1,610 research outputs found
Pheochromocytoma diagnosed during pregnancy: lessons learned from a series of ten patients
BACKGROUND: Pheochromocytoma (PHEO) in pregnancy is a life-threatening condition. Its management is challenging with regards to the timing and type of surgery.
METHODS: A retrospective review of the management of ten patients diagnosed with pheochromocytoma during pregnancy was performed. Data were collected on the initial diagnostic workup, symptoms, treatment, and follow-up.
RESULTS: PHEO was diagnosed in ten patients who were between the 10th and the 29th weeks of pregnancy. Six patients had none to mild symptoms, while four had complications of paroxysmal hypertension. Imaging investigations consisted of MRI, CT scan and ultrasounds. All had urinary metanephrines, measured as part of their workup. Three patients had MEN 2A, one VHL syndrome, one suspected SDH mutation. All patients were treated either with α/β blockers or calcium channel blockers to stabilize their clinical conditions. Seven patients underwent a laparoscopic adrenalectomy before delivery. Three out of these seven patients had a bilateral PHEO and underwent a unilateral adrenalectomy of the larger tumor during pregnancy, followed by a planned cesarean section and a subsequent contralateral adrenalectomy within a few months after delivery. Three patients had emergency surgery for maternal or fetal complications, with C-section followed by concomitant or delayed adrenalectomy. All newborns from the group of planned surgery were healthy, while two out three newborns within the emergency surgery group died shortly after delivery secondary to cardiac and pulmonary complications.
CONCLUSIONS: PHEO in pregnancy is a rare condition. Maternal and fetal prognosis improved over the last decades, but still lethal consequences may be present if misdiagnosed or mistreated. A thorough multidisciplinary team approach should be tailored on an individual basis to better manage the pathology. Unilateral adrenalectomy in a pregnant patient with bilateral PHEO may be an option to avoid the risk of adrenal insufficiency after bilateral adrenalectomy
Relating Physical Observables in QCD without Scale-Scheme Ambiguity
We discuss the St\"uckelberg-Peterman extended renormalization group
equations in perturbative QCD, which express the invariance of physical
observables under renormalization-scale and scheme-parameter transformations.
We introduce a universal coupling function that covers all possible choices of
scale and scheme. Any perturbative series in QCD is shown to be equivalent to a
particular point in this function. This function can be computed from a set of
first-order differential equations involving the extended beta functions. We
propose the use of these evolution equations instead of perturbative series for
numerical evaluation of physical observables. This formalism is free of
scale-scheme ambiguity and allows a reliable error analysis of higher-order
corrections. It also provides a precise definition for as the pole in the associated 't Hooft scheme. A concrete application to
is presented.Comment: Plain TEX, 4 figures (available upon request), 22 pages,
DOE/ER/40322-17
Tau neutrino deep inelastic charged current interactions
The nu_mu -> nu_tau oscillation hypothesis will be tested through nu_tau
production of tau in underground neutrino telescopes as well as long-baseline
experiments. We provide the full QCD framework for the evaluation of tau
neutrino deep inelastic charged current (CC) cross sections, including
next-leading-order (NLO) corrections, charm production, tau threshold, and
target mass effects in the collinear approximation. We investigate the
violation of the Albright-Jarlskog relations for the structure functions F_4,5
which occur only in heavy lepton (tau) scattering. Integrated CC cross sections
are evaluated naively over the full phase space and with the inclusion of DIS
kinematic cuts. Uncertainties in our evaluation based on scale dependence, PDF
errors and the interplay between kinematic and dynamical power corrections are
discussed and/or quantified.Comment: 28 pages, 10 figure
Strong Coupling Constant with Flavour Thresholds at Four Loops in the MS-bar Scheme
We present in analytic form the matching conditions for the strong coupling
constant alpha_s^(n_f)(mu) at the flavour thresholds to three loops in the
modified minimal-subtraction scheme. Taking into account the recently
calculated coefficient beta_3 of the Callan-Symanzik beta function of quantum
chromodynamics, we thus derive a four-loop formula for alpha_s^(n_f)(mu)
together with appropriate relationships between the asymptotic scale parameters
Lambda^(n_f) for different numbers of flavours n_f.Comment: 10 pages (Latex), 3 figures (Postscript
Remarks on a class of renormalizable interpolating gauges
A class of covariant gauges allowing one to interpolate between the Landau,
the maximal Abelian, the linear covariant and the Curci-Ferrari gauges is
discussed. Multiplicative renormalizability is proven to all orders by means of
algebraic renormalization. All one-loop anomalous dimensions of the fields and
gauge parameters are explicitly evaluated in the MSbar scheme.Comment: 24 pages. no figure
Higher moments of nucleon spin structure functions in heavy baryon chiral perturbation theory and in a resonance model
The third moment of the twist-3 part of the nucleon spin structure
function is generalized to arbitrary momentum transfer and is
evaluated in heavy baryon chiral perturbation theory (HBChPT) up to order
and in a unitary isobar model (MAID). We show how to link
as well as higher moments of the nucleon spin structure functions
and to nucleon spin polarizabilities. We compare our results with the
most recent experimental data, and find a good description of these available
data within the unitary isobar model. We proceed to extract the twist-4 matrix
element which appears in the suppressed term in the twist
expansion of the spin structure function for proton and neutron.Comment: 30 pages, 7 figure
Comparison of the Pade Approximation Method to Perturbative QCD Calculations
We present a method of estimating perturbative coefficients in Quantum Field
Theory using Pade Approximants. We test this method on various known QCD
results, and find that the method works very well.Comment: 14 pages (phyzzx macropackage) + 1 postscript figure encoded through
uufiles, appended at the end of the tex file. Additional relevant references
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The nonperturbative propagator and vertex in massless quenched QED_d
It is well known how multiplicative renormalizability of the fermion
propagator, through its Schwinger-Dyson equation, imposes restrictions on the
3-point fermion-boson vertex in massless quenched quantum electrodynamics in
4-dimensions (QED). Moreover, perturbation theory serves as an excellent
guide for possible nonperturbative constructions of Green functions.
We extend these ideas to arbitrary dimensions . The constraint of
multiplicative renormalizability of the fermion propagator is generalized to a
Landau-Khalatnikov-Fradkin transformation law in -dimensions and it
naturally leads to a constraint on the fermion-boson vertex. We verify that
this constraint is satisfied in perturbation theory at the one loop level in
3-dimensions. Based upon one loop perturbative calculation of the vertex, we
find additional restrictions on its possible nonperturbative forms in arbitrary
dimensions.Comment: 13 pages, no figures, latex (uses IOP style files
Testing Landau gauge OPE on the Lattice with a Condensate
Using the operator product expansion we show that the correction
to the perturbative expressions for the gluon propagator and the strong
coupling constant resulting from lattice simulations in the Landau gauge are
due to a non-vanishing vacuum expectation value of the operator .
This is done using the recently published Wilson coefficients of the identity
operator computed to third order, and the subdominant Wilson coefficient
computed in this paper to the leading logarithm. As a test of the applicability
of OPE we compare the estimated from the gluon propagator and
the one from the coupling constant in the flavourless case. Both agree within
the statistical uncertainty: GeV.
Simultaneously we fit \Lams = 233(28) MeV in perfect agreement with previous
lattice estimates. When the leading coefficients are only expanded to two
loops, the two estimates of the condensate differ drastically. As a consequence
we insist that OPE can be applied in predicting physical quantities only if the
Wilson coefficients are computed to a high enough perturbative order.Comment: 15 pages, LaTex file with 5 figure
Nontrivial, Asymptotically Non-free Gauge Theories and Dynamical Unification of Couplings
An evidence for nontriviality of asymptotically non-free (ANF) Yang-Mills
theories is found on the basis of optimized perturbation theory. It is argued
that these theories with matter couplings can be made nontrivial by means of
the reduction of couplings, leading to the idea of dynamical unification of
couplings (DUC) The second-order reduction of couplings in the ANF
-gauged Higgs-Yukawa theory, which is assumed to be nontrivial here, is
carried out to motivate independent investigations on its nontriviality and
DUC
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