Melting of a tetrahedral network model of silica

Thermal properties of an idealised tetrahedral network model of silica are investigated by Monte Carlo simulations. The interatomic potential consists of anharmonic stretching and bending terms, plus a short range repulsion. The model includes a bond interchange rule similar to the well known Wooten, Winer and Weaire (WWW) algorithm (see Phys. Rev. Lett., 1985, 54, 1392). Simulations reveal an apparent first order melting transition at T = 2200 K. The computed changes in the local coordination upon melting are consistent with experimental and ab initio data.

Living through the death of a child: A qualitative study of bereaved parents’ experiences

Design: Cross-sectional qualitative study.

Data sources: Interviews with purposeful sample of 25 recently bereaved parents.

Methods: Semi-structured in-depth interviews.

Results: Four analytically distinct processes were identified in the responses of parents to the death of a child. These are referred to as ‘piloting’, ‘providing’, ‘protecting’ and ‘preserving’. Regardless of individual circumstances, these processes were integral to all parents’ coping, enabling an active ‘doing’ for their child and family throughout the trajectory of their child's illness and into bereavement.

Conclusions: Facilitating the capacity of parents to ‘do’ is central to coping with the stress and uncertainty of living through the death of a child. The provision of informational, instrumental and emotional support by health care professionals in the context of ‘doing’ is core to quality palliative care.

Keywords: Bereaved parents; Cancer; Dying child; End-of-life; Palliative care; Non-malignant

yambo: An ab initio tool for excited state calculations

yambo is an ab initio code for calculating quasiparticle energies and optical properties of electronic systems within the framework of many-body perturbation theory and time-dependent density functional theory. Quasiparticle energies are calculated within the GW approximation for the self-energy. Optical properties are evaluated either by solving the Bethe-Salpeter equation or by using the adiabatic local density approximation. yambo is a plane-wave code that, although particularly suited for calculations of periodic bulk systems, has been applied to a large variety of physical systems. yambo relies on efficient numerical techniques devised to treat systems with reduced dimensionality, or with a large number of degrees of freedom. The code has a user-friendly command-line based interface, flexible 110 procedures and is interfaced to several publicly available density functional ground-state codes.

Tri-axial accelerometers tease apart discrete behaviours in the common cuttlefish Sepia officinalis

Acceleration data loggers can be used to construct time-energy budgets or identify specific behaviours in free living animals. Within a marine context such devices have been largely deployed on vertebrates with comparatively little attention paid to commercially important invertebrates such as cephalopod molluscs. Here we tested the utility of tri-axial accelerometers to tease apart six discrete behaviours in the common cuttlefish Sepia officinalis. By considering depth profiles in conjunction with body pitch and roll and overall dynamic body acceleration we were able to make distinctions between resting at the seabed, active swimming, mating, post-coital panting and active manoeuvring along the seabed. © 2012 Marine Biological Association of the United Kingdom.

Endothelial NADPH oxidase-2 promotes interstitial cardiac fibrosis and diastolic dysfunction through proinflammatory effects and endothelial-mesenchymal transition

Objectives: This study sought to investigate the effect of endothelial dysfunction on the development of cardiac hypertrophy and fibrosis.
Background: Endothelial dysfunction accompanies cardiac hypertrophy and fibrosis, but its contribution to these conditions is unclear. Increased nicotinamide adenine dinucleotide phosphate oxidase-2 (NOX2) activation causes endothelial dysfunction.
Methods: Transgenic mice with endothelial-specific NOX2 overexpression (TG mice) and wild-type littermates received long-term angiotensin II (AngII) infusion (1.1 mg/kg/day, 2 weeks) to induce hypertrophy and fibrosis.
Results: TG mice had systolic hypertension and hypertrophy similar to those seen in wild-type mice but developed greater cardiac fibrosis and evidence of isolated left ventricular diastolic dysfunction (p < 0.05). TG myocardium had more inflammatory cells and VCAM-1-positive vessels than did wild-type myocardium after AngII treatment (both p < 0.05). TG microvascular endothelial cells (ECs) treated with AngII recruited 2-fold more leukocytes than did wild-type ECs in an in vitro adhesion assay (p < 0.05). However, inflammatory cell NOX2 per se was not essential for the profibrotic effects of AngII. TG showed a higher level of endothelial-mesenchymal transition (EMT) than did wild-type mice after AngII infusion. In cultured ECs treated with AngII, NOX2 enhanced EMT as assessed by the relative expression of fibroblast versus endothelial-specific markers.
Conclusions: AngII-induced endothelial NOX2 activation has profound profibrotic effects in the heart in vivo that lead to a diastolic dysfunction phenotype. Endothelial NOX2 enhances EMT and has proinflammatory effects. This may be an important mechanism underlying cardiac fibrosis and diastolic dysfunction during increased renin-angiotensin activation.