184 research outputs found
On Symmetry Enhancement in the psu(1,1|2) Sector of N=4 SYM
Strong evidence indicates that the spectrum of planar anomalous dimensions of
N=4 super Yang-Mills theory is given asymptotically by Bethe equations. A
curious observation is that the Bethe equations for the psu(1,1|2) subsector
lead to very large degeneracies of 2^M multiplets, which apparently do not
follow from conventional integrable structures. In this article, we explain
such degeneracies by constructing suitable conserved nonlocal generators acting
on the spin chain. We propose that they generate a subalgebra of the loop
algebra for the su(2) automorphism of psu(1,1|2). Then the degenerate
multiplets of size 2^M transform in irreducible tensor products of M
two-dimensional evaluation representations of the loop algebra.Comment: 35 pages, v2: references added, sign inconsistency resolved in
(5.5,5.6), v3: Section 3.4 on Hamiltonian added, minor improvements, to
appear in JHE
Macrophages exert homeostatic actions in pregnancy to protect against preterm birth and fetal inflammatory injury
Macrophages are commonly thought to contribute to the pathophysiology of preterm labor by amplifying inflammation — but a protective role has not previously been considered to our knowledge. We hypothesized that given their antiinflammatory capability in early pregnancy, macrophages exert essential roles in maintenance of late gestation and that insufficient macrophages may predispose individuals to spontaneous preterm labor and adverse neonatal outcomes. Here, we showed that women with spontaneous preterm birth had reduced CD209⁺CD206⁺ expression in alternatively activated CD45⁺CD14⁺ICAM3⁻ macrophages and increased TNF expression in proinflammatory CD45⁺CD14⁺CD80⁺HLA-DR⁺ macrophages in the uterine decidua at the materno-fetal interface. In Cd11b(DTR/DTR) mice, depletion of maternal CD11b⁺ myeloid cells caused preterm birth, neonatal death, and postnatal growth impairment, accompanied by uterine cytokine and leukocyte changes indicative of a proinflammatory response, while adoptive transfer of WT macrophages prevented preterm birth and partially rescued neonatal loss. In a model of intra-amniotic inflammation–induced preterm birth, macrophages polarized in vitro to an M2 phenotype showed superior capacity over nonpolarized macrophages to reduce uterine and fetal inflammation, prevent preterm birth, and improve neonatal survival. We conclude that macrophages exert a critical homeostatic regulatory role in late gestation and are implicated as a determinant of susceptibility to spontaneous preterm birth and fetal inflammatory injury.Nardhy Gomez-Lopez, Valeria Garcia-Flores, Peck Yin Chin, Holly M. Groome, Melanie T. Bijland, Kerrilyn R. Diener, Roberto Romero, and Sarah A. Robertso
Scaling Tests of the Cross Section for Deeply Virtual Compton Scattering
We present the first measurements of the \vec{e}p->epg cross section in the
deeply virtual Compton scattering (DVCS) regime and the valence quark region.
The Q^2 dependence (from 1.5 to 2.3 GeV^2) of the helicity-dependent cross
section indicates the twist-2 dominance of DVCS, proving that generalized
parton distributions (GPDs) are accessible to experiment at moderate Q^2. The
helicity-independent cross section is also measured at Q^2=2.3 GeV^2. We
present the first model-independent measurement of linear combinations of GPDs
and GPD integrals up to the twist-3 approximation.Comment: 5 pages, 4 figures, 2 tables. Text shortened for publication.
References added. One figure remove
Exclusive Neutral Pion Electroproduction in the Deeply Virtual Regime
We present measurements of the ep->ep pi^0 cross section extracted at two
values of four-momentum transfer Q^2=1.9 GeV^2 and Q^2=2.3 GeV^2 at Jefferson
Lab Hall A. The kinematic range allows to study the evolution of the extracted
hadronic tensor as a function of Q^2 and W. Results will be confronted with
Regge inspired calculations and GPD predictions. An intepretation of our data
within the framework of semi-inclusive deep inelastic scattering has also been
attempted
Serre Relation and Higher Grade Generators of the AdS/CFT Yangian Symmetry
It was shown that the spin chain model coming from AdS/CFT correspondence
satisfies the Yangian symmetry if we assume evaluation representation, though
so far there is no explicit proof that the evaluation representation satisfies
the Serre relation, which is one of the defining equations of the Yangian
algebra imposing constraints on the whole algebraic structure. We prove
completely that the evaluation representation adopted in the model satisfies
the Serre relation by introducing a three-dimensional gamma matrix. After
studying the Serre relation, we proceed to the whole Yangian algebraic
structure, where we find that the conventional construction of higher grade
generators is singular and we propose an alternative construction. In the
discussion of the higher grade generators, a great simplification for the proof
of the Serre relation is found. Using this expression, we further show that the
proof is lifted to the exceptional superalgebra, which is a non-degenerate
deformation of the original superalgebra.Comment: 24 pages, 1 figure, v2: on exceptional superalgebra, previous
incorrect comments removed and new sections added, v3: clarifications adde
Virtual Compton Scattering and Neutral Pion Electroproduction in the Resonance Region up to the Deep Inelastic Region at Backward Angles
We have made the first measurements of the virtual Compton scattering (VCS)
process via the H exclusive reaction in the nucleon resonance
region, at backward angles. Results are presented for the -dependence at
fixed GeV, and for the -dependence at fixed near 1.5 GeV.
The VCS data show resonant structures in the first and second resonance
regions. The observed -dependence is smooth. The measured ratio of
H to H cross sections emphasizes the different
sensitivity of these two reactions to the various nucleon resonances. Finally,
when compared to Real Compton Scattering (RCS) at high energy and large angles,
our VCS data at the highest (1.8-1.9 GeV) show a striking -
independence, which may suggest a transition to a perturbative scattering
mechanism at the quark level.Comment: 20 pages, 8 figures. To appear in Phys.Rev.
Multi-parametric MR Imaging Biomarkers Associated to Clinical Outcomes in Gliomas: A Systematic Review
[EN] Purpose: To systematically review evidence regarding the association of multi-parametric biomarkers with clinical outcomes and their capacity to explain relevant subcompartments of gliomas.
Materials and Methods: Scopus database was searched for original journal papers from January 1st, 2007 to February 20th , 2017 according to PRISMA. Four hundred forty-nine abstracts of papers were reviewed and scored independently by two out of six authors. Based on those papers we analyzed associations between biomarkers, subcompartments within the tumor lesion, and clinical outcomes. From all the articles analyzed, the twenty-seven papers with the highest scores were highlighted to represent the evidence about MR imaging biomarkers associated with clinical outcomes. Similarly, eighteen studies defining subcompartments within the tumor region were also highlighted to represent the evidence of MR imaging biomarkers. Their reports were critically appraised according to the QUADAS-2 criteria.
Results: It has been demonstrated that multi-parametric biomarkers are prepared for surrogating diagnosis, grading, segmentation, overall survival, progression-free survival, recurrence, molecular profiling and response to treatment in gliomas. Quantifications and radiomics features obtained from morphological exams (T1, T2, FLAIR, T1c), PWI (including DSC and DCE), diffusion (DWI, DTI) and chemical shift imaging (CSI) are the preferred MR biomarkers associated to clinical outcomes. Subcompartments relative to the peritumoral region, invasion, infiltration, proliferation, mass effect and pseudo flush, relapse compartments, gross tumor volumes, and high-risk regions have been defined to characterize the heterogeneity. For the majority of pairwise cooccurrences, we found no evidence to assert that observed co-occurrences were significantly different from their expected co-occurrences (Binomial test with False Discovery Rate correction, alpha=0.05). The co-occurrence among terms in the studied papers was found to be driven by their individual prevalence and trends in the literature.
Conclusion: Combinations of MR imaging biomarkers from morphological, PWI, DWI and CSI exams have demonstrated their capability to predict clinical outcomes in different management moments of gliomas. Whereas morphologic-derived compartments have been mostly studied during the last ten years, new multi-parametric MRI approaches have also been proposed to discover specific subcompartments of the tumors. MR biomarkers from those subcompartments show the local behavior within the heterogeneous tumor and may quantify the prognosis and response to treatment of gliomas.This work was supported by the Spanish Ministry for Investigation, Development and Innovation project with identification number DPI2016-80054-R.Oltra-Sastre, M.; Fuster García, E.; Juan -Albarracín, J.; Sáez Silvestre, C.; Perez-Girbes, A.; Sanz-Requena, R.; Revert-Ventura, A.... (2019). Multi-parametric MR Imaging Biomarkers Associated to Clinical Outcomes in Gliomas: A Systematic Review. 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Dynamics of the O(e,e'p) cross section at high missing energies
We measured the cross section and response functions (R_L, R_T, and R_LT) for the 16O(e,e'p) reaction in quasielastic kinematics for missing energies 25 60 MeV and P_miss > 200 MeV/c, the cross section is relatively constant. Calculations which include contributions from pion exchange currents, isobar currents and short-range correlations account for the shape and the transversity but only for half of the magnitude of the measured cross section
Search for jet extinction in the inclusive jet-pT spectrum from proton-proton collisions at s=8 TeV
Published by the American Physical Society under the terms of the Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published articles title, journal citation, and DOI.The first search at the LHC for the extinction of QCD jet production is presented, using data collected with the CMS detector corresponding to an integrated luminosity of 10.7 fb−1 of proton-proton collisions at a center-of-mass energy of 8 TeV. The extinction model studied in this analysis is motivated by the search for signatures of strong gravity at the TeV scale (terascale gravity) and assumes the existence of string couplings in the strong-coupling limit. In this limit, the string model predicts the suppression of all high-transverse-momentum standard model processes, including jet production, beyond a certain energy scale. To test this prediction, the measured transverse-momentum spectrum is compared to the theoretical prediction of the standard model. No significant deficit of events is found at high transverse momentum. A 95% confidence level lower limit of 3.3 TeV is set on the extinction mass scale
Operation and performance of the ATLAS semiconductor tracker
The semiconductor tracker is a silicon microstrip detector forming part of the inner tracking system of the ATLAS experiment at the LHC. The operation and performance of the semiconductor tracker during the first years of LHC running are described. More than 99% of the detector modules were operational during this period, with an average intrinsic hit efficiency of (99.74±0.04)%. The evolution of the noise occupancy is discussed, and measurements of the Lorentz angle, δ-ray production and energy loss presented. The alignment of the detector is found to be stable at the few-micron level over long periods of time. Radiation damage measurements, which include the evolution of detector leakage currents, are found to be consistent with predictions and are used in the verification of radiation background simulations
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