A new sound mode in liquid Helium 4?

This letter is based on the hypothesis of a small entropy content of the superfluid fraction of liquid helium. We show that such a superfluid entropy gives rise to a new sound mode in a ring-shaped superleak. This mode is named sixth sound. We propose an experiment by which its sound velocity and thereby the superfluid entropy can be measured. A negative experiment would yield a new upper limit for the superfluid entropy.Comment: 9 pages, latex, published in Phys. Lett. A 187 (1994) 8

Social isolation predicts frequent attendance in primary care

Background. Frequent attenders in primary care have complex physical and mental healthcare needs as well as low satisfaction with their healthcare. Interventions targeting mental health or psychoeducation have not been effective in reducing attendance. Here, we test the proposition that both frequent attendance and poor health are partly explained by unmet social needs (i.e., limited social group support networks). Methods. Study 1 (N=1752) was a large cross-sectional community sample of primary care attenders in Scotland. Study 2 (N = 79) was a longitudinal study of a group of young people undergoing a life transition (moving countries and commencing university) that increased their risk of frequent attendance. Study 3 (N=46) was a pre-post intervention study examining whether disadvantaged adults who joined a social group subsequently had reduced frequency of primary care attendance. Results. All three studies found that low social group connectedness was associated with a higher frequency of primary care attendance. This was not attributable to poorer health among those who were socially isolated. In Study 3, joining a social group led to reduced primary care attendance to the extent that participants experienced a (subjective) increase in their social group connectedness. Conclusions. Unmet social needs among frequent attenders warrant closer consideration. Interventions that target social group connectedness show promise for reducing overutilization of primary care services

A Parallel and Distributed Analysis Pipeline for Performance Tree Evaluation

Performance Trees are a unifying framework for the specification of performance queries involving measures and requirements. This paper describes an evaluation environment for Performance Trees comprising a client-side Performance Query Editor, incorporated as a module of the PIPE2 Petri net tool, and a cluster-based server-side evaluation engine. The latter combines the capabilities of a number of parallel and distributed analysis tools

Performance Trees: Implementation And Distributed Evaluation

In this paper, we describe the first realisation of an evaluation environment for Performance Trees, a recently proposed formalism for the specification of performance properties and measures. In particular, we present details of the architecture and implementation of this environment that comprises a client-side model and performance query specification tool, and a server-side distributed evaluation engine, supported by a dedicated computing cluster. The evaluation engine combines the analytic capabilities of a number of distributed tools for steady-state, passage time and transient analysis, and also incorporates a caching mechanism to avoid redundant calculations. We demonstrate in the context of a case study how this analysis pipeline allows remote users to design their models and performance queries in a sophisticated yet easy to use framework, and subsequently evaluate them by harnessing the computing power of a Grid cluster back-end.Accepted versio

Renormalons in the effective potential of the vectorial (φ⃗2)2(\vec{\varphi}^{2})^{2} model

We study the properties of ultraviolet renormalons in the vectorial $(\vec{\phi}^{2})^{2}$ model. This is achieved by studying the effective potential of the theory at next to leading order of the $1/N$ expansion, the appearence ofthe renormalons in the perturbative series and their relation to the imaginary part of the potential. We also consider the mechanism of renormalon cancellation by `irrelevant" higher dimensional operators.Comment: 20 pages, Latex, 3 Postscript figure

Distributed Response Time Analysis of GSPN Models with MapReduce

widely used in the performance analysis of computer and communications systems. Response time densities and quantiles are often key outputs of such analysis. These can be extracted from a GSPN’s underlying semi-Markov process using a method based on numerical Laplace transform inversion. This method typically requires the solution of thousands of systems of complex linear equations, each of rank n, where n is the number of states in the model. For large models substantial processing power is needed and the computation must therefore be distributed. This paper describes the implementation of a Response Time Analysis module for the Platform Independent Petri net Editor (PIPE2) which interfaces with Hadoop, an open source implementation of Google’s MapReduce distributed programming environment, to provide distributed calculation of response time densities in GSPN models. The software is validated with analytically calculated results as well as simulated ones for larger models. Excellent scalability is shown. I

Combining high conductivity with complete optical transparency: A band-structure approach

A comparison of the structural, optical and electronic properties of the recently discovered transparent conducting oxide (TCO), nanoporous Ca12Al14O33, with those of the conventional TCO's (such as Sc-doped CdO) indicates that this material belongs conceptually to a new class of transparent conductors. For this class of materials, we formulate criteria for the successful combination of high electrical conductivity with complete transparency in the visible range. Our analysis suggests that this set of requirements can be met for a group of novel materials called electrides.Comment: 3 pages, 3 figures, submitted for publicatio

Tuning the properties of complex transparent conducting oxides: role of crystal symmetry, chemical composition and carrier generation

The electronic properties of single- and multi-cation transparent conducting oxides (TCOs) are investigated using first-principles density functional approach. A detailed comparison of the electronic band structure of stoichiometric and oxygen deficient In$_2$O$_3$, $\alpha$- and $\beta$-Ga$_2$O$_3$, rock salt and wurtzite ZnO, and layered InGaZnO$_4$ reveals the role of the following factors which govern the transport and optical properties of these TCO materials: (i) the crystal symmetry of the oxides, including both the oxygen coordination and the long-range structural anisotropy; (ii) the electronic configuration of the cation(s), specifically, the type of orbital(s) -- $s$, $p$ or $d$ -- which form the conduction band; and (iii) the strength of the hybridization between the cation's states and the p-states of the neighboring oxygen atoms. The results not only explain the experimentally observed trends in the electrical conductivity in the single-cation TCO, but also demonstrate that multicomponent oxides may offer a way to overcome the electron localization bottleneck which limits the charge transport in wide-bandgap main-group metal oxides. Further, the advantages of aliovalent substitutional doping -- an alternative route to generate carriers in a TCO host -- are outlined based on the electronic band structure calculations of Sn, Ga, Ti and Zr-doped InGaZnO$_4$. We show that the transition metal dopants offer a possibility to improve conductivity without compromising the optical transmittance

On the Aggregation of Inertial Particles in Random Flows

We describe a criterion for particles suspended in a randomly moving fluid to aggregate. Aggregation occurs when the expectation value of a random variable is negative. This random variable evolves under a stochastic differential equation. We analyse this equation in detail in the limit where the correlation time of the velocity field of the fluid is very short, such that the stochastic differential equation is a Langevin equation.Comment: 16 pages, 2 figure

The influence of ground conditions on the performance of shared anchor systems for floating offshore wind

This is the author accepted manuscript.Significant growth of the floating offshore wind sector is anticipated over the next decade as developers target increasingly deeper sites. The efficient design of mooring systems and innovative anchor layouts will be critical in driving down the cost of this technology. Sharing anchors would lead to a reduction in total number of components to be fabricated and installed. It is also perceived that shared anchors may be smaller, facilitating installation by more readily available and cheaper vessels. These shared anchors must, however, be designed to withstand loading from multiple directions and for an increased number of fatigue load cycles. The efficiencies that can be gained from anchor sharing will vary depending on anchor type, mooring line type, applied loading, and ground conditions. This paper presents a study of the anchor types that would typically be considered for three representative sites with a common water depth, but varying ground conditions to include soft clays, dense sands, and shallow bedrock. The suitability of each anchor type for use in a shared anchor system is evaluated for the representative sites, and the anchor performance is com pared across the different soil types