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High-power laser delivery with near-diffraction-limited beam quality is typically limited to tens of metres distances by nonlinearity-induced spectral broadening inside the glass core of delivery fibres. Anti-resonant hollow-core fibres offer not only orders-of-magnitude lower nonlinearity but also loss and modal purity comparable to conventional beam-delivery fibres. Using a single-mode hollow-core nested anti-resonant nodeless fibre with 0.74 dB km−1 loss, we demonstrate the delivery of 1 kW of near-diffraction-limited continuous-wave laser light over a 1 km distance, with a total throughput efficiency of ~80%. From simulations, a further improvement in transmitted power or length of more than one order of magnitude should be possible in such air-filled fibres, and considerably more if the core is evacuated. This paves the way to multi-kilometre, kilowatt-scale power delivery that is potentially useful not only for future manufacturing and subsurface drilling but also for new scientific possibilities in sensing, particle acceleration and gravitational wave detection.Microstructured optical fibre is shown to be able transmit high-power laser light over long distances with high throughput efficiency.

High-performance interferometers, gyroscopes, frequency combs, quantum information experiments and optical clocks rely on the transmission of light beams with the highest possible spatial and polarization purity. Free-space propagation in vacuum unlocks the ultimate performance but becomes impractical at even modest length scales. Glass optical fibres offer a more pragmatic alternative, but degrade polarization purity and suffer from detrimental nonlinear effects. Hollow-core fibres have been heralded for years as the ideal compromise between the two, but achieving high modal purity in both spatial and polarization domains has proved elusive thus far. Here, we show that carefully designed, low-nonlinearity hollow-core antiresonant fibres can transmit a single pair of orthogonal polarization modes with cross-coupling on the scale of 10–10 m–1; that is, orders of magnitude lower than any other solution. This free-space-like optical guidance can immediately provide a leap in performance for photonics-enabled sensors and instruments.Carefully designed hollow-core antiresonant fibres support a pair of orthogonal polarization modes with a level of purity and cross-coupling that is orders of magnitude lower than other fibre designs and beyond the fundamental Rayleigh scattering limit of glass core fibres.

Many scientific and practical applications require the propagation time through cables to be well defined and known, e.g., an error in the evaluation of signal propagation time in the OPERA experiment in 2011 initially erroneously concluded that Neutrinos are faster than light. In fact, there are many other physical infrastructures such as synchrotrons, particle accelerators, telescope arrays and phase arrayed antennae that also rely on precise time synchronization. Time synchronization is also of importance in new practical applications like autonomous manufacturing (e.g., synchronization of assembly line robots) and upcoming 5G networks. Even when the propagation time through a coaxial cable or optical fibre is carefully calibrated, it is affected by changes in the ambient temperature, posing a serious technological challenge. We show how hollow-core optical fibres can address this issue.

We report a hollow core Nested Antiresonant Nodeless Fibre (NANF) with a loss of 0.65dB/km across the full C and L telecommunication bands. The fabricated fibre is 1.23km long, it is effectively single moded over sufficiently long lengths, and is able to transmit data.

We report beyond 100-Gb/s/λ adaptively-loaded discrete multitone (DMT) transmission over the S+C+L-bands using an ultrawide bandwidth hollow-core Nested Antiresonant Nodeless Fibre (NANF) with a low polarisation dependent loss. The results show up to 132.8-Gb/s penalty-free transmission over -1km fibre length without optical amplification.

We report on the longest hollow-core-fiber transmission experiments to date. The enabling fiber is a low-loss (1.18dB/km @1550nm) and record-length (4.8km) nested-antiresonant nodeless fiber (NANF). We reached 125km and 340km in this NANF with 32GBaud PM-16QAM and PM-QPSK transmission, respectively, with 61 WDM channels loading.

Amplified transmission of WDM channels over the O- and C-bands is demonstrated using a bismuth-doped fibre amplifier. The transmission medium is an ultra-wide bandwidth nested antiresonant fibre (NANF) offering uniform loss performance across all wavelengths of interest. Comparable performance is obtained across the two bands.

The pharmacokinetics of abatacept and the association between abatacept exposure and outcomes in patients with severe COVID-19 are unknown. To characterize abatacept pharmacokinetics, relate drug exposure with clinical outcomes, and evaluate the need for dosage adjustments. This study is a secondary analysis of data from the ACTIV-1 (Accelerating COVID-19 Therapeutic Interventions and Vaccines) Immune Modulator (IM) randomized clinical trial conducted between October 16, 2020, and December 31, 2021. The trial included hospitalized adults who received abatacept in addition to standard of care for treatment of COVID-19 pneumonia. Data analysis was performed between September 2022 and February 2024. Single intravenous infusion of abatacept (10 mg/kg with a maximum dose of 1000 mg). Mortality at day 28 was the primary outcome of interest, and time to recovery at day 28 was the secondary outcome. Drug exposure was assessed using the projected area under the serum concentration time curve over 28 days (AUC0-28). Logistic regression modeling was used to analyze the association between drug exposure and 28-day mortality, adjusted for age, sex, and disease severity. The association between time to recovery and abatacept exposure was examined using Fine-Gray modeling with death as a competing risk, and was adjusted for age, sex, and disease severity. Of the 509 patients who received abatacept, 395 patients with 848 serum samples were included in the population pharmacokinetic analysis. Their median age was 55 (range, 19-89) years and most (250 [63.3%]) were men. Abatacept clearance increased with body weight and more severe disease activity at baseline. Drug exposure was higher in patients who survived vs those who died, with a median AUC0-28 of 21 428 (range, 8462-43 378) mg × h/L vs 18 262 (range, 9628-27 507) mg × h/L (P < .001). Controlling for age, sex, and disease severity, an increase of 5000 units in AUC0-28 was associated with lower odds of mortality at day 28 (OR, 0.52 [95% CI, 0.35-0.79]; P = .002). For an AUC0-28 of 19 400 mg × h/L or less, there was a higher probability of recovery at day 28 (hazard ratio, 2.63 [95% CI, 1.70-4.08] for every 5000-unit increase; P < .001). Controlling for age, sex, and disease severity, every 5000-unit increase in AUC0-28 was also associated with lower odds of a composite safety event at 28 days (OR, 0.46 [95% CI, 0.33-0.63]; P < .001). Using the dosing regimen studied in the ACTIV-1 IM trial, 121 of the 395 patients (30.6%) would not achieve an abatacept exposure of at least 19 400 mg × h/L, particularly at the extremes of body weight. Using a modified, higher-dose regimen, only 12 patients (3.0%) would not achieve the hypothesized target abatacept exposure. In this study, patients who were hospitalized with severe COVID-19 and achieved higher projected abatacept exposure had reduced mortality and a higher probability of recovery with fewer safety events. However, abatacept clearance was high in this population, and the current abatacept dosing (10 mg/kg intravenously with a maximum of 1000 mg) may not achieve optimal exposure in all patients. ClinicalTrials.gov Identifier: NCT04593940.

Brownout is the name given to the degraded visual environment that can develop around a helicopter as it operates in dusty conditions. The dust cloud produced reduces visibility and makes landing the helicopter extremely difficult, there is potential for damage to the aircraft or even loss of life. This thesis works towards understanding the physical processes occurring in the generation of the dust cloud and the application of this understanding in a computational model for dust entrainment. Current brownout simulations use empirical entrainment models originally developed for aeolian sand movement. These models use parameters fitted to experimental evidence, whilst they may recreate the dust conditions of certain scenarios there is need for a physical model that can produce accurate results for prospective aircraft or scenarios. The physical brownout system is a multiphase system made up of particle dynamics of the scales less than a millimetre and fluid scales as large as metres. In this thesis computational modelling of particle systems, fluid systems and multiphase flow systems are used to understand how the rotor wake entrains particles. A model scale 3D unsteady rotor simulation was performed both in and out of ground effect. The flow compares well with experimental results. The ground vortex interaction is quantified. The model scale analysis is complemented by a full scale but steady, 2D, axisymmetric rotor flow analysis. The steady flow is demonstrated to provide sufficient aerodynamic force to lift typically medium sized particles from the ground. The Discrete Element Method is a Lagrangian particle simulation method, in this thesis it is investigated numerically and then the physical behaviour is assessed in a simulation of a probe indentation experiment. The dynamic behaviour matched the experiment well. The Discrete Element Method is recommended as a particle modelling method for a brownout modelling solution. Modelling brownout is extremely difficult due to the range of scales involved. This thesis provides an in depth understanding of the helicopter flow field at small and large scales and the aerodynamic forces and entrainment mechanisms of particles on the ground in the wake of a helicopter.

Using micro-optic collimator technology, we present fully integrated 3-port hollow-core-fibre (HCF) components (e.g. 1×2 beam-splitter and WDM coupler), thereby increasing the diversity of inline HCF components and facilitating the use of HCF in a broader range of fibre optic applications.