BEE 4530 - 2003 Student Papers

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Student research papers for Professor Ashim Datta's Biomed BEE 4530/Computer-aided Engineering course for 2003.

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    Transdermal Scopolamine Drug Delivery Systems for Motion Sickness
    Fung, Gloria; Ho, Terence; Lee, Soyoon; Munaretto, Joseph; Tsai, Christine (2003-07-12T20:48:00Z)
    Transdermal drug delivery systems are involved in the continuous administration of drug molecules from the surface of the skin into the circulatory system. Such systems have proved advantageous for delivery of certain drugs, such as scopolamine, nicotine, nitroglycerine, and estradiol. Compared with oral administration, transdermal drug delivery offers better uniformity of drug concentrations in plasma throughout their duration of use. Scopolamine is the active ingredient in motion sickness medication that targets the nerve fibers in the inner ear. The scopolamine patch is effective for about three days, longer than if administered orally which is effective for only several hours. One of the main restraints of this transdermal system is its absorption through the skin, especially through the stratum corneum, its outermost part. This study examines the rate of diffusion of transdermal scopolamine across the skin and into the systemic circulation. Our objective is to optimize the drug delivery by way of a scopolamine patch by minimizing absorption rates, while maintaining its advantage of a long-term effect. A comparative study of the effects in the presence of penetration enhancers were undertaken to show how steady state is approached at different rates. The model we used does offer certain limitations, as diffusivity values specific to human skin and scopolamine are not readily available.
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    Cryopreservation of Umbilical Cord Tissue for Stem Cell Harvesting
    Buchwald, Steven; Chiu, Nicole; Chu, Melvin; Kim, Hesed; Yeang, Calvin (2003-07-12T20:41:27Z)
    Stem cell transplantation has become an important process used to treat patients with bone marrow diseases. When implanted into patients, stem cells from the umbilical cord have been found to successfully proliferate as new neurons and glia, thereby improving the patients? health. Neurons and glia are imperative for the health and normal function of our nervous system. Neurons are electrically active cells that can produce action potentials to transmit signals based on electrochemical impulses. Glia, which comprise a large part of our nervous systems (90% of the brain alone), were once dismissed as mere padding in the nervous system. However, it is now known that they are actually an integral component of the system, serving to facilitate and ensure the proper transmission of signals between neurons. Damage to or loss of neural cells, whether due to physical injury, removal (as in the case of cancer) or diseases such as Motor Neuron Disease (MND) and Parkinson?s disease is severely detrimental to one?s health. Using current tissue engineering technology, stem cells harvested from the matrix of the umbilical cord (known as Wharton?s Jelly), may be differentiated into neurons or glia, effectively replacing those that were lost or damaged. To ensure biocompatibility, umbilical cord matrix cells from direct relatives are used. Therefore, cryopreservation of these cells is imperative to the stem cell treatment to be used in the future. Our goal is to use FIDAP and GAMBIT software solutions and mesh to compare the effectiveness of glycerol, propylene glycol, and DMSO, three commonly used cryopreservatives, in order to determine the cryopreservation agent that will maximize viability of umbilical cord stem cells.
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    Cryopreservation of the Kidney: A Feasibility Study Based on Cooling Rates
    Malvica, Erica; Salter, Ben; Verma, Kush; Watkins, Tara; Shauhgnesy, Michael (2003-07-12T20:35:34Z)
    This project models the cryopreservation of a kidney submerged in liquid nitrogen. Attempts to cryopreserve whole organs have been unsuccessful in the past due to the formation of ice crystals in the intracellular fluid, which cause damage to the cells. Damage can be avoided if cells are vitrified, which causes the intracellular fluid to form a glassy solid rather than ice crystals. The vitrification process is hard to achieve because it generally requires very high cooling rates, but it is aided by the addition of cryoprotectants. This study used Gambit TM and FidapTM software to model cooling rates using different concentrations of glycerol as a cryoprotectant. The concentrations of glycerol were varied to maximize vitrification, and thus cell survival. The results of this study show that the addition of cryoprotectant does alter the cooling rate. Cells closest to the surface of the kidney would likely have been vitrified while cells closer to the center had a slower cooling rate and would most likely have formed ice crystals. Cell survival is predicted to be highest for the 2M concentration of glycerol; however, higher concentrations should be avoided to prevent cell toxicity.
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    Temperature Profile Of the Brain During Suspended Animation
    Ku, Cora; Sakai, Yuichi; Wong, Amy; Yeung, Ophelia (2003-07-12T20:26:34Z)
    In most cases of serious truncal injuries, cardiac arrest occurs within minutes due the severe blood loss. Although many of these injuries are potentially repairable, death is often resulted from fatal brain damage due to insufficient supply of blood. Suspended animation (SA) is a way to preserve the whole organism by lowering brain temperature during prolonged cardiac arrest (often over one hour). A hypothermic flush of cold saline solution is administered through blood vessels to the brain. By lowering the rate of cerebral metabolic activity, damage to the brain is reduced and the brain can be preserved for later cerebral resuscitation. Current studies have focused on animals but no experiment has been implemented on humans yet. In our project, we use GAMBIT and FIDAP to model the temperature profile of the brain during suspended animation. A suitable model of saline flow through blood vessels in the brain is developed to determine how temperature in the outer brain region changes at any given time. From our model, the temperature in the outer brain quickly drops to 8?C after flushing a saline solution of 4?C. While saline is very effective in reducing outer brain temperature, the decrease in brain temperature can be adjusted by using saline solutions of different temperatures.
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    Modeling Heat Flows in a Hibernating Black Bear
    Cottrell, Jocelyn; Hogan, Chris; Jain, Nieraj; Nogal, Bartosz; McWay, Michael (2003-07-12T20:21:58Z)
    The American Black Bear (Ursus americanus) has the ability to sustain a high core temperature throughout the duration of its hibernation cycle, even as outside temperatures fall to -20?C. This ability is largely due the conversion of chemical energy into heat in specialized tissue known as brown fat. We demonstrate temperature variation in a hibernating black bear on a macroscopic scale, without attempting to demonstrate local temperature variation. In this first glimpse of the physical processes underlying thermoregulation in a hibernating black bear, we have incorporated heat generation within a layer of brown fat. Our model indicates that brown fat tissue is capable of providing the energy need to maintain a high temperature. However, our model also points to the importance of the thick fur layer, as well as that of the fat layer, in providing basic insulation. At steady state, a temperature drop of over 40?C occurs in these two layers, keeping the body core at a temperature high above that of the surroundings. Without the insulation provided by these essential layers, along with thermogenesis in brown fat, it is unlikely that the bear would survive a 100-day hibernation cycle.
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    Radiofrequency Ablation to kill Kidney Tumors
    Sharma, Manish; Lafrance, Tim; Ducharme, Richard; Taylor, Kristin; Wobbrock, Nicholas (2003-07-12T20:10:35Z)
    Radiofrequency ablation is a technique to destroy tissue cells by heating them above 460C. This method is specifically used in treating tumors smaller than 5 cm in diameter by placing the heated probe within the dysfunctional tissue mass. Depending on the size and shape of the tumor, the ideal time of treatment, voltage, and shape of probe required to eliminate the cells is decided. This study tested a spherical tumor with a 2 cm diameter to determine the best probe shape, voltage, and time of treatment to destroy cancerous cells while keeping surrounding tissue unaffected. Our results indicated that a lower voltage (0.27 volts) and a longer period of time (700 seconds) yielded the best results when using a T-shaped probe. These results account for the diffusion of the heat within the tumor cells while minimizing the damage to the surrounding tissue. Sensitivity analysis indicated that specific heat and tissue density had very small impact on the temperature profile.
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    An Alternate Treatment for End Stage Coronary Artery Disease: Transmyocardial Laser Revascularization (TMR)
    Danny, Catropa; Dines, Megan; Kimmel, Jeremy; Rubin, Juli; Nocerino, Christina (2003-06-17T20:10:36Z)
    Coronary artery disease involves the buildup of plaque (from cholesterol) on the inside of the arteries, which limits the flow of blood through the vessel. Occlusion of these vessels leads to angina and ultimately to heart attacks. Several common treatments exist to reopen the arteries including angioplasty (with or without a stent), atherectomy, and laser ablation. However, surgical procedures are sometimes necessary and the available options are bypass surgery and transmyocardial laser revascularization, TMR. TMR is a procedure in which ten to forty 1mm channels are created in ischemic heart tissues, where the number of channels made varies from patient to patient based on their individual casesi. This procedure allows for oxygenated blood to flow into the heart and will also result in revascularization the deoxygenated heart tissuesi. This procedure was modeled using Gambit to create the mesh and FIDAP to model the diffusivity of oxygenated blood into deoxygenated heart tissue. The governing equations used to model the flow of oxygenated blood through the channel and diffusion of the oxygen into the deoxygenated tissue layer were the species and momentum equations. No reaction term was used in the species equation because it was assumed there was no elimination of oxygen by the tissue. A fully developed parabolic velocity profile was assumed in conjunction with the momentum equation. The initial conditions included an oxygen concentration of 0.2 ml 02/ml blood at the intake and 0.1 ml 02/ml blood in the deoxygenated muscle. The boundary conditions consisted of a constant zero flux at the top, left wall, right wall, and axis. The exit of the channel is free as is the blood/muscle interface because FIDAP will solve for the 02 concentration based on the other parameters that were specified. Based on this model, it is evident that oxygenated blood in the newly created channels does diffuse into the deoxygenated heart tissue. Although there is diffusion throughout the entire sample, the diffusion nearest the inlet is greatest and decreases along the length of the channel and radially outward from the channel as expected. In addition, the desired oxygen concentration, 80% saturationvii, was achieved at the channel-tissue boundary but not within the tissue layer. These results could be attributed to some of the assumptions that we were forced to make in modeling the procedure due to the limitations of the software in handling a two-phase model. However, with the optimal diameter found, 1.4 mm, and a closer channel spacing, a more optimal diffusion profile may be achieved.
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    Lord of the Mood Rings
    Celia, Chan; Yen, Cu; Jessica, Kadlec; Jennifer, Lee (2003-06-17T20:07:46Z)
    Our main objective is to study the mechanisms by which heat transfer taking place in the human finger will affect the color change in the mood ring. This project uses GAMBIT and FIDAP to model the heat transfer from the finger to the ring. Finding the possible range of heat generations, one can estimate the temperature range of the surface and thus the best type of LC to be used in a ring. By determining the temperature in the ring at steady state the blood flow rate can be quantified, which will provide the required heat generation to change the mood ring to any desired color. We obtained several Q?s ranging from 6800 to 7200 W/m^3 appropriate to blood flow rate, and ambient conditions with no forced convection for the model. Further sensitivity analysis was done for selected data input, such as conductivity and source term, to assess their impact on the results. It was concluded that blood flow rate corresponding to the heat generation values used ranged from 0.245 to 0.265 cm^3/min. From the results it is recommended that the color change in the LCD crystal should be most sensitive over the range of 32 to 35 ?C.
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    Hyperthermic Ablation of Hepatic Tumors by Inductive Heating of Ferromagnetic Alloy Implants
    Androlowicz, Julie; Clark, Iain; Doerr, Georgr; Netravali, Nathan; Wynne, Joseph (2003-06-17T20:05:02Z)
    This study is an investigation into the ability of ferromagnetic thermal therapy to destroy cancerous hepatic tissue. Ferromagnetic rods are implanted in cancerous tissue and heated by induction. Increased temperatures result in tumor destruction. Because alloy implants are minimally invasive, used for multiple treatments and are temperature self-regulating, they represent a superior cancer treatment compared to many alternatives. The focus of modeling ferromagnetic thermal therapy will be to maximize tumor obliteration by considering heating temperature and the placement of alloy rods. Data on the efficacy of different Curie points and probe arrangements as well as sensitivity to variations in material properties are presented. Recommendations are made for the implementation of this treatment based on the modeled results.
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    How Warm is an Igloo?
    Holihan, Rich; Keeley, Dan; Lee, Daniel; Tu, Powen; Yang, Eric (2003-06-17T19:56:15Z)
    Homeostasis maintains the human body temperature within a few degrees of 37oC. However, in severe environments, such as a harsh winter blizzard, the body will not be able to maintain a 37oC temperature without the aid of clothes, shelter, and sources of heat. We find the Igloo, a shelter made of ice and snow, a very interesting means of maintaining body temperature. In this project, we have created a mesh of the Igloo system in GAMBIT and ran simulations in FIDAP to examine temperature variation and air flow inside of the igloo, when the human body is the only source of heat. In the steady state temperature profile obtained, areas of highest temperature were located directly around and above the human, and close to the top of the igloo, the temperature was 289K. The areas of lowest temperature were around 266 K, located at the bottom of the igloo farthest from the human. Natural convection caused the velocity of the air in the igloo to range from 0 to 9mm/s. The FIDAP analysis did not take into account radiative heat transfer, so a separate analysis was done, which revealed that there is considerable heat transfer through radiation in an igloo.