Relaciones entre talla del otolito y talla del pez en algunos peces mesopelágicos y batipelágicos del Mediterráneo (estrecho de Messina, Italia)

The length-weight relationships and the regressions between otolith size (length and width) and fish length of some mesopelagic and bathypelagic fishes living in the central Mediterranean Sea were provided. Images and morphological description of otoliths (sagittae) from 16 species belonging to the families of Gonostomatidae (1), Microstomatidae (2), Myctophidae (8), Phosichthyidae (2), Sternoptychidae (2) and Stomiidae (1) were given. The length-weight relationship showed an isometric growth in 13 species. No differences between right and left otolith sizes were detected by t-test, so a single linear regression was plotted against standard length (SL) for otolith length (OL) and otolith width (OW). Data fitted well to the regression model for both OL and OW to SL, for each species (R2 > 0.8). These relationships offer a helpful tool in feeding studies and also provide support to palaeontologists in their research on fish fossils.En este trabajo se presentan las relaciones talla-peso y las regresiones entre la talla del otolito (longitud y anchura) y la talla del pez (SL) para algunos peces meso y batipelágicos que viven en el Mediterráneo central. Se incluyen imágenes y descripciones morfológicas de los otolitos (sagittae) de 16 especies de las familias Gonostomatidae (1), Microstomatidae (2), Myctophidae (8), Phosichthyidae (2), Sternoptychidae (2) y Stomiidae (1). La relación talla-peso muestra un crecimiento isométrico en 13 especies. No se encontraron diferencias relevantes (t-test) entre la talla del otolito derecho e izquierdo, por lo que se representó una sola regresión lineal entre la longitud estándar y los siguientes parámetros: longitud de otolite (OL) y la anchura (OW). Los datos se ajustaron bien al modelo de regresión lineal para OL y OW, para todas las especies (R2 > 0.8). Las relaciones obtenidas puede ser utilizadas como instrumento en estudios de alimentación y para sustentar estudios de paleontología sobre peces fósiles

Absolute frequency measurement of molecular transitions by a direct link to a comb generated around 3-µm

A 3-microm continuous-wave difference-frequency source is directly referenced to a mid-infrared optical frequency comb synthesizer by measuring their beat-note signal by a fast HgCdTe detector. Absolute frequency metrology of molecular vibration spectra is demonstrated by locking the 3-microm coherent radiation to the nearest comb tooth and tuning the comb mode spacing across the Doppler-broadened absorption profile of a CH(4) ro-vibrational transition

Investigating the resonance spectrum of optical frequency combs in fiber-optic cavities

We report a detailed theoretical and experimental study of fiberoptic cavities under broadband excitation by mode-locked laser combs. We calculate the effects of fiber dispersion on the cavity transmission. For any integer ratio between the comb repetition rate and cavity free spectral range, the theoretical resonant output spectrum exhibits a narrow group of resonant teeth, surrounded by minor, unevenly spaced resonances. Also, the central resonance can be rapidly and precisely tuned over the entire comb span by only acting on its repetition rate. Experimental observations are provided by a single-mode fiber ring and a telecom-wavelength comb laser. The resulting spectral pattern agrees very well with our theoretical prediction, allowing a thorough characterization of the cavity dispersion and opening new perspectives for comb spectroscopy in dielectric resonators. © 2013 Optical Society of America

Non-collinear quasi phase matching and annular profiles in difference frequency generation with focused Gaussian beams.

We present and experimentally test a simple model for difference frequency generation (DFG) in periodically-poled crystals with gaussian pumping beams. Focusing of input beams originates several non-collinear quasi-phase-matching configurations of the interacting wavevectors, which contribute to the idler output field. In this picture, we accurately describe a number of effects, such as the occurrence of annular idler intensity profiles and the asymmetric trend of DFG power vs temperature. Finally, we quantitatively test the model by means of an indirect measurement of the crystal poling period

Localized strain sensing with fiber Bragg-grating ring cavities

We report the theoretical description and the experimental demonstration of an optical resonator formed by inserting a Fiber Bragg Grating (FBG) in a closed fiber loop. The spectral characteristics of such a resonator strongly depend on the reflectivity of the FBG. In the wavelength region where the FBG reflectivity R is negligible, the system behaves like a conventional ring resonator. On the other hand, when R is not vanishing, a split-mode structure can be observed, associated to the degeneracy removal of two counterpropagating resonant modes. The magnitude of the mode splitting can be used to sense small variations of the FBG physical parameters, such as length, temperature or group index. An example of strain sensing with this setup is reported, showing that the mode splitting is sensitive to a mechanical strain applied to the FBG, while it is almost insensitive to a strain applied to any other point of the resonator. This peculiar feature allows to perform cavity-enhanced, local strain measurements with a reduced sensitivity to environmental perturbations, which represents an important improvement in the framework of the fiber-optic sensors. (C)2013 Optical Society of Americ

Investigation of refractive index sensing based on Fano resonance in fiber Bragg grating ring resonators.

In this paper we theoretically investigate a ring resonant cavity obtained by closing on itself a pi-shifted fiber Bragg grating, to be used for refractive index sensing applications. Differently from a conventional pi-shifted fiber Bragg grating, the spectral structure of this cavity is characterized by an asymmetric splitting doublet composed by a right side resonance having an asymmetric Fano profile and a left side resonance having a symmetric Lorentzian profile. The right side resonance shows a narrower and sharper peak than all the other kinds of resonance achievable with both conventional ring resonators and pi-shifted fiber Bragg gratings. A reduction of the resonant linewidth with respect to a conventional pi-shifted Fiber Bragg grating and a fiber ring resonator, having the same physical parameters, is theoretically proved, achieving up to five orders of magnitude improvement with respect to the usual ring resonator. Due to these resonance features, the pi-shifted Bragg grating ring resonator results suitable for RI sensing applications requiring extremely narrow resonances for high resolution measurements. In particular, by assuming a refractive index sensing to detect the presence of sugar in water, the sensor can show a theoretical resolution better than 10(-9) RIU. (C)2015 Optical Society of Americ

Edad y crecimiento del pámpano, Trachinotus ovatus, del Estrecho de Messina (Mediterráneo central)

This is the first paper to provide detailed information on the age and growth of Trachinotus ovatus. The size of the 244 individuals collected in the Strait of Messina ranged from 2.7 to 30.4 cm in fork length (LF) and 0.31 to 508.6 g in body mass (M). The relationship between these parameters (M - LF) was investigated and showed a good fit. Age estimation based on vertebrae and otoliths yielded similar results, suggesting a maximum age of five years. However, the precision and accuracy tests, such as percentage of agreement (PA), mean coefficient of variation (ACV) and average percent error (APE) indicated that the otolith readings (97.83% PA, 0.54% ACV and 0.38% APE) were more reliable for age estimation than vertebrae readings (82.17% PA, 5.33% ACV and 3.77% APE). The multi-model inference approach allowed us to compare different non-linear growth models. The von Bertalanffy model (L∞=29.139, k=0.496 and t0=−0.347) fitted the length-at-age data best. This species has a relatively rapid growth and an estimated longevity of five to seven years. This information could be used for management and first stock assessment studies on T. ovatus in the Mediterranean Sea.Este es el primer artículo que proporciona información detallada sobre la edad y el crecimiento de Trachinotus ovatus. El tamaño de los 244 individuos recolectados en el Estrecho de Messina osciló entre 2.7 y 30.4 cm de longitud a la horquilla (LF) y 0.31 a 508.6 g de masa corporal (M). Se investigó la relación entre estos parámetros (M - LF) y mostró un buen ajuste. La estimación de la edad basada en vértebras y otolitos arrojó resultados similares, lo que sugiere una edad máxima de cinco años. Sin embargo, las pruebas de precisión y exactitud, como el porcentaje de concordancia (PA), el coeficiente medio de variación (ACV) y el porcentaje de error medio (APE), indicaron que las lecturas del otolito (97.83% PA, 0.54% ACV y 0.38 % APE) fueron más confiables para la estimación de la edad que las lecturas de vértebras (82.17% PA, 5.33% ACV y 3.77% APE). El enfoque de inferencia de modelos múltiples nos permitió comparar diferentes modelos de crecimiento no lineal. El modelo de von Bertalanffy (L∞=29.139, k=0.496 and t0=−0.347) se ajusta mejor a los datos de talla por edad. Esta especie tiene un crecimiento relativamente rápido y una longevidad estimada de cinco a siete años. Esta información podría utilizarse para la ordenación y los primeros estudios de evaluación de poblaciones de T. ovatus en el mar Mediterráneo

When opportunistic predators interact with swordfish harpoon fishing activities: shark depredation over catches in the Strait of Messina (central Mediterranean Sea)

We describe the interaction between harpoon fishing activity and sharks, which opportunistically depredated harpoon catches in the Strait of Messina. Shark bite marks were observed on harpooned swordfish during the period 2014–2020, with different damages to the catches. Most of the depredation events have focused on large swordfish, generally weighing more than 60 kg. Data on direct observations were implemented by interviews and questionnaires to fishermen aimed to recover the information on their local fishing and ecological knowledge. Fishermen provided additional data on shark-harpoon fishing interactions also supplying information on by-catch species (i.e., bluefin tuna). Therefore, these results suggest that sharks migrating through the Strait of Messina are occasionally attracted by injured prey, due to their ability to detect chemical cues, fish distress stimuli and body fluids (i.e. blood) in the water. In addition, our investigations showed an increase in shark attacks on harpooned fish over time, likely due to an increase in harpoon swordfish catches. This may be related to the effects of the driftnets' ban enforced by European Regulations in the last decades

Evidence of a predation event on a tagged Mediterranean spearfish (Tetrapturus belone; Pisces, Istiophoridae), inferred from pop-up satellite tagging data

The Strait of Messina is located at the centre of the Mediterranean Sea and is considered a biodiversity hotspot and an obligatory seasonal passage for different pelagic species such as sharks, marine mammals, and billfishes. For the first time, in the Strait of Messina, our research group tagged a Mediterranean spearfish (Tetrapturus belone) using a pop-up satellite archival tag (PSAT). The observation of abiotic parameters (depth, light, and temperature) recorded by the PSAT confirmed that the tagged specimen was predated after about nine hours. The tag was then regurgitated 14 days after the tag deployment date. The analysis of collected data seems to indicate that the predator may be an ectothermic shark, most likely the bluntnose sixgill shark (Hexanchus griseus)

Computed tomography findings and prognosis in older COVID-19 patients

Background: In older and multimorbid patients, chronic conditions may affect the prognostic validity of computed tomography (CT) findings in COVID-19. This study aims at assessing to which extent CT findings have prognostic implications in COVID-19 older patients. Methods: Hospitalized COVID-19 patients aged 60 years or more enrolled in the multicenter, observational and longitudinal GeroCovid study who underwent chest CT were included. Patients were stratified by tertiles of age and pneumonia severity to compare CT findings. Hierarchical clustering based on CT findings was performed to identify CT-related classificatory constructs, if any. The hazard ratio (HR) of mortality was calculated for individual CT findings and for clusters, after adjusting for potential confounders. Results: 380 hospitalized COVID-19 patients, with a mean age of 78 (SD:9) years, underwent chest CT scan. Ground glass opacity (GGO), consolidation, and pleural effusion were the three most common CT findings, with GGO prevalence decreasing from younger to older patients and pleural effusion increasing. More severe the pneumonia more prevalent were GGO, consolidation and pleural effusion. HR of mortality was 1.94 (95%CI 1.24-3.06) for pleural effusion and 13 (95%CI 6.41-27) for cluster with a low prevalence of GGO and a high prevalence of pleural effusion ("LH"), respectively. Out of the three CT based clusters, "LH" was the only independent predictor in the multivariable model. Conclusions: Pleural effusion qualifies as a distinctive prognostic marker in older COVID-19 patients. Research is needed to verify whether pleural effusion reflects COVID-19 severity or a coexisting chronic condition making the patient at special risk of death. Trial registration: ClinicalTrials.gov: NCT04379440