Applications of Lasers for Sensing and Free Space Communications: introduction to the feature issue.

This feature issue highlights the latest developments in laser-based sensing and free space communications. In total, 15 papers were published in Applied Optics, including an invited review paper that celebrates the legacy of David L. Fried.

DSM-flux: A new technology for reliable Combined Sewer Overflow discharge monitoring with low uncertainties.

In the past ten years, governments from the European Union have been encouraged to collect volume and quality data for all the effluent overflows from separated stormwater and combined sewer systems that result in a significant environmental impact on receiving water bodies. Methods to monitor and control these flows require improvements, particularly for complex Combined Sewer Overflow (CSO) structures. The DSM-flux (Device for Stormwater and combined sewer flows Monitoring and the control of pollutant fluxes) is a new pre-designed and pre-calibrated channel that provides appropriate hydraulic conditions suitable for measurement of overflow rates and volumes by means of one water level gauge. In this paper, a stage-discharge relation for the DSM-flux is obtained experimentally and validated for multiple inflow hydraulic configurations. Uncertainties in CSO discharges and volumes are estimated within the Guide to the expression of Uncertainty in Measurement (GUM) framework. Whatever the upstream hydraulic conditions are, relative uncertainties are lower than 15% and 2% for the investigated discharges and volumes, respectively.

Urban domestic wastewater: how to reduce individual injection?

The present paper aims to identify ways to reduce pollution injected by residents in the urban wastewater network system. Two approaches are considered. The first one uses flow and pollutant calculation to test whether a polluter can easily be identified in a neighborhood. The second approach uses a survey to examine what incentive would be most effective to influence residents' behavior. Hydrodynamic simulation results show that concentration profiles at the network outlet corresponding to all possible polluters are similar and thus do not point out specific resident source of pollution. Household-level survey results show that most socio-economic and public-good-related characteristics do not play a significant role in explaining choices to discard in the home wastewater network. Apart from the nature of the waste itself, by far the belief that the respondent has about neighbors' and relatives' discarding behavior is the main driver of the choice.

Spectral degree of linear polarization of light from healthy skin and melanoma.

A non-invasive optical technique, based on a supercontinuum laser source and hyperspectral sensors, is established to measure the spectral degree of linear polarization (DOLP) in a broad spectral range from 525 nm to 1000 nm. Several biomaterials of interest, such as healthy and cancerous skins, are considered. The spectral DOLP of melanoma, from 5 mm to 9 mm diameter, are measured and analyzed. An increase of the spectral DOLP is reported for 100% of the melanoma samples compared to healthy skin samples. The spectral DOLP of a given melanoma appears to be correlated to the stage of its development: the larger the melanoma, the higher the DOLP. Such trend could be explained by a decrease of the surface roughness along the evolution of the disease. In addition, a significant spectral dependence of the DOLP is reported for melanoma samples as it exhibits a decrease in the near infrared from 750 nm to 1000 nm.

Reflectances from a supercontinuum laser-based instrument: hyperspectral, polarimetric and angular measurements.

Recent developments of active hyperspectral systems require optical characterization of man-made materials for instrument calibration. This work presents an original supercontinuum laser-based instrument designed by Onera, The French Aerospace Lab, for fast hyperspectral polarimetric and angular reflectances measurements. The spectral range is from 480 nm to 1000 nm with a 1 nm spectral resolution. Different polarization configurations are made possible in whole spectrum. This paper reviews the design and the calibration of the instrument. Hyper-spectral polarimetric and angular reflectances are measured for reference and man-made materials such as paint coatings. Physical properties of reflectances as positivity, energy conservation and Helmholtz reciprocity are retrieved from measurements.

Mechanical complications in ST-elevation myocardial infarction: The impact of pre-hospital delay.

AIMS: Mechanical complications (MC) (i.e., free wall rupture (FWR), papillary muscle rupture (PMR) and ventricular septal rupture (VSR)) are rare complications of ST- elevation acute myocardial infarction (STEMI). Incidence of MC according to pre-hospital delay remains unknown. We aimed to determine the rates of MC according to pre-hospital delay. METHODS: Analysis was conducted on the MODIF registry data. Patients were allocated to four groups according to pre-hospital delay: 0 to 12 h, 12 to 24 h, 24 to 36 h and 36 to 48 h. RESULTS: 6185 patients with complete data were analyzed. Mean age was 64.1 years old and 75.7% of patients were males. Eighty-three patients (1.34%) presented with MC: 44 (0.71%) experienced a FWR, 17 (0.27%) a PMR, and 22 (0.36%) a VSR. Global rates of MC were 0.82%, 1.43%, 1.24% and 5.07% in the four groups of pre-hospital delays - 0 to 12 h, 12 to 24 h, 24 to 36 h and 36 to 48 h - respectively (p < 0.001). In-hospital mortality rates were high: 44.2%, 47.1% and 54.6% for FWR, PMR and VSR, respectively. In multivariate analysis, factors independently related to the occurrence of MC were older age, female sex, simultaneous COVID-19 infection, absence of dyslipidemia, initial TIMI flow 0 or 1 in the culprit artery, 36 to 48 h-pre-hospital delay and absence of revascularization by percutaneous coronary intervention (PCI) with stent implantation. CONCLUSION: The probability of MC in STEMI increases with pre-hospital delay. Mechanical complications of STEMI remain associated with a very poor prognosis.

ST-segment elevation myocardial infarction: Management and association with prognosis during the COVID-19 pandemic in France.

BACKGROUND: Systems of care have been challenged to control progression of the COVID-19 pandemic. Whether this has been associated with delayed reperfusion and worse outcomes in French patients with ST-segment elevation myocardial infarction (STEMI) is unknown. AIM: To compare the rate of STEMI admissions, treatment delays, and outcomes between the first peak of the COVID-19 pandemic in France and the equivalent period in 2019. METHODS: In this nationwide French survey, data from consecutive STEMI patients from 65 centres referred for urgent revascularization between 1 March and 31 May 2020, and between 1 March and 31 May 2019, were analysed. The primary outcome was a composite of in-hospital death or non-fatal mechanical complications of acute myocardial infarction. RESULTS: A total of 6306 patients were included. During the pandemic peak, a 13.9±6.6% (P=0.003) decrease in STEMI admissions per week was observed. Delays between symptom onset and percutaneous coronary intervention were longer in 2020 versus 2019 (270 [interquartile range 150-705] vs 245 [140-646]min; P=0.013), driven by the increase in time from symptom onset to first medical contact (121 [60-360] vs 150 [62-420]min; P=0.002). During 2020, a greater number of mechanical complications was observed (0.9% vs 1.7%; P=0.029) leading to a significant difference in the primary outcome (112 patients [5.6%] in 2019 vs 129 [7.6%] in 2020; P=0.018). No significant difference was observed in rates of orotracheal intubation, in-hospital cardiac arrest, ventricular arrhythmias and cardiogenic shock. CONCLUSIONS: During the first peak of the COVID-19 pandemic in France, there was a decrease in STEMI admissions, associated with longer ischaemic time, exclusively driven by an increase in patient-related delays and an increase in mechanical complications. These findings suggest the need to encourage the population to seek medical help in case of symptoms.

Imaging tissue-mimic with light sheet microscopy: A comparative guideline.

Tissue mimics (TMs) on the scale of several hundred microns provide a beneficial cell culture configuration for in vitro engineered tissue and are currently under the spotlight in tissue engineering and regenerative medicine. Due to the cell density and size, TMs are fairly inaccessible to optical observation and imaging within these samples remains challenging. Light Sheet Fluorescence Microscopy (LSFM)- an emerging and attractive technique for 3D optical sectioning of large samples- appears to be a particularly well-suited approach to deal with them. In this work, we compared the effectiveness of different light sheet illumination modalities reported in the literature to improve resolution and/or light exposure for complex 3D samples. In order to provide an acute and fair comparative assessment, we also developed a systematic, computerized benchmarking method. The outcomes of our experiment provide meaningful information for valid comparisons and arises the main differences between the modalities when imaging different types of TMs.

Phenotypic plasticity in response to mechanical stress: hydrodynamic performance and fitness of four aquatic plant species.

Plastic responses of plants exposed to mechanical stress can lead to modified, performance-enhancing, morphologies, sometimes accompanied by costs to reproduction. The capacity to present short-term plastic responses to current stress, the resulting performance (expected lower mechanical forces), and the costs of such responses to reproduction were tested for four aquatic plant species. Two ramets of the same genet were submitted to running vs standing water treatment. Traits describing the morphology, hydrodynamic performance and reproduction (sexual and vegetative) were measured. For one species, plastic responses led to reduced hydrodynamic forces, without apparent costs to reproduction, indicating that the plastic response could be beneficial for plant maintenance in stressful habitats. For two species, plastic responses were not associated with variations in performance and reproduction, possibly because of the low hydrodynamic forces experienced, even for morphologies produced under standing conditions. For one species, plastic responses were associated with a sharp decrease in sexual reproduction, without variations in performance, revealing the negative impact of currents over a short time scale. Species maintenance is linked to the capacity of individuals to tolerate mechanical forces. The contrasting responses to currents may be a key element for predicting community dynamics.