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- Title
- A PSEUDO-SPECTRAL EFFECT FOR THE ACOUSTIC OSCILLATIONS OF A HELIUM AFTERGLOW.
- Creator
- KILPATRICK, WALLACE DORMAN, Florida Atlantic University, Burnett, Clyde R., Charles E. Schmidt College of Science, Department of Physics
- Abstract/Description
-
The purpose of this experimental study of the helium afterglow in a hollow cathode discharge is to identify the mechanisms which cause an apparent unequal acoustic modulation of the red and violet wings of observed optical spectrum lines. The unequal red-violet effect is traceable to the fact that curved spectrum lines are formed at the exit slit of a monochromator which is equipped with straight entrance and exit slits. Curved spectrum lines emphasize the red and violet wings differently,...
Show moreThe purpose of this experimental study of the helium afterglow in a hollow cathode discharge is to identify the mechanisms which cause an apparent unequal acoustic modulation of the red and violet wings of observed optical spectrum lines. The unequal red-violet effect is traceable to the fact that curved spectrum lines are formed at the exit slit of a monochromator which is equipped with straight entrance and exit slits. Curved spectrum lines emphasize the red and violet wings differently, depending on the light contributions from different portions of the entrance slit, so that spatial variations in the optical image due to acoustic standing waves show unequal integrated light intensities for the modulation of each wing. Only the central portion of the radial standing wave in the afterglow (Bessel function J (kr) distribution) was explored, and the ratio of the red to violet amplitude calculated as 1 : 1.58 agrees qualitatively with experimental results.
Show less - Date Issued
- 1970
- PURL
- http://purl.flvc.org/fcla/dt/13423
- Subject Headings
- Helium
- Format
- Document (PDF)
- Title
- A COMPARISON OF SODIUM ABUNDANCES CALCULATED FROM DAYLIGHT ABSORPTION AND TWILIGHT EMISSION IN THE D(2) LINE.
- Creator
- LASHER, RICHARD WILLIAM, Florida Atlantic University, Burnett, Clyde R., Charles E. Schmidt College of Science, Department of Physics
- Abstract/Description
-
A method is presented, in which the Pepsios is used to measure abundances of atomic sodium present in the upper atmosphere as calculated from the twilight glow. These abundances are compared with daylight absorption abundances, also measured using the Pepsios. Ten measurements taken during March, 1971 show an average twilight abundance of (6.1 +- 1.8) x 10^9 atoms/cm^2. This compares with an average absorption abundance of (3.3 +- 1.1) x 10^9 atoms/cm^2. These limited data and their attendant...
Show moreA method is presented, in which the Pepsios is used to measure abundances of atomic sodium present in the upper atmosphere as calculated from the twilight glow. These abundances are compared with daylight absorption abundances, also measured using the Pepsios. Ten measurements taken during March, 1971 show an average twilight abundance of (6.1 +- 1.8) x 10^9 atoms/cm^2. This compares with an average absorption abundance of (3.3 +- 1.1) x 10^9 atoms/cm^2. These limited data and their attendant uncertainties reveal no significant discrepancy between twilight and daytime sodium abundances.
Show less - Date Issued
- 1971
- PURL
- http://purl.flvc.org/fcla/dt/13449
- Subject Headings
- Sodium--Spectra, Absorption spectra
- Format
- Document (PDF)
- Title
- THE NECESSITY FOR A PHYSICS PROGRAM AT THE JUNIOR HIGH SCHOOL LEVEL.
- Creator
- JAROSH, STANLEY E., Florida Atlantic University, Matthews, Herman E., Charles E. Schmidt College of Science, Department of Physics
- Abstract/Description
-
This thesis covers a brief description of current problems and the present status of physics courses at the secondary level; a review of standardized programs presently being used; and the necessity for change. The paper will show that a separate program for teaching physics should be instituted below the high school level. It will discuss a means for accomplishing this and propose how this can be done through the use of middle schools or through a change in the continuum.
- Date Issued
- 1972
- PURL
- http://purl.flvc.org/fcla/dt/13486
- Subject Headings
- Physics--Study and teaching (Secondary), Junior high schools--Curricula
- Format
- Document (PDF)
- Title
- METASTABLE EXCITATION OF POPULATION INVERSION IN A HELIUM-HYDROGEN AFTERGLOW PLASMA.
- Creator
- WOO, KING NIEN., Florida Atlantic University, Burnett, Clyde R., Charles E. Schmidt College of Science, Department of Physics
- Abstract/Description
-
A spectroscopic study of a helium-hydrogen afterglow plasma in a pulsed discharge hollow-cathode has been made to determine the energy transfer process which results in a population inversion in atomic hydrogen. Time-resolved emission measurements were made for the Balmer series in hydrogen and self-absorption measurements with lambda 3889 A (2s 3S - 3p 3P) and lambda 4650 A (2s 3sigma - 3p 3n) of helium were taken to monitor the metastable populations. Observations were made as a function of...
Show moreA spectroscopic study of a helium-hydrogen afterglow plasma in a pulsed discharge hollow-cathode has been made to determine the energy transfer process which results in a population inversion in atomic hydrogen. Time-resolved emission measurements were made for the Balmer series in hydrogen and self-absorption measurements with lambda 3889 A (2s 3S - 3p 3P) and lambda 4650 A (2s 3sigma - 3p 3n) of helium were taken to monitor the metastable populations. Observations were made as a function of impurity concentration and as a function of helium pressure. The energy transfer from the 3S atomic metastables appears highly probable with only a minor contribution from the 3sigma molecular metastables.
Show less - Date Issued
- 1975
- PURL
- http://purl.flvc.org/fcla/dt/13746
- Subject Headings
- Physics--Experiments, Energy transfer--Experiments
- Format
- Document (PDF)
- Title
- MODE-MODE COUPLING OF PLASMA WAVES IN SYSTEMS WITH STRONG NON-LINEARITIES.
- Creator
- LODDEN, JAMES ALAN, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics
- Abstract/Description
-
The coupled equations of motion describing electrostatic plasma oscillations are derived using a collective coordinate approach. The boundary between the physical and nonphysical regions of phase space is discussed. The two mode case is studied in detail for both small and large initial disturbances. For small initial disturbances the motion was found to be periodic. For large initial disturbances, non-periodic growing solutions were found that approached one of two asymptotic limits. For...
Show moreThe coupled equations of motion describing electrostatic plasma oscillations are derived using a collective coordinate approach. The boundary between the physical and nonphysical regions of phase space is discussed. The two mode case is studied in detail for both small and large initial disturbances. For small initial disturbances the motion was found to be periodic. For large initial disturbances, non-periodic growing solutions were found that approached one of two asymptotic limits. For these solutions, the variables became infinitely large in a finite time.
Show less - Date Issued
- 1976
- PURL
- http://purl.flvc.org/fcla/dt/13828
- Subject Headings
- Coupled mode theory, Plasma waves
- Format
- Document (PDF)
- Title
- TRANSPORT MEASUREMENTS ON SEMICONDUCTING TCNQ SALTS.
- Creator
- LANE, JOHN EUGENE, Florida Atlantic University, Blakemore, John S., Charles E. Schmidt College of Science, Department of Physics
- Abstract/Description
-
This work consists mainly of two parts. First was the development of the necessary experimental techniques for measuring single crystal conductivity of anisotropic charge transfer salts. Difficulties included high impedance problems and limited size of available crystals. Cs2(TCNQ)3 was used as a test material with which to develop these techniques. An extensive investigation was undertaken to study the possibility of intrinsic and extrinsic behavior in this material. The second phase of this...
Show moreThis work consists mainly of two parts. First was the development of the necessary experimental techniques for measuring single crystal conductivity of anisotropic charge transfer salts. Difficulties included high impedance problems and limited size of available crystals. Cs2(TCNQ)3 was used as a test material with which to develop these techniques. An extensive investigation was undertaken to study the possibility of intrinsic and extrinsic behavior in this material. The second phase of this work was the study of TCNQ charge transfer salts in which the donors were structurally related pyridinium ion radicals. Four types of donors were synthesized using a methyl or benzyl substituent along with a cyano group in the 3 or 4 position of the ring. A total of eight compounds were studied including salts of the 1:1 and 1:2 stochiometry. Compaction conductivity was measured for all eight materials along with single crystal conductivity of three of the salts.
Show less - Date Issued
- 1977
- PURL
- http://purl.flvc.org/fcla/dt/13835
- Subject Headings
- Charge transfer, One-dimensional conductors, Organic semiconductors, Salts--Electric properties
- Format
- Document (PDF)
- Title
- MEASUREMENTS OF TERRESTRIAL OH ABUNDANCES BY SPECTROSCOPIC OBSERVATION OF RESONANCE ABSORPTION OF SUNLIGHT.
- Creator
- SPERANZA, PATRICK DANIEL, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics
- Abstract/Description
-
Measurements of the atmospheric hydroxyl radical (OH) abundance were made at Boca Raton, Florida, (26° 22' N, 80° 6' W) during the period March 14 through April 9, 1977. Observations were made on the P1(1) line of the A^2sigma+ - x^2pi(0,0) rotation band of OH at 3081.7A. By the use of the high resolution Pepsios (poly-etalon pressure scanning interferometric optical spectrometer) spectrometer, the narrow absorption curve due to terrestrial OH was distinguished from the broad solar Fraunhofer...
Show moreMeasurements of the atmospheric hydroxyl radical (OH) abundance were made at Boca Raton, Florida, (26° 22' N, 80° 6' W) during the period March 14 through April 9, 1977. Observations were made on the P1(1) line of the A^2sigma+ - x^2pi(0,0) rotation band of OH at 3081.7A. By the use of the high resolution Pepsios (poly-etalon pressure scanning interferometric optical spectrometer) spectrometer, the narrow absorption curve due to terrestrial OH was distinguished from the broad solar Fraunhofer line. Measurements of the amount of atmospheric OH absorption indicated an average vertical column abundance of (2.0 +- 0.8) (10^13) molecules/cm^2 for this observation period.
Show less - Date Issued
- 1977
- PURL
- http://purl.flvc.org/fcla/dt/13848
- Subject Headings
- Hydroxides--Absorption and adsorption, Atmospheric ozone
- Format
- Document (PDF)
- Title
- SPECTROSCOPIC MEASUREMENTS OF OH ABUNDANCES IN THE TERRESTRIAL ATMOSPHERE.
- Creator
- LANGSTON, JAMES HUTTON, II., Florida Atlantic University, Burnett, Clyde R., Charles E. Schmidt College of Science, Department of Physics
- Abstract/Description
-
Spectroscopic observations were made of the resonance absorption of sunlight by the atmospheric hydroxyl radical (OH). The abundance of 0 terrestrial OH was measured from the Fritz Peak Observatory (39.92 N, 105.50°W) in Colorado during September of 1978. These measurements were made on the absorption of the P1 (1) line of the A^2sigma^+ - x^2pi(O , O) rotational band of OH at 3081.7 A. The instrument used was the PEPSIOS (Poly Etalon Pressure Scanned Interferometric Optical Spectrometer)...
Show moreSpectroscopic observations were made of the resonance absorption of sunlight by the atmospheric hydroxyl radical (OH). The abundance of 0 terrestrial OH was measured from the Fritz Peak Observatory (39.92 N, 105.50°W) in Colorado during September of 1978. These measurements were made on the absorption of the P1 (1) line of the A^2sigma^+ - x^2pi(O , O) rotational band of OH at 3081.7 A. The instrument used was the PEPSIOS (Poly Etalon Pressure Scanned Interferometric Optical Spectrometer) because of its high luminosity - resolution product . The computer methods ·~sed in the analysis procedure are described . These measurements indicated an average daytime vertical column abundance of (5.40 ± 0.67) x 10^13 OH molecules/cm^2.
Show less - Date Issued
- 1979
- PURL
- http://purl.flvc.org/fcla/dt/13968
- Subject Headings
- Spectrum analysis, Absorption spectra, Atmospheric chemistry
- Format
- Document (PDF)
- Title
- PREDICTING FREQUENCIES AND POWER FOR A CYLINDRICAL CERENKOV SLOW WAVE STRUCTURE.
- Creator
- HOLSTEIN, DANNY GUY, Florida Atlantic University, Lamborn, Bjorn, Charles E. Schmidt College of Science, Department of Physics
- Abstract/Description
-
The dispersion relation for a dielectrically loaded cylindrical waveguide, both with and without a beam of electrons, is found. It is shown that in the limit of Cerenkov threshold, the frequency goes to infinity. Also, using the fields derived, the Poynting vector is computed. It is shown that the Poynting vector increases and the operating frequency decreases with the thickness of the liner.
- Date Issued
- 1982
- PURL
- http://purl.flvc.org/fcla/dt/14136
- Subject Headings
- Dielectric wave guides, Cherenkov radiation
- Format
- Document (PDF)
- Title
- RAMAN SPECTRA OF ZIRCONIA CERAMICS.
- Creator
- KIM, JAE HOON, Florida Atlantic University, Medina, Fernando D., Charles E. Schmidt College of Science, Department of Physics
- Abstract/Description
-
Raman spectroscopy was used to investigate how phase structure and phase stability of zirconia mixtures depend on temperature, type and concentration of added rare earth oxides, and fabrication process. All 8wt% yttria samples exhibited the tetragonal structure between 300 and 10 K. The TZP sample, prepared under pressure and fully hardened, exhibited the most completely stabilized tetragonal structure. The plasma coating process did not improve the stability of the tetragonal structure....
Show moreRaman spectroscopy was used to investigate how phase structure and phase stability of zirconia mixtures depend on temperature, type and concentration of added rare earth oxides, and fabrication process. All 8wt% yttria samples exhibited the tetragonal structure between 300 and 10 K. The TZP sample, prepared under pressure and fully hardened, exhibited the most completely stabilized tetragonal structure. The plasma coating process did not improve the stability of the tetragonal structure. Adding ceria to zirconia did not completely stabilize the tetragonal structure, while adding alumina actually destabilized it. Mode Gruneisen parameters, obtained from changes in frequency for yttria samples with different concentration, agreed with published results under pressure, except for one Eg mode. The negative value obtained for this mode was ascribed to changes in cation-anion interactions. The temperature dependence of the linewidth for this mode was quantitatively explained by cubic anharmonic interactions.
Show less - Date Issued
- 1987
- PURL
- http://purl.flvc.org/fcla/dt/14401
- Subject Headings
- Zirconium oxide, Spectrum analysis
- Format
- Document (PDF)
- Title
- A starting potential for band theory calculations generated from Thomas-Fermi theory.
- Creator
- Horvath, Eva Antoinette, Florida Atlantic University, Faulkner, J. Samuel, Charles E. Schmidt College of Science, Department of Physics
- Abstract/Description
-
The purpose of this thesis is to generate a starting potential from Thomas-Fermi theory and verify that this leads to expedient convergence of the energy eigenvalues. The potential was generated for various elements, representative of the 3d and 4d elements, as well as the simple metals, for different lattice constants. They were inserted into a quadratic Korringa-Kohn-Rostoker band theory program. They lead to self-consistent results at a faster rate than the potentials given by Moruzzi,...
Show moreThe purpose of this thesis is to generate a starting potential from Thomas-Fermi theory and verify that this leads to expedient convergence of the energy eigenvalues. The potential was generated for various elements, representative of the 3d and 4d elements, as well as the simple metals, for different lattice constants. They were inserted into a quadratic Korringa-Kohn-Rostoker band theory program. They lead to self-consistent results at a faster rate than the potentials given by Moruzzi, Janak, and Williams for lattice constants for which the lattice was not in equilibrium.
Show less - Date Issued
- 1988
- PURL
- http://purl.flvc.org/fcla/dt/14487
- Subject Headings
- Energy-band theory of solids
- Format
- Document (PDF)
- Title
- The equation of state for modeling stellar core collapse.
- Creator
- Judd, David Michael, Florida Atlantic University, Bruenn, Stephen W., Charles E. Schmidt College of Science, Department of Physics
- Abstract/Description
-
A realistic equation of state is essential for accurate modeling of stellar core collapse. In this thesis, we present a derivation of the equation of state for stellar matter up to nuclear density. We begin with the lepton contribution to the equation of state. The thermodynamic equations of state for the leptons are derived from the grand potential. Two approximations for the lepton equations of state which obtain in different regimes are presented. A discussion of the computer programs that...
Show moreA realistic equation of state is essential for accurate modeling of stellar core collapse. In this thesis, we present a derivation of the equation of state for stellar matter up to nuclear density. We begin with the lepton contribution to the equation of state. The thermodynamic equations of state for the leptons are derived from the grand potential. Two approximations for the lepton equations of state which obtain in different regimes are presented. A discussion of the computer programs that were developed to calculate the solutions to these equations is included, and the results are compared with those of similar programs. A formalism is introduced for treating the nuclear component of the equation of state. The energy per baryon of nuclei at zero temperature is derived using a compressible liquid drop model. Finite temperature effects are incorporated by (1) including the thermal excitation energy, and (2) by introducing a second phase (the drip phase) of like particles (neutrons, protons, and $\alpha$-particles) that coexist with the nuclei. Equilibrium conditions for the two phases and the nuclear mass number A are derived. Expressions for the nuclear thermodynamic quantities of interest are presented.
Show less - Date Issued
- 1989
- PURL
- http://purl.flvc.org/fcla/dt/14551
- Subject Headings
- Equations of state
- Format
- Document (PDF)
- Title
- Raman spectroscopic studies of stabilized zirconia at elevated temperatures.
- Creator
- Lacher, Nathan, Florida Atlantic University, Liu, David, Charles E. Schmidt College of Science, Department of Physics
- Abstract/Description
-
Raman spectroscopy was used to determine the phase structure and phase stability of zirconia mixtures for various elevated temperatures, type and concentration of oxides added to zirconia, and fabrication process. All 8 wt.% yttria samples showed mostly the tetragonal structure at room temperature. Three of the four 8 wt.% yttria samples exhibited the tetragonal structure at elevated temperatures, while no conclusion was inferred for the powdered sample. As compared with yttria, ceria is a...
Show moreRaman spectroscopy was used to determine the phase structure and phase stability of zirconia mixtures for various elevated temperatures, type and concentration of oxides added to zirconia, and fabrication process. All 8 wt.% yttria samples showed mostly the tetragonal structure at room temperature. Three of the four 8 wt.% yttria samples exhibited the tetragonal structure at elevated temperatures, while no conclusion was inferred for the powdered sample. As compared with yttria, ceria is a less effective stabilizer with respect to the zirconia tetragonal structure. A monoclinic transformation between 400 K and 800 K was observed in the 4 wt.% yttria sample which had been processed by rapid quenching. Adding alumina to 4 wt.% yttria did not completely stabilize the tetragonal structure at or above room temperature, making it a less effective stabilizer than yttria or ceria. The phase transformation was responsible for the unusual values in the Gr uneisen parameters obtained for the 4 wt.% yttria sample.
Show less - Date Issued
- 1990
- PURL
- http://purl.flvc.org/fcla/dt/14589
- Subject Headings
- Zirconium oxide--Spectra, Raman spectroscopy
- Format
- Document (PDF)
- Title
- Photoemission investigation of the electronic structure in ordered and disordered copper gold.
- Creator
- Jiang, Yongjin, Florida Atlantic University, Jordan, Robin G., Charles E. Schmidt College of Science, Department of Physics
- Abstract/Description
-
The techniques of x-ray and ultra-violet photoelectron spectroscopies have been used to investigate the electronic structures in ordered (L10-structure) and disordered (fcc) CuAu. Large changes are observed in the valence band regions of the different phases, particularly in the vicinity of the Au-related states. The binding energies of the Cu-2p and Au-4f core levels in the ordered phase are shifted from the pure metal value by 0.27 +- 0.05 eV and 0.30 +- 0.05 eV, respectively. A small...
Show moreThe techniques of x-ray and ultra-violet photoelectron spectroscopies have been used to investigate the electronic structures in ordered (L10-structure) and disordered (fcc) CuAu. Large changes are observed in the valence band regions of the different phases, particularly in the vicinity of the Au-related states. The binding energies of the Cu-2p and Au-4f core levels in the ordered phase are shifted from the pure metal value by 0.27 +- 0.05 eV and 0.30 +- 0.05 eV, respectively. A small reduction of the Au-4f core level shift is found in the disordered phase. Details of the valence band structure and the shifts for the ordered phase are in accord with recently published calculations of the density of states. Investigations of the composition of the surface region using Auger electron spectroscopy indicate that there is excess Au in the surface region, in agreement with previous studies.
Show less - Date Issued
- 1991
- PURL
- http://purl.flvc.org/fcla/dt/14702
- Subject Headings
- Photoemission, Order-disorder in alloys
- Format
- Document (PDF)
- Title
- Narrow and broad band photoluminescence spectroscopy of Cd(x)Zn(1-x)Se semiconductor.
- Creator
- Sweiti, Ayman, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics
- Abstract/Description
-
In this dissertation I have used photoluminescence (PL) spectrometric analysis to measure the temperature dependence of the spectral features of the direct band gap semiconductor CdxZn1-xSe , for two nominal concentrations x = 0.25, 0.50, in the temperature range 25--300 K. The effective concentrations were obtained from analysis of the spectra. The parameters that describe the temperature dependence of the line width broadening have been evaluated using different models. The PL broadband...
Show moreIn this dissertation I have used photoluminescence (PL) spectrometric analysis to measure the temperature dependence of the spectral features of the direct band gap semiconductor CdxZn1-xSe , for two nominal concentrations x = 0.25, 0.50, in the temperature range 25--300 K. The effective concentrations were obtained from analysis of the spectra. The parameters that describe the temperature dependence of the line width broadening have been evaluated using different models. The PL broadband characteristics of Cd0.22Zn0.78Se and Cd0.41Zn0.59Se are also investigated within the energy range 1.36--2.40 eV and temperature range 25--305 K. Two broad bands are observed, the higher energy band I centered at 1.991 and 1.773 eV, the lower energy band II centered at 1.844 and 1.705 eV for the two samples, respectively. The emission bands are attributed to donor-acceptor pair transitions. The energy scheme shows two donors and two acceptor levels, the binding energies of the donors for Cd 0.22Zn0.78Se are 29 and 208 meV below the conduction band, the binding energies of the acceptors 472 and 511 meV above the valence band. The binding energies of the donors for Cd0.41Zn 0.59Se are 27 and 137 meV, the binding energies of the acceptors 393 and 423 eV. A significant blue shift in energy with increasing temperature was observed for the lower energy band. The ionization temperatures for the deep donors are 279 and 287 K for Cd0.22Zn0.78Se and Cd0.41Zn0.59Se, respectively.
Show less - Date Issued
- 2003
- PURL
- http://purl.flvc.org/fau/fd/FADT12075
- Subject Headings
- Chemistry, Analytical, Physics, Condensed Matter
- Format
- Document (PDF)
- Title
- Structural, electrical and magnetic properties of transition metal nickel oxides.
- Creator
- Wu, Guoqing, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics
- Abstract/Description
-
Neutron powder diffraction, high pressure, magnetic susceptibility, and heat capacity measurements, as well as x-ray powder diffraction and iodometric titration, have been conducted on transition metal nickel oxides (TMOs), representative Ruddlesden-Popper (RP) phases Lan+1NinO3n+1 (n = 1, 2, ..., infinity) and hole-doped La2-xSr xNiO4 (0
Show moreNeutron powder diffraction, high pressure, magnetic susceptibility, and heat capacity measurements, as well as x-ray powder diffraction and iodometric titration, have been conducted on transition metal nickel oxides (TMOs), representative Ruddlesden-Popper (RP) phases Lan+1NinO3n+1 (n = 1, 2, ..., infinity) and hole-doped La2-xSr xNiO4 (0 < x < 1.2). The first complete study of La 2-xSrxNiO4 (0 < x < 1.2) and La n+1NinO3n+1 (n = 2 and 3) phases under high pressure is produced. Strong direct experimental evidence for polaron dominated electrical conduction in these charge transfer (CT) gap La2-xSr xNiO4 compounds is provided. Temperature evolution of the crystal structure of La2-xSrxNiO4 (x = 1/4 and 1/3) is revealed through neutron powder diffraction, structural relationships among n = 1, 2, and 3 phases are exhibited, and charge density wave (CDW) in multilayer Lan+1NinO3n+1 phases is strongly suggested. No superconductivity is observed at pressures up to 1.6 GPa and temperatures down to 4.2 K.
Show less - Date Issued
- 2002
- PURL
- http://purl.flvc.org/fcla/dt/11997
- Subject Headings
- Physics, Condensed Matter
- Format
- Document (PDF)
- Title
- Magnetic, thermodynamic, and structural studies of manganese oxides.
- Creator
- Terashita, Hirotoshi, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics
- Abstract/Description
-
Magnetic, thermodynamic, and structural properties of the manganese oxides La1-xCa xMnO3 are studied. Neutron powder diffraction reveals two distinct crystallographic phases as well as two magnetic (ferromagnetic and antiferromagnetic) phases for 0.08
Show moreMagnetic, thermodynamic, and structural properties of the manganese oxides La1-xCa xMnO3 are studied. Neutron powder diffraction reveals two distinct crystallographic phases as well as two magnetic (ferromagnetic and antiferromagnetic) phases for 0.08 < x < 0.14. Details of the compositional dependence of the phase fractions is discussed in the context of local ferromagnetism. Comparisons of magnetic and crystallographic properties are made to the analogous electron-doped Ca1- yLayMnO3 (0 < y < 0.20) system. Thermodynamic properties of La1- xCaxMnO 3 (0 < x < 0.54) are investigated for possible applications in magnetic refrigeration. A maximum magnetic entropy change of 5.5 J/kg K and a corresponding temperature change of 2 K are estimated for x = 0.28. The magnetocaloric effect in antiferromagnetic and charge-ordering compounds is found to be small.
Show less - Date Issued
- 2005
- PURL
- http://purl.flvc.org/fau/fd/FADT12133
- Subject Headings
- Physics, Condensed Matter
- Format
- Document (PDF)
- Title
- Measurements of output factors for small photon fields up to 10 cm x 10 cm.
- Creator
- Bacala, Angelina, Pella, Silvia, Charles E. Schmidt College of Science, Department of Physics
- Abstract/Description
-
Field output factors (OF) for photon beams from a 6 MV medical accelerator were measured using five different detectors in a scanning water phantom. The measurements were taken for square field sizes of integral widths ranging from 1 cm to 10 cm for two reference source-to-surface distances (SSD) and depths in water. For the diode detectors, square field widths as small as 2.5 mm were also studied. The photon beams were collimated by using either the jaws or the multileaf collimators....
Show moreField output factors (OF) for photon beams from a 6 MV medical accelerator were measured using five different detectors in a scanning water phantom. The measurements were taken for square field sizes of integral widths ranging from 1 cm to 10 cm for two reference source-to-surface distances (SSD) and depths in water. For the diode detectors, square field widths as small as 2.5 mm were also studied. The photon beams were collimated by using either the jaws or the multileaf collimators. Measured OFs are found to depend upon the field size, SSD, depth and also upon the type of beam collimation, size and type of detector used. For field sizes larger than 3 cm x 3 cm, the OF measurements agree to within 1% or less. The largest variation in OF occurs for jawsshaped field of size 1 cm x 1cm, where a difference of more than 18% is observed.
Show less - Date Issued
- 2013
- PURL
- http://purl.flvc.org/fau/fd/FA0004003
- Subject Headings
- Integrated circuits, Photonics, Quantum electrodynamics, Quantum theory
- Format
- Document (PDF)
- Title
- A novel method to evaluate local control of lung cancer in stereotactic body radiation therapy (SBRT) treatment using 18f-Fdg positron emission tomography (PET).
- Creator
- Kathriarachchi, Vindu, Shang, Charles, Charles E. Schmidt College of Science, Department of Physics
- Abstract/Description
-
An improved method is introduced for prediction of local tumor control following lung stereotactic body radiation therapy (SBRT) for early stage non-small cell lung cancer (NSCLC) patients using 18F-fluorodeoxyglucose positron emission tomography (18F-FDG PET). A normalized background-corrected tumor maximum Standard Uptake Value (SUVcmax) is introduced using the mean uptake of adjacent aorta (SUVref), instead of the maximum uptake of lung tumor (SUVmax). This method minimizes the variations...
Show moreAn improved method is introduced for prediction of local tumor control following lung stereotactic body radiation therapy (SBRT) for early stage non-small cell lung cancer (NSCLC) patients using 18F-fluorodeoxyglucose positron emission tomography (18F-FDG PET). A normalized background-corrected tumor maximum Standard Uptake Value (SUVcmax) is introduced using the mean uptake of adjacent aorta (SUVref), instead of the maximum uptake of lung tumor (SUVmax). This method minimizes the variations associated with SUVmax and objectively demonstrates a strong correlation between the low SUVcmax (< 2.5-3.0) and local control of post lung SBRT. The false positive rates of both SUVmax and SUVcmax increase with inclusion of early (<6 months) PET scans, therefore such inclusion is not recommended for assessing local tumor control of post lung SBRT.
Show less - Date Issued
- 2013
- PURL
- http://purl.flvc.org/fau/fd/FA0004029
- Subject Headings
- Cancer -- Radiotherapy, Image guided radiation therapy, Lung cancer -- Treatment, Radiopharmaceuticals, Tomography, Emission
- Format
- Document (PDF)
- Title
- Binary neutron star mergeres: simulations with arbitrarily spinning stars.
- Creator
- Tsatsin, Petr, Marronetti, Pedro, Charles E. Schmidt College of Science, Department of Physics
- Abstract/Description
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The starting point of any general relativistic numerical simulation is a solution of the Hamiltonian and momentum constraints that (ideally) represents an astrophysically realistic scenario. This dissertation presents a new method to produce initial data sets for binary neutron stars with arbitrary spins and orbital eccentricities. The method only provides approximate solutions to the constraints. However, it was shown that the corresponding constraint violations subside after a few orbits,...
Show moreThe starting point of any general relativistic numerical simulation is a solution of the Hamiltonian and momentum constraints that (ideally) represents an astrophysically realistic scenario. This dissertation presents a new method to produce initial data sets for binary neutron stars with arbitrary spins and orbital eccentricities. The method only provides approximate solutions to the constraints. However, it was shown that the corresponding constraint violations subside after a few orbits, becoming comparable to those found in evolutions of standard conformally flat, helically symmetric binary initial data. This dissertation presents the first spinning neutron star binary simulations in circular orbits with a orbital eccentricity less then 0.01. The initial data sets corresponding to binaries with spins aligned, zero and anti-aligned with the orbital angular momentum were evolved in time. These simulations show the orbital “hang-up” effect previously seen in binary black holes. Additionally, they show orbital eccentricities that can be up to one order of magnitude smaller than those found in helically symmetric initial sets evolutions.
Show less - Date Issued
- 2013
- PURL
- http://purl.flvc.org/fau/fd/FA0004067
- Subject Headings
- Astrophysics, Black holes (Astronomy), General relativity (Physics), Gravitational waves, Neutron stars, Particles (Nuclear physics)
- Format
- Document (PDF)