Zeroing the Stellar Isochrone Scale: The Red Giant Clump Luminosity at Intermediate Metallicity

The color-magnitude diagrams of the open clusters NGC 2420 and NGC 2506 have been investigated as intermediate links between the solar neighborhood and the Magellanic Clouds. Two sets of theoretical isochrones which include convective overshoot are zeroed to the sun at solar abundance and to the unevolved main sequence dwarfs of the Hipparcos catalog at [Fe/H] = -0.4, requiring a differential of 0.4 mag between the unevolved main sequences at a given color. Adopting E(B-V) = 0.04 and [Fe/H] = -0.39 for NGC 2506 and 0.04 and -0.29 for NGC 2420,the respective apparent moduli are 12.70 and 12.15, while the ages of both clusters are approximately 1.9 +/- 0.2 or 2.2 +/- 0.2 Gyr, depending on the choice of isochrones. From the composite giant branch of the two clusters, the mean clump magnitudes in V and I are found to be 0.47 and -0.48 (-0.17,+0.14). Applying a metallicity correction to the M_I values, the cluster sample of Udalski (1998) leads to (m-M)_0 = 18.42 (+0.17,--0.15) and 18.91 (+0.18,--0.16) for the LMC and SMC, respectively. A caveat to this discussion and to the claim that clusters of the same abundance and age are identical is the observation that the (V-I) colors of the red giants in NGC 2506 are significantly redder at a given (B-V) than the giants in clusters of comparable age and/or metallicity. If the CCD photometry for NGC 2506 is tied to the standard system rather than using a general cluster relation between (B-V) and (V-I), the M_I for the clump will decrease by 0.1 mag.Comment: 1 table, 12 figures. Replaced 20-jan-99 by version with all figures. Accepted for April 1999 Astronomical Journa

Clients' reasons for prenatal ultrasonography in Ibadan, South West of Nigeria

<p>Abstract</p> <p>Background</p> <p>Prenatal ultrasonography has remained a universal tool but little is known especially from developing countries on clients' reasons for desiring it. Then aim was to determine the reasons why pregnant women will desire a prenatal ultrasound.</p> <p>Methods</p> <p>It was a cross-sectional survey of consecutive 222 women at 2 different ultrasonography facilities in Ibadan, South-west Nigeria.</p> <p>Results</p> <p>The mean age of the respondents was 30.1 ± 4.5 years. The commonest reason for requesting for prenatal ultrasound scans was to check for fetal viability in 144 women (64.7%) of the respondents, followed by fetal gender determination in 50 women (22.6%. Other reasons were to check for number of fetuses, fetal age and placental location. Factors such as younger age, artisans profession and low level of education significantly influenced the decision to check for fetal viability on bivariate analysis but all were not significant on multivariate analysis. Concerning fetal gender determination, older age, Christianity, occupation and gravidity were significant on bivariate analysis, however, only gravidity and occupation remained significant independent predictor on logistic regression model. Women with less than 3 previous pregnancies were about 4 times more likely to request for fetal sex determination than women with more than 3 previous pregnancies, (OR 3.8 95%CI 1.52 – 9.44). The professionals were 7 times more likely than the artisans to request to find out about their fetal sex, (OR 7.0 95%CI 1.47 – 333.20).</p> <p>Conclusion</p> <p>This study shows that Nigerian pregnant women desired prenatal ultrasonography mostly for fetal viability, followed by fetal gender determination. These preferences were influenced by their biosocial variables.</p