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OBJECTIVE: COVID-19 clinical presentation ranges from asymptomatic infection to an inflammatory cytokine storm with multi-organ failure and fatal outcomes. The identification of high-risk patients for severe disease is crucial to plan an early treatment and intensive follow-up. We aimed to investigate negative prognostic factors in a group of patients hospitalized for COVID-19. PATIENTS AND METHODS: 181 patients (90 men and 91 women, mean age 66.56 ± 13.53 years) were enrolled. Each patient received a work-up including medical history, clinical examination, arterial blood gas analysis, laboratory blood tests, feasible ventilatory support required during hospital stay, intensive care setting required, duration of illness and length of hospital stay (>or<25 days). For the assessment of the severity of COVID-19, three main indicators were considered: 1) the intensive care unit (ICU) admission 2) the hospitalization length >25 days; 3) the need of non-invasive ventilation (NIV). RESULTS: The independent risk factor associated with the ICU admission were lactic dehydrogenase elevation (p=0.046), C reactive protein elevation (p=0.014) at hospital admission and direct oral anticoagulant home therapy (p=0.048); for hospital length >25 days: early corticosteroid therapy (p=0.035); for NIV treatment: ferritin elevation at hospital admission (p=0.006). CONCLUSIONS: The presence of the above factors may be useful to identify patients at high risk of developing a severe COVID-19 that need an early treatment and intensive follow-up. [ABSTRACT FROM AUTHOR]

Realistic nuclear potentials, derived within chiral perturbation theory, are a major breakthrough in modern nuclear structure theory, since they provide a direct link between nuclear physics and its underlying theory, namely the QCD. As a matter of fact, chiral potentials are tailored on the low-energy regime of nuclear structure physics, and chiral perturbation theory provides on the same footing two-nucleon forces as well as many-body ones. This feature fits well with modern advances in ab-initio methods and realistic shell-model. Here, we will review recent nuclear structure calculations, based on realistic chiral potentials, for both finite nuclei and infinite nuclear matter.

We investigate the pairing properties of an effective shell-model interaction defined within a model space outside 132Sn and derived by means of perturbation theory from the CD-Bonn free nucleon-nucleon potential. It turns out that the neutron pairing component of the effective interaction is significantly weaker than the proton one, which accounts for the large pairing gap difference observed in the two-valence identical particle nuclei 134Sn and 134Te. The role of the contribution arising from one particle-one hole excitations in determining the pairing force is discussed and its microscopic structure is also analyzed in terms of the multipole decomposition.

The study of the collective properties of nuclear excitations far from stability provides information about the shell structure at extreme conditions. Spectroscopic observables such as the energy or the transition probabilities of the lowest states, in nuclei with large neutron excess, allow to probe the density and isospin dependence of the effective interaction. Indeed, it was recently shown that tensor and three-body forces play an important role in breaking and creating magic numbers. Emblematic is the case of the evolution of the Ni isotopic chain where several features showed up moving from the most neutron rich stable isotope (64Ni) towards the 78Ni nucleus where the large neutron excess coincides with a double shell closure. In this framework, we have recently performed an experiment with the goal to extract the B(E2; 0+ → 2+) value for the 74Ni nucleus in an intermediate-energy Coulomb excitation experiment: preliminary results are discussed.

The study of the evolution of nuclear shells far from stability provides fundamental information about the shape and symmetry of the nuclear mean field. Nuclei with large neutron/proton ratio allow to probe the density dependence of the effective interaction. Indeed, it was recently shown that tensor and three-body forces play an important role in breaking and creating magic numbers. Of particular interest is the region of 78Ni where the large neutron excess coincides with a double shell closure. We have recently measured the B(E2; 0+ → 2+) of the 74Ni nucleus in an intermediate-energy Coulomb excitation experiment performed at the National Superconducting Cyclotron Laboratory of the Michigan State University. The 74Ni secondary beam has been produced by fragmentation of 86Kr at 140 AMeV on a thick Be target. Selected radioactive fragments impinged on a secondary 197Au target where the measurement of the emitted γ-rays allows to extract the Coulomb excitation cross section and related structure information. Preliminary B(E2) values do not point towards an enhancement of the transition matrix element and the comparison to what was already measured by Aoi and co-workers in [1] opens new scenarios in the interpretation of the shell evolution of the Z=28 isotopes.

The understanding of the convergence properties of the shell-model effective Hamiltonian, within the framework of the many-body perturbation theory, is a long-standing problem. The infinite summation of a certain class of diagrams, the so-called 'bubble diagrams,' may be provided calculating the Kirson-Babu-Brown induced interaction, and provides a valid instrument to study whether or not the finite summation of the perturbative series is well-grounded. Here, we perform an application of the calculation of the Kirson-Babu-Brown induced interaction to derive the shell-model effective Hamiltonian for -shell nuclei starting from a modern nucleon-nucleon potential, obtained by way of the chiral perturbation theory. The outcome of our calculation is compared with a standard calculation of the shell-model Hamiltonian, where the core-polarization effects are calculated only up to third-order in perturbation theory. The results of the two calculations are very close to each other, evidencing that the perturbative approach to the derivation of the shell-model Hamiltonian is still a valid tool for nuclear structure studies. [ABSTRACT FROM AUTHOR]

We calculate the nuclear and neutron matter equations of state from microscopic nuclear forces at different orders in chiral effective held theory and with varying momentum-space cutoff scales. We focus attention on how the order-by-order convergence depends on the choice of resolution scale and the implications for theoretical uncertainty estimates on the isospin asymmetry energy. Specifically we study the equations of state using consistent NLO and N²LO (next-to-next-to-leading order) chiral potentials where the low-energy constants cD and cE associated with contact vertices in the N²LO chiral three-nucleon force are fitted to reproduce the binding energies of ³H and ³He as well as the beta-decay liletime of ³H. At these low orders in the chiral expansion there is little sign of convergence, while an exploratory study employing the N³LO two-nucleon force together with the N³LO three-nucleon force give first indications for (slow) convergence with low-cutoff potentials and poor convergence with higher-cutoff potentials. The consistent NLO and N²LO potentials described in the present work provide the basis for estimating theoretical uncertainties associated with the order-by-order convergence of nuclear many-body calculations in chiral effective field theory. [ABSTRACT FROM AUTHOR]

A realistic shell-model study is performed for neutron-deficient tin isotopes up to mass A = 108. All shellmodel ingredients, namely, two-body matrix elements, single-particle energies, and effective charges for electric quadrupole transition operators, have been calculated by way of the many-body perturbation theory, starting from a low-momentum interaction derived from the high-precision CD-Bonn free nucleon-nucleon potential The focus has been on the enhanced quadrupole collectivity of these nuclei, which is testified by the observed large B(E2;01+ →21+)s. Our results give evidence of the crucial role played by the Z = 50 cross-shell excitations that need to be taken into account explicitly to obtain a satisfactory theoretical description of light tin isotopes. We find also that a relevant contribution comes from the calculated neutron effective charges, whose magnitudes exceed the standard empirical values. An original double-step procedure has been introduced to reduce effectively the model space in order to overcome the computational problem. [ABSTRACT FROM AUTHOR]

We compute the energy per particle of infinite symmetric nuclear matter from chiral N³LO (next-to-next-to-next-to-leading order) two-body potentials plus N2LO three-body forces. The low-energy constants of the chiral three-nucleon force that cannot be constrained by two-body observables are fitted to reproduce the triton binding energy and the ³H-³He Gamow-Teller transition matrix element. In this way, the saturation properties of nuclear matter are reproduced in a parameter-free approach. The equation of state is computed up to third order in many-body perturbation theory, with special emphasis on the role of the third-order particle-hole diagram. The dependence of these results on the cutoff scale and regulator function is studied. We find that the inclusion of three-nucleon forces consistent with the applied two-nucleon interaction leads to a reduced dependence on the choice of the regulator only for lower values of the cutoff. [ABSTRACT FROM AUTHOR]

We perform realistic shell-model calculations for nuclei with valence nucleons outside 48Ca, employing two different model spaces. The matrix elements of the effective two-body interaction and electromagnetic multipole operators have been calculated within the framework of many-body perturbation theory, starting from a low-momentum potential derived from the high-precision CD-Bonn free nucleon-nucleon potential. The role played by the neutron orbital 1ds/2 has been investigated by comparing experimental data on yrast quadrupole excitations of isotopic chains north-east of 48Ca with the results of calculations including or not including this single-particle state in the model space. [ABSTRACT FROM AUTHOR]

We have performed shell-model calculations for the two one-valence-neutron isotones 135Te and 137Xe and the two one-valence-proton isotopes 135,137Sb. The main aim of our study has been to investigate the evolution of single-particle states with increasing nucleon number. To this end, we have focused attention on the spectroscopic factors and the effective single-particle energies. In our calculations, we have employed a realistic low-momentum two-body effective interaction derived from the CD-Bonn nucleon-nucleon potential that has already proved quite successful in describing the spectroscopic properties of nuclei in the 132Sn region. Comparison shows that our results reproduce very well the available experimental data. This gives confidence in the evolution of the single-particle states predicted by the present study. [ABSTRACT FROM AUTHOR]

We calculate the energy per particle in infinite neutron matter perturbatively using chiral N3LO (next-to-next-to-next-to-leading order) two-body potentials plus N2LO three-body forces. The cutoff dependence of the predictions is investigated by employing chiral interactions with different regulators. We find that the inclusion of three-nucleon forces, which are consistent with the applied two-nucleon interaction, leads to a strongly reduced regulator dependence of the results. [ABSTRACT FROM AUTHOR]

We perform shell-model calculations for nuclei below 100Sn, focusing attention on the two N= Z nuclei, 96Cd and 92Pd, the latter having recently been the subject of great experimental and theoretical interest. We consider nuclei for which the 0g9/2 orbit plays a dominant role and employ a realistic low-momentum two-body effective interaction derived from the CD-Bonn nucleon-nucleon potential. This implies that no phenomenological input enters our effective Hamiltonian. The calculated results for 92Pd are in very good agreement with the available experimental data, which gives us confidence in our predictions for 96Cd. An analysis of the wave functions of both 96Cd and 92Pd is performed to investigate the role of the isoscalar spin-aligned coupling. [ABSTRACT FROM AUTHOR]

We report on a shell-model study of nuclei with two valence nucleons in the 132Sn and 208Pb regions, focusing attention on the similarity between the spectroscopy of these two regions. In our study we make use of realistic effective interactions derived from the CD-Bonn nucleon-nucleon potential renormalized by use of the Vlow-k approach. We show that the behavior of the proton-proton, neutron-neutron and proton-neutron multiplets in 134Te, 134Sn and 134Sb, respectively, is quite similar to that of the analogous multiplets in the counterpart nuclei in the 208Pb region, 210Po, 210Pb and 210Bi. [ABSTRACT FROM AUTHOR]

Abstract: A review is presented of the development and current status of nuclear shell-model calculations, in which the two-body effective interaction between valence nucleons is derived from the free nucleon–nucleon potential. The significant progress made in this field within the last decade is emphasized, in particular as regards the so-called approach to the renormalization of the bare nucleon–nucleon interaction. In the last part of the review, we first give a survey of realistic shell-model calculations from early to present days. Then, we report recent results for neutron-rich nuclei near doubly magic 132Sn, and for the whole even-mass isotonic chain. These illustrate how shell-model effective interactions derived from modern nucleon–nucleon potentials are able to provide an accurate description of nuclear structure properties. [Copyright &y& Elsevier]

Abstract: In this paper, we first give a brief review of the theoretical framework for microscopic shell-model calculations starting from the free nucleon–nucleon potential. In this context, we discuss the use of the low-momentum nucleon–nucleon interaction in the derivation of the shell-model effective interaction and emphasize its practical value as an alternative to the Brueckner -matrix method. Then, we present some results of our current study of exotic nuclei around doubly magic 132Sn, which have been obtained starting from the CD-Bonn potential renormalized by use of the approach. Attention is focused on the nuclei 134Te, 134Sn, and 136Te, in particular on the latter which is a direct source of information on the proton–neutron effective interaction in the 132Sn region. Comparison shows that our results are in very good agreement with the available experimental data. [Copyright &y& Elsevier]

Abstract: First self-consistent realistic shell-model calculation for the light p-shell nuclei is performed, starting from the high-precision nucleon–nucleon (NN) CD-Bonn potential. This realistic potential is renormalized deriving a low-momentum NN potential that preserves exactly the two-nucleon low-energy physics. This is suitable to derive a self-consistent Hartree–Fock basis that is employed to derive both effective single-particle energies and residual two-body matrix elements for the shell-model Hamiltonian. Results obtained show the reliability of such a fundamental microscopic approach. [Copyright &y& Elsevier]

We have performed shell-model calculations for the nucleus 137Xe, which was recently studied experimentally using the 136Xe(d,p) reaction in inverse kinematics. The main aim of our study has been to investigate the single-neutron properties of the observed states, focusing attention on the spectroscopic factors. We have employed a realistic low-momentum two-body effective interaction derived from the CD-Bonn nucleon-nucleon potential that has already proved quite successful in describing the spectroscopic properties of nuclei in the 132Sn region. Comparison shows that our calculations reproduce very well the experimental excitation energies and yield spectroscopic factors that come close to those extracted from the data. [ABSTRACT FROM AUTHOR]

We present a study of the role played by realistic three-body forces in providing a reliable monopole component of the effective shell-model Hamiltonian. To this end, starting from a nuclear potential built up within the chiral perturbation theory, we derive effective shell-model Hamiltonians with and without the contribution of the three-body potential and compare the results of shell-model calculations with a set of observables that evidence shell-evolution properties. The testing ground of our investigation is nuclei belonging to the fp shell, since the shell-evolution towards shell closures in 48Ca and 56Ni provides a paradigm for shell-model Hamiltonians. Our analysis shows that only by including contributions of the three-body force is the monopole component of the effective shell-model Hamiltonian then able to reproduce the experimental shell evolution towards and beyond the closure at N=28. [ABSTRACT FROM AUTHOR]

In nuclear structure calculations, the choice of a limited model space, due to computational needs, leads to the necessity to renormalize the Hamiltonian as well as any transition operator. Here, we present a study of the renormalization procedure and effects of the Gamow-Teller operator within the framework of the realistic shell model. Our effective shell-model operators are obtained, starting from a realistic nucleon-nucleon potential, by way of the many-body perturbation theory in order to take into account the degrees of freedom that are not explicitly included in the chosen model space. The theoretical effective shell-model Hamiltonian and transition operators are then employed in shell-model calculations, whose results are compared with data of Gamow-Teller transition strengths and double-β half-lives for nuclei which are currently of interest for the detection of the neutrinoless double-β decay process, in a mass interval ranging from A=48 up to A=136. We show that effective operators are able to reproduce quantitatively the spectroscopic and decay properties without resorting to an empirical quenching neither of the axial coupling constant gA, nor of the spin and orbital gyromagnetic factors. This should assess the reliability of applying present theoretical tools to this problematic. [ABSTRACT FROM AUTHOR]

We report on the calculation of Gamow-Teller and double-ß decay properties for nuclei around 132Sn within the framework of the realistic shell model. The effective shell-model Hamiltonian and Gamow-Teller transition operator are derived by way of many-body perturbation theory, without resorting to the empirical effective quenching factor for the Gamow-Teller operator. The results are then compared with the available experimental data, in order to establish the reliability of our approach. This is a mandatory step before we apply the same methodology, in forthcoming studies, to the calculation of the neutrinoless double-ß decay nuclear matrix elements for nuclei that are currently considered among the best candidates for the detection of this process. [ABSTRACT FROM AUTHOR]

We present a procedure that is helpful to reduce the computational complexity of large-scale shell-model calculations, by preserving as much as possible the role of the rejected degrees of freedom in an effective approach. Our truncation is driven first by the analysis of the effective single-particle energies of the original large-scale shell-model Hamiltonian, in order to locate the relevant degrees of freedom to describe a class of isotopes or isotones, namely the single-particle orbitals that will constitute a new truncated model space. The second step is to perform a unitary transformation of the original Hamiltonian from its model space into the truncated one. This transformation generates a new shell-model Hamiltonian, defined in a smaller model space, that retains effectively the role of the excluded single-particle orbitals. As an application of this procedure, we have chosen a realistic shell-model Hamiltonian defined in a large model space, set up by seven proton and five neutron single-particle orbitals outsider88Sr. We study the dependence of shell-model results upon different truncations of the original model space for the Zr, Mo, Ru, Pd, Cd, and Sn isotopic chains, showing the reliability of this truncation procedure. [ABSTRACT FROM AUTHOR]

We compare nuclear and neutron matter predictions based on two different ab initio approaches to nuclear forces and the nuclear many-body problem. The first consists of a realistic meson-theoretic nucleon-nucleon potential together with the relativistic counterpart of the Brueckner-Hartree-Fock theory of nuclear matter. The second is based on chiral effective field theory, with density-dependent interactions derived from leading-order chiral three-nucleon forces. We find the results to be very close and conclude that both approaches contain important features governing the physics of nuclear and neutron matter. [ABSTRACT FROM AUTHOR]

Three-nucleon force and continuum play important roles in reproducing the properties of atomic nuclei around driplines. Therefore it is valuable to build up a theoretical framework where both effects can be taken into account to solve the nuclear Schrödinger equation. To this end, in this letter, we have expressed the chiral three-nucleon force within the continuum Berggren representation, so that bound, resonant and continuum states can be treated on an equal footing in the complex-momentum space. To reduce the model dimension and computational cost, the three-nucleon force is truncated at the normal-ordered two-body level and limited in the sd -shell model space, with the residual three-body term being neglected. We choose neutron-rich oxygen isotopes as the test ground because they have been well studied experimentally, with the neutron dripline determined. The calculations have been carried out within the Gamow shell model. The quality of our results in reproducing the properties of oxygen isotopes around the neutron dripline shows the relevance of the interplay between three-nucleon force and the coupling to continuum states. We also analyze the role played by the chiral three-nucleon force, by dissecting the contributions of the 2 π exchange, 1 π exchange and contact terms. [ABSTRACT FROM AUTHOR]

The low-lying structures of the midshell ν g 9 / 2 Ni isotopes 72 Ni and 74 Ni have been investigated at the RIBF facility in RIKEN within the EURICA collaboration. Previously unobserved low-lying states were accessed for the first time following β decay of the mother nuclei 72 Co and 74 Co. As a result, we provide a complete picture in terms of the seniority scheme up to the first ( 8 + ) levels for both nuclei. The experimental results are compared to shell-model calculations in order to define to what extent the seniority quantum number is preserved in the first neutron g 9 / 2 shell. We find that the disappearance of the seniority isomerism in the ( 8 1 + ) states can be explained by a lowering of the seniority-four ( 6 + ) levels as predicted years ago. For 74 Ni, the internal de-excitation pattern of the newly observed ( 6 2 + ) state supports a restoration of the normal seniority ordering up to spin J = 4 . This property, unexplained by the shell-model calculations, is in agreement with a dominance of the single-particle spherical regime near 78 Ni. [ABSTRACT FROM AUTHOR]