Browsing Dissertations by Title
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Quantum Dots Targeted to VEGFR2 for Molecular Imaging of Colorectal CancerAdvances in optical imaging have provided methods for visualizing molecular expression in tumors in vivo, allowing the opportunity to study the complexity of the tumor microenvironment. The development of fluorescent contrast agents targeted to molecules expressed in cancer cells is critical for in vivo imaging of the tumors. Contrast agents emitting in the near infrared (NIR) allow for an increased depth of penetration in tissue due to decreased absorption and scattering. There is also significantly less autofluorescence from tissue in the NIR. Quantum dots are nanoscopic particles of semiconductors whose fluorescent emission wavelength is tunable by the size of the particle with desirable fluorescent qualities such as a wide range of excitation wavelengths, a narrow emission band, high quantum efficiency, high photostablility, and they can be produced to emit throughout the NIR imaging window. It has been shown that vascular endothelial growth factor receptor 2 (VEGFR2) is upregulated in many cancers, including colorectal, as it is important in tumor angiogenesis and is considered a predictor for clinical outcome and, in some instances, is used for targeted therapy with antiangiogenic drugs. For these reasons, quantum dots bioconjugated to VEGFR2 antibodies have the potential to provide contrast between normal tissue and cancer, as well as a mechanism for evaluating the molecular changes associated with cancer in vivo. In this dissertation, we present on the design of two contrast agents using quantum dots targeted to VEGFR2 for use in the molecular imaging of colon cancer, both ex vivo and in vivo. First, as a preliminary ex vivo investigation into their efficacy, Qdot655® (655nm emission) were bioconjugated to antiVEGFR2 antibodies through streptavidin/biotin linking. The resulting QD655VEGFR2 contrast agent was used to label colon adenoma in vivo and imaged ex vivo with significant increase in contrast between diseased and undiseased tissue, allowing for fluorescence based visualization of the VEGFR2 expressing diseased areas of the colon with high sensitivity and specificity. Then, QD655VEGFR2 was used in a longitudinal in vivo study to investigate ability to correlate fluorescence signal to tumor development over time using optical coherence tomography and laser induced fluorescence spectroscopy (OCT/LIF) dualmodality imaging. The contrast agent was able to target VGEFR2 expressing diseased areas of colon; however, challenges in fully flushing the unbound contrast agent from the colon before imaging arise when moving from ex vivo imaging to in vivo image. Lastly, lead sulfide (PbS) quantum dots were made by colloidal synthesis to emit at a 940 nm (QD940) and conjugated to antiVEGFR2 primary antibodies through streptavidin/biotin linking. The resulting QD940VEGFR2 contrast agent was then used to label cells in vitro. The QD940VEGFR2 molecules were able to positively label VEGFR2 expressing cells and did not label VEGFR2 negative cells. Very low photoluminescence and large amounts of aggregation after conjugation of the quantum dot to streptavidin was detected. Improvements to the quantum dot stability through synthesis, capping and conjugation techniques must be made for this contrast agent to be effective as a contrast agent for cancer imaging.

Quantum induction and Higgs massWith our newly proposed dynamical Higgs mechanism and Quantum Induction programme, Higgs mass is predicted at M(H) ≈ 190 GeV by using our modified renormalization group equations. The same procedure also explains the top quark mass correctly.

Quantum Information Science with Neutral AtomsWe study a system of neutral atoms trapped in a threedimensional optical lattice suitable for the encoding, initialization and manipulation of atomic qubits. The qubits are manipulated by applied electromagnetic fields interacting with dipole moments of the atoms via light shifts, Raman transitions, Zeeman shifts, and microwave transitions. Our lattice is formed by three orthogonal onedimensional lattices, which have different frequencies so that interference terms average to zero. This geometry allows considerable freedom in designing the component onedimensional lattices, so that they provide not only confinement but also independent control in each dimension. Our atomic qubits are initialized from a lasercooled atomic sample by Raman sideband cooling in individual lattice potential wells. We have demonstrated accurate and robust onequbit manipulation using resonant microwave fields. In practice such control operations are always subject to errors, in our case spatial inhomogeneities in the microwave Rabi frequency and the light shifted qubit transition frequency. Observation of qubit dynamics in near real time allows us to minimize these inhomogeneities, and therefore optimize qubit logic gates. For qubits in the lattice, we infer a fidelity of 0.990(3) for a single pipulse. We have also explored the use of NMRtype pulse techniques in order to further reduce the effect of errors and thus improve gate robustness in the atom/lattice system. Our schemes for twoqubit quantum logic operations are based on controlled collisional interactions. We have experimented with two schemes in order to probe these collisions. The first involves manipulation of the centerofmass wavepackets of two qubits in a geometry corresponding to two partially overlapping MachZender interferometers. Unfortunately, this scheme has proven extremely sensitive to phase errors, as the wavepackets are moved by the optical lattice. The other scheme starts with two qubits in spatially separated traps, and utilizes microwaves to drive one or both qubits into a third trap inbetween the two qubits. Once the wavepackets overlap, the collisions create a large energy shift which can be probed spectroscopically.

Quantum state preparation in an optical latticeThis dissertation reports on quantum state preparation of cesium atoms in a twodimensional optical lattice, by resolvedsideband Raman cooling. An optical lattice is a periodic potential produced by the light shift interaction between an atom and light field. Laser cooled atoms can become strongly localized about the bottom of potential wells in an optical lattice, where they occupy a discrete spectrum of bound vibrational energy levels. The distribution over vibrational levels of atoms in the lattice is characterized by the mean vibrational excitation, n . In an optical lattice, absorption and emission of photons from lattice beams causes n to increase in time. This source of heating is always present, but its rate can be greatly reduced in a lattice detuned far from the atomic resonance. Sideband cooling is an efficient means of transferring atoms from higher into lowerlying vibrational levels and, thus, it reduces n for the ensemble. If the sideband cooling rate is much greater than the heating rate, then n approaches zero and virtually all atoms are in the lowest vibrational level in their potential wells. Our sideband cooling scheme involves stimulated Raman transitions between bound states in the potential wells of a pair of magnetic sublevels, followed by optical pumping, for a net loss of one quantum of vibration per cooling cycle. The process accumulates 98% of atoms in the ground vibrational level of a potential well associated with a single Zeeman substate. Each atom in the lattice is then very close to a pure state. For twodimensional lattice with sideband cooling we find nx≈ny≈0.008 &parl0;16&parr0; . Various issues related to state preparation and sideband cooling are also discussed in the context of a one dimensional lin ⊥ lin optical lattice. These include improvement of laser cooling in a near resonance lattice by application of weak magnetic fields, transfer of atoms from near into far offresonance lattices, and heating rates in far offresonance lattices.

Quantum Systems in Bernoulli PotentialsQuantum mechanics is a theory developed to explain both particle and wavelike properties of small matter such as light and electrons. The consequences of the theory can be counterintuitive but lead to mathematical and physical theory rich in fascinating phenomena and challenging questions. This dissertation investigates the nature of quantum systems in Bernoulli distributed random potentials for systems on the one dimensional lattice {0, 1, ..., L, L+1} ⊂ Z in the large system limit L → ∞. For single particle systems, the behavior of the low energy states is shown to be approximated by systems where positive potential is replaced by infinite potential. The approximate shape of these states is described, the asymptotics of their eigenvalues are calculated in the large system limit L → ∞, and a Lifschitz tail estimate on the sparsity of low energy states is proven. For interacting multiparticle systems, a LiebLiniger model with Bernoulli distributed potential is studied in the GrossPitaevskii approximation. First, to investigate localization in these settings, a general inequality is proven to bound from below the support of the meanfield. The bound depends on the per particle energy, number of particles, and interaction strength. Then, the ground state for the onedimensional lattice with Bernoulli potential is studied in the large system limit. Specifically, the case where the product of interaction strength and particle density is near zero is considered to investigate whether localization can be recovered.

Quantum theories of selflocalizationIn the classical dynamics of coupled oscillator systems, nonlinearity leads to the existence of stable solutions in which energy remains localized for all time. Here the quantummechanical counterpart of classical selflocalization is investigated in the context of two model systems. For these quantum models, the terms corresponding to classical nonlinearities modify a subset of the stationary quantum states to be particularly suited to the creation of nonstationary wavepackets that localize energy for long times. The first model considered here is the Quantized Discrete SelfTrapping model (QDST), a system of anharmonic oscillators with linear dispersive coupling used to model local modes of vibration in polyatomic molecules. A simple formula is derived for a particular symmetry class of QDST systems which gives an analytic connection between quantum selflocalization and classical local modes. This formula is also shown to be useful in the interpretation of the vibrational spectra of some molecules. The second model studied is the Frohlich/Einstein Dimer (FED), a twosite system of anharmonically coupled oscillators based on the Frohlich Hamiltonian and motivated by the theory of Davydov solitons in biological protein. The BornOppenheimer perturbation method is used to obtain approximate stationary state wavefunctions with error estimates for the FED at the first excited level. A second approach is used to reduce the first excited level FED eigenvalue problem to a system of ordinary differential equations. A simple theory of lowenergy selflocalization in the FED is discussed. The quantum theories of selflocalization in the intrinsic QDST model and the extrinsic FED model are compared.

QUANTUM THEORY OF MULTIWAVE MIXING (RESONANCE FLUORESCENCE, SATURATION SPECTROSCOPY, MODULATION, PHASE CONJUGATION, QUANTUM NOISE).This dissertation formulates and applies a theory describing how one or two strong classical waves and one or two weak quantum mechanical waves interact in a twolevel medium. The theory unifies many topics in quantum optics, such as resonance fluorescence, saturation spectroscopy, modulation spectroscopy, the build up of laser and optical bistability instabilities, and phase conjugation. The theory is based on a quantum population pulsation approach that resembles the semiclassical theories, but is substantially more detailed. Calculations are performed to include the effects of inhomogeneous broadening, spatial hole burning, and Gaussian transverse variations. The resonance fluorescence spectrum in a high finesse optical cavity is analyzed in detail, demonstrating how stimulated emission and multiwave processes alter the spectrum from the usual three peaks. The effects of quantum noise during the propagation of weak signal and conjugate fields in phase conjugation and modulation spectroscopy are studied. Our analysis demonstrates that quantum noise affects not only the intensities of the signal and conjugate, but also their relative phase, and in particular we determine a quantum limit to the semiclassical theory of FM modulation spectroscopy. Finally, we derive the corresponding theory for the twophoton, twolevel medium. This yields the first calculation of the twophoton resonance fluorescence spectrum. Because of the greater number of possible interactions in the twophoton twolevel model, the theoretical formalism is considerably more complex, and many effects arise that are absent in the onephoton problem. We discuss the role of the Stark shifts on the emission spectrum and show how the Rayleigh scattering is markedly different.

Quantum transport theory.Within the framework of the quantum transport theory based on the Wigner transform of the density matrix I study first in nonrelativistic and subsequently in relativistic formulation a number of applications. I also develop further the recently proposed relativistic theory: the classical limit is carefully derived and the integral equations of the relativistic Wigner function derived explicitly. I show how it is possible to obtain the Schwinger like particle production rate from relativistic quantum transport equations. Noteworthy numerical results address the shape of the relativistic Wigner function of a given quantum state. Other numerical studies are primarily oriented towards the time evolution of the Wigner functionI can presently solve only the nonrelativistic case in which there is no mixing between particle production and flow phenomena: I consider numerically the fate of the muon after muon catalyzed fusion.

Quantum tunneling and coherent wavepacket dynamics in an optical latticeThis dissertation reports on the experimental study of coherent wavepacket dynamics of cesium atoms in the doublewell potentials of a onedimensional, faroffresonance optical lattice. An optical lattice is the periodic potential produced by the light shift interaction of an atom with the light field of interfering laser beams. With the proper choice of laser parameters and external magnetic fields, an array of doublewell potentials is created. Using the techniques of laser cooling, atoms are trapped in the lattice and are prepared in a pure state through a combination of enhanced laser cooling in a nearresonance lattice and state selection in an accelerated faroffresonance lattice. The atoms are prepared on one side of the doublewell potential, and the atomic wavepackets will then oscillate between the left and right localized states of the doublewell potential. Entanglement between the internal and external degrees of freedom makes it possible to follow the centerofmass motion of the atoms by measuring the ground state magnetic populations via SternGerlach analysis. The coherent dynamics of these wavepackets was studied under various combinations of lattice parameters such as lattice depth, applied transverse and longitudinal magnetic fields. There is excellent agreement between the experimentally measured oscillation frequencies and those predicted from a numerical analysis of the bandstructure of the lattice. For certain lattice parameters the total energy of the atom is below the potential barrier and the coherent motion corresponds to tunneling through a classically forbidden barrier. At specific times during the oscillation the atomic wavepacket corresponds to a coherent superposition of the mesoscopically distinct left and right localized states.

Quantum weak turbulence with applications to semiconductor lasersBased on a model Hamiltonian appropriate for the description of fermionic systems such as semiconductor lasers, we describe a natural asymptotic closure of the BBGKY hierarchy in complete analogy with that derived for classical weak turbulence. The main features of the interaction Hamiltonian are the inclusion of full Fermi statistics containing Pauli blocking and a simple, phenomenological, uniformly weak two particle interaction potential equivalent to the static screening approximation. The resulting asymytotic closure and quantum kinetic Boltzmann equation are derived in a self consistent manner without resorting to a priori statistical hypotheses or cumulant discard assumptions. We find a new class of solutions to the quantum kinetic equation which are analogous to the Kolmogorov spectra of hydrodynamics and classical weak turbulence. They involve finite fluxes of particles and energy across momentum space and are particularly relevant for describing the behavior of systems containing sources and sinks. We explore these solutions by using differential approximation to collision integral. We make a prima facie case that these finite flux solutions can be important in the context of semiconductor lasers. We show that semiconductor laser output efficiency can be improved by exciting these finite flux solutions. Numerical simulations of the semiconductor Maxwell Bloch equations support the claim.

Quantum Well Intermixing For Photonic Integrated CircuitsIn this thesis, several aspects of GaAsSb/AlSb multiple quantum well (MQW) heterostructures have been studied. First, it was shown that the GaAsSb MQWs with a direct band gap near 1.5 μm at room temperature could be monolithically integrated with AlGaSb/AlSb or AlGaAsSb/AlAsSb Bragg mirrors, which can be applied to Vertical Cavity Surface Emitting Lasers (VCSELs). Secondly, an enhanced photoluminescence from GaAsSb MQWs was reported. The photoluminescence strength increased dramatically with arsenic fraction as conjectured. The peak photoluminescence from GaAs(0.31)Sb(0.69) was 208 times larger than that from GaSb. Thirdly, the strong photoluminescence from GaAsSb MQWs and the direct nature of the band gap near 1.5 μm at room temperature make the material favorable for intermixing studies. The samples were treated with ion implantation followed by rapid thermal annealing (RTA). A band gap blueshift as large as 198 nm was achieved with a modest ion dose and moderate annealing temperature. Photoluminescence strength for implanted samples generally increased with the annealing temperature. The energy blueshift was attributed to the interdiffusion of both the group III and group V sublattices. Finally, based on the interesting properties of GaAsSb MQWs, including the direct band gap near 1.5 μm, strong photoluminescence, a wide range of wavelength (1300 – 1500 nm) due to ion implantationinduced quantum well intermixing (QWI), and subpicosecond spin relaxation reported by Hall et al, we proposed to explore the possibilities for ultrafast optical switching by investigating spin dynamics in semiconductor optical amplifiers (SOAs) containing InGaAs and GaSb MQWs. For circularly polarized pump and probe waves, the numerical simulation on the modal indices showed that the difference between the effective refractive index of the TE and TM modes was quite large, on the order of 0.03, resulting in a significant phase mismatch in a traveling length larger than 28 μm. Thus the FWM conversion efficiency was exceedingly small and the FWM mechanism in SOAs used for investigation of alloptical polarization switching was strongly limited.

Quasars in galaxy cluster environments.The evolution of radio loud quasars is found to be strongly dependent upon their galaxy cluster environment. Previous studies (Yee and Green 1987) have shown that bright quasars at z ∼ 0.6 are found in clusters as rich as Abell richness class 1, while high luminosity quasars at lower redshifts are found only in poorer environments. An observational study of the environments of 66 low luminosity quasars with 0.3 < z < 0.6 yields several objects in rich clusters of galaxies. This result implies that radio loud quasars in these environments have faded approximately 3 magnitudes in the interval between redshifts 0.6 and 0.4, corresponding to a luminosity efolding fading time of 900 million years, similar to the dynamical timescale of these environments. The analysis of low luminosity radio quiet quasars indicate that they are never found in rich environments, suggesting that they are a physically different class of objects. Properties of the quasar environment are investigated to determine constraints on the physical mechanisms of quasar formation and evolution. The optical cluster morphology indicates that the cluster cores have smaller radii and higher galaxy densities than are typical for low redshift clusters of similar richness. Radio morphologies may indicate that the formation of a dense intracluster medium is associated with the quasars' fading at these epochs. Galaxy colors appear to be normal, but there may be a tendency for clusters associated with high luminosity quasars to contain a higher fraction of gasrich galaxies than those associated with low luminosity quasars, a result consistent with the formation of an ICM. Multislit spectroscopic observations of galaxies associated with high luminosity quasars indicate that quasars are preferentially located in regions of low relative velocity dispersion, either in rich clusters of abnormally low velocity dispersion, or in poor groups which are dynamically normal. This suggests that galaxygalaxy interactions may play a role in quasar formation and sustenance. Virialization of rich clusters and the subsequent increase in galaxy velocities may therefore be responsible for the fading of quasars in rich environments.

Quasifourlevel laser design and analysis of Nd:YAG operating at the 946 nm transitionNd:YAG, well known for its operation at 1064nm, has a weaker transition at 946nm, whose lower level is thermally populated. This dissertation describes the design and development of a diode pumped, room temperature, quasifourlevel laser operating at the 946nm transition of Nd:YAG. The design addresses two primary issues in obtaining an efficient, high energy oscillator at 946nm. These are the ground state reabsorption losses due to the thermally occupied lower laser level, and the population inversion losses incurred at the much stronger 1064nm, transition. With 55 mJ in the normal mode, and 25 mJ in the qswitched mode, the output energies obtained are the highest energies per pulse reported to date for a diode pumped, 946mn Nd:YAG laser. A quasifourlevel laser theory is developed and used to optimize oscillator parameters affected by the thermally occupied lower laser level. The laser material length and the folded V shaped cavity are selected to maximize the gain per round trip in the cavity. The availability of stacked and microlensed diode array bars, along with an efficient pump coupling technique, allows the use of an end pumped configuration which provides the high pump density required to reach threshold in quasifourlevel lasers. The oscillator design was further refined to eliminate possible parasitic lasing paths and minimize amplified spontaneous emission losses at the 1064nm, transition. A large diameter laser disk with a Samarium doped cladding, which absorbs the 1064nm, radiation, reduces the number of 1064nm, ASE paths which deplete the inversion density in the pumped volume. The cladding significantly improves the storage efficiency, and hence the qswitched efficiency, of the oscillator. Although the oscillator was developed specifically for remote sensing of atmospheric water vapor, other applications can also benefit from the development of an efficient 946nm laser source. When frequency doubled, this wavelength allows access to the blue, which is highly desirable for high density data storage, displays, biological applications, and underwater communications.

QuasiOptical Spherical Balloon TelescopesAstronomy constantly pushes the limits of technology in order to decipher the workings of the Universe. There is a constant need for higher resolution observations across a wide range of wavelengths, at preferably a minimal cost. The terahertz regime (lambda=100 um to lambda=1000 um) covers a region of the electromagnetic spectrum that is blocked by Earth's atmosphere, which limits observations to high altitude plane and balloon telescopes and space telescopes. These current options limit the resolution achievable due to the size of telescopes that can be launched. This dissertation investigates a new approach, the Large Balloon Reflector (LBR), where a 20 meter diameter spherical balloon can be inflated and used as a 10 meter telescope inside a larger carrier balloon. Detailed in this dissertation are design considerations for the terahertz regime and a series of scaled versions of this balloon concept where I work to develop onaxis spherical corrector designs. Chapters 1 through 6 focus on the LBR designs and their variants, including investigations for a 3 meter rooftop proof of concept model, a 5 meter test flight model, and the final 20 meter LBR. The successful modeling and proof of concepts from the LBR studies then prompted an investigation into a Terahertz Space Telescope (TST), a proposed 20 meter inflatable telescope adapted from the LBR technology. Starting with Chapter7, this dissertation explores the application of using 1 meter diameter inflatable balloons as rapidly deployable communications satellites from standard CubeSats. The concept, design and test results of an electronically steerable line feed antenna array are presented which allows for instantaneous, non mechanical pointing of a 10 GHz signal within a 500 km ground footprint. Alternative uses of the 1 meter inflatable balloon CubeSat are also discussed, such as low cost astronomical galactic plane surveys.

A quasilinear theory of timedependent nonlocal dispersion in geologic media.A theory is presented which accounts for a particular aspect of nonlinearity caused by the deviation of plume "particles" from their mean trajectory in threedimensional, statistically homogeneous but anisotropic porous media under an exponential covariance of log hydraulic conductivities. Quasilinear expressions for the timedependent nonlocal dispersivity and spatial covariance tensors of ensemble mean concentration are derived, as a function of time, variance σᵧ² of log hydraulic conductivity, degree of anisotropy, and flow direction. One important difference between existing linear theories and the new quasilinear theory is that in the former transverse nonlocal dispersivities tend asymptotically to zero whereas in the latter they tend to nonzero Fickian asymptotes. Another important difference is that while all existing theories are nominally limited to situations where σᵧ² is less than 1, the quasilinear theory is expected to be less prone to error when this restriction is violated because it deals with the above nonlinearity without formally limiting σᵧ². The theory predicts a significant drop in dimensionless longitudinal dispersivity when σᵧ² is large as compared to the case where σᵧ² is small. As a consequence of this drop the real asymptotic longitudinal dispersivity, which varies in proportion to σᵧ² when σᵧ² is small, is predicted to vary as σᵧ when σᵧ² is large. The dimensionless transverse dispersivity also drops significantly at early dimensionless time when σᵧ² is large. At late time this dispersivity attains a maximum near σᵧ² = 1, varies asymptotically at a rate proportional to σᵧ² when σᵧ² is small, and appears inversely proportional to σᵧ when σᵧ² is large. The actual asymptotic transverse dispersivity varies in proportion to σᵧ⁴ when σᵧ² is small and appears proportional to σᵧ when σᵧ² is large. One of the most interesting findings is that when the mean seepage velocity vector μ is at an angle to the principal axes of statistical anisotropy, the orientation of longitudinal spread is generally offset from μ toward the direction of largest log hydraulic conductivity correlation scale. When local dispersion is active, a plume starts elongating parallel to μ. With time the long axis of the plume rotates toward the direction of largest correlation scale, then rotates back toward μ, and finally stabilizes asymptotically at a relatively small angle of deflection. Application of the theory to depthaveraged concentration data from the recent tracer experiment at Borden, Ontario, yields a consistent and improved fit without any need for parameter adjustment.

Quasioptical Systems & Components for Terahertz AstronomyOver the past two decades, submillimeter and terahertz astronomy has grown rapidly and become an important new window for studying the universe. This growth has been enabled by the confluence of several technologies which make the design and fabrication of high frequency single and multipixel heterodyne receivers possible. This dissertation reviews the development of a new generation of terahertz instrumentation at the University of Arizona, with specific emphasis on their optical components and systems. These instruments include several receivers for the Antarctic Submillimeter Telescope and Remote Observatory (formerly installed at the South Pole), including a dualfrequency 492/810 GHz receiver called Wanda, a 4pixel 810 GHz heterodyne array called PoleSTAR, and a 1.5 THz receiver called TREND. It also covers receivers for the Heinrich Hertz Submillimeter Telescope on Mt. Graham in southern Arizona. These receivers include a 7pixel 345 GHz heterodyne array called DesertSTAR, a 64pixel polarimeter/bolometer system called Hertz, and a 64pixel 345 GHz heterodyne array called SuperCam. After reviewing these instruments, concepts for the next generation of arrays and terahertz telescopes designed for the high Atacama desert, Antarctica, high altitude balloon missions, and orbiting observatories will be presented. This dissertation will also cover other contributions made to terahertz astronomy, including the creation of a Gaussian beam propagation program to help design terahertz optical systems and an integrated optics design for a waveguide interferometer to be used as an alternative to traditional bulk optics systems.

QUATERNARY STRATIGRAPHY, GEOCHRONOLOGY, AND CARBON ISOTOPE GEOLOGY OF ALLUVIAL DEPOSITS IN THE TEXAS PANHANDLE (RADIOCARBON).Sedimentology, stratigraphy, and stablecarbon isotopy were used to reconstruct geologic and climatic events on the Texas southern High Plains from ca. 13,000 yr B.P. to the present. The alluvial sediments in Yellowhouse and Blackwater Draws were used to construct the geologic history. The oldest valley alluvium comprises the > 13,000yrB.P. fluvial sediments that were incised and buried by fluvial and lacustrine sediments dating ca. 13,000 to 4900 yr B.P. Lacustrine waters changed from oligotrophic to eutrophic and finally calcalitrophic. Regional valley erosion at 4900 yr B.P. developed a widespread disconformity within the Yellowhouse Draw formation, which separates lower fluvial and lacustrine sediments (ca. 13,0004900 yr B.P.) from the overlying sediments dating 4900 yr B.P. to present. After 4900 yr B.P., intermittent streams and eolian processes deposited several meters of sand the length of each valley. Cienegas returned to downstream reaches of both draws after 15002000 yr B.P. Methods were developed to extract purified collagen residues and hydroxyproline from heavily contaminated fossil bones. Reliable δ¹³C measurements on collgen require isolation of single amino acids, whereas less specific purifications may yield accurate bone collagen ¹⁴C dates. Collagenous residues were extracted from 13,000200yrB.P. fossil bison bones from the Lubbock Lack Site at Lubbock, Texas, and δ¹³C values were determined. Collagen δ¹³C values changed from 8 per mil at 200 yr B.P. to 10 per mil at 4900 yr B.P. and to 17 per mil at 12,500 yr B.P. The δ¹³C changes imply that the Lubbock area grasslands contained 30 to 40 percent C₄ grass biomass at 12,500 yr B.P. in contrast to the 95 percent C₄ grass biomass in today's grasslands. The stratigraphic and isotopic results gave similar paleoecological histories for the Texas southern High Plains. At 12,500 yr B.P. permanent streams existed and grasslands may have resembled those in the northern central Great Plains today. The climate warmed gradually, and the water table dropped until 5000 yr B.P. when a major hydrologic shift occurred. After 4900 yr B.P., modern climatic depositional and vegetation communities were developed. Geomorphic thresholds apparently controlled the regional disconformities, depositional events, and pedogenetic episodes. Climatic change was the ultimate cause of stratigraphic changes, but individual geologic events were not coeval with any similar climatic shift.

Que siga el corrido: Tucson pachucos and their times.The pachuco culture is a rich contemporary tradition born in the southwestern United States in the early 20th century. The innovative youth culture emerged in U.S.Mexico border towns, but contemporary, urbanhip cholo forms are now found in cities in both countries, many distant from the border. Among workingclass and informal sector youth partial to a particular dress style, (the zootsuit is best known), and a cryptic, hybrid language, being pachuco is a form of life with demonstrable continuity over sixty years, in social organization, language, and style. This research is the first ethnography with older men and women of the earliest Southwest generations associated with the culture. Their life history and linguistic narratives speak of the formative moments of being pachuco in Tucson, Arizona. The interpretive frameworks used by consultants are explored as they discuss history, culture, language and identity. To do this, I use recently developed theoretical tools in linguistic anthropology, especially the concepts of metapragmatics and indexicality (Silverstein 1985, 1979) and dialogicality (Bakhtin 1984, 1929). Uniquely among ethnographies of pachucos, I attend to the language use of women, their experiences and perspectives. The major findings are: (1) The youth culture was present in Tucson and the Southwest in at least 1929, if not earlier; (2) research on the regional Indian roots of the culture has been neglected; (3) females have participated in the youth culture from early on; (4) stigmatization and criminalization of the culture continues today in forms resembling the dynamics surrounding the socalled "Zootsuit Riots" of 1943; and (5) in linguistic theory, formulations relating to the transmission of indexical information may need reformulation to account for languages like Pachuco where the interplay of a number of systems creates a high degree of symbolic ambiguity.