108 research outputs found
Precision direct photon and W-boson spectra at high p_T and comparison to LHC data
The differential p_T spectrum for vector boson production is computed at
next-to-leading fixed order and including the resummation of threshold
logarithms at next-to-next-to-leading logarithmic accuracy. A comparison is
made to ATLAS data on direct photon and W production at high transverse
momentum p_T, finding excellent agreement. The resummation is achieved by
factorizing contributions associated with different scales using Soft-Collinear
Effective Theory. Each part is then calculated perturbatively and the
individual contributions are combined using renormalization group methods. A
key advantage of the effective theory framework is that it indicates a set of
natural scale choices, in contrast to the fixed-order calculation. Resummation
of logarithms of ratios of these scales leads to better agreement with data and
reduced theoretical uncertainties.Comment: 24 pages, 10 figures; v2: journal version; v3: corrections in (20),
(37), (38
Transverse-momentum spectra of electroweak bosons near threshold at NNLO
We obtain the next-to-next-to-leading order corrections to
transverse-momentum spectra of W, Z and Higgs bosons near the partonic
threshold. In the threshold limit, the electroweak boson recoils against a
low-mass jet and all radiation is either soft, or collinear to the jet or the
beam directions. We extract the virtual corrections from known results for the
relevant two-loop four-point amplitudes and combine them with the soft and
collinear two-loop functions as defined in Soft-Collinear Effective Theory. We
have implemented these results in a public code PeTeR and present numerical
results for the threshold resummed cross section of W and Z bosons at
next-to-next-to-next-to-leading logarithmic accuracy, matched to
next-to-leading fixed-order perturbation theory. The two-loop corrections lead
to a moderate increase in the cross section and reduce the scale uncertainty by
about a factor of two. The corrections are significantly larger for Higgs
production.Comment: 33 pages, 3 figures; v2: journal version, correction in (73); v3:
corrected qg-channel in (73
The transverse-momentum spectrum of Higgs bosons near threshold at NNLO
We give next-to-next-to-leading order (NNLO) predictions for the Higgs
production cross section at large transverse momentum in the threshold limit.
Near the partonic threshold, all radiation is either soft or collinear to the
final state jet which recoils against the Higgs boson. We find that the real
emission corrections are of moderate size, but that the virtual corrections are
large. We discuss the origin of these corrections and give numerical
predictions for the transverse-momentum spectrum. The threshold result is
matched to the known NLO result and implemented in the public code PeTeR.Comment: 17 pages, 9 Figures; v2: journal version, correction in the qg
channe
International guidelines for contrast-enhanced ultrasonography:ultrasound imaging in the new millennium
The intent of this review is to discuss and comment on common clinical scenarios in which contrast-enhanced ultrasonography (CEUS) may play a decisive role and to illustrate important points with typical cases. With the advent of CEUS, the scope of indications for ultrasonography has been dramatically extended, and now includes functional imaging and tissue characterization, which in many cases enable tumor diagnosis without a biopsy. It is virtually impossible to imagine the practice of modern medicine as we know it in high-income countries without the use of imaging, and yet, an estimated two thirds of the global population may receive no such care. Ultrasound imaging with CEUS has the potential to correct this inequity
Model Comparison and Calibration Assessment: User Guide for Consistent Scoring Functions in Machine Learning and Actuarial Practice
One of the main tasks of actuaries and data scientists is to build good
predictive models for certain phenomena such as the claim size or the number of
claims in insurance. These models ideally exploit given feature information to
enhance the accuracy of prediction. This user guide revisits and clarifies
statistical techniques to assess the calibration or adequacy of a model on the
one hand, and to compare and rank different models on the other hand. In doing
so, it emphasises the importance of specifying the prediction target functional
at hand a priori (e.g. the mean or a quantile) and of choosing the scoring
function in model comparison in line with this target functional. Guidance for
the practical choice of the scoring function is provided. Striving to bridge
the gap between science and daily practice in application, it focuses mainly on
the pedagogical presentation of existing results and of best practice. The
results are accompanied and illustrated by two real data case studies on
workers' compensation and customer churn.Comment: 68 pages, 22 figure
Resummation for W and Z production at large pT
Soft-Collinear Effective theory is used to perform threshold resummation for
W and Z production at large transverse momentum to next-to-next-to-leading
logarithmic accuracy including matching to next-to-leading fixed-order results.
The results agree very well with data from the Tevatron, and predictions are
made for the high-pT spectra at the LHC. While the higher-log terms are of
moderate size, their inclusion leads to a substantial reduction of the
perturbative uncertainty. With these improvements, the PDF uncertainties now
dominate the error on the predicted cross section.Comment: 5 pages, 5 figure
Neuroplasticity at Home: Improving Home-Based Motor Learning Through Technological Solutions. A Review
Background: Effective science-based motor rehabilitation requires high volume of individualized, intense physical training, which can be difficult to achieve exclusively through physical 1-on-1 sessions with a therapist. Home-based training, enhanced by technological solutions, could be a tool to help facilitate the important factors for neuroplastic motor improvements.Objectives: This review aimed to discover how the inclusion of modern information and communications technology in home-based training programs can promote key neuroplastic factors associated with motor learning in neurological disabilities and identify which challenges are still needed to overcome.Methods: We conducted a thorough literature search on technological home-based training solutions and categorized the different fundamental approaches that were used. We then analyzed how these approaches can be used to promote certain key factors of neuroplasticity and which challenges still need to be solved or require external personalized input from a therapist.Conclusions: The technological approaches to home-based training were divided into three categories: sensory stimuli training, digital exchange of information training, and telerehabilitation. Generally, some technologies could be characterized as easily applicable, which gave the opportunity to promote flexible scheduling and a larger overall training volume, but limited options for individualized variation and progression. Other technologies included individualization options through personalized feedback that might increase the training effect, but also increases the workload of the therapist. Further development of easily applicable and intelligent solutions, which can return precise feedback and individualized training suggestions, is needed to fully realize the potential of home-based training in motor learning activities
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Resummation for W and Z Production at Large p T
Soft-Collinear Effective theory is used to perform threshold resummation for W and Z production at large transverse momentum to next-to-next-to-leading logarithmic accuracy including matching to next-to-leading fixed-order results. The results agree very well with data from the Tevatron, and predictions are made for the high-pT spectra at the LHC. While the higher-log terms are of moderate size, their inclusion leads to a substantial reduction of the perturbative uncertainty. With these improvements, the PDF uncertainties now dominate the error on the predicted cross section.Physic
Transcutaneous spinal direct current stimulation increases corticospinal transmission and enhances voluntary motor output in humans
Optimization of motor performance is of importance in daily life, in relation to recovery following injury as well as for elite sports performance. The present study investigated whether transcutaneous spinal direct current stimulation (tsDCS) may enhance voluntary ballistic activation of ankle muscles and descending activation of spinal motor neurons in ableâbodied adults. Fortyâone adults (21 men; 24.0 Âą 3.2 years) participated in the study. The effect of tsDCS on ballistic motor performance and plantar flexor muscle activation was assessed in a doubleâblinded shamâcontrolled crossâover experiment. In separate experiments, the underlying changes in excitability of corticospinal and spinal pathways were probed by evaluating soleus (SOL) motor evoked potentials (MEPs) following singleâpulse transcranial magnetic stimulation (TMS) over the primary motor cortex, SOL Hâreflexes elicited by tibial nerve stimulation and TMSâconditioning of SOL Hâreflexes. Measures were obtained before and after cathodal tsDCS over the thoracic spine (T11âT12) for 10 min at 2.5 mA. We found that cathodal tsDCS transiently facilitated peak acceleration in the ballistic motor task compared to sham tsDCS. Following tsDCS, SOL MEPs were increased without changes in Hâreflex amplitudes. The shortâlatency facilitation of the Hâreflex by subthreshold TMS, which is assumed to be mediated by the fast conducting monosynaptic corticomotoneuronal pathway, was also enhanced by tsDCS. We argue that tsDCS briefly facilitates voluntary motor output by increasing descending drive from corticospinal neurones to spinal plantar flexor motor neurons. tsDCS can thus transiently promote withinâsession CNS function and voluntary motor output and holds potential as a technique in the rehabilitation of motor function following central nervous lesions
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