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101.
In this study, the relationship between the concentration of extra-heavy crude petroleum in a clayey material and the toxicity, field capacity, temperature, and growth of a tropical forage grass (Brachiara humidicola) was determined empirically. For this type of petroleum the acute toxicity (Microtox®) was slight (CE50 = 63200 - 76400 mg/kg) even at high hydrocarbon concentrations (29279 mg/kg). Nonetheless, serious impacts were encountered in terms of an increase in soil temperature (+ 1.3 °C), reduction in field capacity (-10.7%) and reduction in aerial biomass (-97%). The relationship between hydrocarbon concentration and biomass resulted in a typical dose-response curve (r = 0.99), where a concentration of 2626 mg/kg of hydrocarbons corresponds to a maintenance of 90% biomass. Furthermore, during the duration of this study (one year) the biodegradation was proportional to the pasture biomass production (r = 0.997) indicating a synergistic relationship between the petroleum biodegrading microorganisms in the rhizosphere and the pasture. 相似文献
102.
Isolation by oceanic distance and spatial genetic structure in an overharvested international fishery 下载免费PDF全文
Nathan K. Truelove Stephen J. Box Karl A. Aiken Azra Blythe‐Mallett Erik M. Boman Catherine J. Booker Tamsen T. Byfield Courtney E. Cox Martha H. Davis Gabriel A. Delgado Bob A. Glazer Sarah M. Griffiths Kimani Kitson‐Walters Andy S. Kough Ricardo Pérez Enríquez Richard F. Preziosi Marcia E. Roy Iris Segura‐García Mona K. Webber Allan W. Stoner 《Diversity & distributions》2017,23(11):1292-1300
103.
Michael DR Phillips AO Krupa A Martin J Redman JE Altaher A Neville RD Webber J Kim MY Bowen T 《The Journal of biological chemistry》2011,286(22):19523-19532
104.
Angela Karp Steve J.Hanley Sviatlana O.Trybush William Macalpine Ian Shield 《Acta Botanica Sinica》2011,(2)
Willows (Salix spp.) are a very diverse group of catkin-bearing trees and shrubs that are widely distributed across temperate regions of the globe.Some species respond well to being grown in short rotation coppice (SRC) cycles,which are much shorter than conventional forestry.Coppicing reinvigorates growth and the biomass rapidly accumulated can be used as a source of renewable carbon for bioenergy and biofuels.As SRC willows re-distribute nutrients during the perennial cycle they require only minimal nitro... 相似文献
105.
Martha K. Raynolds Donald A. Walker Kenneth J. Ambrosius Jerry Brown Mikhail Kanevskiy Gary P. Kofinas Vladimir E. Romanovsky Yuri Shur Patrick J. Webber 《Global Change Biology》2014,20(4):1211-1224
Many areas of the Arctic are simultaneously affected by rapid climate change and rapid industrial development. These areas are likely to increase in number and size as sea ice melts and abundant Arctic natural resources become more accessible. Documenting the changes that have already occurred is essential to inform management approaches to minimize the impacts of future activities. Here, we determine the cumulative geoecological effects of 62 years (1949–2011) of infrastructure‐ and climate‐related changes in the Prudhoe Bay Oilfield, the oldest and most extensive industrial complex in the Arctic, and an area with extensive ice‐rich permafrost that is extraordinarily sensitive to climate change. We demonstrate that thermokarst has recently affected broad areas of the entire region, and that a sudden increase in the area affected began shortly after 1990 corresponding to a rapid rise in regional summer air temperatures and related permafrost temperatures. We also present a conceptual model that describes how infrastructure‐related factors, including road dust and roadside flooding are contributing to more extensive thermokarst in areas adjacent to roads and gravel pads. We mapped the historical infrastructure changes for the Alaska North Slope oilfields for 10 dates from the initial oil discovery in 1968–2011. By 2010, over 34% of the intensively mapped area was affected by oil development. In addition, between 1990 and 2001, coincident with strong atmospheric warming during the 1990s, 19% of the remaining natural landscapes (excluding areas covered by infrastructure, lakes and river floodplains) exhibited expansion of thermokarst features resulting in more abundant small ponds, greater microrelief, more active lakeshore erosion and increased landscape and habitat heterogeneity. This transition to a new geoecological regime will have impacts to wildlife habitat, local residents and industry. 相似文献
106.
Linda C. McCarthy Marie-Therese Bihoreau Susanna L. Kiguwa Julie Browne Takeshi K. Watanabe Haretsugu Hishigaki Atsushi Tsuji Susanne Kiel Caleb Webber Maria E. Davis Catherine Knights Angela Smith Ricky Critcher Patrick Huxtall James R. Hudson Jr. Toshihide Ono Hiroumi Hayashi Toshihisa Takagi Yusuke Nakamura Akira Tanigami Peter N. Goodfellow G. Mark Lathrop Michael R. James 《Mammalian genome》2000,11(9):791-795
107.
Shannyn E. Wolfe Daniel E. Howard John A. Schetz Caroline J. Cheng Robert Webber Diane M. Beatty Bibie M. Chronwall & Stephen J. Morris 《Journal of neurochemistry》1999,72(2):479-490
Abstract : Dopamine D2 receptors both acutely and chronically inhibit high-voltage-activated Ca2+ channels (HVA-CCs). Two alternatively spliced isoforms, D2L (long) and D2S (short), are expressed at high levels in rat pituitary intermediate lobe melanotropes but are lacking in anterior lobe corticotropes. We stably transfected D2L and D2S into corticotrope-derived AtT20 cells. Both isoforms coupled to inhibition of Q-type calcium channels through pertussis toxin-sensitive G proteins. Thus, we have created a model system in which to study the kinetics of D2 -receptor regulation of Ca2+ channels. Rapid inhibition of HVA-CCs was characterized using a novel fluorescence video imaging technique for the measurement of millisecond kinetic events. We measured the time elapsed (lag time) between the arrival of depolarizing isotonic 66 m M K+ , sensed by fluorescence from included carboxy-X-rhodamine (CXR), and the beginning of increased intracellular Ca2+ levels (sensed by changes in indo 1 fluorescence ratio). The lag time averaged 350-550 ms, with no significant differences among cell types. Addition of the D2 -agonist quinpirole (250 μ M ) to the K+ /CXR solution significantly increased the lag times for D2 -expressing cells but did not alter the lag time for AtT20 controls. The increased lag times for D2L - and D2S -transfected cells suggest that at least a fraction of the Ca2+ channels was inhibited within the initial 350-550 ms. As this inhibition time is too fast for a multistep second messenger pathway, we conclude that inhibition occurs via a membrane-delimited diffusion mechanism. 相似文献
108.
Purified rat-liver dihydropteridine reductase is homogeneous by gel filtration (Mr approximately 51,000), sodium dodecyl sulfate-polyacrylamide gel electrophoresis (Mr approximately 25,500), and native polyacrylamide gel electrophoresis, suggesting that the enzyme is composed of two identical subunits. However, analysis by isoelectric focusing has revealed three enzyme forms with approximate isoelectric points of 6.5, 5.9, and 5.7 (designated forms, I, II, and III, respectively). The three forms, isolated in 65% yield by preparative chromatofocusing, are stable in 0.05 M phosphate buffer, pH 6.8, containing 1 mM beta-mercaptoethanol and exhibit similar kinetic constants when the catalytic activities of the isolated forms are compared with quinonoid dihydrobiopterin as substrate. All forms generate complexes with the enzymatic cofactor NADH which are also detectable by IEF. When examined further by IEF under denaturing conditions in 6 M urea the enzyme demonstrates a differing subunit composition for its three forms. Two distinct subunits, designated alpha and beta, can be identified, and additional evidence suggests that the native enzyme forms I, II, and III represent the three differing dimeric combinations alpha alpha (form I), alpha beta (form II), and beta beta (form III). 相似文献
109.
110.
Adam NR Wall GW Kimball BA Pinter PJ Lamorte RL Hunsaker DJ Adamsen FJ Thompson T Matthias AD Leavitt SW Webber AN 《Photosynthesis research》2000,66(1-2):65-77
We have examined the photosynthetic acclimation of wheat leaves grown at an elevated CO2 concentration, and ample and limiting N supplies, within a field experiment using free-air CO2 enrichment (FACE). To understand how leaf age and developmental stage affected any acclimation response, measurements were
made on a vertical profile of leaves every week from tillering until maturity. The response of assimilation (A) to internal
CO2 concentration (Ci) was used to estimate the in vivo carboxylation capacity (Vcmax) and maximum rate of ribulose-1,5-bisphosphate limited photosynthesis (A
sat). The total activity of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), and leaf content of Rubisco and the Light
Harvesting Chlorophyll a/b protein associated with Photosystem II (LHC II), were determined. Elevated CO2 did not alter Vcmax in the flag leaf at either low or high N. In the older shaded leaves lower in the canopy, acclimatory decline in Vcmax and A
sat was observed, and was found to correlate with reduced Rubisco activity and content. The dependency of acclimation on N supply
was different at each developmental stage. With adequate N supply, acclimation to elevated CO2 was also accompanied by an increased LHC II/Rubisco ratio. At low N supply, contents of Rubisco and LHC II were reduced in
all leaves, although an increased LHC II/Rubisco ratio under elevated CO2 was still observed. These results underscore the importance of leaf position, leaf age and crop developmental stage in understanding
the acclimation of photosynthesis to elevated CO2 and nutrient stress.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献