Stripe Disordering Transition

We have recently begun Monte Carlo simulations of the dynamics of stripe phases in the cuprates. A simple model of spinodal decomposition of the holes allows us to incorporate Coulomb repulsion and coherency strains. We find evidence for a possible stripe disordering transition, at a temperature below the pseudogap onset. Experimental searches for such a transition can provide constraints for models of stripe formation.Comment: 4 pages LaTex, 2 ps figures (U. of Miami Conference HTS99

SO(6)-Generalized Pseudogap Model of the Cuprates

The smooth evolution of the tunneling gap of Bi_2Sr_2CaCu_2O_8 with doping from a pseudogap state in the underdoped cuprates to a superconducting state at optimal and overdoping reflects an underlying SO(6) instability structure of the (pi,0) saddle points. The pseudogap is probably not associated with superconductivity, but is related to competing nesting instabilities, which are responsible for the stripe phases. We earlier introduced a simple Ansatz of this competition in terms of a pinned Balseiro-Falicov (pBF) model of competing charge density wave and (s-wave) superconductivity. This model gives a good description of the phase diagram and the tunneling and photoemission spectra. Here, we briefly review these results, and discuss some recent developments: experimental evidence for a non-superconducting component to the pseudogap; and SO(6) generalizations of the pBF model, including flux phase and d-wave superconductivity.Comment: 6 pages LaTex, 4 ps figures (U. of Miami Conference HTS99

A sketch planning methodology for determining interventions for bicycle and pedestrian crashes: an ecological approach

Bicycle and pedestrian safety planning have recently been gaining increased attention. With this focus, however, comes increased responsibilities for planning agencies and organizations tasked with evaluating and selecting safety interventions, a potentially arduous task given limited staff and resources. This study presents a sketch planning framework based on ecological factors that attempts to provide an efficient and effective method of selecting appropriate intervention measures. A Chicago case study is used to demonstrate how such a method may be applied

The Contemporary Presidency Reconsidering Presidential Policy Czars

Since controversy began to swirl surrounding then-President-elect Barack Obama\u27s alleged overreliance on policy czars in late 2008, political scientists and pundits alike have been quick to view this approach to White House staffing as an extension of the imperial presidency and, to some, a threat to the constitutional order. In this article, I take a step back and ask whether the phenomenon under attack is exactly what scholars assume it is. In doing so, I investigate the conceptualization problem czars pose as well as how and why presidents actually use czars. I conclude with a series of suggestion for future presidents on how best to use policy czars to advance the interests of their administration and manage the executive institution

Is George W Bush a Burden or Blessing for Jeb Bush’s 2016 Campaign?

Now that Jeb Bush has finally officially announced his bid for the White House, the chattering class can shift its conversation to whether he will win and what hurdles stand in his way

Long-term experimental evolution in Escherichia coli. X. Quantifying the fundamental and realized niche

BACKGROUND: Twelve populations of the bacterium, Escherichia coli, adapted to a simple, glucose-limited, laboratory environment over 10,000 generations. As a consequence, these populations tended to lose functionality on alternative resources. I examined whether these populations in turn became inferior competitors in four alternative environments. These experiments are among the first to quantify and compare dimensions of the fundamental and realized niches. RESULTS: Three clones were isolated from each of the twelve populations after 10,000 generations of evolution. Direct competition between these clones and the ancestor in the selective environment revealed average fitness improvements of ~50%. When grown in the wells of Biolog plates, however, evolved clones grew 25% worse on average than the ancestor on a variety of different carbon sources. Next, I competed each evolved population versus the ancestor in four foreign environments (10-fold higher and lower glucose concentration, added bile salts, and dilute LB media). Surprisingly, nearly all populations were more fit than the ancestor in each foreign environment, though the margin of improvement was least in the most different environment. Most populations also evolved increased sensitivity to novobiocin. CONCLUSIONS: Reduced functionality on numerous carbon sources suggested that the fundamental niche of twelve E. coli populations had narrowed after adapting to a specific laboratory environment. However, in spite of these results, the same populations were competitively superior in four novel environments. These findings suggest that adaptation to certain dimensions of the environment may compensate for other functional losses and apparently enhance the realized niche