3 resultados para rotational bands in Ir-176
em DRUM (Digital Repository at the University of Maryland)
Resumo:
The purpose of this dissertation project identifies contemporary solo saxophone literature, specifically sonatas between the years 1980 and 2010. The overwhelming majority of repertoire written during these thirty years consisted primarily of either multi-movement or through-composed character pieces. By limiting the selected repertoire to sonatas one can still investigate the breadth of the literature that has helped validate the saxophone in the realm of classical music in a format that has seemingly fallen out of favor with composers. The saxophone had developed a unique voice by the middle of the twentieth century in both Europe and in the United States. European composers such as Claude Debussy, Florent Schmidt, Jacques Ibert, Darius Milhaud, Alexander Glazounov, Erwin Schulhoff and Bernard Heiden recognized the potential and beauty of the instrument, while the saxophone had found quite a different niche in vaudeville, jazz, and military bands in the United States. If not for the dynamic performances by concert saxophonist such as Marcel Mule, Sigurd Rascher, Jean-Marie Londeix, Daniel Deffayet, Cecil Lesson, Larry Teal, Eugene Rousseau, Fredrick Hemke and Donald Sinta, the timbral possibilities and technical virtuosity of the saxophone would not have been discovered. The awe inspiring performances by these soloists led to the commissioning of a multitude of works by composers looking to expand the sonic possibilities of this relatively new instrument. Through the 1970's American composers such as Leslie Bassett, Paul Creston, Henry Brant, Robert Muczynski, and Karel Husa were writing significant works for the saxophone, while European composers such as IngolfDahl, Edison Denisov, Alfred Desenclos, Henri Tomasi and Marius Constant were each making their own contributions, all leading to a significant quantity of repertoire that met the quality demands set by the performers. The compositions chosen for this dissertation project were selected after numerous performance, pragmatic, programming and pedagogical considerations were taken into account. The three recitals occurred on: March 7, 2010, December 10, 2010 and May 1, 2011 in either the Gildenhorn Recital Hall or Lecture Hall 2100.
Resumo:
Ɣ-ray bursts (GRBs) are the Universe's most luminous transient events. Since the discovery of GRBs was announced in 1973, efforts have been ongoing to obtain data over a broader range of the electromagnetic spectrum at the earliest possible times following the initial detection. The discovery of the theorized ``afterglow'' emission in radio through X-ray bands in the late 1990s confirmed the cosmological nature of these events. At present, GRB afterglows are among the best probes of the early Universe (z ≳ 9). In addition to informing theories about GRBs themselves, observations of afterglows probe the circum-burst medium (CBM), properties of the host galaxies and the progress of cosmic reionization. To explore the early-time variability of afterglows, I have developed a generalized analysis framework which models near-infrared (NIR), optical, ultra-violet (UV) and X-ray light curves without assuming an underlying model. These fits are then used to construct the spectral energy distribution (SED) of afterglows at arbitrary times within the observed window. Physical models are then used to explore the evolution of the SED parameter space with time. I demonstrate that this framework produces evidence of the photodestruction of dust in the CBM of GRB 120119A, similar to the findings from a previous study of this afterglow. The framework is additionally applied to the afterglows of GRB 140419A and GRB 080607. In these cases the evolution of the SEDs appears consistent with the standard fireball model. Having introduced the scientific motivations for early-time observations, I introduce the Rapid Infrared Imager-Spectrometer (RIMAS). Once commissioned on the 4.3 meter Discovery Channel Telescope (DCT), RIMAS will be used to study the afterglows of GRBs through photometric and spectroscopic observations beginning within minutes of the initial burst. The instrument will operate in the NIR, from 0.97 μm to 2.37 μm, permitting the detection of very high redshift (z ≳ 7) afterglows which are attenuated at shorter wavelengths by Lyman-ɑ absorption in the intergalactic medium (IGM). A majority of my graduate work has been spent designing and aligning RIMAS's cryogenic (~80 K) optical systems. Design efforts have included an original camera used to image the field surrounding spectroscopic slits, tolerancing and optimizing all of the instrument's optics, thermal modeling of optomechanical systems, and modeling the diffraction efficiencies for some of the dispersive elements. To align the cryogenic optics, I developed a procedure that was successfully used for a majority of the instrument's sub-assemblies. My work on this cryogenic instrument has necessitated experimental and computational projects to design and validate designs of several subsystems. Two of these projects describe simple and effective measurements of optomechanical components in vacuum and at cryogenic temperatures using an 8-bit CCD camera. Models of heat transfer via electrical harnesses used to provide current to motors located within the cryostat are also presented.
Resumo:
Experiments with ultracold atoms in optical lattice have become a versatile testing ground to study diverse quantum many-body Hamiltonians. A single-band Bose-Hubbard (BH) Hamiltonian was first proposed to describe these systems in 1998 and its associated quantum phase-transition was subsequently observed in 2002. Over the years, there has been a rapid progress in experimental realizations of more complex lattice geometries, leading to more exotic BH Hamiltonians with contributions from excited bands, and modified tunneling and interaction energies. There has also been interesting theoretical insights and experimental studies on “un- conventional” Bose-Einstein condensates in optical lattices and predictions of rich orbital physics in higher bands. In this thesis, I present our results on several multi- band BH models and emergent quantum phenomena. In particular, I study optical lattices with two local minima per unit cell and show that the low energy states of a multi-band BH Hamiltonian with only pairwise interactions is equivalent to an effec- tive single-band Hamiltonian with strong three-body interactions. I also propose a second method to create three-body interactions in ultracold gases of bosonic atoms in a optical lattice. In this case, this is achieved by a careful cancellation of two contributions in the pair-wise interaction between the atoms, one proportional to the zero-energy scattering length and a second proportional to the effective range. I subsequently study the physics of Bose-Einstein condensation in the second band of a double-well 2D lattice and show that the collision aided decay rate of the con- densate to the ground band is smaller than the tunneling rate between neighboring unit cells. Finally, I propose a numerical method using the discrete variable repre- sentation for constructing real-valued Wannier functions localized in a unit cell for optical lattices. The developed numerical method is general and can be applied to a wide array of optical lattice geometries in one, two or three dimensions.