1,233 research outputs found
The 14C(n,g) cross section between 10 keV and 1 MeV
The neutron capture cross section of 14C is of relevance for several
nucleosynthesis scenarios such as inhomogeneous Big Bang models, neutron
induced CNO cycles, and neutrino driven wind models for the r process. The
14C(n,g) reaction is also important for the validation of the Coulomb
dissociation method, where the (n,g) cross section can be indirectly obtained
via the time-reversed process. So far, the example of 14C is the only case with
neutrons where both, direct measurement and indirect Coulomb dissociation, have
been applied. Unfortunately, the interpretation is obscured by discrepancies
between several experiments and theory. Therefore, we report on new direct
measurements of the 14C(n,g) reaction with neutron energies ranging from 20 to
800 keV
Capabilities of macroscopic forming simulation for large-scale forming processes of dry and impregnated textiles
Forming of continuously fibre-reinforced polymers (CoFRP) has a significant impact on the structural performance of composite components, underlining the importance of forming simulation for CoFRP product development processes. For an integrated development of industrial composite components, efficient forming simulation methods are in high demand. Application-oriented method development is particularly crucial for industrial needs, where large and complex multi-layer components are manufactured, commercial FE software is used, and yet high prediction accuracy is required. To meet industrial demands, this contribution gives an insight in macroscopic forming simulation approaches that utilize the FE software Abaqus in combination with user-defined material models and finite elements. Three CoFRP forming technologies are considered, which are in industrial focus due to their suitability for mass production: textile forming of dry unidirectional non-crimp fabrics (UD-NCF), thermoforming of pre-impregnated UD tapes and wet compression moulding (WCM). In addition to the highly anisotropic, large-strain material behaviour that composite forming processes have in common, the three process technologies face various process-specific modelling challenges. UD-NCFs require material models that capture the deformation behaviour and the slippage of the stitching. Thermoforming of UD tapes is highly rate- and temperature-dependent, calling for rheological membrane and bending modelling. Moreover, a thermomechanical approach including crystallisation kinetics enables the prediction of potential phase-transition during forming and resulting defects in the semi-crystalline thermoplastic matrix. For simultaneous forming and infiltration in wet compression moulding, a finite Darcy-Progression-Element is superimposed with the membrane and shell elements for forming simulation, capturing infiltration-dependent material properties. The three outlined technologies illustrate the complexity and importance of further simulation method development to support future process development
Trichuris suis ova in relapsing-remitting multiple sclerosis and clinically isolated syndrome (TRIOMS): study protocol for a randomized controlled trial
BACKGROUND: Trichuris suis ova is a probiotic treatment based on the hygiene hypothesis. It has been demonstrated as safe and effective in autoimmune inflammatory bowel diseases and clinical trials indicate that helminth infections also have an immunomodulatory effect in multiple sclerosis.We hypothesize that administering 2,500 Trichuris suis ova eggs orally every two weeks for 12 months is--due to its immunomodulatory and anti-inflammatory effect--significantly more effective than oral placebo in preventing new T2 and Gd+ lesions, as quantified by cerebral MRI and clinical examination, in relapsing-remitting multiple sclerosis and clinically isolated syndrome. METHODS/DESIGN: Fifty patients with relapsing-remitting multiple sclerosis or clinically isolated syndrome with clinical activity, not undergoing any standard therapies, will be randomized 1:1 to Trichuris suis ova 2,500 eggs every two weeks or matching placebo. The safety, tolerability and effect on disease activity and in vivo mechanisms of action of Trichuris suis ova in MS will be assessed by neurological, laboratory and immunological exams and magnetic resonance imaging throughout the 12-month treatment period and over a follow-up period of 6 months. Various immunological analyses will be used to assess the overall patient immune response prior to and at varying time points following treatment with Trichuris suis ova. DISCUSSION: We anticipate that Trichuris suis ova will be well tolerated and more effective than the placebo in preventing new T2 and Gd+ lesions, as quantified by MRI. We also expect the Th1/Th17 proinflammatory response to shift towards the more anti-inflammatory Th2 response. This study has important clinical implications and will involve extensive research on the immunology of helminth therapy. TRIAL REGISTRATION: ClinicalTrials.gov: NCT01413243
High-sensitivity cardiac troponin T and copeptin assays to improve diagnostic accuracy of exercise stress test in patients with suspected coronary artery disease
Background: The average diagnostic sensitivity of exercise stress tests (ESTs) is lower than that of other non-invasive cardiac stress tests. The aim of the study was to examine whether high-sensitivity cardiac troponin T (hs-cTnT) or copeptin concentrations rise in response to inducible myocardial ischaemia and may improve the diagnostic accuracy of ESTs.
Methods and results: An EST was performed stepwise on a bicycle ergometer by 383 consecutive patients with suspected or progression of coronary artery disease (CAD). In addition venous blood samples for measurement of hs-cTnT and copeptin were collected prior to EST, at peak exercise, and 4 h after EST. Coronary angiography was assessed for all patients. Patients with significant CAD (n=224) were more likely to be male and older compared to patients with non-significant CAD (n=169). Positive EST was documented in 125 (55.8%) patients with significant CAD and in 69 (43.4%) patients with non-significant CAD. Copeptin and hs-cTnT concentrations at baseline were higher in patients with significant CAD (copeptin: 10.8 pmol/l (interquartile range (IQR) 8.115.6) vs 9.4 pmol/l (IQR 7.113.9); p=0.04; hs-cTnT: 3.0 ng/l (IQR <3.05.4) vs <3.0 ng/l (IQR <3.0); p=0.006). Hs-cTnT improved sensitivity (61.6% vs 55.8%), specificity (67.7% vs 56.6%) and the positive predictive value (PPV) (72.3% vs 64.4%) and negative (55.2% vs 47.6%) predictive value (NPV) of EST. Copeptin could not improve sensitivity (55.4% vs 55.8%) and reduced specificity, PPV and NPV.
Conclusions: The measurement of hs-cTnT during EST improves sensitivity, specificity, and positive and negative predictive values. In contrast, measurement of copeptin does not improve diagnostic sensitivity and reduces specificity
Синтез и свойства реагентов на основе иодзамещенных гидроксиполиэтил бензоатов
Поиск новых органических производных иода и изучение препаративных возможностей данных соединений в окислительных процессах позволит ввести в практику органического синтеза новые реагенты для окисления. В результате работы получены новые соединения - иодзамещенные гидроксиполиэтил бензоаты. При окислении данных соединений будут получены водорастворимые соединения поливалентного иода, которые в свою очередь должны проявить свойства мягких окислителей в окислительных превращениях спиртов. Таким образом, становится актуальным синтез и изучение препаративных возможностей легко извлекаемых реагентов с требуемой окислительной активностью.The search for new organic derivatives of iodine and the study of the preparative capabilities of these compounds in oxidative processes will make it possible to introduce new reagents for oxidation into the practice of organic synthesis. As a result of the work, new compounds — iodosubstituted hydroxypolyethyl benzoates — were obtained. During the oxidation of these compounds, water-soluble compounds of polyvalent iodine will be obtained, which in turn should exhibit the properties of soft oxidizing agents in the oxidative transformations of alcohols. Thus, the synthesis and study of the preparative capabilities of easily recoverable reagents with the required oxidative activity becomes relevant
High prevalence of vitamin D insufficiency in professional handball athletes
OBJECTIVES: Vitamin D affects multiple body functions through the regulation of gene expression. In sports medicine, its influence on musculoskeletal health and performance is of particular interest. Vitamin D insufficiency might decrease athletic performance and increase the risk of musculoskeletal injuries. Several studies have demonstrated vitamin D deficiency in professional athletes; however, the prevalence of vitamin D insufficiency in professional handball players is yet unknown.
METHODS: The study was planned as a prospective, non-interventional study. We examined 70 male elite handball athletes (first league) in a pre-competition medical assessment in July. Age, height, weight, body mass index, 25-OH vitamin D, calcium, and parathyroid hormone were evaluated, and a sun exposure score was calculated. Players were then divided into two groups of vitamin D levels: insufficient (<30 ng/mL) and sufficient (≥30 ng/mL).
RESULTS: The mean 25-OH vitamin D level of the 70 players was 33.5 ± 10.9 ng/mL (median 32.2, IQR 26.5-38.9 ng/mL). Thirty-nine (55.7%) had sufficient and 31 (44.3%) insufficient levels. Athletes with sufficient vitamin D levels had significantly lower parathyroid hormone levels than athletes with insufficiency (24.9 ± 12.1 vs. 33.5 ± 15.1 ng/mL, p = 0.02). All other parameters evaluated demonstrated no significant difference between the two groups.
CONCLUSION: Vitamin D insufficiency is a common finding in professional handball athletes even in summer, which might negatively affect physical performance. Furthermore, it might lead to an increased risk of musculoskeletal injuries and infections. This should be evaluated in further studies
On the applicability of thermoforming characterization and simulation approaches to glass mat thermoplastic composites
Chopped fiber composite materials offer the potential to be used for complex geometries, including local thickness changes, ribs and beads, offering significant potential for functional lightweighting. Depending on the initial mold coverage and flowability of the material, the processing behaves either more like a compression molding or a thermoforming process. The latter is applicable to high initial mold coverages and includes typical thermoforming defects such as local wrinkling. Such defects are not predictable by conventional compression molding simulation approaches usually adopted for this material class. Therefore, thermoforming characterization and simulation approaches and their applicability to glass mat thermoplastic (47 vol.% long glass fiber, Tepex Flowcore) for high initial mold coverages is investigated. Abaqus in combination with several user-subroutines is applied. Valid material characterization results from torsion bar and rheometer bending tests are obtained and applied to an automotive structure in thermoforming simulation. Results indicate that the high stiffness and high viscosity captured by the rheometer bending test at low shear-rates are necessary to reproduce the wrinkling behavior observed in the experimental results. Discrepancy is most likely reducible to thermomechanical effects, and that the modelling approach does not account for thickness deformation due to transverse compression
Rapid sea ice changes in the future Barents Sea
Observed and future winter Arctic sea ice loss is strongest in the Barents Sea.
However, the anthropogenic signal of the sea ice decline is superimposed by pronounced internal variability that represents a large source of uncertainty in future climate projections.
A notable manifestation of internal variability is rapid ice change events (RICEs) that greatly exceed the anthropogenic trend.
These RICEs are associated with large displacements of the sea ice edge which could potentially have both local and remote impacts on the climate system.
In this study we present the first investigation of the frequency and drivers of RICEs in the future Barents Sea, using multi-member ensemble simulations from CMIP5 and CMIP6.
A majority of RICEs are triggered by trends in ocean heat transport or surface heat fluxes.
Ice loss events are associated with increasing trends in ocean heat transport and decreasing trends in surface heat loss.
RICEs are a common feature of the future Barents Sea until the region becomes close to ice-free.
As their evolution over time is closely tied to the average sea ice conditions, rapid ice changes in the Barents Sea may serve as a precursor for future changes in adjacent seas.</p
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Paleotethys was a highly mobile oceanic realm pinching into the supercontinent Pangea between Gondwana and Eurasia in the late Paleozoic/early Mesozoic. Published Paleotethyan reconstructions reveal that the time of Paleotethys closure and the position of its suture are highly debated. We present new magmatic and detrital zircon ages, separated from pre-Alpine basement and Permian to Triassic cover rocks exposed in the External Hellenides of Crete. These age data reveal Variscan and Cimmerian docking of microplates along the southern margin of Laurasia and help to constrain the time of Paleotethys closure.46% of detrital zircons from quartzite in the Variscan basement, are Pennsylvanian with concordant ages at 321. ±. 2. Ma, 310. ±. 3. Ma, and 300. ±. 3. Ma. The basement is unconformably overlain by arc-related volcanics of the Tyros Unit, magmatic zircons of which yielded a concordant U-Pb zircon age at 285. ±. 2. Ma. Thus, the metasediments of the basement, interpreted as former trench sediments, were deposited, metamorphosed and exhumed in latest Carboniferous to early Permian times (302-283. Ma). Magmatic activity during this late Variscan phase is also indicated by igneous boulders within Olenekian (meta)conglomerates of the Tyros Unit, which yielded concordant U-Pb zircon ages at 291. ±. 2 and 310. ±. 2. Ma. The late Variscan orogenic phase is attributed to the collision of the Gondwana-derived southern Minoan terrane (SMT) with Laurasia subsequent to northward subduction of Paleotethys lithosphere and Viséan collision of the northern Minoan terrane (NMT).Magmatic activity ceased during the late Permian, but revived in the Lower Triassic as is indicated by felsic volcanics (249. ±. 2. Ma, concordant U-Pb zircon) and by detrital zircons (242. ±. 3, 240. ±. 5. Ma, 237. ±. 3. Ma concordant U-Pb zircon) of the Tyros Unit. At the same time the Variscan chain was exhumed and removed as is shown by the detritus in the Lower to Middle Triassic Tyros sediments, which includes high-grade metamorphic rocks and detrital zircons with U-Pb ages ranging from 280 to 335. Ma.A significant change in the detrital components occurred in the Ladinian when the Variscan basement with its Permo-Triassic cover was thrust on top of clastic sediments, today represented by the Phyllite-Quartzite Unit s.str. The Phyllite-Quartzite Unit s.str. shows Cadomian and older - but no Variscan - detritus because of its position along the northern margin of the Cimmerian ribbon continent. Thus, in the eastern Mediterranean, Paleotethys was closed during the Ladinian and the related suture in the External Hellenides is situated between the Variscan basement (active margin in the north) and the Phyllite-Quartzite Unit s.str (passive margin in the south). Carnian crustal extension led to subsidence of the Variscan/Cimmerian chain, most parts of which merged below sea level. This is the reason why 90% of the detritus of the Carnian Tyros Beds are not related to the Variscan, but to the Cadomian and Grenvillian basement of the E-Gondwana derived Cimmerian ribbon continent
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