Hydrogen fluence in Genesis collectors: Implications for acceleration of solar wind and for solar metallicity     

Gary R. Huss  Elizabeth Koeman‐Shields  Amy J. G. Jurewicz  Donald S. Burnett  Kazuhide Nagashima  Ryan Ogliore  Chad T. Olinger 《Meteoritics & planetary science》2020,55(2):326-351

NASA's Genesis mission was flown to capture samples of the solar wind and return them to the Earth for measurement. The purpose of the mission was to determine the chemical and isotopic composition of the Sun with significantly better precision than known before. Abundance data are now available for noble gases, magnesium, sodium, calcium, potassium, aluminum, chromium, iron, and other elements. Here, we report abundance data for hydrogen in four solar wind regimes collected by the Genesis mission (bulk solar wind, interstream low‐energy wind, coronal hole high‐energy wind, and coronal mass ejections). The mission was not designed to collect hydrogen, and in order to measure it, we had to overcome a variety of technical problems, as described herein. The relative hydrogen fluences among the four regimes should be accurate to better than ±5–6%, and the absolute fluences should be accurate to ±10%. We use the data to investigate elemental fractionations due to the first ionization potential during acceleration of the solar wind. We also use our data, combined with regime data for neon and argon, to estimate the solar neon and argon abundances, elements that cannot be measured spectroscopically in the solar photosphere.  相似文献   

Trace elements and polycyclic aromatic hydrocarbons (PAHs) concentrations in deep Gulf of Mexico sediments     

Terry L. Wade  Yousra Soliman  Stephen T. Sweet  Gary A. Wolff  Bobby J. Presley 《Deep Sea Research Part II: Topical Studies in Oceanography》2008,55(24-26):2585

The concentrations of polycyclic aromatic hydrocarbons (PAHs) and trace elements were determined for surface (top 2 cm) sediment samples collected during the deep Gulf of Mexico benthos (DGoMB) study .These elements and compounds are known to be toxic to organisms at high concentrations and may affect biological communities. There is no indication of major anthropogenic input of the elements Be, Co, Cr, Fe, Si, Tl, V, K, Mg, Ca, Sr and Zn, based on normalization to Al. The concentrations of these metals in the sediment are a function of the relative amounts of trace-metal-rich Mississippi River-derived silicate material and trace-metal-poor plankton-derived carbonate. This is not true for the elements Ba, Ni, Pb, Cd, As, Cu and Mn, whose concentrations show considerable scatter when normalized to Al and a general enrichment. On a normalized basis, Mn is enriched 5–10 fold, Cu and Ni 2–3 fold and Pb 2 fold over Mississippi River-derived material. These enrichments are likely the result of remobilization of metals from depths in the sediment column where reducing conditions exist. The Ba concentrations at selected sites are higher than those of average clay-rich sediments, but are typical of sediments from near oil well platforms in the northern Gulf of Mexico. In the case of Ba, it seems likely that the enrichments, as high as a factor of 10, are due to disposal of oil well drilling mud. The Ba-enriched samples are from the three shallowest water sites in the Mississippi Trough (sites MT1, 2 and 3) and from site C1 and WC5. All are in an area of intense petroleum exploration and development. PAH concentrations are also elevated at MT1, MT3 and C1. The total PAH concentration ranged from not detected (ND) to 1033 ng/g with a mean of 140 ng/g. Even at the sites most enriched in PAHs and trace elements, the concentrations are not at the levels expected to adversely affect the biota. However, these predicted non-effects are based on research using mostly near-shore estuarine species, not on the indigenous species at the sampling sites.  相似文献   

Influence of the Atlantic Multidecadal Oscillation on the winter climate of East China   总被引：11，自引：0，他引：11  

李双林 《大气科学进展》2007,24(1):126-135

The Atlantic Multidecadal Oscillation （AMO）, the multidecadal variation of North Atlantic sea surface temperature （SST）, exhibits an oscillation with a period of 65-80 years and an amplitude of 0.4℃. Observational composite analyses reveal that the warm phase AMO is linked to warmer winters in East China, with enhanced precipitation in the north of this region and reduced precipitation in the south, on multidecadal time scales. The pattern is reversed during the cold phase AMO. Whether the AMO acts as a forcing of the multidecadal winter climate of East China is explored by investigating the atmospheric response to warm AMO SST anomalies in a large ensemble of atmospheric general circulation model （AGCM） experiments. The results from three AGCMs are consistent and suggest that the AMO warmth favors warmer winters in East China. This influence is realized through inducing negative surface air pressure anomalies in the hemispheric-wide domain extending from the midlatitude North Atlantic to midlatitude Eurasia. These negative surface anomalies favor the weakening of the Mongolian Cold High, and thus induce a weaker East Asian Winter Monsoon.  相似文献   

双差定位法在地震丛集精确定位中的应用   总被引：4，自引：0，他引：4       下载免费PDF全文

刘劲松  Kin-Yip Chun  刘福田  郝天珧 《地球物理学进展》2007,22(1):137-141

应用双差定位方法(hypodd)对北美Loma Prieta 地区的分属于3个地震丛集的47个地震进行了精确定位.采用交叉谱法精确求取信号的走时差;同时采用人机联做方式在时域调整、修正按自动方式无法准确提取时差的信号,确保每个事件对的走时差精度.重定位后,在几百米的范围内,原来相互重叠的震源位置聚集为三个明显分离的丛集;水平方向的相对位置平均误差为8.5米,震源深度方向的平均误差为23.4 m.  相似文献   

Revised recommended methods for analyzing crater size-frequency distributions          下载免费PDF全文

Stuart J. Robbins  Jamie D. Riggs  Brian P. Weaver  Edward B. Bierhaus  Clark R. Chapman  Michelle R. Kirchoff  Kelsi N. Singer  Lisa R. Gaddis 《Meteoritics & planetary science》2018,53(4):891-931

Impact crater populations help us to understand solar system dynamics, planetary surface histories, and surface modification processes. A single previous effort to standardize how crater data are displayed in graphs, tables, and archives was in a 1978 NASA report by the Crater Analysis Techniques Working Group, published in 1979 in Icarus. The report had a significant lasting effect, but later decades brought major advances in statistical and computer sciences while the crater field has remained fairly stagnant. In this new work, we revisit the fundamental techniques for displaying and analyzing crater population data and demonstrate better statistical methods that can be used. Specifically, we address (1) how crater size-frequency distributions (SFDs) are constructed, (2) how error bars are assigned to SFDs, and (3) how SFDs are fit to power-laws and other models. We show how the new methods yield results similar to those of previous techniques in that the SFDs have familiar shapes but better account for multiple sources of uncertainty. We also recommend graphic, display, and archiving methods that reflect computers’ capabilities and fulfill NASA's current requirements for Data Management Plans.  相似文献   

Estimating impacts of warming temperatures on California's electricity system     

Jayant A. Sathaye  Larry L. Dale  Peter H. Larsen  Gary A. Fitts  Kevin Koy  Sarah M. Lewis  André Frossard Pereira de Lucena 《Global Environmental Change》2013,23(2):499-511

Despite a clear need, little research has been carried out at the regional-level to quantify potential climate-related impacts to electricity production and delivery systems. This paper introduces a bottom-up study of climate change impacts on California's energy infrastructure, including high temperature effects on power plant capacity, transmission lines, substation capacity, and peak electricity demand. End-of-century impacts were projected using the A2 and B1 Intergovernmental Panel on Climate Change emission scenarios. The study quantifies the effect of high ambient temperatures on electricity generation, the capacity of substations and transmission lines, and the demand for peak power for a set of climate scenarios. Based on these scenarios, atmospheric warming and associated peak demand increases would necessitate up to 38% of additional peak generation capacity and up to 31% additional transmission capacity, assuming current infrastructure. These findings, although based on a limited number of scenarios, suggest that additional funding could be put to good use by supporting R&D into next generation cooling equipment technologies, diversifying the power generation mix without compromising the system's operational flexibility, and designing effective demand side management programs.  相似文献   

A strontium,neodymium and oxygen isotope study of hydrothermal metamorphism and crustal anatexis in the Trois Seigneurs Massif,Pyrenees, France     

M. J. Bickle  S. M. Wickham  H. J. Chapman  H. P. Taylor Jr. 《Contributions to Mineralogy and Petrology》1988,100(4):399-417

Nd, Sr, and O isotope analyses have been made on metamorphic and igneous rocks and minerals from a 310–340 Ma Hercynian-age metamorphic terrane in the Pyrenees, France. Lower Paleozoic shales and phyllites have ⁸⁷Sr/⁸⁶Sr values of 0.707–0.717 at 310 Ma, but model values at 310 Ma of 0.709–0.736 (based on assumed depositional age of 450 Ma and an initial ⁸⁷Sr/⁸⁶Sr=0.707). On a regional scale, ⁸⁷Sr/⁸⁶Sr was homogenized to about 0.713 to 0.717 in the higher-grade pelitic schists during metamorphism. Much of this ⁸⁷Sr/⁸⁶Sr exchange occurred at very low grades (below the biotite isograd), but significant changes also accompanied the δ ¹⁸O lowering of the phyllites (+13 to +16) during their transformation to andalusite- and sillimanite-grade schists (δ ¹⁸O=+11 to +12); all of these effects are attributed to pervasive interactions with hydrothermal fluids (Wickham and Taylor 1985). The data also show that a syn-metamorphic plutonic complex, dominated by a biotite granite body, was derived by mixing of a relatively mafic magmatic end-member (⁸⁷Sr/⁸⁶Sr～ 0.7025–0.7050 and δ ¹⁸O～ +7.5 to +8.0) with two metasedimentary sources, both having ⁸⁷Sr/⁸⁶Sr～0.715 and δ ¹⁸O～ +10.0 to +12.0, but with one being more homogeneous than the other. The more homogeneous component and the (mantle-derived?) magmatic end-member dominate at low structural levels within the complex. The less homogeneous end-member that dominates at high levels is clearly derived from the local Paleozoic pelitic schists. A Rb-Sr age of 330±20 Ma was obtained on hornblende from a deep level within the complex, which fixes this age for the regional metamorphism, as well. Although a post-metamorphic granodiorite magma body at Trois Seigneurs also displays heterogeneities in δ ¹⁸O and ⁸⁷Sr/⁸⁶Sr (and thus does not give a clear-cut Rb-Sr isochron), the data are consistent with an emplacement age between 260 and 310 Ma, similar to ages of other late granodiorites in the Pyrenees. ¹⁴³Nd/ ¹⁴⁴Nd is very uniform within the Hercynian crust, both at Trois Seigneurs (? _Nd=?3 to ?7) and elsewhere in the Pyrenees; almost all igneous lithologies have depleted-mantle, mid-Proterozoic model ages, consistent with efficient recycling of crustal material following original crustal accretion in this area at about 1600 Ma or earlier. Rb-Sr mineral ages exhibit a complex cooling history reflecting late Hercynian and Mesozoic thermal events. Our results show that profound homogenization of the ⁸⁷Sr/⁸⁶Sr and ¹⁸O/¹⁶O ratios of large volumes of the crust can occur during regional metamorphism and crustal anatexis, particularly in regions undergoing extensional tectonics. Such processes can significantly modify the isotopic compositions of the protoliths of granitic magmas; this may explain why many peraluminous Hercynian granitoids of Western Europe have anomalously low (⁸⁷Sr/⁸⁶Sr) initial values compared to their probable sedimentary parent rocks.  相似文献   

Estuarine macrobenthos in Calcasieu Lake,Louisiana: Community and trophic structure     

Gary R. Gaston  DeAnna L. Lee  Jeanne C. Nasci 《Estuaries and Coasts》1988,11(3):192-200

Macrobenthic assemblages in Calcasieu Lake estuary (Louisiana) were sampled at 11 sites from October 1983 through November 1985. The sites were numerically dominated by subsurface-deposit feeders, consisting mostly of polychaetes. Greater densities of macrofauna were collected at the northern (upper) stations of the lake than were collected in West Cove or the southern stations. Abundances of polychaetes, oligochaetes, and amphipods at the upper lake stations accounted for most of the differences among stations. The numerical dominance by detritivores (97% of the fauna) and lack of strong sediment or salinity gradients across the estuary, resulted in an absence of temporal pattern in trophic structure of the macrofauna.  相似文献   

Origin of sheet structure, 1. Morphology and boundary conditions     

Gary R. Holzhausen 《Engineering Geology》1989,27(1-4):225-278

Sheet structure, or large-scale exfoliation, is the division of a rock mass into lenses, plates or “sheets” approximately parallel to the earth's surface. Sheet fractures, which separate the plates, are characterized by surface markings resembling those formed during the brittle fracture of metals, glass and ceramics and those on joints in rock. Lineations, or hackle marks, parallel to the direction of fracture propagation, are common. Branching occurs during propagation so that the fractures appear as many echelon segments in profile. The opposing surfaces of sheet fractures observed in quarry walls and natural exposures are typically in contact. Damage, if any, to rock adjacent to sheet fractures is generally limited to a zone less than one centimeter wide. Sheets tend to parallel preferred orientations of microcracks in many rock masses. Most sheets that are exposed today are of prehistoric origin, but in some rock masses, such as Chelmsford granite in Massachusetts, new sheets continue to form.

Sheet structure forms in environments of high differential stress, dominated by large-scale compression parallel to an exposed rock surface. In parts of the Chelmsford granite the magnitude of this compression is greater than 30 MPa in the zone of sheeting. High differential stresses near the ground surface can result from several natural agents, including contemporary tectonic forces, vertical unloading of a rock mass that formed at depth under high triaxial compression, and suppression of expansion that would otherwise result from temperature increases or chemical alteration of the rock. Exfoliation of boulders during forest fires and spheroidal weathering of boulders appears to occur under similar states of stress, although the agents responsible for the stresses differ.  相似文献   

A ferrotantalite-ferrotapiolite intergrowth from Spittal a.d. Drau,Carinthia, Austria     

Dr. P. Černý  R. Chapman  L. E. Chackowsky  Dr. T. S. Ercit 《Mineralogy and Petrology》1989,41(1):53-63

Summary Intimate intergrowths of ferrotantalite and ferrotapiolite occur in a pegmatite in Spittal a.d. Drau, Carinthia. They are associated with muscovite, albite, smoky quartz, cassiterite, and microscopic uranmicrolite, zircon and uraninite. An assemblage of secondary uranium minerals is also present, generated by extensive alteration and leaching of the uranmicrolite and zircon. Textures of the ferrotantalite-ferrotapiolite intergrowths suggest considerable recrystallization that obliterated most of their primary features; neither coprecipitation nor exsolution can be recognized with certainty. Despite intersecting tielines indicating disequilibrium, the ferrotantalite and ferrotapiolite compositions show very restricted ranges (Mn/(Mn + Fe) 0.08–0.11, Ta/(Ta + Nb) 0.53–0.57 for ferrotantalite, and 0.01–0.04, 0.84–0.89 for ferrotapiolite, respectively), particularly in comparison with compositions from other localities featuring primary textures. A degree of compositional equilibration could have been attained during recrystallization. This process may also explain the high level of structural order characterizing both minerals; they are considerably disordered in other localities. Extensive deformation typical of pegmatites in the southern Ostalpen in general, and specifically of the Spittal pegmatite, is probably responsible for the recrystallization phenomena in the Ta, Nb, Sn-bearing mineral assemblage.

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Eine Ferrotantalit-Ferrotapiolit Verwachsung von Spittal a.d. Drau, Kärnten, österreich

Zusammenfassung In einem Pegmatit von Spittal a.d. Drau, Kärnten, treten enge Verwachsungen von Ferrotantalit und Ferrotapiolit auf. Diese werden von Muskovit, Albit, Rauchquarz, Zinnstein sowie-in mikroskopischem Masstab-von Uranmikrolith und Zirkon begleitet. Die Textur der Verwachsungen lässt Rekristallisation erheblichen Ausmasses erkennen, die die primären Merkmale weitgehend auslöscht. Weder eine gemeinsame Auskristallisation der beiden Mineralphasen noch eine Bildung durch Entmischung kann mit Sicherheit erkannt werden. Trotz einander kreuzender Verbindungslinien, die einen Hinweis auf Ungleichgewicht darstellen, zeigen die Zusammensetzungen des Ferrotantalits und des Ferrotapiolits lediglich geringe Schwankungsbreiten: Mn/(Mn + Fe) 0,08–0,11, Ta/(Ta + Nb) 0,53–0,57 für den Ferrotantalit beziehungsweise 0,01–0,04 und 0,84–0,89 für den Ferrotapiolit. Dies gilt insbesondere für den Vergleich mit Zusammensetzungen solcher Mineralphasen mit jenen von Fundarten, die primäre Verwachsungstrukturen aufweisen. Bis zu einem gewissen Ausmass ist diese homogene Zusammensetzung möglicherweise auf die Rekristallisation zurück zuführen. Diese Rekristallisation könnte auch den hohen strukturellen Ordnungsgrad der beiden Mineralphasen erklären. An anderen Fundorten zeigen diese Minerale strukturell merklich geringeren Ordnungsgrad. Intensive metamorphe überprägung, wie sie für die Pegmatite in den südlichen Ostalpen und insbesondere für jenen von Spittal typisch sind, kann wahrscheinlich als Ursache der Rekristallisationsphänomene der Ta-Nb-Sn Mineralparagenese angenommen werden.

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