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341.
With proximal and distal obstruction to the lacrimal drainage system, mucus accumulates forming a cyst. In order to diagnose a nasolacrimal duct cyst antenatally, the sonographer must image the region adjacent to the orbits. 相似文献
342.
Landslides into reservoirs and their impacts on banks 总被引:3,自引:0,他引:3
Rita Fernandes de Carvalho José Simão Antunes do Carmo 《Environmental Fluid Mechanics》2007,7(6):481-493
Mass wasting processes, like slope failures, on the margins of dam reservoirs, lakes, bays and oceans may generate large water
waves that can produce disasters due to flooding over the banks, run up along the shoreline and overtopping dam crests. Therefore,
the study of slope failures, the subsequent generation of impulse waves and their consequences are of paramount importance
for safety. In this paper the generation and propagation of water waves in reservoirs induced by landslides and their impact
on banks were investigated by means of a laboratory study carried out at University of Coimbra wave channel, in a flume measuring
12.0 m × 1.5 m × 1.0 m (L × H × W), where two banks with variable slope were placed. The study considered the sliding
of calcareous blocks over a sliding slope bank into the reservoir, the generation of impulse waves, their propagation in the
reservoir and their impact on the downstream bank. A number of waves were generated by different fallings of calcareous blocks,
considering different volumes, sliding slopes, initial positions and reservoir depths. All fallings were recorded by video-camera
and the results were processed afterwards to obtain the time history of the falling. The water surface variations due to transient
waves were measured at five gauges placed between the banks. The waves overtopping and breaking on the downstream bank were
also filmed using a video camera, and the hydrodynamic forces on this bank were also measured using four pressure transducers. 相似文献
343.
Method for Selection of Old-Forest Reserves 总被引:2,自引:0,他引:2
344.
Paula C. Díaz Christoph Grüter Walter M. Farina 《Behavioral ecology and sociobiology》2007,61(10):1589-1597
Floral scents are important information cues used to organize foraging-related tasks in honeybees. The waggle dance, apart
from encoding spatial information about food sources, might facilitate the transfer of olfactory information by increasing
the dissipation of volatiles brought back by successful foragers. By assuming that food scents are more intensive on specific
body parts of returning foragers, i.e., the posterior legs of pollen foragers and mouthparts of nectar foragers, we quantified
the interactions between hive mates and foragers during dances advertising different types of food sources. For natural sources,
a higher proportion of hive mates contacted the hind legs of pollen dancers (where the pollen loads were located) with their
heads compared to non-pollen dancers. On the other hand, the proportion of head-to-head contacts was higher for non-pollen
foragers during the waggle runs. When the food scent was manipulated, dancers collecting scented sugar solution had a higher
proportion of head-to-head contacts and a lower proportion around their hind legs compared to dancers collecting unscented
solution. The presence of food odors did not affect in-hive behaviors of dancers, but it increased the number of trophallaxes
in-between waggle runs (i.e., during circle phases). These results suggest that the honeybee dance facilitates the olfactory
information transfer between incoming foragers and hive mates, and we propose that excitatory displays in other social insect
species serve the same purpose. While recent empirical and theoretical findings suggested that the colony level foraging benefits
of the spatial information encoded in the waggle dance vary seasonally and with habitats, the role of the dance as a compound
signal not only indicating the presence of a profitable resource but also amplifying the information transfer regarding floral
odors may be important under any ecological circumstances. 相似文献
345.
346.
Paula A. White 《Behavioral ecology and sociobiology》2008,62(3):377-361
Among spotted hyenas, Crocuta crocuta, neonatal aggression in twins is a well-known phenomenon and serves to establish intra-litter dominance soon after birth.
As the stronger more aggressive cub presumably attains dominance over its twin, intra-litter dominance presents mothers with
an ideal opportunity to assess individual cub fitness and, thereafter, to selectively favor one cub over the other. This study
quantified maternal response to sibling conflict in 26 sets of twins born to 16 wild-living females to determine whether mothers
of different social ranks exhibited favoritism towards sons or daughters, or in the case of same-sex twins, the dominant or
subordinate cub. Maternal response to sibling conflict did not vary with litter sex composition, suggesting that mothers do
not favor offspring of one sex over the other. All mothers intervened when their cubs fought and sometimes punished their
cubs. Higher-ranking mothers more often punished both cubs, while lower-ranking mothers were more selective and punished the
dominant cub. Where sibling aggression was most extreme, rather than favor the dominant sibling, mothers of all ranks made
concessions to the subordinate cub that included procuring private nursing bouts for the subordinate and temporarily housing
twins in separate dens, presumably to decrease sibling conflict. These findings represent a complex example of parent–offspring
conflict and support both the insurance cub hypothesis and resource tracking hypothesis that mothers endeavor to keep all
offspring alive for as long as possible in the event that the dominant sibling dies or that resources provide for the rearing
of twins.
This contribution is part of the special issue “Sibling competition and cooperation in mammals” (guest editors: Robyn Hudson
and Fritz Trillmich). 相似文献
347.
348.
Marco Antonio Leonel Caetano Douglas Francisco Marcolino Gherardi Gustavo de Paula Ribeiro Takashi Yoneyama 《Ecological modelling》2009,220(19):2536-2542
The recent global financial crisis has highlighted the need for balanced and efficient investments in the reduction of the greenhouse effect caused by emissions of CO2 on a global scale. In a previous paper, the authors proposed a mathematical model describing the dynamic relation of CO2 emission with investment in reforestation and clean technology. An efficient allocation of resources to reduce the greenhouse effect has also been proposed. Here, this model is used to provide estimates of the investments needed in land reforestation and in the adoption of clean technologies for an optimum emission and abatement of CO2, for the period of 1996–2014. The required investments are computed to minimize deviations with respect to the emission targets proposed in the Kyoto Protocol for European Countries. The emission target can be achieved by 2014 with investments in reforestation peaking in 2004, and a reduction of the expected GDP of 42%, relative to 2006. Investments in clean technology should increase between 2008 and 2010 with maximum transfer figures around 70 million American dollars. Total (cumulative) costs are, however, relatively high depending on the price of carbon abatement and the rate at which the expected CO2 concentration in the atmosphere should be reduced. Results highlight the advantages for policy makers to be able to manage investments in climate policy more efficiently, controlling optimum transfers based on a portfolio of actions that tracks a pre-defined CO2 concentration target. 相似文献
349.
Pius Lee Youhua Tang Daiwen Kang Jeff McQueen Marina Tsidulko Ho-Chun Huang Sarah Lu Mary Hart Hsin-Mu Lin Shaocai Yu Geoff DiMego Ivanka Stajner Paula Davidson 《Environmental Fluid Mechanics》2009,9(1):23-42
Discrepancies in grid structure, dynamics and physics packages in the offline coupled NWS/NCEP NAM meteorological model with
the U.S. Environmental Protection Agency Community Multiscale Air Quality (CMAQ) model can give rise to inconsistencies. This
study investigates the use of three vertical mixing schemes to drive chemistry tracers in the National Air Quality Forecast
Capability (NAQFC). The three schemes evaluated in this study represent various degrees of coupling to improve the commonality
in turbulence parameterization between the meteorological and chemistry models. The methods tested include: (1) using NAM
predicted TKE-based planetary boundary height, h, as the prime parameter to derive CMAQ vertical diffusivity; (2) using the NAM mixed layer depth to determine h and then proceeding as in (1); and (3) using NAM predicted vertical diffusivity directly to parameterize turbulence mixing
within CMAQ. A two week period with elevated surface O3 concentrations during the summer 2006 has been selected to test these schemes in a sensitivity study. The study results are
verified and evaluated using the EPA AIRNow monitoring network and other ozonesonde data. The third method is preferred a
priori as it represents the tightest coupling option studied in this work for turbulent mixing processes between the meteorological
and air quality models. It was found to accurately reproduce the upper bounds of turbulent mixing and provide the best agreement
between predicted h and ozonesonde observed relative humidity profile inferred h for sites investigated in this study. However, this did not translate into the best agreement in surface O3 concentrations. Overall verification results during the test period of two weeks in August 2006, did not show superiority
of this method over the other 2 methods in all regions of the continental U.S. Further efforts in model improvement for the
parameterizations of turbulent mixing and other surface O3 forecast related processes are warranted. 相似文献
350.
Top predators are critical to ecosystem function, exerting a stabilising effect on the food web. Brown skuas are opportunistic predators and scavengers. Although skuas are often the dominant land-based predator at seabird colonies, this is the first detailed study of their movements and activity during breeding. The study was carried out at Bird Island, South Georgia (54°00′S, 38°03′W), in the austral summer of 2011/2012 and included GPS data from 33 breeding adults tracked during the late incubation and early chick-rearing periods. Brown skuas spent on average more than 80 % of time in the territory, and it was extremely rare for both partners to leave the territory simultaneously. Much more time was spent foraging at the coast than in penguin colonies and, based on saltwater immersion data, adults never foraged at sea. None of the tracked birds appeared to specialise in catching small petrels at night. Fewer foraging trips were made per day, and hence, more time was spent in the territory, during incubation than chick-rearing. Despite the pronounced sexual size dimorphism, there were no effects of sex on territorial attendance, foraging time or habitat use. Skuas at Bird Island show higher territorial attendance and are less likely to leave the territory unattended than those breeding elsewhere, suggesting closer proximity to more diverse or abundant food resources than at other colonies. The results tie in with previous diet studies, indicating that brown skuas at this site feed mostly on seal placentae and carrion and that birds may rely on a broader range of food resources as the season progresses. 相似文献