A method for determining elements for elemental signature analysis of groundwater and treated Lake Mead water

Elemental signature analysis (ESA) is a term that describes the use of the presence/absence or relative abundance of elements in samples. Several studies have been performed on the identification of these elemental signatures or fingerprints of water using inductively coupled plasma mass spectrometry (ICP-MS); Lake Mead is the primary water supply for the Las Vegas Valley. During the summer months, several large underground aquifers are used to supplement the Lake Mead water supply. Treated Lake Mead water is recharged during the low demand months to several of these aquifers. The Las Vegas Valley is surrounded by many private groundwater wells that tap smaller aquifers. Water quality varies between these aquifers. Many of the wells are exposed to controlled or uncontrolled contamination from a variety of sources, including cross-contamination between aquifers; Aquifers were identified by using the available literature and data obtained from ICP atomic emission spectrometer (ICP-AES) trace-metal analysis of water from 62 private wells in the Las Vegas Valley; Private groundwater wells in the northwest, southwest, and southeast areas of the Las Vegas Valley and water from three recharge wells were sampled and analyzed by ICP-AES for 14 elements and by ICP-MS for 58 elements; Element concentrations obtained using ICP-MS and statistical analysis were used to identify elements for use as an elemental signature of the treated Lake Mead water used for recharge of the Las Vegas Valley aquifers. Ratios of the elements identified as suitable markers for elemental signature analysis, were determined to identify potential trends in the data between areas and treated Lake Mead water; Results of the study indicate that element concentrations vary significantly between areas in the Las Vegas Valley, thus allowing them to be used as criteria to distinguish between two water sources. (Abstract shortened by UMI.)

A checklist of the marine Harpacticoida (Copepoda) of the Caribbean Sea

Recent surveys on the benthic harpacticoids in the northwestern sector of the Caribbean have called attention to the lack of a list of species of this diverse group in this large tropical basin. A first checklist of the Caribbean harpacticoid copepods is provided herein; it is based on records in the literature and on our own data. Records from the adjacent Bahamas zone were also included. This complete list includes 178 species; the species recorded in the Caribbean and the Bahamas belong to 33 families and 94 genera. Overall, the most species family was the Miraciidae (27 species),followed by the Laophontidae (21), Tisbidae (17), and Ameiridae (13). Up to 15 harpacticoid families were represented by one or two species only. Excluding the Bahamian records, the number of species recorded herein for the Caribbean Basin is 139. The distribution of the species richness within the Caribbean Basin is asymmetrical; the northwestern sector (Mexican Caribbean) is the most species, it concentrates up to 45% of the species recorded in the Caribbean. The insular Caribbean is nearly as diverse as the continental areas (75 vs 83 species recorded, respectively). The dominance of taxa related to coastal systems with coarse and fine sands and carbonatesediments reveals the general trend in the type of habitats surveyed in the Caribbean Sea. Up to 37 species found in the Mexican Caribbean represent new records for this country. There are enormous hiatuses in the knowledge of the Caribbean harpacticoids in terms of geographic, bathymetric, and environmental coverage. It is expected this list will grow rapidly and many undescribed forms will be discovered when understudied or unexplored environments are surveyed in detail

A contour matching approach for accurate NOAA-AVHRR image navigation

Although different methods for NOAA AVHRR image navigation have already been established, the multitemporal and multi-satellite character of most studies requires automatic and accurate methods for navigation of satellite images. In the proposed method, a simple Kepplerian orbital model for the NOAA satellites is considered as reference model, and mean orbital elements are given as input to the model from ephemeris data. In order to correct the errors caused by these simplifications, errors resulting from inaccuracies in the positioning of the satellite and failures in the satellite internal clock, an automatic global contour matching approach has been adopted. First, the sensed image is preprocessed to obtain a gradient energy map of the reliable areas (sea-land contours) using a cloud detection algorithm and a morphological gradient operator. An initial estimation of the reliable contour positions is automatically obtained. The final positions of the contours are obtained by means of an iterative local minimization procedure that allows a contour to converge on an area of high image energy (edge). Global transformation parameters are estimated based on the initial and final positions of all reliable contour points. Finally, the performance of this approach is assessed using NOAA 14 AVHRR images from different geographic areas.Postprint (published version

Investigation Of Ground Penetrating Radar For Detection Of Leaking Pipelines Under Roadway Pavements And Development Of Fiber-Wrapping Repair Technique

Nowadays, it has become a common practice to observe urban roadways undergo severe distress characterized by substantial depressions. In some cases, these pavement depressions are caused by leakages in the connecting joints of sewage pipelines laid beneath the roadway pavement. Manual inspection of pipe leakages has become costly and complex since sewage pipes with relative small diameters do not allow inspection from inside and digging may be required. On the other hand, pipes with large diameters, in which inspection can be made from pipe interior, inspector can not remain inside of the pipe for long periods of time because of toxic fumes. In order to overcome this problem, a geophysical technique known as ground penetrating radar (GPR) has been proposed as a candidate to detect the leakages. GPR is a nondestructive reflection technique, which uses high frequency electromagnetic waves to acquire subsurface information. GPR contributes to detect leaks in sewer pipes either by detecting underground voids surrounding the faulty pipe, or by detecting anomalies in the depth of the pipe as the radar propagation velocity varies due to the saturation of the soil near the leak. Once the leakage is detected, on site-repair technique to restore the damaged pipe is not an easy task. In this study, fiber reinforced polymer (FRP) composite created by saturating a fiber sheet with an epoxy resin matrix is proposed to be applied in several layers of overlay to the faulty structure surface. This fiber sheet is typically made of carbon or glass and saturated with the chemical resin matrix and makes the repaired structure even stronger than originally constructed. For the last twenty years, FRP has been used to repair and strengthen concrete columns by employing a practice known as fiber wrapping technique . This method involves the wrapping of unidirectional fiber composite sheets around concrete columns. FRP wrapping approach can be extended to sewage pipelines for repairing and strengthening the distressed pipeline. The purpose of this study is to detect leakages in sewer pipelines using GPR, and develop an on-site fiber-wrapping technique for repairing and strengthening sewage pipes. In detecting sewer leakages, one case study is presented. The case involves the use of GRP for leakage detection in a sewer pipeline overlaid by flexible pavement that already shows signs of subsidence. Moreover, in developing a repair technique, a gypsum cement mold wrapped with carbon fiber composite material is placed around a large-scale faulty pipe joint, and tested using a MTS servo-controlled hydraulic actuator. In addition, both free ends of the pipes are capped and filled with water to determine the effectiveness of the technique in stopping leaks along the repaired joint. During the GPR survey performed in the area of study, no clear indications of leakages were observed along the buried sewer pipeline. This lack of traceable signals from the subsurface was the result of the significant attenuation of the radar signal with depth that made impossible to discern effectively any anomaly along the designated pipeline. Although different antennas having center frequencies of 300 and 80 MHz were used and a variety of settings on the GPR unit were tried, the buried pipeline was barely detectable. Nevertheless, signal reflections generated by buried pipelines in other areas such as stormwater pipes on UCF campus and drainage pipelines at road side of University Boulevard were clearly detected, which makes to believe that the significant attenuation of the radar signal at the area of study is due to the extreme high conductivity of soils which have been severely contaminated by the leakage of sewage from the distressed pipeline. In contrast, favorable results were obtained in the development of the repair technique since the two-component system, Hydro-stone Gypsum Cement and FRP composite material, wrapped around the faulty joint effectively increased its structural capacity even higher than the pipe original strength

Entry-timing strategies: The road ahead

We argue that, despite significant progress, the extant entry timing literature still suffers from several shortcomings and, in particular, it fails to integrate into a coherent and integrative framework the latest findings from contiguous management literature streams. We propose that entry timing literature can be significantly enriched and its predictive power enhanced by incorporating insights from institutional theory, industry life-cycle, categorical dynamics, and by further elaborating on the implications of these theories for the firms' entry timing decisions. Our review also suggests that our understanding of early movers advantages can be improved by considering more explicitly the strategies and business models pursued by later entrants