Coherence and clock shifts in ultracold Fermi gases with resonant interactions

Using arguments based on sum rules, we derive a general result for the average shifts of rf lines in Fermi gases in terms of interatomic interaction strengths and two-particle correlation functions. We show that near an interaction resonance shifts vary inversely with the atomic scattering length, rather than linearly as in dilute gases, thus accounting for the experimental observation that clock shifts remain finite at Feshbach resonances.Comment: 4 pages, 2 figures. Nordita preprint NORDITA-2007-2

Reciprocity and Priority Allocation System for Organ Transplant: An Ethical Analysis

How to increase the supply of organs donations for transplant is a critical issue in healthcare. Although recently xenotransplantation has received much publicity, it may be years before this becomes clinically viable. The Reciprocity and Priority Allocation (RPA) System currently used in Israel and a few other countries may be a reasonable approach to increase organ donation in the foreseeable future. For this approach to be accepted by the public, a robust analysis on its ethical implications is needed. This paper applies two formal ethics frameworks to analyze the implication of the RPA system

Fold Recognition via a Tree

Recently, we developed a pairwise structural alignment algorithm using realistic structural and environmental information (SAUCE). In this paper, we at first present an automatic fold hierarchical classification based on SAUCE alignments. This classification enables us to build a fold tree containing different levels of multiple structural profiles. Then a tree-based fold search algorithm is described. We applied this method to a group of structures with sequence identity less than 35% and did a series of leave one out tests. These tests are approximately comparable to fold recognition tests on superfamily level. Results show that fold recognition via a fold tree can be faster and better at detecting distant homologues than classic fold recognition methods.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/63155/1/cmb.2006.13.1565.pd

Single electron tunneling through high-Q single-wall carbon nanotube NEMS resonators

By first lithographically fabricating contact electrodes and then as last step growing carbon nanotubes with chemical vapour deposition across the ready-made chip, many potential contamination mechanisms for nanotube devices can be avoided. Combining this with pre-defined trenches on the chip, such that the nanotubes are freely suspended above the substrate, enables the formation of highly regular electronic systems. We show that, in addition, such suspended ultra-clean nanotubes provide excellent high-frequency and low-dissipation mechanical resonators. The motion detection mechanism of our experiment is discussed, and we measure the effect of Coulomb blockade and the back-action of single electron tunneling on the mechanical motion. In addition data on the mechanical higher modes is presented.Comment: 7 pages, 6 figure