The effect of aberrations on objectively assessed image quality and depth of focus.

The effects of aberrations on image quality and the objectively assessed depth of focus (DoF) were studied. Aberrometry data from 80 young subjects with a range of refractive errors was used for computing the visual Strehl ratio based on the optical transfer function (VSOTF), and then, through-focus simulations were performed in order to calculate the objective DoF (using two different relative thresholds of 50% and 80%; and two different pupil diameters) and the image quality (the peak VSOTF). Both lower order astigmatism and higher order aberration (HOA) terms up to the fifth radial order were considered. The results revealed that, of the HOAs, the comatic terms (third and fifth order) explained most of the variations of the DoF and the image quality in this population of subjects. Furthermore, computer simulations demonstrated that the removal of these terms also had a significant impact on both DoF and the peak VSOTF. Knowledge about the relationship between aberrations, DoF, image quality, and their interactions is essential in optical designs aiming to produce large values of DoF while maintaining an acceptable level of image quality. Comatic aberration terms appear to contribute strongly towards the configuration of both of these visually important parameters

HIV-1 gp120 Induces Expression of IL-6 through a Nuclear Factor-Kappa B-Dependent Mechanism: Suppression by gp120 Specific Small Interfering RNA

In addition to its role in virus entry, HIV-1 gp120 has also been implicated in HIV-associated neurocognitive disorders. However, the mechanism(s) responsible for gp120-mediated neuroinflammation remain undefined. In view of increased levels of IL-6 in HIV-positive individuals with neurological manifestations, we sought to address whether gp120 is involved in IL-6 over-expression in astrocytes. Transfection of a human astrocyte cell line with a plasmid encoding gp120 resulted in increased expression of IL-6 at the levels of mRNA and protein by 51.3±2.1 and 11.6±2.2 fold respectively; this effect of gp120 on IL-6 expression was also demonstrated using primary human fetal astrocytes. A similar effect on IL-6 expression was observed when primary astrocytes were treated with gp120 protein derived from different strains of X4 and R5 tropic HIV-1. The induction of IL-6 could be abrogated by use of gp120-specific siRNA. Furthermore, this study showed that the NF-κB pathway is involved in gp120-mediated IL-6 over-expression, as IKK-2 and IKKβ inhibitors inhibited IL-6 expression by 56.5% and 60.8%, respectively. These results were also confirmed through the use of NF-κB specific siRNA. We also showed that gp120 could increase the phosphorylation of IκBα. Furthermore, gp120 transfection in the SVGA cells increased translocation of NF-κB from cytoplasm to nucleus. These results demonstrate that HIV-1 gp120-mediated over-expression of IL-6 in astrocytes is one mechanism responsible for neuroinflammation in HIV-infected individuals and this is mediated by the NF-κB pathway

Coherent detection of targets in clutter.

The area of research dedicated to the design and optimisation of radar detection schemes is a constantly evolving held of study. This paper contributes to the held of parametric detection by utilising the Generalised Bessel Function K (GBK) distribution with parameter c = 2, (the Jakeman-Tough model), as a model for radar clutter in the design of an optimum detector. In order to apply standard statistical techniques in the design of our detector, a proof that the Jakeman-Tough model can represent an amplitude distribution of a spherically invariant random process is derived. Optimum detection, in the Neyman-Pearson sense, is then achieved by using the log-likelihood ratio test to implement the detector for the case when the input signal is known

A rank based approach to testing departure from Gaussianity of stationary signals

We present a nonparametric approach for testing Gaussianity of stationary signals. We consider testing for symmetry around zero of the probability density function of the real part of a bispectrum estimator. For this purpose, the Wilcoxon signed rank test is applied. Simulation results indicate that the proposed methodology leads to a powerful test that outperforms existing bispectrum based tests

Instantaneous Frequency Estimation - Confidence Bounds Using the Bootstrap

This paper uses a nonparametric method for estimating confidence intervals for the instantaneous frequency. The method, known as the bootstrap, is computer-intensive but requires very little in the way of modelling and assumption. The confidence intervals are based on the least-squares instantaneous frequency estimator. Simulation results demonstrate the potential of the method in situations where theoretical analysis cannot at all, or only with considerable effort, provide the result

Co-Chairs Time and Location:

New concepts in applied cryptography to secure ad hoc network

Dynamics of Ocular Surface Topography

PURPOSE: To investigate fluctuations in the ocular surface, we used high-speed videokeratoscopy (50 Hz) to measure the dynamics of the ocular surface topography. METHODS: Ocular surface height difference maps were computed to illustrate the changes in the tear film in the inter-blink interval. Topography data were used to derive the ocular surface wavefront aberrations up to the fourth radial order of the Zernike polynomial expansion. We examined the ocular surface dynamics and temporal changes in the ocular surface wavefront aberrations in the inter-blink interval. RESULTS: During the first 0.5 s following a blink, the ocular surface height at the upper edge of the topography map increased by about 2 mum. Temporal changes occurred for some ocular surface wavefront aberrations and appeared to be related to changes in the distribution of tear film. CONCLUSION: In the clinical measurement of ocular surface topography using videokeratoscopy or optics of the eye using wavefront sensors, care should be taken to avoid the initial tear film build-up phase following a blink to achieve more consistent results