Observation of soliton explosions in a passively mode-locked fiber laser

Soliton explosions are among the most exotic dissipative phenomena studied in mode-locked lasers. In this regime, a dissipative soliton circulating in the laser cavity experiences an abrupt structural collapse, but within a few roundtrips returns to its original quasi-stable state. In this work we report on the first observation of such events in a fiber laser. Specifically, we identify clear explosion signatures in measurements of shot-to-shot spectra of an Yb-doped mode-locked fiber laser that is operating in a transition regime between stable and noise-like emission. The comparatively long, all-normal-dispersion cavity used in our experiments also permits direct time-domain measurements, and we show that the explosions manifest themselves as abrupt temporal shifts in the output pulse train. Our experimental results are in good agreement with realistic numerical simulations based on an iterative cavity map.Comment: 5 pages, 5 figures, submitte

Understanding Novel Superconductors with Ab Initio Calculations

This chapter gives an overview of the progress in the field of computational superconductivity. Following the MgB2 discovery (2001), there has been an impressive acceleration in the development of methods based on Density Functional Theory to compute the critical temperature and other physical properties of actual superconductors from first-principles. State-of-the-art ab-initio methods have reached predictive accuracy for conventional (phonon-mediated) superconductors, and substantial progress is being made also for unconventional superconductors. The aim of this chapter is to give an overview of the existing computational methods for superconductivity, and present selected examples of material discoveries that exemplify the main advancements.Comment: 38 pages, 10 figures, Contribution to Springer Handbook of Materials Modellin

Effect of angiotensin-converting enzyme inhibitor and angiotensin receptor blocker initiation on organ support-free days in patients hospitalized with COVID-19

IMPORTANCE Overactivation of the renin-angiotensin system (RAS) may contribute to poor clinical outcomes in patients with COVID-19. Objective To determine whether angiotensin-converting enzyme (ACE) inhibitor or angiotensin receptor blocker (ARB) initiation improves outcomes in patients hospitalized for COVID-19. DESIGN, SETTING, AND PARTICIPANTS In an ongoing, adaptive platform randomized clinical trial, 721 critically ill and 58 non–critically ill hospitalized adults were randomized to receive an RAS inhibitor or control between March 16, 2021, and February 25, 2022, at 69 sites in 7 countries (final follow-up on June 1, 2022). INTERVENTIONS Patients were randomized to receive open-label initiation of an ACE inhibitor (n = 257), ARB (n = 248), ARB in combination with DMX-200 (a chemokine receptor-2 inhibitor; n = 10), or no RAS inhibitor (control; n = 264) for up to 10 days. MAIN OUTCOMES AND MEASURES The primary outcome was organ support–free days, a composite of hospital survival and days alive without cardiovascular or respiratory organ support through 21 days. The primary analysis was a bayesian cumulative logistic model. Odds ratios (ORs) greater than 1 represent improved outcomes. RESULTS On February 25, 2022, enrollment was discontinued due to safety concerns. Among 679 critically ill patients with available primary outcome data, the median age was 56 years and 239 participants (35.2%) were women. Median (IQR) organ support–free days among critically ill patients was 10 (–1 to 16) in the ACE inhibitor group (n = 231), 8 (–1 to 17) in the ARB group (n = 217), and 12 (0 to 17) in the control group (n = 231) (median adjusted odds ratios of 0.77 [95% bayesian credible interval, 0.58-1.06] for improvement for ACE inhibitor and 0.76 [95% credible interval, 0.56-1.05] for ARB compared with control). The posterior probabilities that ACE inhibitors and ARBs worsened organ support–free days compared with control were 94.9% and 95.4%, respectively. Hospital survival occurred in 166 of 231 critically ill participants (71.9%) in the ACE inhibitor group, 152 of 217 (70.0%) in the ARB group, and 182 of 231 (78.8%) in the control group (posterior probabilities that ACE inhibitor and ARB worsened hospital survival compared with control were 95.3% and 98.1%, respectively). CONCLUSIONS AND RELEVANCE In this trial, among critically ill adults with COVID-19, initiation of an ACE inhibitor or ARB did not improve, and likely worsened, clinical outcomes. TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT0273570

Numerical and experimental investigation of slot-blown air over a cylinder

The paper investigates the concept of directional control of helicopters without tail rotor by means of the Coandă effect. Slot-blowing around a a cylinder in a steady flow is modeled computationally, using the unsteady k-ω shear stress transport (SST) solver in NUMECA, as well as experimentally in the wind tunnel of the Université de Liège. While the concept, in general, is promising, it is shown that there are some potential problems, including pitch-yaw coupling and some unsteady flow conditions. These problems exist under various circumstances and are due, at least, in part, due to the complicated flow-field that governs this problem, even in two dimensions

Wearable conformal fiber sensor for high fidelity physiological measurements

Wearable devices are becoming increasingly common, addressing needs in both the fitness and the medical markets. This trend has accelerated with the growth in telemedicine, particularly during COVID-19. In this paper, we describe a novel polyurethane optical fiber, operating through capillary guidance, that acts as a conformal sensor of pressure or deformation. Used on the wrist and ankle, the sensor allows detailed features of the cardiac pulse wave to be identified with high fidelity, while on the chest it allows the simultaneous measurement of breathing rate and walking cadence. Used together, an array of such sensors (with others) could be incorporated into clothing and provide physiologically rich real-time data for health monitoring

Laser processed semiconductors for integrated photonic devices -INVITED

We report results of laser processing of amorphous silicon and silicon-germanium semiconductor materials for the production of integrated photonic platforms. As the materials are deposited and processed at low temperatures, they are flexible, low cost, and suitable for multi-layer integration with other photonic or electronic layers. We demonstrate the formation of waveguides via crystallization of pre-patterned silicon components and functional microstructures through crystallization and compositional tuning of silicon-germanium alloy films. These results open a route for the fabrication of high density, multi-functional integrated optoelectronic chips

Laser processed semiconductors for integrated photonic devices -INVITED

We report results of laser processing of amorphous silicon and silicon-germanium semiconductor materials for the production of integrated photonic platforms. As the materials are deposited and processed at low temperatures, they are flexible, low cost, and suitable for multi-layer integration with other photonic or electronic layers. We demonstrate the formation of waveguides via crystallization of pre-patterned silicon components and functional microstructures through crystallization and compositional tuning of silicon-germanium alloy films. These results open a route for the fabrication of high density, multi-functional integrated optoelectronic chips