362 research outputs found
Analytical and Numerical Estimates for Solar Radiation Pressure Semi-secular Resonances
The aim of this work is to provide new insights on the dynamics associated to
the resonances which arise as a consequence of the coupling of the effect due
to the oblateness of the Earth and the Solar Radiation Pressure (SRP) effect
for an uncontrolled object with moderate to high area-to-mass ratio. Analytical
estimates for the location of the resulting resonant equilibrium points are
provided, together with formulas to compute the maximum amplitude of the
corresponding variation in the eccentricity, as a function of the initial
conditions of the object and of its area-to-mass ratio. The period of the
variations of the eccentricity and inclinations due to such resonances is
estimated using classical formulas. A classification based on the strength of
the SRP resonances is provided. The estimates presented in the paper are
validated using numerical tools, including the use of Fast Lyapunov Indicators
to draw phase portraits and bifurcation diagrams. Many FLI maps depicting the
location and overlapping of SRP resonances are presented. The results from this
paper suggest that SRP resonances could be modeled in the context of either the
Extended Fundamental Model by [1] or the Second Fundamental Model by [2].
[1] S. Breiter. Extended fundamental model of resonance. Celestial Mechanics
and Dynamical Astronomy, 85:209-218, 03 (2003). doi: 10.1023/A:1022569419866
[2] J. Henrard and A. Lemaitre. A second fundamental model for resonance.
Celestial Mechanics, 30:197-218, (1983). doi: 10.1007/BF01234306Comment: 42 pages, 32 figure
Mimicking the kidney: A key role in organ-on-chip development
Pharmaceutical drug screening and research into diseases call for significant improvement in the effectiveness of current in vitro models. Better models would reduce the likelihood of costly failures at later drug development stages, while limiting or possibly even avoiding the use of animal models. In this regard, promising advances have recently been made by the so-called "organ-on-chip"(OOC) technology. By combining cell culture with microfluidics, biomedical researchers have started to develop microengineered models of the functional units of human organs. With the capacity to mimic physiological microenvironments and vascular perfusion, OOC devices allow the reproduction of tissue- and organ-level functions. When considering drug testing, nephrotoxicity is a major cause of attrition during pre-clinical, clinical, and post-approval stages. Renal toxicity accounts for 19% of total dropouts during phase III drug evaluation more than half the drugs abandoned because of safety concerns. Mimicking the functional unit of the kidney, namely the nephron, is therefore a crucial objective. Here we provide an extensive review of the studies focused on the development of a nephron-on-chip device
PBZ*-Lattices: Structure Theory and Subvarieties
We investigate the structure theory of the variety of \emph{PBZ*-lattices}
and some of its proper subvarieties. These lattices with additional structure
originate in the foundations of quantum mechanics and can be viewed as a common
generalisation of orthomodular lattices and Kleene algebras expanded by an
extra unary operation. We lay down the basics of the theories of ideals and of
central elements in PBZ*-lattices, we prove some structure theorems, and we
explore some connections with the theories of subtractive and binary
discriminator varieties.Comment: 29 page
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