High Resolution Study of

The globular cluster NGC 2419 was the first to exhibit a Mg-K anticorrelation, linked to hydrogen burning at temperatures between 80-260 MK. However, the key K-destroying reaction, ^{39}K(p,γ)^{40}Ca, has a large rate uncertainty in this range. We significantly constrain this rate with a high resolution ^{39}K(^{3}He,d)^{40}Ca study. We resolve the E_{r}^{c.m.}=154 keV resonance in ^{39}K+p for the first time, increasing the previous rate by up to a factor 13 and reducing its 1σ width by up to a factor of 42. Reaction network calculations for NGC 2419 suggest that this could lower temperatures needed to reproduce the Mg-K anticorrelation.

Direct Measurement of Resonances in

We have performed the first direct measurement of two resonances of the ^{7}Be(α,γ)^{11}C reaction with unknown strengths using an intense radioactive ^{7}Be beam and the DRAGON recoil separator. We report on the first measurement of the 1155 and 1110 keV resonance strengths of 1.73±0.25(stat)±0.40(syst) eV and 125_{-25}^{+27}(stat)±15(syst) meV, respectively. The present results have reduced the uncertainty in the ^{7}Be(α,γ)^{11}C reaction rate to ∼9.4%-10.7% over T=1.5-3 GK, which is relevant for nucleosynthesis in the neutrino-driven outflows of core-collapse supernovae (νp process). We find no effect of the new, constrained reaction rate on νp-process nucleosynthesis.

Is γ-ray emission from novae affected by interference effects in the 18F(p,α)15O reaction?

The (18)F(p,α)(15)O reaction rate is crucial for constraining model predictions of the γ-ray observable radioisotope (18)F produced in novae. The determination of this rate is challenging due to particular features of the level scheme of the compound nucleus, (19)Ne, which result in interference effects potentially playing a significant role. The dominant uncertainty in this rate arises from interference between J(π)=3/2(+) states near the proton threshold (S(p)=6.411 MeV) and a broad J(π)=3/2(+) state at 665 keV above threshold. This unknown interference term results in up to a factor of 40 uncertainty in the astrophysical S-factor at nova temperatures. Here we report a new measurement of states in this energy region using the (19)F((3)He,t)(19)Ne reaction. In stark contrast to previous assumptions we find at least 3 resonances between the proton threshold and E(cm)=50 keV, all with different angular distributions. None of these are consistent with J(π)=3/2(+) angular distributions. We find that the main uncertainty now arises from the unknown proton width of the 48 keV resonance, not from possible interference effects. Hydrodynamic nova model calculations performed indicate that this unknown width affects (18)F production by at least a factor of two in the model considered.

Effects of repeated crowding on the stress response and growth performance in Atlantic salmon (Salmo salar).

A 64-day growth experiment was conducted in which two groups of Atlantic salmon parr were grown under either control conditions or subjected to a weekly crowding stressor. Subjecting fish to the stressor resulted in a 7.7% reduction in wet weight after 29 days, which was maintained at 7.9% by day 64. This reduction in weight was reflected in a 44% reduction in specific growth rate and 38% increase in feed conversion ratio over the first 29 days of the experiment. Elevation in plasma cortisol was observed in crowded fish on days 1, 29 and 64. Similarly, on days 1 and 29 an increase in both plasma glucose and lactate was detected. On day 64, however, no differences in plasma glucose and lactate were observed, with the magnitude of the cortisol response also significantly reduced. Overall, the relatively moderate impact on growth performance and reduction in magnitude of measured stress parameters at the end of the experiment suggests possible habituation to the applied stressor.

Direct measurement of the 14N(p,gamma)15O S factor.

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.

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.

Studies on the metabolism of dimethylnitrosamine in vitro by rat-liver preparations. III. Effect of cobaltous chloride treatment.

1. The effects of CoCl2 administration to rats on xenobiotic metabolism, dimethylnitrosamine (DMN) metabolism to formaldehyde and methanol, and monoamine oxidase (MAO) enzyme activities in hepatic subcellular fractions have been studied. 2. CoCl2 treatment markedly decreased hepatic mixed-function oxidase enzyme activities and microsomal cytochrome P-450 content. In contrast, the N-oxidation of N, N-dimethylaniline and the activity of microsomal NADPH-cytochrome c reductase was unaffected. 3. The metabolism of DMN to formaldehyde by postmitochondrial supernatant fractions was decreased at substrate concn. of 0 . 5, 5 and 50 mM by CoCl2 treatment but the metabolism of 5 and 50 mM DMN to methanol was affected less. 4. CoCl2 had little effect on MAO activities in whole homogenates, but microsomal MAO activities were markedly inhibited. 5. The inhibition of microsomal MAO indicates that CoCl2 is not a specific inhibitor of cytochrome P-450-dependent biotransformations and consequently the inhibition of DMN metabolism is not evidence of a wholly cytochrome P-450-dependent process.

The excretion of metabolites of the D-glucuronic acid pathway in human urine. Effect of phenobarbitone administration.

1. The urinary excretion of four metabolites of the D-glucuronic acid pathway, namely D-glucaric acid, free (unconjugated) D-glucuronic acid, L-gulonic acid and xylitol, has been studied in normal male volunteers and in male and female epileptic patients receiving phenobarbitone anticonvulsant therapy. 2. In normal male subjects the urinary excretion of the D-glucuronic acid metabolites, expressed per unit of creatinine, was similar in first void and total (24 h) urine samples and was fairly constant over a period of 4 weeks. 3. In male and female epileptic patients phenobarbitone treatment enhanced the urinary excretion of D-glucaric acid and xylitol and the combined excretion of D-glucaric acid, l-gulonic acid and xylitol. 4. It is suggested that the measurement of a spectrum of urinary D-glucuronic acid metabolites may provide a more reliable index for assessment of the induction of hepatic xenobiotic-metabolizing enzyme activities in man than the determination of urinary D-glucaric acid alone.

Studies on the gastrointestinal absorption of N-nitrosamines: effect of dietary constituents.

Studies on the intestinal absorption of N-nitrosodimethylamine (DMN) in the rat have shown that the presence of dietary constituents such as fat markedly reduced the rate of disappearance of this nitrosamine whereas the presence of protein and carbohydrate had little effect on the absorption rate. Fat was also found to reduce the absorption rate of N-nitrosodiethylamine (DEN), N-nitrosopyrrolidine (NPY) and N-nitrosopiperidine (NPIP). Further it was confirmed that the small-intestinal tract of the rat has the ability to degrade DMN. The implications of these findings are discussed in terms of the biological fate of orally ingested nitrosamines.

The hydrolysis of flavouring esters by artificial gastrointestinal juices and rat tissue preparations.

The rates of hydrolysis of sixteen esters used as constituents of artifical flavours have been determined in artificial gastrointestinal juices and in fresh preparations of rat liver and small intestine. The artificial gastrointestinal juices exhibited a limited ability to hydrolyse the esters and of which methyl anthranilate was virtually uneffected. On the other hand, rat liver and small intestinal preparations were found readily to hydrolyse the esters to their component acids and alcohols. These findings showing large differences between the results obtained from the two methods suggest that use of tissue preparations is likely to produce data more relevant to the toxicological assessment of esters.