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261.
M. M. Lyons P. Aas J. D. Pakulski L. Van Waasbergen R. V. Miller D. L. Mitchell W. H. Jeffrey 《Marine Biology》1998,130(3):537-543
Ultraviolet radiation (UVR) has been implicated in coral-bleaching processes and UVR may create stress to marine organisms
by damage to DNA. Absorption of energy from UVB (280 to 320 nm) induces direct damage to DNA via cyclobutane pyrimidine dimer
photoproduct-formation. We examined the extent of DNA damage created by UVR in coral reef microbial communities and whether
the coral-surface microlayer (CSM) provides protection from UVR to the microorganisms found there. Diel patterns and depth
profiles of UVR effects were examined in coral mucus (coral-surface microlayer, CSM) from Montastraea faveolata and Colpophyllia natans, and water-column samples of similar depths. UV-induced photodamage was determined using a radioimmunoassay specific for
cyclobutane pyrimidine dimers (thymine dimers). Significant photodamage was detected in water-column and CSM samples, although
the level of damage in CSM samples was consistently lower than in water-column samples collected from the same depth, suggesting
the presence of photoprotective mechanisms within the CSM. Diel patterns of photodamage were detected in both water-column
and CSM samples, but peak damage occurred earlier in the day for the CSM samples, suggesting differences in damage and repair
kinetics between the water column and CSM. The results suggest that microorganisms within the CSM are afforded some protection
from UVR stress and that changes in the amount of DNA damage in these organisms may be an indicator of changing UVR stress
to corals.
Received: 10 January 1997 / Accepted: 15 September 1997 相似文献
262.
Sawant AA Cocker DR Miller JW Taliaferro T Diaz-Sanchez D Linn WS Clark KW Gong H 《Journal of the Air & Waste Management Association (1995)》2008,58(6):829-837
An idling medium-duty diesel truck operated on ultralow sulfur diesel fuel was used as an emission source to generate diesel exhaust for controlled human exposure. Repeat tests were conducted on the Federal Test Procedure using a chassis dynamometer to demonstrate the reproducibility of this vehicle as a source of diesel emissions. Exhaust was supplied to a specially constructed exposure chamber at a target concentration of 100 microg x m(-3) diesel particulate matter (DPM). Spatial variability within the chamber was negligible, whereas emission concentrations were stable, reproducible, and similar to concentrations observed on the dynamometer. Measurements of nitric oxide, nitrogen dioxide, carbon monoxide, particulate matter (PM), elemental and organic carbon, carbonyls, trace elements, and polycyclic aromatic hydrocarbons were made during exposures of both healthy and asthmatic volunteers to DPM and control conditions. The effect of the so-called "personal cloud" on total PM mass concentrations was also observed and accounted for. Conventional lung function tests in 11 volunteer subjects (7 stable asthmatic) did not demonstrate a significant change after 2-hr exposures to diesel exhaust. In summary, we demonstrated that this facility can be effectively and safely used to evaluate acute responses to diesel exhaust exposure in human volunteers. 相似文献
263.
Laiz L Miller AZ Jurado V Akatova E Sanchez-Moral S Gonzalez JM Dionísio A Macedo MF Saiz-Jimenez C 《Die Naturwissenschaften》2009,96(1):71-79
In the last few years, the microbial colonisation of mural paintings in ancient monuments has been attracting the attention
of microbiologists and conservators. The genus Rubrobacter is commonly found in biodeteriorated monuments, where it has been reported to cause rosy discolouration. However, to date,
only three species of this genus have been isolated, all from thermophilic environments. In this paper, we studied three monuments:
the Servilia and Postumio tombs in the Roman Necropolis of Carmona (Spain), and Vilar de Frades church (Portugal), in search
of Rubrobacter strains. In all cases, biodeterioration and the formation of efflorescences were observed, and five Rubrobacter strains were isolated. These isolates showed different physiology and migration in denaturing gradient gel electrophoresis,
suggesting they might represent new species within this genus. The isolates reproduced some biodeterioration processes in
the laboratory and revealed their biomediation in crystal formation. 相似文献
264.
Benjamin F McPherson Ronald L. Miller 《Journal of the American Water Resources Association》1994,30(1):43-53
ABSTRACT: Vertical attenuation of photosynthetically active radiation (PAR) in clear waters of central Florida theoretically can vary almost 50 percent during a sunny summer day as a result of changing solar elevation. We used a simple formula to partially adjust the attenuation coefficient in Tampa Bay and Charlotte Harbor for changing solar elevation of the direct beam and then used multiple regression analysis to estimate the relative contribution of different water properties or constituents to the adjusted attenuation coefficient, kadj. Color, on an average, was responsible for 18 percent of kadj, chlorophyll a for 21 percent, nonchiorophyll suspended matter for 55 percent, and seawater for the remaining 6 percent. In both estuaries, kadj increased with decreasing salinity as a result of freshwater runoff adding color, suspended matter, and nutrients. Nutrients affected attenuation by stimulating phytoplankton growth and increasing concentrations of chlorophyll a. Reduced nutrient loading to upper Tampa Bay (Hilisborough Bay) in the early to mid-1980's appears to have decreased concentrations of chlorophyll a, increased water clarity, and increased seagrass recolonization. Assuming other attenuating substances remained unchanged, the decrease in the average concentration of chlorophyll a from 30 to 15 μg L?1 would correspond to an increase in the depth of light penetration necessary for seagrass survival (>10 percent incident light) from 1.0 to 1.5 m, which, on a relatively flat sea bed (slope of 2 m/km), would increase the area potentially available for seagram recolonization by 0.25 km2/km of shoreline. 相似文献
265.
Cohen L Miller T Sheppard MA Gordon E Gantz T Atnafou R 《Journal of Safety Research》2003,34(5):473-483
PROBLEM: Intentional and unintentional injury prevention efforts have traditionally been independent and non-integrated. Fostering collaboration between the sub-fields would enhance work within both sub-fields and advance injury prevention work as a whole. METHOD: A systematic assessment of similarities and differences between the sub-fields was performed, including an examination of relevant definitions and norms, research methods and findings, key risk and resiliency factors, and prevention strategies that would promote collaboration and better advance current prevention efforts. RESULTS/SUMMARY: Several areas exist in which injury prevention efforts could be coordinated or ideas and practices could be cross-applied, including training of practitioners, data collection and analysis, application of tools and methodologies, examination of risk and resiliency factors, and identification of funding sources and partners. IMPACT ON INDUSTRY: This paper delineates how intentional and unintentional injury prevention practitioners can more effectively collaborate to promote safer environments and further reduce incidence of injury. An integrated injury prevention approach could significantly impact the underlying contributors to both types of injury, allowing practitioners within both sub-fields to achieve greater outcomes through increased credibility, reduced duplication of efforts, more efficient use of resources, and unified injury prevention messages. 相似文献
266.
Accumulation of potentially toxic elements in plants and their transfer to human food chain. 总被引:21,自引:0,他引:21
Contaminated soils can be a source for crop plants of such elements like As, Cd, Cr, Cu, Ni, Pb, and Zn. The excessive transfer of As, Cu, Ni, and Zn to the food chain is controlled by a "soil-plant barrier"; however, for some elements, including Cd, the soil-plant barrier fails. The level of Cd ingested by average person in USA is about 12 micrograms/day, which is relatively low comparing to Risk Reference Dose (70 micrograms Cd/day) established by USEPA. Food of plant origin is a main source of Cd intake by modern society. Fish and shellfish may be a dominant dietary sources of Hg for some human populations. About half of human Pb intake is through food, of which more than half originates from plants. Dietary intake of Cd and Pb may be increased by application of sludges on cropland with already high levels of these metals. Soils amended with sludges in the USA will be permitted (by USEPA-503 regulations) to accumulate Cr, Cd, Cu, Pb, Hg, Ni, and Se, and Zn to levels from 10 to 100 times the present baseline concentrations. These levels are very permissive by international standards. Because of the limited supply of toxicity data obtained from metals applied in sewage sludge, predictions as to the new regulations will protect crop plants from metal toxicities, and food chain from contamination, are difficult to make. 相似文献
267.
268.
E. Garcia-Anton S. Cuezva V. Jurado E. Porca A. Z. Miller A. Fernandez-Cortes C. Saiz-Jimenez S. Sanchez-Moral 《Environmental science and pollution research international》2014,21(1):473-484
Altamira Cave (north of Spain) contains one of the world's most prominent Paleolithic rock art paintings, which are threatened by a massive microbial colonization of ceiling and walls. Previous studies revealed that exchange rates between the cave and the external atmosphere through the entrance door play a decisive role in the entry and transport of microorganisms (bacteria and fungi) and nutrients to the interior of the cave. A spatial-distributed sampling and measurement of carrier (CO2) and trace (CH4) gases and isotopic signal of CO2 (δ13C) inside the cave supports the existence of a second connection (active gas exchange processes) with the external atmosphere at or near the Well Hall, the innermost and deepest area of the cave. A parallel aerobiological study also showed that, in addition to the entrance door, there is another connection with the external atmosphere, which favors the transport and increases microorganism concentrations in the Well Hall. This double approach provides a more complete knowledge on cave ventilation and revealed the existence of unknown passageways in the cave, a fact that should be taken into account in future cave management. 相似文献
269.
Nucleotide sequences have been determined for 31 homologous 118 base-pair highly repeated DNA sequences from seven species ofAcropora. A matrix was constructed from the sequence data and subjected to phylogenetic analysis using heuristic search routines in the PAUP (phylogenetic analysis using parsimony) program, Version 3.0L. These analyses confirm a close relationship between two species of one subgeneric group (A. pulchra andA. millepora), but identify a division in a group of six species which is contrary to taxonomic groupings based on morphological criteria. 相似文献
270.
Robert U. Ayres Steven M. Miller 《Journal of Environmental Economics and Management》1980,7(4):353-371
We develop an optimal growth model that includes several important new features. First, technological change is endogenously related to the growth of “knowledge.” Investment may be directed either towards physical capital or knowledge (or both). Knowledge becomes an effective substitute for scarce resources by increasing the technical efficiency of resource utilization both for consumption and in capital. Nevertheless, a finite quantity resource must be embodied in capital and a finite flow is required for depreciation. Thus, there is an upper limit to technical efficiency and economic growth is thus ultimately limited by the availability of renewable resources. For a simple aggregate production function it is shown that technical efficiency never approaches unity on an optimal path. 相似文献