β-Delayed One and Two Neutron Emission Probabilities Southeast of ^{132}Sn and the Odd-Even Systematics in r-Process Nuclide Abundances

The β-delayed one- and two-neutron emission probabilities (P_{1n} and P_{2n}) of 20 neutron-rich nuclei with N≥82 have been measured at the RIBF facility of the RIKEN Nishina Center. P_{1n} of ^{130,131}Ag, ^{133,134}Cd, ^{135,136}In, and ^{138,139}Sn were determined for the first time, and stringent upper limits were placed on P_{2n} for nearly all cases. β-delayed two-neutron emission (β2n) was unambiguously identified in ^{133}Cd and ^{135,136}In, and their P_{2n} were measured. Weak β2n was also detected from ^{137,138}Sn. Our results highlight the effect of the N=82 and Z=50 shell closures on β-delayed neutron emission probability and provide stringent benchmarks for newly developed macroscopic-microscopic and self-consistent global models with the inclusion of a statistical treatment of neutron and γ emission. The impact of our measurements on r-process nucleosynthesis was studied in a neutron star merger scenario. Our P_{1n} and P_{2n} have a direct impact on the odd-even staggering of the final abundance, improving the agreement between calculated and observed Solar System abundances. The odd isotope fraction of Ba in r-process-enhanced (r-II) stars is also better reproduced using our new data.

Effects of grape pomace supplementation on the diet of lactating ewes as compared to vitamin E on the meat shelf life of suckling lambs

Forty-eight Churra ewes and their suckling lambs were assigned to four dietary treatments: control (CTRL), VIT-E (500 mg kg-1 TMR vitamin E), GP-5 (5% grape pomace) and GP-10 (10% grape pomace). After slaughter (11.5 kg live weight), longissimus muscle of lambs was sliced, packaged under modified atmosphere (80,20%/O 2:CO 2) and stored in retail conditions. At each sampling point (0, 3, 7, 10, 14 days), microbiological, physicochemical and sensory characteristics were analysed. Vitamin E and GP-5 were found to be effective (p < 0.05) at preventing enterobacteria growth as of day 10. After day 10, vitamin E and grape pomace in the ewe's supplementation reduced metmyoglobin (p < 0.05) lipid oxidation (p < 0.05) and sensory spoilage throughout the storage period. An effect of the grape pomace dosage was observed, with the supplementation at 5% being more effective. Therefore, we can conclude that grape pomace was just as effective as vitamin E in preventing spoilage during retail storage.

Shape Changes in the Mirror Nuclei ^{70}Kr and ^{70}Se

We studied the proton-rich T_{z}=-1 nucleus ^{70}Kr through inelastic scattering at intermediate energies in order to extract the reduced transition probability, B(E2;0^{+}→2^{+}). Comparison with the other members of the A=70 isospin triplet, ^{70}Br and ^{70}Se, studied in the same experiment, shows a 3σ deviation from the expected linearity of the electromagnetic matrix elements as a function of T_{z}. At present, no established nuclear structure theory can describe this observed deviation quantitatively. This is the first violation of isospin symmetry at this level observed in the transition matrix elements. A heuristic approach may explain the anomaly by a shape change between the mirror nuclei ^{70}Kr and ^{70}Se contrary to the model predictions.

Updated Summation Model: An Improved Agreement with the Daya Bay Antineutrino Fluxes

A new summation method model of the reactor antineutrino energy spectrum is presented. It is updated with the most recent evaluated decay databases and with our total absorption gamma-ray spectroscopy measurements performed during the last decade. For the first time, the spectral measurements from the Daya Bay experiment are compared with the antineutrino energy spectrum computed with the updated summation method without any renormalization. The results exhibit a better agreement than is obtained with the Huber-Mueller model in the 2-5 MeV range, the region that dominates the detected flux. A systematic trend is found in which the antineutrino flux computed with the summation model decreases with the inclusion of more pandemonium-free data. The calculated flux obtained now lies only 1.9% above that detected in the Daya Bay experiment, a value that may be reduced with forthcoming new pandemonium-free data, leaving less room for a reactor anomaly. Eventually, the new predictions of individual antineutrino spectra for the ^{235}U, ^{239}Pu, ^{241}Pu, and ^{238}U are used to compute the dependence of the reactor antineutrino spectral shape on the fission fractions.

Publisher's Note: Experimental Neutron Capture Rate Constraint Far from Stability [Phys. Rev. Lett. 116, 242502 (2016)]

This corrects the article DOI: 10.1103/PhysRevLett.116.242502.

Large Impact of the Decay of Niobium Isomers on the Reactor ν[over ¯]_{e} Summation Calculations

Even mass neutron-rich niobium isotopes are among the principal contributors to the reactor antineutrino energy spectrum. They are also among the most challenging to measure due to the refractory nature of niobium, and because they exhibit isomeric states lying very close in energy. The β-intensity distributions of ^{100gs,100m}Nb and ^{102gs,102m}Nb β decays have been determined using the total absorption γ-ray spectroscopy technique. The measurements were performed at the upgraded Ion Guide Isotope Separator On-Line facility at the University of Jyväskylä. Here, the double Penning trap system JYFLTRAP was employed to disentangle the β decay of the isomeric states. The new data obtained in this challenging measurement have a large impact in antineutrino summation calculations. For the first time the discrepancy between the summation model and the reactor antineutrino measurements in the region of the shape distortion has been reduced.

Summation Calculations for Reactor Antineutrino Spectra, Decay Heat and Delayed Neutron Fractions Involving New TAGS Data and Evaluated Databases

Three observables of interest for present and future reactors depend on the β decay properties of the fission products: antineutrinos from reactors, the reactor decay heat and delayed neutron emission. In these proceedings, we present new results from summation calculations of the first two quantities quoted above, performed with evolved independent yields coupled with fission product decay data, from various nuclear data bases or models. New TAGS results from the latest experiment of the TAGS collaboration at the JYFL facility of Jyväskylä will be displayed as well as their impact on the antineutrino spectra and the decay heat associated to fission pulses of the main actinides.

New Results on Excited States in the one-particle one-hole nucleus 56Co measured with MINIBALL detectors

The non-yrast states of the odd-odd nucleus 56Co have been investigated by studying the γ-rays induced in the predominantly fusion-evaporation reaction 56Fe(p,n γ)56Co at an incident energy of 10 MeV. The γ-rays were measured in-beam with four high-resolution MINIBALL-triple germanium (Ge) detectors. The experiment provided excellent data in γ-γ coincidences. The complex level scheme of 56Co was constructed mainly based on the analysis of these γ-γ coincidences. The angular distributions of the γ-rays were also analysed and allowed us to assign spin-parity values to most of the excited states in this nucleus. Despite the extensive work previously done studying the 56Co nucleus, the analysis presented in this work has resulted in a large improvement in the knowledge of its structure.

Efecto del nivel de androstenona en chorizos elaborados a partir de cerdos enteros

Como consecuencia de los cambios en la normativa europea sobre bienestar animal, en un futuro próximo la industria porcina podría afrontar la prohibición de la castración de lechones machos, lo que implicaría un riesgo medio o alto de obtener carne con olor sexual. La castración física afecta a la cantidad de grasa de depósito y a la composición de ácidos grasos de los tejidos magro y graso. Por lo tanto, el uso de cerdos enteros en la industria podría afectar al procesado y a la calidad de los productos cárnicos. El objetivo de este estudio fue evaluar el efecto del nivel de androstenona (AND) en las características de un embutido crudo curado (chorizos). Para ello, se analizó la composición química, el perfil de ácidos grasos y las características sensoriales de chorizos de cerdos castrados y de cerdos machos enteros con dos niveles de AND (Medio: 0,5-0,8 µg/g de grasa, Alto: 1,1-2,9 µg/g de grasa). Los chorizos procedentes de cerdos con niveles de AND medio y alto presentaron el mayor contenido en proteína y el menor contenido de grasa (P

Two-Proton Radioactivity of ^{67}Kr

In an experiment with the BigRIPS separator at the RIKEN Nishina Center, we observed two-proton (2p) emission from ^{67}Kr. At the same time, no evidence for 2p emission of ^{59}Ge and ^{63}Se, two other potential candidates for this exotic radioactivity, could be observed. This observation is in line with Q value predictions which pointed to ^{67}Kr as being the best new candidate among the three for two-proton radioactivity. ^{67}Kr is only the fourth 2p ground-state emitter to be observed with a half-life of the order of a few milliseconds. The decay energy was determined to be 1690(17) keV, the 2p emission branching ratio is 37(14)%, and the half-life of ^{67}Kr is 7.4(30) ms.

First Measurement of Several β-Delayed Neutron Emitting Isotopes Beyond N=126

The β-delayed neutron emission probabilities of neutron rich Hg and Tl nuclei have been measured together with β-decay half-lives for 20 isotopes of Au, Hg, Tl, Pb, and Bi in the mass region N≳126. These are the heaviest species where neutron emission has been observed so far. These measurements provide key information to evaluate the performance of nuclear microscopic and phenomenological models in reproducing the high-energy part of the β-decay strength distribution. This provides important constraints on global theoretical models currently used in r-process nucleosynthesis.

Experimental Neutron Capture Rate Constraint Far from Stability

Nuclear reactions where an exotic nucleus captures a neutron are critical for a wide variety of applications, from energy production and national security, to astrophysical processes, and nucleosynthesis. Neutron capture rates are well constrained near stable isotopes where experimental data are available; however, moving far from the valley of stability, uncertainties grow by orders of magnitude. This is due to the complete lack of experimental constraints, as the direct measurement of a neutron-capture reaction on a short-lived nucleus is extremely challenging. Here, we report on the first experimental extraction of a neutron capture reaction rate on ^{69}Ni, a nucleus that is five neutrons away from the last stable isotope of Ni. The implications of this measurement on nucleosynthesis around mass 70 are discussed, and the impact of similar future measurements on the understanding of the origin of the heavy elements in the cosmos is presented.

Evaluation of different strategies to mask boar taint in cooked sausage

The use of smoking and/or spices was evaluated for their ability to mask boar taint in frankfurters manufactured from entire pigs with high levels of androstenone. Five frankfurter types were considered: control, smoked, flavouring+smoked, spicy and spicy+smoked. A trained panel in androstenone perception carried out a sensory profile on the different sausages. The highest scores for androstenone perception (odour, flavour and aftertaste) were found in frankfurters that included no masking strategy which indicated the effectiveness of the evaluated strategies. Regarding masking strategies, the contribution of spices and smoking to sensory perception of frankfurters was detected by the panellists. Smoking was the best strategy to mask androstenone odour, while the use of spices masked androstenone odour to a greater extent than androstenone flavour. Only the combined use of spices and smoking was able to eliminate the perception of androstenone. The application of this strategy in frankfurters could be an alternative in the commercialization of entire pigs.

Le tempérament, un puissant déterminant des conduites alimentaires de l’enfant

Selon le modèle de Rothbart , le tempérament est défini, d’une part, par le niveau de réactivité des enfants, et d’autre part, par leur capacité d’autorégulation. Au moyen de deux études, nous avons cherché a testé la valeur de ce modèle tempéramental dans le domaine alimentaire enfantin. La première étude est relative à la question du surpoids. Nous avons émis l’hypothèse que les enfants les plus à risque de surpoids étaient les enfants les plus réactifs à la nourriture et s’autorégulant le moins bien. À partir des réponses de 475 pré-adolescents ayant rempli un questionnaire ad hoc et dont on a mesuré l’IMC, l’hypothèse a été confirmée, mais de façon directe pour une des dimensions seulement. La seconde étude concerne la problématique de la néophobie alimentaire, à savoir la réticence à goûter les aliments inconnus qui conduit à une faible consommation de fruits et légumes notamment. Notre hypothèse était que les enfants ayant de faibles capacités à autoréguler leurs émotions consommeraient moins d’un aliment inconnu que des enfants s’autorégulant facilement, et ceci d’autant plus que la consigne de la consommation était incitative plutôt que directive (selon le concept de Goodness of fit suggéré par Thomas et Chess ). Quatre-vingt-dix-huit enfants‚ âgés entre 2 et 3 ans ont participé à une étude expérimentale les amenant à goûter à 5 occasions un aliment inconnu dans un contexte soit incitatif soit directif. Les résultats du post-test ont indiqué que la consommation de l’aliment était supérieure chez les enfants s’autorégulant facilement dans le contexte incitatif, que chez les enfants s’autorégulant difficilement dans le contexte directif. Il apparaît ainsi que le concept de tempérament selon Rothbart, et notamment à travers les capacités d’autorégulation, joue un rôle dans les conduites alimentaires de l’enfant dans leur dimension quantitative (quantités consommées et du surpoids) et qualitative (néophobie et variété du répertoire de consommation).

Nonquenched Isoscalar Spin-M1 Excitations in sd-Shell Nuclei

Differential cross sections of isoscalar and isovector spin-M1 (0(+)→1(+)) transitions are measured using high-energy-resolution proton inelastic scattering at E(p)=295  MeV on (24)Mg, (28)Si, (32)S, and (36)Ar at 0°-14°. The squared spin-M1 nuclear transition matrix elements are deduced from the measured differential cross sections by applying empirically determined unit cross sections based on the assumption of isospin symmetry. The ratios of the squared nuclear matrix elements accumulated up to E(x)=16  MeV compared to a shell-model prediction are 1.01(9) for isoscalar and 0.61(6) for isovector spin-M1 transitions, respectively. Thus, no quenching is observed for isoscalar spin-M1 transitions, while the matrix elements for isovector spin-M1 transitions are quenched by an amount comparable with the analogous Gamow-Teller transitions on those target nuclei.

Total Absorption Spectroscopy Study of (92)Rb Decay: A Major Contributor to Reactor Antineutrino Spectrum Shape

The antineutrino spectra measured in recent experiments at reactors are inconsistent with calculations based on the conversion of integral beta spectra recorded at the ILL reactor. (92)Rb makes the dominant contribution to the reactor antineutrino spectrum in the 5-8 MeV range but its decay properties are in question. We have studied (92)Rb decay with total absorption spectroscopy. Previously unobserved beta feeding was seen in the 4.5-5.5 region and the GS to GS feeding was found to be 87.5(25)%. The impact on the reactor antineutrino spectra calculated with the summation method is shown and discussed.

Enhanced γ-Ray Emission from Neutron Unbound States Populated in β Decay

Total absorption spectroscopy is used to investigate the β-decay intensity to states above the neutron separation energy followed by γ-ray emission in (87,88)Br and (94)Rb. Accurate results are obtained thanks to a careful control of systematic errors. An unexpectedly large γ intensity is observed in all three cases extending well beyond the excitation energy region where neutron penetration is hindered by low neutron energy. The γ branching as a function of excitation energy is compared to Hauser-Feshbach model calculations. For (87)Br and (88)Br the γ branching reaches 57% and 20%, respectively, and could be explained as a nuclear structure effect. Some of the states populated in the daughter can only decay through the emission of a large orbital angular momentum neutron with a strongly reduced barrier penetrability. In the case of neutron-rich (94)Rb the observed 4.5% branching is much larger than the calculations performed with standard nuclear statistical model parameters, even after proper correction for fluctuation effects on individual transition widths. The difference can be reconciled by introducing an enhancement of 1 order of magnitude in the photon strength to neutron strength ratio. An increase in the photon strength function of such magnitude for very neutron-rich nuclei, if it proves to be correct, leads to a similar increase in the (n,γ) cross section that would have an impact on r process abundance calculations.

XRF scanners as a quick screening tool for detecting toxic pollutant elements in sediments from Marín harbour in the Ría de Pontevedra (NW Spain)

X-ray fluorescence scanners, such as the Itrax™ Core Scanner (Itrax) (Cox Analytical Systems, Mölndal, Sweden), provide high-resolution geochemical data within several hours. However, the semi-quantitative nature of these analysers has hampered their use to study pollution. This study explores Itrax's capabilities to detect trace metals, such as Hg and Cd, in the Ría de Pontevedra harbour (NW Spain). A set of Itrax detection levels were proposed for each metal after comparison with quantitative measurements obtained from Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) and Vapour Atomic Absorption Spectrometry (CVAAS) analyses. These quantitative data obtained after a sequential extraction were used to evaluate pollutant bioavailability and to determine metal pollution levels exhibiting Hg pollution. The reliability of inc/coh and Br/Cl ratios to assess the total organic matter variability was also evaluated. The results indicated that the Itrax is an efficient and fast option to monitor contamination, thereby avoiding laborious discrete analyses and reducing analytical cost and time.

Hindered Gamow-Teller decay to the odd-odd N=Z (62)Ga: absence of proton-neutron T=0 condensate in A=62

Search for a new kind of superfluidity built on collective proton-neutron pairs with aligned spin is performed studying the Gamow-Teller decay of the T=1, J(π)=0+ ground state of (62)Ge into excited states of the odd-odd N=Z nucleus (62)Ga. The experiment is performed at GSI Helmholtzzentrum für Shwerionenforshung with the (62)Ge ions selected by the fragment separator and implanted in a stack of Si-strip detectors, surrounded by the RISING Ge array. A half-life of T1/2=82.9(14)  ms is measured for the (62)Ge ground state. Six excited states of (62)Ga, populated below 2.5 MeV through Gamow-Teller transitions, are identified. Individual Gamow-Teller transition strengths agree well with theoretical predictions of the interacting shell model and the quasiparticle random phase approximation. The absence of any sizable low-lying Gamow-Teller strength in the reported beta-decay experiment supports the hypothesis of a negligible role of coherent T=0 proton-neutron correlations in (62)Ga.

Half-life systematics across the N=126 shell closure: role of first-forbidden transitions in the β decay of heavy neutron-rich nuclei

This Letter reports on a systematic study of β-decay half-lives of neutron-rich nuclei around doubly magic (208)Pb. The lifetimes of the 126-neutron shell isotone (204)Pt and the neighboring (200-202)Ir, (203)Pt, (204)Au are presented together with other 19 half-lives measured during the "stopped beam" campaign of the rare isotope investigations at GSI collaboration. The results constrain the main nuclear theories used in calculations of r-process nucleosynthesis. Predictions based on a statistical macroscopic description of the first-forbidden β strength reveal significant deviations for most of the nuclei with N<126. In contrast, theories including a fully microscopic treatment of allowed and first-forbidden transitions reproduce more satisfactorily the trend in the measured half-lives for the nuclei in this region, where the r-process pathway passes through during β decay back to stability.

Observation of the β-delayed γ-proton decay of (56)Zn and its impact on the Gamow-Teller strength evaluation

We report the observation of a very exotic decay mode at the proton drip line, the β-delayed γ-proton decay, clearly seen in the β decay of the T_{z}=-2 nucleus ^{56}Zn. Three γ-proton sequences have been observed after the β decay. Here this decay mode, already observed in the sd shell, is seen for the first time in the fp shell. Both γ and proton decays have been taken into account in the estimation of the Fermi and Gamow-Teller strengths. Evidence for fragmentation of the Fermi strength due to strong isospin mixing is found.

Observation of low- and high-energy Gamow-Teller phonon excitations in nuclei

Gamow-Teller (GT) transitions in atomic nuclei are sensitive to both nuclear shell structure and effective residual interactions. The nuclear GT excitations were studied for the mass number A = 42, 46, 50, and 54 "f-shell" nuclei in ((3)He, t) charge-exchange reactions. In the (42)Ca → (42)Sc reaction, most of the GT strength is concentrated in the lowest excited state at 0.6 MeV, suggesting the existence of a low-energy GT phonon excitation. As A increases, a high-energy GT phonon excitation develops in the 6-11 MeV region. In the (54)Fe → (54)Co reaction, the high-energy GT phonon excitation mainly carries the GT strength. The existence of these two GT phonon excitations are attributed to the 2 fermionic degrees of freedom in nuclei.

Influence of temperature and regeneration cycles on Hg capture and efficiency by structured Au/C regenerable sorbents

The objective of this work is to evaluate a novel regenerable sorbent for mercury capture based on gold nanoparticles supported on a honeycomb structured carbon monolith. A new methodology for gold nanoparticles deposition onto carbon monolith support has been developed to obtain an Au sorbent based on the direct reduction of a gold salt onto the carbon material. For comparison purposes, colloidal gold method was also used to obtain Au/C sorbents. Both types of sorbents were characterized by different techniques in order to obtain the bulk gold content, the particle size distribution and the chemical states of gold after deposition. The mercury capture capacity and mercury capture efficiency of sorbents were tested in a bench scale facility at different experimental conditions. The regenerability of the sorbents was tested along several cycles of Hg capture-regeneration. High retention efficiencies are found for both types of sorbents comparing their gold content. Moreover, the high retention efficiency is maintained along several cycles of Hg capture-regeneration. The study of the fresh sorbent, the sorbent after Hg exposition and after regeneration by XPS and XRD gives insight to explain those results.

Isotopic identification of natural vs. anthropogenic lead sources in marine sediments from the inner Ría de Vigo (NW Spain)

San Simón Bay, the inner part of the Ría de Vigo (NW Spain), an area previously identified as highly polluted by Pb, was selected for the application of Pb stable isotope ratios as a fingerprinting tool in subtidal and intertidal sediment cores. Lead isotopic ratios were determined by inductively coupled plasma mass spectrometry on extracts from bulk samples after total acid digestion. Depth-wise profiles of (206)Pb/(207)Pb, (206)Pb/(204)Pb, (207)Pb/(204)Pb, (208)Pb/(204)Pb and (208)Pb/(207)Pb ratios showed, in general, an upward decrease for both intertidal and subtidal sediments as a consequence of the anthropogenic activities over the last century, or centuries. Waste channel samples from a nearby ceramic factory showed characteristic Pb stable isotope ratios different from those typical of coal and petrol. Natural isotope ratios from non-polluted samples were established for the study area, differentiating sediments from granitic or schist-gneiss sources. A binary mixing model employed on the polluted samples allowed estimating the anthropogenic inputs to the bay. These inputs represented between 25 and 98% of Pb inputs in intertidal samples, and 9-84% in subtidal samples, their contributions varying with time. Anthropogenic sources were apportioned according to a three-source model. Coal combustion-related emissions were the main anthropogenic source Pb to the bay (60-70%) before the establishment of the ceramic factory in the area (in the 1970s) which has since constituted the main source (95-100%), followed by petrol-related emissions. The Pb inputs history for the intertidal area was determined for the 20th century, and, for the subtidal area, the 19th and 20th centuries.

Complete electric dipole response and the neutron skin in 208Pb

A benchmark experiment on (208)Pb shows that polarized proton inelastic scattering at very forward angles including 0° is a powerful tool for high-resolution studies of electric dipole (E1) and spin magnetic dipole (M1) modes in nuclei over a broad excitation energy range to test up-to-date nuclear models. The extracted E1 polarizability leads to a neutron skin thickness r(skin) = 0.156(-0.021)(+0.025) fm in (208)Pb derived within a mean-field model [Phys. Rev. C 81, 051303 (2010)], thereby constraining the symmetry energy and its density dependence relevant to the description of neutron stars.