485 research outputs found
Founders Tell Stories: Gail Thomas
No full textInterview of Gail Thomas discussing the beginnings of the Dallas Institute and the Center for Civic Leadership at the University of Dallas. Thomas mentions many notable contributors to the University of Dallas and in the City of Dallas such as Donald & Louise Cowan and Helen Corbitt. Thomas also discusses her early roles at UD as the Dean of Women, Dean of Students, Assistant of the President and as the Director of the Center for Civic Leadership
Mechanical loss of laser-welded fused silica fibers
No full textThe mechanical quality factor of a carbon dioxide laser-welded fiber was measured and compared to flame-welded fibers to determine the suitability of laser welding for attaching suspension fibers to test masses in precision experiments. The loss in the fiber was found to be limited primarily by thermoelastic damping and surface loss, rather than loss from the weld. This technique is attractive for the attachment of fused silica suspensions where low thermal noise and precision location of the weld are considered.Gregory Harry, Thomas Corbitt, Marat Freytsis, David Ottaway, and Nergis Mavalval
Standard Quantum Limit for Probing Mechanical Energy Quantization
No full textWe derive a standard quantum limit for probing mechanical energy quantization in a class of systems with mechanical modes parametrically coupled to external degrees of freedom. To resolve a single mechanical quantum, it requires a strong-coupling regime—the decay rate of external degrees of freedom is smaller than the parametric coupling rate. In the case for cavity-assisted optomechanical systems, e.g., the one proposed by Thompson et al. [Nature (London) 452, 72 (2008)], zero-point motion of the mechanical oscillator needs to be comparable to the linear dynamical range of the optical system which is characterized by the optical wavelength divided by the cavity finesse.Australian Research CouncilDepartment of Education, Science, and TrainingNational Science FoundationAlexander von Humboldt Foundation’s Sofja Kovalevskaja ProgrammeDavid and Barbara Groce startup fund at CaltechSloan Foundatio
Thomas, Joseph Vineyard, 1837-1924 (SC 782)
No full textFinding aid and scans (Click on Additional Files below) for Manuscripts Small Collection 782. Civil War discharge certificate, 18 January 1865, and pension papers, 1912-1924 (3), of Joseph Vineyard Thomas and his widow, Malinda, Warren County, Kentucky. Also letter, 10 January 1986, written by Ardell Corbitt, Bowling Green, Kentucky, which contains genealogical information
Measurement of radiation-pressure-induced optomechanical dynamics in a suspended Fabry-Perot cavity
No full textWe report on experimental observation of radiation-pressure induced effects in a high-power optical cavity. These effects play an important role in next generation gravitational wave (GW) detectors, as well as in quantum non-demolition (QND) interferometers. We measure the properties of an optical spring, created by coupling of an intense laser field to the pendulum mode of a suspended mirror; and also the parametric instability (PI) that arises from the nonlinear coupling between acoustic modes of the cavity mirrors and the cavity optical mode. Specifically, we measure an optical rigidity of K = 3 x 10⁴ N/m, and PI value R = 3.Thomas Corbitt, David Ottaway, Edith Innerhofer, Jason Pelc, and Nergis Mavalval
Optical dilution and feedback cooling of a gram-scale oscillator to 6.9 mK
No full textWe report on the use of a radiation pressure induced restoring force, the optical spring effect, to optically dilute the mechanical damping of a 1 g suspended mirror, which is then cooled by active feedback (cold damping). Optical dilution relaxes the limit on cooling imposed by mechanical losses, allowing the oscillator mode to reach a minimum temperature of 6.9 mK, a factor of ~40 000 below the environmental temperature. A further advantage of the optical spring effect is that it can increase the number of oscillations before decoherence by several orders of magnitude. In the present experiment we infer an increase in the dynamical lifetime of the state by a factor of ~200.Thomas Corbitt, Christopher Wipf, Timothy Bodiya, David Ottaway, Daniel Sigg, Nicolas Smith, Stanley Whitcomb, and Nergis Mavalval
[Photograph 2012.201.B0240.0345]
No full textPhotograph taken for a story in the Oklahoma Times newspaper. Caption: "Helen Corbitt, noted cookbook author is visiting Oklahoma City.
Structural thermal noise in gram-scale mirror oscillators
No full textThe thermal noise associated with mechanical dissipation is a ubiquitous limitation to the sensitivity of precision experiments ranging from frequency stabilization to gravitational wave interferometry. We report on the thermal noise limits to the performance of 1 gm mirror oscillators that are part of a cavity optomechanics experiment to observe quantum radiation pressure noise. Thermal noise limits the observed cavity displacement spectrum from 80 Hz to 5 kHz. We present a calculation of the thermal noise, based on finite element analysis of the dissipation due to structural damping, and find it to be in excellent agreement with the experimental result. We conclude with the predicted thermal noise for an improved oscillator design, which should be capable of revealing the noise that arises from quantum backaction in this system.National Science Foundation (U.S.) (Grant PHY-1068772
Sequence haplotypes revealed by sequence-tagged site fine mapping of the Ror1 gene in the centromeric region of barley chromosome 1H
No full textWe describe the development of polymerase chain reaction-based, sequence-tagged site (STS) markers for fine mapping of the barley (Hordeum vulgare) Ror1 gene required for broad-spectrum resistance to powdery mildew (Blumeria graminis f. sp. hordei). After locating Ror1 to the centromeric region of barley chromosome 1H using a combined amplified fragment length polymorphism/restriction fragment-length polymorphism (RFLP) approach, sequences of RFLP probes from this chromosome region of barley and corresponding genome regions from the related grass species oat (Avena spp.), wheat, and Triticum monococcum were used to develop STS markers. Primers based on the RFLP probe sequences were used to polymerase chain reaction-amplify and directly sequence homologous DNA stretches from each of four parents that were used for mapping. Over 28,000 bp from 22 markers were compared. In addition to one insertion/deletion of at least 2.0 kb, 79 small unique sequence polymorphisms were observed, including 65 single nucleotide substitutions, two dinucleotide substitutions, 11 insertion/deletions, and one 5-bp/10-bp exchange. The frequency of polymorphism between any two barley lines ranged from 0.9 to 3.0 kb, and was greatest for comparisons involving an Ethiopian landrace. Haplotype structure was observed in the marker sequences over distances of several hundred basepairs. Polymorphisms in 16 STSs were used to generate genetic markers, scored by restriction enzyme digestion or by direct sequencing. Over 2,300 segregants from three populations were used in Ror1 linkage analysis, mapping Ror1 to a 0.2- to 0.5-cM marker interval. We discuss the implications of sequence haplotypes and STS markers for the generation of high-density maps in cereals.Nicholas C. Collins, Thomas Lahaye, Christoph Peterhänsel, Andreas Freialdenhoven, Margaret Corbitt, and Paul Schulze-Lefer
Quantum noise and radiation pressure effects in high power optical interferometers
No full textThesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2008.Includes bibliographical references (p. 181-189).In recent years, a variety of mechanical systems have been approaching quantum limits to their sensitivity of continuous position measurements imposed by the Heisenberg Uncertainty Principle. Most notably, gravitational wave interferometers, such as the Laser Interferometer Gravitational wave Observatory (LIGO), operate within a factor of 10 of the standard quantum limit. Here we characterize and manipulate quantum noise in a variety of alternative topologies which may lead to higher sensitivity GW detectors, and also provide an excellent testbed for fundamental quantum mechanics. Techniques considered include injection and generation of non-classical (squeezed) states of light, and cooling and trapping of macroscopic mirror degrees of freedom by manipulation of the optomechanical coupling between radiation pressure and mirror motion. A computational tool is developed to model complex optomechanical systems in which these effects arise. The simulation tool is used to design an apparatus capable of demonstrating a variety of radiation pressure effects, most notably ponderomotive squeezing and the optical spring effect. A series of experiments were performed, designed to approach measurement of these effects. The experiments use a 1 gram mirror to show progressively stronger radiation pressure effects, but only in the classical regime. The most significant result of these experiments is that we use radiation pressure from two" optical fields to shift the mechanical resonant frequency of a suspended mirror from 172 Hz to 1.8 kHz, while simultaneously damping its motion. The technique could prove useful in advanced gravitational wave interferometers by easing control issues, and also has the side effect of effectively cooling the mirror by removing its thermal energy. We show that with improvements, the technique may allow the quantum ground state of the mirror to be approached. Finally, we discuss future prospects for approaching quantum effects in the experiments.by Thomas Randall Corbitt.Ph.D
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