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Abstract
The initiation mechanism of Earth's plate tectonic cooling system remains uncertain. A growing consensus suggests that multi-plate tectonics was preceded by cooling through a single-plate lithosphere, but models for how this lithosphere was first broken into plates have not converged on a mechanism or a typical early plate scale. A commonality among prior efforts is the use of continuum mechanics approximations to evaluate this solid mechanics problem. Here we use 3D spherical shell models to demonstrate a self-organized fracture mechanism analogous to thermal expansion-driven lithospheric uplift, in which globe-spanning rifting occurs as a consequence of horizontal extension. Resultant fracture spacing is a function of lithospheric thickness and rheology, wherein geometrically-regular, polygonal-shaped tessellation is an energetically favored solution because it minimizes total crack length. Therefore, warming of the early lithosphere itself-as anticipated by previous studies-should lead to failure, propagating fractures, and the conditions necessary for the onset of multi-plate tectonics.
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Affiliation(s)
- C A Tang
- State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology, 116024, Dalian, China.,State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, 430074, Wuhan, China
| | - A A G Webb
- Division of Earth and Planetary Science and Laboratory for Space Research, University of Hong Kong, Pokfulam Road, 999077, Hong Kong, China.
| | - W B Moore
- Department of Atmospheric and Planetary Sciences, Hampton University, Hampton, VA, 23668, USA.,National Institute of Aerospace, Hampton, VA, 23666, USA
| | - Y Y Wang
- Deep Underground Engineering Research Center, Dalian University of Technology, 116024, Dalian, China
| | - T H Ma
- State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology, 116024, Dalian, China.,Deep Underground Engineering Research Center, Dalian University of Technology, 116024, Dalian, China
| | - T T Chen
- School of Resources and Civil Engineering, Northeastern University, 110819, Shenyang, China
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2
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Pothier NM, Weimer DR, Moore WB. Quantitative maps of geomagnetic perturbation vectors during substorm onset and recovery. J Geophys Res Space Phys 2015; 120:1197-1214. [PMID: 26167445 PMCID: PMC4497481 DOI: 10.1002/2014ja020602] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/08/2014] [Accepted: 01/22/2015] [Indexed: 06/04/2023]
Abstract
UNLABELLED We have produced the first series of spherical harmonic, numerical maps of the time-dependent surface perturbations in the Earth's magnetic field following the onset of substorms. Data from 124 ground magnetometer stations in the Northern Hemisphere at geomagnetic latitudes above 33° were used. Ground station data averaged over 5 min intervals covering 8 years (1998-2005) were used to construct pseudo auroral upper, auroral lower, and auroral electrojet (AU*, AL*, and AE*) indices. These indices were used to generate a list of substorms that extended from 1998 to 2005, through a combination of automated processing and visual checks. Events were sorted by interplanetary magnetic field (IMF) orientation (at the Advanced Composition Explorer (ACE) satellite), dipole tilt angle, and substorm magnitude. Within each category, the events were aligned on substorm onset. A spherical cap harmonic analysis was used to obtain a least error fit of the substorm disturbance patterns at 5 min intervals up to 90 min after onset. The fits obtained at onset time were subtracted from all subsequent fits, for each group of substorm events. Maps of the three vector components of the averaged magnetic perturbations were constructed to show the effects of substorm currents. These maps are produced for several specific ranges of values for the peak |AL*| index, IMF orientation, and dipole tilt angle. We demonstrate an influence of the dipole tilt angle on the response to substorms. Our results indicate that there are downward currents poleward and upward currents just equatorward of the peak in the substorms' westward electrojet. KEY POINTS Show quantitative maps of ground geomagnetic perturbations due to substorms Three vector components mapped as function of time during onset and recovery Compare/contrast results for different tilt angle and sign of IMF Y-component.
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Affiliation(s)
- N M Pothier
- Department of Atmospheric and Planetary Sciences, Hampton UniversityHampton, Virginia, USA
- National Institute of AerospaceHampton, Virginia, USA
- Bradley Department of Electrical and Computer Engineering, Center for Space Science and Engineering Research, Virginia TechBlacksburg, Virginia, USA
- Department of Atmospheric, Oceanic, and Space Science, University of MichiganAnn Arbor, Michigan, USA
| | - D R Weimer
- National Institute of AerospaceHampton, Virginia, USA
- Bradley Department of Electrical and Computer Engineering, Center for Space Science and Engineering Research, Virginia TechBlacksburg, Virginia, USA
| | - W B Moore
- Department of Atmospheric and Planetary Sciences, Hampton UniversityHampton, Virginia, USA
- National Institute of AerospaceHampton, Virginia, USA
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3
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Affiliation(s)
- G Schubert
- Department of Earth and Space Sicences, and Institute of Geophysics and Planetary Physics, University of California, Los Angeles 90095-1567, USA.
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4
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Pappalardo RT, Belton MJS, Breneman HH, Carr MH, Chapman CR, Collins GC, Denk T, Fagents S, Geissler PE, Giese B, Greeley R, Greenberg R, Head JW, Helfenstein P, Hoppa G, Kadel SD, Klaasen KP, Klemaszewski JE, Magee K, McEwen AS, Moore JM, Moore WB, Neukum G, Phillips CB, Prockter LM, Schubert G, Senske DA, Sullivan RJ, Tufts BR, Turtle EP, Wagner R, Williams KK. Does Europa have a subsurface ocean? Evaluation of the geological evidence. ACTA ACUST UNITED AC 1999. [DOI: 10.1029/1998je000628] [Citation(s) in RCA: 304] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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5
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Abstract
Radio Doppler data from four encounters of the Galileo spacecraft with the jovian moon Europa have been used to refine models of Europa's interior. Europa is most likely differentiated into a metallic core surrounded by a rock mantle and a water ice-liquid outer shell, but the data cannot eliminate the possibility of a uniform mixture of dense silicate and metal beneath the water ice-liquid shell. The size of a metallic core is uncertain because of its unknown composition, but it could be as large as about 50 percent of Europa's radius. The thickness of Europa's outer shell of water ice-liquid must lie in the range of about 80 to 170 kilometers.
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Affiliation(s)
- J D Anderson
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA
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6
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Abstract
Radio Doppler data from a single encounter (C3) of the Galileo spacecraft with Callisto, the outermost Galilean moon of Jupiter, indicated that Callisto was probably undifferentiated. Now, similar data from a second encounter (C9) corroborate this conclusion, but more accurate data from a third encounter (C10) indicate that the rock and ice within Callisto have partially, but not completely, separated. Callisto may be differentiated into a rock-metal core less than 25 percent of Callisto's radius, an outer layer of clean ice less than 350 km thick, and a middle layer of mixed rock and ice. Models in which ice and rock are mixed all the way to the center of Callisto are also consistent with the data.
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Affiliation(s)
- J D Anderson
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109-8099, USA
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7
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Abstract
Rapid lithospheric thinning by mantle plumes has not been achieved in numerical experiments performed to date. Efficient thinning depends on small-scale instabilities that convectively remove lithospheric material. These instabilities are favored by hotter plumes or stronger temperature dependence of viscosity, and a simple scaling independent of rheology controls their onset. This scaling allows extrapolation of the results of numerical experiments to the Earth's mantle. Mantle plumes between 100 and 150 kelvins hotter than the background mantle should exhibit small-scale convective rolls aligned with the plate motion. The unusual variation in heat flow across the Hawaiian swell may be due to such instabilities. It was found that the spreading of the plume creates a downwelling curtain of material that isolates it from the rest of the mantle for distances of at least 1000 kilometers from the plume origin. This isolation has important consequences for the geochemical heterogeneity of the lithosphere and upper mantle.
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Affiliation(s)
- WB Moore
- W. B. Moore and P. J. Tackley, Department of Earth and Space Sciences, University of California, Los Angeles, 3806 Geology Building, Los Angeles, CA 90095-1567, USA. G. Schubert, Department of Earth and Space Sciences and Institute of G
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Pappalardo RT, Head JW, Greeley R, Sullivan RJ, Pilcher C, Schubert G, Moore WB, Carr MH, Moore JM, Belton MJ, Goldsby DL. Geological evidence for solid-state convection in Europa's ice shell. Nature 1998; 391:365-8. [PMID: 9450750 DOI: 10.1038/34862] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The ice-rich surface of the jovian satellite Europa is sparsely cratered, suggesting that this moon might be geologically active today. Moreover, models of the satellite's interior indicate that tidal interactions with Jupiter might produce enough heat to maintain a subsurface liquid water layer. But the mechanisms of interior heat loss and resurfacing are currently unclear, as is the question of whether Europa has (or had at one time) a liquid water ocean. Here we report on the morphology and geological interpretation of distinct surface features-pits, domes and spots-discovered in high-resolution images of Europa obtained by the Galileo spacecraft. The features are interpreted as the surface manifestation of diapirs, relatively warm localized ice masses that have risen buoyantly through the subsurface. We find that the formation of the features can be explained by thermally induced solid-state convection within an ice shell, possibly overlying a liquid water layer. Our results are consistent with the possibility that Europa has a liquid water ocean beneath a surface layer of ice, but further tests and observations are needed to demonstrate this conclusively.
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Affiliation(s)
- R T Pappalardo
- Department of Geological Sciences, Brown University, Providence, Rhode Island 02912-1846, USA.
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9
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Abstract
Doppler data generated with the Galileo spacecraft's radio carrier wave during two Europa encounters on 19 December 1996 (E4) and 20 February 1997 (E6) were used to measure Europa's external gravitational field. The measurements indicate that Europa has a predominantly water ice-liquid outer shell about 100 to 200 kilometers thick and a deep interior with a density in excess of about 4000 kilograms per cubic meter. The deep interior could be a mixture of metal and rock or it could consist of a metal core with a radius about 40 percent of Europa's radius surrounded by a rock mantle with a density of 3000 to 3500 kilograms per cubic meter. The metallic core is favored if Europa has a magnetic field.
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Affiliation(s)
- J D Anderson
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109-8099, USA
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10
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Abstract
Before the arrival of the Galileo spacecraft at Jupiter, models for the interior structure of the four galilean satellites--Io, Europa, Ganymede and Callisto-ranged from uniform mixtures of rock and ice (that is, undifferentiated objects) or rocky cores surrounded by a mantle of water ice. Now it appears that Io has a large metallic core and that Ganymede is strongly differentiated, most probably into a three-layer structure consisting of a metallic core, a silicate mantle and a deep outer layer of ice. Direct information on the interior structure of Callisto determined from previous spacecraft fly-bys was essentially limited to an estimate of the mean density being intermediate between pure ice and pure rock. Here we report measurements of Callisto's gravitational field which reveal that, in contrast to Io and Ganymede, this galilean satellite is most probably a homogeneous object consisting of a solar mixture of 40% compressed ice and 60% rock (including iron and iron sulphide). Callisto's undifferentiated state is consistent with the apparent lack of an intrinsic magnetic field, and indicates that the outermost galilean satellite has not experienced a heating phase sufficiently high to separate its rock and metal components from the lighter ices.
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Affiliation(s)
- J D Anderson
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena 91109-8099, USA.
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Moore WB, Groth CD. Independent contractors or employees? Reducing reclassification risks. Healthc Financ Manage 1993; 47:118, 120-4. [PMID: 10145802] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/11/2023]
Abstract
With the aggressive stance taken by the IRS regarding worker classification, many organizations may be risking significant retroactive assessments with respect to the use of independent contractors. Employers should be aware of the 20 primary factors considered by the IRS when examining independent contractor relationships and prepare in advance for IRS classification review or audit.
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Moore WB. Don't let uncertainty keep you from action. Hospitals 1993; 67:56. [PMID: 8418008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
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Abstract
Soil microorganisms colonizing soil water sampling devices (lysimeters) reduced concentrations of biodegradable organic chemicals, including 2,4-dichlorophenoxyacetic acid methyl ester, alachlor, methyl
m
-chlorobenzoate, and metolachlor as water entered through porous ceramic cups. In some cases, losses exceeded 99%. Additions of either a biocide (sodium hypochlorite) or a bacteriostat (copper salt) prevented microbial activity so that concentrations of test chemicals inside lysimeters equaled those outside. Field studies further indicated that treating lysimeters with a copper salt effectively prevented microbial activity. Thus, chemically treating soil water samplers could improve the accuracy of soil water data for a wide variety of analytes, including environmentally important organics, such as pesticides and industrial wastes, and inorganics, such as ammonia and nitrate.
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Affiliation(s)
- D L Lewis
- Environmental Research Laboratory and Technology Applications, Inc., U.S. Environmental Protection Agency, Athens, Georgia 30613; Institute of Ecology, University of Georgia, Athens, Georgia 30602 ; Scientific Evaluation Section, Bureau of Pesticides, Department of Agriculture and Consumer Services, State of Florida, Tallahassee, Florida 32311 ; and Pesticide & Review Section, Department of Environmental Regulation, State of Florida, Tallahassee, Florida 32399
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Moore WB. Hospitals win healthy margins by following business basics. Hospitals 1990; 64:56, 58. [PMID: 2323754] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
In today's tough economic environment for hospitals, what separates the winners from the losers? An analysis of the sixth annual CEO Survey, jointly sponsored by Hospitals and Hamilton/KSA, an Atlanta-based consulting firm, points to some answers. Hamilton/KSA cross-tabulated the survey to see what factors were associated with increasing and decreasing margins.
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Moore WB. CEOs plan resource shift for 1986. Hospitals 1985; 59:69-70, 72. [PMID: 4065879] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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Moore WB. A survey of health care benefits in the apparel industry. Health Care Strateg Manage 1985; 3:7-13. [PMID: 10273751] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/12/2023]
Abstract
Each day as Americans prepare to begin their days, many put on their clothing often without a thought as to how or where it was manufactured. The manufacture of clothing in the United States is a labor intensive industry pressed by competition in foreign countries where labor is abundant and less expensive; therefore, the manufacturers must look for every opportunity to reduce their costs. The survey presented here reviews the health benefit plans in the apparel industry and current initiatives for cost reduction. The results are interesting, for they give the hospital administrator vital information on the types of programs that might be in place in local manufacturers and the method of cost containment expected in this industry.
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Moore WB. CEOs plan to expand home health, outpatient services. Hospitals 1985; 59:74-7. [PMID: 3965382] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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Moore WB. Survey shows CEOs' priorities are changing. Hospitals 1984; 58:71-2, 75, 77. [PMID: 6389311] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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Abstract
Different batches of ABTS obtained from the same commercial source varied in their capacity to effect direct mutation in the strains of Salmonella typhimurium used routinely in the incorporation test of Ames. One batch, obtained in 1976, and another obtained early in 1979, both exhibited direct base-pair substitution and frame-shift activities. These activities, however, were absent from each of two batches obtained after 1979, and also from a highly purified preparation from a different source. The possible presence of the unsulphonated immediate precursor of ABTS as a mutagenic impurity is an unlikely explanation for the activity of the mutagenic preparations. It is more probable that the commercial synthesis generated other, mutagenic, impurities which remained in the batches obtained in 1976 and early in 1979, but were absent or were removed from later batches. The identity of these active impurities is unknown. Pure ABTS is neither a direct nor an indirect mutagen.
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Moore WB, Chatfield SN. Evaluation of 4-hydroxymethylbiphenyl (4HMB), 4-chloromethylbiphenyl (4CMB) and benzyl chloride (BC) using the Ames Salmonella/microsome incorporation test for mutagenicity. Mutat Res 1982; 100:35-8. [PMID: 7035895 DOI: 10.1016/0165-1218(82)90017-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
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Abstract
A technique for measuring glucose utilisation by mycoplasmas, in which the disappearance of glucose is monitored by the glucose-oxidase method, is proposed as an alternative to the pH method. For maximum reliability the number of organisms in the test suspension must exceed a critical minimum value. Differences in efficiency of glucose utilisation were demonstrated between species of Mycoplasma and Acholeplasma.
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Moore WB, Matthews TJ, Rabinowitz R. Genitourinary anomalies associated with Klippel-Feil syndrome. J Bone Joint Surg Am 1975; 57:355-7. [PMID: 235554] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Of thirty-nine patients with Klippel-Feil syndrome, twenty-five (64 per cent) had significant genitourinary-tract anomalies demonstrated by intravenous urogram and physical examination. The incidence of these anomalies in Feil's three types of the syndrome was essentially the same, unilateral renal agenesis being the most common. A routine intravenous urogram is indicated in patients with this syndrome.
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Moore WB. Separation, characteristics and minimal amino-acid requirements of six variants derived from a strain of Bacillus cereus. J Gen Microbiol 1965; 40:329-42. [PMID: 4955876 DOI: 10.1099/00221287-40-3-329] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
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