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Articles 3301 - 3330 of 6346

Full-Text Articles in Engineering

Geotechnical Characterization Of Clinker-Stabilized Fly Ash–Coal Mine Overburden Mixes For Subbase Of Mine Haul Road, Soumya Ranjan Mallick, Manoj Kumar Mishra Jan 2013

Geotechnical Characterization Of Clinker-Stabilized Fly Ash–Coal Mine Overburden Mixes For Subbase Of Mine Haul Road, Soumya Ranjan Mallick, Manoj Kumar Mishra

Coal Combustion and Gasification Products Journal Archive

Fly ash is a major by-product of thermal power plants that adversely affects land, water, and air. Its gainful utilization in many areas is being continuously explored. Use of fly ash in opencast coal mine haul road construction is one such option. This article reports detailed laboratory investigations carried out on clinker-stabilized fly ash–mine overburden mixes to evaluate their suitability for subbase of mine haul roads. Composite materials were prepared from fly ash, mine overburden, and clinker at different proportions. Proctor compaction test, unconfined compressive strength (UCS), and ultrasonic pulse velocity tests were carried out at different curing periods. UCS …


Cooperative Semantic Information Processing For Literature-Based Biomedical Knowledge Discovery, Zhiguo Yu Jan 2013

Cooperative Semantic Information Processing For Literature-Based Biomedical Knowledge Discovery, Zhiguo Yu

Theses and Dissertations--Electrical and Computer Engineering

Given that data is increasing exponentially everyday, extracting and understanding the information, themes and relationships from large collections of documents is more and more important to researchers in many areas. In this paper, we present a cooperative semantic information processing system to help biomedical researchers understand and discover knowledge in large numbers of titles and abstracts from PubMed query results.

Our system is based on a prevalent technique, topic modeling, which is an unsupervised machine learning approach for discovering the set of semantic themes in a large set of documents. In addition, we apply a natural language processing technique to …


Investigation Of Usage Of Velocity And Pressure Data Within A Water Distribution Lab Model For Calibrating Hydraulic Models, Robert Craig Ashby Jan 2013

Investigation Of Usage Of Velocity And Pressure Data Within A Water Distribution Lab Model For Calibrating Hydraulic Models, Robert Craig Ashby

Theses and Dissertations--Civil Engineering

Water distribution modeling for hydraulics and water quality is an important tool for managing system performance of water utilities. An important component of a water distribution model is the calibration of a network model with field data in the real world system. The calibration effort requires a protocol or selection criteria for the location of field measurements that best support the calibration effort. A water distribution model was constructed at the University of Kentucky hydraulics lab for the purpose of investigating the performance of water distribution models. The lab model contains numerous hydraulic (pressure, flows) and water quality (concentrations) sensors …


Predicting The Dynamic Behavior Of Coal Mine Tailings Using State-Of-Practice Geotechnical Field Methods, Ali Salehian Jan 2013

Predicting The Dynamic Behavior Of Coal Mine Tailings Using State-Of-Practice Geotechnical Field Methods, Ali Salehian

Theses and Dissertations--Civil Engineering

This study is focused on developing a method to predict the dynamic behavior of mine tailings dams under earthquake loading. Tailings dams are a by-product of coal mining and processing activities. Mine tailings impoundments are prone to instability and failure under seismic loading as a result of the mechanical behavior of the tailings. Due to the existence of potential seismic sources in close proximity to the coal mining regions in the United States, it is necessary to assess the post-earthquake stability of these tailings dams.

To develop the aforementioned methodology, 34 cyclic triaxial tests along with vane shear tests were …


Increases In Rops Pricing From 2006-2012 And The Impact On Rops Demand, Julie A. Sorensen, Paul L. Jenkins, Barbara Bayes, Erin Madden, Mark Purschwitz, John J. May Jan 2013

Increases In Rops Pricing From 2006-2012 And The Impact On Rops Demand, Julie A. Sorensen, Paul L. Jenkins, Barbara Bayes, Erin Madden, Mark Purschwitz, John J. May

Biosystems and Agricultural Engineering Faculty Publications

In 2006, a social marketing campaign was developed to increase the installation of rollover protective structures (ROPS) on unprotected New York tractors. Using data gathered from the program's hotline, the impact of price increases on farmers' interest in ROPS is examined. Pricing data were obtained for all rigid ROPS kits commercially available in the U.S. since 2006. These data were stratified into two groups of ROPS suppliers: (1) tractor manufacturers that sell ROPS for their own tractors, referred to in this study as original equipment manufacturers (OEMs), and (2) aftermarket (AM) ROPS suppliers. The trend in price increases was contrasted …


Development Of A Semi-Automated Tobacco Stripping Machine Utilizing String Trimmers, Robert George Sperry, John H. Wilhoit, George A. Duncan Jan 2013

Development Of A Semi-Automated Tobacco Stripping Machine Utilizing String Trimmers, Robert George Sperry, John H. Wilhoit, George A. Duncan

Biosystems and Agricultural Engineering Faculty Publications

Conventional stripping of burley tobacco is labor intensive and typically requires 50 to 75 worker hours per acre (wkr•h/acre). The goal of the project was to reduce labor by optimizing leaf removal by string trimmer heads using combinations of strings lengths and motor speeds. In tests conducted on a single grade, all leaves outside the grade were removed by hand. Plants were run through the machine for string lengths of 13, 18, and 23 cm (5, 7, and 9 in.) and associated motor speeds which were monitored and recorded. Stripping efficiencies were calculated for each plant and collectively for each …


Designing Contour Weep Berms To Reduce Agricultural Nonpoint Source Pollution, Richard C. Warner, Carmen T. Agouridis, Ross L. Guffey Jan 2013

Designing Contour Weep Berms To Reduce Agricultural Nonpoint Source Pollution, Richard C. Warner, Carmen T. Agouridis, Ross L. Guffey

Biosystems and Agricultural Engineering Faculty Publications

Nonpoint source pollution (NPS) of surface waters is a significant issue in agricultural lands, and best management practices (BMPs) are often used to reduce these impacts. Since the effectiveness of a BMP depends on a large number of widely varying factors, it is important to continue to develop BMPs in order to provide designers with more tools to use to maximize NPS removal. The contour weep berm is a new structural BMP constructed out of earth and subsequently vegetated. It is a linear BMP that is used in combination with a down-gradient vegetated filter strip or forested riparian buffer. Preliminary …


Influence Of Flue Gas Components On The Growth Rate Of Chlorella Vulgaris And Scenedesmus Acutus, Czarena Crofcheck, Aubrey Shea, Michael D. Montross, Mark Crocker, Rodney Andrews Jan 2013

Influence Of Flue Gas Components On The Growth Rate Of Chlorella Vulgaris And Scenedesmus Acutus, Czarena Crofcheck, Aubrey Shea, Michael D. Montross, Mark Crocker, Rodney Andrews

Biosystems and Agricultural Engineering Faculty Publications

Atmospheric carbon dioxide levels have increased since the industrial revolution due to the increase in combustion of fossil fuels. One possible alternative strategy is the use of microalgae for CO2 capture and recycling. Major components in coal-derived flue gas that may accumulate and effect algae growth include both sulfur oxides and fly ash. However, in practical application, sulfur oxides will be converted quickly to the acid product (H2SO4) in the aerobic aqueous conditions of algae cultivation. In this article, the influence of elevated H2SO4 levels and the presence of coal-derived fly ash …


A Correlation-Based Optical Flowmeter For Enclosed Flows, Naiqian Zhang, Joseph S. Dvorak, Yali Zhang Jan 2013

A Correlation-Based Optical Flowmeter For Enclosed Flows, Naiqian Zhang, Joseph S. Dvorak, Yali Zhang

Biosystems and Agricultural Engineering Faculty Publications

A low-cost flowmeter would be very useful in a wide variety of monitoring situations. This article discusses the development of such a flowmeter based on optical components and its testing with water in an enclosed flow system. The sensor consisted of two sets of LEDs and phototransistors spaced 4 cm apart, monitoring the optical properties of the fluid at upstream and downstream locations, respectively. A small amount of dye was injected into the flow, which caused a change in the optical properties of the fluid at both locations. The time required for this change to move from the upstream to …


2013-2014 Kentucky & Tennessee Tobacco Production Guide, Kenneth W. Seebold, Robert C. Pearce, William A. Bailey, Lowell P. Bush, Jonathan D. Green, Robert D. Miller, Laura A. Powers, William M. Snell, Lee H. Townsend, Mark Purschwitz, Larry G. Wells, John H. Wilhoit, Margarita Velandia, Steve Bost, Gene Burgess, Frank Hale, Darrell Hensley, Paul Denton, Neil Rhodes Jan 2013

2013-2014 Kentucky & Tennessee Tobacco Production Guide, Kenneth W. Seebold, Robert C. Pearce, William A. Bailey, Lowell P. Bush, Jonathan D. Green, Robert D. Miller, Laura A. Powers, William M. Snell, Lee H. Townsend, Mark Purschwitz, Larry G. Wells, John H. Wilhoit, Margarita Velandia, Steve Bost, Gene Burgess, Frank Hale, Darrell Hensley, Paul Denton, Neil Rhodes

Agriculture and Natural Resources Publications

Tobacco growers in Kentucky and Tennessee have faced many challenges during the past two years, including weather, labor availability, and rising production costs. However, there have been opportunities as well. Some buying stations have closed or moved, but new buyers have come into the market and contract volumes have been stable overall. Good quality burley tobacco is in relatively short supply, and this has offered opportunities to those who have been able to overcome weather and labor challenges and produce good crops. These changes have had different impacts in different regions of both states, based largely on where buying stations …


A Note On The Occurrence Of Yttrium And Rare Earth Elements In Coal Combustion Products, James C. Hower, Shifeng Dai, Vladimir V. Seredin, Lei Zhao, Irena J. Kostova, Luis F.O. Silva, Sarah M. Mardon, Gulbin Gurdal Jan 2013

A Note On The Occurrence Of Yttrium And Rare Earth Elements In Coal Combustion Products, James C. Hower, Shifeng Dai, Vladimir V. Seredin, Lei Zhao, Irena J. Kostova, Luis F.O. Silva, Sarah M. Mardon, Gulbin Gurdal

Coal Combustion and Gasification Products Journal Archive

There is an international need for a variety of lanthanide elements (rare earth elements, or REEs) in modern electronic and related components. This has led to a desire to broaden production from both previously productive locations and to expand production to new sources, possibly including coal-derived fly ash. The concentration of lanthanides in coal-combustion fly ash depends on a number of factors, one of the most important being the concentration of the elements in the feed coal. Unlike some elements, such as Zn and As, the REE concentration is largely not a function of element volatility. In this study, we …


Fouling Intensity Of Three Indian Coals, S. Balakrishnan, R. Nagarajan Jan 2013

Fouling Intensity Of Three Indian Coals, S. Balakrishnan, R. Nagarajan

Coal Combustion and Gasification Products Journal Archive

Ash particles can arrive at heat-transfer surfaces either in solid (solidified) state or in molten state, depending on the factors such as location inside the boiler, temperature, and residence time. In this study, arrival of ash particles in solid state, which can occur in the convective section of the boiler, was considered. Apart from the inertial force that drives particles .10 mmto the surface, the low-melting inorganic alkali vapors play a vital role in deposit formation by promoting sticking. Chemical equilibrium calculations were performed to calculate the equilibrium composition of flue gas, as well as the amount of condensable inorganic …


Motor Carrier Tax Consolidation Study, Andrew Martin, Mark Bell, Jennifer Walton Jan 2013

Motor Carrier Tax Consolidation Study, Andrew Martin, Mark Bell, Jennifer Walton

Kentucky Transportation Center Research Report

This study analyzed the tax and fee structure for Kentucky motor carriers and details a possible policy scenario for eliminating the weight-distance tax. The report starts out analyzing detailed revenue and rate information for the motor fuel tax, motor fuel surtax, weight distance tax, IRP registration fees, and intrastate registration fees. Consolidation policies in Idaho and Ohio were reviewed, as well as a previous consolidation proposal in Kentucky. A new consolidation framework was developed, where IRP and intrastate plate fees were increased by 129 percent and the weight-distance tax was eliminated. Projections for weight-distance tax and IRP fees (both current …


Supplier Sustainability Evaluation Utilizing Multi Attribute Utility Modeling, Scott E. Ladd Jan 2013

Supplier Sustainability Evaluation Utilizing Multi Attribute Utility Modeling, Scott E. Ladd

Theses and Dissertations--Manufacturing Systems Engineering

Conventionally, the focus during supplier evaluation has been to assess cost, quality and delivery effectiveness due to their impact on profitability. In recent years, there has been increased emphasis on promoting more sustainable business practices that focus on reducing environmental impact and improve societal well-being, in addition to economic benefits. However, most of the existing supplier evaluation methods in literature as well as those used by leading companies fall short of comprehensively assessing suppliers from a Triple Bottom Line (TBL) perspective. TBL defined as holistically looking at the economic, environmental, and societal aspects of an entity. This paper presents a …


An Observational Study Of The Methods And Progress In Enterprise Lean Transformation At A Learning Health Care Organization, Christopher Michael Rosenbaum Jan 2013

An Observational Study Of The Methods And Progress In Enterprise Lean Transformation At A Learning Health Care Organization, Christopher Michael Rosenbaum

Theses and Dissertations--Manufacturing Systems Engineering

The health care industry in the United States is increasingly pressured to improve safety and quality performance and increase revenue. In response, many health care institutions are moving to redesign their processes and practices in an effort to decrease costs and provide safer, higher quality, and more efficient care. The purpose of this paper is to document the Lean implementation strategy and progress in implementation at a large teaching health care organization undergoing Lean transformation in order to understand enterprise transformation strategies and the impact of leadership involvement on culture development and Lean implementation. Through direct observations and involvement and …


Modeling Of Biorefinery Supply Chain Economic Performance With Discrete Event Simulation, Joseph S. Amundson Jan 2013

Modeling Of Biorefinery Supply Chain Economic Performance With Discrete Event Simulation, Joseph S. Amundson

Theses and Dissertations--Manufacturing Systems Engineering

As competition for fossil fuels accelerates, alternative sources of chemicals, fuels, and energy production become more appealing to researchers and the layman. Among the candidates to fill this growing niche is lignocellulosic biomass. Many researchers have examined supply chain design and optimization for biofuel and bioenergy production throughout the years. However, these models often fail to capture the variability and uncertainty inherent to the biomass supply chain. Multiple factors with high degrees of stochasticity can have major impacts on the performance of a biorefinery: weather, biomass quality, feedstock availability, and market demand for products are just a few. To begin …


Kentucky Water Resources Research Institute Annual Technical Report Fy 2012, Kentucky Water Resources Research Institute, University Of Kentucky Jan 2013

Kentucky Water Resources Research Institute Annual Technical Report Fy 2012, Kentucky Water Resources Research Institute, University Of Kentucky

KWRRI Annual Technical Reports (USGS’s 104b Grant Program)

The 2012 Annual Technical Report for Kentucky consolidates reporting requirements for the Section 104(b) base grant award into a single document that includes; 1) a synopsis of each research project that was conducted during the period, 2) citations for related publications, reports, and presentations, 3) a description of information transfer activities, 4) a summary of student support during the reporting period, and 5) notable awards and achievements during the year.


Development Of 15 Psi Safe Haven Polycarbonate Walls For Use In Underground Coal Mines, Rex Allen Meyr Jr. Jan 2013

Development Of 15 Psi Safe Haven Polycarbonate Walls For Use In Underground Coal Mines, Rex Allen Meyr Jr.

Theses and Dissertations--Mining Engineering

Following three major mining accidents in 2006, the MINER Act of 2006 was enacted by MSHA and required every underground coal mine to install refuge alternatives to help prevent future fatalities of trapped miners in the event of a disaster. The following research was performed in response to NIOSH’s call for the investigation into new refuge alternatives. A 15 psi safe haven polycarbonate wall for use in underground coal mines was designed and modeled using finite element modeling in ANSYS Explicit Dynamics. The successful design was tested multiple times in both half-scale and small scale using a high explosive shock …


Experimental Comparison Study Of The Response Of Polycarbonate And Laminated Glass Blast Resistant Glazing Systems To Blast Loading, Joshua Calnan Jan 2013

Experimental Comparison Study Of The Response Of Polycarbonate And Laminated Glass Blast Resistant Glazing Systems To Blast Loading, Joshua Calnan

Theses and Dissertations--Mining Engineering

This thesis recounts the experimental study of the dynamic response of polycarbonate blast resistant glazing systems to explosive loading through the use of triaxial load cells, pressure sensors, and a laser displacement gauge. This instrumentation captured the response of the glazing systems to blast loading over three phases of testing. The first phase of testing characterizes the load distribution around the perimeter and the second phase examines the repeatability of the results. The final phase of testing pushes the samples to failure. The results are then compared to HazL, a commonly used blast resistant glazing system analysis software tool. The …


Modeling Of An Air-Based Density Separator, Tathagata Ghosh Jan 2013

Modeling Of An Air-Based Density Separator, Tathagata Ghosh

Theses and Dissertations--Mining Engineering

There is a lack of fundamental studies by means of state of the art numerical and scale modeling techniques scrutinizing the theoretical and technical aspect of air table separators as well as means to comprehend and improve the efficiency of the process. The dissertation details the development of a workable empirical model, a numerical model and a scale model to demonstrate the use of a laboratory air table unit.

The modern air-based density separator achieves effective density-based separation for particle sizes greater than 6 mm. Parametric studies with the laboratory scale unit using low rank coal have demonstrated the applicability …


Evaluating Food Safety Systems Development And Implementation By Quantifying Haccp Training Durability, Marienne A. Anandappa Jan 2013

Evaluating Food Safety Systems Development And Implementation By Quantifying Haccp Training Durability, Marienne A. Anandappa

Theses and Dissertations--Animal and Food Sciences

HACCP-based food safety programs have been widely acclaimed, accepted and implemented as an effective means of managing food safety risks. While HACCP training is a cornerstone of managing HACCP programs, there is little information about the effectiveness of HACCP training and the durability of HACCP knowledge. Findings reveal a link between involvement level in HACCP activities and the accuracy of HACCP knowledge over time. Opportunities for peer training in HACCP, irrespective of overall experience in the food industry provide favorable circumstances for maintaining accuracy of HACCP knowledge. The optimal window for engaging employees in HACCP is directly following the completion …


The Modeling, Analysis And Control Of Resilient Manufacturing Enterprises, Yao Hu Jan 2013

The Modeling, Analysis And Control Of Resilient Manufacturing Enterprises, Yao Hu

Theses and Dissertations--Electrical and Computer Engineering

The resilience of manufacturing enterprises is an important research topic, since disruptions have severe effects on the normal operation of manufacturing enterprises, especially as manufacturing supply chains become global. Although many case studies have been carried out to address resilience in organizations, a systematic method to model and analyze the resilience dynamics in manufacturing enterprises is not well developed. This study is intended to conduct research on quantitative analysis and control for resilience.

After reviewing the literature addressing resilience, a modeling framework is presented to characterize the resilience of a manufacturing enterprise responding to disruptive events, which includes inventory ow …


The Effects Of Hydrostatic Pressure On Early Endothelial Tubulogenic Processes, Ryan M. Underwood Jan 2013

The Effects Of Hydrostatic Pressure On Early Endothelial Tubulogenic Processes, Ryan M. Underwood

Theses and Dissertations--Biomedical Engineering

The effects of mechanical forces on endothelial cell function and behavior are well documented, but have not been fully characterized. Specifically, fluid pressure has been shown to elicit physical and chemical responses known to be involved in the initiation and progression of endothelial cell-mediated vascularization. Central to the process of vascularization is the formation of tube-like structures. This process—tubulogenesis—is essential to both the physiological and pathological growth of tissues. Given the known effects of pressure on endothelial cells and its ubiquitous presence in the vasculature, we investigated pressure as a magnitude-dependent parameter for the regulation of endothelial tubulogenic activity. To …


Chemical Weathering And Mobility Of Inorganic Species In Dry Disposed Ash: An Insight From Geochemical Fractionation And Physicochemical Analysis, S.A. Akinyemi, W.M. Gitari, A. Akinlua, L.F. Petrik Jan 2013

Chemical Weathering And Mobility Of Inorganic Species In Dry Disposed Ash: An Insight From Geochemical Fractionation And Physicochemical Analysis, S.A. Akinyemi, W.M. Gitari, A. Akinlua, L.F. Petrik

Coal Combustion and Gasification Products Journal Archive

The burning of low-grade coal produces vast amounts of ash and other solid by-products. In South Africa, coal combustion by-products undergo disposal on land as dry heaps or slurried to dams. In this study, the geochemical partitioning, transport, and mobility of elements in dry disposed ash dumps were investigated using a modified sequential extraction scheme. The chemical and mineralogical compositions of 50 drilled core samples were investigated by X-ray fluorescence (XRF), X-ray diffraction (XRD), and inductively coupled plasma mass spectrometry. Ternary plots of major elements as determined by XRF showed that the 15-year-old and 2-week-old dry disposed ashes are sialic, …


Two-Dimensional Hydrodynamic Modeling Of Two-Phase Flow For Understanding Geyser Phenomena In Urban Stormwater System, Zhiyu S. Shao Jan 2013

Two-Dimensional Hydrodynamic Modeling Of Two-Phase Flow For Understanding Geyser Phenomena In Urban Stormwater System, Zhiyu S. Shao

Theses and Dissertations--Civil Engineering

During intense rain events a stormwater system can fill rapidly and undergo a transition from open channel flow to pressurized flow. This transition can create large discrete pockets of trapped air in the system. These pockets are pressurized in the horizontal reaches of the system and then are released through vertical vents. In extreme cases, the transition and release of air pockets can create a geyser feature.

The current models are inadequate for simulating mixed flows with complicated air-water interactions, such as geysers. Additionally, the simulation of air escaping in the vertical dropshaft is greatly simplified, or completely ignored, in …


Camber Control In Simply Supported Prestressed Concrete Bridge Girders, Osamah Ibrahim Mahmood Jan 2013

Camber Control In Simply Supported Prestressed Concrete Bridge Girders, Osamah Ibrahim Mahmood

Theses and Dissertations--Civil Engineering

When designing a bridge, serviceability usually controls and is a more important factor than the ultimate capacity of the bridge or the allowable stresses. Therefore, the behavior of the bridge girder deflection and camber must be predicted as accurately as possible. Therefore, excessive camber has become one of the most common problems when constructing concrete bridges. Different methods have been developed to overcome this problem. The most common and widely used is using haunch with adjustable pedestals to overcome the excessive camber. However, this method has limitations that must be considered. Therefore, this study is evaluating the effectiveness of using …


Biological Control Of Manganese In Water Supplies In The Presence Of Humic Acids, Michael S. Snyder Jan 2013

Biological Control Of Manganese In Water Supplies In The Presence Of Humic Acids, Michael S. Snyder

Theses and Dissertations--Civil Engineering

The main objective of this study was to improve our understanding of biological filtration (biofilm type) treatment for manganese (Mn) removal in drinking water. Biological filtration treatment involves biofilms of Mn(II)-oxidizing microorganisms attached to solid filter material that remove and immobilize dissolved Mn(II) in raw water by conversion to black MnO2(s) precipitates. Mn-biological filtration is an emerging green technology that can serve as an alternative to conventional physicochemical treatments but its full potential is hindered by various factors. These include lack of understanding the: (1) optimal removal conditions for Mn, (2) mechanisms for Mn releases of the accumulated Mn …


Development Of An Eeg Brain-Machine Interface To Aid In Recovery Of Motor Function After Neurological Injury, Elizabeth Salmon Jan 2013

Development Of An Eeg Brain-Machine Interface To Aid In Recovery Of Motor Function After Neurological Injury, Elizabeth Salmon

Theses and Dissertations--Biomedical Engineering

Impaired motor function following neurological injury may be overcome through therapies that induce neuroplastic changes in the brain. Therapeutic methods include repetitive exercises that promote use-dependent plasticity (UDP), the benefit of which may be increased by first administering peripheral nerve stimulation (PNS) to activate afferent fibers, resulting in increased cortical excitability. We speculate that PNS delivered only in response to attempted movement would induce timing-dependent plasticity (TDP), a mechanism essential to normal motor learning. Here we develop a brain-machine interface (BMI) to detect movement intent and effort in healthy volunteers (n=5) from their electroencephalogram (EEG). This could be used in …


Noninvasive Near-Infrared Diffuse Optical Monitoring Of Cerebral Hemodynamics And Autoregulation, Ran Cheng Jan 2013

Noninvasive Near-Infrared Diffuse Optical Monitoring Of Cerebral Hemodynamics And Autoregulation, Ran Cheng

Theses and Dissertations--Biomedical Engineering

Many cerebral diseases are associated with abnormal cerebral hemodynamics and impaired cerebral autoregulation (CA). CA is a mechanism to maintain cerebral blood flow (CBF) stable when mean arterial pressure (MAP) fluctuates. Evaluating these abnormalities requires direct measurements of cerebral hemodynamics and MAP. Several near-infrared diffuse optical instruments have been developed in our laboratory for hemodynamic measurements including near-infrared spectroscopy (NIRS), diffuse correlation spectroscopy (DCS), hybrid NIRS/DCS, and dual-wavelength DCS flow-oximeter. We utilized these noninvasive technologies to quantify CBF and cerebral oxygenation in different populations under different physiological conditions/manipulations. A commercial finger plethysmograph was used to continuously monitor MAP. For investigating …


Effects Of Acute Stretch On Cardiac Electrical Properties In Swine, Anuj Agarwal Jan 2013

Effects Of Acute Stretch On Cardiac Electrical Properties In Swine, Anuj Agarwal

Theses and Dissertations--Biomedical Engineering

Stretch is known to result in an electrically less stable ventricular substrate, yet the reported effects of stretch on measured electrophysiological parameters have been inconsistent and even contradictory. The goal of this study was to evaluate the effects of acute mechanical stretch on cardiac electrical features thought to be key in generation of arrhythmia, namely restitution of action potential duration (APD), electrical memory, and onset of alternans.

Microelectrodes were used to record intracellular potentials pre, during, and post-stretch from isolated right ventricular tissues from swine. In separate experiments, the effects of two levels of stretch were quantified. Pacing protocols employing …