1,393 research outputs found
Set design for A Raisin in the Sun
My husband and I chose to go to Walt Disney World for our honeymoon, because of his interest in animation. When we arrived the world that surrounded us was fascinating. It was amazing and strange how, for the time we were there, this fantasy land became a form of reality for us. While at Walt Disney World, I became very interested in set design. The environments created within Disney World allowed one to be entertained and amused, while traveling through dream lands. Being able to design with this kind of playfulness is very stimulating to me. Upon returning home from Disney World, I began my education at Rochester Institute of Technology (R.I.T). I was introduced to many new technical skills, which I never had the opportunity to learn, during my Fine Arts education. Throughout the year I struggled with these technical skills, and as the year came to a close I understood the necessity for them. However, I still lacked the emotional playfulness that I was exposed to while visiting Disney World. With that in mind I began thinking about my thesis. I wanted to create a three dimensional environment unlike any I had created during my stay at R.I.T. When I was discussing various thesis topics with my advisor, she suggested designing a stage set for a local theatre in Rochester. I was thrilled with the suggestion
Structure and bonding of dense liquid oxygen from first principles simulations
Using first principles simulations we have investigated the structural and
bonding properties of dense fluid oxygen up to 180 GPa. We have found that band
gap closure occurs in the molecular liquid, with a "slow" transition from a
semi-conducting to a poor metallic state occurring over a wide pressure range.
At approximately 80 GPa, molecular dissociation is observed in the metallic
fluid. Spin fluctuations play a key role in determining the electronic
structure of the low pressure fluid, while they are suppressed at high
pressure.Comment: 4 figure
Competing Phases, Strong Electron-Phonon Interaction and Superconductivity in Elemental Calcium under High Pressure
The observed "simple cubic" (sc) phase of elemental Ca at room temperature in
the 32-109 GPa range is, from linear response calculations, dynamically
unstable. By comparing first principle calculations of the enthalpy for five
sc-related (non-close-packed) structures, we find that all five structures
compete energetically at room temperature in the 40-90 GPa range, and three do
so in the 100-130 GPa range. Some competing structures below 90 GPa are
dynamically stable, i.e., no imaginary frequency, suggesting that these
sc-derived short-range-order local structures exist locally and can account for
the observed (average) "sc" diffraction pattern. In the dynamically stable
phases below 90 GPa, some low frequency phonon modes are present, contributing
to strong electron-phonon (EP) coupling as well as arising from the strong
coupling. Linear response calculations for two of the structures over 120 GPa
lead to critical temperatures in the 20-25 K range as is observed, and do so
without unusually soft modes.Comment: 8 pages, 6 figures, 1 table, accepted for publication in Phys. Rev.
Fission yeast SWI/SNF and RSC complexes show compositional and functional differences from budding yeast.
SWI/SNF chromatin-remodeling complexes have crucial roles in transcription and other chromatin-related processes. The analysis of the two members of this class in Saccharomyces cerevisiae, SWI/SNF and RSC, has heavily contributed to our understanding of these complexes. To understand the in vivo functions of SWI/SNF and RSC in an evolutionarily distant organism, we have characterized these complexes in Schizosaccharomyces pombe. Although core components are conserved between the two yeasts, the compositions of S. pombe SWI/SNF and RSC differ from their S. cerevisiae counterparts and in some ways are more similar to metazoan complexes. Furthermore, several of the conserved proteins, including actin-like proteins, are markedly different between the two yeasts with respect to their requirement for viability. Finally, phenotypic and microarray analyses identified widespread requirements for SWI/SNF and RSC on transcription including strong evidence that SWI/SNF directly represses iron-transport genes
SO(5) theory of insulating vortex cores in high- materials
We study the fermionic states of the antiferromagnetically ordered vortex
cores predicted to exist in the superconducting phase of the newly proposed
SO(5) model of strongly correlated electrons. Our model calculation gives a
natural explanation of the recent STM measurements on BSCCO, which in
surprising contrast to YBCO revealed completely insulating vortex cores.Comment: 4 pages, 1 figur
Quasiparticle States at a d-Wave Vortex Core in High-Tc Superconductors: Induction of Local Spin Density Wave Order
The local density of states (LDOS) at one of the vortex lattice cores in a
high Tc superconductor is studied by using a self-consistent mean field theory
including interactions for both antiferromagnetism (AF) and d-wave
superconductivity (DSC). The parameters are chosen in such a way that in an
optimally doped sample the AF order is completely suppressed while DSC
prevails. In the mixed state, we show that the local AF-like SDW order appears
near the vortex core and acts as an effective local magnetic field on the
quasiparticles. As a result, the LDOS at the core exhibits a double-peak
structure near the Fermi level that is in good agreement with the STM
observations on YBCO and BSCCO. The presence of local AF order near the votex
core is also consistent with the recent neutron scattering experiment on LSCO.Comment: 4 pages, 2 ps figure
Star-shaped Local Density of States around Vortices in a Type II Superconductor
The electronic structure of vortices in a type II superconductor is analyzed
within the quasi-classical Eilenberger framework. The possible origin of a
sixfold ``star'' shape of the local density of states, observed by scanning
tunneling microscope experiments on NbSe, is examined in the light of the
three effects; the anisotropic pairing, the vortex lattice, and the anisotropic
density of states at the Fermi surface. Outstanding features of split parallel
rays of this star are well explained in terms of an anisotropic -wave
pairing. This reveals a rich internal electronic structure associated with a
vortex core.Comment: 4 pages, REVTeX, 3 figures available upon reques
Local density of states in the vortex lattice in a type II superconductor
Local density of states (LDOS) in the triangular vortex lattice is
investigated based on the quasi-classical Eilenberger theory. We consider the
case of an isotropic s-wave superconductor with the material parameter
appropriate to NbSe_2. At a weak magnetic field, the spatial variation of the
LDOS shows cylindrical structure around a vortex core. On the other hand, at a
high field where the core regions substantially overlap each other, the LDOS is
sixfold star-shaped structure due to the vortex lattice effect. The orientation
of the star coincides with the experimental data of the scanning tunneling
microscopy. That is, the ray of the star extends toward the nearest-neighbor
(next nearest-neighbor) vortex direction at higher (lower) energy.Comment: 10 pages, RevTex, 32 figure
Absence of Dipole Transitions in Vortices of Type II Superconductors
The response of a single vortex to a time dependent field is examined
microscopically and an equation of motion for vortex motion at non-zero
frequencies is derived. Of interest are frequencies near ,
where is the bulk energy gap and is the fermi energy. The low
temperature, clean, extreme type II limit and maintaining of equilibrium with
the lattice are assumed. A simplification occurs for large planar mass
anisotropy. Thus the results may be pertinent to materials such as and
high temperature superconductors. The expected dipole transition between core
states is hidden because of the self consistent nature of the vortex potential.
Instead the vortex itself moves and has a resonance at the frequency of the
transition.Comment: 12 pages, no figure
Towards a Linear-Scaling DFT Technique: The Density Matrix Approach
A recently proposed linear-scaling scheme for density-functional
pseudopotential calculations is described in detail. The method is based on a
formulation of density functional theory in which the ground state energy is
determined by minimization with respect to the density matrix, subject to the
condition that the eigenvalues of the latter lie in the range [0,1].
Linear-scaling behavior is achieved by requiring that the density matrix should
vanish when the separation of its arguments exceeds a chosen cutoff. The
limitation on the eigenvalue range is imposed by the method of Li, Nunes and
Vanderbilt. The scheme is implemented by calculating all terms in the energy on
a uniform real-space grid, and minimization is performed using the
conjugate-gradient method. Tests on a 512-atom Si system show that the total
energy converges rapidly as the range of the density matrix is increased. A
discussion of the relation between the present method and other linear-scaling
methods is given, and some problems that still require solution are indicated.Comment: REVTeX file, 27 pages with 4 uuencoded postscript figure
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