Rotman Lens Used as a Demultiplexer/Multiplexer

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A new type of microwave demultiplexer is proposed which combines an arrayed waveguide grating (AWG) and a Rotman lens. The dispersion property of an AWG is employed to produce different phase slope responses for different frequencies, while the Rotman lens routes the frequency components onto different ports. To optimize isolation performance, the design constraints of both the AWG and the Rotman lens are re-examined and new design criteria elaborated. The optimized design is demonstrated of being capable of achieving 15 dB channel isolation over a 25% band range centered at 10 GHz. While a design based on a conventional Rotman lens yields isolation level of around 6 dB over a 9% band range centered at 10GHz.

Fourier Transform using a Rotman Lens

In this paper, the design constraints that are required for a Rotman lens to realize discrete Fourier transform (DFT) amplitude and phase functionality are derived. A Fourier Rotman lens has been designed, fabricated and validated. The amplitude and phase response and the array pattern based on the CST™ results are validated with the theoretical DFT results. To the best of the authors' knowledge, this is the first Fourier Rotman lens to be fabricated and validated. The solution provided replaces multilayer Butler matrix solutions with a simple single layer microstrip technology.

Role of glycation in modification of lens crystallins in diabetic and nondiabetic senile cataracts

To assess the significance of glycation, nonenzymatic browning, and oxidation of lens crystallins in cataract formation in elderly diabetic patients, we measured three distinct products of glycation, browning, and oxidation reactions in cataractous lens crystallins from 29 diabetic patients (mean +/- SD age 72.8 +/- 8.8 yr) and 24 nondiabetic patients (age 73.5 +/- 8.3 yr). Compounds measured included 1) fructoselysine (FL), the first stable product of glycation; 2) pentosidine, a fluorescent, carbohydrate-derived protein cross-link between lysine and arginine residues formed during nonenzymatic browning; and 3) N epsilon-(carboxymethyl)lysine (CML), a product of autoxidation of sugar adducts to protein. In diabetic compared with nondiabetic patients, there were significant increases (P less than 0.001) in HbA1 (10.2 +/- 3.1 vs. 7.1 +/- 0.7%), FL (7.6 +/- 5.4 vs. 1.7 +/- 1.2 mmol/mol lysine), and pentosidine (6.3 +/- 2.8 vs. 3.8 +/- 1.9 mumol/mol lysine). The disproportionate elevation of FL compared with HbA1 suggests a breakdown in the lens barrier to glucose in diabetes, whereas the increase in pentosidine is indicative of accelerated nonenzymatic browning of diabetic lens crystallins. CML levels were similar in the two groups (7.1 +/- 2.4 vs. 6.8 +/- 3.0 mmol/mol lysine), providing no evidence for increased oxidative stress in the diabetic cataract. Thus, although the modification of lens crystallins by autoxidation reactions was not increased in diabetes, the increase in glycation and nonenzymatic browning suggests that these processes may acclerate the development of cataracts in diabetic patients.

Focal irradiation of perforating eye injuries

Plaques constructed with 125I were used to irradiate the sites of perforating ocular injuries in rabbits. An approximate dose of 16Gy given over a period of 6 days was shown to significantly reduce intraocular cellular proliferation when irradiation was commenced within 24 hours after injury. If irradiation was delayed until day 5, this reduction in cellular proliferation and intraocular membrane formation did not occur. Smaller radiation doses of approximately 6Gy given within 24 hours post-injury and administered over 6 days also reduced the extent of cellular proliferation but was not as effective as the 16Gy dose.

Newly Acquired Fear of Falling Leads to Altered Eye Movement Patterns and Reduced Stepping Safety: A Case Study

This opportune case study describes visual and stepping behaviours of an 87 year old female (P8), both prior to, and following two falls. Before falling, when asked to walk along a path containing two stepping guides positioned before and after an obstacle, P8 generally visually fixated the first stepping guide until after foot contact inside it. However, after falling P8 consistently looked away from the stepping guide before completing the step into it in order to fixate the upcoming obstacle in her path. The timing of gaze redirection away from the target (in relation to foot contact inside it) correlated with absolute stepping error. No differences in eyesight, cognitive function, or balance were found between pre- and post-fall recordings. However, P8 did report large increases in fall-related anxiety and reduced balance confidence, supporting previously suggested links between anxiety/increased fear or falling and maladaptive visual/stepping behaviours. The results represent a novel insight into how psychological and related behavioural factors can change in older adults following a fall, and provide a possible partial rationalisation for why recent fallers are more likely to fall again in the following 12 months. These findings highlight novel possibilities for falls prevention and rehabilitation.

Liquid crystal based Rotman lens antenna with switchable monopulse patterns

An electronically reconfigurable Rotman lens is described which generates multiple beams that can be switched from monopulse sum to difference radiation patterns when used in conjunction with a six element Vivaldi antenna array. This is achieved by exploiting the voltage-dependent dielectric anisotropy property of nematic state liquid crystals to provide switched 0 degrees and 180 degrees phase shifts in the array feed lines. The viability of the concept is demonstrated by designing an antenna which exhibits dynamically reconfigurable monopulse radiation patterns over the frequency band 6-10 GHz. Measured and simulated results are shown to be in good agreement. (c) 2013 Wiley Periodicals, Inc.

Sidelobe Modulation Scrambling Transmitter Using Fourier Rotman Lens

A means for scrambling the digital modulation content in the sidelobes of a radio transmission from a steerable antenna array is presented. The method uses a Fourier transform beam-forming network simultaneously excited by an RF information stream and orthogonally injected interference streams. The proposed system is implemented using a Fourier Rotman lens and its operational characteristics are validated for a 10 GHz QPSK transmission.

Electronically Scanned Rotman Lens Antenna with Liquid Crystal Phase Shifters

The performance of a Rotman lens, which forms fixed beams at 0°, ±15° and ±30°, is augmented using liquid crystal phase shifters to simultaneously steer each beam by up to ±7.5°. Measured results are used to demonstrate that the true time delay property of the antenna and voltage controlled phase shifters can be exploited to provide continuously scanned beams with full coverage over an angular range of ±37.5°, and with operation over the band 6-10 GHz.

Will VEGF Trap-Eye reduce the treatment burden in neovascular age-related macular degeneration?

Evaluation of: Brown DM, Heier JS, Ciulla T et al. Primary end point results of a Phase II study of vascular endothelial growth factor trap-eye in wet age-related macular degeneration. Ophthalmology 118(6), 1089-1097 (2011); Heier JS, Boyer D, Nguyen QD et al. The 1-year results of CLEAR-IT 2, a Phase 2 study of vascular endothelial growth factor trap-eye dosed as-needed after 12-week fixed dosing. Ophthalmology 118(6), 1098-1106 (2011). Age-related macular degeneration is the most common cause of blindness in older adults in western countries, and is likely to become the largest cause of irreversible sight loss in the developing world. Treatments such as ranibizumab and bevacizumab that inhibit VEGF have improved visual outcomes markedly. Controlled trials and clinical experience have shown that the best outcomes are achieved when monthly treatment has been administered over 2 years. This poses a significant burden on health providers and patients. A novel inhibitor of VEGF, VEGF Trap-Eye, which allows less frequent dosing without loss of efficacy, has emerged as a potential treatment. CLEAR-IT 2 was a prospective randomized Phase II trial designed to assess the safety, tolerability and the anatomic and visual effects of repeated treatments with a range of doses of VEGF Trap-Eye. Impressive anatomic and visual improvements were noted with no safety concerns. © 2011 Expert Reviews Ltd.

Clinical Characteristics of Reticular Pseudodrusen in the Fellow Eye of Patients with Unilateral Neovascular Age-Related Macular Degeneration

Purpose: To describe associations between reticular pseudodrusen, individual characteristics, and retinal function.

Design: Cohort study.

Participants: We recruited 105 patients (age range, 52–93 years) who had advanced neovascular age-related macular degeneration (AMD) in only 1 eye from 3 clinical centers in Europe.

Methods: Minimum follow-up was 12 months. The eye selected for study was the fellow eye without advanced disease. Clinical measures of vision were distance visual acuity, near visual acuity, and results of the Smith-Kettlewell low-luminance acuity test (SKILL). Fundus imaging included color photography, red-free imaging, blue autofluorescence imaging, fluorescein angiography, indocyanine green angiography, and optical coherence tomography using standardized protocols. These were used to detect progression to neovascular AMD in the study eye during follow-up. All imaging outputs were graded for the presence or absence of reticular pseudodrusen (RPD) using a multimodal approach. Choroidal thickness was measured at the foveal center and at 2 other equidistant locations from the fovea (1500 μm) nasally and temporally. Metrics on retinal thickness and volume were obtained from the manufacturer-supplied automated segmentation readouts.

Main Outcome Measures: Presence of RPD, distance visual acuity, near visual acuity, SKILL score, choroidal thickness, retinal thickness, and retinal volume.

Results: Reticular pseudodrusen was found in 43 participants (41%) on 1 or more imaging method. The SKILL score was significantly worse in those with reticular drusen (mean score ± standard deviation [SD, 38±12) versus those without (mean score ± SD, 33±9) (P = 0.034). Parafoveal retinal thickness, parafoveal retinal volume, and all of the choroidal thickness parameters measured were significantly lower in those with reticular drusen than in those without. The presence of RPD was associated with development of neovascular AMD when corrected for age and sex (odds ratio, 5.5; 95% confidence interval, 1.1–28.8; P = 0.042). All participants in whom geographic atrophy developed during follow-up had visible RPD at baseline.

Conclusions: Significant differences in retinal and choroidal anatomic features, visual function, and risk factor profile exist in unilateral neovascular AMD patients with RPD compared with those without; therefore, such patients should be monitored carefully because of the risk of developing bilateral disease.