A
bstract
We present an Mc@Nlo-like matching of next-to-leading order QCD calculations with the Nagy-Soper parton shower. An implementation of the algorithm within the Helac-Dipoles Monte Carlo ...generator is used to address the uncertainties and ambiguities of the matching scheme. First results obtained using the Nagy-Soper parton shower implementation in Deductor in conjunction with the Helac-Nlo framework are given for the
pp
→
t
t
¯
j
+
X
process at the LHC with
s
=
8
TeV. Effects of resummation are discussed for various observables.
Insects are integral to most freshwater and terrestrial food webs, but due to their accumulation of environmental pollutants they are also contaminant vectors that threaten reproduction, development, ...and survival of consumers. Metamorphosis from larvae to adult can cause large chemical changes in insects, altering contaminant concentrations and fractionation of chemical tracers used to establish contaminant biomagnification in food webs, but no framework exists for predicting and managing these effects. We analyzed data from 39 studies of 68 analytes (stable isotopes and contaminants), and found that metamorphosis effects varied greatly. δ15N, widely used to estimate relative trophic position in biomagnification studies, was enriched by ∼1‰ during metamorphosis, while δ13C used to estimate diet, was similar in larvae and adults. Metals and polycyclic aromatic hydrocarbons (PAHs) were predominantly lost during metamorphosis leading to ∼2 to 125-fold higher larval concentrations and higher exposure risks for predators of larvae compared to predators of adults. In contrast, manufactured organic contaminants (such as polychlorinated biphenyls) were retained and concentrated in adults, causing up to ∼3-fold higher adult concentrations and higher exposure risks to predators of adult insects. Both food web studies and contaminant management and mitigation strategies need to consider how metamorphosis affects the movement of materials between habitats and ecosystems, with special regard for aquatic-terrestrial linkages.
Abstract
The massive stars that survive the phase of red supergiants (RSGs) spend the rest of their life in extremity. Their unstable atmospheres facilitate the formation and episodic ejection of ...shells that alter the stellar appearance and surroundings. In the present study, we revise the evolutionary state of eight hypergiants in the Magellanic Clouds, four of early-A type and four of FG type, and complement the short list of the eruptive post-RSGs termed as yellow hypergiants. We refine the outdated temperatures and luminosities of the stars by means of high-resolution spectroscopy with the Fiber-fed Extended Range Optical Spectrograph (FEROS). The A-type stars are suggested to be in their early, post-main-sequence phase, showing spectrophotometric characteristics of redward evolving supergiants. On the other hand, the FG-type stars manifest themselves through the enhanced atmospheric activity that is traced by emission filling in H α and the dynamical modulation of the low-excitation Ba ii line. Of these stars, the dusty HD269723 is suggested to have recently departed from a cool phase. We identify double-peaked emission in the FEROS data of HD269953 that emerges from an orbiting disc-hosting companion. The highlight of the study is an episode of enhanced mass-loss of HD271182 that manifests as a dimming event in the light curve and renders the star ‘modest’ analogue to ρ Cas. The luminosity log (L/L⊙) = 5.6 of HD271182 can serve as an updated threshold for the luminosity of stars exhibiting a post-RSG evolution in the Large Magellanic Cloud.
A
bstract
We present a comprehensive study of the production of top quark pairs in association with one hard jet in the di-lepton decay channel at the LHC. Our predictions, accurate at NLO in QCD, ...focus on the LHC Run II with a center-of-mass energy of 13 TeV. All resonant and non-resonant contributions at the perturbative order
O
α
s
4
α
4
are taken into account, including irreducible backgrounds to
t
t
¯
j
production, interferences and off-shell effects of the top quark and the
W
gauge boson. We extensively investigate the dependence of our results upon variation of renormalisation and factorisation scales and parton distribution functions in the quest for an accurate estimate of the theoretical uncertainties. Additionally, we explore a few possibilities for a dynamical scale choice with the goal of stabilizing the perturbative convergence of the differential cross sections far away from the
t
t
¯
threshold. Results presented here are particularly relevant for searches of new physics as well as for precise measurements of the top-quark fiducial cross sections and top-quark properties at the LHC.
Triggered by ongoing dark matter searches in the top quark sector at the Large Hadron Collider we report on the calculation of the next-to-leading order QCD corrections to the Standard Model process ...pp → tt¯\ \overline{t} \ + Z (Z → νℓv¯\ \overline{v} \ℓ). This calculation is based on matrix elements for e+νeμ−ν¯μbb¯ντν¯τ\ {e}^{+}{\nu}_e{\mu}^{-}{\overline{\nu}}_{\mu }b\overline{b}\kern0.33em {\nu}_{\tau }{\overline{\nu}}_{\tau } \ production and includes all non-resonant diagrams, interferences, and off-shell effects of the top quarks. Non-resonant and off-shell effects due to the finite W -boson width are also consistently taken into account. As it is common for such studies, we present results for both integrated and differential cross sections for a few renormalisation and factorisation scale choices and three different parton distribution functions. Already with the fairly inclusive cut selection and independently of the scale choice and the parton distribution function non-flat differential K\ \mathcal{K} \ -factors are obtained for pTmiss\ {p}_T^{miss} \, ∆ðoeTMℓℓ, ∆ð'´ℓℓ, cos θℓℓ, HT,HT′\ {H}_T^{\prime } \ observables that are relevant for new physics searches. Good theoretical control over the Standard Model background is a fundamental prerequisite for a correct interpretation of possible signals of new physics that may arise in this channel. Thus, these observables need to be carefully reexamined in the presence of more exclusive cuts before any realistic strategies for the detection of new physics signal can be further developed. Since from the experimental point of view both tt¯\ \overline{t} \ and tt¯\ \overline{t} \ + Z (Z → νℓv¯\ \overline{v} \ℓ) comprise the same final states, we additionally study the impact of the enlarged missing transverse momentum on various differential cross section distributions. To this end normalised differential distributions for pp →e+νeμ−ν¯μbb¯ντν¯τ\ {e}^{+}{\nu}_e{\mu}^{-}{\overline{\nu}}_{\mu }b\overline{b}\kern0.33em {\nu}_{\tau }{\overline{\nu}}_{\tau } \ and pp →e+νeμ−ν¯μbb¯\ {e}^{+}{\nu}_e{\mu}^{-}{\overline{\nu}}_{\mu }b\overline{b} \ are compared.
•A novel crashworthy device is proposed for pier protection from barge impact.•A strategy is proposed to limit plastic deformation within certain region after impact.•The effectiveness of the device ...is thoroughly assessed.
Bridges located in navigation waterways are susceptible to ship impact due to the large ship transportation volume nowadays. The development of effective energy-dissipation devices which can protect bridges from ship impact has drawn much attention in recent years. As a result, many different types of protective structures such as composite crashworthy devices have been developed, analyzed and applied in bridge engineering. However, such protective structures are often extremely costly and were difficult to repair after an impact event. This paper aims to develop a novel crashworthy device with a steel-frame configuration of potentially low production cost and to numerically evaluate its mechanical behavior to quantify its energy-dissipation capacity. The strategy of using reduced cross-sections for certain steel beams in the device is proposed to limit plastic mechanisms within certain structural components whilst ensuring that others remain elastic during impact. The effectiveness of this strategy is numerically evaluated based on the assumption that the reduced cross-sections are rigidly connected to form a continuous beam model. The proposed strategy would greatly facilitate the restoration process of such devices after an impact event by replacing only those structural components where plastic deformations have occurred.
To quantify the effects of traumatic brain injury on integrity of thalamocortical projection fibers and to evaluate whether damage to these fibers accounts for impairments in executive function in ...chronic traumatic brain injury.
High-resolution (voxel size: 0.78 mm x 0.78 mm x 3 mm(3)) diffusion tensor MRI of the thalamus was conducted on 24 patients with a history of single, closed-head traumatic brain injury (TBI) (12 each of mild TBI and moderate to severe TBI) and 12 age- and education-matched controls. Detailed neuropsychological testing with an emphasis on executive function was also conducted. Fractional anisotropy was extracted from 12 regions of interest in cortical and corpus callosum structures and 7 subcortical regions of interest (anterior, ventral anterior, ventral lateral, dorsomedial, ventral posterior lateral, ventral posterior medial, and pulvinar thalamic nuclei).
Relative to controls, patients with a history of brain injury showed reductions in fractional anisotropy in both the anterior and posterior corona radiata, forceps major, the body of the corpus callosum, and fibers identified from seed voxels in the anterior and ventral anterior thalamic nuclei. Fractional anisotropy from cortico-cortico and corpus callosum regions of interest did not account for significant variance in neuropsychological function. However, fractional anisotropy from the thalamic seed voxels did account for variance in executive function, attention, and memory.
The data provide preliminary evidence that traumatic brain injury and resulting diffuse axonal injury results in damage to the thalamic projection fibers and is of clinical relevance to cognition.
The helical tomotherapy (HT) Hi-ART system was installed at our department in April 2007. In July 2018 the first Radixact system in Germany has been launched for clinical use. We present differences, ...advantages and disadvantages and show future perspectives in patient treatment using two HT devices. We investigate patient characteristics, image quality, radiotherapy treatment specifications and analyze the time effort for treatments with the Hi-ART system from April 2010 until May 2017 and compare it to the data acquired in the first nine months of usage of the Radixact system. Comparing the Hi-ART and Radixact system, the unique option of integrated MVCT image acquisition has experienced distinct improvement in image quality. Time effort for irradiation treatment could be improved resulting in a mean beam on time for craniospinal axis treatment of 636.2 s for the Radixact system compared to 915.9 s for the Hi-ART system. The beneficial use of tomotherapy for complex target volumes is demonstrated by a head and neck tumor case and craniospinal axis treatment. With the Radixact system MVCT image quality has been improved allowing for fast and precise interfraction dose adaptation. The improved time effort for patient treatment could increase the accessibility for clinical usage.
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