Prospects for the habitability of OGLE-2006-BLG-109L

The extrasolar system OGLE-2006-BLG-109L is the first multiple-planet system to be discovered by gravitational microlensing (Gaudi et al., 2008); the two large planets that have been detected have mass ratios, semimajor axis ratios, and equilibrium temperatures that are similar to those of Jupiter and Saturn; the mass of the host star is only 0.5 M_sun, and the system is more compact than our own Solar system. We find that in the habitable zone of the host star, the two detected planets resonantly excite large orbital eccentricities on a putative earth-mass planet, driving such a planet out of the habitable zone. We show that an additional inner planet of ~>0.3M_earth at <~0.1 AU would suppress the eccentricity perturbation and greatly improve the prospects for habitability of the system. Thus, the planetary architecture of a potentially habitable OGLE-2006-BLG-109L planetary system -- with two ``terrestrial'' planets and two jovian planets -- could bear very close resemblance to our own Solar system.Comment: 11 pages including 4 figures; accepted for publication in ApJ-Letter

Dust outflows and inner gaps generated by massive planets in debris disks

Main sequence stars are commonly surrounded by debris disks, formed by cold far-IR-emitting dust that is thought to be continuously replenished by a reservoir of undetected dust-producing planetesimals. We have investigated the orbital evolution of dust particles in debris disks harboring massive planets. Small dust grains are blown out by radiation pressure, as is well known; in addition, gravitational scattering by the giant planets also creates an outflow of large grains. We describe the characteristics of this large-particle outflow in different planetary architectures and for different particle sizes. In addition, the ejection of particles is responsible for the clearing of dust inside the orbit of the planet. We study the efficiency of particle ejection and the resulting dust density contrast inside and outside the orbit of the planet, as a function of the planet's mass and orbital elements and the particle size. We discuss its implications for exo-planetary debris disks and for the interpretation of in-situ dust detection experiments on space probes traveling in the outer solar system.Comment: 32 pages (pre-print format), including 12 figures. Accepted to ApJ (2005). Due to space constrains Fig. 3-6 are at very low resolutio

Exercise and hypertrophic cardiomyopathy: Two incompatible entities?

A greater understanding of the pathogenic mechanisms underpinning hypertrophic cardiomyopathy (HCM) has translated to improved medical care and better survival of affected individuals. Historically these patients were considered to be at high risk of sudden cardiac death (SCD) during exercise; therefore, exercise recommendations were highly conservative and promoted a sedentary life style. There is emerging evidence that suggests that exercise in HCM has a favorable effect on cardiovascular remodeling and moderate exercise programs have not raised any safety concerns. Furthermore, individuals with HCM have a similar burden of atherosclerotic risk factors as the general population in whom exercise has been associated with a reduction in myocardial infarction, stroke, and heart failure, especially among those with a high-risk burden. Small studies revealed that athletes who choose to continue with regular competition do not demonstrate adverse outcomes when compared to those who discontinue sport, and active individuals implanted with an implantable cardioverter defibrillator do not have an increased risk of appropriate shocks or other adverse events. The recently published exercise recommendations from the European Association for Preventative Cardiology account for more contemporary evidence and adopt a more liberal stance regarding competitive and high intensity sport in individuals with low-risk HCM. This review addresses the issue of exercise in individuals with HCM, and explores current evidence supporting safety of exercise in HCM, potential caveats, and areas of further research

Demonstration of Extracellular Space by Freeze-Drying in the Cerebellar Molecular Layer

In electron micrographs of the molecular layer of the mouse cerebellum frozen within 30 sec of circulatory arrest and subsequently dried at -79 °C an appreciable extracellular space was found between the axons of the granular cells. Tight junctions were regularly observed between pre- and postsynaptic structures and the enveloping glia cells. In micrographs of cerebellum frozen 8 min after decapitation the space between the axons was absent and tight junctions between the nerve fibres were almost exclusively encountered. The extracellular space of asphyxiated and non-asphyxiated tissue in electron micrographs of frozen-dried material is similar to the space in comparable tissues treated by freeze-substitution. These observations suggest that there is an appreciable amount of extracellular material in oxygenated, living tissue which is taken up by cellular elements during asphyxiation

Secular resonance sweeping of the main asteroid belt during planet migration

We calculate the eccentricity excitation of asteroids produced by the sweeping $\nu_6$ secular resonance during the epoch of planetesimal-driven giant planet migration in the early history of the solar system. We derive analytical expressions for the magnitude of the eccentricity change and its dependence on the sweep rate and on planetary parameters; the $\nu_6$ sweeping leads to either an increase or a decrease of eccentricity depending on an asteroid's initial orbit. Based on the slowest rate of $\nu_6$ sweeping that allows a remnant asteroid belt to survive, we derive a lower limit on Saturn's migration speed of \sim0.15\AU\My^{-1} during the era that the $\nu_6$ resonance swept through the inner asteroid belt (semimajor axis range 2.1--2.8\AU). This rate limit is for Saturn's current eccentricity, and scales with the square of Saturn's eccentricity; the limit on Saturn's migration rate could be lower if Saturn's eccentricity were lower during its migration. Applied to an ensemble of fictitious asteroids, our calculations show that a prior single-peaked distribution of asteroid eccentricities would be transformed into a double-peaked distribution due to the sweeping of the $\nu_6$. Examination of the orbital data of main belt asteroids reveals that the proper eccentricities of the known bright ($H \leq10.8$) asteroids may be consistent with a double-peaked distribution. If so, our theoretical analysis then yields two possible solutions for the migration rate of Saturn and for the dynamical states of the pre-migration asteroid belt: a dynamically cold state (single-peaked eccentricity distribution with mean of $\sim0.05$) linked with Saturn's migration speed \sim 4\AU\My^{-1}, or a dynamically hot state (single-peaked eccentricity distribution with mean of $\sim0.3$) linked with Saturn's migration speed \sim 0.8\AU\My^{-1}.Comment: 32 pages, 7 figures. Accepted for publication in ApJ on Mar. 1, 201

Dynamic Resonance Effects in the Statistical Distributions of Asteroids and Comets

Some principles in the distribution of Centaurs and the "Scattered Disk" objects, as well as the Kuiper belt objects for its semi-major axes, eccentricities and inclinations of the orbits have been investigated. It has been established, that more than a half from them move on the resonant orbits and that is what has been predicted earlier. The divergence of the maximum in the observable distribution of the objects of the Kuiper belt for the semi-major axes with an exact orbital resonance has been interpreted.Comment: 7 pages, 5 figures, 1 table. International Conference "100 years since Tunguska phenomenon: Past, present and future", (June 26-28, 2008. Russia, Moscow), International Conference "Modern problems of astronomy" (August 12-18, 2007, Ukraine, Odessa

A Study of the Dynamics of Dust from the Kuiper Belt: Spatial Distribution and Spectral Energy Distribution

The dust produced in the Kuiper Belt (KB) spreads throughout the Solar System forming a dust disk. We numerically model the orbital evolution of KB dust and estimate its equilibrium spatial distribution and its brightness and spectral energy distributions (SED), assuming greybody absorption and emission by the dust grains. We show that the planets modify the KB disk SED, so potentially we can infer the presence of planets in spatially unresolved debris disks by studying the shape of their SEDs. We point out that there are inherent uncertainties in the prediction of structure in the dust disk, owing to the chaotic dynamics of dust orbital evolution imposed by resonant gravitational perturbations of the planets.Comment: 19 pages, 14 figures in jpg, accepted to A

JPL's Real-Time Weather Processor project (RWP) metrics and observations at system completion

As an integral part of the overall upgraded National Airspace System (NAS), the objective of the Real-Time Weather Processor (RWP) project is to improve the quality of weather information and the timeliness of its dissemination to system users. To accomplish this, an RWP will be installed in each of the Center Weather Service Units (CWSUs), located in 21 of the 23 Air Route Traffic Control Centers (ARTCCs). The RWP System is a prototype system. It is planned that the software will be GFE and that production hardware will be acquired via industry competitive procurement. The ARTCC is a facility established to provide air traffic control service to aircraft operating on Instrument Flight Rules (IFR) flight plans within controlled airspace, principally during the en route phase of the flight. Covered here are requirement metrics, Software Problem Failure Reports (SPFRs), and Ada portability metrics and observations

Gravitational Lensing as a Probe of Quintessence

A large number of cosmological studies now suggest that roughly two-thirds of the critical energy density of the Universe exists in a component with negative pressure. If the equation of state of such an energy component varies with time, it should in principle be possible to identify such a variation using cosmological probes over a wide range in redshift. Proper detection of any time variation, however, requires cosmological probes beyond the currently studied range in redshift of $\sim$ 0.1 to 1. We extend our analysis to gravitational lensing statistics at high redshift and suggest that a reliable sample of lensed sources, out to a redshift of $\sim$ 5, can be used to constrain the variation of the equation of state, provided that both the redshift distribution of lensed sources and the selection function involved with the lensed source discovery process are known. An exciting opportunity to catalog an adequate sample of lensed sources (quasars) to probe quintessence is now available with the ongoing Sloan Digital Sky Survey. Writing $w(z)\approx w_0 + z (dw/dz)_0$, we study the expected accuracy to which the equation of state today $w_0$ and its rate of change $(dw/dz)_0$ can simultaneously be constrained. Such a determination can rule out some missing-energy candidates, such as classes of quintessence models or a cosmological constant.Comment: Accepted for publication in ApJ Letters (4 pages, including 4 figures