Beamforming enhances the performance of array-based photoacoustic microscopy (PAM) systems for large-area scan. In this study, we quantify the imaging performance of a large field-of-view ...optical-resolution photoacoustic-microscopy system using an phased-array detector. The system combines a low-cost pulsed-laser diode with a 128-element linear ultrasound probe. Signal-to-noise ratio (SNR) and generalized contrast-to-noise ratio (gCNR) are quantified using the phased-array detector and applying three beamforming strategies: a no-beamforming method equivalent to a single-element flat transducer, a fixed focus beamforming method that mimics a single-element focused transducer, and a dynamic focus beamforming using a delay-and-sum (DAS) algorithm. The imaging capabilities of the system are demonstrated generating high-resolution images of tissue-mimicking phantoms containing sub-millimetre ink tubes and an ex vivo rabbit’s ear. The results show that dynamic focus DAS beamforming increases and homogenizes SNR along 1-cm2 images, reaching values up to 15 dB compared to an unfocused detector and up to 30 dB compared to out-of-focus regions of the fixed focus configuration. Moreover, the obtained values of gCNR using the DAS beamformer indicate an excellent target visibility, both on phantoms and ex vivo. This strategy makes it possible to scan larger surfaces compared to standard configurations using single-element detectors, paving the way for advanced array-based PAM systems.
•We designed a photoacoustic microscopy system combining a PLD with a phased array.•Beamforming increases and homogenizes SNR along large-area PAM images.•Beamforming in PAM enables physical coupling between the sample and ultrasound probe.
The objective of the work was to evaluate the influence of gold nanoparticles, obtained by laser ablation, on the photocatalytic action of titanium dioxide in the improvement of the physical-chemical ...parameters of domestic greywater, with visualization by means of a PLC. The YAG laser equipment was used for the production of spherical gold nanoparticles, whereas the Raman spectroscope allowed characterizing the different particles contained in aqueous solutions. The solar photoreactor programmable and viewable from PLC with connection to sensors allowed determining the variations of the pH, EC, DO and FCL parameters. The work consisted of a control group (greywater + titanium dioxide) and an experimental group (greywater + titanium dioxide + gold nanoparticles). The titanium dioxide doses for both groups were 0.5 mg/L and the gold nanoparticles were 0.20 ml per liter of greywater only for the control group. The experiments were carried out on sunny days with the exposure periods of 30 and 60 minutes around solar noon with an average UV index of 13.35. Once the experiments were carried out, it was determined that the pH improved by 5.30%, EC by 3.03%, DO by 29.3% and FCL by 43.71%, so that the gold nanoparticles dissolved in the aqueous solution of titanium dioxide with greywater positively influenced the improvement of the photocatalytic action of titanium dioxide in the physical-chemical parameters of greywater.
The work consisted in analyzing the influence of an electronic positioning mechanism of an Au metal plate in the XY axes; to optimize the production of Au metal nanoparticles by laser ablation in ...sterile water samples as well as to obtain morphology and size required for environmental nanosensors. The positioning mechanism is constituted by two M35SP stepper motors of 5 V DC with a rotation angle of 7.5° per step; the one that generates the displacement for each axis of XY coordinates, controlled by an algorithm implemented in Arduino Nano ATmega328, being the driver of the stepper motors the H-bridge of the L298N module, with which it was possible to set the speed to 2 mm/s, which enabled to make the wear of the metal plate uniform in the process of generation of gold nanoparticles (AuNPs). With the pulsed laser generator with ablation frequency of 10 Hz and wavelengths of 532 nm and 1064 nm, the Au metal plate was irradiated for 10 min, 20 min and 30 min. AuNPs were generated in colloidal state both for the process with fixed position of the metal plate and for the process using the electronic mechanism of XY positioning; they were characterized by UV-Vis spectroscopy with range from 300 nm to 850 nm. It was found that the production of AuNPs with the Au plates mobilized by the mechanism under study, generates colloids of spherical AuNPs of smaller diameter, close to 10 nm, with an average reduction of 19% in relation to that generated with the fixed position plate; likewise, the concentration of the AuNPs increased by 20.40%; therefore, the influence of the XY positioning electronic mechanism was positive in the production of AuNPs with morphology and sizes suitable for use in environmental nanosensors.
The research sought to evaluate the normalized difference vegetation index (NDVI) of the study area located in the province of Tayacaja, which includes the districts of Acraquia, Ahuaycha, Pampas and ...Daniel Hernández, which is part of the central Andes of Peru. The data were collected in low water seasons with a longitudinal cut of 30 years with one sample per year, starting in 1993 until 2022; these samples corresponded to the month of August of each year. The images were extracted from maps from Landsat satellite databases, which were filtered for low cloud cover to avoid interference with the images. Maps from 1993 to 2012 were obtained from Landsat 5 satellite, while from 2013 to 2022 data were obtained from Landsat 8 satellite. The normalized difference vegetation index was determined using Quantum GIS based on the red and near infrared maps; being the minimum NDVI value obtained -0.18, which corresponds to the aquatic body of the Upamayu River that crosses from west to east the study area; while the highest NDVI obtained was 0.79 indicating a greater vegetation cover constituted by mainly eucalyptus plants. The mean NDVI of the 30 years is close to 0.21; this is an indicator that the vegetation is scarce and that it is decreasing mainly due to population growth.
The ANTARES deep-sea neutrino telescope comprises a three-dimensional array of photomultipliers to detect the Cherenkov light induced by upgoing relativistic charged particles originating from ...neutrino interactions in the vicinity of the detector. The large scattering length of light in the deep sea facilitates an angular resolution of a few tenths of a degree for neutrino energies exceeding 10
TeV. In order to achieve this optimal performance, the time calibration procedures should ensure a relative time calibration between the photomultipliers at the level of ∼1
ns. The methods developed to attain this level of precision are described.
► An experimental method is used to evaluate the hydration state and the speed of the ultrasonic surface waves in the peel of Navelina and Ortanique oranges. ► Ultrasonic nondestructive method is ...used to evaluate the elastic parameters of the sweet orange peel. ► A linear elastic solid model was numerically solved using a simulation scheme based on a 3D-Spherical FDTD method (Finite-Difference Time-Domain). ► The hydration state of the fruit is linearly related to the elastic parameters of the orange peel.
The elastic parameters of fruit and vegetables are normally monitored in quality control processes as there is a good correlation to the degrees of firmness, turgidity and humidity. These parameters have been traditionally measured by means of penetration tests, which are destructive. This has resulted in the increased attention recently given to ultrasonic techniques applied to the quality evaluation of horticultural commodities. Nevertheless, since most of the fruit and vegetables display a viscoelastic behavior, the penetration test should be considered to be quasi-static, especially when compared with the speeds associated with the ultrasonic tests. Both methods should provide different values for the elastic parameters. The aim of this work is to study this discrepancy in the values of the elastic parameters and interpret the elastodynamic behavior of the vegetable tissue under an ultrasound test. Thus, the paper presents an ultrasonic nondestructive method to evaluate the elastic parameters of the sweet orange peel at 40kHz. The complete dehydration process of two sets of oranges (Navelina and Ortanique) was monitored for 2months. A linear elastic solid model with viscous losses was numerically solved using a simulation scheme based on a 3D-Spherical FDTD method (Finite-Difference Time-Domain) in order to interpret the results, which proved that the elastic parameters obtained by penetration and ultrasonic tests differ. The method provides an empirical relation between the hydration state and the elastic parameters of the orange peel. Therefore, the proposed ultrasonic test reported in this work is capable of determining the hydration state of the orange simply by measuring the propagation speed of the Rayleigh waves on the orange peel, and hence, can be used as a fruit quality index during postharvest processes.
This research provides a thorough study of the mechanical response of PCL scaffolds and determines their deformation micromechanisms at different scales by a combination of experimental techniques ...(mechanical tests, scanning electron microscopy, wide angle X-ray diffraction and small-angle X-ray scattering). Scaffolds with different fibre orientation distribution functions were manufactured and subjected to tensile loading. The macromechanical properties were dictated the by the fibre deformation and interaction in terms of fibre straightening, rotation and stretching. The stiffness and the yield strength were directly proportional to the percentage of fibres oriented with the loading direction. The gradual deformation induced a progressive fibre rotation, uncurling and stretching, showing different impact at molecular level for each configuration. The fibres aligned with the loading direction presented a homogeneous plasticity with an inherent loss of the crystal phase, meanwhile the misaligned fibres exhibited a negligible loss of crystallinity due to a predominance of the fibre rotation. The fibre plasticity triggered the macromechanical yielding of the scaffold and for high levels of plastic deformation the fibres developed macromolecular fibrils and microvoids. These findings provide the fundamental observations to develop engineering tissues with highly tunable and tailored mechanical properties for site specific in vivo applications.
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•In-situ SAXS/WAXD characterisation of PCL scaffolds is accomplished.•Evolution of deformation mechanisms at different scales is ascertained.•Contribution of fibre plastic deformation to the ductility of the scaffold is determined.•Evolution of fibre orientation distribution function is presented.
Underwater acoustic detection of ultra-high-energy neutrinos was proposed already in 1950s: when a neutrino interacts with a nucleus in water, the resulting particle cascade produces a pressure pulse ...that has a bipolar temporal structure and propagates within a flat disk-like volume. A telescope that consists of thousands of acoustic sensors deployed in the deep sea can monitor hundreds of cubic kilometres of water looking for these signals and discriminating them from acoustic noise. To study the feasibility of the technique it is critical to have a calibrator able to mimic the neutrino “signature” that can be operated from a vessel. Due to the axial-symmetry of the signal, their very directive short bipolar shape and the constraints of operating at sea, the development of such a calibrator is very challenging. Once the possibility of using the acoustic parametric technique for this aim was validated with the first compact array calibrator prototype, in this paper we describe the new design for such a calibrator composed of an array of piezo ceramic tube transducers emitting in axial direction.
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