4,420 research outputs found
Interplay between multiple scattering, emission, and absorption of light in the phosphor of a white light-emitting diode
We study light transport in phosphor plates of white light-emitting diodes
(LEDs). We measure the broadband diffuse transmission through phosphor plates
of varying YAG:Ce density. We distinguish the spectral ranges where
absorption, scattering, and re-emission dominate. Using diffusion theory, we
derive the transport and absorption mean free paths from first principles. We
find that both transport and absorption mean free paths are on the order of the
plate thickness. This means that phosphors in commercial LEDs operate well
within an intriguing albedo range around 0.7. We discuss how salient parameters
that can be derived from first principles control the optical properties of a
white LED.Comment: 14 pages, 9 figure
Matrix metalloproteinase MMP12 is associated with intervertebral disc degeneration
INTRODUCTION: Intervertebral disc (IVD) degeneration is associated with low back pain. However, the molecular changes during the degeneration process is not entirely clear. The loss of nucleus pulposus (NP) integrity is one of the early events of the degeneration. Chondrogenic markers, such as SOX9 and aggrecan, have been commonly used to assess the degree of IVD degeneration. Recent transcriptomic studies have proposed several other candidates that may mark IVD degeneration. These include cartilage oligomeric matrix protein (COMP), matrix gla protein (MGP)[1], fibulin 1 (FBLN1) [2], cytokeratin 18 (KRT18) [3], cadherin-2 (CDH2) [3], cytokeratin 19 (KRT19) [2], and Runt-related transcription factor 2 (RUNX2) [4]. Studies also demonstrated that degenerated NP attains a fibrocartilaginous phenotype [5,6] with increased ...postprin
Perturbative Approach to the Quasinormal Modes of Dirty Black Holes
Using a recently developed perturbation theory for uasinormal modes (QNM's),
we evaluate the shifts in the real and imaginary parts of the QNM frequencies
due to a quasi-static perturbation of the black hole spacetime. We show the
perturbed QNM spectrum of a black hole can have interesting features using a
simple model based on the scalar wave equation.Comment: Published in PR
T-violation tests for relativity principles
We consider the implications of a violation of the equivalence principle or
of Lorentz invariance in the neutrino sector for the T-asymmetry in a
three-flavour framework. We find that additional mixing due to these
mechanisms, while obeying all present bounds, can lead to a substantial
enhancement, suppression, and/or sign change in for the preferred
energies and baselines of a neutrino factory. This in turn allows for the
possibility of improving existing constraints by several orders of magnitude.Comment: 2 pages; Talk given at the 4th NuFact '02 Workshop (Neutrino
Factories Based On Muon Storage Rings), 1-6 Jul 2002, London, England; To
appear in proceeding
The Phase Diagram and Spectrum of Gauge-Fixed Abelian Lattice Gauge Theory
We consider a lattice discretization of a covariantly gauge-fixed abelian
gauge theory. The gauge fixing is part of the action defining the theory, and
we study the phase diagram in detail. As there is no BRST symmetry on the
lattice, counterterms are needed, and we construct those explicitly. We show
that the proper adjustment of these counterterms drives the theory to a new
type of phase transition, at which we recover a continuum theory of (free)
photons. We present both numerical and (one-loop) perturbative results, and
show that they are in good agreement near this phase transition. Since
perturbation theory plays an important role, it is important to choose a
discretization of the gauge-fixing action such that lattice perturbation theory
is valid. Indeed, we find numerical evidence that lattice actions not
satisfying this requirement do not lead to the desired continuum limit. While
we do not consider fermions here, we argue that our results, in combination
with previous work, provide very strong evidence that this new phase transition
can be used to define abelian lattice chiral gauge theories.Comment: 42 pages, 30 figure
Valence bond solid formalism for d-level one-way quantum computation
The d-level or qudit one-way quantum computer (d1WQC) is described using the
valence bond solid formalism and the generalised Pauli group. This formalism
provides a transparent means of deriving measurement patterns for the
implementation of quantum gates in the computational model. We introduce a new
universal set of qudit gates and use it to give a constructive proof of the
universality of d1WQC. We characterise the set of gates that can be performed
in one parallel time step in this model.Comment: 26 pages, 9 figures. Published in Journal of Physics A: Mathematical
and Genera
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