102 research outputs found
NLO QCD and EW corrections to off-shell production at the LHC
The production of a single top quark in association with a boson
( production) at the LHC is a relevant probe of
the electroweak sector of the Standard Model as well as a window to possible
new-physics effects. The growing experimental interest in performing
differential measurements for this process demands an improved theoretical
modelling in realistic fiducial regions. In this article we present an
NLO-accurate calculation that includes
complete off-shell effects and spin correlations, combining QCD and electroweak
radiative corrections to the LO signal. Integrated and differential
cross-sections are shown for a fiducial setup characterized by three charged
leptons, two jets, and missing energy.Comment: 24 pages, 10 figure
Like-Sign W-Boson Scattering at the LHC -- Approximations and Full Next-to-Leading-Order Predictions
We present a new calculation of next-to-leading-order corrections of the
strong and electroweak interactions to like-sign W-boson scattering at the
Large Hadron Collider, implemented in the Monte Carlo integrator Bonsay. The
calculation includes leptonic decays of the bosons. It comprises
the whole tower of next-to-leading-order contributions to the cross section,
which scale like , ,
, and in the strong and electroweak
couplings and . We present a detailed survey of
numerical results confirming the occurrence of large pure electroweak
corrections of the order of for integrated cross sections and even
larger corrections in high-energy tails of distributions. The electroweak
corrections account for the major part of the complete next-to-leading-order
correction, which amounts to in size, depending on the details of
the event selection chosen for analysing vector-boson-scattering. Moreover, we
compare the full next-to-leading-order corrections to approximate results based
on the neglect of contributions that are not enhanced by the vector-boson
scattering kinematics (VBS approximation) and on resonance expansions for the
-boson decays (double-pole approximation); the quality of this
approximation is good within for integrated cross sections and the
dominating parts of the differential distributions. Finally, for the
leading-order predictions, we construct different versions of effective
vector-boson approximations, which are based on cross-section contributions
that are enhanced by collinear emission of bosons off the
initial-state (anti)quarks; in line with previous findings in the literature,
it turns out that the approximative quality is rather limited for applications
at the LHC.Comment: 57 pages, 70 figure
Percutaneous posterolateral approach for the simulation of a far-lateral disc herniation in an ovine model
This work describes a minimally invasive damage model for ovine lumbar discs via partial nucleotomy using a posterolateral approach. Two cadavers were dissected to analyze the percutaneous corridor. Subsequently, 28 ovine had their annulus fibrosus punctured via awl penetration under fluoroscopic control and nucleus pulposus tissue removed via rongeur. Efficacy was assessed by animal morbidity, ease of access to T12-S1 disc spaces, and production of a mechanical injury as verified by discography, radiography, and histology. T12-S1 were accessible with minimal nerve damage morbidity. Scar tissue sealed the disc puncture site in all animals within 6 weeks, withstanding 1 MP of intradiscal pressure. Partial nucleotomy led to a significant reduction in intervertebral disk height and an increased histological degeneration score. Inducing a reproducible injury pattern of disc degeneration required minimal time, effort, and equipment. The posterolateral approach allows operation on several discs within a single surgery and multiple animal surgeries within a single day.Peer reviewe
Parton Distributions and New Physics Searches: the Drell-Yan Forward-Backward Asymmetry as a Case Study
We discuss the sensitivity of theoretical predictions of observables used in
searches for new physics to parton distributions (PDFs) at large momentum
fraction . Specifically, we consider the neutral-current Drell-Yan
production of gauge bosons with invariant masses in the TeV range, for which
the forward-backward asymmetry of charged leptons from the decay of the gauge
boson in its rest frame is a traditional probe of new physics. We show that the
qualitative behaviour of the asymmetry depends strongly on the assumptions made
in determining the underlying PDFs. We discuss and compare the large-
behaviour of various different PDF sets, and find that they differ
significantly. Consequently, the shape of the asymmetry observed at lower
dilepton invariant masses, where all PDF sets are in reasonable agreement
because of the presence of experimental constraints, is not necessarily
reproduced at large masses where the PDFs are mostly unconstrained by data. It
follows that the shape of the asymmetry at high masses may depend on
assumptions made in the PDF parametrization, and thus deviations from the
traditionally expected behaviour cannot be taken as a reliable indication of
new physics. We demonstrate that forward-backward asymmetry measurements could
help in constraining PDFs at large and discuss the accuracy that would be
required to disentangle the effects of new physics from uncertainties in the
PDFs in this region.Comment: 27 pages, 20 figure
Intervertebral Disc Regeneration Injection of a Cell-Loaded Collagen Hydrogel in a Sheep Model
Degenerated intervertebral discs (IVDs) were treated with autologous adipose-derived stem cells (ASC) loaded into an injectable collagen scaffold in a sheep model to investigate the implant's therapeutic potential regarding the progression of degeneration of previously damaged discs. In this study, 18 merino sheep were subjected to a 3-step minimally invasive injury and treatment model, which consisted of surgically induced disc degeneration, treatment of IVDs with an ASC-loaded collagen hydrogel 6 weeks post-operatively, and assessment of the implant's influence on degenerative tissue changes after 6 and 12 months of grazing. Autologous ASCs were extracted from subcutaneous adipose tissue and cultivated in vitro. At the end of the experiment, disc heights were determined by mu-CT measurements and morphological tissue changes were histologically examined.Histological investigations show that, after treatment with the ASC-loaded collagen hydrogel implant, degeneration-specific features were observed less frequently. Quantitative studies of the degree of degeneration did not demonstrate a significant influence on potential tissue regeneration with treatment. Regarding disc height analysis, at both 6 and 12 months after treatment with the ASC-loaded collagen hydrogel implant a stabilization of the disc height can be seen. A complete restoration of the intervertebral disc heights however could not be achieved.The reported injection procedure describes in a preclinical model a translational therapeutic approach for degenerative disc diseases based on adipose-derived stem cells in a collagen hydrogel scaffold. Further investigations are planned with the use of a different injectable scaffold material using the same test model.Peer reviewe
Micro-computed tomography, scanning electron microscopy and energy X-ray spectroscopy studies of facet joint degeneration : A comparison to clinical imaging
Segmental degeneration in the human lumbar spine affects both the intervertebral discs and facet joints. Facet joint degeneration not only affects the cartilage surface, but also alters the cellular properties of the cartilage tissue and the structure of the subchondral bone. The primary focus of this study is the investigation of these microstructural changes that are caused by facet joint degeneration. Microstructural analyses of degenerated facet joint samples, obtained from patients following operative lumbar interbody fusion, have not previously been extensively investigated. This study analyzes human facet joint samples from the inferior articular process using scanning electron microscopy, micro-computed tomography, and energy dispersive X-ray spectroscopy to evaluate parameters of interest in facet joint degeneration such as elemental composition, cartilage layer thickness and cell density, calcification zone thickness, subchondral bone portion, and trabecular bone porosity. These microstructural analyses demonstrate fragmentation, cracking, and destruction of the cartilage layer, a thickened calcification zone, localized calcification areas, and cell cluster formation as pathological manifestations of facet joint degeneration. The detailed description of these microstructural changes is critical for a comprehensive understanding of the pathology of facet joint degeneration, as well as the subsequent development and efficacy analysis of regenerative treatment strategies.Peer reviewe
Mapping the role of oral cavity physiological factors into the viscoelastic model of denture adhesives for numerical implementation
Physiological parameters of the oral cavity have a profound impact on any restorative solutions designed for edentulous patients including denture adhesives. This study aims to mathematically quantify the influence of three such variables, namely: the temperature, pH, and the swelling of such adhesives under the influence of saliva on its mechanical behavior. The mathematical quantification is further aimed to implement a material model for such adhesives which considers the impact of such physiological factors. The denture adhesive is experimentally investigated by means of rheological steady state frequency sweep tests to obtain the relaxation spectrum of the material. The relaxation behavior is measured for a wide range of oral cavity temperatures and pH. Also, the adhesive is hydrated and upon swelling to different levels again tested to understand the impact of swelling on the mechanical behavior. The experimentally measured continuous relaxation spectrum is modeled as a viscoelastic material using a discrete set of points based on the Prony series discretization technique. The relaxation spectrums for various temperatures are compared and the possibility of a time-temperature superposition is explored for the model. Similarly, the measured values of Storage and loss modulus are investigated to understand the role of pH and swelling. The results in this study clearly indicated a horizontal shift in the relaxation behavior with increase in temperature. And hence, the time-temperature shift factor was calculated for the adhesive. The relaxation spectrum also showed a strong correlation with swelling of the adhesive and the pH. The influence of these two parameters were captured into the model based on the relaxation time parameter in the Prony series approach. Based on this study the impact of these parameters could be appreciated on the performance and mechanical behavior of denture adhesives and implemented into a Prony series based viscoelastic material model which can be used with numerical simulations
- …