Effects of chemical reaction, thermal radiation, internal heat generation, Soret and Dufour on chemically reacting MHD boundary layer flow of heat and mass transfer past a moving vertical plate with suction/injection

In the present analysis, we study the two-dimensional, steady, incompressible electrically conducting, laminar free convection boundary layer flow of a continuously moving vertical porous plate in a chemically reactive medium in the presence of transverse magnetic field, thermal radiation, chemical reaction, internal heat generation and Dufour and Soret effect with suction/injection. The governing nonlinear partial differential equations have been reduced to the coupled nonlinear ordinary differential equations by the similarity transformations. The problem is solved numerically using shooting techniques with the sixth order Runge-Kutta integration scheme. Comparison between the existing literature and the present study were carried out and found to be in excellent agreement. The influence of the various interesting parameters on the flow and heat transfer is analyzed and discussed through graphs in detail. The values of the local Nusselt number, Skin-friction and the Sherwood number for different physical parameters are also tabulated. Comparison of the present results with known numerical results is shown and a good agreement is observed

Aspect-ratio dependence of the spin stiffness of a two-dimensional XY model

We calculate the superfluid stiffness of 2D lattice hard-core bosons at half-filling (equivalent to the S=1/2 XY-model) using the squared winding number quantum Monte Carlo estimator. For L_x x L_y lattices with aspect ratio L_x/L_y=R, and L_x,L_y -> infinity, we confirm the recent prediction [N. Prokof'ev and B.V. Svistunov, Phys. Rev. B 61, 11282 (1999)] that the finite-temperature stiffness parameters \rho^W_x and \rho^W_y determined from the winding number differ from each other and from the true superfluid density \rho_s. Formally, \rho^W_y -> \rho_s in the limit in which L_x -> infinity first and then L_y -> infinity. In practice we find that \rho^W_y converges exponentially to \rho_s for R>1. We also confirm that for 3D systems, \rho^W_x = \rho^W_y = \rho^W_z = \rho_s for any R. In addition, we determine the Kosterlitz-Thouless transition temperature to be T_KT/J=0.34303(8) for the 2D model.Comment: 7 pages, 8 figures, 1 table. Minor changes to published versio

SLIP4EX- a program for routine slope stability analysis to include the effects of vegetation, reinforcement and hydrological changes

SLIP4EX is a straightforward computer program developed in connection with the EU funded ECOSLOPES project for routine stability analysis and the assessment of the contribution of vegetation to slope stability. The slope section is drawn up and dimensions and parameters are fed in to the Microsoft Excel based program for stability calculations and comparisons of Factors of Safety using different methods of analysis (Bishop, Janbu, Fellenius, Simple, Greenwood). The background and assumptions involved in the derivation of each of the methods is briefly described. The simplicity of the program enables the user to understand the nature of the analysis, explore the parameter assumptions made and compare the different methods of analysis. Soil reinforcement by geosynthetic layers or anchors, and vegetation effects of enhanced cohesion, changed water pressures, mass of vegetation, wind forces and root reinforcement forces are readily included in the analysis. The program is freely available on request from the author

Salivary alpha amylase not chromogranin A reflects sympathetic activity: exercise responses in elite male wheelchair athletes with or without cervical spinal cord injury

Background: Salivary alpha-amylase (sAA) and chromogranin A (sCgA) have both been suggested as non-invasive markers for sympathetic nervous system (SNS) activity. A complete cervical spinal cord injury leading to tetraplegia is accompanied with sympathetic dysfunction; the aim of this study was to establish the exercise response of these markers in this in vivo model. Methods: Twenty-six elite male wheelchair athletes (C6-C7 tetraplegia: N=8, T6-L1 paraplegia: N=10 and non spinal cord injured controls: N=8) performed treadmill exercise to exhaustion. Saliva and blood samples were taken pre, post, and 30 min post exercise and analysed for sAA, sCgA and plasma adrenaline concentration, respectively. Results: In all three subgroups, sAA and sCgA were elevated post exercise (P<0.05). Whilst sCgA was not different between subgroups, a group x time interaction for sAA explained the reduced post exercise sAA activity in tetraplegia (162±127 vs 313±99 (paraplegia) and 328±131 U∙mL-1 (controls), P=0.005). The post exercise increase in adrenaline was not apparent in tetraplegia (P=0.74). A significant correlation was found between adrenaline and sAA (r=0.60, P=0.01), but not between adrenaline and sCgA (r=0.06, P=0.79). Conclusions: The blunted post-exercise rise in sAA and adrenaline in tetraplegia implies that both reflect SNS activity to some degree. It is questionable whether sCgA should be used as a marker for SNS activity, both due to the exercise response which is not different between the subgroups and its non-significant relationship with adrenaline

Arm and intensity-matched leg exercise induce similar inflammatory responses

Introduction: The amount of active muscle mass can influence the acute inflammatory response to exercise, associated with reduced risk for chronic disease. This may affect those restricted to upper body exercise, for example due to injury or disability. The purpose of this study was to compare the inflammatory responses for arm exercise and intensity-matched leg exercise. Methods: Twelve male individuals performed three 45-min constant load exercise trials following determination of peak oxygen uptake for arm exercise (V[Combining Dot Above]O2peak A) and cycling (V[Combining Dot Above]O2peak C): (1) arm cranking exercise at 60%V[Combining Dot Above]O2peak A; (2) moderate cycling at 60%V[Combining Dot Above]O2peak C; and (3) easy cycling at 60%V[Combining Dot Above]O2peak A. Cytokine, adrenaline and flow cytometric analysis of monocyte subsets were performed before and up to 4h post exercise. Results: Plasma IL-6 increased from resting concentrations in all trials, however, post exercise concentrations were higher for arm exercise (1.73+/-1.04pg[BULLET OPERATOR]mL-1) and moderate cycling (1.73+/-0.95pg[BULLET OPERATOR]mL-1) compared with easy cycling (0.87+/-0.41pg[BULLET OPERATOR]mL-1,P<0.04). Similarly, the plasma IL-1ra concentration in the recovery period was higher for arm exercise (325+/-139pg[BULLET OPERATOR]mL-1) and moderate cycling (316+/-128pg[BULLET OPERATOR]mL-1) when compared with easy cycling (245+/-77pg[BULLET OPERATOR]mL-1,P<0.04). Arm exercise and moderate cycling induced larger increases in monocyte numbers and larger increases of the classical monocyte subset in the recovery period than easy cycling (P<0.05). The post-exercise adrenaline concentration was lowest for easy cycling (P=0.04). Conclusions: Arm exercise and cycling at the same relative exercise intensity induces a comparable acute inflammatory response; however, cycling at the same absolute oxygen uptake as arm exercise results in a blunted cytokine, monocyte and adrenaline response. Relative exercise intensity appears to be more important to the acute inflammatory response than modality, which is of major relevance for populations restricted to upper body exercise

A frustrated quantum spin-{\boldmath s} model on the Union Jack lattice with spins {\boldmath s>1/2}

The zero-temperature phase diagrams of a two-dimensional frustrated quantum antiferromagnetic system, namely the Union Jack model, are studied using the coupled cluster method (CCM) for the two cases when the lattice spins have spin quantum number $s=1$ and $s=3/2$. The system is defined on a square lattice and the spins interact via isotropic Heisenberg interactions such that all nearest-neighbour (NN) exchange bonds are present with identical strength $J_{1}>0$, and only half of the next-nearest-neighbour (NNN) exchange bonds are present with identical strength $J_{2} \equiv \kappa J_{1} > 0$. The bonds are arranged such that on the $2 \times 2$ unit cell they form the pattern of the Union Jack flag. Clearly, the NN bonds by themselves (viz., with $J_{2}=0$) produce an antiferromagnetic N\'{e}el-ordered phase, but as the relative strength $\kappa$ of the frustrating NNN bonds is increased a phase transition occurs in the classical case ($s \rightarrow \infty$) at $\kappa^{\rm cl}_{c}=0.5$ to a canted ferrimagnetic phase. In the quantum cases considered here we also find strong evidence for a corresponding phase transition between a N\'{e}el-ordered phase and a quantum canted ferrimagnetic phase at a critical coupling $\kappa_{c_{1}}=0.580 \pm 0.015$ for $s=1$ and $\kappa_{c_{1}}=0.545 \pm 0.015$ for $s=3/2$. In both cases the ground-state energy $E$ and its first derivative $dE/d\kappa$ seem continuous, thus providing a typical scenario of a second-order phase transition at $\kappa=\kappa_{c_{1}}$, although the order parameter for the transition (viz., the average ground-state on-site magnetization) does not go to zero there on either side of the transition.Comment: 1

The Extended Coupled Cluster Treatment of Correlations in Quantum Magnets

The spin-half XXZ model on the linear chain and the square lattice are examined with the extended coupled cluster method (ECCM) of quantum many-body theory. We are able to describe both the Ising-Heisenberg phase and the XY-Heisenberg phase, starting from known wave functions in the Ising limit and at the phase transition point between the XY-Heisenberg and ferromagnetic phases, respectively, and by systematically incorporating correlations on top of them. The ECCM yields good numerical results via a diagrammatic approach, which makes the numerical implementation of higher-order truncation schemes feasible. In particular, the best non-extrapolated coupled cluster result for the sublattice magnetization is obtained, which indicates the employment of an improved wave function. Furthermore, the ECCM finds the expected qualitatively different behaviours of the linear chain and the square lattice cases.Comment: 22 pages, 3 tables, and 15 figure

Effect of simplicity and attractiveness on route selection for different journey types

This study investigated the effects of six attributes, associated with simplicity or attractiveness, on route preference for three pedestrian journey types (everyday, leisure and tourist). Using stated choice preference experiments with computer generated scenes, participants were asked to choose one of a pair of routes showing either two levels of the same attribute (experiment 1) or different attributes (experiment 2). Contrary to predictions, vegetation was the most influential for both everyday and leisure journeys, and land use ranked much lower than expected in both cases. Turns ranked higher than decision points for everyday journeys as predicted, but the positions of both were lowered by initially unranked attributes. As anticipated, points of interest were most important for tourist trips, with the initially unranked attributes having less influence. This is the first time so many attributes have been compared directly, providing new information about the importance of the attributes for different journeys. © 2014 Springer International Publishing

Quantum magnetism in two dimensions: From semi-classical N\'eel order to magnetic disorder

This is a review of ground-state features of the s=1/2 Heisenberg antiferromagnet on two-dimensional lattices. A central issue is the interplay of lattice topology (e.g. coordination number, non-equivalent nearest-neighbor bonds, geometric frustration) and quantum fluctuations and their impact on possible long-range order. This article presents a unified summary of all 11 two-dimensional uniform Archimedean lattices which include e.g. the square, triangular and kagome lattice. We find that the ground state of the spin-1/2 Heisenberg antiferromagnet is likely to be semi-classically ordered in most cases. However, the interplay of geometric frustration and quantum fluctuations gives rise to a quantum paramagnetic ground state without semi-classical long-range order on two lattices which are precisely those among the 11 uniform Archimedean lattices with a highly degenerate ground state in the classical limit. The first one is the famous kagome lattice where many low-lying singlet excitations are known to arise in the spin gap. The second lattice is called star lattice and has a clear gap to all excitations. Modification of certain bonds leads to quantum phase transitions which are also discussed briefly. Furthermore, we discuss the magnetization process of the Heisenberg antiferromagnet on the 11 Archimedean lattices, focusing on anomalies like plateaus and a magnetization jump just below the saturation field. As an illustration we discuss the two-dimensional Shastry-Sutherland model which is used to describe SrCu2(BO3)2.Comment: This is now the complete 72-page preprint version of the 2004 review article. This version corrects two further typographic errors (three total with respect to the published version), see page 2 for detail