1,330 research outputs found

    Caves and Karst Hydrology of the Mariana Islands (Abstract)

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    Structural Controls on Megaporosity in Eogenetic Carbonate Rocks: Tinian, CNMI

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    Tinian and Aguijan, Commonwealth of the Northern Mariana Islands (CNMI), are volcanic, back arc islands in the western Pacific formed by Pacific Plate subduction under the Philippine Plate. The islands are composed of Eocene volcanic cores mantled by Plio-Pleistocene carbonate facies and raised Holocene beach and reef deposits. The entire sequence has been tectonically uplifted and contains high-angle normal faults, while isostatic subsidence and scarp failures overprint tectonic brittle failure features. A cave and karst inventory on Tinian and Aguijan surveyed 114 features and is believed to adequately represent the megaporosity (cave) development. Two distinct cave classes were identified: mixing zone caves (flank margin caves and banana holes) and fissure caves. Most mixing zone caves were located in or near scarps and coastlines, often at similar elevations to nearby caves. Fissure caves were located in regions of brittle failure, forming linear features with narrow widths. Three previous sea-level positions were identified based on horizons of mixing zone caves. Seventeen freshwater discharge sites and four allogenic recharge sites were identified on Tinian. Kolmogorov-Smirnov statistical analyses and rose diagram comparisons of orientation trends found significant similarities between megaporosity and geologic structure (brittle failure) on Tinian. Analyses of small regions showed distinct relations between brittle deformation and megaporosity, while at larger scales similarities became less obvious due to the complex geologic history and physiography of the island. Based on similarities in populations of orientation trends, fissure cave development is primarily controlled by brittle failure deformation with development along faults, fractures, and joints, while mixing zone cave development is primarily controlled by fresh-water lens position but significantly influenced by brittle failure deformation. Tinian and Aguijan do not fit neatly into one classification of the Carbonate Island Karst Model. Regions of Tinian best fit the Simple, Carbonate-Cover and Composite Island Karst Models, but none easily fit the entire island. Aguijan must be classified as a Simple Carbonate Island because no geologic data has proved the presence of non-carbonate rocks interfering with the fresh-water lens, however it is probable that Aguijan does contain basement rocks that extend above sea-level as on other carbonate islands in the Marianas

    Additive Factors Do Not Imply Discrete Processing Stages: A Worked Example Using Models of the Stroop Task

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    Previously, it has been shown experimentally that the psychophysical law known as Piéron’s Law holds for color intensity and that the size of the effect is additive with that of Stroop condition (Stafford et al., 2011). According to the additive factors method (Donders, 1868–1869/1969; Sternberg, 1998), additivity is assumed to indicate independent and discrete processing stages. We present computational modeling work, using an existing Parallel Distributed Processing model of the Stroop task (Cohen et al., 1990) and a standard model of decision making (Ratcliff, 1978). This demonstrates that additive factors can be successfully accounted for by existing single stage models of the Stroop effect. Consequently, it is not valid to infer either discrete stages or separate loci of effects from additive factors. Further, our modeling work suggests that information binding may be a more important architectural property for producing additive factors than discrete stages

    2D ELECTRICAL RESISTIVITY AND HYDROLOGICAL STUDY OF A SOLUTE PLUME’S MIGRATION PATHWAY THROUGH SANDY LOAM WITHIN NACOGDOCHES COUNTY, TEXAS, USA

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    combined geophysical and hydrological study was conducted in a sandy loam near the campus of Stephen F. Austin State University in Nacogdoches, Texas. The study area contained three preinstalled piezometers which are located in the Sparta Sand of the Eocene Claiborne Group, a regressive tract of the Eocene sea. Electrical DC resistivity surveys were conducted across one fifty-six-meter-long traverse using AGI’s multi-electrode SuperSting R8 WIFI RES/IP/SP system, which allowed for rapid and reliable data collection. The resistivity line was surveyed using the dipole-dipole array configuration, which has been proven to produce high-quality horizontal resolution. Over the duration of fourteen days, a conductive solution composed of 88 ounces of NaCl combined with 24 liters of water were added into an infiltration pit daily and DC resistivity surveys were conducted every other day. DC resistivity data was processed and interpreted using AGI’s EarthImager 2D inversion software. The electrical resistivity data acquired was paired with a hydrogeological survey of the area in order to better understand the migration of a solute plume through the sandy loam. The hydrogeologic survey consisted numerical modeling values obtained from a fine ii grain analysis of three soil cores using the Bouyoucos hydrometer method. The data acquired provided useful information on the rate of infiltration as well as the migration pathway of any possible future contaminant spills that may occur in similar soils. The principal objective of the study was to track the flow pattern and rate at which a known conductive aqueous solution flows through sandy loam. This geophysical study alongside a parallel hydrologic study will improve tracking of solute plume through sandy loam and allow researchers to monitor any interaction with groundwater

    Handlers' expectations and perceived compatibility regarding the partnership with their first guide dogs

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    The main function of a guide dog is as a mobility aid, but they can also fulfill psychosocial roles as companions, social facilitators, and objects/providers of affection. This study examined the outcome of 50 peoples' (handlers) partnerships with their first guide dog. Overall compatibility and the fulfilment of the handlers' expectations regarding mobility and social factors related to guide dog usage were measured, and relationships between putative risk factors and the out-come of matching success were identified. The findings demonstrate that the dogs are generally exceeding expectations. The high average ratings of compatibility were notable, particularly with respect to the emotional compatibility between handler and dog. Comparing responses of those who felt the handler-dog pairing was a good match with those who felt it was a mismatch revealed it was the working aspects of the relationship that differentiated the two groups. However, the many aspects of life with a guide dog, beyond the complexities of the working relationship, suggest that a more nuanced compatibility measure accommodating both positive and negative aspects of the relationship could assist with matching, training and follow up of the handler-dog team to maximize success

    Physiological correlates of performance in international-standard squash players

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    Tactical, technical and fitness factors are important for success in elite squash. While tactical and endurance fitness aspects have been explored, altered demands that have resulted from rule changes and absence of specific tests of high-intensity exercise capabilities have prevented identification of elements of fitness that correlate with performance in elite-standard players. Accordingly, the purpose of this study was to investigate relationships between test scores and player rank in such players. With institutional ethics approval, 31 players from the England Squash performance programme participated (11 women and 20 men, mean±SD body mass 62.4±5.5 kg and 73.1±7.5 kg respectively). After habituation, participants completed countermovement and drop-jump tests, squash-specific tests of change-of-direction speed and multiple-sprint ability and the multistage fitness test in one test session. Short recoveries were allowed between tests. World rank at the time of testing was obtained from the Professional Squash Association website. In men, change-of-direction speed (??=?0.59, p?=?0.02, n?=?14) multiple-sprint ability (??=?0.78, p<0.01, n?=?13) and fastest sprint from the multiple-sprint test (??=?0.86, p<0.01, n?=?13) correlated with world rank. In women, only fastest repetition from the multiple-sprint test correlated with world rank (??=?0.65, p?=?0.04, n?=?10). Measures of high-intensity exercise capability correlated with world rank in elite-standard men and women players. Endurance capability did not relate to rank in either the men or women. The results suggest that high-intensity, variable-direction exercise capabilities are important for success in elite squash

    Evaporite karst geohazards in the Delaware Basin, Texas: review of traditional karst studies coupled with geophysical and remote sensing characterization

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    Evaporite karst throughout the Gypsum Plain of west Texas is complex and extensive, including manifestations ranging from intrastratal brecciation and hypogene caves to epigene features and suffosion caves. Recent advances in hydrocarbon exploration and extraction has resulted in increased infrastructure development and utilization in the area; as a result, delineation and characterization of potential karst geohazards throughout the region have become a greater concern. While traditional karst surveys are essential for delineating the subsurface extent and morphology of individual caves for speleogenetic interpretation, these methods tend to underestimate the total extent of karst development and require surficial manifestation of karst phenomena. Therefore, this study utilizes a composite suite of remote sensing and traditional field studies for improved karst delineation and detection of potential karst geohazards within gypsum karst. Color InfraRed (CIR) imagery were utilized for delineation of lineaments associated with fractures, while Normalized Density Vegetation Index (NDVI) analyses were used to delineate regions of increased moisture flux and probable zones of shallow karst development. Digital Elevation Models (DEM) constructed from high-resolution LiDAR (Light Detection and Ranging) data were used to spatially interpret sinkholes, while analyses of LiDAR intensity data were used in a novel way to categorize local variations in surface geology. Resistivity data, including both direct current (DC) and capacitively coupled (CC) resistivity analyses, were acquired and interpreted throughout the study area to delineate potential shallow karst geohazards specifically associated with roadways of geohazard concern; however, detailed knowledge of the surrounding geology and local karst development proved essential for proper interpretation of resistivity inversions. The composite suite of traditional field investigations and remotely sensed karst delineations used in this study illustrate how complex gypsum karst terrains can be characterized with greater detail through the utilization of rapidly advancing technologies, especially in arid environments with low vegetation densities

    Hypogenic Speleogenesis within Seven Rivers Evaporites: Coffee Cave, Eddy County, New Mexico

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    Coffee Cave, located in the lower Pecos region of southeastern New Mexico, illustrates processes of hypogenic speleogenesis in the middle Permian Seven Rivers Formation. Coffee Cave is a rectilinear gypsum maze cave with at least four stratigraphically-distinct horizons of development. Morphological features throughout the cave provide unequivocal evidence of hypogenic ascending speleogenesis in a confined aquifer system driven by mixed (forced and free) convection. Morphologic features in individual cave levels include a complete suite that defines original rising flow paths, ranging from inlets for hypogenic fluids (feeders) through transitional forms (rising wall channels) to ceiling half-tube flow features and fluid outlets (cupolas and exposed overlying beds). Passage morphology does not support origins based on epigenic processes and lateral development, although the presence of fine-grained sediments in the cave suggests minimal overprinting by backflooding. Feeder distributions show a lateral shift in ascending fluids, with decreasing dissolutional development in upper levels. It is likely that additional hypogenic karst phenomena are present in the vicinity of Coffee Cave because regional hydrologic conditions are optimum for confined speleogenesis, with artesian discharge still active in the region

    Castile Evaporite Karst Potential Map of the Gypsum Plain, Eddy County, New Mexico and Culberson County, Texas: A GIS Methodological Comparison

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    Castile Formation gypsum crops out over ,1,800 km2 in the western Delaware Basin where it forms the majority of the Gypsum Plain. Karst development is well recognized in the Gypsum Plain (i.e., filled and open sinkholes with associated caves); however, the spatial occurrence has been poorly known. In order to evaluate the extent and distribution of karst development within the Castile portion of the Gypsum Plain, combined field and Geographic Information System (GIS) studies were conducted, which enable a first approximation of regional speleogenesis and delineate karst-related natural resources for management. Field studies included physical mapping of 50, 1-km2 sites, including identification of karst features (sinkholes, caves, and springs) and geomorphic mapping. GIS-based studies involved analyses of karst features based on public data, including Digital Elevation Model (DEM), Digital Raster Graphic, (DRG) and Digital Orthophoto Quad (DOQ) formats. GIS analyses consistently underestimate the actual extent and density of karst development, based on karst features identified during field studies. However, DOQ analyses coupled with field studies appears to produce accurate models of karst development. As a result, a karst potential map of the Castile outcrop region was developed which reveals that karst development within the Castile Formation is highly clustered. Approximately 40% of the region effectively exhibits no karst development (,1 feature/km2). Two small regions (,3 km2 each) display intense karst development (.40 features/km2) located within the northern extent of the Gypsum Plain, while many regions of significant karst development (.15 features/km2) are distributed more widely. The clustered distribution of karst development suggests that speleogenesis within the Castile Formation is dominated by hypogenic, transverse processes

    An investigation of the complexities of successful and unsuccessful guide dog matching and partnerships.

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    Matching a person who is blind or visually impaired with a guide dog is a process of finding the most suitable guide dog available for that individual. Not all guide dog partnerships are successful, and the consequences of an unsuccessful partnership may result in reduced mobility and quality of life for the handler (owner), and are costly in time and resources for guide dog training establishments. This study examined 50 peoples' partnerships with one or more dogs (118 pairings) to ascertain the outcome of the relationship. Forty-three of the 118 dogs were returned to the guide dog training establishment before reaching retirement age, with the majority (n = 40) being categorized as having dog-related issues. Most (n = 26) of these dogs' issues were classified as being behavioral in character, including work-related and non-work-related behavior, and 14 were due to physical causes (mainly poor health). Three dogs were returned due to matters relating to the handlers' behavior. More second dogs were returned than the handlers' first or third dogs, and dogs that had been previously used as a guide could be rematched successfully. Defining matching success is not clear-cut. Not all dogs that were returned were considered by their handlers to have been mismatched, and not all dogs retained until retirement were thought to have been good matches, suggesting that some handlers were retaining what they considered to be a poorly matched dog. Almost all the handlers who regarded a dog as being mismatched conceded that some aspects of the match were good. For example, a dog deemed mismatched for poor working behavior may have shown good home and/or other social behaviors. The same principle was true for successful matches, where few handlers claimed to have had a perfect dog. It is hoped that these results may help the guide dog industry identify important aspects of the matching process, and/or be used to identify areas where a matching problem exists
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