Increased intestinal carbonate precipitate abundance in the sea bream (Sparus aurata L.) in response to ocean acidification

Marine fish contribute to the carbon cycle by producing mineralized intestinal precipitates generated as by-products of their osmoregulation. Here we aimed at characterizing the control of epithelial bicarbonate secretion and intestinal precipitate presence in the gilthead sea bream in response to predicted near future increases of environmental CO2. Our results demonstrate that hypercapnia (950 and 1800 μatm CO2) elicits higher intestine epithelial HCO3- secretion ex vivo and a subsequent parallel increase of intestinal precipitate presence in vivo when compared to present values (440 μatm CO2). Intestinal gene expression analysis in response to environmental hypercapnia revealed the up-regulation of transporters involved in the intestinal bicarbonate secretion cascade such as the basolateral sodium bicarbonate co-transporter slc4a4, and the apical anion transporters slc26a3 and slc26a6 of sea bream. In addition, other genes involved in intestinal ion uptake linked to water absorption such as the apical nkcc2 and aquaporin 1b expression, indicating that hypercapnia influences different levels of intestinal physiology. Taken together the current results are consistent with an intestinal physiological response leading to higher bicarbonate secretion in the intestine of the sea bream paralleled by increased luminal carbonate precipitate abundance and the main related transporters in response to ocean acidification.Agência financiadora Fundacao para a Ciencia e a Tecnologia (FCT) SFRH/BD/113363/2015 PTDC/MAR-BIO/3034/2014 Fundacao para a Ciencia e a Tecnologia (FCT) UID/Multi/04326/2019 Ministry of Science and Higher Education, Polandinfo:eu-repo/semantics/publishedVersio

Tackling 3D ToF Artifacts Through Learning and the FLAT Dataset

Scene motion, multiple reflections, and sensor noise introduce artifacts in the depth reconstruction performed by time-of-flight cameras. We propose a two-stage, deep-learning approach to address all of these sources of artifacts simultaneously. We also introduce FLAT, a synthetic dataset of 2000 ToF measurements that capture all of these nonidealities, and allows to simulate different camera hardware. Using the Kinect 2 camera as a baseline, we show improved reconstruction errors over state-of-the-art methods, on both simulated and real data.Comment: ECCV 201

Generation of all-fiber ultrafast pulses at 2 µm by soliton self-frequency shift in highly nonlinear silica fiber

An efficient and straightforward method to obtain all-fiber pulsed sources at 2 μm is presented and experimentally demonstrated. It is based on the soliton self-frequency shift effect in a highly nonlinear fiber. The output power of a supercontinuum source is previously increased by an optimized homemade thulium-doped fiber amplifier. By coupling the amplified output power in a highly nonlinear fiber, the spectrum is shifted toward 130 nm and the spectral peak is located at 2014 nm. The power conversion factor reaches values as high as 0.93, without employing additional amplifiers. The mean spectral power of the 2 μm source reaches −4.6 dBm nm−1 (0.35 mW nm−1), its output power is 38 mW and the peak power of each pulse is higher than 27 kW

Laboratory experiment with helium-neon laser: Gain and oscillation spectral widths

The relationship between gain and oscillation spectral profiles is studied and analysed from an educational perspective. A theoretical explanation based on simple models is presented. Expressions of spectral profiles and widths are deduced by means of this theory. Spectral profiles and widths are measured with a laboratory experiment based on low-cost lasers. Theoretical and experimental values are in agreement. La relación entre los perfiles de ganancia y de oscilación de un láser es estudiada y analizada desde una perspectiva docente. Se presenta una explicación teórica basada en modelos sencillos. A partir de esta teoría, se formulan dichos perfiles espectrales y se relacionan sus anchuras. Los perfiles y las anchuras son medidos en una práctica de laboratorio realizada con láseres de bajo costo. La comparación entre teoría y experimento resulta satisfactoria

Reflexión total: Luz al otro lado

The evanescent wave associated with the total internal reflection is clearly demonstrated by taking a laboratory photograph. Total internal reflection takes place at the interface of glass (equilateral prism) and water. Fluorescence generated by the evanescent wave can be observed due to a dye (rhodamine B) dissolved in water. Se presenta una fotografía de laboratorio que ilustra la existencia de la onda evanescente asociada al fenómeno de reflexión total. La reflexión total se produce en la superficie de separación entre vidrio (prisma equilátero) y agua. En el agua se ha disuelto un colorante (rodamina B) que emite fluorescencia debido a la energía de la onda evanescente presente en el segundo medio

Near-infrared supercontinuum source by intracavity silica-based highly-nonlinear fiber

Near-infrared supercontinuum generation by using silica-based highly-nonlinear fiber placed inside of the ring-cavity of an erbium-doped fiber laser pulsed by mode-locking is experimentally demonstrated. Only one erbium-doped fiber amplifier is employed to generate supercontinuum with a spectral width as long as 830 nm (from 1205 to 2035 nm) and a spectral power higher than -30 dBm/nm. To generate supercontinuum, it is not necessary a second amplifier to raise the power of the laser pulses coupled into the nonlinear fiber. Moreover, all the devices employed are commercial and available at any photonics laboratory. To the best of our knowledge, this is the first demonstration of this kind of device by pumping the nonlinear fiber in the third window of communications

Fluctuaciones de potencia debidas al a coplamiento de modos longitudinales en láseres microchip de Nd:YVO 4 bombeados por diodo y doblados en frecuencia

Se han analizado las fluctuaciones periódicas de potencia que aparecen en un láser microchip de Nd:YVO 4 doblado en frecuencia, demostrando que se deben a la oscilación simultánea de varios modos longitudinales. Se ha mostrado que , además del doblado de frecuencia, también se produce el efecto de suma de frecuencias , observando hasta 9 máximos espectrales en 532 nm cuando oscilan simultáneamente 5 modos longitudinales en 1064 nm. Power fluctuations in a diode-pumped intracavity-doubled Nd:YVO4 microchip laser have been analysed. Their relationship with the coupling of several longitudinal modes has been experimentally demonstrated. Although second-harmonic power is generated by the nonlinear crystal, the effect of sum-frequency generation is also involved. This effect produced 9 spectral peaks at 532 nm when 5 longitudinal modes at 1064 nm were oscillating simultaneously

Sensitivity enhancement by increasing the nonlinear crystal length in second-order autocorrelators for ultrashort laser pulses measurement

A theoretical model for interferometric autocorrelation with long nonlinear crystal (input depleted) has been developed and applied to the measurement of the duration of ultrashort pulses. The phase-matching condition is assumed throughout pulse spectrum. The interferometric autocorrelation trace of a mode-locked fibre laser (20 nJ energy, 100 kW peak power, centred at 1595 nm) has been measured by employing a fibre interferometer to avoid misalignment effects and a BBO nonlinear crystal as long as 2 mm, in order to generate higher second-harmonic power. BBO crystal was used because it can keep the phase-matching condition throughout a wide spectrum around 1600 nm. By fitting the experimental measurements and computing according to the theoretical model exposed, it has been demonstrated that the autocorrelator sensitivity is clearly enhanced by increasing the nonlinear crystal length. A temporal duration of 0.18 ps has been obtained by fitting theoretical and experimental values

Reference normal values and design of a vision screening for 4 to 5 years old preschoolers

A vision screening program for preschool children of 4-5 years old was designed and analyzed. Information of the prevalence of ocular conditions among preschool children was obtained. The vision health of a group of 127 children was evaluated by a comprehensive examination in their own school. If a child failed one or more screening tests, he was referred to the ophthalmologist. Of the children screened in this study, 61% passed distance visual acuity and retinoscopy tests, 17% were referred to the ophthalmologist and 22% will be annually monitoring. Values of monocular/binocular acuity worse than 0.5/0.6 are too poor for 4 years old children, whereas these limits increase up to 0.6/0.8 for 5 years old children. In conclusion, the prevalence of undetected vision problems in preschool children has been clearly demonstrated. Vision screening programs in schools are highly recommended. Nevertheless, coordination among professionals conducting screening, school personnel and parents are needed to reach high levels of success. The results of this study validate an easy and fast battery of tests. The vision screening has been highly reliable because reference normal values have been defined by analyzing statistically the results of these tests. Se diseñó y analizó un screening visual en preescolares de 4-5 años de edad. Se obtuvo información de la prevalencia de las condiciones oculares entre estos preescolares. Se evaluó la salud visual de un grupo de 127 niños con un examen completo en su propia escuela. Si el niño fallaba uno o más test era referido al oftalmólogo. De los niños revisados en el estudio, el 61% superó los test de agudeza visual y retinoscopía, al 17% se le refirió al oftalmólogo y el 22% será controlado anualmente. Valores de agudeza monocular/binocular peores de 0.5/0.6 son demasiado bajos para niños de 4 años de edad, mientras que estos límites se incrementan a 0.6/0.8 para niños de 5 años. En conclusión, la prevalencia de problemas de visión sin detectar en niños preescolares ha sido claramente demostrada. Sin embargo, es necesaria la coordinación entre profesionales que realicen el screening, personal del colegio y padres para alcanzar niveles altos de éxito. Los resultados de este estudio validan una batería rápida de test. El screening visual ha sido altamente fiable porque los valores normales de referencia han sido definidos analizando estadísticamente los resultados de estos tests

Coherent artifact and time-dependent polarization in amplified ultrafast erbium-doped fibre lasers

Mode-locked erbium-doped fibre lasers are ultrashort pulsed sources widely studied due to their versatility and multiple applications in the near infrared range. Here we present the experimental study of the emission of a passive mode-locked erbium-doped fibre laser with an amplification stage outside the cavity by means of Frequency Resolved Optical Gating (FROG) and spectral interferometry. Due to shot-to-shot instabilities, the FROG traces can be understood as the combination of two different traces, corresponding to the coherent artifact and the average pulse characteristics. We have modified a Principal Components Generalized Projections Algorithm, in order to make it able to retrieve efficiently both the coherent artifact and the average pulse. In addition, we study the temporal dependence of the polarization, showing that the pulses present time-dependent polarization with a stable spectral relative phase between the horizontal and vertical projections. Up to our knowledge, this is the first experimental study that shows the FROG measurements of unstable pulse trains associated with the coherent artifact and analyses the time-dependent polarization in ultrafast fibre lasers