The H Beta Index as an Age Indicator of Old Stellar Systems: The Effects of Horizontal-Branch Stars

The strength of the H$\beta$ index has been computed for the integrated spectra of model globular clusters from the evolutionary population synthesis. These models take into account, for the first time, the detailed systematic variation of horizontal-branch (HB) morphology with age and metallicity. Our models show that the H$\beta$ index is significantly affected by the presence of blue HB stars. Because of the contribution from blue HB stars, the H$\beta$ does not monotonically decrease as metallicity increases at a given age. Instead, it reaches a maximum strength when the distribution of HB stars is centered around 9500 K, the temperature where the H$\beta$ index becomes strongest. Our models indicate that the strength of the H$\beta$ index increases as much as 0.75 {\AA} due to the presence of blue HB stars. The comparison of the recent Keck observations of the globular cluster system in the Milky Way Galaxy with those in giant elliptical galaxies, NGC 1399 and M87, shows a systematic shift in the H$\beta$ against metallicity plane. Our models suggest that this systematic difference is understood if the globular cluster systems in giant elliptical galaxies are several billion years older, in the mean, than the Galactic counterpart. Further observations of globular cluster systems in the external galaxies from the large ground-based telescopes and space UV facilities will enable to clarify whether this difference is indeed due to the age difference or other explanations are also possible.Comment: 21 pages, 8 figures, Accepted for publication in the Astronomical Journal, August 2000 issue, Postscript files are available at http://csaweb.yonsei.ac.kr/~hclee/Hbet

Men and talk about legal abortion in South Africa: equality, support and rights discourses undermining reproductive ‘choice’

Discursive constructions of abortion are embedded in the social and gendered power relations of a particular socio-historical space. As part of research on public discourses concerning abortion in South Africa where there has been a radical liberalisation of abortion legislation, we collected data from male group discussions about a vignette concerning abortion, and newspaper articles written by men about abortion. Our analysis revealed how discourses of equality, support and rights may be used by men to subtly undermine women’s reproductive right to ‘choose’ an abortion. Within an Equal Partnership discourse, abortion, paired with the assumption of foetal personhood, was equated with violating an equal heterosexual partnership and a man’s patriarchal duty to protect a child. A New Man discourse, which positions men as supportive of women, was paired with the assumption of men as rational and women as irrational in decision-making, to allow for the possibility of men dissuading women from terminating a pregnancy. A Rights discourse was invoked to suggest that abortion violates men’s paternal rights

Electron kinetic effects on raman backscatter in plasmas

We augment the usual three-wave cold-fluid equations governing Raman backscatter (RBS) with a new kinetic thermal correction, proportional to an average of particle kinetic energy weighted by the ponderomotive phase. From closed-form analysis within a homogeneous kinetic three-wave model and ponderomotively averaged kinetic simulations in a more realistic pulsed case, the magnitude of these new contributions is shown to be a measure of the dynamical detuning between the pump laser, seed laser, and Langmuir wave. Saturation of RBS is analyzed, and the role of trapped particles illuminated. Simple estimates show that a small fraction of trapped particles (similar to 6%) can significantly suppress backscatter. We discuss the best operating regime of the Raman plasma amplifier to reduce these deleterious kinetic effects.open282

Theory of One-Channel vs. Multi-Channel Kondo Effects for Ce3+^{3+} Impurities

We introduce a model for Ce$^{3+}$ impurities in cubic metals which exhibits competition between the Fermi-liquid fixed point of the single channel Kondo model and the non-Fermi-liquid fixed point of the two- and three-channel Kondo models. Using the non-crossing approximation and scaling theory, we find: (i) A possible three-channel Kondo effect between the one- and two-channel regimes in parameter space. (ii) The sign of the thermopower is a fixed point diagnostic. (iii) Our results will likely survive the introduction of additional $f^2$ and conduction states. We apply this model to interpret the non-Fermi liquid alloy La$_{1-x}$Ce$_x$Cu$_{2.2}$Si$_2$.Comment: 13 pages, Revtex, To appear in Phys. Rev. Let