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711.
712.
Modeling obsolete computer stock under regional data constraints: An Atlanta case study 总被引:1,自引:0,他引:1
Nancey Green Leigh Matthew J. Realff Ning Ai Steven P. French Catherine L. Ross Bert Bras 《Resources, Conservation and Recycling》2007,51(4):847-869
In this paper, we report on our efforts to develop a research framework that can be used to quantify waste flows for different geographical areas in the face of limited waste data availability. We demonstrate this framework in our case study of obsolete computers in the Atlanta metropolitan area. We develop computer obsolescence rates at the national metropolitan level, and couple this data with economic information at the census tract level to generate product inventory estimates (PIE) of the stock of obsolete computers from both business and household sectors in the Atlanta metropolitan area. We seek to improve the accuracy of waste flow estimates for specific geographic areas over those of previous studies, provide an easily replicable and cost effective methodology, highlight the ensuing spatial implications for collection and recycling systems using GIS, and demonstrate the potential economic benefits from diverting electronic wastes within a region. The modeling framework we have developed is intended to be applicable to other regions and to other medium range durable goods discarded by households, businesses, or obtained from buildings. 相似文献
713.
Non-avian theropod dinosaurs attained large body sizes, monopolising terrestrial apex predator niches in the Jurassic–Cretaceous.
From the Middle Jurassic onwards, Allosauroidea and Megalosauroidea comprised almost all large-bodied predators for 85 million
years. Despite their enormous success, however, they are usually considered absent from terminal Cretaceous ecosystems, replaced
by tyrannosaurids and abelisaurids. We demonstrate that the problematic allosauroids Aerosteon, Australovenator, Fukuiraptor and Neovenator form a previously unrecognised but ecologically diverse and globally distributed clade (Neovenatoridae, new clade) with the
hitherto enigmatic theropods Chilantaisaurus, Megaraptor and the Maastrichtian Orkoraptor. This refutes the notion that allosauroid extinction pre-dated the end of the Mesozoic. Neovenatoridae includes a derived
group (Megaraptora, new clade) that developed long, raptorial forelimbs, cursorial hind limbs, appendicular pneumaticity and
small size, features acquired convergently in bird-line theropods. Neovenatorids thus occupied a 14-fold adult size range
from 175 kg (Fukuiraptor) to approximately 2,500 kg (Chilantaisaurus). Recognition of this major allosauroid radiation has implications for Gondwanan paleobiogeography: The distribution of early
Cretaceous allosauroids does not strongly support the vicariant hypothesis of southern dinosaur evolution or any particular
continental breakup sequence or dispersal scenario. Instead, clades were nearly cosmopolitan in their early history, and later
distributions are explained by sampling failure or local extinction. 相似文献
714.
Avian incubation dramatically reduces the abundance and diversity of microbial assemblages on eggshells, and this effect has
been hypothesized as an adaptive explanation for partial incubation, the bouts of incubation that some birds perform during
the egg-laying period. However, the mechanisms for these antimicrobial effects are largely unknown. In this study, we hypothesized
that microbial inhibition is partly achieved through removal of liquid water, which generally enhances microbial growth, from
eggshells, and experimentally tested this hypothesis in two ways. First, we placed the first- and second-laid eggs of tree
swallow (Tachycineta bicolor) clutches in unincubated holding nests with either ambient or increased water on eggshells. Second, we added water to eggshells
in naturally partially incubated nests. We compared microbial growth on shells during a 5-day experimental period and found
that, as predicted, both unincubated groups had higher microbial growth than naturally partially incubated controls, and that
only in the absence of incubation did wetted eggs have higher microbial growth than unwetted eggs. Thus, we have shown that
water increases microbial growth on eggshells and that incubation nullifies these effects, suggesting that removal of water
from egg surfaces is one proximate mechanism for the antimicrobial effects of incubation. 相似文献
715.
Erich M. G. Fitzgerald Matthew T. Carrano Timothy Holland Barbara E. Wagstaff David Pickering Thomas H. Rich Patricia Vickers-Rich 《Die Naturwissenschaften》2012,99(5):397-405
The basal theropod dinosaur clade Ceratosauria, and its subclade Abelisauroidea, is characteristic of late Mesozoic terrestrial vertebrate faunas in western Gondwana (South America, Africa, Madagascar, and India) and Europe. Yet unambiguous records of ceratosaurs have hitherto been absent from Australia, where the theropod assemblage appears to include several typically Laurasian clades. Here, we report the first evidence of ceratosaurs (and potentially abelisauroids) from eastern Gondwana––a diagnostic astragalocalcaneum from the Aptian (121–125?Ma) of Victoria, Australia. Ceratosauria thus occurred in both western and eastern Gondwana during the Early Cretaceous. This fossil adds to the poorly known dinosaur fauna of Australia, a major clade of basal theropods, emphasising that its mid-Cretaceous theropod diversity was surprisingly cosmopolitan despite relative geographic isolation, including clades that have been thought to be typical of both Gondwana and Laurasia––Ceratosauria, Spinosauridae, Carcharodontosauria, Tyrannosauroidea, and Deinonychosauria. Such a contemporaneous association of theropod clades is unknown from other Gondwanan continents and questions the views that the late Mesozoic dinosaur fauna of Australia was dominated by Gondwanan or Laurasian elements, extreme isolation, relictualism, and/or novelty as a ‘centre of origin’. The cosmopolitan theropod fauna of Australia probably reflects the global distribution of these clades early in their history, prior to significant continental breakup. 相似文献
716.
Gräfe M Landers M Tappero R Austin P Gan B Grabsch A Klauber C 《Journal of environmental quality》2011,40(3):767-783
We describe the application of quantitative evaluation of mineralogy by scanning electron microscopy in combination with techniques commonly available at hard X-ray microprobes to define the mineralogical environment of a bauxite residue core segment with the more specific aim of determining the speciation of trace metals (e.g., Ti, V, Cr, and Mn) within the mineral matrix. Successful trace metal speciation in heterogeneous matrices, such as those encountered in soils or mineral residues, relies on a combination of techniques including spectroscopy, microscopy, diffraction, and wet chemical and physical experiments. Of substantial interest is the ability to define the mineralogy of a sample to infer redox behavior, pH buffering, and mineral-water interfaces that are likely to interact with trace metals through adsorption, coprecipitation, dissolution, or electron transfer reactions. Quantitative evaluation of mineralogy by scanning electron microscopy coupled with micro-focused X-ray diffraction, micro-X-ray fluorescence, and micro-X-ray absorption near edge structure (mXANES) spectroscopy provided detailed insights into the composition of mineral assemblages and their effect on trace metal speciation during this investigation. In the sample investigated, titanium occurs as poorly ordered ilmenite, as rutile, and is substituted in iron oxides. Manganese's spatial correlation to Ti is closely linked to ilmenite, where it appears to substitute for Fe and Ti in the ilmenite structure based on its mXANES signature. Vanadium is associated with ilmenite and goethite but always assumes the +4 oxidation state, whereas chromium is predominantly in the +3 oxidation state and solely associated with iron oxides (goethite and hematite) and appears to substitute for Fe in the goethite structure. 相似文献
717.
Nitrate-nitrogen (NO?-N) loading to surface water bodies from subsurface drainage is an environmental concern in the midwestern United States. The objective of this study was to investigate the effect of various land covers on NO?-N loss through subsurface drainage. Land-cover treatments included (i) conventional corn ( L.) (C) and soybean [ (L.) Merr.] (S); (ii) winter rye ( L.) cover crop before corn (rC) and before soybean (rS); (iii) kura clover ( M. Bieb.) as a living mulch for corn (kC); and (iv) perennial forage of orchardgrass ( L.) mixed with clovers (PF). In spring, total N uptake by aboveground biomass of rye in rC, rye in rS, kura clover in kC, and grasses in PF were 14.2, 31.8, 87.0, and 46.3 kg N ha, respectively. Effect of land covers on subsurface drainage was not significant. The NO?-N loss was significantly lower for kC and PF than C and S treatments (p < 0.05); rye cover crop did not reduce NO?-N loss, but NO?-N concentration was significantly reduced in rC during March to June and in rS during July to November (p < 0.05). Moreover, the increase of soil NO?-N from early to late spring in rS was significantly lower than the S treatment (p < 0.05). This study suggests that kC and PF are effective in reducing NO?-N loss, but these systems could lead to concerns relative to grain yield loss and change in farming practices. Management strategies for kC need further study to achieve reasonable corn yield. The effectiveness of rye cover crop on NO-N loss reduction needs further investigation under conditions of different N rates, wider weather patterns, and fall tillage. 相似文献
718.
Feeding habits of the four most abundant deep-sea demersal trawl-caught macrourids on Chatham Rise, New Zealand, were examined
from stomach contents. Two species were predominantly benthic foragers: Coelorinchus bollonsi on infaunal and epifaunal polychaetes, and C. aspercephalus on epifaunal crustaceans; and two species were predominantly mesopelagic foragers; C. oliverianus on calanoid copepods, and Lepidorhynchus denticulatus on mesopelagic crustaceans. The most important predictors of diet variability were identified using distance-based linear
models and included areal predictors in all four species, fish size in C. aspercephalus, C. bollonsi and L. denticulatus, and sample year in C. bollonsi. Cluster analyses showed that the diets of C. aspercephalus and C. bollonsi were most distinct. There was a greater interspecific similarity in diet in the spatial and fish size subgroups of C. oliverianus and L. denticulatus, than at the species level. Failing to account for areal, temporal, and ontogenetic variability in diets may bias evaluations
of resource competition. 相似文献
719.
Spatially stratified sampling using auxiliary information for geostatistical mapping 总被引:3,自引:0,他引:3
Matthew G. Falk Robert J. Denham Kerrie L. Mengersen 《Environmental and Ecological Statistics》2011,18(1):93-108
This paper presents a method of spatial sampling based on stratification by Local Moran’s I
i
calculated using auxiliary information. The sampling technique is compared to other design-based approaches including simple
random sampling, systematic sampling on a regular grid, conditional Latin Hypercube sampling and stratified sampling based
on auxiliary information, and is illustrated using two different spatial data sets. Each of the samples for the two data sets
is interpolated using regression kriging to form a geostatistical map for their respective areas. The proposed technique is
shown to be competitive in reproducing specific areas of interest with high accuracy. 相似文献
720.
Robert J. Denham Matthew G. Falk Kerrie L. Mengersen 《Environmental and Ecological Statistics》2011,18(2):239-255
The measurement error model is a well established statistical method for regression problems in medical sciences, although rarely used in ecological studies. While the situations in which it is appropriate may be less common in ecology, there are instances in which there may be benefits in its use for prediction and estimation of parameters of interest. We have chosen to explore this topic using a conditional independence model in a Bayesian framework using a Gibbs sampler, as this gives a great deal of flexibility, allowing us to analyse a number of different models without losing generality. Using simulations and two examples, we show how the conditional independence model can be used in ecology, and when it is appropriate. 相似文献