Optical Signatures of Quantum Emitters in Suspended Hexagonal Boron Nitride

Hexagonal boron nitride (h-BN) is a tantalizing material for solid-state quantum engineering. Analogously to three-dimensional wide-bandgap semiconductors like diamond, h-BN hosts isolated defects exhibiting visible fluorescence, and the ability to position such quantum emitters within a two-dimensional material promises breakthrough advances in quantum sensing, photonics, and other quantum technologies. Critical to such applications, however, is an understanding of the physics underlying h-BN's quantum emission. We report the creation and characterization of visible single-photon sources in suspended, single-crystal, h-BN films. The emitters are bright and stable over timescales of several months in ambient conditions. With substrate interactions eliminated, we study the spectral, temporal, and spatial characteristics of the defects' optical emission, which offer several clues about their electronic and chemical structure. Analysis of the defects' spectra reveals similarities in vibronic coupling despite widely-varying fluorescence wavelengths, and a statistical analysis of their polarized emission patterns indicates a correlation between the optical dipole orientations of some defects and the primitive crystallographic axes of the single-crystal h-BN film. These measurements constrain possible defect models, and, moreover, suggest that several classes of emitters can exist simultaneously in free-standing h-BN, whether they be different defects, different charge states of the same defect, or the result of strong local perturbations

Spin-Dependent Quantum Emission in Hexagonal Boron Nitride at Room Temperature

Optically addressable spins associated with defects in wide-bandgap semiconductors are versatile platforms for quantum information processing and nanoscale sensing, where spin-dependent inter-system crossing (ISC) transitions facilitate optical spin initialization and readout. Recently, the van der Waals material hexagonal boron nitride (h-BN) has emerged as a robust host for quantum emitters (QEs), but spin-related effects have yet to be observed. Here, we report room-temperature observations of strongly anisotropic photoluminescence (PL) patterns as a function of applied magnetic field for select QEs in h-BN. Field-dependent variations in the steady-state PL and photon emission statistics are consistent with an electronic model featuring a spin-dependent ISC between triplet and singlet manifolds, indicating that optically-addressable spin defects are present in h-BN $-$ a versatile two-dimensional material promising efficient photon extraction, atom-scale engineering, and the realization of spin-based quantum technologies using van der Waals heterostructures.Comment: 38 pages, 34 figure

Gastro-Oesophageal Reflux in Noncystic Fibrosis Bronchiectasis

The clinical presentation of noncystic fibrosis bronchiectasis may be complicated by concomitant conditions, including gastro-oesophageal reflux (GOR). Increased acidic GOR is principally caused by gastro-oesophageal junction incompetence and may arise from lower oesophageal sphincter hypotension, including transient relaxations, hiatus hernia, and oesophageal dysmotility. Specific pathophysiological features which are characteristic of respiratory diseases including coughing may further increase the risk of GOR in bronchiectasis. Reflux may impact on lung disease severity by two mechanisms, reflex bronchoconstriction and pulmonary microaspiration. Symptomatic and clinically silent reflux has been detected in bronchiectasis, with the prevalence of 26 to 75%. The cause and effect relationship has not been established, but preliminary reports suggest that GOR may influence the severity of bronchiectasis. Further studies examining the implications of GOR in this condition, including its effect across the disease spectrum using a combination of diagnostic tools, will clarify the clinical significance of this comorbidity

Development of a core outcome set for physiotherapy trials in adults with bronchiectasis (the COS-PHyBE study): A Delphi study and consensus meeting

Physiotherapy is recommended for bronchiectasis management, but there is disparity in evidence supporting its use. This is partly because of inconsistency and poor reporting of outcomes in available studies. A Core Outcome Set (COS) may improve trial consistency and decrease reporting bias. This study aimed to develop a COS for physiotherapy clinical trials in adults with bronchiectasis. A comprehensive list of outcomes was developed using a systematic review and qualitative semi-structured interviews with patients with bronchiectasis and physiotherapists.An international two-round online Delphi survey was conducted. Outcomes scored 7-9 (crucial) by ≥ 70 % of participants and 1-3 (not that important) by ≤ 15 % of participants from each stakeholder in the Likert scale were nominated for inclusion in the COS. Nominated outcomes and those considered crucial by only one of the stakeholders' groups were further discussed and voted in an international consensus meeting. A list of 137 outcomes was generated; 104 from literature and 33 from interviews. A Delphi survey containing 59 outcomes was completed by 171 participants from 20 countries. After the consensus meeting, representatives agreed on seven outcomes: health-related quality of life, respiratory symptoms, physical functioning, emotional and psychological functioning, fatigue, adherence to treatment, and functional exercise capacity. A minimum set of seven outcomes are recommended to be included as measurements in future trials evaluating physiotherapy interventions for bronchiectasis. [Abstract copyright: © 2024 The Authors. Published by Elsevier Ltd.