Counting Black Holes: The Cosmic Stellar Remnant Population and Implications for LIGO

We present an empirical approach for interpreting gravitational wave signals of binary black hole mergers under the assumption that the underlying black hole population is sourced by remnants of stellar evolution. Using the observed relationship between galaxy mass and stellar metallicity, we predict the black hole count as a function of galaxy stellar mass. We show, for example, that a galaxy like the Milky Way should host millions of $\sim 30~M_\odot$ black holes and dwarf satellite galaxies like Draco should host $\sim 100$ such remnants, with weak dependence on the assumed IMF and stellar evolution model. Most low-mass black holes ($\sim10 M_\odot$) typically reside within massive galaxies ($M_\star \simeq 10^{11} M_\odot$) while massive black holes ($\sim 50~M_\odot$) typically reside within dwarf galaxies ($M_\odot \simeq 10^9 M_\odot$) today. If roughly $1\%$ of black holes are involved in a binary black hole merger, then the reported merger rate densities from Advanced LIGO can be accommodated for a range of merger timescales, and the detection of mergers with $> 50~M_\odot$ black holes should be expected within the next decade. Identifying the host galaxy population of the mergers provides a way to constrain both the binary neutron star or black hole formation efficiencies and the merger timescale distributions; these events would be primarily localized in dwarf galaxies if the merger timescale is short compared to the age of the universe and in massive galaxies otherwise. As more mergers are detected, the prospect of identifying the host galaxy population, either directly through the detection of electromagnetic counterparts of binary neutron star mergers or indirectly through the anisotropy of the events, will become a realistic possibility.Comment: 10 pages, 8 figures. Accepted by MNRA

Sapere Aude — Dare to Be Wise: Elbert D. Glover

Sapere Aude – Dare to Be Wise is a unique editorial conversational interview-type feature. It is an attempt to deep dive into an Academy members’ background, formative experience, and education – specifically, to extract factors that contributed to their development and evolution as a professional, as well as their success as a prominent researcher in the health behavior arena. Every Academy member selected has a different story to tell and numerous models for success will emerge from this exploration of the membership. That said, the first of what we hope to be a series of enlightening interviews is Elbert D. Glover, the founder of The Academy

Keeping the Dream Alive: The Back Story

The purpose of the manuscript was to share the unfamiliar back story of the founding of The Academy. Noted is the unique dilemma and unforeseen obstacles the founder had to overcome to launch The Academy. The dream began with the recognition that most universities waged enormous lip service to quality teaching, however, handsomely rewarded research rarely teaching. Consequently, to overcome his own research limitations, the founder set upon forming a research organization to coalesce with researchers. Detailed is the negative feedback received from colleagues regarding forming The Academy and how he overcame his personal research limitations. The manuscript further notes how the initial founders were recruited, how gender criticism was dealt with, how the bylaws were established, how the meeting venues were selected and how The Academy narrowly missed being a conceivable casualty of 9/11. Similarly, thoughts are offered for keeping The Academy dream alive via the paramount Academy feature; meritocracy. Moreover, further comments are offered regarding Academy admission requirements, prevailing awards within The Academy, the short-lived official journal of The Academy and the limitation of membership. The overall tone is the recognition that organizations grow and change; however, the founder emboldens The Academy to always keep in mind the founding principles that make The Academy unique and distinct from other health organizations

The deformed figures of the Dedekind ellipsoids in the post-Newtonian approximation to general relativity - corrections and amplifications

Two errors in the analysis of an earlier paper on the same subject are corrected. It is found that as a consequence of the corrections, the solution to the post-Newtonian equations (appropriate to determining the deformed figures of the Dedekind ellipsoid) now diverges at a point where the axes of the ellipsoid are in the ratios 1:0.3370:0.2850. In addition, the fourth-harmonic oscillations of the Dedekind ellipsoid are considered. It is found that it becomes dynamically unstable when its axes are in the ratios 1:0.3121:0.2680

On the vanishing viscosity limit in a disk

We say that the solution u to the Navier-Stokes equations converges to a solution v to the Euler equations in the vanishing viscosity limit if u converges to v in the energy norm uniformly over a finite time interval. Working specifically in the unit disk, we show that a necessary and sufficient condition for the vanishing viscosity limit to hold is the vanishing with the viscosity of the time-space average of the energy of u in a boundary layer of width proportional to the viscosity due to modes (eigenfunctions of the Stokes operator) whose frequencies in the radial or the tangential direction lie between L and M. Here, L must be of order less than 1/(viscosity) and M must be of order greater than 1/(viscosity)

Coupling Between An Optical Phonon and the Kondo Effect

We explore the ultra-fast optical response of Yb_{14}MnSb_{11}, providing further evidence that this Zintl compound is the first ferromagnetic, under-screened Kondo lattice. These experiments also provide the first demonstration of coupling between an optical phonon mode and the Kondo effect.Comment: 4 Pages, 3 Figures, submitted to Phys. Rev. Let

An Evaluative Study of the United States Cooperative Extension Service\u27s Role in Bridging the Digital Divide

Raising the level of digital inclusion by increasing the number of Americans using the technology tools of the digital age is a vitally important national goal (U.S. Department of Commerce, 2000). The study reported here focused on Extension administrators throughout the United States to gauge their opinion concerning the role of Extension in bridging the digital divide. It was found that a perceived digital divide existed. Extension administrators expressed that Extension was an adequate mechanism to combat this societal dilemma. Recommendations included establishing strategic partnerships with local community groups to provide technology access and training for residents

A Study of the Communities of Aquatic Macro-Invertebrates of the Merging of the Mississippi and Chippewa Rivers, Using a Biplate Substrate Sampler

Using a biplate substrate sampler, aquatic macro-invertebrates were collected during the fall, winter and spring seasons at the confluence of the Mississippi and Chippewa Rivers along the Minnesota-Wisconsin border. The substrate sampler proved very desirable in pointing out extreme community variations which existed between the two rivers. It was found that the members of a downstream community were a blend of the communities present in upstream tributaries. However, as compared with upstream communities, a shift in dominant organisms occurred. Striking seasonal changes appeared in the invertebrate populations as well as the environment of the rivers. All sampling revealed clean water communities were present and suggested the absence of aquatic pollution

Tubulin cofactors and Arl2 are cage-like chaperones that regulate the soluble αβ-tubulin pool for microtubule dynamics.

Microtubule dynamics and polarity stem from the polymerization of αβ-tubulin heterodimers. Five conserved tubulin cofactors/chaperones and the Arl2 GTPase regulate α- and β-tubulin assembly into heterodimers and maintain the soluble tubulin pool in the cytoplasm, but their physical mechanisms are unknown. Here, we reconstitute a core tubulin chaperone consisting of tubulin cofactors TBCD, TBCE, and Arl2, and reveal a cage-like structure for regulating αβ-tubulin. Biochemical assays and electron microscopy structures of multiple intermediates show the sequential binding of αβ-tubulin dimer followed by tubulin cofactor TBCC onto this chaperone, forming a ternary complex in which Arl2 GTP hydrolysis is activated to alter αβ-tubulin conformation. A GTP-state locked Arl2 mutant inhibits ternary complex dissociation in vitro and causes severe defects in microtubule dynamics in vivo. Our studies suggest a revised paradigm for tubulin cofactors and Arl2 functions as a catalytic chaperone that regulates soluble αβ-tubulin assembly and maintenance to support microtubule dynamics