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836 results on '"Hartman H"'

153. Observations of the radial velocity of the Sun as measured with the novel SONG spectrograph: results from a 1-week campaign

Author

Pallé, P L, primary, Grundahl, F, additional, Hage, A Triviño, additional, Christensen-Dalsgaard, J, additional, Frandsen, S, additional, García, R A, additional, Uytterhoeven, K, additional, Andersen, M F, additional, Rasmussen, P K, additional, Sørensen, A N, additional, Kjeldsen, H, additional, Spano, P, additional, Nilsson, H, additional, Hartman, H, additional, Jørgensen, U G, additional, Skottfelt, J, additional, Harpsøe, K, additional, and Andersen, M I, additional

Published
2013
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154. First storage of ion beams in the Double Electrostatic Ion-Ring Experiment: DESIREE

Author

Schmidt, H. T., primary, Thomas, R. D., additional, Gatchell, M., additional, Rosén, S., additional, Reinhed, P., additional, Löfgren, P., additional, Brännholm, L., additional, Blom, M., additional, Björkhage, M., additional, Bäckström, E., additional, Alexander, J. D., additional, Leontein, S., additional, Hanstorp, D., additional, Zettergren, H., additional, Liljeby, L., additional, Källberg, A., additional, Simonsson, A., additional, Hellberg, F., additional, Mannervik, S., additional, Larsson, M., additional, Geppert, W. D., additional, Rensfelt, K. G., additional, Danared, H., additional, Paál, A., additional, Masuda, M., additional, Halldén, P., additional, Andler, G., additional, Stockett, M. H., additional, Chen, T., additional, Källersjö, G., additional, Weimer, J., additional, Hansen, K., additional, Hartman, H., additional, and Cederquist, H., additional

Published
2013
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156. Enceladus: Cassini observations and implications for the search for life

Author

Parkinson, C. D., Liang, M. C., Hartman, H., Hansen, C. J., Tinetti, G., Meadows, V., Kirschvink, J. L., Yung, Y. L., Parkinson, C. D., Liang, M. C., Hartman, H., Hansen, C. J., Tinetti, G., Meadows, V., Kirschvink, J. L., and Yung, Y. L.

Abstract

Aims. The recent Cassini discovery of water vapor plumes ejected from the south pole of the Saturnian satellite, Enceladus, presents a unique window of opportunity for the detection of extant life in our solar system. Methods. With its significant geothermal energy source propelling these plumes >80 km from the surface of the moon and the ensuing large temperature gradient with the surrounding environment, it is possible to have the weathering of rocks by liquid water at the rock/liquid interface. For the cases of the putatively detected salt-water oceans beneath the ice crusts of Europa and Callisto, an isolated subsurface ocean without photosynthesis or contact with an oxidizing atmosphere will approach chemical equilibrium and annihilate any ecosystems dependent on redox gradients unless there is a substantial alternative energy source. This thermodynamic tendency imposes severe constraints on any biota that is based on chemical energy. On Enceladus, the weathering of rocks by liquid water and any concomitant radioactive emissions are possible incipient conditions for life. If there is CO, CO2 and NH3 present in the spectra obtained from the plume, then this is possible evidence that amino acids could be formed at the rock/liquid interface of Enceladus. The combination of a hydrological cycle, chemical redox gradient and geochemical cycle give favorable conditions for life. Results. We discuss the search for signatures of these species and organics in the Cassini UVIS spectra of the plume and implications for the possible detection of life.

Published
2007

157. Jupiter analogues and planets of active stars

Author

Kürster, M., primary, Zechmeister, M., additional, Endl, M., additional, Lo Curto, G., additional, Hartman, H., additional, Nilsson, H., additional, Henning, T., additional, Hatzes, A.P., additional, and Cochran, W.D., additional

Published
2013
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159. The FERRUM project : experimentally determined metastable lifetimes and transition probabilities for forbidden [Ti II] lines observed in eta Carinae

Author

Hartman, H, Schef, P, Lundin, P, Ellmann, A, Johansson, S, Lundberg, H, Mannervik, S, Norlin, Lars-Olov, Rostohar, D, Royen, P, Hartman, H, Schef, P, Lundin, P, Ellmann, A, Johansson, S, Lundberg, H, Mannervik, S, Norlin, Lars-Olov, Rostohar, D, and Royen, P

Abstract

In the spectrum of an emission-line region ejected from the massive star Eta Carinae, called the strontium filament (SrF), forbidden lines from many elements, in particular [Sr II] and [Ti II], are observed. These lines are strong in this specific region and valuable for plasma diagnostics. Forbidden lines are not easily produced in laboratory light sources and the atomic parameters for these lines can thus not be measured in a straightforward way. We use a combination of laboratory and astrophysical measurements to determine transition probabilities for the [Ti II] lines. Lifetimes for metastable levels in Ti II are measured using a laser probing technique on a stored ion beam at CRYRING, MSL, Stockholm. Branching fractions from some of these levels are derived from Hubble Space Telescope/STIS spectra of the SrF. The astrophysical branching fractions are combined with the experimental lifetimes to determine absolute transition probabilities. We report lifetimes for the Ti II levels b(4)P(3/2), b(2)P(1/2), c(2)D(3/2) and c(2)D(5/2), in the range 0.29-17 s, and transition probabilities for eight parity-forbidden lines from the levels c(2)D(3/2) and c(2)D(5/2), along with uncertainty estimates., QC 20110823

Published
2005
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164. CRIRES-POP

Author

Lebzelter, T., primary, Seifahrt, A., additional, Uttenthaler, S., additional, Ramsay, S., additional, Hartman, H., additional, Nieva, M.-F., additional, Przybilla, N., additional, Smette, A., additional, Wahlgren, G. M., additional, Wolff, B., additional, Hussain, G. A. J., additional, Käufl, H. U., additional, and Seemann, U., additional

Published
2012
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168. Lifetime measurements and calculations in Y+ and Y2+ ions

Author

Biémont, É., primary, Blagoev, K., additional, Engström, L., additional, Hartman, H., additional, Lundberg, H., additional, Malcheva, G., additional, Nilsson, H., additional, Whitehead, R. Blackwell, additional, Palmeri, P., additional, and Quinet, P., additional

Published
2011
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175. Detection of high-velocity material from the wind-wind collision zone of Eta Carinae across the 2009.0 periastron passage

Author

Groh, J. H., primary, Nielsen, K. E., additional, Damineli, A., additional, Gull, T. R., additional, Madura, T. I., additional, Hillier, D. J., additional, Teodoro, M., additional, Driebe, T., additional, Weigelt, G., additional, Hartman, H., additional, Kerber, F., additional, Okazaki, A. T., additional, Owocki, S. P., additional, Millour, F., additional, Murakawa, K., additional, Kraus, S., additional, Hofmann, K.-H., additional, and Schertl, D., additional

Published
2010
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184. Origin of life and iron-rich clays

Author

Hartman, H. H

Subjects
Space Biology
Abstract

The premise that life began with self-replicating iron-rich clays is explored. In association with these clays and UV light, polar organic molecules, such as oxalic acid, were synthesized. The carbonaceous chondrites have both iron-rich clays and organic molecules. It is convenient to classify meteoritic organic matter into 3 categories: insoluble polymer, hydrocarbons and polar organics (soluble in water). Recent work on the delta D, delta N-15 and delta C-13 has made it clear that these three fractions have been made by three different mechanisms. A significant fraction of the insoluble polymer has a delta-D which suggests that it was made in an interstellar medium. The hydrocarbons seem to have been made on a parent body by a Fischer-Tropsch mechanism. The polar organics were probably synthesized in a mixture of carbonate (NH4)2CO3, Fe(++) ion and liquid water by radiolysis. In a set of experiments the radiolysis of (NH4)2CO3 in the presence and absence of Fe(++) ion has been examined. The synthesis of glycine in the presence of Fe(++) ion is 3-4 times that in the absence of ferrous ion. The effects of the addition of hydrocarbons to this mixture are explored. Iron-rich clays at low temperature and pressure are synthesized. So far the results are not sufficiently crystalline to look for replication. It should be noted that organic chelating agents such as oxalic acid do increase the crystallinity of the clays but not sufficiently. The hydrothermal synthesis of iron-rich clays is being examined.

Published
1986

185. Chemical effects of large impacts on the earth's primitive atmosphere

Author

Fegley, B., Jr, Prinn, R. G, Hartman, H, and Watkins, G. H

Subjects
Lunar And Planetary Exploration
Abstract

The production of HCN and H2CO by large impacts on the earth's primitive atmosphere is modelled using thermochemical equilibrium and chemical kinetic calculations of the composition of shocked air parcels for a wide range of temperatures, pressures, and initial compositions. For atmospheres with C/O of one or more, the results suggest that bolide impacts cause HCN volume mixing ratios of approximately 10 to the -3rd to -5th in the impact region and global average ratios of 10 to the -5th to the -12th. The corresponding H2CO mixing ratios in the impact region are 10 to the -7th to -9th; nonglobal mixing can occur, however, as H2CO is rapidly destroyed or rained out of the atmosphere within days to hours. Rainout to the oceans of 3-15 percent of the HCN produced can provide 3-14 x 10 to the 11th mol HCN per year.

Published
1986
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186. Search for the Universal Ancestors

Author

Hartman, H, Lawless, J. G, and Morrison, P

Subjects
Space Biology
Abstract

By its nature, the study of the origins of life is multidisciplinary, requiring contributions from astronomers, biologists, chemists, geologists, physicists, and many others. Partial answers are provided to many questions about organic chemical evolution and the origin of life. It is observed that the gaps in our knowledge concerning the steps from the nonliving to the living are numerous. Among these gaps are: (1) a solar system formation with its accumulation of raw materials; (2) the synthesis of the life forming monomers, such as the amino acids, nucleotides, and lipids; (3) the condensation of these monomers into useful polymers, such as proteins and nucleic acids; (4) the sequestering of these materials into droplets of proteinoid or membrane-like structures; and (5) the development of a chemical memory (the genetic code) to pass on to the progeny the information acquired.

Published
1985

187. The origin of the eukaryotic cell

Author

Hartman, H

Subjects
Life Sciences (General)
Abstract

The endosymbiotic hypothesis for the origin of the eukaryotic cell has been applied to the origin of the mitochondria and chloroplasts. However as has been pointed out by Mereschowsky in 1905, it should also be applied to the nucleus as well. If the nucleus, mitochondria and chloroplasts are endosymbionts, then it is likely that the organism that did the engulfing was not a DNA-based organism. In fact, it is useful to postulate that this organism was a primitive RNA-based organism. This hypothesis would explain the preponderance of RNA viruses found in eukaryotic cells. The centriole and basal body do not have a double membrane or DNA. Like all MTOCs (microtubule organising centres), they have a structural or morphic RNA implicated in their formation. This would argue for their origin in the early RNA-based organism rather than in an endosymbiotic event involving bacteria. Finally, the eukaryotic cell uses RNA in ways quite unlike bacteria, thus pointing to a greater emphasis of RNA in both control and structure in the cell. The origin of the eukaryotic cell may tell us why it rather than its prokaryotic relative evolved into the metazoans who are reading this paper.

Published
1984

188. Receptors signaling gravity orientation in an insect

Author

Hartman, H. B

Subjects
Life Sciences (General)
Abstract

Displacement in any direction from primary orientation is found to evoke tonic activity from at least one of the four interneurons of a certain type of burrowing cockroach; the receptive field for each interneuron is slightly more than a quadrant. The receptive field of each interneuron is found to be the same as the row of receptors providing the input. Displacement about the least stable axis (0-180 deg) or roll, on the one hand, and the most stable axis (90-270 deg) or pitch, on the other, is found to be unambiguously signaled by pairs of interneurons. Indications are obtained that receptors in the lateral row drive a giant interneuron in a contralateral connective and those in the medial row drive one in an ipsilateral connective.

Published
1982

189. Chemical consequences of major impact events on earth

Author

Lewis, J. S, Watkins, G. H, Hartman, H, and Prinn, R. G

Subjects
Geosciences (General)
Abstract

Violent cometary or asteroidal impact events comparable to that which terminated the Cretaceous era must produce large amounts of nitrogen oxides, sufficient to provide NOx mole fractions much larger than 100 ppm over areas of millions of square kilometers. Rapid production of NO2, and subsequent rainout of HNO3 and other strong acids can acidify surface waters, selectively destroying CaCO3 shells. This scenario holds the promise of explaining both the scope of Cretaceous biological extinctions and their extraordinary selectivity.

Published
1982

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