221 research outputs found
The Analytic Bootstrap in Fermionic CFTs
We apply the method of the large spin bootstrap to analyse fermionic
conformal field theories with weakly broken higher spin symmetry. Through the
study of correlators of composite operators, we find the anomalous dimensions
and OPE coefficients in the Gross-Neveu model in dimensions
and the Gross-Neveu-Yukawa model in dimensions, based only on
crossing symmetry. Furthermore a non-trivial solution in the
expansion is found for a fermionic theory in which the fundamental field is not
part of the spectrum. The results are perturbative in and valid
to all orders in the spin, reproducing known results for operator dimensions
and providing some new results for operator dimensions and OPE coefficients.Comment: 42+3 pages, no figure
Taming the -expansion with Large Spin Perturbation Theory
We apply analytic bootstrap techniques to the four-point correlator of
fundamental fields in the Wilson-Fisher model. In an -expansion
crossing symmetry fixes the double discontinuity of the correlator in terms of
CFT data at lower orders. Large spin perturbation theory, or equivalently the
recently proposed Froissart-Gribov inversion integral, then allows one to
reconstruct the CFT data of intermediate operators of any spin. We use this
method to compute the anomalous dimensions and OPE coefficients of leading
twist operators. To cubic order in the double discontinuity arises
solely from the identity operator and the scalar bilinear operator, making the
computation straightforward. At higher orders the double discontinuity receives
contributions from infinite towers of higher spin operators. At fourth order,
the structure of perturbation theory leads to a proposal in terms of functions
of certain degree of transcendentality, which can then be fixed by symmetries.
This leads to the full determination of the CFT data for leading twist
operators to fourth order.Comment: 16 pages. v2: Added discussion on low spin spectru
Stacked Penalized Logistic Regression for Selecting Views in Multi-View Learning
In biomedical research, many different types of patient data can be
collected, such as various types of omics data and medical imaging modalities.
Applying multi-view learning to these different sources of information can
increase the accuracy of medical classification models compared with
single-view procedures. However, collecting biomedical data can be expensive
and/or burdening for patients, so that it is important to reduce the amount of
required data collection. It is therefore necessary to develop multi-view
learning methods which can accurately identify those views that are most
important for prediction. In recent years, several biomedical studies have used
an approach known as multi-view stacking (MVS), where a model is trained on
each view separately and the resulting predictions are combined through
stacking. In these studies, MVS has been shown to increase classification
accuracy. However, the MVS framework can also be used for selecting a subset of
important views. To study the view selection potential of MVS, we develop a
special case called stacked penalized logistic regression (StaPLR). Compared
with existing view-selection methods, StaPLR can make use of faster
optimization algorithms and is easily parallelized. We show that nonnegativity
constraints on the parameters of the function which combines the views play an
important role in preventing unimportant views from entering the model. We
investigate the performance of StaPLR through simulations, and consider two
real data examples. We compare the performance of StaPLR with an existing view
selection method called the group lasso and observe that, in terms of view
selection, StaPLR is often more conservative and has a consistently lower false
positive rate.Comment: 26 pages, 9 figures. Accepted manuscrip
An alternative to diagrams for the critical O(N) model: dimensions and structure constants to order
We apply the methods of modern analytic bootstrap to the critical
model in a expansion. At infinite the model possesses higher spin
symmetry which is weakly broken as we turn on . By studying consistency
conditions for the correlator of four fundamental fields we derive the CFT-data
for all the (broken) currents to order , and the CFT-data for the
non-singlet currents to order . To order our results are in
perfect agreement with those in the literature. To order we reproduce
known results for anomalous dimensions and obtain a variety of new results for
structure constants, including the global symmetry central charge to this
order.Comment: 32 pages + appendices, 2 figures. v2: Improved presentation + new
appendix considering mixed correlator. Version to appear in JHE
Analyzing hierarchical multi-view MRI data with StaPLR: An application to Alzheimer's disease classification
Multi-view data refers to a setting where features are divided into feature
sets, for example because they correspond to different sources. Stacked
penalized logistic regression (StaPLR) is a recently introduced method that can
be used for classification and automatically selecting the views that are most
important for prediction. We introduce an extension of this method to a setting
where the data has a hierarchical multi-view structure. We also introduce a new
view importance measure for StaPLR, which allows us to compare the importance
of views at any level of the hierarchy. We apply our extended StaPLR algorithm
to Alzheimer's disease classification where different MRI measures have been
calculated from three scan types: structural MRI, diffusion-weighted MRI, and
resting-state fMRI. StaPLR can identify which scan types and which derived MRI
measures are most important for classification, and it outperforms elastic net
regression in classification performance.Comment: 36 pages, 9 figures. Accepted manuscrip
Age-Stratified Propofol Dosage for Pediatric Procedural Sedation and Analgesia
Background: Procedural sedation and analgesia (PSA) for diagnostic and minimally invasive therapeutic procedures has become common practice in children of all ages. Based on our clinical experience, we suspected an inverse relation between age and dosage. However, a schedule for age-stratified propofol induction and maintenance dosage for PSA was not available and could be helpful to many anesthesiologists as a reference. Methods: We performed a retrospective cohort study of children who received procedural sedation at the Wilhelmina Children's Hospital (WKZ), a tertiary pediatric hospital part of the University Medical Center Utrecht (UMCU), between June 2007 and December 2020. We studied whether the induction (mg·kg-1) and maintenance (mg·kg-1·h-1) dosage is age-dependent using linear regression models. Results: A total of 6438 pediatric procedures were retrieved from Anesthesia Information Management Systems (AIMS). A total of 5567 records were available for induction dose analysis and 5420 records for analysis of the maintenance dose. After adjustment for sex, American Society of Anesthesiologists (ASA) physical status classification, opioid administration, and diagnostic or interventional, we obtained a coefficient of -0.11 (95% confidence interval [CI], -0.12 to -0.11) for age (years) from a multivariable linear regression model for propofol induction dosage (mg·kg-1) and a coefficient of -0.36 (95% CI, -0.39 to -0.34) for age (years) for propofol maintenance dosage. Conclusions: We found a noteworthy inverse age-effect on propofol dosage for both induction and maintenance of pediatric procedural sedation. Furthermore, our study revealed that remarkably higher propofol sedation doses were needed for infants and toddlers than previously expected and reported
Study protocol: NITric oxide during cardiopulmonary bypass to improve Recovery in Infants with Congenital heart defects (NITRIC trial): a randomised controlled trial
Introduction Congenital heart disease (CHD) is a major cause of infant mortality. Many infants with CHD require corrective surgery with most operations requiring cardiopulmonary bypass (CPB). CPB triggers a systemic inflammatory response which is associated with low cardiac output syndrome (LCOS), postoperative morbidity and mortality. Delivery of nitric oxide (NO) into CPB circuits can provide myocardial protection and reduce bypass-induced inflammation, leading to less LCOS and improved recovery. We hypothesised that using NO during CPB increases ventilator-free days (VFD) (the number of days patients spend alive and free from invasive mechanical ventilation up until day 28) compared with standard care. Here, we describe the NITRIC trial protocol. Methods and analysis The NITRIC trial is a randomised, double-blind, controlled, parallel-group, two-sided superiority trial to be conducted in six paediatric cardiac surgical centres. One thousand three-hundred and twenty infants <2 years of age undergoing cardiac surgery with CPB will be randomly assigned to NO at 20 ppm administered into the CPB oxygenator for the duration of CPB or standard care (no NO) in a 1:1 ratio with stratification by age (<6 and ≥6 weeks), single ventricle physiology (Y/N) and study centre. The primary outcome will be VFD to day 28. Secondary outcomes include a composite of LCOS, need for extracorporeal membrane oxygenation or death within 28 days of surgery; length of stay in intensive care and in hospital; and, healthcare costs. Analyses will be conducted on an intention-to-treat basis. Preplanned secondary analyses will investigate the impact of NO on host inflammatory profiles postsurgery. Ethics and dissemination The study has ethical approval (HREC/17/QRCH/43, dated 26 April 2017), is registered in the Australian New Zealand Clinical Trials Registry (ACTRN12617000821392) and commenced recruitment in July 2017. The primary manuscript will be submitted for publication in a peer-reviewed journal. Trial registration number ACTRN12617000821392.</p
- …