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Proton captures on Mg isotopes play an important role in the Mg-Al cycle active in stellar $H$-shell burning. In particular, the strengths of low-energy resonances with $El200$ keV in $^{25}\mathrm{Mg}$($p,\ensuremath{\gamma}$)$^{26}\mathrm{Al}$ determine the production of $^{26}\mathrm{Al}$ and a precise knowledge of these nuclear data is highly desirable. Absolute measurements at such low energies are often very difficult and hampered by $\ensuremath{\gamma}$-ray background as well as changing target stoichiometry during the measurements. The latter problem can be partly avoided using higher-energy resonances of the same reaction as a normalization reference. Hence the parameters of suitable resonances have to be studied with adequate precision. In the present work we report on new measurements of the resonance strengths $\ensuremath{\omega}\ensuremath{\gamma}$ of the $E=214$, $304$, and $326$ keV resonances in the reactions $^{24}\mathrm{Mg}$($p,\ensuremath{\gamma}$)$^{25}\mathrm{Al}$, $^{25}\mathrm{Mg}$($p,\ensuremath{\gamma}$)$^{26}\mathrm{Al}$, and $^{26}\mathrm{Mg}$($p,\ensuremath{\gamma}$)$^{27}\mathrm{Al}$, respectively. These studies were performed at the LUNA facility in the Gran Sasso underground laboratory using multiple experimental techniques and provided results with a higher accuracy than previously achieved.

The paper describes a multilevel, multichannel R-matrix code, AZURE, for applications in nuclear astrophysics. The code allows simultaneous analysis and extrapolation of low-energy particle scattering, capture, and reaction cross sections of relevance to stellar hydrogen, helium, and carbon burning. The paper presents a summary of R-matrix theory, code description, and a number of applications to demonstrate the applicability and versatility of AZURE.

International audience; Neutrino astrophysics offers a new possibility to observe our Universe: high-energy neutrinos, produced by the most energetic phenomena in our Galaxy and in the Universe, carry complementary (if not exclusive) information about the cosmos: this young discipline extends in fact the conventional astronomy beyond the usual electromagnetic probe. The weak interaction of neutrinos with matter allows them to escape from the core of astrophysical objects and in this sense they represent a complementary messenger with respect to photons. However, their detection on Earth due to the small interaction cross section requires a large target mass. The aim of this article is to review the scientific motivations of the high-energy neutrino astrophysics, the detection principles together with the description of a running apparatus, the experiment ANTARES, the performance of this detector with some results, and the presentation of other neutrino telescope projects.

We summarize and critically evaluate the available data on nuclear fusion cross sections important to energy generation in the Sun and other hydrogen-burning stars and to solar neutrino production. Recommended values and uncertainties are provided for key cross sections, and a recommended spectrum is given for 8B solar neutrinos. We also discuss opportunities for further increasing the precision of key rates, including new facilities, new experimental techniques, and improvements in theory. This review, which summarizes the conclusions of a workshop held at the Institute for Nuclear Theory, Seattle, in January 2009, is intended as a 10-year update and supplement to Reviews of Modern Physics 70 (1998) 1265., 54 pages, 20 figures, version to be published in Reviews of Modern Physics; various typos corrected and several updates made

The rate of the hydrogen-burning carbon-nitrogen-oxygen (CNO) cycle is controlled by the slowest process, 14N(p,γ )15O, which proceeds by capture to the ground and several excited states in 15O. Previous extrapolations for the ground state contribution di

The reaction {sup 24}Mg({alpha},{gamma}){sup 28}Si is involved in the nucleosynthesis of {sup 24}Mg and {sup 28}Si in massive stars. The reaction has not been examined with sufficient sensitivity at {alpha}-particle energies below 1.5 MeV. Several {sup 28}Si states appear favorable for formation by this reaction in the {alpha}-particle energy range of 1.0-1.5 MeV, motivating a new study of this reaction at the University of Notre Dame. To maximize experimental sensitivity, a high efficiency coincidence detection system was developed. Several previously unknown resonances were observed between 1.1 and 1.5 MeV, and an upper limit for any lower energy resonances was obtained. Resonance parameters were determined and reaction rates were calculated. The astrophysical implications of these results are discussed.

The talk will be mainly devoted to the measurement of the cross section of the 3He(alpha,gamma)7Be reaction which belongs to the p-p chain. Actually, solar neutrino fluxes depend both on astrophysical and on nuclear physics inputs, namely on the cross sections of the reactions responsible for neutrino production inside the Solar core. While the flux of solar 8B neutrinos has been recently measured at Superkamiokande with a 3.5% uncertainty and a precise measurement of 7Be neutrino flux is foreseen in the next future, the predicted fluxes are still affected by larger errors. The largest nuclear physics uncertainty to determine the fluxes of 8B and 7Be neutrinos comes from the 3He(alpha,gamma)7Be reaction. The uncertainty on its S-factor is due to an average discrepancy in results obtained using two different experimental approaches: the detection of the delayed gamma rays from 7Be decay and the measurement of the prompt gamma emission. The LUNA Collaboration has performed a new high precision experiment with both techniques at the same time. Thanks to the low background conditions of the Gran Sasso LUNA accelerator facility, the cross section has been measured down to 93 keV, the lowest interaction energy ever reached. The S-factors from the two methods do not show any discrepancy within the experimental errors. An extrapolated S(0) = 0.560±0.017 keV barn is obtained. Moreover, branching ratios between the two prompt gamma -transitions have been measured with 3\u20138% accuracy. Recently, the LUNA Collaboration has presented to the Scientific Board of Gran Sasso Laboratory its experimental program for the next five years based on the existing 400 kV accelerator facility. A Letter of Intent addressing the possibility to install a 3 MV machine at Gran Sasso has also been submitted to the Board. The LUNA scientific programs with both the 400 kV and 3 MV accelerator facilities will be illustrated in the final part of the talk.

Solar neutrino fluxes depend both on astrophysical and on nuclear physics inputs, namely on the cross sections of the reactions responsible for neutrino production inside the Solar core. While the flux of solar $^{8}\mathrm{B}$ neutrinos has been recently measured at Superkamiokande with a 3.5% uncertainty and a precise measurement of $^{7}\mathrm{Be}$ neutrino flux is foreseen in the next future, the predicted fluxes are still affected by larger errors. The largest nuclear physics uncertainty to determine the fluxes of $^{8}\mathrm{B}$ and $^{7}\mathrm{Be}$ neutrinos comes from the $^{3}\mathrm{He}$($\ensuremath{\alpha},\ensuremath{\gamma}$)$^{7}\mathrm{Be}$ reaction. The uncertainty on its S-factor is due to an average discrepancy in results obtained using two different experimental approaches: the detection of the delayed \ensuremath{\gamma} rays from $^{7}\mathrm{Be}$ decay and the measurement of the prompt \ensuremath{\gamma} emission. Here we report on a new high precision experiment performed with both techniques at the same time. Thanks to the low background conditions of the Gran Sasso LUNA accelerator facility, the cross section has been measured at ${E}_{\mathrm{c}.\mathrm{m}.}=170$, 106, and 93 keV, the latter being the lowest interaction energy ever reached. The S-factors from the two methods do not show any discrepancy within the experimental errors. An extrapolated $S(0)=0.560\ifmmode\pm\else\textpm\fi{}0.017$ keV barn is obtained. Moreover, branching ratios between the two prompt \ensuremath{\gamma}-transitions have been measured with 5--8% accuracy.

The flux of {sup 7}Be and {sup 8}B neutrinos from the Sun and the production of {sup 7}Li via primordial nucleosynthesis depend on the rate of the {sup 3}He({alpha},{gamma}){sup 7}Be reaction. In an extension of a previous study showing cross section data at 127-167 keV center-of-mass energy, the present work reports on a measurement of the {sup 3}He({alpha},{gamma}){sup 7}Be cross section at 106 keV performed at Italy's Gran Sasso underground laboratory by the activation method. This energy is closer to the solar Gamow energy than ever reached before. The result is {sigma}=0.567{+-}0.029{sub stat}{+-}0.016{sub syst} nb. The data are compared with previous activation studies at high energy, and a recommended S(0) value for all {sup 3}He({alpha},{gamma}){sup 7}Be activation studies, including the present work, is given.

The nuclear physics input from the 3He(alpha,gamma)7Be cross section is a major uncertainty in the fluxes of 7Be and 8B neutrinos from the Sun predicted by solar models and in the 7Li abundance obtained in big-bang nucleosynthesis calculations. The present work reports on a new precision experiment using the activation technique at energies directly relevant to big-bang nucleosynthesis. Previously such low energies had been reached experimentally only by the prompt-gamma technique and with inferior precision. Using a windowless gas target, high beam intensity, and low background gamma-counting facilities, the 3He(alpha,gamma)7Be cross section has been determined at 127, 148, and 169 keV center-of-mass energy with a total uncertainty of 4%. The sources of systematic uncertainty are discussed in detail. The present data can be used in big-bang nucleosynthesis calculations and to constrain the extrapolation of the 3He(alpha,gamma)7Be astrophysical S factor to solar energies.

In stars, four hydrogen nuclei are converted into a helium nucleus by two competing nuclear fusion processes: the proton ‐ proton chain (p‐p) and the carbon ‐ nitrogen ‐ oxygen (CNO) cycle. At temperatures higher than 2×107 K, the CNO cycle dominates the energy production. In particular, its rate is determined by the slowest reaction: 14N(p,γ)15O. Direct measurement in a laboratory at the surface of the Earth is hampered by the background due to the cosmic rays. Here we report on an experiment performed with the LUNA (Laboratory for Underground Nuclear Astrophysics) accelerator placed deep underground in the INFN Gran Sasso laboratory (Italy). Thanks to the cosmic ray suppression provided by the mountain shield, we could measure the 14N(p,γ)15O cross section for the first time directly at energies corresponding to stellar temperatures and with unpreceedent accuracy. In particular we used a large solid angle BGO detector with a differentially pumped windowless gas target. The lowest measured energy is 70.1 keV. Our results have important consequences for the formation of carbon stars, for an independent lower limit on the age of the universe, and for solar neutrino flux.

The determination of the astrophysical S‐factor of the 14N(p,γ)15O reaction is of great interest because this reaction represents the bottleneck of the CNO cycle, which in turn has a large influence on the determination of the age of globular clusters and also plays a role in the estimation of the Solar neutrino fluxes. We have performed a new underground measurement (LUNA, Gran Sasso Laboratory, Italy) using a high resolution set‐up, extending the investigated energy range down to Ecm=130 keV. This allowed a more reliable extrapolation to astrophysical energies, using an R‐matrix fit to the decay to different final states in 15O.

The CNO cycle is the main process for hydrogen burning in stars somewhat more massive than the Sun. The reaction cross sections at Gamow energies are typically in the femto to pico-barn range and are consequently very difficult to measure experimentally. The CNO reaction rates are based on extrapolations of experimental data from higher energies. We are developing a multi-channel R-matrix code (AZURE) to provide a new and more comprehensive tool for fitting experimental data and making extrapolations to lower energies in all reaction and scattering channels. The 14N(p,γ )15O reaction is the slowest reaction of the CNO cycle and thus it determines the energy production rate of CNO burning. Furthermore, this reaction plays an important role in the determination of Globular Cluster age, since the position of the turnoff point, at which the GC stars escape from the Main Sequence, is powered by the onset of the CNO burning, whose bottleneck is the 14N(p, γ )15O. We have made a reanalysis of the most recent experimental data on the ground state and the 6.18 MeV transitions. The ratio of the cross sections of the 15N(p, γ )16O and 15N(p,α)12C reactions determines how much catalytic material passes to higher CNO cycles and has an effect on the production of heavier elements, particularly 16O and 17O. Simultaneous analysis of both reactions for all channels suggests that the ratio σγ/σα is smaller than previously reported.

We report on a new measurement of the 14N(p,γ) 15O capture cross section at Ep=140 to 400 keV using the 400 kV LUNA accelerator facility at the Laboratori Nazionali del Gran Sasso (LNGS). The uncertainties have been reduced with respect to previous measurements and their analysis. We have analyzed the data using the R-matrix method and we find that the ground state transition accounts for about 15% of the total S-factor. The main contribution to the S-factor is given by the transition to the 6.79 MeV state. We find a total S(0)=1.7±0.2 keVb, in agreement with recent extrapolations. The result has important consequences for the solar neutrino spectrum as well as for the age of globular clusters. © 2004 Elsevier B.V. All rights reserved., info:eu-repo/semantics/published

Rat ventral prostate microsomal fraction was able to biotransform ethanol to acetaldehyde and 1-hydroxyethyl radicals (1HEt) in the presence of NADPH and oxygen. The enzymatic processes involved were not inhibited by desferrioxamine, CO, SKF 525A, 4-methylpyrazole, or polyclonal antibody against P450 reductase but they were significantly inhibited by diethyldithiocarbamate, 2-mercapto-1-methylimidazol, thiobenzamide, or diphenyleneiodonium chloride. Results would suggest the partial participation in these ethanol bioactivation processes of flavin containing monooxygenase (FMO) and/or other flavin dependent oxidases/peroxidases and of a non-iron metal-containing enzymes. Acetaldehyde and free radicals production by prostate microsomal fraction might potentially contribute to tumor promotion in heavy alcohol drinkers.

Recent studies from other laboratories reported that during methanol intoxication lipid peroxidation and protein oxidation in liver occurred. Further, they detected free radicals-PBN adducts in bile and urine of methanol poisoned rats. In this work, we report the presence in liver microsomes and nuclei of NADPH dependent processes of hydroxymethyl (HMet) radical formation. The detection of HMet radicals was performed by GC/MS of the trimethylsilyl derivatives of the PBN (N-tert-butyl-a-phenylnitrone)-radical adducts. The formation of HMet radicals was observed only under nitrogen, in these in vitro conditions. Formation of formaldehyde from methanol was observed in aerobic incubation mixtures containing either microsomes or nuclei but also under nitrogen using microsomes. The latter process was not inhibited by diphenyleneiodonium while the anaerobic microsomal one producing HMet was strongly inhibited by it. This shows that they are independent processes. Results suggest that both, liver nuclei and microsomes are able to generate free radicals during NADPH-mediated methanol biotransformation. Fil: Castro, Gerardo Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. GP. CITEFA - Centro de Investigaciones Toxicológicas (I); Argentina Fil: Costantini, Martin Hernan. Consejo Nacional de Investigaciones Científicas y Técnicas. GP. CITEFA - Centro de Investigaciones Toxicológicas (I); Argentina Fil: Delgado De Layño, Aurora, M. A.. Consejo Nacional de Investigaciones Científicas y Técnicas. GP. CITEFA - Centro de Investigaciones Toxicológicas (I); Argentina Fil: Castro, Jose Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. GP. CITEFA - Centro de Investigaciones Toxicológicas (I); Argentina

The ability of the ventral prostate cytosolic fractions to biotransform ethanol to acetaldehyde and 1-hydroxyethyl (1HEt) radicals was tested. Acetaldehyde formation was determined by GC-FID analysis in the head space of incubation mixtures. 1HEt was determined by spin trapping with PBN followed by extraction, silylation of the adduct and GC-MS of the product. Prostate cytosol was able to biotransform ethanol to acetaldehyde in the presence of NADH, hypoxanthine, xanthine, caffeine, theobromine, theophylline, and 1,7-dimethylxanthine but not in the presence of N-methylnicotinamide. All these biotransformations were inhibited by allopurinol and were sensitive to heating for 5 min at 100 degrees C. The biotransformation of ethanol to acetaldehyde in the presence of purines as cosubstrates was accompanied by the formation of hydroxyl and 1HEt radicals as detected by GC-MS, and the process was inhibited by allopurinol. Results suggest that prostate cytosolic xanthine oxidase is able to bioactivate ethanol to acetaldehyde and free radicals. The potential of these processes to be involved in tumor-promoting effects of heavy alcohol drinking in conjunction with high meat and/or purines consumption is analyzed. Multifactorial epidemiological studies considering that possibility might be convenient. Teratogenesis Carcinog. Mutagen. 21:109-119, 2001.

The stopping power of atomic and molecular deuterons in 3 He gas was measured over the range Ed = 10 to 100 keV using the 3 He pressure dependence of the 3 He(d,p) 4 He reactionyield. At en ergies above 30 keV, the observed stopping power values are in good agreement with a standard compilation. However, near 18 keV the experimental values drop by a factor 50 below the extrapolated values of the compilation. In a simple model, the behavior is due to the minimum 1s → 2s electronexcitationof the He target atoms (= 19.8 eV, corresponding to Ed = 18.2 keV), i.e. it is a quantum effect, by which the atoms become nearly transparent for the ions.

It is in the nature of astrophysics that many of the processes and objects one tries to understand are physically inaccessible. Thus, it is important that those aspects that can be studied in the laboratory be rather well understood. One such aspect are the nuclear fusion reactions, which are at the heart of nuclear astrophysics. They influence sensitively the nucleosynthesis of the elements in the earliest stages of the universe and in all the objects formed thereafter, and control the associated energy generation, neutrino luminosity, and evolution of stars. We review an experimental approach for the study of nuclear fusion reactions based on an underground accelerator laboratory, named LUNA., Invited Review; accepted for publication in Reports on Progress in Physics; 26 pages; 27 figures