Characterisation of ductile crack initiation and growth in mild steel

Imperial Users onl

Diversity oriented synthesis : substitution at C5 in unreactive pyrimidines by Claisen rearrangement and reactivity in nucleophilic substitution at C2 and C4 in pteridines and pyrido[2,3-d]pyrimidines

Diversity oriented synthesis of fused pyrimidines leads to scaffolds with many biological activities. In the case of the preparation of pyrido[2,3-d]pyrimidines from 2-alkylthiopyrimidines, the formation of a new carbon-carbon bond at C5 is required, a reaction that is very limited in scope. However Claisen type rearrangement of simple 4-allylic ethers affords C5 substituted pyrimidines readily; in cases with an ester substituent, rearrangement occurs at room temperature. Subsequent cyclisation to afford 6-methylpyrido[2,3-d]pyrimidin-7(8H)-ones was achieved in high yield. Using allylic ethers derived from 3-chloromethyl-4-arylbut-3-en-2-ones as substrates, a new titanium[IV]chloride catalysed reaction affording 6-arylmethyl-7-methylpyrido[2,3-d]pyrimidines was discovered. In contrast, 2-alkylthiopteridines are readily available. In both cases, substitution at C2 and C4 to generate diversity has been carried out and the reactivity compared; yields of substitution products were generally higher with pteridine substrates. In biological assays unexpected hits were found for activity against the Gram positive bacterium, Nocardia farcinia, and against the parasite Trypanosoma brucei brucei, illustrating the value of diversity oriented synthesis in the discovery of biologically active compound

Geological and Geomorphological Applications of Low-Angle Illumination Satellite Imagery in Northern Ireland

Some geoscientists consider satellite imagery as having limited research potential due to their inability to elicit useful information. However, their lack of information extraction is often partly caused by a poor understanding of the importance of such parameters as illumination angle orwaveband selection. For the analysisof geological or geomorphological features in vegetated terrain, high-angle illumination imagery acquired between March and October reveals little information. However, low-angle illumination imagery (<10o solar elevation) obtained in December clearly displays many geomorphological and geological structures not apparent at a higher sun angle. The North Antrim End Moraine can easily be mapped as a single feature on a December image. The Tempo-Sixmilecross Fault and Omagh Fault can also be readily mapped at low-angle illumination and the spatial relationships of these faults to associated structures readily determined. In vegetated terrain Thematic Mapper band 5 is superior to Thematic Mapper band 4 for information extraction. This is partly due to the lower reflectance variance for vegetation on Thematic Mapper band 5 compared with Thematic Mapper band 4, thus the continuity of features is not disrupted

Application of resistivity and magnetometry geophysical techniques for near-surface investigations in karstic terranes in Ireland

Extensive glacial surficial deposits in Ireland prevent the identification of many karst features. Surface magnetic and resistivity geophysical measurements have been used to identify unknown karstic features. Two dimensional resistivity imaging has located an unknown 210-meter-long, 70-meter-wide and 25- meter-deep collapse feature in eastern Ireland beneath the surficial sediments. A resistivity survey over the Cloyne cave system in County Cork has identified the position of an unknown cave. A magnetic investigation of an infilled paleokarst collapse structure produced a 40 nanoTesla anomaly and illustrates that the technique can be employed in Ireland to locate unknown ones

Evidence for a major Tertiary dyke swarm in County Fermanagh, Northern Ireland, on digitally processed aeromagnetic imagery

Digitally processed aeromagnetic imagery has revealed an extensive swarm of reversely magnetized Tertiary dykes in County Fermanagh, Northern Ireland, 50 km west of the main outcrop of the Tertiary Antrim Lava Group. The swarm covers an area >2000 km 2, and ground magnetometer profiles across one example near Enniskillen show a negative anomaly of c. 2000 nT. Synergistic display of the available gravity and aeromagnetic data for the area shows a close coincidence between the Dromore gravity high and this dyke swarm and suggests the presence of a basic intrusive body at depth as the source of the magma for the dykes

Geophysical characteristics of the Tow Valley fault zone in north-east Ireland

The Tow Valley Fault Zone in north-east Ireland consists of number of ENE–WSW trending major fault segments and shorter N–S ones with different dips, downthrows and geophysical characteristics. The fault zone is associated with high magnetic gradients and a marked north-westerly decrease in gravity. Modelling of gravity data suggests that near Garvagh (south-west) and Ballycastle (north-east) the major fault plane dips to the north-west at about 20°–25° whereas the central section dips at 56° to the north-west. Thick sediments (c. 2.4km), mainly Permo- Triassic in age, occur beneath the Tertiary basalts north-west of the fault zone. Ground-based magnetic profiles across the fault zone yield a range of signatures. At some localities the fault is characterised by a 1km-wide zone of fracturing in the Tertiary basalts. Seismic data indicate that the fault zone continues offshore to the north-east of Rathlin Island

Radar: The Application of Spaceborne Imaging Radar for Archaeological Investigations Radio Detection & Ranging

REMOTE SENSING IN the form of aerial photography has made extensive contributions to archaeology over the years, especially in identifying and mapping ancient sites. Such sites usually have dimensions measured in tens or hundreds of metres, and the high resolution afforded by aerial surveys makes such an approach very cost effective. Spaceborne platforms generally have much poorer spatial resolutions and have not made significant contributions in the field of archaeology. However, the unique imaging capabilities of spaceborne radar systems have provided valuable information to archaeologists and will become increasingly important in the future

Application of resistivity and magnetometry geophysical techniques for near-surface investigations in karstic terranes in Ireland

Extensive glacial surficial deposits in Ireland prevent the identification of many karst features. Surface magnetic and resistivity geophysical measurements have been used to identify unknown karstic features. Two dimensional resistivity imaging has located an unknown 210-meter-long, 70-meter-wide and 25- meter-deep collapse feature in eastern Ireland beneath the surficial sediments. A resistivity survey over the Cloyne cave system in County Cork has identified the position of an unknown cave. A magnetic investigation of an infilled paleokarst collapse structure produced a 40 nanoTesla anomaly and illustrates that the technique can be employed in Ireland to locate unknown ones

Cosmology with liquid mirror telescopes

Liquid mirrors provide an exciting means to obtain large optical telescopes for substantially lower costs than conventional technologies. The liquid mirror concept has been demonstrated in the lab with the construction of a diffraction limited 1.5 m mirror. The mirror surface, using liquid mercury, forms a perfect parabolic shape when the mirror cell is rotated at a uniform velocity. A liquid mirror must be able to support a heavy mercury load with minimal flexure and have a fundamental resonant frequency that is as high as possible, to suppress the amplitude of surface waves caused by small vibrations transmitted to the mirror. To minimize the transmission of vibrations to the liquid surface, the entire mirror rests on an air bearing. This necessitates the mirror cell being lightweight, due to the limited load capabilities of the air bearing. The mirror components must also have physical characteristics which minimize the effects of thermal expansion with ambient temperature fluctuations in the observatory. In addition, the 2.7 m mirror construction is designed so that the techniques used may be readily extended to the construction of large mirrors. To attain the goals of a lightweight, rigid mirror, a composite laminant construction was used. The mirror consists of a foam core cut to the desired parabolic shape, with an accuracy of a few mm. An aluminum hub serves as an anchor for the foam and skin, and allows precise centering of the mirror on the air bearing and drive system. Several plys of Kevlar, covered in an epoxy matrix, are then applied to the foam. A final layer of pure epoxy is formed by spin casting. This final layer is parabolic to within a fraction of a mm. An aluminum ring bonded to the circumference of the mirror retains the mercury, and incorporates stainless-steel hard-points for the attachment of balance weights