SNARE proteins as molecular masters of interneuronal communication

In the beginning of the 20th century the groundbreaking work\ud of Ramon y Cajal firmly established the neuron doctrine, according to which neurons are the basic structural and functional units of the nervous system. Von Weldeyer coined the term “neuron” in 1891, but the huge leap forward in\ud neuroscience was due to Cajal’s meticulous microscopic observations of brain sections stained with an improved version of Golgi’s la reazione nera (black reaction). The latter improvement of Golgi’s technique made it possible to visualize the arborizations of single neurons that were “colored brownish black even to their finest branchlets, standing out with unsurpassable clarity upon a transparent yellow background. All was sharp as a sketch with Chinese ink”. The high quality of both the visualization of individual nerve cells and the work performed on studying the anatomy of the central nervous system lead Ramon y Cajal to the conclusion that axons output the nervous impulses to the dendrites or the soma of other target neurons

The connection between the peaks in velocity dispersion and star-forming clumps of turbulent galaxies

We present Keck/OSIRIS adaptive optics observations with 150-400 pc spatial sampling of 7 turbulent, clumpy disc galaxies from the DYNAMO sample ($0.07<z<0.2$). DYNAMO galaxies have previously been shown to be well matched in properties to main sequence galaxies at $z\sim1.5$. Integral field spectroscopy observations using adaptive optics are subject to a number of systematics including a variable PSF and spatial sampling, which we account for in our analysis. We present gas velocity dispersion maps corrected for these effects, and confirm that DYNAMO galaxies do have high gas velocity dispersion ($\sigma=40-80$\kms), even at high spatial sampling. We find statistically significant structure in 6 out of 7 galaxies. The most common distance between the peaks in velocity dispersion and emission line peaks is $\sim0.5$~kpc, we note this is very similar to the average size of a clump measured with HST H$\alpha$ maps. This could suggest that the peaks in velocity dispersion in clumpy galaxies likely arise due to some interaction between the clump and the surrounding ISM of the galaxy, though our observations cannot distinguish between outflows, inflows or velocity shear. Observations covering a wider area of the galaxies will be needed to confirm this result.Comment: Accepted for publication in MNRA

Assessing an intuitive condition for stability under a range of traffic conditions via a generalised Lu-Kumar network

We argue the importance both of developing simple sufficient conditions for the stability of general multiclass queueing networks and also of assessing such conditions under a range of assumptions on the weight of the traffic flowing between service stations. To achieve the former, we review a peak-rate stability condition and extend its range of application and for the latter, we introduce a generalisation of the Lu-Kumar network on which the stability condition may be tested for a range of traffic configurations. The peak-rate condition is close to exact when the between-station traffic is light, but degrades as this traffic increases.Multiclass queueing networks, stability, fluid model, Lu-Kumar network

The Near-Infrared Number Counts and Luminosity Functions of Local Galaxies

This study presents a wide-field near-infrared (K-band) survey in two fields; SA 68 and Lynx 2. The survey covers an area of 0.6 deg.$^2$, complete to K=16.5. A total of 867 galaxies are detected in this survey of which 175 have available redshifts. The near-infrared number counts to K=16.5 mag. are estimated from the complete photometric survey and are found to be in close agreement with other available studies. The sample is corrected for incompleteness in redshift space, using selection function in the form of a Fermi-Dirac distribution. This is then used to estimate the local near-infrared luminosity function of galaxies. A Schechter fit to the infrared data gives: M$^\ast_K = -25.1 \pm 0.3$, $\alpha = -1.3\pm 0.2$ and $\phi^\ast =(1.5\pm 0.5)\times 10^{-3}$ Mpc$^{-3}$ (for H$_0=50$ Km/sec/Mpc and q$_0=0.5$). When reduced to $\alpha=-1$, this agrees with other available estimates of the local IRLF. We find a steeper slope for the faint-end of the infrared luminosity function when compared to previous studies. This is interpreted as due to the presence of a population of faint but evolved (metal rich) galaxies in the local Universe. However, it is not from the same population as the faint blue galaxies found in the optical surveys. The characteristic magnitude ($M^\ast_K$) of the local IRLF indicates that the bright red galaxies ($M_K\sim -27$ mag.) have a space density of $\le 5\times 10^{-5}$ Mpc$^{-3}$ and hence, are not likely to be local objects.Comment: 24 pages, 8 figures, AASTEX 4.0, published in ApJ 492, 45

Pair Analysis of Field Galaxies from the Red-Sequence Cluster Survey

We study the evolution of the number of close companions of similar luminosities per galaxy (Nc) by choosing a volume-limited subset of the photometric redshift catalog from the Red-Sequence Cluster Survey (RCS-1). The sample contains over 157,000 objects with a moderate redshift range of 0.25 < z < 0.8 and absolute magnitude in Rc (M_Rc) < -20. This is the largest sample used for pair evolution analysis, providing data over 9 redshift bins with about 17,500 galaxies in each. After applying incompleteness and projection corrections, Nc shows a clear evolution with redshift. The Nc value for the whole sample grows with redshift as (1+z)^m, where m = 2.83 +/- 0.33 in good agreement with N-body simulations in a LCDM cosmology. We also separate the sample into two different absolute magnitude bins: -25 < M_Rc < -21 and -21 < M_Rc < -20, and find that the brighter the absolute magnitude, the smaller the m value. Furthermore, we study the evolution of the pair fraction for different projected separation bins and different luminosities. We find that the m value becomes smaller for larger separation, and the pair fraction for the fainter luminosity bin has stronger evolution. We derive the major merger remnant fraction f_rem = 0.06, which implies that about 6% of galaxies with -25 < M_Rc < -20 have undergone major mergers since z = 0.8.Comment: ApJ, in pres

Modeling and analysis of uncertain time-critical tasking problems

Naval Research Logistics, 53 , No. 6, (Sept. 2006), 588-599.This paper describes modeling and operational analysis of a generic asymmetric services-system situation in which (a) Red agents, potentially threatening, but in another but important interpretation, are isolated friendlies, such as downed pilots, that require assistance and "arrive" according to some partially known and potentially changing pattern in time and space: and (b) Reds have effectively limited unknown deadlines or times of availability for Blue service, i.e., detection, classification, and attack in a military setting or emergency assistance in others. We discuss various service options by Blue service agents and devise several approximations allowing one to compute efficiently those proportions of tasks of different classes that are successfully serviced, or more generally, if different rewards are associated with different classes of tasks, the percentage of the possible reward gained. We suggest heuristic policies of a Blue server to select the next task to perform and to decide how much time to allocate to that service. We discuss this for a number of specific examples