1,198 research outputs found
General -- 1959 -- Correspondence, OPV Miscellaneous -- letter, 1959-08-20
No full textLetter from Hammer, Stevens F. to Sabin, Albert B. dated 1959-08-20.Sabin Collection Fair Use Policy</a
Edward F. Stevens Correspondence
No full textEntries include a handwritten biographical sketch and a biographical lecture and traveling museum advertisement of a New England flying Santa and the president of the Boston Author\u27s Club, with the photographic image of Snow at the ship\u27s wheel and a list of publications
At limits of life: multidisciplinary insights reveal environmental constraints on biotic diversity in continental Antarctica
No full textData source: Supporting information, http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0044578#s5Multitrophic communities that maintain the functionality of the extreme Antarctic terrestrial ecosystems, while the simplest of any natural community, are still challenging our knowledge about the limits to life on earth. In this study, we describe and interpret the linkage between the diversity of different trophic level communities to the geological morphology and soil geochemistry in the remote Transantarctic Mountains (Darwin Mountains, 80uS). We examined the distribution and diversity of biota (bacteria, cyanobacteria, lichens, algae, invertebrates) with respect to elevation, age of glacial drift sheets, and soil physicochemistry. Results showed an abiotic spatial gradient with respect to the diversity of the organisms across different trophic levels. More complex communities, in terms of trophic level diversity, were related to the weakly developed younger drifts (Hatherton and Britannia) with higher soil C/N ratio and lower total soluble salts content (thus lower conductivity). Our results indicate that an increase of ion concentration from younger to older drift regions drives a succession of complex to more simple communities, in terms of number of trophic levels and diversity within each group of organisms analysed. This study revealed that integrating diversity across multi-trophic levels of biotic communities with abiotic spatial heterogeneity and geological history is fundamental to understand environmental constraints influencing biological distribution in Antarctic soil ecosystems.Catarina Magalhães, Mark I. Stevens, S. Craig Cary, Becky A. Ball, Bryan C. Storey, Diana H. Wall, Roman Tűrk and Ulrike Ruprech
General -- 1959 -- Correspondence, OPV Miscellaneous -- letter, 1959-09-24
No full textLetter from Sabin, Albert B. to Hammer, Stevens F. dated 1959-09-24.Sabin Collection Fair Use Policy</a
A comparison of a pressure vessel and flywheel for surge mitigation in a long pipeline system
No full textAn investigation was undertaken to identify appropriate mitigation measures required to overcome water hammer related issues associated with an upgrade to a potable water pipeline system. Modelling indicated that column separation would occur over a 14 km section (out of a total length of 34 km) of pipeline downstream of the first pumping station as a result of pump failure. Two viable options were identified to mitigate the column separation: [1] a pressure vessel directly downstream of the pump station and [2] a fly wheel installed at the pump station. A flywheel would not be expected to provide effective mitigation to prevent column separation in such a long system. However, in this case the pipeline profile is such that a flywheel affords a very effective water hammer control solution. A parametric study has been carried out on pumping systems of various profile shapes and different lengths to assess the effectiveness of a flywheel for water hammer protection. © BHR Group 2008.V. Cantone, R. Stevens, Parsons Brinckerhoff, A. R. Simpson, M. F. Lamberthttp://www.bhrconferences.com/pressure_surges_10.asp
Intern experience with William F. Guyton & Associates: an internship report
No full textIncludes author's vita"Submitted to the College of Engineering of Texas A&M University in partial
fulfillment of the requirement for the degree of Doctor of Engineering."Includes bibliographical referencesThis report is a review of the author's experience as an intern with
William F. Guyton & Associates. William F. Guyton & Associates is a consulting
groundwater hydrology firm with offices in Austin and Houston, Texas. The intern worked at the
main office in Austin for the duration of the internship. The author worked on a variety of
projects during the internship. These projects encompassed general groundwater studies,
computer simulation, technical analyses of aquifer parameters, and inspection of water well
construction and testing. General groundwater studies involved the collection of water well
construction and chemical analyses data. The author wrote several computer codes to handle
basic computations, and the author used several existing finite difference codes to simulate
groundwater movement. The technical analyses of pumping test data were analyzed by the author
to determine aquifer parameters. The field work involved on-site inspection of water well
construction and involved quality control of the pumping test after construction. The author
interacted with various agencies of the state and federal government. This interaction was
necessary to many of the projects. The collection of water well data and the use of the finite
difference codes gave the author the opportunity to obtain knowledge of the daily operations
of these agencies
Distinct migratory and non-migratory ecotypes of an endemic New Zealand eleotrid (Gobiomorphus cotidianus) – implications for incipient speciation in island freshwater fish species
No full textBackground: Many postglacial lakes contain fish species with distinct ecomorphs. Similar evolutionary scenarios might be acting on evolutionarily young fish communities in lakes of remote islands. One process that drives diversification in island freshwater fish species is the colonization of depauperate freshwater environments by diadromous (migratory) taxa, which secondarily lose their migratory behaviour. The loss of migration limits dispersal and gene flow between distant populations, and, therefore, is expected to facilitate local morphological and genetic differentiation. To date, most studies have focused on interspecific relationships among migratory species and their non-migratory sister taxa. We hypothesize that the loss of migration facilitates intraspecific morphological, behavioural, and genetic differentiation between migratory and non-migratory populations of facultatively diadromous taxa, and, hence, incipient speciation of island freshwater fish species.
Results: Microchemical analyses of otolith isotopes (Sr-88, Ba-137 and Ca-43) differentiated migratory and non-migratory stocks of the New Zealand endemic Gobiomorphus cotidianus McDowall (Eleotridae). Samples were taken from two rivers, one lake and two geographically-separated outgroup locations. Meristic analyses of oculoscapular lateral line canals documented a gradual reduction of these structures in the non-migratory populations. Amplified fragment length polymorphism (AFLP) fingerprints revealed considerable genetic isolation between migratory and non-migratory populations. Temporal differences in reproductive timing (migratory = winter spawners, non-migratory = summer spawners; as inferred from gonadosomatic indices) provide a prezygotic reproductive isolation mechanism between the two ecotypes.
Conclusion: This study provides a holistic look at the role of diadromy in incipient speciation of island freshwater fish species. All four analytical approaches (otolith microchemistry, morphology, spawning timing, population genetics) yield congruent results, and provide clear and independent evidence for the existence of distinct migratory and non-migratory ecotypes within a river in a geographically confined range. The morphological changes within the non-migratory populations parallel interspecific patterns observed in all non-migratory New Zealand endemic Gobiomorphus species and other derived gobiid taxa, a pattern suggesting parallel evolution. This study indicates, for the first time, that distinct ecotypes of island freshwater fish species may be formed as a consequence of loss of migration and subsequent diversification. Therefore, if reproductive isolation persists, these processes may provide a mechanism to facilitate speciation
Pyloric caecal morphology of brook charr, Salvelinus fontinalis, in relation to diet
No full textBrook charr, Salvelinus fontinafis, shifts its diet from zoobenthos to pelagic prey when living sympatrically with white sucker, Catostomus commersoni, in lakes of the Laurentian Shield. We tested the hypothesis that this diet difference would have a significant impact on their pyloric caecal morphology in 5 lakes containing allopatric brook charr populations and 6 other lakes containing both brook charr and white sucker. We observed that the mean length of the most posterior caecum of charr was significantly greater in sympatry than in allopatry (8 f 1SD: 9.91+ 1.12mm versus 8.44 f 0.67mm). This is equivalent to an increase of 18% of total pyloric caecal mass (dry weight) in sympatric brook charr. These results indicate that this response to differences in diet, well known in birds, also occurs in fish.Source type: Electronic(1
A Study of Cattle "Temperament" and its Measurement
No full textAuthor Institution: State Normal School, Stevens Point, Wisconsi
Development of LRFD Procedures for Bridge Pile Foundations in Iowa, September 2011
No full textIn response to the mandate on Load and Resistance Factor Design (LRFD) implementations by the Federal Highway Administration (FHWA) on all new bridge projects initiated after October 1, 2007, the Iowa Highway Research Board (IHRB) sponsored these research
projects to develop regional LRFD recommendations. The LRFD development was performed using the Iowa Department of Transportation (DOT) Pile Load Test database (PILOT). To
increase the data points for LRFD development, develop LRFD recommendations for dynamic methods, and validate the results of LRFD calibration, 10 full-scale field tests on the most commonly used steel H-piles (e.g., HP 10 x 42) were conducted throughout Iowa.
Detailed in situ soil investigations were carried out, push-in pressure cells were installed, and laboratory soil tests were performed. Pile responses during driving, at the end of driving (EOD), and at re-strikes were monitored using the Pile Driving Analyzer (PDA), following with the CAse Pile Wave Analysis Program (CAPWAP) analysis. The hammer blow counts were recorded for Wave Equation Analysis Program (WEAP) and dynamic formulas. Static load tests (SLTs) were performed and the pile capacities were determined based on the Davisson’s criteria. The extensive experimental research studies generated important data for analytical and computational investigations. The SLT measured load displacements were compared with the simulated results obtained using a model of the TZPILE program and using the modified borehole shear test method. Two analytical pile setup quantification methods, in terms of soil properties, were developed and validated.
A new calibration procedure was developed to incorporate pile setup into LRFD
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