Near-Infrared Photometry of Globular Clusters NGC 6287 and NGC 6341 (M92): The Formation of the Galactic Halo

We present Hubble Space Telescope (HST) Near Infrared Camera and Multi-Object Spectrometer (NICMOS) camera 3 photometry of the inner halo globular cluster NGC 6287 and the intermediate halo globular cluster NGC 6341 (M92). Our photometric measurements range from the lower red giant branch to ≈3 mag below the main-sequence turnoff, allowing us to define accurate mean loci of the two clusters. Our relative age estimate between NGC 6287 and M92 using the color difference between the main-sequence turnoff and the base of the red giant branch shows that they essentially have the same ages within ±2 Gyr. The slightly different chemical compositions between the two clusters do not significantly influence our result. Our simulations using synthetic spectra show that the temperature dependence of the interstellar reddening law for the HST NICMOS photometric system could be a more serious problem in the relative age estimate using the color difference between the main-sequence turnoff and the base of the red giant branch. However, this effect adds no more than ±0.5–1 Gyr to the uncertainty in our relative age estimate. Our color-magnitude diagram of NGC 6287 shows a well-defined blue horizontal branch population. This is consistent with its age and metallicity. We also present the relative interstellar reddening toward NGC 6287 and distance modulus with respect to those of M92. We find E(B-V) = 0.62 and (m-M)0 = 14.35 for NGC 6287, which are generally in good agreement with previous estimates. Our photometry suggests that there exists a differential reddening across NGC 6287 with an amount of ΔE(B-V) = 0.07–0.09 mag, consistent with the previous study of Stetson & West. The Galactocentric distance of NGC 6287 becomes RGC = 1.6 kpc if R0 = 8.0 kpc. Based on our new radial velocity measurement for NGC 6287, the cluster's (minimum) apogalacticon distance is Ra ≈ 5.5 kpc, suggesting that NGC 6287 is an inner halo cluster. Within this framework, our results are consistent with the idea that the globular cluster formation must have been triggered everywhere at the same time in our Galaxy. In the appendices, we discuss that the interstellar extinction law of the HST NICMOS photometric system, particularly in the F110W passband, depends on the temperature of the stars in the sense that hotter stars suffer more interstellar absorption than cooler stars

Endogenous chloride channels of insect sf9 cells. Evidence for coordinated activity of small elementary channel units

The endogenous Cl- conductance of Spodoptera frugiperda (Sf9) cells was studied 20-35 h after plating out of either uninfected cells or cells infected by a baculovirus vector carrying the cloned beta-galactosidase gene (beta-Gal cells). With the cation Tris+ in the pipette and Na+ in the bath, the reversal potential of whole-cell currents was governed by the prevailing Cl- equilibrium potential and could be fitted by the Goldman-Hodgkin-Katz equation with similar permeabilities for uninfected and beta-Gal cells. In the frequency range 0.12 < f < 300 Hz, the power density spectrum of whole-cell Cl- currents could be fitted by three Lorentzians. Independent of membrane potential, >50% of the total variance of whole-cell current fluctuations was accounted for by the low frequency Lorentzian (fc = 0.40 +/- 0.03 Hz, n = 6). Single-Cl- channels showed complex gating kinetics with long lasting (seconds) openings interrupted by similar long closures. In the open state, channels exhibited fast burst-like closures. Since the patches normally contained more than a single channel, it was not possible to measure open and closed dwell-time distributions for comparing single-Cl- channel activity with the kinetic features of whole-cell currents. However, the power density spectrum of Cl- currents of cell-attached and excised outside-out patches contained both high and low frequency Lorentzian components, with the corner frequency of the slow component (fc = 0.40 +/- 0.02 Hz, n = 4) similar to that of whole-cell current fluctuations. Chloride channels exhibited multiple conductance states with similar Goldman-Hodgkin-Katz-type rectification. Single-channel permeabilities covered the range from approximately 0.6.10(-14) cm5/s to approximately 6.10(-14) cm3/s, corresponding to a limiting conductance (gamma 150/150) of approximately 3.5 pS and approximately 35 pS, respectively. All states reversed near the same membrane potential, and they exhibited similar halide ion selectivity, P1 > PCl approximately PBr. Accordingly, Cl- current amplitudes larger than current flow through the smallest channel unit resolved seem to result from simultaneous open/shut events of two or more channel units

Regulation of Cl- channels in normal and cystic fibrosis airway epithelial cells by extracellular ATP.

The rate of Cl- secretion by human airway epithelium is determined, in part, by apical cell membrane Cl- conductance. In cystic fibrosis airway epithelia, defective regulation of Cl- conductance decreases the capability to secrete Cl-. Here we report that extracytosolic ATP in the luminal bath of cultured human airway epithelia increased transepithelial Cl- secretion and apical membrane Cl- permeability. Single-channel studies in excised membrane patches revealed that ATP increased the open probability of outward rectifying Cl- channels. The latter effect occurs through a receptor mechanism that requires no identified soluble second messengers and is insensitive to probes of G protein function. These results demonstrate a mode of regulation of anion channels by binding ATP at the extracellular surface. Regulation of Cl- conductance by external ATP is preserved in cystic fibrosis airway epithelia

Stellar abundances and ages for metal-rich Milky Way globular clusters - Stellar parameters and elemental abundances for 9 HB stars in NGC6352

[ABRIDGED] Metal-rich globular clusters provide important tracers of the formation of our Galaxy. Moreover, and not less important, they are very important calibrators for the derivation of properties of extra-galactic metal-rich stellar populations. Nonetheless, only a few of the metal-rich globular clusters in the Milky Way have been studied using high-resolution stellar spectra to derive elemental abundances. In this paper we present elemental abundances for nine HB stars in the metal-rich globular cluster NGC6352. The elemental abundances are based on high-resolution, high signal-to-noise spectra obtained with VLT/UVES. The elemental abundances have been derived using standard LTE calculations. We find that NGC6352 has [Fe/H]= -0.55, is enhanced in the alpha-elements to about +0.2 dex for Ca, Si, and Ti relative to Fe. For the iron-peak elements we find solar values. Based on the spectroscopically derived stellar parameters we find that an E(B-V)=0.24 and (m-M) roughly equal to 14.05 better fits the data than the nominal values. An investigation of log(gf)-values for suitable FeI lines lead us to the conclusion that the commonly used correction to the May et al.(1974) data should not be employed. Note: only the postscript reproduces the finding chart correctly.Comment: 24 pages (including on-line only table with all equivalent width measurements), 12 figures, Accepted for publication in A&A. Note: only the postscript reproduces the finding chart correctl

A Hubble Space Telescope Survey for Resolved Companions of Planetary-Nebula Nuclei

We report results of an HST "snapshot" survey aimed at finding resolved binary companions of the central stars of Galactic planetary nebulae (PNe). Using WF/PC and WFPC2, we searched the fields of 113 PNe for stars whose close proximity to the central star suggests a physical association. We find 10 binary nuclei that are very likely to be physically associated, and another six that are possible binary associations. By correcting for interstellar extinction and placing the central stars' companions on the main sequence, we derive distances to the objects, and thereby significantly increase the number of PNe with reliable distances. Comparison of our derived distances with those obtained from various statistical methods shows that all of the latter have systematically overestimated the distances, by factors ranging up to a factor of two or more. We show that this error is most likely due to the fact that the properties of our PNe with binary nuclei are systematically different from those of PNe used heretofore to calibrate statistical methods. Specifically, our PNe tend to have lower surface brightnesses at the same physical radius than the traditional calibration objects. This difference may arise from a selection effect: the PNe in our survey are typically nearby, old nebulae, whereas most of the objects that calibrate statistical techniques are low-latitude, high-surface-brightness, and more distant nebulae. As a result, the statistical methods that seem to work well with samples of distant PNe, e.g., those in the Galactic bulge or external galaxies, may not be applicable to the more diverse population of local PNe.Comment: 37 text pages, 17 table pages, 9 figures. Accepted by Astronomical Journal for June 1999 issu

Portrait of Eric Rupert Dibbs as a Lieutenant in the Australian Imperial Force, Salisbury, England, 1916 [picture] /

Title devised by cataloguer from accompanying information.; Part of the Eric Rupert Dibbs collection of photographs.; Inscriptions: "ER Dibbs 1916; Ric [?] 16/11/16"--Right side of photo; "F. Fullton [?], Salisbury"--Bottom right of photo.; Condition: Soiled, scratched.; Also available in an electronic version via the Internet at: http://nla.gov.au/nla.pic-vn4739440