Superconductivity without phonons.

The idea of superconductivity without the mediating role of lattice vibrations (phonons) has a long history. It was realized soon after the publication of the Bardeen-Cooper-Schrieffer (BCS) theory of superconductivity 50 years ago that a full treatment of both the charge and spin degrees of freedom of the electron predicts the existence of attractive components of the effective interaction between electrons even in the absence of lattice vibrations--a particular example is the effective interaction that depends on the relative spins of the electrons. Such attraction without phonons can lead to electronic pairing and to unconventional forms of superconductivity that can be much more sensitive than traditional (BCS) superconductivity to the precise details of the crystal structure and to the electronic and magnetic properties of a material.

Low-frequency spin dynamics in the CeMIn5 materials.

We measure the spin lattice relaxation of the planar In(1) nuclei in the CeMIn5 materials, extract quantitative information about the low energy spin dynamics of the lattice of Ce moments in both CeRhIn5 and CeCoIn5, and identify a crossover in the normal state. Above a temperature T(*) the Ce lattice exhibits "Kondo gas" behavior characterized by local fluctuations of independently screened moments; below T(*) both systems exhibit a "Kondo liquid" regime in which interactions between the local moments contribute to the spin dynamics. Both the antiferromagnetic and superconducting ground states in these systems emerge from the Kondo liquid regime. Our analysis provides strong evidence for quantum criticality in CeCoIn5.

The theory of everything.

We discuss recent developments in our understanding of matter, broadly construed, and their implications for contemporary research in fundamental physics.

The middle way.

Mesoscopic organization in soft, hard, and biological matter is examined in the context of our present understanding of the principles responsible for emergent organized behavior (crystallinity, ferromagnetism, superconductivity, etc.) at long wavelengths in very large aggregations of particles. Particular attention is paid to the possibility that as-yet-undiscovered organizing principles might be at work at the mesoscopic scale, intermediate between atomic and macroscopic dimensions, and the implications of their discovery for biology and the physical sciences. The search for the existence and universality of such rules, the proof or disproof of organizing principles appropriate to the mesoscopic domain, is called the middle way.

Nature of interaction between basic fibroblast growth factor and the antiangiogenic drug 7,7-(Carbonyl-bis[imino-N-methyl-4, 2-pyrrolecarbonylimino[N-methyl-4,2-pyrrole]-carbonylimino] )bis-(1, 3-naphthalene disulfonate).

PNU145156E (7,7-(carbonyl-bis[imino-N-methyl-4, 2-pyrrolecarbonylimino[N-methyl-4,2-pyrrole]-carbonylimino]) -bis-(1, 3-naphthalene disulfonate)) is a naphthalene sulfonic distamycin A derivative that interacts with heparin-binding growth factors. Because PNU145156E inhibits tumor angiogenesis, it was selected for clinical development. Picosecond time-resolved fluorescence emission and anisotropy were used to characterize the binding of PNU145156E to the basic fibroblast growth factor (a protein associated with tumor angiogenesis). A decrease in PNU145156E fluorescence lifetime was observed as a function of human basic fibroblast growth factor (bFGF) concentration. Nonlinear least-squares fitting of the binding isotherm yielded Kd = 145 nM for a single class of binding sites. Time-resolved anisotropy gave Kd = 174 nM. Kd = 150 nM was independently verified by quantitative high-performance affinity chromatography. The displaced volume of the complex, calculated from its rotational correlation time, fitted a sphere of 1:1 stoichiometry. These results account for the formation of a tight yet reversible PNU145156E:bFGF complex. An evaluation of PNU145156E fluorescence lifetimes in various solvents has highlighted the forces involved in stabilizing the complex. These are mostly electrostatic-hydrophobic in nature, with a relatively low contribution from hydrogen bonding. Both polar and nonpolar groups are involved on the protein-binding site within a largely hydrophobic cleft. A potential binding trajectory, based on a combination of these results with site-directed chemical modification and known bFGF x-ray structure, is suggested.

Migration between home country and diaspora: an economic analysis.

"This paper investigates the distribution of a population group between a home country and diaspora, given sequential decision-making regarding migration at the individual level. The home country is attractive to the members of the group, yet their presence there requires a fixed amount of public spending (e.g., on defense). The per-capita tax burden depends then on the size of the domestic population, reflecting a case of ¿fiscal externality'. This results in an inefficient distribution of the group between the home country and the diaspora. Encouraging immigration to the home country is an interest not only of those individuals who are currently in the home country but also of those residing in the diaspora. However, only when the burden of public spending in the home country is large enough do the latter volunteer to bear part of it. Even then, in general, this part is smaller than socially optimal."