Pose and Shape Reconstruction of a Noncooperative Spacecraft Using Camera and Range Measurements

Recent interest in on-orbit proximity operations has pushed towards the development of autonomous GNC strategies. In this sense, optical navigation enables a wide variety of possibilities as it can provide information not only about the kinematic state but also about the shape of the observed object. Various mission architectures have been either tested in space or studied on Earth. The present study deals with on-orbit relative pose and shape estimation with the use of a monocular camera and a distance sensor. The goal is to develop a filter which estimates an observed satellite's relative position, velocity, attitude, and angular velocity, along with its shape, with the measurements obtained by a camera and a distance sensor mounted on board a chaser which is on a relative trajectory around the target. The filter's efficiency is proved with a simulation on a virtual target object. The results of the simulation, even though relevant to a simplified scenario, show that the estimation process is successful and can be considered a promising strategy for a correct and safe docking maneuver

Equivariant KK-theory of GKM bundles

Given a fiber bundle of GKM spaces, $\pi\colon M\to B$, we analyze the structure of the equivariant $K$-ring of $M$ as a module over the equivariant $K$-ring of $B$ by translating the fiber bundle, $\pi$, into a fiber bundle of GKM graphs and constructing, by combinatorial techniques, a basis of this module consisting of $K$-classes which are invariant under the natural holonomy action on the $K$-ring of $M$ of the fundamental group of the GKM graph of $B$. We also discuss the implications of this result for fiber bundles $\pi\colon M\to B$ where $M$ and $B$ are generalized partial flag varieties and show how our GKM description of the equivariant $K$-ring of a homogeneous GKM space is related to the Kostant-Kumar description of this ring.Comment: 15 page

Dopaminergic neurons inhibit striatal output via non-canonical release of GABA

The substantia nigra pars compacta (SNc) and ventral tegmental area (VTA) contain the two largest populations of dopamine (DA)-releasing neurons in the mammalian brain. These neurons extend elaborate projections in striatum, a large subcortical structure implicated in motor planning and reward-based learning. Phasic activation of dopaminergic neurons in response to salient or reward-predicting stimuli is thought to modulate striatal output via the release of DA to promote and reinforce motor action1–4. Here we show that activation of DA neurons in striatal slices rapidly inhibits action potential firing in both direct-and indirect-pathway striatal projection neurons (SPNs) through vesicular release of the inhibitory transmitter γ-aminobutyric acid (GABA). GABA is released directly from dopaminergic axons but in a manner that is independent of the vesicular GABA transporter VGAT. Instead GABA release requires activity of the vesicular monoamine transporter VMAT2, which is the vesicular transporter for DA. Furthermore, VMAT2 expression in GABAergic neurons lacking VGAT is sufficient to sustain GABA release. Thus, these findings expand the repertoire of synaptic mechanisms employed by DA neurons to influence basal ganglia circuits, reveal a novel substrate whose transport is dependent on VMAT2, and demonstrate that GABA can function as a bona fide co-transmitter in monoaminergic neurons

Simultaneous multi-band detection of Low Surface Brightness galaxies with Markovian modelling

We present an algorithm for the detection of Low Surface Brightness (LSB) galaxies in images, called MARSIAA (MARkovian Software for Image Analysis in Astronomy), which is based on multi-scale Markovian modeling. MARSIAA can be applied simultaneously to different bands. It segments an image into a user-defined number of classes, according to their surface brightness and surroundings - typically, one or two classes contain the LSB structures. We have developed an algorithm, called DetectLSB, which allows the efficient identification of LSB galaxies from among the candidate sources selected by MARSIAA. To assess the robustness of our method, the method was applied to a set of 18 B and I band images (covering 1.3 square degrees in total) of the Virgo cluster. To further assess the completeness of the results of our method, both MARSIAA, SExtractor, and DetectLSB were applied to search for (i) mock Virgo LSB galaxies inserted into a set of deep Next Generation Virgo Survey (NGVS) gri-band subimages and (ii) Virgo LSB galaxies identified by eye in a full set of NGVS square degree gri images. MARSIAA/DetectLSB recovered ~20% more mock LSB galaxies and ~40% more LSB galaxies identified by eye than SExtractor/DetectLSB. With a 90% fraction of false positives from an entirely unsupervised pipeline, a completeness of 90% is reached for sources with r_e > 3" at a mean surface brightness level of mu_g=27.7 mag/arcsec^2 and a central surface brightness of mu^0 g=26.7 mag/arcsec^2. About 10% of the false positives are artifacts, the rest being background galaxies. We have found our method to be complementary to the application of matched filters and an optimized use of SExtractor, and to have the following advantages: it is scale-free, can be applied simultaneously to several bands, and is well adapted for crowded regions on the sky.Comment: 39 pages, 18 figures, accepted for publication in A

Temperature Chaos in Two-Dimensional Ising Spin Glasses with Binary Couplings: a Further Case for Universality

We study temperature chaos in a two-dimensional Ising spin glass with random quenched bimodal couplings, by an exact computation of the partition functions on large systems. We study two temperature correlators from the total free energy and from the domain wall free energy: in the second case we detect a chaotic behavior. We determine and discuss the chaos exponent and the fractal dimension of the domain walls.Comment: 5 pages, 6 postscript figures; added reference

Recurrent network activity drives striatal synaptogenesis

Neural activity during development critically shapes postnatal wiring of the mammalian brain. This is best illustrated by the sensory systems, in which the patterned feed-forward excitation provided by sensory organs and experience drives the formation of mature topographic circuits capable of extracting specific features of sensory stimuli1,2. In contrast, little is known about the role of early activity in the development of the basal ganglia, a phylogenetically ancient group of nuclei fundamentally important for complex motor action and reward-based learning3,4. These nuclei lack direct sensory input and are only loosely topographically organized5,6, forming interlocking feed-forward and feed-back inhibitory circuits without laminar structure. Here we use transgenic mice and viral gene transfer methods to modulate neurotransmitter release and neuronal activity in vivo in the developing striatum. We find that the balance of activity among the two inhibitory and antagonist pathways in the striatum regulates excitatory innervation of the basal ganglia during development. These effects indicate that the propagation of activity through a multi-stage network regulates the wiring of the basal ganglia, revealing an important role of positive feedback in driving network maturation

Factors associated with failed treatment : an analysis of 121,744 women embarking on their first IVF cycles

Peer reviewedPublisher PD

ERK and p38 MAPK Activities Determine Sensitivity to PI3K/mTOR Inhibition via Regulation of MYC and YAP

Aberrant activation of the PI3K/mTOR pathway is a common feature of many cancers and an attractive target for therapy, but resistance inevitably evolves as is the case for any cancer cell-targeted therapy. In animal tumor models, chronic inhibition of PI3K/mTOR initially inhibits tumor growth, but over time, tumor cells escape inhibition. In this study, we identified a context-dependent mechanism of escape whereby tumor cells upregulated the proto-oncogene transcriptional regulators c-MYC and YAP1. This mechanism was dependent on both constitutive ERK activity as well as inhibition of the stress kinase p38. Inhibition of p38 relieved proliferation arrest and allowed upregulation of MYC and YAP through stabilization of CREB. These data provide new insights into cellular signaling mechanisms that influence resistance to PI3K/mTOR inhibitors. Furthermore, they suggest that therapies that inactivate YAP or MYC or augment p38 activity could enhance the efficacy of PI3K/mTOR inhibitors.National Institutes of Health (U.S.) (Grant R01CA103866)National Institutes of Health (U.S.) (Grant AI47389