C. Fernández

Effects of Several Class I Antiarrhythmic Drugs on Isolated Rat Aortic Vascular Smooth Muscle

1. The vasorelaxant effects of seven NA+ channel blockers (i.e., class I antiarrhythmic agents), quinidine, disopyramide, imipramine, lidocaine, mexiletine, flecainide, and desipramine, were investigated in isolated endothelium-denuded rat aorta. 2. All drugs induced a concentration-dependent relaxation in aorta precontracted with either 80 mM KCl or 10(-5) M noradrenaline and, with the exception of mexiletine, they were more potent in inhibiting KCl-induced contractions. 3. The degree of inhibition of high KCl-induced contractions produced by quinidine and desipramine increased with the time of depolarization. Furthermore, the inhibitory effect of quinidine also increased in aorta preincubated in 40 mM KCl, whereas the inhibitory effects of other antiarrhythmics were almost similar in 5 or 40 mM KCl solution. 4. In conclusion, all these class I antiarrhythmic drugs inhibited Ca2+ entry through voltage- and receptor-gated channels as well as Ca2+ release from intracellular stores. As a consequence, they decrease the availability of intracellular free Ca2+ required for vascular smooth muscle contraction.

Free space and speed humps detection using lidar and vision for urban autonomous navigation

In this paper, a real-time free space detection system is presented using a medium-cost lidar sensor and a low cost camera. The extrinsic relationship between both sensors is obtained after an off-line calibration process. The lidar provides measurements corresponding to 4 horizontal layers with a vertical resolution of 3.2 degrees. These measurements are integrated in time according to the relative motion of the vehicle between consecutive laser scans. A special case is considered here for Spanish speed humps, since these are usually detected as an obstacle. In Spain, speed humps are directly related with raised zebra-crossings so they should have painted white stripes on them. Accordingly the conditions required to detect a speed hump are: detect a slope shape on the road and detect a zebra crossing at the same time. The first condition is evaluated using lidar sensor and the second one using the camera.

Visual odometry and map fusion for GPS navigation assistance

This paper describes a new approach for improving the estimation of the global position of a vehicle in complex urban environments by means of visual odometry and map fusion. The visual odometry system is based on the compensation of the heterodasticity in the 3D input data using a weighted nonlinear least squares based system. RANdom SAmple Consensus (RANSAC) based on Mahalanobis distance is used for outlier removal. The motion trajectory information is used to keep track of the vehicle position in a digital map during GPS outages. The final goal is the autonomous vehicle outdoor navigation in large-scale environments and the improvement of current vehicle navigation systems based only on standard GPS. This research is oriented to the development of traffic collective systems aiming vehicle-infrastructure cooperation to improve dynamic traffic management. We provide examples of estimated vehicle trajectories and map fusion using the proposed method and discuss the key issues for further improvement.

Quality Metrics in Learning Objects

In todays rapidly evolving society, the range and depth of information available to us is quickly growing which affects educational institutions, who find it difficult to keep their programmes up to date, whilst students struggle to find the right information. The paradigm of learning objects is an emerging technology aimed towards facilitating the managements of the massive amount of (educational) resources available. Enabling users relying on this paradigm to use concise and high quality pieces of knowledge within different contexts represents a key challenge. Therefore, when designing learning objects, reusability must be a key consideration. Bearing this in mind, the current lack of metrics to help measure quality and reusability represents a major issue. Specific metrics for learning objects will eventually appear, probably based on extended and improved metadata. In the meantime, there remains the need to measure the potential reusability of the existing base of learning objects. This paper attempts to bridge this gap by analysing and developing adapted metrics for learning objects, based on existing metrics used in other disciplines such as software engineering.

Extended Floating Car Data system - experimental study

This paper presents the results of a set of extensive experiments carried out in daytime and nighttime conditions in real traffic using an enhanced or extended Floating Car Data system (xFCD) that includes a stereo vision sensor for detecting the local traffic ahead. The detection component implies the use of previously monocular approaches developed by our group in combination with new stereo vision algorithms that add robustness to the detection and increase the accuracy of the measurements corresponding to relative distance and speed. Besides the stereo pair of cameras, the vehicle is equipped with a low-cost GPS and an electronic device for CAN Bus interfacing. The xFCD system has been tested in a 198-minutes sequence recorded in real traffic scenarios with different weather and illumination conditions, which represents the main contribution of this paper. The results are promising and demonstrate that the system is ready for being used as a source of traffic state information.

Vasoconstrictor and vasodilator effects of disopyramide on isolated rat vascular smooth muscle

We investigated the effects of disopyramide on the isometric contractions and intracellular Ca2+ concentrations ([Ca2+]i) measured by Fura-2 fluorescence in isolated rat aorta and portal veins. Disopyramide at concentrations > or = 10(-5) M increased the duration and complexity of the spontaneous contractions in rat portal veins. At > 10(-6) M, it induced a concentration-dependent contraction in the rat aorta. This effect was endothelium independent, associated with an increase in [Ca2+]i and abolished in aortic rings incubated in Ca2+-free solution or pretreated with 10(-7) M nifedipine, suggesting that disopyramide increased [Ca2+]i through the activation of L-type Ca2+ channels. In aortic rings precontracted by KCl (30 and 80 mM), 80 mM KCl in a low-concentration (26.2 mM) Na+ solution or 10(-5) M noradrenaline, disopyramide induced a concentration-dependent relaxation. The relaxant response in 80 mM KCl-precontracted arteries was associated with a parallel reduction in [Ca2+]i, an effect attributable to its Ca2+ channel blocking properties. In contrast, disopyramide had no effect on the concentration-response curves to noradrenaline in the presence of nifedipine. Disopyramide also inhibited in a concentration-dependent manner the relaxation induced by levcromakalim in aortic rings precontracted by 30 mM KCl because of its inhibitory action on K(ATP) channels, whereas it had no effect on the relaxant response to sodium nitroprusside. These effects, together with the negative inotropic effects of the drug, may account for the increase in mean arterial pressure observed in disopyramide-treated patients and the profound hypotension observed after overdosages of disopyramide.

Fusing directional passive UHF RFID and stereo vision for tag association in outdoor scenarios

Stereo-based object detection systems can be greatly enhanced thanks to the use of passive UHF RFID technology. By combining tag localization with its identification capability, new features can be associated with each detected object, extending the set of potential applications. The main problem consists in the association between RFID tags and objects due to the intrinsic limitations of RSSI-based localization approaches. In this paper, a new directional RSSI-distance model is proposed taking into account the angle between the object and the antenna. The parameters of the model are automatically obtained by means of a stereo-RSSI automatic calibration process. A robust data association method is presented to deal with complex outdoor scenarios in medium sized areas with a measurement range up to 15m. The proposed approach is validated in crosswalks with pedestrians wearing portable RFID passive tags.