Fiber optic approach for detecting corrosion

Session 7A - Application of fiber optic sensing for SHM of structuresCorrosion is a multi-billion dollar problem faced by industry. The ability to monitor the hidden metallic structure of an aircraft for corrosion could result in greater availability of existing aircraft fleets. Silica exposed-core microstructured optical fiber sensors are inherently suited towards this application, as they are extremely lightweight, robust, and suitable both for distributed measurements and for embedding in otherwise inaccessible corrosion-prone areas. By functionalizing the fiber with chemosensors sensitive to corrosion by-products, we demonstrate in-situ kinetic measurements of accelerated corrosion in simulated aluminum aircraft joints.Roman Kostecki, Heike Ebendorff-Heidepriem, Claire Davis, Grant McAdam, Tianyu Wang, and Tanya M. Monr

Novel polymer functionalization method for exposed-core optical fiber

We report on a one step functionalization process for optical fiber sensing applications in which a thin film ("50 nm) polymer doped with sensor molecules is applied to a silica exposed-core fiber. The method removes the need for surface attachment of functional groups, while integrating the polymer, silica and sensor molecule elements to create a distributed sensor capable of detecting an analyte of interest anywhere along the fiber’s length. We also show that the thin film coating serves a protective function, reducing deterioration in the transmission properties of the silica exposed-core fiber, but increasing lossRoman Kostecki, Heike Ebendorff-Heidepriem, Shahraam Afshar V., Grant McAdam, Claire Davis, and Tanya M. Monr

Optical fibres for distributed corrosion sensing: Architecture and characterisation

This paper summarises recent work conducted on the development of exposed core microstructured optical fibres for distributed corrosion sensing. Most recently, exposed-core fibres have been fabricated in silica glass, which is known to be reliable under a range of processing and service environments. We characterise the stability of these new silica fibres when exposed to some typical sensing and storage environments. We show the background loss to be the best achieved to date for exposed-core fibres, while the transmission properties are up to ~2 orders of magnitude better than for the previously reported exposed-core fibres produced in soft glass. This provides a more robust fibre platform for corrosion sensing conditions and opens up new opportunities for distributed optical fibre sensors requiring long-term application in harsh environments.Roman Kostecki, Heike Ebendorff-Heidepriem, Stephen C. Warren-Smith, Grant McAdam, Claire Davis, Tanya M. Monr

Silica exposed-core microstructured optical fibers

We report the fabrication of silica microstructured optical fibers with the core exposed along the whole length, and characterize the stability of these new fibers when exposed to some typical sensing and storage environments. We show the fiber loss to be the best achieved to date for exposed-core fibers, while the deterioration in the transmission properties is up to ~2 orders of magnitude better than for the previously reported exposed-core fibers produced in soft glass. This opens up new opportunities for optical fiber sensors requiring long term and/or harsh environmental applications while providing real time analysis anywhere along the fibers length. © 2012 Optical Society of America.Roman Kostecki, Heike Ebendorff-Heidepriem, Claire Davis, Grant McAdam, Stephen C. Warren-Smith, and Tanya M. Monr

Integration of a 3D hydrogel matrix within a hollow core photonic crystal fibre for DNA probe immobilization

In this paper, we demonstrate the integration of a 3D hydrogel matrix within a hollow core photonic crystal fibre (HC-PCF). In addition, we also show the fluorescence of Cy5-labelled DNA molecules immobilized within the hydrogel formed in two different types of HC-PCF. The 3D hydrogel matrix is designed to bind with the amino groups of biomolecules using an appropriate cross-linker, providing higher sensitivity and selectivity than the standard 2D coverage, enabling a greater number of probe molecules to be available per unit area. The HC-PCFs, on the other hand, can be designed to maximize the capture of fluorescence to improve sensitivity and provide longer interaction lengths. This could enable the development of fibre-based point-of-care and remote systems, where the enhanced sensitivity would relax the constraints placed on sources and detectors. In this paper, we will discuss the formation of such polyethylene glycol diacrylate (PEGDA) hydrogels within a HC-PCF, including their optical properties such as light propagation and auto-fluorescence

Fluoride glass microstructured optical fiber with large mode area and mid-infrared transmission

We demonstrate the first fluorozirconate microstructured fiber for use in the mid-infrared. The fiber preform was manufactured via extrusion of a 200 g billet through a complex graphite die. The fiber exhibits large mode area of 6,600 microm(2), loss of 3 dB/m at 4 microm and only marginal excess loss relative to a corresponding unstructured fiber.Heike Ebendorff-Heidepriem, Tze-Cheung Foo, Roger C. Moore, Wenqi Zhang, Yahua Li, Tanya M. Monro, Alexander Hemming and David G. Lancaste

Considering Intra-individual Genetic Heterogeneity to Understand Biodiversity

In this chapter, I am concerned with the concept of Intra-individual Genetic Hetereogeneity (IGH) and its potential influence on biodiversity estimates. Definitions of biological individuality are often indirectly dependent on genetic sampling -and vice versa. Genetic sampling typically focuses on a particular locus or set of loci, found in the the mitochondrial, chloroplast or nuclear genome. If ecological function or evolutionary individuality can be defined on the level of multiple divergent genomes, as I shall argue is the case in IGH, our current genetic sampling strategies and analytic approaches may miss out on relevant biodiversity. Now that more and more examples of IGH are available, it is becoming possible to investigate the positive and negative effects of IGH on the functioning and evolution of multicellular individuals more systematically. I consider some examples and argue that studying diversity through the lens of IGH facilitates thinking not in terms of units, but in terms of interactions between biological entities. This, in turn, enables a fresh take on the ecological and evolutionary significance of biological diversity

Demonstration of an exposed-core fiber platform for two-photon rubidium spectroscopy

We demonstrate a promising fiber architecture for generating strong photon-photon interactions. Exposed-core silica optical fibers possess low-loss guidance between 400 and 1700 nm crucial for quantum-logic applications. The potential of this fiber is demonstrated by exciting a two-photon transition within a rubidium vapor using an exposed-core silica optical fiber. Transit-time broadened spectral features enable measurement of the evanescent-field scale length of (120 +/- 20) nm which shows excellent agreement with the characteristics of the modeled fiber mode (118 +/- 2) nm. We observe a two-photon absorption coefficient of 8.3 cm(-1) for one optical mode in response to a transmitted power of 1.3mW in the second mode. A clear pathway to an exposed-core fiber exhibiting substantial absorption mediated by a single photon is identified

Is bisexuality invisible? A review of sexualities scholarship 1970–2015

This article provides a review of sexualities scholarship within the social sciences between 1970 and 2015. It takes an innovative approach by focusing on the way in which bisexuality is addressed in this body of literature. The article reveals the marginalisation, under-representation and invisibility of bisexuality within and across the social sciences in relation to both bisexual experience and identity. Reasons for this varied across the different eras, including the heterosexist nature of the literature, the impact of gay and lesbian-focused identity politics, and queer deconstructionism. In addition, patterns of bisexual erasure and invisibility were uneven, with some scholarship taking inclusive approaches or criticising prejudice against bisexuality. The initial findings of the review were enriched by critical commentary from key relevant sociologists and political scientists. The article concludes that future sexualities scholarship could be enhanced by greater consideration of bisexuality

Examining the geometry, age and genesis of buried Quaternary valley systems in the Midland Valley of Scotland, UK

Buried palaeo‐valley systems have been identified widely beneath lowland parts of the UK including eastern England, central England, south Wales and the North Sea. In the Midland Valley of Scotland palaeo‐valleys have been identified yet the age and genesis of these enigmatic features remain poorly understood. This study utilizes a digital data set of over 100 000 boreholes that penetrate the full thickness of deposits in the Midland Valley of Scotland. It identified 18 buried palaeo‐valleys, which range from 4 to 36 km in length and 24 to 162 m in depth. Geometric analysis has revealed four distinct valley morphologies, which were formed by different subglacial and subaerial processes. Some palaeo‐valleys cross‐cut each other with the deepest features aligning east–west. These east–west features align with the reconstructed ice‐flow direction under maximum conditions of the Main Late Devensian glaciation. The shallower features appear more aligned to ice‐flow direction during ice‐sheet retreat, and were therefore probably incised under more restricted ice‐sheet configurations. The bedrock lithology influences and enhances the position and depth of palaeo‐valleys in this lowland glacial terrain. Faults have juxtaposed Palaeozoic sedimentary and igneous rocks and the deepest palaeo‐valleys occur immediately down‐ice of knick‐points in the more resistant igneous bedrock. The features are regularly reused and the fills are dominated by glacial fluvial and glacial marine deposits. This suggests that the majority of infilling of the features happened during deglaciation and may be unrelated to the processes that cut them