522 research outputs found
GMOR-like relation in IR-conformal gauge theories
A generalization of the GMOR relation to the case of infrared-conformal gauge
theories is discussed. The starting point is the chiral Ward identity
connecting the isovector pseudoscalar susceptibility to the chiral condensate,
in a mass-deformed theory. A renormalization-group analysis shows that the
pseudoscalar susceptibility is not saturated by the lightest state, but a
contribution from the continuum part of the spectrum survives in the chiral
limit. The computation also shows how infrared-conformal gauge theories behave
differently, depending on whether the anomalous dimension of the chiral
condensate be smaller or larger than 1.Comment: 28 pages, 1 PDF figur
Conformal vs confining scenario in SU(2) with adjoint fermions
The masses of the lowest-lying states in the meson and in the gluonic sector
of an SU(2) gauge theory with two Dirac flavors in the adjoint representation
are measured on the lattice at a fixed value of the lattice coupling for values of the bare fermion mass that span a range
between the quenched regime and the massless limit, and for various lattice
volumes. Even for light constituent fermions the lightest glueballs are found
to be lighter than the lightest mesons. Moreover, the string tension between
two static fundamental sources strongly depends on the mass of the dynamical
fermions and becomes of the order of the inverse squared lattice linear size
before the chiral limit is reached. The implications of these findings for the
phase of the theory in the massless limit are discussed and a strategy for
discriminating between the (near--)conformal and the confining scenario is
outlined.Comment: 5 pages, 4 figures using RevTeX4, Typos corrected, references added.
Versions to appear on PR
Degeneracy Between the Regge Slope of Mesons and Baryons from Supersymmetry
We consider the degeneracy between the Regge slope of mesons and baryons in
QCD. We argue that within the "orientifold large-N approximation"
asymptotically massive mesons and baryons become supersymmetric partners and
hence degenerate. To this end, we generalize QCD by a SU(N) theory with a quark
in the two-index antisymmetric representation. We show that in this framework
the meson is represented by an oriented bosonic QCD-string and the baryon is
represented by an un-oriented fermionic QCD-string. At large-N, due to an
equivalence with super Yang-Mills, the tensions of the bosonic and the
fermionic strings coincide. Our description of mesons and baryons as oriented
and un-oriented bosonic and fermionic QCD-strings is in full agreement with the
spectra of open strings in the dual type 0' string theory.Comment: v2: extended version. Appendices and references adde
Large volumes and spectroscopy of walking theories
A detailed investigation of finite-size effects is performed for SU(2) gauge theory with two fermions in the adjoint representation, which previous lattice studies have shown to be inside the conformal window. The system is investigated with different spatial and temporal boundary conditions on lattices of various spatial and temporal extensions, for two values of the bare fermion mass representing a heavy and light fermion regime. Our study shows that the infinite-volume limit of masses and decay constants in the mesonic sector is reached only when the mass of the pseudoscalar particle MPS and the spatial lattice size L satisfy the relation LMPSâ„15. This bound, which is at least a factor of three higher than what is observed in QCD, is a likely consequence of the different spectral signatures of the two theories, with the scalar isosinglet (0++ glueball) being the lightest particle in our model. In addition to stressing the importance of simulating large lattice sizes, our analysis emphasizes the need to understand quantitatively the full spectrum of the theory rather than just the spectrum in the mesonic isotriplet sector. While for the lightest fermion measuring masses from gluonic operators proves to be still challenging, reliable results for glueball states are obtained at the largest fermion mass and, in the mesonic sector, for both fermion masses. As a byproduct of our investigation, we perform a finite-size scaling of the pseudoscalar mass and decay constant. The data presented in this work support the conformal behavior of this theory with an anomalous dimension Îł*â0.37
Animal models of compulsive eating behavior
In industrialized nations, overeating is a significant problem leading to overweight, obesity, and a host of related disorders; the increase in these disorders has prompted a significant amount of research aimed at understanding their etiology. Eating disorders are multifactorial conditions involving genetic, metabolic, environmental, and behavioral factors. Considering that compulsive eating in the face of adverse consequences characterizes some eating disorders, similar to the way in which compulsive drug intake characterizes drug-addiction, it might be considered an addiction in its own right. Moreover, numerous review articles have recently drawn a connection between the neural circuits activated in the seeking/intake of palatable food and drugs of abuse. Based on this observation, âfood addictionâ has emerged as an area of intense scientific research and accumulating evidence suggests it is possible to model some aspects of food addiction in animals. The development of well-characterized animal models would advance our understanding of the etiologic neural factors involved in eating disorders, such as compulsive overeating, and it would permit to propose targeted pharmacological therapies. However, to date, little evidence has been reported of continued food seeking and intake despite its harmful consequences in rats and mice
TRANSCRIPTOMIC ANALYSIS OF WHOLE PISTILS AND OVULE CELLS TO IDENTIFY GENES RELATED TO APOSPORY IN HYPERICUM PERFORATUM L.
St. John\u2019s wort (Hypericum perforatum L.) is a medicinal plant that produces important
metabolites with antidepressant and anticancer activities. Beside the pharmaceutical interest,
recently gained information has shown that H. perforatum is also an attractive model system for the
study of aposporous apomixis, that is a reproductive strategy, which, unlike sexual reproduction,
permits the inheritance of the maternal genome over generations without genetic recombination
events. This asexual mode of seed formation is believed to be a trait with enormous economic and
social potential in agriculture. Its innovative use in this area relies upon the idea that indefinitely
fixing highly complex genotypes, including hybrid cultivars, through apomixis would have
tremendous advantages in plant breeding, biomass and seed production. During the last decades, the
understanding of the molecular basis of apomixis in this species has been complicated by the lack of
biological data, e.g. genomic or even transcriptomic sequences. The aim of our research project was
the sequencing, annotation and comparative investigation of the H. perforatum flower
transcriptome, as critical steps toward a better understanding of the genetic control of aposporic and
sexual reproduction in the facultative apomict H. perforatum. To this end, next generation
sequencing technologies have been used to sequence the flower transcriptomes of obligate sexual
and unrelated apomictic H. perforatum genotypes. This approach has enabled the assembly and
annotation of large cDNA repositories and their exploitation to design a custom array to be used in
flower expression studies. Global gene expression analysis of H. perforatum was initially
performed on ovaries collected from sexual and aposporic plant accessions for the purpose of
identifying genes and processes potentially associated with apomixis in this model species. Overall,
across two selected developmental stages, 224 and 973 unigenes were found to be significantly upand down-regulated. Ontological annotation of differentially expressed genes indicated that terms
related to cell cycle, single-organism cellular process DNA (cytosine-5-)-methyltransferase activity,
among others, were significantly enriched. In a following step, a laser-capture microdissection
approach was adopted in combination the RNA-seq technology with the aim of identifying genes
differentially expressed in the ovule cell types primarily involved in the differentiation of the
megaspore mother cells and aposporous initials. On the whole, our data suggest that phenotypic
expression of apospory is concomitant with the modulation of key genes involved in the sexual
reproductive pathway and the responsive to hormonal stimuli. Annotation of all identified flower
transcripts as well as their qualitative and quantitative expression data will be presented and
critically discussed as they prove a far better understanding of molecular bases of pistil
development, embyo sac and egg cell formation in sexual and apomictic H. perforatum
Improved Lattice Spectroscopy of Minimal Walking Technicolor
We present a numerical study of spectroscopic observables in the SU(2) gauge
theory with two adjoint fermions using improved source and sink operators. We
compare in detail our improved results with previous determinations of masses
that used point sources and sinks and we investigate possible systematic
effects in both cases. Such comparison enables us to clearly assess the impact
of a short temporal extent on the physical picture, and to investigate some
effects due to the finite spatial box. While confirming the IR-conformal
behaviour of the theory, our investigation shows that in order to make firm
quantitative predictions, a better handle on finite size effects is needed.Comment: 33 pages, 30 figures, 18 table
Domain Walls and Metastable Vacua in Hot Orientifold Field Theories
We consider "Orientifold field theories", namely SU(N) gauge theories with
Dirac fermions in the two-index representation at high temperature. When N is
even these theories exhibit a spontaneously broken Z2 centre symmetry. We study
aspects of the domain wall that interpolates between the two vacua of the
theory. In particular we calculate its tension to two-loop order. We compare
its tension to the corresponding domain wall in a SU(N) gauge theory with
adjoint fermions and find an agreement at large-N, as expected from planar
equivalence between the two theories. Moreover, we provide a non-perturbative
proof for the coincidence of the tensions at large-N. We also discuss the
vacuum structure of the theory when the fermion is given a large mass and argue
that there exist N-2 metastable vacua. We calculate the lifetime of those vacua
in the thin wall approximation.Comment: 29 pages, 4 figures. v2: minor changes in the introduction section.
to appear in JHE
Gd-EOB-DTP-enhanced MRC in the preoperative percutaneous management of intra and extrahepatic biliary leakages: Does it matter?
Postoperative bile leakage is a common complication of abdominal surgical procedures and a precise localization of is important to choose the best management. Many techniques are available to correctly identify bile leaks, including ultrasound (US), computed tomography (CT) or magnetic resonance imaging (MRI), being the latter the best to clearly depict "active" bile leakages. This paper presents the state of the art algorithm in the detection of biliary leakages in order to plan a percutaneous biliary drainage focusing on widely available and safe contrast agent, the Gb-EOB-DPA. We consider its pharmacokinetic properties and impact in biliary imaging explain current debates to optimize image quality. We report common sites of leakage after surgery with special considerations in cirrhotic liver to show what interventional radiologists should look to easily detect bile leaks
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