Physics Commons^™

Tidal Perturbations And Variability In Mesopause Region Over Fort Collins, Co(41n, 105w): Continuous Multi-Day Temperature And Wind Lidar Observations, C. Y. She, T. Li, R. L. Collins, Tao Yuan, B. P. Williams, T. Kawahara, J. D. Vance, P. Acott, D. A. Krueger, H. L. Liu, M. E. Hagan

All Physics Faculty Publications

An unusually long data set was acquired at the sodium lidar facility at Colorado State University (41N, 105W), between Sep 18 and Oct 01, 2003, including a 9-day continuous observation. This time is long enough to average out the perturbations of gravity waves and short-period planetary waves. As such, it can be used to define tidal-period perturbations in temperature and horizontal wind. Assuming the sodium mixing ratio is a constant of motion, the observed tidal-period oscillation in sodium density follows that of vertical wind. Thus, the data set defines tidal-period perturbations of temperature and wind vector. The observed amplitudes and …

Performance Analysis Of Cdma-Based Wireless Communication Systems Using The Simplified Improved Gaussian Approximation Method, H N Kundaeli

Tanzania Journal of Science

The limitations initially prevalent in CDMA-based systems have been gradually solved thereby making CDMA a very promising access mode for future communication systems. Following the move towards higher data transmission rates, however, a number of other problems have emerged that need to be tackled. As a result, current world-wide research on CDMA-based systems is geared towards high speed, highly mobile multimedia communication applications. In this paper, the performance of a multi-user DS-CDMA communication system operating in a Rayleigh fading environment is investigated. Performance expressions are derived and the variation of the performance with various system parameters is presented.

Development Of Dose Conversion Coefficients For Radionuclides Produced In Spallation Neutron Sources: Quarterly Progress Report 9/1/04 – 12/31/04, Phillip W. Patton, Mark Rudin

Transmutation Sciences Physics (TRP)

The research consortium comprised of representatives from several universities and national laboratories has successfully generated internal and external dose conversion coefficients for twenty radionuclides produced in spallation neutron sources. In addition, the group has identified twenty radionuclide that are missing electron capture files and eighteen additional radionuclides missing substantial physical data.

Leptonic Cp Violation In A Two Parameter Model, Joseph Schechter, Samina S. Masood, Salah Nasri

Physics - All Scholarship

We further study the "complementary" Ansatz, Tr(M_\nu)=0, for a prediagonal light Majorana type neutrino mass matrix. Previously, this was studied for the CP conserving case and the case where the two Majorana type CP violating phases were present but the Dirac type CP violating phase was neglected. Here we employ a simple geometric algorithm which enables us to "solve" the Ansatz including all three CP violating phases. Specifically, given the known neutrino oscillation data and an assumed two parameter (the third neutrino mass m_3 and the Dirac CP phase \delta) family of inputs we predict the neutrino masses and Majorana …

Exploring The Optimal Sensitivity Of Sum-Variance Nonseparability Criteria For Spin-1/2 Systems, Irfan Ali Khan, John C. Howell

Mathematics, Physics, and Computer Science Faculty Articles and Research

We report on experimental and theoretical studies on recently introduced entanglement measures which use a sum of spin-variance criteria for two spin-1∕2 particles. Three inequalities are explored which exhibit useful concatenating properties. They are each shown to have greater sensitivities than a Bell’s measurement, while each requiring fewer measurements than a Bell’s measurement to obtain. The simplest inequality, requiring just four measurements, is shown to be efficient at testing for entanglement in down-conversion sources which naturally exhibit maximally polarized noise. The most complex inequality, requiring just 12 measurements, is shown to have a sensitivity equal to that of the Peres …

Pseudorapidity Asymmetry And Centrality Dependence Of Charged Hadron Spectra In D+Au Collisions At √SNn=200 Gev, Star Collaboration, T.D. Gutierrez

Physics

The pseudorapidity asymmetry and centrality dependence of charged hadron spectra in d+Au collisions at √s_NN=200 GeV are presented. The charged particle density at midrapidity, its pseudorapidity asymmetry, and centrality dependence are reasonably reproduced by a multiphase transport model, by HIJING, and by the latest calculations in a saturation model. Ratios of transverse momentum spectra between backward and forward pseudorapidity are above unity for p_T below 5GeV ∕ c. The ratio of central to peripheral spectra in d+Au collisions shows enhancement at 2 < p_T < 6GeV ∕ c, with a larger effect at backward rapidity than forward rapidity. Our measurements are in qualitative agreement with gluon saturation and in contrast to calculations based on incoherent multiple partonic scatterings.

Fixed-Connectivity Membranes, Mark Bowick

Physics - All Scholarship

The statistical mechanics of flexible surfaces with internal elasticity and shape fluctuations is summarized. Phantom and self-avoiding isotropic and anisotropic membranes are discussed, with emphasis on the universal negative Poisson ratio common to the low-temperature phase of phantom membranes and all strictly self-avoiding membranes in the absence of attractive interactions. The study of crystalline order on the frozen surface of spherical membranes is also treated.

Magnetoelectronics With Magnetoelectrics, Christian Binek, Bernard Doudin

Christian Binek Publications

Magnetoelectric films are proposed as key components for spintronic applications. The net magnetic moment created by an electric field in a magnetoelectric thin film influences the magnetization state of a neighbouring ferromagnetic layer through exchange coupling. Pure electrical control of magnetic confi gurations of giant magnetoresistance spin valves and tunnelling magnetoresistance elements is therefore achievable. Estimates based on documented magnetoelectric tensor values show that exchange fields reaching 100 mT can be obtained. We propose a mechanism alternative to current-induced magnetization switching, providing access to a wide range of device impedance values and opening the possibility of simple logic functions.

Scattering Of Low- To Intermediate-Energy Positrons From Molecular Hydrogen, David D. Reid, William B. Klann, J. M. Wadehra

Physics and Astronomy Faculty Research Publications

Using a complex model potential, we have calculated the total, integrated elastic, momentum transfer, absorption, and differential cross sections for positrons scattered from molecular hydrogen. The widely available software package GAUSSIAN is used to generate the radial electronic charge density of the molecule which is used to produce the interaction potentials. The quasifree absorption potential, previously developed and used for positron-atom scattering, is extended to positron scattering from molecular targets. It is shown that this model potential approach produces accurate results even into the low-energy regime.

An Informatics Search For The Low-Molecular Weight Chromium-Binding Peptide, Deendayal Dinakarpandian, Vincent Morrissette, Shveta Chaudhary, Kambiz Amini, Brian Bennett, J David Van Horn

Physics Faculty Research and Publications

Background

The amino acid composition of a low molecular weight chromium binding peptide (LMWCr), isolated from bovine liver, is reportedly E:G:C:D::4:2:2:2, though its sequence has not been discovered. There is some controversy surrounding the exact biochemical forms and the action of Cr(III) in biological systems; the topic has been the subject of many experimental reports and continues to be investigated. Clarification of Cr-protein interactions will further understanding Cr(III) biochemistry and provide a basis for novel therapies based on metallocomplexes or small molecules.

Results

A genomic search of the non-redundant database for all possible decapeptides of the reported composition yields three …

Azimuthal Anisotropy And Correlations At Large Transverse Momenta In P+P And Au+Au Collisions At √SNn=200 Gev, Star Collaboration, T.D. Gutierrez

Physics

Results on high transverse momentum charged particle emission with respect to the reaction plane are presented for Au+Au collisions at √s_NN=200  GeV. Two- and four-particle correlations results are presented as well as a comparison of azimuthal correlations in Au+Au collisions to those in p+p at the same energy. The elliptic anisotropy v₂ is found to reach its maximum at pt∼3  GeV/c, then decrease slowly and remain significant up to p_t≈7–10  GeV/c. Stronger suppression is found in the back-to-back high-p_t particle correlations for particles emitted out of plane compared to those emitted in plane. The …

Optimal Cooling Strategies For Magnetically Trapped Atomic Fermi-Bose Mixtures, Michael Brown-Hayes, Roberto Onofrio

Dartmouth Scholarship

We discuss cooling efficiency for different-species Fermi-Bose mixtures in magnetic traps. A better heat capacity matching between the two atomic species is achieved by a proper choice of the Bose cooler and the magnetically trappable hyperfine states of the mixture. When a partial spatial overlap between the two species is also taken into account, the deepest Fermi degeneracy is obtained for an optimal value of the trapping frequency ratio between the two species. This can be achieved by assisting the magnetic trap with a deconfining light beam, as shown in the case of fermionic 6Li mixed with 23Na, 87Rb, and …

Comparisons Of Long-Term Trends And Variability In The Middle Atmosphere, Troy Wynn, Joshua P. Herron, Vincent B. Wickwar

Posters

The USU Rayleigh Lidar (41.74°N 111.81°W) has been regularly used to measure temperatures in the middle atmosphere from 45 to 90 km. It is well suited for nightly observation; provides excellent vertical temperature resolution; and does not need external calibration. It began operation in August 1993 and a dataset spanning more than ten years has been collected. The analysis here includes 593 nightly temperature profiles from September 1993 through July 2003.

With many sources of variation in the atmosphere, all temperature effects cannot be easily detected. The largest source of temperature variation, and the easiest to measure, is the annual …

The Strange Physics Of Low Frequency Mirror Mode Turbulence In The High Temperature Plasma Of The Magnetosheath, R. A. Treumann, C. H. Jaroschek, O. D. Constantinescu, R. Nakamura

Dartmouth Scholarship

Mirror mode turbulence is the lowest frequency perpendicular magnetic excitation in magnetized plasma proposed already about half a century ago by Rudakov and Sagdeev (1958) and Chandrasekhar et al. (1958) from fluid theory. Its experimental verification required a relatively long time. It was early recognized that mirror modes for being excited require a transverse pressure (or temperature) anisotropy. In principle mirror modes are some version of slow mode waves. Fluid theory, however, does not give a correct physical picture of the mirror mode. The linear infinitesimally small amplitude physics is described correctly only by including the full kinetic theory and …

Medical Image Processing Using Transient Fourier Holography In Bacteriorhodopsin Films, Sri-Rajasekhar Kothapalli, Pengfei Wu, Chandra S. Yelleswarapu, D.V.G.L.N. Rao

Physics Faculty Publications

Real time image processing is demonstrated by recording and reconstructing the transient photoisomerizative grating formed in the bR film using Fourier holography. Desired spatial frequencies including both high and low band in the object beam are reconstructed by controlling the reference beam intensity. The results are in agreement with a theoretical model based on photoisomerization grating. We exploit this technique to process mammograms in real-time for identification of microcalcifications buried in the soft tissue for early detection of breast cancer. A feature of the technique is the ability to transient display of selected spatial frequencies in the reconstructing process which …

Quantum Entanglement Of Anisotropic Magnetic Nanodots, Ralph Skomski, Andrei Y. Istomin, Anthony F. Starace, David J. Sellmyer

Department of Physics and Astronomy: Faculty Publications

Anisotropic magnetic nanodots are promising physical realizations of qubits for quantum computing at finite temperature owing to their well-separated low-lying energy levels and scalability. The entanglement of two interacting magnetic nanodots is investigated and shown both analytically and numerically to be resonantly dependent on their interaction strength and on differences in their properties. These results provide criteria for fabricating and coupling magnetic nanodots so that their low-lying eigenstates can be significantly entangled.

Atomic Force Microscope Conductivity Measurements Of Single Ferritin Molecules, Degao Xu

Theses and Dissertations

Conductive Atomic Force Microscope (c-AFM) was used to measure the conductivity of single horse spleen ferritin (HoSF) and azotobacter vinelandii bacterial ferritin (AvBF) molecules deposited on flat gold surfaces. A 500 micron diameter gold ball was also used as a contact probe to measure the conductivity of a thin film of ferritin molecules. The average current measured for holo HoSF was 13 and 5 times larger than that measured for apo HoSF as measured by c-AFM at 1V and gold ball at 2V and respectively, which indicates that the core of ferritin is more conductive than the protein shell and …

Femtosecond Laser-Induced Formation Of Submicrometer Spikes On Silicon In Water, M. Y. Shen, Catherine Hirshfeld Crouch, J. E. Carey, E. Mazur

Physics & Astronomy Faculty Works

We fabricate submicrometer silicon spikes by irradiating a siliconsurface that is submerged in water with 400 nm, 100 fs laser pulses. These spikes are less than a micrometer tall and about 200 nm wide—one to two orders of magnitude smaller than the microspikes formed by laser irradiation of silicon in gases or vacuum. Scanning electron micrographs of the surface show that the formation of the spikes involves a combination of capillary waves on the molten siliconsurface and laser-induced etching of silicon. Chemical analysis and scanning electron microscopy of the spikes show that they are composed of silicon with a 20-nm-thick …

Spectral Degree Of Coherence Of A Random Three-Dimensional Electromagnetic Field, Olga Korotkova, Emil Wolf

Physics Articles and Papers

The complex spectral degree of coherence of a general random, statistically stationary electromagnetic field is introduced in a manner similar to the way it is defined for a beamlike field, namely, by means of Young’s interference experiment. Both its modulus and its phase are measurable. We illustrate the definition by applying it to blackbody radiation emerging from a cavity. The results are of particular interest for near-field optics.

A Statistical Study Of The Global Structure Of The Ring Current, A. M. Jorgensen, Harlan E. Spence, W. J. Hughes, H. J. Singer

Physics & Astronomy

[1] In this paper we derive the average configuration of the ring current as a function of the state of the magnetosphere as indicated by the Dst index. We sort magnetic field data from the Combined Release and Radiation Effects Satellite (CRRES) by spatial location and by the Dst index in order to produce magnetic field maps. From these maps we calculate local current systems by taking the curl of the magnetic field. We find both the westward (outer) and the eastward (inner) components of the ring current. We find that the ring current intensity varies linearly with Dst as …

High Statistics Search For The Θ+ (1.54) Pentaquark State, M. J. Longo, Timothy Holmstrom, Hypercp Collaboration

Chemistry & Physics Faculty Publications

We have searched for θ⁺(1.54)→K⁰p decays using data from the 1999 run of the HyperCP experiment at Fermilab. We see no evidence for a narrow peak in the K_S⁰p mass distribution near 1.54  GeV/c among 106 000 K_S⁰p candidates, and obtain an upper limit for the fraction of θ⁺(1.54) to K_S⁰p candidates of

Niel Calculations For High-Energy Heavy Ions, John W. Wilson, I. Jun, M. A. Xapsos, E. A. Burke, F. F. Badavi, L. W. Townsend

Nuclear Engineering and Radiation Science Faculty Research & Creative Works

Calculations of NIEL are reported for heavy ions prominent in the space environment for energies ranging from 200 MeV per nucleon to 2 GeV per nucleon.

Rayleigh-Lidar Observations Of Mesospheric Mid-Latitude Density Climatology Above Utah State University, Eric M. Lundell, Vincent B. Wickwar

Posters

Data from Rayleigh lidars have been used extensively to derive temperatures in the mesospheric region of the atmosphere. However, these data have not been used extensively in a similar way to derive neutral densities. We report on one such mid-latitude, density climatology between 45 and ~90 km, based on nearly 600 good nights of observations carried out since 1993 at the Atmospheric Lidar Observatory (ALO) at Utah State University (41.7°N 111.8°W). They produce relative density profiles that are then normalized at 45 km to an empirical model, in this case the MSISe00 model. Despite this normalization, significant differences are found …

Seasonal Variations Of The Gravity Wave Momentum Flux In The Antarctic Mesosphere And Lower Thermosphere, P. J. Espy, G. O.L. Jones, G. R. Swenson, J. Tang, Michael J. Taylor

All Physics Faculty Publications

Airglow imager and dynasonde/imaging Doppler interferometer (IDI) radar wind measurements at Halley Station, Antarctica (75.6S, 26.6W) have been used to estimate the seasonal variation of the vertical fluxes of horizontal momentum carried by highfrequency atmospheric gravity waves. The cross-correlation coefficients between the vertical and horizontal wind perturbations were calculated from sodium (Na) airglow imager data collected during the austral winter seasons of 2000 and 2001. These were combined with wind velocity variances from coincident radar measurements to estimate the daily averaged upper limit of the vertical flux of horizontal momentum due to gravity waves. The resulting momentum flux at the …

The Spectra Of Type Ii Cepheids. Iii. The Hα Line And Helium Emission In Long-Period Stars, Edward G. Schmidt, Dale Johnston, Kevin M. Lee, Shawn Langan, Peter R. Newman, Stephanie A. Snedden

Department of Physics and Astronomy: Faculty Publications

We have obtained Hα profiles from 175 spectra of 37 Cepheids with periods longer than 8 days. About two-thirds of the stars are likely type II Cepheids. In contrast to the situation among short-period stars, the velocity of Hα relative to the metal-line spectrum is not a useful parameter for distinguishing type I and type II Cepheids. On the other hand, at periods longer than 11 days and shorter than 34 days strong emission is observed in many stars and appears to be a good discriminator of type. On this basis we identify one probable type I Cepheid at a …

Spatial Distribution Of Competing Ions Around Dna In Solution, Kurt Andresen, R. Das, Hye Yoon Park, H. Smith, Lisa W. Kwok, Jessica S. Lamb, E. J. Kirkland, D. Herschlag, K. D. Finkelstein, Lois Pollack

Physics and Astronomy Faculty Publications

The competition of monovalent and divalent cations for proximity to negatively charged DNA is of biological importance and can provide strong constraints for theoretical treatments of polyelectrolytes. Resonant x-ray scattering experiments have allowed us to monitor the number and distribution of each cation in a mixed ion cloud around DNA. These measurements provide experimental evidence to support a general theoretical prediction: the normalized distribution of each ion around polyelectrolytes remains constant when ions are mixed at different ratios. In addition, the amplitudes of the scattering signals throughout the competition provide a measurement of the surface concentration parameter that predicts the …

Vertical Nanowire Light-Emitting Diode, Rolf Könenkamp, Robert Campbell Word, C. Schlegel

Physics Faculty Publications and Presentations

We report room-temperature, white-color electroluminescence in vertically oriented ZnO nanowires. Excitonic luminescence around 380 nm is observed as a shoulder on a broader defect-related band covering all of the visible range and centered at 620 nm. The ZnO nanowires are grown in a low-temperature process on SnO₂-coated glass substrates, employing a technique that is suitable for large-area applications. The nanowires are robustly encapsulated in a thin polystyrene film deposited from high-molecular-weight solutions. Electron injection occurs through the transparent SnO₂ layer, while hole injection is mediated by a p-doped polymer and an evaporated Au contact. Stable device operation …

Laboratory Experiments Of Entrainment In Dry Convective Boundary Layers, Harm J.J. Jonker, Thijs Heus, Esther Hagen, Han Van Dop

Physics Faculty Publications

Entrainment in dry convective boundary layers was studied. A saline convection tank set-up was used as a laboratory model for a dry convective atmospheric boundary layer. The entrainment flux was measured using planar laser induced fluorescence (PLIF). It was found that the entrainment flux reveals a much stronger dependence on the inversion strength than large eddy simulations tend to do.

Relativistic And Radiative Corrections To The Mollow Spectrum, Jorg Evers, Ulrich D. Jentschura, Christoph H. Keitel

Physics Faculty Research & Creative Works

The incoherent inelastic part of the resonance fluorescence spectrum of a laser-driven atom is known as the Mollow spectrum [B. R. Mollow, Phys. Rev. 188, 1969 (1969)]. Starting from this level of description, we discuss theoretical foundations of high-precision spectroscopy using the resonance fluorescence light of strongly laser-driven atoms. Specifically, we evaluate the leading relativistic and radiative corrections to the Mollow spectrum, up to the relative orders of ( Z α )² and α ( Z α )² , respectively, and Bloch-Siegert shifts as well as stimulated radiative corrections involving off-resonant virtual states. Complete results are provided for …

Multiple Ionization Of Ne By H2⁺ Ions With Correlated Projectile Electron Loss, M. M. Sant'anna, H. Luna, Antonio C. Santos, C. Mcgrath, M. B. Shah, E. G. Cavalcanti, G. M. Sigaud, E. C. Montenegro

Physics Faculty Research & Creative Works

We consider multiple ionization of Ne by fast H²⁺, with and without projectile electron loss. Measurements of the total cross section for the direct ionization channel support the similarity of ionization of Ne by an H²⁺ projectile that does not break and Ne ionization by an equi-velocity proton. the multiple target ionization with projectile electron loss is analyzed within a proposed model, adapted from the independent particle model, taking into account post-collisional decay channels following the ionization of Ne 2s electrons. We point out that, for the H²⁺ + Ne collision system, the post-collisional decay channels …