A note on bounds for the cop number using tree decompositions

In this short note, we supply a new upper bound on the cop number in terms of tree decompositions. Our results in some cases extend a previously derived bound on the cop number using treewidth

Can guidelines improve referral to elective surgical specialties for adults? A systematic review

Aim To assess effectiveness of guidelines for referral for elective surgical assessment. Method Systematic review with descriptive synthesis. Data sources Medline, EMBASE, CINAHL and Cochrane database up to 2008. Hand searches of journals and websites. Selection of studies Studies evaluated guidelines for referral from primary to secondary care, for elective surgical assessment for adults. Outcome measures Appropriateness of referral (usually measured as guideline compliance) including clinical appropriateness, appropriateness of destination and of pre-referral management (eg, diagnostic investigations), general practitioner knowledge of referral appropriateness, referral rates, health outcomes and costs. Results 24 eligible studies (5 randomised control trials, 6 cohort, 13 case series) included guidelines from UK, Europe, Canada and the USA for referral for musculoskeletal, urological, ENT, gynaecology, general surgical and ophthalmological conditions. Interventions varied from complex (“one-stop shops”) to simple guidelines. Four randomized control trials reported increases in appropriateness of pre-referral care (diagnostic investigations and treatment). No evidence was found for effects on practitioner knowledge. Mixed evidence was reported on rates of referral and costs (rates and costs increased, decreased or stayed the same). Two studies reported on health outcomes finding no change. Conclusions Guidelines for elective surgical referral can improve appropriateness of care by improving prereferral investigation and treatment, but there is no strong evidence in favour of other beneficial effects

Pattern Formation in Polymer Blend Thin Films: Surface Roughening Couples to Phase Separation

We introduce a model for thin films of multicomponent fluids that includes lateral and vertical phase separation, preferential component attraction at both surfaces, and surface roughening. We apply our model to thin films of binary polymer blends, and use simulations of different surface-blend interaction regimes to investigate pattern formation. We demonstrate that surface roughening couples to phase separation. For films undergoing lateral phase separation via a transient wetting layer, this results in distinct stages of roughening as the film evolves between different phase equilibria

Clinical features of a novel TIMP-3 mutation causing Sorsby's fundus dystrophy: implications for disease mechanism

AIMS: To describe the phenotype in three family members affected by a novel mutation in the gene coding for the enzyme tissue inhibitor of metalloproteinase-3 (TIMP-3). METHODS: Three members of the same family were seen with a history of nyctalopia and visual loss due to maculopathy. Clinical features were consistent with Sorsby's fundus dystrophy. Exon 5 of the gene coding for TIMP-3 was amplified by the polymerase chain reaction, single strand conformation polymorphism analysis undertaken and exon 5 amplicons were directly sequenced. RESULTS: Onset of symptoms was in the third to fourth decade. Five of six eyes had geographic macular atrophy rather than neovascularisation as a cause for central visual loss. Peripheral retinal pigmentary disturbances were present. Scotopic ERGs were abnormal in all three. Mutation analysis showed a GT transversion in all three resulting in a premature termination codon, E139X, deleting most of the carboxy terminal domain of TIMP-3. CONCLUSIONS: The patients described had a form of Sorsby's fundus dystrophy which fell at the severe end of the spectrum of this disease. Postulated disease mechanisms include deposition of dimerised TIMP-3 protein

Low Frequency VLA Observations of Abell 754: Evidence for a Cluster Radio Halo and Possible Radio Relics

We present 74 MHz and 330 MHz VLA observations of Abell 754. Diffuse, halo-like emission is detected from the center of the cluster at both frequencies. At 330 MHz the resolution of 90'' distinguishes this extended emission from previously known point sources. In addition to the halo and at a much lower level, outlying steep-spectrum emission regions straddle the cluster center and are seen only at 74 MHz. The location, morphology and spectrum of this emission are all highly suggestive of at least one, and possibly two cluster radio relics. Easily obtained higher resolution, higher sensitivity VLA observations at both frequencies are required to confirm the extended nature of the halo-like emission and the 74 MHz relic detections. However, since there is prior evidence that this cluster is or has recently been in the process of a major merger event, the possible discovery of relics in this system is of great interest in light of recent observational and theoretical evidence in favor of a merger-relic connection. We discuss the possible role the merger shock waves, which are seen in the X-ray emission, may have played in the formation of the halo and radio relics in A754.Comment: 15 pages including 4 figures. Accepted for publication by Ap

Hyperopic Cops and Robbers

We introduce a new variant of the game of Cops and Robbers played on graphs, where the robber is invisible unless outside the neighbor set of a cop. The hyperopic cop number is the corresponding analogue of the cop number, and we investigate bounds and other properties of this parameter. We characterize the cop-win graphs for this variant, along with graphs with the largest possible hyperopic cop number. We analyze the cases of graphs with diameter 2 or at least 3, focusing on when the hyperopic cop number is at most one greater than the cop number. We show that for planar graphs, as with the usual cop number, the hyperopic cop number is at most 3. The hyperopic cop number is considered for countable graphs, and it is shown that for connected chains of graphs, the hyperopic cop density can be any real number in $[0,1/2].

Motivation for developing a qualitative methodological basis for the analysis of historical curriculum changes

Abstract: The qualifications National Diploma (NDip) and Baccalaureus Technologiae (BTech) have been offered by Technikons and since 2006 by Universities of Technology (UoTs). As a result of government drives for a new technology training programme a Bachelor of Engineering Technology (BEngTech) is being introduced. This study of perceptions of change by industry, lecturers and the professional body is meant to serve as feedback to enable curriculum development to be more aligned to the needs of the stakeholders. For engineering researchers the difference between theory and epistemology is still often confusing and while engineering theories are often well established and tacitly understood (essentially positivist); social science theories however embrace different ways of seeing the world and different epistemological positions. With this as background, a choice had to be made between a quantitative and a qualitative research process to accomplish the objectives of the study in question. The present research is aimed at exploring the extent to which stakeholders have inputs (and of what value) in the process of curriculum development, as little is known about the relevant curriculum changes and their impact on technology students in South Africa. As there is no present analysis of such change, the preferred research approach was originally undefined and open to a wider range of methodologies than is common for engineering research – even in engineering education. As a result of an analysis the decision was made to follow a qualitative, exploratory, descriptive and contextual methodology. In particular grounded theory was selected as the research method of choice. The aim of this paper is to describe why a qualitative methodological approach is better suited to an analysis of historical curriculum changes and their impact on technology students in South Africa than a quantitative approach

Device- versus Network-Centric Authentication Paradigms for Mobile Devices: Operational and Perceptual Trade-Offs

The increasing capability and functionality of mobile devices is leading to a corresponding increase in the need for security to prevent unauthorised access. Indeed, as the data and services accessed via mobile devices become more sensitive, the existing method of user authentication (predominately based upon Personal Identification Numbers) appears increasingly insufficient. An alternative basis for authentication is offered by biometric approaches; which have the potential to be implemented in a non-intrusive manner and also enable authentication to be applied in an ongoing manner, beyond initial point-of-entry. However, the implementation of any authentication mechanism, particularly biometric approaches, introduces considerations of where the main elements of functionality (such as the processing of authentication data, decisions making, and storing user templates/profiles) should reside. At the extremes, there are two alternatives: a device-centric paradigm, in which the aforementioned aspects are handled locally; or a network-centric paradigm, in which the actions occur remotely and under the jurisdiction of the network operator. This paper examines the alternatives and determines that each context introduces considerations in relation to the privacy of user data, the processing and storage of authentication data, network bandwidth demands, and service availability. In view of the various advantages and disadvantages, it is concluded that a hybrid approach represents the most feasible solution; enabling data storage and processing to be split between the two locations depending upon individual circumstances. This represents the most flexible approach, and will enable an authentication architecture to be more adaptable to the needs of different users, devices and security requirements

Spin resonance in the superconducting state of Li1−x_{1-x}Fex_{x}ODFe1−y_{1-y}Se observed by neutron spectroscopy

We have performed inelastic neutron scattering measurements on a powder sample of the superconductor lithium iron selenide hydroxide Li$_{1-x}$Fe$_{x}$ODFe$_{1-y}$Se ($x \simeq 0.16, y \simeq 0.02$, $T_{\rm c} = 41$\,K). The spectrum shows an enhanced intensity below $T_{\rm c}$ over an energy range $0.64\times2\Delta < E < 2\Delta$, where $\Delta$ is the superconducting gap, with maxima at the wave vectors $Q_1 \simeq 1.46$\,\AA$^{-1}$ and $Q_2 \simeq 1.97$\,\AA$^{-1}$. The behavior of this feature is consistent with the spin resonance mode found in other unconventional superconductors, and strongly resembles the spin resonance observed in the spectrum of the molecular-intercalated iron selenide, Li$_{0.6}$(ND$_{2}$)$_{0.2}$(ND$_{3}$)$_{0.8}$Fe$_{2}$Se$_{2}$. The signal can be described with a characteristic two-dimensional wave vector $(\pi, 0.67\pi)$ in the Brillouin zone of the iron square lattice, consistent with the nesting vector between electron Fermi sheets