Physical Sciences and Mathematics Commons^™

Macrocyclic Antibiotics As Separation Agents, Daniel W. Armstrong

Chemistry Faculty Research & Creative Works

Macrocyclic antibiotics having ring structures with at least 10 members act as separation agents in crystallization, precipitation, filtration, electrophoresis, and chromatography. The macrocyclic antibiotics include ansamacrolides, macrolides, macrocyclic peptides, polyenes and derivatives thereof. The process has been found to be especially advantageous for separation of optical isomers by electrophoresis and chromatography.

Lamb Shift Of Laser-Dressed Atomic States, Ulrich D. Jentschura, Jorg Evers, Martin K. Haas, Christoph H. Keitel

Physics Faculty Research & Creative Works

We discuss radiative corrections to an atomic two-level system subject to an intense driving laser field. It is shown that the Lamb shift of the laser-dressed states, which are the natural state basis of the combined atom-laser system, cannot be explained in terms of the Lamb shift received by the atomic bare states which is usually observed in spectroscopic experiments. In the final part, we propose an experimental scheme to measure these corrections based on the incoherent resonance fluorescence spectrum of the driven atom.

Probing Scattering Wave Functions Close To The Nucleus, Don H. Madison, Daniel Fischer, Matthew S. Foster, Michael Schulz, Robert Moshammer, Stephenie J. Jones, Joachim Hermann Ullrich

Physics Faculty Research & Creative Works

Recently, three-dimensional imaging of the ejected electrons following 100  MeV/amu C⁶⁺ single ionization of helium led to the observation of a new structure not predicted by theory [M. Schulz et al., Nature (London) 422, 48 (2003)]. Instead of the usual “recoil lobe” centered on the momentum-transfer axis, a ring-shaped structure centered on the beam axis was observed. New measurements at 2  MeV/amu exhibit a similar structure, which is now predicted by theory. We argue that the same theory failed at 100  MeV/amu because the faster projectiles probe distances much closer to the nucleus, where our multiple-scattering model is expected …

Charge Transfer In Slow Collisions Of C⁴⁺ With H Below 1 Kev/Amu, Chen-Nan Liu, Anh-Thu Le, C. D. Lin

Physics Faculty Research & Creative Works

We reexamined charge-transfer cross sections for C⁴⁺ + H collisions for energies from 1 meV/amu to 1 keV/amu using the recently developed hyperspherical close-coupling method. Our results agree with several previous theoretical calculations using molecular-orbital expansion. However, these converged theoretical predictions do not agree with total cross sections from the merged-beam experiments.

Statistics Of Transmission In One-Dimensional Disordered Systems: Universal Characteristics Of States In The Fluctuation Tails, Lev I. Deych, Mikhail V. Erementchouk, Alexander A. Lisyansky, Alexey Yamilov, Hui Cao

Physics Faculty Research & Creative Works

We numerically study the distribution function of the conductance (transmission) in the one-dimensional tight-binding Anderson and periodic-on-average superlattice models in the region of fluctuation states where single parameter scaling is not valid. We show that the scaling properties of the distribution function depend upon the relation between the system's length L and the length l_s determined by the integral density of states. For long enough systems, L ≫ l_s, the distribution can still be described within a new scaling approach based upon the ratio of the localization length l_loc and l_s. In an intermediate …

Mantle Layering Across Central South America, Kelly H. Liu, Stephen S. Gao, Paul G. Silver, Yongkai K. Zhang

Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works

Imaging of seismic velocity discontinuities along a 3000 km profile across central South America at 20°S suggests that the depth variations of the 410-km (d410) and 660-km (d660) discontinuities are closely associated with the high-velocity Nazca slab and juxtaposed low-velocity oceanic mantle beneath the slab. The mantle transition zone thickness ranges from 220 km in the oceanic mantle to 270 km in a 600-km-wide area occupied by the deflected Nazca slab. The slab deflection has also been suggested by previous studies of seismic tomography and seismicity. This 50 km difference in the thickness corresponds to a lateral temperature variation of …

Melanoma And Seborrheic Keratosis Differentiation Using Texture Features, Srinivas V. Deshabhoina, Scott E. Umbaugh, William V. Stoecker, Randy Hays Moss, Subhashini K. Srinivasan

Chemistry Faculty Research & Creative Works

Purpose: To explore texture features in two-dimensional images to differentiate seborrheic keratosis from melanoma.

Methods: A systematic approach to consistent classification of skin tumors is described. Texture features, based on the second-order histogram, were used to identify the features or a combination of features that could consistently differentiate a malignant skin tumor (melanoma) from a benign one (seborrheic keratosis). Two hundred and seventy-one skin tumor images were separated into training and test sets for accuracy and consistency. Automatic induction was applied to generate classification rules. Data analysis and modeling tools were used to gain further insight into the feature space. …

Study Of The Electronic Properties Of Some Ytterbium Filled Skutterudites By Magnetic Susceptibility And X-Ray Absorption And Tin-119 Mössbauer Spectroscopy, Fernande Grandjean, Gary J. Long, Bernard M. Mahieu, Ji Hui Yang, Gregory P. Meisner, Donald T. Morelli

Chemistry Faculty Research & Creative Works

Magnetic susceptibility, ytterbium L_III-edge x-ray absorption and tin-119 Mössbauer spectral measurements have been carried out to probe the electronic structure of ytterbium and tin in the filled or partially filled skutterudite compounds, Yb_yCo₄Sb_12-xSn_x, over a range of x and y values. The ytterbium valence obtained from the magnetic susceptibility and ytterbium L_III-edge x-ray absorption measurements is in excellent agreement and clearly reveals an evolution from intermediate valence ytterbium for x=0 to nearly divalent ytterbium for x=0.8. This evolution parallels an increase in the unit cell volume and hence …

Field-Scale Estimation Of Volumetric Water Content Using Ground-Penetrating Radar Ground Wave Techniques, Katherine R. Grote, Susan Sharpless Hubbard, Yoram N. Rubin

Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works

Ground-penetrating radar (GPR) ground wave techniques were applied to estimate soil water content in the uppermost ∼10 cm of a 3 acre California vineyard several times over 1 year. We collected densely spaced GPR travel time measurements using 900 and 450 MHz antennas and analyzed these data to estimate water content. The spatial distribution of water content across the vineyard did not change significantly with time, although the absolute water content values varied seasonally and with irrigation. The GPR estimates of water content were compared to gravimetric water content, time domain reflectometry, and soil texture measurements. The comparisons of GPR-derived …

Perturbation Approach To The Self-Energy Of Non-S Hydrogenic States, Eric Olivier Le Bigot, Ulrich D. Jentschura, Peter J. Mohr, Paul Indelicato, Gerhard Soff

Physics Faculty Research & Creative Works

We present results on the self-energy correction to the energy levels of hydrogen and hydrogenlike ions. The self energy represents the largest QED correction to the relativistic (Dirac-Coulomb) energy of a bound electron. We focus on the perturbation expansion of the self energy of non-S states, and provide estimates of the so-called A₆₀ perturbative coefficient, which can be considered as a relativistic Bethe logarithm. Precise values of A₆₀ are given for many P, D, F and G states, while estimates are given for other electronic states. These results can be used in high-precision spectroscopy experiments in hydrogen and …

Resonant Photoemission In F-Electron Systems: Pu And Gd, James G. Tobin, Brandon W. Chung, Roland K. Schulze, Jeff Russell Terry, John Douglas Farr, David K. Shuh, K. Heinzelman, Eli Rotenberg, George Daniel Waddill, Gerrit V. Van Der Laan

Physics Faculty Research & Creative Works

Resonant photoemission in the Pu 5f and Pu 6p states is compared to that in the Gd 4f and Gd 5p states. Spectral simulations, based upon an atomic model with angular momentum coupling, are compared to the Gd and Pu results. Additional spectroscopic measurements of Pu, including core level photoemission and x-ray absorption, are also presented.

Single-Walled Carbon Nanotube Bundles Intercalated With Semiconductor Nanoparticles, Manashi Nath, Pallavi V. Teredesai, D. V. S. Muthu, A. K. Sood, Chintamani Nagesa Ramachandra Rao

Chemistry Faculty Research & Creative Works

Nanoparticles of CdSe, CdS and ZnSe have been incorporated in the inter-tubular gaps of single-walled carbon nanotube (SWNT) bundles. Electron microscope, X-ray diffraction (XRD), electronic spectroscopy and Raman studies have been employed to characterize these systems. The lengths of the intercalate inside the bundles could be varied by changing the reaction conditions. Electronic absorption and photoluminescence studies from the semiconductor intercalates show the expected blue-shift with respect to the corresponding bulk samples in CdS and ZnS samples. The SWNT lattice is expanded on incorporating CdSe as confirmed by XRD in the low-angle range. The expansion in the lattice is also …

Black Hole Multiplicity At Particle Colliders (Do Black Holes Radiate Mainly On The Brane?), Marco Cavaglia

Physics Faculty Research & Creative Works

If gravity becomes strong at the TeV scale, we may have the chance to produce black holes at particle colliders. In this Letter we revisit some phenomenological signatures of black hole production in TeV-gravity theories. We show that the bulk-to-brane ratio of black hole energy loss during the Hawking evaporation phase depends crucially on the black hole greybody factors and on the particle degrees of freedom. Since the greybody factors have not yet been calculated in the literature, and the particle content at trans-Planckian energies is not known, it is premature to claim that the black hole emits mainly on …

Two-Loop Bethe-Logarithm Correction In Hydrogenlike Atoms, Krzysztof Pachucki, Ulrich D. Jentschura

Physics Faculty Research & Creative Works

We calculate the two-loop Bethe logarithm correction to atomic energy levels in hydrogenlike systems. The two-loop Bethe logarithm is a low-energy quantum electrodynamic (QED) effect involving multiple summations over virtual excited atomic states. Although much smaller in absolute magnitude than the well-known one-loop Bethe logarithm, the two-loop analog is quite significant when compared to the current experimental accuracy of the 1 S – 2 S transition: It contributes - 8.19 and - 0.84 k H z for the 1 S and the 2 S state, respectively. The two-loop Bethe logarithm has been the largest unknown correction to the hydrogen Lamb …

Rescattering Of Ultralow-Energy Electrons For Single Ionization Of Ne In The Tunneling Regime, Robert Moshammer, Joachim Hermann Ullrich, Bernold Feuerstein, Daniel Fischer, Alexander Dorn, Claus Dieter Schroter, Jose R. Crespo Lopez-Urrutia, C. Hoehr, Horst Rottke, Christoph Trump, M. Wittmann, Georg Korn, Wolfgang Sandner

Physics Faculty Research & Creative Works

Electron emission for single ionization of Ne by 25 fs, 1.0 PW/cm² laser pulses at 800 nm was investigated. Kinematics was studied using a 'reaction microscope'. Results showed a zero longitudinal momentum of a low-energy electron with high resolution.

Dynamic Nonlinear Effect On Lasing In A Random Medium, Boyang Liu, Alexey Yamilov, Yong Ling, Junying Xu, Hui Cao

Physics Faculty Research & Creative Works

We have studied both experimentally and numerically the dynamic effect of nonlinearity on lasing in disordered medium. The third-order nonlinearity not only changes the frequency and size of lasing modes, but also modifies the laser emission intensity and laser pulse width. When the nonlinear response time is longer than the lifetime of the lasing mode, the nonlinearity changes the laser output through modifying the size of the lasing mode. When the nonlinear response is faster than the buildup of the lasing mode, positive nonlinearity always extracts more laser emission from the random medium due to the enhancement of single particle …

Tev Black Hole Fragmentation And Detectability In Extensive Air Showers, Eun-Joo Ahn, Maximo Ave, Marco Cavaglia, Angela V. Olinto

Physics Faculty Research & Creative Works

In models with large extra dimensions, particle collisions with a center-of-mass energy larger than the fundamental gravitational scale can generate nonperturbative gravitational objects. Since cosmic rays have been observed with energies above 10⁸ TeV, gravitational effects in the TeV energy range can, in principle, be observed by ultrahigh energy cosmic ray detectors. We consider the interaction of ultrahigh energy neutrinos in the atmosphere and compare extensive air showers from TeV black hole formation and fragmentation with standard model processes. Departures from the standard model predictions arise in the interaction cross sections and in the multiplicity of secondary particles. Large …

Density Of Resonant States And A Manifestation Of Photonic Band Structure In Small Clusters Of Spherical Particles, Alexey Yamilov, Hui Cao

Physics Faculty Research & Creative Works

We introduce a numerical recipe for calculating the density of the resonant states of the clusters of dielectric spheres. Using truncated multipole expansions (generalized multisphere Mie solution) we obtain the scattering matrix of the problem. By introducing an infinitesimal absorption in the spheres we express the dwell time of the electromagnetic wave in terms of the elements of the scattering matrix. Using the parameters in recent light localization experiments [Phys. Rev. Lett. 87, 153901 (2001)], we demonstrate that the density of the resonant states, related to the dwell time, shows the formation of the photonic band structure in small clusters …

Effect Of Kerr Nonlinearity On Defect Lasing Modes In Weakly Disordered Photonic Crystals, Boyang Liu, Alexey Yamilov, Hui Cao

Physics Faculty Research & Creative Works

We studied the effect of Kerr nonlinearity on lasing in defect modes of weakly disordered photonic crystals. Our time-independent calculation based on self-consistent nonlinear transfer matrix method shows that Kerr nonlinearity modifies both frequencies and quality factors of defect modes. We also used a time-dependent algorithm to investigate the dynamic nonlinear effect. Under continuous pumping, the spatial sizes and intensities of defect lasing modes are changed by Kerr nonlinearity. Such changes are sensitive to the nonlinear response time.

Role Of The Ground State In Electron-Atom Double Ionization, Stephenie J. Jones, Don H. Madison

Physics Faculty Research & Creative Works

Recently, absolute measurements have been reported for double ionization of helium by 5.6 keV electron-impact. At this high energy, one would think that the first Born approximation for the interaction of the projectile with the atom would be valid. However, on the basis of a lowest-order implementation of a Faddeev-type approach, Berakdar concluded that the approximation was not valid. Here we argue that (i) it is valid at this energy and (ii) the previous discrepancy between calculations in the first Born approximation and the overall magnitude of the measurements was due to a poor description of the ground state.

One-Step Processing Of Spinel Ferrites Via The High-Energy Ball Milling Of Binary Oxides, V. G. Harris, D. J. Fatemi, J. O. Cross, E. E. Carpenter, V. M. Browning, J. P. Kirkland, Amitabh Mohan, Gary J. Long

Chemistry Faculty Research & Creative Works

MnZn ferrites have been produced via the high-energy ball milling of binary oxide precursors. The milled ferrites have a nonequilibrium cation site distribution, with an unusually high population of Zn cations on the octahedral sites. The particle size distribution drops precipitously with milling time from 60±1 to ∼14±1 nm at 10 h, but increases to 18.5±1 nm after long durations (20–40 h) concurrent with the formation of nearly pure ferrite. A 1 h anneal at 673 K facilitates a redistribution of cations to their near equilibrium sites. This processing approach circumvents the need for deleterious high-temperature heat treatments that often …

Charge Transfer In Slow Collisions Of H⁺ With Na, Anh-Thu Le, Chen-Nan Liu, C. D. Lin

Physics Faculty Research & Creative Works

We reexamined charge-transfer cross sections for protons colliding with Na(3s) atoms for collision energies from the threshold at 1.7 eV to 40 eV using the recently developed hyperspherical close-coupling method. Our results disagree with the recent calculations by Dutta et al. [Phys. Rev. A 63, 022709 (2001)], but are in good agreement with the earlier calculations of Croft and Dickinson [J. Phys. B 29, 57 (1996)] except at energies below 3 eV. Our calculations support the doubt on the experimental data of Kushawaha.

Extrapolation Of The Zα-Expansion And Two-Loop Bound-State Energy Shifts, Ulrich D. Jentschura

Physics Faculty Research & Creative Works

Quantum electrodynamic (QED) effects that shift the binding energies of hydrogenic energy levels have been expressed in terms of a semi-analytic expansion in powers of Zα and ln[(Zα)^-2], where Z is the nuclear charge number and α is the fine-structure constant. For many QED effects, numerical data are available in the domain of high Z where the Zα expansion fails. In this Letter, we demonstrate that it is possible, within certain limits of accuracy, to extrapolate the Zα-expansion from the low-Z to the high-Z domain. We also review two-loop self-energy effects and provide an estimate for the problematic …

Projectile-Charge Sign Dependence Of Four-Particle Dynamics In Helium Double Ionization, Daniel Fischer, Robert Moshammer, Alexander Dorn, Jose R. Crespo Lopez-Urrutia, Bernold Feuerstein, C. Hohr, Claus Dieter Schroter, Siegbert Hagmann, Holger Kollmus, Rido Mann, Bhas Bapat, Joachim Hermann Ullrich, Holger Kollmus

Physics Faculty Research & Creative Works

Double ionization of helium by 6 MeV proton impact has been explored in a kinematically complete experiment using a “reaction microscope.” For the first time, fully differential cross sections for positively charged projectiles have been obtained and compared with data from 2 keV electron impact. The significant differences observed in the angular distribution of the ejected electrons are attributed to the charge sign of the projectile, resulting in different dynamics of the four-particle Coulomb system, which is not considered in the first Born approximation.

Investigating The Geoelectrical Response Of Hydrocarbon Contamination Undergoing Biodegradation, D. Dale Werkema, Estella A. Atekwana, Anthony L. Endres, William August Sauck, Daniel P. Cassidy

Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works

A newly proposed geoelectrical model for hydrocarbon contaminated sites predicts high conductivities coincident with the contaminated zone as opposed to the traditionally accepted low conductivity. The model attributes the high conductivities to mineral weathering resulting from byproducts of microbial redox processes. To evaluate this conductive model, in situ vertical conductivity measurements were acquired from a light non-aqueous phase liquid (LNAPL) contaminated site. The results showed high conductivities coincident with the zone of contamination and within the smear zone influenced by seasonal water table fluctuations. We infer this zone as an active zone of biodegradation and suggest significant microbial degradation under …

Hyperspherical Close-Coupling Calculations For Charge-Transfer Cross Sections In He²⁺ +H(1s) Collisions At Low Energies, Chen-Nan Liu, Anh-Thu Le, Toru Morishita, B. D. Esry, C. D. Lin

Physics Faculty Research & Creative Works

A theory for ion-atom collisions at low energies based on the hyperspherical close-coupling (HSCC) method is presented. In hyperspherical coordinates the wave function is expanded in analogy to the Born-Oppenheimer approximation where the adiabatic channel functions are calculated with B-spline basis functions while the coupled hyperradial equations are solved by a combination of R-matrix propagation and the slow/smooth variable discretization method. The HSCC method is applied to calculate charge-transfer cross sections for He²⁺ +H(1s)-->He⁺ (n=2) + H⁺ reactions at center-of-mass energies from 10 eV to 4 keV. The results are shown to be in general good agreement with calculations …

Sequence Stratigraphy And Depositional Facies Of Lower Ordovician Cyclic Carbonate Rocks, Southern Missouri, U.S.A., Robert Brandon Overstreet, Francisca Oboh-Ikuenobe, Jay M. Gregg

Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works

Lower Ordovician cyclic carbonate strata of southern Missouri were deposited in a warm, shallow, epeiric sea on a fully aggraded carbonate platform. Sedimentological characteristics distinguish the Jefferson City and Cotter dolomites from the underlying Gasconade and Roubidoux formations. Mixed carbonate-siliciclastic sedimentation characterizes the Roubidoux Formation, with sandstones accounting for up to 60% of sedimentation. The Gasconade, Jefferson City, and Cotter dolomites exhibit an increased occurrence of chalcedonic chert nodules in very similar shape and texture to the gypsum and anhydrite nodules common on modern sabkha supratidal flats. Casts of halite and ghosts of gypsum laths also exist in the Jefferson …

Solvent And Method For Extraction Of Triglyceride Rich Oil, Shubhender Kapila, Paul Ki-Souk Nam, V. J. Flanigan

Chemistry Faculty Research & Creative Works

The present invention relates to a solvent for use in extracting oil from an oil bearing material, such as soybeans, with the solvent resulting in the selective extraction of a triglyceride rich oil, which contains 95% or greater triglycerides and non-polar constituents, with the solvent comprised of a hydrocarbon, preferably hexane, and a fluorocarbon, so that the solvent has a viscosity less than 2.6 centipoise and a polarity of less than 0.1. The present invention also relates to a method of using the solvent to extract the triglyceride rich oil, with the method including preferably extracting the oil at a …

Asymptotic Properties Of Self-Energy Coefficients, Ulrich D. Jentschura, Eric Olivier Le Bigot, Peter J. Mohr, Paul Indelicato, Gerhard Soff

Physics Faculty Research & Creative Works

We investigate the asymptotic properties of higher-order binding corrections to the one-loop self-energy of excited states in atomic hydrogen. We evaluate the historically problematic A₆₀ coefficient for all P states with principal quantum numbers n ≤ 7 and D states with n ≤ 8 and find that a satisfactory representation of the n dependence of the coefficients requires a three-parameter fit. For the high-energy contribution to A₆₀, we find exact formulas. The results obtained are relevant for the interpretation of high-precision laser spectroscopic measurements.

Properties Of A Mixed-Valent Iron Compound With The Kagomé Lattice, Chintamani Nagesa Ramachandra Rao, Geo L. Paul, Amitava Choudhury, Echur Varadadesikan Sampathkumaran, Arup Kumar R. Raychaudhuri, Suryanarayanasastry Ramasesha, Indranil Rudra

Chemistry Faculty Research & Creative Works

An organically templated iron sulfate of the formula [HN(CH₂)₆NH][Fe^III Fe₂ ^IIF₆(SO₄)₂] ·[H₃O] possessing the kagomé lattice has been prepared and characterized by single-crystal crystallography and other techniques. This mixed-valent iron compound shows complex magnetic properties including spin-glass behavior and magnetic hysteresis. The low-temperature specific heat data show deviation from the T² behavior found in two-dimensional frustrated systems. Simple calculations have been carried out to understand the properties of this kagomé compound.