Multimode optical fiber specklegram smart bed sensor array

Significance: Monitoring the movement and vital signs of patients in hospitals and other healthcare environments is a significant burden on healthcare staff. Early warning systems using smart bed sensors hold promise to relieve this burden and improve patient outcomes.We propose a scalable and cost-effective optical fiber sensor array that can be embedded into a mattress to detect movement, both sensitively and spatially. Aim: Proof-of-concept demonstration that a multimode optical fiber (MMF) specklegram sensor array can be used to detect and image movement on a bed. Approach: Seven MMFs are attached to the upper surface of a mattress such that they cross in a 3 × 4 array. The specklegram output is monitored using a single laser and single camera and movement on the fibers is monitored by calculating a rolling zero-normalized cross-correlation. A 3 × 4 image is formed by comparing the signal at each crossing point between two fibers. Results: The MMF sensor array can detect and image movement on a bed, including getting on and off the bed, rolling on the bed, and breathing. Conclusions: The sensor array shows a high sensitivity to movement, which can be used for monitoring physiological parameters and patient movement for potential applications in healthcare settings.Stephen C. Warren-Smith, Adam D. Kilpatrick, Kabish Wisal, and Linh V. Nguye

Comparison of the Oxidation State of Fe in Comet 81P/Wild 2 and Chondritic-Porous Interplanetary Dust Particles

The fragile structure of chondritic-porous interplanetary dust particles (CP- IDPs) and their minimal parent-body alteration have led researchers to believe these particles originate in comets rather than asteroids where aqueous and thermal alteration have occurred. The solar elemental abundances and atmospheric entry speed of CP-IDPs also suggest a cometary origin. With the return of the Stardust samples from Jupiter-family comet 81P/Wild 2, this hypothesis can be tested. We have measured the Fe oxidation state of 15 CP-IDPs and 194 Stardust fragments using a synchrotron-based x-ray microprobe. We analyzed ~300 nanograms of Wild 2 material - three orders of magnitude more material than other analyses comparing Wild 2 and CP-IDPs. The Fe oxidation state of these two samples of material are >2{\sigma} different: the CP-IDPs are more oxidized than the Wild 2 grains. We conclude that comet Wild 2 contains material that formed at a lower oxygen fugacity than the parent body, or parent bodies, of CP-IDPs. If all Jupiter-family comets are similar, they do not appear to be consistent with the origin of CP-IDPs. However, comets that formed from a different mix of nebular material and are more oxidized than Wild 2 could be the source of CP-IDPs.Comment: Earth and Planetary Science Letters, in pres

Challenges of polymer‐based pH sensing in soil

OnlinePublIt is well established that plants need a range of soil nutrients to grow. In farming, these nutrients are generally added to the soil in the form of fertilizers. However, depending on the soil conditions (such as temperature, water content, pH, and soil type), nutrients may not be in the right form for plant uptake. Determining the availability of nutrients in the soil for plant growth is therefore critical for the yield and productivity of modern farming. A considerable amount of research and knowledge has been developed that shows the importance of the soil pH on the availability (or not) of nutrients. Furthermore, pH plays a crucial role in controlling the availability of potential toxic elements, such as aluminum and manganese. This review article discusses recent research aimed at real‐time and continuous soil pH measurement in‐situ. More specifically, it focuses on the development of polymer materials that will ultimately enable pH measurements for the specific application of in‐ground pH sensing. Given the breadth of the polymeric sensor research field, this review has a narrowed focus on optical and electrochemical transduction methods.Esmat Ebadati, Eliza Switalska, Enzo Lombi, Stephen C. Warren-Smith, Drew Evan

RELA governs a network of islet-specific metabolic genes necessary for beta cell function

Published online: 14 June 2023AIMS/HYPOTHESIS: NF-κB activation unites metabolic and inflammatory responses in many diseases yet less is known about the role that NF-κB plays in normal metabolism. In this study we investigated how RELA impacts the beta cell transcriptional landscape and provides network control over glucoregulation. METHODS: We generated novel mouse lines harbouring beta cell-specific deletion of either the Rela gene, encoding the canonical NF-κB transcription factor p65 (βp65KO mice), or the Ikbkg gene, encoding the NF-κB essential modulator NEMO (βNEMOKO mice), as well as βA20Tg mice that carry beta cell-specific and forced transgenic expression of the NF-κB-negative regulator gene Tnfaip3, which encodes the A20 protein. Mouse studies were complemented by bioinformatics analysis of human islet chromatin accessibility (assay for transposase-accessible chromatin with sequencing [ATAC-seq]), promoter capture Hi-C (pcHi-C) and p65 binding (chromatin immunoprecipitation-sequencing [ChIP-seq]) data to investigate genome-wide control of the human beta cell metabolic programme. RESULTS: Rela deficiency resulted in complete loss of stimulus-dependent inflammatory gene upregulation, consistent with its known role in governing inflammation. However, Rela deletion also rendered mice glucose intolerant because of functional loss of insulin secretion. Glucose intolerance was intrinsic to beta cells as βp65KO islets failed to secrete insulin ex vivo in response to a glucose challenge and were unable to restore metabolic control when transplanted into secondary chemical-induced hyperglycaemic recipients. Maintenance of glucose tolerance required Rela but was independent of classical NF-κB inflammatory cascades, as blocking NF-κB signalling in vivo by beta cell knockout of Ikbkg (NEMO), or beta cell overexpression of Tnfaip3 (A20), did not cause severe glucose intolerance. Thus, basal p65 activity has an essential and islet-intrinsic role in maintaining normal glucose homeostasis. Genome-wide bioinformatic mapping revealed the presence of p65 binding sites in the promoter regions of specific metabolic genes and in the majority of islet enhancer hubs (~70% of ~1300 hubs), which are responsible for shaping beta cell type-specific gene expression programmes. Indeed, the islet-specific metabolic genes Slc2a2, Capn9 and Pfkm identified within the large network of islet enhancer hub genes showed dysregulated expression in βp65KO islets. CONCLUSIONS/INTERPRETATION: These data demonstrate an unappreciated role for RELA as a regulator of islet-specific transcriptional programmes necessary for the maintenance of healthy glucose metabolism. These findings have clinical implications for the use of anti-inflammatories, which influence NF-κB activation and are associated with diabetes.Nathan W. Zammit, Ying Ying Wong, Stacey N. Walters, Joanna Warren, Simon C. Barry, Shane T. Gre

Optical fiber refractive index sensor with low detection limit and large dynamic range using a hybrid fiber interferometer

A refractive index (RI) fiber sensor with low detection limit but large dynamic range is proposed and demonstrated using an exposed core microstructured optical fiber. The exposed-core fiber is highly birefringent due to its asymmetry and also supports multimode propagation; thus, can be used simultaneously as a Mach-Zehnder and Sagnac interferometer. The Mach-Zehnder interference is significantly more phase sensitive to RI due to a longer effective path length difference. This leads to a lower detection limit compared to that for the Sagnac interferometer, which has a larger free spectral range that allows the dynamic range of the RI measurement to be extended. By combining these two interferometers, the proposed sensor achieves a detection limit of as low as 6.02 × 10⁻⁶ refractive index units (RIU) while maintaining a large dynamic range from 1.3320 to 1.3465 RIU. The proposed sensor also has the advantages of biocompatibility, low cost, high stability, small size, ability to operate remotely and to be fabricated.Xuegang Li, Stephen C. Warren-Smith, Heike Ebendorff-Heidepriem, Ya-nan Zhang, and Linh V. Nguye

High-sensitivity Sagnac-interferometer biosensor based on exposed core microstructured optical fiber

A novel, high sensitivity Sagnac-interferometer biosensor based on exposed core microstructured optical fiber (ECF) has been designed and implemented in this paper. The exposed core fiber has noncircular symmetry and thus exhibits birefringence and can form a sensing element within a Sagnac loop interferometer. The exposed-core fiber design provides direct access to the evanescent field, allowing the measurement of bulk refractive index (RI) with a sensitivity of up to −3137 nm/RIU while maintaining the fiber’s robustness. The sensor can also detect the localized refractive index changes at the fiber core’s surface as the result of a biological binding event. We demonstrate the use of this sensor for label-free sensing of biological molecules by immobilizing biotin onto the fiber core as the probe to capture the target molecule streptavidin.Xuegang Li, Linh V. Nguyen, Yong Zhao, Heike Ebendorff-Heidepriem, Stephen C. Warren-Smit

Simultaneous measurement of temperature and refractive index using an exposed core microstructured optical fiber

We have demonstrated a novel scheme for simultaneous measurement of temperature and refractive index by using an exposed core microstructured optical fiber (ECF). The ECF allows for high sensitivity to refractive index due to the small exposed-core, while being supported by a standard fiber diameter cladding making it robust compared to optical micro-fibers. The sensor combines a fiber Bragg grating (FBG) inscribed into the core of the ECF and a multimode Mach-Zehnder interferometer (MZI). Both the FBG and MZI are sensitive to refractive index (RI) and temperature through a combination of direct access to the evanescent field via the exposed-core, the thermo-optic effect and thermal expansion. The FBG and MZI respond differently to changes in temperature and RI, thus allowing for the simultaneous measurement of these parameters. In our experiment RI sensitivities of 5.85 nm/RIU and 794 nm/RIU, and temperature sensitivities of 8.72 pm/°C and -57.9 pm/°C, were obtained for the FBG and MZI respectively. We demonstrate that a transfer matrix approach can be used to simultaneously measure both parameters, solving the problem of temperature sensitivity of RI sensors due to the high thermo-optic coefficient of aqueous samples.Xuegang Li, Linh V. Nguyen, Martin Becker, Heike Ebendorff-Heidepriem, Dinh Pham, and Stephen C. Warren-Smit

Multi-point optical fiber pressure sensor

Conference 11200 - AOS Australian Conference on Optical Fibre Technology (ACOFT) and Australian Conference on Optics, Lasers, and Spectroscopy (ACOLS) 2019This paper reports on a multi-point optical fiber pressure sensor using fiber Bragg gratings (FBGs) written on an exposed core optical fiber (ECF) by femtosecond laser. The pressure sensing elements were constructed as Fabry-Perot (FP) interferometers of different cavity lengths using pairs of FBGs with identical resonant wavelength. In this fashion an interference pattern was formed within the FBG bandwidth with much narrower fringes, leading to better detection limit. Fast Fourier transform (FFT) was used to calculate the phase change of the FP interference pattern with respect to applied pressure. The pressure sensitivity was proportional to the cavity FP cavity length, and reached -0.672 rad/MPa for the case of FP with 9 mm cavity length. The proposed sensor has potential to measure pressure at very high temperature thanks to its single material configuration.Linh V. Nguyen, Erik P. Schartner, Dale Otten, Zheng Yu, David Lancaster, Heike Ebendorff- Heidepriem, and Stephen C. Warren-Smit

Multi-point high temperature optical fiber sensor

ANZCOP, 2019, Melbourne, AustraliaAbstract not availableErik P. Schartner, Linh V. Nguyen, Dale Otten, Zheng Yu, David G. Lancaster, and Heike Ebendorff-Heidepriem, and Stephen C. Warren-Smit

Single-peak fiber Bragg gratings in suspended-core optical fibers

Femtosecond laser inscribed fiber Bragg gratings in pure-silica suspended-core optical fibers have previously been demonstrated as a promising platform for high temperature sensing. However, the density of gratings that could be written on a single fiber was limited by undesired reflections associated with higher order modes in these high numerical aperture fibers. This resulted in a complex, broadband reflection spectrum with limited multiplexing capability. In this work we utilize modifications to the fine structure of the suspended core optical fibers to fine tune the relative confinement loss of the optical fiber modes, thus reducing the contribution from such higher order modes. The effects of these changes on mode propagation are modeled, giving a range of fibers with different confinement loss properties which can be tailored to the specific length scale of a desired application. We achieve single-peak reflections from individual fiber Bragg gratings, significantly improving performance for multipoint sensing and demonstrate this technique by writing 20 gratings onto a single fiber.Erik P. Schartner, Stephen C. Warren-Smith, Linh V. Nguyen, Dale Otten, Zheng Yu, David G. Lancaster and Heike Ebendorff-Heideprie