The Nuffield approach to the teaching of mechanisms at key stage 3

Mechanical control has been a significant and popular aspect of technology education throughout it's recent history in England and Wales. It has had a clear place in the latest national curriculum programme of study for design and technology. The Nuffield Design and Technology Project takes a systematic approach to giving pupils the resources to design and make, together with opportunities to develop design and technology capabilities through applying these resources. In establishing the "what" of learning about mechanisms, the project has sought to identify knowledge and understanding which pupils are likely to need, and be able to apply, in the course of their designing and making. In addressing the "how", the project has developed teaching and learning approaches which engage pupils in identifying, selecting, designing, modelling and making mechanisms to fulfil a specification. This paper gives a detailed account of these approaches, and the rationale behind them

Use of fibroscan in assessment of hepatic fibrosis in patients with chronic hepatitis B infection

Introduction: Assessment of the stage of liver fibrosis plays a prominent role in the decision process of treatment in chronic viral hepatitis.Objective: To determine the stage of fibrosis in patients with chronic HBV infection using fibroscan.Method: This is a cross sectional descriptive study involving patients with CHB with a valid transient elastography (TE) measurement. Liver function test and platelet count was determined. APRI and FIB-4 were calculated and Spermans rank coefficient was applied for correlation of transient elastography (TE) with either serum biomarkers.Results: 190 patients were enrolled, mean age 36.3years, 64.2% males and 89.9% were asymptomatic. TE correlated significantly with APRI and FIB-4 (r = 0.58; P < 0.001 and r = 0.42; P < 0.001, respectively). Most of the patients 131(68.9%) had no significant fibrosis (F0,F1) while those with significant fibrosis and cirrhosis were 59 (31.1%) and 23(12.1%) respectively.Conclusion: The prevalence of significant fibrosis and cirrhosis is high in this population.Keywords: Fibroscan, Hepatic fibrosis, APRI, FIB-

Entropy and the variational principle for actions of sofic groups

Recently Lewis Bowen introduced a notion of entropy for measure-preserving actions of a countable sofic group on a standard probability space admitting a generating partition with finite entropy. By applying an operator algebra perspective we develop a more general approach to sofic entropy which produces both measure and topological dynamical invariants, and we establish the variational principle in this context. In the case of residually finite groups we use the variational principle to compute the topological entropy of principal algebraic actions whose defining group ring element is invertible in the full group C*-algebra.Comment: 44 pages; minor changes; to appear in Invent. Mat

A spot check on the prevalence of viral hepatitis B on the plateau

Hepatitis B is a disease which is present globally and over 2 billion people have been infected with hepatitis b according to the World Health Organization. In Nigeria hepatitis B, chronic infection: which is defined as persistence of infection in a human being greater than six months is present in an endemic proportion. In fact Nigeria is described as an area of hyper-endemicity, having a National Prevalence that is greater than 8% of the population.Methodology: The study was carried as part of awareness campaign in a university community. Samples were taken from the participants via finger prick. Two drops of blood were placed on the strip and a buffer was added and read after five minutes.Results: There were a total of 684 participants. Out of which 404 (59.06%) were males and 280(40.94%) were females. The mean age for the study participants was 26.169±.9. Those who were positive for hepatitis b surface antigen were 75(10.96%) while those who are negative were 609(89.04%).Those with history of previous immunization for hepatitis B were 152(22.22%).Conclusion: There is still a very high prevalence of hepatitis with very low uptake of vaccination, these calls for an urgent public health intervention.Keywords: Prevalence, Hepatitis B, Spot check, viru

Cluster Perturbation Theory for Hubbard models

Cluster perturbation theory is a technique for calculating the spectral weight of Hubbard models of strongly correlated electrons, which combines exact diagonalizations on small clusters with strong-coupling perturbation theory at leading order. It is exact in both the strong- and weak-coupling limits and provides a good approximation to the spectral function at any wavevector. Following the paper by S\'en\'echal et al. (Phys. Rev. Lett. {\bf 84}, 522 (2000)), we provide a more complete description and derivation of the method. We illustrate some of its capabilities, in particular regarding the effect of doping, the calculation of ground state energy and double occupancy, the disappearance of the Fermi surface in the $t-t'$ Hubbard model, and so on. The method is applicable to any model with on-site repulsion only.Comment: 11 pages, 10 figures (RevTeX 4

Photovoltaic characterisation of GaAsBi/GaAs multiple quantum well devices

A series of strained GaAsBi/GaAs multiple quantum well diodes are characterised to assess the potential of GaAsBi for photovoltaic applications. The devices are compared with strained and strain-balanced InGaAs based devices. The dark currents of the GaAsBi based devices are around 20 times higher than those of the InGaAs based devices. The GaAsBi devices that have undergone significant strain relaxation have dark currents that are a further 10–20 times higher. Quantum efficiency measurements show the GaAsBi devices have a lower energy absorption edge and stronger absorption than the strained InGaAs devices. These measurements also indicate incomplete carrier extraction from the GaAsBi based devices at short circuit, despite the devices having a relatively low background doping. This is attributed to hole trapping within the quantum wells, due to the large valence band offset of GaAsBi

Effects of site dilution on the magnetic properties of geometrically frustrated antiferromagnets

The effect of site dilution by non magnetic impurities on the susceptibility of geometrically frustrated antiferromagnets (kagome and pyrochlore lattices) is discussed in the framework of the Generalized Constant Coupling model, for both classical and quantum Heisenberg spins. For the classical diluted pyrochlore lattice, excellent agreement is found when compared with Monte Carlo data. Results for the quantum case are also presented and discussed.Comment: 5 pages, 3 figure

Water sensitive urban design in the city of the future

With timeframes for addressing the issues of the City of the Future (CotF) rapidly approaching (e.g. 2020, 2025, 2050), this paper integrates international research knowledge and expertise from four continents. It critically evaluates the role of water sensitive urban design (WSUD) in the CotF in terms of overlapping theory and practice. The aspirations of water sensitive cities are reviewed and multiple drivers for applying WSUD are described from developing and developed country perspectives In addition, the potential for WSUD to support cities in ‘leap-frogging’ towards their visions are explored. The role of WSUD within the wider context of achieving sustainable living objectives (e.g. greater resilience, low carbon living, sustainable transportation, local food supply and social stability) is debated and the concept of the ‘multi-objective city’ introduced. Conclusions are drawn regarding opportunities for the WSUD process to provide a framework within which professionals from many disciplines can support landscape architects and urban planners in achieving multiobjective liveable cities are identified

Quasi-elastic knockout of pions and kaons from nucleons by high-energy electrons and quark microscopy of "soft" meson degrees of freedom in the nucleon

Electro-production of pions and kaons at the kinematics of quasi-elastic knockout (which is well known in the physics of atomic nucleus and corresponds to the $t$-pole diagram) is proposed for obtaining their momentum distribution (MD) in various channels of virtual decay $N \to B+\pi$, $B=N$, $\Delta$, $N^*$, $N^{**}$, and $N \to Y+K$, $Y=\Lambda$, $\Sigma$. It is a powerful tool for investigation of a quark microscopic picture of the meson cloud in the nucleon. A model of scalar $q \bar{q}$ ($^3P_0$) fluctuation in the non-trivial QCD vacuum is used to calculate pion and kaon momentum distributions (MD) in these channels.Comment: 31 pages, 11 figures, submitted to Nucl.Phys.

The critical Ising model via Kac-Ward matrices

The Kac-Ward formula allows to compute the Ising partition function on any finite graph G from the determinant of 2^{2g} matrices, where g is the genus of a surface in which G embeds. We show that in the case of isoradially embedded graphs with critical weights, these determinants have quite remarkable properties. First of all, they satisfy some generalized Kramers-Wannier duality: there is an explicit equality relating the determinants associated to a graph and to its dual graph. Also, they are proportional to the determinants of the discrete critical Laplacians on the graph G, exactly when the genus g is zero or one. Finally, they share several formal properties with the Ray-Singer \bar\partial-torsions of the Riemann surface in which G embeds.Comment: 30 pages, 10 figures; added section 4.4 in version