1,376 research outputs found
Transition to turbulence in slowly divergent pipe flow
The results of a combined experimental and numerical study of the flow in
slowly diverging pipes are presented. Interestingly, an axisymmetric conical
recirculation cell has been observed. The conditions for its existence and the
length of the cell are simulated for a range of diverging angles and expansion
ratios. There is a critical velocity for the appearance of this state. When the
flow rate increases further, a subcritical transition for localized turbulence
arises. The transition and relaminarization experiments described here quantify
the extent of turbulence. The findings suggest that the transition scenario in
slowly diverging pipes is a combination of stages similar to those observed in
sudden expansions and in straight circular pipe flow.Comment: 8 pages, 5 figure
The Lorentzian distance formula in noncommutative geometry
For almost twenty years, a search for a Lorentzian version of the well-known
Connes' distance formula has been undertaken. Several authors have contributed
to this search, providing important milestones, and the time has now come to
put those elements together in order to get a valid and functional formula.
This paper presents a historical review of the construction and the proof of a
Lorentzian distance formula suitable for noncommutative geometry.Comment: 16 pages, final form, few references adde
Can microsatellite data allow identification of oleaster Plio-Pleistocene refuge zones in the Mediterranean Basin?
International audienc
Mol-CycleGAN - a generative model for molecular optimization
Designing a molecule with desired properties is one of the biggest challenges
in drug development, as it requires optimization of chemical compound
structures with respect to many complex properties. To augment the compound
design process we introduce Mol-CycleGAN - a CycleGAN-based model that
generates optimized compounds with high structural similarity to the original
ones. Namely, given a molecule our model generates a structurally similar one
with an optimized value of the considered property. We evaluate the performance
of the model on selected optimization objectives related to structural
properties (presence of halogen groups, number of aromatic rings) and to a
physicochemical property (penalized logP). In the task of optimization of
penalized logP of drug-like molecules our model significantly outperforms
previous results
Vegetation maps based on remote sensing are informative predictors of habitat selection of grassland birds across a wetness gradient
Vegetation is a major environmental factor influencing habitat selection in bird species. High resolution mapping of vegetation cover is essential to model the distribution of populations and improve the management of breeding habitats. However, the task is challenging for grassland birds because microhabitat variations relevant at the territory scale cannot be measured continuously over large areas to delineate areas of higher suitability. Remote sensing may help to circumvent this problem. We addressed this issue by using two methods. We (i) mapped the continuous Ellenberg index of moisture and (ii) identified 5 vegetation classes distributed accross the wetness gradient. These two methods produced consistent output maps, but they also provided more information about vegetation structure, and possibly trophic resources. In spite of the apprent uniformity of meadows, our data show that birds do not settle randomly along the moisture and vegetation gradients. Overall birds tend to avoid the driest vegetation classes, i.e. the highest grounds. Thus, vegetation maps based on remote sensing could be valuable tools to study habitat selection and niche partition in grassland bird communities. It is also a valuable tool for conservation and habitat management
Plastid DNA variation in Prunus serotina var. serotina (Rosaceae), a North American tree invading Europe
Black cherry (Prunus serotina) is a tree from North America, where it is often used for economical purposes, whereas it is widespread and invasive in Europe. Plastid DNA variation was first investigated in both its native and invasive ranges using microsatellite loci and sequences of three intergenic spacers (trnT-trnL, trnD-trnT and trnS-trnG). This analysis was focused on P. serotina var. serotina, with the inclusion of samples of closely related taxa. Length variation at a microsatellite locus (ccmp5) and a few sequence polymorphisms were identified among P. serotina samples. Four new primer pairs were then designed to specifically amplify variable regions and a combination of five markers was finally proposed for phylogeographic studies in P. serotina. These loci allow identification of six chlorotypes in P. serotina var. serotina, which may be particularly useful to depict the maternal origins of European invasive population
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