5,196 research outputs found
Supersymmetric Yang-Mills and Supergravity Amplitudes at One Loop
By applying the known expressions for SYM and SUGRA tree amplitudes, we write
generating functions for the NNMHV box coefficients of SYM as well as the MHV,
NMHV, and NNMHV box coefficients for SUGRA. The all-multiplicity generating
functions utilize covariant, on-shell superspace whereby the contribution from
arbitrary external states in the supermultiplet can be extracted by Grassmann
operators. In support of the relation between dual Wilson loops and SYM
scattering amplitudes at weak coupling, the SYM amplitudes are presented in a
manifestly dual superconformal form. We introduce ordered box coefficients for
calculating SUGRA quadruple cuts and prove that ordered coefficients generate
physical cut amplitudes after summing over permutations of the external legs.
The ordered box coefficients are produced by sewing ordered subamplitudes,
previously used in applying on-shell recursion relations at tree level. We
describe our verification of the results against the literature, and a formula
for extracting the contributions from external gluons or gravitons to NNMHV
superamplitudes is presented.Comment: 46 pages, 2 figures, additional references and clarifications
include
Testing asteroseismology with Gaia DR2: Hierarchical models of the Red Clump
Asteroseismology provides fundamental stellar parameters independent of
distance, but subject to systematics under calibration. Gaia DR2 has provided
parallaxes for a billion stars, which are offset by a parallax zero-point. Red
Clump (RC) stars have a narrow spread in luminosity, thus functioning as
standard candles to calibrate these systematics. This work measures how the
magnitude and spread of the RC in the Kepler field are affected by changes to
temperature and scaling relations for seismology, and changes to the parallax
zero-point for Gaia. We use a sample of 5576 RC stars classified through
asteroseismology. We apply hierarchical Bayesian latent variable models,
finding the population level properties of the RC with seismology, and use
those as priors on Gaia parallaxes to find the parallax zero-point offset. We
then find the position of the RC using published values for the zero-point. We
find a seismic temperature insensitive spread of the RC of ~0.03 mag in the
2MASS K band and a larger and slightly temperature-dependent spread of ~0.13
mag in the Gaia G band. This intrinsic dispersion in the K band provides a
distance precision of ~1% for RC stars. Using Gaia data alone, we find a mean
zero-point of -41 10 as. This offset yields RC absolute magnitudes
of -1.634 0.018 in K and 0.546 0.016 in G. Obtaining these same
values through seismology would require a global temperature shift of ~-70 K,
which is compatible with known systematics in spectroscopy.Comment: Accepted for publication in MNRA
The effectiveness, safety and cost-effectiveness of cytisine versus varenicline for smoking cessation in an Australian population: a study protocol for a randomized controlled non-inferiority trial
Smoking cessation medications are effective but often underutilised because of costs and side effects. Cytisine is a plant-based smoking cessation medication with over 50 years of use in Central and Eastern Europe. While cytisine has been found to be well-tolerated and more effective than nicotine replacement therapy, direct comparison with varenicline have not been conducted. This study evaluates the effectiveness, safety and cost-effectiveness of cytisine compared with varenicline.Two arm, parallel group, randomised, non-inferiority trial, with allocation concealment and blinded outcome assessment.Australian population-based study.Adult daily smokers (N=1266) interested in quitting will be recruited through advertisements and Quitline telephone-based cessation support services.Eligible participants will be randomised (1:1 ratio) to receive either cytisine capsules (25-day supply) or varenicline tablets (12-week supply), prescribed in accordance with the manufacturer's recommended dosing regimen. The medication will be mailed to each participant's nominated residential address. All participants will also be offered standard Quitline behavioural support (up to six 10-12 minute sessions).Assessments will be undertaken by telephone at baseline, 4- and 7-months post-randomisation. Participants will also be contacted twice (two and four weeks post-randomisation) to ascertain adverse events, treatment adherence and smoking status. The primary outcome will be self-reported 6-month continuous abstinence from smoking, verified by carbon monoxide at 7-month follow-up. We will also evaluate the relative safety and cost-effectiveness of cytisine compared with varenicline. Secondary outcomes will include self-reported continuous and 7-day point prevalence abstinence and cigarette consumption at each follow-up interview.If cytisine is as effective as varenicline, its lower cost and natural plant-based composition may make it an acceptable and affordable smoking cessation medication that could save millions of lives worldwide
Randomized trial of complete versus lesion-only revascularization in patients undergoing primary percutaneous coronary intervention for STEMI and Multivessel Disease
BACKGROUND: The optimal management of patients found to have multivessel disease while undergoing primary percutaneous coronary intervention (P-PCI) for ST-segment elevation myocardial infarction is uncertain.  OBJECTIVES: CvLPRIT (Complete versus Lesion-only Primary PCI trial) is a U.K. open-label randomized study comparing complete revascularization at index admission with treatment of the infarct-related artery (IRA) only.  METHODS: After they provided verbal assent and underwent coronary angiography, 296 patients in 7 U.K. centers were randomized through an interactive voice-response program to either in-hospital complete revascularization (n = 150) or IRA-only revascularization (n = 146). Complete revascularization was performed either at the time of P-PCI or before hospital discharge. Randomization was stratified by infarct location (anterior/nonanterior) and symptom onset (≤3 h or >3 h). The primary endpoint was a composite of all-cause death, recurrent myocardial infarction (MI), heart failure, and ischemia-driven revascularization within 12 months.  RESULTS: Patient groups were well matched for baseline clinical characteristics. The primary endpoint occurred in 10.0% of the complete revascularization group versus 21.2% in the IRA-only revascularization group (hazard ratio: 0.45; 95% confidence interval: 0.24 to 0.84; p = 0.009). A trend toward benefit was seen early after complete revascularization (p = 0.055 at 30 days). Although there was no significant reduction in death or MI, a nonsignificant reduction in all primary endpoint components was seen. There was no reduction in ischemic burden on myocardial perfusion scintigraphy or in the safety endpoints of major bleeding, contrast-induced nephropathy, or stroke between the groups.  CONCLUSIONS: In patients presenting for P-PCI with multivessel disease, index admission complete revascularization significantly lowered the rate of the composite primary endpoint at 12 months compared with treating only the IRA. In such patients, inpatient total revascularization may be considered, but larger clinical trials are required to confirm this result and specifically address whether this strategy is associated with improved survival. (Complete Versus Lesion-only Primary PCI Pilot Study [CvLPRIT]; ISRCTN70913605)
Testing General Relativity with 21 cm intensity mapping
We investigate the prospects for constraining alternative theories of gravity
with a typical near-term low-budget 21 cm intensity mapping experiment. We
derive the 21 cm brightness temperature perturbation consistently in linear
theory including all line-of-sight and relativistic effects. We uncover new
terms that are a small correction on large scales, analogous to those recently
found in the context of galaxy surveys. We then perform a Fisher matrix
analysis of the B_0 parametrization of f(R) gravity, where B_0 is proportional
to the square of Compton wavelength of the scalaron. We find that our 21 cm
survey, in combination with CMB information from Planck, will be able to place
a 95% upper limit of 7 x 10^{-5} on B_0 in flat models with a LCDM expansion
history, improving on current cosmological constraints by several orders of
magnitude. We argue that this constraint is limited by our ability to model the
mildly non-linear regime of structure formation in modified gravity. We also
perform a model-independent principal component analysis on the free functions
introduced into the field equations by modified gravity, mu and Sigma. We find
that 20--30 modes of the free functions will be `well-constrained' by our
combination of observables, the lower and upper limits dependent on the
criteria used to define the `goodness' of the constraint. These constraints are
found to be robust to uncertainties in the time-dependence of the bias. Our
analysis reveals that our observables are sensitive primarily to temporal
variations in Sigma and scale variations in mu. We argue that the inclusion of
21 cm intensity maps will significantly improve constraints on any cosmological
deviations from General Relativity in large-scale structure in a very
cost-effective manner.Comment: 26 pages, 8 figures. Added section on general bias, conclusions
unchanged. Matches published versio
Novel polymorphisms influencing transcription of the human CHRM2 gene in airway smooth muscle
Muscarinic receptors are a functionally important family of G-protein-coupled receptors. Using a combination of rapid amplification of 5′ cDNA ends and reporter gene assays, we characterized the 5′ untranslated region of the CHRM2 gene as expressed in human airway smooth muscle (HASM) cells. A splice site is present 46 bp upstream from the ATG start codon. Five exons with alternative splicing patterns are present upstream of this splice site, separated by introns ranging from 87 bp to > 145 kb. There is evidence for the gene being under the control of a TATA-less promoter with Sp1, GATA, and activator protein-2 binding sites. Multiple transcription start sites (TSSs) were identified. We identified a novel 0.5-kb hypervariable region located 648 bp upstream of the most 5′ TSS, a multiallelic (CA) tandem repeat 96 bp downstream of the most 5′ TSS, and a common C→A SNP located 136 bp upstream of the most 5′ TSS. Functional studies in primary HASM cells and the BEAS-2B cell line demonstrated highest promoter activity to be upstream of the most 3′ TSS, with potential repressor elements operating in a cell type-dependent manner, located upstream of the most 5′ TSS. We present functional data to show that the CA repeat may influence the transcription of the gene in HASM and BEAS-2B cells.peer-reviewe
Classification of time series by shapelet transformation
Time-series classification (TSC) problems present a specific challenge for classification algorithms: how to measure similarity between series. A \emph{shapelet} is a time-series subsequence that allows for TSC based on local, phase-independent similarity in shape. Shapelet-based classification uses the similarity between a shapelet and a series as a discriminatory feature. One benefit of the shapelet approach is that shapelets are comprehensible, and can offer insight into the problem domain. The original shapelet-based classifier embeds the shapelet-discovery algorithm in a decision tree, and uses information gain to assess the quality of candidates, finding a new shapelet at each node of the tree through an enumerative search. Subsequent research has focused mainly on techniques to speed up the search. We examine how best to use the shapelet primitive to construct classifiers. We propose a single-scan shapelet algorithm that finds the best shapelets, which are used to produce a transformed dataset, where each of the features represent the distance between a time series and a shapelet. The primary advantages over the embedded approach are that the transformed data can be used in conjunction with any classifier, and that there is no recursive search for shapelets. We demonstrate that the transformed data, in conjunction with more complex classifiers, gives greater accuracy than the embedded shapelet tree. We also evaluate three similarity measures that produce equivalent results to information gain in less time. Finally, we show that by conducting post-transform clustering of shapelets, we can enhance the interpretability of the transformed data. We conduct our experiments on 29 datasets: 17 from the UCR repository, and 12 we provide ourselve
Three-nucleon mechanisms in photoreactions
The C reaction has been measured for
E=150-800 MeV in the first study of this reaction in a target
heavier than He. The experimental data are compared to a microscopic many
body calculation. The model, which predicts that the largest contribution to
the reaction arises from final state interactions following an initial pion
production process, overestimates the measured cross sections and there are
strong indications that the overestimate arises in this two-step process. The
selection of suitable kinematic conditions strongly suppresses this two-step
contribution leaving cross sections in which up to half the yield is predicted
to arise from the absorption of the photon on three interacting nucleons and
which agree with the model. The results indicate measurements on
nuclei may be a valuable tool for obtaining information on the nuclear
three-body interaction.Comment: 5 pages, 3 figure
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