UScholar Works
 
Filters: Department: "Physics" Collection: "ir_uspace"
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CreatorTitleDescriptionSubjectDate
1 Vardeny, Zeev ValentineElectrical and optical studies of gap states in self-assembled molecular aggregatesWe fabricated a variety of two-terminal devices using self-assembled monolayers (SAM) of solid-state mixtures comprised of molecular "wires" [1,4-methane-benzenedithiol (Me-BDT)] and molecular insulator "spacers" [1-pentanethiol], which were prepared at various molar concentrations ratio, r of wires...Gap states; Self-assembled molecular aggregates2007
2 Wu, Yong-ShiIdentification of androgen response elements in the insulin-like growth factor I upstream promoterTestosterone stimulates the expression of IGF-I in cells and tissues that include prostate, muscle and muscle satellite cells, and the uterus. Here, the molecular mechanisms of this effect of testosterone were explored. Testosterone increased IGF-I mRNA levels in HepG2 and LNCaP cells and stimulated...IFG-I; Androgen-responsive elements2007
3 Symko, Orest GeorgeMagnetic memory of oil paintingsThe color in oil paints is obtained sometimes from magnetic minerals. This fact implies that oil paintings could present an intrinsic magnetization. Magnetic imaging of an oil painting consists in the measurement of magnetic flux related to the magnetization of the painting. In this report results o...Magnetic memory; Oil paintings; Authentication2007
4 Bromley, Benjamin C.Periodic standing-wave approzimation: post-Minkowski computationsThe periodic standing-wave method studies circular orbits of compact objects coupled to helically symmetric standing-wave gravitational fields. From this solution an approximation is extracted for the strong field, slowly inspiralling motion of black holes and binary stars. Previous work on this m...Black holes; Binary stars; Gravitational waves2007
5 Lupton, John MarkPicosecond time-resolved photoluminescence spectroscopy of a tetracene film on highly oriented pyrolytic graphite: dynamical relaxation, trap emission and superradianceA detailed time resolved investigation of the photoluminescence of a thin tetracene film deposited on highly oriented pyrolytic graphite is presented. In agreement with Lim et al. [Phys. Rev. Lett. 92, 107402 (2004)], we find strong evidence for superradiance: an increase of the relative intensity...Tetracene film; Pyrolytic graphite Photoluminescence spectroscopy; pi-conjugated polymers; Dynamical relaxation; Trap emission; Superradiance2007
6 Vardeny, Zeev ValentineStudies of polymer microring lasers subject to uniaxial stressThe emission spectra of microring lasers fabricated from ∏-conjugated polymer films casted on nylon microfibers with diameters in the range of 35-90 µm were studied upon application of uniaxial stress with strain up to ~12%. The laser emission spectra substantially change with the applied stress,...pi-conjugated polymers; Microring lasers; Uniaxial stress; DOO-PPV2007
7 Williams, Clayton C.Three-dimensional model of single electron tunneling between a conductive probe and a localized electronic state in a dielectricMotivated by recent measurements of force detected single-electron tunneling, we present a three-dimensional model for the tunneling rate between a metallic tip and a localized electronic state in a dielectric surface. The tip is assumed to be semi-infinite, with electron wave functions approximat...STM; Scanning; Tunneling Microscopy; Electron states2007
8 Mishchenko, Eugene; Williams, Clayton C.Three-dimensional model of single-electron tunneling between a conductive probe and a localized electronic state in a dielectricMotivated by recent measurements of force detected single-electron tunneling, we present a three-dimensional model for the tunneling rate between a metallic tip and a localized electronic state in a dielectric surface. The tip is assumed to be semi-infinite, with electron wave functions approximated...Dielectric surface; Tunneling rate2007
9 Vardeny, Zeev ValentineUnidirectional laser emission from ∏-conjugated polymer microcavities with broken symmetryWe report unidirectional laser emission from ∏-conjugated polymer microcavities with broken symmetry geometries such as spiral and microdisk containing a "line defect," in comparison with plain microdisk cavity having isotropic emission. We found that the laser emission directionality contrast ra...pi-conjugated polymers; Unidirectional laser emission; Microcavities; DOO-PPV; Poly(dioctyloxy) phenyl vinylene2007
10 Vardeny, Zeev Valentine; Ehrenfreund, Eitan A.Comment on "Frequency response and origin of the spin-½ photoluminescence-detected magnetic resonance in a ∏-conjugated polymerIn a recent paper, Segal et al. [Phys. Rev. B 71, 245201 (2005)] advanced a new explanation for the dynamics of spin-1/2 photoluminescence-detected magnetic resonance (PLDMR) in films of a rr-conjugated polymer, namely, a soluble derivative of poly(phenylene-vinylene) (MEH-PPV), using a model [dubbe...Photoluminescence-detected magnetic resonance; PLDMR; pi-conjugated polymers; Poly(phenylene-vinylene); MEH-PPV2007-06
11 Mishchenko, EugeneEffect of electron-electron interactions on the conductivity of clean grapheneMinimal conductivity of a single undoped graphene layer is known to be of the order of the conductance quantum, independent of the electron velocity. We show that this universality does not survive electron-electron interaction, which results in nontrivial frequency dependence. We begin with analyzi...Optical conductivity; Perturbation theory2007-05
12 Lupton, John MarkEfficient dipole-dipole coupling of Mott-Wannier and Frenkel excitons in (Ga,In)N quantum well/polyfluorene semiconductor heterostructuresWe investigate interactions between Mott-Wannier (MW) and Frenkel excitons in a family of hybrid structures consisting of thin organic (polyfluorene) films placed in close proximity (systematically adjusted by GaN cap layer thickness) to single inorganic [(Ga, In)N/GaN] quantum wells (QWs). Charac...Mott-Wannier; Frenkel; Excitons; Dipole-dipole coupling; Semiconductor heterostructures2007-07
13 Vardeny, Zeev ValentineExperimental determination of the charge/neutral branching ratio η in the photoexcitation of ∏-conjugated polymers by broadband ultrafast spectroscopyWe demonstrate a long-sought reliable method for determining the important branching ratio η between photogenerated charged polarons and neutral excitons in ∏-conjugated polymer films and solutions, using femtosecond transient photomodulation spectroscopy with broad spectral range from 0.14 to ...pi-conjugated polymers; Charge/neutral branching ratio; Photoexcitation; nu value; Broadband ultrafast spectroscopy2007-02
14 Vardeny, Zeev Valentine; Ehrenfreund, Eitan A.Illumination-induced metastable polaron-supporting state in poly(p-phenylene vinylene) filmsWe found an illumination-induced metastable polaron-supporting state in films of a soluble derivative of poly-p-phenylene vinylene (MEH-PPV). Pristine, nonilluminated MEH-PPV polymer films do not show longlived photogenerated polarons. Prolonged UV illumination, however, is found to induce a revers...Metastable polaron-supporting state; Poly(p-phenylene vinylene); PPV; MEH-PPV; Excitons2007-07
15 Mattis, Daniel C.Magnetic susceptibilities of finite Ising chains in the presence of defect sitesAny antiferromagnet with zero net magnetic moment exhibits limited response to an external homogeneous magnetic field. This changes dramatically in the presence of defect sites, even those that carry no spin. We examine the excess susceptibilities, longitudinal and transverse, due to one or more d...Antiferromagnets; Defects; Ising chain; Longitudinal field; Transverse field2007-12
16 Vardeny, Zeev Valentine; Nahata, AjayMidinfrared optical response and thermal emission from plasmonic lattices on Al filmsWe studied the midinfrared optical transmission and thermal light emission spectra of subwavelength hole arrays in the form of square lattice with 4 µm periodicity (plasmonic lattice) in aluminum films deposited on silicon substrates. The optical transmission of these films showed temperature inde...Plasmonic lattices; Midinfrared optical response; Thermal emission; Surface plasmon polaritons; Anomalous transmission; Extraordinary optical transmission; EOT2007-11
17 Gerton, JordanNanoscale fluorescence imaging using a single-wall carbon nanotubeA single-wall carbon nanotube attached to an AFM probe is used for near-field optical imaging of 20 nm diameter fluorescent spheres and 5 nm diameter CdSe quantum dots.2007-05
18 Vardeny, Zeev ValentineNonlinear optical spectroscopy of excited states in polyfluoreneWe used a variety of nonlinear optical (NLO) spectroscopies to study the singlet excited-state order and primary photoexcitations in polyfluorene, an important blue-emitting ∏-conjugated polymer. The polarized NLO spectroscopies include ultrafast pump-probe photomodulation in a broad spectral rang...pi-conjugated polymers; Polyfluorene; Photoexcitations2007-03
19 Gerton, JordanOptimizing contrast of tip-enhanced fluorescence microscopy for imaging high-density samplesQuantum dots are imaged using tip-enhanced fluorescence microscopy. Optimization of the operation parameters leads to high-contrast images of high-density samples and a novel photon analysis improves contrast further.2007-05
20 Vardeny, Zeev Valentine; Ehrenfreund, Eitan A.Polaron spin-lattice relaxation time in ∏-conjugated polymers from optically detected magnetic resonanceWe describe a method for obtaining the polaron spin-lattice relaxation time TSL in ∏-conjugated polymers by measuring the optically detected magnetic resonance (ODMR) dynamics as a function of microwave power and laser intensity. The peculiar ODMR dynamics is well described by a spin dependent re...pi-conjugated polymers; Optically detected magnetic resonance; ODMR; MEH-PPV2007-10
21 DeTar, CarletonQCD equation of state with 2+1 flavors of improved staggered quarksWe report results for the interaction measure, pressure, and energy density for nonzero-temperature QCD with 2 + 1 flavors of improved staggered quarks. In our simulations, we use a Symanzik improved gauge action and the Asqtad O(a2) improved staggered quark action for lattices with temporal extent ...Staggered quarks; Quark-gluon plasma2007-05
22 Dawson, KyleRadio point sources toward galaxy clusters at 30 GHzExtra-galactic radio sources are a significant contaminant in cosmic microwave background and Sunyaev-Zel'dovich effect experiments. Deep interferometric observations with the BIMA and OVRO arrays are used to characterize the spatial, spectral, and flux distributions of radio sources toward massive ...Extra-galactic radio sources2007-09
23 Boehme, ChristophRoom temperature electrical detection of spin coherence in C60An experimental demonstration of electrical detection of coherent spin motion of weakly coupled, localized electron spins in thin fullerene C60 films at room temperature is presented. Pulsed electrically detected magnetic resonance experiments on vertical photocurrents through Al/C60/ZnO samples sh...Spin coherence2007-05
24 Lupton, John MarkRoom-temperature exciton storage in elongated semiconductor nanocrystalsThe excited state of colloidal nanoheterostructures consisting of a spherical CdSe nanocrystal with an epitaxially attached CdS rod can be perturbed effectively by electric fields. Field-induced fluorescence quenching coincides with a conversion of the excited state species from the bright exciton ...Exciton storage; Colloidal nanoheterostructures; CdSe nanocrystal2007-01
25 DeTar, CarletonScalar meson spectroscopy with lattice staggered fermionsWith sufficiently light up and down quarks the isovector (a0) and isosinglet (f0) scalar meson propagators are dominated at large distance by two-meson states. In the staggered-fermion formulation of lattice quantum chromodynamics, taste-symmetry breaking causes a proliferation of two-meson states t...Staggered fermions; Chiral theory2007-11
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