7,520 research outputs found
Electromagnetic form factors from the fifth dimension
We analyse various form factors of mesons at strong coupling in
an flavored version of which becomes
conformal in the UV. The quark mass breaks the conformal symmetry in the IR and
generates a mass gap. In the appropriate limit, the gravity dual is described
in terms of probe -branes in . By studying the
fluctuations we find the suitable terms in a "meson effective theory" which
allow us to compute the desired form factors, namely the and
transition form factors. At large we find perfect
agreement with the naive parton model counting, which is a consequence of the
conformal nature of both QCD and our model in the UV. By using the same tools,
we can compute the form factor. However this channel is
more subtle and comparisons to the QCD result are more involved.Comment: 34 pages, 6 figures, pdflatex. References and clarifications adde
Inter-sectoral and multilevel coordination alone do not reduce deforestation and advance environmental justice:Why bold contestation works when collaboration fails
Policy makers, academics, and conservationists often posit that poor coordination between different land use sectors, and between levels of governance, as an underlying challenge for reducing deforestation and forest degradation. This paper analyzes this argument using data from interviews with over 500 respondents from government, nongovernmental organizations, private companies, local and indigenous communities, activists, and individuals involved in 35 diverse land use initiatives in three countries: Peru, Indonesia, and Mexico. We find that while there is strong evidence of widespread coordination failures between sectors and levels, more fundamental political issues preclude effective coordination. We argue that political coalitions act to oppose environmental objectives and to impede their opponents from participating in land use governance. Moreover, we find that where coordination between actors does occur, it does not necessarily produce environmentally sustainable and socially just land use outcomes. Where we do find successful initiatives to reduce deforestation and benefit local people, effective coordination between well-informed actors is often present, but it does not occur spontaneously, and is instead driven by political organizing over time by activists, local people, nongovernmental organizations, and international donors. We suggest that the global environmental community must recognize explicitly these political dimensions of land use governance in order to successfully collaborate with local people to reduce deforestation
Star Formation in Massive Protoclusters in the Monoceros OB1 Dark Cloud
We present far-infrared, submillimetre, and millimetre observations of bright
IRAS sources and outflows that are associated with massive CS clumps in the
Monoceros OB1 Dark Cloud. Individual star-forming cores are identified within
each clump. We show that combining submillimetre maps, obtained with SCUBA on
the JCMT, with HIRES-processed and modelled IRAS data is a powerful technique
that can be used to place better limits on individual source contributions to
the far-infrared flux in clustered regions. Three previously categorized "Class
I objects" are shown to consist of multiple sources in different evolutionary
stages. In each case, the IRAS point source dominates the flux at 12 and 25
microns. In two cases, the IRAS point source is not evident at submillimetre
wavelengths. The submillimetre sources contribute significantly to the 60 and
100 micron fluxes, dominating the flux in the 100 micron waveband. Using fluxes
derived from our technique, we present the spectral energy distribution and
physical parameters for an intermediate-mass Class 0 object in one of the
regions. Our new CO J=2-1 outflow maps of the three regions studied indicate
complex morphology suggestive of multiple driving sources. We discuss the
possible implications of our results for published correlations between outflow
momentum deposition rates and "source" luminosities, and for using these
derived properties to estimate the ratio of mass ejection rates to mass
accretion rates onto protostars.Comment: 12 pages, 11 gzipped gif figures, LaTex file and MNRAS style files,
accepted by MNRAS, v2: reference typos and author affiliation have been
correcte
Electrified Fuzzy Spheres and Funnels in Curved Backgrounds
We use the non-Abelian DBI action to study the dynamics of coincident
-branes in an arbitrary curved background, with the presence of a
homogenous world-volume electric field. The solutions are natural extensions of
those without electric fields, and imply that the spheres will collapse toward
zero size. We then go on to consider the intersection in a curved
background and find various dualities and automorphisms of the general
equations of motion. It is possible to map the dynamical equation of motion to
the static one via Wick rotation, however the additional spatial dependence of
the metric prevents this mapping from being invertible. Instead we find that a
double Wick rotation leaves the static equation invariant. This is very
different from the behaviour in Minkowski space. We go on to construct the most
general static fuzzy funnel solutions for an arbitrary metric either by solving
the static equations of motion, or by finding configurations which minimise the
energy. As a consistency check we construct the Abelian -brane world-volume
theory in the same generic background and find solutions consistent with energy
minimisation. In the 5-brane background we find time dependent solutions to
the equations of motion, representing a time dependent fuzzy funnel. These
solutions match those obtained from the -string picture to leading order
suggesting that the action in the large limit does not need corrections. We
conclude by generalising our solutions to higher dimensional fuzzy funnels.Comment: 38 pages, Latex; references adde
Clostridium difficile in Ready-to-Eat Salads, Scotland
Of 40 ready-to-eat salads, 3 (7.5%) were positive for Clostridium difficile by PCR. Two isolates were PCR ribotype 017 (toxin A–, B+), and 1 was PCR ribotype 001. Isolates were susceptible to vancomycin and metronidazole but variably resistant to other antimicrobial drugs. Ready-to-eat salads may be potential sources for virulent C. difficile
Architectural and biochemical adaptations in skeletal muscle and bone following rotator cuff injury in a rat model
BACKGROUND: Injury to the rotator cuff can cause irreversible changes to the structure and function of the associated muscles and bones. The temporal progression and pathomechanisms associated with these adaptations are unclear. The purpose of this study was to investigate the time course of structural muscle and osseous changes in a rat model of a massive rotator cuff tear. METHODS: Supraspinatus and infraspinatus muscle architecture and biochemistry and humeral and scapular morphological parameters were measured three days, eight weeks, and sixteen weeks after dual tenotomy with and without chemical paralysis via botulinum toxin A (BTX). RESULTS: Muscle mass and physiological cross-sectional area increased over time in the age-matched control animals, decreased over time in the tenotomy+BTX group, and remained nearly the same in the tenotomy-alone group. Tenotomy+BTX led to increased extracellular collagen in the muscle. Changes in scapular bone morphology were observed in both experimental groups, consistent with reductions in load transmission across the joint. CONCLUSIONS: These data suggest that tenotomy alone interferes with normal age-related muscle growth. The addition of chemical paralysis yielded profound structural changes to the muscle and bone, potentially leading to impaired muscle function, increased muscle stiffness, and decreased bone strength. CLINICAL RELEVANCE: Structural musculoskeletal changes occur after tendon injury, and these changes are severely exacerbated with the addition of neuromuscular compromise
Consumption of the Total Western Diet Promotes Colitis and Inflammation-Associated Colorectal Cancer in Mice
Consumption of a Western type diet is a known risk factor for colorectal cancer. Our group previously developed the total Western diet (TWD) for rodents with energy and nutrient profiles that emulate a typical Western diet. In this study, we tested the hypothesis that consumption of the TWD would enhance colitis, delay recovery from gut injury and promote colon tumorigenesis. In multiple experiments using the azoxymethane + dextran sodium sulfate or ApcMin/+ mouse models of colitis-associated colorectal carcinogenesis (CAC), we determined that mice fed TWD experienced more severe and more prolonged colitis compared to their counterparts fed the standard AIN93G diet, ultimately leading to markedly enhanced colon tumorigenesis. Additionally, this increased tumor response was attributed to the micronutrient fraction of the TWD, and restoration of calcium and vitamin D to standard amounts ameliorated the tumor-promoting effects of TWD. Finally, exposure to the TWD elicited large scale, dynamic changes in mRNA signatures of colon mucosa associated with interferon (IFN) response, inflammation, innate immunity, adaptive immunity, and antigen processing pathways, among others. Taken together, these observations indicate that consumption of the TWD markedly enhanced colitis, delayed recovery from gut injury, and enhanced colon tumorigenesis likely via extensive changes in expression of immune-related genes in the colon mucosa
When the optimal is not the best: parameter estimation in complex biological models
Background: The vast computational resources that became available during the
past decade enabled the development and simulation of increasingly complex
mathematical models of cancer growth. These models typically involve many free
parameters whose determination is a substantial obstacle to model development.
Direct measurement of biochemical parameters in vivo is often difficult and
sometimes impracticable, while fitting them under data-poor conditions may
result in biologically implausible values.
Results: We discuss different methodological approaches to estimate
parameters in complex biological models. We make use of the high computational
power of the Blue Gene technology to perform an extensive study of the
parameter space in a model of avascular tumor growth. We explicitly show that
the landscape of the cost function used to optimize the model to the data has a
very rugged surface in parameter space. This cost function has many local
minima with unrealistic solutions, including the global minimum corresponding
to the best fit.
Conclusions: The case studied in this paper shows one example in which model
parameters that optimally fit the data are not necessarily the best ones from a
biological point of view. To avoid force-fitting a model to a dataset, we
propose that the best model parameters should be found by choosing, among
suboptimal parameters, those that match criteria other than the ones used to
fit the model. We also conclude that the model, data and optimization approach
form a new complex system, and point to the need of a theory that addresses
this problem more generally
The Detection and Characterization of cm Radio Continuum Emission from the Low-mass Protostar L1014-IRS
Observations by the Cores to Disk Legacy Team with the Spitzer Space
Telescope have identified a low luminosity, mid-infrared source within the
dense core, Lynds 1014, which was previously thought to harbor no internal
source. Followup near-infrared and submillimeter interferometric observations
have confirmed the protostellar nature of this source by detecting scattered
light from an outflow cavity and a weak molecular outflow. In this paper, we
report the detection of cm continuum emission with the VLA. The emission is
characterized by a quiescent, unresolved 90 uJy 6 cm source within 0.2" of the
Spitzer source. The spectral index of the quiescent component is between 6 cm and 3.6 cm. A factor of two increase in 6 cm
emission was detected during one epoch and circular polarization was marginally
detected at the level with Stokes {V/I} % . We have
searched for 22 GHz H2O maser emission toward L1014-IRS, but no masers were
detected during 7 epochs of observations between June 2004 and December 2006.
L1014-IRS appears to be a low-mass, accreting protostar which exhibits cm
emission from a thermal jet or a wind, with a variable non-thermal emission
component. The quiescent cm radio emission is noticeably above the correlation
of 3.6 cm and 6 cm luminosity versus bolometric luminosity, indicating more
radio emission than expected. We characterize the cm continuum emission in
terms of observations of other low-mass protostars, including updated
correlations of centimeter continuum emission with bolometric luminosity and
outflow force, and discuss the implications of recent larger distance estimates
on the physical attributes of the protostar and dense molecular core.Comment: 14 pages. Accepted for publication in Ap
A shallow though extensive H2 2.12 micron imaging survey of Taurus-Auriga-Perseus: I. NGC1333, L1455, L1448 and B1
We discuss wide-field near-IR imaging of the NGC1333, L1448, L1455 and B1
star forming regions in Perseus. The observations have been extracted from a
much larger narrow-band imaging survey of the Taurus-Auriga-Perseus complex.
These H2 2.12 micron observations are complemented by broad-band K imaging,
mid-IR imaging and photometry from the Spitzer Space Telescope, and published
submillimetre CO J=3-2 maps of high-velocity molecular outflows. We detect and
label 85 H2 features and associate these with 26 molecular outflows. Three are
parsec-scale flows, with a mean flow lobe length exceeding 11.5 arcmin. 37
(44%) of the detected H2 features are associated with a known Herbig-Haro
object, while 72 (46%) of catalogued HH objects are detected in H2 emission.
Embedded Spitzer sources are identified for all but two of the 26 molecular
outflows. These candidate outflow sources all have high near-to-mid-IR spectral
indices (mean value of alpha ~ 1.4) as well as red IRAC 3.6-4.5 micron and
IRAC/MIPS 4.5-24.0 micron colours: 80% have [3.6]-[4.5] > 1.0 and [4.5]-[24] >
1.5. These criteria - high alpha and red [4.5]-[24] and [3.6]-[4.5] colours -
are powerful discriminants when searching for molecular outflow sources.
However, we find no correlation between alpha and flow length or opening angle,
and the outflows appear randomly orientated in each region. The more massive
clouds are associated with a greater number of outflows, which suggests that
the star formation efficiency is roughly the same in each region.Comment: 23 pages (including Appoendix); 11 main text figures, 5 colour
appendix figs uploaded as gifs; accepted by MNRAS; for higher-resolution
figures please visit http://www.jach.hawaii.edu/~cdavis
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