The paper is the third of a series dedicated to the ab initio description of monopole giant resonances in mid-mass closed- and open-shell nuclei via the so-called projected generator coordinate ...method. The present focus is on the computation of the moments mk of the monopole strength distribution, which are used to quantify its centroid energy and dispersion. First, the capacity to compute low-order moments via two different methods is developed and benchmarked for the m1 moment. Second, the impact of the angular momentum projection on the centroid energy and dispersion of the monopole strength is analysed before comparing the results to those obtained from consistent quasi-particle random phase approximation calculations. Next, the so-called energy weighted sum rule (EWSR) is investigated. First, the appropriate ESWR in the center-of-mass frame is derived analytically. Second, the intrinsic EWSR is tested in order to quantify the (unwanted) local-gauge symmetry breaking of the presently employed chiral effective field theory (χEFT) interactions. Finally, the infinite nuclear matter incompressibility associated with the employed χEFT interactions is extracted by extrapolating the finite-nucleus incompressibility computed from the monopole centroid energy.
Giant resonances (GRs) are a striking manifestation of collective motions in atomic nuclei. The present paper is the second in a series of four dedicated to the use of the projected generator ...coordinate method (PGCM) for the ab initio determination of the isoscalar giant monopole resonance (GMR) in closed- and open-shell mid-mass nuclei. While the first paper was dedicated to quantifying various uncertainty sources, the present paper focuses on the first applications to three doubly-open shell nuclei, namely 46Ti, 28Si and 24Mg. In particular, the goal is to investigate, starting from chiral effective field theory nuclear interactions, (i) the coupling of the GMR with the giant quadrupole resonance (GQR) in intrinsically-deformed nuclei, (ii) the possible impact of shape coexistence and shape mixing on the GMR, (iii) the GMR based on shape isomers and (iv) the impact of anharmonic effects on the monopole response. The latter is studied by comparing PGCM results to those obtained via the quasi-particle random phase approximation (QRPA), the traditional many-body approach to giant resonances, performed in a consistent setting. Eventually, PGCM results for sd-shell nuclei are in good agreement with experimental data, which is attributed to the capacity of the PGCM to capture the important fragmentation of the monopole response in light, intrinsically-deformed systems. Still, the comparison to data in 28Si and 24Mg illustrates the challenge (and the potential benefit) of extracting unambiguous experimental information.
Giant resonances (GRs) are a striking manifestation of collective motions in mesoscopic systems such as atomic nuclei. Until recently, theoretical investigations have essentially relied on the ...(quasiparticle) random phase approximation ((Q)RPA), and extensions of it, based on phenomenological energy density functionals (EDFs). As part of a current effort to describe GRs within an ab initio theoretical scheme, the present work promotes the use of the projected generator coordinate method (PGCM). This method, which can handle anharmonic effects while satisfying symmetries of the nuclear Hamiltonian, displays a favorable (i.e. mean-field-like) scaling with system’s size. Presently focusing on the isoscalar giant monopole resonance (GMR) of light- and medium-mass nuclei, PGCM’s potential to deliver wide-range ab initio studies of GRs in closed- and open-shell nuclei encompassing pairing, deformation, and shape coexistence effects is demonstrated. The comparison with consistent QRPA calculations highlights PGCM’s unique attributes and sheds light on the intricate interplay of nuclear collective excitations. The present paper is the first in a series of four and focuses on technical aspects and uncertainty quantification of ab initio PGCM calculations of GMR using the doubly open-shell 46Ti as an illustrative example. The second paper displays results for a set of nuclei of physical interest and proceeds to the comparison with consistent (deformed) ab initio QRPA calculations. While the third paper analyzes useful moments of the monopolar strength function and different ways to access them within PGCM calculations, the fourth paper focuses on the effect of the symmetry restoration on the monopole strength function.
Since the first particle accelerator’s construction in 1931, an exponential spread of these machines occurred worldwide, in different kinds of applications. Nowadays, these are mainly used for ...industrial (60%) and medical (35%) purposes and for scientific research (5%). High energy secondary mixed fields produced by the particle beams interaction with matter imply a complex environmental dosimetry and special radiation protection regulations able to guarantee workers and population safety. In the medical field, this aspect is particularly emphasized in hadrontherapy centres, where high energy charged particles such as protons and carbon ions modify environmental doses, with a significant increase in the neutron contribution. This work proposes a technique to identify points of losses of the primary particle beam around an acceleration ring and has been developed within the radiation protection section at the National Centre for Oncological Hadrontherapy situated in Pavia. In the first part, the radiation field produced by protons and carbon ions interactions with structural materials at different energies was investigated. The main instrument of analysis is the Monte Carlo code for particle transport FLUKA, supported by experimental measurements in the treatment room carried out with the rem counter LUPIN, designed for pulsed neutron fields dosimetry. This first step allowed an analysis of both the angular and energetic instrumental response and a comparison of experimental results with simulations. The second part proposes a description of the technique for beam loss positions reconstruction around the acceleration ring at CNAO based on the application of unfolding codes.
Concern exists that frequent use of topically-applied fusidic acid (FA) and chlorhexidine (CHX) for canine pyoderma is driving clinically relevant resistance, despite rare description of FA and CHX ...genetic resistance determinants in canine-derived staphylococci. This study aimed to determine minimum inhibitory concentrations (MICs) and investigate presence of putative resistance determinants for FA and CHX in canine-derived methicillin-resistant (MR) and -susceptible (MS) staphylococci. Plasmid-mediated resistance genes (fusB, fusC, fusD, qacA/B, smr; PCR) and MICs (agar dilution) of FA and CHX were investigated in 578 staphylococci (50 MR S. aureus SA, 50 MSSA, 259 MR S. pseudintermedius SP, 219 MSSP) from Finland, U.S.A., North (NUK) and South-East U.K. (SEUK) and Germany. In all isolates with FA MIC ≥64 mg/L (n = 27) fusA and fusE were amplified and sequenced.
FA resistance determinants (fusA mutations n = 24, fusB n = 2, fusC n = 36) were found in isolates from all countries bar U.S.A. and correlated with higher MICs (≥1 mg/L), although 4 SP isolates had MICs of 0.06 mg/L despite carrying fusC. CHX MICs did not correlate with qacA/B (n = 2) and smr (n = 5), which were found in SEUK SA, and SP from NUK and U.S.A.
Increased FA MICs were frequently associated with fusA mutations and fusC, and this is the first account of fusB in SP. Despite novel description of qacA/B in SP, gene presence did not correlate with CHX MIC. Selection pressure from clinical use might increase prevalence of these genetic determinants, but clinical significance remains uncertain in relation to high skin concentrations achieved by topical therapy.
Asymmetrical
N
,
N
-bis(alkanol)amine aryl esters (FRA77, GDE6, and GDE19) are potent multidrug resistance (MDR) reversers. Their structures loosely remind that of the Ca
2+
antagonist verapamil. ...Therefore, the aim of this study was to investigate their vascular activity in vitro. Their effects on the mechanical activity of fresh and cultured rat aorta rings on Ca
v
1.2 channel current (
I
Ca1.2
) of A7r5 cells and their cytotoxicity on A7r5 and EA.hy926 cells were analyzed. Docking at the rat α
1C
subunit of the Ca
v
1.2 channel was simulated in silico. Compounds tested were cytotoxic at concentrations >1 μM (FRA77, GDE6, GDE19) and >10 μM (verapamil) in EA.hy926 cells, or >10 μM (FRA77, GDE6, GDE19) and at 100 μM (verapamil) in A7r5 cells. In fresh rings, the three compounds partly antagonized phenylephrine and 60 mM K
+
(K60)-induced contraction at concentrations ≥1 and ≥3 μM, respectively. On the contrary, verapamil fully relaxed rings pre-contracted with both agents. In cultured rings, 10 μM GDE6, GDE19, FRA77, and verapamil significantly reduced the contractile response to both phenylephrine and K60. Similarly to verapamil, the three compounds docked at the α
1C
subunit, interacting with the same amino acids residues. FRA77, GDE6, and GDE19 inhibited
I
Ca1.2
with IC
50
values 1 order of magnitude higher than that of verapamil. FRA77-, GDE6-, and GDE19-induced vascular effects occurred at concentrations that are at least 1 order of magnitude higher than those effectively reverting MDR. Though an unambiguous divergence between MDR reverting and vascular activity is of overwhelming importance, these findings consistently contribute to the design and synthesis of novel and potent chemosensitizers.
► Estrogen-like chemicals at μM–mM concentrations have cytotoxic effects on BeWo and HTR-8/SVneo trophoblast cells. ► Estrogen-like chemicals at non-cytotoxic (pM–nM) concentrations alter β-hCG ...secretion in BeWo trophoblast-like cells. ► BeWo cells are a suitable model for studying the effects of low doses of various environmental chemicals on human placenta.
The identification of reproductive toxicants is a major scientific challenge for human health. We investigated the effects of a selected group of environmental polluting chemicals mostly provided with estrogenic activity on the human trophoblast cell lines BeWo and HTR-8/SVneo. Cells were exposed for 24h to various concentrations (from 0.1pM to 1mM) of atrazine (ATR), diethylstilbestrol (DES), para-nonylphenol (p-NP), resveratrol (RES) and 17 β-estradiol (E2) and assayed for cell viability and human beta-Chorionic Gonadotropin (β-hCG) secretion.
Decrease of cell viability as respect to control, vehicle-treated, cultures was obtained for all chemicals in the concentration range of 1μM–1mM in both cell types.
A parallel decrease of β-hCG secretion was observed in BeWo cells, at 1μM–1mM concentrations, with the only exception of ATR which caused an increase at concentrations up to 1mM. β-hCG release was also unexpectedly inhibited by ATR, DES, p-NP and RES at non-toxic (pM–nM) concentrations.
These findings raise concern about the negative, potential effects of various environmental polluting chemicals on pregnancy success and fetal health.
In spite of missing dynamical correlations, the projected generator coordinate method (PGCM) was recently shown to be a suitable method to tackle the low-lying spectroscopy of complex nuclei. Still, ...describing absolute binding energies and reaching high accuracy eventually requires the inclusion of dynamical correlations on top of the PGCM. In this context, the present work discusses the first realistic results of a novel multi-reference perturbation theory (PGCM-PT) that can do so within a symmetry-conserving scheme for both ground and low-lying excited states. First, proof-of-principle calculations in a small (
e
max
=
4
) model space demonstrate that exact binding energies of closed- (
16
O
) and open-shell (
18
O
,
20
Ne
) nuclei are reproduced within 0.5–
1.5
%
at second order, i.e. through PGCM-PT(2). Moreover, profiting from the pre-processing of the Hamiltonian via multi-reference in-medium similarity renormalization group transformations, PGCM-PT(2) can reach converged values within smaller model spaces than with an unevolved Hamiltonian. Doing so, dynamical correlations captured by PGCM-PT(2) are shown to bring essential corrections to low-lying excitation energies that become too dilated at leading order, i.e., at the strict PGCM level. The present work is laying the foundations for a better understanding of the optimal way to grasp static and dynamical correlations in a consistent fashion, with the aim of accurately describing ground and excited states of complex nuclei via ab initio many-body methods.
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