Biomedical subjects

J José

Publications and source records attributed to J José.

8 recordsLinked to original sources

PubMed2006

Measurement of the Ec.m. = 184 keV resonance strength in the 26gAl (p, gamma)27 Si reaction.

The strength of the Ec.m. = 184 keV resonance in the 26gAl(p, gamma)27 reaction has been measured in inverse kinematics using the DRAGON recoil separator at TRIUMF's ISAC facility. We measure a value of omega gamma = 35 +/- 7 microeV and a resonance energy of Ec.m. = 184 +/- 1 keV, consistent with p-wave proton capture into the 7652(3) keV state in 27Si, and discuss the implications of these values for 26GAl nucleosynthesis in typical oxygen-neon white-dwarf novae.

Journal Article↗

PubMed2005

Hydrogen burning of 17O in classical novae.

We report on the observation of a previously unknown resonance at E(lab)(R)=194.1+/-0.6 keV in the 17O(p,alpha)14N reaction, with a measured resonance strength omegagamma(palpha)=1.6 +/- 0.2 meV. We studied in the same experiment the 17O(p,gamma)18F reaction by an activation method and the resonance-strength ratio was found to be omegagamma(palpha)/omegagamma(pgamma) = 470 +/- 50. The corresponding excitation energy in the 18F compound nucleus was determined to be 5789.8 +/- 0.3 keV by gamma-ray measurements using the 14N(alpha, gamma)18F reaction. These new resonance properties have important consequences for 17O nucleosynthesis and gamma-ray astronomy of classical novae.

Journal Article↗

PubMed2004

Explosive hydrogen burning of 17O in classical novae.

We report on the observation of a new resonance at E(lab)(R)=190 keV in the 17O(p,gamma)18F reaction. The measured resonance strength amounts to omegagamma(pgamma)=(1.2+/-0.2)x10(-6) eV. With this new value, the uncertainties in the 17O(p,gamma)18F and 17O(p,alpha)14N thermonuclear reaction rates are reduced by orders of magnitude at nova temperatures. Our significantly improved reaction rates have major implications for the galactic synthesis of 17O, the stellar production of the radioisotope 18F, and the predicted oxygen isotopic ratios in nova ejecta.

Journal Article↗

PubMed2004

Reevaluation of the 22Na(p,gamma) reaction rate: implications for the detection of 22Na gamma rays from novae.

Understanding the processes which create and destroy 22Na is important for diagnosing classical nova outbursts. Conventional 22Na(p,gamma) studies are complicated by the need to employ radioactive targets. In contrast, we have formed the particle-unbound states of interest through the heavy-ion fusion reaction, 12C(12C,n)23Mg and used the Gammasphere array to investigate their radiative decay branches. Detailed spectroscopy was possible and the 22Na(p,gamma) reaction rate has been reevaluated. New hydrodynamical calculations incorporating the upper and lower limits on the new rate suggest a reduction in the yield of 22Na with respect to previous estimates, implying a reduction in the maximum detectability distance for 22Na gamma rays from novae.

Journal Article↗

PubMed2003

21Na(p,gamma)22Mg reaction and oxygen-neon novae.

The 21Na(p,gamma)22Mg reaction is expected to play an important role in the nucleosynthesis of 22Na in oxygen-neon novae. The decay of 22Na leads to the emission of a characteristic 1.275 MeV gamma-ray line. This report provides the first direct measurement of the rate of this reaction using a radioactive 21Na beam, and discusses its astrophysical implications. The energy of the important state was measured to be E(c.m.)=205.7+/-0.5 keV with a resonance strength omegagamma=1.03+/-0.16(stat)+/-0.14(sys) meV.

Journal Article↗

PubMed1999

Gamma-Ray Emission from Novae Related to Positron Annihilation: Constraints on its Observability Posed by New Experimental Nuclear Data.

Classical novae emit gamma-ray radiation at 511 keV and below (with a cutoff at around 20-30 keV), related to positron annihilation and its Comptonization in the expanding envelope. This emission has been elusive up to now because it occurs at epochs well before the maximum in optical luminosity, but it could be detected by some sensitive instrument on board a satellite, provided that the nova is close enough and that it is observed at the right moment. The detection of this emission, which is a challenge for current and future gamma-ray instruments, would shed light into the physical processes that occur in the early phases of the explosion, which are invisible in other lower energy ranges. A good prediction of the emitted fluxes and of the corresponding detectability distances with different instruments relies critically on a good knowledge of reaction rates relevant to 18F destruction, which have been subject to strong revision after recent nuclear spectroscopy measurements. With respect to previous results, smaller ejected masses of 18F are predicted, leading to smaller emitted fluxes in the 20-511 keV range and shorter detectability distances.

Journal Article↗

PubMed1994

[News on the trip and the diplomatic mission of a Portuguese ambassador to China in 1752. Critical and analytical study].

The author of this report has worked out a critical-analytical study, based on the news of a voyage to China, carried out by a Portuguese ambassador, which was also a diplomatic mission, in 1752, during the Marquis of Pombal era, Prime Minister of king Dom Jose I. This study is directed under two perspectives: medical and historical-diplomatic. The former not only allows the assessment of the high degree of organization of this voyage as far as food supplies and medical support are concerned, but it also shows the reflection and the diagnosis correction of tuberculosis of the lungs, in a seaman, carried out by a surgeon on board, which we totally refute. The latter, which only aims at giving some further data for the study of the Portuguese Diplomatic History, let us know some of the complex procedures and protocols established between our diplomatic representative and the high Chinese rulers, both the Emperor himself and the mandarins. Contrary to other previous attempts of diplomatic, economic and social relations, either partially or totally frustrated, this mission constituted a great success for Portugal and may, indeed, be considered as a decisive step for the recognition of Portuguese sovereignty over the territory of Macao and its dependencies in 1887.

China↗

PubMed1991

Automatic search for maximum similarity between molecular electrostatic potential distributions.

A new computer program has been developed to automatically obtain the relative position of two molecules in which the similarity between molecular electrostatic-potential distributions is greatest. These distributions are considered in a volume around the molecules, and the similarity is measured by the Spearman rank coefficient. The program has been tested using several pairs of molecules: water vs. water; phenylethylamine and phenylpropylamine vs. benzylamine; and methotrexate vs. dihydrofolic acid.

Benzylamines↗