María Bermúdez

Optical Fish Trajectory Measurement in Fishways through Computer Vision and Artificial Neural Networks

Vertical slot fishways are hydraulic structures that allow the upstream migration of fish through obstructions in rivers. The appropriate design of a vertical slot fishway depends on the interplay between hydraulic and biological variables because the hydrodynamic properties of the fishway must match the requirements of the fish species for which it is intended. One of the primary difficulties associated with studies of real fish behavior in fishway models is that the existing mechanisms to measure the behavior of the fish in these assays, such as direct observation or placement of sensors on the specimens, are impractical or unduly affect the animal behavior. This paper proposes a new procedure for measuring the behavior of the fish. The proposed technique uses artificial neural networks and computer vision techniques to analyze images obtained from the assays by means of a camera system designed for fishway integration. It is expected that this technique will provide detailed information about the fish behavior, and it will help to improve fish passage devices, which is currently a subject of interest in the area of civil engineering. A series of assays has been performed to validate this new approach in a full-scale fishway model with living fish. We have obtained very promising results that allow accurate reconstruction of the movements of the fish within the fishway.

Uncertainty and sensitivity analysis of a depth-averaged water quality model for evaluation of Escherichia Coli concentration in shallow estuaries

Sensitivity and uncertainty analysis investigate the robustness of numerical model predictions and provide information about the factors that contribute most to the variability of model output, identifying the most important parameters for model calibration. This paper presents a sensitivity and uncertainty analysis of a 2D depth-averaged water quality model applied to a shallow estuary. The model solves the mass transport equation for Escherichia Coli, including the effects of water temperature, salinity, solar radiation, turbulent diffusion and short wave dispersion. The sensitivity of the concentration of E. Coli in the estuary to input parameters and the different sources of uncertainty are studied using Global Sensitivity Analysis based on Monte Carlo simulation methods and sensitivity measures based on linear and non-linear regression analysis, in order to aid modellers in the calibration process and in the interpretation of model output. The extinction coefficient of light in water and the depth of the vertical layer over which the E. coli spread were found to be the most relevant parameters of the model. In the shallowest regions of the estuary errors in the bathymetry are also an important source of uncertainty on model output. Globally, the combination of these three parameters was found to be very effective for calibration purposes in the whole estuary.

Activity of neurons in the caudate and putamen during a visuomotor task.

Evidence supporting a role of the caudate and putamen nuclei in associative learning is present. We recorded the activity of 21 caudate and 26 putamen cells in one macaque monkey while performing a visuomotor task, which involved a visual stimulus and the execution of a motor response. Ninety-one percent of caudate cells and 65% of putamen cells showed changes in activity while the monkey was performing the task. Approximately half of the caudate cells and one third of the putamen cells showed changes in activity without a motor response. Our results show that caudate and putamen cells are activated regardless of the presence or absence of a motor action. These findings are consistent with the idea that these nuclei may play a role in associative learning.

Response latencies to visual stimulation and disparity sensitivity in single cells of the awake Macaca mulatta visual cortex.

The onset response latencies to dynamic random dot figures (solid figures) and dynamic random dot stereograms were measured in single units recorded from areas V1 and V2 of two awake Macaca mulatta monkeys. We studied 56 cells, 39 from V1 and 17 from V2. In 14 disparity sensitive and 13 disparity unsensitive cells from V1 the median latencies to solid figures were 59.8 and 73.6 ms, respectively, which were statistically different. In 26 disparity sensitive cells from V1 and 17 from V2 the median latencies to stereofigures were 85.6 and 97.9 ms, respectively, which were statistically different. These results indicate that V1 disparity sensitive cells may have shorter integration time than disparity unsensitive cells and that there is a transferring delay for disparity information between areas V1 and V2.

Sensitivity of flood loss estimates to building representation and flow depth attribution methods in micro-scale flood modelling

Thanks to modelling advances and the increase in computational resources in recent years, it is now feasible to perform 2-D urban flood simulations at very high spatial resolutions and to conduct flood risk assessments at the scale of single buildings. In this study, we explore the sensitivity of flood loss estimates obtained in such micro-scale analyses to the spatial representation of the buildings in the 2D flood inundation model and to the hazard attribution methods in the flood loss model. The results show that building representation has a limited effect on the exposure values (i.e. the number of elements at risk), but can have a significant impact on the hazard values attributed to the buildings. On the other hand, the two methods for hazard attribution tested in this work result in remarkably different flood loss estimates. The sensitivity of the predicted flood losses to the attribution method is comparable to the one associated with the vulnerability curve. The findings highlight the need for incorporating these sources of uncertainty into micro-scale flood risk prediction methodologies.

Numerical Modeling of the Impact of a Pumped-Storage Hydroelectric Power Plant on the Reservoirs’ Thermal Stratification Structure: a Case Study in NW Spain

Pumped-storage hydroelectric power plants are generally perceived as an environmentally respectful technology. Nevertheless, the pumping of water from a lower reservoir to an upper impoundment, and the return of that water during power generation, can strongly affect the water quality of the reservoirs. In particular, plant operation can alter their thermal structure, deep water mixing, and water circulation characteristics. The objective of this study is to quantify, through the use of 3D hydrodynamic modeling, the potential impacts of a pumped-storage hydroelectric plant on the thermal stability and mixing of two reservoirs in Galicia, northwest of Spain. To this end, three-dimensional hydrodynamic simulations were conducted using the model Delft3D. Two different coupled models, one for each reservoir, were constructed and subsequently tested for several stratification scenarios, according to measured temperature profiles during the spring and summer season. Several reservoir minimum and maximum operation water levels were also considered. Model simulations demonstrated a high level of mixing in the vicinity of the intake-outlet structures, in particular during startup of the power plant, regardless of the water level in the reservoir. Beyond this area, the results showed a limited overall effect on stratification and mixing in the upper reservoir, owing to the relation between the inflow temperatures and the initial temperature profile of this reservoir. A more significant alteration of the thermal structure is expected in the lower reservoir due to its narrow shape and shallow depth at the structure location, as well as the temperature differences between receiving waters and inflow.

Comparison Between 24-2 SITA-Standard and 24-2 SITA-Fast Strategies in Standard Automated Perimetry

Purpose This work aimed at describing the time course of vitreous clearance through the use of positron emission tomography (PET) as a noninvasive tool for pharmacokinetic studies of intravitreal injection. Methods The pharmacokinetic profile of intravitreal injections of molecules labeled with 18Fluorine (18F) was evaluated in adult Sprague Dawley rats by using a dedicated small-animal PET/computed tomography scanner. Different conditions were studied: three molecules radiolabeled with 18F (18F-FDG, 18F-NaF, and 18F-Choline), three volumes of intravitreal injections (7, 4, and 2 μL), and absence or presence of eye inflammation (uveitis). Results Our results showed that there are significant pharmacokinetic differences among the radiolabeled molecules studied but not among the injected volumes. The presence or absence of uveitis was an important factor in vitreous clearance, since the elimination of the drug was clearly increased when this condition is present. Conclusions Intravitreal pharmacokinetic studies based on the use of dedicated PET imaging can be of potential interest as noninvasive tools in ophthalmic drug development in small animals.

Hydraulic model study of the intake-outlet of a pumped-storage hydropower plant

ABSTRACT The design of intake-outlet structures for pumped-storage hydroelectric power plants requires site-specific location and geometry studies in order to ensure their satisfactory hydraulic performance. This article presents the numerical and physical model studies conducted on the lower intake-outlet of Belesar III power station in Northwest Spain. The proposed location of this structure in a narrow reservoir and at a shallow depth is particularly challenging and required the analysis of both the near-field and far-field flow dynamics in the reservoir. First, the hydrodynamics of the reservoir were studied with a 2D shallow water model. The location of the intake was found to be suitable, with adequate flow conditions in the reservoir even for the lower operating water levels. The intake could be fed with the maximum pumping discharge without being limited by the reservoir’s hydraulics. Second, the flow in the near-field was investigated by complementary use of 3-dimensional numerical simulations and reduced-scale physical modeling. The results allowed the verification of the submergence requirements and the comparison of geometry alternatives. In comparison with the initial design, the final proposed design shows a more symmetrical approach flow into the structure during pumping mode, resulting in a more homogenous flow distribution between the openings and reduced head loss. This study can provide guidance in the application of hydraulic modeling procedures to locate and design intake-outlet structures in existing lakes or reservoirs and to evaluate potential limitations on water levels, inflows and outflows. It can be useful during planning stages of power plants to aim for the shortest possible waterways between the reservoirs while ensuring adequate flow conditions.

Temporal characteristics of visual receptive fields in primary visual cortex and medial superior temporal cortex areas

We mapped the receptive fields of 49 cells from primary visual cortex and 19 cells from medial superior temporal cortex in two awake monkeys. The receptive field structures we obtained lasted a mean time of 32.7 ms in primary visual cortex and 38.4 ms in medial superior temporal cortex, showing no statistical difference. This result suggests that both areas have the same time requirements for processing visual information. In primary visual cortex, 100% of cells had conformed the receptive field structure at 65 ms pre-spike, whereas in medial superior temporal cortex it occurred at 150 ms. In both areas, cells with shorter response latencies had receptive field structures with longer durations. This may indicate that cells tend to synchronize their output to other areas.

Spatial Frequency Components of Images Modulate Neuronal Activity in Monkey Amygdala.

Processing the spatial frequency components of an image is a crucial feature for visual perception, especially in recognition of faces. Here, we study the correlation between spatial frequency components of images of faces and neuronal activity in monkey amygdala while performing a visual recognition task. The frequency components of the images were analyzed using a fast Fourier transform for 40 spatial frequency ranges. We recorded 65 neurons showing statistically significant responses to at least one of the images used as a stimulus. A total of 37 of these neurons (n = 37) showed significant responses to at least three images, and in eight of them (8/37, 22%), we found a statistically significant correlation between neuron response and the modulus amplitude of at least one frequency range present in the images. Our results indicate that high spatial frequency and low spatial frequency components of images influence the activity of amygdala neurons.