1,701 research outputs found
A Model to Predict the Evolution of a Gravel Bed River Under an Imposed Cyclic Hydrograph and its Application to the Trinity River
Major changes in the morphology of the Trinity River in California, such as narrowing of the cross section and sedimentation of fine sediment in pools, occurred after the closure of a system of dams. These changes caused a dramatic reduction in the salmonid population and a resulting decline of the fishery. Gravel augmentation, regulated flood releases, and mechanical channel rehabilitation are currently being implemented to help restore the aquatic habitat of the river. The present paper describes a tool, named the Spawning Gravel Refresher, for designing and predicting the effects of gravel augmentation in gravel bed rivers. The tool assumes an imposed, cycled hydrograph. The model is calibrated and applied to the regulated reach of the Trinity River in four steps: (1) zeroing runs to reproduce conditions of mobile bed equilibrium as best can be estimated for the predam Trinity River, (2) runs to compare the predictions with the results of previous studies, (3) runs at an engineering time scale to reproduce the effects of the dams, and (4) runs to design gravel augmentation schemes. In the fourth group of runs, the combined effects of engineered flood flow releases and gravel augmentation are predicted. At an engineering time scale, the model indicates that the fraction of fine sediment in the surface layer and in the topmost part of the substrate should decrease when subjected to these two restoration measures, with a consequent improvement of the quality of the spawning gravel
Using participatory and creative methods to facilitate emancipatory research with people facing multiple disadvantage: a role for health and care professionals
Participatory and creative research methods are a powerful tool for enabling active engagement in the research process of marginalised people. It can be particularly hard for people living with multiple disadvantage, such as disabled people from ethnic minority backgrounds, to access research projects that are relevant to their lived experience. This article argues that creative and participatory methods facilitate the co-researchersâ engagement in the research process, which thus becomes more empowering. Exploring the congruence of these methods with their professional ethos, health and care professionals can use their skills to develop them further. Both theory and practice examples are presented
Estimating the location of baleen whale calls using dual streamers to support mitigation procedures in seismic reflection surveys
In order to mitigate against possible impacts of seismic surveys on baleen whales it is important to know as much as possible about the presence of whales within the vicinity of seismic operations. This study expands on previous work that analyzes single seismic streamer data to locate nearby calling baleen whales with a grid search method that utilizes the propagation angles and relative arrival times of received signals along the streamer. Three dimensional seismic reflection surveys use multiple towed hydrophone arrays for imaging the structure beneath the seafloor, providing an opportunity to significantly improve the uncertainty associated with streamer-generated call locations. All seismic surveys utilizing airguns conduct visual marine mammal monitoring surveys concurrent with the experiment, with powering-down of seismic source if a marine mammal is observed within the exposure zone. This study utilizes data from power-down periods of a seismic experiment conducted with two 8-km long seismic hydrophone arrays by the R/V Marcus G. Langseth near Alaska in summer 2011. Simulated and experiment data demonstrate that a single streamer can be utilized to resolve left-right ambiguity because the streamer is rarely perfectly straight in a field setting, but dual streamers provides significantly improved locations. Both methods represent a dramatic improvement over the existing Passive Acoustic Monitoring (PAM) system for detecting low frequency baleen whale calls, with ~60 calls detected utilizing the seismic streamers, zero of which were detected using the current R/V Langseth PAM system. Furthermore, this method has the potential to be utilized not only for improving mitigation processes, but also for studying baleen whale behavior within the vicinity of seismic operations
The effect of local wind on seismic noise near 1 Hz at the MELT site and in Iceland
The mantle electromagnetic and tomography (MELT) experiment on the
east Pacific rise near 17°S was the first large teleseismic experiment on a midocean
ridge. During the six-month deployment, no compressional arrivals were well recorded
above 0.5 Hz. In comparison, the ICEMELT experiment in Iceland recorded
compressional arrivals at 1-2 Hz from about 2 earthquakes per month. We compare
noise spectra from the two experiments and show that this difference in detection is
at least in part a result of noise. Near 1 Hz, seismic noise in the oceans is produced
locally by wind-generated waves. At both experiment sites, 1-Hz noise levels are
well correlated with local sea-surface-wind speeds derived from satellite observations.
For a given wind speed, 1-Hz noise levels are about 10-20 dB lower in Iceland.
At the MELT site, cross-correlations of wind speed with the logarithm of noise in a
narrow-frequency band yield correlation coefficients exceeding 0.7 at frequencies
between 0.4 Hz and 2 Hz. Noise levels at 1 Hz increase with wind by 1.3-1.4 dB
per m/sec for wind speeds less than 10 m/sec. For the ICEMELT experiment, high
correlation coefficients extend to markedly higher frequencies for coastal stations,
and there is a 10-dB drop in 1-Hz noise levels 100-km inland. Noise levels increase
by about 0.8 dB per m/sec. The strong correlation between wind speed and l-Hz
seismic noise provides justification for using satellite wind speed data to search for
locations on the global spreading system where there is a better probability of recording
high-frequency arrivals. The calmest sites are found on the northern east
Pacific rise, near the equator in all oceans, and near 34 ° N and 22 ° S on the mid-
Atlantic ridge.This study was supported by the National Science Foundation
under grant OCE-9414299.Peer Reviewe
Diversity of Poisonous Plants and their Antidotes, Affecting Ruminant Livestock Production on Rangelands in Ghana
Acknowledgement We acknowledge the support provided by the government of Ghana through the Agricultural Sub-Sector Investment Project (AgSSIP), funded by the World Bank. The project funded the entire PhD study at the University of Aberdeen, Scotland.Peer reviewedPublisher PD
Diversity of Poisonous Plants and their Antidotes, Affecting Ruminant Livestock Production on Rangelands in Ghana
The survival of the extensive livestock system, the practice for most farmers in the livestock industry in Ghana depends heavily on the natural pastures as forage resource. To efficiently use the rangelands, knowledge of the species composition, especially that of poisonous plants is essential. Documented knowledge in Ghana is scanty; documentation and dissemination of the knowledge resource would enable a wider access and wider benefit to stakeholders. A study was conducted in Ghana on poisonous plants with the aim to discover the existence and diversity of poisonous plants and associated antidotes affecting livestock for documentation and preservation of knowledge. 70 different items were cited; 22 were poisonous plants for which antidotes were not cited, 28 were poisonous plants with known antidotes and 32 antidotes. There were 575 citations of plants from 194 reported cases of suspected plant poisoning, categorized as poisonous plants for which no antidotes were cited (146), poisonous plants with cited antidotes (147) and antidotes (282). 50 plants species were identified and belonged to 29 plant families. Some plants were known only by local names. There was an extensive knowledge of the diversity of poisonous plants and antidotes within the ecological zones along with possible antidotes
Occupational balance: What tips the scales for new students?
The open question, âWhat prevents you from reaching occupational balance?â,
was posed within a questionnaire aimed at exploring the meanings of
occupation, health and wellbeing with a cohort of first-year occupational
therapy students during their initial few weeks at university. Their written
responses to the question about occupational balance were analysed and are
discussed in this paper. Not surprisingly, occupational balance appeared to be
achieved by only a few and more by chance than design.
People, time and money factors were identified as the main impediments
to achieving occupational balance, with psychological and emotional pressures
being at the forefront. Interestingly, despite these barriers, the overall
educational benefit of considering the occupational balance question in this
way raised the studentsâ awareness of its relationship to health and wellbeing.
This increased awareness might have longer-term health benefits, both
personally and professionally, which would be worthy of further research
- âŠ