Structural transitions in granular packs: statistical mechanics and statistical geometry investigations

We investigate equal spheres packings generated from several experiments and from a large number of different numerical simulations. The structural organization of these disordered packings is studied in terms of the network of common neighbours. This geometrical analysis reveals sharp changes in the network's clustering occurring at the packing fractions (fraction of volume occupied by the spheres respect to the total volume, $\rho$) corresponding to the so called Random Loose Packing limit (RLP, $\rho \sim 0.555$) and Random Close Packing limit (RCP, $\rho \sim 0.645$). At these packing fractions we also observe abrupt changes in the fluctuations of the portion of free volume around each sphere. We analyze such fluctuations by means of a statistical mechanics approach and we show that these anomalies are associated to sharp variations in a generalized thermodynamical variable which is the analogous for these a-thermal systems to the specific heat in thermal systems.Comment: 7 pages, 6 figure

Horizontal Branch Stars: The Interplay between Observations and Theory, and Insights into the Formation of the Galaxy

We review HB stars in a broad astrophysical context, including both variable and non-variable stars. A reassessment of the Oosterhoff dichotomy is presented, which provides unprecedented detail regarding its origin and systematics. We show that the Oosterhoff dichotomy and the distribution of globular clusters (GCs) in the HB morphology-metallicity plane both exclude, with high statistical significance, the possibility that the Galactic halo may have formed from the accretion of dwarf galaxies resembling present-day Milky Way satellites such as Fornax, Sagittarius, and the LMC. A rediscussion of the second-parameter problem is presented. A technique is proposed to estimate the HB types of extragalactic GCs on the basis of integrated far-UV photometry. The relationship between the absolute V magnitude of the HB at the RR Lyrae level and metallicity, as obtained on the basis of trigonometric parallax measurements for the star RR Lyrae, is also revisited, giving a distance modulus to the LMC of (m-M)_0 = 18.44+/-0.11. RR Lyrae period change rates are studied. Finally, the conductive opacities used in evolutionary calculations of low-mass stars are investigated. [ABRIDGED]Comment: 56 pages, 22 figures. Invited review, to appear in Astrophysics and Space Scienc

The theory-practice gap: impact of professional-bureaucratic work conflict on newly-qualified nurses

Aim: This paper reports the findings from a naturalistic enquiry undertaken in the United Kingdom into the extent to which the ideals and values of the preregistration nursing course are adopted by individual newly educated Registered Nurses.Background: Research in several countries provides consistent evidence of the existence of a theory–practice gap in nursing. Clear disparities have been demonstrated between the best practice ideals and values that are taught and those actually encountered in everyday practice. Nurse education 'Project 2000' reforms in the United Kingdom were designed, in part, to address this issue. Few studies to date have examined the impact of these reforms on newly qualified Registered Nurses' ability to translate theory into practice.Methods: A longitudinal study was carried out in three educational institutions in the United Kingdom from 1997 to 2000. Final year nursing students (n = 72) in three colleges of nursing completed questionnaires to elicit views on their ideals and values for practice. In-depth interviews with a purposive subsample of 26 participants (at 4–6 and 11–15 months postqualification) indicated the extent to which these ideals and values were adopted in practice. Interviews were tape-recorded, transcribed, and data were analysed using constant comparison and negative case analysis.Findings: Although new nurses emerged from their programmes with a strong set of nursing values, a number of professional and organizational factors effectively sabotaged implementation. Professional sabotage includes obeying covert rules, lack of support and poor nursing role models. Organizational sabotage includes structural and organizational constraints such as time pressures, role constraints, staff shortages and work overload.Conclusion: The disparity between nursing as taught and as practised may have profound implications for the future of the profession both in the United Kingdom and internationally, in terms of morale, job satisfaction and retention. Measures to improve resources and reduce the professional–bureaucratic work conflict are discussed