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Search Results: 1 - 10 of 471265 matches for " Stephen A. Tatarkov "
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Connective Tissue Energy Loss Comparison between Joints with and without Hypermobility  [PDF]
Stephen A. Tatarkov, Angela C. Tesny, Brittany M. Lauck, Louis A. DiBerardino III, Hui Shen
Journal of Biomedical Science and Engineering (JBiSE) , 2017, DOI: 10.4236/jbise.2017.105B003
Joint hypermobility syndrome is a condition in which a joint can move effortlessly beyond the normal limit of motion expected for that joint. This syndrome is affected by some factors including gender and tends to be inherited. It may cause some symptoms such as pain in an individual’s synovial joints. The objective of the current study was to compare the energy loss of connective tissues between joints with and without hypermobility. A differential equation model, namely the Kelvin-Voigt model, was used for the energy loss analysis. The results show the difference in energy loss for the tissues attached to joints with and without joint hypermobility. As the stiffness of the connective tissue decreases, the energy loss increases. Muscle activity about the ankle was measured via electromyography during simple functional tasks, and the recorded data were used to correlate with the theoretical analysis of the energy loss. The result would shed light on the pathology analysis of the symptoms such as the cause of pain.
Culture and Organizational Improvisation in UK Financial Services  [PDF]
Stephen A. Leybourne
Journal of Service Science and Management (JSSM) , 2009, DOI: 10.4236/jssm.2009.24029
Abstract: This paper considers certain aspects of a four-year program of research, and addresses the changing cultural requirements to support the rise of improvisational working practices within the UK financial services sector. Specifically, it reports on some of the outcomes of a study encompassing over 100 hours of interviews, together with a variety of other primary and secondary data. The outcomes of the full study are documented elsewhere, and they identify a number of key factors that contribute to the successful use and control of improvisational working practices. One of these factors is a supportive organizational culture, and this specific area is dealt with in this paper. A particular focus is how the sample of organizations has attempted to identify and create supportive cultural conditions for improvisational work to take place. In order to bring clarity to the outcomes of this study, a matrix of the case study organizations is also offered, which segregates those organizations according to their cultural support for improvisation and apparent improvisation effectiveness. Some comment on the current difficulties in the Financial Services sector has also been included, as it could be argued that improvisation may have contributed to shortcomings in control processes by members of that sector.
Forest Response to the US 1990 Clean Air Act: The Southern Spruce-Fir Ecosystem  [PDF]
Stephen A. Banks
American Journal of Plant Sciences (AJPS) , 2014, DOI: 10.4236/ajps.2014.53050

The history of the Black Mountains in North Carolina and the southern Spruce-Fir ecosystem has been fraught with widespread forest decline since the mid 1960’s. Balsam Woolly Adelgid attacks and acidic deposition were two of the most recognized causes of decline. Uncertainty arose about the future of these forests, and projections were made regarding the endangerment or extinction of the endemic Fraser fir ([Pursh] Poiret). This study analyzed data sets from a permanent plot network in the Black Mountains dating 1985, 2002, and 2012. Indications that the Fraser fir population is stabilizing from a “boom-bust” cycle of population growth and has entered the stem exclusion stage of forest stand development are evident. Fir live stem density increased more than 250% from 1985 to 2002, and then declined 40% by 2012 at the highest elevations in the forest. Overall, fir appeared to be more impacted on western facing slopes than eastern ones. The population of red spruce experienced a steady decrease in live stem counts, but an increase in live basal area through all years, and at all elevation classes (1675 m, 1830 m, and 1980 m), indicating a normal progression through stand development. Red spruce was also most negatively impacted on western facing slopes. Live stem density was significantly higher (P < 0.001) than eastern plots, but live basal area was similar between the two aspects. Atmospheric deposition concentrations of the four main acidic molecules at Mt. Mitchell all peaked in 1998, but decreased by 2012. These reductions, occurring shortly after tightened regulations in the 1990 amendments to the Clean Air Act may have potential implications for increased forest resilience.

Life Cycle Assessment of CCA-Treated Wood Highway Guard Rail Posts in the US with Comparisons to Galvanized Steel Guard Rail Posts  [PDF]
Christopher A. Bolin, Stephen T. Smith
Journal of Transportation Technologies (JTTs) , 2013, DOI: 10.4236/jtts.2013.31007

A cradle-to-grave life cycle assessment is done to identify the environmental impacts of chromated copper arsenate (CCA)-treated timber used for highway guard rail posts, to understand the processes that contribute to the total impacts, and to determine how the impacts compare to the primary alternative product, galvanized steel posts. Guard rail posts are the supporting structures for highway guard rails. Transportation engineers, as well as public and regulatory interests, have increasing need to understand the environmental implications of guard rail post selection, in addition to factors such as costs and service performance. This study uses a life cycle inventory (LCI) to catalogue the input and output data from guard rail post manufacture, service life, and disposition, and a life cycle impact assessment (LCIA) to assess anthropogenic and net greenhouse gas (GHG), acidification, smog, ecotoxicity, and eutrophication potentially resulting from life cycle air emissions. Other indicators of interest also are tracked, such as fossil fuel and water use. Comparisons of guard rail post products are made at a functional unit of one post per year of service. This life cycle assessment (LCA) finds that the manufacture, use, and disposition of CCA-treated wood guard rails offers lower fossil fuel use and lower anthropogenic and net GHG emissions, acidification, smog potential, and ecotoxicity environmental impacts than impact indicator values for galvanized steel posts. Water use and eutrophication impact indicator values for CCA-treated guard rail posts are greater than impact indicator values for galvanized steel guard rail posts.

Life Cycle Assessment of Creosote-Treated Wooden Railroad Crossties in the US with Comparisons to Concrete and Plastic Composite Railroad Crossties  [PDF]
Christopher A. Bolin, Stephen T. Smith
Journal of Transportation Technologies (JTTs) , 2013, DOI: 10.4236/jtts.2013.32015

Creosote-treated wooden railroad crossties have been used for more than a century to support steel rails and to transfer load from the rails to the underlying ballast while keeping the rails at the correct gauge. As transportation engineers look for improved service life and environmental performance in railway systems, alternatives to the creosote-treated wooden crosstie are being considered. This paper compares the cradle-to-grave environmental life cycle assessment (LCA) results of creosote-treated wooden railroad crossties with the primary alternative products: concrete and plastic composite (P/C) crossties. This LCA includes a life cycle inventory (LCI) to catalogue the input and output data from crosstie manufacture, service life, and disposition, and a life cycle impact assessment (LCIA) to evaluate greenhouse gas (GHG) emissions, fossil fuel and water use, and emissions with the potential to cause acidification, smog, ecotoxicity, and eutrophication. Comparisons of the products are made at a functional unit of 1.61 kilometers (1.0 mile) of rail-road track per year. This LCA finds that the manufacture, use, and disposition of creosote-treated wooden railroad crossties offers lower fossil fuel and water use and lesser environmental impacts than competing products manufactured of concrete and P/C.

Effect of screw position on bone tissue differentiation within a fixed femoral fracture  [PDF]
Saghar Nasr, Stephen Hunt, Neil A. Duncan
Journal of Biomedical Science and Engineering (JBiSE) , 2013, DOI: 10.4236/jbise.2013.612A009

Plate and screw constructs are routinely used in the treatment of long bone fractures. Despite considerable advancements in technology and techniques, there can still be complications in the healing of long bone fractures. Non-unions, delayed unions, and hardware failures are common complications observed in clinical practice following open reduction and internal fixation of fractures [1]. Potential causes of these adverse clinical effects may be disruptive to the periosteal and endosteal blood supply, stress shielding effects, and inadequate mechanical stability. The goal of the present study was to explore the effect of screw position on the fracture healing and formation of new bone tissue with mechanoregulatory algorithms in a computational model. An idealized poroelastic 3D finite element (FE) model of a femur with a 5 mm fracture gap, including a plate-screw construct was developed. Nineteen different plate-screw combinations, created by varying the number and position of screws within the plate, were created to identify a construct with the most favourable attributes for fracture healing. The first phase of the study evaluated constructs through mechanical stress analyses to identify those constructs with high loadsupport capability. The second phase of the study evaluated healing and bone formation with a biphasic mechanoregulatory algorithm to simulate tissue differentiation for fixation within selected constructs. The results of our analysis demonstrated a 4-screw symmetrical construct with the largest distance between screws to provide the most favourable balance of stability and optimized conditions to promote fracture healing.


Endovascular Treatment and Selective Image Guided Partial Resection of Epidural Spinal Vascular Malformation in Klippel-Trenaunay Syndrome: Case Report  [PDF]
Ramon Navarro, Stephen Pirris, Ricardo A. Hanel
Open Journal of Modern Neurosurgery (OJMN) , 2014, DOI: 10.4236/ojmn.2014.44035
Abstract: Background: Klippel-Trenaunay-Weber syndrome is a rare congenital condition that may involve the central nervous system with extensive vascular malformations, and soft-tissue hypertrophy of the affected limb. Methods: A 51-year-old patient underwent previous procedures including decompressive laminectomy and endovascular embolization using Onyx and a self-expandable stent. However, recanalization of the malformation was observed, his symptoms progressed, and the decision was made to undergo selective surgical resection with intraoperative image guidance using Stealth system paired with the O-arm. Results: Adequate decompression of the affected spinal cord and cervical roots were obtained, and the patient’s symptoms improved. Conclusion: Since the typical anatomic landmarks were obliterated by the extensive vascular malformation and previous surgery, intraoperative image guidance proved to be very beneficial. This case reports on the usage of spinal navigation to efficiently dissect out the affected nerve roots and avoid vascular injury by referencing the Onyx and stent.
Thermal Stress in HFEF Hot Cell Windows Due to an In-Cell Metal Fire  [PDF]
Charles W. Solbrig, Stephen A. Warmann
World Journal of Nuclear Science and Technology (WJNST) , 2016, DOI: 10.4236/wjnst.2016.61003
Abstract: This work investigates an accident during the pyrochemical extraction of Uranium and Plutonium from PWR spent fuel in an argon atmosphere hot cell. In the accident, the heavy metals (U and Pu) being extracted are accidently exposed to air from a leaky instrument penetration which goes through the cell walls. The extracted pin size pieces of U and Pu metal readily burn when exposed to air. Technicians perform the electrochemical extraction using manipulators through a 4 foot thick hot cell concrete wall which protects them from the radioactivity of the spent fuel. Four foot thick windows placed in the wall allow the technicians to visually control the manipulators. These windows would be exposed to the heat of the metal fire. This analysis determines if the thermal stress caused by the fire would crack the windows and if the heat would degrade the window seals allowing radioactivity to escape from the cell.
Toyota’s Slow Response to Manufacturing Defects Leading to Recalls: Result of Poor Communication Strategy  [PDF]
Oyinkepreye L. Bebeteidoh, Stephen A. Takim
Journal of Transportation Technologies (JTTs) , 2016, DOI: 10.4236/jtts.2016.65034
Abstract: The recall of vehicles in the automobile industry is not limited to any particular company. Recalls most often have been attributed to defective parts supplied by tier one and tier two suppliers. Toyota, a world leader in the manufacture of automobiles, built on world class corporate brand and Principles known as the Toyota Way, and located in about 53 countries in the world, with most of its production taking place in the North America and Japan. Its Communication strategy leading to recalls has brought it into conflict with its customers and regulatory agencies. Toyota’s seeming departure from its core principles in the Toyota Way has also brought it into conflict with suppliers and affected its production. Answers will be sought for the following research questions: 1) Why with its Toyota Way, Communication became a challenge for Toyota? 2) What is the role of the Media, in Toyota’s issues of recall? A detailed literature survey was conducted for Toyota’s communication strategy. A dialectic inquiry was used to analyse the acquired data, from interviews conducted.
Determination of Irrigation Supply Efficiency in Challenging Environment Case Study of Bal’ad District, Middle Shabelle Region in Somalia  [PDF]
Abdirashid A. Omar, Christian Omuto, Stephen Ondieki
Computational Water, Energy, and Environmental Engineering (CWEEE) , 2019, DOI: 10.4236/cweee.2019.81001
Abstract: The paper aims to determine the irrigation water supply efficiency of different irrigation methods used in the challenging environment of Bal’ad district in Somalia. Data was collected from the literature, field visits using field records and scheduled interviews, GPS coordinates and from ancillary information, such as remote sensing images and existing national maps. A comparison was done by use of secondary sources, such as academic journals using information from authorities on irrigation and water loss. Sampling was done by use of Snow balling. The results highlighted response rate for farmers being 80% while that of NGO employees is 75.76%. According to the results, the main ways through which irrigation water is lost is through: evaporation; seepage through the canal bunds; overtopping the bunds; overflow losses and overwatering with the average field application efficiency of 25% and conveyance efficiency of 30%. These generated a scheme irrigation efficiency of 7.5% which is poor for surface irrigation prevalent in the study area. The loss of irrigation water was found to be reduced by the following: daily supervision; proper maintenance; water allocation to farmers; good management; lining of canals; management of irrigation methods; ongoing evaluation; good land preparation; and training farmers.
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