1
|
Precision Mass Measurement of the Proton Dripline Halo Candidate ^{22}Al. PHYSICAL REVIEW LETTERS 2024; 132:152501. [PMID: 38683002 DOI: 10.1103/physrevlett.132.152501] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/27/2023] [Accepted: 03/12/2024] [Indexed: 05/01/2024]
Abstract
We report the first mass measurement of the proton-halo candidate ^{22}Al performed with the low energy beam ion trap facility's 9.4 T Penning trap mass spectrometer at facility for rare isotope beams. This measurement completes the mass information for the lightest remaining proton-dripline nucleus achievable with Penning traps. ^{22}Al has been the subject of recent interest regarding a possible halo structure from the observation of an exceptionally large isospin asymmetry [J. Lee et al., Large isospin asymmetry in Si22/O22 Mirror Gamow-Teller transitions reveals the halo structure of ^{22}Al, Phys. Rev. Lett. 125, 192503 (2020).PRLTAO0031-900710.1103/PhysRevLett.125.192503]. The measured mass excess value of ME=18 092.5(3) keV, corresponding to an exceptionally small proton separation energy of S_{p}=100.4(8) keV, is compatible with the suggested halo structure. Our result agrees well with predictions from sd-shell USD Hamiltonians. While USD Hamiltonians predict deformation in the ^{22}Al ground state with minimal 1s_{1/2} occupation in the proton shell, a particle-plus-rotor model in the continuum suggests that a proton halo could form at large quadrupole deformation. These results emphasize the need for a charge radius measurement to conclusively determine the halo nature.
Collapse
|
2
|
NSCLC Digital PCR Panel Returns Low-Input Sample Results Where Sequencing Fails. Diagnostics (Basel) 2024; 14:243. [PMID: 38337759 PMCID: PMC10854965 DOI: 10.3390/diagnostics14030243] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2023] [Revised: 01/19/2024] [Accepted: 01/21/2024] [Indexed: 02/12/2024] Open
Abstract
Molecular diagnostics has drastically improved the survival rate of patients diagnosed with non-small cell lung cancer (NSCLC) over the last 10 years. Despite advancements in molecular testing, targeted therapies, and national guideline recommendations, more than half of NSCLC patients in the United States either never receive testing or patient care is not informed via molecular testing. Here, we sought to explore the relationship between DNA/RNA input, the molecular testing method, and test success rates. On a shared set of low-input reference test materials (n = 3), we ran both a hybrid capture-based, next-generation sequencing (NGS) assay and a multiplexed digital PCR (dPCR) panel. The dPCR panel was highly sensitive and specific for low-input samples in dilution studies ranging from 40 to 1 ng DNA and from 20 to 2.5 ng RNA, while NGS had up to an 86% loss in sensitivity as contrived sample inputs were serially diluted. The dPCR panel also demonstrated a high PPA (>95%) at diluted inputs as low as 15/7.5 ng DNA/RNA on 23 banked clinical samples with the same NGS hybrid capture assay at a high input. These data suggest that digital PCR is an accurate and effective way of identifying clinically relevant NSCLC mutations at low nucleotide input and quality.
Collapse
|
3
|
Social anxiety and interpersonal risk for suicidal ideation: A longitudinal daily diary analysis. Suicide Life Threat Behav 2023; 53:968-980. [PMID: 37638764 DOI: 10.1111/sltb.12996] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/07/2022] [Revised: 07/24/2023] [Accepted: 08/17/2023] [Indexed: 08/29/2023]
Abstract
INTRODUCTION Social anxiety is associated with elevated suicidal ideation (SI). One potential explanation is that socially anxious persons experience frequent interpersonal stressors that elicit SI. Longitudinal designs with temporal ordering are needed to adequately test this hypothesis. Therefore, this study leveraged a longitudinal design combining trait and daily reports. METHODS Two hundred eleven community adult participants with elevated levels of depression and/or social anxiety completed social anxiety and SI measures at baseline and again at a 1.5-month follow-up. Between these assessments, participants completed a 14-day diary study that assessed three forms of interpersonal distress: unfavorable social comparisons, perceived barriers to seeking social support, and loneliness. RESULTS As predicted, simple mediation models revealed that baseline social anxiety had a significant indirect effect on SI severity at 1.5 months postbaseline via unfavorable social comparisons (indirect effect: β = 0.07, p < 0.05) and barriers to seeking support (indirect effect: β = 0.08, p < 0.05); however, social anxiety did not have a significant indirect effect on SI severity through loneliness. CONCLUSION Study results are consistent with the proposition that increases in interpersonal distress may explain socially anxious persons' vulnerability to SI. Implications of these findings for the research, assessment, and treatment of suicidality in social anxiety are discussed.
Collapse
|
4
|
Analytical Performance and Concordance with Next-Generation Sequencing of a Rapid, Multiplexed dPCR Panel for the Detection of DNA and RNA Biomarkers in Non-Small-Cell Lung Cancer. Diagnostics (Basel) 2023; 13:3299. [PMID: 37958195 PMCID: PMC10650055 DOI: 10.3390/diagnostics13213299] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2023] [Revised: 10/18/2023] [Accepted: 10/20/2023] [Indexed: 11/15/2023] Open
Abstract
FDA approval of targeted therapies for lung cancer has significantly improved patient survival rates. Despite these improvements, barriers to timely access to biomarker information, such as nucleic acid input, still exist. Here, we report the analytical performance and concordance with next-generation sequencing (NGS) of a highly multiplexed research-use-only (RUO) panel using digital PCR (dPCR). The panel's analytical sensitivity and reactivity were determined using contrived DNA and RNA mixes. The limit of blank was established by testing FFPE curls classified as negative by pathology. Concordance was established on 77 FFPE samples previously characterized using the Oncomine Precision Assay®, and any discordant results were resolved with Archer Fusionplex® and Variantplex® panels. The analytical sensitivity, reported as the estimated mutant allele fraction (MAF), for DNA targets ranged from 0.1 to 0.9%. For RNA targets (ALK, RET, ROS, NTRK 1/2/3 Fusions, and MET Exon 14 skipping alteration), the analytical sensitivity ranged from 23 to 101 detected counts with 5 ng of total RNA input. The population prevalence-based coverage ranged from 89.2% to 100.0% across targets and exceeded 99.0% in aggregate. The assay demonstrated >97% concordance with respect to the comparator method.
Collapse
|
5
|
N=16 Magicity Revealed at the Proton Drip Line through the Study of ^{35}Ca. PHYSICAL REVIEW LETTERS 2023; 131:092501. [PMID: 37721823 DOI: 10.1103/physrevlett.131.092501] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2023] [Revised: 06/15/2023] [Accepted: 07/21/2023] [Indexed: 09/20/2023]
Abstract
The last proton bound calcium isotope ^{35}Ca has been studied for the first time, using the ^{37}Ca(p,t)^{35}Ca two neutron transfer reaction. The radioactive ^{37}Ca nuclei, produced by the LISE spectrometer at GANIL, interacted with the protons of the liquid hydrogen target CRYPTA, to produce tritons t that were detected in the MUST2 detector array, in coincidence with the heavy residues Ca or Ar. The atomic mass of ^{35}Ca and the energy of its first 3/2^{+} state are reported. A large N=16 gap of 4.61(11) MeV is deduced from the mass measurement, which together with other measured properties, makes ^{36}Ca a doubly magic nucleus. The N=16 shell gaps in ^{36}Ca and ^{24}O are of similar amplitude, at both edges of the valley of stability. This feature is discussed in terms of nuclear forces involved, within state-of-the-art shell model calculations. Even though the global agreement with data is quite convincing, the calculations underestimate the size of the N=16 gap in ^{36}Ca by 840 keV.
Collapse
|
6
|
^{138}Ba(d,α) Study of States in ^{136}Cs: Implications for New Physics Searches with Xenon Detectors. PHYSICAL REVIEW LETTERS 2023; 131:052501. [PMID: 37595245 DOI: 10.1103/physrevlett.131.052501] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2023] [Accepted: 07/07/2023] [Indexed: 08/20/2023]
Abstract
We used the ^{138}Ba(d,α) reaction to carry out an in-depth study of states in ^{136}Cs, up to around 2.5 MeV. In this Letter, we place emphasis on hitherto unobserved states below the first 1^{+} level, which are important in the context of solar neutrino and fermionic dark matter (FDM) detection in large-scale xenon-based experiments. We identify for the first time candidate metastable states in ^{136}Cs, which would allow a real-time detection of solar neutrino and FDM events in xenon detectors, with high background suppression. Our results are also compared with shell-model calculations performed with three Hamiltonians that were previously used to evaluate the nuclear matrix element (NME) for ^{136}Xe neutrinoless double beta decay. We find that one of these Hamiltonians, which also systematically underestimates the NME compared with the others, dramatically fails to describe the observed low-energy ^{136}Cs spectrum, while the other two show reasonably good agreement.
Collapse
|
7
|
β^{+} Gamow-Teller Strengths from Unstable ^{14}O via the (d,^{2}He) Reaction in Inverse Kinematics. PHYSICAL REVIEW LETTERS 2023; 130:232301. [PMID: 37354417 DOI: 10.1103/physrevlett.130.232301] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2022] [Revised: 04/14/2023] [Accepted: 05/05/2023] [Indexed: 06/26/2023]
Abstract
For the first time, the (d,^{2}He) reaction was successfully used in inverse kinematics to extract the Gamow-Teller transition strength in the β^{+} direction from an unstable nucleus. The new technique was made possible by the use of an active-target time-projection chamber and a magnetic spectrometer, and opens a path to addressing a range of scientific challenges, including in astrophysics and neutrino physics. In this Letter, the nucleus studied was ^{14}O, and the Gamow-Teller transition strength to ^{14}N was extracted up to an excitation energy of 22 MeV. The data were compared to shell-model and state-of-the-art coupled-cluster calculations. Shell-model calculations reproduce the measured Gamow-Teller strength distribution up to about 15 MeV reasonably well, after the application of a phenomenological quenching factor. In a significant step forward to better understand this quenching, the coupled-cluster calculation reproduces the full strength distribution well without such quenching, owing to the large model space, the inclusion of strong correlations, and the coupling of the weak interaction to two nucleons through two-body currents.
Collapse
|
8
|
Multiple Mechanisms in Proton-Induced Nucleon Removal at ∼100 MeV/Nucleon. PHYSICAL REVIEW LETTERS 2023; 130:172501. [PMID: 37172241 DOI: 10.1103/physrevlett.130.172501] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/08/2023] [Revised: 03/17/2023] [Accepted: 03/29/2023] [Indexed: 05/14/2023]
Abstract
We report on the first proton-induced single proton- and neutron-removal reactions from the neutron-deficient ^{14}O nucleus with large Fermi-surface asymmetry S_{n}-S_{p}=18.6 MeV at ∼100 MeV/nucleon, a widely used energy regime for rare-isotope studies. The measured inclusive cross sections and parallel momentum distributions of the ^{13}N and ^{13}O residues are compared to the state-of-the-art reaction models, with nuclear structure inputs from many-body shell-model calculations. Our results provide the first quantitative contributions of multiple reaction mechanisms including the quasifree knockout, inelastic scattering, and nucleon transfer processes. It is shown that the inelastic scattering and nucleon transfer, usually neglected at such energy regime, contribute about 50% and 30% to the loosely bound proton and deeply bound neutron removal, respectively. These multiple reaction mechanisms should be considered in analyses of inclusive one-nucleon removal cross sections measured at intermediate energies for quantitative investigation of single-particle strengths and correlations in atomic nuclei.
Collapse
|
9
|
Direct Measurement of Hexacontatetrapole, E6 γ Decay from ^{53m}Fe. PHYSICAL REVIEW LETTERS 2023; 130:122503. [PMID: 37027850 DOI: 10.1103/physrevlett.130.122503] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2022] [Accepted: 02/09/2023] [Indexed: 06/19/2023]
Abstract
The only proposed observation of a discrete, hexacontatetrapole (E6) transition in nature occurs from the T_{1/2}=2.54(2)-min decay of ^{53m}Fe. However, there are conflicting claims concerning its γ-decay branching ratio, and a rigorous interrogation of γ-ray sum contributions is lacking. Experiments performed at the Australian Heavy Ion Accelerator Facility were used to study the decay of ^{53m}Fe. For the first time, sum-coincidence contributions to the weak E6 and M5 decay branches have been firmly quantified using complementary experimental and computational methods. Agreement across the different approaches confirms the existence of the real E6 transition; the M5 branching ratio and transition rate have also been revised. Shell model calculations performed in the full fp model space suggest that the effective proton charge for high-multipole, E4 and E6, transitions is quenched to approximately two-thirds of the collective E2 value. Correlations between nucleons may offer an explanation of this unexpected phenomenon, which is in stark contrast to the collective nature of lower-multipole, electric transitions observed in atomic nuclei.
Collapse
|
10
|
Dissipative Reactions with Intermediate-Energy Beams: A Novel Approach to Populate Complex-Structure States in Rare Isotopes. PHYSICAL REVIEW LETTERS 2022; 129:242501. [PMID: 36563248 DOI: 10.1103/physrevlett.129.242501] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/27/2022] [Revised: 10/11/2022] [Accepted: 11/18/2022] [Indexed: 06/17/2023]
Abstract
A novel pathway for the formation of multiparticle-multihole excited states in rare isotopes is reported from highly energy- and momentum-dissipative inelastic-scattering events measured in reactions of an intermediate-energy beam of ^{38}Ca on a Be target. The negative-parity, complex-structure final states in ^{38}Ca are observed following the in-beam γ-ray spectroscopy of events in the ^{9}Be(^{38}Ca,^{38}Ca+γ)X reaction in which the scattered projectile loses longitudinal momentum of order Δp_{||}=700 MeV/c. The characteristics of the observed final states are discussed and found to be consistent with the formation of excited states involving the rearrangement of multiple nucleons in a single, highly energetic projectile-target collision. Unlike the far-less-dissipative, surface-grazing reactions usually exploited for the in-beam γ-ray spectroscopy of rare isotopes, these more energetic collisions appear to offer a practical pathway to nuclear-structure studies of more complex multiparticle configurations in rare isotopes-final states conventionally thought to be out of reach with high-luminosity fast-beam-induced reactions.
Collapse
|
11
|
Psychological well-being in US veterans with non-fatal suicide attempts: A multi-cohort population-based study. J Affect Disord 2022; 314:34-43. [PMID: 35803391 DOI: 10.1016/j.jad.2022.07.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/04/2022] [Revised: 06/28/2022] [Accepted: 07/01/2022] [Indexed: 11/25/2022]
Abstract
BACKGROUND Most people who survive suicide attempts neither re-attempt suicide nor die by suicide. Research on suicide attempt survivors has primarily focused on negative endpoints (e.g., increased suicide risk) rather than positive outcomes. One important outcome is psychological well-being (PWB), defined as positive functioning across emotional, intrapersonal, and interpersonal domains. We compared PWB among US military veterans with (i.e., attempt survivors) and without (i.e., non-attempters) a history of suicide attempt(s) using data from three nationally representative cohorts. METHODS Each US veteran cohort (Cohort1: N = 3148; Cohort2: N = 1474; Cohort3: N = 4042) completed measures of suicidality (e.g., attempt history), character strengths (e.g., curiosity, optimism), psychological symptoms (e.g., depression), and indicators of PWB (e.g., happiness). t-Tests were conducted to examine group differences in PWB; hierarchical regressions were conducted to examine suicide attempt status as a predictor of PWB controlling for symptoms and demographics. Multivariable regressions were conducted to identify predictors of PWB among attempt survivors. RESULTS In each cohort, reported PWB was markedly lower among suicide attempt survivors than non-attempters (ds = 0.9-1.2), even after adjusting for mental health symptoms. Individual differences in PWB were observed, with a subset of suicide attempt survivors reporting higher PWB levels than non-attempters (1.4-7.4 %). Curiosity and optimism were positively associated with PWB among suicide attempt survivors (rs = 0.60-0.78). LIMITATIONS Data were cross-sectional, limiting inferences about causation and directionality of associations. CONCLUSIONS Findings highlight diminished PWB as an important and understudied concern among veteran attempt survivors. Collectively, our findings underscore the importance of considering PWB in the research, assessment, and treatment of suicidality.
Collapse
|
12
|
Structure of ^{36}Ca under the Coulomb Magnifying Glass. PHYSICAL REVIEW LETTERS 2022; 129:122501. [PMID: 36179171 DOI: 10.1103/physrevlett.129.122501] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2021] [Revised: 05/05/2022] [Accepted: 08/08/2022] [Indexed: 06/16/2023]
Abstract
Detailed spectroscopy of the neutron-deficient nucleus ^{36}Ca was obtained up to 9 MeV using the ^{37}Ca(p,d)^{36}Ca and the ^{38}Ca(p,t)^{36}Ca transfer reactions. The radioactive nuclei, produced by the LISE spectrometer at GANIL, interacted with the protons of the liquid hydrogen target CRYPTA, to produce light ejectiles (the deuteron d or triton t) that were detected in the MUST2 detector array, in coincidence with the heavy residues identified by a zero-degree detection system. Our main findings are (i) a similar shift in energy for the 1_{1}^{+} and 2_{1}^{+} states by about -250 keV, as compared with the mirror nucleus ^{36}S; (ii) the discovery of an intruder 0_{2}^{+} state at 2.83(13) MeV, which appears below the first 2^{+} state, in contradiction with the situation in ^{36}S; and (iii) a tentative 0_{3}^{+} state at 4.83(17) MeV, proposed to exhibit a bubble structure with two neutron vacancies in the 2s_{1/2} orbit. The inversion between the 0_{2}^{+} and 2_{1}^{+} states is due to the large mirror energy difference (MED) of -516(130) keV for the former. This feature is reproduced by shell model calculations, using the sd-pf valence space, predicting an almost pure intruder nature for the 0_{2}^{+} state, with two protons (neutrons) being excited across the Z=20 magic closure in ^{36}Ca (^{36}S). This mirror system has the largest MEDs ever observed, if one excludes the few cases induced by the effect of the continuum.
Collapse
|
13
|
Motives and Consequences of Alcohol Use in People With Social Anxiety Disorder: A Daily Diary Study. Behav Ther 2022; 53:600-613. [PMID: 35697425 DOI: 10.1016/j.beth.2022.01.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/28/2021] [Revised: 01/12/2022] [Accepted: 01/13/2022] [Indexed: 11/02/2022]
Abstract
People with social anxiety disorder (SAD) are at increased risk for alcohol-related problems. Most research exploring social anxiety and alcohol use has examined negative drinking consequences, with less consideration of positive consequences-namely positive social experiences-that may reinforce alcohol use. In this daily diary study, we examined how adults diagnosed with SAD (N = 26) and a psychologically healthy control group (N = 28) experienced positive drinking consequences in naturally occurring drinking episodes during the study period. For 14 consecutive days, participants answered questions about alcohol use, motives for drinking, and positive consequences of drinking. On days when participants drank, those with SAD were more likely than healthy controls to perceive a reduction in anxiety, but the two groups did not differ in their likelihood of experiencing positive social drinking consequences. For both groups, on days when they were more motivated to drink to enhance social experiences (affiliation motives) or cope with distress (coping motives), they were more likely to obtain positive consequences from drinking. Compared to controls, participants with SAD endorsed stronger trait and daily coping motives (anxiety-coping, social anxiety-coping, and depression-coping). Results are discussed in the context of reinforcement mechanisms that may maintain social anxiety and alcohol use.
Collapse
|
14
|
Constraining the ^{30}P(p, γ)^{31}S Reaction Rate in ONe Novae via the Weak, Low-Energy, β-Delayed Proton Decay of ^{31}Cl. PHYSICAL REVIEW LETTERS 2022; 128:182701. [PMID: 35594108 DOI: 10.1103/physrevlett.128.182701] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2021] [Revised: 01/14/2022] [Accepted: 04/04/2022] [Indexed: 06/15/2023]
Abstract
The ^{30}P(p,γ)^{31}S reaction plays an important role in understanding the nucleosynthesis of A≥30 nuclides in oxygen-neon novae. The Gaseous Detector with Germanium Tagging was used to measure ^{31}Cl β-delayed proton decay through the key J^{π}=3/2^{+}, 260-keV resonance. The intensity I_{βp}^{260}=8.3_{-0.9}^{+1.2}×10^{-6} represents the weakest β-delayed, charged-particle emission ever measured below 400 keV, resulting in a proton branching ratio of Γ_{p}/Γ=2.5_{-0.3}^{+0.4}×10^{-4}. By combining this measurement with shell-model calculations for Γ_{γ} and past work on other resonances, the total ^{30}P(p,γ)^{31}S rate has been determined with reduced uncertainty. The new rate has been used in hydrodynamic simulations to model the composition of nova ejecta, leading to a concrete prediction of ^{30}Si:^{28}Si excesses in presolar nova grains and the calibration of nuclear thermometers.
Collapse
|
15
|
How do people with social anxiety disorder manage daily stressors? Deconstructing emotion regulation flexibility in daily life. JOURNAL OF AFFECTIVE DISORDERS REPORTS 2021. [DOI: 10.1016/j.jadr.2021.100210] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
|
16
|
4D-imaging of drip-line radioactivity by detecting proton emission from 54mNi pictured with ACTAR TPC. Nat Commun 2021; 12:4805. [PMID: 34376669 PMCID: PMC8355099 DOI: 10.1038/s41467-021-24920-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2020] [Accepted: 07/01/2021] [Indexed: 11/16/2022] Open
Abstract
Proton radioactivity was discovered exactly 50 years ago. First, this nuclear decay mode sets the limit of existence on the nuclear landscape on the neutron-deficient side. Second, it comprises fundamental aspects of both quantum tunnelling as well as the coupling of (quasi)bound quantum states with the continuum in mesoscopic systems such as the atomic nucleus. Theoretical approaches can start either from bound-state nuclear shell-model theory or from resonance scattering. Thus, proton-radioactivity guides merging these types of theoretical approaches, which is of broader relevance for any few-body quantum system. Here, we report experimental measurements of proton-emission branches from an isomeric state in 54mNi, which were visualized in four dimensions in a newly developed detector. We show that these decays, which carry an unusually high angular momentum, ℓ = 5 and ℓ = 7, respectively, can be approximated theoretically with a potential model for the proton barrier penetration and a shell-model calculation for the overlap of the initial and final wave functions. Proton radioactivity is useful for studying nuclear structure. Here the authors report two proton emission branches from the 10+ state isomer of 54mNi by using a time projection chamber.
Collapse
|
17
|
New ^{59}Fe Stellar Decay Rate with Implications for the ^{60}Fe Radioactivity in Massive Stars. PHYSICAL REVIEW LETTERS 2021; 126:152701. [PMID: 33929230 DOI: 10.1103/physrevlett.126.152701] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2020] [Revised: 02/20/2021] [Accepted: 03/17/2021] [Indexed: 06/12/2023]
Abstract
The discrepancy between observations from γ-ray astronomy of the ^{60}Fe/^{26}Al γ-ray flux ratio and recent calculations is an unresolved puzzle in nuclear astrophysics. The stellar β-decay rate of ^{59}Fe is one of the major nuclear uncertainties impeding us from a precise prediction. The important Gamow-Teller strengths from the low-lying states in ^{59}Fe to the ^{59}Co ground state are measured for the first time using the exclusive measurement of the ^{59}Co(t,^{3}He+γ)^{59}Fe charge-exchange reaction. The new stellar decay rate of ^{59}Fe is a factor of 3.5±1.1 larger than the currently adopted rate at T=1.2 GK. Stellar evolution calculations show that the ^{60}Fe production yield of an 18 solar mass star is decreased significantly by 40% when using the new rate. Our result eliminates one of the major nuclear uncertainties in the predicted yield of ^{60}Fe and alleviates the existing discrepancy of the ^{60}Fe/^{26}Al ratio.
Collapse
|
18
|
Does negative emotion differentiation influence how people choose to regulate their distress after stressful events? A four-year daily diary study. ACTA ACUST UNITED AC 2021; 21:1000-1012. [PMID: 33829837 DOI: 10.1037/emo0000969] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Much is known about the types of strategies people use to regulate emotions. Less is known about individual differences that influence emotion regulation strategy selection. In this study, we tested the moderating role of negative emotion differentiation (NED; i.e., the ability to label and describe subtle differences among negative emotions) on the relationship between the intensity of stressful daily events and the strategies used to regulate distress arising from these events. Prior research shows that NED is associated with low endorsement of disengagement emotion regulation (e.g., substance use), but less is known about the link to engagement regulation (e.g., problem-solving, seeking social support). Participants were college students (N = 502) completing a 30-day daily diary survey for each of four college years. We preregistered hypotheses that 1) the intensity of each day's most stressful event would be associated with greater use of disengagement and engagement regulation strategies, and 2) people higher in NED would be less likely to use disengagement and more likely to use engagement strategies when highly stressed. Results suggest that higher stress intensity is associated with greater use of all regulation strategies. Greater NED is associated with less use of disengagement regulation strategies, whereas NED was unrelated to engagement regulation strategies and did not moderate the relationship between stress and engagement strategies. The majority of hypothesized moderation effects of NED were nonsignificant, prompting a reconsideration of whether, when, and how NED plays a role in stress responding. (PsycInfo Database Record (c) 2021 APA, all rights reserved).
Collapse
|
19
|
Precision Mass Measurements of Neutron-Rich Scandium Isotopes Refine the Evolution of N=32 and N=34 Shell Closures. PHYSICAL REVIEW LETTERS 2021; 126:042501. [PMID: 33576685 DOI: 10.1103/physrevlett.126.042501] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/01/2020] [Revised: 09/28/2020] [Accepted: 12/14/2020] [Indexed: 06/12/2023]
Abstract
We report high-precision mass measurements of ^{50-55}Sc isotopes performed at the LEBIT facility at NSCL and at the TITAN facility at TRIUMF. Our results provide a substantial reduction of their uncertainties and indicate significant deviations, up to 0.7 MeV, from the previously recommended mass values for ^{53-55}Sc. The results of this work provide an important update to the description of emerging closed-shell phenomena at neutron numbers N=32 and N=34 above proton-magic Z=20. In particular, they finally enable a complete and precise characterization of the trends in ground state binding energies along the N=32 isotone, confirming that the empirical neutron shell gap energies peak at the doubly magic ^{52}Ca. Moreover, our data, combined with other recent measurements, do not support the existence of a closed neutron shell in ^{55}Sc at N=34. The results were compared to predictions from both ab initio and phenomenological nuclear theories, which all had success describing N=32 neutron shell gap energies but were highly disparate in the description of the N=34 isotone.
Collapse
|
20
|
Exploiting Isospin Symmetry to Study the Role of Isomers in Stellar Environments. PHYSICAL REVIEW LETTERS 2021; 126:042701. [PMID: 33576674 DOI: 10.1103/physrevlett.126.042701] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/23/2020] [Revised: 11/23/2020] [Accepted: 01/12/2021] [Indexed: 06/12/2023]
Abstract
Proton capture on the excited isomeric state of ^{26}Al strongly influences the abundance of ^{26}Mg ejected in explosive astronomical events and, as such, plays a critical role in determining the initial content of radiogenic ^{26}Al in presolar grains. This reaction also affects the temperature range for thermal equilibrium between the ground and isomeric levels. We present a novel technique, which exploits the isospin symmetry of the nuclear force, to address the long-standing challenge of determining proton-capture rates on excited nuclear levels. Such a technique has in-built tests that strongly support its veracity and, for the first time, we have experimentally constrained the strengths of resonances that dominate the astrophysical ^{26m}Al(p,γ)^{27}Si reaction. These constraints demonstrate that the rate is at least a factor ∼8 lower than previously expected, indicating an increase in the stellar production of ^{26}Mg and a possible need to reinvestigate sensitivity studies involving the thermal equilibration of ^{26}Al.
Collapse
|
21
|
Shape Changes in the N=28 Island of Inversion: Collective Structures Built on Configuration-Coexisting States in ^{43}S. PHYSICAL REVIEW LETTERS 2020; 125:232501. [PMID: 33337204 DOI: 10.1103/physrevlett.125.232501] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2020] [Revised: 10/06/2020] [Accepted: 10/30/2020] [Indexed: 06/12/2023]
Abstract
The neutron-rich nuclei in the N=28 island of inversion have attracted considerable experimental and theoretical attention, providing great insight into the evolution of shell structure and nuclear shape in exotic nuclei. In this work, for the first time, quadrupole collectivity is assessed simultaneously on top of the 3/2^{-} ground state and the 7/2^{-} shape-coexisting isomer of ^{43}S, putting the unique interpretation of shape and configuration coexistence at N=27 and 28 in the sulfur isotopic chain to the test. From an analysis of the electromagnetic transition strengths and quadrupole moments predicted within the shell model, it is shown that the onset of shape coexistence and the emergence of a simple collective structure appear suddenly in ^{43}S with no indication of such patterns in the N=27 isotone ^{45}Ar.
Collapse
|
22
|
Accessing the Single-Particle Structure of the Pygmy Dipole Resonance in ^{208}Pb. PHYSICAL REVIEW LETTERS 2020; 125:102503. [PMID: 32955313 DOI: 10.1103/physrevlett.125.102503] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2020] [Accepted: 07/28/2020] [Indexed: 06/11/2023]
Abstract
New experimental data on the neutron single-particle character of the Pygmy Dipole Resonance (PDR) in ^{208}Pb are presented. They were obtained from (d,p) and resonant proton scattering experiments performed at the Q3D spectrograph of the Maier-Leibnitz Laboratory in Garching, Germany. The new data are compared to the large suite of complementary, experimental data available for ^{208}Pb and establish (d,p) as an additional, valuable, experimental probe to study the PDR and its collectivity. Besides the single-particle character of the states, different features of the strength distributions are discussed and compared to large-scale shell model (LSSM) and energy-density functional plus quasiparticle-phonon model theoretical approaches to elucidate the microscopic structure of the PDR in ^{208}Pb.
Collapse
|
23
|
Discovery of an Exceptionally Strong β-Decay Transition of ^{20}F and Implications for the Fate of Intermediate-Mass Stars. PHYSICAL REVIEW LETTERS 2019; 123:262701. [PMID: 31951442 DOI: 10.1103/physrevlett.123.262701] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/22/2019] [Revised: 08/15/2019] [Indexed: 06/10/2023]
Abstract
A significant fraction of stars between 7 and 11 solar masses are thought to become supernovae, but the explosion mechanism is unclear. The answer depends critically on the rate of electron capture on ^{20}Ne in the degenerate oxygen-neon stellar core. However, because of the unknown strength of the transition between the ground states of ^{20}Ne and ^{20}F, it has not previously been possible to fully constrain the rate. By measuring the transition, we establish that its strength is exceptionally large and that it enhances the capture rate by several orders of magnitude. This has a decisive impact on the evolution of the core, increasing the likelihood that the star is (partially) disrupted by a thermonuclear explosion rather than collapsing to form a neutron star. Importantly, our measurement resolves the last remaining nuclear physics uncertainty in the final evolution of degenerate oxygen-neon stellar cores, allowing future studies to address the critical role of convection, which at present is poorly understood.
Collapse
|
24
|
Abstract
Abstract
Background
Myocardial infarction (MI) and hypertension lead to myocardial injury, which induces negative remodelling and cardiac fibrosis. Cardiac fibrosis, which involves inflammatory cell infiltration and myofibroblast activation, causes worldwide mortality and morbidity. In response to MI or hypertension induced by prolonged angiotensin II (AngII) exposure, activated myofibroblasts produce extracellular matrix proteins. However, if unchecked, excessive collagen deposition occurs leading to myocardial stiffening, heart failure and arrhythmias.
Purpose
The underlying mechanisms leading to pathological collagen deposition are not fully elucidated. There is debate regarding the involvement of the Wnt signalling pathway and its product Wnt Inducible Signalling pathway protein-1 (WISP-1) in cardiac fibrosis. Therefore, this project aimed to investigate the interaction of AngII and the Wnt/β-catenin signalling pathway in cardiac fibrosis.
Methods
The effect of AngII (100nM) on collagen levels in human cardiac fibroblasts was investigated in vitro (data expressed as fold change from control ± SEM). In vivo experiments (n=6–8) determined the involvement of the Wnt/b-catenin pathway, specifically WISP-1, in response to AngII infusion (500ng/kg/min) for 4 weeks (Apolipoprotein E−/−/WISP-1+/+ vs. ApolipoproteinE−/−/WISP-1−/− mice on a high-fat diet, data expressed as mean positive pixel % ± SEM).
Results
AngII significantly increased collagen type 1 protein levels produced by human cardiac fibroblasts (2.94±0.75 vs 1±0, p<0.05). Inhibition of Wnt/b-catenin signalling with 25nM iCRT14 significantly suppressed AngII-induced collagen levels (0.46±0.07 vs. 1±0, p<0.05). As expected, AngII infusion significantly induced hypertension in all mice. Immunohistochemistry demonstrated type 1 collagen was markedly higher in AngII mice than control mice (1.07±0.27 vs. 0.29±0.06, p<0.05). However, in the absence of WISP-1, AngII did not enhance collagen type 1 levels. Further immunohistochemical analysis of murine hearts demonstrated that AngII infusion caused significant alterations in the Wnt/β-catenin signalling markers AXIN-2 (35±3.9 vs. 10.7±2.6 p<0.05) and PPAR-d (92±1.4 vs. 17.3±4.3 p<0.05). This effect was reduced by WISP-1 deletion. Furthermore, AngII-infusion disrupted N-cadherin junctions (0.55±0.08 vs. 0.29±0.02 p<0.05) suggesting modulation of cell-to-cell contacts and enhanced β-catenin signalling.
Conclusion
This study indicates that AngII enhances cardiac fibrosis via modulation of the Wnt signalling pathway, in part via WISP-1. Further delineation of this interaction may lead to the use of Wnt/β-catenin or WISP-1 inhibitors to suppress myocardial injury induced cardiac fibrosis in post-MI or hypertensive patients.
Acknowledgement/Funding
Elizabeth Blackwell Institute, British Heart Foundation
Collapse
|
25
|
Constraining the Neutron Star Compactness: Extraction of the ^{23}Al(p,γ) Reaction Rate for the rp Process. PHYSICAL REVIEW LETTERS 2019; 122:232701. [PMID: 31298878 DOI: 10.1103/physrevlett.122.232701] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/28/2019] [Revised: 04/10/2019] [Indexed: 06/10/2023]
Abstract
The ^{23}Al(p,γ)^{24}Si reaction is among the most important reactions driving the energy generation in type-I x-ray bursts. However, the present reaction-rate uncertainty limits constraints on neutron star properties that can be achieved with burst model-observation comparisons. Here, we present a novel technique for constraining this important reaction by combining the GRETINA array with the neutron detector LENDA coupled to the S800 spectrograph at the National Superconducting Cyclotron Laboratory. The ^{23}Al(d,n) reaction was used to populate the astrophysically important states in ^{24}Si. This enables a measurement in complete kinematics for extracting all relevant inputs necessary to calculate the reaction rate. For the first time, a predicted close-lying doublet of a 2_{2}^{+} and (4_{1}^{+},0_{2}^{+}) state in ^{24}Si was disentangled, finally resolving conflicting results from two previous measurements. Moreover, it was possible to extract spectroscopic factors using GRETINA and LENDA simultaneously. This new technique may be used to constrain other important reaction rates for various astrophysical scenarios.
Collapse
|
26
|
Is the Structure of ^{42}Si Understood? PHYSICAL REVIEW LETTERS 2019; 122:222501. [PMID: 31283300 DOI: 10.1103/physrevlett.122.222501] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/12/2019] [Revised: 04/23/2019] [Indexed: 06/09/2023]
Abstract
A more detailed test of the implementation of nuclear forces that drive shell evolution in the pivotal nucleus ^{42}Si-going beyond earlier comparisons of excited-state energies-is important. The two leading shell-model effective interactions, SDPF-MU and SDPF-U-Si, both of which reproduce the low-lying ^{42}Si(2_{1}^{+}) energy, but whose predictions for other observables differ significantly, are interrogated by the population of states in neutron-rich ^{42}Si with a one-proton removal reaction from ^{43}P projectiles at 81 MeV/nucleon. The measured cross sections to the individual ^{42}Si final states are compared to calculations that combine eikonal reaction dynamics with these shell-model nuclear structure overlaps. The differences in the two shell-model descriptions are examined and linked to predicted low-lying excited 0^{+} states and shape coexistence. Based on the present data, which are in better agreement with the SDPF-MU calculations, the state observed at 2150(13) keV in ^{42}Si is proposed to be the (0_{2}^{+}) level.
Collapse
|
27
|
Enhanced Electric Dipole Strength for the Weakly Bound States in ^{27}Ne. PHYSICAL REVIEW LETTERS 2018; 121:262501. [PMID: 30636164 DOI: 10.1103/physrevlett.121.262501] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2018] [Revised: 11/07/2018] [Indexed: 06/09/2023]
Abstract
An enhanced low-energy electric dipole (E1) strength is identified for the weakly bound excited states of the neutron-rich isotope ^{27}Ne. The Doppler-shift lifetime measurements employing a combination of the γ-ray tracking array GRETINA, the plunger device, and the S800 spectrograph determine the lower limit of 0.030 e^{2} fm^{2} or 0.052 W.u. for the 1/2^{+}→3/2^{-} E1 transition in ^{27}Ne, representing one of the strongest E1 strengths observed among the bound discrete states in this mass region. This value is at least 30 times larger than that measured for the 3/2^{-} decay to the 3/2_{gs}^{+} ground state. A comparison of the present results to large-scale shell-model calculations points to an important role of core excitations and deformation in the observed E1 enhancement, suggesting a novel example of the electric dipole modes manifested in weakly bound deformed systems.
Collapse
|
28
|
Carotid artery ligation induced intimal thickening and proliferation is unaffected by ageing. J Cell Commun Signal 2018; 12:529-537. [PMID: 29185213 PMCID: PMC6039339 DOI: 10.1007/s12079-017-0431-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2017] [Accepted: 10/27/2017] [Indexed: 01/20/2023] Open
Abstract
Following interventions to treat atherosclerosis, such as coronary artery bypass graft surgery, restenosis occurs in approximately 40% of patients. Identification of proteins regulating intimal thickening could represent targets to prevent restenosis. Our group previously demonstrated that in a murine model of vascular occlusion, Wnt4 protein expression and β-catenin signalling was upregulated which promoted vascular smooth muscle cell (VSMC) proliferation and intimal thickening. In this study, the effect of age on VSMC proliferation, intimal hyperplasia and Wnt4 expression was investigated. In vitro proliferation of VSMCs isolated from young (2 month) or old (18-20 month) C57BL6/J mice was assessed by immunocytochemistry for EdU incorporation. As previously reported, 400 ng/mL recombinant Wnt4 protein increased proliferation of VSMCs from young mice. However, this response was absent in VSMCs from old mice. As our group previously reported reduced intimal hyperplasia in Wnt4+/- mice compared to wildtype controls, we hypothesised that impaired Wnt4 signalling with age may result in reduced neointimal formation. To investigate this, carotid artery ligation was performed in young and old mice and neointimal area was assessed 21 days later. Surprisingly, neointimal area and percentage lumen occlusion were not significantly affected by age. Furthermore, neointimal cell density and proliferation were also unchanged. These data suggest that although Wnt4-mediated proliferation was impaired with age in primary VSMCs, carotid artery ligation induced neointimal formation and proliferation were unchanged in old mice. These results imply that Wnt4-mediated proliferation is unaffected by age in vivo, suggesting that therapeutic Wnt4 inhibition could inhibit restenosis in patients of all ages.
Collapse
|
29
|
Lifetime Measurements and Triple Coexisting Band Structure in ^{43}S. PHYSICAL REVIEW LETTERS 2018; 121:012501. [PMID: 30028163 DOI: 10.1103/physrevlett.121.012501] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/2018] [Revised: 05/07/2018] [Indexed: 06/08/2023]
Abstract
Lifetime measurements of excited states in the neutron-rich nucleus ^{43}S were performed by applying the recoil-distance method on fast rare-isotope beams in conjunction with the Gamma-Ray Energy Tracking In-beam Nuclear Array. The new data based on γγ coincidences and lifetime measurements resolve a doublet of (3/2^{-}) and (5/2^{-}) states at low excitation energies. Results were compared to the π(sd)-ν(pf) shell model and antisymmetrized molecular dynamics calculations. The consistency with the theoretical calculations identifies a possible appearance of three coexisting bands near the ground state of ^{43}S: the K^{π}=1/2^{-} band built on a prolate-deformed ground state, a band built on an isomer with a 1f_{7/2}^{-1} character, and a suggested excited band built on a newly discovered doublet state. The latter further confirms the collapse of the N=28 shell closure in the neutron-rich region.
Collapse
|
30
|
Nuclear Matrix Elements for Tests of Local Lorentz Invariance Violation. PHYSICAL REVIEW LETTERS 2017; 119:192504. [PMID: 29219490 DOI: 10.1103/physrevlett.119.192504] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/18/2016] [Indexed: 06/07/2023]
Abstract
The nuclear matrix elements for the spin operator and the momentum quadrupole operator are important for the interpretation of precision atomic physics experiments that search for violations of local Lorentz and CPT symmetry and for new spin-dependent forces. We use the configuration-interaction nuclear shell model and self-consistent mean-field theory to calculate the momentum matrix elements for ^{21}Ne, ^{23}Na, ^{133}Cs, ^{173}Yb, and ^{201}Hg. We show that these momentum matrix are strongly suppressed by the many-body correlations, in contrast to the well-known enhancement of the spatial quadrupole nuclear matrix elements.
Collapse
|
31
|
Protein kinase CK2 inhibition suppresses neointima formation via a proline-rich homeodomain-dependent mechanism. Vascul Pharmacol 2017; 99:34-44. [PMID: 28927755 PMCID: PMC5718878 DOI: 10.1016/j.vph.2017.09.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2017] [Revised: 09/05/2017] [Accepted: 09/14/2017] [Indexed: 11/19/2022]
Abstract
Neointimal hyperplasia is a product of VSMC replication and consequent accumulation within the blood vessel wall. In this study, we determined whether inhibition of protein kinase CK2 and the resultant stabilisation of proline-rich homeodomain (PRH) could suppress VSMC proliferation. Both silencing and pharmacological inhibition of CK2 with K66 antagonised replication of isolated VSMCs. SiRNA-induced knockdown as well as ectopic overexpression of proline-rich homeodomain indicated that PRH disrupts cell cycle progression. Mutation of CK2 phosphorylation sites Ser163 and Ser177 within the PRH homeodomain enabled prolonged cell cycle arrest by PRH. Concomitant knockdown of PRH and inhibition of CK2 with K66 indicated that the anti-proliferative action of K66 required the presence of PRH. Both K66 and adenovirus-mediated gene transfer of S163C:S177C PRH impaired neointima formation in human saphenous vein organ cultures. Importantly, neither intervention had notable effects on cell cycle progression, cell survival or migration in cultured endothelial cells.
Collapse
MESH Headings
- Animals
- Casein Kinase II/antagonists & inhibitors
- Casein Kinase II/genetics
- Casein Kinase II/metabolism
- Cell Cycle Checkpoints/drug effects
- Cell Proliferation/drug effects
- Cells, Cultured
- Homeodomain Proteins/genetics
- Homeodomain Proteins/metabolism
- Human Umbilical Vein Endothelial Cells/drug effects
- Human Umbilical Vein Endothelial Cells/enzymology
- Humans
- Hyperplasia
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/enzymology
- Muscle, Smooth, Vascular/pathology
- Mutation
- Myocytes, Smooth Muscle/drug effects
- Myocytes, Smooth Muscle/enzymology
- Myocytes, Smooth Muscle/pathology
- Neointima
- Phosphorylation
- Proline-Rich Protein Domains
- Protein Kinase Inhibitors/pharmacology
- RNA Interference
- Rats
- Saphenous Vein/drug effects
- Saphenous Vein/enzymology
- Saphenous Vein/pathology
- Signal Transduction/drug effects
- Tissue Culture Techniques
- Transcription Factors/genetics
- Transcription Factors/metabolism
- Transfection
Collapse
|
32
|
Observation of the Isovector Giant Monopole Resonance via the ^{28}Si(^{10}Be,^{10}B^{*}[1.74 MeV]) Reaction at 100 AMeV. PHYSICAL REVIEW LETTERS 2017; 118:172501. [PMID: 28498679 DOI: 10.1103/physrevlett.118.172501] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Indexed: 06/07/2023]
Abstract
The (^{10}Be,^{10}B^{*}[1.74 MeV]) charge-exchange reaction at 100 AMeV is presented as a new probe for isolating the isovector (ΔT=1) nonspin-transfer (ΔS=0) response of nuclei, with ^{28}Si being the first nucleus studied. By using a secondary ^{10}Be beam produced by fast fragmentation of ^{18}O nuclei at the NSCL Coupled Cyclotron Facility, applying the dispersion-matching technique with the S800 magnetic spectrometer to determine the excitation energy in ^{28}Al, and performing high-resolution γ-ray tracking with the Gamma-Ray Energy Tracking In-beam Nuclear Array (GRETINA) to identify the 1022-keV γ ray associated with the decay from the 1.74-MeV T=1 isobaric analog state in ^{10}B, a ΔS=0 excitation-energy spectrum in ^{28}Al was extracted. Monopole and dipole contributions were determined through a multipole-decomposition analysis, and the isovector giant dipole resonance and isovector giant monopole resonance (IVGMR) were identified. The results show that this probe is a powerful tool for studying the elusive IVGMR, which is of interest for performing stringent tests of modern density functional theories at high excitation energies and for constraining the bulk properties of nuclei and nuclear matter. The extracted distributions were compared with theoretical calculations based on the normal-modes formalism and the proton-neutron relativistic time-blocking approximation. Calculated cross sections based on these strengths underestimate the data by about a factor of 2, which likely indicates deficiencies in the reaction calculations based on the distorted wave Born approximation.
Collapse
|
33
|
Electromagnetic Moments of Radioactive ^{136}Te and the Emergence of Collectivity 2p⊕2n Outside of Double-Magic ^{132}Sn. PHYSICAL REVIEW LETTERS 2017; 118:092503. [PMID: 28306272 DOI: 10.1103/physrevlett.118.092503] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2016] [Indexed: 06/06/2023]
Abstract
Radioactive ^{136}Te has two valence protons and two valence neutrons outside of the ^{132}Sn double shell closure, providing a simple laboratory for exploring the emergence of collectivity and nucleon-nucleon interactions. Coulomb excitation of ^{136}Te on a titanium target was utilized to determine an extensive set of electromagnetic moments for the three lowest-lying states, including B(E2;0_{1}^{+}→2_{1}^{+}), Q(2_{1}^{+}), and g(2_{1}^{+}). The results indicate that the first-excited state, 2_{1}^{+}, composed of the simple 2p⊕2n system, is prolate deformed, and its wave function is dominated by excited valence neutron configurations, but not to the extent previously suggested. It is demonstrated that extreme sensitivity of g(2_{1}^{+}) to the proton and neutron contributions to the wave function provides unique insight into the nature of emerging collectivity, and g(2_{1}^{+}) was used to differentiate among several state-of-the-art theoretical calculations. Our results are best described by the most recent shell model calculations.
Collapse
|
34
|
Low-Energy Magnetic Dipole Radiation in Open-Shell Nuclei. PHYSICAL REVIEW LETTERS 2017; 118:092502. [PMID: 28306274 DOI: 10.1103/physrevlett.118.092502] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/16/2017] [Indexed: 06/06/2023]
Abstract
Low-energy M1 strength functions of ^{60,64,68}Fe are determined on the basis of large-scale shell-model calculations with the goal to study their development from the bottom to the middle of the neutron shell. We find that the zero-energy spike, which characterizes nuclei near closed shells, develops toward the middle of the shell into a bimodal structure composed of a weaker zero-energy spike and a scissorslike resonance around 3 MeV, where the summed strengths of the two structures change within only 8% around a value of 9.8 μ_{N}^{2}. The summed strength of the scissors region exceeds the total γ absorption strength from the ground state by a factor of about three, which explains the discrepancy between total strengths of the scissors resonance derived from (γ, γ^{'}) experiments and from experiments using light-ion induced reactions.
Collapse
|
35
|
Chaos and Regularity in the Doubly Magic Nucleus ^{208}Pb. PHYSICAL REVIEW LETTERS 2017; 118:012501. [PMID: 28106417 DOI: 10.1103/physrevlett.118.012501] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2016] [Indexed: 06/06/2023]
Abstract
High-resolution experiments have recently lead to a complete identification (energy, spin, and parity) of 151 nuclear levels up to an excitation energy of E_{x}=6.20 MeV in ^{208}Pb [Heusler et al., Phys. Rev. C 93, 054321 (2016)PRVCAN2469-998510.1103/PhysRevC.93.054321]. We present a thorough study of the fluctuation properties in the energy spectra of the unprecedented set of nuclear bound states. In a first approach, we group states with the same spin and parity into 14 subspectra, analyze standard statistical measures for short- and long-range correlations, i.e., the nearest-neighbor spacing distribution, the number variance Σ^{2}, the Dyson-Mehta Δ_{3} statistics, and the novel distribution of the ratios of consecutive spacings of adjacent energy levels in each energy sequence, and then compute their ensemble average. Their comparison with a random matrix ensemble which interpolates between Poisson statistics expected for regular systems and the Gaussian orthogonal ensemble (GOE) predicted for chaotic systems shows that the data are well described by the GOE. In a second approach, following an idea of Rosenzweig and Porter [Phys. Rev. 120, 1698 (1960)PHRVAO0031-899X10.1103/PhysRev.120.1698], we consider the complete spectrum composed of the independent subspectra. We analyze their fluctuation properties using the method of Bayesian inference involving a quantitative measure, called the chaoticity parameter f, which also interpolates between Poisson (f=0) and GOE statistics (f=1). It turns out to be f≈0.9. This is so far the closest agreement with a GOE observed in the spectra of bound states in a nucleus. The same analysis is also performed with spectra computed on the basis of shell model calculations with different interactions (surface-delta interaction, Kuo-Brown, Michigan-three-Yukawa). While the simple surface-delta interaction exhibits features typical for nuclear many-body systems with regular dynamics, the other, more realistic interactions yield chaoticity parameters f close to the experimental values.
Collapse
|
36
|
Abstract
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.
Collapse
|
37
|
Strong Neutron-γ Competition above the Neutron Threshold in the Decay of ^{70}Co. PHYSICAL REVIEW LETTERS 2016; 117:142701. [PMID: 27740831 DOI: 10.1103/physrevlett.117.142701] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/18/2016] [Indexed: 06/06/2023]
Abstract
The β-decay intensity of ^{70}Co was measured for the first time using the technique of total absorption spectroscopy. The large β-decay Q value [12.3(3) MeV] offers a rare opportunity to study β-decay properties in a broad energy range. Two surprising features were observed in the experimental results, namely, the large fragmentation of the β intensity at high energies, as well as the strong competition between γ rays and neutrons, up to more than 2 MeV above the neutron-separation energy. The data are compared to two theoretical calculations: the shell model and the quasiparticle random phase approximation (QRPA). Both models seem to be missing a significant strength at high excitation energies. Possible interpretations of this discrepancy are discussed. The shell model is used for a detailed nuclear structure interpretation and helps to explain the observed γ-neutron competition. The comparison to the QRPA calculations is done as a means to test a model that provides global β-decay properties for astrophysical calculations. Our work demonstrates the importance of performing detailed comparisons to experimental results, beyond the simple half-life comparisons. A realistic and robust description of the β-decay intensity is crucial for our understanding of nuclear structure as well as of r-process nucleosynthesis.
Collapse
|
38
|
Isospin Mixing Reveals ^{30}P(p,γ)^{31}S Resonance Influencing Nova Nucleosynthesis. PHYSICAL REVIEW LETTERS 2016; 116:102502. [PMID: 27015475 DOI: 10.1103/physrevlett.116.102502] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2015] [Indexed: 06/05/2023]
Abstract
The thermonuclear ^{30}P(p,γ)^{31}S reaction rate is critical for modeling the final elemental and isotopic abundances of ONe nova nucleosynthesis, which affect the calibration of proposed nova thermometers and the identification of presolar nova grains, respectively. Unfortunately, the rate of this reaction is essentially unconstrained experimentally, because the strengths of key ^{31}S proton capture resonance states are not known, largely due to uncertainties in their spins and parities. Using the β decay of ^{31}Cl, we have observed the β-delayed γ decay of a ^{31}S state at E_{x}=6390.2(7) keV, with a ^{30}P(p,γ)^{31}S resonance energy of E_{r}=259.3(8) keV, in the middle of the ^{30}P(p,γ)^{31}S Gamow window for peak nova temperatures. This state exhibits isospin mixing with the nearby isobaric analog state at E_{x}=6279.0(6) keV, giving it an unambiguous spin and parity of 3/2^{+} and making it an important l=0 resonance for proton capture on ^{30}P.
Collapse
|
39
|
Mass Measurement of 56Sc Reveals a Small A = 56 Odd-Even Mass Staggering, Implying a Cooler Accreted Neutron Star Crust. PHYSICAL REVIEW LETTERS 2015; 115:162501. [PMID: 26550869 DOI: 10.1103/physrevlett.115.162501] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2015] [Indexed: 06/05/2023]
Abstract
We present the mass excesses of (52-57)Sc, obtained from recent time-of-flight nuclear mass measurements at the National Superconducting Cyclotron Laboratory at Michigan State University. The masses of 56Sc and 57Sc were determined for the first time with atomic mass excesses of -24.85(59)((-54)(+0)) MeV and -21.0(1.3) MeV, respectively, where the asymmetric uncertainty for 56Sc was included due to possible contamination from a long-lived isomer. The 56Sc mass indicates a small odd-even mass staggering in the A = 56 mass chain towards the neutron drip line, significantly deviating from trends predicted by the global FRDM mass model and favoring trends predicted by the UNEDF0 and UNEDF1 density functional calculations. Together with new shell-model calculations of the electron-capture strength function of 56Sc, our results strongly reduce uncertainties in model calculations of the heating and cooling at the 56Ti electron-capture layer in the outer crust of accreting neutron stars. We find that, in contrast to previous studies, neither strong neutrino cooling nor strong heating occurs in this layer. We conclude that Urca cooling in the outer crusts of accreting neutron stars that exhibit superbursts or high temperature steady-state burning, which are predicted to be rich in A≈56 nuclei, is considerably weaker than predicted. Urca cooling must instead be dominated by electron capture on the small amounts of adjacent odd-A nuclei contained in the superburst and high temperature steady-state burning ashes. This may explain the absence of strong crust Urca cooling inferred from the observed cooling light curve of the transiently accreting x-ray source MAXI J0556-332.
Collapse
|
40
|
Magnetism of an excited self-conjugate nucleus: precise measurement of the g factor of the 2(1)(+) state in (24)Mg. PHYSICAL REVIEW LETTERS 2015; 114:062501. [PMID: 25723214 DOI: 10.1103/physrevlett.114.062501] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2014] [Indexed: 06/04/2023]
Abstract
A precise measurement of the g factor of the first-excited state in the self-conjugate (N=Z) nucleus (24)Mg is performed by a new time-differential recoil-in-vacuum method based on the hyperfine field of hydrogenlike ions. Theory predicts that the g factors of such states, in which protons and neutrons occupy the same orbits, should depart from 0.5 by a few percent due to configuration mixing and meson-exchange effects. The experimental result, g=0.538±0.013, is in excellent agreement with recent shell-model calculations and shows a departure from 0.5 by almost 3 standard deviations, thus achieving, for the first time, the precision and accuracy needed to test theory. Proof of the new method opens the way for wide applications including measurements of the magnetism of excited states of exotic nuclei produced as radioactive beams.
Collapse
|
41
|
Mass measurements demonstrate a strong N=28 shell gap in argon. PHYSICAL REVIEW LETTERS 2015; 114:022501. [PMID: 25635542 DOI: 10.1103/physrevlett.114.022501] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2014] [Indexed: 06/04/2023]
Abstract
We present results from recent time-of-flight nuclear mass measurements at the National Superconducting Cyclotron Laboratory at Michigan State University. We report the first mass measurements of ^{48}Ar and ^{49}Ar and find atomic mass excesses of -22.28(31) MeV and -17.8(1.1) MeV, respectively. These masses provide strong evidence for the closed shell nature of neutron number N=28 in argon, which is therefore the lowest even-Z element exhibiting the N=28 closed shell. The resulting trend in binding-energy differences, which probes the strength of the N=28 shell, compares favorably with shell-model calculations in the sd-pf shell using SDPF-U and SDPF-MU Hamiltonians.
Collapse
|
42
|
Nuclear structure aspects of neutrinoless double-β decay. PHYSICAL REVIEW LETTERS 2014; 113:262501. [PMID: 25615313 DOI: 10.1103/physrevlett.113.262501] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/25/2014] [Indexed: 06/04/2023]
Abstract
We decompose the neutrinoless double-β decay matrix elements into sums of products over the intermediate nucleus with two less nucleons. We find that the sum is dominated by the J(π)=0(+) ground state of this intermediate nucleus for both the light and heavy neutrino decay processes. This provides a new theoretical tool for comparing and improving nuclear structure models. It also provides the connection to two-nucleon transfer experiments.
Collapse
|
43
|
Breakdown of the isobaric multiplet mass equation for the A = 20 and 21 multiplets. PHYSICAL REVIEW LETTERS 2014; 113:082501. [PMID: 25192091 DOI: 10.1103/physrevlett.113.082501] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/27/2013] [Indexed: 06/03/2023]
Abstract
Using the Penning trap mass spectrometer TITAN, we performed the first direct mass measurements of (20,21)Mg, isotopes that are the most proton-rich members of the A = 20 and A = 21 isospin multiplets. These measurements were possible through the use of a unique ion-guide laser ion source, a development that suppressed isobaric contamination by 6 orders of magnitude. Compared to the latest atomic mass evaluation, we find that the mass of (21)Mg is in good agreement but that the mass of (20)Mg deviates by 3 σ. These measurements reduce the uncertainties in the masses of (20,21)Mg by 15 and 22 times, respectively, resulting in a significant departure from the expected behavior of the isobaric multiplet mass equation in both the A = 20 and A = 21 multiplets. This presents a challenge to shell model calculations using either the isospin nonconserving universal sd USDA and USDB Hamiltonians or isospin nonconserving interactions based on chiral two- and three-nucleon forces.
Collapse
|
44
|
Determining the rp-process flow through 56Ni: resonances in 57Cu(p,γ)58Zn identified with GRETINA. PHYSICAL REVIEW LETTERS 2014; 113:032502. [PMID: 25083636 DOI: 10.1103/physrevlett.113.032502] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/19/2014] [Indexed: 06/03/2023]
Abstract
An approach is presented to experimentally constrain previously unreachable (p, γ) reaction rates on nuclei far from stability in the astrophysical rp process. Energies of all critical resonances in the (57)Cu(p,γ)(58)Zn reaction are deduced by populating states in (58)Zn with a (d, n) reaction in inverse kinematics at 75 MeV/u, and detecting γ-ray-recoil coincidences with the state-of-the-art γ-ray tracking array GRETINA and the S800 spectrograph at the National Superconducting Cyclotron Laboratory. The results reduce the uncertainty in the (57)Cu(p,γ) reaction rate by several orders of magnitude. The effective lifetime of (56)Ni, an important waiting point in the rp process in x-ray bursts, can now be determined entirely from experimentally constrained reaction rates.
Collapse
|
45
|
β+ Gamow-Teller transition strengths from 46Ti and stellar electron-capture rates. PHYSICAL REVIEW LETTERS 2014; 112:252501. [PMID: 25014806 DOI: 10.1103/physrevlett.112.252501] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2014] [Indexed: 06/03/2023]
Abstract
The Gamow-Teller strength in the β(+) direction to (46)Sc was extracted via the (46)Ti(t,(3)He + γ) reaction at 115 MeV/u. The γ-ray coincidences served to precisely measure the very weak Gamow-Teller transition to a final state at 991 keV. Although this transition is weak, it is crucial for accurately estimating electron-capture rates in astrophysical scenarios with relatively low stellar densities and temperatures, such as presupernova stellar evolution. Shell-model calculations with different effective interactions in the pf shell-model space do not reproduce the experimental Gamow-Teller strengths, which is likely due to sd-shell admixtures. Calculations in the quasiparticle random phase approximation that are often used in astrophysical simulations also fail to reproduce the experimental Gamow-Teller strength distribution, leading to strongly overestimated electron-capture rates. Because reliable theoretical predictions of Gamow-Teller strengths are important for providing astrophysical electron-capture reaction rates for a broad set of nuclei in the lower pf shell, we conclude that further theoretical improvements are required to match astrophysical needs.
Collapse
|
46
|
Nuclear structure towards N = 40 60Ca: in-beam γ-ray spectroscopy of 58,60Ti. PHYSICAL REVIEW LETTERS 2014; 112:112503. [PMID: 24702356 DOI: 10.1103/physrevlett.112.112503] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/31/2013] [Indexed: 06/03/2023]
Abstract
Excited states in the neutron-rich N = 38, 36 nuclei (60)Ti and (58)Ti were populated in nucleon-removal reactions from (61)V projectiles at 90 MeV/nucleon. The γ-ray transitions from such states in these Ti isotopes were detected with the advanced γ-ray tracking array GRETINA and were corrected event by event for large Doppler shifts (v/c ∼ 0.4) using the γ-ray interaction points deduced from online signal decomposition. The new data indicate that a steep decrease in quadrupole collectivity occurs when moving from neutron-rich N = 36, 38 Fe and Cr toward the Ti and Ca isotones. In fact, (58,60)Ti provide some of the most neutron-rich benchmarks accessible today for calculations attempting to determine the structure of the potentially doubly magic nucleus (60)Ca.
Collapse
|
47
|
Shell-model analysis of the 136Xe double beta decay nuclear matrix elements. PHYSICAL REVIEW LETTERS 2013; 110:222502. [PMID: 23767716 DOI: 10.1103/physrevlett.110.222502] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/24/2012] [Revised: 03/18/2013] [Indexed: 06/02/2023]
Abstract
Neutrinoless double beta decay, if observed, could distinguish whether the neutrino is a Dirac or a Majorana particle, and it could be used to determine the absolute scale of the neutrino masses. 136Xe is one of the most promising candidates for observing this rare event. However, until recently there were no positive results for the allowed and less rare two-neutrino double beta decay mode. The small nuclear matrix element associated with the long half-life represents a challenge for nuclear structure models used for its calculation. We report a new shell-model analysis of the two-neutrino double beta decay of 136Xe, which takes into account all relevant nuclear orbitals necessary to fully describe the associated Gamow-Teller strength. We further use the new model to analyze the main contributions to the neutrinoless double beta decay matrix element, and show that they are also diminished.
Collapse
|
48
|
Spins and magnetic moments of 49K and 51K: establishing the 1/2+ and 3/2+ level ordering beyond N = 28. PHYSICAL REVIEW LETTERS 2013; 110:172503. [PMID: 23679713 DOI: 10.1103/physrevlett.110.172503] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2013] [Indexed: 06/02/2023]
Abstract
The ground-state spins and magnetic moments of (49,51)K have been measured using bunched-beam high-resolution collinear laser spectroscopy at ISOLDE CERN. For 49K a ground-state spin I = 1/2 was firmly established. The observed hyperfine structure of 51K requires a spin I > 1/2 and strongly suggests I = 3/2. From its magnetic moment μ(51K) = +0.5129(22)μ(N) a spin-parity I(π) = 3/2+ with a dominant π1d(3/2)(-1) hole configuration was deduced. This establishes for the first time the reinversion of the single-particle levels and illustrates the prominent role of the residual monopole interaction for single-particle levels and shell evolution.
Collapse
|
49
|
Spectroscopy of 26F to probe proton-neutron forces close to the drip line. PHYSICAL REVIEW LETTERS 2013; 110:082502. [PMID: 23473138 DOI: 10.1103/physrevlett.110.082502] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2012] [Indexed: 06/01/2023]
Abstract
A long-lived J(π) = 4(1)(+) isomer, T(1/2) = 2.2(1) ms, has been discovered at 643.4(1) keV in the weakly bound (9)(26)F nucleus. It was populated at Grand Accélérateur National d'Ions Lourds in the fragmentation of a (36)S beam. It decays by an internal transition to the J(π) = 1(1)(+) ground state [82(14)%], by β decay to (26)Ne, or β-delayed neutron emission to (25)Ne. From the β-decay studies of the J(π) =1(1)(+) and J(π) = 4(1)(+) states, new excited states have been discovered in (25,26)Ne. Gathering the measured binding energies of the J(π) = 1(1)(+) -4(1)(+) multiplet in (9)(26)F, we find that the proton-neutron π0d(5/2)ν0d(3/2) effective force used in shell-model calculations should be reduced to properly account for the weak binding of (9)(26)F. Microscopic coupled cluster theory calculations using interactions derived from chiral effective field theory are in very good agreement with the energy of the low-lying 1(1)(+), 2(1)(+), 4(1)(+) states in (26)F. Including three-body forces and coupling to the continuum effects improve the agreement between experiment and theory as compared to the use of two-body forces only.
Collapse
|
50
|
Mass measurements of the neutron-deficient 41Ti, 45Cr, 49Fe, and 53Ni nuclides: first test of the isobaric multiplet mass equation in f p-shell nuclei. PHYSICAL REVIEW LETTERS 2012; 109:102501. [PMID: 23005283 DOI: 10.1103/physrevlett.109.102501] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/24/2012] [Indexed: 06/01/2023]
Abstract
Isochronous mass spectrometry has been applied to neutron-deficient 58Ni projectile fragments at the HIRFL-CSR facility in Lanzhou, China. Masses of a series of short-lived T(z)=-3/2 nuclides including 41Ti, 45Cr, 49Fe, and 53Ni have been measured with a precision of 20-40 keV. The new data enable us to test for the first time the isobaric multiplet mass equation (IMME) in fp-shell nuclei. We observe that the IMME is inconsistent with the generally accepted quadratic form for the A=53, T=3/2 quartet. We perform full space shell model calculations and compare them with the new experimental results.
Collapse
|