Tracer-free laser-induced grating spectroscopy using a pulse burst laser at 100 kHz.

This work shows the first application of a burst laser for laser-induced grating spectroscopy (LIGS) diagnostics. High repetition rate (100 kHz) LIGS is performed in non reacting and reacting flows using the fundamental harmonic of a Nd:YAG pulse-burst laser as pump. In the first part of the paper, we demonstrate the first time-resolved, high repetition rate electrostrictive LIGS measurements in a sinusoidally-modulated helium jet, allowed by the highly energetic pulses delivered by the burst laser (around 130 mJ per pulse). In the second part of the paper, we perform thermal LIGS measurements in a premixed laminar methane/air flame. Thermal gratings are generated in the flame products from the water vapour, which weakly absorbs 1064 nm light. Thus, this work demonstrates the potential of seeding-free high repetition rate LIGS as a technique to detect and time-resolve the instantaneous speed of sound, temperature, and composition in unsteady flow processes.

High-frequency measurement of concentration in an isothermal methane-air gas mixture using spontaneous Raman spectroscopy.

A high-frequency (1.5 kHz) spontaneous Raman spectroscopy measurement technique is developed and applied to measure external fluctuations generated in the local concentration of an isothermal binary gas mixture of methane and air. Raman excitation is provided by a high-frequency laser at 527 nm in dual-pulsed mode. The Stokes Raman signal is collected using an EMCCD camera coupled to a high-frequency intensifier as a shutter. The emitted signal is collected over the 596-627 nm wavelength range, which allows for the simultaneous tracking of methane and nitrogen Stokes Q-branch mode signals. Calibration curves are initially obtained for each species ([Formula: see text] and [Formula: see text]) based on steady-state concentrations, and further corrected during use to detect local unsteady mixture fluctuations at gas pulsation frequencies up to 250 Hz. The main novelty is the demonstration of Raman spectroscopy for the simultaneous multispecies measurement of unsteady concentrations of gas-phase methane and air mixtures using a laser beam with a high-repetition rate, low energy per pulse, combined with a high-frequency intensifier and a single camera.

The waste collector: information from a pilot study on the interaction between the common octopus (Octopus vulgaris, Cuvier, 1797) and marine litter in bottom traps fishing and first evidence of plastic ingestion.

Few studies focused on behaviour adaptations of organisms to marine litter (ML) pollution in Mediterranean Sea. This research, investigates on some behavior traits of Octopus vulgaris, focusing on the interaction with ML during the artisanal fishing activities by the bottom traps in a small coastal area of the southern Tyrrhenian Sea. For the first time, this pilot study uses an integrated approach based on the Fishermen Ecological Knowledge as well as the analysis of ML found in the traps. First assessment of plastic ingestion in this species are also reported. Plastic and metal were the predominant ML categories observed into the bottom traps. A total of 62 plastics, mainly small microplastics and fibres shaped, were ingested. The ML finding in the bottom traps suggests an interesting behavior of the common octopus regarding its interaction with ML, in fact, it seems to bring ML inside its dens, as a collector.

Microplastics in the bogue, Boops boops: A snapshot of the past from the southern Tyrrhenian Sea.

The present investigation focuses on Boops boops specimens gathered in the Gulf of Patti in 2010. Providing a snapshot from the past, this paper represents, chronologically, the first record of microplastic ingestion in the Mediterranean bogue. The plastic abundance and composition in gastrointestinal tracts of the bogue was assess, in order to improve the knowledge on spatial-temporal variability of microplastics pollution in the Mediterranean basin and in particular, in the southern Tyrrhenian Sea. In a total of 65 specimens, 180 particles of plastic (2.8 items/specimens), mainly belonging to microplastics class, were found. Fragments (63%) and fibres (30%) were the predominant shape categories. Eleven polymers were identified: polypropylene and polyethylene were the most abundant. Several synthetic polymers belonging to the class of elastomers were also observed. The study area is strongly influenced by the absence of trawl fishing activities and a low mixing level of the seabed that, together with the confluence of different watercourses and the presence of different kind of anthropic impact, including motorway, could make it a 'waste disposal site'. Finally, our results suggest the usefulness to retrieve older samples to better understand spatial-temporal changes in marine litter pollution over time.