Nuclear Charge Radii of the Nickel Isotopes

Collinear laser spectroscopy is performed on the nickel isotopes ^{58-68,70}Ni, using a time-resolved photon counting system. From the measured isotope shifts, nuclear charge radii R_{c} are extracted and compared to theoretical results. Three ab initio approaches all employ, among others, the chiral interaction NNLO_{sat}, which allows an assessment of their accuracy. We find agreement with experiment in differential radii δ⟨r_{c}^{2}⟩ for all employed ab initio methods and interactions, while the absolute radii are consistent with data only for NNLO_{sat}. Within nuclear density functional theory, the Skyrme functional SV-min matches experiment more closely than the Fayans functional Fy(Δr,HFB).

Coupled-Cluster Calculations of Neutrinoless Double-ß Decay in

We use coupled-cluster theory and nuclear interactions from chiral effective field theory to compute the nuclear matrix element for the neutrinoless double-ß decay of ^{48}Ca. Benchmarks with the no-core shell model in several light nuclei inform us about the accuracy of our approach. For ^{48}Ca we find a relatively small matrix element. We also compute the nuclear matrix element for the two-neutrino double-ß decay of ^{48}Ca with a quenching factor deduced from two-body currents in recent ab initio calculation of the Ikeda sum rule in ^{48}Ca [Gysbers et al., Nat. Phys. 15, 428 (2019)NPAHAX1745-247310.1038/s41567-019-0450-7].

Two-Neutron Halo is Unveiled in

We report the measurement of reaction cross sections (σ_{R}^{ex}) of ^{27,29}F with a carbon target at RIKEN. The unexpectedly large σ_{R}^{ex} and derived matter radius identify ^{29}F as the heaviest two-neutron Borromean halo to date. The halo is attributed to neutrons occupying the 2p_{3/2} orbital, thereby vanishing the shell closure associated with the neutron number N=20. The results are explained by state-of-the-art shell model calculations. Coupled-cluster computations based on effective field theories of the strong nuclear force describe the matter radius of ^{27}F but are challenged for ^{29}F.

How Robust is the N=34 Subshell Closure? First Spectroscopy of

The first γ-ray spectroscopy of ^{52}Ar, with the neutron number N=34, was measured using the ^{53}K(p,2p) one-proton removal reaction at ∼210 MeV/u at the RIBF facility. The 2_{1}^{+} excitation energy is found at 1656(18) keV, the highest among the Ar isotopes with N>20. This result is the first experimental signature of the persistence of the N=34 subshell closure beyond ^{54}Ca, i.e., below the magic proton number Z=20. Shell-model calculations with phenomenological and chiral-effective-field-theory interactions both reproduce the measured 2_{1}^{+} systematics of neutron-rich Ar isotopes, and support a N=34 subshell closure in ^{52}Ar.

Cloud Quantum Computing of an Atomic Nucleus.

We report a quantum simulation of the deuteron binding energy on quantum processors accessed via cloud servers. We use a Hamiltonian from pionless effective field theory at leading order. We design a low-depth version of the unitary coupled-cluster ansatz, use the variational quantum eigensolver algorithm, and compute the binding energy to within a few percent. Our work is the first step towards scalable nuclear structure computations on a quantum processor via the cloud, and it sheds light on how to map scientific computing applications onto nascent quantum devices.

Structure of the Lightest Tin Isotopes.

We link the structure of nuclei around ^{100}Sn, the heaviest doubly magic nucleus with equal neutron and proton numbers (N=Z=50), to nucleon-nucleon (NN) and three-nucleon (NNN) forces constrained by data of few-nucleon systems. Our results indicate that ^{100}Sn is doubly magic, and we predict its quadrupole collectivity. We present precise computations of ^{101}Sn based on three-particle-two-hole excitations of ^{100}Sn, and we find that one interaction accurately reproduces the small splitting between the lowest J^{π}=7/2^{+} and 5/2^{+} states.

Evidence for prevalent Z = 6 magic number in neutron-rich carbon isotopes.

The nuclear shell structure, which originates in the nearly independent motion of nucleons in an average potential, provides an important guide for our understanding of nuclear structure and the underlying nuclear forces. Its most remarkable fingerprint is the existence of the so-called magic numbers of protons and neutrons associated with extra stability. Although the introduction of a phenomenological spin-orbit (SO) coupling force in 1949 helped in explaining the magic numbers, its origins are still open questions. Here, we present experimental evidence for the smallest SO-originated magic number (subshell closure) at the proton number six in 13-20C obtained from systematic analysis of point-proton distribution radii, electromagnetic transition rates and atomic masses of light nuclei. Performing ab initio calculations on 14,15C, we show that the observed proton distribution radii and subshell closure can be explained by the state-of-the-art nuclear theory with chiral nucleon-nucleon and three-nucleon forces, which are rooted in the quantum chromodynamics.

Structure of

Doubly magic nuclei have a simple structure and are the cornerstones for entire regions of the nuclear chart. Theoretical insights into the supposedly doubly magic ^{78}Ni and its neighbors are challenging because of the extreme neutron-to-proton ratio and the proximity of the continuum. We predict the J^{π}=2_{1}^{+} state in ^{78}Ni from a correlation with the J^{π}=2_{1}^{+} state in ^{48}Ca using chiral nucleon-nucleon and three-nucleon interactions. Our results confirm that ^{78}Ni is doubly magic, and the predicted low-lying states of ^{79,80}Ni open the way for shell-model studies of many more rare isotopes.

Proton Distribution Radii of

Proton radii of ^{12-19}C densities derived from first accurate charge changing cross section measurements at 900A MeV with a carbon target are reported. A thick neutron surface evolves from ∼0.5 fm in ^{15}C to ∼1 fm in ^{19}C. The halo radius in ^{19}C is found to be 6.4±0.7 fm as large as ^{11}Li. Ab initio calculations based on chiral nucleon-nucleon and three-nucleon forces reproduce the radii well.

Ab initio coupled-cluster effective interactions for the shell model: application to neutron-rich oxygen and carbon isotopes.

We derive and compute effective valence-space shell-model interactions from ab initio coupled-cluster theory and apply them to open-shell and neutron-rich oxygen and carbon isotopes. Our shell-model interactions are based on nucleon-nucleon and three-nucleon forces from chiral effective-field theory. We compute the energies of ground and low-lying states, and find good agreement with experiment. In particular, our computed 2(+) states are consistent with N = 14,16 shell closures in (22,24)O, and a weaker N=14 shell closure in (20)C. We find good agreement between our coupled-cluster effective-interaction results with those obtained from standard single-reference coupled-cluster calculations for up to eight valence neutrons.

Effects of three-nucleon forces and two-body currents on Gamow-Teller strengths.

We optimize chiral interactions at next-to-next-to leading order to observables in two- and three-nucleon systems and compute Gamow-Teller transitions in 14C and (22,24)O using consistent two-body currents. We compute spectra of the daughter nuclei 14N and (22,24)F via an isospin-breaking coupled-cluster technique, with several predictions. The two-body currents reduce the Ikeda sum rule, corresponding to a quenching factor q2≈0.84-0.92 of the axial-vector coupling. The half-life of 14C depends on the energy of the first excited 1+ state, the three-nucleon force, and the two-body current.

Optimized chiral nucleon-nucleon interaction at next-to-next-to-leading order.

We optimize the nucleon-nucleon interaction from chiral effective field theory at next-to-next-to-leading order (NNLO). The resulting new chiral force NNLO(opt) yields χ(2)≈1 per degree of freedom for laboratory energies below approximately 125 MeV. In the A=3, 4 nucleon systems, the contributions of three-nucleon forces are smaller than for previous parametrizations of chiral interactions. We use NNLO(opt) to study properties of key nuclei and neutron matter, and we demonstrate that many aspects of nuclear structure can be understood in terms of this nucleon-nucleon interaction, without explicitly invoking three-nucleon forces.

Spectroscopy of 26F to probe proton-neutron forces close to the drip line.

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 ß decay to (26)Ne, or ß-delayed neutron emission to (25)Ne. From the ß-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.

Continuum effects and three-nucleon forces in neutron-rich oxygen isotopes.

We employ interactions from chiral effective field theory and compute binding energies, excited states, and radii for isotopes of oxygen with the coupled-cluster method. Our calculation includes the effects of three-nucleon forces and of the particle continuum, both of which are important for the description of neutron-rich isotopes in the vicinity of the nucleus 24O. Our main results are the placement of the neutron drip line at 24O, the assignment of spins, parities and resonance widths for several low-lying states of the drip line nucleus, and an efficient approximation that incorporates the effects of three-body interactions.

Evolution of shell structure in neutron-rich calcium isotopes.

We employ interactions from chiral effective field theory and compute the binding energies and low-lying excitations of calcium isotopes with the coupled-cluster method. Effects of three-nucleon forces are included phenomenologically as in-medium two-nucleon interactions, and the coupling to the particle continuum is taken into account using a Berggren basis. The computed ground-state energies and the low-lying J(π) = 2+ states for the isotopes (42,48,50,52)Ca are in good agreement with data, and we predict the excitation energy of the first J(π) = 2+ state in (54)Ca at 1.9 MeV, displaying only a weak subshell closure. In the odd-mass nuclei (53,55,61)Ca we find that the positive parity states deviate strongly from the naive shell model.

A comparison of extrahepatic lipogenesis from a small glucose meal in obob and gold thioglucose obese mice fed low- or high-fat diets with or without the addition of Delta22-5beta-taurocholenic acid.

Extrahepatic fatty acid synthesis from a 250 mg meal of [U-(14)C]-glucose was measured in epidymal fat pads and the remaining carcass of hyperglycemic obese (obob), gold thioglucose obese, and nonobese controls under conditions of maximum and minimum lipogenesis. Also assessed was the effect of Delta(22)-5beta-taurocholenic acid, previously shown to inhibit hepatic fatty acid synthesis. Both types of obese and nonobese mice were fed for 6 weeks glucose-based diets containing either 1% corn oil or 40% lard with or without the addition of 0.05% taurocholenic acid. In mice fed 1% corn oil, incorporation of labeled glucose into carcass fatty acids was 25% greater in nonobese than obese mice of either type of obesity. On this diet incorporation of labeled glucose into epididymal fatty acids was reduced 83% in hyperglycemic obese mice compared with nonobese littermates. The corresponding reduction in lipogenesis in gold thioglucose obese mice was only 23% compared with nonobese controls. Feeding 40% lard reduced incorporation of labeled glucose into epididymal and carcass fatty acid 67 to 95% compared with mice fed 1% corn oil in both types of obese and nonobese mice whether or not taurocholenic acid had been fed. Both types of obesity or feeding 40% lard reduced lipogenesis in fat pads to a greater extent than glucose uptake by the pads with the reductions additive. Feeding taurocholenic acid reduced pad weight 30% across strain and obesity status, increased uptake of labeled glucose into epididymal fat pads and increased the percentage of the labeled glucose in the pad recovered as fatty acid in both types of obese and nonobese mice when the diet was 1% corn oil. Similarities and differences between the two obesity models are discussed.

Effect of delta22-5beta-taurocholenic acid on hepatic cholesterol and fatty acid in gold thioglucose obese mice fed low- or high-fat diets.

We previously demonstrated that hyperglycemic-obese (obob) mice fed a 1% corn oil diet accumulated 10 times as much hepatic cholesterol as did their non-obese (+/?) littermates fed this diet because of difficulty in removal of cholesterol from the liver rather than from increased synthesis. Furthermore, feeding the bile acid analog Delta(22)-5beta-taurocholenic acid completely prevented the accumulation of hepatic cholesterol in obob mice fed the 1% corn oil diet. The hypothesis to be tested in the current study is that these aspects of cholesterol metabolism in the obob mouse do not occur in the hyperinsulinemic and insulin-resistant gold thioglucose obese mouse. Gold thioglucose obese (gtgo) and non-obese (ngtgo) mice were fed diets containing either 1% corn oil or 40% lard each with or without added taurocholenic acid for 6 weeks and then given a 250 mg meal of [U-(14)C]-glucose with incorporation of label into hepatic cholesterol and fatty acid measured 2 hours later. Consistent with earlier results in the obob model, incorporation of labeled glucose was significantly increased in obese compared with non-obese mice fed 1% corn oil and significantly reduced either by feeding 40% lard or by adding taurocholenic acid to the diet. In addition, taurocholenic acid greatly increased incorporation of labeled glucose into hepatic cholesterol in obese or non-obese mice fed either diet. In contrast to obob mice, the percentage of fat in the liver of gtgo mice was increased only 50% compared with ngtgo mice. The comparable increase in obob mice was 480%. Hepatic cholesterol did not increase significantly in the liver of gtgo mice fed 1% corn oil when compared with the ngtgo controls. The comparable increase in obob mice fed 1% corn oil was 350%. Also in marked contrast to obob mice, feeding taurocholenic acid increased hepatic cholesterol compared with non-obese controls fed either diet. The results are discussed in the light of the presence of circulating leptin in gtgo but not in obob mice.

Stress fractures in female army recruits: implications of bone density, calcium intake, and exercise.

OBJECTIVE: To identify characteristics and factors associated with increased risk for stress fractures in military women. DESIGN: Case-control study to retrospectively examine physical activity, prior calcium intake, and bone density as predictors of stress fractures. SETTING: A military training installation which incorporates physical training for women. SUBJECTS: Forty-nine female soldiers with confirmed stress fractures (cases) and 78 female soldiers with no orthopedic injuries (controls), aged 18 to 33 years. MEASURES: Retrospective self-reports of habitual exercise, sports participation, and food intake; current height, weight, and body mass index (BMI); demographic variables (age, ethnicity, menstrual patterns, smoking habits); and bone density on radiologically defined stress fractures. RESULTS: Cases and controls were similar in height, weight, and BMI. Measurements of bone density (g/cm2) at the trochanter (cases, 0.77+/-0.09; controls, 0.77+/-0.08); femoral neck (cases, 0.94+/-0.10; controls, 0.94+/-0.09); Ward's triangle (cases, 0.91+/-0.11; controls, 0.93+/-0.11); lumbar spine (cases, 1.21+/-0.12; controls, 1.24+/-0.10); and radius shaft (cases, 0.67+/-0.09; controls, 0.68+/-0.05) were not different between groups. Calcium intake was not different between groups (cases, 1154+/-751 mg/day; controls, 944+/-513 mg/day) and did not correlate with bone density (r=0.01 to -0.06 at four sites). Sports participation positively correlated with bone density in the hip (r=0.49). Leisure activity energy expenditure (kcal/day) tended toward association with lower stress fracture risk as expenditure level increased (p=0.06). CONCLUSION: Stress fracture in female Army recruits was not correlated with bone density or calcium intake during adolescence, although a weak relationship to prior physical activity was observed.

Complaints and diagnoses in homoeopathic practice

As part of a 4-phase research project, 58 homoeopathic physicians, all members of VHAN(Dutch Association of Homoeopathic Physicians) registered for 1 week the complaints and diagnoses according to ICPC-code of the first 30 patients given exclusively homoeopathic treatment during that week