REVIEW | doi:10.20944/preprints202105.0217.v1
Subject: Medicine & Pharmacology, Allergology Keywords: stem cells; retinal diseases; optic nerve diseases; cell replacement; cell sources
Online: 10 May 2021 (15:34:07 CEST)
The aim of this review was to provide an update on the potential of cell therapies to restore or replace damaged and/or lost cells in retinal degenerative and optic nerve diseases, describing the available cell sources and the challenges involved in such treatments when these techniques are applied in real clinical practice. Sources include human fetal retinal stem cells, allogenic cadaveric human cells, adult hippocampal neural stem cells, human CNS stem cells, ciliary pigmented epithelial cells, limbal stem cells, retinal progenitor cells (RPCs), human pluripotent stem cells (PSCs) (including both human embryonic stem cells (ESCs) and human induced pluripotent stem cells (iPSCs)) and mesenchymal stem cells (MSCs). Of these, RPCs, PSCs and MSCs have already entered early-stage clinical trials since they can all differentiate into RPE, photoreceptors or ganglion cells, and have demonstrated safety, while showing some indicators of efficacy. Stem/progenitor cell therapies for retinal diseases still have some drawbacks, such as the inhibition of proliferation and/or differentiation in vitro (with the exception of RPE) and the limited long-term survival and functioning of grafts in vivo. Some other issues remain to be solved concerning the clinical translation of cell-based therapy, including (1) the ability to enrich for specific retinal subtypes; (2) cell survival; (3) cell delivery, which may need to incorporate a scaffold to induce correct cell polarization, which increases the size of the retinotomy in surgery and, therefore, the chance of severe complications; (4) the need to induce retinal detachment to perform the subretinal placement of the transplanted cell; and (5) the evaluation of the risk of tumor formation caused by the undifferentiated stem cells and prolific progenitor cells. Despite these challenges, stem/progenitor cells represent the most promising strategy for retinal and optic nerve disease treatment in the near future, and therapeutics assisted by gene techniques, neuroprotective compounds and artificial devices can be applied to fulfil clinical needs.
ARTICLE | doi:10.20944/preprints202105.0167.v1
Subject: Medicine & Pharmacology, Clinical Neurology Keywords: Heart arrest; optic nerve sheath diameter; Patient outcome assessment
Online: 10 May 2021 (10:51:42 CEST)
Optic nerve sheath diameter (ONSD) can help predict the neurologic outcome of patients with post-cardiac arrest (CA) return of spontaneous circulation (ROSC). We aimed to investigate the effect of ONSD changes before and after CA on neurologic outcomes in patients with ROSC after CA using brain computed tomography (CT). The study included patients hospitalized after CA, who had undergone pre- and post-CA brain CT from January 2001 to September 2020. The patients were divided into good and poor neurologic outcome (GNO and PNO, respectively) groups based on the neurologic outcome at hospital discharge. We performed between-group comparisons of the amount and rate of ONSD changes on brain CT and calculated the area under the curve (AUC) to determine their predictive value for neurologic outcomes. Among the 96 enrolled patients, 25 had GNO. Compared to the GNO group, the PNO group showed significantly higher amount (0.30 vs. 0.63 mm; p=0.030) and rate of change (5.26 vs. 12.29 %; p=0.041). The AUC for predicting PNO was 0.64 (95% CI=0.53–0.73; p=0.04) and patients with a rate of ONSD change >27.2% had PNO with 100% specificity and positive predictive value. Hence, ONSD changes may predict neurologic outcomes in patients with post-CA ROSC.
ARTICLE | doi:10.20944/preprints202301.0511.v1
Subject: Medicine & Pharmacology, Ophthalmology Keywords: glaucoma; optic neuropathy; mitochondria; optic nerve crush; confocal scanning ophthalmoscope; distribution; Thy1-mito-YFP mice
Online: 28 January 2023 (03:05:08 CET)
Glaucomatous optic neuropathy, a major cause of blindness, is characterized by the loss of retinal gan-glion cells (RGCs) and degeneration of their axons. Mitochondria are deeply involved in maintaining RGCs and their axons. Therefore, lots of attempts have been made to develop diagnostic tools and therapies tar-geting mitochondria. Recently, we reported that mitochondria are uniformly distributed in unmyelinated axons of RGCs, possibly owing to the ATP gradient. Thus, using transgenic mice expressing yellow fluo-rescent protein targeting mitochondria exclusively in RGCs within the retina, we assessed the alteration of mitochondrial distributions induced by optic nerve crush (ONC) via in vitro flat-mount retinal sections and in vivo fundus images captured through the cornea with a confocal scanning ophthalmoscope. We observed that the mitochondrial distribution in unmyelinated axons of RGCs that survived the ONC remained uni-form, although their density increased. Furthermore, via in vitro analysis, we discovered that the mitochon-drial size is attenuated following ONC. These results suggest that ONC induces mitochondrial fission without disrupting the uniform mitochondrial distribution. This mechanism may help to prevent axonal degeneration and apoptosis. The in vivo visualization system of axonal mitochondria in RGCs may be ap-plicable in the diagnosis of progression of optic neuropathy.
REVIEW | doi:10.20944/preprints202206.0164.v1
Subject: Engineering, Electrical & Electronic Engineering Keywords: temperature sensor; polymer fiber optic; fiber optic; Fabry-Perot interferometer; interferometer; fiber optic interferometer
Online: 13 June 2022 (03:48:18 CEST)
Temperature measurements are of great importance in many fields of human activities, including industry, technology, and science. For example, obtaining a certain temperature value or a sudden change in it can be the primary control marker of a chemical process. Fiber optic sensors have remarkable properties giving a broad range of applications. They enable continuous real-time temperature control in difficult-to-reach areas, in hazardous working environments (air pollution, chemical or ionizing contamination), and the presence of electromagnetic disturbances. The use of fiber optic temperature sensors in polymer technology can significantly reduce the cost of their production. Moreover, the installation process and usage would be simplified. As a result, these types of sensors would becoming increasingly popular in industrial solutions. This review provides a critical overview of the latest development of fiber optic temperature sensors based on Fabry-Perot interferometer made with polymer technology.
ARTICLE | doi:10.20944/preprints201810.0698.v1
Subject: Engineering, Biomedical & Chemical Engineering Keywords: optic biosensor; fluorescence; bacterial detection
Online: 30 October 2018 (03:44:11 CET)
The importance of detecting bacteria in various food products is ever-increasing, due to recent food trends that lend themselves to food contamination. Additionally, the detection of probiotics in food products is of increasing importance to consumers, who realize the benefits of probiotics on one’s diet. Existing technologies for detection of bacteria in food are accurate, but most are slow, increasingly costly and unsuitable for applications outside of research laboratories. Optic approaches have recently emerged as an alternative, allowing rapid detection of bacterial presence. This study employs a portable kinetics fluorometer, fabricated in-house, in conjunction with NADH sensitive fluorescence reporter for analysis of various food products. The presence of bacteria is detected in 5 minutes. Both pathogenic and probiotic bacteria were detected in food products, such as raw chicken and beef, spoiled lettuce and contaminated water, yogurt, and kombucha tea. The cellular activity of two probiotic pills was also verified. All samples displayed varying levels of bacterial activity. The study indicates the viability of biosensors being used as an alternate method to detect bacteria in food products – and the viability of a fluorescence-based biosensor to detect viable bacteria. The approach is suitable for both laboratory and field determinations.
ARTICLE | doi:10.20944/preprints202201.0278.v1
Subject: Physical Sciences, Optics Keywords: photonic; plasmonic; surface plasmon; waveguide; resonator; optic
Online: 19 January 2022 (15:32:41 CET)
In this paper, a plasmonic refractive index sensor based on MIM waveguide (metal_insulation_metal) with two plasmonic waveguides and five rings and two teeth and four rectangular cavities is proposed and designed. The refractive index of the resonators as well as the resonant wavelengths will be investigated by the time difference finite difference method. To achieve an optical sensor with excellent quality and performance, we change the number and type of amplifiers and their dimensions. In each stage of the simulation, we will only change the refractive index of the middle ring located in the middle of the two waveguides, and the refractive index of the other amplifiers remains the same. This challenge will help to form a more appropriate structure for optical sensors. The sensor built in this simulation has a balanced and suitable function for integrated circuits and helps researchers to better understand the design of plasmonic structures. It also has important applications in medical research, health care, drug manufacturing, security monitoring and environmental protection, internal security of countries and the battlefield.
ARTICLE | doi:10.20944/preprints202111.0097.v1
Subject: Medicine & Pharmacology, Pathology & Pathobiology Keywords: traumatic optic neuropathy; mice; axon injury; TBI; neurodegeneration
Online: 4 November 2021 (09:26:51 CET)
Injury to the optic nerve, termed, traumatic optic neuropathy (TON) is a known comorbidity of traumatic brain injury (TBI) and is now known to cause chronic and progressive retinal thinning up to 35 years after injury. Although animal models of TBI have described the presence of optic nerve degeneration and research exploring acute mechanisms is underway, few studies in humans or animals have examined chronic TON pathophysiology outside the retina. We used a closed-head weight-drop model of TBI/TON in 6-week-old male C57BL/6 mice. Mice were euthanized 7-, 14-, 30-, 90-, and 150-days post injury (DPI) to assess histological changes in the visual system of the brain spanning a total of 12 regions. We show chronic elevation of FluoroJade-C, indicative of neurodegeneration, throughout the time course. Intriguingly, FJ-C staining revealed a bimodal distribution of mice indicating the possibility of subpopulations that may be more or less sus-ceptible to injury outcomes. Additionally, we show that microglia and astrocytes react to optic nerve damage in both temporally and regionally different ways. Despite these differences, as-trogliosis and microglial changes were alleviated between 14-30 DPI in all regions examined, perhaps indicating a potential critical period for intervention/recovery that may determine chronic outcomes.
ARTICLE | doi:10.20944/preprints202104.0571.v1
Subject: Medicine & Pharmacology, Allergology Keywords: Retinal ganglion cell function; Pattern electroretinogram; Glaucoma; Optic neuropathy
Online: 21 April 2021 (11:38:10 CEST)
As in glaucoma and other optic neuropathies cellular dysfunction often precedes cell death, sensitive assessment of retinal ganglion cell (RGC) function represents a key outcome measure for neuroprotective strategies aimed at targeting distressed but still viable cells. Here we offer a conceptual framework to identify progressive stages of RGC dysfunction leading to cell death in mouse models of glaucoma and other optic neuropathies based on non-invasive pattern electroretinogram (PERG), to differentiate phenotypic and altered RGC response dynamics, to assess susceptibility to stressors and to assess reversible dysfunction.
ARTICLE | doi:10.20944/preprints202112.0175.v2
Subject: Life Sciences, Other Keywords: surround suppression; extra-classical receptive field; optic tectum; size tuning
Online: 10 December 2021 (14:29:15 CET)
Surround modulation is a phenomenon whereby costimulation of the extra-classical receptive field and classical receptive field would modulate the visual responses induced individually by classical receptive field. However, there lacks systematic study about surround modulation properties existing in avian optic tectum. In this study, neuronal activities are recorded from pigeon optic tectum, and the responses to moving and flashed squares and bars of different sizes are compared. The statistical results showed that most tectal neurons presented surround suppression as stimuli size grew larger both in moving and flashed paradigms, and the suppression degree induced by larger flashed square was comparable with that by moving one when it crossed near the cell’s RF center, which corresponds to fully surrounding condition. The suppression degree grew weaker when the stimuli move across the RF border, which corresponds to partially surrounding condition. Meanwhile, the fully surround suppression induced by flashed square was also more intense than partially surrounded by flashed bars. The results provide new insight for understanding the spatial arrangement of lateral inhibitions from feedback or feedforward streams, which would help to make clear the generation mechanism of surround modulation found in avian optic tectum.
ARTICLE | doi:10.20944/preprints201905.0061.v1
Subject: Earth Sciences, Environmental Sciences Keywords: rotational seismograph; fiber optic sensor; rotational events; seismology; rotational seismology
Online: 6 May 2019 (12:09:51 CEST)
The paper presents construction, laboratory tests as well as the first field application of a new fiber-optic rotational seismograph. The system based on fiber-optic gyroscope (FOG) with determined Angle Random Walk of the order of 10-8 rad/Sqrt(s) and a few rad/s maximum detectable amplitude of rotation in the frequency range from DC to 328.12 Hz. It has been designed for rotational seismology area of interest. This work also presents exemplary relevant measurements which were conducted using a set of two devices installed in the geophysical observatory in Książ, Poland.
ARTICLE | doi:10.20944/preprints202111.0544.v1
Subject: Physical Sciences, Optics Keywords: Fiber optic sensor; Refractive index; Mach-Zehnder; Surface plasmon resonance; Etching
Online: 29 November 2021 (15:19:20 CET)
In this paper, an all-fiber Mach-Zehnder interferometer (MZI) sensor for refractive index (RI) measuring is presented, which is based on Multimode–Single-mode–Multimode (MSM) fiber. The effects of both reducing the radius of the sensing part and the surface plasmon resonance (SPR) on its efficiency are investigated. Increasing the interaction of high-order modes with external media, caused by etching the cladding layer of the single-mode fiber part, significantly improves the sensitivity. Both wavelength and intensity interrogation approaches are employed to study the Multimode–etched Single-mode–Multimode (MESM) fiber sensor. The intensity and the wavelength sensitivities for the RI measurement in the range of 1.428-1.458 are obtained as -2308.92 %/RIU and 1313.14 nm/RIU, respectively. Finally, the MESM-SPR sensor is proposed and characterized. Results exhibit high performance in the RI range of 1.333 to 1.357, in which the sensitivity of 1433 nm/RIU is achieved. The advantages like low cost, high sensitivity, and simple fabrication methods make these sensors promising devices for chemical, food industry, and biosensing applications.
ARTICLE | doi:10.20944/preprints201911.0046.v2
Subject: Engineering, Civil Engineering Keywords: Rayleigh backscatter; distributed optical strain measurement; fiber optic; concrete; shrinkage; coating
Online: 5 March 2020 (15:24:39 CET)
The distributed fiber optic strain measurement based on Rayleigh scattering has recently become increasingly popular in automotive or mechanical engineering for strain monitoring and in the construction industry, especially structural health monitoring. This technology enables the monitoring of strain along the entire fiber length. This article addresses integrating optical fibers of different coatings into the concrete matrix to measure the shrinkage deformations. However, previous studies do not give a clear statement about the strain transfer losses of fiber optic sensors in this application. In this context, three different coating types were investigated regarding their strain transfer. The fibers were integrated into fine-grained concrete prisms, and the shrinkage strain was compared with a precise dial gauge. The analysis shows a high correlation between the reference method and the fiber measurement, especially with the Ormocer coating. The used acrylate coating is also consistent in the middle area of the specimen but requires a certain strain introduction length to indicate the actual strain. The main result of this study is a recommendation for fiber coatings for shrinkage measurement in fine-grain concretes using the distributed fiber optic strain measurement. In addition, the advantages and disadvantages of the measurement method are presented.
Subject: Medicine & Pharmacology, Ophthalmology Keywords: non-arteritic anterior ischemic optic neuropathy; NAION; erythropoietin; systemic steroid; neuroprotection
Online: 6 August 2019 (15:52:14 CEST)
Background: To evaluate the effect of systemic erythropoietin, as well as oral steroids, in the management of recent onset non-arteritic anterior ischemic optic neuropathy (NAION). Method: Ninety-nine eyes of 99 patients diagnosed with NAION within 5 days of onset were included in this single masked randomized clinical trial. Thirty-four patients were randomized into group 1 (systemic erythropoietin), group 2 (oral steroids), and group 3 (control). Group A received 10,000 units of erythropoietin twice a day for three days. Group B received oral prednisone 75 mg daily for two weeks followed by a tapering dose (70 mg for 5 days, 60 mg for 5 days, and 5 mg reductions thereafter every 5 days). Functional and structural outcomes were analyzed at 3 and 6 months following treatment. Best corrected visual acuity (BCVA) was the main outcome measure, and mean deviation (MD) of visual field (VF) test and peripapillary retinal nerve fiber layer thickness (PRNFLT) were secondary outcome measures. Results:The mean BCVA (±SD) at the time of presentation was 1 ± 0.56, 1.01 ± 0.6, and 0.94 ± 0.47 logMAR in groups A, B, and C, respectively (P = 0.140); corresponding values were 0.72 ± 0.45, 0.83 ± 0.46, and 0.78 ± 0.4 logMAR (P = 0.417), and at 6-month follow-up, they were 0.70 ± 0.44, 0.73 ± 0.35, and 0.75 ± 0.39 logMAR, respectively (P = 0.597). Fifty-five percent of patients in group A vesus 34.3% in group B, and 31.2% in group C had an improvement of at least 3 lines in the BCVA values at the 6th-month follow-up visit. (P= 0.04) The mean deviation (MD) at the time of presentation was 19.67 ± 6.2, 20.83 ± 4.83, and 18.94 ± 6.92 decibels (db), respectively (P= 0.483).The corresponding values at month 3 were 18.22 ± 7.5, 19.82 ± 7.15, and 17.65 ± 7.22 db, (P = 0.848); and at month 6 they were 16.56 ± 7.08, 18.15 ± 6.57, and 15.9 ± 5.97 db, respectively. (P = 0.699) PRNFLT at presentation was 189 ± 58, 193 ± 64, and 199 ± 62 micrometers, respectively (P = 0.779), which decreased to 110 ± 45, 127 ± 37, and 119 ± 37 at month 3 (P = 0.423). The corresponding values for month 6 were 88 ± 12, 74 ± 25, and 71 ± 18, respectively (P = 0.041). Conclusion: The findings of our study indicate the beneficial effects of systemic erythropoietin in preserving the function and structure of the optic nerve in recent onset NAION.
ARTICLE | doi:10.20944/preprints201704.0100.v1
Subject: Engineering, Civil Engineering Keywords: landslides; fiber optic sensing system; early-warning; energy demodulation; event sensor
Online: 17 April 2017 (12:10:38 CEST)
To help reduce the impact of geohazards, an innovative landslide early-warning technology based on an energy demodulation-based fiber optic sensing (FOS-LW for short) technology, is introduced in this paper. FOS-LW measures the energy change in a sensing fiber at the segment of micro-bending, which can be caused by landslide movements, and automatically raises an alarm as soon as the measured signal intensity in the fiber reaches a pre-set threshold. Based on the sensing of micro-bending losses in the fiber optics, a two-event sensing algorithm has been developed for the landslide early-warning. The feasibility of the FOS-LW technology is verified through laboratory simulation and field tests. The result shows that FOS-LW has some unique features such as the graded alarm, real-time responses, remote monitoring, low cost and passive optical network, and can be applied in the early-warning of landslides.
ARTICLE | doi:10.20944/preprints201608.0077.v1
Subject: Physical Sciences, Optics Keywords: parametric conversion of photons; optically linear and electro-optic parametric interactions
Online: 8 August 2016 (12:12:35 CEST)
An approximation-free and fully quantum optic formalism for parametric processes is presented. Phase-dependent gain coefficients and related phase-pulling effects are identified for quantum Rayleigh emission and the electro-optic conversion of photons providing parametric amplification in small scale integration of photonic devices. These mechanisms can be manipulated to deliver, simultaneously, sub-Poissonian distributions of photons as well as phase-dependent amplification in the same optical quadrature of a signal field.
ARTICLE | doi:10.20944/preprints202102.0586.v1
Subject: Engineering, Control & Systems Engineering Keywords: nonlinear spectrum distortions; signal exposition time; fiber Bragg grating; fiber Bragg sensors; fiber optic sensors; fiber optic interrogator; optical spectrum analyzer; charge-coupled device elements; CCD
Online: 25 February 2021 (13:50:46 CET)
Abstract: Nonlinear spectrum distortions are caused by the peculiarities of the operation of charge-coupled device elements (CCD), in which the signal exposition time (TINT) is one of the significant parameters. A change of TINT on a CCD leads to a nonlinear distortion of the resulting spectrum. Nonlinear distortion of the spectrum, in its turn, leads to errors in determining the central wavelength of Fiber Bragg Gratings (FBG) and spectrally sensitive sensors, which, in general, negatively affects the accuracy of measuring systems. The paper proposes an algorithm for correcting nonlinear distortions of the spectrum obtained on a spectrum analyzer using CCD as a receiver. It is shown that preliminary calibration of the optical spectrum analyzer with subsequent mathematical processing of the signal makes it possible to make corrections in the resulting spectrum, thereby leveling the errors caused by measurements at different TINT.
ARTICLE | doi:10.20944/preprints202105.0744.v1
Subject: Keywords: Distributed fiber optic vibration sensors; Φ-OTDR; Rayleigh backscattering; multi-fiber sensor
Online: 31 May 2021 (11:20:20 CEST)
Distributed fiber optic vibration sensors based on Φ-OTDR using Rayleigh backscattering of highly coherent light source pulses are very popular type in the area of sensors due to many attractive features, mainly due to its distributed manner of sensing, i.e. they can operate as thousands of local sensors simultaneously. The paper summarizes and describes several important modifications of the original sensor scheme to enhance its key performance parameters and to extend its application potential. A multi-fiber sensor form was proposed. Single- and two-fiber sensors were designed, constructed and tested both in the laboratory and in a real environment. Variants of two-fiber sensor utilizing optical switches for the sensor flexibility enhancement are proposed and their applications are described.
ARTICLE | doi:10.20944/preprints202008.0567.v1
Subject: Materials Science, General Materials Science Keywords: Wide band gap semiconductor; Elastic modulus; Optic-electronic properties; Ab–initio calculations
Online: 26 August 2020 (08:57:57 CEST)
The electronic structure and some of its derived properties of Li2CaGeO4 compound have been investigated. The calculations have been performed using the full-potential linearized augmented plane wave plus local orbitals method and ultra-soft pseudo-potentials . The optimized lattice parameters are found to be ingood accord with experiment. Features such as bulk modulus and its pressure derivative, electronic band structure and density of states are reported. The elastic anisotropy of the crystal is discussed and visualized. Moreover, the optical properties reveal that Li2CaGeO4 compound are suitable candidates for optoelectronic devices in the visible and ultraviolet (UV) regions.
COMMUNICATION | doi:10.20944/preprints202103.0013.v1
Subject: Engineering, Automotive Engineering Keywords: temperature sensor; fiber optic sensor; photonic sensor; atomic layer deposition; microsphere; temperature; ZnO
Online: 1 March 2021 (13:24:14 CET)
This study presents of the microsphere-based fiber-optic sensor with the ZnO ALD coating thickness of 100 nm and 200 nm for temperature measurements. Metrological properties of the sensor were investigated over the temperature range of 100°C to 300°C, with a 10°C step. The interferometric signal is used to control whether the microstructure is intact. Spectrum shift of a reflected signal is used to conclude changes in measured parameter for the sensor with a 100 nm coating, while the reflected signal intensity is an indicator during measurements executed by a sensor with a 200 nm coating. With changing temperature, the peak position or intensity of a reflected signal also changes. The R2 coefficient of the presented sensors indicates a linear fit of over 0.99 to the obtained data. The sensitivity of the sensors, investigated in this study, equals 103.5 nW/°C and 0.019 nm/°C for ZnO thickness of 200 nm and 100 nm, respectively.
ARTICLE | doi:10.20944/preprints202012.0627.v1
Subject: Physical Sciences, Acoustics Keywords: Fiber Bragg Structure; microwave photonics; vibration; fiber optic sensor; Address Fiber Bragg Grating
Online: 24 December 2020 (13:56:51 CET)
The paper presents the results of a study of the concept of address fiber Bragg structures in the problem of vibration control. The mathematical model of measuring transformation is presented; the experimental study of a vibration diagnostics system based on Address Fiber Bragg Gratings is carried out; the quantitative and qualitative comparative assessment with electronic accelerometers is made; the gain by an order of magnitude in some parameters is shown.
ARTICLE | doi:10.20944/preprints201806.0335.v1
Subject: Engineering, General Engineering Keywords: structural health monitoring; fiber optic sensor; accelerometer; hetero-core; low-frequency vibration measurement
Online: 21 June 2018 (07:53:45 CEST)
In this paper, a novel pendulum-type accelerometer based on hetero-core fiber optics has been proposed for structural health monitoring targeting large-scale civil infrastructures. Vibration measurement is a non-destructive method for diagnosing the failure of structures by assessing natural frequencies and other vibration patterns. The hetero-core fiber optic sensor utilized in the proposed accelerometer can serve as a displacement sensor with robustness to temperature changes in addition to immunity to electromagnetic interference and chemical corrosions. Thus the hetero-core sensor inside the accelerometer measures applied acceleration by detecting the rotation of an internal pendulum. A series of experiments showed that the hetero-core fiber sensor linearly responded to the rotation angle of the pendulum ranging within ±5°, and furthermore the proposed accelerometer could reproduce the waveform of input vibration in a frequency band of several Hz order.
ARTICLE | doi:10.20944/preprints201802.0152.v1
Subject: Medicine & Pharmacology, Ophthalmology Keywords: glaucoma; lamina cribrosa; optic nerve head; optical coherence tomography; corneal hysteresis; visual field; trabeculectomy
Online: 24 February 2018 (11:06:05 CET)
Purpose: To investigate the relationship of lamina cribrosa displacement to corneal biomechanical properties and visual function after mitomycin C-augmented trabeculectomy. Method: Eighty-one primary open angle eyes were imaged before and after trabeculectomy using an enhanced depth spectral-domain optical coherence tomography (SDOCT). Corneal biomechanical properties were measured with the Ocular Response Analyser before the surgery. The anterior lamina cribrosa (LC) was marked at several points in each of six radial scans to evaluate LC displacement in response to Intraocular pressure (IOP) reduction. A Humphrey visual field test (HVF) was performed before the surgery as well as three and six months postoperatively. Results: Factors associated with a deeper baseline anterior lamina cribrosa depth (ALD) were cup-disc ratio (P=0.04), baseline IOP (P= 0.01), corneal hysteresis (P= 0.001), and corneal resistance factor (P= 0.001). After the surgery, the position of LC became more anterior (negative), posterior (positive) or remained unchanged. The mean LC displacement was -42 μm (P= 0.001) and was positively correlated with the magnitude of IOP reduction (regression coefficient: 0.251, P=0.02), and negatively correlated with age (regression coefficient: - 0.224, P= 0.04) as well as baseline cup-disk ratio (Regression coefficient: -0.212,P= 0.05) Eyes with a larger negative LC displacement were more likely to experience an HVF improvement of more than 3 dB gain in mean deviation (P= 0.002). Conclusion: A lower SDOCT cup-disc ratio, younger age, and a larger IOP reduction were correlated with a larger negative LC displacement and improving HVF. Corneal biomechanics did not predict LC displacement.
Subject: Physical Sciences, Acoustics Keywords: co-design; ITO; thermo-optic phase shifter; mode selective converter; mode selective router; numerical simulation
Online: 14 April 2021 (10:13:38 CEST)
Recently, Indium Tin Oxide, a highly transparent, well conductive, and CMOS-compatible material, has been paying strong attention to the thermo-optic controlled silicon photonics industry because it allows a miniature of the gap between the core silicon and the heater, thus enabling reducing the electric power consumption and enhancing the switching speed. In this article, we propose an ultralow loss and small-size ITO microheater for the phase shift tuning. The designated microheater is manipulated in realizing a numerical co-design of compact and high bandwidth three-mode converter and three-mode selective router. Simulation results illustrate the 3-dB bandwidth for the three-mode converter and three-mode selective router as much as 100-nm and 40-nm during crosstalk under -25 dB, respectively. Besides, co-designed devices attain relatively large fabrication tolerances corresponding to width and height tolerances of ±50 nm and ±5 nm. In addition, the proposed devices consumed less than 90 mW total power consumption and took a fast switching time below 8 μs. Moreover, both two co-designs can be integrated into an estimated compact footprint of 8 μm2160 μm. Such excellent performances demonstrate the attractive potential of ITO as low-loss thermo-optic phase shifters and open an alternative way for enabling ultrafast and high-speed mode division multiplexing systems and very large-scale photonic integrated circuits.
ARTICLE | doi:10.20944/preprints201909.0249.v1
Subject: Physical Sciences, Optics Keywords: channel waveguide; proton exchange; fundamental mode; pyroelectric effect; mobile charge; fiber optic gyroscope; phase modulator
Online: 21 September 2019 (09:27:27 CEST)
It is shown that the termination of the channeling of the fundamental radiation mode in the waveguide can be observed upon heating of an optical integrated circuit based on proton exchange channel waveguides formed in a lithium niobate single crystal. This process is reversible, but restoration of waveguide performance takes tens of minutes. The effect of the waveguide disappearance is observed upon rapid heating (5 °C/min) from a low temperature (minus 40 °C). This effect can lead to a temporary failure of navigation systems using fiber optic gyroscopes with modulators based on a lithium niobate crystal
ARTICLE | doi:10.20944/preprints201706.0050.v1
Subject: Engineering, Mechanical Engineering Keywords: lamb wave; coherent detection; interferometric fiber optic sensors; impact force reconstruction; finite element model; modelling
Online: 12 June 2017 (06:12:41 CEST)
A novel fiber optic sensing technology for high frequency dynamics detection is proposed in this paper, specifically tailored for structural health monitoring applications based on strain wave analysis, including both passive impact identification and active Lamb wave monitoring. The sensing solution relies on a fiber optic-based interferometric architecture associated to an innovative coherent detection scheme, which retrieves in a completely passive way the high-frequency phase information of the received optical signal. The optical fiber can be arranged into different configurations in order to meet the requirement of the specific application, the sensor sensitivity being maximized while still ensuring a limited gauge length if a local measure is required. For the active Lamb wave monitoring, this results in a sensing fiber arranged in multiple loops glued on an aluminum thin panel in order to increase the phase signal relative only to the sensing points of interest. Instead, for passive impact identification, the sensitivity is simply increased by exploiting a longer gauge length glued to the structure. The fiber optic coherent (FOC) sensor detects the strain waves emitted by a piezoelectric transducer placed on the aluminum panel or generated by an impulse hammer, respectively. The FOC sensor measurements have been compared with both a numerical model based on Finite Elements and traditional piezoelectric sensors, confirming a very good agreement between experimental and simulated results for both the active and passive impact monitoring scenarios.
REVIEW | doi:10.20944/preprints202210.0109.v1
Subject: Engineering, Other Keywords: addressed fiber Bragg structure; fiber Bragg grating; fiber-optic sensor; microwave photonics; microwave-photonic sensor systems
Online: 9 October 2022 (08:10:39 CEST)
Five years ago, the concept of addressed fiber Bragg structures (AFBS) was proposed, which simultaneously perform the functions of a two-frequency radiation shaper, the difference frequency of which is the AFBS address, and a sensitive element, since the value of the difference frequency is invariant to measured physical fields, and the set of difference frequencies, moreover, is orthogonal in the array of such sensors, enabling their address multiplexing. In this article, we provide an overview of the theory and technology of AFBS, including the structures with three or more spectral components with various combinations of difference frequencies, symmetrical and asymmetric, performing the functions of the address and converting information signals to the low-frequency range at the same time, along with other functions. The subjects of interrogation of these structures, their fabrication and calibration are discussed as well. We also consider a wide range of applications in which AFBS can be used, covering such areas as oil and gas production, power engineering, transport, medicine, etc. In addition, the prospects of AFBS further development are proposed.
ARTICLE | doi:10.20944/preprints202010.0014.v1
Subject: Materials Science, Surfaces, Coatings & Films Keywords: Bi-substituted; magneto-optic; MCD; Faraday rotation; Figure of merit; imaging; sensing; polarization; Oxygen plasma treatment.
Online: 1 October 2020 (12:21:44 CEST)
Magneto-optic (MO) imaging and sensing are at present the most developed practical applications of thin-film MO garnet materials. However, future component and system-level sensors and imagers technology improvements are still necessary in order to improve sensitivity for a range of established and also the forward-looking applications. These improvements are expected to originate from new material system development. We propose a set of technological modifications for the RF-magnetron sputtering deposition and crystallization annealing of magneto-optic bismuth-substituted iron-garnet films and investigate the improved material properties. Results show that standard crystallization annealing for the as-deposited ultrathin (sputtered 10 nm thick, amorphous phase) films resulted in more than a factor of two loss in the magneto-optical activity of the films in visible spectral region, compared to the liquid-phase grown epitaxial films. Results also show that an additional 10 nm-thick metal-oxide (Bi2O3) protective layer above the amorphous film results in ~2.7 times increase in the magneto-optical quality of crystallized iron-garnet films. On the other hand, the effects of post-deposition oxygen (O2) plasma treatment on the magneto-optical (MO) properties of Bismuth substituted iron garnet thin films material is investigated. Results show that, in the visible part of the electromagnetic spectrum (at 532 nm), the O2 treated (up to 3 minutes) garnet films retain higher specific Faraday rotation and figure of merit than those of non-treated garnet films.
ARTICLE | doi:10.20944/preprints202208.0301.v1
Subject: Medicine & Pharmacology, Oncology & Oncogenics Keywords: corticospinal tract; optic radiations; tractography; transcranial magnetic stimulation; subdural strip electrodes; intra-operative neuro-monitoring; parietal lobe
Online: 17 August 2022 (05:08:09 CEST)
Background: The role played by the non-dominant parietal lobe in motor cognition, attention and spatial awareness networks has potentiated the use of awake surgery. When this is not feasible, asleep monitoring and mapping techniques should be used to achieve an onco-functional balance. Objective: This study aims to assess the feasibility of a dual-strip method to obtain direct cortical stimulation for continuous real-time cortical monitoring and subcortical mapping of motor and visual pathways simultaneously in parietal lobe tumour surgery. Methods: Single-centre prospective study between May’19-November’20 of patients with intrinsic non-dominant parietal-lobe tumours. Two subdural strips were used to simultaneously map and monitor motor and visual pathways. Results: Fifteen patients were included. With regards to motor function, a large proportion of patients had abnormal interhemispheric resting motor threshold ratio (iRMTr) (71.4%), abnormal Cortical Excitability Score (CES) (85.7%), close distance to the corticospinal tract – Lesion-To-Tract Distance (LTD) – 4.2mm, Cavity-To-Tract Distance (CTD) – 7mm and intraoperative subcortical distance - 6.4mm. Concerning visual function, the LTD and CTD for optic radiations (OR) were 0.5mm and 3.4mm, respectively; the mean intensity for positive subcortical stimulation of OR was 12mA±2.3mA and 5/6 patients with deterioration of VEPs>50% had persistent hemianopia and transgression of ORs. 12 patients remained stable, one patient had a de-novo transitory hemiparesis, and two showed improvements in motor symptoms. A higher iRMTr for lower limbs was related with a worse motor outcome (p=0.013) and a longer CTD to OR was directly related with a better visual outcome (p=0.041). At 2 weeks after hospital discharge, all patients were ambulatory at home and all proceeded to have oncological treatment. Conclusion: We propose motor and visual function boundaries for asleep surgery of intrinsic non-dominant parietal tumours. Pre-operative abnormal cortical excitability of the motor cortex, deterioration of the VEP recordings and CTD<2mm from the OR were related to poorer outcomes.
ARTICLE | doi:10.20944/preprints202102.0001.v1
Subject: Medicine & Pharmacology, Allergology Keywords: Giant cell arteritis; anterior ischemic optic neuropathy; clinical prediction rule; diagnostic algorithm; C-reactive protein; temporal compression sonography; ultrasound
Online: 1 February 2021 (08:44:33 CET)
Background: Risk tratification based on pre-test probability may improve the diagnostic accuracy of temporal artery high-resolution compression sonography (hrTCS) in the diagnostic workup of cranial giant cell arteriitis (cGCA). Methods: A logistic regression model with candidate items was derived from a cohort of patients with suspected cGCA (n = 87). The diagnostic accuracy of the model was tested in the derivation cohort and in an independent validation cohort (n = 114) by receiver operator characteristics (ROC)-analysis. The clinical items were composed to a clinical prediction rule, integrated into a stepwise diagnostic algorithm together with CRP-values and hrTCS-values. Results: The model consisted of 4 clinical variables (age > 70, headache, jaw claudication, anterior ischemic optic neuropathy). The diagnostic accuracy of the model for discrimination of patients with and without a final clinical diagnosis of cGCA was excellent in both cohorts (AUC 0.96 and AUC 0.92, respectively). The diagnostic algorithm improved the positive predictive value of hrCTS substantially. Within the algorithm, 32.8% of patients (derivation cohort) and 49.1% (validation cohort) would not have been tested by hrtCS. None of these patients had a final diagnosis of cGCA. Conclusion: A diagnostic algorithm based on a clinical prediction rule improves the diagnostic accuracy of hrTCS.
REVIEW | doi:10.20944/preprints202209.0162.v1
Subject: Materials Science, Surfaces, Coatings & Films Keywords: Bi-substituted; RF magnetron; Sputtering; Annealing; Oxygen plasma treatment; Magneto-optic; Faraday rotation; Figure of merit; Hysteresis loop; Imaging; Sensing.
Online: 13 September 2022 (05:53:32 CEST)
Since 2007, at the Electron Science Research Institute (ESRI) nano-fabrication laboratories, Edith Cowan University, Australia, we have devoted research efforts to the synthesis and characterization of bismuth-containing ferrite-garnet-type thin-film magneto-optic (MO) materials of different compositions. We report on the development and properties of highly bismuth-substituted iron-garnet thin films prepared by using radio frequency (RF) magnetron sputtering. We study the process parameters associated with the RF magnetron sputter deposition technique and investigate the results of optimizing process parameters and implementing several special techniques including the fabrication of co-sputtered nanocomposite films, all-garnet multilayer structures, applying oxygen plasma treatment on amorphous garnet layers just after the deposition process, and designing modifications of the annealing crystallization process and regimes for achieving the best MO properties. We demonstrated significant improvement in MO properties of Bi-containing ferrite-type garnet thin-film materials, including record-high MO figures of merit and improved conventional and un-conventional hysteresis loops of Faraday rotation. The attractive optical, magnetic, and magneto-optic properties obtained in highly bismuth-substituted iron garnet thin-film materials of multiple composition types are relevant in the context of manufacturing next-generation ultra-fast optoelectronic devices, such as light intensity switches and modulators, high-speed flat panel displays, and high-sensitivity sensors.
ARTICLE | doi:10.20944/preprints202206.0293.v2
Subject: Social Sciences, Organizational Economics & Management Keywords: Sensor research; Sensor technology; Network analysis; Technological trajectories; Technological change; Scientific change; Scientific development; Wireless sensor networks; Fiber optic sensors; Biosensors
Online: 5 October 2022 (15:28:11 CEST)
How do sensor research and technologies grow over time? This paper applies the network analysis with a new computational approach to map the structure and evolution of sensor research and technologies over a 30-year time frame (1990-2020).The goal of this study is to analyze the evolution of sensor research for forecasting emerging scientific and technological trajectories. Results show that the scientific interaction within ecosystem (represented with networks) of sensor generates a co-evolution of scientific fields supporting the accelerated growth of different technological tra-jectories, such as: wireless sensors, fiber optic and optical sensors, gas sensors and biosensors. These results suggest main theoretical implications that explain the evolution of sensor research with critical aspects of innovation management to support R&D investments towards new technological trajectories having a high potential of growth.
ARTICLE | doi:10.20944/preprints202206.0292.v1
Subject: Engineering, Other Keywords: environmental monitoring; greenhouse gases; multi-sensor system; combined fiber optic sensors; fiber Bragg grating; addressed fiber Bragg structure; Fabry-Perot resonator; Carunen-Loeff transforms
Online: 21 June 2022 (10:26:11 CEST)
The design and usage of the addressed combined fiber-optic sensors (ACFOS) and the multisensory control systems of the greenhouse gas concentration on their basis are investigated. The main development trend of the combined fiber-optic sensors (CFOS), consisting of the fiber Bragg grating (FBG) and the Fabry-Perot resonator (FPR), which are successively formed at the optical fiber end, is highlighted. The addressed fiber Bragg structures (AFBS) usage instead of the FBG in the CFOS leads not only to significant cheapening of the sensor system due to microwave photonics interrogating methods, but also to increasing its metrological characteristics. The structural scheme of the multisensory gas concentration monitoring system is suggested. The suggested scheme allows detecting four types of the greenhouse gases (СО2, NO2, CH4, OX) depending on the material and thickness of the polymer film, which is the FPR sensitive element. The usage of Karunen-Loeff transform (KLT), which allows separating each component contribution to the reflected spectrum according to its efficiency, is proposed. In the future, it allows determining the gas concentration at the AFBS address frequencies. The estimations have shown that the ACFOS design in the multisensory system allows measuring the environment temperature in the range of −60…+300 °C with an accuracy of 0.1–0.01 °C, and the gas concentration in the range of 10…90% with the accuracy of 0.1–0.5%.