The 14N(p,gamma)15O reaction regulates the rate of energy generation in the stellar CN cycle. Because discrepancies have been found in the analysis and interpretation of previous capture data, we have measured the 14N(p,gamma)15O excitation function for energies in the range E(lab)(p)=155-524 keV. Fits of these data using R-matrix theory yield a value for the S factor at zero energy of 1.68+/-0.09(stat)+/-0.16(syst) keV b, which is significantly smaller than the previous result. The corresponding reduction in the stellar reaction rate for 14N(p,gamma)15O has a number of interesting consequences, including an impact on estimates for the age of the Galaxy derived from globular clusters.
The 17 O(p,γ ) 18 F and 17 O(p,α) 14 N reactions have a profound influence on hydrogen-burning nucleosynthesis in a number of stellar sites, including red giants, asymptotic giant branch (AGB) stars, massive stars, and classical novae. Previously evaluated thermonuclear rates for both reactions carry large uncertainties. We investigated the proton-capture reaction on 17 O in the bombarding energy range of E lab p = 180-540 keV. We observed a previously undiscovered resonance at E lab R = 193.2 ± 0.9 keV. The resonance strength amounts to (ωγ ) pγ = (1.2 ± 0.2) × 10 −6 eV. With this value, the uncertainties of the 17 O(p,γ ) 18 F reaction rates are reduced by orders of magnitude in the peak temperature range of classical novae (T = 0.1-0.4 GK). We also report on a reevaluation of the 17 O(p,γ ) 18 F reaction rates at lower temperatures that are pertinent to red giants, AGB stars, or massive stars. The present work establishes the 17 O(p,γ ) 18 F reaction rates over a temperature range of T = 0.01-1.5 GK with statistical uncertainties of 10-50%. The new recommended reaction rates deviate from the previously accepted values by an order of magnitude around T ≈ 0.2 GK and by factors of 2-3 at T < 0.1 GK.
PurposeThis study analyses seminal vesicle displacement relative to the prostate and in relation to treatment time.MethodA group of eleven patients undergoing prostate cancer radiotherapy were imaged with a continuous 3 T cine-MRI in the standard treatment setup position. Four images were recorded every 4 seconds for 15 minutes in the sagittal plane and every 6.5 seconds for 12 minutes in the coronal plane. The prostate gland and seminal vesicles were contoured on each MRI image. The coordinates of the centroid of the prostate and seminal vesicles on each image was analysed for displacement against time. Displacements between the 2.5 percentile and 97.5 percentile (i.e. the 2.5% trimmed range) for prostate and seminal vesicle centroid displacements were measured for 3, 5, 10 and 15 minutes time intervals in the anterior-posterior (AP), left-right (LR) and superior-inferior (SI) directions. Real time prostate and seminal vesicle displacement was compared for individual patients.ResultsThe 2.5% trimmed range for 3, 5, 10 and 15 minutes for the seminal vesicle centroids in the SI direction measured 4.7 mm; 5.8 mm; 6.5 mm and 7.2 mm respectively. In the AP direction, it was 4.0 mm, 4.5 mm, 6.5 mm, and 7.0 mm. In the LR direction for 3, 5 and 10 minutes; for the left seminal vesicle, it was 2.7 mm, 2.8 mm, 3.4 mm and for the right seminal vesicle, it was 3.4 mm, 3.3 mm, and 3.4 mm. The correlation between the real-time prostate and seminal vesicle displacement varied substantially between patients indicating that the relationship between prostate displacement and seminal vesicles displacement is patient specific with the majority of the patients not having a strong relationship.ConclusionOur study shows that seminal vesicle motion increases with treatment time, and that the prostate and seminal vesicle centroids do not move in unison in real time, and that an additional margin is required for independent seminal vesicle motion if treatment localisation is to the prostate.
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.
Dosimetry for intraoperative radiotherapy (IORT) after wide local excision for breast cancer using a 50 kV X-ray needle (Intrabeam) was performed in vivo using thermoluminescence dosimetry. Eight LiF:Mg,Ti chips were placed on the skin around the incision site after wide local excision while the tumour bed was irradiated to a prescribed dose of 5 Gy 10 mm from the applicator surface. The maximum and mean measured skin dose for 57 patients ranged from 0.64 to 7.1 Gy and 0.56 to 4.78 Gy, respectively, reflecting different tissue thicknesses overlying the applicator. The average maximum dose of 2.93+/-1.46 Gy was below the threshold for severe radiation skin toxicity.
According to common assumptions, matter in the mass range is processed through the so-called NeNa A ≥ 20 cycle during hydrogen-burning nucleosynthesis. The existence of such a reaction cycle implies that the (p, a) reaction on 23 Na is more likely to occur than the competing (p, g) reaction. However, recently evaluated thermonuclear rates for both reactions carry relatively large uncertainties and allow for both possibilities, i.e., a "closed" and an "open" NeNa cycle. We measured the 23 Na(p, g) 24 Mg reaction at the Laboratory for Experimental Nuclear Astrophysics. The present experimental results, obtained with our sensitive g-ray detection apparatus, reduce the reaction rate uncertainties significantly. We demonstrate that a closed NeNa cycle does not 23 Na ϩ p exist at stellar temperatures of GK. The new results have important implications for the nucleo-T p 0.2-0.4 synthesis in classical novae, including the amount of 26 Al ejected by the thermonuclear explosion, the elemental abundances of Mg and Al observed in nova shells, and observations of Mg and Al isotopic ratios in primitive meteorites.
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