1,721,007 research outputs found
Asymmetric correlation matrices: an analysis of financial data
No full textWe analyse the spectral properties of correlation matrices between distinct statistical systems. Such matrices are intrinsically non-symmetric, and lend themselves to extend the spectral analyses usually performed on standard Pearson correlation matrices to the realm of complex eigenvalues. We employ some recent random matrix theory results on the average eigenvalue density of this type of matrix to distinguish between noise and non-trivial correlation structures, and we focus on financial data as a case study. Namely, we employ daily prices of stocks belonging to the American and British stock exchanges, and look for the emergence of correlations between two such markets in the eigenvalue spectrum of their non-symmetric correlation matrix. We find several non trivial results when considering time-lagged correlations over short lags, and we corroborate our findings by additionally studying the asymmetric correlation matrix of the principal components of our datasets
Calcium and phosphorus in relation to the water for diluting milk in the 1st months of life
No full textReproductive mode and genetic polymorphism in different populations of the tardigrade Richtersius coronifer (Eutardigrada, Macrobiotidae)
No full textA particle filter technique for human pose estimation in case of occlusion exploiting holographic human model and virtualized environment
No full textIn a collaborative scenario, robots working side by side with humans might rely on vision sensors to monitor the activity of the other agent. When occlusions of the human body occur, both the safety of the cooperation and the performance of the team can be penalized, since the robot could receive incorrect information about the ongoing cooperation. In this work, we propose a novel particle filter algorithm that, by merging the data acquired through a RGB-D camera and a MR headset, estimates online the human wrist position. This algorithm allows to significantly reduce the uncertainty of the human pose estimation, in case of both static and dynamic occlusions. To this purpose, the proposed particle filter is integrated with a detailed virtual model of the real workspace. Moreover, additional constraints describing the boundaries of the motion of the human upper body are included in a virtualized framework. The results showed that the proposed technique entails significant improvements, determining a relevant reduction of the estimation error and of the uncertainty of the estimate
Increasing knowledge of Antarctic biodiversity: new endemic taxa of tardigrades (Eutardigrada; Ramazzottiidae) and their evolutionary relationships
No full textThe underestimation of biodiversity and scarce knowledge of the biogeographic distributions of terrestrial meiofaunal component limit our understanding of the origin of Antarctic fauna. One of its main components is tardigrades; nonetheless studies on tardigrade diversity are still few in the continental Antarctic area. In order to increase our knowledge of the underreported terrestrial meiofaunal communities within continental Antarctica, as well as to provide new information for biogeographic and evolutionary analysis of these communities, the tardigrade diversity of 11 samples collected along the coast of Victoria Land was considered. The application of an integrative approach in which morphological (Light - LM, scanning electron - SEM, and confocal laser scanning microscopy - CSLM) and molecular analysis (18S, 28S, cox1 genes) were combined allowed us to characterize the tardigrade fauna inhabiting mosses, lichens, and cyanobacterial mats of Victoria Land. These analyses allowed the detection of two tardigrade species new to science (Cryoconicus antiarktos sp. nov., Ramazzottius sabatiniae sp. nov.), and the emendation of known species ((Hebesuncus ryani Dastych and Harris, 1994, Ramazzottius nivalis Dastych, 2006, Cryoconicus ljudmilae comb. nov. (Biserov, 1997/98), and Cryoconicus cataphractus (Maucci, 1974)), together with the genus Cryoconicus. The Ramazzottius type of claws was redefined identifying three subtypes. Also, we investigated the phylogenetic position of some problematic/unresolved lineages all belonging to the family Ramazzottiidae. These data increased the knowledge of the biodiversity in Victoria Land, the number of endemic tardigrades in Antarctica, and provided evidence on the origin of Antarctic endemism. Lastly, new methods for integrative taxonomic studies on tardigrades were presented and discussed
Life history traits and reproductive mode of the tardigrade Acutuncus antarcticus under laboratory conditions: strategies to colonize the Antarctic environment
No full textGlobal climate change has become an important issue, particularly for organisms living in the Antarctic region, as the predicted temperature increase can affect their life history traits. The reproductive mode and life history traits of one of the most widespread species of tardigrades in Antarctica were analyzed. Specimens of the eutardigrade Acutuncus antarcticus from a temporary freshwater pond at Victoria Land (Antarctica) were individually cultured. This species reproduced continuously by thelytokous meiotic parthenogenesis. Its life cycle was short (60–90 days) and the reproductive output was low, with a short generation time (25–26 days). The maternal effect can be responsible of the phenotypic plasticity observed in life history traits of the three analyzed generations that may be seen as a bet-hedging strategy, as also observed in other animals inhabiting stochastic environments. These traits, along with the cryptobiotic capability of A. antarcticus, are advantageous for exploiting the conditions suitable for growth and reproduction during the short Antarctic summer, and can explain its wide distribution on the Antarctic continent. These results open new avenues of research for determining the role of bet-hedging strategy in organisms living in unpredictable environments
A centromeric satellite DNA in the European plethodontid salamanders (Amphibia, Urodela).
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