Extreme events and the morphodynamics of gravel-dominated coastal barriers: Strengthening uncertain ground

The long-term morphodynamic ordering of gravel-dominated coastal systems (GDCS), many of which serve as coastal defences in northwest Europe, is dominated by extreme events that generate barrier crest overflow. An understanding of this morphodynamic ordering is fraught with several unresolved difficulties. These are related to the twin problems of the inadequacy of pertinent morphodynamic parameterisation and of obtaining data from modern shores enabling such parameterisation. Major uncertainties concern the timing of over-crest flow in terms of return period of extreme elevation; the intensity and structure of the overflow field; antecedent beachface characteristics in response to storms; the rate of relative sea-level change; tidal stage control; and barrier resistance to forcing, itself determined by a number of unknowns including barrier form and size, sediment size and mosaics, and barrier resilience. While generalised extreme value modelling may provide a means of characterising overwashing return-period and its variability, exceptional tsunami events are outside the scope of such modelling. The characterisation of GDCS morphodynamics in terms of the forcing extreme events will necessitate integrating some or all of these parameters into a single model.

On the statistics of transverse permeability of randomly distributed fibers

An RVE–based stochastic numerical model is used to calculate the permeability of randomly generated porous media at different values of the fiber volume fraction for the case of transverse flow in a unidirectional ply. Analysis of the numerical results shows that the permeability is not normally distributed. With the aim of proposing a new understanding on this particular topic, permeability data are fitted using both a mixture model and a unimodal distribution. Our findings suggest that permeability can be fitted well using a mixture model based on the lognormal and power law distributions. In case of a unimodal distribution, it is found, using the maximum-likelihood estimation method (MLE), that the generalized extreme value (GEV) distribution represents the best fit. Finally, an expression of the permeability as a function of the fiber volume fraction based on the GEV distribution is discussed in light of the previous results.

Symposium - Organisational transformation in policing: Leadership and change in extreme contexts

Nearly 4000 people died in Northern Ireland’s long running conflict, 314 of them police officers (Brewer and Magee 1991, Brewer 1996, Hennessey 1999, Guelke and Milton-Edwards 2000). The republican and loyalist ceasefires of 1994 were the first significant signal that NI society was moving beyond the ‘troubles’ and towards a normalised political environment. The Belfast (Good Friday) Agreement of 1998 cemented that movement (Hennessey 1999). Policing was a key and seemingly unresolvable element of the conflict, seen as unrepresentative and partisan. Its reform or ‘recasting’ in a new dispensation was an integral part of the conflict transformation endeavour(Ellison 2010). As one of the most controversial elements of the conflicted past, it had remained outside the Agreement and was subject to a specific commission of interest (1999), generally known as the Patten Commission. The Commission’s far reaching proposals included a change of name, badge and uniform, the introduction of 50/50 recruitment (50% Roman Catholic and 50% other), a new focus on human rights, a new district command and headquarter structure, a review of ‘Special Branch’ and covert techniques, a concern for ‘policing with the community’ and a significant voluntary severance process to make room for new recruits, unconnected with the past history of the organisation(Murphy 2013).

This paper reflects upon the first data collection phase of a long term processual study of organisational change within the Royal Ulster Constabulary / Police Service of Northern Ireland. This phase (1996-2002) covers early organisational change initiation (including the pre-change period) and implementation including the instigation of symbolic changes (name, badge, and crest) and structural changes (new HQ structure and District Command structure). It utilises internal documentation including messages from the organisations leaders, interviews with forty key informants (identified through a combination of snow-balling from referrals by initial contacts, and key interviews with significant individuals), as well as external documentation and commentary on public perceptions of the change. Using a processual lens (Langley, Smallman et al. 2013) it seeks to understand this initial change phase and its relative success in a highly politicised environment.

By engaging key individuals internally and externally, setting up a dedicated change team, adopting a non normative, non urgent, calming approach to dissent, communicating in orthodox and unorthodox ways with members, acknowledging the huge emotional strain of letting go of the organisation’s name and all it embodied, and re-emphasising the role of officers as ‘police first’, rather than ‘RUC first’, the organisations leadership remained in control of a volatile and unhappy organisational body and succeeded in moving it on through this initial phase, even while much of the political establishment lambasted them externally. Three years into this change process the organisation had a new name, a new crest, new structures, procedures and was deeply engaged in embedding the joint principles of human rights and community policing within its re-woven fabric. While significant problems remained, the new Police Service of Northern Ireland had successfully begun a long journey to full community acceptance in a post conflict context.

This case illustrates the significant challenges of leading change under political pressure, with external oversight and no space for failure(Hannah, Uhl-Bien et al. 2009). It empirically reflects the reality of change implementation as messy, disruptive and unpredictable and highlights the significance of political skill and contextual understanding to success in the early stages(Buchanan and Boddy 1992). The implications of this for change theory and the practice of change implementation are explored (Eisenhardt and Graebner 2007) and some conclusions drawn about what such an extreme case tells us about change generally and change implementation under pressure.

Analogies between linguistics and information theory

An analogy is established between the syntagm and paradigm from Saussurean linguistics and the message and messages for selection from the information theory initiated by Claude Shannon. The analogy is pursued both as an end itself and for its analytic value in understanding patterns of retrieval from full text systems. The multivalency of individual words when isolated from their syntagm is contrasted with the relative stability of meaning of multi-word sequences, when searching ordinary written discourse. The syntagm is understood as the linear sequence of oral and written language. Saussureâ??s understanding of the word, as a unit which compels recognition by the mind, is endorsed, although not regarded as final. The lesser multivalency of multi-word sequences is understood as the greater determination of signification by the extended syntagm. The paradigm is primarily understood as the network of associations a word acquires when considered apart from the syntagm. The restriction of information theory to expression or signals, and its focus on the combinatorial aspects of the message, is sustained. The message in the model of communication in information theory can include sequences of written language. Shannonâ??s understanding of the written word, as a cohesive group of letters, with strong internal statistical influences, is added to the Saussurean conception. Sequences of more than one word are regarded as weakly correlated concatenations of cohesive units.

Fe XIII emission lines in active region spectra obtained with the Solar Extreme-Ultraviolet Research Telescope and Spectrograph

Recent fully relativistic calculations of radiative rates and electron impact excitation cross-sections for FeXIII are used to generate emission-line ratios involving 3s23p2-3s3p3 and 3s23p2-3s23p3d transitions in the 170-225 and 235-450 Å wavelength ranges covered by the Solar Extreme-Ultraviolet Research Telescope and Spectrograph (SERTS). A comparison of these line ratios with SERTS active region observations from rocket flights in 1989 and 1995 reveals generally very good agreement between theory and experiment. Several new FeXIII emission features are identified, at wavelengths of 203.79, 259.94, 288.56 and 290.81 Å. However, major discrepancies between theory and observation remain for several FeXIII transitions, as previously found by Landi and others, which cannot be explained by blending. Errors in the adopted atomic data appear to be the most likely explanation, in particular for transitions which have 3s23p3d1D2 as their upper level. The most useful FeXIII electron-density diagnostics in the SERTS spectral regions are assessed, in terms of the line pairs involved being (i) apparently free of atomic physics problems and blends, (ii) close in wavelength to reduce the effects of possible errors in the instrumental intensity calibration, and (iii) very sensitive to changes in Ne over the range 108-1011cm-3. It is concluded that the ratios which best satisfy these conditions are 200.03/202.04 and 203.17/202.04 for the 170-225 Å wavelength region, and 348.18/320.80, 348.18/368.16, 359.64/348.18 and 359.83/368.16 for 235-450 Å.

Extreme ultraviolet transitions of Fe XXI in solar, stellar and laboratory spectra

Recent R-matrix calculations of electron impact excitation rates for transitions among the 2s(2)2p(2), 2s2p(3) and 2p(4) levels of Fe XXI are used to derive theoretical electron density (N-e) sensitive emission-line ratios involving 2S2(2)p(2)-2s2p(3) transitions in the similar to 98-146 Angstrom wavelength range. A comparison of these with observations from the PLT tokamak plasma, for which the electron density has been independently determined, reveals generally very good agreement between theory and experiment, and in some instances removes discrepancies found previously. The observed Fe XXI ratios for a solar flare, obtained with the OSO-5 satellite, imply electron densities which are consistent, with discrepancies that do not exceed 0.2 dex. In addition, the derived values of N-e are similar to those estimated for the high-temperature regions of other solar flares. The good agreement between theory and observation, in particular for the tokamak spectra, provides experimental support for the accuracy of the present line-ratio calculations, and hence for the atomic data on which they are based.

A comparison of theoretical line intensity ratios for Ni XII with extreme ultraviolet observations from the JET tokamak

Recent R-matrix calculations of electron impact excitation rates in Ni XII are used to derive the emission line ratios R-1 = I(154.17 Angstrom)/I(152.15 Angstrom), R-2 = I(152.95 Angstrom)/I(152.15 Angstrom) and R-3 = 1(160.55 Angstrom)/I(152.15 Angstrom). This is the first time (to our knowledge) that theoretical emission line ratios have been calculated for this ion. The ratios are found to be insensitive to changes in the adopted electron density (N-e) when N-e greater than or equal to 5 x 10(11) cm(-3), typical of laboratory plasmas. However, they do vary with electron temperature (T-e), with for example R-1 and R-3 changing by factors of 1.3 and 1.8, respectively, between T-e = 10(5) and 10(6) K. A comparison of the theoretical line ratios with measurements from the Joint European Tents (JET) tokamak reveals very good agreement between theory and observation for R-1, with an average discrepancy of only 7%. Agreement between the calculated and experimental ratios for R-2 and R-3 is less satisfactory, with average differences of 30 and 33%, respectively. These probably arise from errors in the JET instrument calibration curve. However, the discrepancies are smaller than the uncertainties in the R-2 and R-3 measurements. Our results, in particular for R-1, provide experimental support for the accuracy of the Ni XIII line ratio calculations, and hence for the atomic data adopted in their derivation.

Simplified theory of wideband spectra of liquid H2O and D2O (from 0 to 1000 cm(-1)) due to reorienting polar and vibrating H-bonded water molecules

A semi-phenomenological molecular model is presented, which is capable of describing with the use of analytical formulae, the wideband dielectric(1) and far-infrared spectra of ordinary and heavy water. In the model the vector of a dipole moment is presented as a sum of two components. The absolute value of the first one is constant; the second one changes harmonically with time. The key aspect of this work is consideration of FIR spectra due to the second component. In the context of the modified hybrid model presented in the work, reorientation of the dipoles in the rectangular potential well is considered, as a result of which the librational (near 700 cm (-1)) and translational (near 200 cm (-1)) absorption bands and the microwave Debye relaxation spectrum arise. It is shown that the time-dependent part of a dipole moment contributes most to the translational band, the relevant mechanism is taken to be stretching vibration of the H-bonded molecules. Previous linear-response molecular models were unsuccessful in describing this band (in heavy water) in terms of the complex dielectric permittivity. The spatial and time scales characteristic of water are estimated. (C) 2002 Elsevier Science B.V. All rights reserved.

An investigation of Fe XVI emission lines in solar and stellar extreme-ultraviolet and soft X-ray spectra

New fully relativistic calculations of radiative rates and electron impact excitation cross-sections for Fe XVI are used to determine theoretical emission-line ratios applicable to the 251-361 and 32-77 angstrom portions of the extreme-ultraviolet (EUV) and soft X-ray spectral regions, respectively. A comparison of the EUV results with observations from the Solar Extreme-Ultraviolet Research Telescope and Spectrograph (SERTS) reveals excellent agreement between theory and experiment. However, for emission lines in the 32-49 angstrom portion of the soft X-ray spectral region, there are large discrepancies between theory and measurement for both a solar flare spectrum obtained with the X-Ray Spectrometer/Spectrograph Telescope (XSST) and for observations of Capella from the Low- Energy Transmission Grating Spectrometer (LETGS) on the Chandra X-ray Observatory. These are probably due to blending in the solar flare and Capella data from both first-order lines and from shorter wavelength transitions detected in second and third order. By contrast, there is very good agreement between our theoretical results and the XSST and LETGS observations in the 50-77 angstrom wavelength range, contrary to previous results. In particular, there is no evidence that the Fe XVI emission from the XSST flare arises from plasma at a much higher temperature than that expected for Fe XVI in ionization equilibrium, as suggested by earlier work.

A density functional theory study of carbon monoxide oxidation on the Cu3Pt(111) alloy surface: Comparison with the reactions on Pt(111) and Cu(111)

Alloying metals is often used as an effective way to enhance the reactivity of surfaces. Aiming to shed light on the effect of alloying on reaction mechanisms, we carry out a comparative study of CO oxidation on Cu3Pt(111), Pt(111), and Cu(111) by means of density functional theory calculations. Alloying effects on the bonding sites and bonding energies of adsorbates, and the reaction pathways are investigated. It is shown that CO preferentially adsorbs on an atop site of Pt and O preferentially adsorbs on a fcc hollow site of three Cu atoms on Cu3Pt(111). It is also found that the adsorption energies of CO (or O-a) decreases on Pt (or Cu) on the alloy surface with respect to those on pure metals. More importantly, having identified the transition states for CO oxidation on those three surfaces, we found an interesting trend for the reaction barrier on the three surfaces. Similar to the adsorption energies, the reaction barrier on Cu3Pt possesses an intermediate value of those on pure Pt and Cu metals. The physical origin of these results has been analyzed in detail. (C) 2001 American Institute of Physics.

Emission lines of Fe X in active region spectra obtained with the Solar Extreme-ultraviolet Research Telescope and Spectrograph

Fully relativistic calculations of radiative rates and electron impact excitation cross-sections for Fe X are used to derive theoretical emission-line ratios involving transitions in the 174-366 angstrom wavelength range. A comparison of these with solar active region observations obtained during the 1989 and 1995 flights of the Solar Extreme-ultraviolet Research Telescope and Spectrograph (SERTS) reveals generally very good agreement between theory and experiment. Several Fe X emission features are detected for the first time in SERTS spectra, while the 3s(2)3p(5) P-2(3/2)-3s(2)3p(4)(S-1)3d D-2(3/2) transition at 195.32 angstrom is identified for the first time (to our knowledge) in an astronomical source. The most useful Fe X electron density (N-e) diagnostic line ratios are assessed to be 175.27/174.53 and 175.27/177.24, which both involve lines close in wavelength and free from blends, vary by factors of 13 between N-e = 10(8) and 10(11) cm(-3), and yet show little temperature sensitivity. Should these lines not be available, then the 257.25/345.74 ratio may be employed to determine N-e, although this requires an accurate evaluation of the instrument intensity calibration over a relatively large wavelength range. However, if the weak 324.73 angstrom line of Fe X is reliably detected, the use of 324.73/345.74 or 257.25/324.73 is recommended over 257.25/345.74. Electron densities deduced from 175.27/174.53 and 175.27/177.24 for the stars Procyon and alpha Cen, using observations from the Extreme-Ultraviolet Explorer (EUVE) satellite, are found to be consistent and in agreement with the values of N-e determined from other diagnostic ratios in the EUVE spectra. A comparison of several theoretical extreme-ultraviolet Fe X line ratios with experimental values for a theta-pinch, for which the plasma parameters have been independently determined, reveals reasonable agreement between theory and observation, providing some independent support for the accuracy of the adopted atomic data.

Bio-folio: applying portfolio theory to biodiversity

Genes, species and ecosystems are often considered to be assets. The need to ensure a sufficient diversity of this asset is being increasingly recognised today. Asset managers in banks and insurance companies face a similar challenge. They are asked to manage the assets of their investors by constructing efficient portfolios. They deliberately make use of a phenomenon observed in the formation of portfolios: returns are additive, while risks diversify. This phenomenon and its implications are at the heart of portfolio theory. Portfolio theory, like few other economic theories, has dramatically transformed the practical work of banks and insurance companies. Before portfolio theory was developed about 50 years ago, asset managers were confronted with a situation similar to the situation the research on biodiversity faces today. While the need for diversification was generally accepted, a concept that linked risk and return on a portfolio level and showed the value of diversification was missing. Portfolio theory has closed this gap. This article first explains the fundamentals of portfolio theory and transfers it to biodiversity. A large part of this article is then dedicated to some of the implications portfolio theory has for the valuation and management of biodiversity. The last section introduces three development openings for further research.

Ultraviolet and extreme-ultraviolet line ratio diagnostics for O IV.

Aims: We generate theoretical ultraviolet and extreme-ultraviolet emission line ratios for O IV and show their strong versatility as electron temperature and density diagnostics for astrophysical plasmas.
Methods: Recent fully relativistic calculations of radiative rates and electron impact excitation cross sections for O IV, supplemented with earlier data for A-values and proton excitation rates, are used to derive theoretical O IV line intensity ratios for a wide range of electron temperatures and densities.
Results: Diagnostic line ratios involving ultraviolet or extreme-ultraviolet transitions in O IV are presented, that are applicable to a wide variety of astrophysical plasmas ranging from low density gaseous nebulae to the densest solar and stellar flares. Comparisons with observational data, where available, show good agreement between theory and experiment, providing support for the accuracy of the diagnostics. However, diagnostics are also presented involving lines that are blended in existing astronomical spectra, in the hope this might encourage further observational studies at higher spectral resolution.