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151.
R. F. Griffin 《Journal of Astrophysics and Astronomy》1981,2(1):115-118
Photoelectric radial-velocity measurements show that 26 Comae is a spectroscopic binary with a very eccentric orbit and a
period of 972 days.
An erratum to this article is available at . 相似文献
152.
153.
We report measurements of the Jupiter brightness spectrum in the 850-μm and 1100-μm atmospheric windows with a spectral resolution of 125 MHz, obtained with a Fourier transform spectrometer on the James Clerk Maxwell Telescope. Three results were obtained. First, the predicted absorption features due to the rotational lines of HCN at 266 and 354 GHz were not detected within our error limits of less than 1%. We establish new upper limits for the HCN abundance in the jovian troposphere for five assumed abundance distributions and for two assumed NH3abundances. The upper limits are 1.7 to 13 times smaller than the abundance value obtained in the only reported detection of HCN in Jupiter prior to the impact of Shoemaker–Levy 9. Second, the continuum brightness temperature spectrum at 850 μm was determined and is in agreement with previous measurements, but has large error bars due to uncertainties in the photometric calibration. We estimate the ammonia abundance in the 1–2 bar region to be 1.7 times solar, but this result is tentative since scattering by NH3cloud particles and absorption by gaseous H2S were neglected in our atmospheric model. Finally, the first rotational line of PH3at 267 GHz was not detected, a result which we demonstrate is consistent with the statistical noise level in these measurements, with current values of the spectroscopic parameters, and with phosphine measurements at other wavelengths. 相似文献
154.
Summary Clinopyroxene phenocrysts in six samples, representing the compositional range in the alkaline rocks of the region, range overall from aluminian titanian diopside (mg = Mg/[Mg + Fe
t
] = 92) to aegirine (mg = 17), but Ca-pyroxenes are dominant (90% of 851 analyses), Ca-Na pyroxenes minor ( 10%) and Na-pyroxenes rare ( 1%). Pyroxenes in associated subalkaline rocks (dolerites and basalts) are lower-Ca augites of distinct trend. Al and Ti correlate positively in the alkaline rock pyroxenes, but negatively with Si, mirroring decreasing CaTiAl2O6 and CaSiAl2O6 components in more felsic host-rocks. Although the most evolved pyroxenes in each host-rock show increasingna (Na/[Na + Ca]) and Zr and decreasingmg as host-rock mg decreases, the most primitive pyroxenes in each host-rock do not change, implying they are not at equilibrium. Over 40 paired logitudinal and lateral traverses across 21 phenocrysts reveal very complex zoning, in which up to five growth zones can be recognized in one crystal, separated by either sharp contacts or gradual transitions. These individual zones may show one of seven zoning trends:normal (na asmg moving outwards towards the rim),reverse (na asmg ),inverse (na asmg ),converse (na asmg ),unzoned (no change),symmetric (na andmg display complementary and trends), oroscillatory (superimposed on normal, reverse or unzoned). Ten distinct crystal types can also be recognized, showing particular sequences of zoning trends: for example, Type 1 shows a green, relatively sodic core surrounded by a more primitive rim or overgrowth, and has similar longitudinal and lateral zoning; whereas Type 6 shows extremely erratic variations which differ longitudinally and laterally. Up to four of these types were found in one host-rock, with little pattern in their distribution between different host-rocks. These pyroxenes are believed to record an intricate history of stop-start differentiation, complicated by magma-mixing, entry or disappearance of coprecipitating phases, and inheritance of high-pressure precipitates. Apparently random superimposed variations of Al, Ti and Si within some individual growth zones most probably reflect kinetic (disequilibrium) effects, due to rapid growth and/or supercooling.
Deceased
With 11 Figures 相似文献
Alkaligesteine und Karbonatite von Amba Dongar und Umgebung Deccan Alkali-Provinz, Gujarat, Indien. 2. Komplex zonierte Klinopyroxenkristalle
Zusammenfassung Klinopyroxenkristalle in sechs Proben, die das ganze Spektrum der Zusammensetzung der Alkaligesteine des Gebietes repräsentieren, schwanken von Aluminium-Titandiopsid (mg = Mg/[Mg + Fe t ] = 92) bis Aegirin (mg = 17), aber C-Pyroxene dominieren (90% von 851 Analysen). Ca-Na-Pyroxene sind Nebengemengteile (10%) und Na-Pyroxene sind selten ( 1%). Pyroxene in assoziierten subalkalischen Gesteinen (Dolerite und Basalte) sind Ca-arme Augite eines eigenständigen Trendes. Al und Ti korrelieren positiv in den Pyroxenen der Alkaligesteine, aber negativ mit Si, und dies spiegelt abnehmende CaTiAl2O6 und CaSiAl2O6 Komponenten in den mehr felsischen Wirtsgesteinen wider. Obwohl Pyroxene in jedem Wirtsgestein zunehmende na-Werte (Na/[Na + Ca]) und Zr-Gehalte und mit demmg des Wirtsgesteines auch abnehmendemg-Werte zeigen, lassen die primitivsten Pyroxene in jedem Wirtsgestein keine Änderung erkennen. Dies weist darauf hin, daß sie nicht im Gleichgewicht sind. Über vierzig paarweise angelegte Längs- und Quertraversen über 21 Kristalle zeigen sehr komplexen Zonarbau, in dem bis zu fünf Wachstumszonen in einem Kristall erkannt werden können, die entweder von scharfen Kontakten oder von graduellen Übergangszonen getrennt werden. Diese individuellen Zonen können einen der folgenden sieben Trends erkennen lassen: Normal (na ;mg ; von innen gegen den Rand zu), reverse (na ,mg ), invers (na undmg ), konvers (na ,mg ), unzoniert (keine Änderung), symmetrisch (na undmg zeigen komplementäre und Trends), oder oszillierend (überlagert den normalen, reversen oder unzonierten Trend). Weiters können zehn definierte Kristalltypen erkannt werden, die besondere Abfolgen von Trends der Zonierung erkennen lassen. Zum Beispiel zeigt Typ 1 einen grünen, relativ Na-reichen Kern, umgeben von einem mehr primitiven Rand oder Überwachsungen, wobei die Zonierung in Längs- und Querrichtung ähnlich ist. Demgegenüber zeigt Typ 6 außerordentlich unregelmäßige Zonierungen, die in Längs- und Querschnitten verschieden sind. Bis zu vier dieser Typen wurden in einem Wirtsgestein nachgewiesen, und sie ließen keine deutlichen Verteilungsmuster zwischen verschiedenen Wirtsgesteinen erkennen. Es wird angenommen, daß diese Pyroxene eine komplexe geschichte von stop-start Differentiation wiedergeben, die durch Magmamischung, durch die Zufuhr oder das Verschwinden von gleichzeitig ausfallenden Phasen und durch die Übernahme von Hochdruck-Bildungen weiter kompliziert wird. Unregelmäßig überlagerte Variationen von Al, Ti und Si innerhalb einzelner Wachstumszonen reflektieren sehr wahrscheinlich kinetische (Ungleichgewicht) Effekte, die auf sehr rasches Wachstum und/oder Überkühlung zurückgehen.
Deceased
With 11 Figures 相似文献
155.
J.P. Zheng M. Sun W.L. Griffin M.F. Zhou G.C. Zhao P. Robinson H.Y. Tang Z.H. Zhang 《Chemical Geology》2008,247(1-2):282-304
The Dabie ultrahigh-pressure (UHP) metamorphic belt, central China, contains two contrasting types of ultramafic–mafic complex. The Bixiling peridotite in the southern Dabie terrane contains abundant garnet (21–32 vol.%) and thus has high CaO +Al2O3 (9.94–15.3 wt.%). The peridotite also has high REE contents with flat REE patterns, high contents of S and other incompatible trace elements, together with low-Mg# olivine and pyroxene and low Ni and PGE contents. Zircons from this peridotite mostly have low Th/U ratios, interpreted to reflect a metamorphic origin, and give dominantly Triassic ages (ca. 210 Ma). Other zircons with high Th/U ratios give upper intercept ages of 745 Ma. Most zircons have positive ?Hf (+- 3.6 ~ +- 8.1) values with depleted-mantle model ages (TDM) of 0.6–1.0 Ga (mean 0.8 Ga) and crustal model ages (Tcrust) of 0.8–1.4 Ga (mean 1.1 Ga). We interpret that the Bixiling complex was formed as cumulates in a Neoproterozoic asthenosphere-derived magma chamber in the continental crust, and was later carried to garnet-stable depths (ca. ~ 4.4 GPa) during the subduction of the Yangtze Craton in the Triassic. In contrast, the Raobazhai peridotite in the northern Dabie terrane was metamorphosed at lower P/T conditions (i.e. 15 Kb and 1000 °C). All zircon grains from the peridotite yield Triassic ages (ca. 212 Ma) and have negative ?Hf values (? 16.6 ~ ? 3.2), Mesoproterozoic model ages (TDM = 1.0–1.5 Ga) and Paleoproterozoic crustal model ages (Tcrust = 1.5–2.3 Ga). The peridotite is enriched in LREE ((La/Yb)n ≈ 3.5), has high-Mg# olivine and pyroxene, high Ni and PGEs but low Pd/Ir (mean 3.0). It represents a highly refractory residue of partial melting (up to 18%) of primitive mantle, and is similar to the cratonic mantle xenoliths in Phanerozoic igneous rocks from the eastern North China Craton (e.g. Mengyin and Hebi areas). Negative Ce, Eu and HFSE anomalies in the peridotites suggest that their protolith was derived from the shallow part of the mantle wedge (e.g. plagioclase-stable field) of the North China Craton, and was pulled to a deeper level (e.g. spinel-stable field) during the subduction of the Yangtze Craton. The mantle wedge, like peridotitic xenoliths in the Jurassic Xinyang diatremes at the southern edge of the North China Craton, was metasomatised by fluids/melts released from the subducted continental crust. The fragments of this modified mantle wedge were incorporated into the Yangtze crust during its subduction. 相似文献
156.
With continued population growth and increasing use of fresh groundwater resources, protection of this valuable resource is critical. A cost effective means to assess risk of groundwater contamination potential will provide a useful tool to protect these resources. Integrating geospatial methods offers a means to quantify the risk of contaminant potential in cost effective and spatially explicit ways. This research was designed to compare the ability of intrinsic (DRASTIC) and specific (Attenuation Factor; AF) vulnerability models to indicate groundwater vulnerability areas by comparing model results to the presence of pesticides from groundwater sample datasets. A logistic regression was used to assess the relationship between the environmental variables and the presence or absence of pesticides within regions of varying vulnerability. According to the DRASTIC model, more than 20% of the study area is very highly vulnerable. Approximately 30% is very highly vulnerable according to the AF model. When groundwater concentrations of individual pesticides were compared to model predictions, the results were mixed. Model predictability improved when concentrations of the group of similar pesticides were compared to model results. Compared to the DRASTIC model, the AF model more accurately predicts the distribution of the number of contaminated wells within each vulnerability class. 相似文献
157.
Frederick J. Griffin Theresa DiMarco Karl L. Menard Joe A. Newman Edmund H. Smith Carol A. Vines Gary N. Cherr 《Estuaries and Coasts》2012,35(5):1229-1236
Pacific herring early life stages provide good model systems for studying effects of suspended sediments on estuarine organisms. To investigate effects on the herring larval stage, we used environmentally relevant particle concentrations for San Francisco Bay (200?C400?mg/L of particles <50???m in size) and exposure times of 16?h in a novel two-pump sediment suspension mesocosm. There were no mortalities during the 16-h suspended sediment incubation. Following sediment exposure, larvae were cultured in sediment-free water for up to 10?days during which survival and condition were measured. None were affected by previous sediment treatment. Four criteria for larval condition included growth, heart rate, prey capture, and critical swimming velocity. These results provide a framework for implementing regulatory decisions on anthropogenic activities such as dredging. 相似文献
158.
Kreshimir Nenadovitch Malitch Elena A. Belousova William L. Griffin Inna Yu Badanina Norman J. Pearson Sergey L. Presnyakov Evgeniya V. Tuganova 《Contributions to Mineralogy and Petrology》2010,159(6):753-768
The ultramafic–mafic Kharaelakh intrusion in the northwestern part of the Siberian Craton (Russia) hosts major economic platinum-group-element
(PGE)–Cu–Ni sulphide deposits. In situ U–Pb, REE and Hf-isotope analyses of zircon from these rocks, combined with detailed
study of crystal morphology and internal structure, identify four zircon populations. U–Pb ages of these populations cover
a significant time span (from 347 ± 16 to 235.7 ± 6.1 Ma) suggesting multiple magmatic events that cluster around 350 and
250 Ma, being consistent with two recognised stages of active tectonism in the development of the Siberian Craton. The oldest
zircon population, however, represents previously unknown stage of magmatic activity in the Noril’sk area. Epsilon-Hf values
of +2.3 to +16.3 in the analysed zircons reflect a dominant role of mantle-derived magmas and suggest that juvenile mantle
material was the main source for the ultramafic–mafic Kharaelakh intrusion. A significant range in initial 176Hf/177Hf values, found in zircons that cluster around 250 Ma, indicate mixing between mantle and crustal magma sources. Our findings
imply that economic intrusions hosting PGE–Cu–Ni deposits of the Noril’sk area have a far more complex geological history
than is commonly assumed. 相似文献
159.
C. D. Scarfe † R. F. Griffin † R. E. M. Griffin † 《Monthly notices of the Royal Astronomical Society》2007,376(4):1671-1679
HR 6046 has long been known as a single-lined binary system, for which preliminary orbital solutions were given in the 1930s, but the nature of the secondary star in the system has to date appeared puzzling. The rather large masses which the component stars were once believed to possess caused much speculation that the secondary was a 'collapsed star', and the large mass function that was originally published encouraged determined, but unsuccessful, efforts to be made to resolve the system by optical interferometry. We have observed the system as a double-lined binary, and now present the orbit. We are unable to specify the exact nature of the secondary star, whose mass is only slightly less than that of the primary, but comparison with late-type standard spectra suggests that it is an evolved star, while the primary is a giant somewhat cooler than the published spectral type indicates. The Hipparcos parallax is consistent with such a model for the system, but it is possible that it is vitiated by the photocentric motion. Our new orbital elements and their improved level of precision show conclusively that the system is by no means as exotic as was once thought. 相似文献
160.
For over a decade, the Hopi Tribe and Navajo Nation of northeastern Arizona have suffered the effects of persistent drought conditions. Severe dry spells have critically impacted natural ecosystems, water resources, and regional livelihoods including dryland farming and ranching. Drought planning and resource management efforts in the region are based largely on the instrumental climate record, which contains a limited number of severe, sustained droughts. In this study, a new network of moisture-sensitive tree-ring chronologies provides the basis for evaluating the longer-term temporal variability of precipitation in the Four Corners region. By analyzing the earlywood and latewood components within each annual tree ring, we are able to generate separate, centuries-long reconstructions of both cool- (October-April) and warm-season (July-August) precipitation. These proxy records offer new insights into seasonal drought characteristics and indicate that the instrumental record fails to adequately represent precipitation variability over the past 400 years. Through the use of two different analysis techniques, we identify multiyear and decadal-scale drought events more severe than any in the modern era. Furthermore, the reconstructions suggest that many of the historically significant droughts of the past (e.g., 17th century Puebloan drought) were not merely winter phenomena, but persisted through the summer season as well. By comparing these proxy records with historical documents, we are able to independently validate the reconstructions and better understand the socioeconomic and environmental significance of past climate anomalies on the tribal lands of northeastern Arizona. 相似文献