Generous statistical tests   总被引：1，自引：1，他引：0  

T. V. Hromadka II  R. J. Whitley  S. B. Horton  M. J. Smith  J. M. Lindquist 《Stochastic Environmental Research and Risk Assessment (SERRA)》2009,23(1):9-12

A common statistical problem is deciding which of two possible sources, A and B, of a contaminant is most likely the actual source. The situation considered here, based on an actual problem of polychlorinated biphenyl contamination discussed below, is one in which the data strongly supports the hypothesis that source A is responsible. The problem approach here is twofold: One, accurately estimating this extreme probability. Two, since the statistics involved will be used in a legal setting, estimating the extreme probability in such a way as to be as generous as is possible toward the defendant’s claim that the other site B could be responsible; thereby leaving little room for argument when this assertion is shown to be highly unlikely. The statistical testing for this problem is modeled by random variables {X _i } and the corresponding sample mean the problem considered is providing a bound ɛ for which for a given number a ₀. Under the hypothesis that the random variables {X _i } satisfy E(X _i ) ≤ μ, for some 0  < μ < 1, statistical tests are given, described as “generous”, because ɛ is maximized. The intent is to be able to reject the hypothesis that a ₀ is a value of the sample mean while eliminating any possible objections to the model distributions chosen for the {X _i } by choosing those distributions which maximize the value of ɛ for the test used.  相似文献   

The solubility of TiO₂ in olivine: implications for the mantle wedge environment     

L. Dobrzhinetskaya  K. N. Bozhilov  H. W. Green II 《Chemical Geology》1999,160(4):731-370

One characteristic of many subduction-zone garnet peridotites is that they contain titanium-bearing phases not otherwise found in mantle rocks. In particular, titanoclinohumite and/or its breakdown assemblage consisting of symplectic intergrowths of olivine and ilmenite is common in many of these bodies. The Alpe Arami garnet lherzolite of the Swiss Alps, while lacking titanoclinohumite, displays instead large numbers of FeTiO₃ rod-shaped precipitates in the oldest generation of olivine, amounting to approximately 1% by volume, indicating that at some time in its past, the peridotite experienced conditions under which the solubility of TiO₂ in olivine was >0.6 wt.%. In order to test the hypothesis that the environment of very high solubility of TiO₂ in olivine is to be found at very high pressures, we have conducted experiments on lherzolite compositions with added ilmenite at pressures between 5 and 12 GPa and temperatures of 1350–1700 K. Our results on anhydrous compositions show that whereas solubility of TiO₂ was not detected in olivine at 5 GPa, 1400 K where it coexists with rutile, when rutile disappeared from the paragenesis, the solubility climbed to 0.4 wt.% at 8 GPa, 0.5 wt.% at 10 GPa and to >1.0 wt.% at 12 GPa, 1700 K. These results support our previous interpretations from titanate morphology and abundance that the Alpe Arami massif has surfaced from P=10 GPa but remove the need to suggest a deeper origin and possible precursor phase such as wadsleyite. They also support the hypothesis that garnet peridotites with unusual Ti-bearing phases reflect a unique mantle environment occurring in the mantle wedge overlying subduction zones.  相似文献   

On the measurement of pigment concentrations by monochromator and diode-array spectrophotometers     

M. Latasa  R. R. Bidigare  M. E. Ondrusek  M. C. Kennicutt II 《Marine Chemistry》1999,66(3-4)

  相似文献   

新疆阿勒泰地区中低产田及其改造措施   总被引：1，自引：0，他引：1  

杨发相  李国振  左恒治  沈玉凌  乔木  李武平  李愚超  冯惠生 《干旱区地理》2000,23(3):239-243

中低产田指农作物产量低下的耕地。中低产田生产潜力大,对其改造的经济和生态效益均大于新垦荒地,在水少地多和生态脆弱的干旱区尤其如此,对其加强研究与改造是十分重要的。阿勒泰地区中低产田分布广,面积大,成因复杂,在新疆有较好的代表性。本文论述阿勒泰地区中低产田的分布、类型,分析中低产田的成因,并提出改造措施。  相似文献   

Effects of phenology and meteorological disturbance on litter rainfall interception for a Pinus elliottii stand in the Southeastern United States   总被引：1，自引：0，他引：1       下载免费PDF全文

John T. Van Stan II  Miriam Coenders‐Gerrits  Michael Dibble  Philine Bogeholz  Zachary Norman 《水文研究》2017,31(21):3719-3728

Litter layers develop across a diverse array of vegetated ecosystems and undergo significant temporal compositional changes due to canopy phenological phases and disturbances. Past research on temporal dynamics of litter interception has focused primarily on litter thickness and leaf fall, yet forest phenophases can change many more litter attributes (e.g., woody debris, bark shedding, and release of reproductive materials). In this study, weekly changes in litter composition over 1 year were used to estimate litter water storage dynamics and model event‐based litter interception. Litter interception substantially reduced throughfall (6–43%), and litter water storage capacity ranged from 1 to 3 mm, peaking when megastrobili release and liana leaf senescence occurred simultaneously during fall 2015. Tropical storm disturbances occurred during the sampling period, allowing evaluation of how meteorological disturbances altered litter interception. High wind speeds and intense rainfall from 2 tropical storms increased litter interception by introducing new woody debris, which, in this study, stored more water than the pre‐existing woody debris. After 2 extreme weather events, a third (Hurricane Hermine) did not increase woody debris (or litter interception), suggesting that the canopy pool of branches susceptible to breakage had been largely depleted. Needle and bark shedding had minor effects on litter interception. Results suggest that the release of reproductive materials and meteorological disturbances appear to be the major compositional drivers of litter interception beyond their obvious contribution to litter thickness.  相似文献   

Reply to comment on “A framework for understanding the hydroecology of impacted wet meadows in the Sierra Nevada and Cascade Ranges, California, USA”: paper published in Hydrogeology Journal (2009) 17:229–246, by Steven P. Loheide II, Richard S. Deitchman, David J. Cooper, Evan C. Wolf, Christopher T. Hammersmark, Jessica D. Lundquist     

Steven P. Loheide II  Richard S. Deitchman  David J. Cooper  Evan C. Wolf  Christopher T. Hammersmark  Jessica D. Lundquist 《Hydrogeology Journal》2010,18(7):1745-1746

  相似文献   

Lithospheric structure and tectonics at Isidis Planitia, Mars     

J. Andreas Ritzer  Steven A. Hauck II 《Icarus》2009,201(2):528-539

We characterize the lithospheric structure of Isidis Planitia on Mars by analyzing Mars Global Surveyor and Mars Odyssey gravity and topography data using a flexural model of a thin elastic shell including bending and membrane stresses. Isidis Planitia is a circular, relatively flat plain formed near the end of the Early Noachian, at the edge of the highlands-lowlands boundary and the site of a large free-air gravity anomaly, features consistent with modification and filling of an impact basin. Our results suggest that the bulk density of the fill material inside Isidis must be more than 2600 kg m⁻³ and higher densities are probable. A comparison of the faulting observed at Nili Fossae to the predicted zone of extensional strain northwest of Isidis constrains the thickness of the elastic lithosphere to be 100-180 km thick beneath the basin at the time of loading. We also find that loads outside of the basin play a significant role in the interpretation of the tectonics; simplified models tend to overestimate the lithospheric thickness. We place relatively narrow bounds on the thermal gradient (3.4-6.5 K km⁻¹) and heat flux (13.6-26 mW m⁻²) at Isidis at the time of loading.  相似文献   

A framework for understanding the hydroecology of impacted wet meadows in the Sierra Nevada and Cascade Ranges, California, USA   总被引：1，自引：0，他引：1  

Steven P. Loheide II  Richard S. Deitchman  David J. Cooper  Evan C. Wolf  Christopher T. Hammersmark  Jessica D. Lundquist 《Hydrogeology Journal》2009,17(1):229-246

Meadows of the Sierra Nevada and Cascade mountains of California, USA, support diverse and highly productive wet-meadow vegetation dominated by sedges, rushes, grasses, and other herbaceous species. These groundwater–dependent ecosystems rely on the persistence of a shallow water table throughout the dry summer. Case studies of Bear Creek, Last Chance, and Tuolumne meadow ecosystems are used to create a conceptual framework describing groundwater–ecosystem connections in this environment. The water requirements for wet-meadow vegetation at each site are represented as a water-table-depth hydrograph; however, these hydrographs were found to vary among sites. Causes of this variation include (1) differences in soil texture, which govern capillary effects and availability of vadose water and (2) elevation-controlled differences in climate that affect the phenology of the vegetation. The field observations show that spatial variation of water-table depth exerts strong control on vegetation composition and spatial patterning. Groundwater-flow modeling demonstrates that lower hydraulic-conductivity meadow sediments, higher groundwater-inflow rates, and a higher ratio of lateral to basal-groundwater inflow all encourage the persistence of a high water table and wet-meadow vegetation, particularly at the margin of the meadow, even in cases with moderate stream incision.  相似文献   

Adsorption of l-aspartate to rutile (α-TiO₂): Experimental and theoretical surface complexation studies     

Caroline M. Jonsson  Christopher L. Jonsson  Charlene Estrada  Dimitri A. Sverjensky  H. James Cleaves II 《Geochimica et cosmochimica acta》2010,74(8):2356-22386

Interactions between aqueous amino acids and mineral surfaces influence many geochemical processes from biomineralization to the origin of life. However, the specific reactions involved and the attachment mechanisms are mostly unknown. We have studied the adsorption of l-aspartate on the surface of rutile (α-TiO₂, pH_PPZC = 5.4) in NaCl(aq) over a wide range of pH, ligand-to-solid ratio and ionic strength, using potentiometric titrations and batch adsorption experiments. The adsorption is favored below pH 6 with a maximum of 1.2 μmol of adsorbed aspartate per m² of rutile at pH 4 in our experiments. The adsorption decreases at higher pH because the negatively charged aspartate molecule is repelled by the negatively charged rutile surface above pH_PPZC. At pH values of 3-5, aspartate adsorption increases with decreasing ionic strength. The adsorption of aspartate on rutile is very similar to that previously published for glutamate (Jonsson et al., 2009). An extended triple-layer model was used to provide a quantitative thermodynamic characterization of the aspartate adsorption data. Two reaction stoichiometries identical in reaction stoichiometry to those for glutamate were needed. At low surface coverages, aspartate, like glutamate, may form a bridging-bidentate surface species binding through both carboxyl groups, i.e. “lying down” on the rutile surface. At high surface coverages, the reaction stoichiometry for aspartate was interpreted differently compared to glutamate: it likely involves an outer-sphere or hydrogen bonded aspartate surface species, as opposed to a partly inner-sphere complex for glutamate. Both the proposed aspartate species are qualitatively consistent with previously published ATR-FTIR spectroscopic results for aspartate on amorphous titanium dioxide. The surface complexation model for aspartate was tested against experimental data for the potentiometric titration of aspartate in the presence of rutile. In addition, the model correctly predicted a decrease of the isoelectric point with increased aspartate concentration consistent with previously published studies of the aspartate-anatase system. Prediction of the surface speciation of aspartate on rutile indicates that the relative proportions of the two complexes are a strong function of environmental conditions, which should be taken into account in considerations of geochemical systems involving the interactions of biomolecules and minerals in electrolyte solutions.  相似文献   

Despinning plus global contraction and the orientation of lobate scarps on Mercury: Predictions for MESSENGER     

Andrew J. Dombard  Steven A. Hauck II 《Icarus》2008,198(1):274-276

Observations by the Mariner 10 spacecraft suggest that the lobate scarps on Mercury, which have been interpreted to record at most 1-2 km of radial contraction of the planet after the end of the Late Heavy Bombardment, possess a global, preferred N-S orientation but lack a strong latitudinal dependence on their surface expression. Here, we reexamine the idea that a decrease in the planetary rotation rate (despinning) coupled with global contraction of at least 3-5.5 km prior to the end of Late Heavy Bombardment resulted in global N-S oriented thrust faults. The surface expression of these faults is assumed to have been erased by the end of the Late Heavy Bombardment, and the faults were subsequently reactivated by later global contraction, producing generally N-S oriented thrust faults from an isotropic stress field. We use the estimate of >3-5.5 km contraction prior to ∼4 Ga as an additional constraint to thermomechanical simulations of the evolution of Mercury, finding that a wide range of models are consistent with this observation. The fact that a wide range of states are consistent with the contraction of Mercury prior to the end of Late Heavy Bombardment but only a restricted set of states are consistent with the at most 1-2 km of subsequent contraction bolsters the idea that there may be hidden strain on Mercury, features unseen by Mariner 10 but likely visible to the MESSENGER spacecraft.  相似文献