Calibration of multibeam echo sounders: a comparison between two methodologies

Multibeam echo sounders (MBES) are widely used in applications like seafloor imaging, fisheries, and habitat mapping. Calibration of acoustic backscatter is an important aspect of understanding and validating the performance of a MBES. Combined transmit/receive beampattern calibrations were performed on a 200 kHz Reson Seabat 7125 MBES in the acoustic tank of the University of New Hampshire utilizing two different methodologies. The first methodology employs fixed standard target spheres and a high accuracy/high resolution rotation mechanism. This method, similar to that proposed by Foote et al [ Protocols forcalibrating multibeam sonar , J. Acoust. Soc. Am. 117(4), 2005], is designed for a calibrationtank and provides accurate results but requires a large amount of operation time and cannot be performed in situ. The second methodology has been designed for field calibration of MBES. It employs a standard target sphere and a 200 kHz Simrad EK60 split-beam sonar system to provide athwartship and alongship angular information of the target sphere position. This method offers the possibility of field calibration for vessel mounted systems and a significantly reduced operation time, but has a potential reduction in accuracy. In this paper, results from these two methods applied to the same MBES are compared

A Method for Field Calibration of a Multibeam Echo Sounder

The use of multibeam echo sounders (MBES) has grown more frequent in applications like seafloor imaging, fisheries, and habitat mapping. Calibration of these instruments is important for understanding and validating the performance of MBES. For echo sounders in general, different calibration methodologies have been developed in controlled environments such as a fresh water tank and in the actual field of operation. While calibration in an indoor tank facility can bring excellent results in terms of accuracy, the amount of time required for a complete calibration can become prohibitively large. A field calibration can reveal the actual radiation beam pattern for shipmounted sonar systems, accounting for acoustic interferences which may be caused by objects around the installed transducers. The standard target method is a common practice for field calibration of split-beam echo sounders. However, when applied to a Mills Cross MBES, this method does not provide means to determine the alongship angle of the target, since the receiver transducer is a line array. A method to determine the combined transmit/receive radiation beam pattern for a ship-mounted multibeam system was developed and tested for a Reson Seabat 7125 MBES inside the fresh water calibration tank of the University of New Hampshire. This calibration methodology employs a tungsten carbide sphere of 38.1 mm diameter as target and a Simrad EK60 split-beam sonar system to provide athwartship and alongship angular information of the target sphere position. The multibeam sonar system was configured for 256 beams equi-angle mode at an operating frequency of 200 kHz; the split-beam system was set to work passively at the same frequency. A combined transmit/receive beam pattern was computed for an athwartship angular range between –6o and +6o and an alongship angular range between –1o and +3o . The limited angular range of the measurements is due to the –3 dB beamwidth of 7.1o in the athwartship and alongship directions of the split-beam sonar system coupled with the alongship offset of 1.6o between the maximum response axes (MRA) of the two sonar systems. Possible acoustic interferences caused by the monofilament line used to suspend the target sphere in the water column were found in the measurements for alongship angle values less than –1o . Beam pattern measurements for the combined transmit/receive beam pattern at a distance of 8 m show a –3 dB beamwidth of 1.1o in the athwartship direction and a –3 dB beamwidth of 2.0o in the alongship direction for the most inner beams. The dynamic range for the measurements was approximately of –40 dB

High Resolution Calibration of a Multibeam Echo Sounder

Calibration can greatly increase the utility of collecting seafloor backscattering strength with multibeam echo sounders (MBES). A calibration procedure to determine high resolution, three dimensional transmit and receive beam patterns of a Reson SeaBat 7125 MBES was performed using the fresh water calibration tank at the University of New Hampshire. The measurements employed an omni-directional Reson TC4034 projector/hydrophone as a reference transducer at an acoustic distance of 13 m. The multibeam sonar system was configured for 256 beams equi-angle mode and operating frequency of 396 kHz. The transmit beam pattern was computed for across-track angular range between +/–90o in 0.1o increments and along-track angular range between +/–2.55o in 0.09o increments. Receive directional characteristics were measured for the across-track range of +/–120o in 0.1o increments with along-track angular range of +/–1.23o in 0.18o increments. With these measurements, a three-dimensional plot of the transmit beam pattern was computed for the entire range of angles, although for the receive beam pattern it was only determined for the 0o along-track angle. The reduced angular coverage of the receive beam pattern was due to discrepancies in the off-axis results that are thought to be related to receiver saturation. Measurements for the transmit beam pattern show a –3 dB beamwidth of 0.99o for across-track angle of 0o with side lobes below –17 dB. The results show an unexplained curvature in the transmit beam pattern that would have gone un-noticed during a two dimensional beam pattern measurement. An interference effect causing ripples and attenuation of the transmit beam pattern was also observed. This effect is thought to be caused by a second 200 kHz projector mounted parallel to the 396 kHz projector. This interference occurs at an across-track angular region between +30o and +75o with gradual decrease in amplitude of about 3 dB. The receive beam pattern measurements show a –3 dB beamwidth of approximately 0.62o for the most inner beams (beams 128 and 129) and of approximately 1.40o for the most outer beams (beams 1 and 256) at along-track angular position of 0o with side-lobes below –26 dB for the most inner beams and below –17 dB for the most outer beams

Modeling Shallow Water Flows on General Terrains

A formulation of the shallow water equations adapted to general complex terrains is proposed. Its derivation starts from the observation that the typical approach of depth integrating the Navier-Stokes equations along the direction of gravity forces is not exact in the general case of a tilted curved bottom. We claim that an integration path that better adapts to the shallow water hypotheses follows the "cross-flow" surface, i.e., a surface that is normal to the velocity field at any point of the domain. Because of the implicitness of this definition, we approximate this "cross-flow" path by performing depth integration along a local direction normal to the bottom surface, and propose a rigorous derivation of this approximation and its numerical solution as an essential step for the future development of the full "cross-flow" integration procedure. We start by defining a local coordinate system, anchored on the bottom surface to derive a covariant form of the Navier-Stokes equations. Depth integration along the local normals yields a covariant version of the shallow water equations, which is characterized by flux functions and source terms that vary in space because of the surface metric coefficients and related derivatives. The proposed model is discretized with a first order FORCE-type Godunov Finite Volume scheme that allows implementation of spatially variable fluxes. We investigate the validity of our SW model and the effects of the bottom geometry by means of three synthetic test cases that exhibit non negligible slopes and surface curvatures. The results show the importance of taking into consideration bottom geometry even for relatively mild and slowly varying curvatures

Coarse-grained debris flow dynamics on erodible beds.

A systematic set of flume experiments is used to investigate the features of velocity profiles within the body of coarse-grained debris flows and the dependence of the transport sediment concentration on the relevant parameters (runoff discharge, bed slope, grain size and form). The flows are generated in a 10 m long laboratory flume, initially filled with a layer consisting of loose debris. After saturation, a prescribed water discharge is suddenly supplied over the granular the runoff triggers a debris flow wave that reaches nearly steady conditions. Three types of material have been used in the tests: gravel with mean grain size of 3 and 5 mm, and 3 mm glass spheres. Measured parameters included: triggering water discharge, volumetric sediment discharges, sediment concentration, flow depth and velocity profiles. The dynamic similarity with full-sized debris flows is discussed on the basis of the relevant dimensionless parameters. Concentration data highlight the dependence on the slope angle and the importance of the quasi-static friction angle. The effects of flow rheology on the shape of velocity profiles are analyzed with attention to the role of different stress generating mechanisms. A remarkable collapse of the dimensionless profiles is obtained by scaling the debris flow velocity with the runoff velocity, and a power law characterization is proposed following a heuristic approach. The shape of the profiles suggests a smooth transition between the different rheological regimes (collisional and frictional) that establish in the upper and lower regions of the flow, and is compatible with the presence of multiple length scales

Oxidative responsiveness to multiple stressors in the key Antarctic species, Adamussium colbecki: interactions between temperature, acidification and cadmium exposure.

Abstract: High-latitude marine ecosystems are ranked to be among the most sensitive regions to climate change since highly stenothermal and specially adapted organisms might be seriously affected by global warming and ocean acidification. The present investigation was aimed to provide new insights on the sensitivity to such environmental stressors in the key Antarctic species, Adamussium colbecki, focussing also on their synergistic effects with cadmium exposure, naturally abundant in this area for upwelling phenomena. Scallops were exposed for 2 weeks to various combinations of Cd (0 and 40 μgL-1), pH (8.05 and 7.60) and temperature (-1 and +1°C). Beside Cd bioaccumulation, a wide panel of early warning biomarkers were analysed in digestive glands and gills including levels of metallothioneins, individual antioxidants and total oxyradical scavenging capacity, onset of oxidative cell damage like lipid peroxidation, lysosomal stability, DNA integrity and peroxisomal proliferation. Results indicated reciprocal interactions between multiple stressors and their elaboration by a quantitative hazard model based on the relevance and magnitude of effects, highlighted a different sensitivity of analysed tissues. Due to cellular adaptations to high basal Cd content, digestive gland appeared more tolerant toward other prooxidant stressors, but sensitive to variations of the metal. On the other hand, gills were more affected by various combinations of stressors occurring at higher temperatur

Antioxidant and Antimicrobial Activity of Algal and Cyanobacterial Extracts: An In Vitro Study

Algae and cyanobacteria, other than their nutritional value, possess different beneficial properties, including antioxidant and antimicrobial ones. Therefore, they can be considered functional ingredients in animal feed and natural substitutes for antibiotics. The aim of this study was to evaluate the antioxidant and antimicrobial capacity against porcine O138 E. coli of Ascophyllum nodosum, Chlorella vulgaris, Lithotamnium calcareum, Schizochytrium spp. as algal species and Arthrospira platensis as cyanobacteria. The antioxidant capacity was determined by ABTS Radical Cation Decolorization Assay testing at three different concentrations (100%; 75%; 50%). The growth inhibition effect of the extracts at concentrations of 25%, 12.5%, 6%, 3% and 1.5% against porcine O138 E. coli was genetically characterized by PCR to detect the presence of major virulence factors; this was evaluated by following the microdilution bacterial growth method. The ABTS assay disclosed that Ascophyllum nodosum was the compound with the major antioxidant properties (57.75 ± 1.44 percentage of inhibition; p < 0.0001). All the extracts tested showed growth inhibition activity at a concentration of 25%. Among all extracts, A. nodosum was the most effective, showing a significant growth inhibition of E. coli; in particular, the log(10) cells/mL of E. coli used as a control resulted in a significantly higher concentration of 25% and 12.5% after 4 h (8.45 ± 0.036 and 7.22 ± 0.025 log(10) cells/mL, respectively; p < 0.005). This also suggests a dose-dependent relationship between the inhibitory activity and the concentration. Also, a synergistic effect was observed on antioxidant activity for the combination of Ascophyllum nodosum and Lithotamnium calcareum (p < 0.0001). Moreover, to determine if this combination could affect the viability of the IPEC-J2 cells under the normal or stress condition, the viability and membrane integrity were tested, disclosing that the combination mitigated the oxidative stress experimentally induced by increasing the cell viability. In conclusion, the results obtained highlight that the bioactive compounds of algal species are able to exert antioxidant capacity and modulate O138 E. coli growth. Also, the combination of Ascophyllum nodosum and Lithotamnium calcareum species can enhance their bioactivity, making them a promising functional feed additive and a suitable alternative to antibiotics

Occupational Therapists and COVID-19 Pandemic: An Observational Survey in Europe

Background: The COVID-19 pandemic has resulted in a health care emergency in Europe since the first wave in 2020. Several challenges have arisen for occupational therapists, as well as all the health care professionals. The aim of this study was to determine what occupational therapists have changed to adapt their therapeutic processes for this catastrophic situation. Method: An online survey was developed and sent in conjunction with the Council of Occupational Therapy for European Countries (COTEC) to European national associations of occupational therapists. Results: The study was based on a sample of 65 occupational therapists who worked with people with COVID-19. More than half of the occupational therapists (54.8%) had changed departments. The main needs patients expressed (n = 136) during hospitalization were to have social contacts (30.9%), and the main clinical complaints (n = 144) were motor impairment and fatigue (35.4%) and depression (25.7%). The most frequently reported goal (n = 141) was recovery of physical performance and fatigue management (32.6%). Among the emotions mentioned by occupational therapists, negative emotions (76%) were the most common. Conclusion: European occupational therapists demonstrated flexibility and resilience to deal with clinical and organizational challenges during the COVID-19 emergency

Angiogenic potential of human dental pulp stromal (stem) cells.

Dental pulp is a heterogeneous microenviroment where unipotent progenitor and pluripotent mesenchymal stem cells cohabit. In this study we investigated whether human Dental Pulp Stromal (Stem) Cells (DP-SCs) committed to the angiogenic fate. DP-SCs showed the specific mesenchymal immunophenotypical profile positive for CD29, CD44, CD73, CD105, CD166 and negative for CD14, CD34, CD45, in accordance with that reported for bone marrow-derived SCs. The Oct-4 expression in DP-SCs, evaluated through RT-PCR analysis, increased in relation with the number of the passages in cell culture and decreased after angiogenic induction. In agreement with their multipotency, DP-SCs differentiated toward osteogenic and adipogenic commitments. In angiogenic experiments, differentiation of DP-SCs, through Vascular Endothelial Growth Factor (VEGF) induction, was evaluated by in vitro matrigel assay and by cytometric analysis. Accordingly, endothelial-specific markers like Flt-1 and KDR were basally expressed and they increased after exposure to VEGF together with the occurrence of ICAM-1 and von Willebrand Factor positive cells. In addition, VEGF-induced DP-SCs maintained endothelial cell-like features when cultured in a 3-D fibrin mesh, displaying focal organization into capillary-like structures. The DP-SC angiogenic potential may prove a remarkable tool for novel approaches to developing tissue-engineered vascular grafts which are useful when vascularization of ischemic tissues is required

Term amniotic membrane is a high throughput source for multipotent mesenchymal stem cells with the ability to differentiate into endothelial cells in vitro

BACKGROUND: Term Amniotic membrane (AM) is a very attractive source of Mesenchymal Stem Cells (MSCs) due to the fact that this fetal tissue is usually discarded without ethical conflicts, leading to high efficiency in MSC recovery with no intrusive procedures. Here we confirmed that term AM, as previously reported in the literature, is an abundant source of hMSCs; in particular we further investigated the AM differentiation potential by assessing whether these cells may also be committed to the angiogenic fate. In agreement with the recommendation of the International Society for Cellular Therapy, the mesenchymal cells herein investigated were named Amniotic Membrane-human Mesenchymal Stromal Cells (AM-hMSC). RESULTS: The recovery of hMSCs and their in vitro expansion potential were greater in amniotic membrane than in bone marrow stroma. At flow cytometry analysis AM-hMSCs showed an immunophenotypical profile, i.e., positive for CD105, CD73, CD29, CD44, CD166 and negative for CD14, CD34, CD45, consistent with that reported for bone marrow-derived MSCs. In addition, amniotic membrane-isolated cells underwent in vitro osteogenic (von Kossa stain), adipogenic (Oil Red-O stain), chondrogenic (collagen type II immunohistochemichal detection) and myogenic (RT-PCR MyoD and Myogenin expression as well as desmin immunohistochemical detection) differentiation. In angiogenic experiments, a spontaneous differentiation into endothelial cells was detected by in vitro matrigel assay and this behaviour has been enhanced through Vascular Endothelial Growth Factor (VEGF) induction. According to these findings, VEGF receptor 1 and 2 (FLT-1 and KDR) were basally expressed in AM-hMSCs and the expression of endothelial-specific markers like FLT-1 KDR, ICAM-1 increased after exposure to VEGF together with the occurrence of CD34 and von Willebrand Factor positive cells. CONCLUSION: The current study suggests that AM-hMSCs may emerge as a remarkable tool for the cell therapy of multiple diseased tissues. AM-hMSCs may potentially assist both bone and cartilage repair, nevertheless, due to their angiogenic potential, they may also pave the way for novel approaches in the development of tissue-engineered vascular grafts which are useful when vascularization of ischemic tissues is required