The Combined Effect of Vegetation and Soil Erosion in the Water Resource Management

Water has always played a vital role in human societies. In order to manage the water resources, many countries have built water reservoirs, for example, dams for sustainable development, growth and poverty reduction. Vegetation, in the watershed region of a dam, plays a very vital role on soil erosion and consequently on the sediments deposition in the water reservoir. This study intends to analyze the impact of vegetation cover on soil erosion and thereby the sediments deposition in the watershed region of a dam by using satellite remote sensing technique. For this, Mangla dam which is one of the most important water reservoirs in Pakistan and its capacity has been reduced by more than 20% since its construction, is selected as the study area. Shuttle Radar Topographic Mission (SRTM) data, onboard the space shuttle Endeavor, was used to calculate the total drainage area for the Mangla watershed. Landsat images for the years 1979, 1980, 1992, 1998 and 2002 were used to estimate the total area of vegetation in the Mangla watershed region. In order to estimate the vegetation area, two vegetation indices, that is, Normalized Difference Vegetation Index (NDVI) and Enhanced Vegetation Index (EVI) were applied on Landsat MSS, TM, and ETM+ images. The comparison of sedimentation and vegetation data indicates that except for the year 1992, the load of sedimentation in Mangla dam decreases with an increase in the vegetation area in the Mangla watershed region. The maximum vegetation in the Mangla watershed region is estimated in the year 2002, and subsequently, the load of sediments in the same year in Mangla dam is minimum. The current study thus indicates that the soil erosion which is the main reason of sedimentation in water reservoir can be controlled with the help of plantation of various species of vegetation in the watershed region of the reservoir.     

Occurrence and biological effect of exogenous steroids in the Elkhorn River, Nebraska, USA

Recent studies of surface waters in North America, Japan and Europe have reported the presence of steroidogenic agents as contaminants. The current study has three objectives: 1) to determine if steroidogenic compounds are present in the Elkhorn River, 2) to determine if sediments collected from the Elkhorn River can act as a source of steroidogenic compounds to aquatic organisms, and 3) to determine if site-specific biological effects are apparent in the hepatic gene expression of fathead minnows. Evidence was obtained using three approaches: 1) deployment of polar organic chemical integrative samplers (POCIS), 2) deployment of caged fathead minnows, and 3) a laboratory experiment in which POCIS and fish were exposed to sediments from the deployment sites. Deployment sites included: the Elkhorn River immediately downstream from a Nebraska wastewater treatment plant, two waterways (Fisher Creek and Sand Creek) likely to be impacted by runoff from cattle feeding operations, and a reference site unlikely to be impacted by waste water inputs. The POCIS extracts were analyzed for a number of natural steroids and metabolites, as well as four different synthetic steroids: ethinylestradiol, zearalonol, 17beta-trenbolone and melengestrol acetate. Estrogenic and androgenic metabolites, as well as progesterone and trace levels of melengestrol acetate were detected in POCIS deployed at each site. POCIS deployed in tanks containing field sediments from the four sites did not accumulate the synthetic steroids except for ethinylestradiol, which was detected in the aquarium containing sediments collected near the wastewater treatment plant. Fish deployed in Sand Creek and at the wastewater treatment plant experienced significantly elevated levels of gene expression for two genes (StAR and P450scc) relative to those deployed in Fisher Creek. Fish exposed to the sediments collected from Sand Creek had significantly higher levels of hepatic StAR and P450scc gene expression than did fish exposed to sediments from the two other field sites, as well as the no-sediment control tank. In conclusion: 1) detectable levels of steroidogenic compounds were detected in passive samplers deployed in the Elkhorn River, 2) sediments do not appear to be a significant source for steroidogenic compounds, and 3) site-specific differences were found in mRNA expression among the different treatment groups of fish; however, a functional explanation for these differences is not readily forthcoming.     

Microfabricated cylindrical multielectrodes for neural stimulation

The effects of spinal cord injuries are likely to be ameliorated with the help of functional electrical stimulation of the spinal cord, a technique that may benefit from a new style of electrode: the cylindrical multielectrode. This paper describes the specifications for, fabrication techniques for, and in vitro evaluation of cylindrical multielectrodes. Four tip shapes were tested to determine which shape required the lowest peak force and would, therefore, be expected to minimize dimpling during implantation. The impedance of the electrode interface was monitored for changes due to insertion as well as repetitive delivery of current pulses. The charge delivery capacity was determined by testing with safe (< or = 0.6 mC/cm2) and damaging levels (> or = 0.8 mC/cm2) of charge density. The results of these tests suggest that this electrode design could be used to stimulate neurons in the ventral horn of the spinal cord.