1,196 research outputs found
Deformed Quantum Cohomology and (0,2) Mirror Symmetry
We compute instanton corrections to correlators in the genus-zero topological
subsector of a (0,2) supersymmetric gauged linear sigma model with target space
P1xP1, whose left-moving fermions couple to a deformation of the tangent
bundle. We then deduce the theory's chiral ring from these correlators, which
reduces in the limit of zero deformation to the (2,2) ring. Finally, we compare
our results with the computations carried out by Adams et al.[ABS04] and Katz
and Sharpe[KS06]. We find immediate agreement with the latter and an
interesting puzzle in completely matching the chiral ring of the former.Comment: AMSLatex, 30 pages, one eps figure. V4: typos corrected, final
version appearing in JHE
Cigarette Smoke Exposure Alters mSin3a and Mi-2α/ÎČ Expression; implications in the control of pro-inflammatory gene transcription and glucocorticoid function
<p>Abstract</p> <p>Background</p> <p>The key co-repressor complex components HDAC-2, Mi-2α/ÎČ and mSin3a are all critical to the regulation of gene transcription. HDAC-2 function is impaired by oxidative stress in a PI3KÎŽ dependant manner which may be involved in the chronic glucocorticoid insensitive inflammation in the lungs of COPD patients. However, the impact of cigarette smoke exposure on the expression of mSin3a and Mi2α/ÎČ and their role in glucocorticoid responsiveness is unknown.</p> <p>Methods</p> <p>Wild type, PI3KÎł knock-out (PI3KÎł<sup>-/-</sup>) and PI3K kinase dead knock-in (PI3KÎŽ<sup>D910/A910</sup>) transgenic mice were exposed to cigarette smoke for 3 days and the expression levels of the co-repressor complex components HDAC-2, mSin3a, Mi-2α and Mi-2ÎČ and HDAC-2 activity in the lungs were assessed.</p> <p>Results</p> <p>Cigarette smoke exposure impaired glucocorticoid function and reduced HDAC-2 activity which was protected in the PI3KÎŽ<sup>D910/A910 </sup>mice. Both mSin3a and Mi-2α protein expression was reduced in smoke-exposed mice. Budesonide alone protected mSin3a protein expression with no additional effect seen with abrogation of PI3KÎł/ÎŽ activity, however Mi-2α, but not Mi-2ÎČ, expression was protected in both PI3KÎŽ<sup>D910/A910 </sup>and PI3KÎł<sup>-/- </sup>budesonide-treated smoke-exposed mice. The restoration of glucocorticoid function coincided with the protection of both HDAC activity and mSin3a and Mi-2α protein expression.</p> <p>Conclusions</p> <p>Cigarette smoke exposure induced glucocorticoid insensitivity and alters co-repressor activity and expression which is prevented by blockade of PI3K signaling with glucocorticoid treatment. Inhibition of PI3KÎŽ signalling in combination with glucocorticoid treatment may therefore provide a therapeutic strategy for restoring oxidant-induced glucocortiocid unresponsiveness.</p
Landscape Study of Target Space Duality of (0,2) Heterotic String Models
In the framework of (0,2) gauged linear sigma models, we systematically
generate sets of perturbatively dual heterotic string compactifications. This
target space duality is first derived in non-geometric phases and then
translated to the level of GLSMs and its geometric phases. In a landscape
analysis, we compare the massless chiral spectra and the dimensions of the
moduli spaces. Our study includes geometries given by complete intersections of
hypersurfaces in toric varieties equipped with SU(n) vector bundles defined via
the monad construction.Comment: 40 pages, 6 figure
Gauged Linear Sigma Models for toroidal orbifold resolutions
Toroidal orbifolds and their resolutions are described within the framework
of (2,2) Gauged Linear Sigma Models (GLSMs). Our procedure describes two-tori
as hypersurfaces in (weighted) projective spaces. The description is chosen
such that the orbifold singularities correspond to the zeros of their
homogeneous coordinates. The individual orbifold singularities are resolved
using a GLSM guise of non-compact toric resolutions, i.e. replacing discrete
orbifold actions by Abelian worldsheet gaugings. Given that we employ the same
global coordinates for both the toroidal orbifold and its resolutions, our GLSM
formalism confirms the gluing procedure on the level of divisors discussed by
Lust et al. Using our global GLSM description we can study the moduli space of
such toroidal orbifolds as a whole. In particular, changes in topology can be
described as phase transitions of the underlying GLSM. Finally, we argue that
certain partially resolvable GLSMs, in which a certain number of fixed points
can never be resolved, might be useful for the study of mini-landscape orbifold
MSSMs.Comment: 71 pages, 2 figure
Non-relativistic Matrix Inflation
We reconsider a string theoretic inflationary model, where inflation is
driven by multiple coincident -branes in the finite limit. We show
that the finite action can be continued to the limit of large , where it
converges to the action for a wrapped -brane with units of U(1) flux.
This provides an important consistency check of the scenario and allows for
more control over certain back-reaction effects. We determine the most general
form of the action for a specific sub-class of models and examine the
non-relativistic limits of the theory where the branes move at speeds much less
than the speed of light. The non-Abelian nature of the world-volume theory
implies that the inflaton field is matrix valued and this results in
modifications to the slow-roll parameters and Hubble-flow equations. A specific
small field model of inflation is investigated where the branes move out of an
AdS throat, and observational constraints are employed to place bounds on the
background fluxes.Comment: 25 page
S100A7 (psoriasin) expression is associated with aggressive features and alteration of Jab1 in ductal carcinoma in situ of the breast
INTRODUCTION: The S100A7 (psoriasin) gene is highly expressed in ductal carcinoma in situ (DCIS) of the breast and can be downregulated in invasive carcinoma. Persistent S100A7 expression in invasive carcinoma is associated with a worse prognosis, and this effect may be mediated in part through interaction with the multifunctional cell signaling protein Jab1. METHODS: In order to investigate the relationship between S100A7 and progression from DCIS to invasive carcinoma, we studied S100A7 expression in 136 patients with DCIS (including 46 patients with associated invasive carcinoma) by immunohistochemistry. RESULTS: S100A7 expression was present in 63 out of 136 (46%) of DCIS lesions and was associated with estrogen receptor negative status (P = 0.0002), higher nuclear grade (P < 0.0001), necrosis (P < 0.0001) and inflammation (P < 0.0001). S100A7 status was no different between DCIS with and DCIS without an invasive component, but higher levels of S100A7 were present in DCIS associated with invasive carcinoma (P < 0.004). Analysis of a subset of cases showed that S100A7 expression was also associated with an increase in nuclear Jab1 (n = 43; P = 0.0019) and reduced p27(kip1 )(n = 47; P = 0.0168). In cases of DCIS associated with invasive carcinoma, there was also a significant reduction in S100A7 between in situ and invasive components (n = 46; P < 0.0001). In pure DCIS cases treated by local excision, there was no difference in frequency of S100A7 expression between patients with recurrence of DCIS (n = 9) and those without (n = 36). CONCLUSION: The findings reported here suggest that, although S100A7 may not be a marker for recurrence of DCIS, it is associated with poor prognostic markers in DCIS and may influence progression of breast carcinoma through its interaction with and influence on Jab1
Jet energy measurement with the ATLAS detector in proton-proton collisions at root s=7 TeV
The jet energy scale and its systematic uncertainty are determined for jets measured with the ATLAS detector at the LHC in proton-proton collision data at a centre-of-mass energy of âs = 7TeV corresponding to an integrated luminosity of 38 pb-1. Jets are reconstructed with the anti-kt algorithm with distance parameters R=0. 4 or R=0. 6. Jet energy and angle corrections are determined from Monte Carlo simulations to calibrate jets with transverse momenta pTâ„20 GeV and pseudorapidities {pipe}η{pipe}<4. 5. The jet energy systematic uncertainty is estimated using the single isolated hadron response measured in situ and in test-beams, exploiting the transverse momentum balance between central and forward jets in events with dijet topologies and studying systematic variations in Monte Carlo simulations. The jet energy uncertainty is less than 2. 5 % in the central calorimeter region ({pipe}η{pipe}<0. 8) for jets with 60â€pT<800 GeV, and is maximally 14 % for pT<30 GeV in the most forward region 3. 2â€{pipe}η{pipe}<4. 5. The jet energy is validated for jet transverse momenta up to 1 TeV to the level of a few percent using several in situ techniques by comparing a well-known reference such as the recoiling photon pT, the sum of the transverse momenta of tracks associated to the jet, or a system of low-pT jets recoiling against a high-pT jet. More sophisticated jet calibration schemes are presented based on calorimeter cell energy density weighting or hadronic properties of jets, aiming for an improved jet energy resolution and a reduced flavour dependence of the jet response. The systematic uncertainty of the jet energy determined from a combination of in situ techniques is consistent with the one derived from single hadron response measurements over a wide kinematic range. The nominal corrections and uncertainties are derived for isolated jets in an inclusive sample of high-pT jets. Special cases such as event topologies with close-by jets, or selections of samples with an enhanced content of jets originating from light quarks, heavy quarks or gluons are also discussed and the corresponding uncertainties are determined. © 2013 CERN for the benefit of the ATLAS collaboration
Measurement of the inclusive and dijet cross-sections of b-jets in pp collisions at sqrt(s) = 7 TeV with the ATLAS detector
The inclusive and dijet production cross-sections have been measured for jets
containing b-hadrons (b-jets) in proton-proton collisions at a centre-of-mass
energy of sqrt(s) = 7 TeV, using the ATLAS detector at the LHC. The
measurements use data corresponding to an integrated luminosity of 34 pb^-1.
The b-jets are identified using either a lifetime-based method, where secondary
decay vertices of b-hadrons in jets are reconstructed using information from
the tracking detectors, or a muon-based method where the presence of a muon is
used to identify semileptonic decays of b-hadrons inside jets. The inclusive
b-jet cross-section is measured as a function of transverse momentum in the
range 20 < pT < 400 GeV and rapidity in the range |y| < 2.1. The bbbar-dijet
cross-section is measured as a function of the dijet invariant mass in the
range 110 < m_jj < 760 GeV, the azimuthal angle difference between the two jets
and the angular variable chi in two dijet mass regions. The results are
compared with next-to-leading-order QCD predictions. Good agreement is observed
between the measured cross-sections and the predictions obtained using POWHEG +
Pythia. MC@NLO + Herwig shows good agreement with the measured bbbar-dijet
cross-section. However, it does not reproduce the measured inclusive
cross-section well, particularly for central b-jets with large transverse
momenta.Comment: 10 pages plus author list (21 pages total), 8 figures, 1 table, final
version published in European Physical Journal
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