The adiabatic cooling of the protons in the solar wind: The case where the interplanetary magnetic-field is of spiral form     

M. Eyni  A. S. Kaufman 《Astrophysics and Space Science》1974,28(1):177-183

This is a sequel to the paper by Eyni and Kaufman (1971) in which the coordinate systems with respect to the magnetic direction and solar radial-direction were assumed coincident. In the present account, it is shown that the theoretical expression for the proton cooling derived in that paper is still applicable in the case of the spiral magnetic-field provided the appropriate transformation of kinetic temperature from the magnetic direction to the radial direction as derived here is used. A detailed comparison is made between the present model and other models based on the spiral form of the magnetic field; the agreement is satisfactory.  相似文献   

A Cerion-based chronostratigraphy and age model from the central Bahama Islands: Amino acid racemization and 14C in land snails and sediments     

Paul J. Hearty  Darrell S. Kaufman 《Quaternary Geochronology》2009,4(2):148-159

The taxonomy of the land-snail genus Cerion, and the relevance of hundreds of shell forms to phylogenetic and evolutionary processes has been the subject of much discussion over the past few decades. Fundamental to understanding evolutionary trends is the independent confirmation of the age, biostratigraphic, and chronostratigraphic order of a comprehensive set of fossil forms. Amino acid racemization (AAR) is a geochronological tool applicable to dating living and fossil Cerion shells. The extent of racemization of aspartic acid (Asp D/L) and glutamic acid (Glu D/L) were determined for 507 Cerion shells dating between the early last interglaciation (marine isotope stage (MIS) 5e, c. 125 ka) and the present from the Bahamas. The AAR data based on Cerion support the established morphostratigraphic succession of deposits younger than MIS 5e and provide greater resolution, particularly for biostratigraphic successions of Holocene age. Age models were constructed for Asp and Glu using D/L values paired with ¹⁴C ages and historical collection dates from 23 Cerion shells. In addition to the relative-age time series, the Holocene age models developed from D/L Glu and Asp apply to the last 7 ka and geographically within the central Bahamas. In two case studies, large numbers of AAR-generated ages provide insights into the age structure of accretionary soils and rates and age constraints on evolutionary processes related to Cerion land snails.  相似文献   

Mineral chemistry and chemical zoning in tourmalines, Pampa del Tamboreo, San Luis, Argentina   总被引：2，自引：0，他引：2  

Darrell J. Henry  Milka K. de Brodtkorb   《Journal of South American Earth Sciences》2009,28(2):132-141

Tourmalinites that are distally associated with tungsten deposits of the Pampa del Tamboreo area, San Luis, Argentina, contain tourmalines retaining evidence for its origin and evolution. Tourmaline grains uncommonly contain small grains of detrital tourmaline. Analysis of a single detrital tourmaline grain reveals that it is a Ca-rich “oxy-dravite”. Proximal to the detrital cores there are inner domains of asymmetric tourmaline overgrowths that developed during low grade metamorphism. Volumetrically dominant tourmaline overgrowths in the outer domain are concentrically zoned aluminous dravite and “oxy-dravite” with Al/(Al + Fe + Mg) = 0.71–0.74 and Mg/(Mg + Fe) = 0.64–0.71. Variability of Al is primarily controlled by the deprotonation substitution R + OH⁻ = Al + O²⁻ (where R = Fe + Mg), and is a function of the activity of H₂O. A likely evolutionary scenario is one in which volcanogenic material is altered by hydrothermal fluids in the sea floor resulting in an aluminous and magnesian residuum. With further hydrothermal circulation and incipient metamorphism, boron-rich fluids are expelled from metasedimentary and metavolcanic basement rocks and develop Mg-rich tourmalinites in the aluminous, magnesian host rocks. The tourmalinization process occurs over a range of metamorphic conditions and with fluids of variable activity of H₂O.  相似文献   

Results from the Huygens probe on Titan     

Jean-Pierre Lebreton  Athena Coustenis  Jonathan Lunine  François Raulin  Tobias Owen  Darrell Strobel 《Astronomy and Astrophysics Review》2009,17(2):149-179

The Cassini–Huygens mission, comprising the NASA Saturn Orbiter and the ESA Huygens Probe, arrived at Saturn in late June 2004. The Huygens probe descended under parachute in Titan’s atmosphere on 14 January 2005, 3 weeks after separation from the Orbiter. We discuss here the breakthroughs that the Huygens probe, in conjunction with the Cassini spacecraft, brought to Titan science. We review the achievements ESA’s Huygens probe put forward and the context in which it operated. The findings include new localized information on several aspects of Titan science: the atmospheric structure and chemical composition; the aerosols distribution and content; the surface morphology and composition at the probe’s landing site; the winds, the electrical properties, and the implications on the origin and evolution of the satellite.  相似文献   

The bias of integrated assessment models that ignore climate catastrophes     

Noah Kaufman 《Climatic change》2012,110(3-4):575-595

Climate scientists currently predict there is a small but real possibility that climate change will lead to civilization threatening catastrophic events. Martin Weitzman has used this evidence along with his controversial “Dismal Theorem” to argue that integrated assessment models of climate change cannot be used to determine an optimal price for carbon dioxide. In this paper, I provide additional support for Weitzman’s conclusions by running numerical simulations to estimate risk premiums toward climate catastrophes. Compared to the assumptions found in most integrated assessment models, I incorporate into the model a more realistic range of uncertainty for both climate catastrophes and societal risk aversion. The resulting range of risk premiums indicates that the conclusions drawn from integrated assessment models that do not incorporate the potential for climate catastrophes are too imprecise to support any particular policy recommendation. The analysis of this paper is more straightforward and less technical than Weitzman’s, and therefore the conclusions should be accessible to a wider audience.  相似文献   

Carbon Dioxide in Star-forming Regions     

Charnley SB  Kaufman MJ 《The Astrophysical journal》2000,535(2):L111-L114

Observations with the Short Wavelength Spectrometer on board the Infrared Space Observatory have led to the first detection of the methyl radical CH(3) in the interstellar medium. The nu(2) Q-branch at 16.5 μm and the R(0) line at 16.0 μm have been unambiguously detected toward the Galactic center Sagittarius A*. The analysis of the measured bands gives a column density of &parl0;8.0+/-2.4&parr0;x1014 cm(-2) and an excitation temperature of 17+/-2 K. Gaseous CO at a similarly low excitation temperature and C(2)H(2) are detected for the same line of sight. Using constraints on the H(2) column density obtained from C(18)O and visual extinction, the inferred CH(3) abundance is &parl0;1.3+2.2-0.7&parr0;x10-8. The chemically related CH(4) molecule is not detected, but the pure rotational lines of CH are seen with the Long Wavelength Spectrometer. The absolute abundances and the CH(3)/CH(4) and CH(3)/CH ratios are inconsistent with published pure gas-phase models of dense clouds. The data require a mix of diffuse and translucent clouds with different densities and extinctions, and/or the development of translucent models in which gas-grain chemistry, freeze-out, and reactions of H with polycyclic aromatic hydrocarbons and solid aliphatic material are included.  相似文献   

Results of recent COCORP profiling in the southeastern United States     

K.D. Nelson  J.H. McBride  J.A. Arnow  D.M. Wille  L.D. Brown  J.E. Oliver  S. Kaufman 《Geophysical Journal International》1987,89(1):141-146

Summary. Recently acquired COCORP profiles in the southeastern United States show that: 1) Reflections associated with the Appalachian detachment are prominent beneath the Inner Piedmont of western Georgia, but do not extend further southeast beneath the Pine Mountain belt. 2) The Brunswick magnetic low is associated with a broad zone of crustal-penetrating dipping reflections that probably marks the Alleghanian suture in the southeastern U.S. 3) The South Georgia basin is a composite feature consisting of several half-graben, locally containing >5 km of Triassic - E. Jurassic basin fill. These basins occur within the interior of the Alleghanian orogen, but are not specifically associated with Alleghanian suture. 4) Across-strike crustal thickness variation, and distribution and character of lower-crust and Moho reflections in the Southern Appalachians is grossly similar to that observed in other parts of the Appalachian/Hercynian orogenic belt. Global comparisons suggest that these regional variations are a consequence of post-collisional extensional tectonics, rather than a primary (Palaeozoic or older) feature of the orogenic belt.  相似文献   

The Atmosphere of Io: Abundances and Sources of Sulfur Dioxide and Atomic Hydrogen     

Darrell F. Strobel  Brian C. Wolven 《Astrophysics and Space Science》2001,277(1-2):271-287

An analysis and interpretation of reflected solar Lyman α intensity data acquired with the Hubble Space Telescope (HST) implies an equatorially confined atmosphere with SO₂ column densities ∼ 1–2 × 10¹⁶ cm^-2. Poleward of 30° the SO₂ density must decrease sharply reaching an asymptotic polar value of < 10¹⁵ cm^-2 at 45° to achieve the observed 2 kR intensity peaks. The corresponding surface reflectivities must be either a constant 0.047 for higher equatorial SO₂ or a variable reflectivity of 0.027 with lower SO₂ densities at the equator increasing to a polar value of ∼ 0.05. The average residence time for an atmospheric SO₂ molecule is ∼ 2–3 days for the canonical mass loading rate of the Io plasma torus = 10³⁰ amu s^-1. With atomic hydrogen in the atmosphere and corona constrained by the HST observations, it is estimated that a pickup proton density ratio of 0.25–0.4% can be sustained by a supply of Io plasma torus protons neutralized in Io's atmosphere/exosphere, if protons constitute 7% of the total torus ion density, which is close to the Chust et al. (1999) pickup proton density ratio and under the widely quoted 10% proton content of the torus. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

HCN formation on Jupiter: The coupled photochemistry of ammonia and acetylene     

Jack A. Kaye  Darrell F. Strobel 《Icarus》1983,54(3):417-433

A model is presented for the formation of HCN in the upper troposphere and lower stratosphere of Jupiter by ultraviolet photolysis of the C₂H₅N isomer aziridine, a product of the recombination of NH₂ and C₂H₃ radicals, which originate, respectively, from ammonia photolysis and addition of H atoms to acetylene. An HCN column density of ～ 2 × 10¹⁷ cm^?2 in the tropopause region, which is comparable to that observed by A. T. Tokunaga, S. C. Beck, T. R. Geballe, J. H. Lacy, and E. Serabyn (Icarus48, 283–289, 1981), is predicted when vertical mixing is slow above the ammonia cloudtops. Sensitivity of the HCN column density to the individual rate constants and the eddy diffusion coefficient profile is discussed, as is the possibility of the existence of additional HCN-yielding pathways. Ammonia, which is saturated in the upper troposphere, is strongly depleted by photolysis in the lower stratosphere. Phosphine is also strongly depleted by photolysis and its abundance in the upper troposphere is shown to depend strongly on vertical mixing in the tropopause region. The possibility of the formation of phosphirane, the P-containing analog of aziridine, is considered but found to be substantially less probable than aziridine.  相似文献   

Data recording and processing for high-resolution frequency analysis     

Pridham  R. Gualtieri  F.  Jr. Kaufman  C. 《Oceanic Engineering, IEEE Journal of》1984,9(2):99-105

This paper discusses the practical considerations associated with analyzing analog data signals to very high resolution in frequency. In the problem considered here, the data set is recorded on analog tape, digitized, and processed on a digital computer. A primary concern is that recorder speed variations, or flutter, can produce artifacts which might become evident when high-resolution spectral analysis is performed. This study concludes that fractional millihertz analysis resolution can be achieved with existing analog tape recorder technology. Another problem which must be considered is the efficient storage of the large data sequences resulting from processing long-time signal records. The use of two-stage frequency analysis is described as an approach to addressing this problem. Finally, the implementation issues associated with the periodogram and AR (autoregressive) estimation algorithms are outlined. It is anticipated that the discussion of practical considerations given here will be useful to researchers who must address problems that are similar to those cited in this paper.  相似文献