Flatness of tracer density profile produced by a point source in turbulence

The average concentration of tracers advected from a point source by a multivariate normal velocity field is shown to deviate from a Gaussian profile. The flatness (kurtosis) is calculated using an asymptotic series expansion valid for velocity fields with short correlation times or weak space dependence. An explicit formula for the excess flatness at first order demonstrates maximum deviation from a Gaussian profile at time t of the order of five times the velocity correlation time, with a t–1 decay to the Gaussian value at large times. Monotonically decaying forms of the velocity time correlation function are shown to yield negative values for the first order excess flatness, but positive values can result when the correlation function has an oscillatory tail

More on A Statistical Analysis of Log-Periodic Precursors to Financial Crashes

We respond to Sornette and Johansen's criticisms of our findings regarding log-periodic precursors to financial crashes. Included in this paper are discussions of the Sornette-Johansen theoretical paradigm, traditional methods of identifying log-periodic precursors, the behavior of the first differences of a log-periodic price series, and the distribution of drawdowns for a securities price.Comment: 12 LaTex pages, no figure

Carbon monoxide binding to iron porphyrins

The carbon monoxide affinities of iron complexes of meso-tetra (α,α,α,α-o-pivalamidophenyl)porphyrin (the "picket fence" porphyrin) and of a "picket fence" porphyrin derivative with an appended axial base have been measured in solution and compared with the CO affinities of various hemoproteins. The model complexes bind CO with much greater affinity than normal hemoproteins; the role of the steric bulk of distal residues in lowering the CO affinities of the hemoproteins is discussed. The significance of this lowered CO affinity is described with regard to endogenous CO. A discussion of mutant hemoglobins lacking distal residues that sterically inhibit the binding of CO is presented. The use of pressure units versus concentration units in equilibrium expressions is analyzed

Outsourcing transitions and the employment relationship implications

Drawing on three longitudinal case studies involving the outsourcing of public leisure services, this paper explores the work transitions of staff as they transfer from one organisation to another using a three-phase analytical framework. The obtained findings confirm the idea that outsourcing can be a difficult transition to go through, with losses occurring in relation to terms and conditions of employment. However, they also show how such changes can occur alongside the development of seemingly positive employment relationships with the new employer that challenge the view that the employment effects of public service outsourcing are invariably perceived in a negative light by employees. In doing so, the study’s findings are seen to point towards the value of exploring outsourcing related work transitions longitudinally and through the lens of the adopted analytical framework. They are also seen to have implications for how such transitions are theorised and managed, including in relation to the role of line managers, and for future research

On the spectrum of a stretched spiral vortex

Corrections are found to the k^–5/3 spectrum of Lundgren [Phys. Fluids 25, 2193 (1982)] for a stretched spiral vortex model (a is the stretching strain rate and k the scalar wave number) of turbulent fine scales. These take the form of additional terms arising from the early time evolution, when the stretching of vortex lines is small. For the special case when the spiral takes the form of a rolled-up shear layer, it is shown that the composite spectrum is divergent, thus requiring the introduction of a finite early cutoff time tau1 in the time integral for the nonaxisymmetric contribution. The identity nuomega2 = 2nu[integral]0[infinity]k^2E(k)dk which gives the dissipation is then satisfied self-consistently. Direct numerical calculation of the energy spectrum from the approximate vorticity field for a special choice of spiral structure nevertheless indicates that the one-term k^–5/3-spectrum result is asymptotically valid in the inertial range provided atau1 is O(1) but that the numerically calculated dissipation spectrum appears to lie somewhere between an exp(–B1k2) and an exp(–B2k) form. It is also shown that the stretched, rolled-up shear-layer model predicts asymptotic shell-summed spectra of the energy dissipation and of the square of the vorticity, each asymptotically constant, with no power-law dependence, for k smaller than the Kolmogorov wave number.The corresponding one-dimensional spectra each show –log(k1) behavior for small k1. The extension of the model given by Pullin and Saffman [Phys. Fluids A 5, 126 (1993)] is reformulated by the introduction of a long-time cutoff in the vortex lifetime and an additional requirement that the vortex structures be approximately space filling. This gives a reduction in the number of model free-parameters but introduces a dependence of the calculated Kolmogorov constant and skewness on the ratio of the initial vortex radius to the equivalent Burgers-vortex radius. A scaling for this ratio in terms of the Taylor microscale Reynolds number is proposed in which the stretching strain is assumed to be provided by the large scales with spatial coherence limited to the maximum stretched length of the structures. Postdictions of the fourth-order flatness factor and of higher moments of the longitudinal velocity gradient statistics are compared with numerical simulation

Analysing public service outsourcing: the value of a regulatory perspective

This article draws on findings from two longitudinal case studies of voluntary organisations engaged in delivering social care services via purchaser – provider relations with local authorities. The study focuses on changes to contractual relations, employment conditions in provider organisations and service quality. The article argues the influence of the market on these changes can only be adequately comprehended by rooting the analysis in an understanding of the way in which surrounding regulatory frameworks shape its structure and operation. In doing so, it reveals how in an era of shifting market conditions characterised by greater competition and dramatic local authority cuts, a ‘soft’ regulatory framework offers little support to partnership relations between voluntary organisations and local authorities. Instead, the regulatory environment undermines financial security among voluntary organisations, degrades employment conditions in them and raises concerns regarding their service quality

Public services outsourcing in an era of austerity: the case of British social care

Utilising an institutional, inter-organisational and inter-personal framework, longitudinal qualitative data are used to examine the changing nature of state – voluntary sector relationships in the area of social care outsourcing and its implications for the terms and conditions of those employed by Scottish voluntary organisations. Over the period 2002 to 2008/09, against the background of funders seeking to pass on efficiencies to voluntary organisations, these relationships have become increasingly cost-based and ‘arms-length’. This has been accompanied by downward pressures on staff terms and conditions, which are intensifying because of more draconian public expenditure cuts. Consequently, voluntary sector employers are increasingly converging on an employment model based on low pay and more limited access to sickness, pension and other benefits that is informed strongly by narrow financial logics