concentration but with lower atomic masses than Fe, can strongly affect trace element partitioning. Experimental studies have provided critical data to determine the effects of light elements in Fe-Ni metallic melts on trace element partitioning behavior. Here I focus on combining numerous experimental results to identify trace elements that provide unique insight into constraining the light element composition of early Solar System Fe-Ni metallic melts. Experimental studies have been conducted at 1 atm in a variety of Fe-Ni systems to investigate the effects of light elements on trace element partitioning behavior. A frequent experimental examination of the effects of light elements in metallic systems involves producing run products with coexisting solid metal and liquid metal phases. Such solid-metal-liquid-metal experiments have been conducted in the Fe-Ni binary system as well as Fe-Ni systems with S, P, and C. Experiments with O-bearing or Si-bearing Fe-Ni metallic melts do not lend themselves to experiments with coexisting solid metal and liquid metal phases, due to the phase diagrams of these elements, but experiments with two immiscible Fe-Ni metallic melts have provided insight into

CHEMICAL EVOLUTION LIBRARY FOR GALAXY FORMATION SIMULATION

International Nuclear Information System (INIS)

Saitoh, Takayuki R.

2017-01-01

We have developed a software library for chemical evolution simulations of galaxy formation under the simple stellar population (SSP) approximation. In this library, all of the necessary components concerning chemical evolution, such as initial mass functions, stellar lifetimes, yields from Type II and Type Ia supernovae, asymptotic giant branch stars, and neutron star mergers, are compiled from the literature. Various models are pre-implemented in this library so that users can choose their favorite combination of models. Subroutines of this library return released energy and masses of individual elements depending on a given event type. Since the redistribution manner of these quantities depends on the implementation of users’ simulation codes, this library leaves it up to the simulation code. As demonstrations, we carry out both one-zone, closed-box simulations and 3D simulations of a collapsing gas and dark matter system using this library. In these simulations, we can easily compare the impact of individual models on the chemical evolution of galaxies, just by changing the control flags and parameters of the library. Since this library only deals with the part of chemical evolution under the SSP approximation, any simulation codes that use the SSP approximation—namely, particle-base and mesh codes, as well as semianalytical models—can use it. This library is named “CELib” after the term “Chemical Evolution Library” and is made available to the community.

CHEMICAL EVOLUTION LIBRARY FOR GALAXY FORMATION SIMULATION

Energy Technology Data Exchange (ETDEWEB)

Saitoh, Takayuki R., E-mail: saitoh@elsi.jp [Earth-Life Science Institute, Tokyo Institute of Technology, 2-12-1, Ookayama, Meguro, Tokyo, 152-8551 (Japan)

2017-02-01

We have developed a software library for chemical evolution simulations of galaxy formation under the simple stellar population (SSP) approximation. In this library, all of the necessary components concerning chemical evolution, such as initial mass functions, stellar lifetimes, yields from Type II and Type Ia supernovae, asymptotic giant branch stars, and neutron star mergers, are compiled from the literature. Various models are pre-implemented in this library so that users can choose their favorite combination of models. Subroutines of this library return released energy and masses of individual elements depending on a given event type. Since the redistribution manner of these quantities depends on the implementation of users’ simulation codes, this library leaves it up to the simulation code. As demonstrations, we carry out both one-zone, closed-box simulations and 3D simulations of a collapsing gas and dark matter system using this library. In these simulations, we can easily compare the impact of individual models on the chemical evolution of galaxies, just by changing the control flags and parameters of the library. Since this library only deals with the part of chemical evolution under the SSP approximation, any simulation codes that use the SSP approximation—namely, particle-base and mesh codes, as well as semianalytical models—can use it. This library is named “CELib” after the term “Chemical Evolution Library” and is made available to the community.

Entanglement entropy evolution under double-trace deformation

Energy Technology Data Exchange (ETDEWEB)

Song, Yushu [College of Physical Science and Technology, Hebei University, Baoding (China)

2017-12-15

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 the quantum correction of the entanglement entropy gives 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 deformation. We also discuss the minimal area correction. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Chemical evolution of the galactic disk

International Nuclear Information System (INIS)

Wyse, R.F.G.; Gilmore, G.

1987-01-01

The distribution of enriched material in the stars and gas of their Galaxy contains information pertaining to the chemical evolution of the Milky Way from its formation epoch to the present day, and provides general constraints on theories of galaxy formation. The separate stellar components of the Galaxy cannot readily be understood if treated in isolation, but a reasonably self-consistent model for Galactic chemical evolution may be found if one considers together the chemical properties of the extreme spheroid, thick disk and thin disk populations of the Galaxy. The three major stellar components of the Galaxy are characterized by their distinct spatial distributions, metallicity structure, and kinematics, with the newly-identified thick disk being approximately three times more massive than the classical metal-poor, non-rotating extreme spheroid. Stellar evolution in the thick disk straightforwardly provides the desired pre-enrichment for resolution of the thin disk G dwarf problem

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.

Chemical evolution coefficients for the study of galactic evolution

International Nuclear Information System (INIS)

Mallik, D.C.V.

1980-01-01

A new evaluation of chemical evolution coefficients has been made using recent stellar evolution and nucleosynthesis data. The role of the low and intermediate mass stars in galactic nuclosynthesis has been emphasized. A significant amount of 4 He, 12 C and neutron-rich species is found to be contributed by these stars. Comparison with observed abundances suggests a primary origin of 14 N. The simple model of galactic evolution with the new coefficients has been used to derive the ratio of helium to heavy element enrichment in the Galaxy. The new stellar evolution data do not explain the large value of this ratio that has been determined observationally. (orig.)

Chemical evolution coefficients for the study of galactic evolution

Energy Technology Data Exchange (ETDEWEB)

Mallik, D C.V. [Indian Inst. of Astrophysics, Bangalore

1980-05-01

A new evaluation of chemical evolution coefficients has been made using recent stellar evolution and nucleosynthesis data. The role of the low and intermediate mass stars in galactic nucleosynthesis has been emphasized. A significant amount of /sup 4/He, /sup 12/C and neutron-rich species is found to be contributed by these stars. Comparison with observed abundances suggests a primary origin of /sup 14/N. The simple model of galactic evolution with the new coefficients has been used to derive the ratio of helium to heavy element enrichment in the Galaxy. The new stellar evolution data do not explain the large value of this ratio that has been determined observationally.

Survey of chemical speciation of trace elements using synchrotron radiation

International Nuclear Information System (INIS)

Gordon, B.M.

1985-01-01

Information concerning the chemical state of trace elements in biological systems generally has not been available. Such information for toxic elements and metals in metalloproteins could prove extremely valuable in the elucidation of their metabolism and other biological processes. The shielding of core electrons by binding electrons affect the energy required for creating inner-shell holes. Furthermore, the molecular binding and the symmetry of the local environment of an atom affect the absorption spectrum in the neighborhood of the absorption edge. X-ray absorption near-edge structure (XANES) using synchrotron radiation excitation can be used to provide chemical speciation information for trace elements at concentrations as low as 10 ppM. The structure and position of the absorption curve in the region of an edge can yield vital data about the local structure and oxidation state of the trace element in question. Data are most easily interpreted by comparing the observed edge structure and position with those of model compounds of the element covering the entire range of possible oxidation states. Examples of such analyses are reviewed. 14 refs., 1 fig

THE CHEMICAL EVOLUTION OF PHOSPHORUS

International Nuclear Information System (INIS)

Jacobson, Heather R.; Thanathibodee, Thanawuth; 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 Å) that is measurable in stars of low metallicity. Using archival Hubble Space Telescope-Space Telescope Imaging Spectrograph 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 key building blocks of life, we also discuss the chemical evolution of the important elements to life, C-N-O-P-S, together

ACTRIS Aerosol, Clouds and Trace Gases Research Infrastructure

Science.gov (United States)

Pappalardo, Gelsomina

2018-04-01

The Aerosols, Clouds and Trace gases Research Infrastructure (ACTRIS) is a distributed infrastructure dedicated to high-quality observation of aerosols, clouds, trace gases and exploration of their interactions. It will deliver precision data, services and procedures regarding the 4D variability of clouds, short-lived atmospheric species and the physical, optical and chemical properties of aerosols to improve the current capacity to analyse, understand and predict past, current and future evolution of the atmospheric environment.

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

Excreted trace organic chemicals, e.g., pharmaceuticals and biocides, typically undergo incomplete elimination in municipal wastewater treatment plants (WWTPs) and are released to surface water via treated effluents and to agricultural soils through sludge amendment and/or irrigation with freshwa......Excreted trace organic chemicals, e.g., pharmaceuticals and biocides, typically undergo incomplete elimination in municipal wastewater treatment plants (WWTPs) and are released to surface water via treated effluents and to agricultural soils through sludge amendment and/or irrigation...... 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...... and a recently developed dynamic soil-plant uptake model. The simulation tool was tested using country-specific (e.g., consumption/emission rates, precipitation and temperature) input data. A Monte Carlo-based approach was adopted to account for the uncertainty associated to physico-chemical and biokinetic model...

Radioisotope 45Ca labeling four calcium chemical compounds and tracing calcium bioavailability

International Nuclear Information System (INIS)

Zheng Hui; Zhen Rong; Niu Huisheng; Li Huaifen

2004-01-01

Objective: To build up a new method of the radioisotope 45 Ca labeling four calcium chemical compounds, observe and tracing bioavailability change of calcium labeled with radioisotope 45 Ca. Methods: The calcium gluconate (Ca-Glu), calcium citrate (Ca-Cit), calcium carbonate (Ca-Car) and calcium L-threonate (Ca-Thr)were labeled by radioisotope 45 Ca. Four calcium chemical compounds of 45 Ca labeling were used of calcium content 200 mg/kg in the rats and measure the absorption content and bioavailability of calcium in tissue of heart, lever spleen, stomach, kidney, brain, intestine, whole blood, urine, faeces. Results: 1) Radioisotope 45 Ca labeling calcium chemical compound has high radio intensity, more steady standard curve and recover rate. 2) The absorption of organic calcium chemical compounds is higher than the inorganic calcium chemical compound in the study of calcium bioavailability. Conclusion: The method of tracing with radioisotope 45 Ca labeling calcium chemical compounds has the characteristic of the sensitive, objective, accurate and steady in the study of calcium bioavailability

ACTRIS Aerosol, Clouds and Trace Gases Research Infrastructure

Directory of Open Access Journals (Sweden)

Pappalardo Gelsomina

2018-01-01

Full Text Available The Aerosols, Clouds and Trace gases Research Infrastructure (ACTRIS is a distributed infrastructure dedicated to high-quality observation of aerosols, clouds, trace gases and exploration of their interactions. It will deliver precision data, services and procedures regarding the 4D variability of clouds, short-lived atmospheric species and the physical, optical and chemical properties of aerosols to improve the current capacity to analyse, understand and predict past, current and future evolution of the atmospheric environment.

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.

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

Science.gov (United States)

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

2016-11-01

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

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

International Nuclear Information System (INIS)

Negron Mendoza, A.; Albarran, G.

1992-01-01

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)

Chemical evolution of galaxies

International Nuclear Information System (INIS)

Vigroux, Laurent

1979-01-01

This research thesis addresses theories on the chemical evolution of galaxies which aim at explaining abundances of different elements in galaxies, and more particularly aims at improving the model by modifying hypotheses. After a description of the simple model and of its uncertainties, the author shows how it is possible to understand the evolution of the main elements. Predictions obtained with this model are then compared with the present knowledge on galaxies by considering them according to an increasing complexity: Sun's neighbourhood, our galaxy, other spiral galaxies, elliptical galaxies, and finally galaxy clusters. A specific attention is given to irregular galaxies which are the simplest systems [fr

Fluorine in the solar neighborhood: Chemical evolution models

Science.gov (United States)

Spitoni, E.; Matteucci, F.; Jönsson, H.; Ryde, N.; Romano, D.

2018-04-01

Context. In light of new observational data related to fluorine abundances in solar neighborhood stars, we present chemical evolution models testing various fluorine nucleosynthesis prescriptions with the aim to best fit those new data. Aim. We consider chemical evolution models in the solar neighborhood testing various nucleosynthesis prescriptions for fluorine production with the aim of reproducing the observed abundance ratios [F/O] versus [O/H] and [F/Fe] versus [Fe/H]. We study in detail the effects of various stellar yields on fluorine production. Methods: We adopted two chemical evolution models: the classical two-infall model, which follows the chemical evolution of halo-thick disk and thin disk phases; and the one-infall model, which is designed only for thin disk evolution. We tested the effects on the predicted fluorine abundance ratios of various nucleosynthesis yield sources, that is, asymptotic giant branch (AGB) stars, Wolf-Rayet (W-R) stars, Type II and Type Ia supernovae, and novae. Results: The fluorine production is dominated by AGB stars but the W-R stars are required to reproduce the trend of the observed data in the solar neighborhood with our chemical evolution models. In particular, the best model both for the two-infall and one-infall cases requires an increase by a factor of 2 of the W-R yields. We also show that the novae, even if their yields are still uncertain, could help to better reproduce the secondary behavior of F in the [F/O] versus [O/H] relation. Conclusions: The inclusion of the fluorine production by W-R stars seems to be essential to reproduce the new observed ratio [F/O] versus [O/H] in the solar neighborhood. Moreover, the inclusion of novae helps to reproduce the observed fluorine secondary behavior substantially.

Climate-chemical interactions and effects of changing atmospheric trace gases

Science.gov (United States)

Ramanathan, V.; Callis, L.; Cess, R.; Hansen, J.; Isaksen, I.

1987-01-01

The paper considers trace gas-climate effects including the greenhouse effect of polyatomic trace gases, the nature of the radiative-chemical interactions, and radiative-dynamical interactions in the stratosphere, and the role of these effects in governing stratospheric climate change. Special consideration is given to recent developments in the investigations of the role of oceans in governing the transient climate responses, and a time-dependent estimate of the potential trace gas warming from the preindustrial era to the early 21st century. The importance of interacting modeling and observational efforts is emphasized. One of the problems remaining on the observational front is the lack of certainty in current estimates of the rate of growth of CO, O3, and NOx; the primary challenge is the design of a strategy that will minimize the sampling errors.

Chemical evolution of the early Martian hydrosphere

International Nuclear Information System (INIS)

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

Isotopic anomalies - chemical memory of Galactic evolution

International Nuclear Information System (INIS)

Clayton, D.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. 20 references

STAR FORMATION HISTORY AND CHEMICAL EVOLUTION OF THE SEXTANS DWARF SPHEROIDAL GALAXY

International Nuclear Information System (INIS)

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

2009-01-01

We present the star formation history (SFH) and chemical evolution of the Sextans dSph galaxy as a function of a galactocentric distance. We derive these from the VI photometry of stars in the 42' x 28' field using the SMART model developed by Yuk and Lee 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 (∼ 65% of the stars formed 13-15 Gyr ago, while ∼ 25% formed 11-13 Gyr ago), detectable star formation continued to at least 8 Gyr ago, the SFH is more extended in the central regions than the outskirts, and the difference in star formation rates between the central and outer regions is most marked 11-13 Gyr ago. Whether blue straggler stars are interpreted as intermediate-age main-sequence stars affects conclusions regarding the SFH for times 4-8 Gyr ago, but this is at most only a trace population. We find that the metallicity of the stars increased rapidly up to [Fe/H] = -1.6 in the central region and to [Fe/H] = -1.8 in the outer region within the first Gyr, and has varied slowly since then. The abundance ratios of several elements derived in this study are in good agreement with the observational data based on the high-resolution spectroscopy in the literature. We conclude that the primary driver for the radial gradient of the stellar population in this galaxy is the SFH, which self-consistently drives the chemical enrichment history.

Galactic chemical evolution in hierarchical formation models

Science.gov (United States)

Arrigoni, Matias

2010-10-01

The chemical properties and abundance ratios of galaxies provide important information about their formation histories. Galactic chemical evolution has been modelled in detail within the monolithic collapse scenario. These models have successfully described the abundance distributions in our Galaxy and other spiral discs, as well as the trends of metallicity and abundance ratios observed in early-type galaxies. In the last three decades, however, the paradigm of hierarchical assembly in a Cold Dark Matter (CDM) cosmology has revised the picture of how structure in the Universe forms and evolves. In this scenario, galaxies form when gas radiatively cools and condenses inside dark matter haloes, which themselves follow dissipationless gravitational collapse. The CDM picture has been successful at predicting many observed properties of galaxies (for example, the luminosity and stellar mass function of galaxies, color-magnitude or star formation rate vs. stellar mass distributions, relative numbers of early and late-type galaxies, gas fractions and size distributions of spiral galaxies, and the global star formation history), though many potential problems and open questions remain. It is therefore interesting to see whether chemical evolution models, when implemented within this modern cosmological context, are able to correctly predict the observed chemical properties of galaxies. With the advent of more powerfull telescopes and detectors, precise observations of chemical abundances and abundance ratios in various phases (stellar, ISM, ICM) offer the opportunity to obtain strong constraints on galaxy formation histories and the physics that shapes them. However, in order to take advantage of these observations, it is necessary to implement detailed modeling of chemical evolution into a modern cosmological model of hierarchical assembly.

Trace element distribution in different chemical fractions of False Bay sediments

International Nuclear Information System (INIS)

Rosental, R.

1984-05-01

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

TRACING THE EVOLUTION OF HIGH-REDSHIFT GALAXIES USING STELLAR ABUNDANCES

Energy Technology Data Exchange (ETDEWEB)

Crosby, Brian D.; O’Shea, Brian W. [Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States); Beers, Timothy C. [Department of Physics and JINA—Center for the Evolution of the Elements, University of Notre Dame, 225 Nieuwland Science Hall, Notre Dame, IN 46556 (United States); Tumlinson, Jason, E-mail: crosby.bd@gmail.com [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)

2016-03-20

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.

Optimizing surface acoustic wave sensors for trace chemical detection

Energy Technology Data Exchange (ETDEWEB)

Frye, G.C.; Kottenstette, R.J.; Heller, E.J. [and others

1997-06-01

This paper describes several recent advances for fabricating coated surface acoustic wave (SAW) sensors for applications requiring trace chemical detection. Specifically, we have demonstrated that high surface area microporous oxides can provide 100-fold improvements in SAW sensor responses compared with more typical polymeric coatings. In addition, we fabricated GaAs SAW devices with frequencies up to 500 MHz to provide greater sensitivity and an ideal substrate for integration with high-frequency electronics.

Climate-chemical interactions and effects of changing atmospheric trace gases

International Nuclear Information System (INIS)

Ramanathan, V.; Callis, L.; Cess, R.; Hansen, J.; Isaksen, I.; Lacis, A.; Kuhn, W.; Luther, F.; Mahlman, J.; Reck, R.; Schlesinger, M.

1992-01-01

The problem concerning the greenhouse effects of human activities has broadened in scope from the CO 2 -climate problem to the trace gas-climate problem. The climate effects of non-CO 2 trace gases are strongly governed by interactions between chemistry, radiation, and dynamics. The authors discuss in detail the nature of the trace gas radiative heating and describe the importance of radiative-chemical interactions within the troposphere and the stratosphere. They make an assessment of the trace gas effects on troposphere-stratosphere temperature trends for the period covering the preindustrial era to the present and for the next several decades. Non-CO 2 greenhouse gases in the atmosphere are now adding to the greenhouse effect by an amount comparable to the effect of CO 2 . The rate of decadal increase of the total greenhouse forcing is now 3-6 times greater than the mean rate for the period 1850-1960. Time-dependent calculations with a simplified one-dimensional diffusive ocean model suggest that a surface warming about 0.4-0.8 K should have occurred during 1850 to 1980. For the various trace gas scenarios considered in this study, the equilibrium surface warming for the period 1980 to 2030 ranges from 0.8 to 4.1 K. This wide range in the projected warming is due to the range in the assumed scenario as well as due to the threefold uncertainty in the sensitivity of climate models. For the 180-year period from 1850 to 2030, their analysis suggests a trace gas-induced cumulative equilibrium surface warming in the range of 1.5 to 6.1 K

The Chemical Evolution of Phosphorus

Science.gov (United States)

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

2014-12-01

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 Å) that is measurable in stars of low metallicity. Using archival Hubble Space Telescope-Space Telescope Imaging Spectrograph spectra, we have measured P abundances in 13 stars spanning -3.3 production in the early universe. As P is one of the key building blocks of life, we also discuss the chemical evolution of the important elements to life, C-N-O-P-S, together. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. This work is supported through program AR-13246. Other portions of this work are based on data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile, and the McDonald Observatory of the University of Texas at Austin.

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.

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…

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

International Nuclear Information System (INIS)

Nidever, David L.; Bovy, Jo; Bird, Jonathan C.; Andrews, Brett H.; Johnson, Jennifer A.; Weinberg, David H.; Hayden, Michael; Holtzman, Jon; Feuillet, Diane; Majewski, Steven R.; García Pérez, Ana E.; Smith, Verne; Robin, Annie C.; Sobeck, Jennifer; Cunha, Katia; Allende Prieto, Carlos; Zasowski, Gail; Schiavon, Ricardo P.; Schneider, Donald P.; Shetrone, Matthew

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 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.

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.

Fluorescent discrimination between traces of chemical warfare agents and their mimics.

Science.gov (United States)

Díaz de Greñu, Borja; Moreno, Daniel; Torroba, Tomás; Berg, Alexander; Gunnars, Johan; Nilsson, Tobias; Nyman, Rasmus; Persson, Milton; Pettersson, Johannes; Eklind, Ida; Wästerby, Pär

2014-03-19

An array of fluorogenic probes is able to discriminate between nerve agents, sarin, soman, tabun, VX and their mimics, in water or organic solvent, by qualitative fluorescence patterns and quantitative multivariate analysis, thus making the system suitable for the in-the-field detection of traces of chemical warfare agents as well as to differentiate between the real nerve agents and other related compounds.

The Impact of Modeling Assumptions in Galactic Chemical Evolution Models

Science.gov (United States)

Côté, Benoit; O'Shea, Brian W.; Ritter, Christian; Herwig, Falk; Venn, Kim A.

2017-02-01

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. This provides a consistent framework for comparing the best-fit solutions generated by our different models. 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. This result supports the similar conclusions originally claimed by Romano & Starkenburg for Sculptor. While the three models have the same capacity to fit the data, the best values recovered for the parameters controlling the number of SNe Ia and the strength of galactic outflows, are substantially different and in fact mutually exclusive from one model to another. For the purpose of understanding how a galaxy evolves, we conclude that only reproducing the evolution of a limited number of elements is insufficient and can lead to misleading conclusions. More elements or additional constraints such as the Galaxy’s star-formation efficiency and the gas fraction are needed in order to break the degeneracy between the different modeling assumptions. Our results show that the successes and failures of chemical evolution models are predominantly driven by the input stellar yields, rather than by the complexity of the Galaxy model itself. Simple models such as OMEGA are therefore sufficient to test and validate stellar yields. OMEGA

UNCERTAINTIES IN GALACTIC CHEMICAL EVOLUTION MODELS

International Nuclear Information System (INIS)

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

2016-01-01

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

Chempy: A flexible chemical evolution model for abundance fitting. Do the Sun's abundances alone constrain chemical evolution models?

Science.gov (United States)

Rybizki, Jan; Just, Andreas; Rix, Hans-Walter

2017-09-01

Elemental abundances of stars are the result of the complex enrichment history of their galaxy. Interpretation of observed abundances requires flexible modeling tools to explore and quantify the information about Galactic chemical evolution (GCE) stored in such data. Here we present Chempy, a newly developed code for GCE modeling, representing a parametrized open one-zone model within a Bayesian framework. A Chempy model is specified by a set of five to ten parameters that describe the effective galaxy evolution along with the stellar and star-formation physics: for example, the star-formation history (SFH), the feedback efficiency, the stellar initial mass function (IMF), and the incidence of supernova of type Ia (SN Ia). Unlike established approaches, Chempy can sample the posterior probability distribution in the full model parameter space and test data-model matches for different nucleosynthetic yield sets. It is essentially a chemical evolution fitting tool. We straightforwardly extend Chempy to a multi-zone scheme. As an illustrative application, we show that interesting parameter constraints result from only the ages and elemental abundances of the Sun, Arcturus, and the present-day interstellar medium (ISM). For the first time, we use such information to infer the IMF parameter via GCE modeling, where we properly marginalize over nuisance parameters and account for different yield sets. We find that 11.6+ 2.1-1.6% of the IMF explodes as core-collapse supernova (CC-SN), compatible with Salpeter (1955, ApJ, 121, 161). We also constrain the incidence of SN Ia per 103M⊙ to 0.5-1.4. At the same time, this Chempy application shows persistent discrepancies between predicted and observed abundances for some elements, irrespective of the chosen yield set. These cannot be remedied by any variations of Chempy's parameters and could be an indication of missing nucleosynthetic channels. Chempy could be a powerful tool to confront predictions from stellar

On the transition period from chemical to biological evolution

International Nuclear Information System (INIS)

Chela-Flores, J.

1991-06-01

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

Chemical evolution of galaxies

International Nuclear Information System (INIS)

Pagel, B.E.J.

1979-01-01

The chemical evolution of disk galaxies is discussed with special reference to results obtained from studies of the oxygen abundance in H II regions. Normal spirals (including our own) display the by now well known radial abundance gradient, which is discussed on the basis of the simple enrichment model and other models. The Magellanic Clouds, on the other hand, and the barred spiral NGC 1365, have been found to have little or no abundance gradient, implying a very different sort of evolution that may involve large-scale mixing. Finally, the simple model is tested against a number of results in H II regions where the ratio of total mass to mass of residual gas can be estimated. It turns out to fit adequately the Magellanic Clouds and a number of H II regions in the outer parts of spiral galaxies, but in more inner parts it fails, as do more sophisticated models involving infall during the formation of galactic disks that have proved very successful in other respects. (Auth.)

Role of manganese oxides in peptide synthesis: implication in chemical evolution

Science.gov (United States)

Bhushan, Brij; Nayak, Arunima; Kamaluddin

2017-10-01

During the course of chemical evolution the role of metal oxides may have been very significant in catalysing the polymerization of biomonomers. The peptide bond formation of alanine (ala) and glycine (gly) in the presence of various oxides of manganese were performed for a period of 35 days at three different temperatures 50, 90 and 120°C without applying drying/wetting cycling. The reaction was monitored every week. The products formed were characterized by high-performance liquid chromatography and electrospray ionization-mass spectrometry techniques. Trace amount of oligomers was observed at 50°C. Maximum yield of peptides was found after 35 days at 90°C. It is important to note that very high temperatures of 120°C favoured the formation of diketopiperazine derivatives. Different types of manganese oxides [manganosite (MnO), bixbyite (Mn2O3), hausmannite (Mn3O4) and pyrolusite (MnO2)] were used as catalyst. The MnO catalysed glycine to cyclic (Gly)2, (Gly)2 and (Gly)3, and alanine, to cyclic (Ala)2 and (Ala)2. Mn3O4 also produced the same products but in lesser yield, while Mn2O3 and MnO2 produced cyclic anhydride of glycine and alanine with a trace amount of dimers and trimmers. Manganese of lower oxidation state is much more efficient in propagating the reaction than higher oxidation states. The possible mechanism of these reactions and the relevance of the results for the prebiotic chemistry are discussed.

Galactic chemical evolution: perspectives and prospects

International Nuclear Information System (INIS)

Trimble, V.

1987-01-01

The first modern, quantitative models of galactic chemical evolution appeared exactly 20 years ago in the PhD dissertation of the late Beatrice M. Tinsley. Such models represent a synthesis of the behavior of the 10 11 or more stars that form over the 10 10 year age of a galaxy like their Milky Way and are vital both for understanding how and why galaxies have the luminosities, colors, and chemical compositions they see now and for interpreting observations of distant galaxies to answer cosmological questions about the size, age, density, inhomogeneities, and geometry of the universe. Since my last status report on the subject, some issues have become much clearer (the distinctness of nucleosynthesis in Type I, low mass, supernovae, from that in Type II's that make pulsars; the importance of galaxy mergers and interactions in triggering bursts of star formation), while others have remained puzzling (the sites of the r and p processes) or newly-surfaced (the nucleosynthetic contributions of pre-galactic massive objects; the nature and roll of dark matter in galaxies). The talk will touch briefly on the past, present, and future of galactic evolution studies

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

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

Energy Technology Data Exchange (ETDEWEB)

Manojkumar, P.A., E-mail: manoj@igcar.gov.in [Indira Gandhi Centre for Atomic Research, Kalpakkam 603102 (India); Chirayath, V.A.; Balamurugan, A.K.; Krishna, Nanda Gopala; Ilango, S.; Kamruddin, M.; Amarendra, G.; Tyagi, A.K. [Indira Gandhi Centre for Atomic Research, Kalpakkam 603102 (India); Raj, Baldev [National Institute of Advanced Studies, Bangalore 560 012 (India)

2016-09-15

Highlights: • Low energy nitrogen ion implantation in titanium was studied. • Chemical and defect states were analyzed using SIMS, XPS and PAS. • SIMS and depth resolved XPS data showed good agreement. • Depth resolved defect and chemical states information were revealed. • Formation of 3 layers of defect states proposed to fit PAS results. - Abstract: Evolution of chemical states and defect structure in titanium during low energy nitrogen ion implantation by Plasma Immersion Ion Implantation (PIII) process is studied. The underlying process of chemical state evolution is investigated using secondary ion mass spectrometry and X-ray photoelectron spectroscopy. The implantation induced defect structure evolution as a function of dose is elucidated using variable energy positron annihilation Doppler broadening spectroscopy (PAS) and the results were corroborated with chemical state. Formation of 3 layers of defect state was modeled to fit PAS results.

General constraints on the effect of gas flows in the chemical evolution of galaxies

International Nuclear Information System (INIS)

Edmunds, M.G.

1990-01-01

The basic equations for the chemical evolution of galaxies in which the 'simple' closed box model is modified to allow any form of inflow or outflow are examined. It is found that there are quite general limiting constraints on the effects that such flows can have. Some implications for the actual chemical evolution of galaxies are discussed, and the constraints should also be useful in understanding the behaviour of detailed numerical models of galactic chemical evolution involving gas flows. (author)

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

KAUST Repository

Regnery, J.; Wing, A.D.; Alidina, M.; Drewes, J.E.

2015-01-01

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

The Advective Flux and Temporal Evolution of Aerosols from the Western Pacific Rim as Observed during TRACE-P

Science.gov (United States)

Anderson, B. E.; Jordan, C. E.; Grant, W. B.; Browell, E. V.; Hudgins, C. H.; Winstead, E. L.; Thornhill, K. L.

2002-12-01

The 2001, NASA Transport and Chemical Evolution over the Pacific (TRACE-P) experiment was conducted during late winter and early spring, the time of year when eastward transport of dust and pollution from southern and central Asia reaches a maximum. From bases of operation in Hong Kong, Japan, and Hawaii, extensive measurements of trace species concentrations and characteristics were made from aboard a P-3B and DC-8 aircraft as they flew coordinated sampling missions within air masses at varying distances from the Asian coast and at altitudes ranging from near surface to over 12 km. Data recorded aboard the DC-8 included total condensation nuclei (CN) number densities and fractional volatility; aerosol size distributions, composition and optical properties; and multi-wavelength profiles of polarized, aerosol backscatter. Examining these data in light of simultaneous meteorological and chemical species measurements, we have calculated the advective flux and mean values of aerosol mass and physical properties at various locations within the Western Pacific Basin. At distances >100 km offshore, we find that the highest fluxes of sub-micron particles occurred below 2 km in the region downwind of Shanghai. These air masses exhibited CN concentrations approaching 50,000 cm-3 and visible scattering coefficients in excess of 200 Mm-1. For near-shore sampling between 26° and 36°N within this height range, these parameters averaged ~8,000 cm-3 and 130 Mm-, respectively, . As a result of dilution, surface deposition, and precipitation scavenging, these values rapidly diminished during eastward transport so that parcels sampled at low altitudes >1500 km from land typically contained ~1000 cm-3 CN and exhibited scattering coefficients <30 Mm-1. Because of the decreased strength of loss processes and greater atmospheric stability, parcels sampled in the 2- to 7-km height range were more apt to maintain their initial aerosol signatures during long-range transport.

Chemical Evolution of a Protoplanetary Disk

Science.gov (United States)

Semenov, Dmitry A.

2011-12-01

In this paper we review recent progress in our understanding of the chemical evolution of protoplanetary disks. Current observational constraints and theoretical modeling on the chemical composition of gas and dust in these systems are presented. Strong variations of temperature, density, high-energy radiation intensities in these disks, both radially and vertically, result in a peculiar disk chemical structure, where a variety of processes are active. In hot, dilute and heavily irradiated atmosphere only the most photostable simple radicals and atoms and atomic ions exist, formed by gas-phase processes. Beneath the atmosphere a partly UV-shielded, warm molecular layer is located, where high-energy radiation drives rich ion-molecule and radical-radical chemistry, both in the gas phase and on dust surfaces. In a cold, dense, dark disk midplane many molecules are frozen out, forming thick icy mantles where surface chemistry is active and where complex polyatomic (organic) species are synthesized. Dynamical processes affect disk chemical composition by enriching it in abundances of complex species produced via slow surface processes, which will become detectable with ALMA.

Contributions of type II and Ib/c supernovae to Galactic chemical evolution

International Nuclear Information System (INIS)

Sahijpal Sandeep

2014-01-01

Type II and Ib/c supernovae (SNe II and Ib/c) have made major stellar nucleosynthetic contributions to the inventories of stable nuclides during chemical evolution of the Galaxy. A case study is performed here with the help of recently developed numerical simulations of Galactic chemical evolution in the solar neighborhood to understand the contributions of SNe II and Ib/c by comparing the stellar nucleosynthetic yields obtained by two leading groups in this field. These stellar nucleosynthetic yields differ in terms of their treatment of stellar evolution and nucleosynthesis. The formulation describing Galactic chemical evolution is developed with the recently revised solar metallicity of ∼0.014. Furthermore, the recent nucleosynthetic yields of stellar models based on the revised solar metallicity are also used. The analysis suggests that it could be difficult to explain, in a self-consistent manner, the various features associated with the elemental evolutionary trends over Galactic timescales by any single adopted stellar nucleosynthetic model that incorporates SNe II and Ib/c

Chemical evolution of galaxies

International Nuclear Information System (INIS)

Pagel, B.E.J.

1990-01-01

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.)

Determination of trace amounts of chemical warfare agent degradation products in decontamination solutions with NMR spectroscopy.

Science.gov (United States)

Koskela, Harri; Rapinoja, Marja-Leena; Kuitunen, Marja-Leena; Vanninen, Paula

2007-12-01

Decontamination solutions are used for an efficient detoxification of chemical warfare agents (CWAs). As these solutions can be composed of strong alkaline chemicals with hydrolyzing and oxidizing properties, the analysis of CWA degradation products in trace levels from these solutions imposes a challenge for any analytical technique. Here, we present results of application of nuclear magnetic resonance spectroscopy for analysis of trace amounts of CWA degradation products in several untreated decontamination solutions. Degradation products of the nerve agents sarin, soman, and VX were selectively monitored with substantially reduced interference of background signals by 1D 1H-31P heteronuclear single quantum coherence (HSQC) spectrometry. The detection limit of the chemicals was at the low part-per-million level (2-10 microg/mL) in all studied solutions. In addition, the concentration of the degradation products was obtained with sufficient confidence with external standards.

Thermal and Chemical Evolution of Collapsing Filaments

Energy Technology Data Exchange (ETDEWEB)

Gray, William J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Scannapieco, Evan [Arizona State Univ., Mesa, AZ (United States). School of Earth and Space Exploration

2013-01-15

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 ≈ 0.1Z_⊙ 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^-3Z_⊙ filaments, the collapse proceeds much more slowly. This is due mostly to the lower initial temperatures, which leads to a much more modest increase in density before the atomic cooling limit is reached, making subsequent molecular cooling much less efficient. Finally, we study how the gravitational potential from a nearby dwarf galaxy affects the collapse of the filament and compare this to NGC 5253, a nearby starbusting dwarf galaxy thought to be fueled by the accretion of filament gas. In contrast to our fiducial case, a substantial density peak forms at the center of the potential. This peak evolves faster than the rest of the filament due to the increased rate at which chemical species form and cooling occur. We find that we achieve similar accretion rates as NGC 5253, but our two-dimensional simulations do not recover the formation of the giant molecular clouds that are seen in radio observations.

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

International Nuclear Information System (INIS)

1995-08-01

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

Tracing Cultural Evolution Through Memetics

OpenAIRE

Tiktik Dewi Sartika

2004-01-01

Viewing human being, as a part of evolution process is still a controversial issue for some people, in fact the evolution runs. As a sociocultural entity, human being has distinctive characters in its evolution process. A Theory inherited from Darwin may have only been able to answer how a simple unit such genes evolve to such complex animal like human. Yet, how among those complex animals interact, communicate, and replicate idea in so forth formed a such self-organized sociocultural complex...

Conference on chemical evolution and the origin of life

International Nuclear Information System (INIS)

1992-10-01

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

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

International Nuclear Information System (INIS)

Liffman, K.; Clayton, D.D.

1989-01-01

The evolution course of refractory 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. 26 refs

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

Late Guadalupian evolution of the Delaware Basin: insights from stable isotope and trace element geochemistry

Science.gov (United States)

Smith, B.; Kerans, C.

2017-12-01

Accurate characterization of mixed carbonate and evaporite deposits requires an understanding of basin-scale physical, chemical, and biological processes. In these settings, carbonate geochemistry often responds to changes in the prevailing conditions in the water column. It follows that the geochemical record presents a potential aid for interpretation of depositional systems provided that it is relatively free of diagenetic overprint. This is seldom the case in shallow-water settings as processes such as meteoric diagenesis and early dolomitization obscure or erase the original geochemical signal. Fine grained deep-water sediments are more likely to retain their original geochemical characteristics. If reliable shelf-to-basin correlations can be established, then basinal deposits provide critical data not only for the interpretation of deep water environments, but overall basin evolution as well. This study examines variations in trace element and stable isotope geochemistry from the Delaware Basin of West Texas and New Mexico. Interpretation of geochemical data within a pre-existing shelf-to-basin stratigraphic framework suggests a link between basin water chemistry and sea level changes during the entirety of the Guadalupian. This link is supported analogies to modern silled basins where changes in sea level and thus recharge across the sill can control nutrient input, circulation, and bottom water oxygenation. In light of these relationships, the filling of the Delaware Basin with basin-centered evaporites at the end of the Guadalupian likely represents the culmination of a more gradual, cyclic evolution towards basin restriction. Ongoing work will continue to focus on tying regional-scale changes in basin water chemistry to the combined geochemical and physical sedimentological records.

The evolution of complex type B Allende inclusion - An ion microprobe trace element study

Science.gov (United States)

Macpherson, Glenn J.; Crozaz, Ghislaine; Lundberg, Laura L.

1989-01-01

Results are presented of a detailed trace-element and isotopic analyses of the constituent phases in each of the major textural parts (mantle, core, and islands) of a Type B refractory inclusion, the USNM 5241 inclusion from Allende, first described by El Goresy et al. (1985). The REE data on 5241 were found to be largely consistent with a model in which the mantle and the core of 5241 formed sequentially out of a single melt by fractional crystallization. The numerical models of REE evolution in the 5241 melt, especially that of Eu, require that a significant mass of spinel-free island material was assimilated into the evolving melt during the last half of the solidification history of 5241. The trace element results pbtained thus strongly support the interpretation of El Goresy et al. (1985) that the spinel-free islands in the 5241 are trapped xenoliths.

Trace impurities in coal by wet chemical methods

International Nuclear Information System (INIS)

Pollock, E.N.

1975-01-01

In determining trace elements in coal by wet chemical methods, conventional atomic absorption spectroscopy (AAS) was used to determine Li, Be, V, Cr, Mn, Co, Ni, Cu, Zn, Ag, Cd, and Pb after dry ashing and acid dissolutions. A graphite furnace accessory was used for the flameless AAS determination of Bi, Se, Sn, Te, Be, Pb, As, Cd, Cr, Sb, and Ge. Mercury can be determined by flameless AAS after oxygen bomb combustion. Arsenic and antimony can be determined as their hydrides by AAS after low temperature ashing. Germanium, tin, bismuth, and tellurium can be determined as their hydrides by AAS after high temperature ashing. Selenium can be determined as its hydride by AAS after a special combustion procedure or after oxygen bomb combustion. Fluorine can be determined by specific ion analysis after oxygen bomb combustion. Boron can be determined colorimetrically. (U.S.)

Chemical evolution of the Galactic bulge as traced by microlensed dwarf and subgiant stars. Detailed abundance analysis of OGLE-2008-BLG-209S

OpenAIRE

Bensby, T.; Johnson, J. A.; Cohen, J.; Feltzing, S.; Udalski, A.; Gould, A.; Huang, W.; Thompson, I.; Simmerer, J.; Adén, D.

2009-01-01

AIMS. Our aims are twofold. First we aim to evaluate the robustness and accuracy of stellar parameters and detailed elemental abundances that can be derived from high-resolution spectroscopic observations of microlensed dwarf and subgiant stars. We then aim to use microlensed dwarf and subgiant stars to investigate the abundance structure and chemical evolution of the Milky Way Bulge. [ABRIDGED] METHODS. We present a detailed elemental abundance analysis of OGLE-2008-BLG-209S, the source star...

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

KAUST Repository

Drewes, Jorg; Li, Dong; Regnery, Julia; Alidina, Mazahirali; Wing, Alexandredavid; Hoppe-Jones, Christiane

2014-01-01

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

Chemical speciation of trace metals in the industrial sludge of Dhaka City, Bangladesh.

Science.gov (United States)

Islam, Md Saiful; Al-Mamun, Md Habibullah; Feng, Ye; Tokumura, Masahiro; Masunaga, Shigeki

2017-07-01

The objective of this study was to assess total concentration and chemical fractionation of trace metals in the industrial wastewater and sludge collected from seven different types of industries in Dhaka City, Bangladesh. The sludge from industries is either dumped on landfills or reused as secondary resources in order to preserve natural resources. Metals were analyzed using inductively coupled plasma mass spectrometry (ICP-MS). The ranges of Cr, Ni, Cu, As, Cd, and Pb in the sludges were 1.4-9,470, 4.8-994, 12.8-444, 2.2-224, 1.9-46.0 and 1.3-87.0 mg/kg, respectively. As a whole, the average concentrations of trace metals in samples were in the decreasing order of Cr > Ni > Cu > As > Pb > Cd. The results of the Community Bureau of Reference (BCR) sequential extraction showed that the studied metals were predominantly associated with the residual fraction followed by the oxidizable fraction. The study revealed that the mobile fractions of trace metals are poorly predictable from the total content, and bioavailability of all fractions of elements tends to decrease.

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

International Nuclear Information System (INIS)

Andrew, A.S.; Giblin, A.M.

2000-01-01

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 87 Sr/ 86 Sr 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 87 Sr/ 86 Sr ratios in the brines are lower than those measured from groundmass carbonates in the host rocks, and that the 87 Sr/ 86 Sr 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

Trace-element analysis of Antarctic H chondrites: Chemical weathering and comparisons with their non-Antarctic counterparts

International Nuclear Information System (INIS)

Kwok, J.E.

1986-01-01

Large numbers of meteorites have been discovered in Antarctica over the last decade (7000 fragments probably representing over 1200 separate events). They are important for their numbers and for their complement of unique or rare specimens; they also have long terrestrial ages (up to 1,000,000 years) compared to non-Antarctic falls (usually < 200 years). We report compositional data for mobile/volatile trace elements Ag, Au, Bi, Cd, Co, Cs, In, Rb, Sb, Se, Te, Ti, U, and Zn in a suite of Antarctic H chondrites. Our data show that heavily oxidized H chondrites are leached of a portion of their trace elements and, therefore, have been chemically compromised by their stay in Antarctica. The less oxidized specimens seem to have retained their chemical integrity. We suggest possibilities for using chemical data to measure the degree of a chondrite's chemical weathering. We compare our data to that obtained previously for non-Antarctic H chondrites (Linger et al., 1986), by petrologic type (H4, H5, H6, H4-6) and shock-loading (moderately shocked facies a-c, heavily shocked facies d-f). Many statistically significant differences are found between non-Antarctic and Victoria Land, Antarctica H chondrites of each petrologic type and of shock facies d-f

Evolution of the Campanian Ignimbrite Magmatic System II: Trace Element and Th Isotopic Evidence for Open-System Processes

Science.gov (United States)

Bohrson, W. A.; Spera, F. J.; Fowler, S.; Belkin, H.; de Vivo, B.

2005-12-01

The Campanian Ignimbrite, a large volume (~200 km3 DRE) trachytic to phonolitic ignimbrite was deposited at ~39.3 ka and represents the largest of a number of highly explosive volcanic events in the region near Naples, Italy. Thermodynamic modeling of the major element evolution using the MELTS algorithm (see companion contribution by Fowler et al.) provides detailed information about the identity of and changes in proportions of solids along the liquid line of descent during isobaric fractional crystallization. We have derived trace element mass balance equations that explicitly accommodate changing mineral-melt bulk distribution coefficients during crystallization and also simultaneously satisfy energy and major element mass conservation. Although major element patterns are reasonably modeled assuming closed system fractional crystallization, modeling of trace elements that represent a range of behaviors (e.g. Zr, Nb, Th, U, Rb, Sm, Sr) yields trends for closed system fractionation that are distinct from those observed. These results suggest open-system processes were also important in the evolution of the Campanian magmatic system. Th isotope data yield an apparent isochron that is ~20 kyr younger than the age of the deposit, and age-corrected Th isotope data indicate that the magma body was an open-system at the time of eruption. Because open-system processes can profoundly change isotopic characteristics of a magma body, these results illustrate that it is critical to understand the contribution that open-system processes make to silicic magma bodies prior to assigning relevance to age or timescale information derived from isotope systematics. Fluid-magma interaction has been proposed as a mechanism to change isotopic and elemental characteristics of magma bodies, but an evaluation of the mass and thermal constraints on such a process suggest large-scale fluid-melt interaction at liquidus temperatures is unlikely. In the case of the magma body associated with

Abundance gradients in disc galaxies and chemical evolution models

International Nuclear Information System (INIS)

Diaz, A.I.

1989-01-01

The present state of abundance gradients and chemical evolution models of spiral galaxies is reviewed. An up to date compilation of abundance data in the literature concerning HII regions over galactic discs is presented. From these data Oxygen and Nitrogen radial gradients are computed. The slope of the Oxygen gradient is shown to have a break at a radius between 1.5 and 1.75 times the value of the effective radius of the disc, i.e. the radius containing half of the light of the disc. The gradient is steeper in the central parts of the disc and becomes flatter in the outer parts. N/O gradients are shown to be rather different from galaxy to galaxy and only a weak trend of N/O with O/H is found. The existing chemical evolution models for spiral galaxies are reviewed with special emphasis in the interpretation of numerical models having a large number of parameters. (author)

Transformation processes influencing physico-chemical forms of radionuclides and trace elements in natural water systems

International Nuclear Information System (INIS)

Salbu, B.; Riise, G.; Oughton, D.H.

1995-01-01

In order to assess short and long term consequences of radionuclides and trace elements introduced to aquatic systems, knowledge on source terms, key factors and key processes influencing the speciation is essential. The mobility, bioavailability and subsequent transfer into food chains depend on the physico-chemical forms on radionuclides and trace metals. In addition, transformation processes and especially the interaction with natural organic matter (NOM) influences the distribution pattern. Furthermore, the prevailing climate conditions, e.g. episodic events and temperature are vital for fluxes and for the kinetics of the transformation processes. In the present work processes in catchments and processes associated with acidification, episodic events, climate conditions (temperature) and mixing zone phenomena influencing the speciation of radionuclides and trace metals are highlighted. These processes should be highly relevant for assessing far field consequences of radionuclides potentially released from disposal sites. (authors). 21 refs., 8 figs., 1 tab

Primordial and Stellar Nucleosynthesis Chemical Evolution of Galaxies

International Nuclear Information System (INIS)

Chiosi, Cesare

2010-01-01

Following a brief introduction to early Universe cosmology, we present in some detail the results of primordial nucleosynthesis. Then we summarize the basic theory of nuclear reactions in stars and sketch the general rules of stellar evolution. We shortly review the subject of supernova explosions both by core collapse in massive stars (Type II) and carbon-deflagration in binary systems when one of the components is a White Dwarf accreting mass from the companion (Type Ia). We conclude the part dedicated to nucleosynthesis with elementary notions on the s- and r-process. Finally, we shortly address the topic of galactic chemical evolution and highlight some simple solutions aimed at understanding the main observational data on abundances and abundance ratios.

Evolution of weak perturbations in gas-solid suspension with chemical reaction

Energy Technology Data Exchange (ETDEWEB)

Sharypov, O.V. [Russian Academy of Sciences, Novosibirsk (Russian Federation). Inst. of Thermophysics; Novosibirsk State Univ. (Russian Federation); Anufriev, I.S. [Novosibirsk State Univ. (Russian Federation)

2013-07-01

Dynamics of weak finite-amplitude perturbations in two-phase homogeneous medium (gas + solid particles) with non-equilibrium chemical reaction in gas is studied theoretically. Non-linear model of plane perturbation evolution is substantiated. The model takes into account wave-kinetic interaction and dissipation effects, including inter-phase heat and momentum transfer. Conditions for uniform state of the system are analyzed. Non-linear equation describing evolution of plane perturbation is derived under weak dispersion and dissipation effects. The obtained results demonstrate self-organization in the homogeneous system: steady-state periodic structure arises, its period, amplitude and velocity depends on the features of the medium. The dependencies of these parameters on dissipation and chemical kinetics are analyzed.

Lagrangian Photochemical Box-Model Calculations of Asian Pacific Rim Outflow During TRACE-P

Science.gov (United States)

Hamlin, A.; Crawford, J.; Olson, J.; Avery, M.; Sachse, G.; Barrick, J.; Blake, D.; Tan, D.; Sandholm, S.; Kondo, Y.; Singh, H.; Eisele, F.; Zondlo, M.; Flocke, F.; Talbot, R.

2006-12-01

NASA's TRACE-P (TRAnsport and Chemical Evolution over the Pacific) mission was conducted over the northwestern Pacific February-April, 2001. During two transit flights across the Pacific, extensive pollution was observed from an Asian outflow event that split into two branches over the central Pacific, one subsiding and moving southward over the central Pacific and the other continuing eastward in the upper troposphere. The subsiding branch was observed as a widespread stagnant pollution layer between 2 and 4 km over the central Pacific during transit flights from Kona, HI to Guam. In this region, high levels of O3 (70 ppbv), CO (217 ppbv), and NOx (114 pptv) were well in excess of typical values observed during TRACE-P along the Asian coast. Evidence suggests that the subsiding branch experienced extensive photochemical processing compared to the branch that remained at altitude. To examine the processes controlling the chemical evolution of ozone and its precursors in this outflow event, data collected during the TRACE-P mission have been combined with lagrangian photochemical box model calculations. One of the largest sources of uncertainty in these calculations was associated with predicted water vapor levels along the transport trajectories calculated using the HYSPLIT model. Water vapor levels predicted by HYSPLIT trajectory calculations in the subsiding layer ranged from 3390 to 4880 ppm, while the median level observed in the pollution layer was only 637 ppm. Simulations of ozone production and associated radical chemistry differed dramatically when using water vapor levels based on trajectory calculations versus observed water vapor levels. Levels of PAN and HO2NO2, NOx reservoir species, are also influenced by uncertainties in temperature along the trajectories. These results highlight the importance of accurately representing the humidification and warming of subsiding air masses in 3-D chemical- transport models.

Chemical evolution of the Magellanic Clouds

Science.gov (United States)

Barbuy, B.; de Freitas Pacheco, J. A.; Idiart, T.

We have obtained integrated spectra for 14 clusters in the Magellanic Clouds, on which the spectral indices Hβ, Mg2, Fe5270, Fe5335 were measured. Selecting indices whose behaviour depends essentially on age and metallicity (Hβ and ), together with (B-V) and (V-K) colours, we were able to determine age and metallicities for these clusters, using calibrations based on single stellar population models (Borges et al. 1995). A chemical evolution model which follows a star formation history as indicated by the field population is checked with the age and metallicity data for our sample star clusters.

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.

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 (

An activated sludge modeling framework for xenobiotic trace chemicals (ASM-X): assessment of diclofenac and carbamazepine.

Science.gov (United States)

Plósz, Benedek Gy; Langford, Katherine H; Thomas, Kevin V

2012-11-01

Conventional models for predicting the fate of xenobiotic organic trace chemicals, identified, and calibrated using data obtained in batch experiments spiked with reference substances, can be limited in predicting xenobiotic removal in wastewater treatment plants (WWTPs). At stake is the level of model complexity required to adequately describe a general theory of xenobiotic removal in WWTPs. In this article, we assess the factors that influence the removal of diclofenac and carbamazepine in activated sludge, and evaluate the complexity required for the model to effectively predict their removal. The results are generalized to previously published cases. Batch experimental results, obtained under anoxic and aerobic conditions, were used to identify extensions to, and to estimate parameter values of the activated sludge modeling framework for Xenobiotic trace chemicals (ASM-X). Measurement and simulation results obtained in the batch experiments, spiked with the diclofenac and carbamazepine content of preclarified municipal wastewater shows comparably high biotransformation rates in the presence of growth substrates. Forward dynamic simulations were performed using full-scale data obtained from Bekkelaget WWTP (Oslo, Norway) to evaluate the model and to estimate the level of re-transformable xenobiotics present in the influent. The results obtained in this study demonstrate that xenobiotic loading conditions can significantly influence the removal capacity of WWTPs. We show that the trace chemical retransformation in upstream sewer pipes can introduce considerable error in assessing the removal efficiency of a WWTP, based only on parent compound concentration measurements. The combination of our data with those from the literature shows that solids retention time (SRT) can enhance the biotransformation of diclofenac, which was not the case for carbamazepine. Model approximation of the xenobiotic concentration, detected in the solid phase, suggest that between

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

KAUST Repository

Alidina, Mazahirali; Li, Dong; Drewes, Jorg

2014-01-01

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

A simple chemical method for the separation of phosphorus interfering the trace element determinations by neutron activation analysis in high doped silicon wafers

International Nuclear Information System (INIS)

Wagler, H.; Flachowsky, J.

1986-01-01

Neutron activation analysis is one of the most available method for the determination of trace elements, but in the case of P-doped silicon wafers the 32 P-activity interferes the gamma spectrometry. It is not possible to determine the trace elements without chemical manipulations. On the other hand, time consuming chemical separations should be avoided. Therefore, a simple and rapid P-separation method has to be developed, in which the following twelve trace elements should be taken into consideration: Ag, As, Au, Co, Cr, Cu, Fe, Mo, Na, Sb, W, and Zn. After acid oxidative dissolution of the activated sample, P is present as phosphate ion. The phosphate ion is removed by precipitation as BiPO 4 . (author)

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

KAUST Repository

Alidina, Mazahirali; Li, Dong; Ouf, Mohamed; Drewes, Jorg

2014-01-01

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

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.

Chemical characteristics and trace element concentration of non ...

African Journals Online (AJOL)

The present study investigates the details on the aspects of Coal quality such as proximate, ultimate, calorific value and trace element concentration and its impact on human health. Trace elements are present in very low percentage in coal but their concentration increases manifold after coal combustion and utilization.

The origin of nitrogen and the chemical evolution of spiral galaxies

OpenAIRE

Díaz, Angeles I.; 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

Modelling of chemical evolution of low pH cements at long term

International Nuclear Information System (INIS)

El Bitouri, Y.; Buffo-Lacarriere, L.; Sellier, A.; Bourbon, X.

2015-01-01

In the context of the underground radioactive waste repository, low-pH cements were developed to reduce interactions between concrete and clay barrier. These cements contain high proportions of mineral additions like silica fume, fly ash or blast furnace slag for example. The high ratio of cement replacement by pozzolanic additions allows to reduce the pH by a global reduction of Ca/Si ratio of the hydrates (according to the one observed on CEM I pastes). In order to predict the short term development of the hydration for each component of this cement, a multiphasic hydration model, previously developed, is used. The model predicts the evolution of hydration degree of each anhydrous phase and consequently the quantity of each hydrate in paste (CH, aluminates, CSH with different Ca/Si ratios). However, this model is not suitable to determine the long term mineralogical and chemical evolution of the material, due to the internal change induced by chemical imbalance between initial hydrates. In order to evaluate the chemical characteristics of low pH cement based materials, and thus assess its chemical stability in the context of radioactive waste storage, a complementary model of chemical evolution at long term is proposed. This original model is based on 'solid-solution' principles. It assumes that the microdiffusion of calcium plays a major role to explain how the different Ca/Si ratio of initial C-S-H tends together toward a medium stabilized value. The main mechanisms and full development of the model equations are presented first. Next, a comparison of the model with experimental data issue from EDS (Energy Dispersive X-ray Spectroscopy) analysis on low pH cement allows to test the model. (authors)

Correlated evolution of herbivory and food chemical discrimination in iguanian and ambush foraging lizards

OpenAIRE

William E. Cooper

2003-01-01

To efficiently locate and assess foods, animal sensory capacities and behavioral discriminations based on them must be appropriate for the diet and method of hunting. In lizards, actively foraging insectivores identify animal prey using lingually sampled chemical cues, but ambush foragers do not. Among plant eaters derived from active foragers, plant chemical discrimination is added to prey chemical discrimination, resulting in correlated evolution of plant diet and plant chemical discriminat...

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.

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.

Monitoring and trace detection of hazardous waste and toxic chemicals using resonance Raman spectroscopy

International Nuclear Information System (INIS)

Sedlacek, A.J. III; Dougherty, D.R.; Chen, C.L.

1993-01-01

Raman scattering is a coherent, inelastic, two-photon process, which shifts the frequency of an outgoing photon according to the vibrational structure of the irradiated species, thereby providing a unique fingerprint of the molecule. When involving an allowed electronic transition (resonance Raman), this scattering cross section can be enhanced by 10 4 to 10 6 and provides the basis for a viable technique that can monitor and detect trace quantities of hazardous wastes and toxic chemicals. Resonance Raman spectroscopy (RRS) possesses many of the ideal characteristics for monitoring and detecting of hazardous waste and toxic chemicals. Some of these traits are: (1) very high selectivity (chemical specific fingerprints); (2) independence from the excitation wavelength (ability to monitor in the solar blind region); (3) chemical mixture fingerprints are the sum of its individual components (no spectral cross-talk); (4) near independence of the Raman fingerprint to its physical state (very similar spectra for gas, liquid, solid and solutions -- either bulk or aerosols); and (5) insensitivity of the Raman signature to environmental conditions (no quenching). Data from a few chemicals will be presented which illustrate these features. In cases where background fluorescence accompanies the Raman signals, an effective frequency modulation technique has been developed, which can completely eliminate this interference

Groundwater evolution in the Continental Intercalaire aquifer of southern Algeria and Tunisia: trace element and isotopic indicators

International Nuclear Information System (INIS)

Edmunds, W.M.; Guendouz, A.H.; Mamou, A.; Moulla, A.; Shand, P.; Zouari, K.

2003-01-01

The geochemical processes taking place along an 800 km flow line in the non-carbonate Continental Intercalaire aquifer (CI) aquifer in North Africa are described using chemical (major and trace element) and isotopic indicators. The aquifer is hydraulically continuous from the Atlas Mountains in Algeria to the Chotts of Tunisia and the geochemical evidence corroborates this. The highest discharge temperature is 73 deg. C but silica geothermometry indicates a maximum temperature of 94 deg. C at depth. Chloride concentrations increase from 200 to 800 mg l -1 and the Br/Cl ratios confirm the dissolution of non-marine evaporites or interstitial waters as the main source of salinity. Fluoride concentrations are low and are likely to be derived from rainfall, recording oscillations in source. Radiocarbon ages, except near outcrop, are at or near detection limits and the δ 18 O and δ 2 H values indicate a cooler recharge regime with rainfall having lower primary evaporation than today. This is shown by the fact that mean isotope ratios of CI waters are around 3 per mille lighter than the present-day weighted mean value for rain. Major ion ratios and most trace elements indicate that despite the complex structure and stratigraphy, uniform evolution with continuous water-rock interaction takes place along the flow lines, which are only disturbed near the Tunisian Chotts by groundwater converging from additional flow lines. The ageing of the water can also be followed by the smooth increase in several indicator elements such as Li, K and Mn which are least affected by solubility controls. Similarly the influence of marine facies in the Tunisian sector may be recognised by the changing Mg/Ca and higher Br/Cl as well as trace element indicators. The groundwaters are oxidising up to 300 km from outcrop (dissolved O 2 has persisted for at least 20 ka) and within this zone the concentrations of several elements forming oxy-anions, such as U and Cr, increase and NO 3 remains

Tracing the Spatial-Temporal Evolution of Events Based on Social Media Data

Directory of Open Access Journals (Sweden)

Xiaolu Zhou

2017-03-01

Full Text Available Social media data provide a great opportunity to investigate event flow in cities. Despite the advantages of social media data in these investigations, the data heterogeneity and big data size pose challenges to researchers seeking to identify useful information about events from the raw data. In addition, few studies have used social media posts to capture how events develop in space and time. This paper demonstrates an efficient approach based on machine learning and geovisualization to identify events and trace the development of these events in real-time. We conducted an empirical study to delineate the temporal and spatial evolution of a natural event (heavy precipitation and a social event (Pope Francis’ visit to the US in the New York City—Washington, DC regions. By investigating multiple features of Twitter data (message, author, time, and geographic location information, this paper demonstrates how voluntary local knowledge from tweets can be used to depict city dynamics, discover spatiotemporal characteristics of events, and convey real-time information.

Relations between the galactic evolution and the stellar evolution

International Nuclear Information System (INIS)

Audouze, J.

1984-01-01

After a quick definition of the galactic evolution and a summary of the basic ingredients (namely the abundances of the chemical elements observed in different astrophysical sites), the parameters directly related to the stellar evolution which govern the galactic evolution are outlined. They are the rates of star formation, the initial mass functions and the various nucleosynthetic yields. The 'classical' models of chemical evolution of galaxies are then briefly recalled. Finally, attention is drawn to three recent contributions concerning both the galactic evolution and the stellar evolution. They are (i) some prediction of the rate of star formation for low mass stars made from the planetary nebula abundance distribution (ii) the chemical evolution of C, O and Fe and (iii) the chemical evolution of the galactic interstellar medium. (Auth.)

Chemical ecotoxicology

International Nuclear Information System (INIS)

Paasivirta, J.

1991-01-01

This book discusses risk assessment, chemical cycles, structure-activity relations, organohalogens, oil residues, mercury, sampling and analysis of trace chemicals, and emissions from the forestry industry. Topics include: Cycles of chemicals in the environment. Rick assessment and management, strucuture and toxicity, sampling and analysis of trace chemicals in environment, interpretation of the environmental analysis results, mercury in the environment, organohalogen compounds in the environment, emissions from forestry industry, oil residues in the environment: oil spills in the marine environment

NSF-RANN trace contaminants abstracts

International Nuclear Information System (INIS)

Copenhaver, E.D.; Harnden, D.S.

1976-10-01

Specific areas of interest of the Environmental Aspects of Trace Contaminants Program are organic chemicals of commerce, metals and organometallic compounds, air-borne contaminants, and environmental assay methodology. Fifty-three abstracts of literature on trace contaminants are presented. Author, keyword, and permuted title indexes are included

Abundance anomalies in RGB stars as probes of galactic chemical evolution

Science.gov (United States)

Charbonnel, C.; Palacios, A.

During the last two decades, extensive spectroscopic studies have revealed chemical abundance anomalies exhibited by low mass RGB stars which bring a new light on some important aspects of stellar nucleosynthesis and chemical evolution. We underline the differences between field and globular cluster populations and discuss their possible origin both in terms of primordial pollution and stellar internal nucleosynthesis and mixing. We suggest some tests to help to understand the influence of metallicity and of a dense environment on abundance anomalies in connection with the second parameter problem and with the stellar yields.

Spontaneous emission and quantum discord: Comparison of Hilbert–Schmidt and trace distance discord

Energy Technology Data Exchange (ETDEWEB)

Jakóbczyk, Lech, E-mail: ljak@ift.uni.wroc.pl

2014-09-12

Hilbert–Schmidt and trace norm geometric quantum discord are compared with regard to their behavior during local time evolution. We consider the system of independent two-level atoms with time evolution given by the dissipative process of spontaneous emission. It is explicitly shown that the Hilbert–Schmidt norm discord has nonphysical properties with respect to such local evolution and cannot serve as a reasonable measure of quantum correlations and the better choice is to use trace norm discord as such a measure. - Highlights: • We compare Hilbert–Schmidt and trace norm geometric quantum discord. • We consider the system of independent two-level atoms with time evolution given by spontaneous emission. • We show explicitly that Hilbert–Schmidt norm discord has nonphysical properties.

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.

Phase and Texture Evolution in Chemically Derived PZT Thin Films on Pt Substrates

Science.gov (United States)

2014-09-01

function of heating rate. The FWHM of the Ill PZT texture components is sim 2978 Journal of the American Ceramic Society Mhin et al. Vol. 97, No. 9...Z39.18 ABSTRACT Phase and Texture Evolution in Chemically Derived PZT Thin Films on Pt Substrates Report Title The crystallization of lead zirconate...phase influencing texture evolution. The results suggest that PZT nucleates directly on Pt, which explains the observation of a more highly oriented

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.

The importance of glyceraldehyde radiolysis in chemical evolution

International Nuclear Information System (INIS)

Cruz-Castaneda, J.; Melendez-Lopez, A.; Buhse, T.; Ramos-Bernal, S.; Camargo-Raya, C.; Negron-Mendoza, A.; Fuentes-Carreon, C.; Universidad Nacional Autonoma de Mexico, Mexico City

2017-01-01

Studies in chemical evolution are intended to demonstrate how compounds of biological importance are generated from substances that could have been found in abiotic conditions on the primitive Earth or in extraterrestrial environments. In this context, the aim of the present work was to examine the behavior of DL-glyceraldehyde in both aqueous solution and solid samples under gamma irradiation. We irradiated dl-glyceraldehyde at different doses and temperatures with a gamma source; even at low doses and temperature (77 K), free radicals were detected. Among the products formed were ethylene glycol and glycolaldehyde. Some sugar-like compounds were also detected. (author)

Chemical evolution studies: the radiolysis and thermal decomposition of malonic acid

International Nuclear Information System (INIS)

Cruz-Castaneda, J.; Negron-Mendoza, A.; Heredia, A.; Ramos-Bernal, S.; Villafane-Barajas, S.; Frias, D.; Colin-Garcia, M.

2015-01-01

In the context of chemical evolution a simulation of a hydrothermal vent was performed. The thermolysis and radiolysis of malonic acid in aqueous solution were studied. The thermolysis was done by heating the samples (95 deg C) and radiolysis using gamma radiation. Products were identified by gas chromatography and gas chromatography-mass spectrometry. The thermal treatment produced acetic acid and CO 2 . The radiolysis experiments yield carbon dioxide, acetic acid, and di- and tricarboxylic acids. A theoretical model of the chemical process occurring under irradiation was developed; this was able to reproduce formation of products and the consumption of malonic acid. (author)

Chemical fingerprinting and source tracing of obsidian: the central Mediterranean trade in black gold.

Science.gov (United States)

Tykot, Robert H

2002-08-01

Chemical fingerprinting using major or trace element composition is used to characterize the Mediterranean island sources of obsidian and can even differentiate as many as nine flows in the Monte Arci region of Sardinia. Analysis of significant numbers of obsidian artifacts from Neolithic sites in the central Mediterranean reveals specific patterns of source exploitation and suggests particular trade mechanisms and routes. The use of techniques such as X-ray fluorescence, the electron microprobe, neutron activation analysis, and laser ablation ICP mass spectrometry are emphasized in order to produce quantitative results while minimizing damage to valuable artifacts.

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.

Chemical evolution of two-component galaxies. II

International Nuclear Information System (INIS)

Caimmi, R.

1978-01-01

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.)

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.

A transformation theory of stochastic evolution in Red Moon methodology to time evolution of chemical reaction process in the full atomistic system.

Science.gov (United States)

Suzuki, Yuichi; Nagaoka, Masataka

2017-05-28

Atomistic information of a whole chemical reaction system, e.g., instantaneous microscopic molecular structures and orientations, offers important and deeper insight into clearly understanding unknown chemical phenomena. In accordance with the progress of a number of simultaneous chemical reactions, the Red Moon method (a hybrid Monte Carlo/molecular dynamics reaction method) is capable of simulating atomistically the chemical reaction process from an initial state to the final one of complex chemical reaction systems. In the present study, we have proposed a transformation theory to interpret the chemical reaction process of the Red Moon methodology as the time evolution process in harmony with the chemical kinetics. For the demonstration of the theory, we have chosen the gas reaction system in which the reversible second-order reaction H 2 + I 2  ⇌ 2HI occurs. First, the chemical reaction process was simulated from the initial configurational arrangement containing a number of H 2 and I 2 molecules, each at 300 K, 500 K, and 700 K. To reproduce the chemical equilibrium for the system, the collision frequencies for the reactions were taken into consideration in the theoretical treatment. As a result, the calculated equilibrium concentrations [H 2 ] eq and equilibrium constants K eq at all the temperatures were in good agreement with their corresponding experimental values. Further, we applied the theoretical treatment for the time transformation to the system and have shown that the calculated half-life τ's of [H 2 ] reproduce very well the analytical ones at all the temperatures. It is, therefore, concluded that the application of the present theoretical treatment with the Red Moon method makes it possible to analyze reasonably the time evolution of complex chemical reaction systems to chemical equilibrium at the atomistic level.

Determination of trace elements: Neutron-activation analysis in geochemistry and cosmochemistry

International Nuclear Information System (INIS)

Kolesov, G.M.

1994-01-01

Geochemistry, like cosmochemistry, open-quotes studies chemical elements hor-ellipsis of the crust and hor-ellipsis the Earth hor-ellipsis their history, their distribution hor-ellipsis their genetic hor-ellipsis connectionsclose quotes and is based on data on the abundance and distribution of elements obtained by various analytical methods. Neutron-activation analysis (NAA) plays a particular role in this respect. This is due to its high sensitivity (detection limit as small as 10 -14 g), which makes possible the use of samples of arbitrary mass, and also due to the possibility of obtaining information about composition without destruction of the object, conserving, if required, the unique material under investigation. Of the most interest are the data on the contents for a number of trace elements (at a level of 10 -7 - 10 -4 %), among which are rare-earth elements (REE), U, Th, Zr, Hf, Ta, W, Ga, Ni, Rb, Cs, platinum-group metals, Ag, Au, etc. These elements are considered as indicators of geochemical processes associated with the genesis and evolution of solar system bodies in early and more recent stages of evolution; they are also used to study processes and phenomena at zone boundaries: river-sea, ocean-atmosphere, and so on. The aim of this work is to show the capabilities of NAA in the determination of trace elements

An investigation of changes in element distribution and chemical states during differentiation of embryonic stem cells

International Nuclear Information System (INIS)

Sugimoto, T.; Ide-Ektessabi, A.; Ishihara, R.; Tanigaki, M.

2004-01-01

Metallic elements and their organic compounds have dynamic regulatory functions in cells. In this study, we implemented a new approach to investigate the mechanism of differentiation of embryonic stem cells, by measuring and analyzing the change in distribution and chemical states of intracellular trace elements. We anticipate that trace metal elements and metalloproteins play important roles in the direction of differentiation, both as active centers, and as factors in the death of neural cells in neurodegenerative disorders. The aim of this study is to analyze the distribution and chemical states of trace elements during the process of differentiation of mouse embryonic stem cells, and to understand how these factors relate to the differentiation process. Using the experimental results, some previously unexplained points are considered, namely (1) how the intracellular elements change during the process of neuronal differentiation, and (2) what the optimal conditions of such elements are for neuronal differentiation. The information obtained during this study is relevant to nervous system development and evolution

An investigation of changes in element distribution and chemical states during differentiation of embryonic stem cells

Energy Technology Data Exchange (ETDEWEB)

Sugimoto, T.; Ide-Ektessabi, A. E-mail: h51167@sakura.kudpc.kyoto-u.ac.jp; Ishihara, R.; Tanigaki, M

2004-07-01

Metallic elements and their organic compounds have dynamic regulatory functions in cells. In this study, we implemented a new approach to investigate the mechanism of differentiation of embryonic stem cells, by measuring and analyzing the change in distribution and chemical states of intracellular trace elements. We anticipate that trace metal elements and metalloproteins play important roles in the direction of differentiation, both as active centers, and as factors in the death of neural cells in neurodegenerative disorders. The aim of this study is to analyze the distribution and chemical states of trace elements during the process of differentiation of mouse embryonic stem cells, and to understand how these factors relate to the differentiation process. Using the experimental results, some previously unexplained points are considered, namely (1) how the intracellular elements change during the process of neuronal differentiation, and (2) what the optimal conditions of such elements are for neuronal differentiation. The information obtained during this study is relevant to nervous system development and evolution.

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.

Xenia: A Probe of Cosmic Chemical Evolution

Science.gov (United States)

Kouveliotou, Chryssa; Piro, L.; Xenia Collaboration

2008-03-01

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 γ-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.

Model of heat transfer by radiation in a pool of spent fuel by TRACE; Modelo de transmision de calor por radiacion en una piscina de combustible gastado mediante TRACE

Energy Technology Data Exchange (ETDEWEB)

Sanchez-Saez, F.; Carlos Alberola, S.; Martorell Alsina, J. J.; Villanueva Lopez, J. F.

2013-07-01

The work involves the simulation thermal-hydraulic of a spent fuel pool to cause a transient loss of coolant with coolant loss through the transfer channel. The simulation performed with the Best Estimate TRACE code. To follow the evolution of behavior of the pool, a variable is important to follow the sheath temperature, whose evolution depends on the heat that gets broadcast. In this simulation was considered the transfer by convection and has been compared with the evolution of Variable considering convection plus radiation. The proposed radiation pattern RADGEN obtains code data for use in TRACE. With this model, obtains an evolution of the temperature in the transient pod less conservative.

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

International Nuclear Information System (INIS)

Mohamed A Abu El-Rus

2003-01-01

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)

A recursive microfluidic platform to explore the emergence of chemical evolution

Directory of Open Access Journals (Sweden)

David Doran

2017-08-01

Full Text Available We propose that a chemically agnostic approach to explore the origin of life, using an automated recursive platform based on droplet microfluidics, could be used to induce artificial chemical evolution by iterations of growth, speciation, selection, and propagation. To explore this, we set about designing an open source prototype of a fully automated evolution machine, comprising seven modules. These modules are a droplet generator, droplet transfer, passive and active size sorting, splitter, incubation chamber, reservoir, and injectors, all run together via a LabVIEWTM program integration system. Together we aim for the system to be used to drive cycles of droplet birth, selection, fusion, and propagation. As a proof of principle, in addition to the working individual modules, we present data showing the osmotic exchange of glycylglycine containing and pure aqueous droplets, showing that the fittest droplets exhibit higher osomolarity relative to their neighbours, and increase in size compared to their neighbours. This demonstrates the ability of our platform to explore some different physicochemical conditions, combining the efficiency and unbiased nature of automation with our ability to select droplets as functional units based on simple criteria.

Chemical evolution of Titan’s aerosol analogues under VUV irradiation

Science.gov (United States)

Carrasco, Nathalie; Gavilan, Lisseth; Tigrine, Sarah; Vettier, Ludovic; Nahon, Laurent; Pernot, Pascal

2017-10-01

Since the Cassini-CAPS measurements, organic aerosols are known to be present and formed at high altitudes in the diluted and partially ionized medium that is Titan’s ionosphere [1].After production in the ionosphere, Titan’s aerosols evolve through microphysics during their sedimentation down to Titan’s surface [2]. Starting with a few nanomers size in the upper atmosphere, they reach a fractal structure of a few hundreds nanometers close to the surface [3]. During sedimentation, aerosols are also submitted to solar irradiation. As laboratory analogs of Titan’s atmospheric aerosols (tholins) show a strong UV absorption [4], we suspect that VUV irradiation could also induce a chemical evolution of Titan’s aerosols during their descent in Titan’s atmosphere.The aim of this work ist to simulate the irradiation process occuring on the aerosols in Titan’s atmosphere and to address whether this irradiation impacts the chemical composition of the organic solids. First aerosol analogues were produced in a N2-CH4 plasma discharge as thin organic films of a few hundreds of nanometers thick [5]. Then those were irradiated at Lyman-α wavelength, the strongest VUV line in the solar spectrum, with a high photon flux on a synchrotron VUV beamline. We will present and discuss the significant chemical evolutions observed on the analogues after VUV irradiation by mid-IR absorption spectroscopy.[1] Waite et al. (2009) Science , 316, p. 870[2] Lavvas et al. (2011) Astrophysical Journal, 728:80[3] Tomasko et al. (2008) Planetary and Space Science, 56, p. 669[4] Mahjoub et al. (2012) Icarus 221, P. 670[5] Carrasco et al. (2016) Planetary and Space Science, 128, p. 52

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

International Nuclear Information System (INIS)

Toulhoat, P.; Beaucaire, C.; Ouzounian, G.

1993-01-01

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

Pollen spectrum, a cornerstone for tracing the evolution of the eastern Central Asian desert

Science.gov (United States)

Lu, Kai-Qing; Xie, Gan; Li, Min; Li, Jin-Feng; Trivedi, Anjali; Ferguson, David K.; Yao, Yi-Feng; Wang, Yu-Fei

2018-04-01

The temperate desert in arid Central Asia (ACA) has acted as a thoroughfare for the ancient Silk Road and today's Belt and Road, linking economic and cultural exchanges between East and West. The interaction between human sustainable development and the dynamic change in the desert ecosystem in this region is an area of concern for governments and scientific communities. Nevertheless, the lack of a pollen spectrum of the dominant taxa within the temperate desert vegetation and a corresponding relation between pollen assemblages and specific desert vegetation types is an obstacle to further understanding the formation and maintenance of this desert ecosystem. In this work, we link pollen assemblages to specific desert vegetation types with a new pollen spectrum with specific pollen grains, specific plant taxa and related habitats, providing a solid foundation for further tracing the evolution of the desert ecosystem in eastern arid Central Asia.

Major and Trace Element Analysis of Natural and Experimental Igneous Systems using LA-ICP-MS

Science.gov (United States)

Jenner, Frances E.; Arevalo, Ricardo D., Jr.

2016-01-01

Major- and trace-element compositions of minerals provide valuable information on a variety of global Earth-system processes, including melting of distinct mantle reservoirs, the growth and evolution of the Earths crust and the formation of economically viable ore deposits. In the mid-1980s and early 1990s, attempts were made to couple laser ablation (LA) systems to inductively coupled plasma mass spectrometry (ICPMS) instruments (e.g. Fryer et al. 1995; Jackson et al. 1992). The goal was to develop a rapid, highly sensitive in situ analytical technique to measure abundances and spatial distributions of trace elements in minerals and other geological samples. Elemental analysis using LAICPMS was envisaged as a quicker and less destructive means of chemical analysis (requiring only g quantities) than labour-intensive sample digestion and solution analysis (requiring mg-levels of material); and it would be a more cost-effective method than secondary ion mass spectrometry (SIMS) for the routine analysis of trace elements from solid samples. Furthermore, it would have lower limits-of-detection than electron probe microanalysis (EPMA) (e.g. Jackson et al. 1992; Eggins 2003).

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

International Nuclear Information System (INIS)

1993-10-01

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

THE INFLUENCE OF RADIAL STELLAR MIGRATION ON THE CHEMICAL EVOLUTION OF THE MILKY WAY

Energy Technology Data Exchange (ETDEWEB)

Wang Yue; Zhao Gang, E-mail: gzhao@nao.cas.cn [Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China)

2013-05-20

Stellar migration is an important dynamical process in the Galactic disk. Here we model radial stellar migration in the Galactic disk with an analytical method, then add it to a detailed Galactic chemical evolution model to study the influence of radial stellar migration on the chemical evolution of the Milky Way, especially for the abundance gradients. We found that the radial stellar migration in the Galactic disk can make the profile of the G-dwarf metallicity distribution of the solar neighborhood taller and narrower, and thus it becomes another solution to the ''G-dwarf problem''. It can also scatter the age-metallicity relation. However, after migration, the abundance distributions along the Galactic radius do not change much; namely, the abundance gradients would not be flattened by the radial stellar migration, which is different from the predictions of many theoretical works. However, it can flatten the radial gradients of the mean chemical abundance of stars, and older stars possess flatter abundance gradients than younger stars. The most significant effect of radial stellar migration on the chemical abundance is that at a certain position it scatters the abundance of stars from a relatively concentrated value to a range.

Trace-element speciation and partitioning in environmental geochemistry and health

Energy Technology Data Exchange (ETDEWEB)

Farmer, J.G.; Gibson, M.J.; Lovell, M.A.

1983-09-01

Establishment of the chemical form and associations of trace elements is important in the scientifc and medical fields related to environmental geochemistry and health. Fundamental understanding of trace-element behavior, the realistic formulation of historical perspectives of trace-element contamination, an assessment of environmental transformation processes and a thorough appraisal of environment-related ill health and disease all depend on knowledge of the chemical speciation and partitioning of trace elements. These topics and the development of analytical speciation techniques and procedures are discussed with reference to trace-element studies in the Department of Forensic Medicine and Science, University of Glasgow, on lacustrine sediments and water, the atmosphere, soil and street dirt of an urban environment, and human biological fluids. 206 references, 4 figures.

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

Directory of Open Access Journals (Sweden)

Sandra Steiger

2014-06-01

Full Text Available 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 that some chemical signals are expressed in relation to an individual’s condition and depend, for example, on age, immunocompetence, fertility, body size or degree of inbreeding. Males or females might benefit by choosing based on those traits, gaining resources or “good genes”. Other chemical traits appear to reliably reflect an individual’s underlying genotype and are suitable to choose a mating partner that matches best the own genotype.

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

International Nuclear Information System (INIS)

Gulfraz, M.; Ahmad, T.; Afzal, H.

2003-01-01

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)

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.

Tracers and tracing methods

International Nuclear Information System (INIS)

Leclerc, J.P.

2001-01-01

The first international congress on 'Tracers and tracing methods' took place in Nancy in May 2001. The objective of this second congress was to present the current status and trends on tracing methods and their applications. It has given the opportunity to people from different fields to exchange scientific information and knowledge about tracer methodologies and applications. The target participants were the researchers, engineers and technologists of various industrial and research sectors: chemical engineering, environment, food engineering, bio-engineering, geology, hydrology, civil engineering, iron and steel production... Two sessions have been planned to cover both fundamental and industrial aspects: 1)fundamental development (tomography, tracer camera visualization and particles tracking; validation of computational fluid dynamics simulations by tracer experiments and numerical residence time distribution; new tracers and detectors or improvement and development of existing tracing methods; data treatments and modeling; reactive tracer experiments and interpretation) 2)industrial applications (geology, hydrogeology and oil field applications; civil engineering, mineral engineering and metallurgy applications; chemical engineering; environment; food engineering and bio-engineering). The program included 5 plenary lectures, 23 oral communications and around 50 posters. Only 9 presentations are interested for the INIS database

The evolution of plant chemical defence - new roles for hydroxynitrile glucosides in Lotus japonicus

DEFF Research Database (Denmark)

Knudsen, Camilla

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...... on hydroxynitrile glucoside metabolism in the legume model plant Lotus japonicus. Lotus japonicus produces both cyanogenic and non-cyanogenic hydroxynitrile glucosides as chemical defence compounds. The cyanogenic glucosides linamarin and lotaustralin are stored in the cell vacuole as inactive glycosides and, upon...... 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...

Concrete Chemical Evolution

International Nuclear Information System (INIS)

D.H. Tang

1998-01-01

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 CO 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

Nuclear traces in glass

International Nuclear Information System (INIS)

Segovia A, M. de N.

1978-01-01

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 252 Cf 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)

Chemical Evolution of Interstellar Methanol Ice Analogs upon Ultraviolet Irradiation: The Role of the Substrate

Science.gov (United States)

Ciaravella, A.; Jiménez-Escobar, A.; Cosentino, G.; Cecchi-Pestellini, C.; Peres, G.; Candia, R.; Collura, A.; Barbera, M.; Di Cicca, G.; Varisco, S.; Venezia, A. M.

2018-05-01

An important issue in the chemistry of interstellar ices is the role of dust materials. In this work, we study the effect of an amorphous water-rich magnesium silicate deposited onto ZnSe windows on the chemical evolution of ultraviolet-irradiated methanol ices. For comparison, we also irradiate similar ices deposited onto bare ZnSe windows. Silicates are produced at relatively low temperatures exploiting a sol–gel technique. The chemical composition of the synthesized material reflects the forsterite stoichiometry. Si–OH groups and magnesium carbonates are incorporated during the process. The results show that the substrate material does affect the chemical evolution of the ice. In particular, the CO2/CO ratio within the ice is larger for methanol ices deposited onto the silicate substrate as a result of concurrent effects: the photolysis of carbonates present in the adopted substrate as a source of CO2, CO, and carbon and oxygen atoms; reactions of water molecules and hydroxyl radicals released from the substrate with the CO formed in the ice by the photolysis of the methanol ice; and changes in the structure and energy of the silicate surface by ultraviolet irradiation, leading to more favorable conditions for chemical reactions or catalysis at the grain surface. The results of our experiments allow such chemical effects contributed by the various substrate material components to be disentangled.

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

Energy Technology Data Exchange (ETDEWEB)

Andrews, Brett H. [PITT PACC, Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA 15260 (United States); Weinberg, David H.; Schönrich, Ralph; Johnson, Jennifer A., E-mail: andrewsb@pitt.edu [Department of Astronomy, The Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States)

2017-02-01

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 stellar initial mass function, the SN Ia delay time distribution, stellar yields, and stellar population mixing. Using flexCE, a flexible one-zone chemical evolution code, we investigate the effects of and trade-offs between parameters. Two critical parameters are SFE and the outflow mass-loading parameter, which shift the knee in [O/Fe]–[Fe/H] and the equilibrium abundances that the simulations asymptotically approach, respectively. One-zone models with simple star formation histories follow narrow tracks in [O/Fe]–[Fe/H] unlike the observed bimodality (separate high- α and low- α sequences) in this plane. A mix of one-zone models with inflow timescale and outflow mass-loading parameter variations, motivated by the inside-out galaxy formation scenario with radial mixing, reproduces the two sequences better than a one-zone model with two infall epochs. We present [X/Fe]–[Fe/H] tracks for 20 elements assuming three different supernova yield models and find some significant discrepancies with solar neighborhood observations, especially for elements with strongly metallicity-dependent yields. We apply principal component abundance analysis to the simulations and existing data to reveal the main correlations among abundances and quantify their contributions to variation in abundance space. For the stellar population mixing scenario, the abundances of α -elements and elements with metallicity-dependent yields dominate the first and second principal components, respectively, and collectively explain 99% of the variance in the model. flexCE is a python package available at https://github.com/bretthandrews/flexCE.

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

International Nuclear Information System (INIS)

Andrews, Brett H.; Weinberg, David H.; Schönrich, Ralph; Johnson, Jennifer A.

2017-01-01

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 stellar initial mass function, the SN Ia delay time distribution, stellar yields, and stellar population mixing. Using flexCE, a flexible one-zone chemical evolution code, we investigate the effects of and trade-offs between parameters. Two critical parameters are SFE and the outflow mass-loading parameter, which shift the knee in [O/Fe]–[Fe/H] and the equilibrium abundances that the simulations asymptotically approach, respectively. One-zone models with simple star formation histories follow narrow tracks in [O/Fe]–[Fe/H] unlike the observed bimodality (separate high- α and low- α sequences) in this plane. A mix of one-zone models with inflow timescale and outflow mass-loading parameter variations, motivated by the inside-out galaxy formation scenario with radial mixing, reproduces the two sequences better than a one-zone model with two infall epochs. We present [X/Fe]–[Fe/H] tracks for 20 elements assuming three different supernova yield models and find some significant discrepancies with solar neighborhood observations, especially for elements with strongly metallicity-dependent yields. We apply principal component abundance analysis to the simulations and existing data to reveal the main correlations among abundances and quantify their contributions to variation in abundance space. For the stellar population mixing scenario, the abundances of α -elements and elements with metallicity-dependent yields dominate the first and second principal components, respectively, and collectively explain 99% of the variance in the model. flexCE is a python package available at https://github.com/bretthandrews/flexCE.

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.

Reading the metal diaries of the universe : tracing cosmic chemical evolution from the reionization epoch till the present

NARCIS (Netherlands)

Vink, J.

2009-01-01

Metals are essential for star formation and their subsequent evolution, and ultimately the formation of planets and the development of life, as we know it. Reconstructing the cosmic history of metals, reaching from the first population of stars to the processes involved in the formation of galaxies

Management strategies for trace organic chemicals in water - A review of international approaches.

Science.gov (United States)

Bieber, Stefan; Snyder, Shane A; Dagnino, Sonia; Rauch-Williams, Tanja; Drewes, Jörg E

2018-03-01

To ensure an appropriate management of potential health risks and uncertainties from the release of trace organic chemicals (TOrCs) into the aqueous environment, many countries have evaluated and implemented strategies to manage TOrCs. The aim of this study was to evaluate existing management strategies for TOrCs in different countries to derive and compare underlying core principles and paradigms and to develop suggestions for more holistic management strategies to protect the environment and drinking water supplies from the discharge of undesired TOrCs. The strategies in different industrial countries were summarized and subsequently compared with regards to three particular questions: 1) Do the approaches different countries have implemented manage all or only specific portions of the universe of chemicals; 2) What implementation and compliance strategies are used to manage aquatic and human health risk and what are their pros and cons; and 3) How are site-specific watershed differences being addressed? While management strategies of the different countries target similar TOrCs, the programs differ in several important aspects, including underlying principles, the balance between aquatic or human health protection, implementation methods, and financing mechanisms used to fund regulatory programs. Copyright © 2017 Elsevier Ltd. All rights reserved.

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.

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)

Rizzio, E.; Bergamaschi, G.; Profumo, A.; Gallorini, M.

2001-01-01

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)

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, X.; Zhang, Y.; Huey, L. G.; Yokelson, R. J.; Wang, Y.; Jimenez, J. L.; Campuzano-Jost, P.; Beyersdorf, A. J.; Blake, D. R.; Choi, Y.;

Chemical Selectivity and Sensitivity of a 16-Channel Electronic Nose for Trace Vapour Detection

Directory of Open Access Journals (Sweden)

Drago Strle

2017-12-01

Full Text Available Good chemical selectivity of sensors for detecting vapour traces of targeted molecules is vital to reliable detection systems for explosives and other harmful materials. We present the design, construction and measurements of the electronic response of a 16 channel electronic nose based on 16 differential microcapacitors, which were surface-functionalized by different silanes. The e-nose detects less than 1 molecule of TNT out of 10+12 N2 molecules in a carrier gas in 1 s. Differently silanized sensors give different responses to different molecules. Electronic responses are presented for TNT, RDX, DNT, H2S, HCN, FeS, NH3, propane, methanol, acetone, ethanol, methane, toluene and water. We consider the number density of these molecules and find that silane surfaces show extreme affinity for attracting molecules of TNT, DNT and RDX. The probability to bind these molecules and form a surface-adsorbate is typically 10+7 times larger than the probability to bind water molecules, for example. We present a matrix of responses of differently functionalized microcapacitors and we propose that chemical selectivity of multichannel e-nose could be enhanced by using artificial intelligence deep learning methods.

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)

Amemiya, Kenta

2015-01-01

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)

Chemical Evolution and the Formation of Dwarf Galaxies in the Early Universe

Science.gov (United States)

Cote, Benoit; JINA-CEE, NuGrid, ChETEC

2018-06-01

Stellar abundances in local dwarf galaxies offer a unique window into the nature and nucleosynthesis of the first stars. They also contain clues regarding how galaxies formed and assembled in the early stages of the universe. In this talk, I will present our effort to connect nuclear astrophysics with the field of galaxy formation in order to define what can be learned about galaxy evolution using stellar abundances. In particular, I will describe the current state of our numerical chemical evolution pipeline which accounts for the mass assembly history of galaxies, present how we use high-redshift cosmological hydrodynamic simulations to calibrate our models and to learn about the formation of dwarf galaxies, and address the challenge of identifying the dominant r-process site(s) using stellar abundances.

Galactic chemical evolution in hierarchical formation models - I. Early-type galaxies in the local Universe

NARCIS (Netherlands)

Arrigoni, Matías; Trager, Scott C.; Somerville, Rachel S.; Gibson, Brad K.

We study the metallicities and abundance ratios of early-type galaxies in cosmological semi-analytic models (SAMs) within the hierarchical galaxy formation paradigm. To achieve this we implemented a detailed galactic chemical evolution model and can now predict abundances of individual elements for

Galactic chemical evolution in hierarchical formation models : I. Early-type galaxies in the local Universe

NARCIS (Netherlands)

Arrigoni, Matias; Trager, Scott C.; Somerville, Rachel S.; Gibson, Brad K.

2010-01-01

We study the metallicities and abundance ratios of early-type galaxies in cosmological semi-analytic models (SAMs) within the hierarchical galaxy formation paradigm. To achieve this we implemented a detailed galactic chemical evolution model and can now predict abundances of individual elements for

Probing Trace-elements in Bitumen by Neutron Activation Analysis

NARCIS (Netherlands)

Nahar, S.N.; Schmets, A.J.M.; Scarpas, Athanasios

Trace elements and their concentrations play an important role in both chemical and physical properties of bitumen. Instrumental Neutron Activation Analysis (INAA) has been applied to determine the concentration of trace elements in bitumen. This method requires irradiation of the material with

Release kinetics and mechanisms of trace heavy metals from cement based material; Cinetiques et mecanismes de relargage des metaux lourds presents en traces dans les matrices cimentaires

Energy Technology Data Exchange (ETDEWEB)

Moudilou, E.

2002-12-15

Chemical species contained in a solid matrix may be transferred to the environment through water leaching. Previous studies of trace metals released from building materials (particularly cement-based ones) highlight an important analytical difficulty. The aim of this study is to determine the kinetics and the mechanisms involved in the release of trace heavy metals (Cr, Cu, Ni, Pb, V and Zn) from industrial cement pastes (usually ranging from 20 to 300 ppm). The development of a dynamic leaching system, named CTG-LEACHCRETE, (used at pH=5, 20 C) which permits the evaluation of the kinetics of trace heavy metals is presented in the first part. Also, innovative solid analysis techniques (ICP-MS-Laser Ablation, local and Grazing Incidence X-rays Diffraction (GIXD) technique) were used to characterise the cement-degraded layers formed during leaching experiments. These techniques enable to monitor the mineralogical evolution and the distribution of trace metals in these areas. The confrontation of these two approaches, kinetic and solid analysis, coupled with a thorough investigation of previously developed models, lead to proposals concerning the mechanisms of release of the trace heavy metals studied. In all the cement pastes studied (CPA-CEM I, CPJ-CEM II/A and CLC-CEM V/A), chromium is trapped in ettringite by substitution SO{sub 4}{sup 2-}(U)CrO{sub 4}{sup 2-} and its release is then controlled by the dissolution of this hydrate. The behaviour of copper, nickel and zinc in degraded areas and in leachates, are correlated to the silicon of the hydrated calcium silicate (CSH), which imply that they are localised there. Lead, was never detected in the leachates. But it is also correlated to the silicon in the degraded layers. (author)

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.

Trace elements in agroecosystems and impacts on the environment.

Science.gov (United States)

He, Zhenli L; Yang, Xiaoe E; Stoffella, Peter J

2005-01-01

Trace elements mean elements present at low concentrations (mg kg-1 or less) in agroecosystems. Some trace elements, including copper (Cu), zinc (Zn), manganese (Mn), iron (Fe), molybdenum (Mo), and boron (B) are essential to plant growth and are called micronutrients. Except for B, these elements are also heavy metals, and are toxic to plants at high concentrations. Some trace elements, such as cobalt (Co) and selenium (Se), are not essential to plant growth but are required by animals and human beings. Other trace elements such as cadmium (Cd), lead (Pb), chromium (Cr), nickel (Ni), mercury (Hg), and arsenic (As) have toxic effects on living organisms and are often considered as contaminants. Trace elements in an agroecosystem are either inherited from soil parent materials or inputs through human activities. Soil contamination with heavy metals and toxic elements due to parent materials or point sources often occurs in a limited area and is easy to identify. Repeated use of metal-enriched chemicals, fertilizers, and organic amendments such as sewage sludge as well as wastewater may cause contamination at a large scale. A good example is the increased concentration of Cu and Zn in soils under long-term production of citrus and other fruit crops. Many chemical processes are involved in the transformation of trace elements in soils, but precipitation-dissolution, adsorption-desorption, and complexation are the most important processes controlling bioavailability and mobility of trace elements in soils. Both deficiency and toxicity of trace elements occur in agroecosystems. Application of trace elements in fertilizers is effective in correcting micronutrient deficiencies for crop production, whereas remediation of soils contaminated with metals is still costly and difficult although phytoremediation appears promising as a cost-effective approach. Soil microorganisms are the first living organisms subjected to the impacts of metal contamination. Being responsive and

Effects of main-sequence mass loss on stellar and galactic chemical evolution

International Nuclear Information System (INIS)

Guzik, J.A.

1988-01-01

L.A. Willson, G.H. Bowen and C. Struck-Marcell have proposed that 1 to 3 solar mass stars may experience evolutionarily significant mass loss during the early part of their main-sequence phase. The suggested mass-loss mechanism is pulsation, facilitated by rapid rotation. Initial mass-loss rates may be as large as several times 10 -9 M mass of sun/yr, diminishing over several times 10 8 years. The author attempts to test this hypothesis by comparing some theoretical implications with observations. Three areas are addressed: Solar models, cluster HR diagrams, and galactic chemical evolution. Mass-losing solar models were evolved that match the Sun's luminosity and radius at its present age. The most extreme viable models have initial mass 2.0 M 0 , and mass-loss rates decreasing exponentially over 2-3 x 10 8 years. Evolution calculations incorporating main-sequence mass loss were completed for a grid of models with initial masses 1.25 to 2.0 M mass of sun and mass loss timescales 0.2 to 2.0 Gry. Cluster HR diagrams synthesized with these models confirm the potential for the hypothesis to explain observed spreads or bifurcations in the upper main sequence, blue stragglers, anomalous giants, and poor fits of main-sequence turnoffs by standard isochrones. Simple closed galactic chemical evolution models were used to test the effects of main-sequence mass loss on the F and G dwarf distribution. Stars between 3.0 M mass of sun and a metallicity-dependent lower mass are assumed to lose mass. The models produce a 30 to 60% increase in the stars to stars-plus-remnants ratio, with fewer early-F dwarfs and many more late-F dwarfs remaining on the main sequence to the present

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

Trace element mapping of pyrite from Archean gold deposits – A comparison between PIXE and EPMA

Energy Technology Data Exchange (ETDEWEB)

Agangi, A., E-mail: aagangi@uj.ac.za [University of Johannesburg, Department of Geology, Auckland Park 2006 (South Africa); Przybyłowicz, W., E-mail: przybylowicz@tlabs.ac.za [Materials Research Department, iThemba LABS, National Research Foundation, Somerset West 7129 (South Africa); AGH University of Science and Technology, Faculty of Physics & Applied Computer Science, Al. A. Mickiewicza 30, 30-059 Krakow (Poland); Hofmann, A., E-mail: ahofmann@uj.ac.za [University of Johannesburg, Department of Geology, Auckland Park 2006 (South Africa)

2015-04-01

Chemical zoning of pyrites can record the evolution of mineralising fluids at widely varying P–T conditions ranging from diagenesis to medium-grade metamorphism. If preserved, zoning can reveal growth textures, brecciation and veining, resorption and recrystallisation events, thus shedding light on the processes that contributed to ore formation. Chemical zoning of sulfides is invisible in optical microscopy, but can be studied by chemical etching, high-contrast back-scattering electron images, and elemental imaging. In this study we compared micro-PIXE and WDS-EPMA elemental maps on the chemically zoned pyrites in mineralised vein-bearing samples from the Sheba and Fairview gold mines in the Barberton Greenstone Belt, South Africa. Elemental images show complex distribution of trace elements, suggesting multiple events of pyrite crystallisation and gold deposition. EPMA maps show fine-scale variations reflecting growth and recrystallisation textures marked, in particular, by variations of As, Ni, and Co. In PIXE maps, gold occurs both as finely-distributed and discrete inclusions, suggesting incorporation in the pyrite structure as solid solution, and deposition as electrum inclusions, respectively. Micro-PIXE and EPMA provide complementary information, forming together a powerful tool to obtain information on chemical zoning of pyrites in ore deposits.

Evolution of camel CYP2E1 and its associated power of binding toxic industrial chemicals and drugs.

Science.gov (United States)

Kandeel, Mahmoud; Altaher, Abdullah; Kitade, Yukio; Abdelaziz, Magdi; Alnazawi, Mohamed; Elshazli, Kamal

2016-10-01

Camels are raised in harsh desert environment for hundreds of years ago. By modernization of live and the growing industrial revolution in camels rearing areas, camels are exposed to considerable amount of chemicals, industrial waste, environmental pollutions and drugs. Furthermore, camels have unique gene evolution of some genes to withstand living in harsh environments. In this work, the camel cytochrome P450 2E1 (CYP2E1) is compromised to detect its evolution rate and its power to bind with various chemicals, protoxins, procarcinogens, industrial toxins and drugs. In comparison with human CYP2E1, camel CYP2E1 more efficiently binds to small toxins as aniline, benzene, catechol, amides, butadiene, toluene and acrylamide. Larger compounds were more preferentially bound to the human CYP2E1 in comparison with camel CYP2E1. The binding of inhalant anesthetics was almost similar in both camel and human CYP2E1 coinciding with similar anesthetic effect as well as toxicity profiles. Furthermore, evolutionary analysis indicated the high evolution rate of camel CYP2E1 in comparison with human, farm and companion animals. The evolution rate of camel CYP2E1 was among the highest evolution rate in a subset of 57 different organisms. These results indicate rapid evolution and potent toxin binding power of camel CYP2E1. Copyright © 2016. Published by Elsevier Ltd.

Evolution of a chemically reacting plume in a ventilated room

Science.gov (United States)

Conroy, D. T.; Smith, Stefan G. Llewellyn; Caulfield, C. P.

2005-08-01

The dynamics of a second-order chemical reaction in an enclosed space driven by the mixing produced by a turbulent buoyant plume are studied theoretically, numerically and experimentally. An isolated turbulent buoyant plume source is located in an enclosure with a single external opening. Both the source and the opening are located at the bottom of the enclosure. The enclosure is filled with a fluid of a given density with a fixed initial concentration of a chemical. The source supplies a constant volume flux of fluid of different density containing a different chemical of known and constant concentration. These two chemicals undergo a second-order non-reversible reaction, leading to the creation of a third product chemical. For simplicity, we restrict attention to the situation where the reaction process does not affect the density of the fluids involved. Because of the natural constraint of volume conservation, fluid from the enclosure is continually vented. We study the evolution of the various chemical species as they are advected by the developing ventilated filling box process within the room that is driven by the plume dynamics. In particular, we study both the mean and vertical distributions of the chemical species as a function of time within the room. We compare the results of analogue laboratory experiments with theoretical predictions derived from reduced numerical models, and find excellent agreement. Important parameters for the behaviour of the system are associated with the source volume flux and specific momentum flux relative to the source specific buoyancy flux, the ratio of the initial concentrations of the reacting chemical input in the plume and the reacting chemical in the enclosed space, the reaction rate of the chemicals and the aspect ratio of the room. Although the behaviour of the system depends on all these parameters in a non-trivial way, in general the concentration within the room of the chemical input at the isolated source passes

Trace elements in brazilian soils

International Nuclear Information System (INIS)

Rocha, Geraldo Cesar

1995-01-01

A literature revision on trace elements (Zn, B, Mn, Mo, Cu, Fe, and Cl) in Brazilian soils was prepared, with special attention to the chemical form and range in the soil, extraction methods and correlation of the amount in soils with soil properties

Chemical evolution, stellar nucleosynthesis and a variable star formation rate

International Nuclear Information System (INIS)

Olive, K.A.; Thielemann, F.K.; Truran, J.W.

1986-04-01

The effects of a decreasing star formation rate (SFR) on the galactic abundances of elements produced in massive stars (M ≥ 10 Msub solar). On the basis of a straightforward model of galactic evolution, a relation between the upper mass limit of type II supernovae (M/sub SN/) contributing to chemical evolution and the decline of the SFR (tau) is derived, when the oxygen abundance is determined only by massive stars. The additional requirement that all intermediate mass elements (Ne-Ti), which are also predominantly due to nucleosynthesis in massive stars, are produced in solar proportions leads to a unique value of M/sub SN/ and tau. The application of this method with abundance yields from Arnett (1978) and Woosley and Weaver (1986) resuults, however, in contradicting solutions: M/sub SN/ ≅ 45 Msub solar, tau = ∞, and M/sub SN/ ≅ 15 Msub solar, tau = 3 x 10 9 y. Thus, in order that this approach provide an effective probe of the SFR over the history of our galaxy it is essential that converging and more accurate predictions of the consequences of stellar and supernova nucleosynthesis will be forthcoming. 54 refs., 2 figs., 2 tabs

Responses of soil physical and chemical properties to karst rocky desertification evolution in typical karst valley area

Science.gov (United States)

Chen, Fei; Zhou, Dequan; Bai, Xiaoyong; zeng, Cheng; Xiao, Jianyong; Qian, Qinghuan; Luo, Guangjie

2018-01-01

In order to reveal the differences of soil physical and chemical properties and their response mechanism to the evolution of KRD. The characteristics of soil physical and chemical properties of different grades of KRD were studied by field sampling method to research different types of KRD in the typical karst valley of southern China. Instead of using space of time, to explore the response and the mechanisms of the soil physical and chemical properties at the different evolution process. The results showed that: (1) There were significant differences in organic matter, pH, total nitrogen, total phosphorus, total potassium, sediment concentration, clay content and AWHC in different levels of KRD environment. However, these indicators are not with increasing desertification degree has been degraded, but improved after a first degradation trends; (2) The correlation analysis showed that soil organic matter, acid, alkali, total nitrogen, total phosphorus, total potassium and clay contents were significantly correlated with other physical and chemical factors. They are the key factors of soil physical and chemical properties, play a key role in improving soil physical and chemical properties and promoting nutrient cycling; (3) The principal component analysis showed that the cumulative contribution rate of organic matter, pH, total nitrogen, total phosphorus, total potassium and sediment concentration was 80.26%, which was the key index to evaluate rocky desertification degree based on soil physical and chemical properties. The results have important theoretical and practical significance for the protection and restoration of rocky desertification ecosystem in southwest China.

Geochemical investigation of groundwater in the Tono area, Japan. Chemical characteristics and groundwater evolution

International Nuclear Information System (INIS)

Iwatsuki, Teruki; Hama, Katsuhiro; Yoshida, Hidekazu

1997-01-01

Geochemical investigations form an important part of the R and D program at the Tono study site, central Japan. Detailed geological structure and groundwater chemistry have been studied to understand the geochemical environment in the sedimentary and crystalline rocks distributed in this area. The chemical evolution of the groundwater in the sedimentary rocks is characterized with the variation in Na + , Ca 2+ and HCO 3 - concentrations, and ion exchange and dissolution of calcite are dominant reactions in the evolution of groundwater. Geological investigation shows that a fracture system of crystalline rock can be classified into:intact zone, moderately fractured zone and intensely fractured zone, according to the frequency and the width of fractures and fractured zones. The groundwater in the intact and fractured zones of crystalline rock are characterized by Na + -Ca 2+ -HCO 3 - or Na + -HCO 3 - dominated water, and Na + -Ca 2+ -Fe 2+ -HCO 3 - dominated water. The chemical evolution of groundwater is, generally, controlled by water-rock interaction between plagioclase, iron minerals and groundwater. The groundwater at depth of G.L.-186m in the crystalline rock at the Tono area is characterized by the mixture between the oxidized surface water and the reduced groundwater. The investigation based on correlation between geological structures and groundwater chemistry can be applied to understand the geochemical environment in deep crystalline rock, and will support the development of a realistic hydrogeochemical model. (author)

Stellar evolution

CERN Document Server

Meadows, A J

2013-01-01

Stellar Evolution, Second Edition covers the significant advances in the understanding of birth, life, and death of stars.This book is divided into nine chapters and begins with a description of the characteristics of stars according to their brightness, distance, size, mass, age, and chemical composition. The next chapters deal with the families, structure, and birth of stars. These topics are followed by discussions of the chemical composition and the evolution of main-sequence stars. A chapter focuses on the unique features of the sun as a star, including its evolution, magnetic fields, act

Use of X-Ray Fluorescence Spectrometry to Determine Trace ...

African Journals Online (AJOL)

This paper deals with application of X-ray fluorescence spectrometry for the detection of trace elements in graphic. An X-ray spectrometer was constructed and used to carry out measurements on graphite spheres impregnated with different chemical elements. The intensities of the lines of these trace elements, as function of ...

SURFACE AND LIGHTNING SOURCES OF NITROGEN OXIDES OVER THE UNITED STATES: MAGNITUDES, CHEMICAL EVOLUTION, AND OUTFLOW

Science.gov (United States)

We use observations from two aircraft during the 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 regional sources, chemical evolution...

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.

Trace elements distribution in the Amazon floodplain soils

International Nuclear Information System (INIS)

Fernandes, E.A.N.; Ferraz, E.S.B.; Oliveira, H.

1994-01-01

Neutron activation analysis was performed on aluvial soil samples from several sites on the foodplains of the Amazon River and its major tributaries for trace elements determination. The spatial and temporal variations of chemical composition of floodland sediments in the Amazon basin are discussed. No significant difference was found in trace elemental distribution in the floodland soils along the Amazon main channel, even after the source material has been progressively diluted with that from lowland draining tributaries. It was also seen that the average chemical composition of floodplain soils compares well with that of the suspended sedimets. (author) 12 refs.; 5 figs.; 2 tabs

Physiological Effects of Trace Elements and Chemicals in Water

Science.gov (United States)

Varma, M. M.; And Others

1976-01-01

The physiological effects on humans and animals of trace amounts of organic and unorganic pollutants in natural and waste waters are examined. The sensitivity of particular organs and species is emphasized. Substances reviewed include mercury, arsenic, cadmium, lead, chromium, fluorides, nitrates and organics, including polychlounated biphenyls.…

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

NARCIS (Netherlands)

Szinay, D.; Wijnker, E.; Berg, van den R.G.; Visser, R.G.F.; Jong, de J.H.S.G.M.; Bai, Y.

2012-01-01

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

Observations of Nitrogen Fractionation in Prestellar Cores: Nitriles Tracing Interstellar Chemistry

Science.gov (United States)

Milam, S. N.; Charnley, S. B.

2012-01-01

Primitive materials provide important clues on the processes that occurred during the formation and early evolution of the Solar System. Space-based and ground-based observations of cometary comae show that comets appear to contain a mixture of the products of both interstellar and nebular chemistries. Significant 15-nitrogen enrichments have been measured in CN and HCN towards a number of comets and may suggest an origin of interstellar chemical fractionation. Additionally, large N-15 enhancements are found in meteorites and has also led to to the view that the N-15 traces material formed in the interstellar medium (ISM), although multiple sources cannot be excluded. Here, we show the results of observations of the nitrogen and carbon fractionation in prestellar cores for various N-bearing species to decipher the origin of primitive material isotopic enrichments.

Trace Element Geochemistry of Silica Phases: Understanding the Evolution of the Cerro Pabellón Geothermal System

Science.gov (United States)

Alvear, B.; Morata, D.; Leisen, M.; Reich, M.; Barra, F.

2017-12-01

The study of mineral textures coupled with trace element geochemistry has proven to be a useful tool to understand the evolution of geological environments. The purpose of this study is to provide new constrains on the formation of an active geothermal system, specifically the Cerro Pabellón field. The Cerro Pabellón system is located at 4500 m above sea level and is the first geothermal power plant in operation in Chile and South America. Thirteen samples were collected from a 550 m long drill core. Samples were first studied under petrographic microscopy followed by scanning electron microscopy coupled with a cathodoluminescence detector (CL-SEM). The different textures recognized using petrography and the CL-SEM technique were later analyzed by Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) in order to determine variations in the trace element concentrations as a function of silica textures. Two vein types (A and B) with different silica polymorphs were identified by CL-SEM. Vein type A has only a colloform texture, whereas vein type B, younger and crosscutting the type A, shows zonation, colloform, and jigsaw textures. LA-ICPMS results show high concentrations of Li, Al, Na, K, As, and Sb for all types of silica. A comparison between vein type A and B, show that vein type A is Al-Na-K-Li poor (2088, 36, 309, and 122 ppm average, respectively) and As-Sb rich (43 and 249 ppm average, respectively). On the other hand, vein type B has variable concentrations of Al-Na-K-Li-Sb, but usually higher than in vein type A. Overall, the Cerro Pabellón geothermal system shows high concentrations of Li and Sb, reaching up to 360 and 703 ppm, respectively. Our preliminary results show that the trace element geochemistry is strongly related to the different silica textures, which formed as a response to different thermodynamic conditions and fluid-rock ratios. This work is a contribution to the FONDAP-CONICYT 15090013 Project.

use of x-ray fluorescence spectrometry to determine trace elements ...

African Journals Online (AJOL)

NIJOTECH

Abstract. This paper deals with application of X-ray fluorescence spectrometry for the detection of trace elements in graphic. An X-ray spectrometer was constructed and used to carry out measurements on graphite spheres impregnated with different chemical elements. The intensities of the lines of these trace elements, ...

Evolution of chemical composition of fogwater in winter in Chengdu, China.

Science.gov (United States)

Yin, Hongling; Ye, Zhixiang; Yang, Yingchun; Yuan, Wei; Qiu, Changyan; Yuan, Huawei; Wang, Min; Li, Shiping; Zou, Changwu

2013-09-01

Two sampling sites representing the urban and suburban area of Chengdu, China were sampled and analyzed for selected chemicals to characterize the evolution of the chemical composition of fogwater. A trend of total organic carbon (TOC) > total nitrogen (TN) > total inorganic carbon (TIC) was observed for both sites. Variation of inorganic ions indicated that inorganic pollutants were not accumulated in the fog. Concentrations of n-alkanes (C11-C37) at the urban site ranged from 7.58 to 27.75 ng/mL while at the suburban site concentrations were 2.57-21.55 ng/mL. The highest concentration of n-alkanes was observed in the mature period of fog (393.12 ng/mL) which was more than ten times that in the fog formation period (27.83 ng/mL) and the fog dissipation period (14.87 ng/mL). Concentrations of Sigma15PAHs were in the range of 7.27-38.52 ng/mL at the urban site and 2.59-22.69 ng/mL at the suburban site. Contents of PAHs in the mature period of fog (27.15 ng/mL) > fog dissipation period (11.59 ng/mL) > fog formation period (6.42 ng/mL). Concentrations of dicarboxylic acids (C5-C9) ranged from 10.92 to 40.78 ng/mL, with glutaric acid (C5) as the dominant dicarboxylic acid. These data provide strong indications of the accumulation of certain organic chemicals of environmental concern in fog and fog water, and provide additional insights about processes in urban and suburban air acting on organic chemicals with similar physical chemical properties.

Tracing the Origin of Black Hole Accretion Through Numerical Hydrodynamic Simulations

Science.gov (United States)

Spicer, Sandy; Somerville, Rachel; Choi, Ena; Brennan, Ryan

2018-01-01

It is now widely accepted that supermassive black holes co-evolve with galaxies, and may play an important role in galaxy evolution. However, the origin of the gas that fuels black hole accretion, and the resulting observable radiation, is not well understood or quantified. We use high-resolution "zoom-in" cosmological numerical hydrodynamic simulations including modeling of black hole accretion and feedback to trace the inflow and outflow of gas within galaxies from the early formation period up to present day. We track gas particles that black holes interact with over time to trace the origin of the gas that feeds supermassive black holes. These gas particles can come from satellite galaxies, cosmological accretion, or be a result of stellar evolution. We aim to track the origin of the gas particles that accrete onto the central black hole as a function of halo mass and cosmic time. Answering these questions will help us understand the connection between galaxy and black hole evolution.

Trace element analysis in soy sauce

International Nuclear Information System (INIS)

Haruyama, Yoichi; Saito, Manabu; Tomiya, Michio

1993-01-01

Trace elements in soy sauce have been measured by means of in-air PIXE. Six kinds of trace elements were detected, such as Mn, Fe, Ni, Zn, Cu and Br. Concentrations of Mn, Fe, Zn and Br which were observed in all samples, have been determined. Each analyzed sample contained considerable amount of Br about 160 ppm. Comparison of Br content of the imported raw materials with those of the domestic ones suggested that the large amount of Br was the residual fumigation chemicals in the imported raw materials. (author)

Study of solid chemical evolution in torrefaction of different biomasses through solid-state "1"3C cross-polarization/magic angle spinning NMR (nuclear magnetic resonance) and TGA (thermogravimetric analysis)

International Nuclear Information System (INIS)

Rodriguez Alonso, Elvira; Dupont, Capucine; Heux, Laurent; Da Silva Perez, Denilson; Commandre, Jean-Michel; Gourdon, Christophe

2016-01-01

The objective of this work is to compare mass loss and chemical evolution of the solid phase, versus time, during dynamic torrefaction of different types of biomass. For this purpose, two experiments, ThermoGravimetric Analysis and solid-state "1"3C Cross-Polarization/Magic Angle Spinning Nuclear Magnetic Resonance, were run on four representative biomasses. Overall mass loss and chemical evolution of the solid phase were followed, respectively, as a function of temperature and time. Thanks to this coupled information, it was shown that the knowledge of both solid mass loss and chemical evolution is necessary to characterize torrefaction severity. Moreover, biomasses containing higher proportions of xylan lost mass faster than those containing lower proportions. Lignin showed a protecting role towards cellulose, which would lead to a faster degradation of non-woody biomasses in comparison with woody biomasses. Three parameters would have an influence on solid chemical evolution during torrefaction: xylan content in hemicellulose, lignin content in biomass, and cellulose crystallinity. - Highlights: • Torrefaction of four biomasses was studied with TGA and solid-state NMR. • Both solid mass loss and chemical evolution characterize torrefaction severity. • Biomasses containing a higher proportion of xylan lose mass faster. • Lignin shows a stronger protecting role in degradation of woody biomasses. • Xylan, lignin and crystalline cellulose values influence solid chemical evolution.

Aerodynamic sampling for landmine trace detection

Science.gov (United States)

Settles, Gary S.; Kester, Douglas A.

2001-10-01

Electronic noses and similar sensors show promise for detecting buried landmines through the explosive trace signals they emit. A key step in this detection is the sampler or sniffer, which acquires the airborne trace signal and presents it to the detector. Practicality demands no physical contact with the ground. Further, both airborne particulates and molecular traces must be sampled. Given a complicated minefield terrain and microclimate, this becomes a daunting chore. Our prior research on canine olfactory aerodynamics revealed several ways that evolution has dealt with such problems: 1) proximity of the sniffer to the scent source is important, 2) avoid exhaling back into the scent source, 3) use an aerodynamic collar on the sniffer inlet, 4) use auxiliary airjets to stir up surface particles, and 5) manage the 'impedance mismatch' between sniffer and sensor airflows carefully. Unfortunately, even basic data on aerodynamic sniffer performance as a function of inlet-tube and scent-source diameters, standoff distance, etc., have not been previously obtained. A laboratory-prototype sniffer was thus developed to provide guidance for landmine trace detectors. Initial experiments with this device are the subject of this paper. For example, a spike in the trace signal is observed upon starting the sniffer airflow, apparently due to rapid depletion of the available signal-laden air. Further, shielding the sniffer from disruptive ambient airflows arises as a key issue in sampling efficiency.

ACTRIS Aerosol, Clouds and Trace Gases Research Infrastructure

OpenAIRE

Pappalardo Gelsomina

2018-01-01

The Aerosols, Clouds and Trace gases Research Infrastructure (ACTRIS) is a distributed infrastructure dedicated to high-quality observation of aerosols, clouds, trace gases and exploration of their interactions. It will deliver precision data, services and procedures regarding the 4D variability of clouds, short-lived atmospheric species and the physical, optical and chemical properties of aerosols to improve the current capacity to analyse, understand and predict past, current and future evo...

Evolution of chemical specifications following the working group of international inter-comparison

International Nuclear Information System (INIS)

Leduc-Brunet, Murielle; Gressier, F.; Mole, D.; Massias, O.; Marescot, O.; Bretelle, Jean Luc

2012-09-01

As part of a continuous improvement process and the inclusion of Experience Feedback, EDF has launched a working group to analyse its reference of Chemical Specifications with regard to the guidelines of EPRI and VGB.. As a result of the analysis of over 1000 lines of specifications, a large number of recommendations were issued, referring either to control of new chemical parameters or to an enhancement of measurement frequencies. These recommendations are to be developed by preliminary studies which will provide supporting evidence for future decisions. To implement these recommendations, EDF launched a dedicated project in 2011, whose main objectives were to: - raise the requirements of chemical specifications in line with international standards and compare the technical basis of the different international standards, - strengthen monitoring and anticipation of corrective actions in the field of plant chemistry with a view to extending nuclear plant lifetime to 60 years. This project, scheduled for 2011 to 2016, covers the following activities: - studies on the technical background of the specifications (2011-14), - study of the possibility of adopting an 'Actions Levels' approach in EDF's own specifications (2012-14), - new propositions evolution of the specifications (2015-16). (authors)

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...

Combining microscopy with spectroscopic and chemical methods for tracing the origin of atmospheric fallouts from mining sites

Energy Technology Data Exchange (ETDEWEB)

Navel, Aline; Uzu, Gaëlle; Spadini, Lorenzo [University Grenoble Alpes — LTHE UMR 5564–CNRS-INSU/UGA/INPG/IRD, 1025 rue de la Piscine, DU BP53 - 38041 Grenoble CEDEX 9 (France); Sobanska, Sophie [LASIR, (UMR CNRS 8516), Université de Lille 1, Bât. C5, 59655 Villeneuve d' Ascq CEDEX (France); Martins, Jean M.F., E-mail: jean.martins@yujf-grenoble.fr [University Grenoble Alpes — LTHE UMR 5564–CNRS-INSU/UGA/INPG/IRD, 1025 rue de la Piscine, DU BP53 - 38041 Grenoble CEDEX 9 (France)

2015-12-30

Highlights: • Numerous ancient mines are left over without specific care for contaminated wastes. • Sources similarity makes the tracing of the origin of metallic fallouts challenging. • Physico-chemical fingerprints of all metal-source sites and fallouts were established. • Combining physical/chemical methods allowed discriminating polluted fallouts origin. • A Hierarchical cluster analysis permitted to identify the dominant particles source. - Abstract: Populations living close to mining sites are often exposed to important heavy metal concentrations, especially through atmospheric fallouts. Identifying the main sources of metal-rich particles remains a challenge because of the similarity of the particle signatures from the polluted sites. This work provides an original combination of physical and chemical methods to determine the main sources of airborne particles impacting inhabited zones. Raman microspectrometry (RMS), X-ray diffraction (DRX), morphology analyses by microscopy and chemical composition were assessed. Geochemical analysis allowed the identification of target and source areas; XRD and RMS analysis identified the main mineral phases in association with their metal content and speciation. The characterization of the dominant minerals was combined with particle morphology analysis to identify fallout sources. The complete description of dust morphologies permitted the successful determination of a fingerprint of each source site. The analysis of these chemical and morphological fingerprints allowed identification of the mine area as the main contributor of metal-rich particles impacting the inhabited zone. In addition to the identification of the main sources of airborne particles, this study will also permit to better define the extent of polluted zones requiring remediation or protection from eolian erosion inducing metal-rich atmospheric fallouts.

Combining microscopy with spectroscopic and chemical methods for tracing the origin of atmospheric fallouts from mining sites

International Nuclear Information System (INIS)

Navel, Aline; Uzu, Gaëlle; Spadini, Lorenzo; Sobanska, Sophie; Martins, Jean M.F.

2015-01-01

Highlights: • Numerous ancient mines are left over without specific care for contaminated wastes. • Sources similarity makes the tracing of the origin of metallic fallouts challenging. • Physico-chemical fingerprints of all metal-source sites and fallouts were established. • Combining physical/chemical methods allowed discriminating polluted fallouts origin. • A Hierarchical cluster analysis permitted to identify the dominant particles source. - Abstract: Populations living close to mining sites are often exposed to important heavy metal concentrations, especially through atmospheric fallouts. Identifying the main sources of metal-rich particles remains a challenge because of the similarity of the particle signatures from the polluted sites. This work provides an original combination of physical and chemical methods to determine the main sources of airborne particles impacting inhabited zones. Raman microspectrometry (RMS), X-ray diffraction (DRX), morphology analyses by microscopy and chemical composition were assessed. Geochemical analysis allowed the identification of target and source areas; XRD and RMS analysis identified the main mineral phases in association with their metal content and speciation. The characterization of the dominant minerals was combined with particle morphology analysis to identify fallout sources. The complete description of dust morphologies permitted the successful determination of a fingerprint of each source site. The analysis of these chemical and morphological fingerprints allowed identification of the mine area as the main contributor of metal-rich particles impacting the inhabited zone. In addition to the identification of the main sources of airborne particles, this study will also permit to better define the extent of polluted zones requiring remediation or protection from eolian erosion inducing metal-rich atmospheric fallouts.

Software evolution with XVCL

DEFF Research Database (Denmark)

Zhang, Weishan; Jarzabek, Stan; Zhang, Hongyu

2004-01-01

This chapter introduces software evolution with XVCL (XML-based Variant Configuration Language), which is an XML-based metaprogramming technique. As the software evolves, a large number of variants may arise, especially whtn such kinds of evolutions are related to multiple platforms as shown in our...... case study. Handling variants and tracing the impact of variants across the development lifecycle is a challenge. This chapter shows how we can maintain different versions of software in a reuse-based way....

Comparison of trace element contamination levels (Cu, Zn, Fe, Cd ...

African Journals Online (AJOL)

SERVER

2008-03-18

Mar 18, 2008 ... Chemical analysis of the trace elements in the soft tissues. The trace elements of interest (Cu, Zn, Fe, Pb, Cd) were then determined in the digested solutions, using Thermoelemental type. M6 brand of an atomic absorption Spectrometer equipped with a flame operated atomisation system and a deuterium ...

Observing the metal-poor solar neighbourhood: a comparison of galactic chemical evolution predictions*†

Science.gov (United States)

Mishenina, T.; Pignatari, M.; Côté, B.; Thielemann, F.-K.; Soubiran, C.; Basak, N.; Gorbaneva, T.; Korotin, S. A.; Kovtyukh, V. V.; Wehmeyer, B.; Bisterzo, S.; Travaglio, C.; Gibson, B. K.; Jordan, C.; Paul, A.; Ritter, C.; Herwig, F.; NuGrid Collaboration

2017-08-01

Atmospheric parameters and chemical compositions for 10 stars with metallicities in the region of -2.2 LTE) and non-LTE (NLTE) approaches. In particular, differences by assuming LTE or NLTE are about 0.10 dex; depending on [Fe/H], Teff, gravity and element lines used in the analysis. We find that the O abundance has the largest error, ranging from 0.10 and 0.2 dex. The best measured elements are Cr, Fe, and Mn; with errors between 0.03 and 0.11 dex. The stars in our sample were included in previous different observational work. We provide a consistent data analysis. The data dispersion introduced in the literature by different techniques and assumptions used by the different authors is within the observational errors, excepting for HD103095. We compare these results with stellar observations from different data sets and a number of theoretical galactic chemical evolution (GCE) simulations. We find a large scatter in the GCE results, used to study the origin of the elements. Within this scatter as found in previous GCE simulations, we cannot reproduce the evolution of the elemental ratios [Sc/Fe], [Ti/Fe], and [V/Fe] at different metallicities. The stellar yields from core-collapse supernovae are likely primarily responsible for this discrepancy. Possible solutions and open problems are discussed.

A Web System Trace Model and Its Application to Web Design

OpenAIRE

Kong, Xiaoying; Liu, Li; Lowe, David

2007-01-01

Traceability analysis is crucial to the development of web-centric systems, particularly those with frequent system changes, fine-grained evolution and maintenance, and high level of requirements uncertainty. A trace model at the level of the web system architecture is presented in this paper to address the specific challenges of developing web-centric systems. The trace model separates the concerns of different stakeholders in the web development life cycle into viewpoints; and c...

Partitioning of Trace Elements Between Hydrous Minerals and Aqueous Fluids : a Contribution to the Chemical Budget of Subduction Zones

Science.gov (United States)

Daniel, I.; Koga, K. T.; Reynard, B.; Petitgirard, S.; Chollet, M.; Simionovici, A.

2006-12-01

Subduction zones are powerful chemical engines where the downgoing lithosphere reacts with asthenospheric mantle and produces magmas. Understanding this deep recycling system is a scientific challenge requiring multiple approaches. Among those, it appears that we lack basic information on the composition of the fluid that begins the process of material transfer in subduction zones. Indeed, no pristine fluid sample has yet been collected from this particular environment. Albeit challenging, the alternative would be experimental study of fluids under the appropriate conditions. Consequently, we developed an experimental protocol to measure the concentration of aqueous fluids equilibrated with minerals up to pressures (P) of 5 GPa, at least and temperatures (T) of 550 C. This includes syntheses at high-P and -T conditions, and determination of the fluid composition. Syntheses were performed in a large volume belt-type press at the conditions, 2-5 GPa and ca. 550 C. Oxides or minerals were loaded with water in a gold capsule sealed afterwards. Presence of free fluid during experiments could be confirmed by direct observation of fluid release from the sealed capsule upon puncturing. The composition in trace elements of the fluids that were equilibrated at high-P and -T with minerals was reconstructed from that of the precipitates deposited at the surface of minerals after evaporation of the capsule. The precipitates were dissolved and analyzed by a leaching technique detailed in Koga et al. (2005). Two hydrous minerals of prime interest for subductions were sofar investigated: the high-pressure variety of serpentine, antigorite, and talc. The partitioning coefficients of a series of trace-elements will be presented, as well as their evolution as a function of pressure. Consequences for the composition of the fluids released during the dehydration of hydrous metamorphic minerals will be drawn. Those measurements are unlikely to be feasible at pressures in excess of 5 GPa

Chemical engineering challenges and investment opportunities in sustainable energy.

Science.gov (United States)

Heller, Adam

2008-01-01

The chemical and energy industries are transforming as they adjust to the new era of high-priced petroleum and severe global warming. As a result of the transformation, engineering challenges and investment opportunities abound. Rapid evolution and fast growth are expected in cathode and anode materials as well as polymeric electrolytes for vehicular batteries and in high-performance polymer-ceramic composites for wind turbines, fuel-efficient aircraft, and lighter and safer cars. Unique process-engineering opportunities exist in sand-oil, coal, and possibly also shale liquefaction to produce transportation fuel; and also in genetic engineering of photosynthesizing plants and other organisms for their processing into high-performance biodegradable polymers and high-value-added environmentally friendly chemicals. Also, research on the feasibility of mitigation of global warming through enhancement of CO(2) uptake by the southern oceans by fertilization with trace amounts of iron is progressing. Because chemical engineers are uniquely well trained in mathematical modeling of mass transport, flow, and mixing, and also in cost analysis, they are likely to join the oceanographers and marine biologists in this important endeavor.

Are CO Observations of Interstellar Clouds Tracing the H2?

Science.gov (United States)

Federrath, Christoph; Glover, S. C. O.; Klessen, R. S.; Mac Low, M.

2010-01-01

Interstellar clouds are commonly observed through the emission of rotational transitions from carbon monoxide (CO). However, the abundance ratio of CO to molecular hydrogen (H2), which is the most abundant molecule in molecular clouds is only about 10-4. This raises the important question of whether the observed CO emission is actually tracing the bulk of the gas in these clouds, and whether it can be used to derive quantities like the total mass of the cloud, the gas density distribution function, the fractal dimension, and the velocity dispersion--size relation. To evaluate the usability and accuracy of CO as a tracer for H2 gas, we generate synthetic observations of hydrodynamical models that include a detailed chemical network to follow the formation and photo-dissociation of H2 and CO. These three-dimensional models of turbulent interstellar cloud formation self-consistently follow the coupled thermal, dynamical and chemical evolution of 32 species, with a particular focus on H2 and CO (Glover et al. 2009). We find that CO primarily traces the dense gas in the clouds, however, with a significant scatter due to turbulent mixing and self-shielding of H2 and CO. The H2 probability distribution function (PDF) is well-described by a log-normal distribution. In contrast, the CO column density PDF has a strongly non-Gaussian low-density wing, not at all consistent with a log-normal distribution. Centroid velocity statistics show that CO is more intermittent than H2, leading to an overestimate of the velocity scaling exponent in the velocity dispersion--size relation. With our systematic comparison of H2 and CO data from the numerical models, we hope to provide a statistical formula to correct for the bias of CO observations. CF acknowledges financial support from a Kade Fellowship of the American Museum of Natural History.

Darwinism: Evolution or Revolution?

Science.gov (United States)

Holt, Niles R.

1989-01-01

Maintains that Darwin's theory of evolution was more than a science versus religion debate; rather it was a revolutionary concept that influenced numerous social and political ideologies and movements throughout western history. Traces the impact of Darwin's work historically, utilizing a holistic approach. (RW)

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.

Trace elements in oral health and disease: An updated review

Directory of Open Access Journals (Sweden)

Noopur Kulkarni

2014-01-01

Full Text Available Enzymes of trace elements are an important part of certain biological and chemical reactions. They work in harmony with proteins and often with certain other co enzymes. They attract substrate molecules and enable their conversion to a specific end product. Some trace elements are involved in redox reactions. Modern day diet, comprising of refined foods is a cause of concern, as it may not have a sufficient amount of these trace elements. Dietary supplements may be of required to combat this shortage. The present paper has thoroughly discussed trace elements, as this area of research has not received the deserved attention. Thus, a comprehensive understanding of these trace elements is essential and significant for disease control and for maintaining optimal health.

Effect of fouling on removal of trace organic compounds by nanofiltration

Directory of Open Access Journals (Sweden)

S. Hajibabania

2011-12-01

Full Text Available The fate of chemical of concern is not yet fully understood during treatment of impaired waters. The aim of this paper is to assess the impact of different organic-based fouling layers on the removal of a large range of trace organics. Both model and real water samples (mixed with trace organic contaminants at environmental concentration of 2 μg l⁻¹ were used to simulate fouling in nanofiltration under controlled environment. The new and fouled membranes were systematically characterised for surface charge, hydrophobicity and roughness. It was observed that fouling generally reduced the membrane surface charge; however, the alterations of the membrane hydrophobicity and surface roughness were dependent on the foulants composition. The rejection of charged trace organics was observed to be improved due to the increased electrostatic repulsion by fouled membranes and the adsorption of the trace organic chemicals onto organic matters. On the other hand, the removal of nonionic compounds decreased when fouling occurred, due to the presence of cake enhanced concentration polarization. The fouling layer structure was found to play an important role in the rejection of the trace organic compounds.

Neuronal tracing of oral nerves in a velvet worm – Implications for the evolution of the ecdysozoan brain

Directory of Open Access Journals (Sweden)

Christine eMartin

2014-02-01

Full Text Available As one of the closest relatives of arthropods, Onychophora plays an important role in understanding the evolution of arthropod body plans. Currently there is controversy surrounding the evolution of the brain among the ecdysozoan clades, which shows a collar-shaped, circumoral organisation in cycloneuralians but a ganglionic architecture in panarthropods. Based on the innervation pattern of lip papillae surrounding the mouth, the onychophoran brain has been interpreted as a circumoral ring, suggesting that this organisation is an ancestral feature of Ecdysozoa. However, this interpretation is inconsistent with other published data. To explore the evolutionary origin of the onychophoran mouth and to shed light on the evolution of the ecdysozoan brains, we analysed the innervation pattern and morphogenesis of the oral lip papillae in the onychophoran Euperipatoides rowelli using DNA labelling, immunocytochemistry and neuronal tracing techniques. Our morphogenetic data revealed that the seven paired and one unpaired oral lip papillae arise from three anterior-most body segments. Retrograde fills show that only the first and the third nerves supplying the lip papillae are associated with cell bodies within the brain, whereas the second nerve exclusively receives fibres from somata of peripheral neurons located in the lip papillae. According to our anterograde fills and immunocytochemical data, the first nerve supplies the anterior-most pair of lip papillae, whereas the second and the third nerves are associated with the second to fifth and second to eighth lip papillae, respectively. These data suggest that the lip papillae of E. rowelli are mainly innervated by the proto- and deutocerebrum, whereas there are only a few additional cell bodies situated posterior to the brain. According to these findings, the overall innervation pattern of the oral lip papillae in E. rowelli is incompatible with the interpretation of the onychophoran brain as a

The Evolution of Empathy

Science.gov (United States)

Hackney, Harold

1978-01-01

Therapeutic empathy has been an often-used construct by counseling professionals. Through that usage, the term has evolved in meaning and significance from its original presentation by Carl Rogers. This article traces that evolution by identifying its users and contributors over the past 20 years. (Author)

Energy efficient trace removal by extractive distillation

NARCIS (Netherlands)

Jongmans, M.T.G.

2012-01-01

Separation processes contribute for about 40–70 % to the total energy requirements of the chemical process industry. Especially when trace removal is required to manufacture high purity products, traditional separation technologies become extremely expensive and are not providing satisfying

Oxygen, climate and the chemical evolution of a 1400 million year old tropical marine setting

DEFF Research Database (Denmark)

Wang, Xiaomei; Zhang, Shuichang; Wang, Huajian

2017-01-01

by oxygenated bottom waters. The transition to unit 3 reflects an increase in primary productivity, and the development of a more biologically active OMZ, that supported anoxygenic phototrophic bacteria. Still, in this unit, the bottom waters remained oxygenated. The overlying unit 2 represents the transition...... for the iron. However, the low organic carbon contents, low hydrogen index (HI) values, and the oxidized nature of the reactive iron pool indicate deposition in oxygenated bottom waters. We interpret unit 4 to represent a low-productivity ferruginous oxygen-minimum zone (OMZ) environment, underlain......The Xiamaling Formation is an exceptionally well-preserved sedimentary succession deposited on a marine passive margin about 1400 million years ago. We used a multi-proxy approach, including iron speciation, trace metal dynamics, and organic geochemistry, to explore the evolution of ocean chemistry...

Sampling strategy and analysis of trace element concentrations by inductively coupled plasma mass spectrometry on medieval human bones--the concept of chemical life history.

Science.gov (United States)

Skytte, Lilian; Rasmussen, Kaare Lund

2013-07-30

Medieval human bones have the potential to reveal diet, mobility and treatment of diseases in the past. During the last two decades trace element chemistry has been used extensively in archaeometric investigations revealing such data. Many studies have reported the trace element inventory in only one sample from each skeleton - usually from the femur or a tooth. It cannot a priori be assumed that all bones or teeth in a skeleton will have the same trace element concentrations. Six different bone and teeth samples from each individual were carefully decontaminated by mechanical means. Following dissolution of ca. 20 mg sample in nitric acid and hydrogen peroxide the assays were performed using inductively coupled plasma mass spectrometry (ICPMS) with quadropole detection. We describe the precise sampling technique as well as the analytical methods and parameters used for the ICPMS analysis. The places of sampling in the human skeleton did exhibit varying trace element concentrations. Although the samples are contaminated by Fe, Mn and Al from the surrounding soil where the bones have been residing for more than 500 years, other trace elements are intact within the bones. It is shown that the elemental ratios Sr/Ca and Ba/Ca can be used as indicators of provenance. The differences in trace element concentrations can be interpreted as indications of varying diet and provenance as a function of time in the life of the individual - a concept which can be termed chemical life history. A few examples of the results of such analyses are shown, which contains information about provenance and diagenesis. Copyright © 2013 John Wiley & Sons, Ltd.

Becoming Classical Artemis: A Glimpse at the Evolution of the Goddess as Traced in Ancient Arcadia

Directory of Open Access Journals (Sweden)

Olga Albert Zolotnikova

2017-04-01

Full Text Available This paper is concerned with the evolution of the goddess Artemis in Ancient Greek religion from prehistoric till late historic times. In the related studies, still there is no certainty as to the beginning of worship of Artemis in Ancient Greece and her original concept. Moreover, Artemis’ appearance in the early historic period with the features of the prehistoric Mountain-Mother-Goddess, the Mistress of Animals, the goddess of lakes, the goddess of trees, the goddess of birth and child-care, on the one hand, and as a virgin-huntress who presented rudimentary traits of bear-goddess and deer-goddess, on the other, raises questions whether Artemis originally had all these hypostases or acquired them gradually through assimilation with different goddesses. This paper argues that the concept of Artemis as attested during the historic period was the result of its long development, which consisted of two major phases. Originally, Artemis was a goddess of wild animals and herself was imagined as a bear and a doe. Perhaps, from the beginning, she was regarded as a guardian of sacred rules and a punisher for inappropriate religious behavior. Gradually, Artemis was identified with the old universal goddess of nature and received from her connection with mountain-tops and lakes, responsibility for plant growth and fertility in general, obligation to protect childbirth, etc.. In this paper, the evolution of the concept of Artemis is traced on the basis of her cults practiced in Arcadia, one of a few areas of Ancient Greece where ethno-cultural continuity remained unbroken from prehistoric to late historic times.

Tectono-metamorphic evolution of the Jomolhari massif: Variations in timing of syn-collisional metamorphism across western Bhutan

Science.gov (United States)

Regis, Daniele; Warren, Clare J.; Young, David; Roberts, Nick M. W.

2014-03-01

Our current understanding of the rates and timescales of mountain-building processes is largely based on information recorded in U-bearing accessory minerals such as monazite, which is found in low abundance but which hosts the majority of the trace element budget. Monazite petrochronology was used to investigate the timing of crustal melting in migmatitic metasedimentary rocks from the Jomolhari massif (NW Bhutan). The samples were metamorphosed at upper amphibolite to granulite facies conditions (~ 0.85 GPa, ~ 800 °C), after an earlier High-Pressure stage (P > 1.4 GPa), and underwent partial melting through dehydration melting reactions involving muscovite and biotite. In order to link the timing of monazite growth/dissolution to the pressure-temperature (P-T) evolution of the samples, we identified 'chemical fingerprints' in major and accessory phases that were used to back-trace specific metamorphic reactions. Variations in Eu anomaly and Ti in garnet were linked to the growth and dissolution of major phases (e.g. growth of K-feldspar and dehydration melting of muscovite/biotite). Differences in M/HREE and Y from garnet core to rim were instead related to apatite breakdown and monazite-forming reactions. Chemically zoned monazite crystals reacted multiple times during the metamorphic evolution suggesting that the Jomolhari massif experienced a prolonged high-temperature metamorphic evolution from 36 Ma to 18 Ma, significantly different from the P-T-time path recorded in other portions of the Greater Himalayan Sequence (GHS) in Bhutan. Our data demonstrate unequivocally that the GHS in Bhutan consists of units that experienced independent high-grade histories and that were juxtaposed across different tectonic structures during exhumation. The GHS may have been exhumed in response to (pulsed) mid-crustal flow but cannot be considered a coherent block.

Features in chemical kinetics. I. Signatures of self-emerging dimensional reduction from a general format of the evolution law.

Science.gov (United States)

Nicolini, Paolo; Frezzato, Diego

2013-06-21

Simplification of chemical kinetics description through dimensional reduction is particularly important to achieve an accurate numerical treatment of complex reacting systems, especially when stiff kinetics are considered and a comprehensive picture of the evolving system is required. To this aim several tools have been proposed in the past decades, such as sensitivity analysis, lumping approaches, and exploitation of time scales separation. In addition, there are methods based on the existence of the so-called slow manifolds, which are hyper-surfaces of lower dimension than the one of the whole phase-space and in whose neighborhood the slow evolution occurs after an initial fast transient. On the other hand, all tools contain to some extent a degree of subjectivity which seems to be irremovable. With reference to macroscopic and spatially homogeneous reacting systems under isothermal conditions, in this work we shall adopt a phenomenological approach to let self-emerge the dimensional reduction from the mathematical structure of the evolution law. By transforming the original system of polynomial differential equations, which describes the chemical evolution, into a universal quadratic format, and making a direct inspection of the high-order time-derivatives of the new dynamic variables, we then formulate a conjecture which leads to the concept of an "attractiveness" region in the phase-space where a well-defined state-dependent rate function ω has the simple evolution ω[over dot]=-ω(2) along any trajectory up to the stationary state. This constitutes, by itself, a drastic dimensional reduction from a system of N-dimensional equations (being N the number of chemical species) to a one-dimensional and universal evolution law for such a characteristic rate. Step-by-step numerical inspections on model kinetic schemes are presented. In the companion paper [P. Nicolini and D. Frezzato, J. Chem. Phys. 138, 234102 (2013)] this outcome will be naturally related to the

Feedback interactions between trace metal nutrients and phytoplankton in the ocean

Directory of Open Access Journals (Sweden)

William eSunda

2012-06-01

Full Text Available In addition to control by major nutrient elements (nitrogen, phosphorus, and silicon the productivity and species composition of marine phytoplankton communities are affected by a number of trace metal nutrients (iron, zinc, cobalt, manganese, copper, and cadmium. Of these, iron exerts the greatest limiting influence on carbon fixation rates and has the greatest effect on algal species diversity. It also plays an important role in limiting di-nitrogen (N2 fixation rates, and thus exerts an important influence on ocean inventories of biologically available fixed nitrogen. Because of these effects, iron is thought to play a key role in controlling the biological cycles of carbon and nitrogen in the ocean, including the biological transfer of carbon to the deep sea, the so-called biological CO2 pump, which helps regulate atmospheric CO2 levels and CO2-linked global warming. Other trace metal nutrients (zinc, cobalt, copper, and manganese have a lesser effect on productivity; but may exert an important influence on the species composition of algal communities because of large differences in metal requirements among algal species. The interactions between trace metals and ocean plankton are reciprocal: not only do the metals affect the plankton, but the plankton regulate the distributions, chemical speciation, and cycling of these metals through cellular uptake and regeneration processes, downward flux of biogenic particles, cellular release of organic chelators, and mediation of redox reactions. This two way interaction has influenced not only the biology and chemistry of the modern ocean, but has had a profound influence on biogeochemistry of the ocean and earth system as a whole, and on the evolution marine and terrestrial biology over geologic history.

Effects of Main-Sequence Mass Loss on Stellar and Galactic Chemical Evolution.

Science.gov (United States)

Guzik, Joyce Ann

1988-06-01

L. A. Willson, G. H. Bowen and C. Struck -Marcell have proposed that 1 to 3 solar mass stars may experience evolutionarily significant mass loss during the early part of their main-sequence phase. The suggested mass-loss mechanism is pulsation, facilitated by rapid rotation. Initial mass-loss rates may be as large as several times 10^{-9}M o/yr, diminishing over several times 10^8 years. We attempted to test this hypothesis by comparing some theoretical implications with observations. Three areas are addressed: Solar models, cluster HR diagrams, and galactic chemical evolution. Mass-losing solar models were evolved that match the Sun's luminosity and radius at its present age. The most extreme viable models have initial mass 2.0 M o, and mass-loss rates decreasing exponentially over 2-3 times 10^8 years. Compared to a constant -mass model, these models require a reduced initial ^4He abundance, have deeper envelope convection zones and higher ^8B neutrino fluxes. Early processing of present surface layers at higher interior temperatures increases the surface ^3He abundance, destroys Li, Be and B, and decreases the surface C/N ratio following first dredge-up. Evolution calculations incorporating main-sequence mass loss were completed for a grid of models with initial masses 1.25 to 2.0 Mo and mass loss timescales 0.2 to 2.0 Gyr. Cluster HR diagrams synthesized with these models confirm the potential for the hypothesis to explain observed spreads or bifurcations in the upper main sequence, blue stragglers, anomalous giants, and poor fits of main-sequence turnoffs by standard isochrones. Simple closed galactic chemical evolution models were used to test the effects of main-sequence mass loss on the F and G dwarf distribution. Stars between 3.0 M o and a metallicity -dependent lower mass are assumed to lose mass. The models produce a 30 to 60% increase in the stars to stars-plus -remnants ratio, with fewer early-F dwarfs and many more late-F dwarfs remaining on the main

Chemical processes in the turbine and exhaust nozzle

Energy Technology Data Exchange (ETDEWEB)

Lukachko, S P; Waitz, I A [Massachusetts Inst. of Tech., Cambridge, MA (United States). Aero-Environmental Lab.; Miake-Lye, R C; Brown, R C; Anderson, M R [Aerodyne Research, Inc., Billerica, MA (United States); Dawes, W N [University Engineering Dept., Cambridge (United Kingdom). Whittle Lab.

1998-12-31

The objective is to establish an understanding of primary pollutant, trace species, and aerosol chemical evolution as engine exhaust travels through the nonuniform, unsteady flow fields of the turbine and exhaust nozzle. An understanding of such processes is necessary to provide accurate inputs for plume-wake modeling efforts and is therefore a critical element in an assessment of the atmospheric effects of both current and future aircraft. To perform these studies, a numerical tool was developed combining the calculation of chemical kinetics and one-, two-, or three-dimensional (1-D, 2-D, 3-D) Reynolds-averaged flow equations. Using a chemistry model that includes HO{sub x}, NO{sub y}, SO{sub x}, and CO{sub x} reactions, several 1-D parametric analyses were conducted for the entire turbine and exhaust nozzle flow path of a typical advanced subsonic engine to understand the effects of various flow and chemistry uncertainties on a baseline 1-D result. These calculations were also used to determine parametric criteria for judging 1-D, 2-D, and 3-D modeling requirements as well as to provide information about chemical speciation at the nozzle exit plane. (author) 9 refs.

Chemical processes in the turbine and exhaust nozzle

Energy Technology Data Exchange (ETDEWEB)

Lukachko, S.P.; Waitz, I.A. [Massachusetts Inst. of Tech., Cambridge, MA (United States). Aero-Environmental Lab.; Miake-Lye, R.C.; Brown, R.C.; Anderson, M.R. [Aerodyne Research, Inc., Billerica, MA (United States); Dawes, W.N. [University Engineering Dept., Cambridge (United Kingdom). Whittle Lab.

1997-12-31

The objective is to establish an understanding of primary pollutant, trace species, and aerosol chemical evolution as engine exhaust travels through the nonuniform, unsteady flow fields of the turbine and exhaust nozzle. An understanding of such processes is necessary to provide accurate inputs for plume-wake modeling efforts and is therefore a critical element in an assessment of the atmospheric effects of both current and future aircraft. To perform these studies, a numerical tool was developed combining the calculation of chemical kinetics and one-, two-, or three-dimensional (1-D, 2-D, 3-D) Reynolds-averaged flow equations. Using a chemistry model that includes HO{sub x}, NO{sub y}, SO{sub x}, and CO{sub x} reactions, several 1-D parametric analyses were conducted for the entire turbine and exhaust nozzle flow path of a typical advanced subsonic engine to understand the effects of various flow and chemistry uncertainties on a baseline 1-D result. These calculations were also used to determine parametric criteria for judging 1-D, 2-D, and 3-D modeling requirements as well as to provide information about chemical speciation at the nozzle exit plane. (author) 9 refs.

Sample handling and chemical procedures for efficacious trace analysis of urine by neutron activation analysis

International Nuclear Information System (INIS)

Blotcky, A.J.; Rack, E.P.; Roman, F.R.

1988-01-01

Important for the determination of trace elements, ions, or compounds in urine by chemical neutron activation analysis is the optimization of sample handling, preirradiation chemistry, and radioassay procedures necessary for viable analysis. Each element, because of its natural abundance in the earth's crust and, hence, its potential for reagent and environmental contamination, requires specific procedures for storage, handling, and preirradiation chemistry. Radioassay techniques for radionuclides vary depending on their half-lives and decay characteristics. Described in this paper are optimized procedures for aluminum and selenium. While 28 Al (T 1/2 = 2.24 min) and 77m Se(T 1/2 = 17.4s) have short half-lives, their gamma-ray spectra are quite different. Aluminum-28 decays by a 1779-keV gamma and 77m Se by a 162-keV gamma. Unlike selenium, aluminum is a ubiquitous element in the environment requiring special handling to minimize contamination in all phases of its analytical determination

Inorganic trace analysis by laser ionization mass spectrometry

International Nuclear Information System (INIS)

Becker, S.; Dietze, H.J.

1991-01-01

Among the different spectrometric techniques for trace analysis Laser Ionization Mass Spectrometry (LIMS) is well established as a trace analytic method with a wide coverage. In the LIMS the sample material is evaporated and ionized by means of a focused pulsed laser beam in a laser microplasma, which is formed in the spot area of the irradiated sample. All chemical elements in the sample materials are evaporated and ionized in the laser plasma. The formed ions are separated according to mass and energy by a time-of-flight, quadrupole or double focusing mass spectrometer. In this review the characteristics and analytical features, some recent developments, and applications of laser ionization mass spectrometry in inorganic trace analysis are described. (orig.)

Laser ionization mass spectrometry in inorganic trace analysis

International Nuclear Information System (INIS)

Becker, J.S.; Dietze, H.J.

1992-01-01

Among the different spectrometric techniques for trace analysis Laser Ionization Mass Spectrometry (LIMS) is well established as a trace analytical method. With the LIMS technique the sample material is evaporated and ionized by means of a focused pulsed laser in a laser microplasma, which is formed in the spot area of the irradiated sample. All chemical elements in the sample materials are evaporated and ionized in the laser plasma. The ions formed are separated according to their mass and energy by a time-of-flight, quadrupole or double focusing mass spectrometer. In this review the characteristics and analytical features, some recent developments and applications of laser ionization mass spectrometry in inorganic trace analysis are described. (orig.)

Uptakes of trace elements in Zn-deficient mice

International Nuclear Information System (INIS)

Ohyama, T.; Yanaga, M.; Yoshida, T.; Maetsu, H.; Suganuma, H.; Omori, T.

2002-01-01

A multitracer technique was used to obtain uptake rates of essential trace elements in various organs and tissues in Zn-deficient mice. A multitracer solution, containing more than 20 radioisotopes, was injected intraperitoneally into Zn-deficient state mice and control ones. Uptake rates of the radioisotopes were compared with concentrations of trace elements determined by instrumental neutron activation analysis (INAA) in order to study a specific metabolism of Zn and other essential trace elements, such as Mn, Co, Se, Rb, and Sr. The result suggests that Zn is supplied from bone to other organs and tissues and an increase in Co concentration in all organs and tissues depends on its chemical form, under the Z-deficient state. (author)

APOGEE Chemical Abundances of the Sagittarius Dwarf Galaxy System

Science.gov (United States)

Hasselquist, Sten; Shetrone, Matthew D.; Smith, Verne V.; Holtzman, Jon A.; McWilliam, Andrew; APOGEE Team

2018-06-01

The Apache Point Observatory Galactic Evolution Experiment provides the opportunity of measuring elemental abundances for C, N, O, Na, Mg, Al, Si, P, K, Ca, V, Cr, Mn, Fe, Co, and Ni in vast numbers of stars. We analyze the chemical-abundance patterns of these elements for 158 red giant stars belonging to the Sagittarius dwarf galaxy (Sgr). This is the largest sample of Sgr stars with detailed chemical abundances, and it is the first time that C, N, P, K, V, Cr, Co, and Ni have been studied at high resolution in this galaxy. We find that the Sgr stars with [Fe/H] > -0.8 are deficient in all elemental abundance ratios (expressed as [X/Fe]) relative to the Milky Way, suggesting that the Sgr stars observed today were formed from gas that was less enriched by Type II SNe than stars formed in the Milky Way. By examining the relative deficiencies of the hydrostatic (O, Na, Mg, and Al) and explosive (Si, P, K, and Mn) elements, our analysis supports the argument that previous generations of Sgr stars were formed with a top-light initial mass function, one lacking the most massive stars that would normally pollute the interstellar medium with the hydrostatic elements. We use a simple chemical-evolution model, flexCE, to further support our claim and conclude that recent stellar generations of Fornax and the Large Magellanic Cloud could also have formed according to a top-light initial mass function. We then exploit the unique chemical abundance patters of the Sgr core to trace stars belonging to the Sgr tidal streams elsewhere in the Milky Way.

Use and abuse of trace metal concentrations in plant tissue for biomonitoring and phytoextraction

International Nuclear Information System (INIS)

Mertens, Jan; Luyssaert, Sebastiaan; Verheyen, Kris

2005-01-01

Some plant species accumulate trace metals from the soil in their aboveground biomass. Therefore, some scientists have concluded that these species are suitable for biomonitoring trace metal concentrations in the soil or for removing excessive trace metals from the soil by means of phytoextraction. A significant correlation between the chemical composition of foliage and soil is not a sufficient condition for using the chemical composition of foliage as a biomonitor for the quality of the soil. The chemical composition of foliage can, however, provide additional information to the traditional soil samples. The phytoextraction potential of a plant species cannot solely be evaluated on the basis of the trace metal concentrations in the plant and soil tissue. Data on the depth of the rooting zone, the density of the soil and the harvestable biomass should also be taken into account. Although plant tissue analysis is a useful tool in a wide range of studies and applications, trace metal concentrations in plant tissue cannot be viewed in isolation. Instead it should be analysed and interpreted in relation to other information such as soil concentrations, rooted zone, biomass production, etc. - Plants that accumulate soil metals in their aboveground biomass are often incorrectly considered to be suitable for monitoring soil pollution or for phytoextraction purposes

Evolution of Scale Worms

DEFF Research Database (Denmark)

Gonzalez, Brett Christopher

) caves, and the interstitium, recovering six monophyletic clades within Aphroditiformia: Acoetidae, Aphroditidae, Eulepethidae, Iphionidae, Polynoidae, and Sigalionidae (inclusive of the former ‘Pisionidae’ and ‘Pholoidae’), respectively. Tracing of morphological character evolution showed a high degree...... of adaptability and convergent evolution between relatively closely related scale worms. While some morphological and behavioral modifications in cave polynoids reflected troglomorphism, other modifications like eye loss were found to stem from a common ancestor inhabiting the deep sea, further corroborating...... the deep sea ancestry of scale worm cave fauna. In conclusion, while morphological characterization across Aphroditiformia appears deceptively easy due to the presence of elytra, convergent evolution during multiple early radiations across wide ranging habitats have confounded our ability to reconstruct...

Polyamorphic Transformations in Fe-Ni-C Liquids: Implications for Chemical Evolution of Terrestrial Planets: Fe-Ni-C liquid structural change

Energy Technology Data Exchange (ETDEWEB)

Lai, Xiaojing [Department of Geology and Geophysics, University of Hawai‘i at Mānoa, Honolulu HI USA; Hawaii Institute of Geophysics and Planetology, University of Hawai‘i at Mānoa, Honolulu HI USA; Chen, Bin [Hawaii Institute of Geophysics and Planetology, University of Hawai‘i at Mānoa, Honolulu HI USA; Wang, Jianwei [Department of Geology and Geophysics, Center for Computation and Technology, Louisiana State University, Baton Rouge LA USA; Kono, Yoshio [HPCAT, Geophysical Laboratory, Carnegie Institution of Washington, Argonne IL USA; Zhu, Feng [Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor MI USA

2017-12-01

During the formation of the Earth's core, the segregation of metallic liquids from silicate mantle should have left behind evident geochemical imprints on both the mantle and the core. Some distinctive geochemical signatures of the mantle-derived rocks likely own their origin to the metal-silicate differentiation of the primitive Earth, setting our planet apart from undifferentiated meteorites as well as terrestrial planets or moons isotopically and compositionally. Understanding the chemical evolution of terrestrial planetary bodies requires knowledge on properties of both liquid iron alloys and silicates equilibrating under physicochemical conditions pertinent to the deep magma ocean. Here we report experimental and computational results on the pressure-induced structural evolution of iron-nickel liquids alloyed with carbon. Our X-ray diffraction experiments up to 7.3 gigapascals (GPa) demonstrate that Fe-Ni (Fe90Ni10) liquids alloyed with 3 and 5 wt % carbon undergo a polyamorphic liquid structure transition at approximately 5 GPa. Corroborating the experimental observations, our first-principles molecular dynamic calculations reveal that the structural transitions result from the marked prevalence of three-atom face-sharing polyhedral connections in the liquids at >5 GPa. The structure and polyamorphic transitions of liquid iron-nickel-carbon alloys govern their physical and chemical properties and may thus cast fresh light on the chemical evolution of terrestrial planets and moons.

The importance of radiochemistry and indicator methods for the chemistry of traces

International Nuclear Information System (INIS)

Benes, P.; Majer, V.

1980-01-01

Sensitivity is compared for common chemical methods with respect to nonradioactive materials and methods for determining trace amounts of radioactive substances. The concept of trace amounts is explained and some other notions and terms are discussed from the point of view of chemistry and radiochemistry. The problem of radiation effect is briefly assessed on a sample of material containing trace amounts of a radionuclide and the isotopic effect problem in hydrogen is treated. (M.S.)

Trace metal assay of uranium silicide fuel

International Nuclear Information System (INIS)

Kulkarni, M.J.; Argekar, A.A.; Thulasidas, S.K.; Dhawale, B.A.; Rajeswari, B.; Adya, V.C.; Purohit, P.J.; Neelam, G.; Bangia, T.R.; Page, A.G.; Sastry, M.D.; Iyer, R.H.

1994-01-01

A comprehensive trace metal assay of uranium silicide, a fuel for nuclear research reactors that employs low-enrichment uranium, is carried out by atomic spectrometry. Of the list of specification elements, 21 metallic elements are determined by a direct current (dc) arc carrier distillation technique; the rare earths yttrium and zirconium are chemically separated from the major matrix followed by a dc arc/inductively coupled argon plasma (ICP) excitation technique in atomic emission spectrometry (AES); silver is determined by electrothermal atomization-atomic absorption spectrometry (ETA-AAS) without prior chemical separation of the major matrix. Gamma radioactive tracers are used to check the recovery of rare earths during the chemical separation procedure. The detection limits for trace metallics vary in the 0.1- to 40-ppm range. The precision of the determinations as evaluated from the analysis of the synthetic sample with intermediate range analyte concentration is better than 25% relative standard deviation (RSD) for most of the elements employing dc arc-AES, while that for silver determination by ETS-AAS is 10% RSD. The precision of the determinations for four crucially important rare earths by ICP-AES is better than 3% RSD

Resolving and modelling trace metal partitioning in a freshwater sediment

International Nuclear Information System (INIS)

Devallois, V.; Boyer, P.; Coulomb, B.; Boudenne, J. L.

2009-01-01

Elevated concentrations of trace metals in sediments pose toxicological risks to biota and may impair water quality. the sediment-water interface is the site where gradients in physical, chemical and biological properties are the greatest. Both chemical and microbiological transformation processes are responsible for cycling elements between water and sediments. (Author)

Simulation of the evolution of fused silica's surface defect during wet chemical etching

Science.gov (United States)

Liu, Taixiang; Yang, Ke; Li, Heyang; Yan, Lianghong; Yuan, Xiaodong; Yan, Hongwei

2017-08-01

Large high-power-laser facility is the basis for achieving inertial confinement fusion, one of whose missions is to make fusion energy usable in the near future. In the facility, fused silica optics plays an irreplaceable role to conduct extremely high-intensity laser to fusion capsule. But the surface defect of fused silica is a major obstacle limiting the output power of the large laser facility and likely resulting in the failure of ignition. To mitigate, or event to remove the surface defect, wet chemical etching has been developed as a practical way. However, how the surface defect evolves during wet chemical etching is still not clearly known so far. To address this problem, in this work, the three-dimensional model of surface defect is built and finite difference time domain (FDTD) method is developed to simulate the evolution of surface defect during etching. From the simulation, it is found that the surface defect will get smooth and result in the improvement of surface quality of fused silica after etching. Comparatively, surface defects (e.g. micro-crack, scratch, series of pinholes, etc.) of a typical fused silica at different etching time are experimentally measured. It can be seen that the simulation result agrees well with the result of experiment, indicating the FDTD method is valid for investigating the evolution of surface defect during etching. With the finding of FDTD simulation, one can optimize the treatment process of fused silica in practical etching or even to make the initial characterization of surface defect traceable.

Epidemic contact tracing via communication traces.

Directory of Open Access Journals (Sweden)

Katayoun Farrahi

Full Text Available Traditional contact tracing relies on knowledge of the interpersonal network of physical interactions, where contagious outbreaks propagate. However, due to privacy constraints and noisy data assimilation, this network is generally difficult to reconstruct accurately. Communication traces obtained by mobile phones are known to be good proxies for the physical interaction network, and they may provide a valuable tool for contact tracing. Motivated by this assumption, we propose a model for contact tracing, where an infection is spreading in the physical interpersonal network, which can never be fully recovered; and contact tracing is occurring in a communication network which acts as a proxy for the first. We apply this dual model to a dataset covering 72 students over a 9 month period, for which both the physical interactions as well as the mobile communication traces are known. Our results suggest that a wide range of contact tracing strategies may significantly reduce the final size of the epidemic, by mainly affecting its peak of incidence. However, we find that for low overlap between the face-to-face and communication interaction network, contact tracing is only efficient at the beginning of the outbreak, due to rapidly increasing costs as the epidemic evolves. Overall, contact tracing via mobile phone communication traces may be a viable option to arrest contagious outbreaks.

Epidemic contact tracing via communication traces.

Science.gov (United States)

Farrahi, Katayoun; Emonet, Rémi; Cebrian, Manuel

2014-01-01

Traditional contact tracing relies on knowledge of the interpersonal network of physical interactions, where contagious outbreaks propagate. However, due to privacy constraints and noisy data assimilation, this network is generally difficult to reconstruct accurately. Communication traces obtained by mobile phones are known to be good proxies for the physical interaction network, and they may provide a valuable tool for contact tracing. Motivated by this assumption, we propose a model for contact tracing, where an infection is spreading in the physical interpersonal network, which can never be fully recovered; and contact tracing is occurring in a communication network which acts as a proxy for the first. We apply this dual model to a dataset covering 72 students over a 9 month period, for which both the physical interactions as well as the mobile communication traces are known. Our results suggest that a wide range of contact tracing strategies may significantly reduce the final size of the epidemic, by mainly affecting its peak of incidence. However, we find that for low overlap between the face-to-face and communication interaction network, contact tracing is only efficient at the beginning of the outbreak, due to rapidly increasing costs as the epidemic evolves. Overall, contact tracing via mobile phone communication traces may be a viable option to arrest contagious outbreaks.

Time evolution studies of laser induced chemical changes in InAs nanowire using Raman spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Pal, Suparna; Aggarwal, R.; Kumari Gupta, Vandna; Ingale, Alka [Laser Physics Application Section, Raja Ramanna Centre for Advanced Technology, Indore 452013, MP (India)

2014-07-07

We report the study of time evolution of chemical changes on the surface of an InAs nanowire (NW) on laser irradiation in different power density regime, using Raman spectroscopy for a time span of 8–16 min. Mixture of metastable oxides like InAsO{sub 4,} As{sub 2}O{sub 3} are formed upon oxidation, which are reflected as sharp Raman peaks at ∼240–254 and 180–200 cm{sup −1}. Evidence of removal of arsenic layer by layer is also observed at higher power density. Position controlled laser induced chemical modification on a nanometer scale, without changing the core of the NW, can be useful for NW based device fabrication.

Geological and Chemical Factors that Impacted the Biological Utilization of Cobalt in the Archean Eon

Science.gov (United States)

Moore, Eli K.; Hao, Jihua; Prabhu, Anirudh; Zhong, Hao; Jelen, Ben I.; Meyer, Mike; Hazen, Robert M.; Falkowski, Paul G.

2018-03-01

The geosphere and biosphere coevolved and influenced Earth's biological and mineralogical diversity. Changing redox conditions influenced the availability of different transition metals, which are essential components in the active sites of oxidoreductases, proteins that catalyze electron transfer reactions across the tree of life. Despite its relatively low abundance in the environment, cobalt (Co) is a unique metal in biology due to its importance to a wide range of organisms as the metal center of vitamin B12 (aka cobalamin, Cbl). Cbl is vital to multiple methyltransferase enzymes involved in energetically favorable metabolic pathways. It is unclear how Co availability is linked to mineral evolution and weathering processes. Here we examine important biological functions of Co, as well as chemical and geological factors that may have influenced the utilization of Co early in the evolution of life. Only 66 natural minerals are known to contain Co as an essential element. However, Co is incorporated as a minor element in abundant rock-forming minerals, potentially representing a reliable source of Co as a trace element in marine systems due to weathering processes. We developed a mineral weathering model that indicates that dissolved Co was potentially more bioavailable in the Archean ocean under low S conditions than it is today. Mineral weathering, redox chemistry, Co complexation with nitrogen-containing organics, and hydrothermal environments were crucial in the incorporation of Co in primitive metabolic pathways. These chemical and geological characteristics of Co can inform the biological utilization of other trace metals in early forms of life.

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

The origin and evolution of silicic magmas during continental rifting: new constraints from trace elements and oxygen isotopes from Ethiopian volcanoes

Science.gov (United States)

Hutchison, W.; Boyce, A.; Mather, T. A.; Pyle, D. M.; Yirgu, G.; Gleeson, M. L.

2017-12-01

The petrologic diversity of rift magmas is generated by two key processes: interaction with the crust via partial melting or assimilation; and closed-system fractional crystallization of the parental magma. It is not yet known whether these two petrogenetic processes vary spatially between different rift settings, and whether there are any significant secular variations during rift evolution. The Ethiopian Rift is the ideal setting to test these hypotheses because it captures the transition from continental rifting to sea-floor spreading and has witnessed the eruption of large volumes of mafic and silicic volcanic rocks since 30 Ma. We use new oxygen isotope (δ18O) and trace element data to fingerprint fractional crystallisation and partial crustal melting processes in Ethiopia and evaluate spatial variations between three active rift segments. δ18O measurements are used to examine partial crustal melting processes. We find that most δ18O data from basalts to rhyolites fall within the bounds of modelled fractional crystallization trajectories (i.e., 5.5-6.5 ‰). Few samples deviate from this trend, emphasising that fractional crystallization is the dominant petrogenetic processes and that little fusible Precambrian crustal material (δ18O of 7-18 ‰) remain to be assimilated beneath the magmatic segments. Trace element systematics (e.g., Ba, Sr, Rb, Th and Zr) further underscore the dominant role of fractional crystallization but also reveal important variations in the degree of melt evolution between the volcanic systems. We find that the most evolved silicic magmas, i.e., those with greatest peralkalinity (molar Na2O+K2O>Al2O3), are promoted in regions of lowest magma flux off-axis and along rift. Our findings provide new information on the nature of the crust beneath Ethiopia's active magmatic segments and also have relevance for understanding ancient rift zones and the geotectonic settings that promote genesis of economically-valuable mineral deposits.

Tracing the French Policy PISA Debate: A Policy Configuration Approach

Science.gov (United States)

Pons, Xavier

2016-01-01

This article traces the evolution of the French policy PISA debate from 2001 to 2014 by analysing the results of two original qualitative researches. Theoretically, this debate is the outcome of specific policy configurations, which predetermine its scope, content and effectiveness. These configurations are themselves described through their…

Insights into the evolution of an alkaline magmatic system: An in situ trace element study of clinopyroxenes from the Ditrău Alkaline Massif, Romania

Science.gov (United States)

Batki, Anikó; Pál-Molnár, Elemér; Jankovics, M. Éva; Kerr, Andrew C.; Kiss, Balázs; Markl, Gregor; Heincz, Adrián; Harangi, Szabolcs

2018-02-01

Clinopyroxene is a major constituent in most igneous rock types (hornblendite, diorite, syenite, nepheline syenite, camptonite, tinguaite and ijolite) of the Ditrău Alkaline Massif, Eastern Carpathians, Romania. Phenocryst and antecryst populations have been distinguished based on mineral zoning patterns and geochemical characteristics. Major and trace element compositions of clinopyroxenes reflect three dominant pyroxene types including primitive high-Cr Fe-diopside, intermediate Na-diopside-hedenbergite and evolved high-Zr aegirine-augite. Clinopyroxenes record two major magma sources as well as distinct magma evolution trends. The primitive diopside population is derived from an early camptonitic magma related to basanitic parental melts, whilst the intermediate diopside-hedenbergite crystals represent a Na-, Nb- and Zr-rich magma source recognised for the first time in the Ditrău magmatic system. This magma fractionated towards ijolitic and later phonolitic compositions. Field observations, petrography and clinopyroxene-melt equilibrium calculations reveal magma recharge and mingling, pyroxene recycling, fractional crystallisation and accumulation. Repeated recharge events of the two principal magmas resulted in multiple interactions between more primitive and more fractionated co-existing magma batches. Magma mingling occurred between mafic and felsic magmas by injection of ijolitic magma into fissures (dykes) containing phonolitic (tinguaite) magma. This study shows that antecryst recycling, also described for the first time in Ditrău, is a significant process during magma recharge and demonstrates that incorporated crystals can crucially affect the host magma composition and so whole-rock chemical data should be interpreted with great care.

Evolution of sorption properties in large-scale concrete structures accounting for long-term physical-chemical concrete degradation - 59297

International Nuclear Information System (INIS)

Perko, Janez; Jacques, Diederik; Mallants, Dirk; Seetharam, Suresh

2012-01-01

, Belgium: (i) The procedure begins by the selection of sorption and solubility values pertinent to the type of concrete used for the Dessel near-surface facility. The selection procedure is transparently documented and published in two NIRAS/ONDRAF reports . These reports define sorption values for four distinct chemical degradation states of concrete used in the safety assessments. Most of the selected data is based on experimental sorption data at laboratory scale with benchmark cements. (ii) Cement, however, occupies only a fraction of the total volume of concrete and rescaling of cement sorption values to concrete is an important issue. Though very obvious, this rescaling could be a source of wrong interpretation and, to authors' knowledge, has never been addressed in long-term safety assessments. (iii) Long term evolution of concrete is modelled by the use of a geochemical model supported by a state-of-the-art thermodynamic database. The long-term evolution of the cementitious near field SSCs at the Dessel facility is based on leaching of the reactive phases from the concrete. Evolution of sorption parameters follows the evolution of these cement phases. Distinct sorption values for specific chemical degradation states are linked to the evolution of the calcium silicate hydrates (C-S-H phases) in the cement because they were judged to offer the most robust and unique behaviour applicable to all radionuclides. (iv) Final use of sorption values in safety assessment depends on the conceptual model and purpose of the model. Few examples are discussed in this paper. (authors)

Evolution of Metallic Trace Elements in Contaminated River Sediments: Geochemical Variation Along River Linear and Vertical Profile

Science.gov (United States)

Kanbar, Hussein; Montarges-Pelletier, Emmanuelle; Mansuy-Huault, Laurence; Losson, Benoit; Manceau, Luc; Bauer, Allan; Bihannic, Isabelle; Gley, Renaud; El Samrani, Antoine; Kobaissi, Ahmad; Kazpard, Veronique; Villieras, Frédéric

2015-04-01

Metal pollution in riverine systems poses a serious threat that jeopardizes water and sediment quality, and hence river dwelling biota. Since those metallic pollutants can be transported for long distances via river flow, river management has become a great necessity, especially in times where industrial activities and global climate change are causing metal release and spreading (by flooding events). These changes are able to modify river hydrodynamics, and as a consequence natural physico-chemical status of different aquatic system compartments, which in turn alter metal mobility, availability and speciation. Vertical profiles of sediments hold the archive of what has been deposited for several tenths of years, thus they are used as a tool to study what had been deposited in rivers beds. The studied area lies in the Orne river, northeastern France. This river had been strongly modified physically and affected by steelmaking industrial activities that had boosted in the middle of the last century. This study focuses on several sites along the linear of the Orne river, as well as vertical profiles of sediments. Sediment cores were collected at sites where sedimentation is favoured, and in particular upstream two dams, built in the second half of the XXth century for industrial purposes. Sediment cores were sliced into 2-5cm layers, according to suitability, and analysed for physical and physico-chemical properties, elemental content and mineralogy. Data of the vertical profile in a sediment core is important to show the evolution of sediments as a function of depth, and hence age, in terms of nature, size and constituents. The physical properties include particle size distribution (PSD) and water content. In addition, the physico-chemical properties, such as pH and oxido-reduction potential (ORP) of interstitial water from undisturbed cores were also detected. Total elemental content of sediment and available ones of extracted interstitial waters was detected using

The Fate of Trace Contaminants in a Crewed Spacecraft Cabin Environment

Science.gov (United States)

Perry, Jay L.; Kayatin, Matthew J.

2016-01-01

Trace chemical contaminants produced via equipment offgassing, human metabolic sources, and vehicle operations are removed from the cabin atmosphere by active contamination control equipment and incidental removal by other air quality control equipment. The fate of representative trace contaminants commonly observed in spacecraft cabin atmospheres is explored. Removal mechanisms are described and predictive mass balance techniques are reviewed. Results from the predictive techniques are compared to cabin air quality analysis results. Considerations are discussed for an integrated trace contaminant control architecture suitable for long duration crewed space exploration missions.

Trace contaminant control simulation computer program, version 8.1

Science.gov (United States)

Perry, J. L.

1994-01-01

The Trace Contaminant Control Simulation computer program is a tool for assessing the performance of various process technologies for removing trace chemical contamination from a spacecraft cabin atmosphere. Included in the simulation are chemical and physical adsorption by activated charcoal, chemical adsorption by lithium hydroxide, absorption by humidity condensate, and low- and high-temperature catalytic oxidation. Means are provided for simulating regenerable as well as nonregenerable systems. The program provides an overall mass balance of chemical contaminants in a spacecraft cabin given specified generation rates. Removal rates are based on device flow rates specified by the user and calculated removal efficiencies based on cabin concentration and removal technology experimental data. Versions 1.0 through 8.0 are documented in NASA TM-108409. TM-108409 also contains a source file listing for version 8.0. Changes to version 8.0 are documented in this technical memorandum and a source file listing for the modified version, version 8.1, is provided. Detailed descriptions for the computer program subprograms are extracted from TM-108409 and modified as necessary to reflect version 8.1. Version 8.1 supersedes version 8.0. Information on a separate user's guide is available from the author.

Trace metal speciation: Finally, correctly addressing trace metal issues

International Nuclear Information System (INIS)

Donard, O.F.X.

2001-01-01

The history of the development of trace metal speciation was discussed and the reasons behind the relatively slow widespread acceptance of its importance were presented. Partially, this was due to the lack of availability of commercial instrumentation and partly to the drive towards improving sensitivity in analytical chemistry which had focused attention on total concentration determinations. The sophistication and control of analytical instrumentation is now such that the spotlight must be turned onto the chemical species of an element present in a sample since this is what governs its behaviour in the biosphere. Indeed, several companies are currently considering the introduction of instrumentation specifically designed for metal species determination

Hydro-chemical study of the evolution of interstellar pre-biotic molecules during the collapse of molecular clouds

International Nuclear Information System (INIS)

Majumdar, Liton; Das, Ankan; Chakrabarti, Sandip K.; Chakrabarti, Sonali

2012-01-01

One of the stumbling blocks for studying the evolution of interstellar molecules is the lack of adequate knowledge about the rate coefficients of various reactions which take place in the interstellar medium and molecular clouds. Some theoretical models of rate coefficients do exist in the literature for computing abundances of complex pre-biotic molecules. So far these have been used to study the abundances of these molecules in space. However, in order to obtain more accurate final compositions in these media, we have calculated the rate coefficients for the formation of some of the most important interstellar pre-biotic molecules by using quantum chemical theory. We use these rates inside our hydro-chemical model to examine the chemical evolution and final abundances of pre-biotic species during the collapsing phase of a proto-star. We find that a significant amount of various pre-biotic molecules could be produced during the collapse phase of a proto-star. We thoroughly study the formation of these molecules via successive neutral-neutral and radical-radical/radical-molecular reactions. We present the time evolution of the chemical species with an emphasis on how the production of these molecules varies with the depth of a cloud. We compare the formation of adenine in interstellar space using our rate-coefficients and using those obtained from existing theoretical models. Formation routes of the pre-biotic molecules are found to be highly dependent on the abundances of the reactive species and the rate coefficients involved in the reactions. The presence of grains strongly affects the abundances of the gas phase species. We also carry out a comparative study between different pathways available for the synthesis of adenine, alanine, glycine and other molecules considered in our network. Despite the huge abundances of the neutral reactive species, production of adenine is found to be strongly dominated by the radical-radical/radical-molecular reaction pathways

Ion Formation Resulting from Freezing, Thawing, and Collisional Processes in Plumes Emitted from Planetary Bodies: Implications for Plume Chemistry and the Detection of Trace Organics Present in Enceladus Geysers

Science.gov (United States)

Beauchamp, J. L.; Wiley, J. S.; Thomas, D. A.

2014-12-01

Icy plumes emitted into space from Enceladus and other planetary bodies offer the intriguing possibility of sampling the composition of subsurface liquid reservoirs that may comprise habitable zones of particular astrobiological significance in our solar system. Mass spectrometric sampling of plume materials enables the detection of molecules that facilitate an assessment of the extent of chemical and biological evolution that may have occurred in a subsurface sea. In laboratory experiments we have investigated the physical and chemical processes that occur in the complex plume environment that lead to ionization of trace organic constituents, both as a result of the freezing of liquid droplets and the thawing of icy particles. We also demonstrate that collisions between icy particles lead to triboelectric charging. Subsequent discharges between oppositely charged particles result not only in the ionization of trace organics but to chemical reactions between molecular components present in the particles. For example, nitriles react with water to form amides and acids. In particular, icy particles doped with small amounts of aminoacetonitrile and water lead to the formation of the simplest amino acid glycine. The implications which these observations may have for sampling plume composition from orbit in a future mission to Enceladus will be discussed.

Chemical Continuous Time Random Walks

Science.gov (United States)

Aquino, T.; Dentz, M.

2017-12-01

Traditional methods for modeling solute transport through heterogeneous media employ Eulerian schemes to solve for solute concentration. More recently, Lagrangian methods have removed the need for spatial discretization through the use of Monte Carlo implementations of Langevin equations for solute particle motions. While there have been recent advances in modeling chemically reactive transport with recourse to Lagrangian methods, these remain less developed than their Eulerian counterparts, and many open problems such as efficient convergence and reconstruction of the concentration field remain. We explore a different avenue and consider the question: In heterogeneous chemically reactive systems, is it possible to describe the evolution of macroscopic reactant concentrations without explicitly resolving the spatial transport? Traditional Kinetic Monte Carlo methods, such as the Gillespie algorithm, model chemical reactions as random walks in particle number space, without the introduction of spatial coordinates. The inter-reaction times are exponentially distributed under the assumption that the system is well mixed. In real systems, transport limitations lead to incomplete mixing and decreased reaction efficiency. We introduce an arbitrary inter-reaction time distribution, which may account for the impact of incomplete mixing. This process defines an inhomogeneous continuous time random walk in particle number space, from which we derive a generalized chemical Master equation and formulate a generalized Gillespie algorithm. We then determine the modified chemical rate laws for different inter-reaction time distributions. We trace Michaelis-Menten-type kinetics back to finite-mean delay times, and predict time-nonlocal macroscopic reaction kinetics as a consequence of broadly distributed delays. Non-Markovian kinetics exhibit weak ergodicity breaking and show key features of reactions under local non-equilibrium.

Retrograde monosynaptic tracing reveals the temporal evolution of inputs onto new neurons in the adult dentate gyrus and olfactory bulb

Science.gov (United States)

Deshpande, Aditi; Bergami, Matteo; Ghanem, Alexander; Conzelmann, Karl-Klaus; Lepier, Alexandra; Götz, Magdalena; Berninger, Benedikt

2013-01-01

Identifying the connectome of adult-generated neurons is essential for understanding how the preexisting circuitry is refined by neurogenesis. Changes in the pattern of connectivity are likely to control the differentiation process of newly generated neurons and exert an important influence on their unique capacity to contribute to information processing. Using a monosynaptic rabies virus-based tracing technique, we studied the evolving presynaptic connectivity of adult-generated neurons in the dentate gyrus (DG) of the hippocampus and olfactory bulb (OB) during the first weeks of their life. In both neurogenic zones, adult-generated neurons first receive local connections from multiple types of GABAergic interneurons before long-range projections become established, such as those originating from cortical areas. Interestingly, despite fundamental similarities in the overall pattern of evolution of presynaptic connectivity, there were notable differences with regard to the development of cortical projections: although DG granule neuron input originating from the entorhinal cortex could be traced starting only from 3 to 5 wk on, newly generated neurons in the OB received input from the anterior olfactory nucleus and piriform cortex already by the second week. This early glutamatergic input onto newly generated interneurons in the OB was matched in time by the equally early innervations of DG granule neurons by glutamatergic mossy cells. The development of connectivity revealed by our study may suggest common principles for incorporating newly generated neurons into a preexisting circuit. PMID:23487772

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

International Nuclear Information System (INIS)

Saas, A.; Denardi, J.L.; Colle, C.; Quinault, J.M.

1980-01-01

Molybdenum 99 and technetium 99 from liquid discharges of base nuclear installations (reactors, reprocessing plants, UF 6 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 [fr

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.

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

Science.gov (United States)

Alidina, Mazahirali; Shewchuk, Justin; Drewes, Jörg E

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. Copyright © 2014 Elsevier Ltd. All rights reserved.

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

International Nuclear Information System (INIS)

Condomines, M.; Allegre, C.J.; Tanguy, J.C.; Kieffer, G.

1982-01-01

Age determinations of several lava flows from Etna through 230 Th- 238 U 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 ( 230 Th/ 232 Th) 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)

Photocatalytic hydrogen evolution from aqueous solutions of organophosphorous compounds

Energy Technology Data Exchange (ETDEWEB)

Kozlova, Ekaterina A.; Vorontsov, Alexander V. [Boreskov Institute of Catalysis and Novosibirsk State University, Novosibirsk 630090 (Russian Federation)

2010-07-15

Photocatalytic hydrogen production from water solutions of dimethyl methylphosphonate (DMMP), trimethyl phosphate (TMP), triethyl phosphate (TEP), and radiation protective amine WR 2721, that imitate nerve chemical warfare agents was studied for the first time. Platinized titianium dioxide Degussa P25 was used as catalyst. No significant hydrogen evolution was detected without organic electron donors - sacrificial agents. The hydrogen evolution rate was shown to grow slowly with the rise of initial DMMP concentration. The initial rate vs. DMMP concentration curve is well fitted by Langmuir-Hinshelwood (L-H) equation. The DMMP adsorption constant obtained from the L-H equation fit is markedly higher than that obtained from the Langmuir adsorption isotherm. Reactions of full destruction into inorganic products of the four organophosphorous compounds were conducted. Amounts of evolved hydrogen and carbon dioxide were completely consistent with stoichiometry of proposed reaction. There were no initial compounds and only trace of total organic carbon after the end of the reaction. Complete water purification and production of an amount of valuable hydrogen was achieved. Intermediates of DMMP oxygen-free destruction were identified by means of GC/MS. They were the same as those in the case of DMMP photocatalytic oxidation. A mechanism of hydrogen evolution that explains smaller rates of mineralization compared to photocatalytic oxidation by oxygen was proposed. (author)

Anion-exchange Studies of Radioactive Trace Elements in Sulphuric Acid Solutions

Energy Technology Data Exchange (ETDEWEB)

Samsahl, K

1963-01-15

As part of a chemical group separation procedure used as a pretreatment in gamma spectrometric analysis, a study has been made of the adsorption from sulphuric acid solutions on strongly basic anion exchange resins, prepared in the hydroxide and the sulphate forms, of trace activities of Na, P, K, Ca, Sc, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Rb, Sr, Zr, Nb, Mo, Tc, Ag, Cd, In, Cs, Ba, La, Ce, Hf, Ta, W, Ir, Pa and Np. Besides adsorbing some of the trace elements in the solution, the anion exchange resin in the hydroxide form will neutralize the bulk of the sulphuric acid. This makes possible the subsequent sequential separation of chloride complexes on short anion-exchange columns by a stepwise increasing of the HCl concentration of the solution. On the basis of the results obtained in the present and earlier experiments, a new improved chemical group-separation procedure for mixtures of radioactive trace elements is outlined.

Sorbent control of trace metals in sewage sludge combustion and incineration

Science.gov (United States)

Naruse, I.; Yao, H.; Mkilaha, I. S. N.

2003-05-01

Coal and wastes combustion have become an important issue not only in terms of energy generation but also environmental conservation. The need for alternative fuels and wastes management has made the two energy sources of importance. However, the utilization of the two is faced with problems of impurity trace metals in the fuel. These metals usually speciate during combustion or incineration leading to generation of fumes and subsequently particles. This paper reports on the study aimed at understanding the speciation of trace metals and their emission from combustion systems as particulates. Experiments carried out using a down-flow furnace and theoretical study carried out using lead, chromium and cadmium as basic metals had shown that their speciation and subsequent emission is controlled by both chemical composition and physical properties of the fuel. The physical and chemical and physical properties of the fuel and their respective compounds and the operating conditions of the incineration and combustion system control the enrichment of the particles with trace metals.

Trace conditioning in insects-keep the trace!

Science.gov (United States)

Dylla, Kristina V; Galili, Dana S; Szyszka, Paul; Lüdke, Alja

2013-01-01

Trace conditioning is a form of associative learning that can be induced by presenting a conditioned stimulus (CS) and an unconditioned stimulus (US) following each other, but separated by a temporal gap. This gap distinguishes trace conditioning from classical delay conditioning, where the CS and US overlap. To bridge the temporal gap between both stimuli and to form an association between CS and US in trace conditioning, the brain must keep a neural representation of the CS after its termination-a stimulus trace. Behavioral and physiological studies on trace and delay conditioning revealed similarities between the two forms of learning, like similar memory decay and similar odor identity perception in invertebrates. On the other hand differences were reported also, like the requirement of distinct brain structures in vertebrates or disparities in molecular mechanisms in both vertebrates and invertebrates. For example, in commonly used vertebrate conditioning paradigms the hippocampus is necessary for trace but not for delay conditioning, and Drosophila delay conditioning requires the Rutabaga adenylyl cyclase (Rut-AC), which is dispensable in trace conditioning. It is still unknown how the brain encodes CS traces and how they are associated with a US in trace conditioning. Insects serve as powerful models to address the mechanisms underlying trace conditioning, due to their simple brain anatomy, behavioral accessibility and established methods of genetic interference. In this review we summarize the recent progress in insect trace conditioning on the behavioral and physiological level and emphasize similarities and differences compared to delay conditioning. Moreover, we examine proposed molecular and computational models and reassess different experimental approaches used for trace conditioning.

Neutron-Capture Nucleosynthesis and the Chemical Evolution of Globular Clusters

Science.gov (United States)

Shingles, Luke J.

2015-09-01

Elements heavier than iron are almost entirely produced in stars through neutron captures and radioactive decays. Of these heavy elements, roughly half are produced by the slow neutron-capture process (s-process), which takes place under extended exposure to low neutron densities. Most of the s-process production occurs in stars with initial masses between roughly 0.8 and 8 solar masses (Msun), which evolve through the Asymptotic Giant Branch (AGB) phase. This thesis explores several topics related to AGB stars and the s-process, with a focus on comparing theoretical models to observations in the literature on planetary nebulae, post-AGB stars, and globular cluster stars. A recurring theme is the uncertainty of carbon-13-pocket formation, which is crucial for building accurate models of s-process nucleosynthesis. We first investigated whether neutron-capture reactions in AGB stars are the cause of the low sulphur abundances in planetary nebulae and post-AGB stars relative to the interstellar medium. Accounting for uncertainties in the size of the partial mixing zone that forms carbon-13 pockets and the rates of neutron-capture and neutron-producing reactions, our models failed to reproduce the observed levels of sulphur destruction. From this, we concluded that AGB nucleosynthesis is not the cause of the sulphur anomaly. We also discovered a new method to constrain the extent of the partial mixing zone using neon abundances in planetary nebulae. We next aimed to discover the stellar sites of the s-process enrichment in globular clusters that have inter- and intra-cluster variation, with the examples of M4 (relative to M5) and M22, respectively. Using a new chemical evolution code developed by the candidate, we tested models with stellar yields from rotating massive stars and AGB stars. We compared our model predictions for the production of s-process elements with abundances from s-poor and s-rich populations. We found that rotating massive stars alone do not

Trace metal physiology in normal and pathological tissues

International Nuclear Information System (INIS)

Hamer, C.J.A. van den; Nooijen, J.L.

1979-01-01

Many of the ionic tumour seeking radiopharmaceuticals consist of a metal ion combined with an anion. The choice of metal depends on the existence of radionuclides with suitable radiological properties, and on their availability. Because several of the metal complexes used in nuclear medicine are of rather recent interest, information about their metabolism is scarce. Although nuclear medicine is limited to those metals which radiochemists can produce, we can manipulate the chemical form in which the metals are introduced into the organism to some extent. The relation between chemical form and biological pathway, e.g., the extent of accumulation in certain tissues, is subject of study related to trace metal physiology. It is the purpose of this paper to try and bridge the gap between nuclear medicine and trace metal physiology by showing the progress made by the latter in the study of the metabolism of copper and zinc. Few trace metals have been studied as thoroughly as these, although iron could have been chosen just as well. This presentation is limited to a study of the fate of a metal derivative after its intravenous injection. Where possible the results obtained are related to the behaviour of metals presently of interest to nuclear medicine. (Auth.)

Galactic chemical evolution with main-sequence mass loss and the distribution of F and G dwarfs

International Nuclear Information System (INIS)

Guzik, J.A.; Struck-Marcell, C.

1988-01-01

Simple closed galactic chemical-evolution models incorporating early main-sequence stellar mass loss have been developed for disk ages of 5, 10, and 15 Gyr. Relative to models without stellar mass loss, the models are shown to produce a 30-60 percent increase in the present mass ratio of dwarfs to dwarfs plus remnants, and a 200-250 percent increase in the total mass of late F dwarfs remaining on the main sequence at the current disk age. For present disk ages 5 and 10 Gyr, the total mass of mid-F dwarfs remaining on the main sequence is also shown to increase by 90-120 percent. It is concluded that models with main-sequence mass loss have a slightly reduced gas metallicity and slightly increased gas fraction midway through the evolution. 30 references

Hyperspectral imaging for non-contact analysis of forensic traces

NARCIS (Netherlands)

Edelman, G. J.; Gaston, E.; van Leeuwen, T. G.; Cullen, P. J.; Aalders, M. C. G.

2012-01-01

Hyperspectral imaging (HSI) integrates conventional imaging and spectroscopy, to obtain both spatial and spectral information from a specimen. This technique enables investigators to analyze the chemical composition of traces and simultaneously visualize their spatial distribution. HSI offers

Diffusive exchange of trace elements between basaltic-andesite and dacitic melt: Insights into potential metal fractionation during magma mixing

Science.gov (United States)

Fiege, A.; Ruprecht, P.; Simon, A. C.; Holtz, F.

2017-12-01

Mafic magma recharge is a common process that triggers physical and chemical mixing in magmatic systems and drives their evolution, resulting in, e.g., hybridization and volcanic eruptions. Once magma-magma contact is initiated, rapid heat-flux commonly leads to the formation of a cooling-induced crystal mush on the mafic side of the interface. Here, on a local scale (µm to cm), at the magma-magma interface, melt-melt diffusive exchange is required to approach equilibrium. Significant chemical potential gradients drive a complex, multi-element mass flux between the two systems (Liang, 2010). This diffusive-equilibration often controls crystal dissolution rates within the boundary layers and, thus, the formation of interconnected melt or fluid networks. Such networks provide important pathways for the transport of volatiles and trace metals from the mafic recharge magma to the felsic host magma, where the latter may feed volcanic activities and ore deposits. While major element diffusion in silicate melts is mostly well understood, even in complex systems, the available data for many trace element metals are limited (Liang, 2010; Zhang et al., 2010). Differences in diffusivity in a dynamic, mixing environment can cause trace element fractionation, in particular during crystallization and volatile exsolution and separation. This may affect trace element signatures in phenocrysts and magmatic volatile phases that can form near a magma-magma boundary. As a result, the chemistry of volcanic gases and magmatic-hydrothermal ore deposits may be partially controlled by such mixing phenomena. We performed melt-melt diffusion-couple experiments at 150 MPa, 1100°C, FMQ, FMQ+1 and FMQ+3 (FMQ: fayalite-magnetite-quartz oxygen fugacity buffer). Hydrated, sulfur-bearing cylinders of dacite and basaltic andesite were equilibrated for up to 20 h. Major and trace element gradients were measured by using laser-ablation ICP-MS and electron microprobe analyses. The results we will

Evolution of Deeply Embedded Protostars

DEFF Research Database (Denmark)

Frimann, Søren

consequences for the evolution of protostellar systems. The sublimation of CO-ice from dust grains in the surrounding envelope can be used to trace accretion variability in protostars, because the increased heating during an accretion burst will cause the CO-ice to sublimate into the gas-phase where the excess...

Second Symposium on Chemical Evolution and the Origin of Life

International Nuclear Information System (INIS)

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)

Geohistory. Global evolution of the earth

Energy Technology Data Exchange (ETDEWEB)

Ozima, Minoru

1987-01-01

A full understanding of the earth's evolution can be achieved only by considering it as a continuous process starting with the birth of the solar system. This book traces the evolution of the earth, mainly on the basis of radiogenic isotopes from long half-life parent elements, and discusses it in terms of the latest developments in astrophysical theory, which impose unique constraints on the earth's origin and early evolution. By its 'historical' nature, geohistorical study also offers a unique approach to forecasting the future of the earth, yielding useful clues for the understanding of environmental problems, such as radioactive waste disposal. This book aims to provide an outline of global evolution of the planet earth for students of general science and for earth scientists.

The dimensionality of stellar chemical space using spectra from the Apache Point Observatory Galactic Evolution Experiment

Science.gov (United States)

Price-Jones, Natalie; Bovy, Jo

2018-03-01

Chemical tagging of stars based on their similar compositions can offer new insights about the star formation and dynamical history of the Milky Way. We investigate the feasibility of identifying groups of stars in chemical space by forgoing the use of model derived abundances in favour of direct analysis of spectra. This facilitates the propagation of measurement uncertainties and does not pre-suppose knowledge of which elements are important for distinguishing stars in chemical space. We use ˜16 000 red giant and red clump H-band spectra from the Apache Point Observatory Galactic Evolution Experiment (APOGEE) and perform polynomial fits to remove trends not due to abundance-ratio variations. Using expectation maximized principal component analysis, we find principal components with high signal in the wavelength regions most important for distinguishing between stars. Different subsamples of red giant and red clump stars are all consistent with needing about 10 principal components to accurately model the spectra above the level of the measurement uncertainties. The dimensionality of stellar chemical space that can be investigated in the H band is therefore ≲10. For APOGEE observations with typical signal-to-noise ratios of 100, the number of chemical space cells within which stars cannot be distinguished is approximately 1010±2 × (5 ± 2)n - 10 with n the number of principal components. This high dimensionality and the fine-grained sampling of chemical space are a promising first step towards chemical tagging based on spectra alone.

Rice flakes produced from commercial wild rice: Chemical compositions, vitamin B compounds, mineral and trace element contents and their dietary intake evaluation.

Science.gov (United States)

Sumczynski, Daniela; Koubová, Eva; Šenkárová, Lenka; Orsavová, Jana

2018-10-30

Non-traditional wild rice flakes were analysed for chemical composition, vitamin B compounds, α-tocopherol, mineral and trace elements. Dietary intakes of vitamins, minerals and trace elements were evaluated using FAO/WHO and Institute of Medicine regulations. Wild rice flakes proved to be significant contributors of pyridoxine, pantothenic and folic acids, niacin, thiamine, chromium, magnesium, manganese, phosphorus, zinc, copper, molybdenum and iron to essential dietary intakes values. Toxic dietary intake values for aluminium, cadmium, tin and mercury were less than 33%, which complies the limits for adults set by FAO/WHO for toxic elements intake related to the body weight of 65 kg for females and 80 kg for males taking 100 g of flakes as a portion. However, concentrations of Hg reaching between 3.67 and 12.20 µg/100 g in flakes exceeded the average Hg value of 0.27-1.90 μg/100 g in cereals consumed in the EU. It has to be respected in the future. Copyright © 2018 Elsevier Ltd. All rights reserved.

Variations in atmospheric PM trace metal content in Spanish towns: Illustrating the chemical complexity of the inorganic urban aerosol cocktail

Science.gov (United States)

Moreno, Teresa; Querol, Xavier; Alastuey, Andrés; Viana, Mar; Salvador, Pedro; Sánchez de la Campa, Ana; Artiñano, Begoña; de la Rosa, Jesús; Gibbons, Wes

The majority of the Spanish urban population breathe air containing inhalable ambient airborne particles at average concentrations of 30-46 μg m -3 (PM 10) and 20-30 μg m -3 (PM 2.5). Even though the average weight of inhaled urban aerosol is commonly similar, however, there can be large chemical differences between the ambient dusts from different towns, including the more bioreactive elements such as some metals. In this context, we compare the source-apportioned trace metal content of airborne PM 10 and PM 2.5 collected daily over a 1-year period from six population centres in Spain: Barcelona, Alcobendas, Llodio, Huelva, Tarragona and Las Palmas de Gran Canaria. Total average trace metal (ΣTM) PM 10 and PM 2.5 contents vary by up to a factor of around 3, reaching a maximum of ΣTM 10 811 ng m -3 and ΣTM 2.5 503 ng m -3 at Llodio, an industrial but humid site with the lowest PM 10 mass levels but high contamination by Zn, Pb, Mn, Sn, Ni and Cr. In contrast, pollution at Huelva, although another industrially influenced site, instead emphasises Cu and As, whereas Barcelona, where traffic emissions and resuspension contribute to some of the highest average PM 10 levels in Spain, has unusually raised levels of Ti, V and Ba. Such variations in both daily and annual average PM bulk chemistry, particularly in potentially toxic trace metals concentrated in the finer aerosols (such as Cd, As, Pb, Hg and Ni), predict that PM health effects on resident populations from different towns are unlikely to be the same.

Trace metals in corals--hind casting environmental chemical changes in the tropical Atlantic waters

Science.gov (United States)

Holmes, C. W.; Koenig, A.; Ridley, W. I.; Wilson, S. A.

2002-12-01

As corals grow, they secrete a calcareous skeleton with the aid of photosynthetic activity of endosymbiotic dinoflagellates (zooxanthellae). The rate of this secretion varies inter-annually. Entrapped with the carbonate are trace substances that record the chemistry of the surrounding ocean. Detailing changes in chemistry requires careful and very tedious high-resolution sampling. The advent of laser ablation inductive couple plasma/mass spectroscopy (LA-ICP/MS) circumvents this sampling problem. This method also permits a continuous scan of the entire coral skeleton. Another problem has been the lack of a carbonate standard which appears to be resolved with the creation of an artificial carbonate standard (USGS MAC-1). This standard is presently undergoing rigorous analysis, but preliminary results are very positive. The LA-ICP/MS data of three Atlantic corals reveals an intriguing distribution of trace metals and boron that may be related to climatic driven chemical changes during the last hundred years. The distribution of the trace metals appears to have an association with three climate signals: 1. the strength of the North Atlantic Oscillation (NAO), 2. the local effects of El Nino in the Florida region and 3. change in oceanic chemistry, possibly due to rising CO2. Aluminum and titanium levels vary with the strength of the NAO. The highest concentrations occur at the time of strong positive NOA when there is large amount of sediment transported off the deserts of North Africa. This relationship is particularly strong in the coral from the Cape Verde Islands. Along the eastern seaboard of the Atlantic, the relationship is not as pronounced but still observable. Nutrients and anthropogenic trace metals, such as zinc, lead, and mercury appear to correlate with local conditions and show a weak correspondence to the El Nino as it affects south Florida. Boron variation is directly related to the high-density bands of the corals. The long-term record of boron

Partitioning of trace metals in the chemical fractions of bed-load sediments of Nahr-Ibrahim river, Lebanon

International Nuclear Information System (INIS)

Korfali, Samira I.; Davies, Brian E.

1999-01-01

Full text.Sediments are the ultimate sink of trace elements. The total metal analysis may only give information concerning possible enrichment of metals. The analysis of metal partitioning in the different chemical components of sediments (exchangeable, carbonate, easily reducible, moderately reducible, organic and residual); give a detailed information on the way in which these metals are bound to sediments, their mobilization capacity and their ability to affect water quality under different environmental conditions. The studied river basin is dominated by limestone formation, the enrichment of metals in the carbonate sediment fraction is a high probability. The objective of the study was to determine the percentage of the total metal content (Fe, Mn, Zn, Cu and Pb) in the six chemical fractions of the bed load sediments of Nahr-Ibrahim river during the dry season and verify the role of carbonate for metal sediment deposition. Bed load sediments were sampled at five locations 13Km stretch, upstream from river mouth at two dates, August and October 1996. the dried samples were sieved into three mechanical fractions (1180-250 μm, 250-75 μm and <75 μm). A sequential chemical extraction was carried on each sized sample sediment, Fe, Mn, Zn, Cu and Pb were determined on the extracts by AAS. The reported data showed that Fe in mainly in the residual fraction, Mn in the residual and carbonate fraction, Zn in the residual, carbonate and Fe oxide fraction, Cu in the residual, carbonate and organic fraction, Pb in the carbonate fraction. The carbonate fraction in sediments played the major common role for metal sediment deposition

Adsorption and Detection of Hazardous Trace Gases by Metal-Organic Frameworks.

Science.gov (United States)

Woellner, Michelle; Hausdorf, Steffen; Klein, Nicole; Mueller, Philipp; Smith, Martin W; Kaskel, Stefan

2018-06-19

The quest for advanced designer adsorbents for air filtration and monitoring hazardous trace gases has recently been more and more driven by the need to ensure clean air in indoor, outdoor, and industrial environments. How to increase safety with regard to personal protection in the event of hazardous gas exposure is a critical question for an ever-growing population spending most of their lifetime indoors, but is also crucial for the chemical industry in order to protect future generations of employees from potential hazards. Metal-organic frameworks (MOFs) are already quite advanced and promising in terms of capacity and specific affinity to overcome limitations of current adsorbent materials for trace and toxic gas adsorption. Due to their advantageous features (e.g., high specific surface area, catalytic activity, tailorable pore sizes, structural diversity, and range of chemical and physical properties), MOFs offer a high potential as adsorbents for air filtration and monitoring of hazardous trace gases. Three advanced topics are considered here, in applying MOFs for selective adsorption: (i) toxic gas adsorption toward filtration for respiratory protection as well as indoor and cabin air, (ii) enrichment of hazardous gases using MOFs, and (iii) MOFs as sensors for toxic trace gases and explosives. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

GALACTIC CHEMICAL EVOLUTION: THE IMPACT OF THE 13C-POCKET STRUCTURE ON THE s -PROCESS DISTRIBUTION

International Nuclear Information System (INIS)

Bisterzo, S.; Travaglio, C.; Wiescher, M.; Käppeler, F.; Gallino, R.

2017-01-01

The solar s -process abundances have been analyzed in the framework of a Galactic Chemical Evolution (GCE) model. The aim of this work is to implement the study by Bisterzo et al., who investigated the effect of one of the major uncertainties of asymptotic giant branch (AGB) yields, the internal structure of the 13 C pocket. We present GCE predictions of s -process elements computed with additional tests in the light of suggestions provided in recent publications. The analysis is extended to different metallicities, by comparing GCE results and updated spectroscopic observations of unevolved field stars. We verify that the GCE predictions obtained with different tests may represent, on average, the evolution of selected neutron-capture elements in the Galaxy. The impact of an additional weak s -process contribution from fast-rotating massive stars is also explored.

Preconcentration and Speciation of Trace Elements and Trace-Element Analogues of Radionuclides by Neutron Activation Analysis

International Nuclear Information System (INIS)

Chatt, A.

1999-01-01

We have developed a number of preconcentration neutron activation analysis (PNAA) methods in our laboratory for the determination of trace elements in a variety of complex sample matrices. We developed a number of cocrystallization and coprecipitation methods for the determination of trace elements in water samples. We developed several methods for the determination of I in foods and diets. We have developed a number of PNAA methods in our laboratory We determined As and Sb in geological materials and natural waters by coprecipitation with Se and Au in silicate rocks and ores by coprecipitation with Te followed by NAA. We developed an indirect NAA method for the determination of B in leachates of borosilicate glass. We have been interested in studying the speciation of Am, Tc, and Np in simulated vitrified groundwater leachates of high-level wastes under oxid and anoxic conditions using a number of techniques. We then used PNAA methods to study speciation of trace-element analogues of radionuclides. We have been able to apply biochemical techniques and NAA for the separation, preconcentration, and characterization of metalloprotein and protein-bound trace-element species in subcellular fractions of bovine kidneys. Lately, we have concentrated our efforts to develop chemical and biochemical methods in conjunction with NAA, NMR, and MS for the separation and identification of extractable organohalogens (EOX) in tissues of beluga whales, cod, and northern pink shrimp

Decomposition of a hierarchy of nonlinear evolution equations

International Nuclear Information System (INIS)

Geng Xianguo

2003-01-01

The generalized Hamiltonian structures for a hierarchy of nonlinear evolution equations are established with the aid of the trace identity. Using the nonlinearization approach, the hierarchy of nonlinear evolution equations is decomposed into a class of new finite-dimensional Hamiltonian systems. The generating function of integrals and their generator are presented, based on which the finite-dimensional Hamiltonian systems are proved to be completely integrable in the Liouville sense. As an application, solutions for the hierarchy of nonlinear evolution equations are reduced to solving the compatible Hamiltonian systems of ordinary differential equations

Trace Detection of Organophosphorus Chemical Warfare Agents in Wastewater and Plants by Luminescent UIO-67(Hf) and Evaluating the Bioaccumulation of Organophosphorus Chemical Warfare Agents.

Science.gov (United States)

Lian, Xiao; Yan, Bing

2018-05-02

Organophosphorus chemical warfare agents (OPCWAs) are a group of organic pollutants characterized by high toxicity and chemical stability, and they are very difficult to be degraded. The trace quality of OPCWAs in water and food will cause great harm to the human body. Therefore, the detection of OPCWAs is a difficult challenge, which has become the research hotspot over the world. In this work, a Hf-based luminescent metal-organic framework (Eu@1) is prepared, and the reactivity of Hf 12 results in a methanephosphonic acid (MPA)-induced luminescence quenching and the charge transfer from MPA to Hf(IV) and generated exciplexes which are responsible for this quenching effect. The excellent performance of Eu@1 in the detection of MPA, with its finer selectivity, high sensitivity (LOD = 0.4 ppm), and large linear range (10 -7 to 10 -3 M), is encouraging for application in wastewater detection. Importantly, MPA is a pollutant that can be absorbed by plants and causes the bioaccumulation effect, and thus, the detection of MPA in real plant samples is a purposeful topic. Eu@1 also achieved satisfactory results in actual plant sample testing, and the bioaccumulation of MPA in onions, turnips, and cabbages is determined via our sensor. This fabricated detector provides a feasible path for the detection of ppm-level OPCWAs in a complex environment, which will help humans to avoid OPCWA-contaminated foods.

General constraints on the age and chemical evolution of the Galaxy

International Nuclear Information System (INIS)

Meyer, B.S.; Schramm, D.N.

1986-05-01

The formalism of Schramm and Wasserburg (1970) for determining the mean age of the elements is extended. Model-independent constraints (constraints that are independent of a specific form for the effective nucleosynthesis rate and Galactic chemical evolution over time) are derived on the first four terms in the expansion giving the mean age of the elements, and from these constraints limits are derived on the total duration of nucleosynthesis. These limits require only input of the Schramm-Wasserburg parameter Δ/sup max/ and of the ratio of the mean time for formation of the elements to the total duration of nucleosynthesis, t/sub nu//T. The former quantity is a function of nuclear input parameters. Limits on the latter are obtained from constraints on the relative rate of nucleosynthesis derived from the 232 Th/ 238 U, 235 U/ 238 U, and shorter-lived chronometric pairs. 65 refs

Role of Metal Oxides in Chemical Evolution: Interaction of Ribose Nucleotides with Alumina

Science.gov (United States)

Arora, Avnish Kumar; Kamaluddin

2009-03-01

Interaction of ribonucleotides—namely, 5‧-AMP, 5‧-GMP, 5‧-CMP, and 5‧-UMP—with acidic, neutral, and basic alumina has been studied. Purine nucleotides showed higher adsorption on alumina in comparison with pyrimidine nucleotides under acidic conditions. Adsorption data obtained followed Langmuir adsorption isotherm, and Xm and KL values were calculated. On the basis of infrared spectral studies of ribonucleotides, alumina, and ribonucleotide-alumina adducts, we propose that the nitrogen base and phosphate moiety of the ribonucleotides interact with the positive charge surface of alumina. Results of the present study may indicate the importance of alumina in concentrating organic molecules from dilute aqueous solutions in primeval seas in the course of chemical evolution on Earth.

Geohistory: Global evolution of the earth

International Nuclear Information System (INIS)

Ozima, M.

1987-01-01

This book traces the evolution of the Earth, mainly on the basis of radiogenic isotopes from half-life parent elements, and discusses it in terms of the latest developments in astrophysical theory, which impose unique constraints on the origin and early evolution of the earth. Owing to its historical nature, this geohistorical study offers an approach to forecasting the future of the Earth yielding clues for the understanding of environmental problems, such as radioactive waste to disposal and climate changes due to CO/sub 2/ increase

Chemical Evolution and Star Formation History of the Disks of Spirals in Local Group

Science.gov (United States)

Yin, J.

2011-05-01

Milky Way (MW), M31 and M33 are the only three spiral galaxies in our Local group. MW and M31 have similar mass, luminosity and morphology, while M33 is only about one tenth of MW in terms of its baryonic mass. Detailed theoretical researches on these three spirals will help us to understand the formation and evolution history of both spiral galaxies and Local group. Referring to the phenomenological chemical evolution model adopted in MW disk, a similar model is established to investigate the star formation and chemical enrichment history of these three local spirals. Firstly, the properties of M31 disk are studied by building a similar chemical evolution model which is able to successfully describe the MW disk. It is expected that a simple unified phenomenological chemical evolution model could successfully describe the radial and global properties of both disks. Comparing with the former work, we adopt an extensive data set as model constraints, including the star formation profile of M31 disk derived from the recent UV data of GALEX. The comparison among the observed properties of these two disks displays very interesting similarities in their radial profiles when the distance from the galactic center is expressed in terms of the corresponding scale length. This implies some common processes in their formation and evolution history. Based on the observed data of the gas mass surface density and SFR surface density, the SFR radial profile of MW can be well described by Kennicutt-Schmidt star formation law (K-S law) or modified K-S law (SFR is inversely proportional to the distance from the galactic center), but this is not applicable to the M31 disk. Detailed calculations show that our unified model describes fairly well all the main properties of the MW disk and most properties of M31 disk, provided that the star formation efficiency of M31 disk is adjusted to be twice as large as that of MW disk (as anticipated from the lower gas fraction of M31). However, the

Trace conditioning in insects – Keep the trace!

Directory of Open Access Journals (Sweden)

Kristina V Dylla

2013-08-01

Full Text Available Trace conditioning is a form of associative learning that can be induced by presenting a conditioned stimulus (CS and an unconditioned stimulus (US following each other, but separated by a temporal gap. This gap distinguishes trace conditioning from classical delay conditioning, where the CS and US overlap. To bridge the temporal gap between both stimuli and to form an association between CS and US in trace conditioning, the brain must keep a neural representation of the CS after its termination – a stimulus trace. Behavioral and physiological studies on trace and delay conditioning revealed similarities between the two forms of learning, like similar memory decay and similar odor identity perception in invertebrates. On the other hand differences were reported also, like the requirement of distinct brain structures in vertebrates or disparities in molecular mechanisms in both vertebrates and invertebrates. For example, in commonly used vertebrate conditioning paradigms the hippocampus is necessary for trace but not for delay conditioning, and Drosophila delay conditioning requires the Rutabaga adenylyl cyclase, which is dispensable in trace conditioning. It is still unknown how the brain encodes CS traces and how they are associated with a US in trace conditioning. Insects serve as powerful models to address the mechanisms underlying trace conditioning, due to their simple brain anatomy, behavioral accessibility and established methods of genetic interference. In this review we summarize the recent progress in insect trace conditioning on the behavioral and physiological level and emphasize similarities and differences compared to delay conditioning. Moreover, we examine proposed molecular and computational models and reassess different experimental approaches used for trace conditioning.

THE STAR FORMATION HISTORY AND CHEMICAL EVOLUTION OF STAR-FORMING GALAXIES IN THE NEARBY UNIVERSE

International Nuclear Information System (INIS)

Torres-Papaqui, J. P.; Coziol, R.; Ortega-Minakata, R. A.; Neri-Larios, D. M.

2012-01-01

We have determined the metallicity (O/H) and nitrogen abundance (N/O) of a sample of 122,751 star-forming galaxies (SFGs) from the Data Release 7 of the Sloan Digital Sky Survey. For all these galaxies we have also determined their morphology and obtained a comprehensive picture of their star formation history (SFH) using the spectral synthesis code STARLIGHT. The comparison of the chemical abundance with the SFH allows us to describe the chemical evolution of the SFGs in the nearby universe (z ≤ 0.25) in a manner consistent with the formation of their stellar populations and morphologies. A high fraction (45%) of the SFGs in our sample show an excess abundance of nitrogen relative to their metallicity. We also find this excess to be accompanied by a deficiency of oxygen, which suggests that this could be the result of effective starburst winds. However, we find no difference in the mode of star formation of the nitrogen-rich and nitrogen-poor SFGs. Our analysis suggests that they all form their stars through a succession of bursts of star formation extended over a period of few Gyr. What produces the chemical differences between these galaxies seems therefore to be the intensity of the bursts: the galaxies with an excess of nitrogen are those that are presently experiencing more intense bursts or have experienced more intense bursts in their past. We also find evidence relating the chemical evolution process to the formation of the galaxies: the galaxies with an excess of nitrogen are more massive, and have more massive bulges and earlier morphologies than those showing no excess. Contrary to expectation, we find no evidence that the starburst wind efficiency decreases with the mass of the galaxies. As a possible explanation we propose that the loss of metals consistent with starburst winds took place during the formation of the galaxies, when their potential wells were still building up, and consequently were weaker than today, making starburst winds more

Classification and Lineage Tracing of SH2 Domains Throughout Eukaryotes.

Science.gov (United States)

Liu, Bernard A

2017-01-01

Today there exists a rapidly expanding number of sequenced genomes. Cataloging protein interaction domains such as the Src Homology 2 (SH2) domain across these various genomes can be accomplished with ease due to existing algorithms and predictions models. An evolutionary analysis of SH2 domains provides a step towards understanding how SH2 proteins integrated with existing signaling networks to position phosphotyrosine signaling as a crucial driver of robust cellular communication networks in metazoans. However organizing and tracing SH2 domain across organisms and understanding their evolutionary trajectory remains a challenge. This chapter describes several methodologies towards analyzing the evolutionary trajectory of SH2 domains including a global SH2 domain classification system, which facilitates annotation of new SH2 sequences essential for tracing the lineage of SH2 domains throughout eukaryote evolution. This classification utilizes a combination of sequence homology, protein domain architecture and the boundary positions between introns and exons within the SH2 domain or genes encoding these domains. Discrete SH2 families can then be traced across various genomes to provide insight into its origins. Furthermore, additional methods for examining potential mechanisms for divergence of SH2 domains from structural changes to alterations in the protein domain content and genome duplication will be discussed. Therefore a better understanding of SH2 domain evolution may enhance our insight into the emergence of phosphotyrosine signaling and the expansion of protein interaction domains.

Assessment of pesticide residues and trace element contamination ...

African Journals Online (AJOL)

ajl10

It was based on the chemical analyses of soil, water and vegetable samples. ... of the fine fraction (under 2 mm) were conserved away from light for ... To assess the migration and accumulation of trace elements ..... metals from sewage sludge in an agricultural soil. ... Pesticides and heavy metals in drinking water, soils.

Role of nuclear analytical probe techniques in biological trace element research

International Nuclear Information System (INIS)

Jones, K.W.; Pounds, J.G.

1985-01-01

Many biomedical experiments require the qualitative and quantitative localization of trace elements with high sensitivity and good spatial resolution. The feasibility of measuring the chemical form of the elements, the time course of trace elements metabolism, and of conducting experiments in living biological systems are also important requirements for biological trace element research. Nuclear analytical techniques that employ ion or photon beams have grown in importance in the past decade and have led to several new experimental approaches. Some of the important features of these methods are reviewed here along with their role in trace element research, and examples of their use are given to illustrate potential for new research directions. It is emphasized that the effective application of these methods necessitates a closely integrated multidisciplinary scientific team. 21 refs., 4 figs., 1 tab

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

International Nuclear Information System (INIS)

Rasolofonirina, M.; Randriamanivo, L.V.; Andrianarilala, M.T.; Raoelina Andriambololona

2004-01-01

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.

Effect of the new C-12(alpha, gamma)O-16 rate on the chemical evolution of the solar neighborhood

International Nuclear Information System (INIS)

Matteucci, F.

1986-01-01

New models of chemical evolution of the solar neighborhood have been computed by taking into account the effect of the revised rate of the C-12(alpha, gamma)O-16 reaction on the chemical yields from massive stars, together with the yields from low- and intermediate-mass stars which also include those from Type I supernova explosions (C-deflagration in white dwarfs). In particular, the evolution of C-12, N-14, O-16, Ne-20, Mg-24, Si-28, and Fe-56 has been followed in detail, and their predicted solar absolute abundances as well as their relative ratios, both in the sun and in metal-poor stars, have been compared with the observed ones. It is concluded that a model with the new yields combined with a Salpeter initial mass function, an upper cutoff mass of 100 solar masses (the mass beyond which stars are not contributing to the galactic enrichment), and an upper limiting mass for intermediate-mass stars of the order of 5 solar masses, is in best agreement with the observations. 34 references

Climatic Change and Human Evolution.

Science.gov (United States)

Garratt, John R.

1995-01-01

Traces the history of the Earth over four billion years, and shows how climate has had an important role to play in the evolution of humans. Posits that the world's rapidly growing human population and its increasing use of energy is the cause of present-day changes in the concentrations of greenhouse gases in the atmosphere. (Author/JRH)

Physico-Chemical Evolution of Organic Aerosol from Wildfire Emissions

Science.gov (United States)

Croteau, P.; Jathar, S.; Akherati, A.; Galang, A.; Tarun, S.; Onasch, T. B.; Lewane, L.; Herndon, S. C.; Roscioli, J. R.; Yacovitch, T. I.; Fortner, E.; Xu, W.; Daube, C.; Knighton, W. B.; Werden, B.; Wood, E.

2017-12-01

Wildfires are the largest combustion-related source of carbonaceous emissions to the atmosphere; these include direct emissions of black carbon (BC), primary organic aerosol (POA) and semi-volatile, intermediate-volatility, and volatile organic compounds (SVOCs, IVOCs, and VOCs). However, there are large uncertainties surrounding the evolution of these carbonaceous emissions as they are physically and chemically transformed in the atmosphere. To understand these transformations, we performed sixteen experiments using an environmental chamber to simulate day- and night-time chemistry of gas- and aerosol-phase emissions from 6 different fuels at the Fire Laboratory in Missoula, MT. Across the test matrix, the experiments simulated 2 to 8 hours of equivalent day-time aging (with the hydroxyl radical and ozone) or several hours of night-time aging (with the nitrate radical). Aging resulted in an average organic aerosol (OA) mass enhancement of 28% although the full range of OA mass enhancements varied between -10% and 254%. These enhancement findings were consistent with chamber and flow reactor experiments performed at the Fire Laboratory in 2010 and 2012 but, similar to previous studies, offered no evidence to link the OA mass enhancement to fuel type or oxidant exposure. Experiments simulating night-time aging resulted in an average OA mass enhancement of 10% and subsequent day-time aging resulted in a decrease in OA mass of 8%. While small, for the first time, these experiments highlighted the continuous nature of the OA evolution as the wildfire smoke cycled through night- and day-time processes. Ongoing work is focussed on (i) quantifying bulk compositional changes in OA, (ii) comparing the near-field aging simulated in this work with far-field aging simulated during the same campaign (via a mini chamber and flow tube) and (iii) integrating wildfire smoke aging datasets over the past decade to examine the relationship between OA mass enhancement ratios, modified

The Evolution of Social Work Ethics.

Science.gov (United States)

Reamer, Frederic G.

1998-01-01

Traces the evolution of ethical norms, principles, and standards in social work during four stages in the profession's history: (1) morality period, (2) values period, (3) ethical theory and decision-making period, and (4) ethical standards and risk-management period. Recent developments in the profession include complex conceptual frameworks and…

Evolution: Tracing the origins of centrioles, cilia, and flagella.

Science.gov (United States)

Carvalho-Santos, Zita; Azimzadeh, Juliette; Pereira-Leal, José B; Bettencourt-Dias, Mónica

2011-07-25

Centrioles/basal bodies (CBBs) are microtubule-based cylindrical organelles that nucleate the formation of centrosomes, cilia, and flagella. CBBs, cilia, and flagella are ancestral structures; they are present in all major eukaryotic groups. Despite the conservation of their core structure, there is variability in their architecture, function, and biogenesis. Recent genomic and functional studies have provided insight into the evolution of the structure and function of these organelles.

The Evolution of Social Welfare and Social Work in Nigeria | Irele ...

African Journals Online (AJOL)

This paper focused on the evolution of social welfare and social work in Nigeria. It traced the historical trajectory of social work from the missionary period through the colonial period to the present day. The paper gave a vivid picture of how individuals who were philanthropists contributed to the evolution of social work and ...

Multivariate cluster analysis of some major and trace elements ...

African Journals Online (AJOL)

UFUOMA

The chemical composition of water infiltrating ... Major and trace metals determined in soil and water from a ... The soil samples were air-dried at 29°C in a dust-free place for ... compact 3K5 X-ray generator (Ital IS Structures, Italy) was used for.

Proceedings of the 6. International Conference on the Biogeochemistry of Trace Elements. CD ed.

Energy Technology Data Exchange (ETDEWEB)

NONE

2001-07-01

This international conference provided a forum for researchers from around the world to exchange research notes of subjects dealing with the biogeochemistry of trace elements. The conference proceedings included 456 papers, of which 34 have been indexed separately for inclusion in the database. Each presentation included an introduction to a study, materials and methods, results and discussion and a conclusion. The conference was divided into special oral symposia (SO), general oral sessions (GO), a special poster session (SP) and a general poster session (GP). A wide range of topics were presented including: biosorption of trace elements and the bioavailability of metals for uptake and effects; chemical remediation; adsorption reactions on soils and sediments; fractionation of metals in soils; diagenetic transformations; arsenic content and distribution; metal speciation; the role of metal-organic interactions; phytoremediation; contents and distribution in soils and waters; soil amendments; mercury and human and animal health; mercury in the environment; aqueous speciation; phyto-, microbial and chemical remediation tools for metal contaminated soils and groundwater; geochemical surface controls on trace element fate; temporal trends of trace metals in biota; biomonitoring; transport in soils and waters; analytical techniques; metal/mineral interactions with microorganisms; the chemistry of trace elements in fly ash; ecotoxicology; groundwater; and, soil amendments. refs., tabs., figs.

Interactive influences of bioactive trace metals on biological production in oceanic waters

International Nuclear Information System (INIS)

Bruland, K.W.; Donat, J.R.; Hutchins, D.A.

1991-01-01

The authors present an overview of the oceanic chemistries of the bioactive trace metals, Mn, Fe, Co, Ni, Cu, and Zn; the authors combine field data with results from laboratory phytoplankton culture-trace metal studies and speculate on the potential influences of these trace metals on oceanic plankton production and species composition. Most field studies have focused on the effects of single metals. However, they propose that synergistic and antagonistic interactions between multiple trace metals could be very important in the oceans. Trace metal antagonisms that may prove particularly important are those between Cu and the potential biolimiting metals Fe, Mn, and Zn. These antagonistic interactions could have the greatest influence on biological productivity in areas of the open ocean isolated from terrestrial inputs, such as the remote high nutrient regions of the Pacific and Antarctic Oceans. The emerging picture of trace metal-biota interactions in these oceanic areas is one in which biology strongly influences distribution and chemical speciation of all these bioactive trace metals. It also seems likely that many of these bioactive trace metals and their speciation may influence levels of primary productivity, species composition, and trophic structure. Future investigations should give more complete consideration to the interactive effects of biologically important trace metals

The Determination of Uranium and Trace Metal Impurities in Yellow Cake Sample by Chemical Method

International Nuclear Information System (INIS)

Busamongkol, Arporn; Rodthongkom, Chouvana

1999-01-01

The purity of uranium cake is very critical in nuclear-grade uranium (UO 2 ) and uranium hexafluoride (UF 6 ) production. The major element in yellow cake is uranium and trace metal impurities. The objective of this study is to determine uranium and 25 trace metal impurities; Aluminum, Barium, Bismuth, Calcium, Cadmium, Cobalt, Chromium, Copper, Iron, Potassium, Iithium, Magnesium, Manganese, Molybdenum, Sodium, Niobium, Nickel, Lead, Antimony, Tin, Strontium, Titanium, Vanadium, Zinc and Zirconium, Uranium is determined by Potassium dichromate titration, after solvent extraction with Cupferon in Chloroform, Trace metal impurities are determined by solvent extraction with Tributyl Phosphate in Carbon-tetrachloride ( for first 23 elements) and N-Benzoyl-N-Phenylhydroxylamine in Chloroform ( for last 2 elements), then analyzed by Atomic Absorption Spectrophotometer (AAS) compared with Inductively Couple Plasma Spectrophotometers (ICP). The accuracy and precision are studied with standard uranium octaoxide

Tracing early stellar evolution with asteroseismology: pre-main sequence stars in NGC 2264

Directory of Open Access Journals (Sweden)

Zwintz Konstanze

2015-01-01

Full Text Available Asteroseismology has been proven to be a successful tool to unravel details of the internal structure for different types of stars in various stages of their main sequence and post-main sequence evolution. Recently, we found a relation between the detected pulsation properties in a sample of 34 pre-main sequence (pre-MS δ Scuti stars and the relative phase in their pre-MS evolution. With this we are able to demonstrate that asteroseismology is similarly powerful if applied to stars in the earliest stages of evolution before the onset of hydrogen core burning.

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

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

Evolution of radiotherapy and chemotherapy practice in malignant gliomas

Directory of Open Access Journals (Sweden)

Anusheel Munshi

2013-01-01

Full Text Available Malignant astrocytomas of the brain carry a poor prognosis. This article traces the evolution of radiotherapy and chemotherapy practice including the development of concurrent chemo-radiation schedules in the context of these tumors.

Expressing stochastic unravellings using random evolution operators

International Nuclear Information System (INIS)

Salgado, D; Sanchez-Gomez, J L

2002-01-01

We prove how the form of the most general invariant stochastic unravelling for Markovian (recently given in the literature by Wiseman and Diosi) and non-Markovian but Lindblad-type open quantum systems can be attained by imposing a single mathematical condition upon the random evolution operator of the system, namely a.s. trace preservation (a.s. stands for almost surely). The use of random operators ensures the complete positivity of the density operator evolution and characterizes the linear/non-linear character of the evolution in a straightforward way. It is also shown how three quantum stochastic evolution models - continuous spontaneous localization, quantum state diffusion and quantum mechanics with universal position localization - appear as concrete choices for the noise term of the evolution random operators are assumed. We finally conjecture how these operators may in the future be used in two different directions: both to connect quantum stochastic evolution models with random properties of space-time and to handle noisy quantum logical gates

Resonant laser mass spectrometry for environmental and industrial chemical trace analysis

International Nuclear Information System (INIS)

Boesl, Ulrich; Rink, Joerg; Distelrath, Volker; Pueffel, Peter

2001-01-01

A promising new method for pollutant trace analysis is resonant laser mass spectrometry. It combines selectivity, sensitivity, and speed of measurement. In this paper, two examples of application are presented: exhaust analysis of combustion engines and analysis of polycylcic aromatic compounds in soil samples. The sensitivity of small, mobile instruments is discussed as well as alternative laser-based techniques in the case formation of cations by nanosecond lasers is improbable

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.

Radiation-induced chemical evolution of glycine to (Gly)2, (Gly)3, and (Gly)4

International Nuclear Information System (INIS)

Matsui, T.; Izumi, Y.; Kamohara, M.; Nakagawa, K.; Yokoya, A.

2006-01-01

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 Xe 2 * 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 N 0 , where N is the number of produced or decomposed molecule, and N 0 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)

Nano-scale chemical evolution in a proton-and neutron-irradiated Zr alloy

Energy Technology Data Exchange (ETDEWEB)

Harte, Allan, E-mail: allan.harte@manchester.ac.uk [The University of Manchester, Oxford Road, Manchester, M13 9PL (United Kingdom); Topping, M.; Frankel, P. [The University of Manchester, Oxford Road, Manchester, M13 9PL (United Kingdom); Jädernäs, D. [Studsvik Nuclear AB, SE 611 82, Nyköping (Sweden); Romero, J. [Westinghouse Electric Company, Columbia, SC (United States); Hallstadius, L. [Westinghouse Electric Sweden AB, SE 72163 Västerås (Sweden); Darby, E.C. [Rolls Royce Plc., Nuclear Materials, Derby (United Kingdom); Preuss, M. [The University of Manchester, Oxford Road, Manchester, M13 9PL (United Kingdom)

2017-04-15

Proton-and neutron-irradiated Zircaloy-2 are compared in terms of the nano-scale chemical evolution within second phase particles (SPPs) Zr(Fe,Cr){sub 2} and Zr{sub 2}(Fe,Ni). This is accomplished through ultra-high spatial resolution scanning transmission electron microscopy and the use of energy-dispersive X-ray spectroscopic methods. Fe-depletion is observed from both SPP types after irradiation with both irradiative species, but is heterogeneous in the case of Zr(Fe,Cr){sub 2}, predominantly from the edge region, and homogeneously in the case of Zr{sub 2}(Fe,Ni). Further, there is evidence of a delay in the dissolution of the Zr{sub 2}(Fe,Ni) SPP with respect to the Zr(Fe,Cr){sub 2}. As such, SPP dissolution results in matrix supersaturation with solute under both irradiative species and proton irradiation is considered well suited to emulate the effects of neutron irradiation in this context. The mechanisms of solute redistribution processes from SPPs and the consequences for irradiation-induced growth phenomena are discussed. - Highlights: •Protons emulate the effects of neutron irradiation in the evolution of chemistry and morphology of second phase particles. •Detailed energy-dispersive X-ray spectroscopy reveals heterogeneity in Zr-Fe-Cr SPPs both before and after irradiation. •Zr-Fe-Ni SPPs are delayed in irradiation-induced dissolution due to their better self-solubility with respect to Zr-Fe-Cr.

Trapping, chemistry, and export of trace gases in the South Asian summer monsoon observed during CARIBIC flights in 2008

Directory of Open Access Journals (Sweden)

A. Rauthe-Schöch

2016-03-01

Full Text Available The CARIBIC (Civil Aircraft for the Regular Investigation of the Atmosphere Based on an Instrument Container passenger aircraft observatory performed in situ measurements at 10–12 km altitude in the South Asian summer monsoon anticyclone between June and September 2008. These measurements enable us to investigate this atmospheric region (which so far has mostly been observed from satellites using the broad suite of trace gases and aerosol particles measured by CARIBIC. Elevated levels of a variety of atmospheric pollutants (e.g. carbon monoxide, total reactive nitrogen oxides, aerosol particles, and several volatile organic compounds were recorded. The measurements provide detailed information about the chemical composition of air in different parts of the monsoon anticyclone, particularly of ozone precursors. While covering a range of 3500 km inside the monsoon anticyclone, CARIBIC observations show remarkable consistency, i.e. with distinct latitudinal patterns of trace gases during the entire monsoon period. Using the CARIBIC trace gas and aerosol particle measurements in combination with the Lagrangian particle dispersion model FLEXPART, we investigated the characteristics of monsoon outflow and the chemical evolution of air masses during transport. The trajectory calculations indicate that these air masses originated mainly from South Asia and mainland Southeast Asia. Estimated photochemical ages of the air were found to agree well with transport times from a source region east of 90–95° E. The photochemical ages of the air in the southern part of the monsoon anticyclone were systematically younger (less than 7 days and the air masses were mostly in an ozone-forming chemical mode. In its northern part the air masses were older (up to 13 days and had unclear ozone formation or destruction potential. Based on analysis of forward trajectories, several receptor regions were identified. In addition to predominantly westward

A Historical Review of Diachrony and Semantic Dimensions of Trace in Neurosciences and Lacanian Psychoanalysis

KAUST Repository

Escobar, Carolina

2017-06-23

Experience leaves a trace in the nervous system through plasticity. However, the exact meaning of the mnesic trace is poorly defined in current literature. This article provides a historical review of the term trace in neuroscience and psychoanalysis literature, to highlight two relevant aspects: the diachronic and the semantic dimensions. There has been a general interest in diachrony, or a form of evolution of the trace, but its indissociable semantic dimension remains partially disregarded. Although frequently implied, the diachronic and semantic dimensions of the trace are rarely clearly articulated. We situate this discussion into the classical opposition of syntax, or rules of inscription of the trace in the nervous system, and semantics, or the content of the trace, which takes into consideration the attempt of the human being to build coherence. A general observation is that the study of the term trace follows trends of the thought of the given epoch. This historical analysis also reveals the decay of the idea that the trace is reliable to the experience. From the articulation between neurosciences and psychoanalysis in a historical perspective, this review shows that the trend is to consider trace as a production of the subject, resulting in a permanent rewriting in an attempt to give meaning to the experience. This trend is becoming increasingly evident in light of recent research in neurosciences and psychoanalysis.

A Historical Review of Diachrony and Semantic Dimensions of Trace in Neurosciences and Lacanian Psychoanalysis

Directory of Open Access Journals (Sweden)

Carolina Escobar

2017-06-01

Full Text Available Experience leaves a trace in the nervous system through plasticity. However, the exact meaning of the mnesic trace is poorly defined in current literature. This article provides a historical review of the term trace in neuroscience and psychoanalysis literature, to highlight two relevant aspects: the diachronic and the semantic dimensions. There has been a general interest in diachrony, or a form of evolution of the trace, but its indissociable semantic dimension remains partially disregarded. Although frequently implied, the diachronic and semantic dimensions of the trace are rarely clearly articulated. We situate this discussion into the classical opposition of syntax, or rules of inscription of the trace in the nervous system, and semantics, or the content of the trace, which takes into consideration the attempt of the human being to build coherence. A general observation is that the study of the term trace follows trends of the thought of the given epoch. This historical analysis also reveals the decay of the idea that the trace is reliable to the experience. From the articulation between neurosciences and psychoanalysis in a historical perspective, this review shows that the trend is to consider trace as a production of the subject, resulting in a permanent rewriting in an attempt to give meaning to the experience. This trend is becoming increasingly evident in light of recent research in neurosciences and psychoanalysis.

A Historical Review of Diachrony and Semantic Dimensions of Trace in Neurosciences and Lacanian Psychoanalysis

KAUST Repository

Escobar, Carolina; Ansermet, Franç ois; Magistretti, Pierre J.

2017-01-01

Experience leaves a trace in the nervous system through plasticity. However, the exact meaning of the mnesic trace is poorly defined in current literature. This article provides a historical review of the term trace in neuroscience and psychoanalysis literature, to highlight two relevant aspects: the diachronic and the semantic dimensions. There has been a general interest in diachrony, or a form of evolution of the trace, but its indissociable semantic dimension remains partially disregarded. Although frequently implied, the diachronic and semantic dimensions of the trace are rarely clearly articulated. We situate this discussion into the classical opposition of syntax, or rules of inscription of the trace in the nervous system, and semantics, or the content of the trace, which takes into consideration the attempt of the human being to build coherence. A general observation is that the study of the term trace follows trends of the thought of the given epoch. This historical analysis also reveals the decay of the idea that the trace is reliable to the experience. From the articulation between neurosciences and psychoanalysis in a historical perspective, this review shows that the trend is to consider trace as a production of the subject, resulting in a permanent rewriting in an attempt to give meaning to the experience. This trend is becoming increasingly evident in light of recent research in neurosciences and psychoanalysis.

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.

Trace elements in brazilian soils; Micronutrientes nos solos do Brasil

Energy Technology Data Exchange (ETDEWEB)

Rocha, Geraldo Cesar [Juiz de Fora Univ., MG (Brazil). Dept. de Geociencias

1995-03-01

A literature revision on trace elements (Zn, B, Mn, Mo, Cu, Fe, and Cl) in Brazilian soils was prepared, with special attention to the chemical form and range in the soil, extraction methods and correlation of the amount in soils with soil properties. 76 refs.

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

International Nuclear Information System (INIS)

Mohamed, Ibtihag El hassan

2000-09-01

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)

Mobility of nutrients and trace metals during weathering in the late Archean

Science.gov (United States)

Hao, Jihua; Sverjensky, Dimitri A.; Hazen, Robert M.

2017-08-01

The evolution of the geosphere and biosphere depends on the availability of bio-essential nutrients and trace metals. Consequently, the chemical and isotopic variability of trace elements in the sedimentary record have been widely used to infer the existence of early life and fluctuations in the near-surface environment on the early Earth, particularly fluctuations in the redox state of the atmosphere. In this study, we applied late Archean weathering models (Hao et al., 2017), developed to estimate the behavior of major elements and the composition of late Archean world average river water, to explore the behavior of nutrient and trace metals and their potential for riverine transport. We focused on P, Mn, Cr, and Cu during the weathering of olivine basalt. In our standard late Archean weathering model (pCO2,g = 10-1.5 bars, pH2,g = 10-5.0 bars), crustal apatite was totally dissolved by the acidic rainwater during weathering. Our model quantitatively links the pCO2,g of the atmosphere to phosphate levels transported by rivers. The development of late Archean river water (pH = 6.4) resulted in riverine phosphate of at least 1.7 μmolar, much higher than at the present-day. At the end of the early Proterozoic snowball Earth event when pCO2,g could be 0.01-0.10 bars, river water may have transported up to 70 μmolar phosphate, depending on the availability of apatite, thereby stimulating high levels of oxygenic photosynthesis in the marine environment. Crustal levels of Mn in olivine dissolved completely during weathering, except at large extents of weathering where Mn was stored as a component of a secondary carbonate mineral. The corresponding Mn content of river water, about 1.2 μmolar, is higher than in modern river water. Whiffs of 10-5 mole O2 gas or HNO3 kg-1 H2O resulted in the formation of pyrolusite (MnO2) and abundant hematite and simultaneous dramatic decreases in the concentration of Mn(II) in the river water. Chromite dissolution resulted in negligible

The Evolution of Special Education in Malaysia

Science.gov (United States)

Lee, Lay Wah; Low, Hui Min

2014-01-01

This article traces the evolution of special education in Malaysia across four chronological stages: before and during the early colonial period (before 1900), pre-independence (1900-1957), post-independence (1957-1990) and modern Malaysia (1990 to the present), through document analysis. By placing current issues and trends within a historical…

Highly sensitive sorption-luminescence determination of trace europium with preconcentration on silica chemically modified with iminodiacetic acid

International Nuclear Information System (INIS)

Voronina, R.D.; Zorov, N.B.

2007-01-01

Features of a sorption-luminescence method for the determination of trace europium were studied. The method includes the preliminary sorption of europium at pH 7.1 from solutions with silica chemically modified with iminodiacetic acid, the subsequent treatment of the sorbent with 2-thenoyltrifluoroacetone at pH 8.0, and the measurement of the intensity of luminescence of the surface three-component europium complex at 613 nm. The effect of moisture as the quencher of luminescence of the surface europium complex was studied, and techniques for its removal were proposed. Sorption in the static mode provides the detection limit of europium of 7 x 10 -5 g/ml. The calibration plot is linear in the range of two orders of magnitude of europium concentration in solutions. The relative standard deviation in the determination of 1.5 x 10 -2 μg/ml europium is 5%. In the dynamic mode of sorption from 1000 ml of an analyzed solution with the use of sorption-desorption, the detection limit of europium of 8 x 10 -7 μg/ml was attained [ru

Galactic evolution of sulphur as traced by globular clusters

Science.gov (United States)

Kacharov, N.; Koch, A.; Caffau, E.; Sbordone, L.

2015-05-01

Context. Sulphur is an important volatile α element, but its role in the Galactic chemical evolution is still uncertain, and more observations constraining the sulphur abundance in stellar photospheres are required. Aims: We derive the sulphur abundances in red giant branch (RGB) stars in three Galactic halo globular clusters (GC) that cover a wide metallicity range (-2.3 noise (S/N ~ 200 per px) spectra in the region of the S I multiplet 3 at 1045 nm for 15 GC stars selected from the literature (six stars in M 4,six stars in M 22, and three stars in M 30). Multiplet 3 is better suited for S abundance derivation than the more commonly used lines of multiplet 1 at 920 nm, since its lines are not blended by telluric absorption or other stellar features at low metallicity. Results: We used spectral synthesis to derive the [S/Fe] ratio of the stars assuming local thermodynamic equilibrium (LTE). We find mean [S/Fe]LTE = 0.58 ± 0.01 ± 0.20 dex (statistical and systematic error) for M 4, [S/Fe]LTE = 0.57 ± 0.01 ± 0.19 dex for M 22, and [S/Fe]LTE = 0.55 ± 0.02 ± 0.16 dex for M 30. The negative NLTE corrections are estimated to be in the order of the systematic uncertainties. We do not detect star-to-star variations of the S abundance in any of the observed GCs, with the possible exception of two individual stars, one in M 22 and one in M 30, which appear to be highly enriched in S. Conclusions: With the tentative exception of two stars with measured high S abundances, we conclude that sulphur behaves like a typical α element in the studied Galactic GCs, showing enhanced abundances with respect to the solar value at metallicities below [Fe/H]-1.0 dex without a considerable spread. Based on observations made with ESO telescopes at the La Silla Paranal Observatory under programmes ID 091.B-0171(A).The reduced spectra and the best fit synthetic models are available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http

Trace elements distribution in environmental compartments

Energy Technology Data Exchange (ETDEWEB)

Queiroz, Juliana C. de; Peres, Sueli da Silva; Godoy, Maria Luiza D.P., E-mail: suelip@ird.gov.br [Instituto de Radioprotecao e Dosimetria (IRD/CNEN-RJ), Rio de Janeiro, RJ (Brazil)

2017-11-01

Trace elements term defines the presence of low concentrations metals at environment. Some of them are considered biologically essential, as Co, Cu and Mn. Others can cause detriment to environment and human health, as Pb, Cd, Hg, As, Ti and U. A large number of them have radioactive isotopes, implying the evaluation of risks for human health should be done considering the precepts of environmental radiological protection. The ecosystem pollution with trace elements generates changes at the geochemistry cycle of these elements and in environmental quality. Soils have single characteristics when compared with another components of biosphere (air, water and biota), cause they introduce themselves not only as a drain towards contaminants, but also as natural buffer that control the transport of chemical elements and other substances for atmosphere, hydrosphere and biota. The main purpose of environmental monitoring program is to evaluate the levels of contaminants in the various compartments of the environment: natural or anthropogenic, and to assess the contribution of a potential contaminant source on the environment. Elemental Composition for the collected samples was determined by inductively coupled plasma mass spectroscopy. The main objective of this work was to evaluate the map baseline of concentration of interest trace elements in environmental samples of water, sediment and soil from Environmental Monitoring Program of Instituto de Radioprotecao e Dosimetria (IRD). The samples were analyzed using an inductively coupled plasma mass spectrometer (ICP-MS) at IRD. >From the knowledge of trace elements concentrations, could be evaluated the environmental quality parameters at the studied ecosystems. The data allowed evaluating some relevant aspects of the study of trace elements in soil and aquatic systems, with emphasis at the distribution, concentration and identification of main anthropic sources of contamination at environment. (author)

Trace elements distribution in environmental compartments

International Nuclear Information System (INIS)

Queiroz, Juliana C. de; Peres, Sueli da Silva; Godoy, Maria Luiza D.P.

2017-01-01

Trace elements term defines the presence of low concentrations metals at environment. Some of them are considered biologically essential, as Co, Cu and Mn. Others can cause detriment to environment and human health, as Pb, Cd, Hg, As, Ti and U. A large number of them have radioactive isotopes, implying the evaluation of risks for human health should be done considering the precepts of environmental radiological protection. The ecosystem pollution with trace elements generates changes at the geochemistry cycle of these elements and in environmental quality. Soils have single characteristics when compared with another components of biosphere (air, water and biota), cause they introduce themselves not only as a drain towards contaminants, but also as natural buffer that control the transport of chemical elements and other substances for atmosphere, hydrosphere and biota. The main purpose of environmental monitoring program is to evaluate the levels of contaminants in the various compartments of the environment: natural or anthropogenic, and to assess the contribution of a potential contaminant source on the environment. Elemental Composition for the collected samples was determined by inductively coupled plasma mass spectroscopy. The main objective of this work was to evaluate the map baseline of concentration of interest trace elements in environmental samples of water, sediment and soil from Environmental Monitoring Program of Instituto de Radioprotecao e Dosimetria (IRD). The samples were analyzed using an inductively coupled plasma mass spectrometer (ICP-MS) at IRD. >From the knowledge of trace elements concentrations, could be evaluated the environmental quality parameters at the studied ecosystems. The data allowed evaluating some relevant aspects of the study of trace elements in soil and aquatic systems, with emphasis at the distribution, concentration and identification of main anthropic sources of contamination at environment. (author)

Effect of increasing helium content and disk dwarfs evolution on the chemical enrichment of the galaxy

Energy Technology Data Exchange (ETDEWEB)

Caimmi, R [Padua Univ. (Italy). Ist. di Astronomia

1979-07-01

The author deals with two main effects: First the empirical metal abundance distribution in Main Sequence disk dwarfs of the solar neighbourhood, and second, the theoretical possibility of (i) an increased helium content as the Galaxy evolves, and (ii) the presence of evolutionary effects in disk dwarfs (i.e., the age of some or all stars considered up to the subgiant phase is not necessarily longer than the age of the galactic disk). Account is taken of a linear increase of helium content with metal content, and some constraints are imposed relative to initial, solar and present-day observed values of Y and Z, and to observed relative helium to heavy element enrichment, ..delta..Y/..delta..Z. In this way, little influence is found on the empirical metal abundance distribution in the range 0<=..delta..Y/..delta..Z<=3, while larger values of ..delta..Y/..delta..Zwould lead to a more significant influence. 'Evolved' and 'unevolved' theoretical metal abundance distributions are derived by accounting for a two-phase model of chemical evolution of galaxies and for a linear mass dependence of star lifetimes in the spectral range G2V-G8V and are compared with the empirical distribution. All are in satisfactory agreement due to systematic shift data by different observations; several values of collapse time Tsub(c) and age of the Galaxy T are also considered. Finally, models of chemical evolution invoking homogeneous collapse without infall and inhomogeneous collapse with infall, are briefly discussed relative to the empirical metal abundance distribution in Main Sequence disk dwarfs of the solar neighbourhood.

Trace metals behaviour during salt and fresh water mixing in the Venice Lagoon

International Nuclear Information System (INIS)

Ghermandi, G.; Campolieti, D.; Cecchi, R.; Costa, F.; Zaggia, L.; Zonta, R.

1993-01-01

Preliminary results of an investigation on trace metals behaviour in the estuarine system of the Dese River (Venice Lagoon) are described. Hydrodynamical and water chemical-physical measurements and PIXE concentrations analysis on size-fractionated samples emphasize the complexity of the processes occurring in the area of salt and fresh water mixing. Suspended load variations in the bottom layer of the water column, which may be mostly ascribed to resuspension, regulate the trace metal concentrations and seem to play a fundamental role in the transport of pollutants in shallow water areas of the estuary. The behaviour of dissolved metals is masked by the presence of suspended matter, but some relationships with chemical-physical variables are distinguishable, furnishing information on the processes affecting their concentration in the system. (orig.)

Computer simulation of dust grain evolution

Science.gov (United States)

Liffman, K.

1989-01-01

The latest results are reported from a Monte Carlo code that is being developed at NASA Ames. The goal of this program, is to derive from the observed and presumed properties of the interstellar medium (ISM) the following information: (1) the size spectrum of interstellar dust; (2) the chemical structure of interstellar dust; (3) interstellar abundances; and (4) the lifetime of a dust grain in the ISM. Presently this study is restricted to refractory interstellar material, i.e., the formation and destruction of ices are not included in the program. The program is embedded in an analytic solution for the bulk chemical evolution of a two-phase interstellar medium in which stars are born in molecular clouds, but new nucleosynthesis products and stellar return are entered into a complementary intercloud medium. The well-mixed matter of each interstellar phase is repeatedly cycled stochastically through the complementary phase and back. Refractory dust is created by thermal condensation as stellar matter flows away from sites of nucleosynthesis such as novae and supernovae and/or from the matter returned from evolved intermediate stars. The history of each particle is traced by standard Monte Carlo techniques as it is sputtered and fragmented by supernova shock waves in the intercloud medium. It also accretes an amorphous mantle of gaseous refractory atoms when its local medium joins with the molecular cloud medium. Finally it encounters the possibility of astration (destruction by star formation) within the molecular clouds.

The EU network on trace element speciation in full swing

DEFF Research Database (Denmark)

Cornelis, R.; Camara, C.; Ebdon, L.

2000-01-01

health and hygiene. The network covers a number of important issues including organotin compounds, chromium and nickel species, chemical characterisation of environmental and industrial particulate samples, risk assessment, selenium and a series of other essential and toxic elements in food, as well......The EC-funded thematic network 'Speciation 21' links scientists in analytical chemistry working in method development for the chemical speciation of trace elements, and potential users from industry and representatives of legislative agencies, in the field of environment, food and occupational...

Chemical evolution with rotating massive star yields - I. The solar neighbourhood and the s-process elements

Science.gov (United States)

Prantzos, N.; Abia, C.; Limongi, M.; Chieffi, A.; Cristallo, S.

2018-05-01

We present a comprehensive study of the abundance evolution of the elements from H to U in the Milky Way halo and local disc. We use a consistent chemical evolution model, metallicity-dependent isotopic yields from low and intermediate mass stars and yields from massive stars which include, for the first time, the combined effect of metallicity, mass loss, and rotation for a large grid of stellar masses and for all stages of stellar evolution. The yields of massive stars are weighted by a metallicity-dependent function of the rotational velocities, constrained by observations as to obtain a primary-like 14N behaviour at low metallicity and to avoid overproduction of s-elements at intermediate metallicities. We show that the Solar system isotopic composition can be reproduced to better than a factor of 2 for isotopes up to the Fe-peak, and at the 10 per cent level for most pure s-isotopes, both light ones (resulting from the weak s-process in rotating massive stars) and the heavy ones (resulting from the main s-process in low and intermediate mass stars). We conclude that the light element primary process (LEPP), invoked to explain the apparent abundance deficiency of the s-elements with A values of ^{12}C/^{13}C in halo red giants, which is rather due to internal processes in those stars.

TRACE ELEMENT CHEMISTRY IN RESIDUAL-TREATED SOIL: KEY CONCEPTS AND METAL BIOAVAILABILITY

Science.gov (United States)

Trace element solubility and availability in land-applied residuals is governed by fundamental chemical reactions between metal constituents, soil, and residual components. Iron, aluminum, and manganese oxides; organic matter; and phosphates, carbonates, and sulfides are importan...

Determination of some trace elements in biological samples using XRF and TXRF techniques

International Nuclear Information System (INIS)

Khuder, A.; Karjou, J.; Sawan, M. K.

2006-07-01

XRF and TXRF techniques were successfully used for the multi-element determination of trace elements in whole blood and human head hair samples. This was achieved by the direct analysis using XRF technique with different collimation units and by the optimized chemical procedures for TXRF analysis. Light element of S and P were preferably determined by XRF with primary x-ray excitation, while, elements of K, Ca, Fe, and Br were determined with a very good accuracy and precision using XRF with Cu- and Mo-secondary targets. The chemical procedure dependent on the preconcentration of trace elements by APDC was superiorly used for the determination of traces of Ni and Pb in the range of 1.0-1.7 μg/dl and 11-23 μg/dl, respectively, in whole blood samples by TXRF technique; determination of other elements as Cu and Zn was also achievable using this approach. Rb in whole blood samples was determined directly after the digestion of samples using PTFE-bomb for TXRF analysis. (author)

Directed evolution strategies for enantiocomplementary haloalkane dehalogenases: from chemical waste to enantiopure building blocks.

Science.gov (United States)

van Leeuwen, Jan G E; Wijma, Hein J; Floor, Robert J; van der Laan, Jan-Metske; Janssen, Dick B

2012-01-02

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 epichlorohydrins-attractive intermediates for the synthesis of enantiopure fine chemicals. A dehalogenase with improved catalytic activity but very low enantioselectivity was used as the starting point. A strategy that made optimal use of the limited capacity of the screening assay, which was based on chiral gas chromatography, was developed. We used pair-wise site-saturation mutagenesis (SSM) of all 16 noncatalytic active-site residues during the initial two rounds of evolution. The resulting best R- and S-enantioselective variants were further improved in two rounds of site-restricted mutagenesis (SRM), with incorporation of carefully selected sets of amino acids at a larger number of positions, including sites that are more distant from the active site. Finally, the most promising mutations and positions were promoted to a combinatorial library by using a multi-site mutagenesis protocol with restricted codon sets. To guide the design of partly undefined (ambiguous) codon sets for these restricted libraries we employed structural information, the results of multiple sequence alignments, and knowledge from earlier rounds. After five rounds of evolution with screening of only 5500 clones, we obtained two strongly diverged haloalkane dehalogenase variants that give access to (R)-epichlorohydrin with 90 % ee and to (S)-epichlorohydrin with 97 % ee, containing 13 and 17 mutations, respectively, around their active sites. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Simultaneous speciation of trace elements using chemical separation and neutron activation

International Nuclear Information System (INIS)

Chatt, A.

2003-01-01

Speciation neutron activation analysis (SNAA) is a sophisticated analytical technique which can be developed for studying the simultaneous speciation of a number of elements in a variety of matrices. The advantages of SNAA are demonstrated with typical examples such as (i) arsenic speciation in sea foods and water, and simultaneous speciation of (ii) arsenic, antimony and selenium in water, (iii) chlorine, bromine and iodine in fish, (iv) lanthanides in simulated vitrified waste, and (v) trace elements bound to proteins. (author)

Evolution of Instrumentation for UV-Visible Spectrophotometry. Part I.

Science.gov (United States)

Altemose, Ines R.

1986-01-01

Traces the development of instruments used in spectrophotometry. Discusses how spectrophotometric measurements are made. Describes the color comparator, the filter photometer, and the spectrophotometer. Outlines the evolution of optical systems, including light sources, the monochromator, the photodetector, double-beam optics, and split-beam…

Speciation of trace elements in the environmental studies

International Nuclear Information System (INIS)

Reddy, A.V.R.

2012-01-01

Elements present at trace levels, often referred as trace elements, play an important role in the environment and in the functioning of life on our planet. Trace elements in environment present as free metal ions or incorporated into colloids or attached to particulate matter or exist in different physical and chemical forms. It is well established that some elements are highly toxic and some are essential, but can become toxic at higher doses. It is also now known that the forms of elements (speciation) and their amounts are more important than the chemical dose of the elements as their interaction depends on different species. For example, Cr(VI) ions are considered far more toxic than Cr(III), whereas As(III) is more toxic than As(V). Similarly, in the case of mercury, both methylmercury and inorganic mercury are toxic but they show different levels of toxicity. Thus the adverse effects depend on the nature of species of the elements and therefore speciation studies are of paramount importance in many areas like toxicology, environmental chemistry and geochemisty. In view of this, speciation studies is a challenge to analytical chemists as the measurement methodologies have to be carefully developed, validated and applied. The grand challenge is to obtain quality data ensuring traceability, as the data obtained will be used in modeling for predicting the environmental impacts. In this talk importance of speciation and challenges to environmental analytical chemists will be discussed along with the following three speciation studies on Cr, U and Hg which were carried out in our laboratories

Influence of Hudiara Drain Water Irrigation on Trace Elements Load ...

African Journals Online (AJOL)

... Drain Water Irrigation on Trace Elements Load In Soil And Uptake By Vegetables. ... This polluted water not only contains organic matter and crop nutrients but also ... Plant samples were collected at maturity from all the monitoring points. ... (DO), Chemical Oxygen Demand (COD) and Biological Oxygen Demand (BOD) ...

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

International Nuclear Information System (INIS)

Karlsson, L.G.; Brandberg, F.

1993-01-01

Ammonia is added to the PFBC process with the purpose to reduce the emissions of NO x 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 NH 3 /l in the pore water of the residues increases the solubilities for copper and silver. If the concentration of ammonia increases to 170 mg NH 3 /l will the solubilities increase also for cadmium, nickel and zinc. (12 refs., 39 figs.)

Chemical evolution of the Galaxy at the initial rapid-collapse phase

Energy Technology Data Exchange (ETDEWEB)

Caimmi, R [Padua Univ. (Italy). Istituto di Astronomia

1978-04-01

Equations for the chemical evolution of the Galaxy are derived, accounting for (i) the dynamical evolution of the Galaxy (i.e. the collapse of the proto-galaxy) and (ii) either a variable mass-spectrum in the birth-rate stellar function of the type B(m,t) = psi(t)phi(m,t), or a constant mass-spectrum with variable lower mass limit for star birth: msub(mf) = msub(mf)(Z). Simple equations are adopted for the collapse of the proto-galaxy, accounting for the experimental data (i.e. axial ratio and major semi-axis) relative to the halo and to the disk, and best fitted for a rapid collapse; gas density is assumed to be always uniform. Numerical computations of several cases show that there is qualitative agreement with the experimental data relative to the Z(t) function when: (i) the mass-spectrum is nearly constant in time: phi(m,t) approximately phi(m) = msup(-2.35); (ii) the efficiency phi(t) proportional to rhosup(..cap alpha..) is sufficiently high; moreover, the super metallic effect (SME) takes place for ..cap alpha.. greater than a given value (..cap alpha.. > approximately 1.5); (iii) the shorter the collapse time Tsub(c), the more rapid is the initial increase of metallicity, the asymptotic value being left nearly unaltered. The theoretical results are not in complete agreement with the observed data bearing on the Nsub(n)(Z) function (Nsub(n) is the number of stars whose Main-Sequence lifetime is not less than the age of the Galaxy), while a hypothesis of star formation with different efficiencies in different zones of the Galaxy, and successive stellar mixing from zone to zone, is not inconsistent with such data.

Chemical evolution of the Galaxy at the initial rapid-collapse phase

International Nuclear Information System (INIS)

Caimmi, R.

1978-01-01

Equations for the chemical evolution of the Galaxy are derived, accounting for (i) the dynamical evolution of the Galaxy (i.e. the collapse of the proto-galaxy) and (ii) either a variable mass-spectrum in the birth-rate stellar function of the type B(m,t) = psi(t)phi(m,t), or a constant mass-spectrum with variable lower mass limit for star birth: msub(mf) = msub(mf)(Z). Simple equations are adopted for the collapse of the proto-galaxy, accounting for the experimental data (i.e. axial ratio and major semi-axis) relative to the halo and to the disk, and best fitted for a rapid collapse; gas density is assumed to be always uniform. Numerical computations of several cases show that there is qualitative agreement with the experimental data relative to the Z(t) function when: (i) the mass-spectrum is nearly constant in time: phi(m,t) approximately phi(m) = msup(-2.35); (ii) the efficiency phi(t) proportional to rhosup(α) is sufficiently high; moreover, the super metallic effect (SME) takes place for α greater than a given value (α > approximately 1.5); (iii) the shorter the collapse time Tsub(c), the more rapid is the initial increase of metallicity, the asymptotic value being left nearly unaltered. The theoretical results are not in complete agreement with the observed data bearing on the Nsub(n)(Z) function (Nsub(n) is the number of stars whose Main-Sequence lifetime is not less than the age of the Galaxy), while a hypothesis of star formation with different efficiencies in different zones of the Galaxy, and successive stellar mixing from zone to zone, is not inconsistent with such data. (Auth.)

The evolution of the elements

International Nuclear Information System (INIS)

Williams, P.M.

1978-01-01

It is believed that only the lightest elements, hydrogen and helium, were created during the 'Big Bang' origin of the Universe and that all heavier elements were synthesized by nuclear reactions in stars, the interstellar medium and possibly in 'little bangs' in the nuclei of galaxies. The composition of the interstellar medium has evolved through enrichment by processed material shed by evolving stars and the composition of the Solar System reflects that of the interstellar medium at the time of its formation. Differentiation processes during the evolution of the Solar System and individual planets account for the different compositions of the Sun and the planets. The measurement of the abundance distribution of the elements has become a very powerful tool in the elucidation of the evolution of the Solar System, stars and the Galaxy. This review attempts to trace the formation of the elements in stars and their subsequent evolution. (author)

Method to determine trace elements in water samples by neutron activation analysis

International Nuclear Information System (INIS)

Kueppers, G.; Erdtmann, G.

1981-05-01

For the determination of trace elements in water by neutron activation analysis irradiation porcedures and chemical separation procedures have been developed. Irradiation in melted quarz glass ampoules in the presence of a platinum wire (for recombination of the oxyhydrogen gas produced by radiolysis) proved successfull with different variants of the irradiation methods, as long irradiation periods without pressure build-up could be achieved. Possible falsifications of the analysis results were investigated in detail (losses by absorption on vessel walls etc.). The irradiated samples can be measured directly with a gamma ray spectrometer and from the radionuclides found the trace element contents may be calculated. More sensitive determinations are possible if the radionuclides are chemically separated. Procedures for removing the matrix activities, for the separation of the radionuclides in groups of elements and for the isolation of single elements have been developed. For especially sensitive determination of some elements selective separation procedures for antimony, cadmium, selenium, mercury and uranium have been developed. The analytical procedures described have been applied to trace element determinations in river water, glacier ice and water solutions from technical processes. (orig./RB) [de

International conference on the performance of engineered barriers. Physical and chemical properties, behaviour and evolution. Short abstracts

Energy Technology Data Exchange (ETDEWEB)

Schaefers, Annika; Fahland, Sandra (eds.)

2014-08-01

The volume includes the abstracts of the papers presented at the international conference on the performance of engineered barrier systems, their physical and chemical properties, behavior and evolution. The papers cover the topics bentonite buffers, radioactive waste repository safety, geophysical and geochemical property monitoring, repository sealing materials, thermo-hydro-mechanical characterization, gas injection tests, hydration and heating tests, clay-iron interaction experiments, water retention behavior, thermal stability of materials, numerical modeling studies, long-term simulations, thermo-hydrologic phenomena, uncertainty and sensitivity studies, probabilistic assessments, preliminary safety analyses of Gorleben.

The chemical evolution of white dwarf atmospheres: Diffusion and accretion

International Nuclear Information System (INIS)

Vauclair, G.; Vauclair, S.; Greenstein, J.L.

1979-01-01

A study of diffusion processes in white dwarfs is presented. We are especially interested in the estimate of the diffusion time scales for C, N, O, Mg, and Ca along the cooling sequence. The effect of the radiative acceleration is important in hot white dwarfs while in cooler ones the thermal diffusion dominates the gravitational settling. In hot white dwarfs, there should be an observable amount of CNO elements unless they have previously left the stars by a selective wind. Observational tests of this result are discussed. The diffusion time scales are always short compared to the evolutionary time scales. It is shown that in both hydrogen and helium envelopes, the convection zone, even at its maximum depth, is not able to bring back to the stellar surface the metals which have previously diffused downwards. The diffusion alone predicts a complete absence of metals in white dwarf atmospheres and envelopes. As metals are observed in white dwarfs, at least at effective temperatures lower than 15,000 K, there must be some mechanism competing with diffusion. We investigate the competition between diffusion and accretion and propose a general scheme for the chemical evolution of white dwarf atmospheres along the cooling sequence. (orig.)

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

International Nuclear Information System (INIS)

West, K.A.; Wilson, T.P.

1992-01-01

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

Fate and effects of anthropogenic chemicals in mangrove ecosystems: A review

Energy Technology Data Exchange (ETDEWEB)

Lewis, Michael, E-mail: lewis.michael@epa.gov [U.S. Environmental Protection Agency, Office of Research and Development, 1 Sabine Island Drive, Gulf Breeze, FL 32561 (United States); Pryor, Rachel; Wilking, Lynn [U.S. Environmental Protection Agency, Office of Research and Development, 1 Sabine Island Drive, Gulf Breeze, FL 32561 (United States)

2011-10-15

The scientific literature for fate and effects of non-nutrient contaminant concentrations is skewed for reports describing sediment contamination and bioaccumulation for trace metals. Concentrations for at least 22 trace metals have been reported in mangrove sediments. Some concentrations exceed sediment quality guidelines suggesting adverse effects. Bioaccumulation results are available for at least 11 trace metals, 12 mangrove tissues, 33 mangrove species and 53 species of mangrove-habitat biota. Results are specific to species, tissues, life stage, and season and accumulated concentrations and bioconcentration factors are usually low. Toxicity tests have been conducted with 12 mangrove species and 8 species of mangrove-related fauna. As many as 39 effect parameters, most sublethal, have been monitored during the usual 3 to 6 month test durations. Generalizations and extrapolations for toxicity between species and chemicals are restricted by data scarcity and lack of experimental consistency. This hinders chemical risk assessments and validation of effects-based criteria. - Chemical risk assessments and resource management are restricted by the limited chemical fate and effects database for mangroves.

Trace organic chemicals contamination in ground water recharge.

Science.gov (United States)

Díaz-Cruz, M Silvia; Barceló, Damià

2008-06-01

Population growth and unpredictable climate changes will pose high demands on water resources in the future. Even at present, surface water is certainly not enough to cope with the water requirement for agricultural, industrial, recreational and drinking purposes. In this context, the usage of ground water has become essential, therefore, their quality and quantity has to be carefully managed. Regarding quantity, artificial recharge can guarantee a sustainable level of ground water, whilst the strict quality control of the waters intended for recharge will minimize contamination of both the ground water and aquifer area. However, all water resources in the planet are threatened by multiple sources of contamination coming from the extended use of chemicals worldwide. In this respect, the environmental occurrence of organic micropollutants such as pesticides, pharmaceuticals, industrial chemicals and their metabolites has experienced fast growing interest. In this paper an overview of the priority and emerging organic micropollutants in the different source waters used for artificial aquifer recharge purposes and in the recovered water is presented. Besides, some considerations regarding fate and removal of such compounds are also addressed.

Trace element emissions from coal

Energy Technology Data Exchange (ETDEWEB)

NONE

2012-09-15

Trace elements are emitted during coal combustion. The quantity, in general, depends on the physical and chemical properties of the element itself, the concentration of the element in the coal, the combustion conditions and the type of particulate control device used, and its collection efficiency as a function of particle size. Some trace elements become concentrated in certain particle streams following combustion such as bottom ash, fly ash, and flue gas particulate matter, while others do not. Various classification schemes have been developed to describe this partitioning behaviour. These classification schemes generally distinguish between: Class 1: elements that are approximately equally concentrated in the fly ash and bottom ash, or show little or no fine particle enrichment, examples include Mn, Be, Co and Cr; Class 2: elements that are enriched in the fly ash relative to bottom ash, or show increasing enrichment with decreasing particle size, examples include As, Cd, Pb and Sb; Class 3: elements which are emitted in the gas phase (primarily Hg (not discussed in this review), and in some cases, Se). Control of class 1 trace elements is directly related to control of total particulate matter emissions, while control of the class 2 elements depends on collection of fine particulates. Due to the variability in particulate control device efficiencies, emission rates of these elements can vary substantially. The volatility of class 3 elements means that particulate controls have only a limited impact on the emissions of these elements.

Determination of trace impurities in iron-based alloy using neutron activation analysis

International Nuclear Information System (INIS)

Zaidi, J.H.; Waheed, S.; Ahmad, S.

2000-01-01

A radiochemical neutron activation analysis procedure has been developed and applied to investigate 40 major, minor, and trace impurities in iron-based alloy. A comparison of RNAA and INAA indicated a significant improvement in the detection limits. The extensive use of these alloys in the heavy mechanical industry, manufacturing of aircraft engines, nuclear applications, medical devices and chemical equipment requires their precise characterization. The concentration of iron in the iron-based alloy was found to be 86.7%, whereas Ca, Cr, K, Mg, Mn, V and W were the other constituents of the alloy, which constituted to around 12.89%. The rest of the elements were present in minor or trace levels. Most of the rare earth elements were also present in trace amounts. (orig.)

Chemical characterization of materials by inductively coupled plasma mass spectrometry

International Nuclear Information System (INIS)

Deb, S.B.; Nagar, B.K.; Saxena, M.K.; Ramakumar, K.L.

2009-11-01

An Inductively Coupled Plasma Mass Spectrometer was procured for trace elemental determination in diverse samples. Since its installation a number of analytical measurements have been carried out on different sample matrices. These include chemical quality control measurements of nuclear fuel and other materials such as uranium metal. Uranium peroxide, ADU, ThO 2 , UO 2 ; isotopic composition of B, Li; chemical characterization of simulated ThO 2 + 2%UO 2 fuel; sodium zirconium phosphate and trace metallic elements in zirconium; Antarctica rock samples and wet phosphoric acid. Necessary separation methodologies required for effective removal of matrix were indigenously developed. In addition, a rigorous analytical protocol, which includes various calibration methodologies such as mass calibration, response calibration, detector cross calibration and linearity check over the entire dynamic range of 109 required for quantitative determination of elements at trace and ultra trace level,, has been standardized. This report summarizes efforts of RACD that have been put in this direction for the application of ICP-MS for analytical measurements. (author)

Radio-tracing 'without' radioactivity: accelerator mass spectrometry in biomedicine

International Nuclear Information System (INIS)

Vogel, J.S.

2005-01-01

Accelerator mass spectrometry (AMS) is a form of isotope-ratio mass spectrometry that quantifies concentrations of certain long-lived radioisotopes independently of their radioactive decay. AMS is primarily used in the geosciences for determining the age of a material that contains naturally occurring radioisotopes. AMS uses the same high specificity for enriched levels of these radioisotopes in tracing low chemical doses for long periods in biological systems, including humans. AMS provides the safety of low radiative exposure to experimental subjects and investigators, while obtaining attomole sensitivities that are not possible with stable isotope tracers because of their natural isotopic abundances. AMS isotope tracing was first applied to quantifying the genotoxicity of low level environmental chemicals in animals and later in humans. Physiologic concentrations of 14 C-labeled trace nutrients (folate, carotene, and tocopherol) are now measured directly in humans without concern about radiation. The radiative exposure is less than the commonly accepted risks of natural background radiation or the radiation fields found in high altitude air flights. AMS measures very small biological samples (such as 20 microliters of blood) that are easily obtained from human volunteers or model animals at frequent intervals for detailed analysis of kinetic profiles. This high data density enables the construction of compartmental models that elucidate nutrient behavior in tissues that cannot be directly sampled. The pharmaceutical industry is enthusiastic about AMS as a detector for 'micro-dosing' in which the human kinetics of an assuredly non-toxic dose of a candidate drug is tested early in a development project. Molecular tracing uses 3 H or 14 C as common isotopic labels, but AMS contributes to elemental tracing with certain radioisotopes having very long lives, such as 26 AL or 41 Ca. Calcium-41 is a particularly useful isotope in biomedical research because it is used

Trace metal distribution in sediments of the Pearl River Estuary and the surrounding coastal area, South China

International Nuclear Information System (INIS)

Ip, Carman C.M.; Li Xiangdong; Zhang Gan; Wai, Onyx W.H.; Li, Y.-S.

2007-01-01

Surface sediments and sediment cores collected at the Pearl River Estuary (PRE) and its surrounding coastal area were analysed for total metal concentrations, chemical partitioning, and Pb isotopic compositions. The distribution of Cu, Cr, Pb, and Zn demonstrated a typical diffusion pattern from the land to the direction of the sea. Two hotspots of trace metal contamination were located at the mixed zone between freshwater and marine waters. The enrichment of metals in the sediments could be attributed to the deposition of the dissolved and particulate trace metals in the water column at the estuarine area. The similar Pb isotopic signatures of the sediments at the PRE and its surrounding coastal area offered strong evidence that the PRE was a major source of trace metals to the adjacent coastal area. Slightly lower 206 Pb/ 207 Pb ratios in the coastal sediments may indicate other inputs of Pb in addition to the PRE sources, including the inputs from Hong Kong and other parts of the region. - The distribution of trace metals in sediments reflected contaminant sources, physical and chemical deposition processes

5th colloquium on atomic spectrometric trace analysis

International Nuclear Information System (INIS)

Welz, B.

1989-01-01

This book deals with apparatus, use-oriented and theoretical aspects of trace analysis and spectroscopy. General articles are concerned with the analysis of environmentally relevant samples; a comparison of modern spectroscopic techniques, the coupling of hydride production, chromatography and spectrometry; chemical modifiers for graphite tube furnace atomic absorption spectroscopy (AAS), and possible applications of flow injection to atomic spectrometric trace analysis - one of the outstanding subjects of the colloquium. About one quarter of the 85 contributions deals with new techniques including flow injection. Other priority subjects are the theory and application of graphite tube furnace AAS, and a comparison between different dissolution methods and direct solid analysis. Medicine and toxicology, analysis of biological materials and environmentally relevant samples are in the foreground of use-oriented papers. (orig./BBR) [de

The evolution of institutions and rules governing communal grazing ...

African Journals Online (AJOL)

This paper traces the tradition and evolution of the institutions and rules governing communal grazing lands in Botswana. It shows how the problem of resource overuse arose partly from the dismantling and delegitimization of traditional resource management institutions that occurred during the colonial period, and was ...

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 (RVY CMa, the archetype for the class of luminous red supergiant stars experiencing high mass loss. Specifically, the objective is to unravel the density 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

Trace and ultratrace level elemental and speciation analysis

International Nuclear Information System (INIS)

Arunachalam, J.

2012-01-01

Accurate determination of elements present at parts per million and billion levels in various matrices is a growing requirement in different fields. In environmental sciences various trace elements need to be analyzed so as establish the dispersal models of pollutants or the adequacy of effluent treatment prior to discharge into water bodies. The issues of bioaccumulation and magnification are important in aquatic systems. In nutrition and biochemistry one has to establish the bio-availability of essential and toxic elemental species as toxic elements prevent assimilation of essential elements. Fission and fusion technologies use a variety of structural materials requiring many trace elements to be present at levels strictly below the specified levels. Ultra-pure bulk semiconductor materials are required for fabrication devices. In metallurgy and materials sciences too, various trace elements are known to influence the properties. In the emerging fields like nanotechnology, it is necessary to understand the passage and accumulation of nano-particles inside the cells, through trace analysis. Many analytical techniques exist which can provide the concentration information in the bulk materials with good accuracy. They include ICP-AES, FAAS, and ICP-MS, which are solution based techniques. Direct solid state analytical techniques are Glow Discharge Mass Spectrometry (GDMS) and XRF. Accelerator based ion-beam analysis techniques can provide information on concentration and depth profiles of different elements in layered structures. Hyphenated techniques such as HPLC/lC-ICPMS, are helpful in identifying various chemical oxidation states in which a given element might be present in a matrix, which is termed as speciation analysis. This presentation will include the existing analytical competencies and the laboratory requirements for trace and ultra trace element elemental and speciation analyses and their applications. (author)

Engineering microbes for efficient production of chemicals

Science.gov (United States)

Gong, Wei; Dole, Sudhanshu; Grabar, Tammy; Collard, Andrew Christopher; Pero, Janice G; Yocum, R Rogers

2015-04-28

This present invention relates to production of chemicals from microorganisms that have been genetically engineered and metabolically evolved. Improvements in chemical production have been established, and particular mutations that lead to those improvements have been identified. Specific examples are given in the identification of mutations that occurred during the metabolic evolution of a bacterial strain genetically engineered to produce succinic acid. This present invention also provides a method for evaluating the industrial applicability of mutations that were selected during the metabolic evolution for increased succinic acid production. This present invention further provides microorganisms engineered to have mutations that are selected during metabolic evolution and contribute to improved production of succinic acid, other organic acids and other chemicals of commercial interest.

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

The Variscan calc-alkalic plutonism of western Corsica: mineralogy and major and trace element geochemistry

Science.gov (United States)

Cocherie, A.; Rossi, Ph.; Le Bel, L.

1984-10-01

Petrographic and structural observations on the calc-alkalic plutonism of western Corsica revealed the existence of several successively emplaced units associated with large basic bodies. The present mineralogical and geochemical study deals with the genesis, evolution and relationships of these different units. Basic plutonism is represented by three genetically linked types of rock: norites and troctolites with cumulate textures characterized by low REE contents and either no Eu anomaly or a positive Eu anomaly; gabbros with enriched LREE relatively to HREE patterns, probably close to an initial basaltic liquid; and diorites ranging up to charnockites which represent liquids evolved to varying degrees, mainly by fractional crystallization. Trace element data and studies on the evolution of pyroxene pairs demonstrate the consanguinity of these calc-alkaline basic rocks which are derived from a high alumina basaltic melt. The various granitoids (granodiorites, monzogranites and leucocratic monzogranites, i.e., adamellites) have distinct evolution trends as shown by the composition of their mafic minerals and by trace element distributions. They cannot be considered as being derivatives of the basic suite and they cannot be related by a common fractionation sequence. Rather, they represent distinctive batches of crustal anatexis. In addition, hybridization phenomena with the basic melt are noticed in granodiorites. The particular problem of the low La/Yb, Eu/Eu∗ and the high U, Th, Cs leucocratic monzogranites is discussed in detail. In addition to more conventional trace element diagrams, the simultaneous statistical treatment of all the geochemical data by correspondence factor analysis is shown to be a very use tool in distinguishing between the different units and to classify the elements according to their geochemical properties.

The Gaia-ESO Survey: Sodium and aluminium abundances in giants and dwarfs. Implications for stellar and Galactic chemical evolution

Science.gov (United States)

Smiljanic, R.; Romano, D.; Bragaglia, A.; Donati, P.; Magrini, L.; Friel, E.; Jacobson, H.; Randich, S.; Ventura, P.; Lind, K.; Bergemann, M.; Nordlander, T.; Morel, T.; Pancino, E.; Tautvaišienė, G.; Adibekyan, V.; Tosi, M.; Vallenari, A.; Gilmore, G.; Bensby, T.; François, P.; Koposov, S.; Lanzafame, A. C.; Recio-Blanco, A.; Bayo, A.; Carraro, G.; Casey, A. R.; Costado, M. T.; Franciosini, E.; Heiter, U.; Hill, V.; Hourihane, A.; Jofré, P.; Lardo, C.; de Laverny, P.; Lewis, J.; Monaco, L.; Morbidelli, L.; Sacco, G. G.; Sbordone, L.; Sousa, S. G.; Worley, C. C.; Zaggia, S.

2016-05-01

Context. Stellar evolution models predict that internal mixing should cause some sodium overabundance at the surface of red giants more massive than ~1.5-2.0 M⊙. The surface aluminium abundance should not be affected. Nevertheless, observational results disagree about the presence and/or the degree of Na and Al overabundances. In addition, Galactic chemical evolution models adopting different stellar yields lead to very different predictions for the behavior of [Na/Fe] and [Al/Fe] versus [Fe/H]. Overall, the observed trends of these abundances with metallicity are not well reproduced. Aims: We readdress both issues, using new Na and Al abundances determined within the Gaia-ESO Survey. Our aim is to obtain better observational constraints on the behavior of these elements using two samples: I) more than 600 dwarfs of the solar neighborhood and of open clusters and II) low- and intermediate-mass clump giants in six open clusters. Methods: Abundances were determined using high-resolution UVES spectra. The individual Na abundances were corrected for nonlocal thermodynamic equilibrium effects. For the Al abundances, the order of magnitude of the corrections was estimated for a few representative cases. For giants, the abundance trends with stellar mass are compared to stellar evolution models. For dwarfs, the abundance trends with metallicity and age are compared to detailed chemical evolution models. Results: Abundances of Na in stars with mass below ~2.0 M⊙, and of Al in stars below ~3.0 M⊙, seem to be unaffected by internal mixing processes. For more massive stars, the Na overabundance increases with stellar mass. This trend agrees well with predictions of stellar evolutionary models. For Al, our only cluster with giants more massive than 3.0 M⊙, NGC 6705, is Al enriched. However, this might be related to the environment where the cluster was formed. Chemical evolution models that well fit the observed [Na/Fe] vs. [Fe/H] trend in solar neighborhood dwarfs

TraceContract

Science.gov (United States)

Kavelund, Klaus; Barringer, Howard

2012-01-01

TraceContract is an API (Application Programming Interface) for trace analysis. A trace is a sequence of events, and can, for example, be generated by a running program, instrumented appropriately to generate events. An event can be any data object. An example of a trace is a log file containing events that a programmer has found important to record during a program execution. Trace - Contract takes as input such a trace together with a specification formulated using the API and reports on any violations of the specification, potentially calling code (reactions) to be executed when violations are detected. The software is developed as an internal DSL (Domain Specific Language) in the Scala programming language. Scala is a relatively new programming language that is specifically convenient for defining such internal DSLs due to a number of language characteristics. This includes Scala s elegant combination of object-oriented and functional programming, a succinct notation, and an advanced type system. The DSL offers a combination of data-parameterized state machines and temporal logic, which is novel. As an extension of Scala, it is a very expressive and convenient log file analysis framework.

Can liming change root anatomy, biomass allocation and trace element distribution among plant parts of Salix × smithiana in trace element-polluted soils?

Science.gov (United States)

Vondráčková, Stanislava; Tlustoš, Pavel; Száková, Jiřina

2017-08-01

Willows (Salix spp.) are considered to be effective for the phytoremediation of trace elements from contaminated soils, but their efficiency is limited in heavily polluted soils because of poor growth. Liming can be a desirable measure to decrease the plant availability of elements, resulting in improved plant development. Notably, large root area and maximum soil penetration are basic parameters that improve the efficiency of phytoremediation. The impact of soil chemical properties on willow root anatomy and the distribution of trace elements below-ground have rarely been studied. The effect of liming on root parameters, biomass allocation and trace element distribution in non-harvestable (coarse roots, fine roots, stumps) and harvestable plant parts (twigs and leaves) of Salix × smithiana was assessed at the end of a 4-year pot experiment with two trace element-polluted soils that differed in terms of soil pH. Stump biomass predominated in weakly acidic soil. In neutral soil, the majority of biomass was located in fine roots and stumps; the difference from other plant parts was minor. Trace elements were the most concentrated in fine roots. Translocation to above-ground biomass increased as follows: Pb roots roots). Lime application decreased the concentrations of mobile Cd and Zn and related levels in plants, improved biomass production and root parameters and increased the removal of all trace elements in weakly acidic soil. None or minimum differences in the monitored parameters were recorded for dolomite treatments in both soils. The dose and source of liming had crucial effects on root anatomy. Growing willows in limed trace element-polluted soils is a suitable measure for combination of two remediation strategies, i.e. phytoextraction of Cd and Zn and assisted phytostabilization of As and Pb.

Time evolution of the Wigner function in the entangled-state representation

International Nuclear Information System (INIS)

Fan Hongyi

2002-01-01

For quantum-mechanical entangled states we introduce the entangled Wigner operator in the entangled-state representation. We derive the time evolution equation of the entangled Wigner operator . The trace product rule for entangled Wigner functions is also obtained

The Diversity of Chemical Composition and the Effects on Stellar Evolution and Planetary Habitability

Science.gov (United States)

Truitt, Amanda R.

2017-08-01

I present a catalog of 1,794 stellar evolution models for solar-type and low-mass stars, which is intended to help characterize real host-stars of interest during the ongoing search for potentially habitable exoplanets. The main grid is composed of 904 tracks, for 0.5-1.2 M solar masses at scaled metallicity values of 0.1-1.5 Z solar masses and specific elemental abundance ratio values of 0.44-2.28 O/Fe solar masses, 0.58-1.72 C/Fe solar masses, 0.54-1.84 Mg/Fe solar masses, and 0.5-2.0 Ne/Fe solar masses. The catalog includes a small grid of late stage evolutionary tracks (25 models), as well as a grid of M-dwarf stars for 0.1-0.45 M solar masses (856 models). The time-dependent habitable zone evolution is calculated for each track, and is strongly dependent on stellar mass, effective temperature, and luminosity parameterizations. I have also developed a subroutine for the stellar evolution code TYCHO that implements a minimalist coupled model for estimating changes in the stellar X-ray luminosity, mass loss, rotational velocity, and magnetic activity over time; to test the utility of the updated code, I created a small grid (9 models) for solar-mass stars, with variations in rotational velocity and scaled metallicity. Including this kind of information in the catalog will ultimately allow for a more robust consideration of the long-term conditions that orbiting planets may experience. In order to gauge the true habitability potential of a given planetary system, it is extremely important to characterize the host-star's mass, specific chemical composition, and thus the timescale over which the star will evolve. It is also necessary to assess the likelihood that a planet found in the "instantaneous" habitable zone has actually had sufficient time to become "detectably" habitable. This catalog provides accurate stellar evolution predictions for a large collection of theoretical host-stars; the models are of particular utility in that they represent the real

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.

Tracing monotreme venom evolution in the genomics era.

Science.gov (United States)

Whittington, Camilla M; Belov, Katherine

2014-04-02

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.

Characterization and mass balance of trace elements in an iron ore sinter plant

Directory of Open Access Journals (Sweden)

Lucas Ladeira Lau

2016-04-01

Full Text Available Environmental legislation is becoming more restrictive in several industrial sectors, especially in the steel industry, which is well known for its large pollution potential. With the recent growth of interest in effects of trace elements on the environment and health, the inclusion of emission limits on these elements in this legislation has become increasingly popular. This article aims to describe the partitioning of trace elements between the products (sinter and plant emissions in an iron ore sinter plant, aiming to better understand the behavior of these elements in the sintering process to eventually support interventions to modify these partitions. Chemical characterization of several sintering inputs was initially performed, revealing that the steel-making residues contained large concentrations of trace elements, whereas low concentrations were observed in the flux. Based on the trace element concentrations, we analyzed the injection of trace elements in a sintering pilot using a sintering mixture. Mass balance was then used to determine the theoretical partitioning of trace elements in the sinter and emissions; cadmium, nickel, lead, mercury, and copper exhibited greater tendencies to concentrate in atmospheric emissions.

Radiolabelled substrates for studying biological effects of trace contaminants

International Nuclear Information System (INIS)

1975-01-01

A programme of coordinated isotopic tracer-aided investigations of the biological side-effects of foreign chemical residues in food and agriculture, initiated in 1973, was reviewed. The current status of representative investigations from the point of view of techniques and priorities was assessed. Such investigations involved radioactive substrates for studying DNA injury and its repair; 14 C-labelled acetylcholine as substrate for measuring enzyme inhibition due to the presence of, or exposure to, anticholinesteratic contaminants; radioactive substrates as indication of side-effects in non-target organisms and of their comparative susceptibilities; radioactive substrates as indicators of persistence or biodegradability of trace contaminants of soil or water; and labelled pools for studying the biological side-effects of trace contaminants. Priorities were identified

The Evolution of the PLO: A Rhetoric of Terrorism.

Science.gov (United States)

Brock, Bernard L.; Howell, Sharon

1989-01-01

Traces the evolution of the Palestine Liberation Organization (PLO) and assesses the effectiveness of the rhetoric of terrorism as a strategy. Applies concepts derived from protest rhetoric of the 1960s to the Palestine movement, noting that current "terrorist" rhetoric is similar to the New Left's confrontational strategies. (MM)

Use of trace elements as indicators for underground fluid circulations in karstic environment; Utilisation des elements en trace comme traceurs des circulations souterraines en milieu karstique (site du Lamalou, Herault)

Energy Technology Data Exchange (ETDEWEB)

Pane-Escribe, M B

1995-06-29

The geochemical study of the trace element behaviour in karstic groundwaters has been carried out over the experimental site of Lamalou (Herault, France). Routine measurements of the physico-chemical parameters and of the dissolved elements concentrations have been achieved during two hydrological cycles. Radon has been monitored by passive detectors and by automatic electronic probes. Trace elements (Sc, Ti, V, Cr, Ni, Cu, Zn, As Rb, Sr, Mo, Cd, Sb, Cs, Ba, Th, U) were analyzed by Inductively Coupled Plasma Mass Spectrometry (ICP-MS). The first part of this work presents the methodologies employed with in particular the improvement of the analytical performances of ICP-MS for water samples analysis. The detection limit for each considered element has been determined. The short and long term reproducibility for the samples analysis has also been tested. The second part of this study presents the treatment and interpretation of the results. This analysis has pointed our the influence of the aquifer structure on the chemical elements distribution. The trace and major elements concentrations are effectively related to the fracturing state of the reservoir and allow to individualize the high transmissivity zones from zones with a lower transmissivity in this mono-lithological context, trace elements appear to be particularly efficient tracers for determining the water origin and circulation their spatial and temporal behaviour leads to identify three different origins for the water mineralization over the studied area: limestones, clays and external sources (rainfalls and occasional pollutions). (author). 154 refs.

Levels of chemical contaminants in nonoccupationally exposed U. S. residents

Energy Technology Data Exchange (ETDEWEB)

Holleman, J.W.; Hammons, A.S.

1978-08-01

Data are presented on the levels of all chemical contaminants resulting from environmental pollution which have been found in human tissues including blood, urine, breast milk, and tissue samples obtained at autopsy. Most data results from specific surveys to determine health hazards. The roles of trace elements and recognition of the need to determine baseline levels of chemicals introduced into the environment are factors which have motivated surveys by individual investigators. Thus, most data on chemicals in human tissues record levels of pesticides (e.g., DDT and metabolites), levels of trace metals such as lead, cadmium, and mercury, or levels of nutritionally essential elements such as zinc, copper, manganese, and fluoride. Data available on iron and calcium are not presented as their presence in the environment is generally not considered hazardous. Data on several uncommon chemicals, such as indium and ytterbium, are included basically as items of interest and to further document their presence in healthy individuals. Baseline data were presented where available to provide perspective as to chemical levels which might be expected under conditions where exposure could be considered normal or not directly related to a pollutant source. Nearly 600 cited surveys or investigations, most of which were reported within the past decade, are listed. Ninety-four different chemical contaminants, primarily trace metals and organochlorine pesticides, are reported. It is estimated that over 75% of the data published during the past 30 years on chemical contaminants derived from environmental pollution and found in human tissue in the United States are represented in this report.

Levels of chemical contaminants in nonoccupationally exposed U.S. residents

International Nuclear Information System (INIS)

Holleman, J.W.; Hammons, A.S.

1978-08-01

Data are presented on the levels of all chemical contaminants resulting from environmental pollution which have been found in human tissues including blood, urine, breast milk, and tissue samples obtained at autopsy. Most data results from specific surveys to determine health hazards. The roles of trace elements and recognition of the need to determine baseline levels of chemicals introduced into the environment are factors which have motivated surveys by individual investigators. Thus, most data on chemicals in human tissues record levels of pesticides (e.g., DDT and metabolites), levels of trace metals such as lead, cadmium, and mercury, or levels of nutritionally essential elements such as zinc, copper, manganese, and fluoride. Data available on iron and calcium are not presented as their presence in the environment is generally not considered hazardous. Data on several uncommon chemicals, such as indium and ytterbium, are included basically as items of interest and to further document their presence in healthy individuals. Baseline data were presented where available to provide perspective as to chemical levels which might be expected under conditions where exposure could be considered normal or not directly related to a pollutant source. Nearly 600 cited surveys or investigations, most of which were reported within the past decade, are listed. Ninety-four different chemical contaminants, primarily trace metals and organochlorine pesticides, are reported. It is estimated that over 75% of the data published during the past 30 years on chemical contaminants derived from environmental pollution and found in human tissue in the United States are represented in this report

Forensic collection of trace chemicals from diverse surfaces with strippable coatings.

Science.gov (United States)

Jakubowski, Michael J; Beltis, Kevin J; Drennan, Paul M; Pindzola, Bradford A

2013-11-07

Surface sampling for chemical analysis plays a vital role in environmental monitoring, industrial hygiene, homeland security and forensics. The standard surface sampling tool, a simple cotton gauze pad, is failing to meet the needs of the community as analytical techniques become more sensitive and the variety of analytes increases. In previous work, we demonstrated the efficacy of non-destructive, conformal, spray-on strippable coatings for chemical collection from simple glass surfaces. Here we expand that work by presenting chemical collection at a low spiking level (0.1 g m(-2)) from a diverse array of common surfaces - painted metal, engineering plastics, painted wallboard and concrete - using strippable coatings. The collection efficiency of the strippable coatings is compared to and far exceeds gauze pads. Collection from concrete, a particular challenge for wipes like gauze, averaged 73% over eight chemically diverse compounds for the strippable coatings whereas gauze averaged 10%.

Chemical analysis report 2014

International Nuclear Information System (INIS)

Elbouzidi, Saliha; Elyahyaoui, Adil; Ghassan, Acil; Marah, Hamid

2014-01-01

This report highlights the results of chemical analyzes related to Major elements, traces and heavy metals carried out at the CNESTEN DASTE in Rabat (Morocco), on behalf of Senegal. These analyzes cover 120 samples. The report presents the analytical techniques used (parameters and methods), a legend and the results tables.

Chemical evolution of Local Group dwarf galaxies in a cosmological context - I. A new modelling approach and its application to the Sculptor dwarf spheroidal galaxy

Science.gov (United States)

Romano, Donatella; Starkenburg, Else

2013-09-01

We present a new approach for chemical evolution modelling, specifically designed to investigate the chemical properties of dwarf galaxies in a full cosmological framework. In particular, we focus on the Sculptor dwarf spheroidal galaxy, for which a wealth of observational data exists, as a test bed for our model. We select four candidate Sculptor-like galaxies from the satellite galaxy catalogue generated by implementation of a version of the Munich semi-analytic model for galaxy formation on the level 2 Aquarius dark matter simulations and use the mass assembly and star formation histories predicted for these four systems as an input for the chemical evolution code. We follow explicitly the evolution of several chemical elements, both in the cold gas out of which the stars form and in the hot medium residing in the halo. We take into account in detail the lifetimes of stars of different initial masses, the distribution of the delay times for Type Ia supernova explosions and the dependence of the stellar yields from the initial metallicity of the stars. We allow large fractions of metals to be deposited into the hot phase, either directly as stars die or through reheated gas flows powered by supernova explosions. We find that, in order to reproduce both the observed metallicity distribution function and the observed abundance ratios of long-lived stars of Sculptor, large fractions of the reheated metals must never re-enter regions of active star formation. With this prescription, all the four analogues to the Sculptor dwarf spheroidal galaxy extracted from the simulated satellites catalogue on the basis of luminosity and stellar population ages are found to reasonably match the detailed chemical properties of real Sculptor stars. However, all model galaxies do severely underestimate the fraction of very metal poor stars observed in Sculptor. Our analysis thus sets further constraints on the semi-analytical models and, at large, on possible metal enrichment

Stellar Physics 2: Stellar Evolution and Stability

CERN Document Server

Bisnovatyi-Kogan, Gennady S

2011-01-01

"Stellar Physics" is a an outstanding book in the growing body of literature on star formation and evolution. Not only does the author, a leading expert in the field, very thoroughly present the current state of knowledge on stellar physics, but he handles with equal care the many problems that this field of research still faces. A bibliography with well over 1000 entries makes this book an unparalleled reference source. "Stellar Evolution and Stability" is the second of two volumes and can be read, as can the first volume "Fundamental Concepts and Stellar Equilibrium," as a largely independent work. It traces in great detail the evolution of protostars towards the main sequence and beyond this to the last stage of stellar evolution, with the corresponding vast range from white dwarfs to supernovae explosions, gamma-ray bursts and black hole formation. The book concludes with special chapters on the dynamical, thermal and pulsing stability of stars. This second edition is carefully updated in the areas of pre...

Assessment of trace element stabilization in soil

OpenAIRE

Kumpiene, Jurate

2005-01-01

The thesis deals with the remediation of trace element contaminated soil by the chemical stabilization technique. The objective is to complement the knowledge about possibilities of applying the stabilization either (1) as an alternate soil remediation method to excavation and landfilling or (2) for a pre-treatment of contaminated soil before landfilling. The work is based on two case studies of the stabilization of 1) Cr, Cu, As, and Zn contaminated soil using metallic iron and 2) Pb and Cu ...

Trace elements and radon in groundwater across the United States, 1992-2003

Science.gov (United States)

Ayotte, Joseph D.; Gronberg, Jo Ann M.; Apodaca, Lori E.

2011-01-01

Trace-element concentrations in groundwater were evaluated for samples collected between 1992 and 2003 from aquifers across the United States as part of the U.S. Geological Survey National Water-Quality Assessment Program. This study describes the first comprehensive analysis of those data by assessing occurrence (concentrations above analytical reporting levels) and by comparing concentrations to human-health benchmarks (HHBs). Data from 5,183 monitoring and drinking-water wells representing more than 40 principal and other aquifers in humid and dry regions and in various land-use settings were used in the analysis. Trace elements measured include aluminum (Al), antimony (Sb), arsenic (As), barium (Ba), beryllium (Be), boron (B), cadmium (Cd), chromium (Cr), cobalt (Co), copper (Cu), iron (Fe), lead (Pb), lithium (Li), manganese (Mn), molybdenum (Mo), nickel (Ni), selenium (Se), silver (Ag), strontium (Sr), thallium (Tl), uranium (U), vanadium (V), and zinc (Zn). Radon (Rn) gas also was measured and is included in the data analysis. Climate influenced the occurrence and distribution of trace elements in groundwater whereby more trace elements occurred and were found at greater concentrations in wells in drier regions of the United States than in humid regions. In particular, the concentrations of As, Ba, B, Cr, Cu, Mo, Ni, Se, Sr, U, V, and Zn were greater in the drier regions, where processes such as chemical evolution, ion complexation, evaporative concentration, and redox (oxidation-reduction) controls act to varying degrees to mobilize these elements. Al, Co, Fe, Pb, and Mn concentrations in groundwater were greater in humid regions of the United States than in dry regions, partly in response to lower groundwater pH and (or) more frequent anoxic conditions. In groundwater from humid regions, concentrations of Cu, Pb, Rn, and Zn were significantly greater in drinking-water wells than in monitoring wells. Samples from drinking-water wells in dry regions had

Ground water chemical evolution of Pocos de Caldas - Minas Gerais State -Brazil

International Nuclear Information System (INIS)

Cruz, W.B.; Peixoto, C.A.M.

1991-01-01

The chemical evolution and the origin of the groundwater, cold and thermal springs composition are analysed related to the geochemical environment of the Pocos de Caldas alkaline complex. The thermal waters origin are related to a large and deep open fracture system in three main directions: N14E, N50E and E-W. The tritium content when simultaneously analysed with the deuterium and oxygen-18 set show that thermal waters are old meteoric waters (30-40 years of age). On the other hand, the cold springs that circulate on the superficial levels are more recent, which is a characteristic of an acid oxidizing environment without sulfides and greater concentration of free CO 2 and Rn 222 . The pH increases slowly with depth and also the H C O 3 - , Na + , SO 4 2- and the Si O 2 content. High concentrations of fluoride follow this process. Reducing environment with an increase in the sulphide content and a decrease in radioactivity are trends in the system studied. (author)

Bioavailability of metals-trace in sediments: a review

International Nuclear Information System (INIS)

Rodrigues, Rafaela E. de A.V.; Souza, Vivianne Lucia Bormann; Lima, Vanessa Lemos de; Hazin, Clovis Abrahao

2014-01-01

The chemical association of metals in sediments provides an indication of its release by physical, chemical and biological processes, with toxic effects under certain environmental conditions. Knowing about their chemical bonds in sediments, can recognize specific sources of pollution, and speciation of trace metals is important for bioavailability and toxicity to animals and plants. The accumulation of these particles in the sediment occur by the following mechanisms: a) adsorption to the finest particles; b) precipitating of the element in the form of compounds; c) co-precipitating of the element with iron and manganese oxides; d) complexation with organic matter; e) incorporation into the crystal lattice of minerals. Currently, five phases are considered when studying the bioavailability of trace elements in sediments: a) the exchangeable phase, MgCl 2 (causes saltiness change); b) leachable phase, (acetic acid causes pH change); c) reducible phase (hydroxylamine hydrochloride causes release of the bound metals linked to Fe and Mn oxides); d) oxidized phase, the peroxide hydrogen (cause the degradation of organic matter); e) the residual pseudo-phase, the aqua regia (cause release of metals associated to minerals). The first three phases are considered the most bioavailable. In the last two fractions, the metals are linked to sediment constituents and not bioavailable. The organic phase is relatively stable and the metal present therein are removed under oxidative conditions. Metals present in the pseudo-phase residual measure the degree of environmental pollution, since great amount of metals at this stage indicates a lower degree of pollution

Considerations on aims and approaches of the study on the transport of trace elements in a river watershed

International Nuclear Information System (INIS)

Matsunaga, Takeshi

2002-10-01

Concerning the study subject on the transport of trace, toxic chemicals and radioactive elements in a river watershed, that has been developed in the Research Group for Terrestrial Environment, its aims and methodological approaches have been discussed in the light of related social and technological aspects of today. It is stressed that a study of the transport of radionuclides originated from a nuclear installation is needed to assess the physiological impact and to provide appropriate countermeasures in case of an accident. A numerical model is prerequisite for these objectives and to be keenly developed. The outcome of the modeling will be also important for a quantitative analysis of cycling of trace toxic elements in the atmosphere- lithosphere-hydrosphere, and also of the mechanisms of contamination of the surface aquatic environment. Accordingly, the study will contribute to the key issues stated in the national programs of science and technologies such as conservation of the natural and living environment. The present large consumption of metals and metalloids may cause an extensive contamination in the future. The study can provide solutions to the problems associated with metals and metalloids, because their environmental behavior resembles to that of radionuclides. From a methodological aspect, an importance of a direct investigation of physicochemical forms of trace, toxic elements must be stressed. A simultaneous use of experimental methods and chemical modeling to study the physico-chemical forms will be a good exemption to be realized hereafter. Experimentally, partitioning between solid and liquid phases using radioisotopes, and identification of solid species using various X-ray spectrometric techniques, for example, have been recognized very promising to investigate physico-chemical form of trace elements. These techniques are much ought to the nuclear sciences, suggesting further possible contribution of the nuclear sciences to the questions of

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.

Origin and Evolution of the Elements

Science.gov (United States)

McWilliam, Andrew; Rauch, Michael

2004-09-01

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

The Evolution of Cost/Schedule Control (Direct Labor) in Naval Shipyards

National Research Council Canada - National Science Library

Gessis, Scott N

1992-01-01

The evolution of a Cost/Schedule Control System (C/SCS), for direct labor, in naval shipyards can be traced from the cost/schedule control concept used in the Air Force in the 1960s, as an initiative toward more reliable data...

Levels of trace elements in MWSS drinking water

International Nuclear Information System (INIS)

Andal, T.T.

1998-01-01

As a water supplier for the metropolis, vigilance over the water quality has not been taken for granted at the Metropolitan Waterworks and Sewerage System (MWSS). By the early 1980's, a control laboratory equipped with modern facilities had been set up to supplement the already existing control laboratory at Filter Plant II handling physical, chemical, bacteriological, biological and mineral analyses and examinations, efficiently. The new central laboratory is intended to monitor trace elements, organic constituents and other elements with health related impact so as to assure the consumers of a safe drinking water supply at all times. This presentation reviews the levels of trace element pollution in MWSS tap water, then and now, in justification of the rehabilitation projects along the distribution network, in the treatment plants and other pertinent innovations corresponding to budgeted capital outlays as invested by the system. (author)

Tracing the evolution of critical evaluation skills in students' use of the Internet.

OpenAIRE

Blumberg, P; Sparks, J

1999-01-01

This paper documents the evolving uses of the Internet made by public health graduate students and traces the development of their search methods and critical evaluative criteria. Early in the first semester and again six months later, twenty-four graduate students in a problem-based learning curriculum, which emphasizes evidence-based critical thinking skills, were required to describe their most helpful resources and to evaluate these resources critically. The answers were coded for the typ...

Use of trace elements as indicators for underground fluid circulations in karstic environment

International Nuclear Information System (INIS)

Pane-Escribe, M.B.

1995-01-01

The geochemical study of the trace element behaviour in karstic groundwaters has been carried out over the experimental site of Lamalou (Herault, France). Routine measurements of the physico-chemical parameters and of the dissolved elements concentrations have been achieved during two hydrological cycles. Radon has been monitored by passive detectors and by automatic electronic probes. Trace elements (Sc, Ti, V, Cr, Ni, Cu, Zn, As Rb, Sr, Mo, Cd, Sb, Cs, Ba, Th, U) were analyzed by Inductively Coupled Plasma Mass Spectrometry (ICP-MS). The first part of this work presents the methodologies employed with in particular the improvement of the analytical performances of ICP-MS for water samples analysis. The detection limit for each considered element has been determined. The short and long term reproducibility for the samples analysis has also been tested. The second part of this study presents the treatment and interpretation of the results. This analysis has pointed our the influence of the aquifer structure on the chemical elements distribution. The trace and major elements concentrations are effectively related to the fracturing state of the reservoir and allow to individualize the high transmissivity zones from zones with a lower transmissivity in this mono-lithological context, trace elements appear to be particularly efficient tracers for determining the water origin and circulation their spatial and temporal behaviour leads to identify three different origins for the water mineralization over the studied area: limestones, clays and external sources (rainfalls and occasional pollutions). (author)

Chemical Ecology of Cave-Dwelling Millipedes: Defensive Secretions of the Typhloiulini (Diplopoda, Julida, Julidae).

Science.gov (United States)

Makarov, Slobodan E; Bodner, Michaela; Reineke, Doris; Vujisić, Ljubodrag V; Todosijević, Marina M; Antić, Dragan Ž; Vagalinski, Boyan; Lučić, Luka R; Mitić, Bojan M; Mitov, Plamen; Anđelković, Boban D; Lucić, Sofija Pavković; Vajs, Vlatka; Tomić, Vladimir T; Raspotnig, Günther

2017-04-01

Cave animals live under highly constant ecological conditions and in permanent darkness, and many evolutionary adaptations of cave-dwellers have been triggered by their specific environment. A similar "cave effect" leading to pronounced chemical interactions under such conditions may be assumed, but the chemoecology of troglobionts is mostly unknown. We investigated the defensive chemistry of a largely cave-dwelling julid group, the controversial tribe "Typhloiulini", and we included some cave-dwelling and some endogean representatives. While chemical defense in juliform diplopods is known to be highly uniform, and mainly based on methyl- and methoxy-substituted benzoquinones, the defensive secretions of typhloiulines contained ethyl-benzoquinones and related compounds. Interestingly, ethyl-benzoquinones were found in some, but not all cave-dwelling typhloiulines, and some non-cave dwellers also contained these compounds. On the other hand, ethyl-benzoquinones were not detected in troglobiont nor in endogean typhloiuline outgroups. In order to explain the taxonomic pattern of ethyl-benzoquinone occurrence, and to unravel whether a cave-effect triggered ethyl-benzoquinone evolution, we classed the "Typhloiulini" investigated here within a phylogenetic framework of julid taxa, and traced the evolutionary history of ethyl-benzoquinones in typhloiulines in relation to cave-dwelling. The results indicated a cave-independent evolution of ethyl-substituted benzoquinones, indicating the absence of a "cave effect" on the secretions of troglobiont Typhloiulini. Ethyl-benzoquinones probably evolved early in an epi- or endogean ancestor of a clade including several, but not all Typhloiulus (basically comprising a taxonomic entity known as "Typhloiulus sensu stricto") and Serboiulus. Ethyl-benzoquinones are proposed as novel and valuable chemical characters for julid systematics.

Seasonal and temporal evolution of nutrient composition of pastures grown on remediated and non remediated soils affected by trace element contamination (Guadiamar Valley, SW Spain)

Energy Technology Data Exchange (ETDEWEB)

Madejon, P.; Dominguez, M. T.; Murillo, J. M.

2010-07-01

Elevated trace element concentrations in soils can affect the solubility and uptake of essential elements, resulting in nutrient deficiencies in plant tissues. The present paper deals with nutrient composition of pastures established on polluted and remediated soils (Green Corridor of the Guadiamar river Valley), in order to check the potential nutritional disorders that could derive from the soil pollution. In addition, nutrient composition of a representative grass, Cynodon dactylon, collected in 1999 and 2008 was compared in remediated and non-remediated sites of the polluted area. In general, nutrient concentrations of pastures were similar or even higher in polluted sites compared to control sites. Therefore, the estimated potential ingestion of main nutrients by horses (the most abundant animals in the area) was also greater in the polluted and remediated soils and covered their nutritional requirements (more than 300 (N), 70 (S), 35 (P), 400 (K), 175 (Ca) and 30 (Mg) mg kg{sup -}1 body weight day {sup -}1 in spring and autumn). Temporal evolution of nutrients and physiological ratios (N/S, Ca/P, K/Na, K/Ca+Mg) in C. dactylon showed a significant variation from 1999 to 2008, especially in the non-remediated area, leading to a recovery of the nutritional quality of this grass. The reasonable nutritional quality of pastures and the absence of negative interactions between nutrients and trace elements seem to indicate a stabilisation of soil pollutants in the affected area. (Author) 41 refs.

Evolution before genes

Directory of Open Access Journals (Sweden)

Vasas Vera

2012-01-01

Full Text Available Abstract Background Our current understanding of evolution is so tightly linked to template-dependent replication of DNA and RNA molecules that the old idea from Oparin of a self-reproducing 'garbage bag' ('coacervate' of chemicals that predated fully-fledged cell-like entities seems to be farfetched to most scientists today. However, this is exactly the kind of scheme we propose for how Darwinian evolution could have occurred prior to template replication. Results We cannot confirm previous claims that autocatalytic sets of organic polymer molecules could undergo evolution in any interesting sense by themselves. While we and others have previously imagined inhibition would result in selectability, we found that it produced multiple attractors in an autocatalytic set that cannot be selected for. Instead, we discovered that if general conditions are satisfied, the accumulation of adaptations in chemical reaction networks can occur. These conditions are the existence of rare reactions producing viable cores (analogous to a genotype, that sustains a molecular periphery (analogous to a phenotype. Conclusions We conclude that only when a chemical reaction network consists of many such viable cores, can it be evolvable. When many cores are enclosed in a compartment there is competition between cores within the same compartment, and when there are many compartments, there is between-compartment competition due to the phenotypic effects of cores and their periphery at the compartment level. Acquisition of cores by rare chemical events, and loss of cores at division, allows macromutation, limited heredity and selectability, thus explaining how a poor man's natural selection could have operated prior to genetic templates. This is the only demonstration to date of a mechanism by which pre-template accumulation of adaptation could occur. Reviewers This article was reviewed by William Martin and Eugene Koonin.

Evolution of near-field physico-chemical characteristics of the SFR repository

International Nuclear Information System (INIS)

Savage, D.; Stenhouse, M.; Benbow, S.

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 -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

Primordial nucleosynthesis and chemical evolution of galaxies

International Nuclear Information System (INIS)

Audouze, J.; Delbourgo-Salvador, P.

1986-07-01

Simple or canonical Big Bang models are claimed to account properly for the abundances of the lightest elements D, 3 He, 4 He and 7 Li if the baryonic cosmological parameter of the Universe is Ω B B is lower than 0.06 i.e. significantly smaller than in the simplest framework. Moreover this hypothesis of significant D destruction during the galactic evolution could be observationally tested

Tracing Geothermal Fluids

Energy Technology Data Exchange (ETDEWEB)

Michael C. Adams; Greg Nash

2004-03-01

Geothermal water must be injected back into the reservoir after it has been used for power production. Injection is critical in maximizing the power production and lifetime of the reservoir. To use injectate effectively the direction and velocity of the injected water must be known or inferred. This information can be obtained by using chemical tracers to track the subsurface flow paths of the injected fluid. Tracers are chemical compounds that are added to the water as it is injected back into the reservoir. The hot production water is monitored for the presence of this tracer using the most sensitive analytic methods that are economically feasible. The amount and concentration pattern of the tracer revealed by this monitoring can be used to evaluate how effective the injection strategy is. However, the tracers must have properties that suite the environment that they will be used in. This requires careful consideration and testing of the tracer properties. In previous and parallel investigations we have developed tracers that are suitable from tracing liquid water. In this investigation, we developed tracers that can be used for steam and mixed water/steam environments. This work will improve the efficiency of injection management in geothermal fields, lowering the cost of energy production and increasing the power output of these systems.

High-throughput trace analysis of explosives in water by laser diode thermal desorption/atmospheric pressure chemical ionization-tandem mass spectrometry.

Science.gov (United States)

Badjagbo, Koffi; Sauvé, Sébastien

2012-07-03

Harmful explosives can accumulate in natural waters in the long term during their testing, usage, storage, and dumping and can pose a health risk to humans and the environment. For the first time, attachment of small anions to neutral molecules in laser diode thermal desorption/atmospheric pressure chemical ionization was systematically investigated for the direct determination of trace nitroaromatics, nitrate esters, and nitramine explosives in water. Using ammonium chloride as an additive improved the instrument response for all the explosives tested and promoted the formation of several characteristic adduct ions. The method performs well achieving good linearity over at least 2 orders of magnitude, with coefficients of determination greater than 0.995. The resulting limits of detection are in the range of 0.009-0.092 μg/L. River water samples were successfully analyzed by the proposed method with accuracy in the range of 96-98% and a response time of 15 s, without any further pretreatment or chromatographic separation.

Morphology evolution and nanostructure of chemical looping transition metal oxide materials upon redox processes

International Nuclear Information System (INIS)

Qin, Lang; Cheng, Zhuo; Guo, Mengqing; Fan, Jonathan A.; Fan, Liang-Shih

2017-01-01

Transition metal are heavily used in chemical looping technologies because of their high oxygen carrying capacity and high thermal reactivity. These oxygen activities result in the oxide formation and oxygen vacancy formation that affect the nanoscale crystal phase and morphology within these materials and their subsequent bulk chemical behavior. In this study, two selected earlier transition metals manganese and cobalt as well as two selected later transition metals copper and nickel that are important to chemical looping reactions are investigated when they undergo cyclic redox reactions. We found Co microparticles exhibited increased CoO impurity presence when oxidized to Co_3O_4 upon cyclic oxidation; CuO redox cycles prefer to be limited to a reduced form of Cu_2O and an oxidized form of CuO; Mn microparticles were oxidized to a mixed phases of MnO and Mn_3O_4, which causes delamination during oxidation. For Ni microparticles, a dense surface were observed during the redox reaction. The atomistic thermodynamics methods and density functional theory (DFT) calculations are carried out to elucidate the effect of oxygen dissociation and migration on the morphological evolution of nanostructures during the redox processes. Our results indicate that the earlier transition metals (Mn and Co) tend to have stronger interaction with O_2 than the later transition metals (Ni and Cu). Also, our modified Brønsted−Evans−Polanyi (BEP) relationship for reaction energies and total reaction barriers reveals that reactions of earlier transition metals are more exergonic and have lower oxygen dissociation barriers than those of later transition metals. In addition, it was found that for these transition metal oxides the oxygen vacancy formation energies increase with the depth. The oxide in the higher oxidation state of transition metal has lower vacancy formation energy, which can facilitate forming the defective nanostructures. The fundamental understanding of these metal

Lunar evolution: is there a global radioactive crust on the moon

International Nuclear Information System (INIS)

Murthy, V.R.

1977-01-01

Chemical and isotopic analyses of various grainsize fractions of lunar soils show the presence of an 'exotic component' in practically all lunar soils. The patterns of enrichments in the grain-size fractions and the Sr-isotopic data show that the regolith evolution displays the combined effects of comminution of local rock types and addition of the exotic component. The chemical characteristics of this exotic component as deduced from the chemical and isotopic data in soils from Apollo 11, 12, 15 and 16 uniformly point to compositions similar to the material from Fra Mauro region collected in the Apollo 14 mission. There is a strong correlation between the amount of exotic component in a soil and its distance from the Fra Mauro region. It is suggested that the exotic component represents trace element enriched material from the Imbrium-Procellarum region, which was surficially deposited during Imbrium excavation and re-exposed from under the mare-lavas in subsequent cratering events. Surficial transport processes have distributed these materials widely over the lunar surface. There appears no need to invoke a global radioactive crust on the Moon nor of 'hot spots' distributed over the entire surface of the Moon to explain the ubiquitous presence of this component in lunar regolith, nor is there a compelling reason at present to postulate a global melting process for the generation of highly differentiated materials such as 'kreep' and the exotic component. (author)

Distributed Sensor Particles for Remote Fluorescence Detection of Trace Analytes: UXO/CW; TOPICAL

International Nuclear Information System (INIS)

SINGH, ANUP K.; GUPTA, ALOK; MULCHANDANI, ASHOK; CHEN, WILFRED; BHATIA, RIMPLE B.; SCHOENIGER, JOSEPH S.; ASHLEY, CAROL S.; BRINKER, C. JEFFREY; HANCE, BRADLEY G.; SCHMITT, RANDAL L.; JOHNSON, MARK S.; HARGIS JR. PHILIP J.; SIMONSON, ROBERT J.

2001-01-01

This report summarizes the development of sensor particles for remote detection of trace chemical analytes over broad areas, e.g residual trinitrotoluene from buried landmines or other unexploded ordnance (UXO). We also describe the potential of the sensor particle approach for the detection of chemical warfare (CW) agents. The primary goal of this work has been the development of sensor particles that incorporate sample preconcentration, analyte molecular recognition, chemical signal amplification, and fluorescence signal transduction within a ''grain of sand''. Two approaches for particle-based chemical-to-fluorescence signal transduction are described: (1) enzyme-amplified immunoassays using biocompatible inorganic encapsulants, and (2) oxidative quenching of a unique fluorescent polymer by TNT

Persistent local chemical bonds in intermetallic phase formation

Energy Technology Data Exchange (ETDEWEB)

Bai, Yanwen [Key Laboratory for Liquid–Solid Structural Evolution and Processing of Materials, Ministry of Education, Shandong University, Jinan 250061 (China); Bian, Xiufang, E-mail: xfbian@sdu.edu.cn [Key Laboratory for Liquid–Solid Structural Evolution and Processing of Materials, Ministry of Education, Shandong University, Jinan 250061 (China); Qin, Xubo [Key Laboratory for Liquid–Solid Structural Evolution and Processing of Materials, Ministry of Education, Shandong University, Jinan 250061 (China); Zhang, Shuo; Huang, Yuying [Shanghai Synchrotron Radiation Facilities, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201204 (China)

2014-05-01

We found a direct evidence for the existence of the local chemical Bi–In bonds in the BiIn{sub 2} melt. These bonds are strong and prevail, dominating the structure evolution of the intermetallic clusters. From the local structure of the melt-quenched BiIn{sub 2} ribbon, the chemical Bi–In bonds strengthen compared with those in the equilibrium solidified alloy. The chemical bonds in BiIn{sub 2} melt retain to solid during a rapid quenching process. The results suggest that the intermetallic clusters in the melt evolve into the as-quenched intermetallic phase, and the intermetallic phase originates from the chemical bonds between unlike atoms in the melt. The chemical bonds preserve the chemical ordered clusters and dominate the clusters evolution.

Tracing the evolution of avian wing digits.

Science.gov (United States)

Xu, Xing; Mackem, Susan

2013-06-17

It is widely accepted that birds are a subgroup of dinosaurs, but there is an apparent conflict: modern birds have been thought to possess only the middle three fingers (digits II-III-IV) of an idealized five-digit tetrapod hand based on embryological data, but their Mesozoic tetanuran dinosaur ancestors are considered to have the first three digits (I-II-III) based on fossil evidence. How could such an evolutionary quirk arise? Various hypotheses have been proposed to resolve this paradox. Adding to the confusion, some recent developmental studies support a I-II-III designation for avian wing digits whereas some recent paleontological data are consistent with a II-III-IV identification of the Mesozoic tetanuran digits. A comprehensive analysis of both paleontological and developmental data suggests that the evolution of the avian wing digits may have been driven by homeotic transformations of digit identity, which are more likely to have occurred in a partial and piecemeal manner. Additionally, recent genetic studies in mouse models showing plausible mechanisms for central digit loss invite consideration of new alternative possibilities (I-II-IV or I-III-IV) for the homologies of avian wing digits. While much progress has been made, some advances point to the complexity of the problem and a final resolution to this ongoing debate demands additional work from both paleontological and developmental perspectives, which will surely yield new insights on mechanisms of evolutionary adaptation. Copyright © 2013 Elsevier Ltd. All rights reserved.

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

Revolution evolution: tracing angular momentum during star and planetary system formation

Science.gov (United States)

Davies, Claire Louise

2015-04-01

Stars form via the gravitational collapse of molecular clouds during which time the protostellar object contracts by over seven orders of magnitude. If all the angular momentum present in the natal cloud was conserved during collapse, stars would approach rotational velocities rapid enough to tear themselves apart within just a few Myr. In contrast to this, observations of pre-main sequence rotation rates are relatively slow (∼ 1 - 15 days) indicating that significant quantities of angular momentum must be removed from the star. I use observations of fully convective pre-main sequence stars in two well-studied, nearby regions of star formation (namely the Orion Nebula Cluster and Taurus-Auriga) to determine the removal rate of stellar angular momentum. I find the accretion disc-hosting stars to be rotating at a slower rate and contain less specific angular momentum than the disc-less stars. I interpret this as indicating a period of accretion disc-regulated angular momentum evolution followed by near-constant rotational evolution following disc dispersal. Furthermore, assuming that the age spread inferred from the Hertzsprung-Russell diagram constructed for the star forming region is real, I find that the removal rate of angular momentum during the accretion-disc hosting phase to be more rapid than that expected from simple disc-locking theory whereby contraction occurs at a fixed rotation period. This indicates a more efficient process of angular momentum removal must operate, most likely in the form of an accretion-driven stellar wind or outflow emanating from the star-disc interaction. The initial circumstellar envelope that surrounds a protostellar object during the earliest stages of star formation is rotationally flattened into a disc as the star contracts. An effective viscosity, present within the disc, enables the disc to evolve: mass accretes inwards through the disc and onto the star while momentum migrates outwards, forcing the outer regions of the

2005 dossier: clay. Tome: phenomenological evolution of the geologic disposal

International Nuclear Information System (INIS)

2005-01-01

This document makes a status of the researches carried out by the French national agency of radioactive wastes (ANDRA) about the phenomenological processes taking place in an argilite-type geologic disposal facility for high-level and long-lived (HLLL) radioactive wastes. Content: 1 - introduction: goal, input data, time and space scales, long-time forecasting of the phenomenological evolution; 2 - the Meuse/Haute-Marne site, the HLLL wastes and the disposal concepts: impact of the repository architecture; 3 - initial state of the geologic environment prior to the building up of the repository: general framework, geologic formations, tectonics and fractures, surface environment, geologic synthesis; 4 - phenomenological processes: storage-related processes, geodynamics-related processes, time scales of processes and of radionuclides migration, independence and evolution similarities of the repository and of the geologic environment; 5 - heat loads: heat transfers between containers and geologic formations, spatial organization of the thermal load, for C-type wastes and spent fuels, for B-type wastes, synthesis of the repository thermal load; 6 - flows and liquid solution and gas transfers: hydraulic behaviour of surrounding Jurassic formations (Tithonian, Kimmeridgian, Callovian, Oxfordian); 7 - chemical phenomena: chemical evolution of ventilated facilities (alveoles, galleries, boreholes), chemical evolution of B-type waste alveoles and of gallery and borehole sealing after closure, far field chemical evolution of Callovo-Oxfordian argilites and of other surrounding formations; 8 - mechanical evolution of the disposal and of the surrounding geologic environment: creation of an initial excavated damaged zone (EDZ), mechanical evolution of ventilated galleries, alveoles and sealing before and after closure, large-scale mechanical evolution; 9 - geodynamical evolution of the Callovo-Oxfordian and other surrounding formations and of the surface environment: internal

Mantle End-Members: The Trace Element Perspective

Science.gov (United States)

Willbold, M.; Stracke, A.; Hofmann, A. W.

2004-12-01

. Although there are some trace element characteristics common to all EM-type basalts, which distinguish them from HIMU-type basalts (e.g. uniformly high Th/U ratios of 4.7 ± 0.3, and enrichment in Cs-U), each suite of EM-type basalts has unique trace element signatures that distinguish them from any other suite of EM-type basalts. This is especially obvious when comparing the trace element composition of EM basalts from one isotopic family, for example EM1-type basalts from Tristan, Gough and Pitcairn. Consequently, the trace element systematics of EM-type basalts suggest that there are many different EM-type sources, whereas the isotopic composition of EM-type basalts suggest derivation from two broadly similar sources, i.e. EM1 and EM2. The large variability in subducting sediments with respect to both parent-daughter (e.g. Rb/Sr, Sm/Nd, U/Pb, Th/Pb,...) and other trace element ratios makes it unlikely that there are reproducible mixtures of sediments leading to two different isotopic evolution paths (EM1 and EM2) while preserving a range of incompatible element contents for each isotopic family, as would be required to reconcile the isotopic and trace element characteristics of EM-type basalts. Although this does not a priori argue against sediments as possible source components for OIB, it does argue against two distinct groups of sediments as EM1 and EM2 sources. Further characterization of sources with the same general origin (e.g. a certain type of crust or lithosphere) or identification of processes leading to reservoirs with similar parent-daughter ratio characteristics but different incompatible trace element contents could resolve the apparent conundrum.

Behavior of radon, chemical compounds and stable elements in underground water

International Nuclear Information System (INIS)

Lopez R, N.; Segovia, N.; Lopez, M.B.E.; Pena, P.; Armienta, M.A.; Godinez, L.; Seidel, J.L.

2001-01-01

The radon behavior, chemical compounds, major and trace elements in water samples of four springs and three wells of urban and agricultural zones around the Jocotitlan volcano and El Oro region was determined, both of them located in the medium part of the Mexican neo-volcanic axis. The 222 Rn was measured by the liquid scintillation method, the analysis of major components was realized with conventional chemical techniques, while the trace elements were quantified using an Icp-Ms. The average values of the radon concentrations obtained during one year were constant relatively, in an interval from 0.97 to 4.99 Bq/lt indicating a fast transport from the reload area toward the sampling points. the compounds, major and trace elements showed differences which indicate distinct origins of water from the site studies. (Author)

Chemical shift-dependent apparent scalar couplings: An alternative concept of chemical shift monitoring in multi-dimensional NMR experiments

International Nuclear Information System (INIS)

Kwiatkowski, Witek; Riek, Roland

2003-01-01

The paper presents an alternative technique for chemical shift monitoring in a multi-dimensional NMR experiment. The monitored chemical shift is coded in the line-shape of a cross-peak through an apparent residual scalar coupling active during an established evolution period or acquisition. The size of the apparent scalar coupling is manipulated with an off-resonance radio-frequency pulse in order to correlate the size of the coupling with the position of the additional chemical shift. The strength of this concept is that chemical shift information is added without an additional evolution period and accompanying polarization transfer periods. This concept was incorporated into the three-dimensional triple-resonance experiment HNCA, adding the information of 1 H α chemical shifts. The experiment is called HNCA coded HA, since the chemical shift of 1 H α is coded in the line-shape of the cross-peak along the 13 C α dimension

The evolution of military technology

CERN Document Server

Hagler, Gina

2018-01-01

War has at some point touched every nation. Beginning with ancient history and following through to the present, this book addresses the question of why war exists, and explains the shapes in which it occurs. It will lead young readers on a journey through time by tracing weapons from the earliest stones and clubs to modern technological military warfare. Along with the evolution of weaponry through the ages, it also goes into the development of protective gear, transportation, communication, and military strategies.

The evolution of balanced scorecard

OpenAIRE

Eremina G.

2016-01-01

The article describes the evolution of the Balanced scorecard (BSC) as one of the world's most popular systems of measuring performance. The BSC, developed by Robert Kaplan and David Norton as a strategic management tool, has been constantly changing with the accumulation of practical experience of its use. The author of the article establishes the chronology of the publication of articles and books that have become milestones on the way of development of the BSC and traces of system changes ...

Hormonally active phytochemicals and vertebrate evolution.

Science.gov (United States)

Lambert, Max R; Edwards, Thea M

2017-06-01

Living plants produce a diversity of chemicals that share structural and functional properties with vertebrate hormones. Wildlife species interact with these chemicals either through consumption of plant materials or aquatic exposure. Accumulating evidence shows that exposure to these hormonally active phytochemicals (HAPs) often has consequences for behavior, physiology, and fecundity. These fitness effects suggest there is potential for an evolutionary response by vertebrates to HAPs. Here, we explore the toxicological HAP-vertebrate relationship in an evolutionary framework and discuss the potential for vertebrates to adapt to or even co-opt the effects of plant-derived chemicals that influence fitness. We lay out several hypotheses about HAPs and provide a path forward to test whether plant-derived chemicals influence vertebrate reproduction and evolution. Studies of phytochemicals with direct impacts on vertebrate reproduction provide an obvious and compelling system for studying evolutionary toxicology. Furthermore, an understanding of whether animal populations evolve in response to HAPs could provide insightful context for the study of rapid evolution and how animals cope with chemical agents in the environment.

Stability and migration of vacancy in V–4Cr–4Ti alloy: Effects of Al, Si, Y trace elements

International Nuclear Information System (INIS)

Zhang, Chong; Zhang, Pengbo; Li, Ruihuan; Zhao, Jijun; Dong, Chuang

2013-01-01

Addition of trace amounts of Al, Si and Y into V–4Cr–4Ti alloy is beneficial for the mechanical properties under irradiation. It is thus important to investigate the influence of solute/trace elements on stabilities, energetics and diffusion behaviors of vacancy defects. We performed first-principles calculations to evaluate vacancy–solute/trace interaction inside dilute V–X (X = Ti, Cr, Al, Si, Y) and V–4Cr–4Ti–(Al, Si, Y) alloys. With addition of Si and Y, vacancy-based complexes tend to form near Ti–Si and Ti–Y pairs, while the effect of Al is negligible. Moreover, diffusion coefficients of solute/trace element in vanadium were derived using nine-frequency model. With high binding energy and low diffusion coefficient, Si atom is strongly attractive to vacancy in vanadium matrix. Our theoretical results suggest that the interactions between vacancy and solute/trace elements play some role in the evolution of microstructures inside vanadium alloys

Chemical Engineering in the "BIO" World.

Science.gov (United States)

Chiarappa, Gianluca; Grassi, Mario; Abrami, Michela; Abbiati, Roberto Andrea; Barba, Anna Angela; Boisen, Anja; Brucato, Valerio; Ghersi, Giulio; Caccavo, Diego; Cascone, Sara; Caserta, Sergio; Elvassore, Nicola; Giomo, Monica; Guido, Stefano; Lamberti, Gaetano; Larobina, Domenico; Manca, Davide; Marizza, Paolo; Tomaiuolo, Giovanna; Grassi, Gabriele

2017-01-01

Modern Chemical Engineering was born around the end of the 19th century in Great Britain, Germany, and the USA, the most industrialized countries at that time. Milton C. Whitaker, in 1914, affirmed that the difference between Chemistry and Chemical Engineering lies in the capability of chemical engineers to transfer laboratory findings to the industrial level. Since then, Chemical Engineering underwent huge transformations determining the detachment from the original Chemistry nest. The beginning of the sixties of the 20th century saw the development of a new branch of Chemical Engineering baptized Biomedical Engineering by Peppas and Langer and that now we can name Biological Engineering. Interestingly, although Biological Engineering focused on completely different topics from Chemical Engineering ones, it resorted to the same theoretical tools such as, for instance, mass, energy and momentum balances. Thus, the birth of Biological Engineering may be considered as a Darwinian evolution of Chemical Engineering similar to that experienced by mammals which, returning to water, used legs and arms to swim. From 1960 on, Biological Engineering underwent a considerable evolution as witnessed by the great variety of topics covered such as hemodialysis, release of synthetic drugs, artificial organs and, more recently, delivery of small interfering RNAs (siRNA). This review, based on the activities developed in the frame of our PRIN 2010-11 (20109PLMH2) project, tries to recount origins and evolution of Chemical Engineering illustrating several examples of recent and successful applications in the biological field. This, in turn, may stimulate the discussion about the Chemical Engineering students curriculum studiorum update. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

Protein change in plant evolution: tracing one thread connecting molecular and phenotypic diversity

Directory of Open Access Journals (Sweden)

Madelaine eBartlett

2013-10-01

Full Text Available Proteins change over the course of evolutionary time. New protein-coding genes and gene families emerge and diversify, ultimately affecting an organism’s phenotype and interactions with its environment. Here we survey the range of structural protein change observed in plants and review the role these changes have had in the evolution of plant form and function. Verified examples tying evolutionary change in protein structure to phenotypic change remain scarce. We will review the existing examples, as well as draw from investigations into domestication, and quantitative trait locus (QTL cloning studies searching for the molecular underpinnings of natural variation. The evolutionary significance of many cloned QTL has not been assessed, but all the examples identified so far have begun to reveal the extent of protein structural diversity tolerated in natural systems. This molecular (and phenotypic diversity could come to represent part of natural selection’s source material in the adaptive evolution of novel traits. Protein structure and function can change in many distinct ways, but the changes we identified in studies of natural diversity and protein evolution were predicted to fall primarily into one of six categories: altered active and binding sites; hypomorphic and hypermorphic alleles; altered protein-protein interactions; altered domain content; altered protein stability; and altered activity as an activator or repressor. Variability was also observed in the evolutionary scale at which particular changes were observed. Some changes were detected at both micro- and macroevolutionary timescales, while others were observed primarily at deep or shallow phylogenetic levels. This variation might be used to determine the trajectory of future investigations in structural molecular evolution.

Silicic melt evolution in the early Izu-Bonin arc recorded in detrital zircons: Zircon U-Pb geochronology and trace element geochemistry for Site U1438, Amami Sankaku Basin

Science.gov (United States)

Barth, A. P.; Tani, K.; Meffre, S.; Wooden, J. L.; Coble, M. A.

2016-12-01

Understanding the petrologic evolution of oceanic arc magmas through time is important because these arcs reveal the processes of formation and the early evolution of juvenile continental crust. The Izu-Bonin (IB) arc system has been targeted because it is one of several western Pacific intraoceanic arcs initiated at 50 Ma and because of its prominent spatial asymmetry, with widespread development of relatively enriched rear arc lavas. We examined Pb/U and trace element compositions in zircons recovered at IODP Site 351-U1438 and compared them to regional and global zircon suites. These new arc zircon data indicate that detrital zircons will yield new insights into the generation of IB silicic melts and form a set of useful geochemical proxies for interpreting ancient arc detrital zircon provenance. Project IBM drilling target IBM1 was explored by Expedition 351 at Site U1438, located in the proximal back-arc of the northern Kyushu-Palau Ridge (KPR) at 27.3°N. A 1.2 km thick section of Paleogene volcaniclastic rocks, increasingly lithified and hydrothermally altered with depth, constitutes a proximal rear arc sedimentary record of IB arc initiation and early arc evolution. The ages and compositions of U1438 zircons are compatible with provenance in one or more edifices of the northern KPR and are incompatible with drilling contamination. Melt zircon saturation temperatures and Ti-in-zircon thermometry suggest a provenance in relatively cool and silicic KPR melts. The abundances of selected trace elements with high native concentrations provide insight into the petrogenesis of U1438 detrital zircon host melts, and may be useful indicators of both short and long-term variations in melt compositions in arc settings. The U1438 zircons are slightly enriched in U and LREE and are depleted in Nb compared to zircons from mid-ocean ridges and the Parece-Vela Basin, as predicted for melts in a primitive oceanic arc setting with magmas derived from a highly depleted mantle

The trace of the CNO cycle in the ring nebula NGC 6888

Energy Technology Data Exchange (ETDEWEB)

Mesa-Delgado, A. [Instituto de Astrofísica, Facultad de Física, Pontificia Universidad Católica de Chile, Av. Vicuña Mackenna 4860, 782-0436 Macul, Santiago (Chile); Esteban, C.; García-Rojas, J. [Instituto de Astrofísica de Canarias, E-38200 La Laguna, Tenerife (Spain); Reyes-Pérez, J.; Morisset, C. [Instituto de Astronomía, Universidad Nacional Autónoma de México, Apdo. Postal 70264, Méx. D. F. 04510 (Mexico); Bresolin, F., E-mail: amesad@astro.puc.cl [Institute for Astronomy, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States)

2014-04-20

We present new results on the chemical composition of the Galactic ring nebula NGC 6888 surrounding the WN6(h) star WR136. The data are based on deep spectroscopical observations taken with the High Dispersion Spectrograph at the 8.2 m Subaru Telescope. The spectra cover the optical range from 3700 to 7400 Å. The effect of the CNO cycle is well-identified in the abundances of He, N, and O, while elements not involved in the synthesis such as Ar, S, and Fe present values consistent with the solar vicinity and the ambient gas. The major achievement of this work is the first detection of the faint C II λ4267 recombination line in a Wolf-Rayet nebula. This allows us to estimate the C abundance in NGC 6888 and therefore investigate for the first time the trace of the CNO cycle in a ring nebula around a Wolf-Rayet star. Although the detection of the C II line has a low signal-to-noise ratio, the C abundance seems to be higher than the predictions of recent stellar evolution models of massive stars. The Ne abundance also shows a puzzling pattern with an abundance of about 0.5 dex lower than the solar vicinity, which may be related to the action of the NeNa cycle. Attending to the constraints imposed by the dynamical timescale and the He/H and N/O ratios of the nebula, the comparison with stellar evolution models indicates that the initial mass of the stellar progenitor of NGC 6888 is between 25 M {sub ☉} and 40 M {sub ☉}.

Dynamical evolution and disintegration of comets

Science.gov (United States)

Kresak, L.

Current concepts of the origin and evolution of comets are reviewed. The place of their formation from which they have been delivered into the Oort reservoir is still an open problem, but the region of the outermost planets appears most probable. The interplay of stellar and planetary perturbations can be traced by model computations which reveal both the general trends and the variety of individual evolutionary paths. The present structure of the system of comets is controlled by the dynamical evolution of its individual members, limited by their physical aging by disintegration. Where the lifetimes are short, as in the Jupiter family of short-period comets, an equilibrium between elimination and replenishment is established. The role of different destructive processes and the resulting survival times are discussed.

PIXE analysis of trace and other mineral elements in Romanian dental composites

International Nuclear Information System (INIS)

Preoteasa, E. A.; Iordan, Andreea; Harangus, Livia; Ciortea, C.; Moldovan, Maria

2002-01-01

Dental composites made of silicates and oxides particles embedded in an organic polymer, show a dynamic evolution but are rather expensive. Recently, the Romanian biomaterial 'Restacril' offered a low-cost alternative. Because the durability of the composite dental fillings depends both on the main chemical composition and on the impurities that may influence the inorganic particles' properties and thus modifying the bio material clinical behaviour, the elemental analysis of the material is necessary for improving its quality. Particle-induced X-ray emission (PIXE), a sensitive method for multielemental trace detection widely used in biomedical applications, allowed us to evidence 21 mineral elements with Z > 14 in some commercial dental composites. Here we evaluate the performances of PIXE for the control of dental composites by carrying out qualitative analysis of three Romanian biomaterials. PIXE measurements on thick composite samples with a flat surface were done with 3 MeV protons at the NIPNE-HH (Horia Hulubei National Institute for Physics and Nuclear Engineering) tandem accelerator, using a hyper-pure Ge detector, 30 mm thick Al absorber foil and integration of beam current. Up to 21 elements with Z > 19 were detected: K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Ga, Sr, Zr, Nb, Ru, Ag, Ba, Yb, Nd, Hf, Au, As and Pb. The orders of magnitude of relative concentrations were evaluated using X-ray yields obtained for another light element thick composite target. The Romanian composites have specific and diverse compositions, containing a great number of minor and trace elements, many of whom are impurities. Use of higher purity raw materials is suggested to reduce the latter and improve the materials' quality. Refinement of X-ray yields by better matching matrixes calculations and use of concentration standards are proposed for quantitative PIXE analysis of the dental composites. (authors)

Effects of nitrogen and water addition on trace element stoichiometry in five grassland species

DEFF Research Database (Denmark)

Cai, Jiangping; Weiner, Jacob; Wang, Ruzhen

2017-01-01

A 9-year manipulative experiment with nitrogen (N) and water addition, simulating increasing N deposition and changing precipitation regime, was conducted to investigate the bioavailability of trace elements, iron (Fe), manganese (Mn), copper (Cu), and zinc (Zn) in soil, and their uptake by plants...... in the organism and the chemical concentration in the growth substrate) and foliar Fe:Mn ratio in each plant was calculated. Our results showed that soil available Fe, Mn and Cu concentrations increased under N addition and were negatively correlated with both soil pH and cation exchange capacity. Water addition...... under the two environmental change factors in a semi-arid grassland of Inner Mongolia. We measured concentrations of trace elements in soil and in foliage of five common herbaceous species including 3 forbs and 2 grasses. In addition, bioaccumulation factors (BAF, the ratio of the chemical concentration...

Storage and pre-neutron-activation-analysis treatment for trace-element analysis in urine

International Nuclear Information System (INIS)

Blotcky, A.J.; Rack, E.P.

1985-01-01

The problems regarding storage and pre-neutron-activation-analysis treatment for the elements aluminum, calcium, vanadium, selenium, copper, iodine, zinc, manganese, and magnesium in a urine matrix are reviewed. The type of collection and storage procedure and pre-neutron activation analysis treatment of urine depend on the specific trace element; that is, its inherent physical and chemical properties. Specifically polyethylene in teflon containers are the most suitable for general determinations. Whether any preservative is added would depend upon the stability of the trace element and its tendency for surface adsorption. Preferably, preservatives should contain no radioactivatable elements for maximum efficacy. Freeze drying or packing urine shipments under dry ice needs to be explored on an individual basis. Each pre- or post-neutron activation analysis treatment is specific and optimized for the trace element analyzed

An image analyzer system for the analysis of nuclear traces

International Nuclear Information System (INIS)

Cuapio O, A.

1990-10-01

Inside the project of nuclear traces and its application techniques to be applied in the detection of nuclear reactions of low section (non detectable by conventional methods), in the study of accidental and personal neutron dosemeters, and other but, are developed. All these studies are based on the fact that the charged particles leave latent traces of dielectric that if its are engraved with appropriate chemical solutions its are revealed until becoming visible to the optical microscope. From the analysis of the different trace forms, it is possible to obtain information of the characteristic parameters of the incident particles (charge, mass and energy). Of the density of traces it is possible to obtain information of the flow of the incident radiation and consequently of the received dose. For carry out this analysis has been designed and coupled different systems, that it has allowed the solution of diverse outlined problems. Notwithstanding it has been detected that to make but versatile this activity is necessary to have an Image Analyzer System that allow us to digitize, to process and to display the images with more rapidity. The present document, presents the proposal to carry out the acquisition of the necessary components for to assembling an Image Analyzing System, like support to the mentioned project. (Author)

Modeling risk evolution of digestive tract functional violations when exposed to chemical environmental factors

Directory of Open Access Journals (Sweden)

M.R. Kamaltdinov

2015-06-01

Full Text Available Modern methods of health risk assessment are based on the representation of individual and public health as a dynamic process of “evolution”, which describes a continuous course of negative (and positive changes in the condition of the body. The article presents a conceptual diagram of multilevel health risk evolution modeling under the influence of environmental factors. The main aspects associated with the simulation of digestive processes in the “meso level” are considered. Some results of solving the problem of the flow in the digestive tract antroduodenal area taken into account tract motility. Further development ways of the model are outlines – account of biochemical reactions, secretory and absorptive functions tract. The proposed approach will enable not only to predict the risk of digestive system functional disorders, but also take into account basic physiological processes, mechanisms of income, distribution, excretion of chemicals.

A guide to the coupled chemical equilibria and migration code CHEQMATE

International Nuclear Information System (INIS)

Haworth, A.; Sharland, S.M.; Tasker, P.W.; Tweed, C.J.

1988-02-01

The CHEQMATE (CHemical EQuilibrium with Migration and Transport Equations) program has been developed to model the evolution of spatially inhomogeneous aqueous chemical systems. CHEQMATE models one-dimensional diffusion and electromigration of ionic species with chemical equilibration provided by the geochemical code PHREEQE. The transport and chemical parts of the CHEQMATE code are iteratively coupled, so that local chemical equilibrium is maintained as the transport processes evolve. CHEQMATE is very flexible and can easily be applied to many different evolving chemical systems. It has principally been used to study the evolution of the chemical environment in and around a nuclear waste repository. (author)

Hydrogen evolution under visible light over LaCoO3 prepared by chemical route

International Nuclear Information System (INIS)

Meziani, D.; Reziga, A.; Rekhila, G.; Bellal, B.; Trari, M.

2014-01-01

Highlights: • Visible-light hydrogen evolution is achieved on the hetero-system LaCoO 3 /SnO 2 . • The crystal field splits the Co 3+ : 3d orbital by a value of 2.05 eV. • The capacitance plot shows p-type conduction with flat band potential of 0 V SCE. • The photo-electrochemistry yields a valence and conduction bands of 3d parentage. - Abstract: The semiconducting properties of the perovskite LaCoO 3 , prepared by nitrate route, are investigated for the first time by the photo-electrochemical technique. The oxide shows a direct optical transition at 1.33 eV, due to Co 3+ : 3d orbital splitting in octahedral site and possesses a chemical stability over a fair pH range (4–14). The conductivity follows an exponential type law with a hole mobility (8.3 × 10 −2 cm 2 V −1 s −1 ), thermally activated. The Mott–Schottky plot in KOH medium is characteristic of p type conduction with a flat band potential of 0 V SCE and a holes density of 1.35 × 10 17 cm −3 . The electrochemical impedance spectroscopy reveals the predominance of the bulk and grains boundaries contributions with a constant phase element and a multi-relaxation type nature. As application, the hydrogen evolution upon visible light is demonstrated on the hetero-junction LaCoO 3 /SnO 2 . The best performance occurs at pH ∼ 12.8 with an evolution rate of 0.25 cm 3 min −1 (mg LaCoO 3 ) −1 and a quantum yield of 0.11%. The improved activity is attributed to the wide depletion width of ∼10 nm and the potential of the conduction band of LaCoO 3 (−1.34 V SCE ), more negative than that of SnO 2 , the latter acts as electrons bridge for the interfacial water reduction. The relevance of 3d orbital of the performance of semi conducting photoelectrode is discussed

The chemical evolution of a travertine-depositing stream: Geochemical processes and mass transfer reactions

Science.gov (United States)

Lorah, Michelle M.; Herman, Janet S.

1988-01-01

This field study focuses on quantitatively defining the chemical changes occurring in Falling Spring Creek, a travertine-depositing stream located in Alleghany County, Virginia. The processes of CO2outgassing and calcite precipitation or dissolution control the chemical evolution of the stream. The observed chemical composition of the water was used with the computerized geochemical model WATEQF to calculate aqueous speciation, saturation indices, and CO2 partial pressure values. Mass balance calculations were performed to obtain mass transfers of CO2 and calcite. Reaction times, estimated from stream discharge, were used with the mass transfer results to calculate rates of CO2, outgassing and calcite precipitation between consecutive sampling points. The stream, which is fed by a carbonate spring, is supersaturated with respect to CO2 along the entire 5.2-km flow path. Outgassing of CO2 drives the solution to high degrees of supersaturation with respect to calcite. Metabolic uptake of CO2 by photosynthetic plants is insignificant, because the high supply rate of dissolved carbon dioxide and the extreme agitation of the stream at waterfalls and rapids causes a much greater amount of inorganic CO2 outgassing to occur. Calcite precipitation is kinetically inhibited until near the crest of a 20-m vertical waterfall. Calcite precipitation rates then reach a maximum at the waterfall where greater water turbulence allows the most rapid escape of CO2. 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.

Trace emissions from gaseous combustion

Energy Technology Data Exchange (ETDEWEB)

Seebold, J.G. [Chevron Research and Technology Co., Richmond, CA (United States)

2000-07-01

The U.S. Clean Air Act (CAA) was amended in 1990 to include the development of maximum achievable control technology (MACT) emission standards for hazardous air pollutants (HAPs) for certain stationary sources by November 2000. MACT emissions standards would affect process heaters and industrial boilers since combustion processes are a potential source for many air toxins. The author noted that one of the problems with MACT is the lack of a clear solid scientific footing which is needed to develop environmentally responsible regulations. In order to amend some of these deficiencies, a 4-year, $7 million research project on the origin and fate of trace emissions in the external combustion of gaseous hydrocarbons was undertaken in a collaborative effort between government, universities and industry. This collaborative project entitled the Petroleum Environmental Research Forum (PERF) Project 92-19 produced basic information and phenomenological understanding in two important areas, one basic and one applied. The specific objectives of the project were to measure emissions while operating different full-scale burners under various operating conditions and then to analyze the emission data to identify which operating conditions lead to low air toxic emissions. Another objective was to develop new chemical kinetic mechanisms and predictive models for the formation of air toxic species which would explain the origin and fate of these species in process heaters and industrial boilers. It was determined that a flame is a very effective reactor and that trace emissions from a typical gas-fired industry burner are very small. An unexpected finding was that trace emissions are not affected by hydrocarbon gaseous fuel composition, nor by the use of ultra low nitrous oxide burners. 2 refs., 8 figs.

Molecular corridors and parameterizations of volatility in the chemical evolution of organic aerosols

Directory of Open Access Journals (Sweden)

Y. Li

2016-03-01

Full Text Available The formation and aging of organic aerosols (OA proceed through multiple steps of chemical reaction and mass transport in the gas and particle phases, which is challenging for the interpretation of field measurements and laboratory experiments as well as accurate representation of OA evolution in atmospheric aerosol models. Based on data from over 30 000 compounds, we show that organic compounds with a wide variety of functional groups fall into molecular corridors, characterized by a tight inverse correlation between molar mass and volatility. We developed parameterizations to predict the saturation mass concentration of organic compounds containing oxygen, nitrogen, and sulfur from the elemental composition that can be measured by soft-ionization high-resolution mass spectrometry. Field measurement data from new particle formation events, biomass burning, cloud/fog processing, and indoor environments were mapped into molecular corridors to characterize the chemical nature of the observed OA components. We found that less-oxidized indoor OA are constrained to a corridor of low molar mass and high volatility, whereas highly oxygenated compounds in atmospheric water extend to high molar mass and low volatility. Among the nitrogen- and sulfur-containing compounds identified in atmospheric aerosols, amines tend to exhibit low molar mass and high volatility, whereas organonitrates and organosulfates follow high O : C corridors extending to high molar mass and low volatility. We suggest that the consideration of molar mass and molecular corridors can help to constrain volatility and particle-phase state in the modeling of OA particularly for nitrogen- and sulfur-containing compounds.

Linking genes to ecosystem trace gas fluxes in a large-scale model system

Science.gov (United States)

Meredith, L. K.; Cueva, A.; Volkmann, T. H. M.; Sengupta, A.; Troch, P. A.

2017-12-01

Soil microorganisms mediate biogeochemical cycles through biosphere-atmosphere gas exchange with significant impact on atmospheric trace gas composition. Improving process-based understanding of these microbial populations and linking their genomic potential to the ecosystem-scale is a challenge, particularly in soil systems, which are heterogeneous in biodiversity, chemistry, and structure. In oligotrophic systems, such as the Landscape Evolution Observatory (LEO) at Biosphere 2, atmospheric trace gas scavenging may supply critical metabolic needs to microbial communities, thereby promoting tight linkages between microbial genomics and trace gas utilization. This large-scale model system of three initially homogenous and highly instrumented hillslopes facilitates high temporal resolution characterization of subsurface trace gas fluxes at hundreds of sampling points, making LEO an ideal location to study microbe-mediated trace gas fluxes from the gene to ecosystem scales. Specifically, we focus on the metabolism of ubiquitous atmospheric reduced trace gases hydrogen (H2), carbon monoxide (CO), and methane (CH4), which may have wide-reaching impacts on microbial community establishment, survival, and function. Additionally, microbial activity on LEO may facilitate weathering of the basalt matrix, which can be studied with trace gas measurements of carbonyl sulfide (COS/OCS) and carbon dioxide (O-isotopes in CO2), and presents an additional opportunity for gene to ecosystem study. This work will present initial measurements of this suite of trace gases to characterize soil microbial metabolic activity, as well as links between spatial and temporal variability of microbe-mediated trace gas fluxes in LEO and their relation to genomic-based characterization of microbial community structure (phylogenetic amplicons) and genetic potential (metagenomics). Results from the LEO model system will help build understanding of the importance of atmospheric inputs to

EIA systems in Nigeria: evolution, current practice and shortcomings

International Nuclear Information System (INIS)

Ogunba, Olusegun A.

2004-01-01

Amidst mounting criticism of Environmental Impact Assessments (EIAs) carried out in Nigeria under the three independent EIA systems--the EIA Decree 86 (1992), the Town and Country Planning Decree 88 (1992) and the Petroleum Act (1969)--the paper traces the evolution of Nigeria's systems and appraises current practice and shortcomings. The path of development of the systems was traced within the framework of Gibson's model of EIA evolution [Impact Assess. Proj. Apprais., 20 (3) 2002, 151-159], while current practice and shortcomings were explored in random interview surveys of consultant firms, approval authorities and the academia. It was seen that Gibson's four-stage model is not exactly representative of the Nigerian situation, and a more appropriate six-stage model was developed. It was also established that the current practices of the three EIA systems were at different stages of evolution: one of the EIA schemes (the Town and Country Planning Decree) has not evolved satisfactorily, while the other two EIA systems have produced intricate legislations and guidelines, but fall short of first-rate practice. The other discovery was that the simultaneous use of three independent systems creates unnecessary duplication of EIA preparation with considerable time and money costs. The paper advises that Nigeria can make substantial progress along the evolutionary path through a correction of observed system shortcomings and a merger of the three systems

Polarographic validation of chemical speciation models

International Nuclear Information System (INIS)

Duffield, J.R.; Jarratt, J.A.

2001-01-01

It is well established that the chemical speciation of an element in a given matrix, or system of matrices, is of fundamental importance in controlling the transport behaviour of the element. Therefore, to accurately understand and predict the transport of elements and compounds in the environment it is a requirement that both the identities and concentrations of trace element physico-chemical forms can be ascertained. These twin requirements present the analytical scientist with considerable challenges given the labile equilibria, the range of time scales (from nanoseconds to years) and the range of concentrations (ultra-trace to macro) that may be involved. As a result of this analytical variability, chemical equilibrium modelling has become recognised as an important predictive tool in chemical speciation analysis. However, this technique requires firm underpinning by the use of complementary experimental techniques for the validation of the predictions made. The work reported here has been undertaken with the primary aim of investigating possible methodologies that can be used for the validation of chemical speciation models. However, in approaching this aim, direct chemical speciation analyses have been made in their own right. Results will be reported and analysed for the iron(II)/iron(III)-citrate proton system (pH 2 to 10; total [Fe] = 3 mmol dm -3 ; total [citrate 3- ] 10 mmol dm -3 ) in which equilibrium constants have been determined using glass electrode potentiometry, speciation is predicted using the PHREEQE computer code, and validation of predictions is achieved by determination of iron complexation and redox state with associated concentrations. (authors)

Monsoon signatures in trace gas records from Cape Rama, India

International Nuclear Information System (INIS)

Bhattacharya, S.K.; Jani, R.A.; Borole, D.V.; Francey, R.J.; Allison, C.E.; Masarie, K.A.

2002-01-01

Concentrations of trace gases CO 2 , CH 4 , CO, N 2 O and H 2 , and the stable carbon and oxygen isotopic composition of CO 2 have been measured in air samples collected from Cape Rama, a coastal station on the west coast of India, since 1993. The data show clear signatures of continental and oceanic air mass resulting in complex seasonal variation of trace gas characteristics. The regional atmospheric circulation in the Indian Ocean and Arabian Sea undergoes biannual reversal in low-level winds associated with the yearly migration of the inter-tropical convergence zone (ITCZ). From June to September, the wind is from the equatorial Indian Ocean to the Indian subcontinent (southwest monsoon) and brings in pristine marine air. From December to February, dry continental winds blow from the northeast and transport continental emissions to the ocean (northeast monsoon). Detailed transport and chemical modelling will be necessary to interpret these records, however the potential to identify and constrain the regional trace gas emissions appears to be high. (author)

Chemical Spill Prevention, Control, and Countermeasures Plan: 100 Areas

Energy Technology Data Exchange (ETDEWEB)

Chien, Y.M.

1989-06-01

The purpose of this Chemical Spill Prevention, Control, and Countermeasures (SPCC) Plan is to identify the chemical spill control practices, procedures, and containment devices Westinghouse Hanford Company (Westinghouse Hanford) employs to prevent a reportable quantity (RQ) of a hazardous substance (as defined in 40 CFR Part 302) from being released to the environment. The chemical systems and chemical storage facilities in the 100 Areas are described. This document traces the ultimate fate of accidental chemical spills at the 100 Areas. Also included in the document destinations, spill containment devices, and systems surveillance frequencies. 2 tabs.

Chemical Spill Prevention, Control, and Countermeasures Plan: 100 Areas

International Nuclear Information System (INIS)

Chien, Y.M.

1989-06-01

The purpose of this Chemical Spill Prevention, Control, and Countermeasures (SPCC) Plan is to identify the chemical spill control practices, procedures, and containment devices Westinghouse Hanford Company (Westinghouse Hanford) employs to prevent a reportable quantity (RQ) of a hazardous substance (as defined in 40 CFR Part 302) from being released to the environment. The chemical systems and chemical storage facilities in the 100 Areas are described. This document traces the ultimate fate of accidental chemical spills at the 100 Areas. Also included in the document destinations, spill containment devices, and systems surveillance frequencies. 2 tabs

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.

Soil amendments reduce trace element solubility in a contaminated soil and allow regrowth of natural vegetation

International Nuclear Information System (INIS)

Madejon, Engracia; Perez de Mora, Alfredo; Felipe, Efrain; Burgos, Pilar; Cabrera, Francisco

2006-01-01

We tested the effects of three amendments (a biosolid compost, a sugar beet lime, and a combination of leonardite plus sugar beet lime) on trace element stabilisation and spontaneous revegetation of a trace element contaminated soil. Soil properties were analysed before and after amendment application. Spontaneous vegetation growing on the experimental plot was studied by three surveys in terms of number of taxa colonising, percentage vegetation cover and plant biomass. Macronutrients and trace element concentrations of the five most frequent species were analysed. The results showed a positive effect of the amendments both on soil chemical properties and vegetation. All amendments increased soil pH and TOC content and reduced CaCl 2 -soluble-trace element concentrations. Colonisation by wild plants was enhanced in all amended treatments. The nutritional status of the five species studied was improved in some cases, while a general reduction in trace element concentrations of the aboveground parts was observed in all treated plots. The results obtained show that natural assisted remediation has potential for success on a field scale reducing trace element entry in the food chain. - Soil amendments affect soil chemistry and allow revegetation of soils contaminated by trace elements

Numerical modelling of the effect of dry air traces in a helium parallel plate dielectric barrier discharge

Science.gov (United States)

Lazarou, C.; Belmonte, T.; Chiper, A. S.; Georghiou, G. E.

2016-10-01

A validated numerical model developed for the study of helium barrier discharges in the presence of dry air impurities is presented in this paper. The model was used to numerically investigate the influence of air traces on the evolution of the helium dielectric barrier discharge (DBD). The level of dry air used as impurity was in the range from 0 to 1500 ppm, which corresponds to the most commonly encountered range in atmospheric pressure discharge experiments. The results presented in this study clearly show that the plasma chemistry and consequently the discharge evolution is highly affected by the concentration level of impurities in the mixture. In particular, it was observed that air traces assist the discharge ignition at low concentration levels (~55 ppm), while on the other hand, they increase the burning voltage at higher concentration levels (~1000 ppm). Furthermore, it was found that the discharge symmetry during the voltage cycle highly depends on the concentration of air. For the interpretation of the results, a detailed analysis of the processes that occur in the discharge gap is performed and the main reaction pathways of ion production are described. Thanks to this approach, useful insight into the physics behind the evolution of the discharge is obtained.

Disk Evolution, Element Abundances and Cloud Properties of Young Gas Giant Planets

Directory of Open Access Journals (Sweden)

Christiane Helling

2014-04-01

Full Text Available We discuss the chemical pre-conditions for planet formation, in terms of gas and ice abundances in a protoplanetary disk, as function of time and position, and the resulting chemical composition and cloud properties in the atmosphere when young gas giant planets form, in particular discussing the effects of unusual, non-solar carbon and oxygen abundances. Large deviations between the abundances of the host star and its gas giants seem likely to occur if the planet formation follows the core-accretion scenario. These deviations stem from the separate evolution of gas and dust in the disk, where the dust forms the planet cores, followed by the final run-away accretion of the left-over gas. This gas will contain only traces of elements like C, N and O, because those elements have frozen out as ices. PRODIMO protoplanetary disk models are used to predict the chemical evolution of gas and ice in the midplane. We find that cosmic rays play a crucial role in slowly un-blocking the CO, where the liberated oxygen forms water, which then freezes out quickly. Therefore, the C/O ratio in the gas phase is found to gradually increase with time, in a region bracketed by the water and CO ice-lines. In this regions, C/O is found to approach unity after about 5 Myrs, scaling with the cosmic ray ionization rate assumed. We then explore how the atmospheric chemistry and cloud properties in young gas giants are affected when the non-solar C/O ratios predicted by the disk models are assumed. The DRIFT cloud formation model is applied to study the formation of atmospheric clouds under the influence of varying premordial element abundances and its feedback onto the local gas. We demonstrate that element depletion by cloud formation plays a crucial role in converting an oxygen-rich atmosphere gas into carbon-rich gas when non-solar, premordial element abundances are considered as suggested by disk models.

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.

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

Science.gov (United States)

Regnery, J; Wing, A D; Alidina, M; Drewes, J E

2015-08-01

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. Copyright © 2015 Elsevier B.V. All rights reserved.

A Global Overview of Exposure Levels and Biological Effects of Trace Elements in Penguins.

Science.gov (United States)

Espejo, Winfred; Celis, José E; GonzÃlez-Acuña, Daniel; Banegas, Andiranel; Barra, Ricardo; Chiang, Gustavo

2018-01-01

Trace elements are chemical contaminants that can be present almost anywhere on the planet. The study of trace elements in biotic matrices is a topic of great relevance for the implications that it can have on wildlife and human health. Penguins are very useful, since they live exclusively in the Southern Hemisphere and represent about 90% of the biomass of birds of the Southern Ocean. The levels of trace elements (dry weight) in different biotic matrices of penguins were reviewed here. Maps of trace element records in penguins were included. Data on exposure and effects of trace elements in penguins were collected from the literature. The most reported trace elements in penguins are aluminum, arsenic, cadmium, lead, mercury, copper, zinc, and manganese. Trace elements have been measured in 11 of the 18 species of penguins. The most studied biotic matrices are feathers and excreta. Most of the studies have been performed in Antarctica and subantarctic Islands. Little is known about the interaction among metals, which could provide better knowledge about certain mechanisms of detoxification in penguins. Future studies of trace elements in penguins must incorporate other metals such as vanadium, cobalt, nickel, and chromium. Data of metals in the species such as Eudyptes pachyrhynchus, Eudyptes moseleyi, Eudyptes sclateri, Eudyptes robustus, Eudyptes schlegeli, Spheniscus demersus, Spheniscus mendiculus, and Megadyptes antipodes are urged. It is important to correlate levels of metals in different biotic matrices with the effects on different species and in different geographic locations.

Trace elements in the sea surface microlayer: rapid responses to changes in aerosol deposition

Directory of Open Access Journals (Sweden)

Alina M. Ebling

2017-08-01

Full Text Available Natural and anthropogenic aerosols are a significant source of trace elements to oligotrophic ocean surface waters, where they provide episodic pulses of limiting micronutrients for the microbial community. However, little is known about the fate of trace elements at the air-sea interface, i.e. the sea surface microlayer. In this study, samples of aerosols, sea surface microlayer, and underlying water column were collected in the Florida Keys during a dusty season (July 2014 and non-dusty season (May 2015 and analyzed for the dissolved and particulate elements Al, Fe, Ni, Cu, Zn, and Pb. Microlayer samples were collected using a cylinder of ultra-pure SiO2 (quartz glass, a novel adaptation of the glass plate technique. A significant dust deposition event occurred during the 2014 sampling period which resulted in elevated concentrations of trace elements in the microlayer. Residence times in the microlayer from this event ranged from 12 to 94 minutes for dissolved trace elements and from 1.3 to 3.4 minutes for particulate trace elements. These residence times are potentially long enough for the atmospherically derived trace elements to undergo chemical and biological alterations within the microlayer. Characterizing the trace element distributions within the three regimes is an important step towards our overall goals of understanding the rates and mechanisms of the solubilization of trace elements following aeolian dust deposition and how this might affect microorganisms in surface waters.

Evolution of interstellar grains

International Nuclear Information System (INIS)

Greenberg, J.M.

1984-01-01

The principal aim of this chapter is to derive the properties of interstellar grains as a probe of local physical conditions and as a basis for predicting such properties as related to infrared emissivity and radiative transfer which can affect the evolution of dense clouds. The first sections will develop the criteria for grain models based directly on observations of gas and dust. A summary of the chemical evolution of grains and gas in diffuse and dense clouds follows. (author)

Aging study on carboxymethyl cellulose-coated zero-valent iron nanoparticles in water: Chemical transformation and structural evolution

Energy Technology Data Exchange (ETDEWEB)

Dong, Haoran, E-mail: dongh@hnu.edu.cn [College of Environmental Science and Engineering, Hunan University, Changsha, Hunan 410082 (China); Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha, Hunan 410082 (China); Zhao, Feng; Zeng, Guangming; Tang, Lin; Fan, Changzheng; Zhang, Lihua; Zeng, Yalan; He, Qi; Xie, Yankai; Wu, Yanan [College of Environmental Science and Engineering, Hunan University, Changsha, Hunan 410082 (China); Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha, Hunan 410082 (China)

2016-07-15

Highlights: • The chemical transformation and structural evolution of CMC-nZVI were investigated. • CMC could slow down the aging rate of nZVI and alter the species transformation. • Fe{sub 3}O{sub 4} and/or γ-Fe{sub 2}O{sub 3} are the dominant corrosion products of bare nZVI after aging. • γ-FeOOH is the primary corrosion product of CMC-nZVI after aging. - Abstract: To assess the long-term fate and the associated risks of nanoscale zero-valent iron (nZVI) used in the water remediation, it is essential to understand the chemical transformations during aging of nZVI in water. This study investigated the compositional and structural evolution of bare nZVI and carboxymethyl cellulose (CMC) coated nZVI in static water over a period of 90 days. Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), X-ray diffraction (XRD) and Raman spectroscopy were used to characterize the corrosion products of nZVI and CMC-nZVI. Results show that both the structures and the compositions of the corrosion products change with the process of aging, but the coating of CMC could slow down the aging rate of nZVI (as indicated by the slower drop in Fe{sup 0} intensity in XRD pattern). For the bare nZVI, magnetite (Fe{sub 3}O{sub 4}) and/or maghemite (γ-Fe{sub 2}O{sub 3}) are the dominant corrosion products after 90 days of aging. However, for the CMC-nZVI, the core-shell spheres collapses to acicular-shaped structures after aging with crystalline lepidocrocite (γ-FeOOH) as the primary end product. Moreover, more lepidocrocite present in the corrosion products of CMC-nZVI with higher loading of CMC, which reveals that the CMC coating could influence the transformation of iron oxides.

Aging study on carboxymethyl cellulose-coated zero-valent iron nanoparticles in water: Chemical transformation and structural evolution

International Nuclear Information System (INIS)

Dong, Haoran; Zhao, Feng; Zeng, Guangming; Tang, Lin; Fan, Changzheng; Zhang, Lihua; Zeng, Yalan; He, Qi; Xie, Yankai; Wu, Yanan

2016-01-01

Highlights: • The chemical transformation and structural evolution of CMC-nZVI were investigated. • CMC could slow down the aging rate of nZVI and alter the species transformation. • Fe_3O_4 and/or γ-Fe_2O_3 are the dominant corrosion products of bare nZVI after aging. • γ-FeOOH is the primary corrosion product of CMC-nZVI after aging. - Abstract: To assess the long-term fate and the associated risks of nanoscale zero-valent iron (nZVI) used in the water remediation, it is essential to understand the chemical transformations during aging of nZVI in water. This study investigated the compositional and structural evolution of bare nZVI and carboxymethyl cellulose (CMC) coated nZVI in static water over a period of 90 days. Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), X-ray diffraction (XRD) and Raman spectroscopy were used to characterize the corrosion products of nZVI and CMC-nZVI. Results show that both the structures and the compositions of the corrosion products change with the process of aging, but the coating of CMC could slow down the aging rate of nZVI (as indicated by the slower drop in Fe"0 intensity in XRD pattern). For the bare nZVI, magnetite (Fe_3O_4) and/or maghemite (γ-Fe_2O_3) are the dominant corrosion products after 90 days of aging. However, for the CMC-nZVI, the core-shell spheres collapses to acicular-shaped structures after aging with crystalline lepidocrocite (γ-FeOOH) as the primary end product. Moreover, more lepidocrocite present in the corrosion products of CMC-nZVI with higher loading of CMC, which reveals that the CMC coating could influence the transformation of iron oxides.

Gas Removal in the Ursa Minor Galaxy: Linking Hydrodynamics and Chemical Evolution Models

Energy Technology Data Exchange (ETDEWEB)

Caproni, Anderson; Lanfranchi, Gustavo Amaral; Baio, Gabriel Henrique Campos; Kowal, Grzegorz [Núcleo de Astrofísica Teórica, Universidade Cruzeiro do Sul, R. Galvão Bueno 868, Liberdade, 01506-000, São Paulo, SP (Brazil); Falceta-Gonçalves, Diego, E-mail: anderson.caproni@cruzeirodosul.edu.br [Escola de Artes, Ciências e Humanidades, Universidade de São Paulo, Rua Arlindo Bettio 1000, CEP 03828-000 São Paulo (Brazil)

2017-04-01

We present results from a non-cosmological, three-dimensional hydrodynamical simulation of the gas in the dwarf spheroidal galaxy Ursa Minor. Assuming an initial baryonic-to-dark-matter ratio derived from the cosmic microwave background radiation, we evolved the galactic gas distribution over 3 Gyr, taking into account the effects of the types Ia and II supernovae. For the first time, we used in our simulation the instantaneous supernovae rates derived from a chemical evolution model applied to spectroscopic observational data of Ursa Minor. We show that the amount of gas that is lost in this process is variable with time and radius, being the highest rates observed during the initial 600 Myr in our simulation. Our results indicate that types Ia and II supernovae must be essential drivers of the gas loss in Ursa Minor galaxy (and probably in other similar dwarf galaxies), but it is ultimately the combination of galactic winds powered by these supernovae and environmental effects (e.g., ram-pressure stripping) that results in the complete removal of the gas content.

The effects of the initial mass function on the chemical evolution of elliptical galaxies

Science.gov (United States)

De Masi, Carlo; Matteucci, F.; Vincenzo, F.

2018-03-01

We describe the use of our chemical evolution model to reproduce the abundance patterns observed in a catalogue of elliptical galaxies from the Sloan Digital Sky Survey Data Release 4. The model assumes ellipticals form by fast gas accretion, and suffer a strong burst of star formation followed by a galactic wind, which quenches star formation. Models with fixed initial mass function (IMF) failed in simultaneously reproducing the observed trends with the galactic mass. So, we tested a varying IMF; contrary to the diffused claim that the IMF should become bottom heavier in more massive galaxies, we find a better agreement with data by assuming an inverse trend, where the IMF goes from being bottom heavy in less massive galaxies to top heavy in more massive ones. This naturally produces a downsizing in star formation, favouring massive stars in largest galaxies. Finally, we tested the use of the integrated Galactic IMF, obtained by averaging the canonical IMF over the mass distribution function of the clusters where star formation is assumed to take place. We combined two prescriptions, valid for different SFR regimes, to obtain the Integrated Initial Mass Function values along the whole evolution of the galaxies in our models. Predicted abundance trends reproduce the observed slopes, but they have an offset relative to the data. We conclude that bottom-heavier IMFs do not reproduce the properties of the most massive ellipticals, at variance with previous suggestions. On the other hand, an IMF varying with galactic mass from bottom heavier to top heavier should be preferred.

Robust numerical simulation of porosity evolution in chemical vapor infiltration III: three space dimension

CERN Document Server

Jin Shi

2003-01-01

Chemical vapor infiltration (CVI) process is an important technology to fabricate ceramic matrix composites (CMC's). In this paper, a three-dimension numerical model is presented to describe pore microstructure evolution during the CVI process. We extend the two-dimension model proposed in [S. Jin, X.L. Wang, T.L. Starr, J. Mater. Res. 14 (1999) 3829; S. Jin. X.L. Wang, T.L. Starr, X.F. Chen, J. Comp. Phys. 162 (2000) 467], where the fiber surface is modeled as an evolving interface, to the three space dimension. The 3D method keeps all the virtue of the 2D model: robust numerical capturing of topological changes of the interface such as the merging, and fast detection of the inaccessible pores. For models in the kinetic limit, where the moving speed of the interface is constant, some numerical examples are presented to show that this three-dimension model will effectively track the change of porosity, close-off time, location and shape of all pores.

Origin of the chemical elements

Energy Technology Data Exchange (ETDEWEB)

Tayler, R J

1984-05-01

The subject is discussed in relation to the composition of initially created matter and changes which have occurred during the life history of the universe, with particular reference to our galaxy and nearby galaxies. Headings are: observations of element abundances (stars, gas clouds in our own and nearby galaxies, hot gas in galaxy clusters, the solar system); the originally created matter (Big Bang theory and early nuclear reactions); processes changing observed composition (galactic evolution; nuclear fusion reactions in stellar interiors; chemical composition of a highly evolved massive star); supernovae (production of heavy elements); chemical evolution of the galaxy; production of very heavy elements (s process, r process).

Dynamical evolution and disintegration of comets

International Nuclear Information System (INIS)

Kresak, L.

1982-01-01

Current concepts of the origin and evolution of comets are reviewed. The place of their formation from which they have been delivered into the Oort reservoir is still an open problem, but the region of the outermost planets appears most probable. The interplay of stellar and planetary perturbations can be traced by model computations which reveal both the general trends and the variety of individual evolutionary paths. The present structure of the system of comets is controlled by the dynamical evolution of its individual members limited by their physical aging by disintegration. Where the lifetimes are short, as in the Jupiter family of short-period comets, an equilibrium between elimination and replenishment is established. The role of different destructive processes and the resulting survival times are discussed. (Auth.)

Contribution of neutron activation analysis and radioanalytical techniques to trace element speciation in environmental analysis

International Nuclear Information System (INIS)

Gallorini, M.; Orvini, E.; Sabbioni, E.; Pietra, R.

1984-01-01

The feasibility of the NAA in contributing to trace element speciation in environmental and biological samples is shown by a few selected applications. They are: (i) the determination of different species of vanadium, arsenic and selenium in freshwater. The pre-irradiation treatments in which the different chemical species are selectively isolated are critically evaluated. Problems arising from possible contaminations or losses and from blanks are discussed; (ii) the use of NAA in metallobiochemical speciation once biochemical methods of cellular fractionation for the isolation of metallobiocomplexes are developed. Examples concern the biochemical speciation of vanadium in human blood and the development of a method for speciation of inorganic and organic arsenic compounds in biological samples. The use of radioanalytical techniques in developing the separation procedures of different trace metal chemical and biochemical species is also briefly discussed. 24 references, 5 figures, 4 tables

Online Continuous Trace Process Analytics Using Multiplexing Gas Chromatography.

Science.gov (United States)

Wunsch, Marco R; Lehnig, Rudolf; Trapp, Oliver

2017-04-04

The analysis of impurities at a trace level in chemical products, nutrition additives, and drugs is highly important to guarantee safe products suitable for consumption. However, trace analysis in the presence of a dominating component can be a challenging task because of noncompatible linear detection ranges or strong signal overlap that suppresses the signal of interest. Here, we developed a technique for quantitative analysis using multiplexing gas chromatography (mpGC) for continuous and completely automated process trace analytics exemplified for the analysis of a CO 2 stream in a production plant for detection of benzene, toluene, ethylbenzene, and the three structural isomers of xylene (BTEX) in the concentration range of 0-10 ppb. Additional minor components are methane and methanol with concentrations up to 100 ppm. The sample is injected up to 512 times according to a pseudorandom binary sequence (PRBS) with a mean frequency of 0.1 Hz into a gas chromatograph equipped with a flame ionization detector (FID). A superimposed chromatogram is recorded which is deconvoluted into an averaged chromatogram with Hadamard transformation. Novel algorithms to maintain the data acquisition rate of the detector by application of Hadamard transformation and to suppress correlation noise induced by components with much higher concentrations than the target substances are shown. Compared to conventional GC-FID, the signal-to-noise ratio has been increased by a factor of 10 with mpGC-FID. Correspondingly, the detection limits for BTEX in CO 2 have been lowered from 10 to 1 ppb each. This has been achieved despite the presence of detectable components (methane and methanol) with a concentration about 1000 times higher than the target substances. The robustness and reliability of mpGC has been proven in a two-month field test in a chemical production plant.

Trace elements record complex histories in diogenites

Science.gov (United States)

Balta, J. B.; Beck, A. W.; McSween, H. Y.

2012-12-01

Diogenite meteorites are cumulate rocks composed mostly of orthopyroxene and chemically linked to eucrites (basaltic) and howardites (brecciated mixtures of diogenites and eucrites). Together, they represent the largest single family of achondrite meteorites delivered to Earth, and have been spectrally linked to the asteroid 4 Vesta, the largest remaining basaltic protoplanet. However, this spectral link is non-unique as many basaltic asteroids likely formed and were destroyed in the early solar system. Recent work suggested that Vesta may be an unlikely parent body for the diogenites based on correlations between trace elements and short-lived isotope decay products, which would be unlikely to survive on a body as large as Vesta due to its long cooling history [1]. Recent analyses of terrestrial and martian olivines have demonstrated that trace element spatial distributions can preserve evidence of their crystallization history even when major elements have been homogenized [2]. We have mapped minor elements including Cr, Al, and Ti in seemingly homogeneous diogenite orthopyroxenes and found a variety of previously unobserved textures. The pyroxenes in one sample (GRA 98108) are seemingly large grains of variable shapes and sizes, but the trace elements reveal internal grain boundaries between roughly-equal sized original subgrains, with equilibrated metamorphic triple junctions between them and trace element depletions at the boundaries. These trends suggest extraction of trace elements by a magma along those relict grain boundaries during a reheating event. Two other samples show evidence of fracturing and annealing, with trace element mobility within grains. One sample appears to have remained a closed system during annealing (MET 01084), while the other has interacted with a fluid or magma to move elements along annealed cracks (LEW 88679). These relict features establish that the history of diogenite pyroxenes is more complex than their homogeneous major

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.

Off the mark : Response to Kaufman's evolution of strategic HRM

NARCIS (Netherlands)

Wright, Patrick M.; Guest, David; Paauwe, Jaap

2015-01-01

Professor Bruce Kaufman's look back at two seminal books published at the beginning of the strategic HRM field and examination of two recent books to trace the evolution of the field identifies some issues, but ones with which the field has dealt for a number of years. His choice of our book HRM and

Effect of Ocean Acidification on Organic and Inorganic Speciation of Trace Metals.

Science.gov (United States)

Stockdale, Anthony; Tipping, Edward; Lofts, Stephen; Mortimer, Robert J G

2016-02-16

Rising concentrations of atmospheric carbon dioxide are causing acidification of the oceans. This results in changes to the concentrations of key chemical species such as hydroxide, carbonate and bicarbonate ions. These changes will affect the distribution of different forms of trace metals. Using IPCC data for pCO2 and pH under four future emissions scenarios (to the year 2100) we use a chemical speciation model to predict changes in the distribution of organic and inorganic forms of trace metals. Under a scenario where emissions peak after the year 2100, predicted free ion Al, Fe, Cu, and Pb concentrations increase by factors of up to approximately 21, 2.4, 1.5, and 2.0 respectively. Concentrations of organically complexed metal typically have a lower sensitivity to ocean acidification induced changes. Concentrations of organically complexed Mn, Cu, Zn, and Cd fall by up to 10%, while those of organically complexed Fe, Co, and Ni rise by up to 14%. Although modest, these changes may have significance for the biological availability of metals given the close adaptation of marine microorganisms to their environment.

TraceContract: A Scala DSL for Trace Analysis

Science.gov (United States)

Barringer, Howard; Havelund, Klaus

2011-01-01

In this paper we describe TRACECONTRACT, an API for trace analysis, implemented in the SCALA programming language. We argue that for certain forms of trace analysis the best weapon is a high level programming language augmented with constructs for temporal reasoning. A trace is a sequence of events, which may for example be generated by a running program, instrumented appropriately to generate events. The API supports writing properties in a notation that combines an advanced form of data parameterized state machines with temporal logic. The implementation utilizes SCALA's support for defining internal Domain Specific Languages (DSLs). Furthermore SCALA's combination of object oriented and functional programming features, including partial functions and pattern matching, makes it an ideal host language for such an API.

Trace elements (Rb, Cs, Sr, Pb, Th, U) bioavailability potential and speciation in the Piracicaba river bottom sediments, Sao Paulo, Brazil

International Nuclear Information System (INIS)

Fernandes, Alexandre Martins; Mortatti, Jefferson; Oliveira, Helder de; Bibian, Joao Paulo Rambelli; Moraes, Graziela Meneghel de; Probst, Jean-Luc

2007-01-01

It was studied the bioavailability potential of Rb, Cs, Sr, Pb, Th and U and their chemical speciation in Piracicaba river bottom sediments. This river system crosses important agricultural and urban areas of Sao Paulo state, which groups about 3 million people and receives a large load of agricultural, industrial and domestic wastes. The procedure used to estimate trace elements bioavailability potential was related to a 7-step sequential chemical extraction. This scheme was designed to dissolved and separate sample chemical phases, which can be affected by changes in physical-chemical conditions; in the following order: water soluble, exchangeable, bound to carbonates or acid fraction, bound to Mn-oxides, bound to Fe-oxides and bound to organic matter. Trace element concentrations were determined by Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES) after each extraction step. With the used extraction procedure, it was possible to identify the fraction where some trace elements could be found in order to evaluate their bioavailability potential. Rb and Cs were particularly involved with the organic fraction, while Sr revealed to be associated mainly to the exchangeable fraction (clay minerals). Pb, Th and U were mainly bound to the residual and Fe-oxide fractions. (author)

Trace Gas Evolution in the Present and Past Atmosphere

DEFF Research Database (Denmark)

Winther, Malte Nordmann

.Continuous incubation experiments are presented with nitrifying bacteria Nitrosomonasmobilis revealing strong indications of N2O production from different chemical reactions.The measurements revealed a three step site preference pattern in the range of nitricationand denitrication and we therefore suggest...... performed 1) on the Arctictundra and 2) on an inclined temperate slope. 1) Previous studies has shown that largeamounts of N2O is being emitted after thawing of permafrost. We investigated a downslopesite covering a moisture gradient area in the arctic tundra. Moss-covered sites revealed highnitrication...

Trace elements in human, cattle and swine teeth, measured by external beam PIXE-PIGE setup

International Nuclear Information System (INIS)

Tabacniks, M.H.; Rizzutto, M.A.; Added, N.; Liguori Neto, R.; Acquadro, J.C.; Vilela, M.; Oliveira, T.R.C.F.; Markarian, R.A.; Mori, M.

2001-01-01

The use of animal teeth to replace human teeth in dentistry school classes and to test chemicals and fillings, motivated for a better characterization of the elementary composition of their enamel, since some of the chemical properties, adhesion and chemical compatibility may depend on these parameters. Cattle, swine and human teeth were collected by dentists of the University of Sao Paulo. These teeth came primarily from Sao Paulo region and were analyzed for trace elements at the Open Nuclear Physics Laboratory, using a high energy external proton beam, PIXE-PIGE setup

The η/s of hadrons out of chemical equilibrium

International Nuclear Information System (INIS)

Wiranata, A; Wang, X N; Prakash, M; Huovinen, P; Koch, V

2014-01-01

We study how the shear viscosity, η, entropy density, s, and η/s depend on growing hadron chemical potentials resulting from the loss of chemical equilibrium during the evolution of a relativistic heavy-ion collision. Our calculations here are for an interacting pion gas in a system of net baryon number zero. Time evolution of the temperature and pion chemical potential are taken from ideal fluid hydrodynamic calculations of RHIC and LHC collisions. We find that the shear viscosity decreases whereas the entropy density increases with increasing pion chemical potential resulting in values of η/s that are slightly reduced from the case of chemical potentials being zero when chemical equilibrium prevails. Our results indicate that the inclusion of additional mesons and baryons will likely lead to further reduction in the value of η/s.

Piezoelectric trace vapor calibrator

International Nuclear Information System (INIS)

Verkouteren, R. Michael; Gillen, Greg; Taylor, David W.

2006-01-01

The design and performance of a vapor generator for calibration and testing of trace chemical sensors are described. The device utilizes piezoelectric ink-jet nozzles to dispense and vaporize precisely known amounts of analyte solutions as monodisperse droplets onto a hot ceramic surface, where the generated vapors are mixed with air before exiting the device. Injected droplets are monitored by microscope with strobed illumination, and the reproducibility of droplet volumes is optimized by adjustment of piezoelectric wave form parameters. Complete vaporization of the droplets occurs only across a 10 deg. C window within the transition boiling regime of the solvent, and the minimum and maximum rates of trace analyte that may be injected and evaporated are determined by thermodynamic principles and empirical observations of droplet formation and stability. By varying solution concentrations, droplet injection rates, air flow, and the number of active nozzles, the system is designed to deliver--on demand--continuous vapor concentrations across more than six orders of magnitude (nominally 290 fg/l to 1.05 μg/l). Vapor pulses containing femtogram to microgram quantities of analyte may also be generated. Calibrated ranges of three explosive vapors at ng/l levels were generated by the device and directly measured by ion mobility spectrometry (IMS). These data demonstrate expected linear trends within the limited working range of the IMS detector and also exhibit subtle nonlinear behavior from the IMS measurement process

Chemical analysis of useful trace elements in sea water

International Nuclear Information System (INIS)

Katoh, Shunsaku; Fujii, Ayako; Miyai, Yoshitaka; Sakane, Kohji; Ogata, Noboru.

1983-01-01

The methods for the analysis of useful trace elements in sea water which have been tried so far are reviewed, and these methods are described briefly from the standpoint of studying the collection of resources. Ag and Au can be determined by concentrating sea water by ion-exchange method, solvent extraction method and electrodeposition method, then the elements are measured quantitatively by activation analysis and atomic absorption spectrochemical analysis. Sr, B and Li, which exist in relatively high concentration in sea water, are determined easily by atomic absorption spectrochemical analysis and absorption spectrometry. U, Mo and V are measured suitably by concentrating the elements by coprecipitation or solvent extraction method, and measuring by fluorescence analysis and arsenazo-3 method for U and through graphite-atomic absorption analysis for Mo and V. It has been revealed that the concentration of Ag and Au in sea water is extremely low, accordingly the recovery study is not conducted recently. On the other hand, the adsorption method using hydrated titanium oxide and amidoxim adsorbents for U, Mo and V, the adsorption method using aluminum adsorbent for Li, and the adsorption method using magnesium oxide and zirconium hydroxide and the solvent extraction method for B are hopeful to recover these elements. (Yoshitake, I.)

Particulate Trace Element Cycling in a Diatom Bloom at Station ALOHA

Science.gov (United States)

Weisend, R.; Morton, P. L.; Landing, W. M.; Fitzsimmons, J. N.; Hayes, C. T.; Boyle, E. A.

2014-12-01

Phytoplankton in oligotrophic marine deserts depend on remote sources to supply trace nutrients. To examine these sources, marine particulate matter samples from the central North Pacific (Station ALOHA) were collected during the July-August 2012 HOE-DYLAN cruises and analyzed for a suite of trace (e.g., Fe, Mn) and major (e.g. Al, P) elements. Daily surface SPM samples were examined for evidence of atmospheric deposition and biological uptake, while five vertical profiles were examined for evidence of surface vertical export and subsurface horizontal transport from nearby sources (e.g., margin sediments, hydrothermal plumes). Maxima in surface particulate P (a biological tracer) corresponded with a diatom bloom, and surprisingly also coincided with maxima in particulate Al (typically a tracer for lithogenic inputs). The surface particulate Al distributions likely result from the adsorption of dissolved Al onto diatom silica frustules, not from atmospheric dust deposition. In addition, a subsurface maximum in particulate Al and P was observed four days later at 75m, possibly resulting from vertical export of the surface diatom bloom. The distributions of other bioactive trace elements (e.g. Cd, Co, Cu) will be presented in the context of the diatom bloom and other biological, chemical and physical features. A second, complementary poster is also being presented which examines the cycling of trace elements in lithogenic particles (Morton et al., "Trace Element Cycling in Lithogenic Particles at Station ALOHA").

Evaluation of physico-chemical parameters of agricultural soils ...

African Journals Online (AJOL)

Evaluation of physico-chemical parameters of agricultural soils irrigated by the waters of the hydrolic basin of Sebou River and their influences on the transfer of trace elements into sugar crops (the case of sugar cane)

Models of nanoparticles movement, collision, and friction in chemical mechanical polishing (CMP)

Energy Technology Data Exchange (ETDEWEB)

Ilie, Filip, E-mail: filip@meca.omtr.pub.ro [Polytechnic University of Bucharest, Department of Machine Elements and Tribology (Romania)

2012-03-15

Nanoparticles have been widely used in polishing slurry such as chemical mechanical polishing (CMP) process. The movement of nanoparticles in polishing slurry and the interaction between nanoparticles and solid surface are very important to obtain an atomic smooth surface in CMP process. Polishing slurry contains abrasive nanoparticles (with the size range of about 10-100 nm) and chemical reagents. Abrasive nanoparticles and hydrodynamic pressure are considered to cause the polishing effect. Nanoparticles behavior in the slurry with power-law viscosity shows great effect on the wafer surface in polishing process. CMP is now a standard process of integrated circuit manufacturing at nanoscale. Various models can dynamically predict the evolution of surface topography for any time point during CMP. To research, using a combination of individual nanoscale friction measurements for CMP of SiO{sub 2}, in an analytical model, to sum these effects, and the results scale CMP experiments, can guide the research and validate the model. CMP endpoint measurements, such as those from motor current traces, enable verification of model predictions, relating to friction and wear in CMP and surface topography evolution for different types of CMP processes and patterned chips. In this article, we explore models of the microscopic frictional force based on the surface topography and present both experimental and theoretical studies on the movement of nanoparticles in polishing slurry and collision between nanoparticles, as well as between the particles and solid surfaces in time of process CMP. Experimental results have proved that the nanoparticle size and slurry properties have great effects on the polishing results. The effects of the nanoparticle size and the slurry film thickness are also discussed.

Application of micro-PIXE analysis to investigate trace elements in deciduous teeth enamel

International Nuclear Information System (INIS)

Igari, K.; Takahashi, A.; Ando, H.

2010-01-01

The early life environment has widespread consequences for later health and disease. To prevent the disease in later life, the assessment of fetal environment is very important. In Japan, birthweight has fallen rapidly during recent two decades. The reduction of birthweight represents reduced fetal nutrition. Deciduous tooth enamel contains pre- and postnatal enamel and its chemical composition reflects the status of metabolism of trace elements during formation period. Deciduous tooth enamel is considered to be a suitable indicator of trace elements exposure in utero. We applied micro-PIXE analysis to investigate the trace elemental content in deciduous tooth enamel. Two deciduous canines from one healthy Japanese boy were used for this study. The enamel section including pre- and postnatal enamel was prepared for micro-PIXE analysis. Five trace elements (Na, Mg, Cl, Zn, and Sr) were detected in the scanning area of tooth. The distribution profiles of 5 elements were obtained as X-ray maps. The distribution profiles of zinc and chlorine were specific, and showed higher concentration in surface enamel. No elements showed different profiles of X-ray maps between pre- and postnatal enamel in this sample. The results of this study suggested that micro-PIXE analysis would be able to estimate the trace elements in prenatal and postnatal enamel, respectively. (author)

Nanoscale Chemical and Valence Evolution at the Metal/Oxide Interface: A Case Study of Ti/SrTiO 3

KAUST Repository

Li, Yangyang

2016-06-27

Metal/oxide interfaces are ubiquitous in a wide range of applications such as electronics, photovoltaics, memories, catalysis, and sensors. However, there have been few investigations dedicated to the nanoscale structural and chemical characteristics of these buried interfaces. In this work, the metal/oxide interface between Ti and SrTiO3 (STO) is examined as a prototypical system using high-resolution scanning transmission electron microscopy and electron energy loss spectroscopy. An atomic-thin Ti2O3-like layer at the Ti/STO interface prepared at room temperature is discovered, and first-principles calculations predict a metallic band structure of this 2D electron system. As a universal feature of such interfaces prepared at different temperatures, near the interface nanoscale oxygen-deficient domains and continuous modulation of Ti oxidation states are found. Overall, these results directly reveal complex chemical and valence evolutions at the metal/oxide interfaces, providing microscopic insights on such heterostructures. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Trace elements in wild and orchard honeys

Energy Technology Data Exchange (ETDEWEB)

Almeida-Silva, M.; Canha, N.; Galinha, C.; Dung, H.M. [Instituto Tecnologico e Nuclear, URSN, E.N. 10, 2686-953 Sacavem (Portugal); Freitas, M.C., E-mail: cfreitas@itn.pt [Instituto Tecnologico e Nuclear, URSN, E.N. 10, 2686-953 Sacavem (Portugal); Sitoe, T. [Instituto Tecnologico e Nuclear, URSN, E.N. 10, 2686-953 Sacavem (Portugal)

2011-11-15

The present study aims the identification and quantification of trace elements in two types of honey samples: Orchard honey and Wild honey from mainland Portugal. Chemical elements content was assessed by Instrumental Neutron Activation Analysis (INAA). Concentrations were determinated for Ag, As, Br, Ca, Cl, Cs, Cu, Fe, K, La, Mg, Mn, Na, Rb, Sb, Sc, U, V and Zn. The nutritional values of both honey types were evaluated since this product contains some elements that are essential dietary nutrients for humans. Physical properties of the honey samples, such as electrical conductivy and pH, were assessed as well.

Online monitoring of N-nitrosodimethylamine rejection as a performance indicator of trace organic chemical removal by reverse osmosis.

Science.gov (United States)

Fujioka, Takahiro; Takeuchi, Haruka; Tanaka, Hiroaki; Kodamatani, Hitoshi

2018-06-01

The security of recycled water quality in potable reuse can be enhanced by improving the credibility of reverse osmosis (RO) treatment for the removal of trace organic chemicals (TOrCs). This study evaluated the potential of online monitoring of N-nitrosodimethylamine (NDMA) before and after RO treatment as a surrogate indicator for TOrC removal by RO. This pilot-scale study monitored NDMA concentrations in RO feedwater (ultrafiltration-treated wastewater) and RO permeate every 22 min using novel online NDMA analyzers-high-performance liquid chromatography followed by photochemical reaction and chemiluminescence detection. NDMA rejection by RO varied considerably in response to changes in operating conditions (permeate flux and feedwater temperature). A high linear correlation between NDMA rejection and the rejection of six other TOrCs was observed. The linear correlation was also identified for an RO membrane damaged with chlorine. The correlation between another potential surrogate indicator (conductivity rejection) and TOrC rejection was relatively low. NDMA, which is the smallest compound among regulated TOrCs, revealed rejections lower than the other TOrCs, indicating that NDMA rejection can be a conservative surrogate indicator capable of predicting changes in TOrC removal. Copyright © 2018 Elsevier Ltd. All rights reserved.

Physical, chemical, microbiological and sensorial behaviour evolution of non cooked pressed cheese paste while in refrigerated storage, made with red chilli powder, treated by heat or ionization

International Nuclear Information System (INIS)

Iben El Hadj Mohamed, A.

1998-01-01

The evolution of different physical, chemical, microbiological and sensorial characteristics of a Tunisian manufactured cheese made of non cooked pressed cheese paste with red chilli powder treated by heat, was measured while in refrigerated storage and compared to the one treated by ionization (author)