Radio Cores in Low-Luminosity AGN: ADAFs or Jets?

We have surveyed two large samples of nearby low-luminosity AGN with the VLA to search for flat-spectrum radio cores, similar to Sgr A* in the Galactic Center. Roughly one third of all galaxies are detected (roughly one half if HII transition objects are excluded from the sample), many of which have compact radio cores. Follow-up observations with the VLBA have confirmed that these cores are non-thermal in origin, with lower limits for the brightness temperatures around ~10^8 K. The brightest of these are resolved into linear structures. The radio spectral indices of the cores are quite flat (alpha~0), with no evidence for the highly inverted radio cores predicted in the ADAF model. Spectrum and morphology of the compact radio emission is typical for radio jets seen also in more luminous AGN. The emission-line luminosity seems to be correlated with the radio core flux. Together with the VLBI observations this suggests that optical and radio emission in at least half the low-luminosity Seyferts and LINERs are black hole powered. We find only a weak correlation between bulge luminosity and radio flux and an apparently different efficiency between elliptical and spiral galaxies for producing radio emission at a given optical luminosity.Comment: 5 pages, 2 figures, (ESO) LaTex, to appear in ``Black Holes in Binaries and Galactic Nuclei'', ESO workshop, eds. L. Kaper, E.P.J. van den Heuvel, P.A. Woudt, Springer Verlag; also available at http://www.mpifr-bonn.mpg.de/staff/hfalcke/publications.html#eso9

Synthesis and Cell Adhesive Properties of Linear and Cyclic RGD Functionalized Polynorbornene Thin Films

Described herein is the efficient synthesis and evaluation of bioactive arginine-glycine-aspartic acid (RGD) functionalized polynorbornene-based materials for cell adhesion and spreading. Polynorbornenes containing either linear or cyclic RGD peptides were synthesized by ring-opening metathesis polymerization (ROMP) using the well-defined ruthenium initiator [(H_(2)IMes)(pyr)_(2)(Cl)_(2)Ru═CHPh]. The random copolymerization of three separate norbornene monomers allowed for the incorporation of water-soluble polyethylene glycol (PEG) moieties, RGD cell recognition motifs, and primary amines for postpolymerization cross-linking. Following polymer synthesis, thin-film hydrogels were formed by cross-linking with bis(sulfosuccinimidyl) suberate (BS^3), and the ability of these materials to support human umbilical vein endothelial cell (HUVEC) adhesion and spreading was evaluated and quantified. When compared to control polymers containing either no peptide or a scrambled RDG peptide, polymers with linear or cyclic RGD at varying concentrations displayed excellent cell adhesive properties in both serum-supplemented and serum-free media. Polymers with cyclic RGD side chains maintained cell adhesion and exhibited comparable integrin binding at a 100-fold lower concentration than those carrying linear RGD peptides. The precise control of monomer incorporation enabled by ROMP allows for quantification of the impact of RGD structure and concentration on cell adhesion and spreading. The results presented here will serve to guide future efforts for the design of RGD functionalized materials with applications in surgery, tissue engineering, and regenerative medicine

On the Origin of Ultraviolet Emission and the Accretion Model of Low-luminosity AGNs

Low-luminosity active galactic nuclei (LLAGNs) are generally believed to be powered by an inner radiatively inefficient, advection-dominated accretion flow (ADAF), an outer truncated thin disk, and a jet. Maoz (2007) recently challenged this picture based on the observation that the strength of ultraviolet emission relative to the X-ray and radio bands does not depart from empirical trends defined by more luminous sources. He advocates that AGNs across all luminosities have essentially the same accretion and radiative processes, which in luminous sources are described by a standard optically thick, geometrically thin disk. We calculate ADAF models and demonstrate that they can successfully fit the observed spectral energy distributions of the LLAGNs in Maoz's sample. Our model naturally accommodates the radio and X-ray emission, and the ultraviolet flux is well explained by a combination of the first-order Compton scattering in the ADAF, synchrotron emission in the jet, and black body emission in the truncated thin disk. It is premature to dismiss the ADAF model for LLAGNs. The UV data can be fit equally well using a standard thin disk, but an additional corona and jet would be required to account for the X-ray and radio emission. We argue that there are strong theoretical reasons to prefer the ADAF model over the thin disk scenario. We discuss testable predictions that can potentially discriminate between the two accretion models.Comment: 20 pages, 3 figures; ApJ in pres

ACUTE EFFECTS OF STRENGTH TRAINING ON RUNNING ECONOMY

Sequencing strength training before aerobic conditioning is practised without empirical support. This study explored the acute effects of strength training on running economy and 3-D kinematics in five males. Running was performed on a treadmill at 12 and 14 km/h on three separate occasions. Trial 1 and 2 involved no strength training with data used to assess response stability of the variables. Before Trial 3, three sets of three repetitions at 85% of 1 repetition maximum of squat, bench press and deadlift with 3-5 minutes of rest were performed. Compared to Trial 2 no significant differences were observed when strength training was performed. Only a tendency of increased knee flexion (4.5°) at foot strike at the higher running velocity was observed. This suggests that running kinematics were changed exposing participants to long-term chronic injuries

Two Populations of Molecular Clouds in the Antennae Galaxies

Super star clusters --- extremely massive clusters found predominately in starburst environments --- are essential building blocks in the formation of galaxies and thought to dominate star formation in the high-redshift universe. However, the transformation from molecular gas into these ultra-compact star clusters is not well understood. To study this process, we used the Submillimeter Array and the Plateau de Bure Interferometer to obtain high angular resolution (~1.5" or 160 pc) images of the Antennae overlap region in CO(2--1) to search for the molecular progenitors of the super star clusters. We resolve the molecular gas distribution into a large number of clouds, extending the differential cloud mass function down to a 5\sigma completeness limit of 3.8x10^5 M_sun. We identify a distinct break in the mass function around log M_mol/M_sun ~ 6.5, which separates the molecular clouds into two distinct populations. The smaller, less massive clouds reside in more quiescent areas in the region, while the larger, more massive clouds cluster around regions of intense star formation. A broken power-law fit to the mass function yields slopes of \alpha = -1.39+/-0.10 and \alpha = -1.44+/-0.14 for the low- and high-mass cloud population, well-matched to the mass function found for super star clusters in the Antennae galaxies. We find large velocity gradients and velocity dispersions at the locations of intense star formation, suggestive of compressive shocks. It is likely that these environmental factors contribute to the formation of the observed massive molecular clouds and super star clusters in the Antennae galaxies.Comment: 20 pages, 13 figures, accepted by Ap

Parasitic copepods from Egyptian Red Sea fishes: Bomolochidae Claus, 1875

© The Author(s) 2015 Open Access - This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The attached file is the published version of the article

Revisiting the "Fundamental Plane" of Black Hole Activity at Extremely Low Luminosities

We investigate the origin of the X-ray emission in low-luminosity AGNs (LLAGNs). Yuan & Cui (2005) predicted that the X-ray emission should originate from jets rather than from an advection-dominated accretion flow (ADAF) when the X-ray luminosity $L_{\rm X}$ of the source is below a critical value of $L_{\rm X,crit} \approx 10^{-6}L_{\rm Edd}$. This prediction implies that the X-ray spectrum in such sources should be fitted by jets rather than ADAFs. Furthermore, below $L_{\rm X,crit}$ the correlation between radio ($L_{\rm R}$) and X-ray ($L_{\rm X}$) luminosities and the black hole mass ($M$)--the so-called fundamental plane of black hole activity--should deviate from the general correlation obtained by Merloni, Heinz & Di Matteo (2003) and become steeper. The Merloni et al. correlation is described by ${\rm log}L_{\rm R} =0.6{\rm log}L_{\rm X}+0.78{\rm log}M+7.33$, while the predicted correlation is ${\rm log}L_{\rm R}=1.23{\rm log}L_{\rm X} +0.25{\rm log}M-13.45$. We collect data from the literature to check the validity of these two expectations. We find that among the 16 LLAGNs with good X-ray and radio spectra, 13 are consistent with the Yuan & Cui prediction. For the 22 LLAGNs with $L_{\rm X} < L_{\rm X,crit}$, the fundamental plane correlation is described by ${\rm log}L_{\rm R}=1.22{\rm log}L_{\rm X}+0.23{\rm log}M-12.46$, also in excellent agreement with the prediction.Comment: 24 pages, 2 tables, 3 figures; accepted by Ap

Quantification of O-glycosylation stoichiometry and dynamics using resolvable mass tags

Mechanistic studies of O-GlcNAc glycosylation have been limited by an inability to monitor the glycosylation stoichiometries of proteins obtained from cells. Here we describe a powerful method to visualize the O-GlcNAc–modified protein subpopulation using resolvable polyethylene glycol mass tags. This approach enables rapid quantification of in vivo glycosylation levels on endogenous proteins without the need for protein purification, advanced instrumentation or expensive radiolabels. In addition, it establishes the glycosylation state (for example, mono-, di-, tri-) of proteins, providing information regarding overall O-GlcNAc site occupancy that cannot be obtained using mass spectrometry. Finally, we apply this strategy to rapidly assess the complex interplay between glycosylation and phosphorylation and discover an unexpected reverse 'yin-yang' relationship on the transcriptional repressor MeCP2 that was undetectable by traditional methods. We anticipate that this mass-tagging strategy will advance our understanding of O-GlcNAc glycosylation, as well as other post-translational modifications and poorly understood glycosylation motifs