Search

The efficiency of the weak s process in low-metallicity rotating massive stars depends strongly on the rates of the competing ^{17}O(α,n)^{20}Ne and ^{17}O(α,γ)^{21}Ne reactions that determine the potency of the ^{16}O neutron poison. Their reaction rates are poorly known in the astrophysical energy range of interest for core helium burning in massive stars because of the lack of spectroscopic information (partial widths, spin parities) for the relevant states in the compound nucleus ^{21}Ne. In this Letter, we report on the first experimental determination of the α-particle spectroscopic factors and partial widths of these states using the ^{17}O(^{7}Li,t)^{21}Ne α-transfer reaction. With these the ^{17}O(α,n)^{20}Ne and ^{17}O(α,γ)^{21}Ne reaction rates were evaluated with uncertainties reduced by a factor more than 3 with respect to previous evaluations and the present ^{17}O(α,n)^{20}Ne reaction rate is more than 20 times larger. The present (α,n)/(α,γ) rate ratio favors neutron recycling and suggests an enhancement of the weak s process in the Zr-Nd region by more than 1.5 dex in metal-poor rotating massive stars.

Cultural confirmation following detection of a Listeria monocytogenespresumptive positive can take 3-7 days to finalize; this uncertainty is a point of frustration for food producers needing to make time-sensitive disposition decisions. To address the demand for shortened time-to-results, an alternative L. monocytogenes confirmation method consisting of two components, (i) a secondary screen using a different rapid method, and (ii) concurrent cultural isolation followed by next-day colony identification was evaluated. For the study, four food matrices (hot dogs, peanut butter, frozen vegetables, and multicomponent frozen meals) were inoculated with low levels (0.36-1.39 MPN/125 g) of L. monocytogenes per the AOAC guidelines for a matrix study. Analyses were performed on 125 g test portions and started with a PCR primary screen (Bio-Rad iQ-Check Listeria monocytogenes II). Next, all enriched food samples underwent a secondary screen by bioMérieux's GENE-UP LMO2 Real-Time PCR and VIDAS LMX ELFA along with streaking onto RAPID'L.mono Agar. Presumptive positive L. monocytogenes colonies were identified utilizing a high throughput rapid identification method (Hygiena's BAX System L. monocytogenes Real-Time PCR assay, Neogen's ANSR isothermal nucleic acid amplification assay, and Bruker's MALDI Biotyper). Importantly, this study evaluated multiple commercially available options for the secondary screen (n = 2) and rapid identification (n = 3) to allow for easy adoption by testing laboratories. Overall, there was no statistically significant difference (p ≤ 0.05) between the number of L. monocytogenes-positive 125 g samples obtained by the cultural reference method and the alternative confirmation methods (regardless of which method combinations were evaluated). Additionally, this study supports that, when both the primary and secondary screen methods yield a positive result, the sample could be considered a confirmed positive for L. monocytogenes., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.)