Generating Evidence to Guide Merger Enforcement

The challenge of effective merger enforcement is tremendous. U.S. antitrust agencies must, by statute, quickly forecast the competitive effects of mergers that occur in virtually every sector of the economy to determine if mergers can proceed. Surprisingly, given the complexity of the regulators task, there is remarkably little empirical evidence on the effects of mergers to guide regulators. This paper describes the necessity of retrospective analysis of past mergers in building an empirical basis for antitrust enforcement, and provides guidance on the key measurement issues researchers confront in estimating the price effects of mergers. We also describe how evidence from merger retrospectives can be used to evaluate the economic models used to predict the competitive effects of mergers.Corporate mergers, antitrust enforcement

Determining the Gamma-Ray Burst Rate as a Function of Redshift

We exploit the 14 gamma-ray bursts (GRBs) with known redshifts z and the 7 GRBs for which there are constraints on z to determine the GRB rate R_{GRB}(z), using a method based on Bayesian inference. We find that, despite the qualitative differences between the observed GRB rate and estimates of the SFR in the universe, current data are consistent with R_{GRB}(z) being proportional to the SFR.Comment: To appear in Procs. of Gamma-Ray Bursts in the Afterglow Era: 2nd Workshop, 3 pages, 3 figures, LaTe

Ethnicity: A Conceptual Approach

The essays compiled here examine ethnicity from many perspectives. The authors explore it conceptually--with periodic disagreement-and attempt to come to terms with its impact on American society. They serve as an introduction to this exciting and complex influence on American life. Original publication date 1976.https://engagedscholarship.csuohio.edu/clevmembks/1059/thumbnail.jp

Molecular Characterization of Mammalian De Novo DNA Methyltransferase Chromatin Recruitment

Precise deposition of CpG methylation is critical for mammalian development and tissue homeostasis and is often dysregulated in human diseases. The genomic localization of de novo DNA methyltransferases 3A (DNMT3A) and 3B (DNMT3B) is facilitated in part by chromatin “reader” domains to establish DNA methylation patterns genome-wide. Recent work has highlighted a role for the PWWP reader domain in directing recruitment of DNMT3B to actively transcribed gene bodies. However, our understanding of de novo DNA methyltransferase chromatin recruitment remains incomplete. Here I demonstrate using a variety of biochemical and cellular techniques that DNMT3A genomic localization is regulated by competing chromatin recruitment pathways. Under steady-state conditions, DNMT3A is targeted to non-coding intergenic regions through PWWP reader domain recognition of H3K36me2, an abundant histone post-translational modification (PTM) in cells. Following depletion of cellular H3K36me2 levels, DNMT3A is re-targeted to actively transcribed gene bodies through PWWP domain interaction with H3K36me3, thereby resembling the genomic localization of DNMT3B. Lastly, loss of PWWP domain reader functionality reveals the presence of a previously uncharacterized chromatin reader domain within DNMT3A that serves as an alternative targeting mechanism to facilitate de novo methylation of Polycomb-regulated regions, including a subset of CpG islands. Perturbations to these recruitment mechanisms may underlie the pathology of developmental overgrowth and undergrowth syndromes associated with distinct germline mutations in DNMT3A and may also contribute to the altered DNA methylation landscapes observed in diverse cancers

Signatures of gravitational fixed points at the LHC

We study quantum-gravitational signatures at the CERN Large Hadron Collider (LHC) in the context of theories with extra spatial dimensions and a low fundamental Planck scale in the TeV range. Implications of a gravitational fixed point at high energies are worked out using Wilson¿s renormalization group. We find that relevant cross sections involving virtual gravitons become finite. Based on gravitational lepton pair production we conclude that the LHC is sensitive to a fundamental Planck scale of up to 6 TeV

Thermonuclear .Ia Supernovae from Helium Shell Detonations: Explosion Models and Observables

During the early evolution of an AM CVn system, helium is accreted onto the surface of a white dwarf under conditions suitable for unstable thermonuclear ignition. The turbulent motions induced by the convective burning phase in the He envelope become strong enough to influence the propagation of burning fronts and may result in the onset of a detonation. Such an outcome would yield radioactive isotopes and a faint rapidly rising thermonuclear ".Ia" supernova. In this paper, we present hydrodynamic explosion models and observable outcomes of these He shell detonations for a range of initial core and envelope masses. The peak UVOIR bolometric luminosities range by a factor of 10 (from 5e41 - 5e42 erg/s), and the R-band peak varies from M_R,peak = -15 to -18. The rise times in all bands are very rapid (<10 d), but the decline rate is slower in the red than the blue due to a secondary near-IR brightening. The nucleosynthesis primarily yields heavy alpha-chain elements (40Ca through 56Ni) and unburnt He. Thus, the spectra around peak light lack signs of intermediate mass elements and are dominated by CaII and TiII features, with the caveat that our radiative transfer code does not include the non-thermal effects necessary to produce He features.Comment: Accepted for publication in The Astrophysical Journal; 9 pages, 9 figures; v2: Minor changes to correct typos and clarify conten