An Evolution of Excellence

The Rockefeller University Graduate Program: An Evolution of Excellence by David Rockefeller, 1984 The remarks were delivered by David Rockefeller Chairman of he Executive Committee, The Rockefeller University on the occasion of the 25th Anniversary of the Conferring of Degrees at The Rockefeller University 11 June 1984https://digitalcommons.rockefeller.edu/artifacts-ephemera/1057/thumbnail.jp

Spatial Distribution of Nucleosynthesis Products in Cassiopeia A: Comparison Between Observations and 3D Explosion Models

We examine observed heavy element abundances in the Cassiopeia A supernova remnant as a constraint on the nature of the Cas A supernova. We compare bulk abundances from 1D and 3D explosion models and spatial distribution of elements in 3D models with those derived from X-ray observations. We also examine the cospatial production of 26Al with other species. We find that the most reliable indicator of the presence of 26Al in unmixed ejecta is a very low S/Si ratio (~0.05). Production of N in O/S/Si-rich regions is also indicative. The biologically important element P is produced at its highest abundance in the same regions. Proxies should be detectable in supernova ejecta with high spatial resolution multiwavelength observations.Comment: To appear in the Conference Proceedings for the "10th Symposium on Nuclei in the Cosmos (NIC X)", July 27 - August 1 2008, Mackinack Island, Michigan, US

Convective-reactive proton-C12 combustion in Sakurai's object (V4334 Sagittarii) and implications for the evolution and yields from the first generations of stars

Depending on mass and metallicity as well as evolutionary phase, stars occasionally experience convective-reactive nucleosynthesis episodes. We specifically investigate the situation when nucleosynthetically unprocessed, H-rich material is convectively mixed with a He-burning zone, for example in convectively unstable shell on top of electron-degenerate cores in AGB stars, young white dwarfs or X-ray bursting neutron stars. Such episodes are frequently encountered in stellar evolution models of stars of extremely low or zero metal content [...] We focus on the convective-reactive episode in the very-late thermal pulse star Sakurai's object (V4334 Sagittarii). Asplund etal. (1999) determined the abundances of 28 elements, many of which are highly non-solar, ranging from H, He and Li all the way to Ba and La, plus the C isotopic ratio. Our simulations show that the mixing evolution according to standard, one-dimensional stellar evolution models implies neutron densities in the He that are too low to obtain a significant neutron capture nucleosynthesis on the heavy elements. We have carried out 3D hydrodynamic He-shell flash convection [...] we assume that the ingestion process of H into the He-shell convection zone leads only after some delay time to a sufficient entropy barrier that splits the convection zone [...] we obtain significantly higher neutron densities (~few 10^15 1/cm^3) and reproduce the key observed abundance trends found in Sakurai's object. These include an overproduction of Rb, Sr and Y by about 2 orders of magnitude higher than the overproduction of Ba and La. Such a peculiar nucleosynthesis signature is impossible to obtain with the mixing predictions in our one-dimensional stellar evolution models. [...] We determine how our results depend on uncertainties of nuclear reaction rates, for example for the C13(\alpha, n)O16 reaction.Comment: ApJ in press, this revision contains several changes that improve clarity of presentation reflecting the suggestions made by the referee; this version represents no change in substance compared to version 1; some technical material has been moved to an appendix; an additional appendix deals in more detail with the combustion time scales; this version is practically identical to the ApJ versio

The State of White Supremacy in America: It Is Time to Stand Together

The United States has numerous social-cultural issues affecting its population. One of these problems is white supremacy. This concept refers to a racist perception that white persons are naturally superior to individuals of other races and should thus dominate them. While white supremacy in previous centuries galvanized a lot of support among white people, the concept is now regarded vicious by white, African American, Latino as well as other races. The modern American society is structured under cultural sensitiveness, racial equality, and religious tolerance. Unlike the years of slavery or reconstruction, all citizens in the United States are afforded equal rights irrespective of their cultural identities. Nevertheless, white supremacist notions persist in a nation that prides itself for its democratic model, cultural diversity, religious tolerance and socioeconomic transcendence. The state of white supremacy is that America can be manifested by violence, imperialistic tendencies, discrimination in the society, unfair immigration policies, poor political leadership, and the deplorable role of the media. With the growing number of atrocities being committed around the United States by both members of identified and non-identified white supremacist group, it is time to address this issue together. This paper, is a constructive discussion venting the many ills of racial discrimination in every aspect that affects minorities at all spheres of the society and the deplorable state of white supremacy in America

Racial Disparities in the United States Criminal Justice System: “With Liberty and Justice for All?”

Racial discrimination remains a prevalent issue in the contemporary U.S. despite efforts to promote equality. Many young African American and Hispanic males are easy target for law enforcement agents. Minorities experience a higher and more unfair form of racial discrimination, racial profiling, police brutality, unfair sentencing, and mass incarceration for offences which are the same or less than those committed by White males. The rate of incarceration in the United States is five to eight times higher than most developed countries, and Black males constitute the largest percentage of inmates in the U.S. prison system. Once arrested, Black Americans are more likely to remain in prison longer, and await trial for minor offenses at a higher rate than Whites. Black and Latino males sentenced in state and federal courts face significantly greater odds of incarceration than White offenders for the same or even higher crimes. Vagins and McCurdy in a 2006 ACLU on “cracks in the system” reported that “There is no rational medical or penological reason for the 100:1 disparity between crack and powder cocaine and instead it causes an unjustified racial disparity in our penal system” (p. 7). There is a racial disparity in the proportion of Black males in prison serving sentences of life without the possibility of parole (LWOP). In addition, The United States Criminal Justice System needs to be carefully examined as a top priority agenda needing immediate call of action that needs reform to guarantee the constitutional rights accorded to every American “with liberty and justice for all”

New Calendra

8 p. ; 24 cm