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1.
Edward P. F. Rose 《Geology Today》2019,35(3):107-114
During the Second World War, the Allied invasion of the French coast of Normandy on D‐Day, 6 June 1944, was the greatest amphibious assault in world history. An article in Geology Today (v.11, for 1995, pp.58–63) marked the 50th anniversary of the end of the war in Europe, on 8 May 1945, by describing how British military geologists had participated in planning for D‐Day and in the NW Europe campaign that followed it. The work of these geologists provides a classic case history, revealing that ‘military geology’ has many potential applications. Geological factors influenced site selection for temporary airfields, predictions of trafficability for the Normandy beaches, the development of potable water supplies, and quarrying for road metal—and more besides. This new article helps to mark the 75th anniversary of D‐Day by further details of how geologists and geology contributed to Allied victory. 相似文献
2.
Randy L. Korotev 《Meteoritics & planetary science》1996,31(3):403-412
Abstract Two types of texturally and compositionally similar breccias that consist largely of fragmental debris from meteorite impacts occur at the Apollo 16 lunar site: Feldspathic fragmental breccias (FFBs) and ancient regolith breccias (ARBs). Both types of breccia are composed of a suite of mostly feldspathic components derived from the early crust of the Moon and mafic impact-melt breccias produced during the time of basin formation. The ARBs also contain components, such as agglutinates and glass spherules, indicating that the material of which they are composed occurred at the surface of the Moon as fine-grained regolith prior to lithification of the breccias. These components are absent from the FFBs, suggesting that the FFBs might be the protolith of the ARBs. However, several compositional differences exist between the two types of breccia, making any simple genetic relationship implausible. First, clasts of mafic impact-melt breccia occurring in the FFBs are of a different composition than those in the ARBs. Also the feldspathic “prebasin” components of the FFBs have a lower average Mg/Fe ratio than the corresponding components of the ARBs; the average composition of the plagioclase in the FFBs is more sodic than that of the ARBs; and there are differences in relative abundances of rare earth elements. The two breccia types also have different provenances: the FFBs occur primarily in ejecta from North Ray crater and presumably derive from the Descartes Formation, while the ARBs are restricted to the Cayley plains. Together these observations suggest that although some type of fragmental breccia may have been a precursor to the ARBs, the FFBs of North Ray crater are not a significant component of the ARBs and, by inference, the Cayley plains. The average compositions of the prebasin components of the two types of fragmental breccia are generally similar to the composition of the feldspathic lunar meteorites. With 30–31% Al2O3, however, they are slightly richer in plagioclase than the most feldspathic lunar meteorites (~29% Al2O3), implying that the crust of the early central nearside of the Moon contained a higher abundance of highly feldspathic anorthosite than typical lunar highlands, as inferred from the lunar meteorites. The ancient regolith breccias, as well as the current surface regolith of the Cayley plains, are more mafic than (1) prebasin regoliths in the Central Highlands and (2) regions of highlands presently distant from nearside basins because they contain a high abundance (~30%) of mafic impact-melt breccias produced during the time of basin formation that is absent from other regoliths. 相似文献
3.
Steven J. Ostro Lance A. M. Benner Christopher Magri Jon D. Giorgini Randy Rose Raymond F. Jurgens Donald K. Yeomans Alice A. Hine Michael C. Nolan Daniel J. Scheeres Stephen B. Broschart Mikko Kaasalainen Jean‐Luc Margot 《Meteoritics & planetary science》2005,40(11):1563-1574
Abstract— We present June 2004 radar images of asteroid 25143 Itokawa (1998 SF36) that improve upon the longitude‐latitude coverage of images obtained in 2001 by Ostro et al. (2004) and use the 2001–2004 data to refine that paper's constraints on Itokawa's shape. The 2004 images, the first of the asteroid's southern side, look distinctly different from the 2001 images, revealing leading edges that are much more curved and rugged than the nearly convex leading edges seen at northern latitudes in 2001. Itokawa is shaped like a slightly asymmetrical, bent, lumpy ellipsoid with dimensions along the principal axes within 10% of 594 times 320 times 288 m. To illustrate the uncertainty space associated with shape reconstruction from images with suboptimal orientational coverage, we present two alternative three‐dimensional models of the object. 相似文献
4.
P. A. M. Van Hoof M. E. Foord R. F. Heeter J. E. Bailey H.-K. Chung M. E. Cuneo W. H. Goldstein V. Jonauskas F. P. Keenan R. Kisielius D. A. Liedahl C. Ramsbottom S. J. Rose P. T. Springer R. S. Thoe 《Astrophysics and Space Science》2005,298(1-2):147-153
In experiments at the high-power Z-facility at Sandia National Laboratory in Albuquerque, New Mexico, we have been able to
produce a low density photoionized laboratory plasma of Fe mixed with NaF. The conditions in the experiment allow a meaningful
comparison with X-ray emission from astrophysical sources. The charge state distributions of Fe, Na and F are determined in
this plasma using high resolution X-ray spectroscopy. Independent measurements of the density and radiation flux indicate
unprecedented values for the ionization parameter ξ = 20–25 erg cm s−1 under nearly steady-state conditions. First comparisons of the measured charge state distributions with X-ray photoionization
models show reasonable agreement, although many questions remain. 相似文献
5.
6.
The prevalence of dermal neoplasia among neotenic tiger salamanders (Ambystoma tigrinum) collected from the Reese Air Force Base sewage lagoon far exceeded that among salamanders from nearby uncontaminated lagoons. Perylene was the predominant pglycyclic aromatic hydrocarbon contaminant in this lagoon. Perylene was shown to be a substrate for monooxygenases in skin and liver homogenates and formed DNA-binding metabolites. Perylene exposure appeared to augment subsequent perylene metabolism by dermal enzymes but it was not a strong inducer of hepatic monooxygenases. Aroclor 1254 induced benzo(a)pyrene and perylene metabolism by both skin and liver enzymes. However, perylene apparently was not activated by salamander enzymes, as suggested by its lack of in vitro mutagenicity and failure to induce tumors. 相似文献
7.
Robert J. Diaz G. Randy Cutter Donald C. Rhoads 《Deep Sea Research Part II: Topical Studies in Oceanography》1994,41(4-6)
Even though the continental slope off Cape Hatteras has sediment accumulation rates on the order of 1 cm/year, large areas of soft sediment are intensively reworked by infaunal organisms. Primary sedimentary structures have been completely replaced with biogenic structures. Surface sedimentary structures are dominated by the bioturbational activities of a deep burrowing infauna (to at least 30 cm). The layer actively mixed by the benthos, as evidenced by sediment profile and X-ray images, is estimated to range from 5 to 20 cm, with the residence time for particles within the surface mixed layer ranging from about 4.5 to 18 years. The biological mixing parameter (G) ranges from 0.4 to 5.5, which indicates moderate to strong biological mixing relative to accumulation and strata formation. Bioturbation contributes to the dynamic forces affecting the surface sediments by decreasing compaction of sediment layers and dilating sediment fabrics by sediment mixing, and introducing large water-filled burrows and voids to subsurface sediments. The sediment profile images captured numerous subsurface feeding voids, and worms in the process of making deep burrows, many of which extended below the 5 to 10 cm average depth of the apparent color redoxpotential discontinuity layer. High rates of accumulation of organic-rich sediment lead to high standing stocks of benthos and intensive feeding/burrowing activity that result in organic rich stratagraphic sequences that are thoroughly mixed. Cape Hatteras is a apparent focusing point for the transport of shallow water sediments to the deep sea. Sediments across other areas of the continental slope just 100's of kilometers south of Cape Hatteras are not as thoroughly mixed or biologically active. 相似文献
8.
Concentrations of fifteen unsubstituted polynuclear aromatic hydrocarbons (PNAH) were measured in Mytilus edulis from two sites in Yaquina Bay, Oregon, USA, during 1979–1980. There were significant differences in PNAH levels between the two populations. The average total concentration in mussels inhabiting the more industrialized bayfront was 986·2 μg/kg compared with 273·9 μg/kg in mussels from a more remote site across the bay. Substantial differences were found in the concentrations of different PNAH in M. edulis examined during this study. The smaller more water soluble, compounds were concentrated to one or two orders of magnitude above the larger, less soluble PNAH. 相似文献
9.
10.
G. Randy Cutter Jr Robert J. Diaz John Lee 《Deep Sea Research Part II: Topical Studies in Oceanography》1994,41(4-6)
The recent benthic meiofaunal foraminiferal assemblage from the continental slope (590-2 003 m) off Cape Hatteras, North Carolina exhibits high species richness and evenness, moderate diversity values, and lacks numerically dominant species. The preserved planktic assemblage has relatively low species richness, high evenness, low diversity, and a few numerically dominant species. Approximately 9% of the benthic species are those that typically live within continental shelf depth ranges. The benthic assemblage abundances and diversities do not follow depth patterns or geophysical characteristics. No biogeographic boundary can be described within the study area for meiofaunal foraminifera. Oxygen limitation does not appear to be a factor affecting the benthos of the North Carolina continental slope based upon the community structure of the benthic foraminifera, if total assemblage is assumed to reflect the recently living community. The high carbonate content of sediments in the area may be explained by foraminiferal tests. Within the study area, the foraminiferal assemblages are uniform, and probably reflect relative consistency of primary environmental variables as well as dynamic downslope transport and high influx of material from the water column in the vicinity where the Gulf Stream and the Western Boundary Undercurrent cross. 相似文献