7 research outputs found
Scalar Decay in Chaotic Mixing
I review the local theory of mixing, which focuses on infinitesimal blobs of
scalar being advected and stretched by a random velocity field. An advantage of
this theory is that it provides elegant analytical results. A disadvantage is
that it is highly idealised. Nevertheless, it provides insight into the
mechanism of chaotic mixing and the effect of random fluctuations on the rate
of decay of the concentration field of a passive scalar.Comment: 35 pages, 15 figures. Springer-Verlag conference style svmult.cls
(included). Published in "Transport in Geophysical Flows: Ten Years After,"
Proceedings of the Grand Combin Summer School, 14-24 June 2004, Valle
d'Aosta, Italy. Fixed some typo
Stirring up trouble: Multi-scale mixing measures for steady scalar sources
The mixing efficiency of a flow advecting a passive scalar sustained by
steady sources and sinks is naturally defined in terms of the suppression of
bulk scalar variance in the presence of stirring, relative to the variance in
the absence of stirring. These variances can be weighted at various spatial
scales, leading to a family of multi-scale mixing measures and efficiencies. We
derive a priori estimates on these efficiencies from the advection--diffusion
partial differential equation, focusing on a broad class of statistically
homogeneous and isotropic incompressible flows. The analysis produces bounds on
the mixing efficiencies in terms of the Peclet number, a measure the strength
of the stirring relative to molecular diffusion. We show by example that the
estimates are sharp for particular source, sink and flow combinations. In
general the high-Peclet number behavior of the bounds (scaling exponents as
well as prefactors) depends on the structure and smoothness properties of, and
length scales in, the scalar source and sink distribution. The fundamental
model of the stirring of a monochromatic source/sink combination by the random
sine flow is investigated in detail via direct numerical simulation and
analysis. The large-scale mixing efficiency follows the upper bound scaling
(within a logarithm) at high Peclet number but the intermediate and small-scale
efficiencies are qualitatively less than optimal. The Peclet number scaling
exponents of the efficiencies observed in the simulations are deduced
theoretically from the asymptotic solution of an internal layer problem arising
in a quasi-static model.Comment: 37 pages, 7 figures. Latex with RevTeX4. Corrigendum to published
version added as appendix
Land-use and sustainability under intersecting global change and domestic policy scenarios: trajectories for Australia to 2050
Understanding potential future influence of environmental, economic, and social drivers on land-use and sustainability is critical for guiding strategic decisions that can help nations adapt to change, anticipate opportunities, and cope with surprises. Using the Land-Use Trade-Offs (LUTO) model, we undertook a comprehensive, detailed, integrated, and quantitative scenario analysis of land-use and sustainability for Australia’s agricultural land from 2013–2050, under interacting global change and domestic policies, and considering key uncertainties. We assessed land use competition between multiple land-uses and assessed the sustainability of economic returns and ecosystem services at high spatial (1.1 km grid cells) and temporal (annual) resolution. We found substantial potential for land-use transition from agriculture to carbon plantings, environmental plantings, and biofuels cropping under certain scenarios, with impacts on the sustainability of economic returns and ecosystem services including food/fibre production, emissions abatement, water resource use, biodiversity services, and energy production. However, the type, magnitude, timing, and location of land-use responses and their impacts were highly dependent on scenario parameter assumptions including global outlook and emissions abatement effort, domestic land-use policy settings, land-use change adoption behaviour, productivity growth, and capacity constraints. With strong global abatement incentives complemented by biodiversity-focussed domestic land-use policy, land-use responses can substantially increase and diversify economic returns to land and produce a much wider range of ecosystem services such as emissions abatement, biodiversity, and energy, without major impacts on agricultural production. However, better governance is needed for managing potentially significant water resource impacts. The results have wide-ranging implications for land-use and sustainability policy and governance at global and domestic scales and can inform strategic thinking and decision-making about land-use and sustainability in Australia. A comprehensive and freely available 26 GB data pack (http://doi.org/10.4225/08/5604A2E8A00CC) provides a unique resource for further research. As similarly nuanced transformational change is also possible elsewhere, our template for comprehensive, integrated, quantitative, and high resolution scenario analysis can support other nations in strategic thinking and decision-making to prepare for an uncertain future
The phonon dispersion in 6H-SiC investigated by inelastic neutron scattering
Using coherent inelastic neutron scattering we have investigated the phonon
dispersion relation of bulk hexagonal 6H-SiC. The complete set of
phonon branches has been determined along the and 14 out of 36
branches
along the direction.
The experimental data are compared to ab initio
calculations for cubic 3C-SiC transposed to 6H-SiC.
Good agreement between theory and experiment is found for the
direction.
The discrepancies encountered for the direction are interpreted
as evidence for a dependence of the dynamical response
in the SiC system on the stacking sequence
Intravenous NPA for the treatment of infarcting myocardium early: InTIME-II, a double-blind comparison on of single-bolus lanoteplase vs accelerated alteplase for the treatment of patients with acute myocardial infarction
Aims to compare the efficacy and safety of lanoteplase, a single-bolus thrombolytic drug derived from alteplase tissue plasminogen activator, with the established accelerated alteplase regimen in patients presenting within 6 h of onset of ST elevation acute myocardial infarction. Methods and Results 15 078 patients were recruited from 855 hospitals worldwide and randomized in a 2:1 ratio to receive either lanoteplase 120 KU. kg-1 as a single intravenous bolus, or up to 100 mg accelerated alteplase given over 90 min. The primary end-point was all-cause mortality at 30 days and the hypothesis was that the two treatments would be equivalent. By 30 days, 6.61% of alteplase-treated patients and 6.75% lanoteplase-treated patients had died (relative risk 1.02). Total stroke occurred in 1.53% alteplase- and 1.87% lanoteplase-treated patients (ns); haemorrhagic stroke rates were 0.64% alteplase and 1.12% lanoteplase (P=0.004). The net clinical deficit of 30-day death or non-fatal disabling stroke was 7.0% and 7.2%, respectively. By 6 months, 8.8% of alteplase-treated patients and 8.7% of lanoteplase-treated patients had died. Conclusion Single-bolus weight-adjusted lanoteplase is an effective thrombolytic agent, equivalent to alteplase in terms of its impact on survival and with a comparable risk-benefit profile. The single-bolus regimen should shorten symptoms to treatment times and be especially convenient for emergency department or out-of-hospital administration. (C) 2000 The European Society of Cardiology