Extracellular ATP/adenosine dynamics in the brain and its role in health and disease

Extracellular ATP and adenosine are neuromodulators that regulate numerous neuronal functions in the brain. Neuronal activity and brain insults such as ischemic and traumatic injury upregulate these neuromodulators, which exert their effects by activating purinergic receptors. In addition, extracellular ATP/adenosine signaling plays a pivotal role in the pathogenesis of neurological diseases. Virtually every cell type in the brain contributes to the elevation of ATP/adenosine, and various mechanisms underlying this increase have been proposed. Extracellular adenosine is thought to be mainly produced via the degradation of extracellular ATP. However, adenosine is also released from neurons and glia in the brain. Therefore, the regulation of extracellular ATP/adenosine in physiological and pathophysiological conditions is likely far more complex than previously thought. To elucidate the complex mechanisms that regulate extracellular ATP/adenosine levels, accurate methods of assessing their spatiotemporal dynamics are needed. Several novel techniques for acquiring spatiotemporal information on extracellular ATP/adenosine, including fluorescent sensors, have been developed and have started to reveal the mechanisms underlying the release, uptake and degradation of ATP/adenosine. Here, we review methods for analyzing extracellular ATP/adenosine dynamics as well as the current state of knowledge on the spatiotemporal dynamics of ATP/adenosine in the brain. We focus on the mechanisms used by neurons and glia to cooperatively produce the activity-dependent increase in ATP/adenosine and its physiological and pathophysiological significance in the brain

The Extragalactic Distance Scale without Cepheids IV

The Cepheid period-luminosity relation is the primary distance indicator used in most determinations of the Hubble constant. The tip of the red giant branch (TRGB) is an alternative basis. Using the new ANU SkyMapper Telescope, we calibrate the Tully Fisher relation in the I band. We find that the TRGB and Cepheid distance scales are consistent.Comment: ApJ in press 201

Dark and luminous matter in the NGC 3992 group of galaxies, I. The large barred spiral NGC 3992

Detailed neutral hydrogen observations have been obtained of the large barred spiral galaxy NGC 3992 and its three small companion galaxies, UGC 6923, UGC 6940, and UGC 6969. For the main galaxy, the HI distribution is regular with a low level radial extension outside the stellar disc. However, at exactly the region of the bar, there is a pronounced central HI hole in the gas distribution. Likely gas has been transported inwards by the bar and because of the emptyness of the hole no large accretion events can have happened in recent galactic times. The gas kinematics is very regular and it is demonstrated that the influence of the bar potential on the velocity field is negligible. A precise and extended rotation curve has been derived showing some distinct features which can be explained by the non-exponential radial light distribution of NGC 3992. The decomposition of the rotation curve gives a slight preference for a sub maximal disc, though a range of disc contributions, up to a maximum disc situation fits nearly equally well. For such a maximum disc contribution, which might be expected in order to generate and maintain the bar, the required mass-to-light ratio is large but not exceptional.Comment: accepted for publication in Astronomy and Astrophysics. A copy with high resolution graphics will shortly become available at http://www.astro.rug.nl/Preprints/preprints.htm

Development of Space-Flight Compatible Room-Temperature Electronics for the Lynx X-Ray Microcalorimeter

We are studying the development of space-flight compatible room-temperature electronics for the Lynx x-ray microcalorimeter (LXM) of the Lynx mission. The baseline readout technique for the LXM is microwave SQUID multiplexing. The key modules at room temperature are the RF electronics module and the digital electronics and event processor (DEEP). The RF module functions as frequency converters and mainly consists of local oscillators and I/Q mixers. The DEEP performs demultiplexing and event processing, and mainly consists of field-programmable gate arrays, ADCs, and DACs. We designed the RF electronics and DEEP to be flight ready, and estimated the power, size, and mass of those modules. There are two boxes each for the RF electronics and DEEP for segmentation, and the sizes of the boxes are 13 in: 13 in: 9 in: for the RF electronics and 15.5 in: 11.5 in: 9.5 in: for the DEEP. The estimated masses are 25.1 kgbox for the RF electronics box and 24.1 kgbox for the DEEP box. The maximum operating power for the RF electronics is 141 W or 70.5 Wbox, and for the DEEP box is 615 W or 308 Wbox. The overall power for those modules is 756 W. We describe the detail of the designs as well as the approaches to the estimation of resources, sizes, masses, and powers

The distance of M33 and the stellar population in its outskirts

We present deep V,I photometry of two $9.4' x 9.4' field in the outer regions of the M33 galaxy. We obtain a robust detection of the luminosity of the Red Giant Branch Tip (I{TRGB}=20.72 +- 0.08) from which we derived a new estimate of the distance modulus of M33, (m-M)_0=24.64 +- 0.15, corresponding to a distance D=847 +- 60 Kpc. By comparison of the color and magnitude of the observed Red Giant Branch stars with ridge lines of template globular clusters we obtained the photometric metallicity distribution of the considered fields in three different metallicity scales. The derived metallicity distributions are very similar over a range of distances from the galactic center 10' <= R <= 33', and are characterized by a well defined peak at [M/H] ~ -0.7 ([Fe/H] ~ -1.0, in the Zinn & West scale) and a weak metal-poor tail reaching [M/H] ~ -2.0. Our observations demonstrate that Red Giant Branch and Asymptotic Giant Branch stars have a radial distribution that is much more extended than the young MS stars associated with the star-forming disc.Comment: 10 pages,10 figures,accepted for publication in Astronomy & Astrophysic

Antlia Dwarf Galaxy: Distance, quantitative morphology and recent formation history via statistical field correction

We apply a statistical field correction technique originally designed to determine membership of high redshift galaxy clusters to Hubble Space Telescope imaging of the Antlia Dwarf Galaxy; a galaxy at the very edge of the Local Group. Using the tip of the red giant branch standard candle method coupled with a simple Sobel edge detection filter we find a new distance to Antlia of 1.31 +/- 0.03 Mpc. For the first time for a Local Group Member, we compute the concentration, asymmetry and clumpiness (CAS) quantitative morphology parameters for Antlia from the distribution of resolved stars in the HST/ACS field, corrected with a new method for contaminants and complement these parameters with the Gini coefficient (G) and the second order moment of the brightest 20 per cent of the flux (M_20). We show that it is a classic dwarf elliptical (C = 2.0, A = 0.063, S = 0.077, G = 0.39 and M_20 = -1.17 in the F814W band), but has an appreciable blue stellar population at its core, confirming on-going star-formation. The values of asymmetry and clumpiness, as well as Gini and M_20 are consistent with an undisturbed galaxy. Although our analysis suggests that Antlia may not be tidally influenced by NGC 3109 it does not necessarily preclude such interaction.Comment: Accepted for publication in MNRA

Thick disks and halos of spiral galaxies M 81, NGC 55 and NGC 300

By using images from the HST/WFPC2/ACS archive, we have analyzed the spatial distribution of the AGB and RGB stars along the galactocentric radius of nearby spiral galaxies M~81, NGC 300 and NGC 55. Using color-magnitude diagrams and stellar luminosity functions, we gauge the stellar contents of the surroundings of three galaxies. The red giant population (RGB) identified at large galactocentric radii yields a distance of $3.85\pm0.08$ Mpc for M~81, $2.12\pm0.10$ Mpc for NGC 55, and $2.00\pm0.13$ Mpc for NGC 300, and a mean stellar metallicity of $-$0.65, $-$1.25, and $-$0.87. We find that there are two number density gradients of RGB stars along the radius, which correspond to the thick disk and halo components of the galaxies. We confirm the presence of metallicity gradient of evolved stars at these galaxies, based on the systematic changes of the color distribution of red giant stars. These results imply that thick disk might be a general feature of the spiral galaxies, and endorse a further investigation of the outer stellar edges of nearby spirals, which is critical in constraining the origin and evolution of galaxies.Comment: 17 pages, 2 tables, 13 figures, accepted to A&

Age and Metallicity Distribution of the Galactic Bulge from Extensive Optical and Near-IR Stellar Photometry

We present a new determination of the metallicity distribution, age, and luminosity function of the Galactic bulge stellar population. By combining near-IR data from the 2MASS survey, from the SOFI imager at ESO NTT and the NICMOS camera on board HST we were able to construct color-magnitude diagrams (CMD) and luminosity functions (LF) with large statistics and small photometric errors from the Asymptotic Giant Branch (AGB) and Red Giant Branch (RGB) tip down to $\sim 0.15 M_\odot$. This is the most extended and complete LF so far obtained for the galactic bulge. Similar near-IR data for a disk control field were used to decontaminate the bulge CMDs from foreground disk stars, and hence to set stronger constraint on the bulge age, which we found to be as large as that of Galactic globular clusters, or \gsim 10 Gyr. No trace is found for any younger stellar population. Synthetic CMDs have been constructed to simulate the effect of photometric errors, blending, differential reddening, metallicity dispersion and depth effect in the comparison with the observational data. By combining the near-IR data with optical ones, from the Wide Field Imager at the ESO/MPG 2.2m telescope, a disk-decontaminated $(M_K,V-K)$ CMD has been constructed and used to derive the bulge metallicity distribution, by comparison with empirical RGB templates. The bulge metallicity is found to peak at near solar value, with a sharp cutoff just above solar, and a tail towards lower metallicity that does not appreciably extend below [M/H]$\sim-1.5$.Comment: 28 pages, 27 figures, A&A in press Full resolution version available at http://www.eso.org/~mzoccali/bulgepap

PE-46 The Design of the Lynx X-Ray Microcalorimeter

Lynx is an x-ray telescope, one of four large satellite mission concepts currently being studied by NASA to be the next astrophysics flagship mission after WFIRST. One of Lynx's three instruments is an imaging spectrometer consisting of an x-ray microcalorimeter behind an X-ray optic with an angular resolution of 0.5 arc-seconds and approximately 3 sq m of area at 1 keV. This instrument will provide unparalleled diagnostics of distant extended structures and in particular will allow the detailed study of the role of cosmic feedback in the evolution of the Universe. We discuss the design and read-out of the of the array configuration including a number of sub-array options for increasing the capabilities to maximize the scientific return of the Lynx observatory