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15 results on '"B.C. Clark"'

1. An Examination of Soil Crusts on the Floor of Jezero Crater, Mars

Author

E.M. Hausrath, C.T. Adcock, A. Bechtold, P. Beck, K. Benison, A. Brown, E.L. Cardarelli, N.A. Carman, B. Chide, J. Christian, B.C. Clark, E. Cloutis, A. Cousin, O. Forni, T.S.J. Gabriel, O. Gasnault, M. Golombek, F. Gómez, M.H. Hecht, T.L.J. Henley, J. Huidobro, J. Johnson, M. W. M. Jones, P. Kelemen, A. Knight, J.A. Lasue, S. Le Mouélic, J.M. Madariaga, J. Maki, L. Mandon, G. Martinez, J. Martínez‐Frías, T.H. McConnochie, P‐Y. Meslin, M‐P. Zorzano, H. Newsom, G. Paar, N. Randazzo, C. Royer, S. Siljeström, M.E. Schmidt, S. Schröder, Mark A Sephton, R. Sullivan, N. Turenne, A. Udry, S. VanBommel, A. Vaughan, R.C. Wiens, N. Williams, null the SuperCam team, and null the Regolith working group

Subjects
Geophysics, Space and Planetary Science, Geochemistry and Petrology, Earth and Planetary Sciences (miscellaneous)
Published
2023

2. The operational environment and rotational acceleration of asteroid (101955) Bennu from OSIRIS-REx observations

Author

C. W. Hergenrother, C. K. Maleszewski, M. C. Nolan, J.-Y. Li, C. Y. Drouet d’Aubigny, F. C. Shelly, E. S. Howell, T. R. Kareta, M. R. M. Izawa, M. A. Barucci, E. B. Bierhaus, S. R. Chesley, B. E. Clark, E. J. Christensen, D. N. DellaGiustina, S. Fornasier, D. R. Golish, C. M. Hartzell, B. Rizk, D. J. Scheeres, P. H. Smith, X.-D. Zou, D. S. Lauretta, Jason Peter Dworkin, D.E. Highsmith, J. Small, D. Vokrouhlický, N.E. Bowles, E. Brown, K.L. Donaldson Hanna, T. Warren, C. Brunet, R.A. Chicoine, S. Desjardins, D. Gaudreau, T. Haltigin, S. Millington-Veloza, A. Rubi, J. Aponte, N. Gorius, A. Lunsford, B. Allen, J. Grindlay, D. Guevel, D. Hoak, J. Hong, D.L. Schrader, J. Bayron, O. Golubov, P. Sánchez, J. Stromberg, M. Hirabayashi, C.M. Hartzell, S. Oliver, M. Rascon, A. Harch, J. Joseph, S. Squyres, D. Richardson, J.P. Emery, L. McGraw, R. Ghent, R.P. Binzel, M.M. Al Asad, C.L. Johnson, L. Philpott, H.C.M. Susorney, E.A. Cloutis, R.D. Hanna, H.C. Connolly Jr, F. Ciceri, A.R. Hildebrand, E.-M. Ibrahim, L. Breitenfeld, T. Glotch, A.D. Rogers, B.E. Clark, S. Ferrone, C.A. Thomas, H. Campins, Y. Fernandez, W. Chang, A. Cheuvront, D. Trang, S. Tachibana, H. Yurimoto, J.R. Brucato, G. Poggiali, M. Pajola, E. Dotto, E. Mazzotta Epifani, M.K. Crombie, C. Lantz, M.R.M. Izawa, J. de Leon, J. Licandro, J.L.Rizos Garcia, S. Clemett, K. Thomas-Keprta, S. Van wal, M. Yoshikawa, J. Bellerose, S. Bhaskaran, C. Boyles, S.R. Chesley, C.M. Elder, D. Farnocchia, A. Harbison, B. Kennedy, A. Knight, N. Martinez-Vlasoff, N. Mastrodemos, T. McElrath, W. Owen, R. Park, B. Rush, L. Swanson, Y. Takahashi, D. Velez, K. Yetter, C. Thayer, C. Adam, P. Antreasian, J. Bauman, C. Bryan, B. Carcich, M. Corvin, J. Geeraert, J. Hoffman, J.M. Leonard, E. Lessac-Chenen, A. Levine, J. McAdams, L. McCarthy, D. Nelson, B. Page, J. Pelgrift, E. Sahr, K. Stakkestad, D. Stanbridge, D. Wibben, B. Williams, K. Williams, P. Wolff, P. Hayne, D. Kubitschek, M.A. Barucci, J.D.P. Deshapriya, M. Fulchignoni, P. Hasselmann, F. Merlin, A. Praet, E.B. Bierhaus, O. Billett, A. Boggs, B. Buck, S. Carlson-Kelly, J. Cerna, K. Chaffin, E. Church, M. Coltrin, J. Daly, A. Deguzman, R. Dubisher, D. Eckart, D. Ellis, P. Falkenstern, A. Fisher, M.E. Fisher, P. Fleming, K. Fortney, S. Francis, S. Freund, S. Gonzales, P. Haas, A. Hasten, D. Hauf, A. Hilbert, D. Howell, F. Jaen, N. Jayakody, M. Jenkins, K. Johnson, M. Lefevre, H. Ma, C. Mario, K. Martin, C. May, M. McGee, B. Miller, C. Miller, G. Miller, A. Mirfakhrai, E. Muhle, C. Norman, R. Olds, C. Parish, M. Ryle, M. Schmitzer, P. Sherman, M. Skeen, M. Susak, B. Sutter, Q. Tran, C. Welch, R. Witherspoon, J. Wood, J. Zareski, M. Arvizu-Jakubicki, E. Asphaug, E. Audi, R.-L. Ballouz, R. Bandrowski, K.J. Becker, T.L. Becker, S. Bendall, C.A. Bennett, H. Bloomenthal, D. Blum, W.V. Boynton, J. Brodbeck, K.N. Burke, M. Chojnacki, A. Colpo, J. Contreras, J. Cutts, C. Y. Drouet d'Aubigny, D. Dean, D.N. DellaGiustina, B. Diallo, D. Drinnon, K. Drozd, H.L. Enos, R. Enos, C. Fellows, T. Ferro, M.R. Fisher, G. Fitzgibbon, M. Fitzgibbon, J. Forelli, T. Forrester, I. Galinsky, R. Garcia, A. Gardner, D.R. Golish, N. Habib, D. Hamara, D. Hammond, K. Hanley, K. Harshman, C.W. Hergenrother, K. Herzog, D. Hill, C. Hoekenga, S. Hooven, E.S. Howell, E. Huettner, A. Janakus, J. Jones, T.R. Kareta, J. Kidd, K. Kingsbury, S.S. Balram-Knutson, L. Koelbel, J. Kreiner, D. Lambert, D.S. Lauretta, C. Lewin, B. Lovelace, M. Loveridge, M. Lujan, C.K. Maleszewski, R. Malhotra, K. Marchese, E. McDonough, N. Mogk, V. Morrison, E. Morton, R. Munoz, J. Nelson, M.C. Nolan, J. Padilla, R. Pennington, A. Polit, N. Ramos, V. Reddy, M. Riehl, Y.H. Tang, M. Westermann, C.W.V. Wolner, D. Worden, T. Zega, Z. Zeszut, A. Bjurstrom, L. Bloomquist, C. Dickinson, E. Keates, J. Liang, V. Nifo, A. Taylor, F. Teti, M. Caplinger, H. Bowles, S. Carter, S. Dickenshied, D. Doerres, T. Fisher, W. Hagee, J. Hill, M. Miner, D. Noss, N. Piacentine, M. Smith, A. Toland, P. Wren, M. Bernacki, D. Pino Munoz, S.-i. Watanabe, S. A. Sandford, A. Aqueche, B. Ashman, M. Barker, A. Bartels, K. Berry, B. Bos, R. Burns, A. Calloway, R. Carpenter, N. Castro, R. Cosentino, J. Donaldson, J.P. Dworkin, J. Elsila Cook, C. Emr, D. Everett, D. Fennell, K. Fleshman, D. Folta, D. Gallagher, J. Garvin, K. Getzandanner, D. Glavin, S. Hull, K. Hyde, H. Ido, A. Ingegneri, N. Jones, P. Kaotira, L.F. Lim, A. Liounis, C. Lorentson, D. Lorenz, J. Lyzhoft, E.M. Mazarico, R. Mink, W. Moore, M. Moreau, S. Mullen, J. Nagy, G. Neumann, J. Nuth, D. Poland, D.C. Reuter, L. Rhoads, S. Rieger, D. Rowlands, D. Sallitt, A. Scroggins, G. Shaw, A.A. Simon, J. Swenson, P. Vasudeva, M. Wasser, R. Zellar, J. Grossman, G. Johnston, M. Morris, J. Wendel, A. Burton, L.P. Keller, L. McNamara, S. Messenger, K. Nakamura-Messenger, A. Nguyen, K. Righter, E. Queen, K. Bellamy, K. Dill, S. Gardner, M. Giuntini, B. Key, J. Kissell, D. Patterson, D. Vaughan, B. Wright, R.W. Gaskell, L. Le Corre, J.L. Molaro, E.E. Palmer, M.A. Siegler, P. Tricarico, J.R. Weirich, T. Ireland, K. Tait, P. Bland, S. Anwar, A.S. French, J.W. McMahon, D.J. Scheeres, E.R. Jawin, T.J. McCoy, S. Russell, M. Killgore, W.F. Bottke, V.E. Hamilton, H.H. Kaplan, K.J. Walsh, J.L. Bandfield, B.C. Clark, M. Chodas, M. Lambert, R.A. Masterson, M.G. Daly, J. Freemantle, J.A. Seabrook, O.S. Barnouin, K. Craft, R.T. Daly, C. Ernst, R.C. Espiritu, M. Holdridge, M. Jones, A.H. Nair, L. Nguyen, J. Peachey, M.E. Perry, J. Plescia, J.H. Roberts, R. Steele, R. Turner, J. Backer, K. Edmundson, J. Mapel, M. Milazzo, S. Sides, C. Manzoni, B. May, M. Delbo’, G. Libourel, P. Michel, A. Ryan, F. Thuillet, and B. Marty

Subjects
Geosciences (General)
Abstract

During its approach to asteroid (101955) Bennu, NASA’s Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) spacecraft surveyed Bennu’s immediate environment, photometric properties, and rotation state. Discovery of a dusty environment, a natural satellite, or unexpected asteroid characteristics would have had consequences for the mission’s safety and observation strategy. Here we show that spacecraft observations during this period were highly sensitive to satellites (sub-meter scale) but reveal none, although later navigational images indicate that further investigation is needed. We constrain average dust production in September 2018 from Bennu’s surface to an upper limit of 150 g/s averaged over 34 min. Bennu’s disk-integrated photometric phase function validates measurements from the pre-encounter astronomical campaign. We demonstrate that Bennu’s rotation rate is accelerating continuously at 3.63 ± 0.52 × 10^(–6) degrees/sq. day, likely due to the Yarkovsky–O’Keefe–Radzievskii–Paddack (YORP) effect, with evolutionary implications.

Published
2019
Full Text
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4. SERUM MAGNESIUM AND BONE HEALTH: A STUDY OF THE ELDERLY NUTRITION AND HEALTH SURVEY IN TAIWAN 1999

Author

M. Bann, M. Nakazawa, B.C. Clark, W. Pan, and J. Gau

Subjects
Abstracts, medicine.medical_specialty, Health (social science), business.industry, Family medicine, medicine, Health survey, Life-span and Life-course Studies, Intensive care medicine, business, Health Professions (miscellaneous), Bone health
Abstract

We analyzed data from the Elderly Nutrition and Health Survey in Taiwan 1999. We chose this dataset as it has data on both serum Mg levels and bone health. Among participants who had blood samples obtained (N=1,509), 210 older adults had reported fracture(s). Variables included in our linear regression models for BUA were age, sex, blood levels of hemoglobin, albumin, and creatinine. For logistic regression models for self-reported fracture, BUA measurement was included in addition to the above covariates. Our study revealed that self-reported fracture cases (N=210, female 56%, mean age 72.6 ± 6.2) and controls (N=1,352, female 47%, mean age 71.8 ± 5.2) had similar mean serum Mg levels (2.20 ± 0.19 vs. 2.18 ± 0.19 mg/dL). Fracture cases had significantly lower mean BUA compared to controls (54 ± 21 vs. 61 ± 19, p

Published
2017

6. The acid catalyzed cyclization of citral

Author

B.C. Clark, C.C. Powell, and T. Radford

Subjects
chemistry.chemical_compound, Aqueous solution, chemistry, Acid catalyzed, Organic Chemistry, Drug Discovery, Organic chemistry, Citral, Biochemistry
Abstract

Fourteen compounds have been identified as products of the acid catalyzed cyclization of citral under mild aqueous acid conditions. Three major products of the reaction, 1,8-epoxy-p-menth-2-ene (11) and trans- and cis-p-menth-2-ene-1,8-diol (16 and 18) are reported here for the first time as products from citral. Possible mechanistic pathways leading to the products are discussed.

Published
1977

7. X-Ray Fluorescence Analysis at Room Temperature with an Energy Dispersive Mercuric Iodide Spectrometer

Author

G.C. Huth, A.K. Baird, M. Singh, B.C. Clark, A.J. Dabrowski, and Jan S. Iwanczyk

Subjects
Materials science, Spectrometer, Radiochemistry, Analytical chemistry, X-ray fluorescence, Mercuric iodide, General Medicine, Energy (signal processing)
Abstract

We have previously reported on the uniqueness and potential of room-temperature spectrometry of low-energy x-rays with a mercuric iodide (HgI2) detector (1,2,3). In this paper we emphasize the use of HgI2 detectors for x-ray fluorescence (XRF) analysis.Because no vacuum plumbing or cryogenic cooling is required, the design of a mercuric iodide room-temperature x-ray spectrometer is extremely simple. Our present design consists of coupling a detector directly to the first-stage FET in a modified Tennelec 161 D preamplifier and making the configuration “light-tight”. Aside from providing a suitable entrance window, there are no other requirements for routine spectroscopy.

Published
1979

8. Background and Sensitivity Considerations of X-Ray Fluorescence Analysis with a Room-Temperature Mercuric Iodide Spectrometer

Author

M. Singh, D.E. Leyden, A.K. Baird, Jan S. Iwanczyk, A.J. Dabrowski, and B.C. Clark

Subjects
Materials science, Spectrometer, Radiochemistry, Analytical chemistry, Mercuric iodide, X-ray fluorescence, General Medicine, Sensitivity (control systems)
Abstract

Continued development of mercuric iodide (HgI2) detectors for x-ray spectroscopy at room-temperature has led to a considerable improvement in energy resolution and a better understanding of the various detector parameters which affect sensitivity. The basic properties of a mercuric iodide detector and some of its characteristics pertinent to x-ray fluorescence analysis have been previously reported (1,2,3). In this paper we present results of studies to determine the shape o£ peaks and continuum background. Also, the use of Hgl2 in characterizing water pollutants by XRF analysis has been investigated and compared to cryogenically cooled Si(Li) and room-temperature proportional counter systems.

Published
1980

9. Comets as a source of preformed material for prebiotic evolution

Author

B.C. Clark

Subjects
Atmospheric Science, Solar System, Prebiotic evolution, Aerospace Engineering, Astronomy and Astrophysics, Cosmic ray, Astrophysics, Early Earth, Silicate, Accretion (astrophysics), Astrobiology, chemistry.chemical_compound, Geophysics, chemistry, Space and Planetary Science, General Earth and Planetary Sciences, Molecule, Earth (chemistry)
Abstract

Comets are known to contain ices, organic compounds, and silicate dust grains. During final accretion by the early Earth, comets will have contributed chemical ingredients in several ways: as bulk additions to the volatile inventory; as particles, molecules, radicals, and atoms; and perhaps in rare cases as localized concentrated matter. Having originated in the outer solar system and/or interstellar space, these constituents are, not surprisingly, unique compared to those otherwise found at the surface of the early Earth. Comets are apparently rich in materials that may be vital to successful prebiotic evolution, including light elements, catalytic elements, organic compounds, and microparticles of various types down to the submicrometer size range. Because of their exceptional chemical nature and great abundance, comets deserve serious consideration in models of accretion and early protobiological activity.

Published
1989

11. Generation and spectroscopy of ultrasoft X-rays by non-dispersive methods

Author

D. Srdoč and B.C. Clark

Subjects
Physics, Range (particle radiation), Spectrometer, business.industry, Bremsstrahlung, Proportional counter, General Medicine, Photon energy, Spectral line, Optics, Monochromatic color, Atomic physics, business, Spectroscopy
Abstract

A number of conventional techniques used to generate soft X-rays can be successfully applied to the ultrasoft region (100 eV to 1000 eV). In this work, fluorescent radiation and selected radioisotope sources were employed and a miniature X-ray tube was designed for generating characteristic X-rays from various targets. A new method has been developed for producing a nearly monochromatic ultrasoft X-ray beam by heavily filtering bremsstrahlung radiation. A proportional counter has been used to measure the ultrasoft X-rays generated by the different methods. When the internal gas multiplication is not excessive, a linear relationship between the photon energy and the mean pulse height is found over the range of measurement, 158 eV to 5890 eV.

Published
1970

13. System for 14Co2 radioassay in the presence of a high background radiation

Author

B.C. Clark

Subjects
Physics, Optics, business.industry, Beta particle, Ionization chamber, Figure of merit, Proportional counter, General Medicine, Radiation, Scintillator, business, Sensitivity (electronics), Background radiation
Abstract

The detection system consist of a 30 cm3 spherical proportional counter to measure the beta rays from 14C labelled gas. This counter is built inside a plastic scintillator. Pulses from the photo-multiplier tube which views this scintillator and from the wire anode of the proportional counter are amplified and fed to an anti-coincidence circuit which passes the proportional counter pulses only when no pulse occurs in the scintillator. The purpose of the scintillator and anti-coincidence circuitry is to reduce sensitivity to background radiation. Rejection factors of as high as 80 have been achieved for gamma radiation. Under optimum operating conditions, the detection system achieves a figure of merit of 6.2 in the presence of a SNAP-19 unit and 27 in the laboratory environment. This allows lower limits of detectability of 7 pCi and 1.4 pCi of 14CO2, respectively, at a confidence level of 0.999999. The system has been designed for possible use on a Mars mission.

Published
1970

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