Testing Planet Formation Models with Gaia μ\muas Astrometry

In this paper, we first summarize the results of a large-scale double-blind tests campaign carried out for the realistic estimation of the Gaia potential in detecting and measuring planetary systems. Then, we put the identified capabilities in context by highlighting the unique contribution that the Gaia exoplanet discoveries will be able to bring to the science of extrasolar planets during the next decade.Comment: 4 pages, 1 figure. To appear in the proceedings of "IAU Symposium 248 - A Giant Step: from Milli- to Micro-arcsecond Astrometry", held in Shanghai, China, 15-19 Oct. 200

Arginine 125 is an essential residue for the function of MRAP2

MRAP2 is a small simple transmembrane protein arranged in a double antiparallel topology on the plasma membrane. It is expressed in the paraventricular nucleus of the hypothalamus, where it interacts with various G protein-coupled receptors, such as the prokineticin receptors, and regulates energy expenditure and appetite. The aim of this work was to analyze the functional role of the specific arginine residue at position 125 of MRAP2, which affects protein conformation, dimer formation, and PKR2 binding. Results obtained with the MRAP2 mutants R125H and R125C, which are found in human patients with extreme obesity, and mouse MRAP2, in which arginine 125 is normally replaced by histidine, were compared with those obtained with human MRAP2. Understanding the mechanism by which MRAP2 regulates G protein-coupled receptors helps in elucidating the metabolic pathways involved in metabolic dysfunction and in developing new drugs as specific targets of the MRAP2-PKR2 complex

The GSC-II-based survey of ancient cool white dwarfs I. The sample of spectroscopically confirmed WDs

The GSC-II white dwarf survey was designed to identify faint and high proper motion objects, which we used to define a new and independent sample of cool white dwarfs. With this survey we aim to derive new constraints on the halo white dwarf space density. Also, these data can provide information on the age of thick disk and halo through the analysis of the luminosity function. On the basis of astrometric and photometric parameters, we selected candidates with mu > 0.28 as/yr and R_F > 16 in an area of 1150 square degrees. Then, we separated white dwarfs from late type dwarfs and subdwarfs by means of the reduced proper motion diagram. Finally, spectroscopic follow-up observations were carried out to confirm the white dwarf nature of the selected candidates. We found 41 white dwarfs of which 24 are new discoveries. Here we present the full sample and for each object provide positions, absolute proper motions, photometry, and spectroscopy.Comment: 14 pages, 7 figures, submitted to A&

Narrow-Angle Astrometry with the Space Interferometry Mission: The Search for Extra-Solar Planets. II. Detection and Characterization of Planetary Systems

(Abridged) The probability of detecting additional companions is essentially unchanged with respect to the single-planet configurations, but after fitting and subtraction of orbits with astrometric signal-to-noise ratio $\alpha/\sigma_d\to 1$ the false detection rates can be enhanced by up to a factor 2; the periodogram approach results in robust multiple-planet detection for systems with periods shorter than the SIM mission length, even at low values of $\alpha/\sigma_d$, while the least squares technique combined with Fourier series expansions is arguably preferable in the long-period regime. The accuracy on multiple-planet orbit reconstruction and mass determination suffers a typical degradation of 30-40% with respect to single-planet solutions; mass and orbital inclination can be measured to better than 10% for periods as short as 0.1 yr, and for $\alpha/\sigma_d$ as low as $\sim 5$, while $\alpha/\sigma_d\simeq 100$ is required in order to measure with similar accuracy systems harboring objects with periods as long as three times the mission duration. For systems with all components producing $\alpha/\sigma_d\simeq 10$ or greater, quasi-coplanarity can be reliably established with uncertainties of a few degrees, for periods in the range $0.1\leq T\leq 15$ yr; in systems where at least one component has $\alpha/\sigma_d\to 1$, coplanarity measurements are compromised, with typical uncertainties on the mutual inclinations of order of $30^\circ-40^\circ$. Our findings are illustrative of the importance of the contribution SIM will make to the fields of formation and evolution of planetary systems.Comment: 61 pages, 14 figures, 5 tables, to appear in the September 2003 Issue of the Publications of the Astronomical Society of the Pacifi

Controlling chaos in diluted networks with continuous neurons

Diluted neural networks with continuous neurons and nonmonotonic transfer function are studied, with both fixed and dynamic synapses. A noisy stimulus with periodic variance results in a mechanism for controlling chaos in neural systems with fixed synapses: a proper amount of external perturbation forces the system to behave periodically with the same period as the stimulus.Comment: 11 pages, 8 figure

Lessons from the Congested Clique Applied to MapReduce

The main results of this paper are (I) a simulation algorithm which, under quite general constraints, transforms algorithms running on the Congested Clique into algorithms running in the MapReduce model, and (II) a distributed $O(\Delta)$-coloring algorithm running on the Congested Clique which has an expected running time of (i) $O(1)$ rounds, if $\Delta \geq \Theta(\log^4 n)$; and (ii) $O(\log \log n)$ rounds otherwise. Applying the simulation theorem to the Congested-Clique $O(\Delta)$-coloring algorithm yields an $O(1)$-round $O(\Delta)$-coloring algorithm in the MapReduce model. Our simulation algorithm illustrates a natural correspondence between per-node bandwidth in the Congested Clique model and memory per machine in the MapReduce model. In the Congested Clique (and more generally, any network in the $\mathcal{CONGEST}$ model), the major impediment to constructing fast algorithms is the $O(\log n)$ restriction on message sizes. Similarly, in the MapReduce model, the combined restrictions on memory per machine and total system memory have a dominant effect on algorithm design. In showing a fairly general simulation algorithm, we highlight the similarities and differences between these models.Comment: 15 page

Testing planet formation models with Gaia μas astrometry

In this paper, we first summarize the results of a large-scale double-blind tests campaign carried out for the realistic estimation of the Gaia potential in detecting and measuring planetary systems. Then, we put the identified capabilities in context by highlighting the unique contribution that the Gaia exoplanet discoveries will be able to bring to the science of extrasolar planets during the next decad

Abnormal Pain Sensation in Mice Lacking the Prokineticin Receptor PKR2: Interaction of PKR2 with Transient Receptor Potential TRPV1 and TRPA1

The amphibian Bv8 and the mammalian prokineticin 1 (PROK1) and 2 (PROK2) are new chemokine-like protein ligands acting on two G protein-coupled receptors, prokineticin receptor 1 (PKR1) and 2 (PKR2), participating to the mediation of diverse physiological and pathological processes. Prokineticins (PKs), specifically activating the prokineticin receptors (PKRs) located in several areas of the central and peripheral nervous system associated with pain, play a fundamental role in nociception. In this paper, to improve the understanding of the prokineticin system in the neurobiology of pain, we investigated the role of PKR2 in pain perception using pkr2 gene-deficient mice. We observed that, compared to wildtype, pkr2-null mice were more resistant to nociceptive sensitization to temperatures ranging from 46 to 48 \ub0C, to capsaicin and to protons, highlighting a positive interaction between PKR2 and the non-selective cation channels TRPV1. Moreover, PKR2 knock-out mice showed reduced nociceptive response to cold temperature (4 \ub0C) and to mustard oil-induced inflammatory hyperalgesia, suggesting a functional interaction between PKR2 and transient receptor potential ankyrin 1 ion (TRPA1) channels. This notion was supported by experiments in dorsal root ganglia (DRG) cultures from pkr1 and\u2013pkr2-null mice, demonstrating that the percentage of Bv8-responsive DRG neurons which were also responsive to mustard oil was much higher in PKR1 12/ 12 than in PKR2 12/ 12 mice. Taken together, these findings suggest a functional interaction between PKR2 and TRP channels in the development of hyperalgesia. Drugs able to directly or indirectly block these targets and/or their interactions may represent potential analgesics