BackgroundBehavioral laterality is known for a variety of vertebrate and invertebrate animals. Laterality in social interactions has been described for a wide range of species including humans. Although evidence and theoretical predictions indicate that in social species the degree of population level laterality is greater than in solitary ones, the origin of these unilateral biases is not fully understood. It is especially poorly studied in the wild animals. Little is known about the role, which laterality in social interactions plays in natural populations. A number of brain characteristics make cetaceans most suitable for investigation of lateralization in social contacts.Methodology/Principal FindingsObservations were made on wild beluga whales (Delphinapterus leucas) in the greatest breeding aggregation in the White Sea. Here we show that young calves (in 29 individually identified and in over a hundred of individually not recognized mother-calf pairs) swim and rest significantly longer on a mother's right side. Further observations along with the data from other cetaceans indicate that found laterality is a result of the calves' preference to observe their mothers with the left eye, i.e., to analyze the information on a socially significant object in the right brain hemisphere.Conclusions/SignificanceData from our and previous work on cetacean laterality suggest that basic brain lateralizations are expressed in the same way in cetaceans and other vertebrates. While the information on social partners and novel objects is analyzed in the right brain hemisphere, the control of feeding behavior is performed by the left brain hemisphere. Continuous unilateral visual contacts of calves to mothers with the left eye may influence social development of the young by activation of the contralateral (right) brain hemisphere, indicating a possible mechanism on how behavioral lateralization may influence species life and welfare. This hypothesis is supported by evidence from other vertebrates.

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A computer simulation of a cerebral aneurysm is performed. Based on real surgery data, 3D geometry of the anomaly is reconstructed, hydrodynamic parameters of the blood flow (velocity, pressure, gradient) are calculated, strains and stress are obtained on the vascular walls in the case of the aneurysm and after stent installation changing the geometry of a vessel. It is shown that successful surgery is characterized by lowering the flow velocity, pressure, its gradient, and stresses on the vascular walls.A cerebral arterial aneurysm is a local distension, i.e., a local protrusion of a vascular wall. An arterial wall has several layers, an aneurysm generally consists of an inner layer called intima. It has no muscular structure, is less tensile than the wall of a healthy vessel and hence can be broken under a load which a healthy vessel can withstand well. In most cases the aneurysm occurs under anatomical variations or pathological changes in the structure of cerebral vessels, as well as at the points of vessel bifurcations or under arteriovenous malformations. This anomaly is one of the most frequent and dangerous diseases of cerebral arteries. The treatment of aneurysms is very difficult, their appearance and development proceeds for a long time without any symptoms up to the moment of breaking. If the presence of an aneurysm *