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The 4 He monopole form factor is studied by computing the transition matrix element of the electromagnetic charge operator between the 4 He ground-state and the p + 3 H and n + 3 He scattering states. The nuclear wave functions are calculated using the hyperspherical harmonic method, by starting from Hamiltonians including two- and three-body forces derived in chiral effective field theory. The electromagnetic charge operator retains, beyond the leading order (impulse approximation) term, also higher order contributions, as relativistic corrections and meson-exchange currents. The results for the monopole form factor are in fair agreement with recent MAMI data. Comparison with other theoretical calculations are also provided. [ABSTRACT FROM AUTHOR]

The correlation function is a useful tool to study the interaction between hadrons. The theoretical description of this observable requires the knowledge of the scattering wave function, whose asymptotic part is distorted when two or more particles are charged. For a system of three (or more) particles, with more than two particles asymptotically free and at least two of them charged, the asymptotic part of the wave function is not known in a closed form. In the present study we introduce a screened Coulomb potential and analyze the impact of the screening radius on the correlation function. As we will show, when a sufficiently large screening radius is used, the correlation function results almost unchanged if compared to the case in which the unscreened Coulomb potential is used. This fact allows the use of free asymptotic matching conditions in the solution of the scattering equation simplifying noticeably the calculation of the correlation function. As an illustration we discuss the pp and ppp correlation functions. [ABSTRACT FROM AUTHOR]

Starting from a complete set of relativistic nucleon–nucleon contact operators up to order O (p 4) of the expansion in the soft (relative or nucleon) momentum p, we show that non-relativistic expansions of relativistic operators involve twenty-six independent combinations, two starting at O (p 0) , seven at order O (p 2) and seventeen at order O (p 4) . This demonstrates the existence of two low-energy free constants that parameterize interactions dependent on the total momentum of the pair of nucleons P. The latter, through the use of a unitary transformation, can be removed in the two-nucleon fourth-order contact interaction of the Chiral Effective Field Theory, generating a three-nucleon interaction at the same order. Within a hybrid approach in which this interaction is considered together with the phenomenological potential AV18, we show that the LECs involved can be used to fit very accurate data on the polarization observables of the low-energy p - d scattering, in particular the A y asymmetry. [ABSTRACT FROM AUTHOR]

Context. Zeeman-Doppler imaging (ZDI) is used to reconstruct the surface magnetic field of late-type stars from high-resolution spectropolarimetric observations. The results are usually described in terms of characteristics of the field topology, such as poloidality versus toroidality and axisymmetry versus non-axisymmetry, in addition to the field strength. Aims. In this study, we want to test how well these characteristics are preserved when applying the ZDI method to simulated data. We are particularly interested in how accurately the field topology is preserved and to what extent stellar parameters, such as projected rotation velocity and rotation axis inclination, influence the reconstruction. Methods. For these tests, we used published magnetic field vector data from direct numerical magnetohydrodynamic simulations taken near the surface of the simulation domain. These simulations have variable rotation rates and therefore represent different levels of activity of an otherwise Sun-like setup with a convective envelope of solar thickness. Our ZDI reconstruction is based on spherical harmonics expansion. By comparing the original values to those of the reconstructed images, we study the ability to reconstruct the surface magnetic field in terms of various characteristics of the field. Results. In general, the ZDI method works as expected. The main large-scale features are reasonably well recovered, but the strength of the recovered magnetic field is just a fraction of the original input. The quality of the reconstruction shows clear correlations with the data quality. Furthermore, there are some spurious dependencies between stellar parameters and the characteristics of the field. Conclusions. Our study uncovers some limits of ZDI. Firstly, the recovered field strength will generally be lower than the 'real' value, as smaller structures with opposite polarities will be blurred in the inversion. This is also seen in the relative distribution of magnetic energy in terms of the angular degree ℓ. Secondly, the axisymmetry is overestimated. The poloidality versus toroidality is better recovered. The reconstruction works better for a stronger field and faster rotation velocity. Still, the ZDI method works surprisingly well even for a weaker field and slow rotation provided the data have a high signal-to-noise ratio and good rotation phase coverage. [ABSTRACT FROM AUTHOR]

Context. Results from global magnetoconvection simulations of solar-like stars are at odds with observations in many respects: simulations show a surplus of energy in the kinetic power spectrum at large scales; anti-solar differential rotation profiles with accelerated poles, and a slow equator for the solar rotation rate; and a transition from axi- to nonaxisymmetric dynamos at a much lower rotation rate than what is observed. Even though the simulations reproduce the observed active longitudes in fast rotators, their motion in the rotational frame (the so-called azimuthal dynamo wave, ADW) is retrograde, in contrast to the prevalent prograde motion in observations. Aims. We study the effect of a more realistic treatment of heat conductivity in alleviating the discrepancies between observations and simulations. Methods. We use physically motivated heat conduction by applying Kramers opacity law to a semi-global spherical setup that describes the convective envelopes of solar-like stars, instead of a prescribed heat conduction profile from mixing-length arguments. Results. We find that some aspects of the results now better correspond to observations: the axi- to nonaxisymmetric transition point is shifted towards higher rotation rates. We also find a change in the propagation direction of ADWs that means that prograde waves are also now found. However, the transition from an anti-solar to solar-like rotation profile is also shifted towards higher rotation rates, leaving the models in an even more unrealistic regime. Conclusions. Although Kramers-based heat conduction does not help in reproducing the solar rotation profile, it does help in the faster rotation regime, where the dynamo solutions now better match the observations. [ABSTRACT FROM AUTHOR]

Physical systems characterized by a shallow two-body bound or virtual state are governed at large distances by continuous scale invariance, which is broken into discrete scale invariance when three or more particles come into play. This symmetry induces a universal behavior for different systems that is independent of the details of the underlying interaction and rooted in the smallness of the ratio ℓ/aB ≪ 1, where the length aB is associated with the binding energy of the two-body system , and ℓ is the natural length given by the interaction range. Efimov physics refers to this universal behavior, which is often hidden by the onset of system-specific nonuniversal effects. In this review, we identify universal properties by providing an explicit link of physical systems to their unitary limit, in which aB → ∞, and we show that nuclear systems belong to this class of universality. [ABSTRACT FROM AUTHOR]

This paper presents a methodology to develop the control systems of a surface vessel by using both computational fluid dynamics techniques and model-based control design. The model-based control design is supported by a simulation platform where both the ship hydrodynamics and the propulsion plant are modelled together. The application of CFD is related to the direct evaluation of the hull forces in the ship hydrodynamic model, for different manoeuvring conditions. The developed design tool is essential in the preliminary design phase, as a benchmark to test the control algorithms for autonomous ships. The comparison between numerical assessment and regression-based formulae has been performed on non-standard manoeuvres to quantify the difference in thrust allocation from the point of view of control design. Eventually, to validate the effectiveness of the proposed methodology, the results of the sea trials for different manoeuvres are shown. [ABSTRACT FROM AUTHOR]

Global and semi-global convective dynamo simulations of solar-like stars are known to show a transition from an antisolar (fast poles, slow equator) to solar-like (fast equator, slow poles) differential rotation (DR) for increasing rotation rate. The dynamo solutions in the latter regime can exhibit regular cyclic modes, whereas in the former one, only stationary or temporally irregular solutions have been obtained so far. In this paper we present a semi-global dynamo simulation in the transition region, exhibiting two coexisting dynamo modes, a cyclic and a stationary one, both being dynamically significant. We seek to understand how such a dynamo is driven by analyzing the large-scale flow properties (DR and meridional circulation) together with the turbulent transport coefficients obtained with the test-field method. Neither an αΩ dynamo wave nor an advection-dominated dynamo are able to explain the cycle period and the propagation direction of the mean magnetic field. Furthermore, we find that the α effect is comparable or even larger than the Ω effect in generating the toroidal magnetic field, and therefore, the dynamo seems to be of α2Ω or α2 type. We further find that the effective large-scale flows are significantly altered by turbulent pumping. [ABSTRACT FROM AUTHOR]

We consider the effect of a subadiabatic layer at the base of the convection zone on convection itself and the associated large-scale dynamos in spherical wedge geometry. We use a heat conduction prescription based on the Kramers opacity law which allows the depth of the convection zone to dynamically adapt to changes in the physical characteristics such as rotation rate and magnetic fields. We find that the convective heat transport is strongly concentrated towards the equatorial and polar regions in the cases without a substantial radiative layer below the convection zone. The presence of a stable layer below the convection zone significantly reduces the anisotropy of radial enthalpy transport. Furthermore, the dynamo solutions are sensitive to subtle changes in the convection zone structure. We find that the kinetic helicity changes sign in the deeper parts of the convection zone at high latitudes in all runs. This region expands progressively towards the equator in runs with a thicker stably stratified layer. [ABSTRACT FROM AUTHOR]

Presents a study that investigated the superconducting properties of binary and ternary niobium compounds for radio frequency (rf) applications. Fundamental parameter that characterizes the rf behavior; Procedures known to obtain niobium nitride; Description of the cryogenic experimental apparatus.

Sm-Doped ceria is one of the most promising materials to be used as electrolyte in solid oxide fuel cells due to its remarkable ionic conductivity values in the intermediate temperature range. Transport properties and local structural features of Ce1−xSmxO2−x/2 (0.1 ≤x≤ 0.7) were studied by an impedance/μ-Raman spectroscopy coupled approach up to 1073 K. Results suggest that C-based nanosized defect clusters are responsible for the drop in ionic conductivity observed even at x = 0.2, i.e. at a Sm content lower than necessary to allow C domains to reach the percolation threshold through crystallites. Moreover, within the fluorite-type compositional region, with increasing the Sm content, defect clusters undergo a rearrangement resulting in the enlargement of C-based domains rather than in the increase of their number; at higher x, on the contrary, both the size and amount of C domains increase in parallel. [ABSTRACT FROM AUTHOR]

Traumatic spinal cord injury is a devastating condition that leads to significant neurological deficits and reduced quality of life. Therapeutic interventions after spinal cord lesions are designed to address multiple aspects of the secondary damage. However, the lack of detailed knowledge about the cellular and molecular changes that occur after spinal cord injury restricts the design of effective treatments. Li and colleagues using a rat model of spinal cord injury and in vivo microscopy reveal that pericytes play a key role in the regulation of capillary tone and blood flow in the spinal cord below the site of the lesion. Strikingly, inhibition of specific proteins expressed by pericytes after spinal cord injury diminished hypoxia and improved motor function and locomotion of the injured rats. This work highlights a novel central cellular population that might be pharmacologically targeted in patients with spinal cord trauma. The emerging knowledge from this research may provide new approaches for the treatment of spinal cord injury. [ABSTRACT FROM AUTHOR]

Pericytes are defined by their anatomical location encircling blood vessels' walls with their long projections. The exact embryonic sources of cerebral pericytes remain poorly understood, especially because of their recently revealed diversity. Yamamoto et al. (Sci Rep 7(1):3855, 2017) using state-of-the-art techniques, including several transgenic mice models, reveal that a subpopulation of brain pericytes are derived from phagocytic macrophages during vascular development. This work highlights a new possible ancestor of brain pericytes. The emerging knowledge from this research may provide new approaches for the treatment of several neurodevelopmental disorders in the future. [ABSTRACT FROM AUTHOR]

Bone marrow fibrosis is a reactive process, and a central pathological feature of primary myelofibrosis. Revealing the origin of fibroblastic cells in the bone marrow is crucial, as these cells are considered an ideal, and essential target for anti-fibrotic therapy. In 2 recent studies,Decker et al. (2017) andSchneider et al. (2017), by using state-of-the-art techniques includingin vivolineage-tracing, provide evidence that leptin receptor (LepR)-expressing and Gli1-expressing cells are responsible for fibrotic tissue deposition in the bone marrow. However, what is the relationship between these 2 bone marrow cell populations, and what are their relative contributions to bone marrow fibrosis remain unclear. From a drug development perspective, these works bring new cellular targets for bone marrow fibrosis. [ABSTRACT FROM PUBLISHER]

Background Playgroups are a relatively unique form of family support programme that is common in Australia which has high community acceptance and significant government investment. However, limited evidence exists regarding the effectiveness of playgroups to achieve better outcomes for children and their parents. This study describes patterns of playgroup participation for Aboriginal and Torres Strait Islander families with young children and examines the extent to which participation from birth to three years is associated with subsequent child, parent and community outcomes. Methods This study uses three years of longitudinal data for 622 Aboriginal and Torres Strait Islander children who were participants in the Longitudinal Study of Indigenous Children (LSIC). Longitudinal associations between playgroup attendance when children were age 2 and 3 years and outcome measures for child vocabulary, motor skills, behaviour problems, prosocial development, parent home learning engagement, resilience, advice-seeking and health service use, and community trustworthiness were examined using path analysis. Results Rates of playgroup participation in this sample group were generally lower than for Australian children overall. Playgroup attendance when children were age 2 to 3 years was associated with higher parental engagement in home learning activities when children were aged 4 years which, in turn, was associated with stronger expressive vocabulary scores for children. Conclusion The findings from this study suggest that playgroup participation can enhance the home learning environments for Aboriginal and Torres Strait Islander children. Playgroups as a parent support programme hold strong potential to reach and engage families, particularly in areas of high geographic isolation, which can realize improved outcomes for children, parents and communities. [ABSTRACT FROM AUTHOR]

We undertook a prospective observational cohort study in intensive care unit (ICU) patients requiring mechanical ventilation for four days or more to evaluate normal and abnormal bacterial carriage on admission detected by surveillance cultures of throat and rectum. We assessed the importance of surveillance and diagnostic cultures for the early detection of resistance to third generation cephalosporins employed as the parenteral component of the selective decontamination of the digestive tract. Finally, we sought the risk factors of abnormal carriage on admission to the ICU. During the 58-month study 621 patients were included: 186 patients (30%) carried abnormal flora including methicillin-resistant Staphylococcus aureus (MRSA) and aerobic Gram negative bacilli (AGNB) on admission to the ICU Both MRSA and AGNB carriers were more commonly present in the hospital group of patients than in patients referred from the community (P < 0.001), although overgrowth was equally present both in community and in hospital patients. The incidence of infections during ICU stay was higher in abnormal (n=120, 64.5%) than in normal carriers (n=185, 42.5%) (P < 0.0001), with an odds ratio of 2.46 (95% confidence interval 1.72 to 3.51). Third generation cephalosporins covered ICU admission flora in 482 (78%) of the studied population. AGNB resistant to cephalosporins and MRSA were detected in surveillance cultures of 139 patients (22%), while the same resistant micro-organisms were identified only in 49 diagnostic samples (7.9%). Parenteral cephalosporins were modified in patients with abnormal flora (P < 0.0001). One hundred and ninety-six patients received antibiotics before admission to the ICU and 42% carried AGNB resistant to cephalosporins. Previous antibiotic use was the only risk factor for abnormal carriage in the multivariate analysis (OR 3.5; 95% confidence interval 2.1 to 5.8). The knowledge of carriage on admission using surveillance cultures may help intensivists to identify patients with abnormal carriage on admission and resistant bacterial strains at an early stage even when diagnostic samples are negative. Third generation cephalosporins covered admission flora in about 80% of the enrolled population and were modified in patients with abnormal flora who received antibiotic therapy before ICU admission. Our finding of overgrowth present on admission may justify the immediate administration of enteral antimicrobials. [ABSTRACT FROM AUTHOR]

In this work we describe a numerical method devised to compute continuum three-body wave functions. The method is implemented using the hyperspherical adiabatic expansion for the three-body wave function imposing a box boundary condition. The continuum energy spectrum results discretized and, for specific quantum number values, all the possible incoming and outgoing channels are simultaneously computed. For a given energy, the hyperradial continuum functions form a matrix whose ij-term refers to specific incoming and outgoing channels. When applied to three-body systems interacting only through the Coulomb potential, this method provides the adiabatic representation of the regular three-body Coulomb wave function. The computation of the irregular Coulomb wave function representation is also discussed. These regular and irregular Coulomb functions can be used to extract the $${\mathcal {S}}$$ -matrix for those reactions where, together with some short-range potential, the Coulomb interaction is also present. The method is illustrated in the case of the $$3\rightarrow 3$$ process of three alpha particles. [ABSTRACT FROM AUTHOR]

Interconnect coatings are extremely important to ensure an optimal performance of a solid oxide fuel cell (SOFC) stack. Nowadays the most common material used to produce SOFC interconnects is a ferritic stainless steel (FSS) rich in chromium which is much less expensive than the previously used ceramic interconnects. Nevertheless interconnects have to be coated in order to provide protection from the aggressive environment that surrounds them and reduce chromium species migration to the cell's cathode. In this work three different coatings were applied to Crofer® 22 H substrates via atmospheric plasma spraying (APS): two different stoichiometries of copper manganese oxide (CuxMn3-xO4, where x = 1.4 and 1.5) and one of cobalt manganese oxide (CoxMn3-xO4, where x = 1.5), considered the state of the art coating for SOFC interconnects. X-ray diffraction (XRD) was used to check the composition of deposited layers. Area specific resistance (ASR) of samples has been characterized for different samples in the range 673-1,073 K and during a 100 hours ageing test at 1,073 K. Microstructural changes and Cr-barrier properties have been characterized by SEM-EDX analyses. [ABSTRACT FROM AUTHOR]

In this work we investigate the structure and dynamics of small clusters of Helium atoms. We consider bound states of clusters having A = 2, 3, 4, 5, 6 atoms and continuum states in the three-atom system. Motivated by the fact that the He-He system has a very large scattering length a compared to the range r of the He-He potential ( r/ a < 1/10), we propose the use of a soft-core interparticle potential. We use an attractive gaussian potential that reproduces the values of the dimer binding energy and the atomatom scattering length obtained with one of the widely used He-He interactions, the LM2M2 potential. In addition, we include a repulsive three-body force to reproduce the trimer binding energy. With this model, consisting in the sum of a two- and a three-body potential, we show the spectrum of the four, five, and sixparticle systems and phase-shifts and inelasticities in the three-atom system. Comparisons to calculations using realistic He-He potentials are given. In addition some universal relations are explored. [ABSTRACT FROM AUTHOR]

We present a theoretical study of three- and four-nucleon continuum within the hyperspherical harmonics method, using a representative variety of realistic nucleon–nucleon potential models, i.e. one of phenomenological type, the Argonne v18 (AV18), one obtained within chiral effective field theory up to next-to-next-to-next-leading order, the Idaho N3LO (I-N3LO), and a “low-k” model derived from the CD-Bonn potential. In particular, the convergence pattern for the four-nucleon system is found to be problematic for the P-waves phase-shifts in the case of the AV18 potential at higher energies. An extrapolation procedure is presented and discussed. Finally, we present the theoretical results for p− d and p− 3 scattering observables at two selected energies, and we compare these with the available experimental data. In particular, some spread in the unpolarized cross section and in some polarization observables has been observed using the three potential models, in particular for A =  4. Furthermore the well known discrepancy in the vector polarization observables remains for the three potential models. [ABSTRACT FROM AUTHOR]

The paper is focused on some benefits gained by the integration of CFD results into the simulation process over time, in order to develop a whole numerical model representing the dynamics of a large merchant ship during towing/escorting operations in severe weather conditions. In particular, the shown application is referred to the simulation of a container ship, towed by two tugboats in a typical Mediterranean harbor. The developed simulator consists of a set of ordinary differential equations, mathematical relationships and numerical tables which represent the ship and the propulsion system dynamics, while CFD method is used in order to model the wind forces, eventually influenced by the presence of some harbor breakwaters, acting on the considered ship. The proposed simulator can be used as a powerful tool to plan safer towing arrangements and procedures, or to analyze in post-processing possible human errors in the case of unfortunate marine accidents. [ABSTRACT FROM AUTHOR]

We study small clusters of bosons, A = 2, 3, 4, 5, 6, characterized by a resonant interaction. Firstly, we use a soft-gaussian interaction that reproduces the values of the dimer binding energy and the atom-atom scattering length obtained with LM2M2 potential, a widely used He-He interaction. We change the intensity of the potential to explore the clusters' spectra in different regions with large positive and large negative values of the two-body scattering length and we report the clusters' energies on Efimov plot, which makes the scale invariance explicit. Secondly, we repeat our calculation adding a repulsive three-body force to reproduce the trimer binding energy. In all the region explored, we have found that these systems present two states, one deep and one shallow close to the A − 1 threshold, and scale invariance has been investigated for these states. The calculations are performed by means of Hyperspherical Harmonics basis set. [ABSTRACT FROM AUTHOR]

The effect of the inclusion of different models of three nucleon (3N) forces in p − He elastic scattering at low energies is studied. Two models have been considered: one derived from effective field theory at next-to-next-to-leading order and one derived from a more phenomenological point of view-the so-called Illinois model. The four nucleon scattering observables are calculated using the Kohn variational principle and the hyperspherical harmonic technique and the results are compared with available experimental data. We have found that with the inclusion of both 3N force models the agreement with the experimental data is improved, in particular for the proton vector analyzing power A. [ABSTRACT FROM AUTHOR]

In the first part of the contribution, we discuss the results of a recent benchmark calculation of n − H and p − He phase-shifts below the trinucleon disintegration thresholds. Three different methods-Alt, Grassberger and Sandhas, Hyperspherical Harmonics, and Faddeev-Yakubovsky-have been used and their results are compared. For both n − H and p − He we observe a rather good agreement between the three different theoretical methods. In the second part of the contribution, we study the longitudinal asymmetry $${A_z^{n^3{\rm He}}}$$ in the He( n, p)H reaction in order to obtain information about the parity-violating components of the nucleon-nucleon interaction. [ABSTRACT FROM AUTHOR]

In this work we show results for light nuclear systems and small clusters of helium atoms using the hyperspherical harmonics basis. We use the basis without previous symmetrization or antisymmetrization of the state. After the diagonalization of the Hamiltonian matrix, the eigenvectors have well defined symmetry under particle permutation and the identification of the physical states is possible. We show results for systems composed up to six particles. As an example of a fermionic system, we consider a nucleon system interacting through the Volkov potential, used many times in the literature. For the case of bosons, we consider helium atoms interacting through a potential model which does not present a strong repulsion at short distances. We have used an attractive gaussian potential to reproduce the values of the dimer binding energy, the atom-atom scattering length, and the effective range obtained with one of the most widely used He-He interaction, the LM2M2 potential. In addition, we include a repulsive hypercentral three-body force to reproduce the trimer binding energy. [ABSTRACT FROM AUTHOR]

Relativistic covariance restricts the number of two-nucleon contact operators. We show that these constraints can be implemented starting from a complete set of relativistically invariant contact operators up to order Q in the parity-violating sector and order Q in the parity-conserving one. [ABSTRACT FROM AUTHOR]

Sloshing describes the movement of liquids inside partially filled tanks, generating dynamic loads on the tank structure. The resulting impact pressures are of great importance in assessing structural strength, and their correct evaluation still represents a challenge for the designer due to the high level of nonlinearities involved, with complex free surface deformations, violent impact phenomena and influence of air trapping. In the present paper, a set of two-dimensional cases, for which experimental results are available, is considered to assess the merits and shortcomings of different numerical methods for sloshing evaluation, namely two commercial RANS solvers (FLOW-3D and LS-DYNA), and two academic software (Smoothed Particle Hydrodynamics and RANS). Impact pressures at various critical locations and global moment induced by water motion in a partially filled rectangular tank, subject to a simple harmonic rolling motion, are evaluated and predictions are compared with experimental measurements. [ABSTRACT FROM AUTHOR]

The article discusses the importance of the use of surveillance cultures of throat and rectum to evaluate the normal and abnormal bacterial carriage of intensive care unit (ICU) patients needing mechanical ventilation for four days or more upon admission. In a study conducted among 621 patients, 30 percent were found to have carried abnormal flora like methicillin-resistant Staphylococcus aureus (MRSA) and aerobic Gram negative bacilli (AGNB). The results could justify the immediate administration of enteral antimicrobials.

The catalytic activity of Ni-based anodic materials was investigated in complete solid oxide fuel cells (SOFCs) by electrochemical analysis. Button cells, consisting of supporting yttria-stabilized zirconia (YSZ) electrolyte layer, (La1− xSr x) y MnO3 (LSM) cathode and (cermet) Ni0.5Co0.5–YSZ anode were employed. Powders for anodes were obtained by wet impregnation. This procedure allowed easy production of composite electrodes with homogeneous distribution of phases and controlled microstructure. Two electrodes impedance spectroscopy was carried out at different temperatures and partial pressures of reacting gases in order to evaluate contribution of each component to overall cell losses. Current–voltage characteristic curves were also collected. Feeding with CH4 was tested and compared to H2. No deterioration of cell performance due to carbon formation at anode was observed over a test period of 100 h. [ABSTRACT FROM AUTHOR]

We propose to use the hyperspherical harmonics (HH) basis to solve the A-body system problem without explicit symmetrization or anti-symmetrization of the basis functions as required by the statistic of the system. Therefore, the HH basis set is expressed with respect to a given ordering of the A particles. However, after diagonalization, the eigenvectors reflect the symmetries of the Hamiltonian, and it is possible to identify the physical states having the expected symmetry under particle permutation. As an example we study the case of four particles interacting through a short-range spin-dependent interaction and the Coulomb potential. [ABSTRACT FROM AUTHOR]