Protein kinase a distribution in meningioma

Deregulation of intracellular signal transduction pathways is a hallmark of cancer cells, clearly differentiating them from healthy cells. Differential intracellular distribution of the cAMP-dependent protein kinases (PKA) was previously detected in cell cultures and in vivo in glioblastoma and medulloblastoma. Our goal is to extend this observation to meningioma, to explore possible differences among tumors of different origins and prospective outcomes. The distribution of regulatory and catalytic subunits of PKA has been examined in tissue specimens obtained during surgery from meningioma patients. PKA RI subunit appeared more evenly distributed throughout the cytoplasm, but it was clearly detectable only in some tumors. RII was present in discrete spots, presumably at high local concentration; these aggregates could also be visualized under equilibrium binding conditions with fluorescent 8-substituted cAMP analogues, at variance with normal brain tissue and other brain tumors. The PKA catalytic subunit showed exactly overlapping pattern to RII and in fixed sections could be visualized by fluorescent cAMP analogues. Gene expression analysis showed that the PKA catalytic subunit revealed a significant correlation pattern with genes involved in meningioma. Hence, meningioma patients show a distinctive distribution pattern of PKA regulatory and catalytic subunits, different from glioblastoma, medulloblastoma, and healthy brain tissue. These observations raise the possibility of exploiting the PKA intracellular pathway as a diagnostic tool and possible therapeutic interventions

A Determination of the Hubble Constant from Cepheid Distances and a Model of the Local Peculiar Velocity Field

We present a measurement of the Hubble Constant based on Cepheid distances to 27 galaxies within 20 Mpc. We take the Cepheid data from published measurements by the Hubble Telescope Key Project on the Distance Scale (H0KP). We calibrate the Cepheid Period-Luminosity (PL) relation with data from over 700 Cepheids in the LMC obtained by the OGLE collaboration; we assume an LMC distance modulus of 18.50 mag (d=50.1 kpc). Using this PL calibration we obtain new distances to the H0KP galaxies. We correct the redshifts of these galaxies for peculiar velocities using two distinct velocity field models: the phenomenological model of Tonry et al. and a model based on the IRAS density field and linear gravitational instability theory. We combine the Cepheid distances with the corrected redshifts for the 27 galaxies to derive H_0, the Hubble constant. The results are H_0 = 85 +/- 5 km/s/Mpc (random error) at 95% confidence when the IRAS model is used, and 92 +/- 5 km/s/Mpc when the phenomenological model is used. The IRAS model is a better fit to the data and the Hubble constant it returns is more reliable. Systematic error stems mainly from LMC distance uncertainty which is not directly addressed by this paper. Our value of H_0 is significantly larger than that quoted by the H0KP, H_0 = 71 +/- 6 km/s/Mpc. Cepheid recalibration explains ~30% of this difference, velocity field analysis accounts for ~70%. We discuss in detail possible reasons for this discrepancy and future study needed to resolve it.Comment: 33 pages, 8 embedded figures. New table, 5 new references, text revision

Relation between Brown Dwarfs and Exoplanets

One of the most debated subjects in Astronomy since the discovery of exoplanets is how can we distinguish the most massive of such objects from very-low mass stars like Brown Dwarfs (BDs)? We have been looking for evidences of a difference in physical characteristics that could be related to different formation processes. Using a new diagnostic diagram that compares the baryonic gravitational potential (BGP) with the distances from their host stars, we have classified a sample of 355 well-studied exoplanets according to their possible structures. We have then compared the exoplanets to a sample of 87 confirmed BDs, identifying a range in BGP that could be common to both objects. By analyzing the mass-radius relations (MRR) of the exoplanets and BDs in those different BGP ranges, we were able to distinguish different characteristic behaviors. By comparing with models in the literature, our results suggest that BDs and massive exoplanets might have similar structures dominated by liquid metallic hydrogen (LMH).Comment: Poster #149 from proceeding of The 19th Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun; 06-10 June 2016, Uppsala, Swede

Asymptotic behavior of the Kleinberg model

We study Kleinberg navigation (the search of a target in a d-dimensional lattice, where each site is connected to one other random site at distance r, with probability proportional to r^{-a}) by means of an exact master equation for the process. We show that the asymptotic scaling behavior for the delivery time T to a target at distance L scales as (ln L)^2 when a=d, and otherwise as L^x, with x=(d-a)/(d+1-a) for ad+1. These values of x exceed the rigorous lower-bounds established by Kleinberg. We also address the situation where there is a finite probability for the message to get lost along its way and find short delivery times (conditioned upon arrival) for a wide range of a's

A road to hydrogenating graphene by a reactive ion etching plasma

We report the hydrogenation of single and bilayer graphene by an argon-hydrogen plasma produced in a reactive ion etching (RIE) system. Electronic transport measurements in combination with Raman spectroscopy are used to link the electric mean free path to the optically extracted defect concentration. We emphasize the role of the self-bias of the graphene in suppressing the erosion of the akes during plasma processing. We show that under the chosen plasma conditions the process does not introduce considerable damage to the graphene sheet and that hydrogenation occurs primarily due to the hydrogen ions from the plasma and not due to fragmentation of water adsorbates on the graphene surface by highly accelerated plasma electrons. For this reason the hydrogenation level can be precisely controlled. The hydrogenation process presented here can be easily implemented in any RIE plasma system.Comment: 7 page