Isospin splitting of the nucleon mean field

The isospin splitting of the nucleon mean field is derived from the Brueckner theory extended to asymmetric nuclear matter. The Argonne V18 has been adopted as bare interaction in combination with a microscopic three body force. The isospin splitting of the effective mass is determined from the Brueckner-Hartree-Fock self-energy: It is linear acording to the Lane ansatz and such that $m^*_n > m^*_p$ for neutron-rich matter. The symmetry potential is also determined and a comparison is made with the predictions of the Dirac-Brueckner approach and the phenomenological interactions. The theoretical predictions are also compared with the empirical parametrizations of neutron and proton optical-model potentials based on the experimental nucleon-nucleus scattering and the phenomenological ones adopted in transport-model simulations of heavy-ion collisions. The direct contribution of the rearrangement term due to three-body forces to the single particle potential and symmetry potential is discussed.Comment: 8 pages, 10 figure

The baryonic Y-shape confining potential energy and its approximants

We discuss the validity of replacing the complicated three-body confinement operator of the Y string junction type by three kinds of approximation which are numerically much simpler to handle: a one-body operator with the junction point at the centre of mass, a two-body operator corresponding to half the perimeter of the triangle formed by the three particles, and the average of both. Two different approaches for testing the quality of the approximations are proposed: a geometrical treatment based on the comparison of the potential energy strengths for the various inter quark distances, and a dynamical treatment based on the comparison of the corresponding effective string tensions using a hyperspherical approach. Both procedures give very similar results. It is shown how to simulate the genuine string junction operator by the approximations proposed above. Exact three-body calculations are presented in order to compare quantitatively the various approximations and to confirm our analysis.Comment: 28 pages, 5 figures, submitted to EPJ

Is the abundance of Faecalibacterium prausnitzii relevant to Crohn's disease?

Reports that bacteria within the Firmicutes phylum, especially the species Faecalibacterium prausnitzii, are less abundant in Crohn’s disease (CD) patients and supernatants from cultures of this bacterium are anti-inflammatory prompted the investigation of the possible correlations between the abundance of F.prausnitzii and the response to treatment in patients with gut diseases and healthy controls. In a randomized, double-blind trial, faeces were collected from healthy volunteers, and from patients with active CD, ulcerative colitis (UC) and irritable bowel syndrome before and after treatment. The levels of F. prausnitzii DNA in faecal suspensions were determined by PCR. Treatment by an elemental diet was effective, resulting in decreases in both the Harvey and Bradshaw index (P<0.001) and the concentrations of serum C-reactive protein (P<0.05). The total levels of F. prausnitzii in faecal samples from CD patients at presentation were lower than those in the other groups both before and after the treatment. There was no correlation between F. prausnitzii abundance and the severity of CD before treatment. Clinical improvement unexpectedly correlated with a significant decrease in the abundance of F. prausnitzii, especially the A2-165 subgroup (P<0.05). Our data suggest that a paucity of F. prausnitzii in the gastrointestinal microbial communities is likely to be a minor aetiological factor in CD: recovery following elemental diet is attributed to lower levels of gut flora

Carrying capacity and goat botanical diet composition in an arid ecosystem, Lavalle, Argentina

8 págs, 1 tabla.-- Comunicación presentada a la XLV Reunión Científica de la Sociedad Española para el Estudio de los Pastos: "Producciones agroganaderas: gestión eficiente y conservación del medio natural" (Gijón, 28 de mayo al 3 de junio de 2005).[ES] El trabajo se llevó a cabo en el departamento de Lavalle, Mendoza, Argentina. Las unidades de pastos, más importantes desde el punto de vista forrajero son: Algarrobal de Prosopis flexuosa; Matorral con Atriplex lampa (zampal); Matorral con Tricomaria usillo (usillar); Matorral degradado con Larrea cuneifolia (jarillal) y Medanal. Los objetivos del estudio fueron estimar la capacidad sustentadora de las diferentes unidades y la composición botánica de la ingesta de los caprinos. La estimación de dicha capacidad, expresada en hectáreas por Unidades Ganadera Caprinas (ha UGC–1), se realizó mediante el método de Point Quadrat modificado para el Monte. Y por medio del análisis microhistológico de heces se determinó la composición estacional de la ingesta.Los valores medios anuales de capacidad sustentadora fueron: Algarrobal, 1,2; Zampal, 1,7; Usillar, 3,5; Jarillal, 5,8 y Médanos, 4,3 ha UGC-1. La composición de la ingesta varió durante las estaciones, observándose una predominancia de las especies arbustivas, las gramíneas perennes aparecieron en muy baja frecuencia en todas las estaciones. El Algarrobal y el Zampal son las unidades de mayor importancia forrajera, presentando receptividades ganaderas más altas y una oferta forrajera más estable a lo largo del año, respecto del resto de las unidades de pastos analizadas.[EN] The work was carried out in the department of Lavalle, Mendoza, Argentina. The units of pastures, more important from the forage matter are: Algarrobal of Prosopis flexuosa; Shrubland with Atriplex lampa (zampal); Shrubland with Tricomaria usillo (usillar); Shrubland degraded with Larrea cuneifolia (jarillal) and Dunes. The aims of the study were to estimate the carrying capacity of the different units and the botanical composition of goat diets. The carrying capacity, expressed in hectares by Units Goat (ha UG-1), was measured by the method of Point Quadrat modified for Monte and the seasonal botanical composition of goat diets, was determined by microhistological analysis of faeces. The annual average values of carrying capacity were: Algarrobal, 1.2; Zampal, 1.7; Usillar, 3.5; Jarillal, 5.8 and Dunes, 4.3 ha UG-1. The composition of the diet varied during the seasons, the predominance of the shrubs species were observed, the perennial grass appeared in low frequency in all the seasons. The Algarrobal and the Zampal are the units of greater forage importance, where forage receptivity are higher and with more stable production throughout the year, respect to the others units of pastures analyzed.Peer reviewe

Management of vertebral osteomyelitis over an eight-year period: The UDIPROVE (UDIne PROtocol on VErtebral osteomyelitis)

Objectives: Vertebral osteomyelitis (VO) is a compelling clinical entity for clinicians because of its insidious and indolent course, which makes diagnosis difficult. Methods: All patients with a suspected diagnosis of VO were analyzed over an 8-year period (January 2009 to January 2017). The UDIPROVE protocol (UDIne PROtocol on VErtebral osteomyelitis) was applied in all cases. The primary endpoint was the performance of the UDIPROVE protocol to obtain the causal bacteria of infection. Results: During the study period, 133 episodes of confirmed VO were observed. The etiology of infection was obtained in 73.6% of cases: 70.5% were gram-positive, 16.3% were gram-negative, and 13.2% were mycobacteria. 18F-Fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) showed that for tubercular VO, the median standard uptake value (SUV) was higher when compared with VO caused by other bacteria. Clinical cure at the end of therapy was reported in 85.7% of patients. Previous antimicrobial therapy and a delay of more than 5 days in performing biopsy were associated with an undiagnosed etiology of VO. Targeted antibacterial therapy and follow-up with FDG-PET/CT were associated with clinical cure at the end of therapy, while the involvement of more than two vertebrae and inadequate drainage were associated with failure. Conclusions: Rigorous application of the UDIPROVE protocol allowed the causative pathogens of VO to be obtained \u2013 at about twice the rate reported in the literature. The use of FDG-PET/CT for the follow-up of infection was more reliable when compared to magnetic resonance imaging (MRI)

Towards a fully self-consistent spectral function of the nucleon in nuclear matter

We present a calculation of nuclear matter which goes beyond the usual quasi-particle approximation in that it includes part of the off-shell dependence of the self-energy in the self-consistent solution of the single-particle spectrum. The spectral function is separated in contributions for energies above and below the chemical potential. For holes we approximate the spectral function for energies below the chemical potential by a $\delta$-function at the quasi-particle peak and retain the standard form for energies above the chemical potential. For particles a similar procedure is followed. The approximated spectral function is consistently used at all levels of the calculation. Results for a model calculation are presented, the main conclusion is that although several observables are affected by the inclusion of the continuum contributions the physical consistency of the model does not improve with the improved self-consistency of the solution method. This in contrast to expectations based on the crucial role of self-consistency in the proofs of conservation laws.Comment: 26 pages Revtex with 4 figures, submitted to Phys. Rev.