Implications of New JHK Photometry and a Deep Infrared Luminosity Function for the Galactic Bulge

We present deep near-IR photometry for Galactic bulge stars in Baade's Window, $(l,b) = (1.0\deg, -3.9\deg),$ and another minor axis field at $(l,b) = (0^\circ,-6^\circ)$. We combine our data with previously published photometry and construct a luminosity function over the range $5.5 \leq K_0 \leq 16.5$, deeper than any previously published. The slope of this luminosity function and the magnitude of the tip of the first ascent giant branch are consistent with theoretical values derived from isochrones with appropriate age and metallicity. We use the relationship between [Fe/H] and the giant branch slope derived from near-IR observations of metal rich globular clusters by Kuchinski {\it et al.} [AJ, 109, 1131 (1995)] to calculate the mean metallicity for several bulge fields along the minor axis. For Baade's Window we derive $\langle {\rm[Fe/H]}\rangle = -0.28 \pm 0.16$, consistent with the recent estimate of McWilliam \& Rich [ApJS, 91, 749 (1994)], but somewhat lower than previous estimates based on CO and TiO absorption bands and the $JHK$ colors of M giants by Frogel {\it et al.} [ApJ, 353, 494 (1990)]. Between $b = -3\deg$ and $-12\deg$ we find a gradient in $\langle {\rm [Fe/H]}\rangle$ of $-0.06 \pm 0.03$ dex/degree or $-0.43 \pm 0.21$ dex/kpc for $R_0 = 8$ kpc, consistent with other independent derivations. We derive a helium abundance for Baade's Window with the $R$ and $R^\prime$ methods and find that $Y = 0.27 \pm 0.03$ implying $\Delta Y / \Delta Z = 3.3 \pm 1.3$. Next, we find that the bolometric corrections for bulge K giants ($V - K \leq 2$) are in excellent agreement with empirical derivations based on observations of globular cluster and local field stars. However, for the redder M giants weComment: Accepted by the Astronomical Journal. 43 pages, uuencoded compressed PostScript, no figures or tables. A complete (text, figs and tables) preprint is also available at ftp://bessel.mps.ohio-state.edu/pub/terndrup/bwphot.tar.Z (compressed tar file with PostScript

Vimentin expression influences flow dependent VASP phosphorylation and regulates cell migration and proliferation

The cytoskeleton plays a central role for the integration of biochemical and biomechanical signals across the cell required for complex cellular functions. Recent studies indicate that the intermediate filament vimentin is necessary for endothelial cell morphogenesis e.g. in the context of leukocyte transmigration. Here, we present evidence, that the scaffold provided by vimentin is essential for VASP localization and PKG mediated VASP phosphorylation and thus controls endothelial cell migration and proliferation. Vimentin suppression using siRNA technique significantly decreased migration velocity by 50% (videomicroscopy), diminished transmigration activity by 42.5% (Boyden chamber) and reduced proliferation by 43% (BrdU-incorporation). In confocal microscopy Vimentin colocalized with VASP and PKG in endothelial cells. Vimentin suppression was accompanied with a translocation of VASP from focal contacts to the perinuclear region. VASP/Vimentin and PKG/Vimentin colocalization appeared to be essential for proper PKG mediated VASP phosphorylation because we detected a diminished expression of PKG and p(Ser239)-VASP in vimentin-suppressed cells, Furthermore, the induction of VASP phosphorylation in perfused arteries was markedly decreased in vimentin knockout mice compared to wildtypes. A link is proposed between vimentin, VASP phosphorylation and actin dynamics that delivers an explanation for the important role of vimentin in controlling endothelial cell morphogenesis

Antibody mimetic receptor proteins for label-free biosensors

The development of high sensitivity biosensors, for example for clinical diagnostics, requires the identification of suitable receptor molecules which offer high stability, specificity and affinity, even when embedded into solid-state biosensor transducers. Here, we present an electrochemical biosensor employing small synthetic receptor proteins (Mw < 15 kDa) which emulate antibodies but with improved stability, sensitivity and molecular recognition properties, in particular when immobilized on a solid sensor surface. The synthetic receptor protein is a non-antibody-based protein scaffold with variable peptide regions inserted to provide the specific binding, and was designed to bind anti-myc tag antibody (Mw � 150 kDa), as a proof-of-principle exemplar. Both the scaffold and the selected receptor protein were found to have high thermostability with melting temperatures of 101 �C and 85 �C, respectively. Furthermore, the secondary structures of the receptor protein were found to be very similar to that of the original native scaffold, despite the insertion of variable peptide loops that create the binding sites. A label-free electrochemical sensor was fabricated by functionalising a microfabricated gold electrode with the receptor protein. A change in the phase of the electrochemical impedance was observed when the biosensor was subjected to anti-myc tag antibodies at concentrations between 6.7 pM and 6.7 nM. These findings demonstrate that these non-antibody receptor proteins are excellent candidates for recognition molecules in label-free biosensors

Study of damage control systems for space station

Damage control systems for detecting and locating overboard and onboard leak and damage modes on space station

Bayesian Accretion Modeling: Axisymmetric Equatorial Emission in the Kerr Spacetime

The Event Horizon Telescope (EHT) has produced images of two supermassive black holes, Messier~87* (M 87*) and Sagittarius~A* (Sgr A*). The EHT collaboration used these images to indirectly constrain black hole parameters by calibrating measurements of the sky-plane emission morphology to images of general relativistic magnetohydrodynamic (GRMHD) simulations. Here, we develop a model for directly constraining the black hole mass, spin, and inclination through signatures of lensing, redshift, and frame dragging, while simultaneously marginalizing over the unknown accretion and emission properties. By assuming optically thin, axisymmetric, equatorial emission near the black hole, our model gains orders of magnitude in speed over similar approaches that require radiative transfer. Using 2017 EHT M 87* baseline coverage, we use fits of the model to itself to show that the data are insufficient to demonstrate existence of the photon ring. We then survey time-averaged GRMHD simulations fitting EHT-like data, and find that our model is best-suited to fitting magnetically arrested disks, which are the favored class of simulations for both M 87* and Sgr A*. For these simulations, the best-fit model parameters are within ${\sim}10\%$ of the true mass and within ${\sim}10^\circ$ for inclination. With 2017 EHT coverage and 1\% fractional uncertainty on amplitudes, spin is unconstrained. Accurate inference of spin axis position angle depends strongly on spin and electron temperature. Our results show the promise of directly constraining black hole spacetimes with interferometric data, but they also show that nearly identical images permit large differences in black hole properties, highlighting degeneracies between the plasma properties, spacetime, and most crucially, the unknown emission geometry when studying lensed accretion flow images at a single frequency.Comment: Accepted to ApJ, 16 pages, 10 figure

The Frequency of Barred Spiral Galaxies in the Near-IR

We have determined the fraction of barred galaxies in the H-band for a statistically well-defined sample of 186 spirals drawn from the Ohio State University Bright Spiral Galaxy survey. We find 56% of our sample to be strongly barred at H, while another 16% is weakly barred. Only 27% of our sample is unbarred in the near-infrared. The RC3 and the Carnegie Atlas of Galaxies both classify only about 30% of our sample as strongly barred. Thus strong bars are nearly twice as prevalent in the near-infrared as in the optical. The frequency of genuine optically hidden bars is significant, but lower than many claims in the literature: 40% of the galaxies in our sample that are classified as unbarred in the RC3 show evidence for a bar in the H-band, while for the Carnegie Atlas this fraction is 66%. Our data reveal no significant trend in bar fraction as a function of morphology in either the optical or H-band. Optical surveys of high redshift galaxies may be strongly biased against finding bars, as bars are increasingly difficult to detect at bluer rest wavelengths.Comment: LaTeX with AASTeX style file, 23 pages with 6 figures. Accepted for publication in The Astronomical Journal (Feb. 2000

Role of tyrosine M210 in the initial charge separation of reaction centers of Rhodobacter sphaeroides

Femtosecond spectroscopy was used in combination with site-directed mutagenesis to study the influence of tyrosine M210 (YM210) on the primary electron transfer in the reaction center of Rhodobacter sphaeroides. The exchange of YM210 to phenylalanine caused the time constant of primary electron transfer to increase from 3.5 f 0.4 ps to 16 f 6 ps while the exchange to leucine increased the time constant even more to 22 f 8 ps. The results suggest that tyrosine M210 is important for the fast rate of the primary electron transfer

The IRAC Shallow Survey

The IRAC shallow survey covers 8.5 square degrees in the NOAO Deep Wide-Field Survey in Bootes with 3 or more 30 second exposures per position. An overview of the survey design, reduction, calibration, star-galaxy separation, and initial results is provided. The survey includes approximately 370,000, 280,000, 38,000, and 34,000 sources brighter than the 5 sigma limits of 6.4, 8.8, 51, and 50 microJy at 3.6, 4.5, 5.8, and 8 microns respectively, including some with unusual spectral energy distributions.Comment: To appear in ApJS, Spitzer special issue. For full resolution see http://cfa-www.harvard.edu/irac/publication

Probing the atmosphere of a solar-like star by galactic microlensing at high magnification

We report a measurement of limb darkening of a solar-like star in the very high magnification microlensing event MOA 2002-BLG-33. A 15 hour deviation from the light curve profile expected for a single lens was monitored intensively in V and I passbands by five telescopes spanning the globe. Our modelling of the light curve showed the lens to be a close binary system whose centre-of-mass passed almost directly in front of the source star. The source star was identified as an F8-G2 main sequence turn-off star. The measured stellar profiles agree with current stellar atmosphere theory to within ~4% in two passbands. The effective angular resolution of the measurements is <1 micro-arcsec. These are the first limb darkening measurements obtained by microlensing for a Solar-like star.Comment: Accepted for publication in A&A Letters. 5 pages, 2 embedded colour ps figures plus 1 jpg figure. Version with all figures embedded available from: http://www.roe.ac.uk/~iab/moa33paper