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Andrew Harrison

Publications and source records attributed to Andrew Harrison.

28 records · Page 2Linked to original sources
PubMed2003

In situ neutron diffraction studies of single crystals and powders during microwave irradiation.

Microwave dielectric heating has become an important method in chemical synthesis and materials processing over the past 15 years, and in the case of the reactions in solutions, there is a well-developed understanding of heating mechanisms and their influence on reaction rate. In the solid-state however, there is much less clarity, despite the advantages to be gained from better insight into the way in which such electromagnetic radiation may couple directly to charge carriers, accelerating reactions in good conductors. The related issue of the influence of microwave irradiation on biological systems, in particular, proteins, and the way in which this may pose hazards to health is similarly poorly understood despite the obvious relevance this may have to the current debate on the influence of electromagnetic radiation, in particular, microwave transmission, on human health. One reason for the paucity of fundamental insight in both fields is because most work has been performed with microwave equipment whose design is derived from that of a domestic oven, and which is not ideal for in situ studies of microwave driven processes. We have been developing new methods of irradiating a variety of solid samples while measuring structural parameters through a range of diffraction techniques, and describe apparatus that will enable X-ray or neutron scattering measurements to be performed on powders or single crystals under microwave irradiation with controlled power level. We also describe preliminary studies of a single crystal of the molecular solid aspirin, and a powder of the microwave-susceptible ionic material BaTiO3, during microwave irradiation.

Aspirin↗
PubMed2002

Quantifying the similarities within fold space.

We have used GRATH, a graph-based structure comparison algorithm, to map the similarities between the different folds observed in the CATH domain structure database. Statistical analysis of the distributions of the fold similarities has allowed us to assess the significance for any similarity. Therefore we have examined whether it is best to represent folds as discrete entities or whether, in fact, a more accurate model would be a continuum wherein folds overlap via common motifs. To do this we have introduced a new statistical measure of fold similarity, termed gregariousness. For a particular fold, gregariousness measures how many other folds have a significant structural overlap with that fold, typically comprising 40% or more of the larger structure. Gregarious folds often contain commonly occurring super-secondary structural motifs, such as beta-meanders, greek keys, alpha-beta plait motifs or alpha-hairpins, which are matching similar motifs in other folds. Apart from one example, all the most gregarious folds matching 20% or more of the other folds in the database, are alpha-beta proteins. They also occur in highly populated architectural regions of fold space, adopting sandwich-like arrangements containing two or more layers of alpha-helices and beta-strands.Domains that exhibit a low gregariousness, are those that have very distinctive folds, with few common motifs or motifs that are packed in unusual arrangements. Most of the superhelices exhibit low gregariousness despite containing some commonly occurring super-secondary structural motifs. In these folds, these common motifs are combined in an unusual way and represent a small proportion of the fold (<10%). Our results suggest that fold space may be considered as continuous for some architectural arrangements (e.g. alpha-beta sandwiches), in that super-secondary motifs can be used to link neighbouring fold groups. However, in other regions of fold space much more discrete topologies are observed with little similarity between folds.

Algorithms↗
PubMed2002

Effects of the rider on the linear kinematics of jumping horses.

This study examined the effects of the rider on the linear projectile kinematics of show-jumping horses. SVHS video recordings (50 Hz) of eight horses jumping a vertical fence 1 m high were used for the study. Horses jumped the fence under two conditions: loose (no rider or tack) and ridden. Recordings were digitised using Peak Motus. After digitising the sequences, each rider's digitised data were removed from the ridden horse data so that three conditions were examined: loose, ridden (including the rider's data) and riderless (rider's data removed). Repeated measures ANOVA revealed significant differences between ridden and loose conditions for CG height at take-off (p < 0.001), CG distance to the fence at take-off (p = 0.001), maximum CG during the suspension phase (p < 0.001), CG position over the centre of the fence (p < 0.001), CG height at landing (p < 0.001), and vertical velocity at take-off (p < 0.001). The results indicated that the rider's effect on jumping horses was primarily due to behavioural changes in the horses motion (resulting from the rider's instruction), rather than inertial effects (due to the positioning of the rider on the horse). These findings have implications for the coaching of riders and horses.

Animals↗
PubMed2002

The CATH protein family database: a resource for structural and functional annotation of genomes.

Over the last decade, there have been huge increases in the numbers of protein sequences and structures determined. In parallel, many methods have been developed for recognising similarities between these proteins, arising from their common evolutionary background, and for clustering such relatives into protein families. Here we review some of the protein family resources available to the biologist and describe how these can be used to provide structural and functional annotations for newly determined sequences. In particular we describe recent developments to the CATH domain database of protein structural families which have facilitated genome annotation and which have also revealed important caveats that must be considered when transferring functional data between homologous proteins.

Databases, Protein↗
PubMedDate not supplied

Persistent blurred vision after blepharoplasty and ptosis repair.

BACKGROUND: Visual disturbance after upper (eyelid) blepharoplasty is a relatively common postoperative complaint. Recent ophthalmology literature has demonstrated alternations of corneal curvature after procedures that reposition the upper eyelid using corneal topography. Astigmatic changes induced by eyelid repositioning may be a cause of persistent blurred vision after upper eyelid procedures. This observation has not been reported in the facial plastic literature. OBJECTIVE: To determine the incidence of persistent visual disturbance after upper blepharoplasty. METHODS: A retrospective review of upper blepharoplasty by 1 facial plastic surgeon and 2 oculoplastic surgeons during the year 2000. Patient interviews were conducted via telephone. RESULTS: A total of 146 patients were identified, and 106 of them responded to the study request. Six patients (5.7%) had subjective visual acuity changes 1 year after upper blepharoplasty, and 4 of the 6 patients had combined blepharoplasty and ptosis repair. Three patients had worse vision, 2 had improved vision, and 1 was unable to wear rigid contact lenses because of fogging. CONCLUSIONS: Prior studies have shown that most patients have measurable astigmatic changes 3 months after blepharoplasty and ptosis repair. We found that only a small percentage of them have persistent subjective symptoms 1 year postoperatively. It is important for facial plastic surgeons to properly advise patients, especially those with combined procedures, that upper eyelid repositioning procedures may induce long-term vision changes. Patients may need to obtain new prescription spectacles and contact lenses postoperatively.

Astigmatism↗
PubMedDate not supplied

Orbital chondroma.

A 9-year-old boy was referred for increasing ptosis in the left eye. CT and MRI revealed a well-circumscribed mass in the superonasal orbit. An anterior orbitotomy was performed and the mass was excised in toto. Pathologic evaluation revealed a pure chondroma. Chondroma is an uncommon tumor that may rarely present as an orbital mass.

Child↗