A fresh perspective on canonical extensions for bounded lattices

This paper presents a novel treatment of the canonical extension of a bounded lattice, in the spirit of thetheory of natural dualities. At the level of objects, this can be achieved by exploiting the topological representation due to M. Ploscica, and the canonical extension can be obtained in the same manner as can be done in the distributive case by exploiting Priestley duality. To encompass both objects and morphismsthe Ploscica representation is replaced by a duality due to Allwein and Hartonas, recast in the style of Ploscica's paper. This leads to a construction of canonical extension valid for all bounded lattices,which is shown to be functorial, with the property that the canonical extension functor decomposes asthe composite of two functors, each of which acts on morphisms by composition, in the manner of hom-functors

Exploring the Influence of Peer-Assisted Learning Strategies (PALS) in Increasing Reading Comprehension of Grade-Level Biology Text and Biology Self-Efficacy in Students with Learning Disabilities: A Formative Experiment

The present study used a formative design experiment framework which does not answer a research question but addresses a pedagogical goal. The goal of this study was to determine the influence of Peer-Assisted Learning Strategies (PALS) on the reading comprehension of grade-level biology text and biology self-efficacy with students diagnosed with learning disabilities. As a result of this intervention, it was expected that students would better understand biology text and feel better about themselves as a biology student. Students were separated into pairs, or dyads, with each pair having a stronger reader and a weaker reader. These dyads participated in a series of three structured learning activities: Partner Reading, Paragraph Shrinking and Prediction Relay. Biology self-efficacy assessments and researcher-developed reading comprehensive assessments were administered both pre-and postintervention and after each biology unit. Student notebooks, the researcher notebook, teacher interviews, and focus student interviews were used to gather qualitative data throughout the study. The results suggested that the PALS intervention can have a positive effect on the reading comprehension of grade-level biology text and biology self-efficacy for students with learning disabilities

Serial clustering of extratropical cyclones over Western Europe: dynamics and associated impacts

Extratropical cyclones are a key process in the atmospheric variability of the North Atlantic and western Europe. They are associated with heavy precipitation and extreme winds which can result in considerable socio-economic impacts. Throughout the winter season these intense extratropical cyclones have been shown to occur in groups (this is known as clustering), which is more prevalent over the eastern North Atlantic and western Europe. In this thesis the drivers of cyclone clustering are investigated, particularly focussing on the large-scale dynamical mechanisms and the role secondary cyclones. During clustering events the upper-troposphere over the North Atlantic is characterised by a strong and zonally extended jet which steers large numbers of cyclones toward western Europe. The extended jet is associated with anomalous Rossby wave breaking on one or both flanks, with the balance on each flank being associated with changes in the angle of the jet and the latitude at which the clustering occurs. Secondary cyclones are objectively identified and are shown to contribute approximately 50% to the increase in cyclone numbers during periods of intense clustering. This increase is mainly a result to the large-scale flow steering more secondary cyclones along a similar track toward western Europe with there also being a slight increase in genesis rate near western Europe. The climate model HiGEM is used to examine the impact of cyclone clustering on seasonal wind damage estimates across Europe. HiGEM is able to represent the large-scale dynamics associated with clustering and a wind speed proxy, the storm severity index, is used to estimate the associated losses. It is found that clustering acts to increase the losses that are experienced across Europe by 10-20% for high return period seasonal losses compared to a random series of cyclones in a season. These results demonstrate the importance of correctly representing clustering in modelling studies and loss estimations

Curriculum Development Through Critical Collaborative Professional Enquiry

In recent years, there has been considerable interest within education policy in collaborative professional enquiry/inquiry methodologies, both as an alternative to top-down implementation of change and for the purpose of fostering educational improvement. However, researchers have been critical of this approach, pointing to various concerns: these include the risk of reducing a developmental methodology to an instrumental means for delivering policy, as well as issues around sustainability of practices. This paper describes a Scottish university/local authority partnership, which developed an approach entitled Critical Collaborative Professional Enquiry, designed to address some of these concerns. The paper also reports on empirical outcomes related to the partnership project.  This interpretivist study generated qualitative data from multiple sources, utilising a range of methods including semi-structured interviews with teachers and school leaders, evaluation surveys and analysis of artefacts developed during the inquiry phases of the project. This programme exerted a powerful effect on the teachers who participated. The research suggests that teachers developed better understandings of the curriculum, and of curriculum development processes. There is evidence of innovation in pedagogy, some sustained and radical in nature, and further evidence of changes to the cultures of the participating schools, for example a shift towards more democratic ways of working. This paper reports upon an original approach to curriculum development, with considerable potential to transform the ways in which schools approach innovation

Earthquake distribution patterns in Africa: their relationship to variations in lithospheric and geological structure, and their rheological implications

We use teleseismic waveform inversion, along with depth phase analysis, to constrain the centroid depths and source parameters of large African earthquakes. The majority of seismic activity is concentrated along the East African Rift System, with additional active regions along stretches of the continental margins in north and east Africa, and in the Congo Basin. We examine variations in the seismogenic thickness across Africa, based on a total of 227 well-determined earthquake depths, 112 of which are new to this study. Seismogenic thickness varies in correspondence with lithospheric thickness, as determined from surface wave tomography, with regions of thick lithosphere being associated with seismogenic thicknesses of up to 40 km. In regions of thin lithosphere, the seismogenic thickness is typically limited to ≤20 km. Larger seismogenic thicknesses also correlate with regions that have dominant tectonothermal ages of ≥1500 Ma, where the East African Rift passes around the Archean cratons of Africa, through the older Proterozoic mobile belts. These correlations are likely to be related to the production, affected by method and age of basement formation, and preservation, affected by lithospheric thickness, of a strong, anhydrous lower crust. The Congo Basin contains the only compressional earthquakes in the continental interior. Simple modelling of the forces induced by convective support of the African plate, based on long-wavelength free-air gravity anomalies, indicates that epeirogenic effects are sufficient to account for the localization and occurrence of both extensional and compressional deformation in Africa. Seismicity along the margins of Africa reflects a mixture between oceanic and continental seismogenic characteristics, with earthquakes in places extending to 40 km depth

The state of the upper mantle beneath Southern Africa

We present a new upper mantle seismic model for southern Africa based on the fitting of a large (3622 waveforms) multi-mode surface wave data set with propagation paths significantly shorter (≤ 6000 km) than those in globally-derived surface wave models. The seismic lithosphere beneath the cratonic region of southern Africa in this model is about 175 ± 25 km thick, consistent with other recent surface wave models, but significantly thinner than indicated by teleseismic body-wave tomography. We determine the in situ geotherm from kimberlite nodules from beneath the same region and find the thermal lithosphere model that best fits the nodule data has a mechanical boundary layer thickness of 186 km and a thermal lithosphere thickness of 204 km, in very good agreement with the seismic measurement. The shear wave velocity determined from analyzes of the kimberlite nodule compositions agree with the seismic shear wave velocity to a depth of not, vert, similar150 km. However, the shear wave velocity decrease at the base of the lid seen in the seismic model does not correspond to a change in mineralogy. Recent experimental studies of the shear wave velocity in olivine as a function of temperature and period of oscillation demonstrate that this wave speed decrease can result from grain boundary relaxation at high temperatures at the period of seismic waves. This decrease in velocity occurs where the mantle temperature is close to the melting temperature (within not, vert, similar100 °C)

Frequency-dependent Lg attenuation in the Indian Platform

We use seismograms from regional earthquakes recorded on digital seismographs in peninsular India to determine the frequency-dependent Q of Lg for the Indian platform. We measure Lg attenuation by determining the decay of spectral amplitudes with distance. The available data suggest some spatial variation in attenuation but a much denser ray-path coverage would be required to validate such observations. We, therefore, combine all the measurements of overlapping regions that span both the shield and intervening terranes to obtain an average value of attenuation for the Indian platform: Lg–Q = 665 ± 10 with the frequency exponent n = 0.67 ± 0.03. This average value of Lg attenuation for the Indian platform is similar to the average for other stable regions of the globe

The 2015 April 25 Gorkha (Nepal) earthquake and its aftershocks: implications for lateral heterogeneity on the Main Himalayan Thrust

The 2015 Gorkha earthquake (M-w 7.8) occurred by thrust faulting on a similar to 150 km long and similar to 70 km wide, locked downdip segment of the Main Himalayan Thrust (MHT), causing the Himalaya to slip SSW over the Indian Plate, and was followed by major-to-moderate aftershocks. Back projection of teleseismic P-wave and inversion of teleseismic body waves provide constraints on the geometry and kinematics of the main-shock rupture and source mechanism of aftershocks. The main-shock initiated similar to 80 km west of Katmandu, close to the locking line on the MHT and propagated eastwards along similar to 117 degrees. azimuth for a duration of similar to 70 s, with varying rupture velocity on a heterogeneous fault surface. The main-shock has been modelled using four subevents, propagating from west-to-east. The first subevent (0-20 s) ruptured at a velocity of similar to 3.5 km s(-1) on a similar to 6 degrees N dipping flat segment of the MHT with thrust motion. The second subevent (20-35 s) ruptured a similar to 18 degrees. Wdipping lateral ramp on the MHT in oblique thrust motion. The rupture velocity dropped from 3.5 km s(-1) to 2.5 km s(-1), as a result of updip propagation of the rupture. The third subevent (35-50 s) ruptured a similar to 7 degrees. N dipping, eastward flat segment of the MHT with thrust motion and resulted in the largest amplitude arrivals at teleseismic distances. The fourth subevent (50-70 s) occurred by left-lateral strike-slip motion on a steeply dipping transverse fault, at high angle to the MHT and arrested the eastward propagation of the main-shock rupture. Eastward stress build-up following the main-shock resulted in the largest aftershock (M-w 7.3), which occurred on the MHT, immediately east of the main-shock rupture. Source mechanisms of moderate aftershocks reveal stress adjustment at the edges of the main-shock fault, flexural faulting on top of the downgoing Indian Plate and extensional faulting in the hanging wall of the MHT.Peer reviewe

Variation of rayleigh wave group velocity dispersion and seismic heterogeneity of the Indian crust and uppermost mantle

We present group velocity dispersion results from a study of regional fundamental mode Rayleigh waves propagating across the Indian region. 1-D, path-averaged dispersion measurements have been made for 1001 source-receiver paths and these combined to produce tomographic images between 15 and 45 s period. Because of the dense station coverage in peninsular India, these images have substantially higher lateral resolution for this region than is currently available from global and regional group velocity studies. Testing of the group velocity model shows that the average resolution across the region is about 7.5° for the periods used in this study. The tomographic maps demonstrate that while the Indian shield is characterized by high crustal and uppermost-mantle group velocities, comparatively lower velocities exist beneath the Himalaya due to the thickened crust and beneath the Gangetic plains caused by the mollasse sediments and recent alluvium cover in the Himalayan foredeep. Northeastern India north of the Shillong Plateau also displays higher velocities, similar to the south Indian shield, indicative of colder crust beneath the region. The northern Bay of Bengal shows extremely low velocities due to the thick sediment blanket of the Bengal fan. Likewise, the Katawaz Basin in southern Pakistan shows lower velocities that resemble those seen in the Bay of Bengal. The geometry of the velocity contours south of the Katawaz Basin closely matches the prograding Indus fan in the Arabian Sea. Finally, the Tibetan Plateau has lower group velocities compared to the Indian shield at all periods as a result of the thick crust beneath southern Tibet