Design and application of a semi-automated filtration system to study the distribution of particulate organic carbon in the water column of a coastal upwelling system     

Rachel R. Holser  Miguel A. Goni  Burke Hales 《Marine Chemistry》2011,123(1-4):67-77

The processes controlling the production, transport and ultimate fate of particulate organic carbon (POC) in marine systems play a major role in the global carbon cycle. Direct measurements of POC concentrations in oceanic waters have been used extensively to investigate these processes, but because of the time-intensive effort associated with manual collection and filtration of water samples, this approach often results in limited temporal or spatial coverage. To increase the frequency of POC measurements, we designed and built a semi-automated filtration system (SAFS) that can be linked to a ship's underway surface water flow system and/or a towed profiling vehicle with pumping capabilities. Our results show that, compared to manual filtration, SAFS provides the ability to easily perform filtrations at high enough frequency to measure POC concentrations at spatial and temporal resolutions that are closer to those possible with in situ sensors. When combined with optical measurements, SAFS allows for the characterization of several distinct pools of particles within different geographical and depth regions of the water column off the Oregon Coast. These initial applications yielded data that provide considerable insight into the sources and character of particles in the water column and prove that this approach can be used to gain valuable information on the biogeochemistry of this and other similar ocean margins.  相似文献   

The case for an international commission for the conservation and management of sharks (ICCMS)     

Andrew Herndon  Vincent F. Gallucci  Douglas DeMaster  William Burke 《Marine Policy》2010

The current rate of shark global exploitation and mortality is arguably so high under current management regimes that unless a renewed initiative is undertaken some species of shark will become effectively extinct. Current efforts to sustainably manage shark mortality are driven primarily by domestic laws in a few countries, big international non-governmental organizations (BINGOs) promoting environmental laws in the countries or regions where they exist, a handful of regional fisheries management organizations (e.g., IATTC and ICCAT), and inter-governmental organizations such as CITES. The absence of enforcement capability is often argued as the critical component in the failure to protect sharks from overexploitation. The remedy advanced here goes far beyond the need for stepped up enforcement, and calls for the creation of an entirely new international management regime, the International Commission for the Conservation and Management of Sharks (ICCMS). Such an agency could learn from the experiences of management bodies tasked with conservation of species biologically similar to sharks, such as the International Whaling Commission (IWC), to improve its efficacy. Critics have identified many organizational flaws that reduced the IWC’s effectiveness during its earliest years. Some of those flaws are examined here and remedies are suggested that an ICCMS could use to create a more effective management regime. The life histories of elasmobranches and large whales are compared to illustrate their similarities as a biological foundation for the selection of the IWC as a model.  相似文献   

The XMM Cluster Survey: forecasting cosmological and cluster scaling-relation parameter constraints     

Martin Sahlén  Pedro T. P. Viana  rew R. Liddle  A. Kathy Romer  Michael Davidson  Mark Hosmer  Ed Lloyd-Davies  Kivanc Sabirli  Chris A. Collins  Peter E. Freeman  Matt Hilton  Ben Hoyle  Scott T. Kay  Robert G. Mann  Nicola Mehrtens  Christopher J. Miller  Robert C. Nichol  S. Adam Stanford  Michael J. West  † 《Monthly notices of the Royal Astronomical Society》2009,397(2):577-607

We forecast the constraints on the values of  σ₈, Ω_m  and cluster scaling-relation parameters which we expect to obtain from the XMM Cluster Survey (XCS). We assume a flat Λ cold dark matter Universe and perform a Monte Carlo Markov Chain analysis of the evolution of the number density of galaxy clusters that takes into account a detailed simulated selection function. Comparing our current observed number of clusters shows good agreement with predictions. We determine the expected degradation of the constraints as a result of self-calibrating the luminosity–temperature relation (with scatter), including temperature measurement errors, and relying on photometric methods for the estimation of galaxy cluster redshifts. We examine the effects of systematic errors in scaling relation and measurement error assumptions. Using only  ( T , z )  self-calibration, we expect to measure Ω_m to ±0.03 (and  Ω_Λ  to the same accuracy assuming flatness), and σ₈ to ±0.05, also constraining the normalization and slope of the luminosity–temperature relation to ±6 and ±13 per cent (at 1σ), respectively, in the process. Self-calibration fails to jointly constrain the scatter and redshift evolution of the luminosity–temperature relation significantly. Additional archival and/or follow-up data will improve on this. We do not expect measurement errors or imperfect knowledge of their distribution to degrade constraints significantly. Scaling-relation systematics can easily lead to cosmological constraints 2σ or more away from the fiducial model. Our treatment is the first exact treatment to this level of detail, and introduces a new 'smoothed ML' (Maximum Likelihood) estimate of expected constraints.  相似文献   

Oil and gas in offshore tracts: Bias in estimates of reserves     

L. A. Thomsen  Matt Joggerst 《Mathematical Geology》1985,17(4):353-365

Two independent data sets show that current means of estimating reserves of oil and gas in offshore fields are biased. The bias which is established here is that small fields (with less than about 10 million barrels of oil equivalent) are overestimated, and larger fields (at least up to 200 MMBOE) are underestimated. This systematic bias occurs with or without a significant overall bias, and in addition to a large scatter. Because bias (as opposed to scatter) has serious implications for national energy policy, and in particular for conduct of offshore lease sales, these results indicate that evaluation methods should be revised, or that ad hoc adjustments (based on historical data) should be applied.  相似文献   

Fluid flow, alteration and polysulphide mineralisation associated with a low-angle reverse shear zone in the Lower Palaeozoic of the Anglo-Brabant fold belt, Belgium     

K. Piessens  Muchez  S. Dewaele  A. Boyce  W. De Vos  M. Sintubin  T. N. Debacker  E. A. J. Burke  W. Viaene 《Tectonophysics》2002,348(1-3)

In the Lower Palaeozoic rocks of the Brabant Massif (Belgium), a recently discovered polysulphide mineralisation is related to a low-angle reverse shear zone. This shear zone has been attributed to the main early Devonian deformation event. Data from boreholes and outcrops allow a detailed investigation of the alteration pattern and palaeofluid flow along this shear zone. Macroscopic observations of the mineralogy and quantitative changes in the phyllosilicate mineralogy indicate that this shear zone is characterised by an envelope of intense sericitisation and silicification. In addition, chloritisation is associated with this alteration. The alteration zone may reach a thickness of 250 m. Ore mineralisation occurred synkinematically and is spatially related to the shear zone. The mineralisation consists of pyrite, marcasite, arsenopyrite, pyrrhotite, chalcopyrite, sphalerite, galena, stibnite and smaller amounts of tetrahedrite and other sulphosalts. It is concentrated in quartz–sulphide veins or occurs diffusely in the host rock. The mineralising fluids have a low-salinity H₂O–CO₂–CH₄–NaCl–(KCl) composition and a minimum temperature of 250–320 °C. The δ¹⁸O values of quartz vary between +12.3‰ and +14.5‰ SMOW, and δD compositions of the fluid inclusions in the quartz crystals range from −65‰ to −35‰ V-SMOW. The δD and the calculated δ¹⁸O values of the mineralising fluids fall in the range typical for metamorphic fluids and partly overlap with that for primary magmatic fluids. The δ³⁴S values, between +4.7‰ and +10.6‰ CDT, fall outside the interval typical for I-type magmas. Important migration of likely metamorphic fluids, causing a widespread alteration and a polysulphide mineralisation along a low-angle shear zone, has, thus, been identified for the first time in the Caledonian Anglo-Brabant fold belt.  相似文献   

Observed heating effects of conjugate photoelectrons     

William J. Burke  Rita C. Sagalyn  Madhoo Kanal 《Planetary and Space Science》1979,27(5):583-591

A gridded spherical electrostatic analyzer aboard Injun 5 has been used to measure fluxes of thermal and hyperthermal electrons at subauroral latitudes in the midnight sector of the northern ionosphere between altitudes of 2500 and 850 km. Due to the offset between the geomagnetic and geographic poles hyperthermal fluxes, consisting of energetic photoelectrons that have escaped from the sunlit southern hemisphere are observed along orbits over the Atlantic Ocean and North America but not over Asia. The ambient electron temperatures (T_e) near 2500 km have their highest values at trough latitudes for all longitudes. At altitudes near 1000 km elevated electron temperatures in the trough were not a consistent feature of the data. Equatorward of the trough, in the longitude sector to which conjugate photoelectrons have access, T_e ～ 4000 K at 2500 km and ～ 3000 K at 1000 km. For regions with the conjugate point in darkness T_e ? 2300 K over the 1000–2500 km altitude range. The effective thermal characteristics of conjugate photoelectrons are studied as functions of altitude and latitude. The observations indicate that (1) at trough latitudes elevated electron temperatures in the topside ionosphere are mostly produced by sources other than conjugate photoelectrons, and (2) at subtrough latitudes, in the Alantic Ocean-North American longitude sector, conjugate photoelectrons contribute significantly to the heating of topside electrons. Much of the conjugate photoelectron energy is deposited at altitudes >2500 km then conducted along magnetic field lines into the ionosphere.  相似文献   

Low density regions observed at high altitudes and their connection with equatorial spread F     

W.J. Burke  D.E. Donatelli  R.C. Sagalyn  M.C. Kelley 《Planetary and Space Science》1979,27(5):593-601

Observations from the high resolution spherical electrostatic analyzer experiment aboard ISIS 1 have been used to study large amplitude irregularities at low latitudes in the tipside ionosphere. The irregularities appeared as plasma depletions near the magnetic equator and were observed up to satellite apogee (3500 km). The altitude local time distribution of the depletions was such that those at altitudes greater than 2000 km were found only in the post-midnight sector. This result agrees with the predictions of a model for plasma bubbles drifting under the influence of gravity-buoyancy forces. Evidence is presented that the initial steep gradients observed at low altitudes are reduced by anomalous diffusion due to drift waves.  相似文献   

A review of present techniques and methodological advances in analyzing Th in aquatic systems     

Michiel Rutgers van der Loeff  Manmohan M. Sarin  Mark Baskaran  Claudia Benitez-Nelson  Ken O. Buesseler  Matt Charette  Minhan Dai   rjan Gustafsson  Pere Masque  Paul J. Morris  Kent Orlandini  Alessia Rodriguez y Baena  Nicolas Savoye  Sabine Schmidt  Robert Turnewitsch  Ingrid Vge  James T. Waples 《Marine Chemistry》2006,100(3-4):190

The short-lived thorium isotope ²³⁴Th (half-life 24.1 days) has been used as a tracer for a variety of transport processes in aquatic systems. Its use as a tracer of oceanic export via sinking particles has stimulated a rapidly increasing number of studies that require analyses of ²³⁴Th in both marine and freshwater systems. The original ²³⁴Th method is labor intensive. Thus, there has been a quest for simpler techniques that require smaller sample volumes. Here, we review current methodologies in the collection and analysis of ²³⁴Th from the water column, discuss their individual strengths and weaknesses, and provide an outlook on possible further improvements and future challenges. Also included in this review are recommendations on calibration procedures and the production of standard reference materials as well as a flow chart designed to help researchers find the most appropriate ²³⁴Th analytical technique for a specific aquatic regime and known sampling constraints.  相似文献   

Is the Ventersdorp Rift System of Southern Africa related to a continental collision between the Kaapvaal and Zimbabwe Cratons at 2.64 Ga ago?     

Kevin Burke  W.S.F. Kidd  Tim Kusky 《Tectonophysics》1985,115(1-2)

Rocks of the Ventersdorp Supergroup were deposited in a system of northeast trending grabens on the Kaapvaal Craton approximately 2.64 Ga ago contemporary with a continental collision between the Kaapvaal and Zimbabwe Cratons. We suggest that it was this collision that initiated the Ventersdorp rifting. Individual grabens strike at high angles toward the continental collision zone now exposed in the Limpopo Province where late orogenic left-lateral strike-slip faulting and anatectic granites are recognized. We relate the Ventersdorp rift province to extension in the Kaapvaal Craton associated with the collision, and see some analogy with such rifts as the Shansi and Baikal Systems associated with the current India-Asia continental collision.  相似文献   

Iron porphyrins in coal from the United States     

R. Bonnett  P.J. Burke 《Geochimica et cosmochimica acta》1985,49(6):1487-1489

Iron porphyrins have been isolated from seven U.S. humic coals of various geological ages. Mass spectrometry shows that for the higher rank coals the porphyrins comprise an homologous series of alkyl derivatives (C₂₇-C₃₂). Mesoheme is detected in a Cretaceous lignite from Montana.  相似文献