2,963 research outputs found
Multiclass Semi-Supervised Learning on Graphs using Ginzburg-Landau Functional Minimization
We present a graph-based variational algorithm for classification of
high-dimensional data, generalizing the binary diffuse interface model to the
case of multiple classes. Motivated by total variation techniques, the method
involves minimizing an energy functional made up of three terms. The first two
terms promote a stepwise continuous classification function with sharp
transitions between classes, while preserving symmetry among the class labels.
The third term is a data fidelity term, allowing us to incorporate prior
information into the model in a semi-supervised framework. The performance of
the algorithm on synthetic data, as well as on the COIL and MNIST benchmark
datasets, is competitive with state-of-the-art graph-based multiclass
segmentation methods.Comment: 16 pages, to appear in Springer's Lecture Notes in Computer Science
volume "Pattern Recognition Applications and Methods 2013", part of series on
Advances in Intelligent and Soft Computin
Heavy Flavour Production at Tevatron and Parton Shower Effects
We present hadron-level predictions from the Monte Carlo generator Cascade
and numerical calculations of charm and beauty production at the Fermilab
Tevatron within the framework of the -factorization QCD approach. Our
consideration is based on the CCFM-evolved unintegrated gluon densities in a
proton. The performed analysis covers the total and differential cross sections
of open charm and beauty quarks, and mesons (or rather muons from their
semileptonic decays) and the total and differential cross sections of di-jet hadroproduction. We study the theoretical uncertainties of our
calculations and investigate the effects coming from parton showers in initial
and final states. Our predictions are compared with the recent experimental
data taken by the D0 and CDF collaborations. Special attention is put on the
specific angular correlations between the final-state particles. We demonstrate
that the final state parton shower plays a crucial role in the description of
such observables. The decorrelated part of angular separations can be fully
described, if the process is included.Comment: Fig 8,9 10 replaced, small corrections in text A discussion of the
delta phi results is adde
Explaining the t tbar forward-backward asymmetry without dijet or flavor anomalies
We consider new physics explanations of the anomaly in the top quark
forward-backward asymmetry measured at the Tevatron, in the context of flavor
conserving models. The recently measured LHC dijet distributions strongly
constrain many otherwise viable models. A new scalar particle in the
antitriplet representation of flavor and color can fit the t tbar asymmetry and
cross section data at the Tevatron and avoid both low- and high-energy bounds
from flavor physics and the LHC. An s-channel resonance in uc to uc scattering
at the LHC is predicted to be not far from the current sensitivity. This model
also predicts rich top quark physics for the early LHC from decays of the new
scalar particles. Single production gives t tbar j signatures with high
transverse momentum jet, pair production leads to t tbar j j and 4 jet final
states.Comment: 7 pages, 6 figures; v2: notation clarified, references adde
Biomechanical analysis of body movements of myoelectric prosthesis users during standardized clinical tests
Objective: The objective clinical evaluation of user's capabilities to handle their prosthesis is done using various tests which primarily focus on the task completion speed and do not explicitly account for the potential presence of compensatory motions. Given that the excessive body compensation is a common indicator of inadequate prosthesis control, tests which include subjective observations on the quality of performed motions have been introduced. However, these metrics are then influenced by the examiner's opinions, skills, and training making them harder to standardize across patient pools and compare across different prosthetic technologies. Here we aim to objectively quantify the severity of body compensations present in myoelectric prosthetic hand users and evaluate the extent to which traditional objective clinical scores are still able to capture them. Methods: We have instructed 9 below-elbow prosthesis users and 9 able-bodied participants to complete three established objective clinical tests: Box-and-Blocks-Test, Clothespin-Relocation-Test, and Southampton-Hand-Assessment-Procedure. During all tests, upper-body kinematics has been recorded. Results: While the analysis showed that there are some correlations between the achieved clinical scores and the individual body segment travel distances and average speeds, there were only weak correlations between the clinical scores and the observed ranges of motion. At the same time, the compensations were observed in all prosthesis users and, for the most part, they were substantial across the tests. Conclusion: The sole reliance on the currently available objective clinical assessment methods seems inadequate as the compensatory movements are prominent in prosthesis users and yet not sufficiently accounted for
The ideal healthcare: priorities of people with chronic conditions and their carers
Background It is well established that health consumer opinions should be considered in the design, delivery, and evaluation of health services. However, the opinions of people with chronic conditions and their carers and what they actually consider as ideal healthcare is limited. The aim of this study is to investigate the healthcare priorities of consumers with chronic conditions and their carers, if there are differences between these two groups, and if priorities differ depending on geographical location. Methods The nominal group technique was used as a method to identify what is currently important to, or valued by, participants. This method was also particularly suited to learning about healthcare problems and generating important solutions, thereby helping to bridge the gap between research and policy. Recruitment was carried out via purposive sampling, with the assistance of community pharmacies, general practices, various health agencies, government and non-government organisations. A total of 11 nominal groups were conducted; five groups consisted predominantly of consumers (n = 33 participants), two groups consisted predominantly of carers (n = 12 participants) and four were mixed groups, i.e. consumers, carers, and both (n = 26 participants). Results The findings suggested that to create a model of ideal healthcare for people with chronic conditions and their carers, appropriate and timely healthcare access was of paramount importance. Continuity and coordinated care, patient-centred care and affordability were equally the second most important healthcare priorities for all groups. When compared with other groups, access was discussed more frequently among participants residing in the rural area of Mount Isa. Compared to consumers, carers also discussed priorities that were more reminiscent with their caring roles, such as increased access and continuity and coordinated care. Conclusions Access to healthcare is the most important priority for people with chronic conditions and their carers. In the event of inappropriate access for certain groups, all other efforts to increase the quality of healthcare delivery, e.g. patient-centred care, may be pointless. However, health professionals alone may be limited in their ability to address the concerns related to healthcare access; structural changes by health policy makers may be needed
LHC Predictions from a Tevatron Anomaly in the Top Quark Forward-Backward Asymmetry
We examine the implications of the recent CDF measurement of the top-quark
forward-backward asymmetry, focusing on a scenario with a new color octet
vector boson at 1-3 TeV. We study several models, as well as a general
effective field theory, and determine the parameter space which provides the
best simultaneous fit to the CDF asymmetry, the Tevatron top pair production
cross section, and the exclusion regions from LHC dijet resonance and contact
interaction searches. Flavor constraints on these models are more subtle and
less severe than the literature indicates. We find a large region of allowed
parameter space at high axigluon mass and a smaller region at low mass; we
match the latter to an SU(3)xSU(3)/SU(3) coset model with a heavy vector-like
fermion. Our scenario produces discoverable effects at the LHC with only 1-2
inverse femtobarns of luminosity at 7-8 TeV. Lastly, we point out that a
Tevatron measurement of the b-quark forward-backward asymmetry would be very
helpful in characterizing the physics underlying the top-quark asymmetry.Comment: 35 pages, 10 figures, 4 table
On theories of enhanced CP violation in B_s,d meson mixing
The DO collaboration has measured a deviation from the standard model (SM)
prediction in the like sign dimuon asymmetry in semileptonic b decay with a
significance of 3.2 sigma. We discuss how minimal flavour violating (MFV)
models with multiple scalar representations can lead to this deviation through
tree level exchanges of new MFV scalars. We review how the two scalar doublet
model can accommodate this result and discuss some of its phenomenology. Limits
on electric dipole moments suggest that in this model the coupling of the
charged scalar to the right handed u-type quarks is suppressed while its
coupling to the d-type right handed quarks must be enhanced. We construct an
extension of the MFV two scalar doublet model where this occurs naturally.Comment: 10 pages, 7 figures, v3 final JHEP versio
Impact of the Specific Mutation in KRAS Codon 12 Mutated Tumors on Treatment Efficacy in Patients with Metastatic Colorectal Cancer Receiving Cetuximab-Based First-Line Therapy: A Pooled Analysis of Three Trials
Purpose: This study investigated the impact of specific mutations in codon 12 of the Kirsten-ras (KRAS) gene on treatment efficacy in patients with metastatic colorectal cancer (mCRC). Patients: Overall, 119 patients bearing a KRAS mutation in codon 12 were evaluated. All patients received cetuximab-based first-line chemotherapy within the Central European Cooperative Oncology Group (CECOG), AIO KRK-0104 or AIO KRK-0306 trials. Results: Patients with KRAS codon 12 mutant mCRC showed a broad range of outcome when treated with cetuximab-based first-line regimens. Patients with tumors bearing a KRAS p.G12D mutation showed a strong trend to a more favorable outcome compared to other mutations (overall survival 23.3 vs. 14-18 months; hazard ratio 0.66, range 0.43-1.03). An interaction model illustrated that KRAS p.G12C was associated with unfavorable outcome when treated with oxaliplatin plus cetuximab. Conclusion: The present analysis suggests that KRAS codon 12 mutation may not represent a homogeneous entity in mCRC when treated with cetuximab-based first-line therapy. Copyright (C) 2012 S. Karger AG, Base
The validity of using ICD-9 codes and pharmacy records to identify patients with chronic obstructive pulmonary disease
Background: Administrative data is often used to identify patients with chronic obstructive pulmonary disease (COPD), yet the validity of this approach is unclear. We sought to develop a predictive model utilizing administrative data to accurately identify patients with COPD.
Methods: Sequential logistic regression models were constructed using 9573 patients with postbronchodilator spirometry at two Veterans Affairs medical centers (2003-2007). COPD was defined as: 1) FEV1/FVC <0.70, and 2) FEV1/FVC < lower limits of normal. Model inputs included age, outpatient or inpatient COPD-related ICD-9 codes, and the number of metered does inhalers (MDI) prescribed over the one year prior to and one year post spirometry. Model performance was assessed using standard criteria.
Results: 4564 of 9573 patients (47.7%) had an FEV1/FVC < 0.70. The presence of ≥1 outpatient COPD visit had a sensitivity of 76% and specificity of 67%; the AUC was 0.75 (95% CI 0.74-0.76). Adding the use of albuterol MDI increased the AUC of this model to 0.76 (95% CI 0.75-0.77) while the addition of ipratropium bromide MDI increased the AUC to 0.77 (95% CI 0.76-0.78). The best performing model included: ≥6 albuterol MDI, ≥3 ipratropium MDI, ≥1 outpatient ICD-9 code, ≥1 inpatient ICD-9 code, and age, achieving an AUC of 0.79 (95% CI 0.78-0.80).
Conclusion: Commonly used definitions of COPD in observational studies misclassify the majority of patients as having COPD. Using multiple diagnostic codes in combination with pharmacy data improves the ability to accurately identify patients with COPD.Department of Veterans Affairs, Health Services Research and Development (DHA), American Lung Association (CI- 51755-N) awarded to DHA, the American Thoracic Society Fellow Career Development AwardPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/84155/1/Cooke - ICD9 validity in COPD.pd
Nonlinear Localization in Metamaterials
Metamaterials, i.e., artificially structured ("synthetic") media comprising
weakly coupled discrete elements, exhibit extraordinary properties and they
hold a great promise for novel applications including super-resolution imaging,
cloaking, hyperlensing, and optical transformation. Nonlinearity adds a new
degree of freedom for metamaterial design that allows for tuneability and
multistability, properties that may offer altogether new functionalities and
electromagnetic characteristics. The combination of discreteness and
nonlinearity may lead to intrinsic localization of the type of discrete
breather in metallic, SQUID-based, and symmetric metamaterials. We
review recent results demonstrating the generic appearance of breather
excitations in these systems resulting from power-balance between intrinsic
losses and input power, either by proper initialization or by purely dynamical
procedures. Breather properties peculiar to each particular system are
identified and discussed. Recent progress in the fabrication of low-loss,
active and superconducting metamaterials, makes the experimental observation of
breathers in principle possible with the proposed dynamical procedures.Comment: 19 pages, 14 figures, Invited (Review) Chapte
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