Hollow core fiber Fabry-Perot interferometers with reduced sensitivity to temperature: erratum.

In the original publication of our research article "Hollow core fiber Fabry-Perot interferometers with reduced sensitivity to temperature" [Opt. Lett.47, 2510 (2022)10.1364/OL.456589OPLEDP0146-9592], we identified an error that requires correction. The authors sincerely apologize for any confusion that may have arisen from this error. The correction does not affect the overall conclusions of the paper.

Hollow-core fiber with stable propagation delay between -150°C and +60°C.

Optical fibers with a low thermal coefficient of delay (TCD) have been developed for frequency and timing transmission/distribution. However, their temperature sensitivity changes as a function of temperature and, to date, no study of such fibers has demonstrated improved performance over extended temperature ranges, especially at sub-zero temperatures. Here, we show that a hollow core fiber (HCF) with a thin acrylate coating can have a TCD within ±2.0 ps/km/°C over a broad temperature range from -150°C to +60°C. In addition, this thinly coated HCF can be fully insensitive to temperature around -134°C, making it of interest, e.g., for laser stabilization close to cryogenic temperatures.

Hollow-core fiber Fabry-Perot interferometers with reduced sensitivity to temperature.

We demonstrate a 3× thermal phase sensitivity reduction for a hollow-core fiber (HCF) Fabry-Perot interferometer by winding the already low temperature sensitivity HCF on to a spool made from an ultralow thermal expansion material. A record low room temperature fiber coil phase thermal sensitivity of 0.13 ppm/K is demonstrated. The result is of particular interest in reducing the thermal sensitivity of HCF-based Fabry-Perot interferometers (for which existing thermal sensitivity reduction methods are not applicable). Our theoretical analysis predicts that significantly lower (or even zero) thermal sensitivity should be achievable when a spool with a slightly negative coefficient of thermal expansion is used. We also suggest a method to fine-tune the thermal sensitivity and analyze it with simulations.

Efficacy of a Digital Sports Vision Training Program for Improving Visual Abilities in Collegiate Baseball and Softball Athletes.

SIGNIFICANCE: Dynamic reactive sports involve visual abilities such as visual acuity, depth perception, contrast sensitivity, and visual-motor reaction speed. This randomized, double-blinded control design showed no significant improvement in the visual parameters among athletes after training on a digital sports vision training program. PURPOSE: There is a need for evidence supporting the efficacy of recently developed digital training programs. METHODS: Thirty-two athletes from National Collegiate Athletic Association Division III softball and baseball teams were randomly divided into experimental and placebo training groups, undergoing three 20-minute training sessions per week for 3 weeks. The experimental group trained on procedures designed to improve dynamic visual acuity and depth perception, and the placebo group trained on procedures designed to have no direct impact on those same parameters. All measures were recorded at baseline, post-training, and after a month of no training. The athletes also completed a questionnaire to determine the efficacy of the placebo effect. RESULTS: There was no significant effect of evaluation type (post-training and follow-up) and condition (experimental and placebo) on any of the visual parameters. However, stereoacuity, contrast sensitivity, depth perception, and dynamic visual acuity showed minimum effect sizes of 0.5. Fifteen of 16 athletes in the placebo group thought they trained on experimental procedures. CONCLUSIONS: No significant improvement differences were seen between experimental and placebo training groups. However, stereoacuity, contrast sensitivity, and depth perception achieved minimum clinical relevance.

Compact micro-optic based components for hollow core fibers.

Using micro-optic collimator technology, we present compact, low-loss optical interconnection devices for hollow core fibers (HCFs). This approach is one of the key manufacturing platforms for commercially available fiber optic components and most forms of HCFs can readily be incorporated into this platform without the need for any substantial or complicated adaptation or physical deformation of the fiber structure. Furthermore, this technique can provide for very low Fresnel reflection interconnection between solid-core fiber and HCF and in addition provides a hermetic seal for HCFs, which can be a critical issue for many HCF applications. In this paper, several exemplar HCF components are fabricated with low insertion loss (0.5-2 dB), low Fresnel reflection (-45 dB) and high modal purity (>20 dB) using various state-of-the-art HCFs.

Composite material anti-resonant optical fiber electromodulator with a 3.5 dB depth.

The hollow regions of an anti-resonant fiber (ARF) offer an excellent template for the deposition of functional materials. When the optical properties of such materials can be modified via external stimuli, it offers a method to control the transmission properties of the fiber device. In this Letter, we show that the integration of a ${{\rm MoS}_2}$MoS2 film into the ARF voids allows the fiber to act as an electro-optical modulator. We record a maximum modulation depth of 3.5 dB at 744 nm, with an average insertion loss of 7.5 dB.

Fabrication of tubular anti-resonant hollow core fibers: modelling, draw dynamics and process optimization.

The fabrication of hollow core microstructured fibers is significantly more complex than solid fibers due to the necessity to control the hollow microstructure with high precision during the draw. We present the first model that can recreate tubular anti-resonant hollow core fiber draws, and accurately predict the draw parameters and geometry of the fiber. The model was validated against two different experimental fiber draws and very good agreement was found. We identify a dynamic within the draw process that can lead to a premature and irreversible contact between neighboring capillaries inside the hot zone, and describe mitigating strategies. We then use the model to explore the tolerance of the draw process to unavoidable structural variations within the preform, and to study feasibility and limiting phenomena of increasing the produced yield. We discover that the aspect ratio of the capillaries used in the preform has a direct effect on the uniformity of drawn fibers. Starting from high precision preforms the model predicts that it could be possible to draw 100 km of fiber from a single meter of preform.

Triple-clad photonic lanterns for mode scaling.

We propose a novel triple-clad photonic lanterns for mode scaling. This novel structure alleviates the adiabatic tapering requirement for the fabrication of large photonic lanterns. A 10-mode photonic lantern with insertion losses ranging from 0.6 to 2.0 dB across all the modes and a record-low pairwise 4-dB mode-dependent loss at C-band was demonstrated.

Brain Injury Vision Symptom Survey (BIVSS) Questionnaire.

PURPOSE: Validation of the Brain Injury Vision Symptom Survey (BIVSS), a self-administered survey for vision symptoms related to traumatic brain injury (TBI). METHODS: A 28-item vision symptom questionnaire was completed by 107 adult subjects (mean age 42.1, 16.2 SD, range 18-75) who self-reported as having sustained mild-to-moderate TBI and two groups of reference adult subjects (first-year optometry students: mean age 23.2, 2.8 SD, range 20-39; and 71 third-year optometry students: mean age 26.0, 2.9 SD, range 22-42) without TBI. Both a Likert-style method of analysis with factor analysis and a Rasch analysis were used. Logistic regression was used to determine sensitivity and specificity. RESULTS: At least 27 of 28 questions were completed by 93.5% of TBI subjects, and all 28 items were completed by all of the 157 reference subjects. BIVSS sensitivity was 82.2% for correctly predicting TBI and 90.4% for correctly predicting the optometry students. Factor analysis identified eight latent variables; six factors were positive in their risk for TBI. Other than dry eye and double vision, the TBI patients were significantly more symptomatic than either cohort of optometry students by at least one standard deviation (p < 0.001). Twenty-five of 28 questions were within limits for creating a single-dimension Rasch scale. CONCLUSIONS: Nearly all of the adult TBI subjects were able to self-complete the BIVSS, and there was significant mean score separation between TBI and non-TBI groups. The Rasch analysis revealed a single dimension associated with TBI. Using the Likert method with the BIVSS, it may be possible to identify different vision symptom profiles with TBI patients. The BIVSS seems to be a promising tool for better understanding the complex and diverse nature of vision symptoms that are associated with brain injury.

Investigation of the Thermal Stability of Nd(x)Sc(y)Zr(1-x-y)O(2-δ) Materials Proposed for Inert Matrix Fuel Applications.

Inert matrix fuels (IMF) consist of transuranic elements (i.e., Pu, Am, Np, Cm) embedded in a neutron transparent (inert) matrix and can be used to "burn up" (transmute) these elements in current or Generation IV nuclear reactors. Yttria-stabilized zirconia has been extensively studied for IMF applications, but the low thermal conductivity of this material limits its usefulness. Other elements can be used to stabilize the cubic zirconia structure, and the thermal conductivity of the fuel can be increased through the use of a lighter stabilizing element. To this end, a series of Nd(x)Sc(y)Zr(1-x-y)O(2-δ) materials has been synthesized via a co-precipitation reaction and characterized by multiple techniques (Nd was used as a surrogate for Am). The long-range and local structures of these materials were studied using powder X-ray diffraction, scanning electron microscopy, and X-ray absorption spectroscopy. Additionally, the stability of these materials over a range of temperatures has been studied by annealing the materials at 1100 and 1400 °C. It was shown that the Nd(x)Sc(y)Zr(1-x-y)O(2-δ) materials maintained a single cubic phase upon annealing at high temperatures only when both Nd and Sc were present with y ≥ 0.10 and x + y > 0.15.

Radiation risk reduction in cardiac electrophysiology through use of a gridless imaging technique.

AIMS: It has been previously demonstrated that use of appropriate frame rates coupled with minimal use of high-dose digital acquisition can limit radiation risk to patients undergoing diagnostic and therapeutic electrophysiology (EP). Imaging without the anti-scatter grid has been proposed as a means of achieving further radiation reduction. We evaluate application of a gridless imaging technique to deliver further reductions in radiation risk to both patients and personnel. METHODS AND RESULTS: Radiation and clinical data for EP procedures performed for 16 months from March 2012 were monitored. The period was divided into three phases: Phase 1 (March 2012-June 2012) provided a performance baseline (radiation output modelling and procedural risk adjustment calibration), Phase 2 (July 2012-September 2012) confirmation of performance with the grid, and Phase 3 (September 2012-June 2013) gridless imaging period. Statistical process control (SPC) charts were used to monitor for changes in radiation use and clinical outcomes (procedural success). Imaging without the grid halved the levels of radiation delivered in undertaking EP procedures. Although there was a perceptible impact on image quality with the grid removed. Review of the SPC chart monitoring procedural outcomes did not identify any discernable adverse impact on success rates. Selected use of the gridless technique is recommended with re-introduction of the grid in larger patients or during aspects of the procedure where image quality is important (e.g. transeptal punctures). CONCLUSION: Use of a gridless imaging technique can contribute to a significant reduction in radiation risk to both patients and operators during cardiac EP procedures.

Single-fluxon controlled resistance switching in centimeter-long superconducting gallium-indium eutectic nanowires.

The ability to manipulate a single quantum object, such as a single electron or a single spin, to induce a change in a macroscopic observable lies at the heart of nanodevices of the future. We report an experiment wherein a single superconducting flux quantum, or a fluxon, can be exploited to switch the resistance of a nanowire between two discrete values. The experimental geometry consists of centimeter-long nanowires of superconducting Ga-In eutectic, with spontaneously formed Ga nanodroplets along the length of the nanowire. The nonzero resistance occurs when a Ga nanodroplet traps one or more superconducting fluxons, thereby driving a Josephson weak-link created by a second nearby Ga nanodroplet normal. The fluxons can be inserted or flipped by careful manipulation of the magnetic field or temperature to produce one of many metastable states of the system.

Anti-resonant hexagram hollow core fibers.

Various simple anti-resonant, single cladding layer, hollow core fiber structures are examined. We show that the spacing between core and jacket glass and the shape of the support struts can be used to optimize confinement loss. We demonstrate the detrimental effect on confinement loss of thick nodes at the strut intersections and present a fabricated hexagram fiber that mitigates this effect in both straight and bent condition by presenting thin and radially elongated nodes. This fiber has loss comparable to published results for a first generation, multi-cladding ring, Kagome fiber with negative core curvature and has tolerable bend loss for many practical applications.

Accurate modelling of fabricated hollow-core photonic bandgap fibers.

We report a novel approach to reconstruct the cross-sectional profile of fabricated hollow-core photonic bandgap fibers from scanning electron microscope images. Finite element simulations on the reconstructed geometries achieve a remarkable match with the measured transmission window, surface mode position and attenuation. The agreement between estimated scattering loss from surface roughness and measured loss values indicates that structural distortions, in particular the uneven distribution of glass across the thin silica struts on the core boundary, have a strong impact on the loss. This provides insight into the differences between idealized models and fabricated fibers, which could be key to further fiber loss reduction.

Investigating the Geochemical Model for Molybdenum Mineralization in the JEB Tailings Management Facility at McClean Lake, Saskatchewan: An X-ray Absorption Spectroscopy Study.

The geochemical model for Mo mineralization in the JEB Tailings Management Facility (JEB TMF), operated by AREVA Resources Canada at McClean Lake, Saskatchewan, was investigated using X-ray Absorption Near-Edge Spectroscopy (XANES), an elemental-specific technique that is sensitive to low elemental concentrations. Twenty five samples collected during the 2013 sampling campaign from various locations and depths in the TMF were analyzed by XANES. Mo K-edge XANES analysis indicated that the tailings consisted primarily of Mo(6+) species: powellite (CaMoO4), ferrimolybdite (Fe2(MoO4)3·8H2O), and molybdate adsorbed on ferrihydrite (Fe(OH)3 - MoO4). A minor concentration of a Mo(4+) species in the form of molybdenite (MoS2) was also present. Changes in the Mo mineralization over time were inferred by comparing the relative amounts of the Mo species in the tailings to the independently measured aqueous Mo pore water concentration. It was found that ferrimolybdite and molybdate adsorbed on ferrihydrite initially dissolves in the TMF and precipitates as powellite.

Leakage channel fibers with microstuctured cladding elements: a unique LMA platform.

We present a novel design of leakage channel fiber (LCF) that incorporates an air-hole lattice to define the modal filtering characteristics. The approach has the potential to offer single-mode, large mode area (LMA) fibers in a single-material platform with bend loss characteristics comparable to all-solid (LCFs) whilst at the same time providing significant fabrication benefits. We compare the performance of the proposed fiber with that of rod-type photonic crystal fibers (PCFs) and all-solid LCFs offering a similar effective mode area of ~1600µm(2) at 1.05µm. Our calculations show that the proposed fiber concept succeeds in combining the advantages of the use of small air holes and the larger design space of rod-type PCFs with the improved bend tolerance and greater higher order mode discrimination of all-solid LCFs, while alleviating their respective issues of rigidity and restricted material design space. We report the fabrication and experimental characterization of a first exemplar fiber, which we demonstrate offers a single-mode output with a fundamental mode area ~1440µm(2) at 1.06µm, and that can be bent down to a radius of 20cm with a bend loss of <3dB/turn. Finally we show that the proposed design concept can be adopted to achieve larger mode areas (> 3000µm(2)), albeit at the expense of reduced bend tolerance.

Low-loss and low-bend-sensitivity mid-infrared guidance in a hollow-core-photonic-bandgap fiber.

Hollow-core-photonic-bandgap fiber, fabricated from high-purity synthetic silica, with a wide operating bandwidth between 3.1 and 3.7 µm, is reported. A minimum attenuation of 0.13 dB/m is achieved through a 19-cell core design with a thin core wall surround. The loss is reduced further to 0.05 dB/m following a purging process to remove hydrogen chloride gas from the fiber-representing more than an order of magnitude loss reduction as compared to previously reported bandgap-guiding fibers operating in the mid-infrared. The fiber also offers a low bend sensitivity of <0.25 dB per 5 cm diameter turn over a 300 nm bandwidth. Simulations are in good agreement with the achieved losses and indicate that a further loss reduction of more than a factor of 2 should be possible by enlarging the core using a 37-cell design.

Analysis of the Mo speciation in the JEB tailings management facility at McClean Lake, Saskatchewan.

The JEB Tailings Management Facility (TMF) is central to reducing the environmental impact of the uranium ore processing operation located at the McClean Lake facility and operated by AREVA Resources Canada (AREVA). The geochemical controls of this facility are largely designed around the idea that elements of concern, such as Mo, will be controlled in the very long term through equilibrium with supporting minerals. However, these systems are far from equilibrium when the tailings are first placed in the TMF, and it can take years, decades, or centuries to reach equilibrium. Therefore, it is necessary to understand how these reactions evolve toward an equilibrium state to understand the very long-term behavior of the TMF and to ensure that the elements of concern will be adequately contained. To this end, the Mo speciation in a series of samples taken from the JEB TMF during the 2008 sampling campaign has been analyzed. This analysis was performed using powder X-ray diffraction (XRD), X-ray fluorescence mapping (µ-XRF), and X-ray absorption near-edge spectroscopy (XANES). These results show that only XANES was effective in speciating Mo in the tailings samples, because it was both element-specific and sensitive enough to detect the low concentrations of Mo present. These results show that the predominant Mo-bearing phases present in the TMF are powellite, ferrimolybdite, and molybdate adsorbed on ferrihydrite.

Pacific acuity test: testability, validity, and interobserver reliability.

PURPOSE: The Pacific Acuity Test (PAT) is a new vanishing optotype test designed to measure recognition visual acuities in preverbal children using a face and opposing oval figure in a forced-choice preferential looking format. This study evaluates the testability, validity, and interobserver reliability of the PAT. METHODS: Fifty-two subjects, aged 6 to 36 months, were tested by a primary observer to determine both recognition and resolution visual acuities using the PAT. Subjects were also tested using the Cardiff Acuity Test (CAT) to provide comparative resolution acuities. Two additional observers independently evaluated video-recorded subject responses for testability and interobserver reliability analysis. An independent grader determined acuity thresholds from each observer's observations, and a logistic regression model was used for additional analysis of acuity thresholds, validity, and testability. RESULTS: Forty-seven of 52 subjects completed testing to obtain visual acuities with the PAT. Sixty-nine percent of subjects followed the desired forced-choice strategy to yield recognition acuities with the PAT. Testability for children younger than 18 months was 44%, whereas 96% of children 18 months and older responded to the recognition testing format. Testability for resolution acuity was 92% and 98% for the PAT and CAT, respectively. The mean difference between PAT recognition and CAT resolution acuity thresholds (PAT-CAT) was +0.11 logMAR (0.15 SD, p < 0.001). The observers were in agreement as determined by intraclass correlation coefficients of 0.90 for both PAT recognition and the CAT. CONCLUSIONS: High testability and valid recognition acuity measures were achieved using the PAT with children by approximately 18 months of age. The recognition acuities obtained with the PAT were higher, particularly for younger subjects, than comparative resolution acuities found with both the PAT and CAT. Interobserver reliability of observers was the same between the PAT and the CAT.

Evaluating Barriers to Opioid Use Disorder Treatment From Patients' Perspectives.

Introduction: Utilizing medications to treat opioid use disorder (MOUD) is both highly effective and unfortunately underutilized in the US health care system. Stigma surrounding substance use disorders, insufficient provider knowledge about substance use disorders and MOUD, and historical lack of physicians with X-waivers to prescribe buprenorphine contribute to this underutilization. Our study aimed to elucidate barriers to accessing MOUD in Milwaukee, Wisconsin. Methods: We conducted semistructured interviews with patients receiving MOUD at a family medicine residency program in Milwaukee, Wisconsin. Interviews were audio-recorded, transcribed verbatim, and analyzed using the qualitative analysis Framework Method. Researchers in our team reviewed transcripts, coding for specific topics of discussion. Coded transcript data were then sorted into a matrix to identify common themes. Results: Interviews with 30 participants showed that motivations to seek treatment appeared self-driven and/or for loved ones. Eighteen patients noted concerns with treatment including treatment denial and efficacy of treatment. Housing instability, experiences with incarceration, insurance, and transportation were common structural barriers to treatment. Conclusions: Primary drivers to seek treatment were patients themselves and/or loved ones. Barriers to care include lack of effective transportation, previous experience with the carceral system, and relative scarcity of clinicians offering MOUD. Future studies may further explore effects of structural inadequacies and biases on MOUD access and quality.