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The calcium isotopes are an ideal system to investigate the evolution of shell structure and magic numbers. Although the properties of surface nucleons in calcium have been well studied, probing the structure of deeply bound nucleons remains a challenge. Here, we report on the first measurement of unbound states in 53Ca and 55Ca, populated from 54,56Ca(p,pn) reactions at a beam energy of around 216 MeV/nucleon at the RIKEN Radioactive Isotopes Beam Factory. The resonance properties, partial cross sections, and momentum distributions of these unbound states were analyzed. Orbital angular momentum l assignments were extracted from momentum distributions based on calculations using the distorted wave impulse approximation (DWIA) reaction model. The resonances at excitation energies of 5516(41)keV in 53Ca and 6000(250)keV in 55Ca indicate a significant l =3 component, providing the first experimental evidence for the ν0f7/2 single-particle strength of unbound hole states in the neutron-rich Ca isotopes. The observed excitation energies and cross-sections point towards extremely localized and well separated strength distributions, with some fragmentation for the ν0f7/2 orbital in 55Ca. These results are in good agreement with predictions from shell-model calculations using the effective GXPF1Bs interaction and ab initio calculations and diverge markedly from the experimental distributions in the nickel isotones at Z=28.

Pumice sand is a volcanic material widely distributed in volcanic areas such as Japan, Indonesia, and countries traversed by volcanic mountains. Geotechnical problems regarding pumice sand often occur in these areas, such as landslides because of the pumice crushable structure. Based on previous research, some failure phenomena are caused by the existing pumice layer, and not so many studies describe the behavior of pumice single particle located at Kyushu Island, Japan. This study conducted a series of tests to clarify pumice material's microscopic and mechanical properties. Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) tests were carried out on pumice materials to determine the microscopic and chemical compounds in the pumice material. Then, single-particle crushability tests were carried out as representative of the mechanical behavior of pumice sand particles. The approach using linear regression fitting is carried out using conventional frequentist and Bayesian hierarchical approaches to obtain the strength behavior of the pumice sand. An overview of pumice microscopy conditions and minerals can be helpful when ground improvement and soil stabilization are discussed for this pumice material and the effect of particle shape on pumice strength is observed. According to this study, oxygen, silica, and alumina dominate pumice sand chemical components. The aspect ratio and the roundness coefficient of pumice sand do not significantly impact particle stress. Particle size reduces and increases particle stress in single-particle crushability tests. Single-particle crushability reduces pumice particle pore area and increases the number of pores. [ABSTRACT FROM AUTHOR]

Particle breakage is one of the issues that significantly affect the strength characteristics of aggregate. In this paper, the strength of pre-crushed limestone aggregate was evaluated through investigating the friction angle, stress–strain behaviour, and single-particle strength. The particle breakage phenomenon was studied for samples prepared at different conditions, including non-soaked samples, water-soaked samples, and acid-soaked samples. The purpose of preparing the samples at different conditions was to simulate the effect of environmental factors on the breakage behaviour of limestone aggregate. The test program of this paper consists of two phases of triaxial tests: the initial shearing and second shearing. The test results showed remarkable variations among the samples since limestone aggregate tended to experience more particle breakage after being soaked in water and acid solution. Also, the volume change results exhibited an increase in dilation as the breakage index increases. The test results of this study presented the importance of considering the role of environmental factors in evaluating the particle breakage of limestone aggregate. [ABSTRACT FROM AUTHOR]

The calcium isotopes are an ideal system to investigate the evolution of shell structure and magic numbers. Although the properties of surface nucleons in calcium have been well studied, probing the structure of deeply bound nucleons remains a challenge. Here, we report on the first measurement of unbound states in 53Ca and 55Ca, populated from 54,56Ca(p , p n) reactions at a beam energy of around 216 MeV/nucleon at the RIKEN Radioactive Isotopes Beam Factory. The resonance properties, partial cross sections, and momentum distributions of these unbound states were analyzed. Orbital angular momentum l assignments were extracted from momentum distributions based on calculations using the distorted wave impulse approximation (DWIA) reaction model. The resonances at excitation energies of 5516(41) keV in 53Ca and 6000(250) keV in 55Ca indicate a significant l = 3 component, providing the first experimental evidence for the ν 0 f 7 / 2 single-particle strength of unbound hole states in the neutron-rich Ca isotopes. The observed excitation energies and cross-sections point towards extremely localized and well separated strength distributions, with some fragmentation for the ν 0 f 7 / 2 orbital in 55Ca. These results are in good agreement with predictions from shell-model calculations using the effective GXPF1Bs interaction and ab initio calculations and diverge markedly from the experimental distributions in the nickel isotones at Z = 28. [ABSTRACT FROM AUTHOR]

Strength and deformation behaviors of rockfill materials, key factors for determining the stability of dams, pertain strongly to the grain crushing characteristics. In this study, single-particle crushing tests were carried out on rockfill materials with nominal particle diameters of 2.5 mm, 5 mm and 10 mm to investigate the particle size effect on the single-particle strength and the relationship between the characteristic stress and probability of non-failure. Test data were found to be described by the Weibull distribution with the Weibull modulus of 3.24. Assemblies with uniform nominal grains were then subjected to one-dimensional compression tests at eight levels of vertical stress with a maximum of 100 MPa. The yield stress in one-dimensional compression tests increased with decreasing the particle size, which could be estimated from the single-particle crushing tests. The void ratio-vertical stress curve could be predicted by an exponential function. The particle size distribution curve increased obviously with applied stresses less than 16 MPa and gradually reached the ultimate fractal grading. The relative breakage index became constant with stress up to 64 MPa and was obtained from the ultimate grading at the fractal dimension (α = 2.7). A hyperbolical function was also found useful for describing the relationship between the relative breakage index and input work during one-dimensional compression tests. Image 1 • A further investigation of the Weibull distribution for rockfill materials. • Particle size has a great influence on the fracture strength of rockfill materials. • The fractal dimension of rockfill materials could be obtained. • The relationship between the relative breakage index and input work could be described. [ABSTRACT FROM AUTHOR]

We propose a phenomenological approach to examine the role of short- and long-range nucleon-nucleon correlations in the quenching of single-particle strength in atomic nuclei and their evolution in asymmetric nuclei and neutron matter. These correlations are thought to be the reason for the quenching of spectroscopic factors observed in (e , e ′ p) , (p , 2p) and transfer reactions. We show that the recently observed increase of the high-momentum component of the protons in neutron-rich nuclei is consistent with the reduced proton spectroscopic factors. Our approach connects recent results on short-range correlations from high-energy electron scattering experiments with the quenching of spectroscopic factors and addresses for the first time quantitatively this intriguing question in nuclear physics, in particular regarding its isospin dependence. We also speculate about the nature of a quasi-proton (nuclear polaron) in neutron matter and its kinetic energy, an important quantity for the properties of neutron stars. [ABSTRACT FROM AUTHOR]