Literatura académica sobre el tema "17O(p,p)"

Objective In the early stages of cartilage damage, diagnostic methods focusing on the mechanism of maintaining the hydrostatic pressure of cartilage are thought to be useful. 17O-labeled water, which is a stable isotope of oxygen, has the advantage of no radiation exposure or allergic reactions and can be detected by magnetic resonance imaging (MRI). This study aimed to evaluate MRI images using 17O-labeled water in a rabbit model. Design Contrast MRI with 17O-labeled water and macroscopic and histological evaluations were performed 4 and 8 weeks after anterior cruciate ligament transection surgery in rabbits. A total of 18 T2-weighted images were acquired, and 17O-labeled water was manually administered on the third scan. The 17O concentration in each phase was calculated from the signal intensity at the articular cartilage. Macroscopic and histological grades were evaluated and compared with the 17O concentration. Results An increase in 17O concentration in the macroscopic and histologically injured areas was observed by MRI. Macroscopic evaluation showed that the 17O concentration significantly increased in the damaged site group. Histological evaluations also showed that 17O concentrations significantly increased at 36 minutes 30 seconds after initiating MRI scanning in the Osteoarthritis Research Society International (OARSI) grade 3 (0.493 in grade 0, 0.659 in grade 1, 0.4651 in grade 2, and 0.9964 in grade 3, P < 0.05). Conclusion 17O-labeled water could visualize earlier articular cartilage damage, which is difficult to detect by conventional methods.

Coupling constants 1J(17O,11B) of borates, borane adducts and boranes with boron-oxygen bonds have been calculated on the basis of optimised molecular structures using the B3LYP/6-311+G(d,p) level of theory. This indicates that such coupling constants can be of either sign and that their magnitudes can be rather small. Since both 11B and 17O are quadrupole nuclei, it is therefore difficult to measure representative data. In the cases of trimethoxyborane and tetraethyldiboroxanes, it proved possible to obtain experimental data 1J(17O,11B) (22 and 18 Hz) by measurement of 17O NMR spectra at high temperature (120 °C and 160 °C) respectively. The magnitude of these coupling constants is in reasonable agreement with calculated data. In the case of the diboroxane, this points towards a bond angle B-O-B more close to 180◦ than to 140°

We report synthesis of 17O-labeling and solid-state 17O NMR measurements of three N-acyl imidazoles of the type R-C(17O)-Im: R = p-methoxycinnamoyl (MCA-Im), R = 4-(dimethylamino)benzoyl (DAB-Im), and R = 2,4,6-trimethylbenzoyl (TMB-Im). Solid-state 17O NMR experiments allowed us to determine for the first time the 17O quadrupole coupling and chemical shift tensors in this class of organic compounds. We also determined the crystal structures of these compounds using single-crystal X-ray diffraction. The crystal structures show that, while the C(O)–N amide bond in DAB-Im exhibits a small twist, those in MCA-Im and TMB-Im are essentially planar. We found that, in these N-acyl imidazoles, the 17O quadrupole coupling and chemical shift tensors depend critically on the torsion angle between the conjugated acyl group and the C(O)–N amide plane. The computational results from a plane-wave DFT approach, which takes into consideration the entire crystal lattice, are in excellent agreement with the experimental solid-state 17O NMR results. Quantum chemical computations also show that the dependence of 17O NMR parameters on the Ar–C(O) bond rotation is very similar to that previously observed for the C(O)–N bond rotation in twisted amides. We conclude that one should be cautious in linking the observed NMR chemical shifts only to the twist of the C(O)–N amide bond.

17O quadrupole and 17O-proton magnetic dipolar coupling data are used to discriminate between three alternative phase transition driving mechanisms in KH2PO4 type H-bonded systems: (i) the proton order-disorder model; (ii) the P (or Se) ion order-disorder model, and (iii) the PO4 (or SeO3) orientational order-disorder model.The data for KH3(SeO3)2, CsH2PO4 and KH2PO4 definitely exclude models (ii) and (iii) and agree with the predictions of model (i).

L’IBA (Ion Beam Analysis) a été largement utilisée pour analyser quantitativement et avec une grande sensibilité la composition et les profils de profondeur des éléments dans les régions superficielles des solides. Pour l’analyse des éléments légers, on peut trouver des réactions nucléaires appropriées et, en particulier, les réactions induites par les deutérons, (d,p) ou (d,α), ont souvent des chaleurs de réaction Q élevées et des sections efficaces appréciables. Dans de nombreux cas de NRA (Nuclear Reaction Analysis) de films minces, des pics isolés de particules de réaction peuvent être obtenus avec un choix judicieux de l’angle de diffusion, de l’énergie du faisceau incident et des feuilles de filtrage devant le détecteur de particules chargées. Cependant, en général, la NRA génère des spectres complexes avec des pics qui se chevauchent, en particulier pour les échantillons épais. La connaissance des sections efficaces pour les cas de pics isolés est déjà utile pour concevoir des expériences visant à déterminer les contenus élémentaires des films minces. De nombreuses sections efficaces de ce type, par exemple 16O(d,p0)17O, 16O(d,p1)17O, 12C(d,p0), 14N(d,α0), ont été soigneusement mesurées dans des gammes d’énergie et d’angle d’intérêt analytique [87–90]. Il est parfois possible d’analyser plusieurs éléments légers simultanément par NRA. La connaissance des sections efficaces des réactions qui ne sont pas nécessairement d’un intérêt primordial pour l’analyse des couches minces, est alors souvent nécessaire pour les cas où les cibles contiennent des éléments donnant lieu à des réactions produisant des groupes de particules qui interfèrent avec le pic analytique primaire, et encore plus dans le cas de la NRA sur cible épaisse où l’élargissement des spectres de particules dû à l’épaisseur non nulle de la cible entraîne une probabilité beaucoup plus grande d’interférences élémentaires [26, 38, 91]. La nécessité de disposer de sections efficaces précises, même lorsqu’elles ne présentent pas un intérêt primordial pour un problème analytique spécifique, ou dans des gammes d’énergie qui ne sont pas directement utiles sur le plan analytique, s’est également accentuée récemment, avec l’introduction du concept d’IBA totale [92–94], dans lequel toutes les informations des spectres IBA [95] sont exploitées, et l’utilisation croissante de l’intelligence artificielle et des approches d’apprentissage automatique pour optimiser l’extraction d’informations de toutes les parties des spectres IBA. Jusqu’à présent, les réseaux neuronaux artificiels (ANN) ont été appliqués au cas de la spectrométrie de rétrodiffusion de Rutherford, où les sections efficaces sont connues analytiquement, mais l’extension fiable de ces techniques avancées de traitement des données à la NRA nécessite les meilleures sections efficaces de réaction nucléaire possibles. En outre, des sections efficaces de réaction nucléaire expérimentale précises sont nécessaires pour fournir des paramètres appropriées pour les approximations et les expressions appropriées des modèles théoriques de mécanismes de réaction nucléaire. L’oxygène étant l’élément le plus abondant de la croûte terrestre et en raison de l’importance universelle des oxydes dans les sciences de la terre et des matériaux, des sections efficaces précises pour les réactions nucléaires sur 16O et 18O ont déjà été déterminées [87, 96]. Le deuxième élément le plus abondant est le silicium, et bien qu’il s’agisse d’un élément de masse intermédiaire du point de vue de l’IBA, il y a également des réactions nucléaires d’intérêt analytique qui ont été déterminées [88, 97]. L’aluminium, troisième élément le plus abondant, est largement utilisé dans l’industrie pour ses propriétés mécaniques et électriques, ses applications décoratives et sa résistance aux agressions environnementales, notamment après une passivation électrochimique appropriée. L’aluminium est également largement présent dans les roches [...]
The overall objective of this thesis is to contribute experimentally determined and evaluated cross sections to a differential cross-section database for Ion Beam Analysis (IBA) that contains accurate and reliable data freely available to the user community, such as the Ion Beam Analysis Nuclear Data Library (IBANDL) database (https://www-nds. iaea.org/exfor/ibandl.htm) [1]. In the first part of the present thesis, we determined differential cross-sections of the reactions 27Al(d, p&α) and benchmarked them with thick target spectra derived from pure aluminum in two independent laboratories. The differential cross section of 27Al(d, p&α) reactions was determined between 1.4 MeV and 2 MeV at scattering angles of 165◦, 150◦, and 135◦ in the VDGT laboratory in Tehran (Iran), as well as measuring them again, including target preparation, at a scattering angle of 150° with independent equipment at INSP in Paris (France). We found close agreement between these two experimental measurements in two different laboratories at 150°. There is no nuclear reaction model that can be adjusted to represent these cross sections since the compound nucleus has a level structure that cannot be treated with current models. We proposed a fitted Fourier series function to represent the evaluated data to define the Al-cross sections. The evaluated differential cross sections have been benchmarked and validated using thick target charged particle spectra obtained using incident deuteron beams of energies between 1.6 MeV and 2 MeV at both laboratories. The validation was performed by fitting deuteroninduced particle spectra obtained from a high purity bulk Al target with SIMNRA, and the thick target spectra are reproduced, allowing the recommendation of the use of these cross sections for NRA. In the second part of the present thesis, the elastic proton scattering cross sections on 17O were measured for the first time at the SAFIR platform at INSP in Paris. Thin films of 17O were prepared by thermal oxidation of Si at 1100 ◦C under 17O2. The physical thickness of the silica was determined by ellipsometry and the atomic thickness by RBS with an uncertainty of 3%. The small quantities of 18O and 16O, present as impurities in the highly enriched 17O2 gas used to grow these films, were determined by the established NRA techniques using the 18O(p, α)15N and 16O(d, p1)17O nuclear reactions. We determined the yield of elastically scattered protons using the corresponding peak in the Elastic Backscattering (EBS) spectra; however, this peak sits on the large continuiiious signal from the silicon substrate. The Si signal was significantly suppressed by aligning the incident beam with the < 100 > axis of the single crystal silicon by ion channeling. The solid angle of the detector, placed at a scattering angle of 165◦, was determined by elastic scattering measurements of 2 MeV alpha particles on a reference sample of Bi implanted in Si. The measured 17O(p, p) cross section, with a systematic uncertainty of about 14%, consists of several resonant structures superimposed on a smoothly varying component increasing ranging from about 1.2 times the Rutherford cross section at 600 keV to about 3 times Rutherford at 2 MeV. A resonance at 1230 keV shows promise for EBS depth profiling, especially at large backscattering angles

Foram medidas distribuições angulares do espalhamento elástico 17O + p e da reação de transferência p(17O,a)14N nas energias ECM = 1,39 e 2,33 MeV. Foi utilizado feixe de 17O produzido no Laboratório Pelletron, com energias de 25 e 42 MeV. As medidas foram efetuadas utilizando-se alvos plásticos de mylar aluminizado (C10H10O4) e polietileno (CH2) com espessuras de 354µg/cm² e 6mg/cm², respectivamente. As distribuições angulares experimentais do espalhamento elástico e da reação de transferência foram analisadas por cálculos de Modelo Óptico e Aproximação de Born de Ondas Distorcidas (DWBA), ambos levando em conta uma estimativa da contribuição do núcleo composto através de cálculos de Hauser-Feshbach. Em 42 MeV, foi medida uma função de excitação do espalhamento elástico utilizando o Método de Espalhamento Ressonante com alvo grosso de (CH2). Várias ressonâncias do núcleo composto 18F são observadas.
Angular distributions of the elastic scattering 17O + p and of the transfer reaction p(17O, a)14N have been measured at the energies, ECM = 1.39 and 2.33 MeV. The 17O beam was produced by the Pelletron accelerator at the energies of 25 and 42 MeV. The measurements have been performed using plastic targets of aluminized mylar (C10H10O4) and polyethylene (CH2) with thicknesses 354µg/cm² and 6mg/cm², respectively. The experimental angular distributions of the elastic scattering and of the transfer reaction have been analyzed by optical model and Distorted Waves Born Approximation (DWBA) calculations, both taking into account the compound nucleus contribution via Hauser-Feshbach calculations. At 42 MeV, an excitation function of the elastic scattering has been measured using the Resonant Scattering Method with thick targets of (CH2). Resonances in the 18F compound nucleus are observed.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 1985.
MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE.
Bibliography: leaves 183-193.
by Billy Gene Pugh, Jr.
Ph.D.

Natural organic matter (NOM) is a major intermediate in the global carbon, nitrogen, sulfur, and phosphorus cycles. NOM is also the environmental matrix that frequently controls binding, transport, degradation, and toxicity of many organic and inorganic contaminants. Despite its importance, NOM is poorly understood at the structural chemistry level because of its molecular complexity and heterogeniety. Nuclear magnetic resonance (NMR) spectroscopy is one of the most useful spectrometric methods used to investigate NOM structure because qualitative and quantitative organic structure information for certain organic elements can be generated by NMR for NOM in both the solution and solid states under nondegradative conditions. However, NMR spectroscopy is not as sensitive as infrared or ultraviolet-visible spectroscopy; it is not at present applicable to organic oxygen and sulfur, and quantification of NMR spectra is difficult under certain conditions. The purpose of this overview is to present briefly the “state of the art” of NMR characterization of NOM, and to suggest future directions for NMR research into NOM. More comprehensive texts concerning the practice of NMR spectroscopy and its application to NOM in various environments have been produced by Wilson and by Wershaw and Mikita. Carbon, hydrogen, and oxygen are the major elements of NOM; together they comprise about 90% of the mass. The minor elements that constitute the remainder are nitrogen, sulfur, phosphorus, and trace amounts of the various halogen elements. With the exception of coal, in which carbon is the most abundant element, the order of relative abundance in NOM on an atomic basis is H > C > O > N > S > P = halogens. The optimum NMR-active nuclei for these elements are 1H, 13C, 17O, 15N, 33S, 31P, and 19F. The natural abundances and receptivities of these nuclei relative to 1H are given in Table 12.1. Quadrupolar effects for 17O, 33S, and halogen elements other than 19F lead to line broadening that greatly limits resolution in NMR studies of these elements in NOM.