A hibonite‐corundum inclusion from Murchison: A first‐generation condensate from the solar nebula     

S. B. Simon  A. M. Davis  L. Grossman  K. D. McKeegan 《Meteoritics & planetary science》2002,37(4):533-548

Abstract— Through freeze‐thaw disaggregation of the Murchison (CM) carbonaceous chondrite, we have recovered a ?90 times 75 μm refractory inclusion that consists of corundum and hibonite with minor perovskite. Corundum occurs as small (?10 μm), rounded grains enclosed in hibonite laths (?10 μm wide and 30–40 μm long) throughout the inclusion. Perovskite predominantly occurs near the edge of the inclusion. The crystallization sequence inferred petrographically‐corundum followed by hibonite followed by perovskite‐is that predicted for the first phases to form by equilibrium condensation from a solar gas for P^tot ≤5 times 10^?3 atm. In addition, the texture of the inclusion, with angular voids between subhedral hibonite laths and plates, is also consistent with formation of the inclusion by condensation. Hibonite has heavy rare earth element (REE) abundances of ?40 × CI chondrites, light REE abundances ?20 × CI chondrites, and negative Eu anomalies. The chondrite‐normalized abundance patterns, especially one for a hibonite‐perovskite spot, are quite similar to the patterns of calculated solid/gas partition coefficients for hibonite and perovskite at 10^?3 atm and are not consistent with formation of the inclusion by closed‐system fractional crystallization. In contrast with the features that are consistent with a condensation origin, there are problems with any model for the formation of this inclusion that includes a molten stage, relic grains, or volatilization. If thermodynamic models of equilibrium condensation are correct, then this inclusion formed at pressures <5 times 10^?3 atm, possibly with enrichments (<1000x) in CI dust relative to gas at low pressures (below 10^?4 atm). Both hibonite and corundum have δ17O ? δ18O ? ?50%, indicating formation from an 16O‐rich source. The inclusion does not contain radiogenic ²⁶Mg and apparently did not contain live ²⁶Al when it formed. If the short‐lived radionuclides were formed in a supernova and injected into the early solar nebula, models of this process suggest that ²⁶Al‐free refractory inclusions such as this one formed within the first ?6 times 10⁵ years of nebular collapse.  相似文献   

Refractory inclusions in the pristine carbonaceous chondrites DOM 08004 and DOM 08006          下载免费PDF全文

Steven B. Simon  Lawrence Grossman 《Meteoritics & planetary science》2015,50(6):1032-1049

The Antarctic carbonaceous chondrites DOM 08004 and DOM 08006 have been paired and classified as CO3.0s. There is some uncertainty as to whether they should be paired and whether they are best classified as CO chondrites, but they provide an opportunity for the study of refractory inclusions that have not been modified by parent body processes. In this work, refractory inclusions in thin sections of DOM 08004 and 08006 are studied and compared with inclusions in ALHA77307 (CO3.0) and Acfer 094 (C3.0, ungrouped). Results show that the DOM samples have refractory inclusion populations that are similar to each other but not typical of CO3 chondrites; main differences are that the DOM samples are slightly richer in inclusions in general and, more specifically, in the proportions of grossite‐bearing inclusions. In DOM 08004 and DOM 08006, 12.4% and 6.6%, respectively, of the inclusions are grossite‐bearing. This is higher than the proportion found in Acfer 094 (5.2%), whereas none were found in ALHA77307. Like those in Acfer 094, DOM inclusions are small (mostly <100 μm across) and fine‐grained, and thin rims of aluminous diopside±melilite are very common. Also like Acfer 094, most phases in the DOM inclusions have FeO contents higher than expected for primary refractory phases. In addition to typical inclusions, some unusual ones were found in DOM 08004, including a perovskite‐rich one with a rare, recently reported Sc‐, Al‐oxide and davisite; a very grossite‐rich inclusion with a small, hibonite‐rich core enclosed in a grossite mantle; and a relict, grossite‐rich inclusion enclosed in an Al‐rich chondrule. The CAI populations in the DOM samples are similar to each other and, based on grossite abundances, FeO enrichments and occurrences of rims are more Acfer 094‐like than CO3‐like. An earlier history on an FeO‐rich parent was previously favored over nebular equilibria or in situ reactions to account for FeO enrichments in CAIs in the otherwise pristine chondrite Acfer 094, and a similar history is indicated for the DOM CAIs. Acfer 094, DOM 08004 and 08006 might best be classified as a new subgroup of CO3 chondrites.  相似文献   

WMO     

LLOYD W. SWIFT JR  WAYNE T. SWANK 《水文科学杂志》2013,58(3):245-246

ABSTRACT

Long term changes in streamflow following forest cutting are presented for three experimental basins at Coweeta Hydrologic Laboratory, North Carolina, USA. Previous analyses have shown that, following forest cutting, streamflow increases and then declines with the logarithm of time as the forest regrows. Recent data indicate that the streamflow decline following cutting is related to vegetation regrowth, but the relationship is not a consistent function of simple stand measurements. The mixed hardwood forest of one basin was clearcut twice in the past 40 years. During the second regrowth period, streamflow increases after the first year were about one-half the increases at the same points in time after the first treatment. Concurrent with the second cutting, two other basins were cut whose mid-elevations are 400 m higher. The increases for the upper basins were similar, even though basal area was reduced by only 65% on one. Both streamflow increases were less than for either cutting on the lower basin. Variability of flow increases for the three concurrent treatments is similar and appears partly related to precipitation.  相似文献   

The Meteoritical Bulletin,No. 81, 1997 Jul     

Jeffrey n. Grossman 《Meteoritics & planetary science》1997,32(Z4):A159-A166

Abstract— Meteoritical Bulletin, No. 81 lists 181 new meteorites. Noteworthy among these are a new lunar meteorite (Dar al Gani 262), four observed falls (Dong Ujimqin Qi, Galkiv, Mount Tazerzait, and Piplia Kalan), four irons (Albion, Great Sand Sea 003, Hot Springs, and Mont Dieu), two mesosiderites (Dong Ujimqin Qi and Lamont), an acapulcoite (FRO 95029), a eucrite (Piplia Kalan), two probably-paired ureilites (Dar al Gani 164 and 165), an R chondrite (Hammadah al Hamra 119), an ungrouped type-3 chondrite (Hammadah al Hamra 180), a highly unequilibrated ordinary chondrite (Wells, LL3.3), and a variety of carbonaceous and unequilibrated ordinary chondrites from Libya and Antarctica. All italicized abbreviations refer to addresses listed in the appendix.  相似文献   

Geographical information systems and planning in the USA: selected municipal adoption trends and educational concerns     

WILLIAM R. GORDON JR  NADER M. SOUBRA 《International journal of geographical information science》2013,27(4):267-278

Abstract

Practitioners and academics from many fields of study are currently facing numerous issues involving the diffusion of technologies from geographical information systems within their respective professions. This paper has two aims. The first is to report the partial results of a postal survey of selected municipal planning departments in the U.S.A. In measuring trends related to the adoption of computer and geographical information system technologies, the survey focuses on the availability of trained geographical information system and computer literate staff and on alternative means of training existing staff, as well as on the adequacy of collegiate education. The presentation of survey results is used to establish a framework for the principal discussion of this paper. The second part examines the relationship between planning and education in geographical information systems. Parallels within other disciplines and professions are derived. Curricula and training considerations within academic programmes and professional practice are suggested.  相似文献   

Characterization and origin of dissolved organic carbon in Yegua ground water in Brazos County, Texas     

Routh J  Grossman EL  Murphy EM  Benner R 《Ground water》2001,39(5):760-767

Dissolved organic carbon (DOC) concentrations in five shallow (< 20 m) and three deeper wells (27 to 30 m) in the Eocene Yegua Formation (Brazos County in east-central Texas) ranged from 92 to 500 microns. Characterization of high, intermediate, and low molecular weight DOC fractions (HMW > 3000 amu, IMW 1000 to 3000 amu, and LMW 500 to 1000 amu) and combined neutral sugar analyses provide information on organic matter sources in the Yegua aquifers. Combined neutral sugars ranged in concentration from 0.6 to 2.7 mumol/L and comprised 0.8% to 6.7% of DOC in ground water. Glucose was the most abundant neutral sugar, followed by xylose and galactose, arabinose, mannose, rhamnose, and fucose. These combined neutral sugars were more diagenetically altered in shallow, oxic ground water as indicated by high mole % fucose + rhamnose and low neutral sugar yield. The precursors for neutral sugars are most probably angiosperm leaves, which show a similar distribution pattern of neutral sugars. Ground water DOC was depleted in 13C relative to soil-zone organic matter (OM) (-16@1000 to -19@1000). The delta 13C values of bulk DOC and HMW DOC ranged from -24@1000 to -32@1000, whereas LMW and IMW DOC ranged from -32@1000 to -34@1000 and -16@1000 to -28@1000, respectively. This variability in delta 13C values is probably related to microbial processes and selective preservation of OM. Carbon isotope analyses in bulk and different molecular weight DOC fractions imply a predominantly C3 OM source and a low contribution of soil-zone OM to DOC.  相似文献   

Size Selective Predation by the Asteroid Pisaster ochraceus on the Bivalve Mytilus calif ornianus: A Cost-Benefit Analysis     

James B.  Mcclintock Truman J.  Robnett JR. 《Marine Ecology》1986,7(4):321-332

Abstract. When simultaneously presented with equal numbers of four sizes of clumped Mytilus californianus (20, 35, 55 and 85 mm shell length), Pisaster ochraceus (arm length of 70-110mm R) showed a preference for the medium sizes (35 and 55mm length). Prey-size preference was positively correlated with predator size. Mean prey-digestion times (insertion of the stomach, opening of the valves and digestive period) decreased significantly following fiiing of an artificial gape between the valves of mussels. When presented with different sizes of clumped filed mussels, starfish still chose medium mussels, indicating that stomach insertion, valve opening, and digestion rate may not be important constraints determining size selective predation. Measurements of the force required to dislodge mussels from the substratum and conspecifics showed an increasing exponential relationship with mussel size. Size selective feeding may be an energy maximizing and time minimizing strategy, where energy gained from choosing larger mussels is balanced against disproportionately increased costs in energy and time of removing large mussels from the substratum.  相似文献   

Planning the American Indian Reservation: From Theory to Empowerment          下载免费PDF全文

Zoltán Grossman 《Geographical review》2018,108(1):168-170

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An analysis of vertical velocity spectra obtained in the bomex fair-weather,trade-wind boundary layer   总被引：1，自引：1，他引：1  

Robert L. Grossman 《Boundary-Layer Meteorology》1982,23(3):323-357

Spectra of vertical velocity fluctuations measured on board an aircraft flying over the sea along and across the wind during the Barbados Oceanographic and Meteorological Experiment (BOMEX) are stratified and composited according to estimates of the Monin-Obukhov stability length. This was done to test the hypothesis that a hierarchy of physical mechanisms, responding to wind shear and buoyancy, is active in the turbulent transfer processes of the oceanic subcloud layer. Despite the possibility that the data contain a heading-independent bias, it is concluded that a major change of eddy structure occurs over a narrow range of stability. This agrees well with an early theory on convection over land and observations of herring gull flight characteristics. The vertical variation of the spectral-composites compares favorably with other observations over land and sea. Physical models are suggested to explain the data. One of these models is in agreement with theoretical results concerning ringlike convection. The spectral data, which begin to lose confidence at about 10 km, suggest that a limiting size of eddies over the ocean is approximately twice the depth of the subcloud layer (in this case 600 m) regardless of the kind of eddy structure.The National Center for Atmospheric Research is sponsored by the National Science Foundation.  相似文献   

Mineralogy, Petrology, and Magmatic Conditions from the Fish Canyon Tuff, Central San Juan Volcanic Field, Colorado   总被引：2，自引：4，他引：2  

WHITNEY  JAMES A.; STORMER  JOHN C.  JR. 《Journal of Petrology》1985,26(3):726-762

The Fish Canyon Tuff is one of the largest currently recognizedash-flow tuffs (> 3000 km³). It is a crystal-rich quartzlatite containing about 40 per cent phenocrysts of plagioclase,sanidine, biotite, hornblende, quartz, magnetite, sphene, andilmenite. Pyrrhotite occurs as inclusions in magnetite, sphene,and hornblende. The consistency of mineralogy and whole rockchemistry confirms that the Fish Canyon tuff is remarkably homogeneous.Most chemical variations can be accounted for by phenocryst-matrixfractionation, probably due to glass winnowing during eruptionand emplacement. The composition of the parent magma, correctedfor such winnowing, is very similar to that of calc-alkalinebatholiths such as the Boulder and the Sierra Nevada batholiths. Fe-Ti oxide geothermometers indicate temperatures of 800 ? 30?C for most of the outflow tuff. No evidence for a regular thermalgradient in the magma chamber could be detected. Two feldsparand Fe-Ti oxide equilibria indicate that the magma developedat depths of 25 to 30 km (about 9 kb pressure), and was eruptedwithout time for phenocryst re-equilibration. The reconstructedcomposition of the liquid in equilibrium with the phenocrystsalso suggests a deep source for this ash flow. A late, upperpackage of flow units have mineralogical characteristics whichmay reflect partial re-equilibration in a shallower environment. Oxygen fugacities are moderately high (log fO₂ = — 11.5?0.3) but are similar to those obtained from other continentalcalc-alkaline ash-flow tuffs. The water fugacity is limitedby calculations using biotite equilibria and experimental workrelating to the stability of the phenocryst assemblage. Bestestimates are that water fugacity was 2000 ? 1000 bars. Theactivities of sulphurous gases are estimated at fSO₂ = 2 to4 bars, fso₂ = 150 to 200 bars, fH₂S = 70 to 80 bars. The Fish Canyon Tuff therefore came from a deep, homogeneous,granitic magma body of batholithic proportions. Calculationsof its probable viscosity, density, and size indicate that thesystem should convect with any reasonable thermal gradient.Convective mixing may account for the homogeneity of the parentmagma body.  相似文献