CCD UBV(RI)CUBV(RI)_{C} Photometry of Twenty Open Clusters

Fundamental astrophysical parameters have been derived for 20 open clusters (O\!Cs) using CCD~$U\!BV\!(RI)_C$ photometric data observed with the 84~cm telescope at the San Pedro M\'artir National Astronomical Observatory, M\'exico. The interstellar reddenings, metallicities, distances, and ages have been compared to the literature values. Significant differences are usually due to the usage of diverse empirical calibrations and differing assumptions, such as concerning cluster metallicity, as well as distinct isochrones which correspond to differing element-abundance ratios, internal stellar physics, and photometric systems. Different interstellar reddenings, as well as varying reduction and cluster-membership techniques, are also responsible for these kinds of systematic differences and errors. The morphological ages, which are derived from the morphological indices ($\delta V$ and $\delta 1$) in the CM diagrams, are in good agreement with the isochrone ages of 12 O\!Cs, those with good red clump (RC) and red giant (RG) star candidates. No metal abundance gradient is detected for the range $6.82 \leq R_{GC} \leq 15.37$ kpc, nor any correlation between the cluster ages and metal abundances for these 20 O\!Cs. Young, metal-poor O\!Cs, observed here in the third Galactic quadrant, may be associated with stellar over-densities, such as that in Canis Major (Martin et al.) and the Monoceros Ring (Newberg et al.), or signatures of past accretion events, as discussed by Yong et al. and Carraro et al.Comment: 68 pages, 33 figures, 15 tables. Accepted in New Astronom

Evaluation of Acoustic Reflex and Reflex Decay Tests in Geriatric Group

Objective: To determine average acoustic reflex thresholds in geriatric groups by assessing ipsilateral and contralateral acoustic reflex and reflex decay tests.Methods: A total of 25 elders between ages 65-84 years (74.3±5.4) and 25 individuals between ages 18-45 years (30.4±4.2) were recruited for the study. After ear, nose, and throat examination, ipsilateral and contralateral acoustic reflex thresholds at 500, 1000, 2000, and 4000 Hertz (Hz) were determined and a reflex decay test at contralateral 500 Hz was conducted. Ipsilateral acoustic reflex thresholds were obtained with high-frequency band, low-frequency band, and wide band noise, and the results were compared with ipsilateral acoustic reflexes at 500, 1000, 2000, and 4000 Hz.Results: There was no statistically significant difference between the two groups in ipsilateral and contralateral acoustic reflex measurements at 500, 1000, 2000, and 4000 Hz (p>0.05). Negative reflex decay was obtained in all participants and no statistically significant difference between the two groups was observed in terms of reflex decay thresholds (p>0.05). Acoustic reflex with high-frequency band noise was observed in five of nine elders whose acoustic reflexes were not obtained at 2000 and 4000 Hz, whereas acoustic reflex with low-frequency band noise was observed in one of six elders who did not show reflexes at 500 and 1000 Hz.Conclusion: It was concluded that although some changes were observed due to age, middle ear and stapes muscles work normally in geriatric group. In the reflex decay test, reliable results were obtained at contralateral 500 Hz. Acoustic reflex measurements with low- and high-frequency band noise may also be used to assess middle ear functions

Metallicities and ages of stellar populations at a high Galactic latitude field

We present an analysis of $UBVRI$ data from the Selected Area SA 141. By applying recalibrated methods of measuring ultraviolet excess (UVX), we approximate abundances and absolute magnitudes for 368 stars over 1.3 square degrees out to distances over 10 kpc. With the density distribution constrained from our previous photometric parallax investigations and with sufficient accounting for the metallicity bias in the UVX method, we are able to compare the vertical abundance distribution to those measured in previous studies. We find that the abundance distribution has an underlying uniform component consistent with previous spectroscopic results that posit a monometallic thick disk and halo with abundances of $[Fe/H]$ = $-$0.8 and $-$1.4, respectively. However, there are a number of outlying data points that may indicate contamination by more metal-rich halo streams. The absence of vertical abundance gradients in the Galactic stellar populations and the possible presence of interloping halo streams would be consistent with expectations from merger models of Galaxy formation. We find that our UVX method has limited sensitivity in exploring the metallicity distribution of the distant Galactic halo, owing to the poor constraint on the $UBV$ properties of very metal-poor stars. The derivation of metallicities from broadband $UBV$ photometry remains fundamentally sound for the exploration of the halo but is in need of both improved calibration and superior data.Comment: 11 pages, 11 figures, accepted for publication in MNRAS Journa

New intrinsic-colour calibration for uvbyuvby--β\beta photometry

A new intrinsic-colour calibration ($(b$--$y)_{o}$--$\beta$) is presented for the $uvby$--$\beta$ photometric system, making use of re-calibrated Hipparcos parallaxes and published reddening maps. This new calibration for $(b$--$y)_{o}$--$\beta$, our Equation (1), has been based upon stars with $d_{Hip} < 70$ pc in the photometric catalogues of Schuster et al. (1988, 1993, 2006), provides a small dispersion, $\pm0.009$, and has a positive ``standard'' $+2.239\Delta\beta$ coefficient, which is not too different from the coefficients of Crawford (+1.11; 1975a) and of Olsen (+1.34; 1988). For 61 stars with spectra from CASPEC, UVES/VLT, and FIES/NOT databases, without detectable Na I lines, the average reddening value $= -0.001\pm0.002$ shows that any zero-point correction to our intrinsic-colour equation must be minuscule.Comment: 18 pages, 3 figures, accepted to New Astronom