1,417 research outputs found
Hard photon production and matrix-element parton-shower merging
We present a Monte-Carlo approach to prompt-photon production, where photons
and QCD partons are treated democratically. The photon fragmentation function
is modelled by an interleaved QCD+QED parton shower. This known technique is
improved by including higher-order real-emission matrix elements. To this end,
we extend a recently proposed algorithm for merging matrix elements and
truncated parton showers. We exemplify the quality of the Monte-Carlo
predictions by comparing them to measurements of the photon fragmentation
function at LEP and to measurements of prompt photon and diphoton production
from the Tevatron experiments.Comment: 18 pages, 5 figures, revised version with minor update
Bottom-quark mass effects in associated production with and bosons
In this study, predictions obtained in the four and in the five flavour
schemes are compared for two important processes involving heavy flavours at
the LHC: the production of a or a Higgs boson in association with
quarks. In particular we obtain predictions with \Sherpa's \MCatNLO
implementation for the four--flavour scheme, treating the 's as massive, and
with multijet merging at leading and next-to leading order for the
five--flavour scheme. While differences between the two schemes, at the
inclusive level, are well understood from resummation of possibly large logs
into the -PDFs, differences in shape present a major problem for
experimental measurements. We make use of data for production at
the TeV LHC to exhibit strengths and weaknesses of the different approaches
and we use these results to validate predictions for -associated Higgs-boson
production at the 13 TeV Run II.Comment: Proceedings of XXV International Workshop on Deep-Inelastic
Scattering and Related Subjects, 3-7 April 2017, University of Birmingham,
UK. 10 pages, 6 figure
Sensory augmentation:Integration of an auditory compass signal into human perception of space
Bio-mimetic approaches to restoring sensory function show great promise in that they rapidly produce perceptual experience, but have the disadvantage of being invasive. In contrast, sensory substitution approaches are non-invasive, but may lead to cognitive rather than perceptual experience. Here we introduce a new non-invasive approach that leads to fast and truly perceptual experience like bio-mimetic techniques. Instead of building on existing circuits at the neural level as done in bio-mimetics, we piggy-back on sensorimotor contingencies at the stimulus level. We convey head orientation to geomagnetic North, a reliable spatial relation not normally sensed by humans, by mimicking sensorimotor contingencies of distal sounds via head-related transfer functions. We demonstrate rapid and long-lasting integration into the perception of self-rotation. Short training with amplified or reduced rotation gain in the magnetic signal can expand or compress the perceived extent of vestibular self-rotation, even with the magnetic signal absent in the test. We argue that it is the reliability of the magnetic signal that allows vestibular spatial recalibration, and the coding scheme mimicking sensorimotor contingencies of distal sounds that permits fast integration. Hence we propose that contingency-mimetic feedback has great potential for creating sensory augmentation devices that achieve fast and genuinely perceptual experiences
Atypical miRNA expression in temporal cortex associated with dysregulation of immune, cell cycle, and other pathways in autism spectrum disorders.
BackgroundAutism spectrum disorders (ASDs) likely involve dysregulation of multiple genes related to brain function and development. Abnormalities in individual regulatory small non-coding RNA (sncRNA), including microRNA (miRNA), could have profound effects upon multiple functional pathways. We assessed whether a brain region associated with core social impairments in ASD, the superior temporal sulcus (STS), would evidence greater transcriptional dysregulation of sncRNA than adjacent, yet functionally distinct, primary auditory cortex (PAC).MethodsWe measured sncRNA expression levels in 34 samples of postmortem brain from STS and PAC to find differentially expressed sncRNA in ASD compared with control cases. For differentially expressed miRNA, we further analyzed their predicted mRNA targets and carried out functional over-representation analysis of KEGG pathways to examine their functional significance and to compare our findings to reported alterations in ASD gene expression.ResultsTwo mature miRNAs (miR-4753-5p and miR-1) were differentially expressed in ASD relative to control in STS and four (miR-664-3p, miR-4709-3p, miR-4742-3p, and miR-297) in PAC. In both regions, miRNA were functionally related to various nervous system, cell cycle, and canonical signaling pathways, including PI3K-Akt signaling, previously implicated in ASD. Immune pathways were only disrupted in STS. snoRNA and pre-miRNA were also differentially expressed in ASD brain.ConclusionsAlterations in sncRNA may underlie dysregulation of molecular pathways implicated in autism. sncRNA transcriptional abnormalities in ASD were apparent in STS and in PAC, a brain region not directly associated with core behavioral impairments. Disruption of miRNA in immune pathways, frequently implicated in ASD, was unique to STS
Matching Parton Showers and Matrix Elements
We compare different procedures for combining fixed-order tree-level matrix
element generators with parton showers. We use the case of W-production at the
Tevatron and the LHC to compare different implementations of the so-called CKKW
scheme and one based on the so-called MLM scheme using different matrix element
generators and different parton cascades. We find that although similar results
are obtained in all cases, there are important differences.Comment: Proceedings of the "HERA and the LHC" workshop, CERN/DESY 2004/200
Emergence of noise-induced barren plateaus in arbitrary layered noise models
In variational quantum algorithms the parameters of a parameterized quantum
circuit are optimized in order to minimize a cost function that encodes the
solution of the problem. The barren plateau phenomenon manifests as an
exponentially vanishing dependence of the cost function with respect to the
variational parameters, and thus hampers the optimization process. We discuss
how, and in which sense, the phenomenon of noise-induced barren plateaus
emerges in parameterized quantum circuits with a layered noise model. Previous
results have shown the existence of noise-induced barren plateaus in the
presence of local Pauli noise [arXiv:2007.14384]. We extend these results
analytically to arbitrary completely-positive trace preserving maps in two
cases: 1) when a parameter-shift rule holds, 2) when the parameterized quantum
circuit at each layer forms a unitary -design. The second example shows how
highly expressive unitaries give rise not only to standard barren plateaus
[arXiv:1803.11173], but also to noise-induced ones. In the second part of the
paper, we study numerically the emergence of noise-induced barren plateaus in
QAOA circuits focusing on the case of MaxCut problems on -regular graphs and
amplitude damping noise.Comment: 34 pages, 9 Figures, added Refs. [31,32] and fixed typo in Eq (B.30
Recent Advances and the Potential for Clinical Use of Autofluorescence Detection of Extra-Ophthalmic Tissues
The autofluorescence (AF) characteristics of endogenous fluorophores allow the label-free assessment and visualization of cells and tissues of the human body. While AF imaging (AFI) is well-established in ophthalmology, its clinical applications are steadily expanding to other disciplines. This review summarizes clinical advances of AF techniques published during the past decade. A systematic search of the MEDLINE database and Cochrane Library databases was performed to identify clinical AF studies in extra-ophthalmic tissues. In total, 1097 articles were identified, of which 113 from internal medicine, surgery, oral medicine, and dermatology were reviewed. While comparable technological standards exist in diabetology and cardiology, in all other disciplines, comparability between studies is limited due to the number of differing AF techniques and non-standardized imaging and data analysis. Clear evidence was found for skin AF as a surrogate for blood glucose homeostasis or cardiovascular risk grading. In thyroid surgery, foremost, less experienced surgeons may benefit from the AF-guided intraoperative separation of parathyroid from thyroid tissue. There is a growing interest in AF techniques in clinical disciplines, and promising advances have been made during the past decade. However, further research and development are mandatory to overcome the existing limitations and to maximize the clinical benefits
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