638 research outputs found

    Measurement of the 70Ge(n,γ) cross section up to 300 keV at the CERN n_TOF facility

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    Neutron capture data on intermediate mass nuclei are of key importance to nucleosynthesis in the weak component of the slow neutron capture processes, which occurs in massive stars. The (n,γ) cross section on 70Ge, which is mainly produced in the s process, was measured at the neutron time-of-flight facility n_TOF at CERN. Resonance capture kernels were determined up to 40 keV neutron energy and average cross sections up to 300 keV. Stellar cross sections were calculated from kT =5 keV tokT =100 keV and are in very good agreement with a previous measurement by Walter and Beer (1985) and recent evaluations. Average cross sectionsareinagreementwithWalterandBeer(1985)overmostoftheneutronenergyrangecovered,whilethey aresystematicallysmallerforneutronenergiesabove150keV.Wehavecalculatedisotopicabundancesproduced in s-process environments in a 25 solar mass star for two initial metallicities (below solar and close to solar). While the low metallicity model reproduces best the solar system germanium isotopic abundances, the close to solar model shows a good global match to solar system abundances in the range of mass numbers A=60–80.Austrian Science Fund J3503Adolf Messer Foundation ST/M006085/1European Research Council ERC2015-StGCroatian Science Foundation IP-2018-01-857

    Global survey of guidelines for the management of epilepsy in pregnancy: A report from the international league against epilepsy task force on women and pregnancy

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    The ILAE Task Force on Women and Pregnancy conducted a survey among ILAE Chapters of their use of guidelines or recommendations for the management of women with epilepsy during pregnancy. A web-based questionnaire including 10 questions was sent to the 118 ILAE Chapters in December 2017 with repeated reminders until the end of February 2018. In total, 77 chapters (65%) responded, although not to all questions. Out of those responding, 68% reported having guidelines or recommendations, 34% of which were from 2014 or earlier. At least 20% of the guidelines did not include information on possible risk to cognitive development, information regarding specific risks with specific antiepileptic drugs, nor recommendations regarding selection of antiepileptic drugs. Among those responding to the question, 91% reported that recommendations were made regarding folate supplementation, but the recommended dose ranged from 0.4 mg/d to 4 mg/d or more; 34% did not include recommendations regarding drug level monitoring during pregnancy, and 19% did not include guidelines on breastfeeding. Our survey demonstrates that there is a need for the development of up-to-date, globally applicable recommendations for the management of epilepsy during pregnancy.Fil: Tomson, Torbjörn. Karolinska Huddinge Hospital. Karolinska Institutet; Suecia. Karolinska University Hospital. Department of Neurology; SueciaFil: Battino, Dina. Fondazione IRCCS Istituto Neurologico Carlo Besta. Department of Neurophysiology and Experimental Epileptology. Epilepsy Center; ItaliaFil: Bromley, Rebecca. Central Manchester University Hospitals NHS Foundation Trust; Reino Unido. University of Manchester; Reino UnidoFil: Kochen, Sara Silvia. Universidad Nacional Arturo Jauretche. Unidad Ejecutora de Estudios en Neurociencias y Sistemas Complejos. Provincia de Buenos Aires. Ministerio de Salud. Hospital Alta Complejidad en Red El Cruce Dr. Néstor Carlos Kirchner Samic. Unidad Ejecutora de Estudios en Neurociencias y Sistemas Complejos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Unidad Ejecutora de Estudios en Neurociencias y Sistemas Complejos; ArgentinaFil: Meador, Kimford J.. University of Stanford; Estados UnidosFil: Pennell, Page B.. Brigham and Women's Hospital. Harvard Medical School. Department of Neurology. Divisions of Epilepsy and Women's Health; Estados UnidosFil: Thomas, Sanjeev V.. Sree Chitra Tirunal Institute of Medical Sciences and Technology. Department of Neurology; Indi

    The s process in rotating low-mass AGB stars: Nucleosynthesis calculations in models matching asteroseismic constraints

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    Aims. We investigate the s-process during the AGB phase of stellar models whose cores are enforced to rotate at rates consistent with asteroseismology observations of their progenitors and successors. Methods. We calculated new 2 M⊙ , Z  =  0.01 models, rotating at 0, 125, and 250 km s-1 at the start of main sequence. An artificial, additional viscosity was added to enhance the transport of angular momentum in order to reduce the core rotation rates to be in agreement with asteroseismology observations. We compared rotation rates of our models with observed rotation rates during the MS up to the end of core He burning, and the white dwarf phase. Results. We present nucleosynthesis calculations for these rotating AGB models that were enforced to match the asteroseismic constraints on rotation rates of MS, RGB, He-burning, and WD stars. In particular, we calculated one model that matches the upper limit of observed rotation rates of core He-burning stars and we also included a model that rotates one order of magnitude faster than the upper limit of the observations. The s-process production in both of these models is comparable to that of non-rotating models. Conclusions. Slowing down the core rotation rate in stars to match the above mentioned asteroseismic constraints reduces the rotationally induced mixing processes to the point that they have no effect on the s-process nucleosynthesis. This result is independent of the initial rotation rate of the stellar evolution model. However, there are uncertainties remaining in the treatment of rotation in stellar evolution, which need to be reduced in order to confirm our conclusions, including the physical nature of our approach to reduce the core rotation rates of our models, and magnetic processes

    Impact of newly measured 26Al(n, p)26Mg and 26Al(n, α)23Na reaction rates on the nucleosynthesis of 26Al in stars

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    The cosmic production of the short-lived radioactive nuclide 26Al is crucial for our understanding of the evolution of stars and galaxies. However, simulations of the stellar sites producing 26Al are still weakened by significant nuclear uncertainties. We re-evaluate the 26Al(n, p)26Mg, and 26Al(n, α)23Na ground state reactivities from 0.01 GK to 10 GK, based on the recent n TOF measurement combined with theoretical predictions and a previous measurement at higher energies, and test their impact on stellar nucleosynthesis. We computed the nucleosynthesis of low- and high-mass stars using the Monash nucleosynthesis code, the NuGrid mppnp code, and the FUNS stellar evolutionary code. Our low-mass stellar models cover the 2-3 M☉ mass range with metallicities between Z = 0.01 and 0.02, their predicted 26Al/27Al ratios are compared to 62 meteoritic SiC grains. For high-mass stars, we test our reactivities on two 15 M☉ models with Z = 0.006 and 0.02. The new reactivities allow low-mass AGB stars to reproduce the full range of 26Al/27Al ratios measured in SiC grains. The final 26Al abundance in high-mass stars, at the point of highest production, varies by a factor of 2.4 when adopting the upper, or lower limit of our rates. However, stellar uncertainties still play an important role in both mass regimes. The new reactivities visibly impact both low- and high-mass stars nucleosynthesis and allow a general improvement in the comparison between stardust SiC grains and low-mass star models. Concerning explosive nucleosynthesis, an improvement of the current uncertainties between T9∼0.3 and 2.5 is needed for future studies

    The Influence of In Vitro Gastrointestinal Digestion on the Anticancer Activity of Manuka Honey

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    Manuka honey (MH) is a natural food with many beneficial properties to human health, thanks to its high variety of bioactive compounds; however, little is known about its bioaccessibility. The aim of this study was to evaluate and compare the polyphenol compounds, the antioxidant capacity and the anticancer activity of MH subjected to an in vitro gastrointestinal digestion in human HCT-116 colon cancer cells. Raw MH and digested MH (DMH) were assessed for total polyphenols and flavonoids by spectrophotometric and HPLC-ESI-MS/MS analysis, and total antioxidant capacity (TAC) using different methods. Cell viability, intracellular ROS production, apoptosis, cell cycle and colony formation capacity were tested after treatment with MH or DMH. Results showed that total polyphenols, total flavonoids and TAC were significantly (p < 0.05) reduced after in vitro digestion. In addition, MH and DMH at 8, 16 and 24 mg/mL had similar effects in inducing intracellular ROS production and in inhibiting the colon formation ability; MH induced a more marked apoptosis compared to DMH, while cell cycle was blocked in S phase by MH and in Sub G1 phase by DMH. Our results increase knowledge of the effect of gastrointestinal digestion on the biological effect of honey against colorectal cancer

    Application of a theory and simulation-based convective boundary mixing model for AGB star evolution and nucleosynthesis

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    The s-process nucleosynthesis in Asymptotic giant branch (AGB) stars depends on the modeling of convective boundaries. We present models and s-process simulations that adopt a treatment of convective boundaries based on the results of hydrodynamic simulations and on the theory of mixing due to gravity waves in the vicinity of convective boundaries. Hydrodynamics simulations suggest the presence of convective boundary mixing (CBM) at the bottom of the thermal pulse-driven convective zone. Similarly, convection-induced mixing processes are proposed for the mixing below the convective envelope during third dredge-up (TDU), where the ¹³C pocket for the s process in AGB stars forms. In this work, we apply a CBM model motivated by simulations and theory to models with initial mass M=2 and M = 3 Mʘ, and with initial metal content Z = 0.01 and Z = 0.02. As reported previously, the He-intershell abundances of ¹²C and ¹⁶O are increased by CBM at the bottom of the pulse-driven convection zone. This mixing is affecting the ²²Ne(α, n)²⁵Mg activation and the s-process efficiency in the ¹³C-pocket. In our model, CBM at the bottom of the convective envelope during the TDU represents gravity wave mixing. Furthermore, we take into account the fact that hydrodynamic simulations indicate a declining mixing efficiency that is already about a pressure scale height from the convective boundaries, compared to mixing-length theory. We obtain the formation of the ¹³C-pocket with a mass of ≈10⁻⁴ Mʘ. The final s-process abundances are characterized by 0.36 < [s Fe] < 0.78 and the heavy-to-light s-process ratio is -0.23 < [hs ls] < 0.45. Finally, we compare our results with stellar observations, presolar grain measurements and previous work

    Radiative neutron capture cross-section measurement of ge isotopes at n_TOF CERN facility and its importance for stellar nucleosynthesis

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    This manuscript summarizes the results of radiative neutron capture cross-section measurements on two stable germanium isotopes, 70Ge and 73Ge. Experiments were performed at the n_TOF facility at CERN via the time-of-flight technique, over a wide neutron energy range, for all stable germanium isotopes (70,72,73,74, and 76). Results for 70Ge [Phys. Rev. C 100, 045804 (2019)] and 73Ge [Phys. Lett. B 790, 458 (2019)] are already published. In the field of nuclear structure, such measurements allow to study excited levels close to the neutron binding energy and to obtain information on nuclear properties. In stellar nucleosynthesis research, neutron induced reactions on germanium are of importance for nucleosynthesis in the weak component of the slow neutron capture processes. © 2021 Polish Academy of Sciences. All rights reserved.Austrian Science Fund FWFUK Science and Facilities Council ST/M006085/1European Research Council (ERC) ERC-2015-StG No. 677497National Science Center. Poland UMO2016/22/M/ST2/00183MSMT of the Czech Republic IP-2018-01-8570Croatian Science Foundation IP-2018-01-857

    Loss of Bone Mineral Density Associated with Age in Male Rats Fed on Sunflower Oil Is Avoided by Virgin Olive Oil Intake or Coenzyme Q Supplementation

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    The role of dietary fat unsaturation and the supplementation of coenzyme Q have been evaluated in relation to bone health. Male Wistar rats were maintained for 6 or 24 months on two diets varying in the fat source, namely virgin olive oil, rich in monounsaturated fatty acids, or sunflower oil, rich in n-6 polyunsaturated fatty acids. Both dietary fats were supplemented or not with coenzyme Q10 (CoQ10). Bone mineral density (BMD) was evaluated in the femur. Serum levels of osteocalcin, osteopontin, receptor activator of nuclear factor κB ligand (RANKL), osteoprotegerin (OPG), adrenocorticotropin (ACTH) and parathyroid hormone (PTH), as well as urinary F2-isoprostanes were measured. Aged animals fed on virgin olive oil showed higher BMD than those fed on sunflower oil. In addition, CoQ10 prevented the age-related decline in BMD in animals fed on sunflower oil. Urinary F2-isoprostanes analysis showed that sunflower oil led to the highest oxidative status in old animals, which was avoided by supplementation with CoQ10. In conclusion, lifelong feeding on virgin olive oil or the supplementation of sunflower oil on CoQ10 prevented, at least in part mediated by a low oxidative stress status, the age-related decrease in BMD found in sunflower oil fed animals.This work was supported by the Spanish Ministry of Education and Science (AGL2008-01057) and the Autonomous Government of Andalusia (AGR832)

    Filling an Emulsion Drop with Motile Bacteria

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    We have measured the spatial distribution of motile Escherichia coli inside spherical water droplets emulsified in oil. At low cell concentrations, the cell density peaks at the water-oil interface; at increasing concentration, the bulk of each droplet fills up uniformly while the surface peak remains. Simulations and theory show that the bulk density results from a `traffic' of cells leaving the surface layer, increasingly due to cell-cell scattering as the surface coverage rises above 10%\sim 10\%. Our findings show similarities with the physics of a rarefied gas in a spherical cavity with attractive walls.Comment: 5 pages, 4 figures, Supporting Information (5 pages, 5 figures
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