Infrared CO emission and disks around young stars     

John S. Carr 《Astrophysics and Space Science》1995,224(1-2):25-28

High-resolution near-infrared spectroscopy of CO overtone emission bands has provided some of the best kinematic evidence for the existence of circumstellar disks around young stars. The CO emission flux and the detailed shape of the overtone bands are well matched by simple Keplerian disk models. A brief overview of the use of infrared CO emission as a diagnostic of the kinematics and conditions of gas in the inner disks of young stars is presented.  相似文献   

Carbon Stable Isotope Analyses of Individual Deep-Sea Spherules     

I. P. Wright  R. H. Carr  C. T. Pillinger 《Meteoritics & planetary science》1988,23(4):339-347

Abstract— A preliminary investigation into the carbon isotopic composition of deep-sea spherules has been undertaken. A variety of particles have been analysed including both melted and unmelted samples of type S (stony) and type I (iron) spherules, emphasis being placed on surveying the carbon in different sorts of particles rather than analysing large numbers of samples. Some general observations can be made: there appear to be four different sorts of carbonaceous materials in the spherules. Melted and unmelted spherules of either type I or S, apparently contain two forms of low temperature combustible carbon distinguished, not by combustion temperature, but by isotopic composition. The low temperature of combustion is commensurate with these forms of carbon being organic in nature. The most likely explanation for this carbon is terrestrial biogenic contamination although there exists the possibility that there are some indigenous organic materials. Unmelted type S spherules contain a high temperature carbon component, characterised by a very minor ¹³C-enrichment, which is considered to be indigenous to the sample. All melted samples contain only small amounts of high temperature carbon with an isotopic composition suggestive of handling blank.  相似文献   

Mechanics of particulate materials. The principlesJaroslav Feda, Developments in Geotechnical Engineering, 30, Elsevier, Amsterdam (1982), 447 pp., US $86.00, Dfl. 185.00 (hardcover)     

John S. Carr 《Engineering Geology》1984,20(3):271-272

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Rethinking the Land: An Exhibition of Ulster Maps     

Garrett Carr 《The Cartographic journal》2017,54(2):173-180

The author curates a touring exhibition of Northern Ireland cartography, called Mapping Alternative Ulster. The project emerged from a dissatisfaction with how Northern Ireland is represented in maps, and one example is given. To counter them, he sought independent cartographers making original maps. The curator discusses the criteria he applied when selecting work for the show. He wanted maps with politics, although not the region’s traditional sectarian politics. All the selected maps constitute arguments, critiquing problems in the lived environment or drawing attention to valuable things that may be at risk. The latter sections of the article discuss five of the contributors and looks at their work in detail. In the conclusion, the impact of the exhibition is assessed by examining visitor comments. The paper is illustrated.  相似文献   

Cross-arc geochemical variations in volcanic fields in Honduras C.A.: progressive changes in source with distance from the volcanic front   总被引：1，自引：0，他引：1  

Lina C. Patino  Michael J. Carr  Mark D. Feigenson 《Contributions to Mineralogy and Petrology》1997,129(4):341-351

A geochemical traverse across Honduras reveals the heterogeneity of the mantle underneath Central America. Alkali basalts from Lake Yojoa (170 km behind the front) have low ⁸⁷Sr/⁸⁶Sr but high La/Yb, and elevated incompatible trace element abundances, consistent with derivation from a normal mid-ocean ridge basalt source mantle via low degrees of melting. These lavas lack evidence for an enriched source thought to be intermingled with normal mid-ocean ridge basalt source mantle beneath most of Central America. The amplitude of the subducted slab signature decreases smoothly with distance from the volcanic front. Lavas from Zacate Grande, the area nearest to the volcanic front (17 km behind the arc), display large ion lithophile element enrichment and high field strength element depletion indicating the involvement of subducted material in magma genesis. Components of subducted material are not evident in lavas from Lake Yojoa, the area furthest from the arc. Basalts and basaltic andesites from Tegucigalpa, 102 km behind the volcanic front, are geochemically intermediate between those of Lake Yojoa and Zacate Grande. The lavas from Tegucigalpa show a decreased influence of the subduction component, and are affected by assimilation-fractional crystallization processes at shallow depths. The gradual decrease in the subducted component from the volcanic front to Zacate Grande, Tegucigalpa and finally Lake Yojoa contrasts with the abrupt decrease documented for southeast Guatemala, the only other area in Central America where a cross-arc transect has been studied. Received: 1 July 1995 / Accepted: 16 July 1997  相似文献   

Application of spatial filter theory to kriging     

James R. Carr 《Mathematical Geology》1990,22(8):1063-1079

Data-processing requirements for remotely sensed, digital images include spatial filtering to suppress image noise, enhance edges/contacts, and improve image clarity. Spatial filter theory demonstrates that the addition of a high-pass filtered image to a low-pass filtered image yields the original digital image. Application of this principle in kriging can be accomplished by using the same covariance matrix to solve for two weighting vectors to yield a result analogous to low- and high-pass filtering. The addition of kriged estimates calculated using both weighting vectors is analogous to summing high-, and low-pass filtered digital images. This modified method of kriging yields estimates associated with less smoothing compared to ordinary kriging. Statistical moments of original sample data are better preserved through estimation by this method.  相似文献   

The effects of tributyltin within aThalassia seagrass ecosystem     

John R. Kelly  Suzanne N. Levine  Linda A. Buttel  Kelly A. Carr  David T. Rudnick  R. Dana Morton 《Estuaries and Coasts》1990,13(3):301-310

Flow-through seagrass core microcosms were used to examine responses of species and processes to a logarithmic gradient of dosing with¹⁴C-labeled tributyltin-chloride (TBT-CI). Experiments involved delivery of TBT-CI to the water column of replicate cores of a treatment (n=16) once per week; one-half of the cores were sacrificed after 3 wk of dosing, the others were dosed for 6 wk. Initial water column concentrations for the three treatments averaged 0.205, 2.23, and 22.21 μg I^?1, expressed as the TBT⁺ cation, but these concentrations dropped rapidly. Retained¹⁴C tracer, an estimate of total organotin species, was distributed to sediments, plants, and other biological tissues, all of whose tracer concentrations increased with time. Measures to indicate responses of both autotrophic and heterotrophic organisms were made; in general, treatment effects were demonstrable statistically only at the highest dose level. Accumulation of chlorophyll and biomass on glass slides was highest when suspended for the entire experiment in the water of the highest treatment; this unexpected result was perhaps an indirect effect related to reduced grazing activity in the microcosms. The highest dose of TBT-CI resulted in virtual population mortality of a few macrobenthic species and decreased loss of plant material in litter bags, both demonstrated within the first 3 wk of dosing. Reduced litter loss was coincident with mortality of an amphipod (Cymadusa compta) capable of shredding plant material, and a causal relation between the two effects is plausible. Thus, if concentrated to similar levels in aThalassia bed, TBT⁺ may have direct species-level effects and process-level effects, potentially causing ecosystem change via disruption of a species-process linkage influential in seagrass detrital food web dynamics.  相似文献   

Observations and modeling of infrared and millimeter molecular lines towards GL2591     

A. Neal  J. Evans II  B. John  H. Lacy  C. John  S. Carr  D. Shudong Zhou 《Astrophysics and Space Science》1995,224(1-2):181-184

We have observed C₂H₂ and HCN rovibrational transitions near 13µm in absorption against GL2591. We also have observed rotational transitions at 0.6-3 mm of CS, HCN, H₂CO, and HCO⁺. Analysis of the rotational lines, which arise in the extended cloud around the source, shows that no single density model can explain all the data. Models with density and temperature gradients do much better; in particular models withn(r) r ^–1.5 can reproduce the observed pattern of emission line strengths. The abundances show significant depletion compared to models of gas-phase chemistry. The rovibrational data were analyzed in comparison to the absorption line analysis of CO by Mitchellet al. (1989). Our data are consistent with the C₂H₂ and HCN absorption arising in the same warm (200 K) and hot (1010 K) components seen in CO, but we see little evidence for the cold (38 K) component seen in CO. The rovibrational lines from higher states (J 21) indicate that the hot HCN deviates from LTE, leading to a density of about 3 × 10⁷ cm^–3. Comparison of the two data sets shows that the rovibrational absorption of HCN, rather than arising in the extended envelope, must come from a region with a small angular extent. A model in which early-time gas phase abundances are preserved on grain mantles and released at high temperature can explain the data.  相似文献   

The Expanding Spaces of Law: A Timely Legal Geography          下载免费PDF全文

John Carr 《Geographical review》2016,106(1):e4-e6

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Stability of sulfur slopes on Io     

Gary D. Clow  Michael H. Carr 《Icarus》1980,44(2):268-279

The mechanical properties of elemental sulfur are such that the upper crust of Io cannot be primarily sulfur. For heat flows in the range 100–1000 ergs cm^?2, sec^?1, sulfur becomes ductile within several hundred meters of the surface and would prevent the formation of calderas with depths greater than this. However, the one caldera for which precise depth data are available is 2 km deep, and this value may be typical. A study of the mechanical equilibrium of simple slopes shows that the depth to the zone of rapid ductile flow strongly controls the maximum heights for sulfur slopes. Sulfur scarps with heights greater than 1 km will fail for all heat flows greater than 180 ergs cm^?2 sec^?1 and slope angles greater than 22.5°. The observed relief on Io is inconsistent with that anticipated for a predominantly sulfur crust. However, a silicate crust with several percent sulfur included satisfies both the mechanical constraints and the observed presence of sulfur on Io.  相似文献