A electronically collimated prototype detector was built with commercially available cadmium zinc telluride (CZT) modules and assessed by experiment and simulation. Sensitivity was roughly equivalent to a common hand held 1"x1" NaI(Tl) detector. The maximum useful count rate was 300 counts per second (cps) per module. Overall angular error was less than 7°, which is generally less than source placement uncertainty, and angular resolution was between 20° and 40° for several common isotopes with photon energies between 511 keV and 1333 keV. Prototype data and backprojections were used to verify a simple three dimensional model of charge induction in pixellated CZT using an uncollided flux Monte Carlo code. The goal was to devise a hand held radiation detector that can be made with rugged and commercially available parts that can see a 0.1 mCi source with an energy range of 70 keV to 2 MeV at three meters distance with an annular resolution of less than 25° full width at half maximum (FWHM). The prototype lacked sensitivity to meet this stringent goal but proved the modules and prototype concept useful for a variety of health physics applications.

Purpose: To develop a system for measuring 2D dose distributions in the cranium and to use this system to evaluate the accuracy of coplanar conformal therapy using ExacTrac image guidance. Methods: Techniques were developed to measure dose distributions in each principal plane using a CIRS anthropomorphic head phantom with a custom internal film cassette. Sections of EDR2 film were cut, processed, and digitized using custom templates. Spatial and dosimetric accuracy and precision of the film system was assessed. BrainScan was used to plan a coplanar-beam treatment conforming to irradiate a 2-cm diameter x 2-cm cylindrical target. Prior to delivery phantom misalignments were imposed in combinations of ±8-mm offsets in each of the principal directions. ExacTrac X-ray correction was applied until the phantom was within an acceptance criteria of 1mm-1° (first two measurement sessions) or 0.4mm-0.4º (last two measurement sessions). Measured dose distributions on film were registered to the treatment plan and compared. Results: Alignment errors(displacement between midpoints of planned and measured 70% isodose contours), were 0.48±0.40, -0.20±0.44 and 0.45±0.43mm along the Posterior-Anterior, Right-Left and Superior-Inferior directions, respectively, using acceptance criteria of 1mm-1°, and 0.72±0.18, 0.12±0.18 and -0.14±0.34mm, respectively, using acceptance criteria, 0.4mm-0.4°. Positional errors of the 80% isodose line were -0.36±0.43, 0.38±0.38, and 0.03±0.44mm, on the Posterior, Right, and Inferior edges of each profile, respectively, and 0.68 ±0.40, -0.14 ±0.38, and 0.88±0.40mm for the Anterior, Left, and Superior edges, respectively for the 1mm-1° criteria. Using the 0.4mm-0.4° criteria, errors were -0.35±0.23, 0.31± 0.18, and 0.72±0.27mm on the Posterior, Left and Inferior portion of each profile respectively and 1.12±0.18, 0.22±0.23, and 0.35±0.33mm for the Anterior, Left and Superior portions, respectively. Data ranged approximately two standard deviations about the mean. Winston-Lutz tests with errors of approximately 0.5mm correlated with increased Anterior error in three measurement sessions. Conclusions: The ExacTrac system is capable of achieving sub-mm(2Ï) accuracy given the alignment errors were small(<0.3mm) when Winston-Lutz results were small(<0.2mm), indicating pre-treatment corrections could be made.

Significance: Photon activated Auger electron therapy utilizes a keV-ranged, monoenergetic x-ray beam, and radiobiological and animal experiments studying this therapy require accurate dosimetry techniques. However, there exist few dosimetry protocols for low-energy x-ray beams. This research intended to use the CAMD synchrotron as a source of monochromatic, 35-keV x-rays and test dosimetry techniques of film and ion chamber. The hypothesis of my research was that depth-dose measured in a PMMA phantom using an air-equivalent ionization chamber and radiochromic film dosimeters in a PMMA phantom irradiated by a 35-keV, monochromatic x-ray beam will agree to within 5% of each other and to within 5% of dose determined from fluence-scaled Monte Carlo dose simulations. Methods: The narrow beam produced on the CAMD tomography beamline (0.1×2.8 cm2) was effectively broadened (2.5×2.8 cm2) by vertically oscillating experimental apparatus. Beam energy selected by the monochromator was verified using a Compton scatterer and powder diffraction methods. Depth-dose in PMMA was measured by an air-equivalent ion chamber using a modified AAPMs TG-61 (100-300 kV) formalism and by Gafchromic EBT film using 125-kVp calibration curves. Depth-dose was also determined from scaling MCNP5 Monte Carlo output by fluence measured using a NaI detector. Results: The powder diffraction energy measurement agreed closest to the monochromators setting (mean = -0.1±0.3 keV). Depth-doses performed on 5 separate experimental dates showed that beam fluence did not accurately scale to synchrotron ring current between dates. Depth-dose measurements from ion chamber and film at 2 cm resulted in film-measured dose underestimating ion-chamber measured dose by an average of 5.0±2.1%. Fractional Monte Carlo depth-dose simulations agreed well with ion chamber and film measurements, with maximum disagreements of 3.9% at 9.0-cm depth and 0.9% at 8.25 cm, respectively. Fluence-scaled, Monte Carlo dose determination overestimated ion chamber-measured depth-dose by 6.4±0.8% and overestimated film-measured depth-dose by 9.1±0.7%. Conclusions: Results of this research were unable to prove or disprove the hypothesis regarding 5% agreement of ion chamber and film dose measurements. Results also proved the hypothesis false for achieving 5% agreement between either ion chamber-measured dose or film-measured dose and dose determined from fluence-scaled Monte Carlo simulations.

The gravitational wave detectors at the LIGO Observatories have achieved record sensitivity to gravitational-waves produced by astrophysical systems. The LIGO Scientific Collaboration has analyzed data taken in several science runs, searching for different signals. We describe a search for black holes with less than a solar mass in the LIGO data taken from February 22 to March 24, 2005. No gravitational waves were found, and an upper limit was set on the rate of mergers of such binary systems. This search, as well as other searches for binary systems, are affected by non-stationary noise. We describe the sophisticated pipeline that attempted to reduce the false trigger rate while maximizing the sensitivity to simulated signals. Details regarding this search and interpretation of this search are presented along with new strategies to increase the confidence in detection through signal based vetoes and better template waveforms.

LIGO observatories in Livingston, LA and Hanford, WA may detect gravitational waves emitted from coalescing binary systems composed of two compact objects. In order to detect compact binary coalescence (CBC) events, LIGO searches utilize matched filtering techniques. Matched filtering is the optimal detection strategy for stationary, Gaussian noise, however, LIGO noise is often non-stationary, non-Gaussian. Non-stationary noise result in an excess of false candidate events, commonly known as false alarms. This thesis develops the r² test to reduce the false alarm rate for LIGO CBC searches. Results of the search for primordial black hole binary systems (where each object has less than 1M_solar), in LIGO's Third Science Run (S3) is also presented. <br> Results of the r² test are shown for several LIGO CBC searches, including the binary neutron star searches in the Third and Fourth Science Runs (S3/S4), the S3/S4 primordial black hole searches, and the binary black hole search in the first three months of the Fifth Science Run (S5). The r² test significantly reduces the false alarm rate in these searches, while only falsely dismissing a small fraction of simulated events.

An extended SU(3) shell model that for the first time explicitly includes particles from the unique-parity levels in nuclei is introduced. Its relevance is established through calculations performed with realistic interactions for a group of upper fp-shell isotopes where valence nucleons beyond the N=28=Z core occupy levels of the normal-parity upper $fp$-shell ($f_{5/2},p_{3/2},p_{1/2}$) and the unique-parity $g_{9/2}$ intruder configuration. Specifically, the outcome suggests that the pseudo-SU(3) symmetry is quite good throughout the region and that only part of the configurations are relevant for the structure of the low-lying states. The levels of the upper $fp$-shell are handled within the framework of an m-scheme basis as well as its pseudo-SU(3) counterpart, and respectively, the $g_{9/2}$ as a single level and as a member for the complete $gds$ shell. More detailed analyses of the extended SU(3) model are done for two nuclei of special interest in astrophysics, namely the waiting-point nuclei $^{64}$Ge and $^{68}$Se. The strengths and limitations of the theory are demonstrated by its ability to describe various nuclear characteristics. Specifically, energy spectra, B(E2) transition strengths and wave-function content are compared with the realistic results. In addition, the dominance of configurations with different distribution of particles and the role that several newly-introduced terms play in the Hamiltonian are investigated. The extended SU(3) approach allows one to better probe the effects of deformation and account for these key properties of the system within a highly-truncated model space. The model also promises to be useful for nuclei from the rare-earth and actinide regions. Specifically, by ensuring a robust number of collective degrees of freedom and Hamiltonians with a larger number of degrees of freedom, it should allow one to give a satisfactory explanation of the experimentally-observed existence of an abundance of low-lying $0^{+}$ states and very strongly enhanced B(E2) strengths found in these nuclei. This version of the theory will extend previous results from the pseudo-SU(3) model where the role of nucleons in the intruder levels was relegated to a very simple renormalization of the dynamics defined by nucleons in the normal-parity spaces only.

In this dissertation work, I report on the interesting results of our detailed investigations of the synthesis, structural, electrical and magnetic characterization of three different classes of intermetallic systems. Mo₃Sb₇ wires, thin films and microfibers exhibit the highest T_c ~ 8 K, which is substantially higher than the 2.2 K reported for the single crystal and powder of Mo₃Sb₇. The suppression of the spin fluctuations in Mo₃Sb₇ is evident by the absence of a parabolic dependence of magnetic susceptibility at 1 T. MoN wires, thin films and coated microfibers have T_c ~13 K which is consistent with the values reported in the literature. To my knowledge, for the first time we report on the magnetotransport and critical current measurements in MoN and Mo₃Sb₇ in these forms. We show (1 - (T/Tc)²)^3/2 dependence of the critical current density of MoN- and Mo₃Sb₇-coated microfibers near the transition temperature, T_c. The extrapolated values of the critical current density to zero temperature for the MoN- and Mo₃Sb₇-coated fibers are J_c(0) = 1.66 x 10⁸ A/cm² and J_c(0) = 7.7 x 10⁵ A/cm² , respectively. The results of magnetic susceptibility and transport properties measurements of Mg_1-xBe_xCNi₃ and Mg_1-xLi_xCNi₃ for x = 0 to 0.2 showed a very small change in T_c and H_c2 due to Be and Li doping in MgCNi₃. The heat treatment of the carbon deficient samples MgC_xNi₃ for 2 h in N gas improved the superconductivity of the compounds. In MgC_0.7Ni₃, the superconductivity re-appeared after the treatment. Single crystals and polycrystalline samples of VB₂ and other transition metal diborides were synthesized. Cr_1-xV_xB₂ are paramagnetic for x > 0.23, and no superconductivity is observed above 1.8 K. We also present the results of magnetotransport and de Haasvan Alphen (dHvA) measurements on high quality single crystals of VB₂ grown from a molten aluminum flux. At low temperature the magnetoresistance of VB₂ is very large (∼1100%) and is found to be extremely sensitive to sample quality (RRR value).

Positron emission tomography (PET) and computed tomography (CT) together are a powerful diagnostic tool, but imperfect image quality contributes to false positive and false negative diagnoses by an observer despite experience and training. This work investigated a PET standard uptake value (SUV) correction scheme, based on partial volume effect (PVE), on the classification of lesions as benign or malignant in PET/CT images. The correction scheme comprised several steps. The observer drew a region of interest (ROI) around the lesion using the CT dataset. The ROI was blurred with the assumed point spread function (PSF) of the PET scanner then re-sampled to the PET voxel size. The magnitude of the ROI-based PVE was used as a scaling factor to correct the lesions tumor-to-background ratio (TBR), which was used as a surrogate for SUV in the PET images of the phantom. Computer simulations showed that the accuracy of the correction depends strongly on the accuracy of the ROI drawn on the CT images, especially for small lesions. Correction accuracy was affected slightly by mismatch of the simulation PSF to the actual scanner PSF. A receiver operating characteristic (ROC) study, using phantom data, was performed to evaluate the effect of the correction scheme on diagnostic performance. The correction scheme significantly increased sensitivity and slightly increased accuracy for all acquisition and reconstruction modes at the cost of a small decrease in specificity. Corrected TBRs more accurately represented actual TBRs than uncorrected TBRs. The observer study also found that, when using PET data alone, 3D ordered subset expectation maximization (OSEM) outperformed 3D filtered back-projection (FBP), 2D OSEM, and 2D FBP in terms of sensitivity, specificity, and area-under-the-ROC-curve values. However, when PET data was displayed with correlated CT data, with and without PVE correction, no combination of reconstruction algorithm and acquisition mode outperformed any other.

This thesis studies important dynamical observables of strong interactions such as form factors. It is known that Quantum Chromodynamics (QCD) is a theory which describes strong interactions. For large energies, one can apply perturbative techniques to solve some of the QCD problems. However, for low energies QCD enters into the nonperturbative regime, where different analytical or numerical tools have to be applied to solve problems of strong interactions. The holographic dual model of QCD is such an analytical tool that allows one to solve some nonperturbative QCD problems by translating them into a dual five-dimensional theory defined on some warped Anti de Sitter (AdS) background. Working within the framework of the holographic dual model of QCD, we develop a formalism to calculate form factors and wave functions of vector mesons and pions. As a result, we provide predictions of the electric radius, the magnetic and quadrupole moments which can be directly verified in lattice calculations or even experimentally. To find the anomalous pion form factor, we propose an extension of the holographic model by including the Chern-Simons term required to reproduce the chiral anomaly of QCD. This allows us to find the slope of the form factor with one real and one slightly off-shell photon which appeared to be close to the experimental findings. We also analyze the limit of large virtualities (when the photon is largely off-shell) and establish that predictions of the holographic model analytically coincide with those of perturbative QCD with asymptotic pion distribution amplitude. We also study the effects of higher dimensional terms in the AdS/QCD model and show that these terms improve the holographic description towards a more realistic scenario. We show this by calculating corrections to the vector meson form factors and corrections to the observables such as electric radii, magnetic and quadrupole moments.

The formalism of covariant quantum theory, introduced by Reisenberger and Rovelli, casts the description of quantum states and evolution into a framework compatible with the principles of general relativity. The leap to this covariant formalism, however, outstripped the standard interpretation used to connect quantum theory to experimental predictions, leaving the predictions of the theory ambiguous. In particular, the absence of a pre-defined time variable or background causal structure resulted in an ``order of projections" ambiguity, in which the usual rule for multiple-measurement probabilities (obtained by time-ordered projections) is not defined. Equally troublesome, the probability postulate of Reisenberger and Rovelli fails to reproduce the Born interpretation for the case of simple quantum mechanical systems. Here, we develop an alternative quantum measurement formalism, based on basic principles of quantum information. After reviewing how this can be done in the context of the traditional formulation of quantum mechanics and noting its implications for the quantum measurement problem, we find that this approach can be generalized to the covariant setting, where it essentially solves the correspondence problems of covariant quantum theory. We show explicit agreement with the Born interpretation of standard quantum mechanics in the context of simple systems. We also demonstrate the origin of the quantum mechanical arrow of time within our framework, and use this to solve the order of projections ambiguity. In addition to compatibility with general covariance, we show that our framework has other attractive and satisfying features - it is fully unitary, realist, and self-contained. The full unitarity of the formalism in the presence of measurements allows us to invoke time-reversal symmetry to obtain new predictions closely related to the quantum Zeno effect.