412 research outputs found
Direct Mediation and Metastable Supersymmetry Breaking for SO(10)
We examine a metastable Macroscopic SO(N) SQCD model of
Intriligator, Seiberg and Shih (ISS). We introduce various baryon and meson
deformations, including multitrace operators and explore embedding an SO(10)
parent of the standard model into two weakly gauged flavour sectors. Direct
fundamental messengers and the symmetric pseudo-modulus messenger mediate SUSY
breaking to the MSSM. Gaugino and sfermion masses are computed and compared for
each deformation type. We also explore reducing the rank of the magnetic quark
matrix of the ISS model and find an additional fundamental messenger.Comment: 43 pages, Latex. Version to appear in JHEP
Holographic Anyons in the ABJM Theory
We consider the holographic anyons in the ABJM theory from three different
aspects of AdS/CFT correspondence. First, we identify the holographic anyons by
using the field equations of supergravity, including the Chern-Simons terms of
the probe branes. We find that the composite of Dp-branes wrapped over CP3 with
the worldvolume magnetic fields can be the anyons. Next, we discuss the
possible candidates of the dual anyonic operators on the CFT side, and find the
agreement of their anyonic phases with the supergravity analysis. Finally, we
try to construct the brane profile for the holographic anyons by solving the
equations of motion and Killing spinor equations for the embedding profile of
the wrapped branes. As a by product, we find a BPS spiky brane for the dual
baryons in the ABJM theory.Comment: 1+33 pages, 3 figures; v2 discussion for D4-D6 case added, references
added; v3 comments adde
Holomorphic variables in magnetized brane models with continuous Wilson lines
We analyze the action of the target-space modular group in toroidal type IIB
orientifold compactifications with magnetized D-branes and continuous Wilson
lines. The transformation of matter fields agree with that of twisted fields in
heterotic compactifications, constituting a check of type I/heterotic duality.
We identify the holomorphic N = 1 variables for these compactifications. Matter
fields and closed string moduli are both redefined by open string moduli. The
redefinition of matter fields can be read directly from the perturbative Yukawa
couplings, whereas closed string moduli redefinitions are obtained from D-brane
instanton superpotential couplings. The resulting expressions reproduce and
generalize, in the presence of internal magnetic fields, previous results in
the literature.Comment: 9 pages, no figures; v2: conventions for Wilson lines changed, major
simplifications in expressions, discussions extended, typos corrected, some
references adde
Fluoromycobacteriophages for rapid, specific, and sensitive antibiotic susceptibility testing of Mycobacterium tuberculosis
Rapid antibiotic susceptibility testing of Mycobacterium tuberculosis is of paramount importance as multiple- and extensively- drug resistant strains of M. tuberculosis emerge and spread. We describe here a virus-based assay in which fluoromycobacteriophages are used to deliver a GFP or ZsYellow fluorescent marker gene to M. tuberculosis, which can then be monitored by fluorescent detection approaches including fluorescent microscopy and flow cytometry. Pre-clinical evaluations show that addition of either Rifampicin or Streptomycin at the time of phage addition obliterates fluorescence in susceptible cells but not in isogenic resistant bacteria enabling drug sensitivity determination in less than 24 hours. Detection requires no substrate addition, fewer than 100 cells can be identified, and resistant bacteria can be detected within mixed populations. Fluorescence withstands fixation by paraformaldehyde providing enhanced biosafety for testing MDR-TB and XDR-TB infections. © 2009 Piuri et al
Drivers of Bornean orangutan distribution across a multiple-use tropical landscape
Logging and conversion of tropical forests in Southeast Asia have resulted in the expansion of landscapes containing a mosaic of habitats that may vary in their ability to sustain local biodiversity. However, the complexity of these landscapes makes it difficult to assess abundance and distribution of some species using ground-based surveys alone. Here we deployed a combination of ground-transects and aerial surveys to determine drivers of the Critically Endangered Bornean Orangutan (Pongo pygmaeus) distribution across a large multiple-use landscape in Sabah, Malaysian Borneo. Ground-transects and aerial surveys using drones were conducted for orangutan nests and strangler fig trees (an important food resource) in 48 survey areas across 76 km2, within a study landscape of 261 km2 Orangutan nest count data were fitted to models accounting for variation in land use, above-ground carbon density (ACD; a surrogate for forest quality), strangler fig density, and elevation (between 117 and 675 m). Orangutan nest counts were significantly higher in all land uses possessing natural forest cover, regardless of degradation status, than in monoculture plantations. Within these natural forests, nest counts increased with higher ACD and strangler fig density, but not with elevation. In logged forest (ACD 14 – 150 Mg ha-1), strangler fig density had a significant, positive relationship with orangutan nest counts, but this relationship disappeared in forest with higher carbon content (ACD 150- 209 Mg ha-1). Based on an area-to-area comparison, orangutan nest counts from ground transects were higher than from counts derived from aerial surveys, but this did not constitute a statistically significant difference. Although the difference in nest counts was not significantly different, this analysis indicates that both methods under-sample the total number of nests present within a given area. Aerial surveys are therefore a useful method for assessing orangutan habitat use over large areas, however the under-estimation of nest counts by both methods suggests that a small number of ground surveys should be retained in future surveys using this technique, particularly in areas with dense understory vegetation. This study shows that even highly degraded forests may be suitable orangutan habitat as long as strangler fig trees remain intact after areas of forest are logged. Enrichment planting of strangler figs may therefore be a valuable tool for orangutan conservation in these landscapes
A holographic model for the fractional quantum Hall effect
Experimental data for fractional quantum Hall systems can to a large extent
be explained by assuming the existence of a modular symmetry group commuting
with the renormalization group flow and hence mapping different phases of
two-dimensional electron gases into each other. Based on this insight, we
construct a phenomenological holographic model which captures many features of
the fractional quantum Hall effect. Using an SL(2,Z)-invariant
Einstein-Maxwell-axio-dilaton theory capturing the important modular
transformation properties of quantum Hall physics, we find dyonic diatonic
black hole solutions which are gapped and have a Hall conductivity equal to the
filling fraction, as expected for quantum Hall states. We also provide several
technical results on the general behavior of the gauge field fluctuations
around these dyonic dilatonic black hole solutions: We specify a sufficient
criterion for IR normalizability of the fluctuations, demonstrate the
preservation of the gap under the SL(2,Z) action, and prove that the
singularity of the fluctuation problem in the presence of a magnetic field is
an accessory singularity. We finish with a preliminary investigation of the
possible IR scaling solutions of our model and some speculations on how they
could be important for the observed universality of quantum Hall transitions.Comment: 86 pages, 16 figures; v.2 references added, typos fixed, improved
discussion of ref. [39]; v.3 more references added and typos fixed, several
statements clarified, v.4 version accepted for publication in JHE
Graphene Photonics and Optoelectronics
The richness of optical and electronic properties of graphene attracts
enormous interest. Graphene has high mobility and optical transparency, in
addition to flexibility, robustness and environmental stability. So far, the
main focus has been on fundamental physics and electronic devices. However, we
believe its true potential to be in photonics and optoelectronics, where the
combination of its unique optical and electronic properties can be fully
exploited, even in the absence of a bandgap, and the linear dispersion of the
Dirac electrons enables ultra-wide-band tunability. The rise of graphene in
photonics and optoelectronics is shown by several recent results, ranging from
solar cells and light emitting devices, to touch screens, photodetectors and
ultrafast lasers. Here we review the state of the art in this emerging field.Comment: Review Nature Photonics, in pres
Longitudinal peak strain detects a smaller risk area than visual assessment of wall motion in acute myocardial infarction
<p>Abstract</p> <p>Background</p> <p>Opening of an occluded infarct related artery reduces infarct size and improves survival in acute ST-elevation myocardial infarction (STEMI). In this study we performed tissue Doppler analysis (peak strain, displacement, mitral annular movement (MAM)) and compared with visual assessment for the study of the correlation of measurements of global, regional and segmental function with final infarct size and transmurality. In addition, myocardial risk area was determined and a prediction sought for the development of infarct transmurality ≥50%.</p> <p>Methods</p> <p>Twenty six patients with STEMI submitted for primary percutaneous coronary intervention (PCI) were examined with echocardiography on the catheterization table. Four to eight weeks later repeat echocardiography was performed for reassessment of function and magnetic resonance imaging for the determination of final infarct size and transmurality.</p> <p>Results</p> <p>On a global level, wall motion score index (WMSI), ejection fraction (EF), strain, and displacement all showed significant differences (p ≤ 0.001, p ≤ 0.001, p ≤ 0.001 and p = 0.03) between the two study visits, but MAM did not (p = 0.17). On all levels (global, regional and segmental) and both pre- and post PCI, WMSI showed a higher correlation with scar transmurality compared to strain. We found that both strain and WMSI predicted the development of scar transmurality ≥50%, but strain added no significant information to that obtained with WMSI in a logistic regression analysis.</p> <p>Conclusions</p> <p>In patients with acute STEMI, WMSI, EF, strain, and displacement showed significant changes between the pre- and post PCI exam. In a ROC-analysis, strain had 64% sensitivity at 80% specificity and WMSI around 90% sensitivity at 80% specificity for the detection of scar with transmurality ≥50% at follow-up.</p
Multiple populations in globular clusters. Lessons learned from the Milky Way globular clusters
Recent progress in studies of globular clusters has shown that they are not
simple stellar populations, being rather made of multiple generations. Evidence
stems both from photometry and spectroscopy. A new paradigm is then arising for
the formation of massive star clusters, which includes several episodes of star
formation. While this provides an explanation for several features of globular
clusters, including the second parameter problem, it also opens new
perspectives about the relation between globular clusters and the halo of our
Galaxy, and by extension of all populations with a high specific frequency of
globular clusters, such as, e.g., giant elliptical galaxies. We review progress
in this area, focusing on the most recent studies. Several points remain to be
properly understood, in particular those concerning the nature of the polluters
producing the abundance pattern in the clusters and the typical timescale, the
range of cluster masses where this phenomenon is active, and the relation
between globular clusters and other satellites of our Galaxy.Comment: In press (The Astronomy and Astrophysics Review
A review of elliptical and disc galaxy structure, and modern scaling laws
A century ago, in 1911 and 1913, Plummer and then Reynolds introduced their
models to describe the radial distribution of stars in `nebulae'. This article
reviews the progress since then, providing both an historical perspective and a
contemporary review of the stellar structure of bulges, discs and elliptical
galaxies. The quantification of galaxy nuclei, such as central mass deficits
and excess nuclear light, plus the structure of dark matter halos and cD galaxy
envelopes, are discussed. Issues pertaining to spiral galaxies including dust,
bulge-to-disc ratios, bulgeless galaxies, bars and the identification of
pseudobulges are also reviewed. An array of modern scaling relations involving
sizes, luminosities, surface brightnesses and stellar concentrations are
presented, many of which are shown to be curved. These 'redshift zero'
relations not only quantify the behavior and nature of galaxies in the Universe
today, but are the modern benchmark for evolutionary studies of galaxies,
whether based on observations, N-body-simulations or semi-analytical modelling.
For example, it is shown that some of the recently discovered compact
elliptical galaxies at 1.5 < z < 2.5 may be the bulges of modern disc galaxies.Comment: Condensed version (due to Contract) of an invited review article to
appear in "Planets, Stars and Stellar
Systems"(www.springer.com/astronomy/book/978-90-481-8818-5). 500+ references
incl. many somewhat forgotten, pioneer papers. Original submission to
Springer: 07-June-201
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