871 research outputs found

    Retrieving Neptune's aerosol properties from Keck OSIRIS observations. I. Dark regions

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    We present and analyze three-dimensional data cubes of Neptune from the OSIRIS integral-field spectrograph on the 10-m Keck telescope, from July 2009. These data have a spatial resolution of 0.035"/pixel and spectral resolution of R~3800 in the H and K broad bands. We focus our analysis on regions of Neptune's atmosphere that are near-infrared dark- that is, free of discrete bright cloud features. We use a forward model coupled to a Markov chain Monte Carlo algorithm to retrieve properties of Neptune's aerosol structure and methane profile above ~4 bar in these near-infrared dark regions. Using a set of high signal-to-noise spectra in a cloud-free band from 2-12N, we find that Neptune's cloud opacity is dominated by a compact, optically thick cloud layer with a base near 3 bar and composed of low albedo, forward scattering particles, with an assumed characteristic size of ~1ÎĽ\mum. Above this cloud, we require a vertically extended haze of smaller (~0.1 ÎĽ\mum) particles, which reaches from the upper troposphere (~0.6 bar) into the stratosphere. The particles in this haze are brighter and more isotropically scattering than those in the deep cloud. When we extend our analysis to 18 cloud-free locations from 20N to 87S, we observe that the optical depth in aerosols above 0.5 bar decreases by a factor of 2-3 or more at mid- and high-southern latitudes relative to low latitudes. We also consider Neptune's methane (CH4_4) profile, and find that our retrievals indicate a strong preference for a low methane relative humidity at pressures where methane is expected to condense. Our preferred solution at most locations is for a methane relative humidity below 10% near the tropopause in addition to methane depletion down to 2.0-2.5 bar. We tentatively identify a trend of lower CH4_4 columns above 2.5 bar at mid- and high-southern latitudes over low latitudes.Comment: Published in Icarus: 15 September 201

    Sampling Hypergraphs with Given Degrees

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    There is a well-known connection between hypergraphs and bipartite graphs, obtained by treating the incidence matrix of the hypergraph as the biadjacency matrix of a bipartite graph. We use this connection to describe and analyse a rejection sampling algorithm for sampling simple uniform hypergraphs with a given degree sequence. Our algorithm uses, as a black box, an algorithm A\mathcal{A} for sampling bipartite graphs with given degrees, uniformly or nearly uniformly, in (expected) polynomial time. The expected runtime of the hypergraph sampling algorithm depends on the (expected) runtime of the bipartite graph sampling algorithm A\mathcal{A}, and the probability that a uniformly random bipartite graph with given degrees corresponds to a simple hypergraph. We give some conditions on the hypergraph degree sequence which guarantee that this probability is bounded below by a constant

    Observational constraints on the distribution and temperature dependence of H_2O_2 on the surface of Europa

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    We use Keck NIRSPEC to investigate the geographic distribution of hydrogen peroxide, a potentially biologically important oxidant, on the surface of Europa. Contrary to expectation, we see the highest abundances at low latitudes, potentially correlated with geologically young chaos terrain. We also use NASA IRTF SpeX spectra of Europa before and after eclipse to investigate the extent to which temperature controls equilibrium hydrogen peroxide concentrations on the surface. During eclipse, Europa's surface temperature falls 10-20 K. If temperature were a significant control on peroxide concentrations, then the hydrogen peroxide band strengths should be different pre- and post-eclipse. Ultimately, these investigations will help further our understanding of the surface, and perhaps subsurface, composition of Europa

    Thermal Properties of the Icy Galilean Satellites from Millimeter ALMA Observations

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    We present spatially-resolved maps of the leading and trailing hemispheres of Europa, Ganymede, and Callisto from ALMA millimeter wavelength observations

    Heat shock protein 60 reactive T cells in juvenile idiopathic arthritis: what is new?

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    Juvenile idiopathic arthritis (JIA) is a disease characterized by chronic joint inflammation, caused by a deregulated immune response. In patients with JIA, heat shock proteins (HSPs) are highly expressed in the synovial lining tissues of inflamed joints. HSPs are endogenous proteins that are expressed upon cellular stress and are able to modulate immune responses. In this review, we concentrate on the role of HSPs, especially HSP60, in modulating immune responses in both experimental and human arthritis, with a focus on JIA. We will mainly discuss the tolerogenic immune responses induced by HSPs, which could have a beneficial effect in JIA. Overall, we will discuss the immune modulatory capacity of HSPs, and the underlying mechanisms of HSP60-mediated immune regulation in JIA, and how this can be translated into therapy

    A Nearby M Star with Three Transiting Super-Earths Discovered by K2

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    Small, cool planets represent the typical end-products of planetary formation. Studying the architectures of these systems, measuring planet masses and radii, and observing these planets' atmospheres during transit directly informs theories of planet assembly, migration, and evolution. Here we report the discovery of three small planets orbiting a bright (K_s = 8.6 mag) M0 dwarf using data collected as part of K2, the new ecliptic survey using the re-purposed Kepler spacecraft. Stellar spectroscopy and K2 photometry indicate that the system hosts three transiting planets with radii 1.5–2.1 R_⊕, straddling the transition region between rocky and increasingly volatile-dominated compositions. With orbital periods of 10–45 days the planets receive just 1.5–10× the flux incident on Earth, making these some of the coolest small planets known orbiting a nearby star; planet d is located near the inner edge of the system's habitable zone. The bright, low-mass star makes this system an excellent laboratory to determine the planets' masses via Doppler spectroscopy and to constrain their atmospheric compositions via transit spectroscopy. This discovery demonstrates the ability of K2 and future space-based transit searches to find many fascinating objects of interest

    Microbiological Quality of Raw Goat Milk in Bogor, Indonesia

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    Milk samples were investigated for counts and prevalence of indicator bacteria, which were TPC, coliforms, coagulase positive Staphylococci (CPS), and coagulase negative Staphylococci (CNS). Ten potential risk factors were also evaluated in relation to the prevalence of indicator bacteria. The results showed that the median values of indicator bacterial counts from overall udder-half milk samples were 3.74, 0.70, 1.70, and 2.52 log cfu/ml and from bulk milk samples were 5.69, 2.98, 3.66 and 3.32 log cfu/ml for TPC, coliforms, CPS, and CNS, respectively. None of the median values of overall udder-half milk samples exceeded the maximum limit of the standards for all indicator bacteria. However, in the bulk milk samples only the median value of TPC below the maximum limit of the standards. Overall prevalence of coliforms, CPS and CNS from udder-half milk samples were 46.3%, 37.7%, and 66.0%, respectively, and from bulk milk samples were 86.7%, 76.7%, and 86.7%, respectively. Saanen crossbreed, fifth parity and udders with inflammation were found to be risk factors. This study results indicated that the hygienic practices in the dairy goat farms are still need to be increased.  To increase the hygienic level of the milk, the identified significant risk factors must be controlled
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