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Identified charged-particle spectra of π ± , K ± , p, and p at midrapidity (|y| < 0.1) measured by the dE/dx method in the STAR (solenoidal tracker at the BNL Relativistic Heavy Ion Collider) time projection chamber are reported for pp and d + Au collisions at √ s NN = 200 GeV and for Au + Au collisions at 62.4, 130, and 200 GeV. Average transverse momenta, total particle production, particle yield ratios, strangeness, and baryon production rates are investigated as a function of the collision system and centrality. The transverse momentum spectra are found to be flatter for heavy particles than for light particles in all collision systems; the effect is more prominent for more central collisions. The extracted average transverse momentum of each particle species follows a trend determined by the total charged-particle multiplicity density. The Bjorken energy density estimate is at least several GeV/fm 3 for a formation time less than 1 fm/c. A significantly larger net-baryon density and a stronger increase of the net-baryon density with centrality are found in Au + Au collisions at 62.4 GeV than at the two higher energies. Antibaryon production relative to total particle multiplicity is found to be constant over centrality, but increases with the collision energy. Strangeness production relative to total particle multiplicity is similar at the three measured RHIC energies. Relative strangeness production increases quickly 034909-2 SYSTEMATIC MEASUREMENTS OF IDENTIFIED . . . (2009) with centrality in peripheral Au + Au collisions, to a value about 50% above the pp value, and remains rather constant in more central collisions. Bulk freeze-out properties are extracted from thermal equilibrium model and hydrodynamics-motivated blast-wave model fits to the data. Resonance decays are found to have little effect on the extracted kinetic freeze-out parameters because of the transverse momentum range of our measurements. The extracted chemical freeze-out temperature is constant, independent of collision system or centrality; its value is close to the predicted phase-transition temperature, suggesting that chemical freeze-out happens in the vicinity of hadronization and the chemical freeze-out temperature is universal despite the vastly different initial conditions in the collision systems. The extracted kinetic freeze-out temperature, while similar to the chemical freeze-out temperature in pp, d + Au, and peripheral Au + Au collisions, drops significantly with centrality in Au + Au collisions, whereas the extracted transverse radial flow velocity increases rapidly with centrality. There appears to be a prolonged period of particle elastic scatterings from chemical to kinetic freeze-out in central Au + Au collisions. The bulk properties extracted at chemical and kinetic freeze-out are observed to evolve smoothly over the measured energy range, collision systems, and collision centralities. PHYSICAL REVIEW C 79, 034909

Three sex-determining (SD) genes, SRY (mammals), Dmy (medaka), and DM-W (Xenopus laevis), have been identified to date in vertebrates. However, how and why a new sex-determining gene appears remains unknown, as do the switching mechanisms of the master sex-determining gene. Here, we used positional cloning to search for the sex-determining gene in Oryzias luzonensis and found that Gsdf Y (gonadal soma derived growth factor on the Y chromosome) has replaced Dmy as the master sex-determining gene in this species. We found that Gsdf Y showed high expression specifically in males during sex differentiation. Furthermore, the presence of a genomic fragment that included Gsdf Y converts XX individuals into fertile XX males. Luciferase assays demonstrated that the upstream sequence of Gsdf Y contributes to the male-specific high expression. Gsdf is downstream of Dmy in the sex-determining cascade of O. latipes, suggesting that emergence of the Dmy-independent Gsdf allele led to the appearance of this novel sexdetermining gene in O. luzonensis. IN most vertebrates, sex is determined genetically. Mammals and birds with cytogenetically well-differentiated sex chromosomes have sex determination systems that differ between the taxonomic classes but not within them (Solari 1994). In mammals, for example, the sex-determining (SD) gene SRY/Sry on the Y chromosome has a universal role in sex determination (Gubbay et al. 1990;Sinclair et al. 1990;Koopman et al. 1991;Foster et al. 1992). By contrast, some fish groups, such as salmonids, sticklebacks, and Oryzias fishes, have sex chromosomes that differ among closely related species (Devlin and Nagahama 2002;Woram et al. 2003;Takehana et al. 2007a;Ross et al. 2009).A DM-domain gene, Dmy, was the first SD gene identified in a nonmammalian vertebrate, the fish medaka Oryzias latipes (Matsuda et al. 2002(Matsuda et al. , 2007. In this species, the term Y chromosome is employed to refer to a recombining chromosome that carries the male-determining gene Dmy, and X is used for the homologous chromosome; these are not a heteromorphic pair. This gene is conserved among all wild populations of O. latipes examined to date . The closely related species O. curvinotus also has Dmy on its Y chromosome, which is orthologous to the O. latipes Y chromosome (Matsuda et al. 2003). However, Dmy has not been detected in any other type of fish, including other Oryzias fishes (Kondo et al. 2003). Analysis of the Y-specific region of the O. latipes sex chromosome has demonstrated that Dmy arose from duplication of the autosomal Dmrt1 gene (Nanda et al. 2002;Kondo et al. 2006). This Dmrt1 duplication is estimated to have occurred within the last 10 million years in a common ancestor of O. latipes, O. curvinotus, and O. luzonensis. In O. luzonensis, however, no functional duplicated copy of Dmrt1 has been detected (Kondo et al. 2003) (Figure 5A).O. luzonensis possesses an XX-XY system, which is homologous to an autosomal linkage group (LG 12) and Uwa 1985). In the d-rR strain, the wild-type alle...

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