An HST/WFPC Survey of Bright Young Clusters in M31. II. Photometry of Less Luminous Clusters in the Fields

We report on the properties of 89 low mass star clusters located in the vicinity of luminous young clusters (blue globulars) in the disk of M31. 82 of the clusters are newly detected. We have determined their integrated magnitudes and colors, based on a series of Hubble Space Telescope Wide Field/Planetary Camera 2 exposures in blue and red (HST filters F450W and F814W). The integrated apparent magnitudes range from F450W = 17.5 to 22.5, and the colors indicate a wide range of ages. Stellar color-magnitude diagrams for all clusters were obtained and those with bright enough stars were fit to theoretical isochrones to provide age estimates. The ages range from 12 Myr to >500 Myr. Reddenings, which average E(F450 - F814) = 0.59 with a dispersion of 0.21 magnitudes, were derived from the main sequence fitting for those clusters. Comparison of these ages and integrated colors with single population theoretical models with solar abundances suggests a color offset of 0.085 magnitudes at the ages tested. Estimated ages for the remaining clusters are based on their measured colors. The age-frequency diagram shows a steep decline of number with age, with a large decrease in number per age interval between the youngest and the oldest clusters detected.Comment: 20 pages, 9 figure

Albumin-coupled methotrexate (MTX-HSA) is a new anti-arthritic drug which acts synergistically to MTX

Objective. To evaluate the anti-arthritic effects of the new inflammation-targeted drug MTX-HSA and to investigate whether peripheral blood mononuclear cells (PBMC) are potential target cells for albumin-mediated drug delivery. Methods. The murine model of collagen-induced arthritis (CIA) was used to measure the anti-arthritic effect of MTX, MTX-HSA or a combination of both (n = 30 to 35 per group). In addition, the uptake of fluorescence-labelled albumin (AFLc-HSA) in PBMC of 14 patients with RA was measured by fluorescence-activated cell sorting (FACS). Results. In equivalent doses of 7.5 mg/kg intravenously (IV) twice a week, MTX-HSA is significantly (P<0.02) superior to MTX in inhibiting the development of CIA and reducing the joint count as well as the number of affected paws. When given in lower doses as combination therapy, both drugs act synergistically (P<0.03). A mean of 96, 72 and 64% of the CD14-, CD16- and CD20-positive cells from peripheral blood of rheumatoid arthritis (RA) patients showed an uptake of albumin after incubation with AFLc-HSA in vitro. This finding was not significantly different in comparison to healthy controls. In contrast, the number of CD3-positive cells taking up albumin is increased significantly in RA patients in comparison to controls (26.3 ± 12.9% s.d. vs 11.6 ± 7.3% s.d.; P = 0.005). Conclusion. The data show that the effectiveness of MTX-HSA in CIA is superior to MTX and that both drugs act synergistically. In addition, albumin appears to be taken up by peripheral blood cells, suggesting that they might be one of the potential target cells of this novel anti-arthritic treatment approac

HST/ACS colour-magnitude diagrams of M31 globular clusters

With the aim of increasing the sample of M31 clusters for which a colour magnitude diagram is available, we searched the HST archive for ACS images containing objects included in the Revised Bologna Catalogue of M31 globular clusters. Sixty-three such objects were found. We used the ACS images to confirm or revise their classification and we obtained useful CMDs for 11 old globular clusters and 6 luminous young clusters. We obtained simultaneous estimates of the distance, reddening, and metallicity of old clusters by comparing their observed field-decontaminated CMDs with a grid of template clusters of the Milky Way. We estimated the age of the young clusters by fitting with theoretical isochrones. For the old clusters, we found metallicities in the range -0.4<=[Fe/H]<=-1.9, that generally agree with existing spectroscopic extimates. At least four of them display a clear blue HB, indicating ages >10 Gyr. All six candidate young clusters are found to have ages <1Gyr. With the present work the total number of M31 GCs with reliable optical CMD increases from 35 to 44 for the old clusters, and from 7 to 11 for the young ones. The old clusters show similar characteristics to those of the MW. We discuss the case of the cluster B407, with a metallicity [Fe/H] ~-0.6 and located at a large projected distance from the centre of M31 and from the galaxy major axis. Metal-rich globulars at large galactocentric distances are rare both in M31 and in the MW. B407, in addition, has a velocity in stark contrast with the rotation pattern shared by the bulk of M31 clusters of similar metallicity. This, along with other empirical evidence, supports the hypothesis that the cluster is physically associated with a substructure in the M31 halo that has been interpreted as the relic of a merging event.Comment: 19 pages, 14 figures, 6 tables. Accepted for publication on Astronomy and Astrophysic

Carbon Star Survey of Local Group Dwarf Galaxies. II. Pegasus, DDO 210 and Tucana

We present the latest results of our ongoing four filter photometric survey of C stars in Local Group dwarf irregular galaxies. Observations of the two low luminosity dwarf irregular galaxies, Pegasus and DDO 210, revealed respectively 40 and 3 C stars, assuming that the reddening of Pegasus is negligible. No C stars were identified in Tucana. Our observations permit the estimation of the CMD contamination by foreground M dwarf thus yielding reliable C/M ratios. Our R, I photometry of the C stars cannot be used to solve the extinction controversy toward Pegasus. The three C stars in DDO 210 are quite bright when compared to C star populations in dwarf galaxies. A larger fainter population in that galaxy seems however improbable. The statistics of C stars, currently on hand for dwarf galaxies, show a well-defined trend with the absolute magnitude of galaxies.Comment: 18 pages, 7 figures, 6 table

A HST/WFPC2 survey of bright young clusters in M31. I. VdB0, a massive star cluster seen at ~= 25 Myr

{Aims.} We introduce our imaging survey of possible young massive globular clusters in M31 performed with the Wide Field and Planetary Camera 2 (WFPC2) on the Hubble Space Telescope (HST). We present here details of the data reduction pipeline that is being applied to all the survey data and describe its application to the brightest among our targets, van den Bergh 0 (VdB0), taken as a test case. {Methods.} The reddening, the age and the metallicity of the cluster are estimated by comparison of the observed Color Magnitude Diagram (CMD) with theoretical isochrones. {Results.} Under the most conservative assumptions the stellar mass of VdB0 is M > 2.4 x 10^4 M_sun, but our best estimates lie in the range ~ 4-9 x 10^4 M_sun. The CMD of VdB0 is best reproduced by models having solar metallicity and age = 25 Myr. Ages smaller than = 12 Myr and larger than = 60 Myr are clearly ruled out by the available data. The cluster has a remarkable number of Red Super Giants (> 18) and a CMD very similar to Large Magellanic Cloud clusters usually classified as young globulars such as NGC 1850, for example. {Conclusions.} VdB0 is significantly brighter (>~ 1 mag) than Galactic open clusters of similar age. Its present-day mass and half-light radius (r_h=7.4 pc) are more typical of faint globular clusters than of open clusters. However, given its position within the disk of M31 it is expected to be destroyed by dynamical effects, in particular by encounters with giant molecular clouds, within the next ~ 4 Gyr.Comment: 18 pages, 16 figures (quality of Figures 1,2,3 and 4 reduced). Accepted for publication in Astronomy & Astrophysics. Minor revisions to sect. 1.

Analysis of the first bridge diagram of liquid bromine

The first bridge diagrams of the classical theory of liquids are discussed for two fluids of Lennard-Jones spheres and for a fluid of a two-centre Lennard-Jones model of liquid bromine. The bridge diagram of liquid bromine is calculated using a biased Monte-Carlo method. We investigate the first bridge diagrams, the bonds of which are either Mayer functions f or total correlation functions h. The Mayer f-bond representation leads to very high values of the first bridge diagram, which can not be used alone in a truncated expansion of the diagrammatic series of the bridge function. We analyse the origin of these high values. In the case of the h-function representation, the bridge function series truncated to the sole first bridge diagram is introduced into the closure of the Ornstein-Zernike equation and leads to some improvement of the pair distribution function upon the HNC result, as compared to the exact simulated values

Nutrient Management Suggestions for Corn

Fertilizer nutrient requirements for corn are based on expected yield and soil nutrient availability. The preplant nitrogen (N) recommendation equation, with adjustment for fertilizer cost and time of application, is retained from the previous edition of this publication. Suggestions for in-season nitrogen decisions are briefly outlined. The major change is providing a phosphorus (P) recommendation based on yield history with an implied intent to build and maintain soil test P above the critical level, which has not changed

Iterative Solution of the Ornstein-Zernike Equation with Various Closures Using Vector Extrapolation

The solution of the Ornstein-Zernike equation with various closure approximations is studied. This problem is rewritten as an integral equation that can be solved iteratively on a grid. The convergence of the fixed point iterations is relatively slow. We consider transformations of the sequence of solution vectors using non-linear sequence transformations, so-called vector extrapolation processes. An example is the vector J transformation. The transformed vector sequences turn out to converge considerably faster than the original sequences.Comment: 21 pages, postscript, three figures included in the postscript. Comput. Phys. Commun., in press. Also available via http://rchs1.uni-regensburg.de/preprint.html , ftp://rchs1.uni-regensburg.de/pub/preprint , gopher://rchs1.uni-regensburg.de:70/11./pub/preprin