Growth history of fault-related folds and interaction with seabed channels in the toe-thrust region of the deep-water Niger delta

The deep-water fold and thrust belt of the southern Niger Delta has prominent thrusts and folds oriented perpendicular to the regional slope that formed as a result of the thin-skinned gravitational collapse of the delta above overpressured shale. The thrust-related folds have grown in the last 12.8 Ma and many of the thrusts are still actively growing and influencing the pathways of modern seabed channels. We use 3D seismic reflection data to constrain and analyse the spatial and temporal variation in shortening of four thrusts and folds having seabed relief in a study area of 2600 km2 size in 2200–3800 m water depth. Using these shortening measurements, we have quantified the variation in strain rates through time for both fault-propagation and detachment folds in the area, and we relate this to submarine channel response. The total amount of shortening on the individual structures investigated ranges from 1 to 4 km, giving a time-averaged maximum shortening rate of between 90 ± 10 and 350 ± 50 m/Myr (0.1 and 0.4 mm/yr). Fold shortening varies both spatially and temporally: The maximum interval shortening rate occurred between 9.5 Ma and 3.7 Ma, and has reduced significantly in the last 3.7 Ma. We suggest that the reduction in the Pliocene-Recent fold shortening rate is a response to the slow-down in extension observed in the up-dip extensional domain of the Niger Delta gravitational system in the same time interval. In the area dominated by the fault-propagation folds, the channels are able to cross the structures, but the detachment fold is a more significant barrier and has caused a channel to divert for 25 km parallel to the fold axis. The two sets of structures have positive bathymetric expressions, with an associated present day uphill slope of between 1.5° and 2°. However, the shorter uphill slopes of the fault-propagation folds and increased sediment blanketing allow channels to cross these structures. Channels that develop coevally with structural growth and that cross structures, do so in positions of recent strain minima and at interval strain rates that are generally less than −0.02 Ma−1 (−1 × 10−16 s−1). However, the broad detachment fold has caused channel diversion at an even lower strain rate of c. −0.002 Ma−1 (−7 × 10−17 s−1)

Separating weak lensing and intrinsic alignments using radio observations

We discuss methods for performing weak lensing using radio observations to recover information about the intrinsic structural properties of the source galaxies. Radio surveys provide unique information that can benefit weak lensing studies, such as HI emission, which may be used to construct galaxy velocity maps, and polarized synchrotron radiation; both of which provide information about the unlensed galaxy and can be used to reduce galaxy shape noise and the contribution of intrinsic alignments. Using a proxy for the intrinsic position angle of an observed galaxy, we develop techniques for cleanly separating weak gravitational lensing signals from intrinsic alignment contamination in forthcoming radio surveys. Random errors on the intrinsic orientation estimates introduce biases into the shear and intrinsic alignment estimates. However, we show that these biases can be corrected for if the error distribution is accurately known. We demonstrate our methods using simulations, where we reconstruct the shear and intrinsic alignment auto and cross-power spectra in three overlapping redshift bins. We find that the intrinsic position angle information can be used to successfully reconstruct both the lensing and intrinsic alignment power spectra with negligible residual bias.Comment: 17 pages, 10 figures, submitted to MNRA

Improvising Linguistic Style: Social and Affective Bases for Agent Personality

This paper introduces Linguistic Style Improvisation, a theory and set of algorithms for improvisation of spoken utterances by artificial agents, with applications to interactive story and dialogue systems. We argue that linguistic style is a key aspect of character, and show how speech act representations common in AI can provide abstract representations from which computer characters can improvise. We show that the mechanisms proposed introduce the possibility of socially oriented agents, meet the requirements that lifelike characters be believable, and satisfy particular criteria for improvisation proposed by Hayes-Roth.Comment: 10 pages, uses aaai.sty, lingmacros.sty, psfig.st

Are we using the most appropriate methodologies to assess the sensitivity of rainforest biodiversity to habitat disturbance?

Accurately assessing how biodiversity responds in the Anthropocene is vital. To do so, a number of indicator taxa are commonly used to monitor human-impacted forests and the subsequent recovery of their biodiversity. This makes monitoring more economically feasible, yet only valuable if the responses observed truly reflect the status of biodiversity. Many challenges exist for getting this monitoring right, including choosing the most effective indicators and ultimately choosing the most appropriate methods to capture trends. We have reason to believe that the methods currently used to assess humanimpacted tropical forest might be misrepresenting trends related to the degree of impact of disturbance to biodiversity and to the value of secondary forests for biodiversity conservation. Using recent case studies that assessed butterflies, we challenge the paradigm that fruit-baited butterfly traps are the best method for assessing human-impacted tropical forests, and that their use solely along the forest floor is underestimating the impacts to biodiversity in tropical forests. We suggest that alternative or additional methods could provide a more representative picture of the overall butterfly biodiversity responses to human-impacted tropical forests and that similar assessments of other groups and methods should be carried out

How Can Research and Theory Enhance Understanding of Professional Decision-Making in Reviews of Cases of Child Death and Serious Injury?

Abstract In most child protection jurisdictions, a case of child death or serious injury through the actions or inaction of a parent or carer is responded to with an inquiry into the circumstances that led to the death of the child. A key objective of such inquiries is to discern what may have been done by public agencies to prevent the child’s death or serious injury and this may, in turn, lead to changes in existing policies or the development of new policies. Such changes have, at times, been criticised as ‘knee jerk’ reactions and can lead to well-meaning but possibly counter-productive initiatives. A general observation is that, in some inquiry reports, there is little, if any, reference to research and theory about child protection practice and policy. In this article, an anonymised case study of a child death inquiry is used to analyse the decision-making processes of child protection practitioners using a range of theory and research. The aim is to demonstrate how the use of insights from theory and research can lead to an enhanced understanding of the circumstances that led to a child death or serious injury, one which is grounded in current knowledge and evidence

A numerical study of the dynamics of subduction

The mechanics and dynamics of subduction have been studied using 2-D finite element analysis. Two finite element formulations have been employed; one formulation for Newtonian viscous flow and one formulation for linear elasticity and viscoelasticity. Quadratic isoparametric quadrilateral and triangular elements are used for both formulations. Models of flow in the mantle driven by oblique subduction produce an asymmetric depression of the surface above the slab. The width and depth of this depression are dependent on the value of the viscosity of the lower mantle, the length and mechanical strength of the slab. Analysis of the flow patterns suggests that the viscosity contrast at the 670 km sesmic discontinuity is likely to be of the order x 10. The stress regime at an island arc margin with a subducting slab dipping at 45 has been modelled using an elastic-viscoelastic rheology. The body forces of the slab produce an asymmetric depression of the surface above the slab which generates horizontal deviatoric compression in the plates. Unlocking the thrust zone between the subducting and overriding plates eliminates the shear stress in the fault plane resulting in regional horizontal tension in both plates, uplift of the leading edge of the overriding plate and depression of the subducting plate. The regional tension is interpreted as the source of the plate driving forces of slab pull and trench suction. Local horizontal compression in the arc-forearc region produced by the surface depression exceeds the regional tension and this may be the source of lateral variation in stress that is ob- served across the strike of convergent margins. It may also be the source of backarc compression for low angle slabs at Chilean type margins. Depression of the surface provides partial compensation of the slab body forces. Thus the downdip force is reduced and the resulting stress regime in the slab is controlled by the isostatic upthrust at the trench and the viscosity contrast at 670 km depth. A low pressure zone above and high pressure zone below the slab may act against the body forces which rotate the slab towards vertical subduction. Anomalous pressures in the mantle are created and sustained by continuous subduction and rollback, and may behave in a self-regulating mechanism. A low viscosity zone in the mantle wedge above the slab leads to the development of double seismic zones as suggested by Sleep (1979)

Investigating the canon in A-Level music: Musical Prescription in A-Level Music Syllabuses (for first examination in 2018)

The canon forming the backbone of most conceptions of Western music has been a feature of musical culture for decades, exerting an influence upon musical study in educational settings. In English school contexts, the once perceived superiority of classical music in educational terms has been substantially revised and reconsidered, opening up school curricula to other musical traditions and styles on an increasingly equal basis. However, reforms to GCSE and A-levels (examinations taken aged 16 and 18 respectively) which have taken place from 2010 onwards have refocused attention on canonic knowledge rather than skills-based learning. In musical terms, this has reinforced the value of ‘prescribed works’ in A-level music specifications. Thus far, little attention has been paid to the extent to which a kind of scholastic canon is maintained in the Western European Art Music section of the listening and appraising units in current A-level music specifications. Though directed in part by guidance from Ofqual (Office of Qualifications and Examinations Regulation, the regulatory body for qualifications in England), there is evidence of a broader cultural trend at work. The present article seeks to compare the historical evidence presented in Robert Legg’s 2012 article with current A-level specifications. Such a comparison establishes points of change and similarity in the canon of composers selected for close study in current A-levels, raising questions about the purpose and function of such qualifications

Saddle Points and Stark Ladders: Exact Calculations of Exciton Spectra in Superlattices

A new, exact method for calculating excitonic absorption in superlattices is described. It is used to obtain high resolution spectra showing the saddle point exciton feature near the top of the miniband. The evolution of this feature is followed through a series of structures with increasing miniband width. The Stark ladder of peaks produced by an axial electric field is investigated, and it is shown that for weak fields the line shapes are strongly modified by coupling to continuum states, taking the form of Fano resonances. The calculated spectra, when suitably broadened, are found to be in good agreement with experimental results.Comment: 9 pages Revtex v3.0, followed by 4 uuencoded postscript figures, SISSA-CM-94-00

Quantum integrability of the deformed elliptic Calogero-Moser problem

The integrability of the deformed quantum elliptic Calogero-Moser problem introduced by Chalykh, Feigin and Veselov is proven. Explicit recursive formulae for the integrals are found. For integer values of the parameter this implies the algebraic integrability of the systems.Comment: 23 page