Absence of Low-Energy Shape Coexistence in ^{80}Ge: The Nonobservation of a Proposed Excited 0_{2}^{+} Level at 639 keV

The ^{80}Ge structure was investigated in a high-statistics β-decay experiment of ^{80}Ga using the GRIFFIN spectrometer at TRIUMF-ISAC through γ, β-e, e-γ, and γ-γ spectroscopy. No evidence was found for the recently reported 0_{2}^{+} 639-keV level suggested as evidence for low-energy shape coexistence in ^{80}Ge. Large-scale shell model calculations performed in ^{78,80,82}Ge place the 0_{2}^{+} level in ^{80}Ge at 2 MeV. The new experimental evidence combined with shell model predictions indicate that low-energy shape coexistence is not present in ^{80}Ge.

Erratum: Direct Observation of Proton Emission in ^{11}Be [Phys. Rev. Lett. 123, 082501 (2019)]

This corrects the article DOI: 10.1103/PhysRevLett.123.082501.

Direct Observation of Proton Emission in ^{11}Be

The elusive β^{-}p^{+} decay was observed in ^{11}Be by directly measuring the emitted protons and their energy distribution for the first time with the prototype Active Target Time Projection Chamber in an experiment performed at ISAC-TRIUMF. The measured β^{-}p^{+} branching ratio is orders of magnitude larger than any previous theoretical model predicted. This can be explained by the presence of a narrow resonance in ^{11}B above the proton separation energy.

Advances at TRIUMF-ISAC and decay of neutron-rich Cd studied with GRIFFIN

The β-decay half lives of nuclei near the r-process path are critical information required for abundance calculations, especially those near neutron number N = 82. Specifically, the nuclei below doubly-magic 132Sn are key, and play an important role in the formation and shape of the second r-process abundance peak. The half lives in this region are challenging to measure due to the significant β-delayed neutron decay branches and the population of isomeric states with half lives comparable to the ground states. However, by measuring the time distribution of γ rays, these complications can be eliminated. This requires, however, a very effcient γ-ray spectrometer since the production of isotopes in this region is very limited. The new GRIFFIN array at TRIUMF-ISAC provides the high effciency required for these measurements. Recent improvements in the quality of the beams produced at TRIUMF, employing the IG-LIS device, are outlined, as well as the current status of the ARIEL facility. The GRIFFIN spectrometer and its use are briefly described. The experiment to measure the half lives of 128-130Cd is outlined and the results given, and some examples of the power of GRIFFIN to expand decay schemes, specifically for the decay of 128Cd to 128In, are given.

Evolution of ELNES spectra as a function of experimental settings for any uniaxial specimen: A fully relativistic study

We perform calculations of the fully relativistic, corrected geometrical weighting of the pi* and sigma* transitions measured from the 1s core loss electron energy loss spectroscopy (EELS) spectrum in any uniaxial specimen. We present a complete calculation of the differential scattering cross-section (DSCS), taking into account the collection angle, the illumination angle and the tilt of the sample over the optical axis. Owing to high electron velocity in an EELS experiment, the relativistic correction has to be considered. We thus, present a relativistic, corrected DSCS by using the theory recently developed by Jouffrey et al. [Ultramicroscopy 102 (2004) 61] and P. Schattschneider et al. [Phys. Rev. B 72 (2005) 045142]. The relativistic correction is first performed in the natural coordinate system of the scattering event. We then point out a straightforward method to introduce this correction in the microscopic coordinate system, where all calculations have to be done to be experimentally useful. Using the fully corrected DSCS, we present an expression predicting the evolution of the R=pi*/(pi*+sigma*) ratio (related to the ratio of sp2 and sp3 bondings) as a function of experimental settings. We show how the R-evolution can be predicted, for any experimental setting, by the knowledge of one unique reference value. We verify on graphite specimens, the validity of the R-calculation by comparing theoretical predictions presented in this work with experimental data published elsewhere [Daniels et al., Ultramicroscopy 96 (2003) 523 and Menon et al., Ultramicroscopy 74 (1998) 83].

[Diet of an anecic earthworm from the Colombian savannas: questioning ecological groups]

An ecological classification based on a set of morphological characters may be used to describe earthworm functions in soil. However these relationships have been seldom verified. Gizzards of the earthworm Martiodrilus carimaguensis (Glossoscolecidae) were studied to find out if its anecic morphology was in agreement with its diet (shallow litter remains and deep organo-mineral material). By direct observation of 13 adults' gizzard contents with a dissecting and a phase contrast microscope, the volumetric percentage of plant fragments, roots, amorphous organic matter and mineral particles reached respectively 63, 5, 6.5 and 30% v/v. Eighty percent of plant fragments were microscopic, and mostly incorporated into the organo-mineral earthworm casts well preserved in the gizzard. Coprophagy and rhizophagy were the dominant feature of M. carimaguensis diet. Yet, the casts produced revealed a high variability in its diet, what could be related to transitional adoption of a typical anecic diet during some periods.

Control of catecholamine and serotonin release from the chromaffin tissue of the Atlantic hagfish

An in situ saline-perfused systemic heart/posterior cardinal vein preparation of the Atlantic hagfish (Myxine glutinosa) was used to assess (1) the ability of the chromaffin tissue to release catecholamines in response to adrenocorticotropic hormone (ACTH; 7.5 i.u. kg-1), serotonin (250 nmol kg-1), carbachol (100 µmol kg-1), [Asn1-Val5]angiotensin II (Ang II; 100 nmol kg-1), histamine (0.3­300 µmol l-1) and a high-[K+] saline (60 mmol l-1), (2) whether serotonin is co-released with the catecholamines of the chromaffin tissues, and (3) the potential modulatory effects of NECA, an adenosine receptor agonist, and DPSPX, an adenosine receptor antagonist, on catecholamine release. Bolus injections of ACTH, serotonin or carbachol, or perfusion with high-[K+] saline, all elicited the release of both adrenaline and noradrenaline. Pre-treatment with the serotonergic receptor antagonist methysergide or the cholinergic receptor antagonist hexamethonium abolished the serotonin- and carbachol-mediated catecholamine releases, respectively. Neither receptor antagonist affected the ACTH-mediated catecholamine release. Bolus injections of Ang II or perfusion with a range of histamine concentrations, two potent secretagogues in other vertebrates, did not elicit catecholamine secretion in hagfish. While injections of Ang II or perfusion with the high-[K+] saline both elicited the release of serotonin, treatments with ACTH, carbachol or histamine did not. Hence, co-release of catecholamines and serotonin was elicited by non-specific cell membrane depolarization using K+, but not by the specific secretagogues assessed in this study. The adenosine receptor agonist NECA and antagonist DPSPX significantly modified the secretory responses elicited by ACTH, serotonin and carbachol. The results suggest that adenosine may inhibit catecholamine release induced by serotonin or carbachol, while stimulating ACTH-induced release. Although the contribution of the different secretagogues identified in this study has yet to be explored in vivo, our results suggest that the control of catecholamine and serotonin release from the aneural chromaffin tissue of the Atlantic hagfish can be achieved through hormonal and/or paracrine means.

Adenosine receptor blockade and hypoxia-tolerance in rainbow trout and Pacific hagfish. I. Effects on anaerobic metabolism

The physiological properties of adenosine may be essential in the control of energy metabolism for the survival of animals exposed to oxygen shortages. Accordingly, we tested the hypothesis that adenosine modulates metabolic regulation in rainbow trout and Pacific hagfish exposed to acute hypoxia. Treatment of hypoxic rainbow trout (PwO2=3.33 or 4.00 kPa) with the adenosine receptor (AR) blocker theophylline was associated with greater increases in plasma [lactate], more rapid and pronounced metabolic acidosis, higher tissue [lactate], and lower heart creatine charge and glycogen content than in the hypoxic controls. The recruitment of anaerobic metabolism in hypoxic trout treated with enprofylline, an AR blocker with very weak affinity, was intermediate to that of the hypoxic theophylline-injected and control groups. In hagfish, plasma [lactate] increased following exposure to a PwO2 of 1.33 kPa but did not increase following exposure to 3.33 kPa and, like plasma acidosis, it was greatest in the animals treated with theophylline. These findings indicate that AR blockade results in a more rapid and pronounced recruitment of anaerobic metabolism following acute hypoxic exposure, and while rainbow trout and Pacific hagfish show marked differences in their responses to hypoxia, adenosine appears to play an important protective role in both species.

Adenosine receptor blockade and hypoxia-tolerance in rainbow trout and Pacific hagfish. II. Effects on plasma catecholamines and erythrocytes

The purpose of this study was to examine the role of adenosine receptors (ARs) in (1) the regulation of catecholamine secretion and (2) the modulation of blood oxygen capacitance by catecholamines. To this end, we assessed the response of rainbow trout and Pacific hagfish treated with either an AR blocker, theophylline, or saline under hypoxic and normoxic conditions. Compared with the control hypoxic rainbow trout, AR blockade resulted in a smaller increase in haematocrit and haemoglobin (Hb) concentration of the blood, smaller red blood cell transmembrane pH differences and mean cellular [Hb] (MCHC), as well as a 16-fold higher plasma adrenaline concentration after only 10 min of acute hypoxic exposure. In hypoxic hagfish, AR blockade had no effect on the [Hb] of the blood, and there was no regulation of red blood cell pH or changes in MCHC. However, whereas plasma [adrenaline] did not change following exposure to a PwO2 of 1.33 kPa in the hypoxic sham group, the concentration increased 3.8-fold within 10 min in the theophylline-injected group. These results suggest that adenosine modulates the circulating level of catecholamines in both hypoxic rainbow trout and hypoxic Pacific hagfish.