Potentially harmful Ostreopsis spp. in the coastal waters of Alexandria - Egypt

Ostreopsis spp. has been reported for the first time from the Egyptian Mediterranean waters. Macroalgal samples were collected monthly between June 2005 and December 2007, from the rocks at Abu Qir, from less than 1.5 m depth, and their associated microalgae examined. Populations of two Ostreopsis morphotypes were found to occur in this location, east of Alexandria, viz., O. cf ovata Fukuyo and Ostreopsis morph1. The Ostreopsis spp. was abundant and dominant during the summer. They were more abundant as epiphytes of the brown algae Padina sp. and Sargassum sp., less abundant on the red algae Corallina sp., Jania sp., Laurencia sp. and even less so on the green algae Ulva spp. Ostreopsis cf. ovata was also identified during the summer months on the same macroalgal species, although in a much lower abundance. Ostreopsis spp. alternated in dominance with the benthic cyanobacteria Oscillatoria spp. and the diatom Licmophora sp. Other benthic dinoflagellates recorded at low abundance included Amphidinium carterae, Gymnodinium sp. and Prorocentrum lima

Nonlinear Model Predictive Control-based Collision Avoidance for Mobile Robot

This work proposes an efficient and safe single-layer Nonlinear Model Predictive Control (NMPC) system based on LiDAR to solve the problem of autonomous navigation in cluttered environments with previously unidentified static and dynamic obstacles of any shape. Initially, LiDAR sensor data is collected. Then, the Density-Based Spatial Clustering of Applications with Noise (DBSCAN) algorithm, is used to cluster the (Lidar) points that belong to each obstacle together. Moreover, a Minimum Euclidean Distance (MED) between the robot and each obstacle with the aid of a safety margin is utilized to implement safety-critical obstacle avoidance rather than existing methods in the literature that depend on enclosing the obstacles with a circle or minimum bounding ellipse. After that, to impose avoidance constraints with feasibility guarantees and without compromising stability, an NMPC for set-point stabilization is taken into consideration with a design strategy based on terminal inequality and equality constraints. Consequently, numerous obstacles can be avoided at the same time efficiently and rapidly through unstructured environments with narrow corridors.  Finally, a case study with an omnidirectional wheeled mobile robot (OWMR) is presented to assess the proposed NMPC formulation for set-point stabilization. Furthermore, the efficacy of the proposed system is tested by experiments in simulated scenarios using a robot simulator named CoppeliaSim in combination with MATLAB which utilizes the CasADi Toolbox, and Statistics and Machine Learning Toolbox. Two simulation scenarios are considered to show the performance of the proposed framework. The first scenario considers only static obstacles while the second scenario is more challenging and contains static and dynamic obstacles. In both scenarios, the OWMR successfully reached the target pose (1.5m, 1.5m, 0°) with a small deviation. Four performance indices are utilized to evaluate the set-point stabilization performance of the proposed control framework including the steady-state error in the posture vector which is less than 0.02 meters for position and 0.012 for orientation, and the integral of norm squared actual control inputs which is 19.96 and 21.74 for the first and second scenarios respectively. The proposed control framework shows a positive performance in a narrow-cluttered environment with unknown obstacles

Non-Inertial Quantum Clock Frames Lead to Non-Hermitian Dynamics

The operational approach to time is a cornerstone of relativistic theories, as evidenced by the notion of proper time. In standard quantum mechanics, however, time is an external parameter. Recently, many attempts have been made to extend the notion of proper time to quantum mechanics within a relational framework. Here, we use similar ideas combined with the relativistic mass-energy equivalence to study an accelerating massive quantum particle with an internal clock system. We show that the ensuing evolution from the perspective of the particle’s internal clock is non-Hermitian. This result does not rely on specific implementations of the clock. As a particular consequence, we prove that the effective Hamiltonian of two gravitationally interacting particles is non-Hermitian from the perspective of the clock of either particle

Título: Descripción de Zamora

Incluye (p.1-16): Aguas de Calabor : guia de dichas aguas minero-medicinalesTit. del lomo: Descripción de ZamoraCopia digital. Valladolid : Junta de Castilla y León. Consejería de Cultura y Turismo, 2009-201

Generalized observers and velocity measurements in General Relativity

To resolve some unphysical interpretations related to velocity measurements by static observers, we discuss the use of generalized observer sets, give a prescription for defining the speed of test particles relative to those observers and show that, for any locally inertial frame, the speed of a freely falling material particle is always less than the speed of light at the Schwarzschild black hole surface.Comment: 20 pages, 1 figure, submitted to General Relativity and Gravitatio