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Discovery of Extreme Carbon Stars in the Large Magellanic Cloud
(American Astronomical Society, 2008)
Using Spitzer IRAC and MIPS observations of the Large Magellanic Cloud, we have identified 13 objects that have extremely red mid-IR colors. Follow-up Spitzer IRS observations of seven of these sources reveal varying amounts ...
Orbital ordering and exchange interaction in the manganites
(American Physical Society, 2001)
The microscopic origin of the exchange interaction in manganites is studied by solving an electronic model Hamiltonian for the Mn-O-Mn triad. It is shown that the magnetic structure of La1-xCaxMnO3 is correctly described ...
Wannier-like functions and tight-binding parametrization for the manganese bands in CaMnO3
(Institute of Physics, 2003)
We study the electronic band structure of CaMnO3, in order to understand the origin of the dispersion of the Mn(eg) bands, which is in contrast with the predicted dispersionless bands within the Anderson-Hasegawa double-exchange ...
On the Anomalous Silicate Emission Features of AGNs: A Possible Interpretation Based on Porous Dust
(arXiv, 2008)
The recent Spitzer detections of the 9.7 micron Si--O silicate emission in type 1 AGNs provide support for the AGN unification scheme. The properties of the silicate dust are of key importance to understanding the physical, ...
On buckyonions as an interstellar grain component
(arXiv, 2008)
The carrier of the 2175 Angstrom interstellar extinction feature remains unidentified since its first detection over 40 years ago. In recent years carbon buckyonions have been proposed as a carrier of this feature, based ...
The Effect of Stellar Evolution on SiC Dust Grain Sizes
(American Astronomical Society, 2005)
Stars on the asymptotic giant branch (AGB) produce dust in their circumstellar shells. The nature of the dust-forming environment is influenced by the evolution of the stars, in terms of both chemistry and density, leading ...
The Multitude of Molecular Hydrogen Knots in the Helix Nebula
(Institute of Physics, 2005)
We present Hubble Space Telescope NICMOS imaging of the H2 2.12 μm emission in five fields in the Helix Nebula ranging in radial distance from 250'' to 450'' from the central star. The images reveal arcuate structures with ...
The Nature and Origin of Molecular Knots in Planetary Nebulae
(American Institute of Physics, 2005)
Planetary Nebulae (PNe) are major contributors to the enrichment of the interstellar medium (ISM). Knots and filaments in the ionized gas images of PNe are common, if not ubiquitous. Additionally, it has been shown that ...
Gravitomagnetic Jets
(arXiv, 2010)
We present a family of dynamic rotating cylindrically symmetric Ricci-flat gravitational fields whose geodesic motions have the structure of gravitomagnetic jets. These correspond to helical motions of free test particles ...
Necessity of Acceleration-Induced Nonlocality
(arXiv, 2010)
The purpose of this paper is to explain clearly why nonlocality must be an essential part of the theory of relativity. In the standard local version of this theory, Lorentz invariance is extended to accelerated observers ...
Gravitomagnetic Accelerators
(arXiv, 2010)
We study a simple class of time-dependent rotating Ricci-flat cylindrically symmetric spacetime manifolds whose geodesics admit gravitomagnetic jets. The helical paths of free test particles in these jets up and down ...
Nonlinear Spin-Polarized Transport through a Ferromagnetic Domain Wall
(American Physical Society, 2002)
A domain wall separating two oppositely magnetized regions in a ferromagnetic semiconductor exhibits, under appropriate conditions, strongly nonlinear I-V characteristics similar to those of a p-n diode. We study these ...
Failure of the local density approximation in time-dependent spin density functional theory
(arXiv, 2002)
It has been known for some time that the exchange-correlation potential in time- dependent density functional theory is an intrinsically nonlocal functional of the density as soon as one goes beyond the adiabatic approximation. ...
Magnetic tweezers for intracellular applications
(American Institute of Physics, 2003)
We have designed and constructed a versatile magnetic tweezer primarily for intracellular investigations. The micromanipulator uses only two coils to simultaneously magnetize to saturation micron-size superparamagnetic ...
Functional Imaging Using InGaAs/GaAs Photorefractive Multiple Quantum Wells
(American Institute of Physics, 2005)
We propose the use of an InGaAs/GaAs photorefractive quantum well (PRQW) as an adaptive beam combiner for holographic optical coherence imaging applications. Holograms have been observed by using a diode laser and an ...
Limitations of Radar Coordinates
(arXiv, 2004)
The construction of a radar coordinate system about the world line of an observer is discussed. Radar coordinates for a hyperbolic observer as well as a uniformly rotating observer are described in detail. The utility of ...
The Hypothesis of Locality and its Limitations
(arXiv, 2003)
The hypothesis of locality, its origin and consequences are discussed. This supposition is necessary for establishing the local spacetime frame of accelerated observers; in this connection, the measurement of length in a ...
On the gravitomagnetic clock effect
(arXiv, 2001)
General relativity predicts that two freely counter-revolving test particles in the exterior field of a central rotating mass take different periods of time to complete the same full orbit; this time difference leads to ...
Entropy driven spontaneous formation of highly porous films from polymer-nanoparticle composites
(Institute of Physics, 2009)
Nanoporous materials have become indispensable in many fields ranging from photonics, catalysis and semiconductor processing to biosensor infrastructure. Rapid and energy efficient process fabrication of these materials ...
The search for quantum critical scaling in a classical system
(American Institute of Physics, 2009)
Order-disorder phase transitions in magnetic metals that occur at zero temperature have been studied in great detail. Theorists have advanced scenarios for these quantum critical systems in which the unusual response can ...