Luís Mário Ribeiro

Estimation of shrub height for fuel-type mapping combining airborne lidar and simultaneous color infrared ortho imaging

A fuel-type map of a predominantly shrub-land area in central Portugal was generated for a fire research experimental site, by combining airborne light detection and ranging (LiDAR), and simultaneous color infrared ortho imaging. Since the vegetation canopy and the ground are too close together to be easily discerned by LiDAR pulses, standard methods of processing LiDAR data did not provide an accurate estimate of shrub height. It was demonstrated that the standard process to generate the digital ground model (DGM) sometimes contained height values for the top of the shrub canopy rather than from the ground. Improvement of the DGM was based on separating canopy from ground hits using color infrared ortho imaging to detect shrub cover, which was measured simultaneously with the LiDAR data. Potentially erroneous data in the DGM was identified using two criteria: low vegetation height and high Normalized Difference Vegetation Index (NDVI), a commonly used spectral index to identify vegetated areas. Based on the height of surrounding pixels, a second interpolation of the DGM was performed to extract those erroneously identified as ground in the standard method. The estimation of the shrub height improved significantly after this correction, and increased determination coefficients from R2 = 0.48 to 0.65. However, the estimated shrub heights were still less than those observed in the field.

GABAA receptor dephosphorylation followed by internalization is coupled to neuronal death in in vitro ischemia

Cerebral ischemia is characterized by an early disruption of GABAergic neurotransmission contributing to an imbalance of the excitatory/inhibitory equilibrium and neuronal death, but the molecular mechanisms involved are not fully understood. Here we report a downregulation of GABA(A) receptor (GABA(A)R) expression, affecting both mRNA and protein levels of GABA(A)R subunits, in hippocampal neurons subjected to oxygen-glucose deprivation (OGD), an in vitro model of ischemia. Similar alterations in the abundance of GABA(A)R subunits were observed in in vivo brain ischemia. OGD reduced the interaction of surface GABA(A)R with the scaffold protein gephyrin, followed by clathrin-dependent receptor internalization. Internalization of GABA(A)R was dependent on glutamate receptor activation and mediated by dephosphorylation of the β3 subunit at serine 408/409. Expression of phospho-mimetic mutant GABA(A)R β3 subunits prevented receptor internalization and protected hippocampal neurons from ischemic cell death. The results show a key role for β3 GABA(A)R subunit dephosphorylation in the downregulation of GABAergic synaptic transmission in brain ischemia, contributing to neuronal death. GABA(A)R phosphorylation might be a therapeutic target to preserve synaptic inhibition in brain ischemia.

Multi-UAV Experiments: Application to Forest Fires

This Chapter presents the application of a multi-UAV system to forest fires. Particularly the experiments carried out with the COMETS system will be presented. After the introduction and motivation, the UAVs, sensors and basic methods are presented. The third section deals with the general description of the fire detection, localization and monitoring. The next sections are devoted to the multi-UAV surveillance and fire alarm detection, fire observation and monitoring, and cooperative fire monitoring. These sections include short summaries of experiments carried out in the Lousa airfield and the Serra de Gestosa, near Coimbra (Portugal).

Linear model for spread rate and mass loss rate for mixed-size fuel beds

A linearised model to estimate the properties of composite fuel beds based on the mass fraction of each fuel component is proposed. Laboratory experiments to determine combustibility properties of fuel beds composed of two, three and four components were performed under no-slope and no-wind conditions. Results of the rate of spread and mass loss rate compared favourably with model predictions. Results from tests with wind-induced fire fronts were also compared with the present model. The linear model provides a simple method to estimate of the rate of spread of composite fuels.

Impacts of Fire on Society: Extreme Fire Propagation Issues

Human activities namely forest management interact with natural conditions to determine fire occurrence and fire impact in a complex form. Climate change tends to facilitate even larger and more dangerous fires. The wildland urban interface is an emerging problem derived from the expansion of urban areas associated to high risk fire conditions. Extreme fire behaviour in the form of eruptive fires, crown fires and spot fires are associated to great damage to the environment and to loss of human lives. Some cases of fatal accidents that occurred recently in Europe are presented to illustrate the proposed concepts.

Effect of two-way coupling on the calculation of forest fire spread: model development

The present work addresses the problem of how wind should be taken into account in fire spread simulations. The study was based on the software system FireStation, which incorporates a surface fire spread model and a solver for the fluid flow (Navier–Stokes) equations. The standard procedure takes the wind field computed from a single simulation in the absence of fire, but this may not be the best option, especially for large fires. The two-way coupling method, however, considers the buoyancy effects caused by the fire heat release. Fire rate of spread is computed with the semi-empirical Rothermel model, which takes as input local terrain slope, fuels properties and wind speed and direction. Wind field is obtained by solving the mass, momentum and energy equations. Effects of turbulence on the mean flow field are taken into account with the k – ϵ turbulence model. The calculation procedure consists of an interchange between the fire spread model and the wind model through a dynamic interaction. The present work describes the first part of this research, presenting the underlying models and a qualitative sensitivity analysis. It is shown that the update frequency for the dynamic interaction markedly influences the total calculation time. The best strategy for updating the wind field during the fire progression is presented. The dependence of results on mesh size is also described.

Monitoring fire-fighters' smoke exposure and related health effects during Gestosa experimental fires

The main objective of this study is to contribute to the scientific knowledge regarding fire-fighters’ exposure to smoke and its related health effects. Forest fire experiments were developed with an extensive number of measurements of individual exposure to smoke pollutants and of medical parameters for a group of fire-fighters. For the smoke exposure monitoring, ten fire-fighters from four different fire brigades were selected. The fire-fighters’ individual exposure to toxic gases and particulate matter was monitored with portable devices, and their location in time was registered with GPS equipment. For all the monitored fire-fighters, air pollutant concentration values acquired during the fire experiments were beyond the limits recommended by the World Health Organization (WHO), namely for PM2.5, CO and NO2. Daily averages of PM2.5 concentration values as high as 738 µg.m -3 were obtained, well above the recommended limit of 25 µg.m -3 . In terms of CO, hourly averaged values higher than 73,000 µg.m -3 were monitored, clearly above the 30,000 µg.m -3