The unresolved hard X-ray background: the missing source population implied by the Chandra and XMM–Newton deep fields     

M. A. Worsley  A. C. Fabian  F. E. Bauer  D. M. Alexander  G. Hasinger  S. Mateos  H. Brunner  W. N. Brandt  D. P. Schneider 《Monthly notices of the Royal Astronomical Society》2005,357(4):1281-1287

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Observations of a fast burst of the deep western boundary undercurrent and sediment transport in South Wilmington Canyon from DSRVAlvin     

Stephen J. Culver  Charlotte A. Brunner  Charles A. Nittrouer 《Geo-Marine Letters》1988,8(3):159-165

On October 3 and 4, 1986, DSRVAlvin dives encountered a strong current at 2,300 m in South Wilmington Canyon. The current, estimated at 1 knot, transported surficial sediment and constructed and modified bedforms. It appears to have been constant in its direction of flow from 30 to 40°. The observed current was probably a burst of fast flow in a region of slow average currents in the Deep Western Boundary Undercurrent. Such episodic events may have a greater influence on the stratigraphic record than the temporally longer more tranquil flow conditions.  相似文献   

Reduced oxygen concentrations in herring wintering areas   总被引：1，自引：0，他引：1  

Dommasnes  Are; Rey  Francisco; Rottingen  Ingolf 《ICES Journal of Marine Science》1994,51(1):63-69

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Theory of the local scale parameter method for EDM     

F. K. Brunner  J. M. Rüeger 《Journal of Geodesy》1992,66(4):355-364

The determination of a representative refractive index for the wave path is the main limitation of the attainable accuracy in electronic distance measurement. To overcome this limitation the length ratio method was initially proposed and later developed into the local scale parameter (LSP) method. In this paper, the mathematical model of the LSP method is derived for electro-optical distance measurement from first principles based on the physics of the atmospheric boundary layer. The model does not rely on standard atmospheres. It is shown that atmospheric temperatures and pressures must be observed at instrument stations but not at reflector stations. Appropriate LSP field procedures and the results of some field experiments are summarized. The method consistently produces accuracies of better than ±1 ppm. Use of the method is recommended for high precision (trilateration) networks, which need to be measured repeatedly and where absolute scale is not relevant.  相似文献   

Sulfur isotope fractionation during growth of sulfate-reducing bacteria on various carbon sources   总被引：1，自引：0，他引：1  

Jutta Kleikemper  Martin H. Schroth  Benjamin Brunner 《Geochimica et cosmochimica acta》2004,68(23):4891-4904

Stable sulfur isotope fractionation during microbial sulfate reduction is a potential tool to estimate sulfate reduction rates at field sites. However, little is known about the influence of the utilized carbon source on the magnitude of sulfur isotope fractionation. To investigate this effect, both a pure culture (strain PRTOL1) and enrichment cultures from a petroleum hydrocarbon (PHC)-contaminated aquifer were used and grown in batch cultures on various carbon sources with an initial sulfate concentration of 1 mmol/L. As sole carbon sources the PHC components naphthalene, 1,3,5-trimethylbenzene, and heating oil (enrichment culture) and the organic acids acetate, pyruvate, benzoate, and 3-phenylpropionate (enrichment culture and PRTOL1) were used. Sulfate reduction rates of all cultures ranged from 6 ± 1 nmol cm⁻³ d⁻¹ (enrichment culture grown on 1,3,5-trimethylbenzene) to 280 ± 6 nmol cm⁻³ d⁻¹ (enrichment culture grown on pyruvate). Cell-specific sulfate reduction rates ranged from 1.1 × 10⁻¹⁴ mol cell⁻¹ d⁻¹ (PRTOL1 grown on pyruvate) to 1.5 × 10⁻¹³ mol cell⁻¹ d⁻¹ (PRTOL1 grown on acetate). Sulfur isotope enrichment factors (ε) for the enrichment culture ranged from 16.1‰ (3-phenylpropionate) to 34.5‰ (1,3,5-trimethylbenzene) and for PRTOL1 from 30.0‰ (benzoate) to 36.0‰ (pyruvate). Cultures of PRTOL1 always showed higher ε values than the enrichment culture when grown on the same carbon source due to culture-specific properties. Higher ε values were obtained when the enrichment culture was grown on PHC components than on organic acids. No relationship between ε values and cell-specific sulfate reduction rate existed when all data were combined. When comparing the magnitude of ε values determined in this laboratory study with ε values measured at contaminated and uncontaminated field sites, it becomes evident that a multitude of factors influences ε values at field sites and complicates their interpretation. The results of this study help us assess some of the general parameters that govern the magnitude of ε in sulfate-reducing environments.  相似文献   

A model for oxygen and sulfur isotope fractionation in sulfate during bacterial sulfate reduction processes     

Benjamin Brunner  Stefano M. Bernasconi  Jutta Kleikemper 《Geochimica et cosmochimica acta》2005,69(20):4773-4785

We present a model of bacterial sulfate reduction that includes equations describing the fractionation relationship between the sulfur and the oxygen isotope composition of residual sulfate (δ³⁴S_{SO4_residual}, δ¹⁸O_{SO4_residual}) and the amount of residual sulfate. The model is based exclusively on oxygen isotope exchange between cell-internal sulfur compounds and ambient water as the dominating mechanism controlling oxygen isotope fractionation processes. We show that our model explains δ³⁴S_{SO4_residual} vs. δ¹⁸O_{SO4_residual} patterns observed from natural environments and from laboratory experiments, whereas other models, favoring kinetic isotope fractionation processes as dominant process, fail to explain many (but not all) observed δ³⁴S_{SO4_residual} vs. δ¹⁸O_{SO4_residual} patterns. Moreover, we show that a “typical” δ³⁴S_{SO4_residual} vs. δ¹⁸O_{SO4_residual} slope does not exist. We postulate that measurements of δ³⁴S_{SO4_residual} and δ¹⁸O_{SO4_residual} can be used as a tool to determine cell-specific sulfate reduction rates, oxygen isotope exchange rates, and equilibrium oxygen isotope exchange factors. Data from culture experiments are used to determine the range of sulfur isotope fractionation factors in which a simplified set of equations can be used. Numerical examples demonstrate the application of the equations. We postulate that, during denitrification, the oxygen isotope effects in residual nitrate are also the result of oxygen isotope exchange with ambient water. Consequently, the equations for the relationship between δ³⁴S_{SO4_residual}, δ¹⁸O_{SO4_residual}, and the amount of residual sulfate could be modified and used to calculate the fractionation-relationship between δ¹⁵N_{NO3_residual}, δ¹⁸O_{NO3_residual}, and the amount of residual nitrate during denitrification.  相似文献   

Determination of line averages of sensible heat flux using an optical method     

Fritz K. Brunner 《Boundary-Layer Meteorology》1982,22(2):193-207

An optical method is discussed for the determination of the line average of the vertical temperature gradient, which is subsequently used for the calculation of the scaling temperature and of the sensible heat flux. The method requires conventional surveying instrumentation only, and the measurements are carried out easily. The attainable accuracy is estimated as 10% or better. Observations are also possible during night or light-wind conditions. In a field experiment, results from this optical method were compared with measurements taken with a conventional covariance eddy-flux instrument. Excellent agreement between both methods was found.  相似文献   

Paleoceanography of surface waters in the Gulf of Mexico during the late Quaternary     

Charlotte A. Brunner 《Quaternary Research》1982,17(1):105-119

Late Quaternary paleotemperatures and paleosalinities of surface waters of the Gulf of Mexico were estimated using a multivariate statistical analysis of census data of planktonic foraminifera. Two climatic extremes were selected for detailed basinwide study, the climatic optimum 125,000 yr ago and the glacial maximum 18,000 yr ago. In addition, patterns of climatic change were examined in seven piston cores from 127,000 yr ago to the present day. During the climatic optimum 125,000 yr ago temperature distributions in surface waters were similar to those of the present. The 22°C winter isotherm trended northeastward across the central basin and paleotemperatures decreased northward. Summer distributions were nearly homogeneous and ranged between 28° and 29°C. Winter salinities were 1‰ fresher than present values in the northmost Gulf and 0.4‰ fresher in the central basin. Summer salinities were similar during both times. In contrast, during the last glacial maximum temperatures were 1° to 2°C cooler in winter and 1°C cooler in summer, and isotherms formed a circular pattern in the Gulf during both seasons. Salinity was 0.3‰ fresher in winter than at present but 0.6‰ saltier in summer. Conditions deteriorated from the climatic optimum to the glacial maximum. In the Mexico Basin, winter temperatures were 2°C cooler from 75,000 to 45,000 yr ago (Y6 to Y3 Subzones), summer temperatures reached a minimum (3°C cooler) 32,000 yr ago (Y2–Y3 boundary), and seasonality reached minimal values (5°C) from 45,000 to 15,000 yr ago. All three parameters became similar in value to those in the Straits of Florida from 45,000 to 15,000 yr ago, suggesting that the exchange of surface waters was enhanced at this time between the two regions. Summer salinities remained similar to present conditions in the Mexico Basin, whereas, winter salinities increased 2‰ by 32,000 yr ago and then fell 0.5‰ until the glacial maximum ended. The Westerlies may have migrated southward over the Mexico Basin in winter from 32,000 to 15,000 yr ago.  相似文献   

Context and climate change: an integrated assessment for Barrow, Alaska     

Amanda H. Lynch  Ronald D. Brunner 《Climatic change》2007,82(1-2):93-111

An intensive approach to Barrow, Alaska’s adaptations to climate change and variability during recent decades suggests reconsideration of the interconnected roles of science, policy, and decision-making structures. First, profound uncertainties are inherent in unique interactions among the many natural and human factors affecting Barrow’s vulnerability. Science cannot significantly reduce these uncertainties through extensive approaches, but intensive approaches can reconstruct and update local trends, clarify the underlying dynamics, and harvest experience for policy purposes. Second, sound policies to reduce Barrow’s vulnerability to coastal erosion and flooding must incorporate these profound uncertainties and the multiple values of the community. Minimizing vulnerability to climate change is only one of the community’s interests, and must compete with other interests for limited time, attention, funds and other resources. Third, the community itself is in the best position to understand its own context, to decide on sound policies, and to take responsibility for those decisions. In short, local context matters in science, policy, and decision-making structures for adaptation to climate change and variability. Overall, cognitive constraints may be the most important human dimension of climate change. Factoring the global problem into more tractable local problems would make the most of our cognitive capacity.  相似文献   

The 2dF-SDSS LRG and QSO (2SLAQ) Luminous Red Galaxy Survey     

Russell Cannon  Michael Drinkwater  Alastair Edge  Daniel Eisenstein  Robert Nichol  Phillip Outram  Kevin Pimbblet  Roberto De Propris  Isaac Roseboom  David Wake  Paul Allen  Joss Bland-Hawthorn  Terry Bridges  Daniel Carson  Kuenley Chiu  Matthew Colless  Warrick Couch  Scott Croom  Simon Driver  Stephen Fine  Paul Hewett  Jon Loveday  Nicholas Ross  Elaine M. Sadler  Tom Shanks  Robert Sharp  J. Allyn Smith  Chris Stoughton  Peter Weilbacher  Robert J. Brunner  Avery Meiksin  Donald P. Schneider 《Monthly notices of the Royal Astronomical Society》2006,372(1):425-442

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