211 research outputs found

    Integration of new and revised chronological data to constrain the terrace evolution of the Danube River (Gerecse Hills, Pannonian Basin)

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    Terrace ages deduced from diverse geochronological records yielded inconsistent data in the Danube valley in Hungary. The problem of discrepancies in the different chronological datasets has to be resolved before the Quaternary tectonic and climatic processes leading to valley incision and terrace formation may be properly evaluated. To establish a more robust chronology of the Danube valley in Hungary, new cosmogenic nuclide- (⁠10Be depth profiles, ⁠26Al/⁠10Be burial durations and burial depth profile) and luminescence-based (pIRIR⁠290) terrace ages were acquired and compared to revised paleontological and published U/Th and magnetostratigraphic data. All the applied geo-chronometers led to concordant terrace ages, with the exception of the U/Th method applied on travertine deposits covering terraces. U/Th ages predating the last interglacial manifest a bias towards younger ages, and so they were ignored in relation to the quantification of terrace ages. As a result, terrace ages from the Late Pliocene to Late Pleistocene were settled. With regard to data from the Middle Pleistocene onwards, the combination of diverse methodologies led to a tighter bracketing of terrace ages than would be possible using a single dating method. The modelling of cosmogenic ⁠26Al and ⁠10Be concentrations enabled to derive surface denudation rates and their combination with paleontological data also allowed us to decide between diverse landscape evolution scenarios

    Growth, cell division and sporulation in mycobacteria

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    Bacteria have the ability to adapt to different growth conditions and to survive in various environments. They have also the capacity to enter into dormant states and some bacteria form spores when exposed to stresses such as starvation and oxygen deprivation. Sporulation has been demonstrated in a number of different bacteria but Mycobacterium spp. have been considered to be non-sporulating bacteria. We recently provided evidence that Mycobacterium marinum and likely also Mycobacterium bovis bacillus Calmette–GuĂ©rin can form spores. Mycobacterial spores were detected in old cultures and our findings suggest that sporulation might be an adaptation of lifestyle for mycobacteria under stress. Here we will discuss our current understanding of growth, cell division, and sporulation in mycobacteria

    A balanced view of scale in spatial statistical analysis

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    Concepts of spatial scale, such as extent, grain, resolution, range, footprint, support and cartographic ratio are not interchangeable. Because of the potential confusion among the definitions of these terms, we suggest that authors avoid the term "scale" and instead refer to specific concepts. In particular, we are careful to discriminate between observation scales, scales of ecological phenomena and scales used in spatial statistical analysis. When scales of observation or analysis change, that is, when the unit size, shape, spacing or extent are altered, statistical results are expected to change. The kinds of results that may change include estimates of the population mean and variance, the strength and character of spatial autocorrelation and spatial anisotropy, patch and gap sizes and multivariate relationships, The First three of these results (precision of the mean, variance and spatial autocorrelation) can sometimes be estimated using geostatistical support-effect models. We present four case studies of organism abundance and cover illustrating some of these changes and how conclusions about ecological phenomena (process and structure) may be affected. We identify the influence of observational scale on statistical results as a subset of what geographers call the Modifiable Area Unit Problem (MAUP). The way to avoid the MAUP is by careful construction of sampling design and analysis. We recommend a set of considerations for sampling design to allow useful tests for specific scales of a phenomenon under study. We further recommend that ecological studies completely report all components of observation and analysis scales to increase the possibility of cross-study comparisons
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