1,239 research outputs found
Reconstruction of the trachea with a tubed radial forearm free flap
AbstractBackgroundWe present the case of a patient with adenoid cystic carcinoma of the trachea who had 60 mm of the trachea excised and reconstructed with a stented radial forearm free flap. The patient was well in the immediate postoperative period with good function of the neotrachea. Problems developing after the reconstruction included proximal stricture, sputum retention, and recurrent pneumonia.ResultThe patient died of malignant hypercalcemia 16 months after the reconstruction. To our knowledge this is the first reported case of a total tracheal resection and reconstruction with a combination of free tissue transfer and internal stenting.ConclusionWe conclude that tracheal reconstruction has the potential to provide a reliable airway in patients not able to be reconstructed with a primary anastomosis
Number-phase entropic uncertainty relations and Wigner functions for solvable quantum systems with discrete spectra
In this letter, the number-phase entropic uncertainty relation and the
number-phase Wigner function of generalized coherent states associated to a few
solvable quantum systems with nondegenerate spectra are studied. We also
investigate time evolution of number-phase entropic uncertainty and Wigner
function of the considered physical systems with the help of temporally stable
Gazeau-Klauder coherent states.Comment: 10 pages, 9 figures; To appear in Phys Lett A 200
H2 in the interstitial channels of nanotube bundles
The equation of state of H2 adsorbed in the interstitial channels of a carbon
nanotube bundle has been calculated using the diffusion Monte Carlo method. The
possibility of a lattice dilation, induced by H2 adsorption, has been analyzed
by modeling the cohesion energy of the bundle. The influence of factors like
the interatomic potentials, the nanotube radius and the geometry of the channel
on the bundle swelling is systematically analyzed. The most critical input is
proved to be the C-H2 potential. Using the same model than in planar graphite,
which is expected to be also accurate in nanotubes, the dilation is observed to
be smaller than in previous estimations or even inexistent. H2 is highly
unidimensional near the equilibrium density, the radial degree of freedom
appearing progressively at higher densities.Comment: Accepted for publication in PR
Non-linear regression models for Approximate Bayesian Computation
Approximate Bayesian inference on the basis of summary statistics is
well-suited to complex problems for which the likelihood is either
mathematically or computationally intractable. However the methods that use
rejection suffer from the curse of dimensionality when the number of summary
statistics is increased. Here we propose a machine-learning approach to the
estimation of the posterior density by introducing two innovations. The new
method fits a nonlinear conditional heteroscedastic regression of the parameter
on the summary statistics, and then adaptively improves estimation using
importance sampling. The new algorithm is compared to the state-of-the-art
approximate Bayesian methods, and achieves considerable reduction of the
computational burden in two examples of inference in statistical genetics and
in a queueing model.Comment: 4 figures; version 3 minor changes; to appear in Statistics and
Computin
Cosmic Acceleration in Brans-Dicke Cosmology
We consider Brans-Dicke theory with a self-interacting potential in Einstein
conformal frame. We show that an accelerating expansion is possible in a
spatially flat universe for large values of the Brans-Dicke parameter
consistent with local gravity experiments.Comment: 10 Pages, 3 figures, To appear in General Relativity and Gravitatio
Isotopic and spin selectivity of H_2 adsorbed in bundles of carbon nanotubes
Due to its large surface area and strongly attractive potential, a bundle of
carbon nanotubes is an ideal substrate material for gas storage. In addition,
adsorption in nanotubes can be exploited in order to separate the components of
a mixture. In this paper, we investigate the preferential adsorption of D_2
versus H_2(isotope selectivity) and of ortho versus para(spin selectivity)
molecules confined in the one-dimensional grooves and interstitial channels of
carbon nanotube bundles. We perform selectivity calculations in the low
coverage regime, neglecting interactions between adsorbate molecules. We find
substantial spin selectivity for a range of temperatures up to 100 K, and even
greater isotope selectivity for an extended range of temperatures,up to 300 K.
This isotope selectivity is consistent with recent experimental data, which
exhibit a large difference between the isosteric heats of D_2 and H_2 adsorbed
in these bundles.Comment: Paper submitted to Phys.Rev. B; 17 pages, 2 tables, 6 figure
Dexamethasone and supportive care with or without whole brain radiotherapy in treating patients with non-small cell lung cancer with brain metastases unsuitable for resection or stereotactic radiotherapy (QUARTZ): results from a phase 3, non-inferiority, randomised trial
Background
Whole brain radiotherapy (WBRT) and dexamethasone are widely used to treat brain metastases from
non-small cell lung cancer (NSCLC), although there have been no randomised clinical trials showing that WBRT
improves either quality of life or overall survival. Even after treatment with WBRT, the prognosis of this patient group
is poor. We aimed to establish whether WBRT could be omitted without a signifi cant eff ect on survival or quality of life.
Methods
The Quality of Life after Treatment for Brain Metastases (QUARTZ) study is a non-inferiority, phase 3
randomised trial done at 69 UK and three Australian centres. NSCLC patients with brain metastases unsuitable for
surgical resection or stereotactic radiotherapy were randomly assigned (1:1) to optimal supportive care (OSC)
including dexamethasone plus WBRT (20 Gy in five daily fractions) or OSC alone (including dexamethasone). The
dose of dexamethasone was determined by the patients’ symptoms and titrated downwards if symptoms improved.
Allocation to treatment group was done by a phone call from the hospital to the Medical Research Council Clinical
Trials Unit at University College London using a minimisation programme with a random element and stratifi cation
by centre, Karnofsky Performance Status (KPS), gender, status of brain metastases, and the status of primary lung
cancer. The primary outcome measure was quality-adjusted life-years (QALYs). QALYs were generated from overall
survival and patients’ weekly completion of the EQ-5D questionnaire. Treatment with OSC alone was considered noninferior
if it was no more than 7 QALY days worse than treatment with WBRT plus OSC, which required 534 patients
(80% power, 5% [one-sided] signifi cance level). Analysis was done by intention to treat for all randomly assigned
patients. The trial is registered with ISRCTN, number ISRCTN3826061.
Findings
Between March 2, 2007, and Aug 29, 2014, 538 patients were recruited from 69 UK and three Australian
centres, and were randomly assigned to receive either OSC plus WBRT (269) or OSC alone (269). Baseline characteristics
were balanced between groups, and the median age of participants was 66 years (range 38–85). Signifi cantly more
episodes of drowsiness, hair loss, nausea, and dry or itchy scalp were reported while patients were receiving WBRT,
although there was no evidence of a difference in the rate of serious adverse events between the two groups. There was
no evidence of a diff erence in overall survival (hazard ratio 1·06, 95% CI 0·90–1·26), overall quality of life, or
dexamethasone use between the two groups. The diff erence between the mean QALYs was 4·7 days (46·4 QALY days
for the OSC plus WBRT group vs 41·7 QALY days for the OSC group), with two-sided 90% CI of –12·7 to 3·3.
Interpretation
Although the primary outcome measure result includes the prespecifi ed non-inferiority margin, the
combination of the small diff erence in QALYs and the absence of a diff erence in survival and quality of life between
the two groups suggests that WBRT provides little additional clinically signifi cant benefi t for this patient group
Effective interaction between helical bio-molecules
The effective interaction between two parallel strands of helical
bio-molecules, such as deoxyribose nucleic acids (DNA), is calculated using
computer simulations of the "primitive" model of electrolytes. In particular we
study a simple model for B-DNA incorporating explicitly its charge pattern as a
double-helix structure. The effective force and the effective torque exerted
onto the molecules depend on the central distance and on the relative
orientation. The contributions of nonlinear screening by monovalent counterions
to these forces and torques are analyzed and calculated for different salt
concentrations. As a result, we find that the sign of the force depends
sensitively on the relative orientation. For intermolecular distances smaller
than it can be both attractive and repulsive. Furthermore we report a
nonmonotonic behaviour of the effective force for increasing salt
concentration. Both features cannot be described within linear screening
theories. For large distances, on the other hand, the results agree with linear
screening theories provided the charge of the bio-molecules is suitably
renormalized.Comment: 18 pages, 18 figures included in text, 100 bibliog
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