1,264 research outputs found
Anomalous dimensions of leading twist conformal operators
We extend and develop a method for perturbative calculations of anomalous
dimensions and mixing matrices of leading twist conformal primary operators in
conformal field theories. Such operators lie on the unitarity bound and hence
are conserved (irreducible) in the free theory. The technique relies on the
known pattern of breaking of the irreducibility conditions in the interacting
theory. We relate the divergence of the conformal operators via the field
equations to their descendants involving an extra field and accompanied by an
extra power of the coupling constant. The ratio of the two-point functions of
descendants and of their primaries determines the anomalous dimension, allowing
us to gain an order of perturbation theory. We demonstrate the efficiency of
the formalism on the lowest-order analysis of anomalous dimensions and mixing
matrices which is required for two-loop calculations of the former. We compare
these results to another method based on anomalous conformal Ward identities
and constraints from the conformal algebra. It also permits to gain a
perturbative order in computations of mixing matrices. We show the complete
equivalence of both approaches.Comment: 21 pages, 4 figures; references adde
Dogs are more permissive than cats or guinea pigs to experimental infection with a human isolate of Bartonella rochalimae
Bartonella rochalimae was first isolated from the blood of a human who traveled to Peru and was exposed to multiple insect bites. Foxes and dogs are likely natural reservoirs for this bacterium. We report the results of experimental inoculation of two dogs, five cats and six guinea pigs with the only human isolate of this new Bartonella species. Both dogs became bacteremic for 5–7 weeks, with a peak of 103–104 colony forming units (CFU)/mL blood. Three cats had low bacteremia levels (< 200 CFU/mL) of 6–8 weeks’ duration. One cat that remained seronegative had two bacterial colonies isolated at a single culture time point. A fifth cat never became bacteremic, but seroconverted. None of the guinea pigs became bacteremic, but five seroconverted. These results suggest that dogs could be a reservoir of this strain of B. rochalimae, in contrast to cats and guinea pigs
Using participatory and creative methods to facilitate emancipatory research with people facing multiple disadvantage: a role for health and care professionals
Participatory and creative research methods are a powerful tool for enabling active engagement in the research process of marginalised people. It can be particularly hard for people living with multiple disadvantage, such as disabled people from ethnic minority backgrounds, to access research projects that are relevant to their lived experience. This article argues that creative and participatory methods facilitate the co-researchers’ engagement in the research process, which thus becomes more empowering. Exploring the congruence of these methods with their professional ethos, health and care professionals can use their skills to develop them further. Both theory and practice examples are presented
Comparison of the stand-alone Cox-Maze IV procedure to the concomitant Cox-Maze IV and mitral valve procedure for atrial fibrillation
BACKGROUND: The majority of patients undergoing surgical ablation for atrial fibrillation (AF) worldwide receive a concomitant mitral valve (MV) procedure. This study compared outcomes of the Cox-Maze IV (CMIV) in patients with lone AF to those with AF and MV disease. METHODS: A retrospective review of 335 patients receiving either a stand-alone CMIV for AF (n=151) or a CMIV with a MV procedure (n=184) was performed from January 2002 through December of 2012. Data were obtained at 3, 6, 12, 24, and 48 months and patients were evaluated for recurrence of AF. Twenty-four preoperative and perioperative variables were evaluated to identify predictors of AF recurrence at one year. RESULTS: The two groups differed in that stand-alone CMIV patients were younger, had AF of longer duration and had more failed catheter ablations, while patients with AF and MV disease had larger left atria and worse New York Heart Association class (P≤0.001). Operative mortality was higher in the concomitant MV group (1% vs. 5%, P=0.015). Freedom from AF and antiarrhythmic drugs at 12 and 24 months were similar between the two groups (73% and 76% at 12 months; 77% vs. 78% at 24 months). Predictors of recurrence included failure to use a box-lesion to isolate the pulmonary veins and posterior left atria, early recurrence of atrial tachyarrhythmias (ATAs) and the presence of a preoperative pacemaker (P=0.001). CONCLUSIONS: The efficacy of the CMIV procedure was similar in patients with and without co-existent MV pathology. Patients receiving a concomitant CMIV and MV procedure represented an older and sicker patient population and had higher mortality rates than those receiving a stand-alone CMIV procedure
The cusp anomalous dimension at three loops and beyond
We derive an analytic formula at three loops for the cusp anomalous dimension
Gamma_cusp(phi) in N=4 super Yang-Mills. This is done by exploiting the
relation of the latter to the Regge limit of massive amplitudes. We comment on
the corresponding three loops quark anti-quark potential. Our result also
determines a considerable part of the three-loop cusp anomalous dimension in
QCD. Finally, we consider a limit in which only ladder diagrams contribute to
physical observables. In that limit, a precise agreement with strong coupling
is observed.Comment: 34 pages, 6 figures. v2: references added, typos correcte
Adenosine triphosphate-sensitive potassium channel Kir subunits implicated in cardioprotection by diazoxide
BACKGROUND: ATP-sensitive potassium (K(ATP)) channel openers provide cardioprotection in multiple models. Ion flux at an unidentified mitochondrial K(ATP) channel has been proposed as the mechanism. The renal outer medullary kidney potassium channel subunit, potassium inward rectifying (Kir)1.1, has been implicated as a mitochondrial channel pore-forming subunit. We hypothesized that subunit Kir1.1 is involved in cardioprotection (maintenance of volume homeostasis and contractility) of the K(ATP) channel opener diazoxide (DZX) during stress (exposure to hyperkalemic cardioplegia [CPG]) at the myocyte and mitochondrial levels. METHODS AND RESULTS: Kir subunit inhibitor Tertiapin Q (TPN-Q) was utilized to evaluate response to stress. Mouse ventricular mitochondrial volume was measured in the following groups: isolation buffer; 200 μmol/L of ATP; 100 μmol/L of DZX+200 μmol/L of ATP; or 100 μmol/L of DZX+200 μmol/L of ATP+TPN-Q (500 or 100 nmol/L). Myocytes were exposed to Tyrode’s solution (5 minutes), test solution (Tyrode’s, cardioplegia [CPG], CPG+DZX, CPG+DZX+TPN-Q, Tyrode’s+TPN-Q, or CPG+TPN-Q), N=12 for all (10 minutes); followed by Tyrode’s (5 minutes). Volumes were compared. TPN-Q, with or without DZX, did not alter mitochondrial or myocyte volume. Stress (CPG) resulted in myocyte swelling and reduced contractility that was prevented by DZX. TPN-Q prevented the cardioprotection afforded by DZX (volume homeostasis and maintenance of contractility). CONCLUSIONS: TPN-Q inhibited myocyte cardioprotection provided by DZX during stress; however, it did not alter mitochondrial volume. Because TPN-Q inhibits Kir1.1, Kir3.1, and Kir3.4, these data support that any of these Kir subunits could be involved in the cardioprotection afforded by diazoxide. However, these data suggest that mitochondrial swelling by diazoxide does not involve Kir1.1, 3.1, or 3.4
Investigation of A1g phonons in YBa2Cu3O7 by means of LAPW atomic-force calculations
We report first-principles frozen-phonon calculations for the determination
of the force-free geometry and the dynamical matrix of the five Raman-active
A1g modes in YBa2Cu3O7. To establish the shape of the phonon potentials atomic
forces are calculated within the LAPW method. Two different schemes - the local
density approximation (LDA) and a generalized gradient approximation (GGA) -
are employed for the treatment of electronic exchange and correlation effects.
We find that in the case of LDA the resulting phonon frequencies show a
deviation from experimental values of approximately -10%. Invoking GGA the
frequency values are significantly improved and also the eigenvectors are in
very good agreement with experimental findings.Comment: 15 page
No triangles on the moduli space of maximally supersymmetric gauge theory
Maximally supersymmetric gauge theory in four dimensions has a remarkably
simple S-matrix at the origin of its moduli space at both tree and loop level.
This leads to the question what, if any, of this structure survives at the
complement of this one point. Here this question is studied in detail at one
loop for the branch of the moduli space parameterized by a vacuum expectation
value for one complex scalar. Motivated by the parallel D-brane picture of
spontaneous symmetry breaking a simple relation is demonstrated between the
Lagrangian of broken super Yang-Mills theory and that of its higher dimensional
unbroken cousin. Using this relation it is proven both through an on- as well
as an off-shell method there are no so-called triangle coefficients in the
natural basis of one-loop functions at any finite point of the moduli space for
the theory under study. The off-shell method yields in addition absence of
rational terms in a class of theories on the Coulomb branch which includes the
special case of maximal supersymmetry. The results in this article provide
direct field theory evidence for a recently proposed exact dual conformal
symmetry motivated by the AdS/CFT correspondence.Comment: 39 pages, 4 figure
Integrated measures of lead and manganese exposure improve estimation of their joint effects on cognition in Italian school-age children
Every day humans are exposed to mixtures of chemicals, such as lead (Pb) and manganese (Mn). An underappreciated aspect of studying the health effects of mixtures is the role that the exposure biomarker media (blood, hair, etc.) may play in estimating the effects of the mixture. Different biomarker media represent different aspects of each chemical's toxicokinetics, thus no single medium can fully capture the toxicokinetic profile for all the chemicals in a mixture. A potential solution to this problem is to combine exposure data across different media to derive integrated estimates of each chemical's internal concentration. This concept, formalized as a multi-media biomarker (MMB) has proven effective for estimating the health impacts of Pb exposure, but may also be useful to estimate mixture effects, such as the joint effects of metals like Pb and Mn, while factoring in how the association changes based upon the biomarker media. Levels of Pb and Mn were quantified in five media: blood, hair, nails, urine, and saliva in the Public Health Impact of Metals Exposure (PHIME) project, a study of Italian adolescents aged 10–14 years. MMBs were derived for both metals using weighted quantile sum (WQS) regression across the five media. Age-adjusted Wechsler Intelligence Scale for Children (WISC) IQ scores, measured at the same time as the exposure measures, were the primary outcome and models were adjusted for sex and socioeconomic status. The levels Pb and Mn were relatively low, with median blood Pb of 1.27 (IQR: 0.84) μg/dL and median blood Mn of 1.09 (IQR: 0.45) μg/dL. Quartile increases in a Pb-Mn combination predicted decreased Full Scale IQ of 1.9 points (95% CI: 0.3, 3.5) when Pb and Mn exposure levels were estimated using MMBs, while individual regressions for each metal were not associated with Full Scale IQ. Additionally, a quartile increase in the WQS index of Pb and Mn, measured using MMBs, were associated with reductions in Verbal IQ by 2.8 points (1.0, 4.5). Weights that determine the contributions of the metals to the joint effect highlighted that the contribution of the Pb-Mn was 72–28% for Full Scale IQ and 42–58% for Verbal IQ. We found that the joint effects of Pb and Mn are strongly affected by the medium used to measure exposure and that the joint effects of the Pb and Mn MMBs on cognition were the stronger than any individual biomarker. Thus, increase power and accuracy for measuring mixture effects compared to individual biomarkers. As the number of chemicals in mixtures increases, appropriate biomarker selection will become increasingly important and MMBs are a natural way to reduce bias in such analyses
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