1,215 research outputs found
Detecting z > 10 objects through carbon, nitrogen and oxygen emission lines
By redshift of 10, star formation in the first objects should have produced
considerable amounts of Carbon, Nitrogen and Oxygen. The submillimeter lines of
C, N and O redshift into the millimeter and centimeter bands (0.5 mm -- 1.2
cm), where they may be detectable. High spectral resolution observations could
potentially detect inhomogeneities in C, N and O emission, and see the first
objects forming at high redshift. We calculate expected intensity fluctuations
and discuss frequency and angular resolution required to detect them. For CII
emission, we estimate the intensity using two independent methods: the line
emission coefficient argument and the luminosity density argument. We find they
are in good agreement. At 1+z \sim 10, the typical protogalaxy has a velocity
dispersion of 30 km s^{-1} and angular size of 1 arcsecond. If CII is the
dominant coolant, then we estimate a characteristic line strength of \sim 0.1 K
km s^{-1}. We also discuss other atomic lines and estimate their signal.
Observations with angular resolution of 10^{-3} can detect moderately nonlinear
fluctuations of amplitude 2 \cdot 10^{-5} times the microwave background. If
the intensity fluctuations are detected, they will probe matter density
inhomogeneity, chemical evolution and ionization history at high redshifts.Comment: 15 pages, 1 postscript figures included; Uses aaspp4.sty (AASTeX
v4.0); Submitted to The Astrophysical Journa
Exploratory Visual Analysis of Statistical Results from Microarray Experiments Comparing High and Low Grade Glioma
The biological interpretation of gene expression microarray results is a daunting challenge. For complex diseases such as cancer, wherein the body of published research is extensive, the incorporation of expert knowledge provides a useful analytical framework. We have previously developed the Exploratory Visual Analysis (EVA) software for exploring data analysis results in the context of annotation information about each gene, as well as biologically relevant groups of genes. We present EVA as a flexible combination of statistics and biological annotation that provides a straightforward visual interface for the interpretation of microarray analyses of gene expression in the most commonly occuring class of brain tumors, glioma. We demonstrate the utility of EVA for the biological interpretation of statistical results by analyzing publicly available gene expression profiles of two important glial tumors. The results of a statistical comparison between 21 malignant, high-grade glioblastoma multiforme (GBM) tumors and 19 indolent, low-grade pilocytic astrocytomas were analyzed using EVA. By using EVA to examine the results of a relatively simple statistical analysis, we were able to identify tumor class-specific gene expression patterns having both statistical and biological significance. Our interactive analysis highlighted the potential importance of genes involved in cell cycle progression, proliferation, signaling, adhesion, migration, motility, and structure, as well as candidate gene loci on a region of Chromosome 7 that has been implicated in glioma. Because EVA does not require statistical or computational expertise and has the flexibility to accommodate any type of statistical analysis, we anticipate EVA will prove a useful addition to the repertoire of computational methods used for microarray data analysis. EVA is available at no charge to academic users and can be found at http://www.epistasis.org
Wormhole Cosmology and the Horizon Problem
We construct an explicit class of dynamic lorentzian wormholes connecting
Friedmann-Robertson-Walker (FRW) spacetimes. These wormholes can allow two-way
transmission of signals between spatially separated regions of spacetime and
could permit such regions to come into thermal contact. The cosmology of a
network of early Universe wormholes is discussed.Comment: 13 pages, in RevTe
Tolman wormholes violate the strong energy condition
For an arbitrary Tolman wormhole, unconstrained by symmetry, we shall define
the bounce in terms of a three-dimensional edgeless achronal spacelike
hypersurface of minimal volume. (Zero trace for the extrinsic curvature plus a
"flare-out" condition.) This enables us to severely constrain the geometry of
spacetime at and near the bounce and to derive general theorems regarding
violations of the energy conditions--theorems that do not involve geodesic
averaging but nevertheless apply to situations much more general than the
highly symmetric FRW-based subclass of Tolman wormholes. [For example: even
under the mildest of hypotheses, the strong energy condition (SEC) must be
violated.] Alternatively, one can dispense with the minimal volume condition
and define a generic bounce entirely in terms of the motion of test particles
(future-pointing timelike geodesics), by looking at the expansion of their
timelike geodesic congruences. One re-confirms that the SEC must be violated at
or near the bounce. In contrast, it is easy to arrange for all the other
standard energy conditions to be satisfied.Comment: 8 pages, ReV-TeX 3.
BPS Force Balances via Spin-Spin Interactions
We study two systems of BPS solitons in which spin-spin interactions are
important in establishing the force balances which allow static, multi-soliton
solutions to exist. Solitons in the Israel-Wilson-Perjes (IWP) spacetimes each
carry arbitrary, classical angular momenta. Solitons in the Aichelburg-Embacher
"superpartner" spacetimes carry quantum mechanical spin, which originates in
the zero-modes of the gravitino field of N=2 supergravity in an extreme
Reissner-Nordstrom background. In each case we find a cancellation between
gravitational spin-spin and magnetic dipole-dipole forces, in addition to the
usual one between Newtonian gravitational attraction and Coulombic
electrostatic repulsion. In both cases, we analyze the forces between two
solitons by treating one of the solitons as a probe or test particle, with the
appropriate properties, moving in the background of the other. In the IWP case,
the equation of motion for a spinning test particle, originally due to
Papapetrou, includes a coupling between the background curvature and the spin
of the test particle. In the superpartner case, the relevant equation of motion
follows from a kappa-symmetric superparticle action.Comment: 11 page
Electron transport through self-assembled monolayers of tripeptides
We report how the electron transport through a solid-state metal/Gly-Gly-His
tripeptide (GGH) monolayer/metal junction and the metal/GGH work function are
modified by the GGH complexation with Cu2+ ions. Conducting AFM is used to
measure the current-voltage histograms. The work function is characterized by
combining macroscopic Kelvin probe and Kelvin probe force microscopy at the
nanoscale. We observe that the Cu2+ ions complexation with the GGH monolayer is
highly dependent on the molecular surface density and results in opposite
trends. In the case of a high density monolayer the conformational changes are
hindered by the proximity of the neighboring peptides, hence forming an
insulating layer in response to copper-complexation. Whereas the slightly lower
density monolayers allow for the conformational change to a looped peptide
wrapping the Cu-ion, which results in a more conductive monolayer. Copper-ion
complexation to the high- and low-density monolayers systematically induces an
increase of the work functions. Copper-ion complexation to the low-density
monolayer induces an increase of electron transport efficiency, while the
copper-ion complexation to the high-density monolayer results in a slight
decrease of electron transport. Both of the observed trends are in agreement
with first-principle calculations. Complexed copper to low density
GGH-monolayer induces a new gap state slightly above the Au Fermi energy that
is absent in the high density monolayer.Comment: Full paper with supporting informatio
Space Mobile Network Concepts for Missions Beyond Low Earth Orbit
The Space Mobile Network (SMN) is an architectural framework that will allow for quicker, more efficient and more easily available space communications services, providing user spacecraft with an experience similar to that of terrestrial mobile network users. While previous papers have described SMN concept using examples of users in low-Earth orbit, the framework can also be applied beyond the near-Earth environment. This paper details how SMN concepts such as user-initiated services, which will enable users to request access to high-performance link resources in response to real-time science or operational events, would be applied in and beyond the near-Earth regime. Specifically, the paper explores the application of user-initiated services to direct-to-Earth (DTE), relay, and DTE/relay hybrid scenarios in near-Earth, lunar, Martian and other space regimes
Small-particle Inhaled Corticosteroid as First-line or Step-up Controller Therapy in Childhood Asthma
Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.Peer reviewedPublisher PD
Gravity/CFT correspondence for three dimensional Einstein gravity with a conformal scalar field
We study the three dimensional Einstein gravity conformally coupled to a
scalar field. Solutions of this theory are geometries with vanishing scalar
curvature. We consider solutions with a constant scalar field which corresponds
to an infinite Newton's constant. There is a class of solutions with possible
curvature singularities which asymptotic symmetries are given by two copies of
the Virasoro algebra. We argue that the central charge of the corresponding CFT
is infinite. Furthermore, we construct a family of Schwarzschild solutions
which can be conformally mapped to the Martinez-Zanelli solution of Einstein's
equations with a negative cosmological constant coupled to conformal scalar
field.Comment: 27 pages, to appear in Nucl. Phys.
Space Mobile Network Concepts for Missions Beyond Low Earth Orbit
The Space Mobile Network (SMN) is an architectural framework that will allow for quicker, more efficient and more easily available space communications services, providing user spacecraft with an experience similar to that of terrestrial mobile network users. While previous papers have described SMN concept using examples of users in low-Earth orbit, the framework can also be applied beyond the near-Earth environment.This paper details how SMN concepts such as user-initiated services, which will enable users to request access to high-performance link resources in response to real-time science or operational events, would be applied in and beyond the near-Earth regime. Specifically, the paper explores the application of user-initiated services to direct-to-Earth (DTE), relay, and DTE/relay hybrid scenarios in near-Earth, lunar, martian and other space regimes
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