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Upper Limits On A Possible Gluon Mass, Shmuel Nussinov, Robert Shrock 2010 Chapman University

Upper Limits On A Possible Gluon Mass, Shmuel Nussinov, Robert Shrock

Mathematics, Physics, and Computer Science Faculty Articles and Research

We analyze upper limits on a possible gluon mass, mg. We first discuss various ways to modify quantum chromodynamics to include m(g) not equal 0, including a bare mass, a Higgs mechanism, and dynamical breaking of color SU(3)(c). From an examination of experimental data, we infer an upper limit m(g) < O(1) MeV. As part of our analysis, we show that a claim, hitherto unrefuted in the literature, of a much stronger upper limit on m(g), is invalid. We discuss subtleties in interpreting gluon mass limits in view of the fact that at scales below Lambda(QCD), quantum chromodynamics is strongly coupled, perturbation theory is not reliable, and the physics is not accurately described in terms of the Lagrangian degrees of freedom, including gluons. We also point out a fundamental difference in the behavior of quantum chromodynamics with a nonzero gluon mass and a weakly coupled gauge theory with a gauge boson mass.


Modeling Decision Making Related To Incident Delays During Hurricane Evacuations, Robert Michael Robinson 2010 Old Dominion University

Modeling Decision Making Related To Incident Delays During Hurricane Evacuations, Robert Michael Robinson

Computational Modeling and Simulation Engineering Theses & Dissertations

Successful evacuations from metropolitan areas require optimizing the transportation network, monitoring conditions, and adapting to changes. Evacuation plans seek to maximize the city's ability to evacuate traffic to flee the endangered region, but once an evacuation begins, real time events degrade even the best plans.

To better understand behavioral responses made during a hurricane evacuation, a survey of potential evacuees obtained data on demographics, driving characteristics, and the traffic information considered prior to and during an evacuation. Analysis showed significant levels of correlation between demographic factors (e.g., gender, age, social class, etc.) and self-assessed driver characteristics, but limited ...


Learning And Engaging The Information Values Of A Karst Community Of Practice., Kaya van Beynen, E S. Fleury 2010 University of South Florida St. Petersburg

Learning And Engaging The Information Values Of A Karst Community Of Practice., Kaya Van Beynen, E S. Fleury

Faculty Publications

The Communities of Practice model is an innovative means to explore a local knowledge community and how informal practitioners contribute to karst science. By exploring the information values, this article strategizes how the Karst Information Portal can promote trust, engagement, and expand the scientific understanding and protection of karst environments.


Low-Temperature Adsorption Of H2s On Ag(111), Selena M. Russell, Da-Jiang Liu, Maki Kawai, Yousoo Kim, Patricia A. Thiel 2010 Iowa State University

Low-Temperature Adsorption Of H2s On Ag(111), Selena M. Russell, Da-Jiang Liu, Maki Kawai, Yousoo Kim, Patricia A. Thiel

Chemistry Publications

H2S forms a rich variety of structures on Ag(111) at low temperature and submonolayer coverage. The molecules decorate step edges, exist as isolated entities on terraces, and aggregate into clusters and islands, under various conditions. One type of island exhibits a (×)R25.3° unit cell. Typically, molecules in the clusters and islands are separated by about 0.4 nm, the same as the S–S separation in crystalline H2S. Density functional theory indicates that hydrogen-bonded clusters contain two types of molecules. One is very similar to an isolated adsorbed H2S molecule, with both ...


Adsorbate-Enhanced Transport Of Metals On Metal Surfaces: Oxygen And Sulfur On Coinage Metals, Patricia A. Thiel, Mingmin Shen, Da-Jiang Liu, James W. Evans 2010 Iowa State University

Adsorbate-Enhanced Transport Of Metals On Metal Surfaces: Oxygen And Sulfur On Coinage Metals, Patricia A. Thiel, Mingmin Shen, Da-Jiang Liu, James W. Evans

Chemistry Publications

Coarsening (i.e., ripening) of single-atom-high, metal homoepitaxial islands provides a useful window on the mechanism and kinetics of mass transport at metal surfaces. This article focuses on this type of coarsening on the surfaces of coinage metals (Cu, Ag, Au), both clean and with an adsorbed chalcogen (O, S) present. For the clean surfaces, three aspects are summarized: (1) the balance between the two major mechanisms—Ostwald ripening (the most commonly anticipated mechanism) and Smoluchowski ripening—and how that balance depends on island size; (2) the nature of the mass transport agents, which are metal adatoms in almost all ...


Variation Of Growth Morphology With Chemical Composition Of Terraces: Ag On A Twofold Surface Of A Decagonal Al-Cu-Co Quasicrystal, T. Duguet, Barış Ünal, Yong Han, James W. Evans, J. Ledieu, Cynthia J. Jenks, J.-M. Dubois, V. Fournée, Patricia A. Thiel 2010 Institut Jean Lamour

Variation Of Growth Morphology With Chemical Composition Of Terraces: Ag On A Twofold Surface Of A Decagonal Al-Cu-Co Quasicrystal, T. Duguet, Barış Ünal, Yong Han, James W. Evans, J. Ledieu, Cynthia J. Jenks, J.-M. Dubois, V. Fournée, Patricia A. Thiel

Chemistry Publications

Growth of Ag thin films on the twofold surface of a decagonal Al-Cu-Co quasicrystal is characterized by scanning tunneling microscopy, at different temperatures, and for coverages ranging from submonolayer to 11 monolayers. From prior work, three types of clean surface terraces are known to exist. By correlation with a bulk structural model, the major difference between them lies in their transition-metal (TM) content, two being aluminum-rich (0 and 15 at. % TM) and one being TM-rich (40–50 at. % TM). The present article focuses on understanding the difference between Ag film morphologies on these terminations, in terms of their chemical content ...


Formation And Coarsening Of Ag(110) Bilayer Islands On Nial(110): Stm Analysis And Atomistic Lattice-Gas Modeling, Yong Han, Barış Ünal, Dapeng Jing, Feili Qin, Cynthia J. Jenks, Da-Jiang Liu, Patricia A. Thiel, James W. Evans 2010 Iowa State University

Formation And Coarsening Of Ag(110) Bilayer Islands On Nial(110): Stm Analysis And Atomistic Lattice-Gas Modeling, Yong Han, Barış Ünal, Dapeng Jing, Feili Qin, Cynthia J. Jenks, Da-Jiang Liu, Patricia A. Thiel, James W. Evans

Chemistry Publications

Scanning tunneling microscopy analysis of the initial stages of film growth during deposition of Ag on NiAl(110) reveals facile formation of bilayer Ag(110) islands at temperatures of 130 K and above. Annealing subsequent to deposition at 130 K induces coarsening of the bilayer island distribution. The thermodynamic driving force for bilayer island formation reflects a lower relative surface energy for films of even layer thicknesses. This feature derives from quantum size effects due to electron confinement in the Ag film. The kinetics of island formation and relaxation is controlled by terrace and edge-diffusion barriers, detachment barriers, interlayer diffusion ...


Lattice Expansion In Islands Stabilized By Electron Confinement: Ag On Si(111)-7×7, Barış Ünal, Alex Belianinov, Patricia A. Thiel, Michael C. Tringides 2010 Iowa State University

Lattice Expansion In Islands Stabilized By Electron Confinement: Ag On Si(111)-7×7, Barış Ünal, Alex Belianinov, Patricia A. Thiel, Michael C. Tringides

Chemistry Publications

Ag on Si(111)-7×7 was one of the first systems where height selection of metal islands was attributed to electron confinement, i.e., stabilization of selected heights through a quantum size effect (QSE). However, it has been puzzling how the requisite electron standing waves can form, because the Fermi level EF (along the growth [111] direction) is within the gap for bulk Ag. With detailed experiments over a wide coverage and temperature range, we show that a large increase of 12% is present in the interlayer spacing within the bilayer islands. This can shift EF below ...


Islands And Holes As Measures Of Mass Balance In Growth Of The (√3×√3)R30° Phase Of Ag On Si(111), Alex Belianinov, Barış Ünal, Ning Lu, Min Ji, Kai-Ming Ho, Cai-Zhuang Wang, Michael C. Tringides, Patricia A. Thiel 2010 Iowa State University

Islands And Holes As Measures Of Mass Balance In Growth Of The (√3×√3)R30° Phase Of Ag On Si(111), Alex Belianinov, Barış Ünal, Ning Lu, Min Ji, Kai-Ming Ho, Cai-Zhuang Wang, Michael C. Tringides, Patricia A. Thiel

Chemistry Publications

It is well known that conversion of Si(111)-(7×7) into the (√3×√3)R30° phase of adsorbed Ag requires a change in the Si density, and causes formation of islands and holes at the surface. By mass balance, the ratio of areas of islands and holes (RIH) should be approximately 1. However, we find that the ratio is significantly higher, depending on preparation conditions. A possible explanation would be that there are different types of (√3×√3)R30° structures. However, neither scanning tunneling microscopy nor density-functional theory (implemented as a genetic algorithm search) supports this explanation. We ...


Nanoscale “Quantum” Islands On Metal Substrates: Microscopy Studies And Electronic Structure Analyses, Yong Han, Barış Ünal, Dapeng Jing, Patricia A. Thiel, James W. Evans 2010 Iowa State University

Nanoscale “Quantum” Islands On Metal Substrates: Microscopy Studies And Electronic Structure Analyses, Yong Han, Barış Ünal, Dapeng Jing, Patricia A. Thiel, James W. Evans

Chemistry Publications

Confinement of electrons can occur in metal islands or in continuous films grown heteroepitaxially upon a substrate of a different metal or on a metallic alloy. Associated quantum size effects (QSE) can produce a significant height-dependence of the surface free energy for nanoscale thicknesses of up to 10–20 layers. This may suffice to induce height selection during film growth. Scanning STM analysis has revealed remarkable flat-topped or mesa-like island and film morphologies in various systems. We discuss in detail observations of QSE and associated film growth behavior for Pb/Cu(111), Ag/Fe(100), and Cu/fcc-Fe/Cu(100 ...


Periodic Step Arrays On The Aperiodic I-Al-Pd-Mn Quasicrystal Surface At High Temperature, Y. Sato, Barış Ünal, Thomas A. Lograsso, Patricia A. Thiel, A. K. Schmid, T. Duden, N. C. Bartelt, K. F. McCarty 2010 University of California, Davis

Periodic Step Arrays On The Aperiodic I-Al-Pd-Mn Quasicrystal Surface At High Temperature, Y. Sato, Barış Ünal, Thomas A. Lograsso, Patricia A. Thiel, A. K. Schmid, T. Duden, N. C. Bartelt, K. F. Mccarty

Chemistry Publications

We have observed the configuration and motion of surface steps on the aperiodic icosahedral (i-) Al-Pd-Mn quasicrystal using low-energy electron microscopy and scanning tunneling microscopy. As the quasicrystal is cooled from high temperature, bulk vacancies migrate to the surface causing the surface to be etched. Surprisingly, this etching occurs by two types of steps with different heights moving in different directions with different velocities. The steady-state surface morphology is a uniformly spaced rhomboidal step network. This network requires that the layer stacking near the surface deviates from the bulk quasicrystal stacking.


On The Reliability Of Wireless Fingerprinting Using Clock Skews, Chrisil Arackaparambil, Sergey Bratus, Anna Shubina, David Kotz 2010 Dartmouth College

On The Reliability Of Wireless Fingerprinting Using Clock Skews, Chrisil Arackaparambil, Sergey Bratus, Anna Shubina, David Kotz

Open Dartmouth: Faculty Open Access Scholarship

Determining whether a client station should trust an access point is a known problem in wireless security. Traditional approaches to solving this problem resort to cryptography. But cryptographic exchange protocols are complex and therefore induce potential vulnerabilities in themselves. We show that measurement of clock skews of access points in an 802.11 network can be useful in this regard, since it provides fingerprints of the devices. Such fingerprints can be used to establish the first point of trust for client stations wishing to connect to an access point. Fingerprinting can also be used in the detection of fake access ...


Hygroscopic Growth And Deliquescence Of Nacl Nanoparticles Mixed With Surfactant Sds, Christopher W. Harmon, Ronald L. Grimm, Theresa M. McIntire, Mark D. Peterson, Bosiljka Njegic, Vanessa M. Angel, Ahmad Alshawa, Joelle S. Underwood, Douglas J. Tobias, R. Benny Gerber, Mark S. Gordon, John C. Hemminger, Sergey A. Nizkorodov 2010 University of California - Irvine

Hygroscopic Growth And Deliquescence Of Nacl Nanoparticles Mixed With Surfactant Sds, Christopher W. Harmon, Ronald L. Grimm, Theresa M. Mcintire, Mark D. Peterson, Bosiljka Njegic, Vanessa M. Angel, Ahmad Alshawa, Joelle S. Underwood, Douglas J. Tobias, R. Benny Gerber, Mark S. Gordon, John C. Hemminger, Sergey A. Nizkorodov

Chemistry Publications

Several complementary experimental and theoretical methodologies were used to explore water uptake on sodium chloride (NaCl) particles containing varying amounts of sodium dodecyl sulfate (SDS) to elucidate the interaction of water with well-defined, environmentally relevant surfaces. Experiments probed the hygroscopic growth of mixed SDS/NaCl nanoparticles that were generated by electrospraying aqueous 2 g/L solutions containing SDS and NaCl with relative NaCl/SDS weight fractions of 0, 5, 11, 23, or 50 wt/wt %. Particles with mobility-equivalent diameters of 14.0(±0.2) nm were size selected and their hygroscopic growth was monitored by a tandem nano-differential mobility analyzer ...


Open-Shell Formulation Of The Fragment Molecular Orbital Method, Spencer Pruitt, Dmitri G. Fedorov, Kazuo Kitaura, Mark S. Gordon 2010 Iowa State University

Open-Shell Formulation Of The Fragment Molecular Orbital Method, Spencer Pruitt, Dmitri G. Fedorov, Kazuo Kitaura, Mark S. Gordon

Chemistry Publications

Performing accurate calculations on large molecular systems is desirable for closed- and open-shell systems. In this work, the fragment molecular orbital method is extended to open-shell systems and implemented in the GAMESS (General Atomic and Molecular Electronic Structure System) program package. The accuracy of the method is tested, and the ability to reproduce reaction enthalpies is demonstrated. These tests also demonstrate its utility in providing an efficient means to model large open-shell systems.


Aqueous Solvation Of Bihalide Anions, Daniel David Kemp, Mark S. Gordon 2010 Iowa State University

Aqueous Solvation Of Bihalide Anions, Daniel David Kemp, Mark S. Gordon

Chemistry Publications

Second-order Møller−Plesset perturbation theory (MP2) is used to perform geometry optimizations on XHX−·(H2O)n for X = Br, I, with n = 1 to 6 water molecules. Of particular interest is the manner in which the solvent molecules orient themselves around the solute and which configurations are lowest in energy. Although for most values of n, water molecules may donate all of their hydrogen atoms for hydrogen bonding to the solute, this type of structure is the lowest in energy only for n = 0 to 2 and is only a local minimum for n = 3, 4, and 6. For n ...


Book Review Of Quantum Chemistry, 2nd Edition, Thomas Holme 2010 Iowa State University

Book Review Of Quantum Chemistry, 2nd Edition, Thomas Holme

Chemistry Publications

This article presents a review of the second edition of Quantum Chemistry by D.A. McQuarrie.


K23au12sn9—An Intermetallic Compound Containing A Large Gold−Tin Cluster: Synthesis, Structure, And Bonding, Bin Li, Sung-Jin Kim, Gordon J. Miller, John D. Corbett 2010 Iowa State University

K23au12sn9—An Intermetallic Compound Containing A Large Gold−Tin Cluster: Synthesis, Structure, And Bonding, Bin Li, Sung-Jin Kim, Gordon J. Miller, John D. Corbett

Chemistry Publications

A polyanionic unit {Au12Sn9} with a novel “corrugated sheet” shape occurs in K23Au12Sn9. The compound was obtained by fusion of the pure elements in tantalum ampules at high temperatures followed by programmed cooling, and the structure was determined by X-ray diffraction: I4̅2m (No. 121), a = 20.834(3), c = 6.818(1) Å, Z = 2. The large heteroatomic cluster has D2d point symmetry and features a central four bonded (4b-) Sn, eight 3b- or 2b-Sn on the perimeter, and 24 linking nearly linear ...


Euagxal11−X With The Bahg11-Type Structure: Composition, Coloring, And Competition With The Bacd11-Type Structure, Fei Wang, Karen N. Pearson, Warren E. Straszheim, Gordon J. Miller 2010 Iowa State University

Euagxal11−X With The Bahg11-Type Structure: Composition, Coloring, And Competition With The Bacd11-Type Structure, Fei Wang, Karen N. Pearson, Warren E. Straszheim, Gordon J. Miller

Chemistry Publications

EuAgxAl11−x phases adopting the BaHg11-type structure (space group Pmm, Z = 3) were synthesized with high yield by arc melting a mixture loaded as “EuAg3.5Al7.5” and annealing at 500 °C for 40 days. This phase has a very narrow phase width around EuAg4.0Al7.0; and it is unstable at 600 and 700 °C, at which it transforms into other phases. Magnetometry indicates that Eu is divalent, which gives the valence electron concentration per Ag/Al atom as 2.45 e/atom, higher than in ...


Pd2.28(1)Zn10.37(1)Al0.35(1), A Ternary Y-Brass-Type Structure, Srinivasa Thimmaiah, Gordon J. Miller 2010 Iowa State University

Pd2.28(1)Zn10.37(1)Al0.35(1), A Ternary Y-Brass-Type Structure, Srinivasa Thimmaiah, Gordon J. Miller

Chemistry Publications

No abstract provided.


Influence Of Y Substitutions On The Magnetism Of Gd5ge4, Durga Paudyal, Yaroslav Mudryk, Vitalij K. Pecharsky, Sumohan Misra, Gordon J. Miller, Karl A. Gschneidner Jr. 2010 Iowa State University

Influence Of Y Substitutions On The Magnetism Of Gd5ge4, Durga Paudyal, Yaroslav Mudryk, Vitalij K. Pecharsky, Sumohan Misra, Gordon J. Miller, Karl A. Gschneidner Jr.

Chemistry Publications

The interrelation between the specific crystallographic positions and their influence on the magnetism of neighboring atoms is examined from first principles electronic structure calculations using the Gd5Ge4 compound as a model system. The predicted preferences of the specific occupations by nonmagnetic yttrium atoms and the resulting magnetism of substituted Gd5Ge4 have been confirmed, respectively, by single crystal x-ray diffraction and magnetization experiments.


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