A FIRST DETERMINATION OF THE SURFACE DENSITY OF GALAXY CLUSTERS AT VERY LOW X--RAY FLUXES

We present the first results of a serendipitous search for clusters of galaxies in deep ROSAT-PSPC pointed observations at high galactic latitude. The survey is being carried out using a Wavelet based Detection Algorithm which is not biased against extended, low surface brightness sources. A new flux--diameter limited sample of 10 cluster candidates has been created from $\rm\sim 3 \, deg^2$ surveyed area. Preliminary CCD observations have revealed that a large fraction of these candidates correspond to a visible enhancement in the galaxy surface density, and several others have been identified from other surveys. We believe these sources to be either low--moderate redshift groups or intermediate to high redshift clusters. We show X-ray and optical images of some of the clusters identified to date. We present, for the first time, the derived number density of the galaxy clusters to a flux limit of $\rm 1\cdot 10^{-14} erg cm^{-2} s^{-1}$ (0.5--2.0 keV). This extends the $\log N$--$\log S$ of previous cluster surveys by more than one decade in flux. Results are compared to theoretical predictions for cluster number counts.Comment: uuencoded compressed Postscript, 7 pages including 4 figures. Accepted for publication in Ap. J. Letters

Magma Transfer and Evolution in Channels within the Arc Crust: the Pyroxenitic Feeder Pipes of Sapat (Kohistan, Pakistan)

Our understanding of the mode of transfer and evolution of arc magmas in the lower arc crust is limited by the accessibility of arc roots, which are mainly documented by remote geophysical methods. At the same time, the fractionation processes of primitive parental melts defining a liquid line of descent from basalt to dacite are well defined by experimental petrology. However, the structural evidence for transfer of magmas evolving during their ascent remains basically uncharacterized. The Sapat Complex represents a lower crust segment of the exhumed Kohistan paleo-island arc and exposes kilometer-sized pyroxenite bodies that grew at the expense of host metagabbroic sill sequences. The largest of these pyroxenite bodies are mainly composed of wehrlite to olivine-clinopyroxenite, whereas the smaller bodies show a sequence of cumulative rocks, from ol-clinopyroxenite through various gabbros to tonalite. Inside the bodies, vertical magmatic and reactional structures indicate magma ascent accompanied by cumulate formation. Altogether, cumulates document the evolution of an initially primitive basaltic melt (at ∼7 kbar) that contained ≥5 wt % H2O. After cotectic olivine and clinopyroxene fractionation, the appearance of hornblende at the expense of clinopyroxene marks a stepping stone in the melt evolution. From this point, the appearance of orthopyroxene and hornblende at the expense of olivine drives the magma towards an andesitic composition, from which the crystallization of An-rich plagioclase and hornblende drives the melt to evolve further. During peritectic hornblende crystallization fluid-precipitated assemblages occur showing that the melts have reached water-saturation while they were crystallizing and percolating, thus degassing H2O-rich fluids. Structural observations, mineral and bulk-rock compositions, and calculated seismic P-wave velocities identify the ultramafic pipe-shaped bodies as magmatic conduits in which melt ascended from the mantle through the lower crust to feed upper crustal magma chambers and volcanic system

The competitive NMDA antagonist CPP protects substantia nigra neurons from MPTP-induced degeneration in primates

Degeneration of nigrostriatal dopaminergic neurons is the primary histopathological feature of Parkinson's disease. The neurotoxin MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) induces a neurological syndrome in man and non-human primates very similar to idiopathic Parkinson's disease by selectively destroying dopaminergic nigrostriatal neurons. This gives rise to the hypothesis that Parkinson's disease may be caused by endogenous or environmental toxins. Endogenous excitatory amino acids (EAAs) such as L-glutamate could be involved in neurodegenerative disorders including Parkinson's disease. We report in this study that the competitive NMDA antagonist CPP (3-((+/-)-2-carboxypiperazin-4-yl)-propyl-1-phosphonic acid) protects nigral tyrosine hydroxylase (TH) positive neurons from degeneration induced by systemic treatment with MPTP in common marmosets. This indicates that EAAs are involved in the pathophysiological cascade of MPTP-induced neuronal cell death and that EAA antagonists may offer a neuroprotective therapy for Parkinson's disease

Integrated measurement of the mass and surface charge of discrete microparticles using a suspended microchannel resonator

Supporting Information Available: Detailed examinations of the algorithms that have been described in the manuscript for use in signal processing. (PDF) This information is available free of charge via the Internet at http://pubs.acs.org.Measurements of the mass and surface charge of microparticles are employed in the characterization of many types of colloidal dispersions. The suspended microchannel resonator (SMR) is capable of measuring individual particle masses with femtogram resolution. Here, we employ the high sensitivity of the SMR resonance frequency to changes in particle position, relative to the cantilever tip, to determine the electrophoretic mobility of discrete particles in an applied electric field. When a sinusoidal electric field is applied to the suspended microchannel, the transient resonance frequency shift corresponding to a particle transit can be analyzed by digital signal processing to extract both the buoyant mass and electrophoretic mobility of each particle. These parameters, together with the mean particle density, can be used to compute the size, absolute mass, and surface charge of discrete microspheres, leading to a true representation of the mean and polydispersity of these quantities for a population. We have applied this technique to an aqueous suspension of two types of polystyrene microspheres, to differentiate them based on their absolute mass and their surface charge. The integrated measurement of electrophoretic mobility using the SMR is determined to be quantitative, based on comparison with commercial instruments, and exhibits favorable scaling properties that will ultimately enable measurements from mammalian cells.National Cancer Institute (U.S.) (Platform Partnership Grant R01-CA119402)Institute for Collaborative Biotechnologie

Pion photoproduction off the proton in a gauge-invariant chiral unitary framework

We investigate pion photoproduction off the proton in a manifestly gauge-invariant chiral unitary extension of chiral perturbation theory. In a first step, we consider meson-baryon scattering taking into account all next-to-leading order contact interactions. The resulting low-energy constants are determined by a fit to s-wave pion-nucleon scattering and the low-energy data for the reaction pi- p --> eta n. To assess the theoretical uncertainty, we perform two different fit strategies. Having determined the low-energy constants, we then analyse the data on the s-wave multipole amplitudes E0+ of pion and eta photoproduction. These are parameter-free predictions, as the two new low-energy constants are determined by the neutron and proton magnetic moments.Comment: 23 pages, 17 figure

The use of social media in undergraduate curriculum

Social media (SoMe) and mobile technology (MT) have been topics of interest to many educators, health professionals and policy developers over the last decade. This year, two editorials in leading nursing journals have described the potential for SoMe in nursing (Jones & Hayter 2013; Ferguson 2013). A recent Australian journal publication further supports the potential of SoMe and in particular Twitter (Wilson, R, et al. 2013). Increasingly, nurses and other health professionals and the general public are actively utilizing new technology to improve health and enhance practice (Barton, A 2012)]. To-date, there is limited evidence on the use of information technology and SoMe within the undergraduate nursing curriculum. Today’s students have a variety of technologies at their fingertips, from mobile devices to cloud technologies. It is imperative that higher education facilities look at innovative teaching methods to engage students in this digital era and enhance their learning. For the nursing and midwifery profession to innovate and remain current it must connect and collaborate with health care practitioners that exist outside of the traditional classroom. SoMe allows for this method of learning