Optical Physics of Imaging and Interferometric Phased Arrays

Microwave, submillimetre-wave, and far-infrared phased arrays are of considerable importance for astronomy. We consider the behaviour imaging phased arrays and interferometric phased arrays from a functional perspective. It is shown that the average powers, field correlations, power fluctuations, and correlations between power fluctuations at the output ports of an imaging or interferometric phased array can be found once the synthesised reception patterns are known. The reception patterns do not have to be orthogonal or even linearly independent. It is shown that the operation of phased arrays is intimately related to the mathematical theory of frames, and that the theory of frames can be used to determine the degree to which any class of intensity or field distribution can be reconstructed unambiguously from the complex amplitudes of the travelling waves at the output ports. The theory can be used to set up a likelihood function that can, through Fisher information, be used to determine the degree to which a phased array can be used to recover the parameters of a parameterised source. For example, it would be possible to explore the way in which a system, perhaps interferometric, might observe two widely separated regions of the sky simultaneously

Simulations of astronomical imaging phased arrays

We describe a theoretical procedure for analyzing astronomical phased arrays with overlapping beams, and apply the procedure to simulate a simple example. We demonstrate the effect of overlapping beams on the number of degrees of freedom of the array, and on the ability of the array to recover a source. We show that the best images are obtained using overlapping beams, contrary to common practise, and show how the dynamic range of a phased array directly affects the image quality.Comment: 16 pages, 26 figures, submitted to Journal of the Optical Society of America

Diffraction Considerations for Planar Detectors in the Few-Mode Limit

Filled arrays of bolometers are currently being employed for use in astronomy from the far-infrared through millimeter parts of the electromagnetic spectrum. Because of the large range of wavelengths for which such detectors are applicable, the number of modes supported by a pixel will vary according to the specific application of a given available technology. We study the dependence of image fidelity and induced polarization on the size of the pixel by employing a formalism in which diffraction due to the pixel boundary is treated by propagating the second-order statistical correlations of the radiation field through a model optical system. We construct polarized beam pattern images of square pixels for various ratios of p/\lambda where p is the pixel size and \lambda is the wavelength of the radiation under consideration. For the limit in which few modes are supported by the pixel (p/\lambda<1), we find that the diffraction due to the pixel edges is non-negligible and hence must be considered along with the telescope diffraction pattern in modeling the ultimate spatial resolution of an imaging system. For the case in which the pixel is over-moded (p/\lambda>1), the geometric limit is approached as expected. This technique gives a quantitative approach to optimize the imaging properties of arrays of planar detectors in the few-mode limit.Comment: 20 pages, 8 figure

Detector Modeling and CMB Polarimetry Technology Development at GSFC

Pixel size limits the resolution in the focal plane. This should be accounted for in optical design. Alternatively, this reduces the effective number of independent detectors. Polarization and scattering are intrinsically related, and both are more severe at low pnambda. Future work: Quantification of the pixel cross-coupling- calculate a theoretical covariance matrix to predict performance of future detector arrays

Transcriptional control of the human aggrecan gene

Osteoarthritis (OA) is a degenerative joint disease and is the leading cause of physical disability in industrialised nations. Cartilage has received the most attention in the study of OA due to articular chondrocytes acting as potential instigators of disease. These cells are responsible for the anabolic-catabolic balance required for matrix maintenance due to their ability to synthesise the structural components of the extra-cellular matrix along with matrix-degrading proteases. In order to better understand the mechanism by which this balance is shifted in OA, it would be useful to investigate the roles of the genes that are expressed in these cells. One of the most powerful tools to do this would be an inducible and chondrocyte-specific system that utilises a cartilage-specific promoter, such as the aggrecan promoter. Aggrecan, one of the major structural components of cartilage, is a large aggregating chondroitin sulphate proteoglycan. This PhD set out to further our understanding of the transcriptional regulatory mechanisms that govern the chondrocyte-specific expression of the gene. A series of constructs containing various combinations of non-coding aggrecan DNA (mostly upstream of the transcriptional start site and including the first untranslated exon) were used to generate transgenic mouse embryos and an adult line in which the cartilage-specific expression of the transgene indicated the presence of cis-regulatory elements. These studies have identified three putatively important regions. One serves as a basal/core promoter at and around the transcriptional start site (TSS) (containing what could possibly be a non-essential 92bp sequence depending on the developmental stage of the mouse). Another located 10kb upstream of the TSS can serve as an enhancer, and finally another located within a 7kb region further upstream. One or more of these elements seem to respond to injury as indicated by increased promoter activity in the OA-induced knees of the adult line containing all three regulatory regions. Using a combination of our data alongside published work (Han and Lefebvre, 2008), a cartilage-specific Cre recombinase line was generated and tested for specificity and continual gene expression under the induction of OA. The work presented in this thesis can now be used to contribute to knowledge on the pathogenesis of OA.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

HspB1 deficiency results in increased neutrophil but slightly decreased macrophage infiltration of wounds.

<p>A, Neutrophil infiltration in d1 wound granulation tissue assessed by IHC for neutrophil elastase (NE) and macrophage infiltration at d3 detected by F4/80 staining. B, Plot shows elastase positive neutrophils (NE+) per high power field (hpf); 7 fields/wound; 2 wounds per mouse; n = 4 mice; **P<0.01. B, Plot as for (B) showing F4/80-positive cells/hpf; *P<0.05.</p