1,705 research outputs found

    Geographic trends in range sizes explain patterns in bird responses to urbanization in Europe

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    The probability of occurrence of bird species in towns/cities increases with their range sizes, and Rapoport’s rule states that range sizes increase with latitude. To test the hypothesis that the increasing number of bird species persisting in cities at higher latitudes of Europe is linked to their larger range sizes, we compiled data on bird communities of: a) 41 urban bird atlases; b) 37 city core zones from published sources; c) regions of nine grid cells of the EBCC Atlas of European Breeding Birds around each city. We tested whether the proportion of species from particular regional bird assemblages entering cities (i.e., proportional richness) was related to the geographical  position, mean range size of regional avifaunas, proportion of vegetated areas and city habitat heterogeneity. The mean range sizes of the observed and randomly selected urban avifaunas were contrasted. The proportional richness of urban avifaunas was positively related to the geographic position and mean range size of birds in regional assemblages. The evidence favoured range sizes if considering the European range sizes or latitudinal extents, but was limited for global range sizes. Randomizations tended to show larger range sizes for the real avifaunas than in the randomly selected ones. For urban core zones, the results were less clear-cut with some evidence only in favour of the European range sizes. No role of vegetation or habitat heterogeneity was found. In conclusion, while vegetation availability or heterogeneity did not show any effects, spatial position and range sizes of birds in regional assemblages seemed to influence the proportional richness of cities and their core zones. Factors correlated with spatial position (e.g., climate) might increase the attractivity of particular cities to birds. However, the effects of range sizes indicated that urbanization possibly has more negative impacts on the avifauna in the regions occupied by less widespread species

    Non-additivity of optical and Casimir-Polder potentials

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    An atom irradiated by an off-resonant laser field near a surface is expected to experience the sum of two fundamental potentials, the optical potential of the laser field and the Casimir--Polder potential of the surface. Here, we report a new non-additive potential, namely the laser-induced Casimir--Polder potential, which arises from a correlated coupling of the atom with both the laser and the quantum vacuum. We apply this result to an experimentally realizable scenario of an atomic mirror with an evanescent laser beam leaking out of a surface. We show that the non-additive term is significant for realistic experimental parameters, transforming potential barriers into potential wells, which can be used to trap atoms near surfaces.Comment: 5 pages, 3 figure

    A U-statistic estimator for the variance of resampling-based error estimators

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    We revisit resampling procedures for error estimation in binary classification in terms of U-statistics. In particular, we exploit the fact that the error rate estimator involving all learning-testing splits is a U-statistic. Therefore, several standard theorems on properties of U-statistics apply. In particular, it has minimal variance among all unbiased estimators and is asymptotically normally distributed. Moreover, there is an unbiased estimator for this minimal variance if the total sample size is at least the double learning set size plus two. In this case, we exhibit such an estimator which is another U-statistic. It enjoys, again, various optimality properties and yields an asymptotically exact hypothesis test of the equality of error rates when two learning algorithms are compared. Our statements apply to any deterministic learning algorithms under weak non-degeneracy assumptions. In an application to tuning parameter choice in lasso regression on a gene expression data set, the test does not reject the null hypothesis of equal rates between two different parameters

    Cytotoxic effects of curcumin on osteosarcoma cell lines

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    Summary: Curcumin (diferuloylmethane), one of the main components of the Indian spice turmeric, is known to possess potent anti-inflammatory and anti-oxidant properties. In addition, curcumin has also been shown to have in vitro and in vivo efficacy against a variety of malignancies. In the current study we examined the cytotoxic effect of curcumin on seven osteosarcoma (OS) cell lines with varying degrees of in vivo metastatic potential. Curcumin inhibited the growth of all OS cell lines tested with half-maximal inhibitory concentration values ranging from 14.4 to 24.6μM. Growth inhibition was associated with a dose dependent increase in the number of apoptotic cells and accumulation of cells in the G2/M phase of the cell cycle. Curcumin treatment also resulted in cleavage of caspase-3 and poly adenosine diphosphate-ribose polymerase. Moreover, curcumin treatment was associated with an increase in cellular levels of the apoptotic B-cell leukemia/lymphoma 2 (Bcl-2)-associated X protein and a decrease in cellular content of the anti-apoptotic protein Bcl-2. In addition, curcumin treatment also inhibited the migration of OS cell lines. These data indicate that the potent cytotoxic activity of curcumin on OS cell lines is mediated by induction of apoptotic processes. Thus, curcumin has potential to be a novel OS chemotherapeutic agen

    Cytotoxic effects of curcumin on osteosarcoma cell lines

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    Summary: Curcumin (diferuloylmethane), one of the main components of the Indian spice turmeric, is known to possess potent anti-inflammatory and anti-oxidant properties. In addition, curcumin has also been shown to have in vitro and in vivo efficacy against a variety of malignancies. In the current study we examined the cytotoxic effect of curcumin on seven osteosarcoma (OS) cell lines with varying degrees of in vivo metastatic potential. Curcumin inhibited the growth of all OS cell lines tested with half-maximal inhibitory concentration values ranging from 14.4 to 24.6μM. Growth inhibition was associated with a dose dependent increase in the number of apoptotic cells and accumulation of cells in the G2/M phase of the cell cycle. Curcumin treatment also resulted in cleavage of caspase-3 and poly adenosine diphosphate-ribose polymerase. Moreover, curcumin treatment was associated with an increase in cellular levels of the apoptotic B-cell leukemia/lymphoma 2 (Bcl-2)-associated X protein and a decrease in cellular content of the anti-apoptotic protein Bcl-2. In addition, curcumin treatment also inhibited the migration of OS cell lines. These data indicate that the potent cytotoxic activity of curcumin on OS cell lines is mediated by induction of apoptotic processes. Thus, curcumin has potential to be a novel OS chemotherapeutic agen

    Taurolidine: a novel anti-neoplastic agent induces apoptosis of osteosarcoma cell lines

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    Summary: Taurolidine, the active agent of Taurolin®, is a broad spectrum anti-biotic that has been used for over 15years for the treatment of severe surgical infections. Recently, taurolidine has been shown to possess anti-neoplastic properties in vitro and in vivo against a variety of cancers including ovarian, colon and prostate. In this study we assessed the cytotoxic activity of taurolidine against human osteosarcoma (OS) cell lines and normal human bone cells. Treatment with taurolidine inhibited the growth of all ten osteosarcoma cell lines tested and taurolidine was equally potent against cell lines with and without distinct genetic defects (i.e. p53, Rb). Moreover, taurolidine-induced growth inhibition was found to be associated with a dose dependent increase in the number of apoptotic cells and apoptosis was shown to be caspase-dependent. Taurolidine treatment was also found to inhibit adhesion of OS cell lines. Compared to OS cell lines, normal bone cells in primary culture were found to be less sensitive to the cytotoxic and anti-adhesive effects of taurolidine. These data indicate that taurolidine possesses potent anti-neoplastic activity against osteosarcoma cell lines and may have potential as a novel OS chemotherapeutic agen
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