Quincuncial adaptive closed Kohonen (QuACK) map for the irregularly shaped comet 67P/Churyumov-Gerasimenko

Context. Standard global map projections cannot display the complete surface of a highly irregular body such as the Rosetta target comet 67P/Churyumov-Gerasimenko because different points on the surface can have the same longitude and latitude. Aims. We present a concept of generalized longitudes and latitudes that allows us to display the complete comet in generalized versions of any standard map projection. Methods. A self-organizing Kohonen map can be used to sample the surface of any 3D shape, but the unfolded map misses some area beyond its edges. Here, we combine two square grids into an inherently closed structure that really maps the complete surface of the comet. Beyond this, the closed map is topologically equivalent to the Peirce quincuncial projection of the world, which enables the definition of generalized longitudes and latitudes. Results. While the generalized version of any map projection does not exactly share the properties of the original, such as preservation of area or shape, it behaves very similar. In particular, the generalized version of the quincuncial projection behaves very well over most of the surface area and shares the tessellation properties with its original. Conclusions. The quincuncial adaptive closed Kohonen (QuACK) map and the concept of generalized longitudes and latitudes provide means for global maps of arbitrarily irregular shapes.

Acute Neuroinflammatory Response in the Substantia Nigra Pars Compacta of Rats after a Local Injection of Lipopolysaccharide

Models of Parkinson’s disease with neurotoxins have shown that microglial activation does not evoke a typical inflammatory response in the substantia nigra, questioning whether neuroinflammation leads to neurodegeneration. To address this issue, the archetypal inflammatory stimulus, lipopolysaccharide (LPS), was injected into the rat substantia nigra. LPS induced fever, sickness behavior, and microglial activation (OX42 immunoreactivity), followed by astrocyte activation and leukocyte infiltration (GFAP and CD45 immunoreactivities). During the acute phase of neuroinflammation, pro- and anti-inflammatory cytokines (TNF-α, IL-1β, IL-6, IL-4, and IL-10) responded differentially at mRNA and protein level. Increased NO production and lipid peroxidation occurred at 168 h after LPS injection. At this time, evidence of neurodegeneration could be seen, entailing decreased tyrosine hydroxylase (TH) immunoreactivity, irregular body contour, and prolongation discontinuity of TH+ cells, as well as apparent phagocytosis of TH+ cells by OX42+ cells. Altogether, these results show that LPS evokes a typical inflammatory response in the substantia nigra that is followed by dopaminergic neurodegeneration.

Mapping Orbits regarding Perturbations due to the Gravitational Field of a Cube

The orbital dynamics around irregular shaped bodies is an actual topic in astrodynamics, because celestial bodies are not perfect spheres. When it comes to small celestial bodies, like asteroids and comets, it is even more import to consider the nonspherical shape. The gravitational field around them may generate trajectories that are different from Keplerian orbits. Modeling an irregular body can be a hard task, especially because it is difficult to know the exact shape when observing it from the Earth, due to their small sizes and long distances. Some asteroids have been observed, but it is still a small amount compared to all existing asteroids in the Solar System. An approximation of their shape can be made as a sum of several known geometric shapes. Some three-dimensional figures have closed equations for the potential and, in this work, the formulation of a cube is considered. The results give the mappings showing the orbits that are less perturbed and then have a good potential to be used by spacecrafts that need to minimize station-keeping maneuvers. Points in the orbit that minimizes the perturbations are found and they can be used for constellations of nanosatellites.