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971.
Joseph F. Donnermeyer Peter F. Korsching Rabel J. Burdge 《Journal of the American Water Resources Association》1974,10(1):91-100
ABSTRACT This article reports information on the economic costs not covered by resettlement procedures to forced migrants from a flood-control reservoir. Data come from a sample of 200 families relocated due to construction of the Carr Fork Reservoir in the Coal Regions of Eastern Kentucky (Knott County). Responses indicated that economic costs were greater than the monetary settlement provided by the Corps of Engineers and that economic loss was not randomly distributed among the relocated persons. Analysis showed that persons who were more likely to be victims of greater economic costs due to relocation were landowners, older families with one or two members, persons with lower incomes and persons who were long time residents of the area. It is suggested that change angencies not only include property purchased by necessity in the cost-benefit ratio, but also other costs that have a direct affect on the welfare of the target population. In addition, it is suggested that case workers visit migrants during and after the relocation process to assist in solving various adjustment problems. 相似文献
972.
973.
Mole rats inhabit extensive individual tunnel systems. Since the energetic cost of burrowing far exceeds that of surface locomotion, excellent orientation ability is crucial. Here we examined whether mole rats can bypass an obstacle (ditch) intersecting an existing tunnel in order to rejoin the two tunnel sections. The mole rats dug two bypass types, depending on the size of the obstacle confronting them: a bypass around the small ditches, parallel and close to the ditch walls; or a bypass beneath the floor of the large ditches. These results demonstrate that the mole rat has the ability to avoid obstacles by digging accurate and energy-conserving bypass tunnels. In order to utilize such a capacity, the mole rat must possess both the means to evaluate the size of the obstacle as well as the ability to perceive its exact position relative to the original tunnel that it will rejoin. Possible mechanisms of orientation that could explain such ability are briefly discussed. 相似文献
974.
The prenatal diagnosis of thrombocytopenia absent radius syndrome in both dizygotic twins utilizing ultrasound, radiography and fetoscopy is described. 相似文献
975.
Scyphomedusae are ubiquitous in marine and estuarine systems, where they frequently play an important role in trophodynamics. Many scyphomedusae are cruising predators, and feeding rates depend, in part, on swimming behavior. Yet, no model of medusa swimming exists. An individual-based correlated random walk (CRW) model of medusa swimming behavior in three dimensions was developed. The model was validated using a previously published dataset of the swimming of 19 Chrysaora quinquecirrha (Desor, 1848) medusae that were observed in the presence or absence of zooplankton prey in laboratory mesocosms in August–October 1998 (Matanoski et al. in Mar Biol 139:191–200, 2001). In the presence of prey, medusae swam at a constant moderate rate in looping trajectories. In the absence of prey, medusae alternated periods of slow and fast swimming in more linear trajectories. In the model, looping trajectories were reproduced only when changes in movement by a medusa were oriented to its current position and orientation; more linear trajectories were reproduced by movement oriented to a fixed framework. This suggests that medusae change from swimming behavior oriented to local stimuli (e.g., contact with prey) to long-range stimuli (e.g., gravity) depending on the availability of prey. The model reproduced cyclical changes in swimming speeds by medusae in the absence of prey by simulating switching in the behavior controlling the strength of swimming bell pulsations using a probabilistic function. Model results also demonstrated that medusae tend to swim toward the surface, avoid contact with the bottom, increase time spent in prey patches if they alter swimming patterns in the presence of prey, and exhibit significant periodicities in swimming patterns that are the result of deterministic behavior. The model will permit the simulation of the complex behavior of medusae. 相似文献
976.
We examined patterns of concurrent multiple mating in a live-bearing poeciliid fish, the sailfin molly (Poecilia latipinna). We tested whether the probability of multiple paternity was related to female body size or fertility and whether the rate
of multiple paternity varied among four populations that differed in their distributions of female body size and fertility.
We analyzed data on mother and offspring genotypes for three polymorphic allozymes by three techniques, including a maximum-likelihood
estimator that accounts for sampling error in both parental and offspring allele frequencies. The estimated rate of multiple
paternity varied between 0.09 and 0.85, and the rate in one population varied seasonally between 0.33 (spring) and 0.85 (autumn).
The variation in these rates was not associated with variation in body-size distributions among populations but was closely
associated with variation in size-specific fertility: populations with greater variation in female fertility had higher multiple-paternity
rates. Within two populations, logistic regression revealed that individual females of larger body size and greater size-specific
fertility were more likely to carry multiply sired broods. This result is consistent with observations made in one of the
populations 5 years earlier. In general, the results strongly suggest that the mating system varies markedly among conspecific
populations of sailfin mollies and that larger, more fertile females are the objects of intermale competition.
Received: 6 May 1996 / Accepted in revised form: 5 December 1996 相似文献
977.
978.
The stability, mixing and effect of downstream control on axisymmetric turbulent buoyant jets discharging vertically into
shallow stagnant water is studied using 3D Reynolds-averaged Navier–Stokes equations (RANS) combined with a buoyancy-extended
k –ε model. The steady axisymmetric turbulent flow, temperature (or tracer concentration) and turbulence fields are computed using
the finite volume method on a high resolution grid. The numerical predictions demonstrate two generic flow patterns for different
turbulent heated jet discharges and environmental parameters (i) a stable buoyant discharge with the mixed fluid leaving the
vertical jet region in a surface warm water layer; and (ii) an unstable buoyant discharge with flow recirculation and re-entrainment
of heated water. A stratified counterflow region always appears in the far-field for both stable and unstable buoyant discharges.
Provided that the domain radius L exceeds about 6H, the near field interaction and hence discharge stability is governed chiefly by the jet momentum length scale to depth ratio
lM/H, regardless of downstream control. The near field jet stability criterion is determined to be lM/H = 3.5. A radial internal hydraulic jump always exists beyond the surface impingement region, with a 3- to 6-fold increase
in dilution across the jump compared with vertical buoyant jet mixing. The predicted stability category, velocity and temperature/concentration
fields are well-supported by experiments of all previous investigators. 相似文献
979.
Patricia Habuda OByrne Jon P Nelson Joseph J Seneca 《Journal of Environmental Economics and Management》1985,12(2):169-178
Two unresolved issues about airport noise-property value studies are addressed. The first issue concerns the comparability of empirical results from aggregate census data vs individual sales values, and the second issue concerns the homogeneity and stability of results from housing price studies over time and across markets. Hedonic price models from two sets of data for a residential area near the Atlanta International Airport are estimated at two points in time 1979–1980 and 1970–1972. The available data yield similar estimates of the noise discount over time, and from the prices of individual house sales vs owner-appraised census block aggregates. 相似文献
980.
Summary The threat-sensitive predator avoidance hypothesis predicts that prey can assess the relative threat posed by a predator and adjust their behaviour to reflect the magnitude of the threat. We tested the ability of larval threespine sticklebacks to adjust their foraging in the presence of predators by exposing them to conspecific predators of various sizes and recording their foraging and predator avoidance behaviours. Larvae (<30 days post-hatch) displayed predator escape behaviours only towards attacking predators. At 3 weeks post-hatch larvae approached the predator after fleeing, a behaviour which may be the precursor to predator inspection. Larvae reduced foraging and spent less time in the proximity of large and medium-sized predators compared to small predators. The reduction in foraging was negatively correlated to the predator/larva size ratio, indicating that larvae increased their foraging as they increased in size relative to the predator. We conclude that larval sticklebacks can assess the threat of predation early in their ontogeny and adjust their behaviour accordingly.Correspondence to: J.A. Brown 相似文献