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111.
Esler D Ballachey BE Trust KA Iverson SA Reed JA Miles AK Henderson JD Woodin BR Stegeman JJ McAdie M Mulcahy DM Wilson BW 《Marine pollution bulletin》2011,62(3):609-614
We examined hepatic EROD activity, as an indicator of CYP1A induction, in Barrow’s goldeneyes captured in areas oiled during the 1989 Exxon Valdez spill and those from nearby unoiled areas. We found that average EROD activity differed between areas during 2005, although the magnitude of the difference was reduced relative to a previous study from 1996/1997, and we found that areas did not differ by 2009. Similarly, we found that the proportion of individuals captured from oiled areas with elevated EROD activity (?2 times unoiled average) declined from 41% in winter 1996/1997 to 10% in 2005 and 15% in 2009. This work adds to a body of literature describing the timelines over which vertebrates were exposed to residual Exxon Valdez oil and indicates that, for Barrow’s goldeneyes in Prince William Sound, exposure persisted for many years with evidence of substantially reduced exposure by 2 decades after the spill. 相似文献
112.
Samuel Kinsley 《Geoforum》2011,42(2):231-240
Visions of the future predict spaces apparently teaming with ever more novel and pervasive technologies. Significant amongst such forecasts is the notion of ‘ubiquitous computing’ (ubicomp), understood as an affordance or capacity tied (in)to people, places and things. This article stages an encounter between the futurity of ubicomp and recent debates in geography around anticipation. So, first, the future orientation in ubicomp research and development (R&D) is investigated as a mode of anticipation. ‘Knowledges’, and ‘logics’ of anticipation are subsequently, and second, discussed as the conceptual apparatus that constructs and perpetuates the ‘proximate future’ of ubicomp. This analysis connects recent discussion about ‘anticipation’ in social sciences research with the methods of ubicomp research, which fits with an emergent agenda around futurity in human geography. Third, the conceptual articulation of ‘anticipatory logic’ is applied to the analysis of empirical investigations of ubicomp R&D to identify the specific logics of anticipation at play. This article accordingly examines the logics of anticipation that both support and destabilise the certainty with which the future is imagined within ubicomp. In conclusion, the multiple ways of anticipating a future world and the ways in which they discipline understandings of futurity are framed as a politics of anticipation. 相似文献
113.
The cable shovel is widely used in surface mining. High operating and ownership costs necessitate efficient use of the cable
shovel. Operator practices have long been suspected to contribute towards the inefficient use of the shovel. Crowd arm and
hoist rope speeds are key measures of operator practices. The objective of this work is to find the crowd arm and hoist rope
speeds for optimal shovel performance for given initial conditions and material properties. Shovel kinematics and dynamic modeling, using shovel
geometry and the simultaneous constraint method, respectively, have been employed to build models of the excavation process.
Dynamic models of the shovel payload and the material cutting resistance have also been developed using geometric simulation
and passive soil pressures techniques, respectively. These models are solved numerically by combining Runge–Kutta and Gaussian
elimination algorithms to compute the work done and the resistive forces during shovel excavation. The algorithms have been
combined into a shovel simulator. The simulator has been used to simulate the P&H 2100BL shovel. The simulation results indicate
that input energy and digging time increase with increasing crowd arm and decreasing hoist rope speeds. The input energy per
unit loading rate is proposed as an appropriate measure of shovel performance. High energy per unit loading rate occurs for
high crowd speeds and low hoist rope speeds. For the simulated conditions and crowd arm and hoist rope speeds ranging from
0.25 to 0.5 ms−1 and 0.5 to 0.7 ms−1, respectively, the optimal crowd arm and hoist rope speeds were found to be 0.25 ms−1 and 0.7 ms−1, respectively, and the objective function value was 0.21 KJs/kg. This work establishes, theoretically, the fact that operator
practices have an effect on shovel performance and is useful in establishing optimum practices. The results are the initial
steps towards full automation of the excavation process. 相似文献
114.
Sandow Mark Yidana Samuel Ganyaglo Bruce Banoeng-Yakubo Thomas Akabzaa 《Journal of African Earth Sciences》2011,59(2-3):185-194
A conceptual groundwater flow model was developed for the crystalline aquifers in southeastern part of the Eastern region, Ghana. The objective was to determine approximate levels of groundwater recharge, estimate aquifer hydraulic parameters, and then test various scenarios of groundwater extraction under the current conditions of recharge. A steady state groundwater flow model has been calibrated against measured water levels of 19 wells in the area. The resulting recharge is estimated to range from 8.97 × 10?5 m/d to 7.14 × 10?4 m/d resulting in a basin wide average recharge of about 9.6% of total annual precipitation, which results in a basin wide quantitative recharge of about 2.4 million m3/d in the area. This compares to recharge estimated from the chloride mass balance of 7.6% of precipitation determined in this study. The general groundwater flow in the area has also been determined to conform to the general northeast–southwest structural grain of the country. The implication is that the general hydrogeology is controlled by post genetic structural entities imposed on the rocks to create ingresses for sufficient groundwater storage and transport. Calibrated aquifer hydraulic conductivities range between 0.99 m/d and over 19.4 m/d. There is a significant contribution of groundwater discharge to stream flow in the study area. Increasing groundwater extraction will have an effect on stream flow. This study finds that the current groundwater extraction levels represent only 0.17% of the annual recharge from precipitation, and that groundwater can sustain future increased groundwater demands from population growth and industrialization. 相似文献
115.
Samuel Giersch Eberhard Frey Wolfgang Stinnesbeck Christina Ifrim José Manuel Padilla Gutierrez 《Swiss Journal of Geoscience》2011,104(1):73-84
A new species of the clupeid genus Scombroclupea is described from the Upper Cretaceous (Cenomanian) Plattenkalk locality “Loma la Mula” in Coahuila, northeastern Mexico. The material provides new osteological data for the genus, which clarify its systematic position. The Mexican Scombroclupea points to an occurrence of the genus in the western Tethys and indicates a vicariant event between S. macrophthalma from Lebanon and Croatia and the new species described herein. The analysis of the functional morphology of Scombroclupea supports the reconstruction of an oscillatory locomotion mode in this genus. 相似文献
116.
Beach nets are preventative devices used to minimize interactions between potentially harmful sharks and unsuspecting swimmers. Quantitative studies demonstrated that beach nets drastically reduced local elasmobranch populations, as well as caused considerable bycatch mortality. For this experiment, a beach net-like device was constructed and the behaviors of six juvenile lemon sharks (Negaprion brevirostris) were analyzed. Induced by olfactory and gustatory cues, sharks were given the choice to swim through a magnetic or control opening in the net. In the first trial, all six sharks avoided the magnetic region and significantly preferred to swim through the control region of the fence. The magnetic stimulus no longer affected the swimming behavior of three sharks retested after resting 24 h. Results from the retested sharks were correlated with those from repeated tonic immobility trials, which demonstrated a linear decrease in sensitivity to repeated magnetic stimulation. This study serves as a baseline experiment demonstrating that permanent magnets may substantially decrease elasmobranch mortality within beach nets. 相似文献
117.
Zhenghong Tang Samuel D. BrodyRuopu Li Courtney QuinnNan Zhao 《Ocean & Coastal Management》2011,54(5):415-426
Local jurisdictions play a critical role in climate change mitigation and adaptation. This study analyzes the theoretical framework of locally driven climate change actions and uses geographic information system (GIS) to map local jurisdictions’ climate change policy efforts in three Pacific states - California, Oregon, and Washington. The results of our study indicate statistically significant differences in geographic clusters and variations across jurisdictions. An Ordinary Least Squares (OLS) regression model was used to examine climate risk, emission stress, and socioeconomic context variables to detect influence on local climate change policy efforts. The explanatory results indicate that coastal proximity, population density, vehicles emission, and education variables significantly influence local jurisdictions’ climate change actions. The findings contribute to local organizational decision model research and can help local communities to develop more effective climate change policies. 相似文献
118.
Doris Sadek Ghabrial Michael Dawood Samuel Hilmy Essa Moussa 《Arabian Journal of Geosciences》2013,6(10):3635-3649
The south Solaf zone in SW Sinai comprises a metasedimentary sequence of metagraywackes intercalated with minor metavolcanic sheets, metasiltstones, meta-arenites, and calc–silicates. The metavolcanics (basalt–andesite) show high- to medium-K calc–alkaline nature. They exhibit distinctive Nb-Ta negative anomalies relative to enriched LILE, being highly similar to active continental margin lavas, but they also have the characteristics of rift-related magmatism. Magmas of similar composition are interpreted to be formed in an extensional environment and their source regions are zones of enriched subcontinental lithosphere. The metasediments are poor to moderate sorting, intercalated to the north with minor impure calcareous layers. Geochemical investigation shows that they are immature to semi-mature sediments derived from a source of mafic to felsic composition. These metasediments are chemically similar to the active continental margins and are comparable to the Feiran gneisses and metagraywackes that were deposited before 800 Ma in an extensional environment. The investigated rocks suffered LP-HT amphibolite facies metamorphism. The P-T estimates using various thermobarometric calibrations gave temperatures of 554–610 °C and pressures of 2.2–4.0 kbar. 相似文献
119.
Rusty A. Gonser Ryan R. Jensen Samuel E. Wolf 《Applied geography (Sevenoaks, England)》2009,29(4):527-532
Deer–vehicle collisions (DVCs) are a constant problem in North America that cost millions of dollars of damage and loss of human life. This study investigated the spatial relationship of DVCs for a county in western Indiana using nearest neighbor analysis, chi-square test of independence, and a landscape metric: the percentage of like adjacencies. The study was able to show that DVCs are not randomly located, and that habitat type and structure may play an important role in the location of DVCs. 相似文献
120.
Cassandra R. Fenton Samuel Niedermann Mirjam M. Goethals Björn Schneider Jan Wijbrans 《Quaternary Geochronology》2009,4(6):475-492
Combining cosmogenic 3He and 21Ne (3Hec and 21Nec) measurements on both pyroxene and olivine from the Pleistocene Bar Ten flows (85–107 ka) greatly increases our ability to evaluate the accuracy of 3Hec and 21Nec production rates and, therefore, 3Hec and 21Nec surface exposure ages. Comparison of 3Hec and 21Nec age-pairs yielded by experimentally determined production rates and composition-based model calculations indicates that the former give more accurate surface exposure ages than the latter in this study. However, experimental production rates should be adjusted to the composition of the minerals being analyzed to obtain the best agreement between 3Hec and 21Nec ages for any given sample. 21Nec/3Hec values are 0.400 ± 0.029 and 0.204 ± 0.014 for olivine and pyroxene, respectively, in Bar Ten lava flows, in agreement with previously published values, and indicate that 21Nec/3Hec in olivine and pyroxene is not affected by erosion and remains constant with latitude, elevation, and time (up to 10 Myr). Samples with 21Nec/3Hec that do not agree with these values may indicate the presence of non-cosmogenic helium and/or neon. The neon three-isotope diagram can also indicate whether or not all excess neon in mineral separates comes from cosmogenic sources. An error-weighted regression for olivine defines a spallation line [y = (1.033 ± 0.031)x + (0.09876 ± 0.00033)], which is indistinguishable from that for pyroxene (Schäfer et al., 1999). We have derived a production rate of 25 ± 8 at/g/yr for 21Nec in clinopyroxene (En43–44) based on the 40Ar/39Ar age of the upper Bar Ten flow. Our study indicates that the production rate of 21Nec in olivine may be slightly higher than previously determined. Cosmogenic 3He and 21Ne remain extremely useful, particularly when paired, in determining accurate eruption ages of young olivine- and pyroxene-rich basaltic lava flows. 相似文献