Physics Commons^™

Testing Diagnostics Of Nuclear Activity And Star Formation In Galaxies At Z > 1, Jonathan R. Trump, Nicholas P. Konidaris, Guillermo Barro, David C. Koo, Dale D. Kocevski, Stéphanie Juneau, Benjamin J. Weiner, S. M. Faber, Ian S. Mclean, Renbin Yan, Pablo G. Pérez-González, Victor Villar

Physics and Astronomy Faculty Publications

We present some of the first science data with the new Keck/MOSFIRE instrument to test the effectiveness of different AGN/SF diagnostics at z ~ 1.5. MOSFIRE spectra were obtained in three H-band multi-slit masks in the GOODS-S field, resulting in 2 hr exposures of 36 emission-line galaxies. We compare X-ray data with the traditional emission-line ratio diagnostics and the alternative mass-excitation and color-excitation diagrams, combining new MOSFIRE infrared data with previous HST/WFC3 infrared spectra (from the 3D-HST survey) and multiwavelength photometry. We demonstrate that a high [O III]/Hβ ratio is insufficient as an active galactic nucleus (AGN) indicator …

The Central Molecular Gas Structure In Liners With Low-Luminosity Active Galactic Nuclei: Evidence For Gradual Disappearance Of The Torus, F. Müller-Sánchez, M. A. Prieto, M. Mezcua, R. I. Davies, M. A. Malkan, Moshe Elitzur

Physics and Astronomy Faculty Publications

We present observations of the molecular gas in the nuclear environment of three prototypical low-luminosity active galactic nuclei (LLAGNs), based on VLT/SINFONI AO-assisted integral-field spectroscopy of H₂ 1-0 S(1) emission at angular resolutions of ~0.''17. On scales of 50-150 pc, the spatial distribution and kinematics of the molecular gas are consistent with a rotating thin disk, where the ratio of rotation (V) to dispersion (σ) exceeds unity. However, in the central 50 pc, the observations reveal a geometrically and optically thick structure of molecular gas (V/σ < 1 and N _H > 10²³ cm^{–2 …}

Transforming Fabry-Pérot Resonances Into A Tamm Mode, Maxim Durach, Anastasia Rusina

Department of Physics and Astronomy Faculty Publications

We propose an optical structure composed of two metal nanolayers enclosing a distributed Bragg reflector (DBR) mirror. The structure is an open photonic system whose bound modes are coupled to external radiation. We apply the special theoretical treatment based on inversion symmetry of the structure to classify its resonances. We show that the structure supports resonances transitional between Fabry-Pérot modes and Tamm plasmons. When the dielectric contrast of the DBR is removed these modes are a pair of conventional Fabry-Pérot resonances. They spectrally merge into a Tamm mode at high contrast. The optical properties of the structure in the frequency …

Measures Of Centrality Based On The Spectrum Of The Laplacian, Scott D. Pauls, Daniel Remondini

Dartmouth Scholarship

We introduce a family of new centralities, the k-spectral centralities. k-Spectral centrality is a measurement of importance with respect to the deformation of the graph Laplacian associated with the graph. Due to this connection, k-spectral centralities have various interpretations in terms of spectrally determined information.

We explore this centrality in the context of several examples. While for sparse unweighted net- works 1-spectral centrality behaves similarly to other standard centralities, for dense weighted net- works they show different properties. In summary, the k-spectral centralities provide a novel and useful measurement of relevance (for single network elements as well as whole subnetworks) …

Ferroelectric Instability Under Screened Coulomb Interactions, Yong Wang, Xiaohui Liu, John D. Burton, Sitaram S. Jaswal, Evgeny Y. Tsymbal

Evgeny Tsymbal Publications

We explore the effect of charge carrier doping on ferroelectricity using density functional calculations and phenomenological modeling. By considering a prototypical ferroelectric material, BaTiO₃, we demonstrate that ferroelectric displacements are sustained up to the critical concentration of 0.11 electron per unit cell volume. This result is consistent with experimental observations and reveals that the ferroelectric phase and conductivity can coexist. Our investigations show that the ferroelectric instability requires only a short-range portion of the Coulomb force with an interaction range of the order of the lattice constant. These results provide a new insight into the origin of ferroelectricity …

Changes In Thermospheric Temperature Induced By High-Speed Solar Wind Streams, Larry Gardner, Jan Josef Sojka, Robert W. Schunk, Rod Heelis

All Physics Faculty Publications

During high-speed stream (HSS) events the solar wind speed increases, and the cross polar cap potential increases, leading to increased Joule heating at high latitudes. The heat input at high latitudes heats the polar regions, which then conducts to lower latitudes, producing global heating. The heating occurs during the risetime of the cross polar cap potential and throughout the period of high cross polar cap potential as seen in our simulation. These simulations are performed using the Utah State University global thermosphere model driven by Joule heating rates that are consistent with electric fields observed by DMSP-15 observations of HSS …

Unresolved Question Of The 10he Ground State Resonance, Z. Kohley, J. Snyder, T. Baumann, G. Christian, P.A. Deyoung, J.E. Finck, R.A. Haring-Kaye, M. Jones, E. Lunderberg, B. Luther, S. Mosby, A. Simon, J.K. Smith, A. Spyrou, Sharon L. Stephenson, M. Thoennessen

Physics and Astronomy Faculty Publications

The group state of ¹⁰He was populated using a 2p2n-removal from a 59 MeV/u ¹⁴Be beam. The decay energy of the three body system, 8He + n + n, was measured and a resonance was observed at E = 1.60(25) MeV with a 1.8(4) MeV width. This result is in agreement with previous invariant mass spectroscopy measurements, using the ¹¹Li(-p) reaction, but is consistent with recent transfer reaction results. The proposed explanation that the difference, about 500 keV, is due to the effect of the extended halo nature of ¹¹Li in the one-proton knockout reaction is …

Spectroscopy Of 88Y By The (P,Dγ) Reaction, T. J. Ross, C. W. Beausang, R. O. Hughes, N. D. Scielzo, J. T. Burke, J. M. Allmond, C. Angell, M. S. Basunia, D. L. Bleuel, R. J. Casperson, J. Escher, P. Fallon, R. Hatarik, J. Munson, S. Paschalis, M. Petri, L. Phair, J. J. Ressler

Physics Faculty Publications

Low-spin, high-excitation energy states in ⁸⁸Y have been studied using the ⁸⁹Y(p,dγ) reaction. For this experiment a 25 MeV proton beam was incident upon a monoisotopic ⁸⁹Y target. A silicon telescope array was used to detect deuterons, and coincident γ rays were detected using a germanium clover array. Most of the known low-excitation-energy low-spin states populated strongly via the (p,d) reaction mechanism are confirmed. Two states are seen for the first time and seven new transitions, including one which bypasses the two low-lying isomeric states, are observed.

Weak Values Are Universal In Von Neumann Measurements, Justin Dressel, Andrew N. Jordan

Mathematics, Physics, and Computer Science Faculty Articles and Research

We refute the widely held belief that the quantum weak value necessarily pertains to weak measurements. To accomplish this, we use the transverse position of a beam as the detector for the conditioned von Neumann measurement of a system observable. For any coupling strength, any initial states, and any choice of conditioning, the averages of the detector position and momentum are completely described by the real parts of three generalized weak values in the joint Hilbert space. Higher-order detector moments also have similar weak value expansions. Using the Wigner distribution of the initial detector state, we find compact expressions for …

Calipso Observations Of Transatlantic Dust: Vertical Stratification And Effect Of Clouds, W. Yang, A. Marshak, T. Varnai, O. V. Kalashnikova, A. Kostinski

Department of Physics Publications

We use CALIOP nighttime measurements of lidar backscatter, color and depolarization ratios, as well as particulate retrievals during the summer of 2007 to study transatlantic dust properties downwind of Saharan sources, and to examine the influence of nearby clouds on dust. Our analysis suggests that (1) under clear skies, while lidar backscatter and color ratio do not change much with altitude and longitude in the Saharan Air Layer (SAL), depolarization ratio increases with altitude and decreases westward in the SAL; (2) the vertical lapse rate of dust depolarization ratio, introduced here, increases within SAL as plumes move westward; (3) nearby …

First Temperature Observations With The Usu Very Large Rayleigh Lidar: An Examination Of Mesopause Temperatures, Leda Sox, Vincent B. Wickwar, Joshua P. Herron, Marcus J. Bingham, Lance W. Petersen, Matthew T. Emerick

Posters

As the impetus for extended observational measurements throughout the middle atmosphere has increased1 , the limits of previous instrumentation need to be pushed. The Rayleigh lidar group at the Atmospheric Lidar Observatory (ALO) at Utah State University has pushed such limits on existing Rayleigh scatter lidar technology and, through major upgrades to the previous lidar system, has been able to gather temperature measurements in the upper mesosphere and lower thermosphere from approximately 70P109 km. A data campaign with the new system was conducted around the annual temperature minimum, centered on late June 2012, in this region. The temperatures from this …

Multiple Peaks In Saber Mesospheric Oh Emission Altitude Profiles, Jordan Rozum, Gene A. Ware, Doran J. Baker, Martin G. Wlynczak, James M. Russell

Browse All Undergraduate research

No abstract provided.

Lunar Radiation Environment And Space Weathering From The Cosmic Ray Telescope For The Effects Of Radiation (Crater), Nathan A. Schwadron, T. Baker, B. Blake, A. W. Case, J. F. Cooper, M. Golightly, Andrew P. Jordan, Colin J. Joyce, J. Kasper, K. Kozarev, J. Mislinski, J. Mazur, Harlan E. Spence

Physics & Astronomy

[1] The Cosmic Ray Telescope for the Effects of Radiation (CRaTER) measures linear energy transfer by Galactic Cosmic Rays (GCRs) and Solar Energetic Particles (SEPs) on the Lunar Reconnaissance Orbiter (LRO) Mission in a circular, polar lunar orbit. GCR fluxes remain at the highest levels ever observed during the space age. One of the largest SEP events observed by CRaTER during the LRO mission occurred on June 7, 2011. We compare model predictions by the Earth-Moon-Mars Radiation Environment Module (EMMREM) for both dose rates from GCRs and SEPs during this event with results from CRaTER. We find agreement between these …

Jitter Impact On Clock Distribution In Lhc Experiments, S. Baron, Themis Mastoridis, J. Troska, P. Baudrenghien

Physics

The LHC Bunch Clock is one of the most important accelerator signals delivered to the experiments. Being directly derived from the Radio Frequency driving the beams in the accelerator by a simple division of its frequency by a factor of 10, the Bunch Clock signal represents the frequency at which the bunches are crossing each other at each experiment. It is thus used to synchronize all the electronics systems in charge of event detection. Its frequency is around 40.079 MHz, but varies with beam parameters (energy, particle type, etc) by a few hundreds of Hz. The present paper discusses the …

Swift Follow-Up Observations Of Candidate Gravitational-Wave Transient Events, P. A. Evans, J. K. Fridriksson, N. Gehrels, J. Homan, J. P. Osborne, M. Siegel, A. Beardmore, P. Handbauer, J. Gelbord, J. A. Kennea, M. Smith, Q. Zhu, J. Aasi, J. Abadie, B. P. Abbott, R. Abbott, T. D. Abbott, M. Abernathy, T. Accadia, F. Acernese, C. Adams, T. Adams, P. Addesso, R. Adhikari, C. Affeldt, M. Agathos, K. Agatsuma, P. Ajith, B. Allen, A. Allocca, Marc Favata, Shaon Ghosh

Department of Physics and Astronomy Faculty Scholarship and Creative Works

We present the first multi-wavelength follow-up observations of two candidate gravitational-wave (GW) transient events recorded by LIGO and Virgo in their 2009-2010 science run. The events were selected with low latency by the network of GW detectors (within less than 10 minutes) and their candidate sky locations were observed by the Swift observatory (within 12 hr). Image transient detection was used to analyze the collected electromagnetic data, which were found to be consistent with background. Off-line analysis of the GW data alone has also established that the selected GW events show no evidence of an astrophysical origin; one of them …

Microfluidic Experiments Reveal That Antifreeze Proteins Bound To Ice Crystals Suffice To Prevent Their Growth, Yeliz Celik, Ran Drori, Natalya Pertaya-Braun, Aysun Altan, Tyler Barton, Maya Bar-Dolev, Alex Groisman, Peter L. Davies, Ido Braslavsky

Physics Faculty Research

Antifreeze proteins (AFPs) are a subset of ice-binding proteins that control ice crystal growth. They have potential for the cryopreservation of cells, tissues, and organs, as well as for production and storage of food and protection of crops from frost. However, the detailed mechanism of action of AFPs is still unclear. Specifically, there is controversy regarding reversibility of binding of AFPs to crystal surfaces. The experimentally observed dependence of activity of AFPs on their concentration in solution appears to indicate that the binding is reversible. Here, by a series of experiments in temperature-controlled microfluidic devices, where the medium surrounding ice …

Logistic Curves, Extraction Costs And Peak Oil, Robert J. Brecha

Physics Faculty Publications

Debates about the possibility of a near-term maximum in world oil production have become increasingly prominent over the past decade, with the focus often being on the quantification of geologically available and technologically recoverable amounts of oil in the ground. Economically, the important parameter is not a physical limit to resources in the ground, but whether market price signals and costs of extraction will indicate the efficiency of extracting conventional or nonconventional resources as opposed to making substitutions over time for other fuels and technologies. We present a hybrid approach to the peak-oil question with two models in which the …

Protein Nano-Object Integrator (Pronoi) For Generating Atomic Style Objects For Molecular Modeling, Nicholas Smith, Brandon Campbell, Lin Li, Chuan Li, Emil Alexov

Publications

Background

With the progress of nanotechnology, one frequently has to model biological macromolecules simultaneously with nano-objects. However, the atomic structures of the nano objects are typically not available or they are solid state entities. Because of that, the researchers have to investigate such nano systems by generating models of the nano objects in a manner that the existing software be able to carry the simulations. In addition, it should allow generating composite objects with complex shape by combining basic geometrical figures and embedding biological macromolecules within the system.

Results

Here we report the Protein Nano-Object Integrator (ProNOI) which allows for …

The First Cosmic Ray Albedo Proton Map Of The Moon, Jody K. Wilson, Harlan E. Spence, Justin Kasper, Michael Golightly, J. B. Blake, J. E. Mazur, L. W. Townsend, A. W. Case, M. D. Looper, C. Zeitlin, Nathan A. Schwadron

Physics & Astronomy

[1] Neutrons emitted from the Moon are produced by the impact of galactic cosmic rays (GCRs) within the regolith. GCRs are high-energy particles capable of smashing atomic nuclei in the lunar regolith and producing a shower of energetic protons, neutrons and other subatomic particles. Secondary particles that are ejected out of the regolith become “albedo” particles. The neutron albedo has been used to study the hydrogen content of the lunar regolith, which motivates our study of albedo protons. In principle, the albedo protons should vary as a function of the input GCR source and possibly as a result of surface …

Saturation-Dependence Of Dispersion In Porous Media, B. Ghanbarian-Alavijeh, Thomas E. Skinner, Allen Hunt

Physics Faculty Publications

In this study, we develop a saturation-dependent treatment of dispersion in porous media using concepts from critical path analysis, cluster statistics of percolation, and fractal scaling of percolation clusters. We calculate spatial solute distributions as a function of time and calculate arrival time distributions as a function of system size. Our previous results correctly predict the range of observed dispersivity values over ten orders of magnitude in experimental length scale, but that theory contains no explicit dependence on porosity or relative saturation. This omission complicates comparisons with experimental results for dispersion, which are often conducted at saturation less than 1. …

Nnll Resummation For W-Boson Production At Large Pt, Nikolaos Kidonakis, Richard J. Gonsalves

Faculty and Research Publications

We present new results for W-boson production at large transverse momentum at the LHC and the Tevatron. The contribution of soft-gluon corrections is derived from NNLL resummation and added to the exact NLO result. Numerical results and their uncertainties for the approximate NNLO W-boson transverse momentum distributions are derived and compared to recent data from the LHC.

Clustering Of Sloan Digital Sky Survey Iii Photometric Luminous Galaxies: The Measurement, Systematics, And Cosmological Implications, Shirley Ho, Antonio J. Cuesta, Hee-Jong Seo, Roland De Putter, Ashley J. Ross, Martin White, Nikhil Padmanabhan, Shun Saito, For Full List Of Authors, See Publisher's Website.

Physics Faculty Research & Creative Works

The Sloan Digital Sky Survey (SDSS) surveyed 14,555 deg², and delivered over a trillion pixels of imaging data. We present a study of galaxy clustering using 900,000 luminous galaxies with photometric redshifts, spanning between z = 0.45 and z = 0.65, constructed from the SDSS using methods described in Ross et al. This data set spans 11,000 deg² and probes a volume of 3 h^-3 Gpc³, making it the largest volume ever used for galaxy clustering measurements. We describe in detail the construction of the survey window function and various systematics affecting our measurement. …

Force-Feedback High-Speed Atomic Force Microscope For Studying Large Biological Systems, Byung I. Kim, Ryan Boehm

Physics Faculty Publications and Presentations

We designed and developed a high-speed atomic force microscope (HSAFM) utilizing a force-feedback scheme for imaging large biological samples. The system collects three simultaneous images: a deflection image, a topographic image, and a force image. We demonstrated that this force-feedback HSAFM is capable of acquiring large topographic images of Escherichia coli biofilms at approximately one frame per second in air. We discuss how the self-actuating cantilever and the piezo tube follow those larger biological topographic features during the HSAFM imaging process.

The Harmonica As A Blues Instrument, Gordon Ramsey, Christopher Banaszak, Joseph Wiseman

Physics: Faculty Publications and Other Works

The modern harmonica,or harp, has been around since the early 19th century. It is typically used in blues, country, rock and roll and folk music. These musical genres are somewhat similar in structure and form, and often borrow ideas from each other. The harmonica is appropriate as a back up to the main vocal melody and instruments due to its rich harmonic structure and subdued intensity. The ability to apply vibrato and gradual slurs make it a perfect instrument to achieve a ``bluesy" sound. Our harp research group has investigated the physical properties of harmonica structure to illustrate how different …

High-Order-Harmonic-Generation Spectroscopy With An Elliptically Polarized Laser Field, M. V. Frolov, N. L. Manakov, T. S. Sarantseva, Anthony F. Starace

Anthony F. Starace Publications

Analytic formulas describing high-order-harmonic generation (HHG) by atoms in an intense laser field with small ellipticity are obtained quantum mechanically in the tunneling limit. The results show that factorization of the HHG yield in terms of an electron wave packet and the photorecombination cross section (PRCS) is valid only for s states of a bound atomic electron, whereas the HHG yield for p states involves two different atomic parameters. For the latter case, elliptic HHG spectroscopy enables one to retrieve both the energy and angular dependence of the PRCS of the target atom, as we illustrate for the case of …

Laser-Induced Electron Diffraction For Probing Rare Gas Atoms, Junliang Xu, Cosmin I. Blaga, Anthony D. Dichiara, Emily Sistrunk, Kaikai Zhang, Zhangjin Chen, Anh-Thu Le, Toru Morishita, C. D. Lin, Pierre Agostini, Louis F. Dimauro

Physics Faculty Research & Creative Works

Recently, using midinfrared laser-induced electron diffraction (LIED), snapshots of a vibrating diatomic molecule on a femtosecond time scale have been captured [C.I. Blaga et al., Nature (London) 483, 194 (2012)]. In this Letter, a comprehensive treatment for the atomic LIED response is reported, a critical step in generalizing this imaging method. Electron-ion differential cross sections (DCSs) of rare gas atoms are extracted from measured angular-resolved, high-energy electron momentum distributions generated by intense midinfrared lasers. Following strong-field ionization, the high-energy electrons result from elastic rescattering of a field-driven wave packet with the parent ion. For recollision energies [greater or equal] 100eV, …

Assessment Of Passive Fire Protection On Steel-Girder Bridges, Michael Davidson

Masters Theses & Specialist Projects

Bridges in the US are severely damaged or suffer collapse from fires at significant rates, even when compared to other hazards such as earthquakes. Fire-induced bridge collapses are perpetuated by the general lack of installed fire protection systems. Therefore, new materials and applications are needed to mitigate structural damage that can be caused to civil infrastructure by severe fires. Accordingly, the objective of this study is to further the development of new fire protection applications in transportation structures. Specifically, the investigation centers on the development of new applications in passive fire protection materials, within the context of shielding steel-girder bridges …

Engaging The Community Through An Undergraduate Biomedical Physics Course, Grace Van Ness, Ralf Widenhorn

Physics Faculty Publications and Presentations

We report on the development of an undergraduate biomedical physics course at Portland State University, motivated by both student interest and the desire of the university?s Physics Department to provide an interdisciplinary intermediate-level physics course. The course was developed through the community engagement of physicians, clinical researchers, and basic science researchers. Class meetings were a combination of regular and guest lectures, hands-on exercises, web-based activities, class discussions, and a student poster information session for patrons at a local science museum. The course inspired students to engage in research projects in biomedical physics that enhance their understanding of science and education …

Rounding Of A First-Order Quantum Phase Transition To A Strong-Coupling Critical Point, Fawaz Hrahsheh, Jose A. Hoyos, Thomas Vojta

Physics Faculty Research & Creative Works

We investigate the effects of quenched disorder on first-order quantum phase transitions on the example of the N-color quantum Ashkin-Teller model. By means of a strong-disorder renormalization group, we demonstrate that quenched disorder rounds the first-order quantum phase transition to a continuous one for both weak and strong coupling between the colors. In the strong-coupling case, we find a distinct type of infinite-randomness critical point characterized by additional internal degrees of freedom. We investigate its critical properties in detail and find stronger thermodynamic singularities than in the random transverse field Ising chain. We also discuss the implications for higher spatial …

Ultrafast Laser-Induced Damage And The Influence Of Spectral Effects, Jeremy R. Gulley

Faculty and Research Publications

Numerous studies have investigated the prerequisite role of photoionization in ultrafast laser-induced damage (LID) of bulk dielectrics. This study examines the role of spectral width and instantaneous laser frequency in LID using a frequency dependent multiphoton ionization (MPI) model and numerical simulation of initially 800 nm laser pulses propagating through fused silica. Assuming a band gap of 9 eV, MPI by an 800 nm field is a six-photon process, but when the instantaneous wavelength is greater than 827 nm an additional photon is required for photoionization, reducing the probability of the event by many orders of magnitude. Simulation results suggest …