Purifying single photon emission from giant shell CdSe/CdS quantum dots at room temperature.

Giant shell CdSe/CdS quantum dots are bright and flexible emitters, with near-unity quantum yield and suppressed blinking, but their single photon purity is reduced by efficient multiexcitonic emission. We report the observation, at the single dot level, of a large blueshift of the photoluminescence biexciton spectrum (24 ± 5 nm over a sample of 32 dots) for pure-phase wurtzite quantum dots. By spectral filtering, we demonstrate a 2.3 times reduction of the biexciton quantum yield relative to the exciton emission, while preserving as much as 60% of the exciton single photon emission, thus improving the purity from g2(0) = 0.07 ± 0.01 to g2(0) = 0.03 ± 0.01. At a larger pump fluency, spectral purification is even more effective with up to a 6.6 times reduction in g2(0), which is due to the suppression of higher order excitons and shell states experiencing even larger blueshifts. Our results indicate the potential for the synthesis of engineered giant shell quantum dots, with further increased biexciton blueshifts, for quantum optical applications requiring both high purity and brightness.

Electrical control of single-photon emission in highly charged individual colloidal quantum dots.

Electron transfer to an individual quantum dot promotes the formation of charged excitons with enhanced recombination pathways and reduced lifetimes. Excitons with only one or two extra charges have been observed and exploited for very efficient lasing or single-quantum dot light-emitting diodes. Here, by room-temperature time-resolved experiments on individual giant-shell CdSe/CdS quantum dots, we show the electrochemical formation of highly charged excitons containing more than 12 electrons and 1 hole. We report the control over intensity blinking, along with a deterministic manipulation of quantum dot photodynamics, with an observed 210-fold increase in the decay rate, accompanied by 12-fold decrease in the emission intensity, while preserving single-photon emission characteristics. These results pave the way for deterministic control over the charge state, and room-temperature decay rate engineering for colloidal quantum dot-based classical and quantum communication technologies.

Sputum and blood transcriptomics characterisation of the inhaled PDE4 inhibitor CHF6001 on top of triple therapy in patients with chronic bronchitis.

BACKGROUND: Although phosphodiesterase-4 (PDE4) inhibitors have been shown to reduce COPD exacerbation rate, their biological mechanism of action is not completely elucidated at the molecular level. We aimed to characterise the whole genome gene expression profile of the inhaled PDE4-inhibitor CHF6001 on top of triple therapy in sputum cells and whole blood of patients with COPD and chronic bronchitis. METHODS: Whole genome gene expression analysis was carried out by microarray in 54 patients before and after 32 days treatment with CHF6001 800 and 1600 µg and placebo twice daily (BID) in a randomised crossover study. RESULTS: CHF6001 had a strong effect in sputum, with 1471 and 2598 significantly differentially-expressed probe-sets relative to placebo (p-adjusted for False Discovery Rate < 0.05) with 800 and 1600 µg BID, respectively. Functional enrichment analysis showed significant modulation of key inflammatory pathways involved in cytokine activity, pathogen-associated-pattern-recognition activity, oxidative stress and vitamin D with associated inhibition of downstream inflammatory effectors. A large number of pro-inflammatory genes coding for cytokines and matrix-metalloproteinases were significantly differentially expressed for both doses; the majority (> 87%) were downregulated, including macrophage inflammatory protein-1-alpha and 1-beta, interleukin-27-beta, interleukin-12-beta, interleukin-32, tumour necrosis factor-alpha-induced-protein-8, ligand-superfamily-member-15, and matrix-metalloproteinases-7,12 and 14. The effect in blood was not significant. CONCLUSIONS: Inhaled PDE4 inhibition by CHF6001 on top of triple therapy in patients with COPD and chronic bronchitis significantly modulated key inflammatory targets and pathways in the lung but not in blood. Mechanistically these findings support a targeted effect in the lung while minimising unwanted systemic class-effects. TRIAL REGISTRATION: ClinicalTrial.gov, EudraCT, 2015-005550-35. Registered 15 July 2016.

Dynamical Control of Broadband Coherent Absorption in ENZ Films.

Interferometric effects between two counter-propagating beams incident on an optical system can lead to a coherent modulation of the absorption of the total electromagnetic radiation with 100% efficiency even in deeply subwavelength structures. Coherent perfect absorption (CPA) rises from a resonant solution of the scattering matrix and often requires engineered optical properties. For instance, thin film CPA benefits from complex nanostructures with suitable resonance, albeit at a loss of operational bandwidth. In this work, we theoretically and experimentally demonstrate a broadband CPA based on light-with-light modulation in epsilon-near-zero (ENZ) subwavelength films. We show that unpatterned ENZ films with different thicknesses exhibit broadband CPA with a near-unity maximum value located at the ENZ wavelength. By using Kerr optical nonlinearities, we dynamically tune the visibility and peak wavelength of the total energy modulation. Our results based on homogeneous thick ENZ media open a route towards on-chip devices that require efficient light absorption and dynamical tunability.

Author Correction: Towards spontaneous parametric down conversion from monolayer MoS2.

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has been fixed in the paper.

Extrafine triple therapy delays COPD clinically important deterioration vs ICS/LABA, LAMA, or LABA/LAMA.

BACKGROUND: Current pharmacological therapies for COPD improve quality of life and symptoms and reduce exacerbations. Given the progressive nature of COPD, it is arguably more important to understand whether the available therapies are able to delay clinical deterioration; the concept of "clinically important deterioration" (CID) has therefore been developed. We evaluated the efficacy of the single-inhaler triple combination beclometasone dipropionate, formoterol fumarate, and glycopyrronium (BDP/FF/G), using data from three large 1-year studies. METHODS: The studies compared BDP/FF/G to BDP/FF (TRILOGY), tiotropium (TRINITY), and indacaterol/glycopyrronium (IND/GLY; TRIBUTE). All studies recruited patients with symptomatic COPD, FEV1 <50%, and an exacerbation history. We measured the time to first CID and to sustained CID, an endpoint combining FEV1, St George's Respiratory Questionnaire (SGRQ), moderate-to-severe exacerbations, and death. The time to first CID was based on the first occurrence of any of the following: a decrease of ≥100 mL from baseline in FEV1, an increase of ≥4 units from baseline in SGRQ total score, the occurrence of a moderate/severe COPD exacerbation, or death. The time to sustained CID was defined as: a CID in FEV1 and/or SGRQ total score maintained at all subsequent visits, an exacerbation, or death. RESULTS: Extrafine BDP/FF/G significantly extended the time to first CID vs BDP/FF (HR 0.61, P<0.001), tiotropium (0.72, P<0.001), and IND/GLY (0.82, P<0.001), and significantly extended the time to sustained CID vs BDP/FF (HR 0.64, P<0.001) and tiotropium (0.80, P<0.001), with a numerical extension vs IND/GLY. CONCLUSION: In patients with symptomatic COPD, FEV1 <50%, and an exacerbation history, extrafine BDP/FF/G delayed disease deterioration compared with BDP/FF, tiotropium, and IND/GLY. TRIAL REGISTRATION: The studies are registered in ClinicalTrials.gov: TRILOGY, NCT01917331; TRINITY, NCT01911364; TRIBUTE, NCT02579850.

Nanoscale Design of the Local Density of Optical States.

We propose a design concept for tailoring the local density of optical states (LDOS) in dielectric nanostructures, based on the phase distribution of the scattered optical fields induced by point-like emitters. First we demonstrate that the LDOS can be expressed in terms of a coherent summation of constructive and destructive contributions. By using an iterative approach, dielectric nanostructures can be designed to effectively remove the destructive terms. In this way, dielectric Mie resonators, featuring low LDOS for electric dipoles, can be reshaped to enable enhancements of 3 orders of magnitude. To demonstrate the generality of the method, we also design nanocavities that enhance the radiated power of a circular dipole, a quadrupole, and an arbitrary collection of coherent dipoles. Our concept provides a powerful tool for high-performance dielectric resonators and affords fundamental insights into light-matter coupling at the nanoscale.

Towards spontaneous parametric down conversion from monolayer MoS2.

We present a detailed study of the second order nonlinearity of 2D (mono-atomic layer) dichalcogenide MoS2, both in the visible and in the IR regime, and test its potential for spontaneous parametric down-conversion (SPDC), the amplification of vacuum fluctuations mediated by optical nonlinearity. We develop a model of SPDC from a deeply subwavelength nonlinear medium, where phase matching conditions are completely relaxed, and make predictions about the rate of emitted photons, their momentum, polarisation and spectrum. We show that detection in the visible spectral region is hindered by the strong photoluminescence background. Moving to the IR regime we observe indications of SPDC by performing polarization, power dependence and lifetime measurements around 1560 nm. We show that the signal from a single monolayer is qualitatively different from that generated by multi-layer MoS2. Finally, we characterize the latter as a new kind of photo-luminescence emission which is enhanced at the edges of multi-layer MoS2.

Extrafine inhaled triple therapy versus dual bronchodilator therapy in chronic obstructive pulmonary disease (TRIBUTE): a double-blind, parallel group, randomised controlled trial.

BACKGROUND: Evidence is scarce on the relative risk-benefit of inhaled triple therapy, consisting of inhaled corticosteroid, long-acting muscarinic antagonist, and long-acting ß2-agonist, versus dual bronchodilation for chronic obstructive pulmonary disease (COPD). We aimed to compare a single-inhaler triple combination of beclometasone dipropionate, formoterol fumarate, and glycopyrronium (BDP/FF/G) versus a single-inhaler dual bronchodilator combination of indacaterol plus glycopyrronium (IND/GLY) in terms of the rate of moderate-to-severe COPD exacerbations over 52 weeks of treatment. METHODS: This randomised, parallel-group, double-blind, double-dummy study was done at 187 sites across 17 countries. Eligible patients had symptomatic COPD, severe or very severe airflow limitation, at least one moderate or severe exacerbation in the previous year, and were receiving inhaled maintenance medication. After a 2 week run-in period with one inhalation per day of IND/GLY (85 µg/43 µg), patients were randomly assigned (1:1), via an interactive response technology system, to receive 52 weeks of treatment with two inhalations of extrafine BDP/FF/G (87 µg/5 µg/9 µg) twice per day or one inhalation of IND/GLY (85 µg/43 µg) per day. Randomisation was stratified by country and severity of airflow limitation. The primary endpoint was the rate of moderate-to-severe COPD exacerbations across 52 weeks of treatment in all randomised patients who received at least one dose of study drug and had at least one post-baseline efficacy assessment. Safety was assessed in all patients who received at least one dose of study drug. This study is registered with ClinicalTrials.gov, number NCT02579850. FINDINGS: Between May, 29 2015, and July 10, 2017, 1532 patients received BDP/FF/G (n=764) or IND/GLY (n=768). Moderate-to-severe exacerbation rates were 0·50 per patient per year (95% CI 0·45-0·57) for BDP/FF/G and 0·59 per patient per year (0·53-0·67) for IND/GLY, giving a rate ratio of 0·848 (0·723-0·995, p=0·043) in favour of BDP/FF/G. Adverse events were reported by 490 (64%) of 764 patients receiving BDP/FF/G and 516 (67%) of 768 patients receiving IND/GLY. Pneumonia occurred in 28 (4%) patients receiving BDP/FF/G versus 27 (4%) patients receiving IND/GLY. One treatment-related serious adverse event occurred in each group: dysuria in a patient receiving BDP/FF/G and atrial fibrillation in a patient receiving IND/GLY. INTERPRETATION: In patients with symptomatic COPD, severe or very severe airflow limitation, and an exacerbation history despite maintenance therapy, extrafine BDP/FF/G significantly reduced the rate of moderate-to-severe exacerbations compared with IND/GLY, without increasing the risk of pneumonia. FUNDING: Chiesi Farmaceutici.

Optical Time Reversal from Time-Dependent Epsilon-Near-Zero Media.

Materials with a spatially uniform but temporally varying optical response have applications ranging from magnetic field-free optical isolators to fundamental studies of quantum field theories. However, these effects typically become relevant only for time variations oscillating at optical frequencies, thus presenting a significant hurdle that severely limits the realization of such conditions. Here we present a thin-film material with a permittivity that pulsates (uniformly in space) at optical frequencies and realizes a time-reversing medium of the form originally proposed by Pendry [Science 322, 71 (2008)SCIEAS0036-807510.1126/science.1162087]. We use an optically pumped, 500 nm thick film of epsilon-near-zero (ENZ) material based on Al-doped zinc oxide. An incident probe beam is both negatively refracted and time reversed through a reflected phase-conjugated beam. As a result of the high nonlinearity and the refractive index that is close to zero, the ENZ film leads to time reversed beams (simultaneous negative refraction and phase conjugation) with near-unit efficiency and greater-than-unit internal conversion efficiency. The ENZ platform therefore presents the time-reversal features required, e.g., for efficient subwavelength imaging, all-optical isolators and fundamental quantum field theory studies.

The efficacy of extrafine beclomethasone dipropionate-formoterol fumarate in COPD patients who are not "frequent exacerbators": a post hoc analysis of the FORWARD study.

The GOLD 2017 strategy document recommends that the pharmacological management of COPD patients be based on the risk of future exacerbations and the severity of symptoms. A threshold of two moderate exacerbations or one hospitalization is used to define high-risk patients. The FORWARD study was a randomized, double-blind, parallel-group trial that compared 48 weeks' treatment with extrafine beclomethasone dipropionate plus formoterol fumarate (BDP-FF) versus FF in severe COPD patients with a history of one or more exacerbations in the previous year. The new GOLD 2017 recommendations mean that many patients in the FORWARD study are now reclassified as GOLD B. We conducted a post hoc analysis of the FORWARD study, in order to investigate the effects of extrafine BDP/FF in patients with one exacerbation in the previous year, focusing on those categorized as group B using the GOLD 2017 definition. The analysis showed a 35% reduction in exacerbation rate with an inhaled corticosteroid (ICS) + long-acting ß-agonist (LABA) versus LABA. We propose that ICS-LABA treatment is a therapeutic option for COPD patients with one exacerbation in the previous year.

Bronchodilator efficacy of extrafine glycopyrronium bromide: the Glyco 2 study.

An extrafine formulation of the long-acting muscarinic antagonist glycopyrronium bromide (GB) is in development for chronic obstructive pulmonary disease (COPD), in combination with beclometasone dipropionate and formoterol fumarate - a "fixed triple". This two-part study was randomized, double blind, placebo controlled in patients with moderate-to-severe COPD: Part 1: single-dose escalation, GB 12.5, 25, 50, 100 or 200 µg versus placebo; Part 2: repeat-dose (7-day), four-period crossover, GB 12.5, 25 or 50 µg twice daily (BID) versus placebo, with an open-label extension in which all patients received tiotropium 18 µg once daily. On the morning of Day 8 in all five periods, patients also received formoterol 12 µg. In study Part 1, 27 patients were recruited. All GB doses significantly increased from baseline forced expiratory volume in 1 second (FEV1) area under the curve (AUC0-12h) and peak FEV1, with a trend toward greater efficacy with higher GB dose. All adverse events were mild-moderate in severity, with a lower incidence with GB than placebo and no evidence of a dose-response relationship. In study Part 2, of 38 patients recruited, 34 completed the study. Adjusted mean differences from placebo in 12 h trough FEV1 on Day 7 (primary) were 115, 142 and 136 mL for GB 12.5, 25 and 50 µg BID, respectively (all P<0.001). GB 25 and 50 µg BID were superior (P<0.05) to GB 12.5 µg BID for pre-dose morning FEV1 on Day 8. For this endpoint, GB 25 and 50 µg BID were also superior to tiotropium. Compared with Day 7, addition of formoterol significantly increased Day 8 FEV1 peak and AUC0-12h with all GB doses and placebo (all P<0.001). All adverse events were mild-moderate in severity and there was no indication of a dose-related relationship. This study provides initial evidence on bronchodilation, safety and pharmacokinetics of extrafine GB BID. Overall, the results suggest that GB 25 µg BID is the optimal dose in patients with COPD.

Single inhaler extrafine triple therapy versus long-acting muscarinic antagonist therapy for chronic obstructive pulmonary disease (TRINITY): a double-blind, parallel group, randomised controlled trial.

BACKGROUND: Limited data are available for the efficacy of triple therapy with two long-acting bronchodilators and an inhaled corticosteroid in chronic obstructive pulmonary disease (COPD). We compared treatment with extrafine beclometasone dipropionate, formoterol fumarate, and glycopyrronium bromide (BDP/FF/GB; fixed triple) with tiotropium, and BDP/FF plus tiotropium (open triple). METHODS: For this double-blind, parallel-group, randomised, controlled trial, eligible patients had COPD, post-bronchodilator forced expiratory volume in 1 s (FEV1) of less than 50%, at least one moderate-to-severe COPD exacerbation in the previous 12 months, and a COPD Assessment Test total score of at least 10. After a 2-week run-in period receiving one inhalation per day via single-dose dry-powder inhaler of open-label 18 µg tiotropium, patients were randomised (2:2:1) using a interactive response technology system to 52 weeks treatment with tiotropium, fixed triple, or open triple. Randomisation was stratified by country and severity of airflow limitation. The primary endpoint was moderate-to-severe COPD exacerbation rate. The key secondary endpoint was change from baseline in pre-dose FEV1 at week 52. The trial is registered with ClinicalTrials.gov, number NCT01911364. FINDINGS: Between Jan 21, 2014, and March 18, 2016, 2691 patients received fixed triple (n=1078), tiotropium (n=1075), or open triple (n=538). Moderate-to-severe exacerbation rates were 0·46 (95% CI 0·41-0·51) for fixed triple, 0·57 (0·52-0·63) for tiotropium, and 0·45 (0·39-0·52) for open triple; fixed triple was superior to tiotropium (rate ratio 0·80 [95% CI 0·69-0·92]; p=0·0025). For week 52 pre-dose FEV1, fixed triple was superior to tiotropium (mean difference 0·061 L [0·037 to 0·086]; p<0·0001) and non-inferior to open triple (-0·003L [-0·033 to 0·027]; p=0·85). Adverse events were reported by 594 (55%) patients with fixed triple, 622 (58%) with tiotropium, and 309 (58%) with open triple. INTERPRETATION: In our TRINITY study, treatment with extrafine fixed triple therapy had clinical benefits compared with tiotropium in patients with symptomatic COPD, FEV1 of less than 50%, and a history of exacerbations. FUNDING: Chiesi Farmaceutici SpA.

Hot exciton cooling and multiple exciton generation in PbSe quantum dots.

Multiple exciton generation (MEG) is a promising process to improve the power conversion efficiency of solar cells. PbSe quantum dots (QDs) have shown reasonably high MEG quantum yield (QY), although the photon energy threshold for this process is still under debate. One of the reasons for this inconsistency is the complicated competition of MEG and hot exciton cooling, especially at higher excited states. Here, we investigate MEG QY and the origin of the photon energy threshold for MEG in PbSe QDs of three different sizes by studying the transient absorption (TA) spectra, both at the band gap (near infrared, NIR) and far from the band gap energy (visible range). The comparison of visible TA spectra and dynamics for different pump wavelengths, below, around and above the MEG threshold, provides evidence of the role of the Σ transition in slowing down the exciton cooling process that can help MEG to take over the phonon relaxation process. The universality of this behavior is confirmed by studying QDs of three different sizes. Moreover, our results suggest that MEG QY can be determined by pump-probe experiments probed above the band gap.

Single inhaler triple therapy versus inhaled corticosteroid plus long-acting ß2-agonist therapy for chronic obstructive pulmonary disease (TRILOGY): a double-blind, parallel group, randomised controlled trial.

BACKGROUND: Few data are available for the efficacy of "triple therapy" with two long-acting bronchodilators and an inhaled corticosteroid in chronic obstructive pulmonary disease (COPD). We designed this study to assess efficacy of single-inhaler combination of an extra fine formulation of beclometasone dipropionate, formoterol fumarate, and glycopyrronium bromide (BDP/FF/GB) in COPD compared with beclometasone dipropionate and formoterol fumarate (BDP/FF) treatment. METHODS: TRILOGY was a randomised, parallel group, double-blind, active-controlled study done in 159 sites across 14 countries. The sites were a mixture of primary, secondary, and tertiary care providers, and specialist investigation units. Eligible patients with COPD had post-bronchodilator forced expiratory volume in 1 s (FEV1) of lower than 50%, one or more moderate-to-severe COPD exacerbation in the previous 12 months, COPD Assessment Test total score of 10 or more, and a Baseline Dyspnea Index focal score of 10 or less. Patients who met the inclusion and exclusion criteria at screening entered a 2-week open-label run-in period where they received beclometasone dipropionate (100 µg) and formoterol fumarate (6 µg) in two actuations twice daily. Patients were then randomly assigned (1:1) with an interactive response technology system to either continue BDP (100 µg) and FF (6 µg) or step-up to BDP (100 µg), FF (6 µg), and GB (12·5 µg) in two actuations twice daily for 52 weeks via pressurised metered-dose inhaler. The three co-primary endpoints were pre-dose FEV1, 2-h post-dose FEV1, and Transition Dyspnea Index (TDI) focal score, all measured at week 26 in the intention-to-treat population (all patients who were randomly assigned and received at least one dose of study drug and had at least one post-baseline efficacy assessment). Safety outcomes were measured in the safety population (all patients who were randomly assigned and received at least one dose of study drug). Secondary endpoints included moderate-to-severe COPD exacerbation rate over 52 weeks. This study is registered with ClinicalTrials.gov number NCT01917331. FINDINGS: Between March 21, 2014, and Jan 14, 2016, 1368 patients received either BDP/FF/GB (n=687) or BDP/FF (n=681). At week 26, BDP/FF/GB improved pre-dose FEV1 by 0·081 L (95% CI 0·052-0·109; p<0·001) and 2-h post-dose FEV1 by 0·117 L (0·086-0·147; p<0·001) compared with BDP/FF. Mean TDI focal scores at week 26 were 1·71 for BDP/FF/GB and 1·50 for BDP/FF, with a difference of 0·21 (95% CI -0·08 to 0·51; p=0·160). Adjusted annual moderate-to-severe exacerbation frequencies were 0·41 for BDP/FF/GB and 0·53 for BDP/FF (rate ratio 0·77 [95% CI 0·65-0·92]; p=0·005), corresponding to a 23% reduction in exacerbations with BDP/FF/GB compared with BDP/FF. Adverse events were reported by 368 (54%) patients with BDP/FF/GB and 379 (56%) with BDP/FF. One serious treatment-related adverse event occurred (atrial fibrillation) in a patient in the BDP/FF/GB group. INTERPRETATION: We provide evidence for the clinical benefits of stepping up patients with COPD from an inhaled corticosteroid/long-acting ß2-agonist combination treatment to triple therapy using a single inhaler. FUNDING: Chiesi Farmaceutici SpA.

Quantum super-oscillation of a single photon.

Super-oscillation is a counterintuitive phenomenon describing localized fast variations of functions and fields that happen at frequencies higher than the highest Fourier component of their spectra. The physical implications of this effect have been studied in information theory and optics of classical fields, and have been used in super-resolution imaging. As a general phenomenon of wave dynamics, super-oscillations have also been predicted to exist in quantum wavefunctions. Here we report the experimental demonstration of super-oscillatory behavior of a single-quantum object, a photon. The super-oscillatory behavior is demonstrated by tight localization of the photon wavefunction after focusing with an appropriately designed slit mask to create an interference pattern with a sub-diffraction hotspot (~0.45 λ). Such quantum super-oscillation can be used for low-intensity far-field super-resolution imaging techniques even down to single-photon counting regime, which would be of interest to quantum physics and non-invasive and label-free biological studies.

Exciton Fine Structure of CdSe/CdS Nanocrystals Determined by Polarization Microscopy at Room Temperature.

We present a method that allows determining the band-edge exciton fine structure of CdSe/CdS dot-in-rods samples based on single particle polarization measurements at room temperature. We model the measured emission polarization of such single particles considering the fine structure properties, the dielectric effect induced by the anisotropic shell, and the measurement configuration. We use this method to characterize the band-edge exciton fine structure splitting of various samples of dot-in-rods. We show that, when the diameter of the CdSe core increases, a transition from a spherical like band-edge exciton symmetry to a rod-like band edge exciton symmetry occurs. This explains the often reported large emission polarization of such particles compared to spherical CdSe/CdS emitters.