Search results for "absorption."
showing 10 items of 2682 documents
The 16O(γ, 2N) reaction measured with tagged photons
1991
The results of tagged-photon measurements of the 4He(γ, pn)d, 4He(γ, pn)pn and 4He(γ, pp)nn reactions, carried out with photons of energies 80–131 MeV, are presented. The (γ, pn)d three-body-breakup cross section dominates the four-body-breakup cross section. The three-body-breakup cross section and the corresponding deuteron recoil-momentum spectrum are reasonably accounted for by a mechanism of photon absorption on correlated proton-neutron pairs. In contrast the four-body-breakup mechanism appears to have two components: absorption on correlated proton-neutron pairs and a more complex additional component which has a distribution similar to phase space. The data rule out substantial phot…
The (γ, n) reaction on 16O between giant resonance and pion threshold
1982
Abstract A new TOF facility has been built for measurements of differential (γ, n) cross sections to discrete final states of light nuclei in the photon energy range between giant resonance and pion threshold. The observed neutron angle θn can continuously be varied between 0° and 150°, and additionally measurements at 175° and 180° are possible. Differential cross sections for the reaction 16O(γ, n0)15O are presented for Eγ = 60 MeV (40° ⩽ θn ⩽ 149°) and for θn = 90° (60 MeV ⩽ Eγ ⩽ 160 MeV). The results, combined with the corresponding (γ, p0) cross sections, indicate an absorption mechanism of high energy photons by neutron-proton pairs.
Total cross sections of reactions induced by neutron-rich light nuclei
1989
Total nuclear reaction cross-sections are determined by means of a 4π-γ method. The results cover a wide span of targets for various stable beams. The validity of the method is shown in a combined systematics including also the results of transmission-type experiments. The data are very well described by the formula developed by Kox et al. The same method is applied to secondary fragment beams produced from a 44 MeV/u22Ne beam on a 332mg/cm2 181Ta target. Using the LISE spectrometer the fragments4, 6He,6–9, 11Li,7, 9–12, 14Be,10–15, 17B11–19C,13–19N,15–21O,18– 21F and20,21 Ne are analyzed and transported to interact with a 199.4 mg/cm2 Cu target surrounded by a 4π-γ counter. The measured to…
Nuclear data activities at the n_TOF facility at CERN
2016
International audience; Nuclear data in general, and neutron-induced reaction cross sections in particular, are important for a wide variety of research fields. They play a key role in the safety and criticality assessment of nuclear technology, not only for existing power reactors but also for radiation dosimetry, medical applications, the transmutation of nuclear waste, accelerator-driven systems, fuel cycle investigations and future reactor systems as in Generation IV. Applications of nuclear data are also related to research fields as the study of nuclear level densities and stellar nucleosynthesis. Simulations and calculations of nuclear technology applications largely rely on evaluate…
The 236U neutron capture cross-section measured at the n TOF CERN facility
2016
International audience; The $^{236}$U isotope plays an important role in nuclear systems, both for future and currently operating ones. The actual knowledge of the capture reaction of this isotope is satisfactory in the thermal region, but it is considered insufficient for Fast Reactor and ADS applications. For this reason the $^{236} \text{U}(n, \gamma)$ reaction cross-section has been measured for the first time in the whole energy region from thermal energy up to 1 MeV at the n_TOF facility with two different detection systems: an array of C$_6$D$_6$ detectors, employing the total energy deposited method, and a 4$\pi$ total absorption calorimeter (TAC), made of 40 BaF$_2$ crystals. The t…
The renin–angiotensin system in gastrointestinal functions
2023
In this chapter, we describe the role played by classical and alternative renin–angiotensin system (RAS) in the physiological regulation of gastrointestinal functions. RAS modulates gut motility and mucosal functions, including secretion, fluid, and nutrient absorption. We focus mainly on the activation of angiotensin II type 1 and 2 receptors located on the smooth muscle and epithelial cells or on the enteric neurons. Few studies indicate that alternative RAS may counteract classical RAS functions. Although data on the enteric RAS system are still scarce, they encourage further investigations in consideration also of a potential involvement in gastrointestinal disorders.
Bioavailability of plant sterol-enriched milk-based fruit beverages: In vivo and in vitro studies
2015
Abstract This study for the first time compares the in vivo (response in serum from individuals of an interventional study) and in vitro effects (bioaccessibility determined from simulated gastrointestinal digestion) of two plant sterol (PS)-enriched milk-based fruit beverages (with and without tangerine fruit juice rich in β-cryptoxanthin (β-Cx)) in order to assess their suitability as PS-enriched food matrixes, and the possible interactions between the two bioactive compounds (β-Cx and PS) that might affect their absorption. The randomized, double-blind, crossover study (performed in 36 postmenopausal women) showed the β-sitosterol and campesterol serum concentrations after four weeks of …
A comparison of growth, gas exchange and productivity in Olea europaea cultivars growing on Mediterranean hills.
2008
This work concerns the ecophysiology of olive cultivars growing on Mediterranean hills. Our aim was to quantify the photosynthetic efficiency of the cultivars in cultivation. In two hill areas, we tested the phenological and ecophysio- logical variability of olive cultivars grown on non-irrigated land, with different pedo-climatic characteristics. Cultivation area 1 falls within a natural protected area, while area 2 is on farming land. The cultivars selected (‘Biancolilla’, ‘Nocellara del Belice’ and ‘Giarraffa’) belong to the local genetic pool and require different amounts of water. We followed the phe- nological phases of shoot growth and drupe production. We studied leaf anatomy and ch…
Population Pharmacokinetics of Palbociclib in aReal-World Situation
2021
Palbociclib is an oral cyclin-dependent kinase inhibitor that is used in combination with aromatase inhibitors in the treatment of postmenopausal women with metastatic breast cancer. Its metabolism profile is associated with an important interpatient variability. We performed a population pharmacokinetics study of palbociclib in women routinely followed in a cancer center. One hundred and fifty-one samples were analyzed. The sampling times after administration ranged from 0.9 to 75 h and the samples were taken between 1 and 21 days after the beginning of the palbociclib cycle. Palbociclib was determined using a validated mass spectrometry method. The best model that described the concentrat…
Light absorption and conversion in solar cell based on Si:O alloy
2013
Thin film Si:O alloys have been grown by plasma enhanced chemical vapor deposition, as intrinsic or highly doped (1 to 5 at. % of B or P dopant) layers. UV-visible/near-infrared spectroscopy revealed a great dependence of the absorption coefficient and of the optical gap (Eg) on the dopant type and concentration, as Eg decreases from 2.1 to 1.9 eV, for the intrinsic or highly p-doped sample, respectively. Thermal annealing up to 400 °C induces a huge H out-diffusion which causes a dramatic absorption increase and a reduction of Eg, down to less than 1.8 eV. A prototypal solar cell has been fabricated using a 400 nm thick, p-i-n structure made of Si:O alloy embedded within flat transparent c…