537 research outputs found
Renormalization-Scheme Dependence of Pade Summation in QCD
We study the renormalization-scheme (RS) dependence of Pade Approximants
(PA's), and compare them with the Principle of Minimal Sensitivity (PMS) and
the Effective Charge (ECH) approaches. Although the formulae provided by the
PA, PMS and ECH predictions for higher-order terms in a QCD perturbation
expansion differ in general, their predictions can be very close numerically
for a wide range of renormalization schemes. Using the Bjorken sum rule as a
test case, we find that Pade Summation (PS) reduces drastically the RS
dependence of the Bjorken effective charge. We use these results to estimate
the theoretical error due to the choice of RS in the extraction of
from the Bjorken sum rule, and use the available data at to
estimate , where the first
error is experimental, and the second is theoretical.Comment: 12 pages (latex), including 6 embedded figures; uses epsfig.st
Modeling power corrections to the Bjorken sum rule for the neutrino structure function F_1
Direct measurements of the the structure functions F_1^{nu p} and F_1^{nu n}
at a neutrino factory would allow for an accurate extraction of alpha_s from
the Q^2-dependence of the Bjorken sum rule, complementing that based on the
Gross-Llewellyn-Smith sum rule for F_3. We estimate the power (1/Q^2-)
corrections to the Bjorken sum rule in the instanton vacuum model. For the
reduced matrix element of the flavor-nonsinglet twist-4 operator
ubar_g_Gdual_gamma_gamma5_u - (u -> d) we obtain a value of 0.18 GeV^2, in good
agreement with the QCD sum rule calculations of Braun and Kolesnichenko. Our
result allows to reduce the theoretical error in the determination of alpha_s.Comment: 3 pages, 1 figure, uses iopart.cls. Proceedings of the 4th NuFact'02
Workshop "Neutrino Factories based on Muon Storage Rings", Imperial College,
London, July 1-6, 200
Quantization of Wilson loops in Wess-Zumino-Witten models
We describe a non-perturbative quantization of classical Wilson loops in the
WZW model. The quantized Wilson loop is an operator acting on the Hilbert space
of closed strings and commuting either with the full Kac-Moody chiral algebra
or with one of its subalgebras. We prove that under open/closed string duality,
it is dual to a boundary perturbation of the open string theory. As an
application, we show that such operators are useful tools for identifying fixed
points of the boundary renormalization group flow.Comment: 24 pages. Version published in JHE
Incidence of and predictors for antiseizure medication gaps in Medicare beneficiaries with epilepsy: a retrospective cohort study.
BACKGROUND
For the two-thirds of patients with epilepsy who achieve seizure remission on antiseizure medications (ASMs), patients and clinicians must weigh the pros and cons of long-term ASM treatment. However, little work has evaluated how often ASM discontinuation occurs in practice. We describe the incidence of and predictors for sustained ASM fill gaps to measure discontinuation in individuals potentially eligible for ASM withdrawal.
METHODS
This was a retrospective cohort of Medicare beneficiaries. We included patients with epilepsy by requiring International Classification of Diseases codes for epilepsy/convulsions plus at least one ASM prescription each year 2014-2016, and no acute visit for epilepsy 2014-2015 (i.e., potentially eligible for ASM discontinuation). The main outcome was the first day of a gap in ASM supply (30, 90, 180, or 360âdays with no pills) in 2016-2018. We displayed cumulative incidence functions and identified predictors using Cox regressions.
RESULTS
Among 21,819 beneficiaries, 5191 (24%) had a 30-day gap, 1753 (8%) had a 90-day gap, 803 (4%) had a 180-day gap, and 381 (2%) had a 360-day gap. Predictors increasing the chance of a 180-day gap included number of unique medications in 2015 (hazard ratio [HR] 1.03 per medication, 95% confidence interval [CI] 1.01-1.05) and epileptologist prescribing physician (â„25% of that physician's visits for epilepsy; HR 2.37, 95% CI 1.39-4.03). Predictors decreasing the chance of a 180-day gap included Medicaid dual eligibility (HR 0.75, 95% CI 0.60-0.95), number of unique ASMs in 2015 (e.g., 2 versus 1: HR 0.37, 95% CI 0.30-0.45), and greater baseline adherence (>â80% versus â€80% of days in 2015 with ASM pill supply: HR 0.38, 95% CI 0.32-0.44).
CONCLUSIONS
Sustained ASM gaps were rarer than current guidelines may suggest. Future work should further explore barriers and enablers of ASM discontinuation to understand the optimal discontinuation rate
Flavor in Minimal Conformal Technicolor
We construct a complete, realistic, and natural UV completion of minimal
conformal technicolor that explains the origin of quark and lepton masses and
mixing angles. As in "bosonic technicolor", we embed conformal technicolor in a
supersymmetric theory, with supersymmetry broken at a high scale. The exchange
of heavy scalar doublets generates higher-dimension interactions between
technifermions and quarks and leptons that give rise to quark and lepton masses
at the TeV scale. Obtaining a sufficiently large top quark mass requires strong
dynamics at the supersymmetry breaking scale in both the top and technicolor
sectors. This is natural if the theory above the supersymmetry breaking also
has strong conformal dynamics. We present two models in which the strong top
dynamics is realized in different ways. In both models, constraints from
flavor-changing effects can be easily satisfied. The effective theory below the
supersymmetry breaking scale is minimal conformal technicolor with an
additional light technicolor gaugino. We argue that this light gaugino is a
general consequence of conformal technicolor embedded into a supersymmetric
theory. If the gaugino has mass below the TeV scale it will give rise to an
additional pseudo Nambu-Goldstone boson that is observable at the LHC.Comment: 37 pages; references adde
Effective and Asymptotic Critical Exponents of Weakly Diluted Quenched Ising Model: 3d Approach Versus -Expansion
We present a field-theoretical treatment of the critical behavior of
three-dimensional weakly diluted quenched Ising model. To this end we analyse
in a replica limit n=0 5-loop renormalization group functions of the
-theory with O(n)-symmetric and cubic interactions (H.Kleinert and
V.Schulte-Frohlinde, Phys.Lett. B342, 284 (1995)). The minimal subtraction
scheme allows to develop either the -expansion series or to
proceed in the 3d approach, performing expansions in terms of renormalized
couplings. Doing so, we compare both perturbation approaches and discuss their
convergence and possible Borel summability. To study the crossover effect we
calculate the effective critical exponents providing a local measure for the
degree of singularity of different physical quantities in the critical region.
We report resummed numerical values for the effective and asymptotic critical
exponents. Obtained within the 3d approach results agree pretty well with
recent Monte Carlo simulations. -expansion does not allow
reliable estimates for d=3.Comment: 35 pages, Latex, 9 eps-figures included. The reference list is
refreshed and typos are corrected in the 2nd versio
Antiseizure medication withdrawal risk estimation and recommendations: A survey of American Academy of Neurology and EpiCARE members
Objective
Choosing candidates for antiseizure medication (ASM) withdrawal in wellâcontrolled epilepsy is challenging. We evaluated (a) the correlation between neurologists' seizure risk estimation (âclinician predictionsâ) vs calculated predictions, (b) how viewing calculated predictions influenced recommendations, and (c) barriers to using risk calculation.MethodsWe asked US and European neurologists to predict 2âyear seizure risk after ASM withdrawal for hypothetical vignettes. We compared ASM withdrawal recommendations before vs after viewing calculated predictions, using generalized linear models.
Results
Threeâhundred and fortyâsix neurologists responded. There was moderate correlation between clinician and calculated predictions (Spearman coefficient 0.42). Clinician predictions varied widely, for example, predictions ranged 5%â100% for a 2âyear seizureâfree adult without epileptiform abnormalities. Mean clinician predictions exceeded calculated predictions for vignettes with epileptiform abnormalities (eg, childhood absence epilepsy: clinician 65%, 95% confidence interval [CI] 57%â74%; calculated 46%) and surgical vignettes (eg, focal cortical dysplasia 6âmonth seizureâfree mean clinician 56%, 95% CI 52%â60%; calculated 28%). Clinicians overestimated the influence of epileptiform EEG findings on withdrawal risk (26%, 95% CI 24%â28%) compared with calculators (14%, 95% 13%â14%). Viewing calculated predictions slightly reduced willingness to withdraw (â0.8/10 change, 95% CI â1.0 to â0.7), particularly for vignettes without epileptiform abnormalities. The greatest barrier to calculator use was doubting its accuracy (44%).
Significance
Clinicians overestimated the influence of abnormal EEGs particularly for lowârisk patients and overestimated risk and the influence of seizureâfree duration for surgical patients, compared with calculators. These data may question widespread ordering of EEGs or timeâbased seizureâfree thresholds for surgical patients. Viewing calculated predictions reduced willingness to withdraw particularly without epileptiform abnormalities
Minimal Conformal Technicolor and Precision Electroweak Tests
We study the minimal model of conformal technicolor, an SU(2) gauge theory
near a strongly coupled conformal fixed point, with conformal symmetry softly
broken by technifermion mass terms. Conformal symmetry breaking triggers chiral
symmetry breaking in the pattern SU(4) -> Sp(4), which gives rise to a
pseudo-Nambu-Goldstone boson that can act as a composite Higgs boson. The top
quark is elementary, and the top and electroweak gauge loop contributions to
the Higgs mass are cut off entirely by Higgs compositeness. In particular, the
model requires no top partners and no "little Higgs" mechanism. A nontrivial
vacuum alignment results from the interplay of the top loop and technifermion
mass terms. The composite Higgs mass is completely determined by the top loop,
in the sense that m_h/m_t is independent of the vacuum alignment and is
computable by a strong-coupling calculation. There is an additional composite
pseudoscalar A with mass larger than m_h and suppressed direct production at
LHC. We discuss the electroweak fit in this model in detail. Corrections to Z
-> bb and the T parameter from the top sector are suppressed by the enhanced
Sp(4) custodial symmetry. Even assuming that the strong contribution to the S
parameter is positive and usuppressed, a good electroweak fit can be obtained
for v/f ~ 0.25, where v and f are the electroweak and chiral symmetry breaking
scales respectively. This requires fine tuning at the 10% level.Comment: 34 pages, 4 figures; v2: updated precision electroweak fi
Associations between use of the 21âgene recurrence score assay and chemotherapy regimen selection in a statewide registry
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/136480/1/cncr30429.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/136480/2/cncr30429_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/136480/3/cncr30429-sup-0001-suppinfo.pd
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