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Huntington Beach, California, one of the most popular surfing spots in the world, is plagued by sporadic, elevated levels of fecal bacteria. To assist with pollution source identification, we analyzed antibiotic resistance patterns (ARPs) of enterococci from four known sources (bird feces, urban runoff, coastal marsh sediment and sewage effluent from local sanitation district) and one unknown source (seawater) using seven antibiotics at four concentrations each. Of 2491 enterococci tested, all were resistant to at least one antibiotic at some level. Discriminant analysis indicated that the average correct classification rates for bird feces and urban runoff sources were above 80%. Sewage effluent contained mixed fecal sources. Sixty-four percent of the sewage isolates classified with the sewage category, while the other 35% of isolates were assigned evenly across the other three categories. When enterococci isolated from the seawater were classified using the known ARP database, it was evident that bird feces were the source of surf zone contamination on some days while the coastal salt marsh and sewage plume may have impacted the surf zone water quality to various degrees during other times. 相似文献
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Bottom trawling causes physical disturbance to sediments particularly in shelf areas. The disturbance due to trawling is most
significant in deeper areas with softer sediments where levels of natural disturbance due to wave and tidal action are low.
In heavily fished areas, trawls may impact the same area of seabed more than four times per year. A single pass of a beam
trawl, the heaviest gear routinely used in shelf sea fisheries, can kill 5–65% of the resident fauna and mix the top few cm
of sediment. We expect that sediment community function, carbon mineralisation and biogeochemical fluxes will be strongly
affected by trawling activity because the physical effects of trawling are equivalent to those of an extreme bioturbator,
and yet, unlike bioturbating macrofauna, trawling does not directly contribute to community metabolism. We used an existing
box-model of a generalised soft sediment system to examine the effects of trawling disturbance on carbon mineralisation and
chemical concentrations. We contrasted the effects of a natural scenario, where bioturbation is a function of macrobenthos
biomass, with an anthropogenic impact scenario where physical disturbance results from trawling rather than the action of
bioturbating macrofauna. Simulation results suggest that the effects of low levels of trawling disturbance will be similar
to those of natural bioturbators but that high levels of trawling disturbance prevent the modelled system from reaching equilibrium
due to large carbon fluxes between oxic and anoxic carbon compartments. The presence of macrobenthos in the natural disturbance
scenario allowed sediment chemical storage and fluxes to reach equilibrium. This is because the macrobenthos are important
carbon consumers in the system whose presence reduces the magnitude of available carbon fluxes. In soft sediment systems,
where the level physical disturbance due to waves and tides is low, model results suggest that intensive trawling disturbance
could cause large fluctuations in benthic chemical fluxes and storage. 相似文献
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Bergström D Boezio M Carlson P Francke T Grinstein S Khalchukov F Suffert M Hof M Kremer J Menn W Simon M Stephens SA Ambriola ML Bellotti R Cafagna F Ciacio F Circella M De Marzo C Finetti N Papini P Piccardi S Spillantini P Bartalucci S Ricci M Casolino M De Pascale MP Morselli A Picozza P Sparvoli R Bonvicini V Schiavon P Vacchi A Zampa N Mitchell JW Ormes JF Streitmatter RE Bravar U Stochaj SJ 《The Astrophysical journal》2000,534(2):L177-L180
We report new results for the cosmic-ray antiproton-to-proton ratio from 3 to 50 GeV at the top of the atmosphere. These results represent the first measurements, on an event-by-event basis, of mass-resolved antiprotons above 18 GeV. The results were obtained with the NMSU-WIZARD/CAPRICE98 balloon-borne magnet spectrometer equipped with a gas-RICH (Ring-Imaging Cerenkov) counter and a silicon-tungsten imaging calorimeter. The RICH detector was the first ever flown that is capable of identifying charge-one particles at energies above 5 GeV. The spectrometer was flown on 1998 May 28-29 from Fort Sumner, New Mexico. The measured p&d1;/p ratio is in agreement with a pure secondary interstellar production. 相似文献
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Bacterial mineralization patterns in basaltic aquifers: implications for possible life in martian meteorite ALH84001 总被引:1,自引:0,他引:1
Thomas-Keprta KL McKay DS Wentworth SJ Stevens TO Taunton AE Allen CC Coleman A Gibson EK Romanek CS 《Geology》1998,26(11):1031-1034
To explore the formation and preservation of biogenic features in igneous rocks, we have examined the organisms in experimental basaltic microcosms using scanning and transmission electron microscopy. Four types of microorganisms were recognized on the basis of size, morphology, and chemical composition. Some of the organisms mineralized rapidly, whereas others show no evidence of mineralization. Many mineralized cells are hollow and do not contain evidence of microstructure. Filaments, either attached or no longer attached to organisms, are common. Unattached filaments are mineralized and are most likely bacterial appendages (e.g., prosthecae). Features similar in size and morphology to unattached, mineralized filaments are recognized in martian meteorite ALH84001. 相似文献
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许多碳酸盐地台都有着不同程度的白云石化作用,白云石化作用的机理至今仍有争议、在许多例子中,白云石出现于沉积物成岩历史的早期阶段,但在埋藏过程中常有重结晶作用,因此,许多化学标志如同位素、痕量元素和有序度发生重排,不再反映形成白云石的原始孔隙流体的成分(Hardie,1987)。Urgonian地台位于法国Subal…ne山脉北部,这条山脉是一个位于法国东南部的NE─SW向这山带,部分为西阿尔卑斯的延伸带。Subalpine山脉包括了所有在Daupinois/Helvetlc盆地、Jura/BasDauphine他台和Provencal他台沉积的沉积物。该地区是被动边… 相似文献