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19 results on '"Hartnett, H."'

1. Reconstructing Extreme Space Weather from Planet Hosting Stars

Author

Airapetian, V. S., Adibekyan, V., Ansdell, M., Alexander, D., Bastian, T., Saikia, S. Boro, Brun, A. S., Cohen, O., Cuntz, M., Danchi, W., Davenport, J., DeNolfo, J., DeVore, R., Dong, C. F., Drake, J. J., France, K., Fraschetti, F., Herbst, K., Garcia-Sage, K., Gillon, M., Glocer, A., Grenfell, J. L., Gronoff, G., Gopalswamy, N., Guedel, M., Hartnett, H., Harutyunyan, H., Hinkel, N. R., Jensen, A. G., Jin, M., Johnstone, C., Kalas, P., Kane, S. R., Kay, C., Kitiashvili, I. N., Kochukhov, O., Kondrashov, D., Lazio, J., Leake, J., Li, G., Linsky, J., Lueftinger, T., Lynch, B., Lyra, W., Mandell, A. M., Mandt, K. E., Maehara, H., Miesch, M. S., Mickaelian, A. M., Mouchou, S., Notsu, Y., Ofman, L., Oman, L. D., Osten, R. A., Oran, R., Petre, R., Ramirez, R. M., Rau, G., Redfield, S., Réville, V., Rugheimer, S., Scheucher, M., Schlieder, J. E., Shibata, K., Schnittman, J. D., Soderblom, David, Strugarek, A., Turner, J. D., Usmanov, A., Der Holst, Van, Vidotto, A., Vourlidas, A., Way, M. J., Wolk, Zank, G. P., R., P. Zarka, Kopparapu, Babakhanova, S., Pevtsov, A. A., Lee, Y., Henning, W., Colón, K. D., and Wolf, E. T.

Subjects
Astrophysics - Earth and Planetary Astrophysics
Abstract

The field of exoplanetary science is making rapid progress both in statistical studies of exoplanet properties as well as in individual characterization. As space missions provide an emerging picture of formation and evolution of exoplanetary systems, the search for habitable worlds becomes one of the fundamental issues to address. To tackle such a complex challenge, we need to specify the conditions favorable for the origin, development and sustainment of life as we know it. This requires the understanding of global (astrospheric) and local (atmospheric, surface and internal) environments of exoplanets in the framework of the physical processes of the interaction between evolving planet-hosting stars along with exoplanetary evolution over geological timescales, and the resulting impact on climate and habitability of exoplanets. Feedbacks between astrophysical, physico-chemical atmospheric and geological processes can only be understood through interdisciplinary studies with the incorporation of progress in heliophysics, astrophysics, planetary, Earth sciences, astrobiology, and the origin of life communities. The assessment of the impacts of host stars on the climate and habitability of terrestrial (exo)planets and potential exomoons around them may significantly modify the extent and the location of the habitable zone and provide new directions for searching for signatures of life. Thus, characterization of stellar ionizing outputs becomes an important task for further understanding the extent of habitability in the universe. The goal of this white paper is to identify and describe promising key research goals to aid the theoretical characterization and observational detection of ionizing radiation from quiescent and flaring upper atmospheres of planet hosts as well as properties of stellar coronal mass ejections and stellar energetic particle events., Comment: White Paper submitted to the Astronomy and Astrophysics Decadal Survey (Astro2020), 8 pages, 1 figure

Published
2019

2. Exploring Extreme Space Weather Factors of Exoplanetary Habitability

Author

Airapetian, V. S., Adibekyan, V., Ansdell, M., Cohen, O., Cuntz, M., Danchi, W., Dong, C. F., Drake, J. J., Fahrenbach, A., France, K., Garcia-Sage, K., Glocer, A., Grenfell, J. L., Gronoff, G., Hartnett, H., Henning, W., Hinkel, N. R., Jensen, A. G., Jin, M., Kalas, P., Kane, S. R., Kobayashi, K., Kopparapu, R., Leake, J., López-Puertas, M., Lueftinger, T., Lynch, B., Lyra, W., Mandell, A. M., Mandt, K. E., Moore, W. B., Nna-Mvondo, D., Notsu, Y., Maehara, H., Yamashiki, Y., Shibata, K., Oman, L. D., Osten, R. A., Pavlov, A., Ramirez, R. M., Rugheimer, S., Schlieder, J. E., Schnittman, J. D., Shock, E. L., Sousa-Silva, C., Way, M. J., Yang, Y., Young, P. A., and Zank, G. P.

Subjects
Astrophysics - Earth and Planetary Astrophysics
Abstract

It is currently unknown how common life is on exoplanets, or how long planets can remain viable for life. To date, we have a superficial notion of habitability, a necessary first step, but so far lacking an understanding of the detailed interaction between stars and planets over geological timescales, dynamical evolution of planetary systems, and atmospheric evolution on planets in other systems. A planet mass, net insolation, and atmospheric composition alone are insufficient to determine the probability that life on a planet could arise or be detected. The latter set of planetary considerations, among others, underpin the concept of the habitable zone (HZ), defined as the circumstellar region where standing bodies of liquid water could be supported on the surface of a rocky planet. However, stars within the same spectral class are often treated in the same way in HZ studies, without any regard for variations in activity among individual stars. Such formulations ignore differences in how nonthermal emission and magnetic energy of transient events in different stars affect the ability of an exoplanet to retain its atmosphere.In the last few years there has been a growing appreciation that the atmospheric chemistry, and even retention of an atmosphere in many cases, depends critically on the high-energy radiation and particle environments around these stars. Indeed, recent studies have shown stellar activity and the extreme space weather, such as that created by the frequent flares and coronal mass ejections (CMEs) from the active stars and young Sun, may have profoundly affected the chemistry and climate and thus habitability of the early Earth and terrestrial type exoplanets. The goal of this white paper is to identify and describe promising key research goals to aid the field of the exoplanetary habitability for the next 20 years., Comment: 6 pages, the white paper submitted to the US National Academy of Sciences call on Exoplanet Science Strategy

Published
2018

6. Reconstructing Extreme Space Weather From Planet Hosting Stars

Author

Airapetian, V., Adibekyan, V., Ansdell, M., Alexander, D., Barklay, T., Bastian, T., Boro Saikia, S., Cohen, O., Cuntz, M., Danchi, W., Davenport, J., DeNolfo, G., DeVore, R., Dong, C., Drake, J., France, K., Fraschetti, F., Herbst, K., Garcia-Sage, K., Gillon, M., Glocer, A., Grenfell, J., Gronoff, G., Gopalswamy, N., Guedel, M., Hartnett, H., Harutyunyan, H., Hinkel, N., Jensen, A., Jin, M., Johnstone, C., Kahler, S., Kalas, P., Kane, S., Kay, C., Kitiashvili, I., Kochukhov, O., Kondrashov, D., Lazio, J., Leake, J., Li, G., Linsky, J., Lueftinger, T., Lynch, B., Lyra, W., Mandell, A., Mandt, K., Maehara, H., Miesch, M., Mickaelian, A., Mouschou, S., Notsu, Y., Ofman, L., Oman, L., Osten, R., Oran, R., Petre, R., Ramirez, R., Rau, G., Redfield, S., Réville, V., Rugheimer, S., Scheucher, M., Schlieder, J., Shibata, K., Schnittman, J., Soderblom, D., Strugarek, A., Turner, J., Usmanov, A., Van Der Holst, B., Vidotto, A., Vourlidas, A., Way, M., Wolk, S., Zank, G., Zarka, P., Kopparapu, R., Babakhanova, S., Pevtsov, A., Lee, Y., Henning, W., Colón, K., and Wolf, E.

Subjects
Physics::Space Physics, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Astrophysics::Galaxy Astrophysics
Abstract

The goal of this white paper is to identify and describe promising key research goals to aid the theoretical characterization and observational detection of ionizing radiation from quiescent and flaring upper atmospheres of planet hosts as well as properties of stellar coronal mass ejections (CMEs) and stellar energetic particle (SEP) events.

Published
2019

7. Life Beyond the Solar System: Remotely Detectable Biosignatures

Author

Domagal-Goldman, S., Kiang, N., Parenteau, N., Kamakolanu, U., Finster, K., Martin-Torres, J., Danielache, S., DasSarma, P., Tamura, M., Hori, Y., Rugheimer, S., Hartnett, H., Stockwell, B., Vazan, A., Hu, R., Cronin, L., Méndez, A., Smith, H., Demergasso, C., Meadows, V., Blank, D., Grenfell, J., Kane, S., Gavilan, L., Tan, G., Plavchan, P., Fauchez, T., Patty, C., Telesco, C., Shkolnik, E., Lyons, T., Owens, J., López-Morales, M., Lustig-Yaeger, J., ten Kate, I., Banerjee, S., Sohl, L., Gao, P., Lopez, E., Corkrey, R., Molaverdikhani, K., Deming, D., Dong, C., O'Meara, J., Kite, E., Rogers, L., Robinson, T., Tanner, A., Cleaves, H., Cahoy, K., Walker, S., Caldwell, D., Dressing, C., Ngo, H., Cochran, W., Cadillo-Quiroz, H., Blecic, J., Laine, P., Solmaz, A., Ramirez, K., Theiling, B., Dodson-Robinson, S., Zimmerman, N., Line, M., Marchis, F., Redfield, S., Pahlevan, K., Walkowicz, L., Gaudi, B., Curry, S., Pidhorodetska, D., Pyo, T., Chopra, A., Hinkel, N., Young, P., Angerhausen, D., Apai, D., Arney, G., Airapetian, V., Batalha, N., Catling, D., Cockell, C., Deitrick, R., Del Genio, A., Fisher, T., Fujii, Y., Gelino, D., Harman, C., Hegde, S., Kaçar, B., Krissansen-Totten, J., Lenardic, A., Mandt, K., Moore, W., Narita, N., Olson, S., Pallé, E., Rauer, H., Reinhard, C., Roberge, A., Schneider, J., Siegler, N., and Stapelfeldt, K.

Abstract

This white paper reviews the scientific community's ability to use data from future telescopes to search for life on exoplanets. It summarizes products from the Exoplanet Biosignatures Workshop Without Walls (EBWWW). This effort led to papers that constituted the Exoplanet Analysis Group's (ExoPAG) 16th Science Assessment Group (SAG 16).

Published
2019

8. Mineral-assisted production of benzene under hydrothermal conditions: Insights from experimental studies on C6 cyclic hydrocarbons

Author

Venturi S.[1, Tassi F.[1, Gould I.[3], Shock E.[3, Hartnett H.[3, Lorance E. [5], Bockisch C.[3], Fecteau K.[3], Capecchiacci F.[1], and Vaselli O.[1

Subjects
hydrothermal gases, benzene, laboratory experiments, mineral catalysis, organic compounds, catalytic reforming
Abstract

Volatile Organic Compounds (VOCs) are ubiquitously present at low but detectable concentrations in hydrothermal fluids from volcanic and geothermal systems. Although their behavior is strictly controlled by physical and chemical parameters, the mechanisms responsible for the production of most VOCs in natural environments are poorly understood. Among them, benzene, whose abundances were found to be relatively high in hydrothermal gases, can theoretically be originated from reversible catalytic reforming processes, i.e. multi-step dehydrogenation reactions, involving saturated hydrocarbons. However, this hypothesis and other hypotheses are difficult to definitively prove on the basis of compositional data obtained by natural gas discharges only. In this study, therefore, laboratory experiments were carried out to investigate the production of benzene from cyclic hydrocarbons at hydrothermal conditions, specifically 300 °C and 85 bar. The results of experiments carried out in the presence of water and selected powdered minerals, suggest that cyclohexane undergoes dehydrogenation to form benzene, with cyclohexene and cyclohexadiene as by-products, and also as likely reaction intermediates. This reaction is slow when carried out in water alone and competes with isomerization and hydration pathways. However, benzene formation was increased compared to these competing reactions in the presence of sulfide (sphalerite and pyrite) and iron oxide (magnetite and hematite) minerals, whereas no enhancement of any reaction products was observed in the presence of quartz. The production of thiols was observed in experiments involving sphalerite and pyrite, suggesting that sulfide minerals may act both to enhance reactivity and also as reactants after dissolution. These experiments demonstrate that benzene can be effectively produced at hydrothermal conditions through dehydrogenation of saturated cyclic organic structures and highlight the crucial role played by minerals in this process.

Published
2017

9. Using MEMS Sensor Arrays to Measure Temperature at Small Spatial Scales in Hot Spring Environments

Author

Oiler, J, Schliep, K, Hartnett, H E, Shock, E, Yu, Hongyu, Oiler, J, Schliep, K, Hartnett, H E, Shock, E, and Yu, Hongyu

Abstract

In situ measurement of temperature across the transition zones between chemosynthetic and photosynthetic microbial communities, or between different photosynthetic microbial communities in hot springs, can be ambiguous using current robust bulk measurement techniques due to the small spatial scale at of the transitions. Outflow channels are often narrow and shallow as they transport water away from the source, creating additional constraints on the size of the instrument and measurement technique used. Micro-Electro-Mechanical Systems (MEMS) technology is well-suited to take measurements of temperature within hot spring environments or other chemical parameters such as conductivity or pH. With recent advances in materials and fabrication techniques, devices can be fabricated to be chemically and thermally tolerant to the conditions present in the hot springs. The small size of the sensing elements (micron scale) provides the high spatial resolution necessary to interrogate the sharp transition zones between chemotrophic and photosynthetic communities. Owing to the small size of each sensor and the ability to batch-fabricate many sensors at once, an array of sensors can be made to measure a particular parameter simultaneously at short spatial intervals. Arrays of MEMS sensors were fabricated to measure temperature changes at intervals of ~1 cm. Our sensors consist of thermistors fabricated from a bi-layer of titanium and platinum. When heated, the electrical resistance of the thermistors will increase, and through calibration the resistance value is paired to a temperature value. The sensors and wires are covered with an inert biocompatible water-resistant polymer, Parylene-C, that protects them from chemical attack in the hot spring water. Using the arrays, a two-dimensional map of depth and distance was created at the Geothermal Explosion site in Tengchong, China, by placing the array vertically into a channel at spatial intervals of ~2 cm. Vertical measurements ta

Published
2011

10. Birth of biomolecules from the warm wet sheets of clays near spreading centers

Author

Williams, L., Holloway, J., Canfield, B., Glein, C., Dick, Jeffrey, Hartnett, H., Shock, E., Williams, L., Holloway, J., Canfield, B., Glein, C., Dick, Jeffrey, Hartnett, H., and Shock, E.

Abstract

The role of clay minerals in the abiotic synthesis of organic molecules near seafloor spreading centers was simulated experimentally. Clays are common hydrothermal alteration products of volcanic glass and due to their nano-scale crystal size, provide extensive and variably charged surfaces that interact with aqueous organic species. Volcanic gases H2 and CO2 have been shown to react on magnetite surfaces to form methanol, a primary organic molecule, under hydrothermal conditions. Therefore, our experiments simulated the temperature and pressure conditions (300°C, 100 MPa) that exist beneath hydrothermal vents, in stockwork fractures through which hydrothermal fluids interact with fresh basalt. We examined the products of reactions between aqueous methanol and three common clay minerals found in those environments (montmorillonite, saponite, illite). Montmorillonite reacted to ~60% illite over 6 weeks, while saponite and illite were mineralogically stable. Organic products extracted with dichloromethane from the two expandable smectite clays (montmorillonite, saponite) contained a variety of complex organic molecules including: alkanes, alkyl-benzenes, alkyl-naphthalenes, alkyl-phenols, alkyl-naphthols, alkyl-anthrols, methoxy and alkyl-methoxy-phenols, methoxy and alkyl-methoxy-naphthols, and long-chain methyl esters. Experiments with the non-expandable illite yielded only traces of alkanes and alkyl-benzene after 6 weeks. We infer that the interlayer surfaces of smectites provide crystallographic sites involved in the organic synthesis of polycyclic aromatic hydrocarbons. The largest variety and quantity of organic products was produced from montmorilloniteas the layer charge increased during conversion to illite.

Published
2011

12. Twelve testable hypotheses on the geobiology of weathering

Author

BRANTLEY, S. L., primary, MEGONIGAL, J. P., additional, SCATENA, F. N., additional, BALOGH-BRUNSTAD, Z., additional, BARNES, R. T., additional, BRUNS, M. A., additional, VAN CAPPELLEN, P., additional, DONTSOVA, K., additional, HARTNETT, H. E., additional, HARTSHORN, A. S., additional, HEIMSATH, A., additional, HERNDON, E., additional, JIN, L., additional, KELLER, C. K., additional, LEAKE, J. R., additional, MCDOWELL, W. H., additional, MEINZER, F. C., additional, MOZDZER, T. J., additional, PETSCH, S., additional, PETT-RIDGE, J., additional, PREGITZER, K. S., additional, RAYMOND, P. A., additional, RIEBE, C. S., additional, SHUMAKER, K., additional, SUTTON-GRIER, A., additional, WALTER, R., additional, and YOO, K., additional

Published
2011
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15. An analysis of the political activities of NASW state chapters.

Author

Scanlon E, Hartnett H, and Harding S

Abstract

NASW state chapters provide a mechanism through which members can become involved in formal political and community advocacy practice. However, there is little understanding of the strategies and processes undertaken by NASW to affect legislative and electoral outcomes. Through a mailed survey to state NASW chapters, this paper describes the scope of chapters' political practices, their policy goals and priorities, and their perceived effectiveness in advocacy work. [ABSTRACT FROM AUTHOR]

Published
2006
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16. NASW chapters: director's perceptions of factors which impede and encourage active member participation.

Author

Hartnett H, Harding S, and Scanlon E

Abstract

NASW state chapters provide a mechanism through which members can become involved in formal political and community advocacy practice. However, there is little understanding of the extent to which members are actively involved in policy and political practice and the factors that encourage or discourage participation. Through a mailed survey to state NASW chapter directors, this paper describes the extent to which members are involved in advocacy and the perceived factors which contribute to or impede participation. [ABSTRACT FROM AUTHOR]

Published
2005
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18. Binuclear cobalt complexes of Schiff-base calixpyrroles and their roles in the catalytic reduction of dioxygen.

Author

Volpe M, Hartnett H, Leeland JW, Wills K, Ogunshun M, Duncombe BJ, Wilson C, Blake AJ, McMaster J, and Love JB

Abstract

The syntheses and characterization of a series of binuclear cobalt complexes of the octadentate Schiff-base calixpyrrole ligand L are described. The cobalt(II) complex [Co(2)(L)] was prepared by a transamination method and was found to adopt a wedged, Pac-man geometry in the solid state and in solution. Exposure of this compound to dioxygen resulted in the formation of a 90:10 mixture of the peroxo [Co(2)(O(2))(L)] and superoxo [Co(2)(O(2))(L)](+) complexes in which the peroxo ligand was found to bind in a Pauling mode in the binuclear cleft in pyridine and acetonitrile adducts in the solid state. The dioxygen compounds can also be prepared directly from Co(OAc)(2) and H(4)L under aerobic conditions in the presence of a base. The reduction of dioxygen catalyzed by this mixture of compounds was investigated using cyclic voltammetry and rotating ring disk electrochemistry and, in acidified ferrocene solutions, using UV-vis spectrophotometry, and although no formation of peroxide was seen, reaction rates were slow and had limited turnover. The deactivation of the catalyst material is thought to be due to a combination of the formation of stable hydroxy-bridged binuclear complexes, for example, [Co(2)(OH)(L)](+), an example of which was characterized structurally, and the catalytic resting point, the superoxo cation, is formed by a pathway independent of the major peroxo product. Collision-induced dissociation mass spectrometry experiments showed that, while [Co(2)(O(2))(L)]H(+) ions readily lose a single O atom, the resulting Co-O(H)-Co core remains resistant to further fragmentation. Furthermore, DFT calculations show that the O-O bond distance in the dioxygen complexes is not a good indicator of the degree of reduction of the O(2) unit and provide a reduction potential of ca. +0.40 V versus the normal hydrogen electrode for the [Co(2)(O(2))(L)](+/0) couple in dichloromethane solution.

Published
2009
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