Phase and fringe order determination in wavelength scanning interferometry.

A method to obtain unambiguous surface height measurements using wavelength scanning interferometry with an improved repeatability, comparable to that obtainable using phase shifting interferometry, is reported. Rather than determining the conventional fringe frequency-derived z height directly, the method uses the frequency to resolve the fringe order ambiguity, and combine this information with the more accurate and repeatable fringe phase derived z height. A theoretical model to evaluate the method's performance in the presence of additive noise is derived and shown to be in good agreement with experiments. The measurement repeatability is improved by a factor of ten over that achieved when using frequency information alone, reaching the sub-nanometre range. Moreover, the z-axis non-linearity (bleed-through or ripple error) is reduced by a factor of ten. These order of magnitude improvements in measurement performance are demonstrated through a number of practical measurement examples.

Quadrature wavelength scanning interferometry.

A novel method to double the measurement range of wavelength scanning interferometery (WSI) is described. In WSI the measured optical path difference (OPD) is affected by a sign ambiguity, that is, from an interference signal it is not possible to distinguish whether the OPD is positive or negative. The sign ambiguity can be resolved by measuring an interference signal in quadrature. A method to obtain a quadrature interference signal for WSI is described, and a theoretical analysis of the advantages is reported. Simulations of the advantages of the technique and of signal errors due to nonideal quadrature are discussed. The analysis and simulation are supported by experimental measurements to show the improved performances.

Photometric stereo data for the validation of a structural health monitoring test rig.

Photometric stereo uses images of objects illuminated from various directions to calculate surface normals which can be used to generate 3D meshes of the object. Such meshes can be used by engineers to estimate damage of a concrete surface, or track damage progression over time to inform maintenance decisions. This dataset [1] was collected to quantify the uncertainty in a photometric stereo test rig through both the comparison with a well characterised method (coordinate measurement machine) and experiment virtualisation. Data was collected for 9 real objects using both the test rig and the coordinate measurement machine. These objects range from clay statues to damaged concrete slabs. Furthermore, synthetic data for 12 objects was created via virtual renders generated using Blender (3D software) [2]. The two methods of data generation allowed the decoupling of the physical rig (used to light and photograph objects) and the photometric stereo algorithm (used to convert images and lighting information into 3D meshes). This data can allow users to: test their own photometric stereo algorithms, with specialised data created for structural health monitoring applications; provide an industrially relevant case study to develop and test uncertainty quantification methods on test rigs for structural health monitoring of concrete; or develop data processing methodologies for the alignment of scaled, translated, and rotated data.

Methodologies for assessing local surface texture features that are relevant to cell attachment.

In this paper, we describe techniques for extracting features from surface topography data, gathered by a 3D-microscopy system, on a length scale that is relevant for cell attachment. The feature parameters considered include standard surface roughness parameters applied to the complete surface as well as new feature parameters designed to quantify local variations in surface topography potentially influencing cell behaviour. Methodologies have been developed both to determine the degree of homogeneity or isotropy of a surface and to compare the topographies of different samples. The approaches followed include wavelet decomposition and linear and nonlinear filtering techniques. The analysis has been used to investigate the correlation between osteoblast cell attachment and structural features of titanium-coated surfaces representative of orthopaedic implants. The results confirm that there is a discernible correlation between cell orientation and the underlying surface lay.

NCF1 (p47phox) and ncf1 pseudogenes are not associated with inflammatory bowel disease.

Crohn's disease (CD) and ulcerative colitis (UC) have a strong genetic component, contributing to a patient's susceptibility for inflammatory bowl disease (IBD). Linkage analysis has detected an IBD susceptibility locus in a region on chromosome 7q that encompasses the p47 (NCF1) gene and p47 (PsiNCF1) pseudogenes. Involvement of the NCF1 locus in IBD was supported by the observation that chronic inflammation of the bowel is a feature of chronic granulomatous disease caused by NCF1 mutation in 25% of cases. The pseudogenes have a dinucleotide deletion (PsiGT) at the beginning of exon 2, resulting in a frameshift and premature stop codon. APsiNCF1 (DeltaGT) to NCF1 (GTGT) ratio of 2:1 has been proposed as the predominant ratio in humans; but variability may occur after DNA exchange by recombination between PsiNCF1 and NCF1 to produce a potentially functional gene hybrid (type IIPsiNCF1). A preliminary study suggested an association between individuals with a 1:1 ratio and susceptibility to IBD. The possible presence of type IIPsiNCF1 was proposed as a susceptibility factor. We have now established the PsiNCF1 to NCF1 ratio for a significant number of IBD patients (n = 488) and control subjects (n = 181) and show that there is no statistically significant difference between the frequency of the 1:1 ratio in CD (11.2%) or UC (12.2%) patients and controls (13.4%). The 2:1 ratio was identified as the most common ratio (83.3%). Our data show there is no association of the 1:1 ratio with IBD and that susceptibility is unlikely to be a consequence of an inherited 1:1, rather than a 2:1 (PsiNCF1:NCF1) ratio.

Mathematics for modern precision engineering.

The aim of precision engineering is the accurate control of geometry. For this reason, mathematics has a long association with precision engineering: from the calculation and correction of angular scales used in surveying and astronomical instrumentation to statistical averaging techniques used to increase precision. This study illustrates the enabling role the mathematical sciences are playing in precision engineering: modelling physical processes, instruments and complex geometries, statistical characterization of metrology systems and error compensation.