The Luminosity Function and Mass Function in the Galactic Bulge

We present deep photometry obtained with the Hubble Space Telescope (HST) in a field in Baade's Window in the Galactic bulge. We derive a luminosity function down to I ~ 24.3, or V ~ 27.5, corresponding to M ~ 0.3 Msun. The luminosity function from the turnoff down to this level appears remarkably similar to that observed in the solar neighborhood. We derive a mass function using both an empirical local mass-luminosity relation and a mass-luminosity relation from recent stellar model calculations, allowing for the presence of binaries and photometric errors. The mass function has a power law form with dN/dM proportional to M^{-2.2} for M >~ 0.7 Msun. However, we find strong evidence for a break in the mass function slope around 0.5-0.7 Msun, with a significantly shallower slope at lower masses. The value of the slope for the low masses depends on the assumed binary fraction and the accuracy of our completeness correction. This mass function should directly reflect the initial mass function.Comment: 26 pages, 9 figures, to be published in the Astronomical Journa

Practical detection of a definitive biomarker panel for Alzheimer's disease: comparisons between matched plasma and cerebrospinal fluid

Previous mass spectrometry analysis of cerebrospinal fluid (CSF) has allowed the identification of a panel of molecular markers that are associated with Alzheimer’s disease (AD). The panel comprises Amyloid beta, Apolipoprotein E, Fibrinogen alpha chain precursor, Keratin type I cytoskeletal 9, Serum albumin precursor, SPARC-like 1 protein and Tetranectin. Here we report the development and implementation of immunoassays to measure the abundance and diagnostic capacity of these putative biomarkers in matched lumbar CSF and blood plasma samples taken in life from individuals confirmed at post-mortem as suffering from AD (n=10) and from screened ‘cognitively healthy’ subjects (n=18). The inflammatory components of Alzheimer’s disease were also investigated. Employment of supervised learning techniques permitted examination of the interrelated expression patterns of the putative biomarkers and identified inflammatory components, resulting in biomarker panels with a diagnostic accuracy of 87.5% and 86.7% for the plasma and CSF datasets respectively. This is extremely important as it offers an ideal high-throughput and relatively inexpensive population screening approach. It appears possible to determine the presence or absence of AD based on our biomarker panel and it seems likely that a cheap and rapid blood test for AD is feasible

Practical detection of a definitive biomarker panel for Alzheimer's disease: comparisons between matched plasma and cerebrospinal fluid

Previous mass spectrometry analysis of cerebrospinal fluid (CSF) has allowed the identification of a panel of molecular markers that are associated with Alzheimer’s disease (AD). The panel comprises Amyloid beta, Apolipoprotein E, Fibrinogen alpha chain precursor, Keratin type I cytoskeletal 9, Serum albumin precursor, SPARC-like 1 protein and Tetranectin. Here we report the development and implementation of immunoassays to measure the abundance and diagnostic capacity of these putative biomarkers in matched lumbar CSF and blood plasma samples taken in life from individuals confirmed at post-mortem as suffering from AD (n=10) and from screened ‘cognitively healthy’ subjects (n=18). The inflammatory components of Alzheimer’s disease were also investigated. Employment of supervised learning techniques permitted examination of the interrelated expression patterns of the putative biomarkers and identified inflammatory components, resulting in biomarker panels with a diagnostic accuracy of 87.5% and 86.7% for the plasma and CSF datasets respectively. This is extremely important as it offers an ideal high-throughput and relatively inexpensive population screening approach. It appears possible to determine the presence or absence of AD based on our biomarker panel and it seems likely that a cheap and rapid blood test for AD is feasible

An association study of DRD2 and COMT polymorphisms with novelty seeking and harm avoidance scores, in two independent samples of depressed patients

BACKGROUND: It was recently reported that an interaction of the dopamine D2 receptor (DRD2) and catechol-O-methyltransferase (COMT) influences the behavioural approach system – as measured using Carver and White's Behavioural Inhibition and Behavioural Approach System (BIS/BAS) scales – in a sample of healthy German subjects. The Temperament and Character Inventory (TCI), in particular the novelty seeking (NS) and harm avoidance (HA) scales, correlates moderately with the BIS/BAS measure. This study aimed to examine support for an association of DRD2 and COMT with behavioural activation, using the TCI within two independent samples of depressed outpatients (for both samples n = 146). METHODS: Two clinical samples of depressed patients were ascertained to assess the efficacy of two different pharmacotherapy and psychotherapy treatments. Analysis of variance (ANOVA) was used to analyse NS and HA scale and subscale scores with respect to gene loci within each clinical sample. Analysis of covariance were undertaken to examine the association of age and gender with NS and HA scores. An association of age group or gender with gene loci were explored using chi-squared tests, in each sample. RESULTS: No significant effect of DRD2 or COMT, either independently or as an interaction, on NS or HA scores was observed, within either sample. Whilst age was significantly negatively associated with NS scores, including age in the two- and three-way interactions did not affect the significance of the association of personality with gene loci. CONCLUSION: This study suggests that the COMT-DRD2 Equilibrium Model of Positive Emotionality recently proposed by Reuter and his colleagues is not applicable amongst currently depressed individuals, whose behavioural approach and inhibition tendencies have been assessed using the TCI

Hubble Space Telescope Planetary Camera images of R136

The Planetary Camera of the Hubble Space Telescope has been used to obtain broad and narrowband images ofR136, the core of the massive star cluster 30 Doradus in the Large Magellanic Cloud. R136a, the brightest component ofR136, is shown to have at least 12 separate components, including the eight originally identified by speckle interferometry. Three of the 12 components are previously unidentified close companions of the speckle components. The stars within R136a are found to have luminosities and colors of normal evolved (Wolf-Rayet and blue supergiants) and zero-age main-sequence (ZAMS) massive stars. A narrowband He II filter was used to investigate the Wolf-Rayet stellar population. We find that three stars in R136a are of the Wolf-Rayet type; of the two identified from ground-based data, one is now resolved into two components. We present color-magnitude diagrams and a luminosity function of the stars within the larger region (~2 pc) defined as R136. We find that the stars in R136 are similar in color and luminosity to those of cluster members that lie outside that crowded inner region. The lower end of the color-magnitude diagram corresponds to ZAMS spectral type B3. No red supergiants have been detected within R136. The luminosity per unit area in the inner 1" (0.25 pc) of R136 is ≥ 50 times that of the center of Orion for a comparable area and seven times that of the core of NGC 3603. The luminosity per unit area of all of R136 is comparable to that of Orion but is sustained over 130 times the area. An F336W surface brightness profile is constructed for R136 based on the stellar photometry. The distribution is found to be consistent with a pure power law with l(r}ɑ r^y with y=-1.72±0.06 or with a small core with r_c 5 X 10^4 M_☉ pc^(-3). The implied upper limit on the relaxation time for the cluster is much smaller than the age of 3.5 X 10^6 yrs required by the presence of Wolf-Rayet stars. This suggests that relaxation effects have been very important in determining the observed structure of the cluster unless a large population of lower mass stars is also present

In situ surface analysis of palladium-platinum alloys in methane oxidation conditions

Palladium and palladium-platinum foils were analysed using temperature-programmed near-ambient pressure x-ray photoelectron spectroscopy (TP-NAP-XPS) under methane oxidation conditions. Oxidation of palladium is inhibited by the presence of water, and in oxygen-poor environments. Pt addition further inhibits oxidation of palladium across all reaction conditions, preserving metallic palladium to higher temperatures. Bimetallic foils underwent significant restructuring under reaction conditions, with platinum preferentially migrating to the bulk under select conditions

The core of the nearby S0 galaxy NGC 7457 imaged with the HST planetary camera

We have observed the nearby S0 galaxy NGC 7457 with the Planetary Camera of the Hubble Space Telescope. Spatial structure is observable at the diffraction-limited resolution of the 2.4 m HST primary despite the effects of spherical aberration. The central distribution of starlight appears consistent with a y ~ -1.0 power law for r 3 x 10^4 L_☉ pc^(-3) (V band). This is now the second densest core known after M32. From the ground, NGC 7457 resembles any number of unresolved elliptical galaxies, which suggests that compact dense cores may be common. The images of NGC 7457 demonstrate that HST can still provide unique and astrophysically interesting information on the central structure of galaxies