Metal donation and apo-metalloenzyme activation by stable isotopically labeled metallothionein     

Mason AZ  Perico N  Moeller R  Thrippleton K  Potter T  Lloyd D 《Marine environmental research》2004,58(2-5):371-375

Coupled HPLC-ICP-MS has been used to quantitatively study the effects of GSSG and GSH on the ability of metallothionein (MTII) to donate essential and non-essential metals to apo-carbonic anhydrase. Stable isotopically labeled (67)Zn(3)Cd(4) MTII was used to enable Zn donated from MTII to be differentiated from extraneous sources of Zn. Transfer of both (67)Zn and Cd from MTII to apo-carbonic anhydrase was noted in the absence of either GSSG or GSH. GSSG increased the initial transfer of both Zn and Cd. Thereafter, a gradual increase in the (67)Zn content at the expense of Cd was noted over 24-h indicating continued interaction and exchange between MTII and the enzyme commensurate with the relative preferences shown by the proteins for these two metals. Although GSH also increased transfer of (67)Zn from MT it reduced the simultaneous transfer of Cd to the enzyme thereby conferring protection against Cd induced activation.  相似文献   

Stratigraphic models for microtidal tidal deltas; examples from the Florida Gulf coast   总被引：1，自引：0，他引：1  

Richard A. Davis  Jr.  C. Kelly Cuffe  Katherine A. Kowalski  Eric J. Shock 《Marine Geology》2003,200(1-4):49-60

Extensive vibracoring of both flood- and ebb-tidal deltas along the central Gulf Coast of the Florida peninsula reveals a strong overall similarity with subtle distinctions between flood and ebb varieties. Although the coast in question is microtidal, the inlets range from tide-dominated to distinctly wave-dominated. Both types of tidal deltas overlie a muddy sand interpreted to have been deposited in a back-barrier environment. The sharp contact at the base of the tidal delta sequence is typically overlain by a thin shell gravel layer. The ebb-tidal delta sequence is characterized by fine quartz sand with shell gravel in various concentrations; coarse and massive at the margins of the main ebb channel, and finer and imbricated at the marginal flood channels. The flood-tidal deltas are characterized by the same facies but with a small amount of mud. Shelly facies on the channels on flood deltas are not as well developed as on the ebb deltas. The combination of the stratigraphic sequence and the lithofacies make tidal deltas readily identifiable in the ancient record. The differences between flood and ebb varieties are subtle but consistent.  相似文献   

Stabilisation of the Stanton Lees Landslip Using an Embedded Pile Retaining Wall     

Steve J. Hodgetts  Brendan C. O’Kelly  Matthew J. Raybould 《Geotechnical and Geological Engineering》2007,25(6):705-715

A landslip occurred near the village of Stanton Lees, Derbyshire, UK, in November 2000 following a prolonged period of heavy rainfall. The slip resulted in the gradual, progressive down-slope movement of a steep embankment that was supporting an existing gabion retaining wall and a minor road which was subsequently closed to vehicular traffic. This paper describes the site; the sequence of events leading up to the start of the landslide; an interpretation of the ground conditions and onsite monitoring data; and the engineering works carried out in order to stabilise the slip and return the road to serviceability. The landslip occurred due to the superficial deposits moving over the weathered bedrock after the groundwater levels had been elevated following a prolonged period of heavy rainfall. A stability analysis indicated that the embankment was at a state of limiting equilibrium and its factor of safety on slope instability was found to be particularly sensitive to fairly minor changes in the groundwater levels. The remedial works replaced the existing gabion wall with a new cantilevered, bored pile retaining wall that comprised two rows of piles (600-mm in diameter), which were staggered in plan arrangement.  相似文献   

Hydroacoustics as a tool for assessing fish biomass and size distribution associated with discrete shallow water estuarine habitats in Louisiana   总被引：1，自引：0，他引：1  

Kevin M. Boswell  Matthew P. Wilson  Charles A. Wilson 《Estuaries and Coasts》2007,30(4):607-617

We developed a relative index of fish biomass and size distribution in ultra-shallow waters (< 2 m) of Barataria Bay, Louisiana, based on the comparison of horizontal hydroacoustic data with gill net and push trawl catches in an effort to understand the role that habitat plays in both fish biomass and distribution. Exclosure net experiments indicated that the contribution of acoustic backscattering from sources other than fishes were negligible. Split-beam transducer, gill net, and push trawl sampling were conducted concurrently in Barataria Bay to provide information on fish composition and length distributions and for comparisons among gear types. Results suggest that acoustic fish biomass was generally higher in the low salinity stations and lower at the high salinity stations, at least in March 2004. We observed a greater mean length of fishes associated with oyster shell habitats when compared to adjacent sand-mud habitats. This paper demonstrates the utility of hydroacoustics as a tool to quantify relative acoustic fish biomass and size distribution associated with common estuarine habitats in ultra-shallow waters. This study also illustrates the potential of using acoustics for augmenting traditional sampling procedures.  相似文献   

Environmental assessment of the East African Rift Valley lakes     

Eric O. Odada  Daniel O. Olago  Fred Bugenyi  Kassim Kulindwa  Jerome Karimumuryango  Kelly West  Micheni Ntiba  Shem Wandiga  Peninah Aloo-Obudho  Pius Achola 《Aquatic Sciences - Research Across Boundaries》2003,65(3):254-271

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Simulation of a Ground Water Recirculation Well with a Dual-Column Laboratory Setup     

Suzanne Lesage  Susan Brown  Kelly Millar  Helena Steer 《Ground Water Monitoring & Remediation》2003,23(2):102-110

This paper describes a dual-column laboratory setup consisting of a glass column and a stainless-steel column filled with aquifer material. The setup was used to replicate a ground water recirculation well that serves as an in situ reactor and a combined injection/withdrawal well. The treatment solution consisted of a buffered titanium (III) citrate/vitamin B₁₂ mixture. The first column, representing the well, was made of glass, allowing for visual inspection of the mixing. The stainless-steel column was instrumented with redox (Eh) probes to monitor the changes in redox conditions. The redox measurement showed that, although the sand contained large quantities of iron oxides, the oxidation rate was relatively slow and the titanium solution would remain reduced for some time in the aquifer, continuing to react with the contaminants. This laboratory setup was used to optimize the reagent concentrations and rate of delivery for field implementation. It was found that 4 mM titanium citrate and 3 mg/L vitamin B₁₂ were sufficient to degrade 1,1,2,2-tetrachloroethane and carbon tetrachloride within one day, but not trichloroethylene, which required five days with 10 mM titanium citrate and 5 mg/L vitamin B₁₂.  相似文献   

Australia's Box–Ironbark Forests and Woodlands: saving the fragments of a threatened ecosystem     

Max Kelly 《The Australian geographer》2005,36(1):19-37

Australia's box–ironbark forests and woodlands once covered about 14 per cent of the State of Victoria on the riverine plains and foothills of the Great Dividing Range. But approximately 83 per cent of the total original habitat has been destroyed and what remains of this significant ecosystem is now highly fragmented and vulnerable to further degradation. Moreover, only 14 per cent of the area remaining is on public land. A 10 year campaign on the part of the environmental movement eventually succeeded in forcing the State government to conduct an independent inquiry into this ecosystem and make recommendations on future management. This paper outlines the innovative public participation process adopted by the Victorian State government and the outcomes of the inquiry. A subsequent compensation package for commercial operations disadvantaged by the proclamation of a series of new national parks is also discussed, as are the shortcomings of a process that can have little or no impact on what happens on private land.  相似文献   

Iron reduction and alteration of nontronite NAu-2 by a sulfate-reducing bacterium     

Yi-Liang Li  S.Kelly Sears  Baolin Deng 《Geochimica et cosmochimica acta》2004,68(15):3251-3260

Iron-rich clay minerals are abundant in the natural environment and are an important source of iron for microbial metabolism. The objective of this study was to understand the mechanism(s) of enhanced reduction of Fe(III) in iron-rich 2:1 clay minerals under sulfate-reducing conditions. In particular, biogenic reduction of structural Fe(III) in nontronite NAu-2, an Fe-rich smectite-group mineral, was studied using a Desulfovibrio spp. strain G-11 with or without amended sulfate. The microbial production of Fe(II) from NAu-2 is about 10% of total structural Fe(III) (30 mM) when Fe(III) is available as the sole electron acceptor. The measured production of Fe(II), however, can reach 29% of the total structural Fe(III) during sulfate reduction by G-11 when sulfate (50 mM) is concurrently added with NAu-2. In contrast, abiotic production of Fe(II) from the reaction of NAu-2 with Na₂S (50 mM) is only ca. 7.5% of the total structural Fe(III). The enhanced reduction of structural Fe(III) by G-11, particularly in the presence of sulfate, is closely related to the growth rate and metabolic activities of the bacteria. Analyses by X-ray diffraction, transmission electron microscopy, and energy dispersive spectroscopy reveal significant changes in the structure and composition of NAu-2 during its alteration by bacterial sulfate reduction. G-11 can also derive nutrients from NAu-2 to support its growth in the absence of amended minerals and vitamins. Results of this study suggest that sulfate-reducing bacteria may play a more significant role than previously recognized in the cycling of Fe, S, and other elements during alteration of Fe-rich 2:1 clay minerals and other silicate minerals.  相似文献   

The persistence of memory: the fate of ancient sedimentary organic carbon in a modern sedimentary system   总被引：3，自引：0，他引：3  

Neal E Blair  Elana L Leithold  Kelly A Peeler  Jennifer C Holmes 《Geochimica et cosmochimica acta》2003,67(1):63-73

The cycle of organic carbon burial and exhumation moderates atmospheric chemistry and global climate over geologic timescales. The burial of organic carbon occurs predominantly at sea in association with clay-sized particles derived from the erosion of uplifted continental rocks. It follows that the history of the fine-grained particles on land may bear on the nature of the organic carbon buried. In this study, the evolution of clay-associated organic matter was followed from bedrock source to the seabed in the Eel River sedimentary system of northern California using natural abundance ¹³C and ¹⁴C tracers. Approximately half of the fine-grained organic carbon delivered to the shelf is derived from ancient sedimentary organic carbon found in the uplifted Mesozoic-Tertiary Franciscan Complex of the watershed. The short residence time of friable soils on steep hill slopes, coupled with rapid sediment accumulation rates on the shelf-slope, act to preserve the ancient organic carbon. A comparable quantity of modern organic carbon is added to particles in the watershed and on the shelf and slope. The bimodal mixture of ancient and modern C in soils and sediments may be characteristic of many short, mountainous rivers. If the Eel River chemistry is typical of such rivers, more than 40 Tg of ancient organic C may be delivered to the world’s oceans each year. A flux of that magnitude would have a significant influence on marine and global C-cycles.  相似文献   

The neutral carbon distribution in a bipolar outflow/molecular disc source configuration: G35.2−0.74N     

Little  Kelly  & Murphy 《Monthly notices of the Royal Astronomical Society》1998,294(1):105-117

Maps are presented of ³ P ₁→³ P ₀[C  i ] and J =2→1 C¹⁸O line emission from the interstellar molecular cloud G35.2−0.74N. The maps are interpreted with reference to a previous model for the structure of the cloud in which opposing jets from a central object, embedded in a rotating interstellar disc, precess and drive a bipolar molecular outflow. The C¹⁸O emission traces the rotating interstellar disc, but the [C  i ] emission shows several features. An unresolved component is observed which probably results from dissociation of CO in the centre of the disc by UV radiation from the central source. Background [C  i ] emission is also observed which shares the rotation of the disc on larger scales. The C  i /CO ratio in these components is typically a few per cent. High-velocity [C  i ] emission, where C  i /CO is high (>0.1–0.4), is observed between the CO molecular outflow and the cavity exacavated by the jet. This material has probably been accelerated by the jet but dissociated by far-UV radiation propagating through the cavity. The C  i /CO ratio falls as the shocked outflow later sweeps up CO.  相似文献