Molecular and Morphological Characterization of Segmentation in Artemia franciscana

In the animal kingdom, only the annelids, arthropods and chordates are segmented. Whether the common bilateran ancestor to these three phyla was segmented, remains debated. One way to address the origins of the evolution of segmentation is to compare the molecular mechanisms underlying this complex process between the phyla and across each phylum. This thesis first examines what we already know about segmentation in each of the three phyla, and compares the models of segmentation in each phylum as well as between the three. Then, the role of γ-secretase mediated signaling in segmentation was examined in the branchiopod crustacean, Artemia franciscana. These findings were further compared to another crustacean Thamnocephalus platyurus. Both of these species develop their thoracic segments sequentially from anterior to posterior, and exposure to a γ-secretase inhibitor slows segmentation in a dose dependent manner, but does not affect the overall growth. My results suggest that Delta/Notch signaling is an essential for segment patterning in these two species, although it may not function as a molecular oscillator, as is the case in vertebrates. Similar findings in other arthropods suggest that the role of Notch in segmentation is not as unique to vertebrates as once thought. Finding such similarities in the molecular pathways that pattern segments across segmented phyla suggests that the Urbilaterian may have indeed been segmented

Distribution of Azolla filiculoides Lam. [Azollaceae] in Poland

Azolla filiculoides has been an ephemeral plant in Poland since the end of the 20th century. In the last 15 years this species appeared in 5 locations in south-west Poland. Habitat and plants of two populations became destroyed, three other still exist. A. filiculoides occurs in eutrophic or even polluted water where it forms dense mats, up to 10 cm thick. It stays sterile and propagates only in a vegetative manner. Frost resistance of Lower Silesia populations is higher than reported so far; fern may winter and rebuild the population after frost reaching 22oC. Size of the populations is changeable during the vegetation season. A. filiculoides occurs in water habitats and plant communities in which it substitutes Lemna minor

Mixture model in high-order statistics for peak factor estimation on low-rise building

peer reviewedTo design reliable structures, extreme pressures and peak factors are required. In many applications of Wind Engineering, their statistical analysis has to be performed taking into account the non-Gaussianity of the wind pressures. With the increasing precision and sampling frequency of pressure sensors, large short and local peak events are more usually captured. Their relevance is naturally questioned in the context of a structural design. Furthermore, the increasing computational power allows for accumulation and analysis of larger data sets revealing the detailed nature of wind flows around bluff bodies. In particular, in the shear layers and where local vortices form, it is commonly admitted that the Probability Density Function (PDF) of measured pressures might exhibit two or more significant components. These mixed flows can be modelled with mixture models [Cook (2016)]. Whenever several processes coexist, and when one of them is leading in the tail of the statistical distribution, as will be seen next in the context of corner vortices over a flat roof, it is natural to construct the extreme value model with this leading process and not with the mixed observed pressures. It is therefore important to separate the different processes that can be observed in the pressure histories. Once this is done, specific analytical formulations of non-Gaussian peak factors can be used to evaluate the statistics of extreme values [Kareem and Zhao (1994), Chen (2009)]. The separation of mixed processes is usually done by means of the PDF of the signals [Cook (2016)]. This information is of course essential to perform an accurate decomposition but it might be facilitated by considering higher rank information like auto-correlations and higher correlations like the triple or quadruple correlation. Indeed, the two phenomena that need to be separated and identified might be characterized by significantly different timescales, which are not reflected in the PDF. In this paper, the large negative pressures measured on a flat roof are analyzed and decomposed into two elementary processes, namely, the flapping corner vortex and the turbulent flow detaching from the sharp upstream edge. The full paper will finally show that an accurate decomposition of the recorded pressures into their underlying modes provides a more meaningful evaluation of the extreme pressures