OSSOS III - Resonant Trans-Neptunian Populations: Constraints from the first quarter of the Outer Solar System Origins Survey

The first two observational sky "blocks" of the Outer Solar System Origins Survey (OSSOS) have significantly increased the number of well-characterized observed trans-Neptunian objects (TNOs) in Neptune's mean motion resonances. We describe the 31 securely resonant TNOs detected by OSSOS so far, and we use them to independently verify the resonant population models from the Canada-France Ecliptic Plane Survey (CFEPS; Gladman et al. 2012), with which we find broad agreement. We confirm that the 5:2 resonance is more populated than models of the outer Solar System's dynamical history predict; our minimum population estimate shows that the high eccentricity (e>0.35) portion of the resonance is at least as populous as the 2:1 and possibly as populated as the 3:2 resonance. One OSSOS block was well-suited to detecting objects trapped at low libration amplitudes in Neptune's 3:2 resonance, a population of interest in testing the origins of resonant TNOs. We detected three 3:2 objects with libration amplitudes below the cutoff modeled by CFEPS; OSSOS thus offers new constraints on this distribution. The OSSOS detections confirm that the 2:1 resonance has a dynamically colder inclination distribution than either the 3:2 or 5:2 resonances. Using the combined OSSOS and CFEPS 2:1 detections, we constrain the fraction of 2:1 objects in the symmetric mode of libration to be 0.2-0.85; we also constrain the fraction of leading vs. trailing asymmetric librators, which has been theoretically predicted to vary depending on Neptune's migration history, to be 0.05-0.8. Future OSSOS blocks will improve these constraints.Comment: Accepted for publication in A

On the existence of energetic atoms in the upper atmosphere of exoplanet HD209458b

Stellar irradiation and particles forcing strongly affect the immediate environment of extrasolar giant planets orbiting near their parent stars. Here, we use far-ultraviolet emission spectra from HD209458 in the wavelength range (1180-1710)A to bring new insight to the composition and energetic processes in play in the gas nebula around the transiting planetary companion. In that frame, we consider up-to-date atmospheric models of the giant exoplanet where we implement non-thermal line broadening to simulate the impact on the transit absorption of superthermal atoms (HI, OI, and CII) populating the upper layers of the nebula. Our sensitivity study shows that for all existing models, a significant line broadening is required for OI and probably for CII lines in order to fit the observed transit absorptions. In that frame, we show that OI and CII are preferentially heated compared to the background gas with effective temperatures as large as T_{OI}/T_B~10 for OI and T_{CII}/T_B~5 for CII. By contrast, the situation is much less clear for HI because several models could fit the Lyman-a observations including either thermal HI in an atmosphere that has a dayside vertical column [HI]~1.05x10^{21} cm^{-2}, or a less extended thermal atmosphere but with hot HI atoms populating the upper layers of the nebula. If the energetic HI atoms are either of stellar origin or populations lost from the planet and energized in the outer layers of the nebula, our finding is that most models should converge toward one hot population that has an HI vertical column in the range [HI]_{hot}(2-4)x10^{13} cm^{-2} and an effective temperature in the range T_{HI}(1-1.3)x10^6 K, but with a bulk velocity that should be rather slow.Comment: 15 pages, 10 figures, corrected for typos, references remove

Ridge Formation and De-Spinning of Iapetus via an Impact-Generated Satellite

We present a scenario for building the equatorial ridge and de-spinning Iapetus through an impact-generated disk and satellite. This impact puts debris into orbit, forming a ring inside the Roche limit and a satellite outside. This satellite rapidly pushes the ring material down to the surface of Iapetus, and then itself tidally evolves outward, thereby helping to de-spin Iapetus. This scenario can de-spin Iapetus an order of magnitude faster than when tides due to Saturn act alone, almost independently of its interior geophysical evolution. Eventually, the satellite is stripped from its orbit by Saturn. The range of satellite and impactor masses required is compatible with the estimated impact history of Iapetus.Comment: 19 pages, 3 figures; Icarus, in pres

The Dynamics of Stellar Coronae Harboring Hot-jupiters II. A Space Weather Event on A Hot-jupiter

We carry out a numerical simulation depicting the effects of a Coronal Mass Ejection (CME) event on a close-in giant planet in an extrasolar system. We drive the CME in a similar manner as in simulations of space weather events on Earth. The simulation includes the planetary orbital motion, which leads to the forming of a comet-like planetary magnetotail which is oriented almost perpendicular to the direction of propagation of the CME. The combination of this feature and the fact that the CME does not expand much by the time it reaches the planet leads to a unique CME-magnetosphere interaction, where the CME itself is highly affected by the presence of the planetary magnetosphere. We find that the planet is well-shielded from CME penetration, even for a relatively weak internal magnetic field. The planetary angular momentum loss associated with such an event is negligible compared to the total planetary angular momentum. We also find that the energy which is deposited in the magnetosphere is much higher than in the case of the Earth, and our simulation suggests there is a large-scale change in the orientation of the magnetosphere-ionosphere current system during the CME event.Comment: 16 pages, 10 figures, accepted to Ap

Checkpoints are blind to replication restart and recombination intermediates that result in gross chromosomal rearrangements

Replication fork inactivation can be overcome by homologous recombination, but this can cause gross chromosomal rearrangements that subsequently missegregate at mitosis, driving further chromosome instability. It is unclear when the chromosome rearrangements are generated and whether individual replication problems or the resulting recombination intermediates delay the cell cycle. Here we have investigated checkpoint activation during HR-dependent replication restart using a site-specific replication fork-arrest system. Analysis during a single cell cycle shows that HR-dependent replication intermediates arise in S phase, shortly after replication arrest, and are resolved into acentric and dicentric chromosomes in G2. Despite this, cells progress into mitosis without delay. Neither the DNA damage nor the intra-S phase checkpoints are activated in the first cell cycle, demonstrating that these checkpoints are blind to replication and recombination intermediates as well as to rearranged chromosomes. The dicentrics form anaphase bridges that subsequently break, inducing checkpoint activation in the second cell cycle

A key role for STIM1 in store operated calcium channel activation in airway smooth muscle

BACKGROUND: Control of cytosolic calcium plays a key role in airway myocyte function. Changes in intracellular Ca(2+ )stores can modulate contractile responses, modulate proliferation and regulate synthetic activity. Influx of Ca(2+ )in non excitable smooth muscle is believed to be predominantly through store operated channels (SOC) or receptor operated channels (ROC). Whereas agonists can activate both SOC and ROC in a range of smooth muscle types, the specific trigger for SOC activation is depletion of the sarcoplasmic reticulum Ca(2+ )stores. The mechanism underlying SOC activation following depletion of intracellular Ca(2+ )stores in smooth muscle has not been identified. METHODS: To investigate the roles of the STIM homologues in SOC activation in airway myocytes, specific siRNA sequences were utilised to target and selectively suppress both STIM1 and STIM2. Quantitative real time PCR was employed to assess the efficiency and the specificity of the siRNA mediated knockdown of mRNA. Activation of SOC was investigated by both whole cell patch clamp electrophysiology and a fluorescence based calcium assay. RESULTS: Transfection of 20 nM siRNA specific for STIM1 or 2 resulted in robust decreases (>70%) of the relevant mRNA. siRNA targeted at STIM1 resulted in a reduction of SOC associated Ca(2+ )influx in response to store depletion by cyclopiazonic acid (60%) or histamine but not bradykinin. siRNA to STIM2 had no effect on these responses. In addition STIM1 suppression resulted in a more or less complete abrogation of SOC associated inward currents assessed by whole cell patch clamp. CONCLUSION: Here we show that STIM1 acts as a key signal for SOC activation following intracellular Ca(2+ )store depletion or following agonist stimulation with histamine in human airway myocytes. These are the first data demonstrating a role for STIM1 in a physiologically relevant, non-transformed endogenous expression cell model

Genome-to-genome analysis highlights the effect of the human innate and adaptive immune systems on the hepatitis C virus

Outcomes of hepatitis C virus (HCV) infection and treatment depend on viral and host genetic factors. Here we use human genome-wide genotyping arrays and new whole-genome HCV viral sequencing technologies to perform a systematic genome-to-genome study of 542 individuals who were chronically infected with HCV, predominantly genotype 3. We show that both alleles of genes encoding human leukocyte antigen molecules and genes encoding components of the interferon lambda innate immune system drive viral polymorphism. Additionally, we show that IFNL4 genotypes determine HCV viral load through a mechanism dependent on a specific amino acid residue in the HCV NS5A protein. These findings highlight the interplay between the innate immune system and the viral genome in HCV control

Origin and Evolution of Saturn's Ring System

The origin and long-term evolution of Saturn's rings is still an unsolved problem in modern planetary science. In this chapter we review the current state of our knowledge on this long-standing question for the main rings (A, Cassini Division, B, C), the F Ring, and the diffuse rings (E and G). During the Voyager era, models of evolutionary processes affecting the rings on long time scales (erosion, viscous spreading, accretion, ballistic transport, etc.) had suggested that Saturn's rings are not older than 100 My. In addition, Saturn's large system of diffuse rings has been thought to be the result of material loss from one or more of Saturn's satellites. In the Cassini era, high spatial and spectral resolution data have allowed progress to be made on some of these questions. Discoveries such as the ''propellers'' in the A ring, the shape of ring-embedded moonlets, the clumps in the F Ring, and Enceladus' plume provide new constraints on evolutionary processes in Saturn's rings. At the same time, advances in numerical simulations over the last 20 years have opened the way to realistic models of the rings's fine scale structure, and progress in our understanding of the formation of the Solar System provides a better-defined historical context in which to understand ring formation. All these elements have important implications for the origin and long-term evolution of Saturn's rings. They strengthen the idea that Saturn's rings are very dynamical and rapidly evolving, while new arguments suggest that the rings could be older than previously believed, provided that they are regularly renewed. Key evolutionary processes, timescales and possible scenarios for the rings's origin are reviewed in the light of tComment: Chapter 17 of the book ''Saturn After Cassini-Huygens'' Saturn from Cassini-Huygens, Dougherty, M.K.; Esposito, L.W.; Krimigis, S.M. (Ed.) (2009) 537-57

Comparison of SPECT bone scintigraphy with MRI for diagnosis of meniscal tears

BACKGROUND: Scintigraphy has been considered as competitive to MRI, but limited data are available on the accuracy of single photon emission tomography (SPECT) compared with MRI for the assessment of meniscal tears. Our objective was to assess the value of SPECT in comparison to MRI. METHODS: Between January 2003 and March 2004, sixteen patients were studied with both modalities and the accuracy rates of SPECT scan results, and MRI findings in the diagnosis of meniscal tears were compared. Arthroscopy was the gold standard. RESULTS: The respective sensitivity rate, specificity rate, and positive and negative predictive accuracies of MRI were 89%, 94%, 93%, and 79% and for SPECT those were 78%, 94%, 94%, and 88%. There was good agreement on the presence or absence of tears between two modalities (κ statistic = 0.699). CONCLUSION: SPECT and MRI are both valuable imaging techniques. SPECT is a useful alternative when MRI is unavailable or unsuitable and it is beneficial when more possible accuracy is desired (such as when MRI results are either inconclusive or conflict with other clinical data)

Implementation of a suite of components for Software Defined Radio using an SCA-compliant framework

The aim of this work is to introduce Software Defined Radio (SDR) technology, present an open source SCA-compliant framework whose name is Redhawk, which derives from the OSSIE project and describes an implementation example of some processing instances. Since in SDR applications it is necessary to run the same software on different hardware, portability becomes the main important aspect in the development of software radio applica- tions. The use of a SCA-compliant framework solves this issue making hardware transparent to the programmer and reducing time and costs of code development. This aspect can be exploited for prototyping applications quickly without the need of a spe- cific hardware or testing new standards and protocols. We will introduce some basic concepts of SDR, of the SCA architecture, based on CORBA, and Redhawk. We will then talk about of the implementation of a suite of components, writ- ten by using Redhawk IDE and C++ programming language. These will be tied together to form an application called waveform. We will also present the results obtained by enforcing a certain level of parallelism in our algorithm to speed up computation in Redhawk components and boost performances against a more simpler non concurrent implementation of the same algorithms