Temperature scaling, glassiness and stationarity in the Bak-Sneppen model

We show that the emergence of criticality in the locally-defined Bak-Sneppen model corresponds to separation over a hierarchy of timescales. Near to the critical point the model obeys scaling relations, with exponents which we derive numerically for a one-dimensional system. We further describe how the model can be related to the glass model of Bouchaud [{\em J. Phys. I France {\bf 2}, 1705 (1992)}], and we use this insight to comment on the usual assumption of stationarity in the Bak-Sneppen model. Finally, we propose a general definition of self-organised criticality which is in partial agreement with other recent definitions.Comment: 5 pages, 4 figures; differences to previous work clarified. To appear in EPJ

The Anisotropic Bak-Sneppen model

The Bak-Sneppen model is shown to fall into a different universality class with the introduction of a preferred direction, mirroring the situation in spin systems. This is first demonstrated by numerical simulations and subsequently confirmed by analysis of the multitrait version of the model, which admits exact solutions in the extremes of zero and maximal anisotropy. For intermediate anisotropies, we show that the spatiotemporal evolution of the avalanche has a power law `tail' which passes through the system for any non-zero anisotropy but remains fixed for the isotropic case, thus explaining the crossover in behaviour. Finally, we identify the maximally anisotropic model which is more tractable and yet more generally applicable than the isotropic system

Rheological instability in a simple shear thickening model

We study the strain response to steady imposed stress in a spatially homogeneous, scalar model for shear thickening, in which the local rate of yielding \Gamma(l) of mesoscopic `elastic elements' is not monotonic in the local strain l. Despite this, the macroscopic, steady-state flow curve (stress vs. strain rate) is monotonic. However, for a broad class of \Gamma(l), the response to steady stress is not in fact steady flow, but spontaneous oscillation. We discuss this finding in relation to other theoretical and experimental flow instabilities. Within the parameter ranges we studied, the model does not exhibit rheo-chaos.Comment: 8 pages, 3 figs. Minor corrections made. To appear in Euro. Phys. Let

A Systematic Review of Telehealth in Palliative Care: Caregiver Outcomes

Objective: Telehealth interventions have proven efficacy in healthcare, but little is known about the results of such interventions in palliative care. We conducted a systematic review to evaluate caregiver outcomes related to palliative telehealth interventions. Materials and Methods: We searched multiple databases for articles published between January 2003 and January 2015 related to telehealth in palliative care. Two hundred twenty-one articles were considered; nine of these met study inclusion criteria. Data on study design, population, interventions, methods, outcomes, conclusions, and methodological quality were extracted and evaluated by three investigators. Results: Of the nine studies, five measured caregiver quality of life, three measured caregiver anxiety, and two measured caregiver burden. All the studies measuring caregiver quality of life showed no significant difference after telehealth interventions. The caregiver anxiety score decreased after the intervention in two studies, and one study reported significantly reduced caregiver burden. Although feasibility of or caregiver satisfaction with the telehealth intervention was not the focus of this review, most studies reported such findings. Of the nine studies, the majority were rated as having moderate quality using the Cochrane Collaboration’s tool for assessing risk of bias. Conclusions: This systematic review suggests there is evidence of overall satisfaction in caregivers who undergo a telehealth intervention, but outcomes reported were often not substantial. Methodological flaws and small sample sizes negatively affected study quality. More rigorous research to test and evaluate such palliative interventions is needed

Microscopic basis for pattern formation and anomalous transport in two-dimensional active gels

Active gels are a class of biologically-relevant material containing embedded agents that spontaneously generate forces acting on a sparse filament network. In vitro experiments of protein filaments and molecular motors have revealed a range of non- equilibrium pattern formation resulting from motor motion along filament tracks, and there are a number of hydrodynamic models purporting to describe such systems. Here we present results of extensive simulations designed to elucidate the microscopic basis underpinning macroscopic flow in active gels. Our numerical scheme includes thermal fluctuations in filament positions, excluded volume interactions, and filament elasticity in the form of bending and stretching modes. Motors are represented individually as bipolar springs governed by rate-based rules for attachment, detachment and unidirectional motion of motor heads along the filament contour. We systematically vary motor density and speed, and uncover parameter regions corresponding to unusual statics and dynamics which overlap but do not coincide. The anomalous statics arise at high motor densities and take the form of end-bound localized filament bundles for rapid motors, and extended clusters exhibiting enhanced small-wavenumber density fluctuations and power-law cluster-size distributions for slow, processive motors. Anomalous dynamics arise for slow, processive motors over a range of motor densities, and are most evident as superdiffusive mass transport, which we argue is the consequence of a form of effective self-propulsion resulting from the polar coupling between motors and filaments.Comment: 14 pages, 17 figures. Minor clarifications and updated/additional references. To appear in Soft Matte

Geology of the Venus equatorial region from Pioneer Venus radar imaging

The surface characteristics and morphology of the equatorial region of Venus were first described by Masursky et al. who showed this part of the planet to be characterized by two topographic provinces, rolling plains and highlands, and more recently by Schaber who described and interpreted tectonic zones in the highlands. Using Pioneer Venus (PV) radar image data (15 deg S to 45 deg N), Senske and Head examined the distribution, characteristics, and deposits of individual volcanic features in the equatorial region, and in addition classified major equatorial physiographic and tectonic units on the basis of morphology, topographic signature, and radar properties derived from the PV data. Included in this classification are: plains (undivided), inter-highland tectonic zones, tectonically segmented linear highlands, upland rises, tectonic junctions, dark halo plains, and upland plateaus. In addition to the physiographic units, features interpreted as coronae and volcanic mountains have also been mapped. The latter four of the physiographic units along with features interpreted to be coronae

The validity of capillary blood sampling in the determination of human growth hormone concentration during exercise in men

This is an open access article - Copyright © 2004 BMJ Publishing Group LtdBACKGROUND: Studies measuring human growth hormone (hGH) in blood during exercise have mainly used venous sampling. The invasive nature of this procedure makes evaluation of hGH impossible in various exercise environments. OBJECTIVE: To determine whether capillary sampling could offer an alternative sampling method. METHODS: Capillary and venous blood samples were collected for determination of hGH at the end of each exercise stage during an incremental exercise test in 16 male club level competitive cyclists (mean (SD) age 30.8 (8.0) years, body mass 72.2 (7.1) kg, body fat 12.9 (3.5)%, peak oxygen consumption 4.18 (0.46) l⋅min−1). Linear regression, from a plot of venous v capillary blood hGH concentration, showed a correlation coefficient of r = 0.986 (p<0.001). When geometric means and log transformations were used, a coefficient of variation of 14.2% was demonstrated between venous and capillary flow for hGH concentration. The mean ratio limits of agreement were 0.62 (1.72)—that is, 95% of the ratios were contained between 0.36 and 1.07, with a mean of 0.62. CONCLUSIONS: Capillary blood sampling is an acceptable alternative to venous sampling for determining hGH concentration during rest and exercise. Sample sites should not be used interchangeably: one site should be chosen and its use standardised

Voting at 16 – lessons for the future from the Scottish Referendum

The 2014 Referendum on Scottish independence raised many issues about the future of Scotland. It also produced an innovation as regards the electoral process by making 16 years the minimum age of participation. This article examines issues surrounding the voting age and draws on a schools-based study, which shed light on teacher and pupil opinion about this lower than usual threshold for voting. It is also concerned with how schools cover the teaching of politics and prepared students for the Referendum debate within a context of expected neutrality on a highly divisive matter. Some implications of extending the lower voting age for future elections are discussed