Results 1 - 10 of 5373
Results 1 - 10 of 5373. Search took: 0.027 seconds
|Sort by: date | relevance|
[en] While p-boronophenylalanine (p-BPA) is known as a useful pharmaceutical for Boron Neutron Capture Therapy (BNCT), it is also reported that the boron content after it is accumulated in melanomas decreases gradually with time. 2-hydroxy-5-(2' carboxy-2'-aminoethyl) phenyl boric acid (HBPA) is suggested for alternative candidate to be used, as the compound (HBPA) resembles more in chemical nature to tyrosine and is more difficult to be oxidized by tyrosinase than p-BPA. The authors tried to synthesize HBPA via isocyanoethylacetate, employing 1-bromo-2-methoxy-5-methylbenzene as a starting material. The structure of the synthesized compounds at each steps in the course of the scheme was determined using 1H, 13C and 11B NMR spectrometer. (S. Ohno)
[en] The Q-value for the reaction 10B(3He,p)12C (4.439 MeV) was measured as 15305.46 +- 0.3 keV. Therefrom the mass excess of the ground state of 10B could be derived as 12051.2 +- 0.45 keV which is by 0.5 keV lower than the value of the 1977 mass evaluation. (orig.)
[en] Coulomb excitation of the 0.718-MeV, Jsup(π) = 1+, first excited state of 10B has been studied using projectile excitation by 208Pb and observing the backward scattered particles. The results give a clear indication of the virtual excitation of the giant dipole resonance as a second-order effect. The observed magnitude is consistent with the usual hydrodynamic model estimate and with a recent shell-model calculation
[en] The 10B(p,α)7Be reaction is the main responsible for 10B destruction in stellar interior. In such environments this p-capture process occurs at a Gamow energy of ∼10 keV, and takes places mainly through a resonant state (Ex=8.701 MeV) of the compound 11C nucleus. Thus, a resonance right in the region of the Gamow peak is expected to significantly influence the behaviour of the astrophysical S(E)-factor. The 10B(p,α)7Be reaction has been investigated by means of the Trojan Horse Method (THM) applied to the 2H(10B,α7Be)n three-body process. The experiment was performed at Ebeam=27 MeV at the Instituto de Fisica Nuclear de Sao Paulo. Preliminary results concerning the extraction of the bare-nucleus S(E)-factor will be presented
[en] The use of the 10B(n, α)7Li reaction makes it possible to demonstrate the boron component in boron steels. Steel samples that have previously undergone suitable heat treatment are placed against an Ilford C-2 nuclear plate and subjected to slow neutron irradiation. It is thus possible to demonstrate fine boron precipitation in 0.010 pc B steels. Reprint of a paper published in 'Comptes Rendus des Seances de l'Academie des Sciences', t. 35, sitting of Oct 6, 1952, p. 714-716.
[fr]L'emploi de la reaction 10B(n, α)7Li rend possible la mise en evidence du constituant bore dans les aciers au bore. Les echantillons d'acier ayant prealablement subi un traitement thermique convenable sont places contre une plaque nucleaire Ilford C2 et soumis a l'irradiation en neutrons lents. Il est ainsi possible de mettre en evidence de fines precipitations de bore dans des aciers a 0,010 pc B. Reproduction d'un article publie dans les 'Comptes Rendus des Seances de l'Academie des Sciences', t. 35, seance du 6 octobre 1952, p. 714-716.
[en] The study of fusion barriers and corresponding fusion cross sections has seen a renewed attention in recent years. This renewed interest is mainly due to the fact that above understanding is a gateway for the synthesis of superheavy elements, production of new neutron-rich nuclide as well as understanding of nuclear structure effects. In the present study, total 150 reactions with combined mass (A1 + A2) varies between 20 (10B + 10B) and 294 (86Kr + 208Pb) are taken into account. This comparison covering almost the entire periodic table will give us unique possibility to compare various pocket formulas for fusion barriers
[en] A collimated beam of fast protons, with energies as high as 10 MeV and total number of 109, confined in a cone angle of 40 deg. ±10 deg. has been observed when a 10 TW laser with frequencies either ω0 (corresponding to 1 μm) or 2ω0 was focused to an intensity of a few times 1018 W/cm2 on the surface of a thin film target. The protons, which originate from impurities on the front side of the target, are accelerated over a region extending into the target and exit out the backside in a direction normal to the target surface. Acceleration field gradients of ∼10 GeV/cm are inferred. The maximum proton energy for 2ω0 can be explained by the charge-separation electrostatic-field acceleration due to ''vacuum heating.'' In other set of experiments when a deuterated polystyrene layer was deposited on a surface of a Mylar film and a 10B sample was placed behind the target, we observed the production of ∼105 atoms of positron active isotope 11C from the nuclear reaction 10B(d,n)11C
[en] In n+10B reactions, 5He cluster emission has been discussed with the updated level scheme and the new optical model parameters. In this paper the reaction channels related to 5He emission are listed in detail. By using the new reaction model for light nuclei, the double-differential cross sections of total outgoing neutrons for n+10B reactions at En = 14.2 MeV have been calculated, and the results agree fairly well with the measurements. Particularly, in the energy-angular spectra the contribution from the 5He-emission to the total outgoing neutron double-differential cross sections has also been analyzed, and the partial energy-angular spectra of 600 at En = 14.2 MeV have been given. The calculated results indicate that once the 5He emission is taken into account, the fitting with the double-differential measurements of total outgoing neutrons at the low energy region could be improved. Therefore, to consider the 5He emission properly in the reaction processes of light nuclei is necessary.
[en] p-boronophenylalanine (p-BPA) is now employed in Boron Neutron Capture Therapy (BNCT) for cancer. However, it has been confirmed that 10B content accumulated in melanomas decreases with time. It is suggested that p-BPA has suppressive ability for the formation of the melanin polymer substrate which would stabilize the p-BPA taken in. To make clear the mechanism for this, the present authors investigated chemical reactions taking place in the DOPA chrome solution added with p-BPA using 11B-NMR method. It was concluded that p-BPA when complexed with dihydroxy derivatives of melanin precursors (L-DOPA, DHICA) reacts with dissolved oxygen to give boric acid and tyrosine. Effects of the pH and the concentration of DOPA chrome on the reaction were also studied. (S. Ohno)