158 research outputs found
Hadronic Form Factors: Combining QCD Calculations with Analyticity
I discuss recent applications of QCD light-cone sum rules to various form
factors of pseudoscalar mesons. In this approach both soft and hard
contributions to the form factors are taken into account. Combining QCD
calculation with the analyticity of the form factors, one enlarges the region
of accessible momentum transfers.Comment: 12 pages, 3 figures, Talk at the Workshop "Shifmania, Crossing the
boundaries: Gauge dynamics at strong coupling", May 14-17,2009, Minneapolis,
USA; table entry and reference update
Constraints on B--->pi,K transition form factors from exclusive semileptonic D-meson decays
According to the heavy-quark flavour symmetry, the transition
form factors could be related to the corresponding ones of D-meson decays near
the zero recoil point. With the recent precisely measured exclusive
semileptonic decays and , we perform a
phenomenological study of transition form factors based on this
symmetry. Using BK, BZ and Series Expansion parameterizations of the form
factor slope, we extrapolate transition form factors from
to . It is found that, although being consistent with
each other within error bars, the central values of our results for form factors at , , are much smaller than
predictions of the QCD light-cone sum rules, but are in good agreements with
the ones extracted from hadronic B-meson decays within the SCET framework.
Moreover, smaller form factors are also favored by the QCD factorization
approach for hadronic B-meson decays.Comment: 19 pages, no figure, 5 table
Possible evidence for the breakdown of the CKM-paradigm of CP-violation
Using primarily experimental inputs for S(B -> psi Ks), Delta M_Bs, Delta
M_Bd, BR(B -> tau nu) and epsilon_K along with necessary inputs from the
lattice, we find that the measured value of sin(2 beta) is smaller than
expectations of the Standard Model by as much as 3.3 sigma, and also that the
measured value of the BR(B -> tau nu) seems to be less than the predicted value
by about 2.8 sigma. However, through a critical study we show that most likely
the dominant source of these deviations is in B_d(s) mixings and in sin(2 beta)
and less so in B -> tau nu, and also that the bulk of the problem persists even
if input from epsilon_K is not used. The fact that kaon mixing and epsilon_K
are not the dominant source of the deviation from the Standard Model has the
very important consequence that model independent considerations imply that the
scale of the relevant new CP-violating physics is below O(2 TeV), thus
suggesting that direct signals of the new particle(s) may well be accessible in
collider experiments at the LHC and perhaps even at the Tevatron.Comment: 6 pages, 8 figures. Added another fit and some more discussion
showing that BR(B->tau nu) comes out in good agreement with predictions of
the SM if the measured value of sin2beta is not used as an input. References
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Brief review on semileptonic B decays
We concisely review semileptonic B decays, focussing on recent progress on
both theoretical and experimental sides.Comment: 18 pages, 2 figures; version to be published in Mod. Phys. Lett.
Choroid Plexus Papillomas in two Siblings: Case Report [İki Kardeşte Görülen Koroid Pleksus Papillomu: Olgu Sunumu]
Choroid plexus papilloma (CPP) is a rare, benign epithelial brain tumor of the nervous system seen particularly in infants. Familial cases are extremely uncommon. Some other form of malignant tumors was noted in the relatives of patients with CPPs, and some genetic defects regarding this coincidence were reported in the literature. These neoplasms are occasionally bilateral and hydrocephalus is an associated sign in most of the cases. We report three lateral ventricle CPPs in two siblings, at the age of 7 month and 2 years respectively. All tumors were resected with parietotemporal craniotomy and a superior temporal sulcus approach to the lateral ventricle. To avoid a concomitant need of ventriculoperitoneal shunt insertion, external ventricular drainage was inserted for a week in the postoperative period relieving symptoms of hydrocephalus. Search for a hereditary defect in the p53 gene of the second infant (7 months old) revealed no mutation. Postoperative courses were uneventful and the patients were followed for three years without any recurrence. Bilateral CPPS are rare and unusual in two siblings. A genetic predisposition such as the p53 mutation should be investigated in bilateral CPPs in particular
High-Precision Charm-Quark Mass and QCD Coupling from Current-Current Correlators in Lattice and Continuum QCD
We use lattice QCD simulations, with MILC gluon configurations and HISQ
c-quark propagators, to make very precise determinations of moments of
charm-quark pseudoscalar, vector and axial-vector correlators. These moments
are combined with new four-loop results from continuum perturbation theory to
obtain several new determinations of the MSbar mass of the charm quark and of
the MSbar coupling. We find m_c(3GeV)=0.986(10)GeV, or, equivalently,
m_c(m_c)=1.268(9)GeV, both for n_f=4 flavors; and
alpha_msb(3GeV,n_f=4)=0.251(6), or, equivalently,
alpha_\msb(M_Z,n_f=5)=0.1174(12). The new mass agrees well with results from
continuum analyses of the vector correlator using experimental data for e+e-
annihilation (instead of using lattice QCD simulations). These lattice and
continuum results are the most accurate determinations to date of this mass.
Ours is also one of the most accurate determinations of the QCD coupling by any
method.Comment: 12 pages, 5 figures, 5 table
Deep Mining of Oxysterols and Cholestenoic Acids in Human Plasma and Cerebrospinal Fluid: Quantification using Isotope Dilution Mass Spectrometry
Both plasma and cerebrospinal fluid (CSF) are rich in cholesterol and its metabolites. Here we describe in detail a methodology for the identification and quantification of multiple sterols including oxysterols and sterol-acids found in these fluids. The method is translatable to any laboratory with access to liquid chromatography – tandem mass spectrometry. The method exploits isotope-dilution mass spectrometry for absolute quantification of target metabolites. The method is applicable for semi-quantification of other sterols for which isotope labelled surrogates are not available and approximate quantification of partially identified sterols. Values are reported for non-esterified sterols in the absence of saponification and total sterols following saponification. In this way absolute quantification data is reported for 17 sterols in the NIST SRM 1950 plasma along with semi-quantitative data for 8 additional sterols and approximate quantification for one further sterol. In a pooled (CSF) sample used for internal quality control, absolute quantification was performed on 10 sterols, semi-quantification on 9 sterols and approximate quantification on a further three partially identified sterols. The value of the method is illustrated by confirming the sterol phenotype of a patient suffering from ACOX2 deficiency, a rare disorder of bile acid biosynthesis, and in a plasma sample from a patient suffering from cerebrotendinous xanthomatosis, where cholesterol 27-hydroxylase is deficient
The Surgical Infection Society revised guidelines on the management of intra-abdominal infection
Background: Previous evidence-based guidelines on the management of intra-abdominal infection (IAI) were published by the Surgical Infection Society (SIS) in 1992, 2002, and 2010. At the time the most recent guideline was released, the plan was to update the guideline every five years to ensure the timeliness and appropriateness of the recommendations.
Methods: Based on the previous guidelines, the task force outlined a number of topics related to the treatment of patients with IAI and then developed key questions on these various topics. All questions were approached using general and specific literature searches, focusing on articles and other information published since 2008. These publications and additional materials published before 2008 were reviewed by the task force as a whole or by individual subgroups as to relevance to individual questions. Recommendations were developed by a process of iterative consensus, with all task force members voting to accept or reject each recommendation. Grading was based on the GRADE (Grades of Recommendation Assessment, Development, and Evaluation) system; the quality of the evidence was graded as high, moderate, or weak, and the strength of the recommendation was graded as strong or weak. Review of the document was performed by members of the SIS who were not on the task force. After responses were made to all critiques, the document was approved as an official guideline of the SIS by the Executive Council.
Results: This guideline summarizes the current recommendations developed by the task force on the treatment of patients who have IAI. Evidence-based recommendations have been made regarding risk assessment in individual patients; source control; the timing, selection, and duration of antimicrobial therapy; and suggested approaches to patients who fail initial therapy. Additional recommendations related to the treatment of pediatric patients with IAI have been included.
Summary: The current recommendations of the SIS regarding the treatment of patients with IAI are provided in this guideline
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