Proton-Capture Rates on Carbon Isotopes and Their Impact on the Astrophysical

The ^{12}C/^{13}C ratio is a significant indicator of nucleosynthesis and mixing processes during hydrogen burning in stars. Its value mainly depends on the relative rates of the ^{12}C(p,γ)^{13}N and ^{13}C(p,γ)^{14}N reactions. Both reactions have been studied at the Laboratory for Underground Nuclear Astrophysics (LUNA) in Italy down to the lowest energies to date (E_{c.m.}=60 keV) reaching for the first time the high energy tail of hydrogen burning in the shell of giant stars. Our cross sections, obtained with both prompt γ-ray detection and activation measurements, are the most precise to date with overall systematic uncertainties of 7%-8%. Compared with most of the literature, our results are systematically lower, by 25% for the ^{12}C(p,γ)^{13}N reaction and by 30% for ^{13}C(p,γ)^{14}N. We provide the most precise value up to now of 3.6±0.4 in the 20-140 MK range for the lowest possible ^{12}C/^{13}C ratio that can be produced during H burning in giant stars.

Direct Measurement of the

One of the main neutron sources for the astrophysical s process is the reaction ^{13}C(α,n)^{16}O, taking place in thermally pulsing asymptotic giant branch stars at temperatures around 90 MK. To model the nucleosynthesis during this process the reaction cross section needs to be known in the 150-230 keV energy window (Gamow peak). At these sub-Coulomb energies, cross section direct measurements are severely affected by the low event rate, making us rely on input from indirect methods and extrapolations from higher-energy direct data. This leads to an uncertainty in the cross section at the relevant energies too high to reliably constrain the nuclear physics input to s-process calculations. We present the results from a new deep-underground measurement of ^{13}C(α,n)^{16}O, covering the energy range 230-300 keV, with drastically reduced uncertainties over previous measurements and for the first time providing data directly inside the s-process Gamow peak. Selected stellar models have been computed to estimate the impact of our revised reaction rate. For stars of nearly solar composition, we find sizeable variations of some isotopes, whose production is influenced by the activation of close-by branching points that are sensitive to the neutron density, in particular, the two radioactive nuclei ^{60}Fe and ^{205}Pb, as well as ^{152}Gd.

The baryon density of the Universe from an improved rate of deuterium burning.

Light elements were produced in the first few minutes of the Universe through a sequence of nuclear reactions known as Big Bang nucleosynthesis (BBN)1,2. Among the light elements produced during BBN1,2, deuterium is an excellent indicator of cosmological parameters because its abundance is highly sensitive to the primordial baryon density and also depends on the number of neutrino species permeating the early Universe. Although astronomical observations of primordial deuterium abundance have reached percent accuracy3, theoretical predictions4-6 based on BBN are hampered by large uncertainties on the cross-section of the deuterium burning D(p,γ)3He reaction. Here we show that our improved cross-sections of this reaction lead to BBN estimates of the baryon density at the 1.6 percent level, in excellent agreement with a recent analysis of the cosmic microwave background7. Improved cross-section data were obtained by exploiting the negligible cosmic-ray background deep underground at the Laboratory for Underground Nuclear Astrophysics (LUNA) of the Laboratori Nazionali del Gran Sasso (Italy)8,9. We bombarded a high-purity deuterium gas target10 with an intense proton beam from the LUNA 400-kilovolt accelerator11 and detected the γ-rays from the nuclear reaction under study with a high-purity germanium detector. Our experimental results settle the most uncertain nuclear physics input to BBN calculations and substantially improve the reliability of using primordial abundances to probe the physics of the early Universe.

Direct Capture Cross Section and the E_{p}=71 and 105 keV Resonances in the

The ^{22}Ne(p,γ)^{23}Na reaction, part of the neon-sodium cycle of hydrogen burning, may explain the observed anticorrelation between sodium and oxygen abundances in globular cluster stars. Its rate is controlled by a number of low-energy resonances and a slowly varying nonresonant component. Three new resonances at E_{p}=156.2, 189.5, and 259.7 keV have recently been observed and confirmed. However, significant uncertainty on the reaction rate remains due to the nonresonant process and to two suggested resonances at E_{p}=71 and 105 keV. Here, new ^{22}Ne(p,γ)^{23}Na data with high statistics and low background are reported. Stringent upper limits of 6×10^{-11} and 7×10^{-11} eV (90% confidence level), respectively, are placed on the two suggested resonances. In addition, the off-resonant S factor has been measured at unprecedented low energy, constraining the contributions from a subthreshold resonance and the direct capture process. As a result, at a temperature of 0.1 GK the error bar of the ^{22}Ne(p,γ)^{23}Na rate is now reduced by 3 orders of magnitude.

Erratum: Three New Low-Energy Resonances in the

This corrects the article DOI: 10.1103/PhysRevLett.115.252501.

Improved Direct Measurement of the 64.5 keV Resonance Strength in the

The ^{17}O(p,α)^{14}N reaction plays a key role in various astrophysical scenarios, from asymptotic giant branch stars to classical novae. It affects the synthesis of rare isotopes such as ^{17}O and ^{18}F, which can provide constraints on astrophysical models. A new direct determination of the E_{R}=64.5 keV resonance strength performed at the Laboratory for Underground Nuclear Astrophysics (LUNA) accelerator has led to the most accurate value to date ωγ=10.0±1.4_{stat}±0.7_{syst} neV, thanks to a significant background reduction underground and generally improved experimental conditions. The (bare) proton partial width of the corresponding state at E_{x}=5672 keV in ^{18}F is Γ_{p}=35±5_{stat}±3_{syst} neV. This width is about a factor of 2 higher than previously estimated, thus leading to a factor of 2 increase in the ^{17}O(p, α)^{14}N reaction rate at astrophysical temperatures relevant to shell hydrogen burning in red giant and asymptotic giant branch stars. The new rate implies lower ^{17}O/^{16}O ratios, with important implications on the interpretation of astrophysical observables from these stars.

Three New Low-Energy Resonances in the

The ^{22}Ne(p,γ)^{23}Na reaction takes part in the neon-sodium cycle of hydrogen burning. This cycle affects the synthesis of the elements between ^{20}Ne and ^{27}Al in asymptotic giant branch stars and novae. The ^{22}Ne(p,γ)^{23}Na reaction rate is very uncertain because of a large number of unobserved resonances lying in the Gamow window. At proton energies below 400 keV, only upper limits exist in the literature for the resonance strengths. Previous reaction rate evaluations differ by large factors. In the present work, the first direct observations of the ^{22}Ne(p,γ)^{23}Na resonances at 156.2, 189.5, and 259.7 keV are reported. Their resonance strengths are derived with 2%-7% uncertainty. In addition, upper limits for three other resonances are greatly reduced. Data are taken using a windowless ^{22}Ne gas target and high-purity germanium detectors at the Laboratory for Underground Nuclear Astrophysics in the Gran Sasso laboratory of the National Institute for Nuclear Physics, Italy, taking advantage of the ultralow background observed deep underground. The new reaction rate is a factor of 20 higher than the recent evaluation at a temperature of 0.1 GK, relevant to nucleosynthesis in asymptotic giant branch stars.

Anti-laminin-1 antibodies in sera and follicular fluid of women with endometriosis undergoing in vitro fertilization.

There is increasing evidence that autoimmune phenomena, including auto-antibody production, may affect fertility in women with endometriosis. The aims of this study are to evaluate anti-laminin-1 antibody (aLN-1) presence in sera and in follicular fluids (FF) of women with endometriosis undergoing IVF and its impact on oocyte maturation and IVF outcome. aLN-1 were measured by a home-made enzyme linked immunosorbent assay in sera and FF obtained from 35 infertile women with endometriosis and in sera from 50 fertile controls and 27 infertile women without endometriosis (IWWE). aLN-1 serum levels were significantly higher in women with endometriosis in comparison with both fertile controls and IWWE (P<0.001 and P<0.05, respectively) and a positive correlation was found between serum- and FF-aLN-1 (r=0.47, P=0.004). According to the cut-off (mean+3 SD of fertile controls), 31% of women with endometriosis were aLN-1 positive. Metaphase II oocyte counts showed inverse correlation with FF-aLN-1 levels (r=-0.549, P=0.0006). Ongoing pregnancy (i.e pregnancy progressing beyond the 12th week of gestation) occurred in 4/11 aLN-1 positive patients and in 7/24 aLN-1 negative with no significant difference (P=0.7). In conclusion, our results highlight that aLN-1 are increased in women with endometriosis and their presence in FF may affect oocyte maturation leading to a reduced fertility. However, aLN-1 seem to have no effect on IVF outcome.

Impact of chronic viral diseases on semen parameters.

The aim of this study was to assess the effect of human immunodeficiency virus (HIV), hepatitis C (HCV) and B (HBV) virus infection on semen parameters. Semen samples were obtained from 27 HCV, 34 HIV, 30 HBV and 41 HCV-HIV-seropositive patients and compared with those of a control population of healthy seronegative subjects. Tests for detection of HIV, HCV and HBV were performed on seminal samples. The sperm concentration was significantly decreased in HCV- and HBV-seropositive males compared to that of controls (P < 0.001). The mean sperm motility (a + b) was significantly decreased in HCV- and HBV-seropositive (P < 0.001) and in HCV-HIV-seropositive subjects (P < 0.05) compared to that of controls. The sperm viability was significantly lower in HCV- and HBV-seropositive men than in controls (P < 0.001). The normal morphology was significantly reduced in HCV-seropositive and HBV-seropositive men (P < 0.05) with respect to that of controls (P < 0.05). The sperm concentration after sperm wash was significantly higher in controls than in HCV-, HIV-, HBV- and HIV-HCV-seropositive men (P < 0.001). We can conclude that HBV- and HCV-infected men have a significantly impaired sperm quality compared with that of controls. The reason for the better sperm quality in our series of HIV- and HCV-HIV-infected men is still under debate. Further investigations in a larger case series are warranted.

Anticardiolipin antibody levels in women undergoing first in vitro fertilization/embryo transfer.

BACKGROUND: The clinical relevance of antiphospholipid antibodies (aPL) in women undergoing in vitro fertilization/embryo transfer (IVF/ET) and the role of IVF treatment in affecting antiphospholipid levels are controversial. The aim of this study was to evaluate anticardiolipin antibody (aCL) levels and the effect of IVF treatment on aCL in women undergoing their first IVF/ET cycle. METHODS: Immunoglobulin G (IgG)- and IgM-aCL were determined by enzyme-linked immunosorbent assay in 50 women undergoing IVF/ET, 18 due to endometriosis, 16 to tubal factor (TF) and 16 to male factor, before starting treatment (T0), on the day of oocyte retrieval (T1) and 14 days after ET (T2). A group of 31 age-matched fertile women served as controls. RESULTS: aCL levels detected at T0 in patients were not significantly different compared with the control group. IgG- but not IgM-aCL significantly increased at T2 in comparison with T0 (P < 0.001) and T1 (P < 0.05). The difference between T2 and T0 reached statistical significance in patients with endometriosis (P = 0.003) or TF (P = 0.018). No relationship was found between aCL and pregnancy. CONCLUSIONS: Our results indicate that IVF treatment increases IgG-aCL levels in patients with endometriosis and TF, but their presence seems to have no clinical relevance.

Relationship between gonadotropin releasing hormone agonist dosage and in vitro fertilization outcome.

A prospective study in 132 women undergoing in vitro fertilization was performed in order to assess whether lower doses of gonadotropin releasing hormone agonists (GnRH-a) may ensure adequate oocyte retrieval and pregnancy rate, without pituitary oversuppression. Forty-five patients received subcutaneous tryptorelin depot (Decapeptyl 3.75, IPSEN SpA), 41 received subcutaneous tryptorelin acetate daily (Decapeptyl 0.1 mg, IPSEN SpA) and 46 received 0.05 mg tryptorelin acetate daily from day 21 of the cycle. From day 3 of the new cycle, if the estradiol levels were < 30 pg/ml, patients received two or three ampules of gonadotropin daily. In the group receiving subcutaneous tryptorelin acetate depot, the mean number of total gonadotropin ampules was significantly higher (p < 0.05), otherwise estradiol levels and the number of oocytes retrieved, fertilized and cleaved were significantly lower (p < 0.05). Pituitary oversuppression induced by GnRH-a causes an increase in the gonadotropin requirement for assisted reproductive techniques (ART) and a reduction in the number of oocytes retrieved and fertilized. There is a high risk of oversuppression in normal-weight or underweight women, because there is greater bioavailability of the peptide, hence elevated circulating levels of GnRH-a. Thus, ovarian stimulation in ART cycles depends on many factors, not least the identification of the best GnRH-a dose.