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Articles 1 - 13 of 13
Full-Text Articles in Physical Sciences and Mathematics
Isotope Shifts In Francium Isotopes Fr206-213 And Fr-221, R. Collister, G. Gwinner, M. Tandecki, Seth Aubin
Isotope Shifts In Francium Isotopes Fr206-213 And Fr-221, R. Collister, G. Gwinner, M. Tandecki, Seth Aubin
Arts & Sciences Articles
We present the isotope shifts of the 7s(1/2) to 7p(1/2) transition for francium isotopes Fr206-213 with reference to Fr-221 collected from two experimental periods. The shifts are measured on a sample of atoms prepared within a magneto-optical trap by a fast sweep of radio-frequency sidebands applied to a carrier laser. King plot analysis, which includes literature values for 7s(1/2) to 7p(3/2) isotope shifts, provides a field shift constant ratio of 1.0520(10) and a difference between the specific mass shift constants of 170(100) GHz amu between the D-1 and D-2 transitions, of sufficient precision to differentiate between ab initio calculations.
Matter, Energy, And Heat Transfer In A Classical Ballistic Atom Pump, Tommy A. Byrd, Kunal K. Das, Kevin Mitchell, Seth Aubin, John B. Delos
Matter, Energy, And Heat Transfer In A Classical Ballistic Atom Pump, Tommy A. Byrd, Kunal K. Das, Kevin Mitchell, Seth Aubin, John B. Delos
Arts & Sciences Articles
A ballistic atom pump is a system containing two reservoirs of neutral atoms or molecules and a junction connecting them containing a localized time-varying potential. Atoms move through the pump as independent particles. Under certain conditions, these pumps can create net transport of atoms from one reservoir to the other. While such systems are sometimes called “quantum pumps,” they are also models of classical chaotic transport, and their quantum behavior cannot be understood without study of the corresponding classical behavior. Here we examine classically such a pump's effect on energy and temperature in the reservoirs, in addition to net particle …
Ballistic Atom Pumps, Megan K. Ivory, Tommy A. Byrd, Andrew J. Pyle, Et Al., John B. Delos
Ballistic Atom Pumps, Megan K. Ivory, Tommy A. Byrd, Andrew J. Pyle, Et Al., John B. Delos
Arts & Sciences Articles
We examine a classically chaotic system consisting of two reservoirs of particles connected by a channel containing oscillating potential-energy barriers. We investigate whether such a system can preferentially pump particles from one reservoir to the other, a process often called “quantum pumping.” We show how to make a “particle diode” which under specified conditions permits net particle pumping in only one direction. Then we examine systems having symmetric barriers. We find that if all initial particle energies are considered, a system with symmetric barriers cannot preferentially pump particles. However, if only finite initial energy bands are considered, the system can …
The Influence Of Ca2+ Buffers On Free [Ca2+] Fluctuations And The Effective Volume Of Ca2+ Microdomains, Seth H. Weinberg, Gregory D. Smith
The Influence Of Ca2+ Buffers On Free [Ca2+] Fluctuations And The Effective Volume Of Ca2+ Microdomains, Seth H. Weinberg, Gregory D. Smith
Arts & Sciences Articles
Intracellular calcium (Ca2+) plays a significant role in many cell signaling pathways, some of which are localized to spatially restricted microdomains. Ca2+ binding proteins (Ca2+ buffers) play an important role in regulating Ca2+ concentration ([Ca2+]). Buffers typically slow [Ca2+] temporal dynamics and increase the effective volume of Ca2+ domains. Because fluctuations in [Oa(2+)] decrease in proportion to the square-root of a domain's physical volume, one might conjecture that buffers decrease [Ca2+] fluctuations and, consequently, mitigate the significance of small domain volume concerning Ca2+ signaling. We test this hypothesis through mathematical and computational analysis of idealized buffer-containing domains and their stochastic …
Symbolic Arma Model Analysis, Keith H. Webb, Lawrence Leemis
Symbolic Arma Model Analysis, Keith H. Webb, Lawrence Leemis
Arts & Sciences Articles
ARMA models provide a parsimonious and flexible mechanism for modeling the evolution of a time series. Some useful measures of these models (e.g., the autocorrelation function or the spectral density function) are tedious to compute by hand. This paper uses a computer algebra system, not simulation, to calculate measures of interest associated with ARMA models.
Early Results From The Qweak Experiment, D. Androic, David S. Armstrong, A. Asaturyan, Todd Averett
Early Results From The Qweak Experiment, D. Androic, David S. Armstrong, A. Asaturyan, Todd Averett
Arts & Sciences Articles
A subset of results from the recently completed Jefferson Lab Qweak experiment are reported. This experiment, sensitive to physics beyond the Standard Model, exploits the small parity-violating asymmetry in elastic ~ep scattering to provide the first determination of the proton’s weak charge Q p w. The experiment employed a 180 µA longitudinally polarized 1.16 GeV electron beam on a 35 cm long liquid hydrogen target. Scattered electrons in the angular range 6◦ < θ < 12◦ corresponding to Q2 = 0.025 GeV2 were detected in eight Cerenkov detectors arrayed symmetrically around the beam axis. The goals of the experiment were to provide a measure of Q p w to 4.2% (combined statistical and systematic error), which implies a measure of sin2 (θw) at the level of 0.3%, and to help constrain the vector weak quark charges C1u and C1d. The experimental method is described, with particular focus on the challenges associated with the world’s highest power LH2 target. The new constraints on C1u and C1d provided by the subset of the experiment’s data analyzed to date will also be shown, together with the extracted weak charge of the neutron.
Topological Analysis Of Chaotic Transport Through A Ballistic Atom Pump, Tommy A. Byrd, John B. Delos
Topological Analysis Of Chaotic Transport Through A Ballistic Atom Pump, Tommy A. Byrd, John B. Delos
Arts & Sciences Articles
We examine a system consisting of two reservoirs of particles connected by a channel. In the channel are two oscillating repulsive potential-energy barriers. It is known that such a system can transport particles from one reservoir to the other, even when the chemical potentials in the reservoirs are equal. We use computations and the theory of chaotic transport to study this system. Chaotic transport is described by passage around or through a heteroclinic tangle. Topological properties of the tangle are described using a generalization of homotopic lobe dynamics, which is a theory that gives some properties of intermediate-time behavior from …
Amine- And Sulfide-Sensing Copper(I) Iodide Films, James P. Killarney, Meaghan Mckinnon, Caitlin Murphy, Et Al., Robert D. Pike
Amine- And Sulfide-Sensing Copper(I) Iodide Films, James P. Killarney, Meaghan Mckinnon, Caitlin Murphy, Et Al., Robert D. Pike
Arts & Sciences Articles
Copper(I) iodide films were cast onto glass from solution. The CuI films absorb vapor-phase amine and sulfide molecules, producing a range of photoluminescent emission colors. Spectroscopic data suggest the presence of low energy CuI cluster-centered transitions.
Structure, Dynamics, And Photophysics In The Copper(I) Iodide–Tetrahydrothiophene System, Kylie M. Henline, Charles Wang, Robert D. Pike, John C. Ahern, Et Al.
Structure, Dynamics, And Photophysics In The Copper(I) Iodide–Tetrahydrothiophene System, Kylie M. Henline, Charles Wang, Robert D. Pike, John C. Ahern, Et Al.
Arts & Sciences Articles
Combination of CuI and tetrahydrothiophene (THT) in MeCN or neat THT produces various phases, depending upon experimental conditions. Green luminescent product (CuI)4(THT)2 (1) consists of Cu4I4 cubane units knit into a 3-D network by μ2-THT ligands. Dull yellow luminescent (CuI)10(THT)7(MeCN) (2) contains {[Cu4I4(THT)](μ2-THT)2(Cu2I2)(μ2-THT)2[Cu4I4(NCMe)]} “rungs” linked into 1-D ladders by pairs of μ2-THT ligands. Two molecular (CuI)4(THT)4 phases were found: orange luminescent 3a and yellow luminescent 3b. Triclinic 3b is the more stable phase at 25 °C, but it undergoes endothermic transformation to monoclinic 3a at 38 °C. Compound 3a transforms to a triclinic phase (3a′) that retains orange emission at …
Photodetachment Near A Repulsive Center: Closed-Orbit Theory For The Total Cross Section, B. C. Yang, John B. Delos, M. L. Du
Photodetachment Near A Repulsive Center: Closed-Orbit Theory For The Total Cross Section, B. C. Yang, John B. Delos, M. L. Du
Arts & Sciences Articles
The total photodetachment cross section of a negative ion near a repulsive center is studied based on the closed-orbit theory. An analytical expression, written as a product of the zero-field photodetachment cross section and a modulation function, is obtained for energy above and below threshold. The expression also incorporates the different wave sources produced by different negative ions. The present results are shown to be accurate by comparing with quantum calculations based on the exact Coulomb Green's function. We also compared the photodetachment cross section near a repulsive center with that in a homogeneous electric field and found interesting connections …
Buffer- And Diffusion-Mediated Calcium Concentration Fluctuations Accelerate The Stochastic Dynamics Of Calcium-Triggered Events, Seth H. Weinberg, Gregory D. Smith
Buffer- And Diffusion-Mediated Calcium Concentration Fluctuations Accelerate The Stochastic Dynamics Of Calcium-Triggered Events, Seth H. Weinberg, Gregory D. Smith
Arts & Sciences Articles
No abstract provided.
Dynamical Monodromy, C. Chen, Megan K. Ivory, Seth Aubin, John B. Delos
Dynamical Monodromy, C. Chen, Megan K. Ivory, Seth Aubin, John B. Delos
Arts & Sciences Articles
Integrable Hamiltonian systems are said to display nontrivial monodromy if fundamental action-angle loops defined on phase-space tori change their topological structure when the system is carried around a circuit. In an earlier paper it was shown that this topological change can occur as a result of time evolution under certain rather abstract flows in phase space. In the present paper, we show that the same topological change can occur as a result of application of ordinary forces. We also show how this dynamical phenomenon could be observed experimentally in classical or in quantum systems.
Copper(I) Cyanide Networks With 1-Phenylpiperazine, Robert D. Pike, Thomas M. Dziura, Jordan C. Debutts, Courtney A. Murray, Et Al.
Copper(I) Cyanide Networks With 1-Phenylpiperazine, Robert D. Pike, Thomas M. Dziura, Jordan C. Debutts, Courtney A. Murray, Et Al.
Arts & Sciences Articles
Aqueous reactions of copper(I) cyanide with 1-phenylpiperazine (PhPip) in the presence of KCN produce network compounds having CuCN:PhPip stoichiometries of 1:1, 3:2, and 4:1 depending on the mixing ratio used. In addition to these phases, hydrothermal synthesis yields a 5:3 network. Crystal structures of these four compounds are reported herein. The (CuCN)(PhPip) network (1) forms sheets consisting of Cu centers that coordinate all PhPip via NH only, and are linked together by μ3-cyano bridges. The (CuCN)3(PhPip)2 network (2) exists as a series of dual-chain ladders. All Cu centers are 3-coordinate and half of the PhPip ligands bridge pairs of chains …