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Physics and Astronomy Comps Papers
Related Documents
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Floberg, John 1 May 2005 There is no one treatment for cancer, and the search for ways to combat cancer have led to many different treatments, including surgery, chemotherapy, and radiation therapy. However, these treatments are not always effective, and in such cases new treatments must be developed. Boron neutron capture therapy (BNCT) is a treatment that has been proposed to combat glioblastomas of the brain and malignant melanomas, two tumors that are resistant to traditional cancer therapies. BNCT is based on the 10B(n,)7Li reaction, which can potentially deliver a very high and fatal radiation dose to cancerous cells by concentrating boron in them. It is a promising, though complicated treatment. Neutron beams must be generated with an adequate neutron flux, and moderated to therapeutically useful energy levels. The dose is difficult to calculate in BNCT because of all the types of radiation involved: photons, neutrons, and heavy charged particles. Dose is also highly dependent on boron distributions, which are not uniform and are difficult to measure. This makes accurate treatment plans difficult to develop. However, progress has been made on all these fronts and clinical trials have been conducted and shown that BNCT is a potentially safe and effective treatment for glioblastoma and melanoma. It provides an excellent example of the importance of innovation in the search for a cure to cancer.
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Grogg, Kira 1 May 2005 Alternative energy sources have become much more necessary as fossil fuels are depleted and pollute the environment. Wind energy is one of the most cost effective of all types of renewable energy. It does not create pollution or waste and the fuel, wind, is not used faster than it is produced. However, to make wind a viable source of energy--electricity in particular--careful design of wind-capturing machines is necessary. A variety of principles of physics are used to create wind turbines that can efficiently capture energy from the wind. This paper discusses the wind and how the parts of a wind turbine--blades, rotor, gears, generator, and electronics--operate to capture wind energy and turn it into electricity. Focus is given to horizontal axis wind turbines (HAWT), the most common and efficient type of wind energy conversion device.
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Libson, Adam 29 September 2004 This paper discusses the Laser Interferometer Gravitational-Wave Observatory (LIGO). It is hoped that with these detectors, it will be possible to detect gravitational waves from distant astronomical sources. Though gravitational radiation has been predicted for most of the last century, it has never been directly observed. This is the goal of the LIGO detectors. There are currently two interferometer sites in the United States, one in Hanford, Washington, and the other in Livingston, Louisiana, with other interferometers under construction around the world. Each LIGO detector is a long baseline Michelson interferometer with Fabry-Perot resonant cavities in the arms. This paper addresses the general relativity needed to talk about gravity waves, though I restrict myself to the linear approximation for simplicity. I also discuss how an idealized passing gravity wave will affect the LIGO detectors, along with the physics of the Michelson interferometer with Fabry-Perot cavities. Finally, I look at some of the noise sources in the interferometers, and for a few of them address possible ways around this noise. In closing, this paper will discuss the current research, which, it is hoped, will aid in the detection of gravitational radiation.
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Durham, Joseph 1 May 2004 A feedback controlled system is a system that compares its own output to a desired value and automatically takes corrective action. This paper will examine linear feedback systems, including the basics of automobile cruise control, operational amplifiers, and PID controllers. System performance can be improved by the use of feedback, especially when faced with external disturbances. To realize these gains, however, the feedback system must be properly designed. Design tools such as Nyquist stability criteria, Bode plots, and pole-zero placement will be examined.
Europa (16701803 KB PDF Document)
Engel, Theresa 1 May 2004 This paper tells the story of the moon of Jupiter named Europa. Discussed are Europa's discovery, basic parameters, orbit, tides, surface features, interior, magnetic field, atmosphere, and possible future data-gathering missions to Europa. This paper shows that Europa's surface features, induced magnetic field, and observed thin oxygen atmosphere indicate the presence of a liquid salty ocean beneath Europa's icy surface layer.
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Fink, Andrew J. P. 1 May 2004 The ear is able to detect sound energies spanning 12 orders of magnitude at frequencies ranging from 20-20,000 Hz. This paper discusses the physical mechanisms underlying the stunning capabilities of the auditory system. We follow a sound wave from the external ear to transduction into an electro-chemical signal for processing by the brain. We discuss the middle ear in terms of impedance matching and derive an expression for sound transmission from one medium to another. We focus on the inner ear and pay particular attention to the function of the basilar membrane and the properties of the traveling wave both in terms of differential equations that describe the system as well as the impedance of the membrane itself. Finally, we examine the properties of the outer and inner hair cells with particular focus placed on the motile properties of the outer hair cells. We explain the mechano-electrical transduction of the inner hair cells.
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Ritz, Clark 1 May 2004 Booming and squeaking sands produce incredible acoustic emissions when they avalanche (in the case of booming sands) or are struck or compressed (in the case of squeaking sands). Understanding this phenomenon could lead to advances in other areas of granular physics, such as the problem of treating granular flows with fluid mechanical models. This paper gives a brief overview of several topics in granular physics, reviews experimental work done to determine the properties of booming sands, and outlines two theories of the physical mechanism that produces acoustic emissions, the first mechanical, the second fluid mechanical.
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Silva, Jorge 1 May 2004 The 2003 Nobel Prize in Physics was awarded to Alexei Abrikosov and Vitaly Ginzburg, for their theories related to superconductivity, and to Anthony Leggett for his theory related to superfluidity. Superconductors and superfluids have become very important over the years due to their many theoretical and experimental applications. Superconductivity was discovered by Kamerlingh Onnes in 1911, while superfluidity in 4He was discovered in 1938 by Pyotr Kapitsa, and independently by J.F. Allen and A.D. Misener. Superfluidity in 3He was not discovered until 1972 by David Lee, Douglas Osheroff and Robert Richardson. Abrikosov's theory of Type-II superconductors is the basis of the current "hot" research area of high-temperature superconductors while Leggett's theory of superfluid phase transitions has wide applications to many fields, including particle physics, cosmology, and liquid crystal physics. A brief history will be presented as well as an introduction to technical terms used in the theories. Afterwards, a descriptive analysis of the Ginzburg-Landau theory as well as the theory of type-II superconductors, and anisotropic superfluidity will be developed.
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