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611.
612.
MD.?Monir.?HossainEmail author Andrew?B.?Lawson 《Environmental and Ecological Statistics》2005,12(3):259-273
This paper illustrates a method based on local likelihood (LL) for detecting disease clusters. The approach is based on estimating
a lasso distance for each region: within which regions are considered to be clustered. An important advantage in implementing
this approach is that it does not require any special Monte Carlo Markov Chain (MCMC) algorithm, e.g., reversible jump MCMC,
which is essential in hidden Markov model approach. Another advantage is that extending the model to incorporate covariates
is straightforward. We illustrate three ways of doing this by using Eastern Germany lip cancer data. By using simulated data,
we have made a comparison with the BYM model [Besag et al. (1991) Annals of the Institute of Statistical Mathematics, 43, 1–59] and the mixture model [Lawson and Clark (2002) Disease Mapping and Risk Assessment for Public Health, Chapman and Hall]. We also did a limited examination of the ability of the LL model to recover true relative risk under
different priors for lasso parameter. In order to check the edge effects, which has been overlooked in many spatial clustering
models for disease mapping but deserves special attention as it lacks observable neighbors, we have adapted here a simple
approach to observe the changes in relative risks when the edge regions are omitted.
An erratum to this article is available at . 相似文献
613.
Two salt marsh cores were collected from the Venice Lagoon, Italy, and analysed for PCDD/Fs. The samples were undisturbed and had an approximately constant accumulation rate. Radiochemical chronologies were established for the different core sections. The PCDD/F pattern in the surficial layers was very similar to that of atmospheric deposition measured in the same area. However, the pattern changed with increasing depth and was very different in the deeper sections, where the highest PCDD/F concentrations were measured. This layer was dated around the 1950s. Deeper layers have a profile similar to the surficial one. Undisturbed salt marsh cores appear to be a reliable tool for the reconstruction of temporal trends in the atmospheric deposition of persistent organic pollutants. It is proposed that the trends in the core reflect atmospheric deposition that probably results from the sum of two different contributions: emissions of the industrial district of Porto Marghera on the edge of the lagoon and the regional background. 相似文献
614.
615.
(Crustacea:Hippidae) from three southern California (U.S.A.) beaches contained 0.9 to 24.1 μg/g dry wt saturated hydrocarbons, and 3.6 to 21.4 μg/g dry wt unsaturated hydrocarbons. Major constituents were (in wt. % total): n-alkanes (13.1%), heneicosapentaene plus heneicosahexaene (1.0%), squalene (5.1%), and unidentified polyenes (7.8%). Crabs from beaches exposed to small boat traffic and natural oil seepage were slightly and severely tainted, respectively, with petroleum hydrocarbons. Animals from San Nicolas Island (85 km offshore) contained only biogenic compounds. 相似文献
616.
In many bird species, the female alone incubates the eggs, but the male provides her with some food during the incubation period. In cooperatively breeding species, helpers might be expected to assist the breeding male in provisioning the female, but their contribution has been generally ignored. Here, I show that in the green woodhoopoe, Phoeniculus purpureus, the breeding male and helpers of both sexes bring food to the incubating female. The helpers did not increase the overall amount of provisioning the female received: groups of all sizes delivered a similar amount of food per hour. Helpers did, however, reduce the workload of the breeding male. Male and female helpers provisioned incubating females equally, as expected in a species where both sexes are likely to derive equal benefits from their helping behaviours. Female nest attendance was positively related to the level of group provisioning, but only in the short term. Thus, the female-nutrition hypothesis, which suggests that incubation feeding can provide an important source of energy to the breeding female, is supported in the green woodhoopoe.Communicated by I. Hartley 相似文献
617.
Regardless of whether the bulk of decision-making in an economy is done by a central unit or by decentralized smaller units, the government can act to propose guidelines to individual agents. This is of particular importance when the activities of the latter cause aggregative or social problems which are not directly acted upon by the smaller agents. The purpose of this paper is to set up a model by which a central authority can make choices in the presence of two pressing social problems, namely, a diminishing domestic supply of an exhaustible resource and the contamination of the environment through discharged waste materials.The model itself takes the form of an integer-linear programming problem which runs through discrete time to a finite horizon. Besides the traditional modes of “virgin” exploration and production and/or importation from abroad, society is also given the choice of recycling. Society will choose combinations of the above three to minimize the costs of satisfying fixed (projected) oil product demands in the future. The costs include those for increasing exploration for virgin refineries; for collection, refining and transportation for refineries and for the cost to society of discharges of waste-oil into the environment. The constraints include process flow restrictions, import quotas, capacity limits and discharge restrictions as well as fixed demands.An effort was made to keep the model as general as possible. Although no numerical solution is obtained in this paper, we feel that the policy implications of some presumed solution (possible through the use of a well-known algorithm for mixed variable problems) are worth examining. They revolve around the model itself, citing the potential attractiveness of recycling as the other two alternatives become increasingly expensive, and as development of alternatives to oil progresses at an alarmingly slow rate. Also mentioned are problems relating to the potential demands for recycled versus virgin oil products, balance-of-trade problems, and the mutability of social and economic institutions in the crisis of economic adjustment that much of the world is now facing. 相似文献
618.
Regional extent of an ecosystem engineer: earthworm invasion in northern hardwood forests. 总被引:3,自引:0,他引:3
The invasion of exotic earthworms into northern temperate and boreal forests previously devoid of earthworms is an important driver of ecosystem change. Earthworm invasion can cause significant changes in soil structure and communities, nutrient cycles, and the diversity and abundance of herbaceous plants. However, the regional extent and patterns of this invasion are poorly known. We conducted a regional survey in the Chippewa and Chequamegon National Forests, in Minnesota and Wisconsin, U.S.A., respectively, to measure the extent and patterns of earthworm invasion and their relationship to potential earthworm introduction sites. We sampled earthworms, soils, and vegetation in 20 mature, sugar maple-dominated forest stands in each national forest and analyzed the relationship between the presence of five earthworm taxonomic groups, habitat variables, and distance to the nearest potential introduction site. Earthworm invasion was extensive but incomplete in the two national forests. Four of the six earthworm taxonomic groups occurred in 55-95% of transects; however 20% of all transects were invaded by only one taxonomic group that has relatively minor ecological effects. Earthworm taxonomic groups exhibited a similar sequence of invasion found in other studies: Dendrobaena > Aporrectodea = Lumbricus juveniles > L. rubellus > L. terrestris. Distance to the nearest road was the best predictor of earthworm invasion in Wisconsin while distance to the nearest cabin was the best predictor in Minnesota. These data allow us to make preliminary assessments of landscape patterns of earthworm invasion. As an example, we estimate that 82% of upland mesic hardwood stands in the Wisconsin region are likely invaded by most taxonomic groups while only 3% are unlikely to be invaded at present. Distance to roads and cabins provides a coarse-scale predictor of earthworm invasion to focus stand-level assessments that will help forest managers better understand current and potential forest conditions and identify uninvaded areas that could serve as important refugia for plant species threatened by earthworm invasion. 相似文献
619.
Summary The sex ratios of nestling Falconiformes in which males are smaller than females are often female biased, despite the apparent costs involved in producing very large female offspring. In Australian peregrine falcons, Falco peregrinus, this bias is most pronounced in broods produced early in the season, and the first eggs to be laid are most likely to produce females. Females that lay early are most likely to be successful breeders. Very large chicks tend to occur in female-biased broods. Collectively, these data suggest that females likely to produce large offspring produce daughters. A modified version of the Trivers/Willard hypothesis is suggested to account for this pattern.Offprint requests to: P.D. Olsen at the second address 相似文献
620.
Derbyshire was one of the best known centres of endemic goitre in Great Britain. Some 160 km from the coast in the direction of the prevailing wind, topsoils in the area are generally low in iodine (mean = 5.44 mg l/kg). Weathered rocks and soils are richer in iodine than the unweathered bedrocks, with soils developed over limestones being richer than those over sandstones, shales and dolomites. Highest iodine contents in soil profiles over limestones occur in the upper horizons while over sandstones, iodine concentrates in the lower horizons. The major cause of endemic goitre in north Derbyshire is likely to be relatively low levels of iodine, while the calcium rich soils of the area may contribute by reducing plant iodine uptake. 相似文献