Articles de revues : « Ion chemistry and composition »

1

Ip, W. H. "Ion composition and chemistry." Advances in Space Research 9, no. 3 (1989): 141–50. http://dx.doi.org/10.1016/0273-1177(89)90253-6.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

2

Breig, E. L. "Thermospheric ion and neutral composition and chemistry." Reviews of Geophysics 25, no. 3 (1987): 455. http://dx.doi.org/10.1029/rg025i003p00455.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

3

Vuitton, V., R. V. Yelle, and P. Lavvas. "Composition and chemistry of Titan's thermosphere and ionosphere." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 367, no. 1889 (2008): 729–41. http://dx.doi.org/10.1098/rsta.2008.0233.

Texte intégral

Résumé :

Titan has long been known to harbour the richest atmospheric chemistry in the Solar System. Until recently, it had been believed that complex hydrocarbons and nitriles were produced through neutral chemistry that would eventually lead to the formation of micrometre sized organic aerosols. However, recent measurements by the Cassini spacecraft are drastically changing our understanding of Titan's chemistry. The Ion and Neutral Mass Spectrometer (INMS) and the Cassini Plasma Spectrometer (CAPS) revealed an extraordinary complex ionospheric composition. INMS detected roughly 50 positive ions with m / z <100 and a density higher than 0.1 cm −3 . CAPS provided evidence for heavy (up to 350 amu) positively and negatively charged (up to 4000 amu) ions. These observations all indicate that Titan's ionospheric chemistry is incredibly complex and that molecular growth starts in the upper atmosphere rather than at lower altitude. Here, we review the recent progress made on ionospheric chemistry. The presence of heavy neutrals in the upper atmosphere has been inferred as a direct consequence of the presence of complex positive ions. Benzene (C 6 H 6 ) is created by ion chemistry at high altitudes and its main photolysis product, the phenyl radical (C 6 H 5 ), is at the origin of the formation of aromatic species at lower altitude.

Styles APA, Harvard, Vancouver, ISO, etc.

4

Zhao, Chenglong, Qidi Wang, Zhenpeng Yao, et al. "Rational design of layered oxide materials for sodium-ion batteries." Science 370, no. 6517 (2020): 708–11. http://dx.doi.org/10.1126/science.aay9972.

Texte intégral

Résumé :

Sodium-ion batteries have captured widespread attention for grid-scale energy storage owing to the natural abundance of sodium. The performance of such batteries is limited by available electrode materials, especially for sodium-ion layered oxides, motivating the exploration of high compositional diversity. How the composition determines the structural chemistry is decisive for the electrochemical performance but very challenging to predict, especially for complex compositions. We introduce the “cationic potential” that captures the key interactions of layered materials and makes it possible to predict the stacking structures. This is demonstrated through the rational design and preparation of layered electrode materials with improved performance. As the stacking structure determines the functional properties, this methodology offers a solution toward the design of alkali metal layered oxides.

Styles APA, Harvard, Vancouver, ISO, etc.

5

Feistel, Rainer. "On the Physical Chemistry of Seawater with Deviating Ion Composition." Zeitschrift für Physikalische Chemie 204, Part_1_2 (1998): 27–44. http://dx.doi.org/10.1524/zpch.1998.204.part_1_2.027.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

6

Johnston, Kathryn A., Lisa M. Stabryla, Ashley M. Smith, Xing Yee Gan, Leanne M. Gilbertson, and Jill E. Millstone. "Impacts of broth chemistry on silver ion release, surface chemistry composition, and bacterial cytotoxicity of silver nanoparticles." Environmental Science: Nano 5, no. 2 (2018): 304–12. http://dx.doi.org/10.1039/c7en00974g.

Texte intégral

Résumé :

We determine the impact of bacterial growth media on silver nanoparticle surface chemistry, this surface chemistry on silver ion release from the nanoparticles, and ultimately the antimicrobial implications of those parameters.

Styles APA, Harvard, Vancouver, ISO, etc.

7

Vigren, Erik. "Analytic model of comet ionosphere chemistry." Astronomy & Astrophysics 616 (August 2018): A59. http://dx.doi.org/10.1051/0004-6361/201832704.

Texte intégral

Résumé :

Context. We consider a weakly to moderately active comet and make the following simplifying assumptions: (i) The partial ionization frequencies are constant throughout the considered part of the coma. (ii) All species move radially outward with the same constant speed. (iii) Ion-neutral reactions affect the chemical composition of the ions, but ion removal through dissociative recombination with free electrons is negligible. Aims. We aim to derive an analytical model for the radial variation of the abundances of various cometary ions. Methods. We present two methods for retrieving the ion composition as a function of r. The first method, which has previously been used frequently, solves a series of coupled differential equations. The new method introduced here is based on probabilistic arguments and is analytical in nature. Results. For a pure H2O coma, the resulting closed-form expressions yield results that are identical to the standard method, but are computationally much less expensive. Conclusions. In addition to the computational simplicity, the analytical model provides insight into how the various abundances depend on parameters such as comet production rate, outflow speed, and reaction rate coefficients. It can also be used to investigate limiting cases. It cannot easily be extended to account for a radially varying flow speed or dissociative recombination in the way a code based on numerical integrations can.

Styles APA, Harvard, Vancouver, ISO, etc.

8

Verronen, P. T., E. Turunen, Th Ulich, and E. Kyrölä. "Modelling the effects of the October 1989 solar proton event on mesospheric odd nitrogen using a detailed ion and neutral chemistry model." Annales Geophysicae 20, no. 12 (2002): 1967–76. http://dx.doi.org/10.5194/angeo-20-1967-2002.

Texte intégral

Résumé :

Abstract. Solar proton events and electron precipitation affect the concentrations of middle atmospheric constituents. Ionization caused by precipitating particles enhances the production of important minor neutral constituents, such as nitric oxide, through reaction chains in which ionic reactions play an important role. The Sodankylä Ion Chemistry model (SIC) has been modified and extended into a detailed ion and neutral chemistry model of the mesosphere. Our steady-state model (containing 55 ion species, 8 neutral species, and several hundred chemical reactions) is used to investigate the effect of the October 1989 solar proton event on odd nitrogen at altitudes between 50–90 km. The modelling results show that the NO concentration is significantly enhanced due to the proton precipitation, reaching 107 –108 cm-3 throughout the mesosphere on the 20 October when the proton forcing was most severe. A comparison between the chemical production channels of odd nitrogen indicates that ion chemical reactions are an important factor in the total odd nitrogen production during intense ionization. The modelled electron concentration for the 23 October is compared with EISCAT incoherent scatter radar measurements and a reasonable agreement is found.Key words. Atmospheric composition and structure (Middle atmosphere – composition and chemistry); Ionosphere (Particle precipitation)

Styles APA, Harvard, Vancouver, ISO, etc.

9

Litvin, A., W. Kofman, and B. Cabrit. "Ion composition measurements and modelling at altitudes from 140 to 350 km using EISCAT measurements." Annales Geophysicae 16, no. 10 (1998): 1159–68. http://dx.doi.org/10.1007/s00585-998-1159-6.

Texte intégral

Résumé :

Abstract. This work aims at processing the data of CP1 and CP2 programs of EISCAT ionospheric radar from 1987 to 1994 using the "full profile" method which allows to solve the "temperature-composition" ambiguity problem in the lower F region. The program of data analysis was developed in the CEPHAG in 1995–1996. To improve this program, we implemented another analytical function to model the ion composition profile. This new function better reflects the real profile of the composition. Secondly, we chose the best method to select the initial conditions for the "full profile" procedure. A statistical analysis of the results was made to obtain the averages of various parameters: electron concentration and temperature, ion temperature, composition and bulk velocity. The aim is to obtain models of the parameter behaviour defining the ion composition profiles : z50 (transition altitude between atomic and molecular ions) and dz (width of the profile), for various seasons and for high and low solar activities. These models are then compared to other models. To explain the principal features of parameters z50 and dz, we made an analysis of the processes leading to composition changes and related them to production and electron density profile. A new experimental model of ion composition is now available.Key words. Auroral ionosphere · Ion chemistry and composition · Instruments and techniques · EISCAT

Styles APA, Harvard, Vancouver, ISO, etc.

10

Kalakoski, Niilo, Pekka T. Verronen, Annika Seppälä, Monika E. Szeląg, Antti Kero, and Daniel R. Marsh. "Statistical response of middle atmosphere composition to solar proton events in WACCM-D simulations: the importance of lower ionospheric chemistry." Atmospheric Chemistry and Physics 20, no. 14 (2020): 8923–38. http://dx.doi.org/10.5194/acp-20-8923-2020.

Texte intégral

Résumé :

Abstract. Atmospheric effects of solar proton events (SPEs) have been studied for decades, because their drastic impact can be used to test our understanding of upper stratospheric and mesospheric chemistry in the polar cap regions. For example, odd hydrogen and odd nitrogen are produced during SPEs, which leads to depletion of ozone in catalytic reactions, such that the effects are easily observed from satellites during the strongest events. Until recently, the complexity of the ion chemistry in the lower ionosphere (i.e., in the D region) has restricted global models to simplified parameterizations of chemical impacts induced by energetic particle precipitation (EPP). Because of this restriction, global models have been unable to correctly reproduce some important effects, such as the increase in mesospheric HNO3 or the changes in chlorine species. Here we use simulations from the WACCM-D model, a variant of the Whole Atmosphere Community Climate Model, to study the statistical response of the atmosphere to the 66 strongest SPEs which occurred in the years 1989–2012. Our model includes a set of D-region ion chemistry, designed for a detailed representation of the atmospheric effects of SPEs and EPP in general. We use superposed epoch analysis to study changes in O3, HOx (OH + HO2), Clx (Cl + ClO), HNO3, NOx (NO + NO2) and H2O. Compared to the standard WACCM which uses an ion chemistry parameterization, WACCM-D produces a larger response in O3 and NOx and a weaker response in HOx and introduces changes in HNO3 and Clx. These differences between WACCM and WACCM-D highlight the importance of including ion chemistry reactions in models used to study EPP.

Styles APA, Harvard, Vancouver, ISO, etc.

11

Yutkin, M. P., C. J. Radke, and T. W. Patzek. "Chemical Compositions in Salinity Waterflooding of Carbonate Reservoirs: Theory." Transport in Porous Media 136, no. 2 (2021): 411–29. http://dx.doi.org/10.1007/s11242-020-01517-7.

Texte intégral

Résumé :

AbstractHigher oil recovery after waterflood in carbonate reservoirs is attributed to increasing water wettability of the rock that in turn relies on complicated surface chemistry. In addition, calcite mineral reacts with aqueous solutions and can alter substantially the composition of injected water by mineral dissolution. Carefully designed chemical and/or brine flood compositions in the laboratory may not remain intact while the injected solutions pass through the reactive reservoir rock. This is especially true for a low-salinity waterflood process, where some finely tuned brine compositions can improve flood performances, whereas others cannot. We present a 1D reactive transport numerical model that captures the changes in injected compositions during water flow through porous carbonate rock. We include highly coupled bulk aqueous and surface carbonate-reaction chemistry, detailed reaction and mass transfer kinetics, 2:1 calcium ion exchange, and axial dispersion. At typical calcite reaction rates, local equilibrium is established immediately upon injection. In SI, we validate the reactive transport model against analytic solutions for rock dissolution, ion exchange, and longitudinal dispersion, each considered separately. Accordingly, using an open-source algorithm (Charlton and Parkhurst in Comput Geosci 37(10):1653–1663, 2011. 10.1016/j.cageo.2011.02.005), we outline a design tool to specify chemical/brine flooding formulations that correct for composition alteration by the carbonate rock. Subsequent works compare proposed theory against experiments on core plugs of Indiana limestone and give examples of how injected salinity compositions deviate from those designed in the laboratory for water-wettability improvement.

Styles APA, Harvard, Vancouver, ISO, etc.

12

Bobonich, F. M. "Chemical composition and ion exchange properties of zeolites." Theoretical and Experimental Chemistry 26, no. 3 (1990): 355–59. http://dx.doi.org/10.1007/bf00641351.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

13

Odom, Robert W. "Molecular surface analysis by TOF-SIMS." Proceedings, annual meeting, Electron Microscopy Society of America 50, no. 2 (1992): 1556–57. http://dx.doi.org/10.1017/s0424820100132418.

Texte intégral

Résumé :

Time-of-flight secondary ion mass spectrometry (TOF-SIMS) performs surface sensitive analysis of the elemental and molecular composition of solids. TOFSIMS is a relatively new embodiment of static secondary ion mass spectrometry (SSIMS) in which the dose of primary ions incident on the surface is typically less than 1012 ions/cm2. Since typical solid surfaces have an atomic density of 1015 atoms/cm2, this primary ion dose nominally removes less than 0.1% of a monolayer. Hence, SIMS analyses performed under these static conditions represent near surface analysis in which secondary ions are produced from the top few monolayers of the surface. The actual sampling depth is determined by the primary ion momentum, angle of incidence and chemistry of the surface. Since low dose primary ions cause minimal perturbation of the chemistry of the solid surface, SSIMS analyses often produce molecular or pseudo-molecular ions characteristic of the chemical composition of the surface. Thus, molecular ions or structurally significant fragment ions are often observed in SSIMS analyses of surfaces containing inorganic and organic residues, polymers surfaces, coatings, and biological materials such as tissues and membranes.

Styles APA, Harvard, Vancouver, ISO, etc.

14

Mikhailov, A. V., and W. Kofman. "An interpretation of ion composition diurnal variation deduced from EISCAT observations." Annales Geophysicae 19, no. 3 (2001): 351–58. http://dx.doi.org/10.5194/angeo-19-351-2001.

Texte intégral

Résumé :

Abstract. Physical interpretation is made of the O+/Ne diurnal variations in summer, revealed by Litvine et al. (1998) from the EISCAT observations. It is shown that the observed anti-correlation between the Z50 parameter, corresponding to the transition region between 50% of molecular and atomic ions, and the width Dz of the transition, defined as the altitude width between 10% and 90% of the O+/Ne ratio, can be reproduced in model calculations and the result of different recombination laws (quadratic in the lower and linear in the upper ionosphere) as well as diurnal variations in the photo-ionization rates.Key words.Ionosphere (ion chemistry and composition; modeling and forecasting)

Styles APA, Harvard, Vancouver, ISO, etc.

15

Fuse, Yasufumi, Yusuke Ide, and Makoto Ogawa. "Composition-Dependent Ion-Exchange Reactivity of Potassium Lithium Titanates." Bulletin of the Chemical Society of Japan 81, no. 6 (2008): 767–72. http://dx.doi.org/10.1246/bcsj.81.767.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

16

Cicconi, Maria Rita, Eric Pili, Lucie Grousset, and Daniel R. Neuville. "The Influence of Glass Composition on Iodine Solubility." MRS Advances 4, no. 17-18 (2019): 971–79. http://dx.doi.org/10.1557/adv.2018.665.

Texte intégral

Résumé :

AbstractTwo glass series in the ternary systems K2O-B2O3-SiO2 (KBS) and Na2O-B2O3-SiO2 (NBS) were studied in order to identify the main factors influencing the solubility of iodine. We established that iodine incorporation is strongly linked to the bulk chemistry, i.e. the SiO2/(B2O3+SiO2) molar ratio, and to the physical properties of the glasses, and we assessed three different solubility limits. Iodine in Si-rich glasses has a low solubility (≤1 mol% I) regardless of the alkali ion present. On the contrary, in B-rich glasses, the solubility is five times higher than in Si-rich glasses for Na-glasses, and more than six times higher for K-glasses. The strong dependence of iodine solubility on the bulk chemistry is related to the adaptability of the glass network. Furthermore, our data suggest that iodine is stable with different redox states in the glasses here analyzed.

Styles APA, Harvard, Vancouver, ISO, etc.

17

Verronen, P. T., and R. Lehmann. "Analysis and parameterisation of ionic reactions affecting middle atmospheric HO<sub>x</sub> and NO<sub>y</sub> during solar proton events." Annales Geophysicae 31, no. 5 (2013): 909–56. http://dx.doi.org/10.5194/angeo-31-909-2013.

Texte intégral

Résumé :

Abstract. In the polar regions, precipitation of solar high-energy protons and electrons affects the neutral composition of the middle atmosphere. Here we use the Sodankylä Ion and Neutral Chemistry model to calculate ionic production and loss rates of neutral HOx and NOy species, imposed by particle precipitation, for a range of atmospheric conditions and levels of ionization. We also analyse in detail the ionic reaction sequences leading to the HOx and NOy changes. Our results show that particle impact ionization and positive ion chemistry cause net production of N, NO, HNO2, H, andOH from N2 and H2O. On the other hand, negative ion chemistry redistributes the NOy species, without net production or loss, so that NO, NO2, and N2O5 are converted to HNO3 and NO3. Based on the model results, we provide tables of so-called P/Q numbers (i.e. production and loss rates of neutral species divided by ionization rates) at altitudes between 20 and 90 km. These numbers can be easily used to parameterise the ion chemistry effects when modelling atmospheric response to particle precipitation. Compared to earlier studies, our work is the first to consider in detail the NOy effect of negative ion chemistry, and the diurnal and seasonal variability of the P/Q numbers.

Styles APA, Harvard, Vancouver, ISO, etc.

18

Allen, Jan L., Bria A. Crear, Rishav Choudhury, et al. "Fast Li-Ion Conduction in Spinel-Structured Solids." Molecules 26, no. 9 (2021): 2625. http://dx.doi.org/10.3390/molecules26092625.

Texte intégral

Résumé :

Spinel-structured solids were studied to understand if fast Li+ ion conduction can be achieved with Li occupying multiple crystallographic sites of the structure to form a “Li-stuffed” spinel, and if the concept is applicable to prepare a high mixed electronic-ionic conductive, electrochemically active solid solution of the Li+ stuffed spinel with spinel-structured Li-ion battery electrodes. This could enable a single-phase fully solid electrode eliminating multi-phase interface incompatibility and impedance commonly observed in multi-phase solid electrolyte–cathode composites. Materials of composition Li1.25M(III)0.25TiO4, M(III) = Cr or Al were prepared through solid-state methods. The room-temperature bulk Li+-ion conductivity is 1.63 × 10−4 S cm−1 for the composition Li1.25Cr0.25Ti1.5O4. Addition of Li3BO3 (LBO) increases ionic and electronic conductivity reaching a bulk Li+ ion conductivity averaging 6.8 × 10−4 S cm−1, a total Li-ion conductivity averaging 4.2 × 10−4 S cm−1, and electronic conductivity averaging 3.8 × 10−4 S cm−1 for the composition Li1.25Cr0.25Ti1.5O4 with 1 wt. % LBO. An electrochemically active solid solution of Li1.25Cr0.25Mn1.5O4 and LiNi0.5Mn1.5O4 was prepared. This work proves that Li-stuffed spinels can achieve fast Li-ion conduction and that the concept is potentially useful to enable a single-phase fully solid electrode without interphase impedance.

Styles APA, Harvard, Vancouver, ISO, etc.

19

Wei, Hongyang, Xiujuan Liang, Shuhui Liu, Mingjun Liu, and Changlai Xiao. "Hydrochemical Evolution of Groundwater in Dehui, China." Water 12, no. 12 (2020): 3378. http://dx.doi.org/10.3390/w12123378.

Texte intégral

Résumé :

Although Dehui City has excellent agricultural conditions, long-term large-scale over-cultivation and human activities in recent years have caused significant changes in the local groundwater chemical characteristics. This study analyzes the causes, evolution, and prediction of groundwater chemistry via multi-disciplinary theoretical cross-cutting methods, such as groundwater ion composition-ratio analysis and groundwater influencing factor analysis, and artificial neural networks. The lithological characteristics of the groundwater aquifer were combined with ion composition-ratio mapping to explore the cause of groundwater chemistry composition in the study area. Piper three-line diagrams and Gibbs diagrams were used to analyze the evolution characteristics and influencing factors of groundwater chemistry in the study area. Based on these data, time series predictions were made for hydrochemical data. The results demonstrate that the chemical origins of groundwater in the study area are mainly background stratum and cation exchange, influenced by human activities. The main factors of groundwater chemical characteristics have changed from rock weathering to evaporation/precipitation in the past two decades. The hydrochemical characteristics changed from secondary alkalinity to secondary salinity. The predicted data from long short-term memory neural networks indicated that groundwater would continue salinization without the changes in the conditions, leading to land degradation in the study area.

Styles APA, Harvard, Vancouver, ISO, etc.

20

Sadeghi, Rahmat. "Modification of the NRTL and Wilson models for the representation of phase equilibrium behavior of aqueous amino acid – electrolyte solutions." Canadian Journal of Chemistry 86, no. 12 (2008): 1126–37. http://dx.doi.org/10.1139/v08-166.

Texte intégral

Résumé :

The extended NRTL and Wilson local composition models for amino acid solutions have been modified for the representation of the phase equilibrium behavior of aqueous amino acid – electrolyte solutions by considering cells with random composition for the reference Gibbs energies or enthalpies of local composition cells with a central amino acid molecule and also with a central ion. These new local composition models, which have a molecular thermodynamic framework, have been used to model the vapor–liquid and solid–liquid equilibrium behavior of amino acids and small peptides in aqueous solutions as functions of temperature, ionic strength, and amino acid compositions. The utility of the models is demonstrated with a successful representation of the activity coefficients and the solubility of several amino acids in different aqueous solutions.Key words: amino acid, NRTL, Wilson, activity coefficient, solubility, aqueous solution.

Styles APA, Harvard, Vancouver, ISO, etc.

21

Krämer, M., L. Schütz, W. Elbert, and N. Beltz. "Ion composition of cloud processed continental aerosol particles." Journal of Aerosol Science 31 (September 2000): 64–65. http://dx.doi.org/10.1016/s0021-8502(00)90071-5.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

22

Soldin, Željka, Boris-Marko Kukovec, Dubravka Matković-Čalogović, and Zora Popović. "The Solvent Effect on Composition and Dimensionality of Mercury(II) Complexes with Picolinic Acid." Molecules 26, no. 16 (2021): 5002. http://dx.doi.org/10.3390/molecules26165002.

Texte intégral

Résumé :

Three new mercury(II) coordination compounds, {[HgCl(pic)]}n (1), [HgCl(pic)(picH)] (2), and [HgBr(pic)(picH)] (3) (picH = pyridine-2-carboxylic acid, picolinic acid) were prepared by reactions of the corresponding mercury(II) halides and picolinic acid in an aqueous (1) or alcohol–methanol or ethanol (2 and 3) solutions. Two different types of coordination compounds were obtained depending on the solvent used. The crystal structures were determined by the single-crystal X-ray structural analysis. Compound 1 is a one-dimensional (1-D) coordination polymer with mercury(II) ions bridged by chelating and bridging N,O,O′-picolinate ions. Each mercury(II) ion is four-coordinated with a bidentate picolinate ion, a carboxylate O atom from the symmetry-related picolinate ion and with a chloride ion; the resulting coordination environment can be described as a highly distorted tetrahedron. Compounds 2 and 3 are isostructural mononuclear coordination compounds, each mercury(II) ion being coordinated with the respective halide ion, N,O-bidentate picolinate ion, and N,O-bidentate picolinic acid in a highly distorted square-pyramidal coordination environment. Compounds 1–3 were characterized by IR spectroscopy, PXRD, and thermal methods (TGA/DSC) in the solid state and by 1H and 13C NMR spectroscopy in the DMSO solution.

Styles APA, Harvard, Vancouver, ISO, etc.

23

Baergen, Alyson M., Sarah A. Styler, Dominik van Pinxteren, Konrad Müller, Hartmut Herrmann, and D. James Donaldson. "Chemistry of Urban Grime: Inorganic Ion Composition of Grime vs Particles in Leipzig, Germany." Environmental Science & Technology 49, no. 21 (2015): 12688–96. http://dx.doi.org/10.1021/acs.est.5b03054.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

24

Winograd, Nicholas. "Gas Cluster Ion Beams for Secondary Ion Mass Spectrometry." Annual Review of Analytical Chemistry 11, no. 1 (2018): 29–48. http://dx.doi.org/10.1146/annurev-anchem-061516-045249.

Texte intégral

Résumé :

Gas cluster ion beams (GCIBs) provide new opportunities for bioimaging and molecular depth profiling with secondary ion mass spectrometry (SIMS). These beams, consisting of clusters containing thousands of particles, initiate desorption of target molecules with high yield and minimal fragmentation. This review emphasizes the unique opportunities for implementing these sources, especially for bioimaging applications. Theoretical aspects of the cluster ion/solid interaction are developed to maximize conditions for successful mass spectrometry. In addition, the history of how GCIBs have become practical laboratory tools is reviewed. Special emphasis is placed on the versatility of these sources, as size, kinetic energy, and chemical composition can be varied easily to maximize lateral resolution, hopefully to less than 1 micron, and to maximize ionization efficiency. Recent examples of bioimaging applications are also presented.

Styles APA, Harvard, Vancouver, ISO, etc.

25

Rubin, Martin, Kenneth C. Hansen, Tamas I. Gombosi, Michael R. Combi, Kathrin Altwegg, and Hans Balsiger. "Ion composition and chemistry in the coma of Comet 1P/Halley—A comparison between Giotto's Ion Mass Spectrometer and our ion-chemical network." Icarus 199, no. 2 (2009): 505–19. http://dx.doi.org/10.1016/j.icarus.2008.10.009.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

26

Ren, YuRong, MeiZhen Qu, and ZuoLong Yu. "SiO/CNTs: A new anode composition for lithium-ion battery." Science in China Series B: Chemistry 52, no. 12 (2009): 2047–50. http://dx.doi.org/10.1007/s11426-009-0287-5.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

27

Mohnen, Volker A., and Richard J. Vong. "A climatology of cloud chemistry for the eastern United States derived from the mountain cloud chemistry project." Environmental Reviews 1, no. 1 (1993): 38–54. http://dx.doi.org/10.1139/a93-005.

Texte intégral

Résumé :

The chemical composition of clouds collected in the eastern United States has been intensely monitored over a 4-year period as part of the Mountain Cloud Chemistry Project. On the basis of these measurements we prepared a climatology for cloud chemistry, using simple statistical analyses tools and incorporating meteorological and cloud physical and chemical information. Five mountain stations have been established for cloud collection covering the northern and southern Appalachian Mountain range: Whiteface Mountain, New York; Mount Moosilauke, New Hampshire; Shenandoah Mountain, Virginia; Whitetop Mountain, Virginia; and Mount Mitchell, North Carolina. This review presents the major result from this 4-year measurement program. Cloud cover and cloud base over the eastern United States were deduced from the global real-time nephanalysis archives produced by the U.S. Air Force, augmented by local observations. Both active and passive cloud collectors were deployed to sample cloud water on an hourly basis, i.e., with sufficient time resolution to resolve synoptic scale phenomena. Chemical analysis of cloud water was performed by a central analytical laboratory with occasional on-site analysis to satisfy quality control procedures. Reliable methods now exist for collecting cloud-water samples in sufficient quantities for detailed chemical analysis. The chemical composition of cloud water varied significantly between sites. However, the differences in cloud-water ion concentration do not necessarily establish a geographic gradient between the sites but rather reflect differences in air-mass trajectories associated with the synoptic air-flow pattern and differences in sample location above cloud base. The dependence of cloud-water ion concentrations on synoptic weather type and observed differences in relative frequencies of warm sector, marine flow, and post-cold frontal synoptic types between northern and southern sites suggest that the north–south differences in cloud-water ion concentrations are related to cloud climatology at the northern sites. When air-mass trajectories shift from southwest to northwest, the concentrations of H+, SO42−, NO3− and NH4+ normally decrease but the southern sites continue to receive high concentrations under northwest flow. The height of cloud-water sample collection above cloud base was found to be an additional source of variability in both cloud-water chemistry and liquid-water content. Seasonal variation in cloud-water chemical composition was investigated at one site only. Sulfate levels were found to be significantly lower in supercooled clouds (i.e., during the 'cold' season) than in 'warm' clouds, but nitrate levels remained about the same.Key words: cloud chemistry, cloud frequency, air-mass trajectories, ANOVA.

Styles APA, Harvard, Vancouver, ISO, etc.

28

Samulewski, Rafael Block, Josué Martins Gonçalves, Alexandre Urbano, et al. "Magnetite Synthesis in the Presence of Cyanide or Thiocyanate under Prebiotic Chemistry Conditions." Life 10, no. 4 (2020): 34. http://dx.doi.org/10.3390/life10040034.

Texte intégral

Résumé :

Magnetite is an iron oxide mineral component of primitive Earth. It is naturally synthesized in different ways, such as magma cooling as well as olivine decomposition under hydrothermal conditions. It is probable magnetite played a significant role in biogenesis. The seawater used in the current work contained high Mg2+, Ca2+ and SO42− concentrations, unlike the seawater of today that has high Na+ and Cl− concentrations. It is likely that this seawater better resembled the ion composition of the seas of the Earth from 4 billion years ago. Cyanide and thiocyanate were common molecules in prebiotic Earth, and especially in primitive oceans, where they could act on the magnetite mechanism synthesis via Fe2+ interaction. In this research, magnetite samples that were synthesized under prebiotic conditions in the presence of cyanide or thiocyanate, (both with and without artificial seawater), showed that, besides magnetite, goethite and ferrihydrite can be produced through different Fe2+-ion interactions. Cyanide apparently acts as a protective agent for magnetite production; however, thiocyanate and seawater 4.0 Gy ions produced goethite and ferrihydrite at different ratios. These results validate that Fe3+ oxides/hydroxides were possibly present in primitive Earth, even under anoxic conditions or in the absence of UV radiation. In addition, the results show that the composition of water in early oceans should not be neglected in prebiotic chemistry experiments, since this composition directly influences mineral formation.

Styles APA, Harvard, Vancouver, ISO, etc.

29

Yan, Tiejun, Ping Zhou, Fei Long, et al. "Unraveling the Difference in the Composition/Content of the Aroma Compounds in Different Tobacco Leaves: For Better Use." Journal of Chemistry 2022 (December 29, 2022): 1–10. http://dx.doi.org/10.1155/2022/3293899.

Texte intégral

Résumé :

The composition/content of aroma compounds in tobacco leaves in the different producing areas varies too much, and it is very meaningful to develop advanced analysis techniques to investigate the composition/content-producing area correlation. Here, gas chromatography-ion mobility spectroscopy (GC-IMS) was used to analyze the composition/content of aroma compounds in tobacco samples from eight different producing areas. With this technique, ion mobility spectrum, differential ion mobility spectrum, and fingerprint spectrum were constructed for two-dimensional analysis. Then, the principal component analysis (PCA) and similarity analysis were performed for the eight tobacco samples. The results showed that the GC-IMS can detect 197 volatile aroma compounds in tobacco leaves and 75 of them are well identified. The fingerprint spectrum directly showed the difference in the composition/content of volatile aroma compounds in tobacco leaves from different producing areas. PCA and similarity analysis can clearly distinguish tobacco samples from different producing areas. This work demonstrated that the application of GC-IMS in analyzing the composition/content of aroma compounds in tobacco leaves is efficient. GC-IMS is a very powerful tool to give a direct and visual comparison of the composition/content of aroma compounds in tobacco leaves from different producing areas. The relationship between the composition/content of aroma compounds and producing areas could be established by this advanced technology. This work offers the possibility of planting or grading tobacco with different taste and smell more precisely in the future.

Styles APA, Harvard, Vancouver, ISO, etc.

30

METSON, J. B., and M. J. GUSTAFSSON. "COMPLEMENTARY TECHNIQUES TO HIGH ENERGY ION BEAM ANALYSIS." Modern Physics Letters B 15, no. 28n29 (2001): 1402–10. http://dx.doi.org/10.1142/s0217984901003329.

Texte intégral

Résumé :

Ion beam analysis methods generally rely on either the scattering of a high energy primary particle, or secondary process arising from the stopping of this particle in the substrate. The information typically obtained is the identification and quantitation of elements present, often resolved in terms of their depth distribution. However, there are a variety of techniques which offer complementary information on the structure composition and chemistry of a surface. These are typified by rather softer interactions with the surface, typified by low energy (kV) ion beams or photons, which interact with the surface in rather more complex manner than higher energy ion beams. The combination of energy and momentum transfer for the ion beams, makes these methods less quantitative, but opens up the potential for more chemically detailed information on the nature of the surface. Secondary ion mass spectrometry (SIMS), both static and dynamic, and X-ray Photoelectron Spectroscopy (XPS) will be discussed in some detail. SIMS offers excellent compositional depth profiling capability, but offers poor quantitation, while XPS offers unparalleled chemical detail, but limited lateral and depth resolution. The underlying processes which dictate the strengths and limitations of these techniques are discussed, along with a number of typical applications to the analysis of oxide films and polymeric materials.

Styles APA, Harvard, Vancouver, ISO, etc.

31

del Pozo, C. F., E. Turunen, and T. Ulich. "Negative ions in the auroral mesosphere during a PCA event around sunset." Annales Geophysicae 17, no. 6 (1999): 782–93. http://dx.doi.org/10.1007/s00585-999-0782-1.

Texte intégral

Résumé :

Abstract. This is a study of the negative ion chemistry in the mesosphere above Tromsø using a number of EISCAT observations of high energy proton precipitation events during the last solar maximum, and in particular around sunset on 23 October, 1989. In these conditions it is possible to look at the relative importance of the various photodetachment and photodissociation processes controlling the concentration of negative ions. The data analysed are from several UHF GEN11 determinations of the ion-plasma ACF together with the pseudo zero-lag estimate of the `raw' electron density, at heights between 55 km and 85 km, at less than 1 km resolution. The power profiles from the UHF are combined with the 55-ion Sodankylä model to obtain consistent estimates of the electron density, the negative ion concentrations, and the average ion mass with height. The neutral concentrations and ion temperature are given by the MSIS90 model. These parameters are then used to compare the calculated widths of the ion-line with the GEN11 determinations. The ion-line spectrum gives information on the effects of negative ions below 70 km where they are dominant; the spectral width is almost a direct measure of the relative abundance of negative ions.Key words. Ionosphere (auroral ionosphere; ion chemistry and composition; particle precipitation).

Styles APA, Harvard, Vancouver, ISO, etc.

32

Hiraki, Y., Y. Kasai, and H. Fukunishi. "Chemistry of sprite discharges through ion-neutral reactions." Atmospheric Chemistry and Physics Discussions 8, no. 1 (2008): 2311–36. http://dx.doi.org/10.5194/acpd-8-2311-2008.

Texte intégral

Résumé :

Abstract. We estimate the concentration changes, caused by a single streamer in sprites, of ozone and related minor species as odd nitrogen (NOx) and hydrogen (HOx) families in the upper stratosphere and mesosphere. The streamer has an intense electric field and high electron density at its head where a large number of chemically-radical ions and atoms are produced through electron impact on neutral molecules. After propagation of the streamer, the densities of minor species can be perturbed through ion-neutral chemical reactions initiated by the relaxation of these radical products. We evaluate the production rates of ions and atoms using electron kinetics model and assuming the electric field and electron density in the streamer head. We calculate the density variations mainly for NOx, Ox, and HOx species using a one-dimensional model of the neutral and ion composition of the middle atmosphere, including the effect of the sprite streamer. Results at the nighttime condition show that the densities of NO, O3, H, and OH increase suddenly through reactions triggered by firstly produced atomic nitrogen and oxygen, and electrons just after streamer initiation. It is shown that NO and NO2 still remain for 1 h by a certain order of increase with their source-sink balance predominantly around 60 km; for other species, increases in O3, OH, HO2, and H2O2 still remain in the range of 40–70 km. From this affirmative result of long time behavior previously not presented, we emphasize that sprites would have a power to impact on local chemistry at night. We also discuss comparison with previous studies and suggestion for satellite observations.

Styles APA, Harvard, Vancouver, ISO, etc.

33

Hiraki, Y., Y. Kasai, and H. Fukunishi. "Chemistry of sprite discharges through ion-neutral reactions." Atmospheric Chemistry and Physics 8, no. 14 (2008): 3919–28. http://dx.doi.org/10.5194/acp-8-3919-2008.

Texte intégral

Résumé :

Abstract. We estimate the concentration changes, caused by streamer discharge in sprites, of ozone and related minor species as odd nitrogen (NOx) and hydrogen (HOx) families in the upper stratosphere and mesosphere. The streamer has an intense electric field and high electron density at its head, where a large number of chemically-radical ions and atoms are produced through electron impact on neutral molecules. After its propagation, densities of minor species can be perturbed through ion-neutral chemical reactions initiated by the relaxation of these radical products. We evaluate the production rates of ions and atoms using an electron kinetics model and by assuming that the electric field and electron density are in the head region. We calculate the density variations mainly for NOx, Ox, and HOx species using a one-dimensional model of the neutral and ion composition of the middle atmosphere, including the effect of the sprite streamer. Results at the nighttime condition show that the densities of NO, O3, H, and OH increase suddenly through reactions triggered by the first atomic nitrogen and oxygen product, and electrons just after streamer initiation. It is shown that NO and NO2 still remain for 1 h by a certain order of increase with their source-sink balance, predominantly around 60 km; for other species, increases in O3, OH, HO2, and H2O2 still remain in the range of 40–70 km. From this affirmative result of long-time behavior previously not presented, we emphasize that sprites would have the power to impact local chemistry at night. We also discuss the consistency with previous theoretical and observational studies, along with future suggestions.

Styles APA, Harvard, Vancouver, ISO, etc.

34

Maslova, M. V., L. G. Gerasimova, R. F. Okhrimenko, and A. S. Chugunov. "Composition of ion-exchange materials based on titanium phosphate." Russian Journal of Applied Chemistry 79, no. 11 (2006): 1793–97. http://dx.doi.org/10.1134/s1070427206110103.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

35

Radhi, M., M. A. Box, G. P. Box, et al. "Size-resolved chemical composition of Australian dust aerosol during winter." Environmental Chemistry 8, no. 3 (2011): 248. http://dx.doi.org/10.1071/en10134.

Texte intégral

Résumé :

Environmental contextMineral dust aerosol is both an efficient scatterer of solar radiation, potentially cooling the planet, and a moderate absorber, potentially warming it: the exact balance is both uncertain, and geographically variable. Australian desert soils are noticeably more reddish than most Northern Hemisphere deserts, most probably a result of enhanced iron mineralogy. This paper contains results from a field campaign designed to increase our understanding of the chemistry of Australian mineral dust aerosol, especially in relation to iron and salt. AbstractAustralia is the dominant source of mineral dust aerosol in the Southern Hemisphere, yet the physical, chemical and optical properties of this aerosol remain poorly understood. Four sets of size-resolved aerosol samples were collected at a site on the edge of the Lake Eyre Basin (LEB), in the south-east dust transport pathway. Back trajectory analysis shows that three samples were sourced from the LEB (one during a rare winter dust storm), and one from coastal regions to the south. All samples were subjected to both ion beam analysis and ion chromatography. A Fe/Al ratio of 0.9 was found, consistent with results from our other campaigns to sites in the LEB, significantly higher than typical Northern Hemisphere values (~0.45–0.6). This confirms the iron-rich character of central Australian soils. Clear evidence of marine advection in the fourth sample was also found, and evidence of chloride depletion by nitric acid in two samples.

Styles APA, Harvard, Vancouver, ISO, etc.

36

Zhang, Jun, Li Li, Lipeng Zhang, Shilu Zhao, and Qiang Guo. "Composition demixing effect on cathodic arc ion plating." Journal of University of Science and Technology Beijing, Mineral, Metallurgy, Material 13, no. 2 (2006): 125–30. http://dx.doi.org/10.1016/s1005-8850(06)60028-5.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

37

Lamhonwah, Daniel, M. J. Lafrenière, S. F. Lamoureux, and B. B. Wolfe. "Multi-year impacts of permafrost disturbance and thermal perturbation on High Arctic stream chemistry." Arctic Science 3, no. 2 (2017): 254–76. http://dx.doi.org/10.1139/as-2016-0024.

Texte intégral

Résumé :

Permafrost disturbances (such as active layer detachment (ALD) slides) and thermal perturbation (deep ground thaw from high soil temperatures) alter Arctic surface water chemistry. However, the potential multi-year impacts on water chemistry and the ultimate recovery time are not well understood. This study evaluates the impacts on surface waters and recovery following disturbance of a High Arctic catchment in 2007 from ALDs. We measured ion concentrations and stable isotopes in surface waters collected between 2006 and 2014 from paired catchments — one disturbed and the other not. The years 2007 and 2012 were exceptionally warm and represent unusual thermal perturbation for both catchments. Results indicate that the exposure and mobilization of soluble ions in near surface soil is a key control over dissolved ion concentrations and composition following ALDs. Runoff in the disturbed catchment shows increased total dissolved solute (TDS) concentrations and seasonal TDS fluxes and changes to the relative composition of individual ions in surface water. These impacts persisted for the 7 year study duration after disturbance and are consistent with the thawing of the solute-rich transient layer and upper permafrost. Thermal perturbation increased TDS concentrations and seasonal fluxes in runoff for up to 2 years, as ions released from ground thaw appear to be available for flushing in subsequent summers.

Styles APA, Harvard, Vancouver, ISO, etc.

38

Barone, Teresa L., Thomas H. Dubaniewicz, Sherri A. Friend, Isaac A. Zlochower, Aleksandar D. Bugarski, and Naseem S. Rayyan. "Lithium-ion battery explosion aerosols: Morphology and elemental composition." Aerosol Science and Technology 55, no. 10 (2021): 1183–201. http://dx.doi.org/10.1080/02786826.2021.1938966.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

39

Chung, Meng-Chen, and I. Colbeck. "Ion composition of atmospheric aerosol at South Eastern England." Journal of Aerosol Science 29 (September 1998): S745—S746. http://dx.doi.org/10.1016/s0021-8502(98)90555-9.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

40

Truhlík, V., L. Trísková, and J. Šmilauer. "Manifestation of solar activity in the global topside ion composition − a study based on satellite data." Annales Geophysicae 23, no. 7 (2005): 2511–17. http://dx.doi.org/10.5194/angeo-23-2511-2005.

Texte intégral

Résumé :

Abstract. The solar cycle variation of the most important parameters characterizing the ion composition in the topside ionosphere is studied. For this purpose data from the ACTIVE mission (the IK-24 satellite) for the maximum of solar cycle 22 (aver F10.7~200), complemented by data available from the Atmosphere Explorer (AE) satellites, for the minimum of solar cycle 21 (average F10.7~85), were processed. OGO-6 data from the low maximum of solar cycle 20 (average F10.7~150) were used for medium solar activity conditions. The results for the equinox from the recently developed empirical model of ion composition are analyzed and presented, and typical vertical profiles from solar maxima and minima are shown. It was found that the logarithm of the O+, H+, He+, and N+ densities in the topside ionosphere at a fixed altitude, latitude, and local time is, in the first approximation, a linear function of solar activity characterized by the daily F10.7. On the other hand, the upper transition height is generally a non linear function of the daily F10.7, the deviation from linear dependence increases with latitude. Keywords. Ionosphere (Plasma temperature and density; Ion chemistry and composition; Modeling and forecasting)

Styles APA, Harvard, Vancouver, ISO, etc.

41

Engel, Kathrin M., Ulrike Jakop, Karin Müller, Sonja Grunewald, Uwe Paasch, and Jürgen Schiller. "MALDI MS Analysis to Investigate the Lipid Composition of Sperm." Current Analytical Chemistry 16, no. 1 (2020): 79–91. http://dx.doi.org/10.2174/1573411014666181030123256.

Texte intégral

Résumé :

Background: The sperm plasma membrane meets the requirements of sperm transit through the female genital tract and subsequent fertilization. Commonly, the (phospho)lipid composition of sperm is characterized by tremendous amounts of highly unsaturated fatty acyl residues such as docosahexaenoic and docosapentaenoic acid. While human sperm contain almost exclusively diacyl lipids, many animal sperm additionally contain significant amounts of ether lipids such as alkylacyl- and alkenyl-acyl lipids (plasmalogens). Hypothesis/Objective: It is suggested that deviations from the typical lipid composition are indicative of pathological changes. Therefore, simple methods to elucidate the sperm lipid composition are essential. Method: Matrix-assisted laser desorption and ionization (MALDI) mass spectrometry (MS) is a fast and simple method. Since the selection of the most suitable matrix is a crucial step in MALDI MS, this topic will be highlighted. It will also be shown that MALDI MS can be easily combined with thin-layer chromatography to overcome ion suppression effects. Results: The lipid composition of sperm from different species can be elucidated by MALDI MS. However, different matrix compounds have to be used to record positive and negative ion mass spectra. Since some sperm (glyco)lipids are characterized by the presence of sulfate residues which suppress the detection of less acidic lipids in the negative ion mode, previous separation is often necessary. It will be also emphasized that plasmalogens can be easily identified by either enzymatic digestion or treatment with acids. Conclusion: MALDI MS is a reliable method to obtain sperm lipid fingerprints in a simple and convenient way.

Styles APA, Harvard, Vancouver, ISO, etc.

42

Chin, Clare Davis-Wheeler, Marissa A. Ringgold, Erica M. Redline, et al. "Fabrication, thermal analysis, and heavy ion irradiation resistance of epoxy matrix nanocomposites loaded with silane-functionalized ceria nanoparticles." Physical Chemistry Chemical Physics 24, no. 11 (2022): 6552–69. http://dx.doi.org/10.1039/d1cp05033h.

Texte intégral

Résumé :

This paper describes a detailed understanding of how nanofillers function as radiation barriers within the polymer matrix, and how their effectiveness is impacted by factors such as composition, size, loading, surface chemistry, and dispersion.

Styles APA, Harvard, Vancouver, ISO, etc.

43

Deang, Amira Beatriz Gaces, Rustom Steven Adalim Alcantara, Jezza B. Bayot, Nikko Kirby D. Ledesma, V. L. Janerikther L. Vasquez, and Jeremiah C. Millare. "Nanozeolite-Impregnated Polysulfone/Polyethylene Glycol Nanocomposite Membrane for Ion Adsorption Application." Key Engineering Materials 907 (January 21, 2022): 173–78. http://dx.doi.org/10.4028/www.scientific.net/kem.907.173.

Texte intégral

Résumé :

Polysulfone (PSf) is a high-performance polymer often used in water treatment applications. Polyethylene glycol (PEG) and Nanozeolite (NZ) were used as additives to improve the membrane’s porosity, chemistry, and overall performance in ion adsorption. PSf, PSf with PEG, and PSf with PEG and varying concentrations of Nanozeolite were prepared via non-solvent induced phase separation (NIPS) and tested using: Scanning Electron Microscopy (SEM) for the surface morphology, Fourier Transform Infrared Spectroscopy (FTIR) for the chemical composition, Contact Angle Goniometer for the wettability, Zeta Potential for the stability, and conductivity test through salt-water bath for ion adsorption application.

Styles APA, Harvard, Vancouver, ISO, etc.

44

Lalrosanga and N. Mohondas Singh. "Thermodynamic Studies on Ion Association of Lithium Chloride and Lithium Nitrate in Acetonitrile + Water Mixed Solvents at Different Temperatures." Asian Journal of Chemistry 34, no. 1 (2021): 230–34. http://dx.doi.org/10.14233/ajchem.2022.23557.

Texte intégral

Résumé :

The present study reports the ion association of lithium chloride (LiCl) and lithium nitrate (LiNO3) electrolytes in acetonitrile + water (AN+W) mixtures at 283.15 K to 311.15 K. Their limiting molar conductance (Λo), the association constant values (KA) for their different mole fractions, i.e. 0.0000, 0.0588, 0.1233, 0.1942, 0.2727, 0.3600, 0.4576, 0.5676, 0.6923, 0.8351 and 1.0000 have been evaluated using Shedlovsky technique. The KA and Walden products (Λoηo) for LiCl and LiNO3 salts have been calculated in the acetonitrile-water solvent at experimental temperatures. The calculated values qualitatively examined the possible nature of the solvent-solvent, their ion-ion, and ion-solvent and interactions of the two selected compounds mixed solvents of (acetonitrile + water). Then dependence of KA temperature has also been investigated to obtain the thermodynamic functions of different parameters, such as ΔGº, ΔSº, ΔHº and Ea, as a function of the mixed composition of the composition solvents AN+W (acetonitrile + water).

Styles APA, Harvard, Vancouver, ISO, etc.

45

Mikhailov, A. V., and K. Schlegel. "Geomagnetic storm effects at F1-layer heights from incoherent scatter observations." Annales Geophysicae 21, no. 2 (2003): 583–96. http://dx.doi.org/10.5194/angeo-21-583-2003.

Texte intégral

Résumé :

Abstract. Storm effects at F1-layer heights (160–200 km) were analyzed for the first time using Millstone Hill (mid-latitudes) and EISCAT (auroral zone) incoherent scatter (IS) observations. The morphological study has shown both increases (positive effect) and decreases (negative effect) in electron concentration. Negative storm effects prevail for all seasons and show a larger magnitude than positive ones, the magnitude of the effect normally increasing with height. At Millstone Hill the summer storm effects are small compared to other seasons, but they are well detectable. At EISCAT this summer decrease takes place only with respect to the autumnal period and the autumn/spring asymmetry in the storm effects is well pronounced. Direct and significant correlation exists between deviations in electron concentration at the F1-layer heights and in the F2-layer maximum. Unlike the F2-layer the F1-region demonstrates a relatively small reaction to geomagnetic disturbances despite large perturbations in thermospheric parameters. Aeronomic parameters extracted from IS observations are used to explain the revealed morphology. A competition between atomic and molecular ion contributions to Ne variations was found to be the main physical mechanism controlling the F1-layer storm effect. The revealed morphology is shown to be related with neutral composition (O, O2, N2) seasonal and storm-time variations. The present day understanding of the F1-region formation mechanisms is sufficient to explain the observed storm effects.Key words. Atmospheric composition and structure (thermosphere-composition and chemistry); ionosphere (ion chemistry and composition; ionospheric disturbances)

Styles APA, Harvard, Vancouver, ISO, etc.

46

Szostak, R., J. C. Silva, S. H. Turren-Cruz, et al. "Nanoscale mapping of chemical composition in organic-inorganic hybrid perovskite films." Science Advances 5, no. 10 (2019): eaaw6619. http://dx.doi.org/10.1126/sciadv.aaw6619.

Texte intégral

Résumé :

Lead-based organic-inorganic hybrid perovskite (OIHP) solar cells can attain efficiencies over 20%. However, the impact of ion mobility and/or organic depletion, structural changes, and segregation under operating conditions urge for decisive and more accurate investigations. Hence, the development of analytical tools for accessing the grain-to-grain OIHP chemistry is of great relevance. Here, we used synchrotron infrared nanospectroscopy (nano-FTIR) to map individual nanograins in OIHP films. Our results reveal a spatial heterogeneity of the vibrational activity associated to the nanoscale chemical diversity of isolated grains. It was possible to map the chemistry of individual grains in CsFAMA [Cs0.05FA0.79MA0.16Pb(I0.83Br0.17)3] and FAMA [FA0.83MA0.17Pb(I0.83Br0.17)3] films, with information on their local composition. Nanograins with stronger nano-FTIR activity in CsFAMA and FAMA films can be assigned to PbI2 and hexagonal polytype phases, respectively. The analysis herein can be extended to any OIHP films where organic cation depletion/accumulation can be used as a chemical label to study composition.

Styles APA, Harvard, Vancouver, ISO, etc.

47

Enell, C. F., A. Kero, E. Turunen, et al. "Effects of D-region RF heating studied with the Sodankylä Ion Chemistry model." Annales Geophysicae 23, no. 5 (2005): 1575–83. http://dx.doi.org/10.5194/angeo-23-1575-2005.

Texte intégral

Résumé :

Abstract. The upper mesosphere and lower thermosphere, or ionospheric D region, is an atmospheric layer which is difficult to access experimentally. A useful method that also has a large potential for further studies is artificial heating of electrons by means of powerful radio transmitters. Here we estimate the effect of D-region heating for a few typical cases of high electron density – daylight, typical auroral electron precipitation, and a solar proton event – by coupling a model of RF electron heating to the Sodankylä Ion Chemistry (SIC) model. The predicted effects are among others an increase in the ratio of the concentration of negative ions to that of free electrons, and an increase in the absorption of cosmic noise as measured by riometers. For the model runs presented in this paper we have calculated the absorption for the frequency (38.2MHz) of the IRIS imaging riometer in Kilpisjärvi, Finland, as observing the ionosphere above the EISCAT Heater in Tromsø, Norway. The predicted enhancements of the absorption are 0.2–0.8dB, an effect which is clearly detectable. Keywords. Ionosphere (Active experiments; Ion chemistry and composition; Wave propagation)

Styles APA, Harvard, Vancouver, ISO, etc.

48

Li, Ying Yu, Yan Yan Chu, Hao Shen, and Dong Liang. "Study on Fire Residues in Pure Cotton Fabric Combustion." Advanced Materials Research 391-392 (December 2011): 1479–82. http://dx.doi.org/10.4028/www.scientific.net/amr.391-392.1479.

Texte intégral

Résumé :

Residual accelerant from fire debris is the major evidence in the fire investigation. Because all evidences are almost damaged by fire, many isolation methods of analytical chemistry has been already used in extracting trace residue. In this paper, ultrasonic extraction is applied to isolate the residual accelerant and hexane as the solvent. The solution obtained from the residue is tested by GC-MS to analyze their total ion chromatogram (TIC). The chromatographic patterns observed for ignitable liquids are different from the patterns observed for without ignitable liquids. The composition of two samples and content of the fire residues have been analyzed. It’s very important for forensic chemist to distinguish the arson or natural fire.

Styles APA, Harvard, Vancouver, ISO, etc.

49

Singh, S. K., Prashant K. Srivastava, M. Gupta, and S. Mukherjee. "Modeling mineral phase change chemistry of groundwater in a rural-urban fringe." Water Science and Technology 66, no. 7 (2012): 1502–10. http://dx.doi.org/10.2166/wst.2012.338.

Texte intégral

Résumé :

This research paper aims to determine the genetic origin of the chemical elements in groundwater. It deals with the results of physicochemical parameters, to evaluate the hydro-geochemistry of groundwater in rural-urban fringe of district Bareilly, India. Pre- and post-monsoon sampling has been carried out, which reveals inter-seasonal variability effect on the hydro-geochemical processes. Geochemical modeling especially computation of saturation index was undertaken using the WATEQ4F model. Majority of samples fall in the category of undersaturation, which further suggests that groundwater still has potential to dissolve more minerals. Chemical categorizations of groundwater samples were performed with the help of the Aquachem model. Grouping of groundwater on the Piper diagram reveals a common composition and origin. In most of the area, water facies is of Ca2+−HCO3− type in both the seasons. It also indicates that in pre-monsoon, ion exchange is the dominant process, whereas in post-monsoon, both ion exchanges as well as reverse ion exchanges are reported in the groundwater of the study area.

Styles APA, Harvard, Vancouver, ISO, etc.

50

Haines, Robert I., and Sandra J. Northcott. "Kinetics and mechanism of oxidation of nickel(II) tetraazamacrocycles by the peroxydisulphate anion in aqueous and binary aqueous mixtures." Canadian Journal of Chemistry 70, no. 11 (1992): 2785–91. http://dx.doi.org/10.1139/v92-354.

Texte intégral

Résumé :

The kinetics of oxidation of several nickel(II) tetraazamacrocycles by the peroxydisulphate anion have been studied in water and in binary aqueous mixtures. The reactions proceed via an ion-pairing pre-equilibrium, followed by metal ion-assisted peroxy-bond fissure within the ion-pair solvent shell. The derived rate law is[Formula: see text]Ion-pairing constants have been determined and have been found to be little influenced by steric factors, but do depend on solvent composition. Rate constants have been extracted using the rate expression and activation energies have been estimated from temperature dependences.

Styles APA, Harvard, Vancouver, ISO, etc.

Articles de revues sur le sujet « Ion chemistry and composition »

Créez une référence correcte selon les styles APA, MLA, Chicago, Harvard et plusieurs autres