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81.
Germana Barone Mauro Francesco La Russa Antonino Lo Giudice Paolo Mazzoleni Antonino Pezzino 《Environmental Geology》2008,55(3):499-504
The Cathedral of St. Giorgio in Ragusa Ibla (Sicily) is one of the most important Baroque monuments of eastern Sicily. The restoration of the monument underway has put forward notable questions regarding the stone materials used and their state of degradation. The façade appears to be made mainly of a creamy white calcarenite, and of mortars and plasters. However, detailed analysis has highlighted a more complex use of the raw material. The mortar and plaster have a different composition in regards to their architectural use while the natural stone material is distinguished not only by a creamy-white calcarenite but also by a dark coloured bituminous calcarenite (pitch rock), which now appears whiter because of superficial chromatic alterations. This process was reproduced in the laboratory using an accelerated aging technique on samples of bituminous calcarenite, which allowed the cause of the alternation to be identified as photo-oxidation of the asphaltenes. Following this process of photo-oxidation, other forms of chromatic alterations affected the façade (brown–orange-coloured patinas). FTIR, Scanning Electron Microscope and thin section microscopic observation allowed the characterization of also the products of this process to be carried out, highlighting the complex mechanism which the processes underwent. 相似文献
82.
Jan Laštovička 《Studia Geophysica et Geodaetica》1991,35(2):100-108
Summary Geomagnetic storms belong to the most important phenomena of solar origin which affect the ionosphere and atmosphere. We study the responses of the lower ionosphere, middle stratospheric ozone, total ozone and the troposphere (vorticity area index at 500 hPa) to isolated and major geomagnetic storms. The expected positive effect is observed in the lower ionosphere. No observable effect is detected in the middle stratospheric ozone. An effect (not very significant) can be found in the total ozone and the troposphere.Contribution No, 109/90, Geophysical Institute, Czechosl. Acad. Sci., Prague. 相似文献
83.
Summary The measurements of nitric oxide density were made by the photoionization method at 30–90km in several rocket flights near Volgograd. TheseNO densities are well within the range of other measurements below 60km, but become rather high above 70km. The upper mesosphericNO densities estimated by two different methods from ionospheric data in Central Europe (50 °N) are rather high, as well. The appropriateNO densities in the upper mesosphere still seem to be an open question. 相似文献
84.
Mark E. Byrnes R. Wayne Nelson Robert G. La Poe Dennis E. Lundquist William McNeill 《Ground Water Monitoring & Remediation》1990,10(4):90-95
A remedial investigation (RI) was performed in an area downgradient from an abandoned missile silo at Vandenberg Air Force Base, California, as part of the United States Air Force Installation Restoration Program (IRP). A number of complementary investigative techniques were used to assure a reliable assessment of site contamination. These included the review of aerial photographs, the use of an organic vapor analyzer (OVA) and carbon adsorption/mass spectrometer (MS) method to conduct a soil-gas survey; magnetic and electromagnetic geophysical surveys; bedrock permeability testing; and the chemical analysis of soil, sediment, surface water, and ground water samples. The results from this investigation revealed the presence of an undocumented landfill and a small trichloroethylene plume in ground water at concentrations ranging from 6.7 ppb to 31 ppb. The investigation also identified local ground water flow direction, provided strong evidence of the location of potential sources of contamination, and defined the downgradient extent of ground water contamination. Because the identified contaminants have not as yet reached the environmentally sensitive wetland at the base of the slope below this facility, there is still time to propose remedial alternatives that would serve to protect this environmentally sensitive area. 相似文献
85.
86.
Diel feeding of the transparent goby Aphia minuta (Pisces,Gobiidae) in the Northwestern Adriatic Sea in spring time
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Valentina Tirelli Sara Legovini Diego Borme Elena Di Poi Mario La Mesa 《Marine Ecology》2016,37(4):920-926
The present study provides the first estimate of the daily ration for a goby species in the Mediterranean Sea, using a new approach to determine the mass of fish stomach contents through the sum of individual prey dry mass derived indirectly from prey size. Diel feeding activity and daily ration of the pelagic goby Aphia minuta were studied under natural conditions in the coastal waters off Comacchio (Northwestern Adriatic Sea) during the spring season. A total of 318 individuals of A. minuta, collected by 14 trawls carried out on 4 consecutive days, was examined for gut contents. The diel pattern of the vacuity index and the stomach fullness index indicated that A. minuta has nocturnal feeding behaviour. The daily ration, computed over a period of 16 h, was equivalent to 2.23% wet body mass. 相似文献
87.
Heterotrophic bacteria community and pollution indicators of mussel--farm impact in the Gulf of Gaeta (Tyrrhenian Sea). 总被引:6,自引:0,他引:6
T La Rosa S Mirto A Marino V Alonzo T L Maugeri A Mazzola 《Marine environmental research》2001,52(4):301-321
Field studies were carried out to determine and compare the impact of organic loads due to the biodeposition of a mussel farm on the water quality and sediment in a coastal area of the Tyrrhenian Sea (Western Mediterranean). A total of five environmental and five microbial parameters were examined from March, 1997 to February, 1998 on a monthly basis at three stations: the first was located under the mussel farm, the second located at about 40 m away from the mussel farm, while the third designed as a control was at about 1-km. No clear changes in the physical characteristics of the water masses were observed, comparing the three sampling sites and the water column generally showed homogeneous conditions (in terms of temperature and salinity). Changes in density of aerobic heterotrophic bacteria, Escherichia coli and Enterococci in the water column are apparently independent from changes in environmental parameters. At all stations a constant significant correlation between temperature and presumptive Vibrio parahaemolyticus was reported suggesting that this abiotic factor exerted a major control on this bacterial group and its distribution in the water column is not related to the biodeposition of the mussel farm. The major impact identified was on the sediment where variations in bacterial abundance was observed. In the Mussel station sediment enrichment of organic compounds, and the consequent modification of the characteristics of the benthic environment, determined an increase in aerobic heterotrophic bacteria, and particularly of vibrios density (on average about 60%), suggesting that these bacteria are good indicators of organic enrichment. 相似文献
88.
Effects of oil on phytoplankton metabolism in natural and experimental estuarine ponds 总被引:1,自引:0,他引:1
Armando A. De La Cruz 《Marine environmental research》1982,7(4):257-263
A low level oil spill was simulated in small shallow natural estuarine marsh ponds in Ocean Springs and in experimental impoundments near St. Louis Bay, Mississippi. In the natural tidal pond in situ light and dark BOD bottle experiments on the phytoplankton community revealed a 44 to 65 % reduction in primary production and a 30 to 50 % reduction in respiration 2 weeks after spillage of 1·45 mg Empire Mix crude oil per litre of water. Two months after the spill, primary productivity and respiration in the oiled pond were only 17% and 7% lower, respectively than in the control pond. In the experimental impoundments at a concentration of 0·2 mg Arabian, Empire Mix and Nigerian oil per litre of water, in situ radiocarbon uptake by phytoplankton was lower—but not significantly lower—than that of the control impoundment. One to two months later, primary productivity was significantly higher in the Nigerian and Arabian oil ponds than control and Empire Mix ponds. The changes in plankton metabolism in both natural ponds and impoundments were evaluated on the basis of data simultaneously obtained from adjoining control ponds. 相似文献
89.
J. I. García De La Rosa 《Solar physics》1984,92(1-2):161-172
The analysis of high-resolution H and white-light observations on the emergence of 73 active regions shows an intrinsically different behaviour for both the large and small ones. The small active regions (magnetic flux as 5 × 1021 Mx) display circular structures of supergranular size with pores only at the borders, whereas the large active regions show elongated structures with pores which develop at the center and later migrate towards the extremes. These observations are used to suggest two different models for the emergence of these two kinds of active regions: the small ones are produced by the superficial convective concentration of loosely packed dux and the large ones are the result of tightly wound flux ropes. 相似文献
90.
Multiwavelength observations of the two unidentified EGRET sources 3EG J0616-3310 and 3EG J1249-8330
N. La Palombara R. P. Mignani E. Hatziminaoglou M. Schirmer G. F. Bignami P. Caraveo 《Astrophysics and Space Science》2007,309(1-4):209-213
We report on the X-ray and optical observation of the two unidentified EGRET sources 3EG J0616-3310 and 3EG J1249-8330. The X-ray coverage performed by the ESA space telescope XMM–Newton provided ∼150 X-ray sources within each of the two γ-ray error-circles. The optical follow-up carried on with the Wide Field Imager at the ESO/MPG 2.2 m telescope have found no candidate counterpart for 125 of these X-ray sources. Among these, we have selected
9 sources with f
X/f
opt≥100, which we consider promising INS candidates. 相似文献