Systematic variation of the 12CO/13CO ratio as a function of star-formation rate surface density

We show that the12CO/13CO intensity ratio in nearby galaxies varies systematically as a function of the star formation rate surface density and gas surface density. The same effect is observed in different transitions, and in the 12CO/C18O ratio, while the 13CO/C18O ratio appears to remain constant as a function of the star formation rate surface density. We discuss the cause of these variations, considering both changes in the physical state of the gas, and chemical changes that lead to abundance variations. We used the observed correlations with C18O to suggest that abundance variations are unlikely to be causing the systematic trend observed with the star formation rate surface density, and thus that the mean gas temperature and/or velocity dispersion are systematically higher in higher star-formation rate surface density regions. We present the best fitting relations between the star formation rate surface density and the 12CO/13CO and 12CO/C18O ratios, and discuss how this effect can help us predict CO isotope emission from galaxies across the known universe.Comment: 7 pages, 4 figures, accepted to MNRA

The ℓ2\ell^2-homology of even Coxeter groups

Given a Coxeter system (W,S), there is an associated CW-complex, Sigma, on which W acts properly and cocompactly. We prove that when the nerve L of (W,S) is a flag triangulation of the 3-sphere, then the reduced $\ell^2$-homology of Sigma vanishes in all but the middle dimension.Comment: 15 pages, 1 figur

Impinging Jet Resonant Modes at Mach 1.5

High speed impinging jets have been the focus of several studies owing to their practical application and resonance dominated flow-field. The current study focuses on the identification and visualization of the resonant modes at certain critical impingement heights for a Mach 1.5 normally impinging jet. These modes are associated with high amplitude, discrete peaks in the power spectra and can be identified as having either axisymmetric or azimuthal modes. Their visualization is accomplished through phase-locked Schlieren imaging and fast-response pressure sensitive paint (PC-PSP) applied to the ground plane.Comment: videos and figures are attache

America’s Race-Based Caste Structure: Its Impact in College and Professional Sports

Racial inequities in college and professional sports remain prevalent and persistent despite the awareness of such inequities by those with the power to effectuate change. This Article proposes that explanations frequently offered for the slow pace of progress often fail to account for the hierarchy derived from a race-based caste system embedded in American society. Relying on the work of author Isabel Wilkerson, Part II describes major pillars of America’s race-based caste structure. Part III examines how stereotypes of Blacks’ presumed intellectual inferiority and a lack of fitness for leadership roles adversely impact their access to positions of power in both college and professional sports. Part IV discusses how the caste-system hierarchy and its accompanying mindset manifests in the academic marginalization of Black college athletes and the transfer of revenue disproportionately generated by them to predominantly White coaches, athletic administrators, and athletes in non-revenue generating sports. This Article discusses the limited effectiveness of legal doctrine, including anti-discrimination laws and contract law principles, to significantly diminish the above-referenced racial inequities in college and professional sport. In addition, it proposes specific policies that may assist in achieving greater racial equity in sport. It concludes, however, that a necessary step in moving toward greater racial equity in college and professional sports is an honest recognition that systemic racial inequities are, in part, a product of a caste-system mindset

Assessing the Racial Implications of NCAA Academic Measures

In 1983, the NCAA’s adoption of heightened initial eligibility standards for incoming intercollegiate athletes was met with applause and criticism. Proponents lauded the measure as a legitimate means of restoring academic integrity within intercollegiate athletics. Opponents questioned whether seemingly racially neutral eligibility standards had a disproportionately negative impact on African American athletes. It is against this backdrop that the Article examines the racial implications of the NCAA’s past and present academic standards. These standards consist of initial eligibility rules, progress-toward-degree requirements, the graduation success rate, and academic progress rate, the latter two of which comprise the NCAA’s Academic Performance Program. Through these measures, the NCAA states that it seeks to increase the likelihood that college athletes will develop academically while participating in intercollegiate athletics and graduate from their colleges and universities. As was true of past academic reforms such as Propositions 48, critics question the success of these measures in achieving their stated goals. Legitimate concerns have also been raised in the past and present regarding the disproportionate impact of the NCAA’s academic rules on Black Division I college athletes and historically Black colleges and universities (HBCUs). In addition to examining the NCAA’s past and current academic rules, the Article discusses the NCAA’s likely adoption of a rule to eliminate the standardized test score component of its initial eligibility criteria for matriculating scholarship intercollegiate athletes. This measure is likely to be perceived as beneficial to Black athletes. Advocates for enhanced racial fairness within college athletics have argued in favor of eliminating standardized test scores as an eligibility factor and believe it will be beneficial to athletes from under-represented communities, particularly Black athletes. While thoughtful arguments can be made in support of the proposal, the Article examines whether the proposal could inadvertently exacerbate the academic marginalization of Black Division I intercollegiate athletes. The Article also examines other practices that erode the value of the educational opportunity afforded Division I intercollegiate athletes