1,126 research outputs found
Vacuum Values for Auxiliary String Fields
Auxiliary string fields are introduced in light-cone gauge string field
theory in order to express contact interactions as contractions of cubic
vertices. The auxiliary field in the purely closed-string bosonic theory may be
given a non-zero expectation value, leading to a phase in which world-sheets
have boundaries.Comment: 13 pages, DAMTP/94-2
A Comparison and Joint Analysis of Sunyaev-Zel'dovich Effect Measurements from Planck and Bolocam for a set of 47 Massive Galaxy Clusters
We measure the SZ signal toward a set of 47 clusters with a median mass of
M and a median redshift of 0.40 using data from
Planck and the ground-based Bolocam receiver. When Planck XMM-like masses are
used to set the scale radius , we find consistency between
the integrated SZ signal, , derived from Bolocam and Planck
based on gNFW model fits using A10 shape parameters, with an average ratio of
(allowing for the % Bolocam flux calibration
uncertainty). We also perform a joint fit to the Bolocam and Planck data using
a modified A10 model with the outer logarithmic slope allowed to vary,
finding (measurement error followed by
intrinsic scatter). In addition, we find that the value of scales with
mass and redshift according to . This mass scaling is in good agreement with recent
simulations. We do not observe the strong trend of with redshift seen
in simulations, though we conclude that this is most likely due to our sample
selection. Finally, we use Bolocam measurements of to test the
accuracy of the Planck completeness estimate. We find consistency, with the
actual number of Planck detections falling approximately below the
expectation from Bolocam. We translate this small difference into a constraint
on the the effective mass bias for the Planck cluster cosmology results, with
.Comment: Updated to include one additional co-author. Also some minor changes
to the text based on initial feedbac
Microchip Electrophoresis with Amperometric Detection Method for Profiling Cellular Nitrosative Stress Markers
The overproduction of nitric oxide (NO) in cells results in nitrosative stress due to the generation of highly reactive species such as peroxynitrite and N2O3. These species disrupt the cellular redox processes through the oxidation, nitration, and nitrosylation of important biomolecules. Microchip electrophoresis (ME) is a fast separation method that can be used to profile cellular nitrosative stress through the separation of NO and nitrite from other redox-active intracellular components such as cellular antioxidants. This paper describes a ME method with electrochemical detection (ME-EC) for the separation of intracellular nitrosative stress markers in macrophage cells. The separation of nitrite, azide (interference), iodide (internal standard), tyrosine, glutathione, and hydrogen peroxide (neutral marker) was achieved in under 40 s using a run buffer consisting of 7.5 to 10 mM NaCl, 10 mM boric acid, and 2 mM TTAC at pH 10.3 to 10.7. Initially, NO production was monitored by the detection of nitrite (NO2−) in cell lysates. There was a 2.5- to 4-fold increase in NO2− production in lipopolysaccharide (LPS)-stimulated cells. The concentration of NO2− inside a single unstimulated macrophage cell was estimatedto be 1.41 mM using the method of standard additions. ME-EC was then used for the direct detection of NO and glutathione in stimulated and native macrophage cell lysates. NO was identified in these studies based on its migration time and rapid degradation kinetics. The intracellular levels of glutathione in native and stimulated macrophages were also compared, and no significant difference was observed between the two conditions
Superstrings from theories with N>1 world-sheet supersymmetry
String theories with (N,N') local world-sheet supersymmetries are related to
each other by marginal deformations. This connects N=1 and N=0 theories in
which the target-spaces are interpreted as space-times, N=2 theories in which
the target spaces can be interpreted as world-volumes, and theories with , in which the central charge vanishes -- theories with zero target-space
dimensions.Comment: Typos corrected and comments added about D-instanton, 20 page
Unpacking Giftedness : Research and Strategies for Promoting Racial and Socioeconomic Equity
Giftedness as a construct continues to be contested in academia, in the classroom and around kitchen tables. It means different things to different communities and, as a result, acquiring the gifted label looks different around the country. Once labeled, student giftedness produces different responses depending on state and district guidelines. A constant among the patchwork of defining, identifying and responding to student giftedness, though, is a serious racial and economic disparity in who is considered gifted and who is not. This report provides key takeaways from research literature on gifted and talented (GT) programs. It is organized according to five questions: 1) What does it mean to be gifted? 2) Who receives gifted services? 3) Why does this matter? 4) What factors contribute to disparities in gifted services? and 5) What strategies help to address disparities in gifted education
Decoupling of net community and export production on submesoscales in the Sargasso Sea
Author Posting. © American Geophysical Union, 2015. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Global Biogeochemical Cycles 29 (2015): 1266–1282, doi:10.1002/2014GB004913.Determinations of the net community production (NCP) in the upper ocean and the particle export production (EP) should balance over long time and large spatial scales. However, recent modeling studies suggest that a horizontal decoupling of flux-regulating processes on submesoscales (≤10 km) could lead to imbalances between individual determinations of NCP and EP. Here we sampled mixed-layer biogeochemical parameters and proxies for NCP and EP during 10, high-spatial resolution (~2 km) surface transects across strong physical gradients in the Sargasso Sea. We observed strong biogeochemical and carbon flux variability in nearly all transects. Spatial coherence among measured biogeochemical parameters within transects was common but rarely did the same parameters covary consistently across transects. Spatial variability was greater in parameters associated with higher trophic levels, such as chlorophyll in >5.0 µm particles, and variability in EP exceeded that of NCP in nearly all cases. Within sampling transects, coincident EP and NCP determinations were uncorrelated. However, when averaged over each transect (30 to 40 km in length), we found NCP and EP to be significantly and positively correlated (R = 0.72, p = 0.04). Transect-averaged EP determinations were slightly smaller than similar NCP values (Type-II regression slope of 0.93, standard deviation = 0.32) but not significantly different from a 1:1 relationship. The results show the importance of appropriate sampling scales when deriving carbon flux budgets from upper ocean observations.NASA Ocean Carbon and Biogeochemistry program Grant Number: NNX11AL94G; WHOI Postdoctoral Scholar fellowship;
NASA ACE Grant Number: NNX12AJ25G; NSF Grant Number: OCE-07523662016-02-2
Faint NUV/FUV Standards from Swift/UVOT, GALEX and SDSS Photometry
At present, the precision of deep ultraviolet photometry is somewhat limited
by the dearth of faint ultraviolet standard stars. In an effort to improve this
situation, we present a uniform catalog of eleven new faint (u sim17)
ultraviolet standard stars. High-precision photometry of these stars has been
taken from the Sloan Digital Sky Survey and Galaxy Evolution Explorer and
combined with new data from the Swift Ultraviolet Optical Telescope to provide
precise photometric measures extending from the Near Infrared to the Far
Ultraviolet. These stars were chosen because they are known to be hot (20,000 <
T_eff < 50,000 K) DA white dwarfs with published Sloan spectra that should be
photometrically stable. This careful selection allows us to compare the
combined photometry and Sloan spectroscopy to models of pure hydrogen
atmospheres to both constrain the underlying properties of the white dwarfs and
test the ability of white dwarf models to predict the photometric measures. We
find that the photometry provides good constraint on white dwarf temperatures,
which demonstrates the ability of Swift/UVOT to investigate the properties of
hot luminous stars. We further find that the models reproduce the photometric
measures in all eleven passbands to within their systematic uncertainties.
Within the limits of our photometry, we find the standard stars to be
photometrically stable. This success indicates that the models can be used to
calibrate additional filters to our standard system, permitting easier
comparison of photometry from heterogeneous sources. The largest source of
uncertainty in the model fitting is the uncertainty in the foreground reddening
curve, a problem that is especially acute in the UV.Comment: Accepted for publication in Astrophysical Journal. 31 pages, 13
figures, electronic tables available from ApJ or on reques
Fermions and Loops on Graphs. I. Loop Calculus for Determinant
This paper is the first in the series devoted to evaluation of the partition
function in statistical models on graphs with loops in terms of the
Berezin/fermion integrals. The paper focuses on a representation of the
determinant of a square matrix in terms of a finite series, where each term
corresponds to a loop on the graph. The representation is based on a fermion
version of the Loop Calculus, previously introduced by the authors for
graphical models with finite alphabets. Our construction contains two levels.
First, we represent the determinant in terms of an integral over anti-commuting
Grassman variables, with some reparametrization/gauge freedom hidden in the
formulation. Second, we show that a special choice of the gauge, called BP
(Bethe-Peierls or Belief Propagation) gauge, yields the desired loop
representation. The set of gauge-fixing BP conditions is equivalent to the
Gaussian BP equations, discussed in the past as efficient (linear scaling)
heuristics for estimating the covariance of a sparse positive matrix.Comment: 11 pages, 1 figure; misprints correcte
Optimal Location of Sources in Transportation Networks
We consider the problem of optimizing the locations of source nodes in
transportation networks. A reduction of the fraction of surplus nodes induces a
glassy transition. In contrast to most constraint satisfaction problems
involving discrete variables, our problem involves continuous variables which
lead to cavity fields in the form of functions. The one-step replica symmetry
breaking (1RSB) solution involves solving a stable distribution of functionals,
which is in general infeasible. In this paper, we obtain small closed sets of
functional cavity fields and demonstrate how functional recursions are
converted to simple recursions of probabilities, which make the 1RSB solution
feasible. The physical results in the replica symmetric (RS) and the 1RSB
frameworks are thus derived and the stability of the RS and 1RSB solutions are
examined.Comment: 38 pages, 18 figure
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