Solution of fully-coupled shallow water equations and contaminant transport using a primitive-variable Riemann method

A Riemann-solver scheme, using primitive variables rather than conserved variables, is configured and tuned for the solution of the fully-coupled two-dimensional shallow water and contaminant transport equations. This scheme is based on the unstructured finite volume discretization using primitive-variable Roe-flux approximation with an entropy fix. The primitive-variable flux associated with the exact source-term balancing is well-behaved and well-balanced for both still-water and dry regions with arbitrary bed topography. Second-order accuracy is used in space and time. The present study uses a nonlinear implicit scheme based on Newton-iterative algorithm for the time integration. In order to show the accuracy of the scheme, numerical results are verified by different test cases for contaminant advection and diffusion. A scenario of contaminant transport in a complex geometry with wet and dry elements is also simulated to demonstrate that the present work can be implemented on practical applications involving flooding and contaminant transport.     

Male spotted bowerbirds preferentially choose,arrange and proffer objects that are good predictors of mating success

Females from a wide range of species have been shown to prefer males producing exaggerated, elaborate sexual displays. The question of whether males can adapt their behaviour in order to accentuate these preferred aspects has received less attention. Male bowerbirds provide an excellent system in which to address this question. Males build and decorate structures--bowers--which females use to assess males. Males exhibiting high numbers of particular decorations on their bowers receive increased mating success. Males can choose what objects to place on bowers and where to put them. Therefore, their behaviour can directly influence their mating success. I studied a population of spotted bowerbirds Chlamydera maculata in central Queensland, Australia. I show, using two sets of observations and a choice experiment, that males exhibit strong and consistent preferences for certain objects. The male's preferences have an adaptive value, targeting objects that predict his mating success. Such behaviour operates at three levels. Fundamentally, object selection and acquisition is biased in favour of certain objects for use as decorations. These decorations are then placed prominently on the bower, within the avenue. Finally, males actively proffer influential decorations, used as props, to visiting females, ensuring that crucial components of the sexual display cannot be ignored.     

Model-Based Assessment of Aspen Responses to Elk Herbivory in Rocky Mountain National Park,USA

In Rocky Mountain National Park (RMNP), aspen (Populus tremuloides Michx.) has been observed to be declining on elk (Cervus elaphus nelsoni) winter range for many decades. To support elk management decisions, the SAVANNA ecosystem model was adapted to explore interactions between elk herbivory and aspen dynamics. The simulated probability of successful vegetative regeneration for senescent aspen stands declines sharply when elk densities reach levels of 3–5 elk/km², depending on model assumptions for the seasonal duration of elk foraging activities. For aspen stands with a substantial component of younger trees, the simulated regeneration probability declines more continuously with increasing elk density, dropping below 50% from densities at 8–14 elk/km².At the landscape scale, simulated aspen regeneration probability under a scenario of extensive seasonal use was little affected by elk population level, when this level was above 300–600 elk (25%–50% current population) over the ca. 107 km² winter range. This was because elk distribution was highly aggregated, so that a high density of elk occupied certain areas, even at low population levels overall. At approximately current elk population levels (1000–1200 elk), only 35%–45% of senescent aspen stands are simulated as having at least a 90% probability of regeneration, nearly all of them located on the periphery of the winter range. Successful management for aspen persistence on core winter range will likely require some combination of elk population reduction, management of elk distribution, and fencing to protect aspen suckers from elk browsing.     

Relationship of daily and circatidal activity rhythms of the fiddler crab,<Emphasis Type="Italic"> Uca princeps</Emphasis>, to the harmonic structure of semidiurnal and mixed tides

Intertidal organisms may employ circatidal rhythms to track the tidal cycle, but tidal patterns may vary within a species range and necessitate adaptation to the local tides. Circatidal rhythms were examined in populations of the eastern Pacific fiddler crab Uca princeps (Smith) from four sites with differing tidal characteristics, La Paz (24°10N; 110°21W), San Blas (21°33N; 105°18W) and Manzanillo (19°6N; 104°24W), Mexico (lower amplitude, mixed semidiurnal tides) and Mata de Limon, Costa Rica (9°55N; 84°43W) (high-amplitude, semidiurnal tides). Local tides were characterized by harmonic constants of M₂, S₂, K₁, and O₁, partial tides that largely determine their semidiurnal and diurnal features. Rhythmic structure in continuously recorded locomotor activity of individual crabs held under laboratory conditions was described by cosinor and periodogram methods of time-series analysis. Both daily and circatidal rhythms were found in crabs studied in light–dark cycles set to local conditions at the time of collection. Crabs at all four sites shared a tendency toward bimodality, with a mid-morning activity peak and varying degrees of nocturnal activity. Circatidal rhythms closely matching the period of the 12.42-h M₂ partial tide were consistently present at all sites except Manzanillo. At Mata de Limon, the circatidal rhythm clearly dominated locomotor activity, but was strongly modulated by a daily rhythm in a repeating pattern at a semilunar interval. In contrast, the amplitude of the daily rhythm was higher than that of the circatidal rhythm in crabs from the three mixed tide sites on the Mexican coast, where the tidal pattern is dominated by a diurnal inequality arising from the diurnal K₁ and O₁ partial tides. These results suggest that populations of U. princeps use both daily and circatidal timing systems to track local forms of the tide generated by their M₂, S₂, K₁, and O₁ geophysical counterparts.Communicated by J.P. Grassle, New Brunswick     

Attitudes Toward Wilderness Study Areas: A Survey of Six Southeastern Utah Counties

Southeastern Utah is a region of world-renowned red-rock sandstone formations, large tracts of federal public land, rural communities centered on agriculture and extractive industries, and is often at the epicenter of environmental protection efforts in the western United States. Environmental groups have proposed formal Wilderness designations for much of the regions public land—proposals that have been actively fought by rural community leaders who do not want large areas locked-up from traditional livelihood and recreational uses. The debate over wilderness designation in the region has been characterized in the media as one that is particularly contentious and polarizing. A survey of southeastern Utah residents was conducted in order to better understand this conflict. The survey focused on attitudes toward wilderness designation and management. We found that residents of southeastern Utah have negative attitudes towards the designation and management of Wilderness Study Areas. We propose that these attitudes should be carefully considered and engaged in future policy and management decisions. We suggest that negative opinions expressed by residents of southeastern Utah are not directed primarily at the concept of environmental protection but rather at the strong perception that these programs and initiatives have been carried out in a heavy-handed manner and dominated by outside influences that have overwhelmed local voices.     

Low mating frequency of queens in the stingless bee<Emphasis Type="Italic"> Scaptotrigona postica</Emphasis><Superscript>1</Superscript> and worker maternity of males

Kin selection models of intracolonial conflict over the maternity of males predict that social hymenopteran workers should favour the production of sons and nephews over brothers when the effective mating frequency (m_e) of the queen is low (m_e<2) but that they should police other workers' reproductive efforts and favour the production of brothers when m_e>2. Stingless bees have been used to support these models in that m_e within the group is considered low and workers are thought often to monopolise the parentage of males. We genetically analysed 20 worker and 20 male pupae from each of 10 colonies of the stingless bee Scaptotrigona postica (= Scaptotrigona aff. depilis) using six microsatellite loci and demonstrate queen monandry in eight nests and apparent low m_e in the other two. However, four colonies contained an additional matriline, possibly due to queen supersedure (serial polygyny), which complicated their genetic structure. Across colonies, workers were responsible for the maternity of 13% of all males. These data are broadly in agreement with predictions from kin selection theory, though the question remains open as to why workers do not secure a greater share of male maternity in this and other stingless bee species in which workers are more closely related to nephews than brothers.     

MANAGING THE NATION'S WATER IN A CHANGING CLIMATE1

ABSTRACT: Among the many concerns associated with global climate change, the potential effects on water resources are frequently cited as the most worrisome. In contrast, those who manage water resources do not rate climatic change among their top planning and operational concerns. The difference in these views can be associated with how water managers operate their systems and the types of stresses, and the operative time horizons, that affect the Nation's water resources infrastructure. Climate, or more precisely weather, is an important variable in the management of water resources at daily to monthly time scales because water resources systems generally are operated on a daily basis. At decadal to centennial time scales, though, climate is much less important because (1) forecasts, particularly of regional precipitation, are extremely uncertain over such time periods, and (2) the magnitude of effects due to changes in climate on water resources is small relative to changes in other variables such as population, technology, economics, and environmental regulation. Thus, water management agencies find it difficult to justify changing design features or operating rules on the basis of simulated climatic change at the present time, especially given that reservoir-design criteria incorporate considerable buffering capacity for extreme meteorological and hydro-logical events.     

The velocity of DNAPL fingering in water-saturated porous media: laboratory experiments and a mobile–immobile–zone model

Dense nonaqueous phase liquids (DNAPLs) are immiscible with water and can give rise to highly fingered fluid distributions when infiltrating through water-saturated porous media. In this paper, a conceptual mobile–immobile–zone (MIZ) model is presented to describe the structure of a DNAPL finger in water-saturated porous media and the velocity of finger propagation. A finger is composed of a finger body and a tip. The finger body has a mobile core and an immobile sheath. All the DNAPL within the tip of a finger is mobile. Lab experiments utilizing image analyses of a DNAPL (PCE) penetrating into water-saturated homogeneous glass beads were carried out in a two-dimensional transparent chamber. The results show that the fingers elongated almost linearly with time. The fingers did not grow laterally after the tip of the finger had passed. The average finger diameters were between 3.9 and 5.4 mm for PCE propagation in water-saturated glass bead porous media with mean particle diameters from 0.32 to 1.36 mm. The estimated mobile core diameters were 51–60% of the average finger diameters.     

夹层电缆引发火灾的实验研究

模拟现代建筑夹层中贮藏大量未加金属导管防护的电线电缆所引发的火灾效应.在一个全尺寸燃烧套房模型中进行了起火室和顶棚夹层空间电缆火灾的实验研究,并采用大涡模拟的方法对实验中烟气速度场进行了数值模拟.结果表明,加明火源可以加强电缆的火灾功率;通风状况对夹层电缆火灾的温度场、烟气遮光度和火灾功率有明显影响.电缆燃烧产物中主要毒性气体为CO.电缆在夹层燃烧时,CO和CO2浓度均高于目标室和起火室中的浓度.而夹层毒气最为集中,其CO浓度远远超出OSHA和IDLH标准.电缆在夹层燃烧时发生火灾的危险性较大.