122 research outputs found
Data protection, safeguarding and the protection of children's privacy: exploring local authority guidance on parental photography at school events
Should parents be allowed to take photographs at school events? Media reports suggest that increasingly schools are answering no to this question, either prohibiting or imposing stringent restrictions upon such photography. The legal justifications for such restrictions are, however, unclear. Accordingly, in 2013 freedom of information requests were sent to local education authorities across England, Scotland and Wales, the aim being to determine what advice local education authorities provide to schools in relation to parental photography at school events, and to identify how education authoritiesâ understandings of the law influence the advice they offer. That research reveals that local education authoritiesâ understandings of the law vary significantly and that where authorities do not fully appreciate the extent of the legal obligations arising this may have significant repercussions for the children concerned
Ab initio vibrations in nonequilibrium nanowires
We review recent results on electronic and thermal transport in two different
quasi one-dimensional systems: Silicon nanowires (SiNW) and atomic gold chains.
For SiNW's we compute the ballistic electronic and thermal transport properties
on equal footing, allowing us to make quantitative predictions for the
thermoelectric properties, while for the atomic gold chains we evaluate
microscopically the damping of the vibrations, due to the coupling of the chain
atoms to the modes in the bulk contacts. Both approaches are based on a
combination of density-functional theory, and nonequilibrium Green's functions.Comment: 16 pages, to appear in Progress in Nonequilibrium Green's Functions
IV (PNGF4), Eds. M. Bonitz and K. Baltzer, Glasgow, August 200
Effects of DensityâDriven Flows on the LongâTerm Morphodynamic Evolution of FunnelâShaped Estuaries
Subtidal flows driven by density gradients affect the tideâaveraged sediment transport in estuaries and, therefore, can influence their longâterm morphodynamic evolution. The threeâdimensional Coupled OceanâAtmosphereâWaveâSediment Transport modeling system is applied to numerically analyze the effects of baroclinicity and Earth\u27s rotation on the longâterm morphodynamic evolution of idealized funnelâshaped estuaries. The morphodynamic evolution in all the analyzed cases reproduced structures identified in many tideâdominated estuaries: a meandering region in the fluvialâtidal transition zone, a tidal maximum area close to the head, and a turbidity maxima region in the brackish zone. As the morphology of the estuaries evolved, the tidal propagation (including its asymmetry), the salinity gradient, and the strength of subtidal flows changed, which reflects the strong bathymetric control of these systems. The comparison with barotropic simulations showed that the threeâdimensional structure of the flow (induced by density gradients) has leading order effects on the morphodynamic evolution. Density gradientâdriven subtidal flows (1) promote nearâbed flood dominance and, consequently, the import of sediment into the estuary, (2) accelerate the morphodynamic evolution of the upper/middle estuary, (3) promote a more concave shape of the upper estuary and reduce the ebbâtidal delta volume, and (4) produce an asymmetric bathymetry and inhibit the formation of alternate bars that would form under barotropic conditions. This latter effect is the consequence of the combined effect of Earth\u27s rotation and baroclinicity
On correlation functions of Wilson loops, local and non-local operators
We discuss and extend recent conjectures relating partial null limits of
correlation functions of local gauge invariant operators and the expectation
value of null polygonal Wilson loops and local gauge invariant operators. We
point out that a particular partial null limit provides a strategy for the
calculation of the anomalous dimension of short twist-two operators at weak and
strong coupling.Comment: 29 pages, 8 figure
Limits to scale invariance in alluvial rivers
Assumptions about fluvial processes and processâform relations are made in general models and in many siteâspecific applications. Many standard assumptions about reachâscale flow resistance, bedâmaterial entrainment thresholds and transport rates, and downstream hydraulic geometry involve one or other of two types of scale invariance: a parameter (e.g. critical Shields number) has the same value in all rivers, or doubling one variable causes a fixed proportional change in another variable in all circumstances (e.g. powerâlaw hydraulic geometry). However, rivers vary greatly in size, gradient, and bed material, and many geomorphologists regard particular types of river as distinctive. This review examines the tension between universal scaling assumptions and perceived distinctions between different types of river. It identifies limits to scale invariance and departures from simple scaling, and illustrates them using large data sets spanning a wide range of conditions. Scaling considerations and data analysis support the commonly made distinction between coarseâbed and fineâbed reaches, whose different transport regimes can be traced to the different settlingâvelocity scalings for coarse and fine grains. They also help identify two endâmember subâtypes: steep shallow coarseâbed âtorrentsâ with distinctive flowâresistance scaling and increased entrainment threshold, and very large, lowâgradient âmega riversâ with predominantly suspended load, subdued secondary circulation, and extensive backwater conditions
Moisture conditions in coated wood panels during 24 months natural weathering at five sites in Europe
Precision calculation of 1/4-BPS Wilson loops in AdS(5) x S-5
We study the strong coupling behaviour of 1/4-BPS circular Wilson loops (a family of âlatitudesâ) in N=4 Super Yang-Mills theory, computing the one-loop corrections to the relevant classical string solutions in AdS5 ĂS5. Supersymmetric localization provides an exact result that, in the large ât Hooft coupling limit, should be reproduced by the sigma-model approach. To avoid ambiguities due to the absolute normalization of the string partition function, we compare the ratio between the generic latitude and the maximal 1/2-BPS circle: any measure-related ambiguity should simply cancel in this way. We use the Gelâfand-Yaglom method with Dirichlet boundary conditions to calculate the relevant functional determinants, that present some complications with respect to the standard circular case. After a careful numerical evaluation of our final expression we still find disagreement with the localization answer: the difference is encoded into a precise âremainder functionâ. We comment on the possible origin and resolution of this discordance
- âŚ