Properties of KCo2_2As2_2 and Alloys with Fe and Ru: Density Functional Calculations

Electronic structure calculations are presented for KCo$_2$As$_2$ and alloys with KFe$_2$As$_2$ and KRu$_2$As$_2$. These materials show electronic structures characteristic of coherent alloys, with a similar Fermi surface structure to that of the Fe-based superconductors, when the $d$ electron count is near six per transition metal. However, they are less magnetic than the corresponding Fe compounds. These results are discussed in relation to superconductivity.Comment: 5 page

Willingness to use mobile technologies for data collection in a probability household panel

We asked members of the Understanding Society Innovation Panel about their willingness to participate in various data collection tasks on their mobile devices. We find that stated willingness varies considerably depending on the type of activity involved: respondents are less willing to participate in tasks that involve downloading and installing an app, or where data are collected passively. Stated willingness also varies between smartphones and tablets, and between types of respondents: respondents who report higher concerns about the security of data collected with mobile technologies and those who use their devices less intensively are less willing to participate in mobile data collection tasks

Density profiles and density oscillations of an interacting three-component normal Fermi gas

We use a semiclassical approximation to investigate density variations and dipole oscillations of an interacting three-component normal Fermi gas in a harmonic trap. We consider both attractive and repulsive interactions between different pairs of fermions and study the effect of population imbalance on densities. We find that the density profiles significantly deviate from those of non-interacting profiles and extremely sensitive to interactions and population imbalance. Unlike for a two-component Fermi system, we find density imbalance even for balanced populations. For some range of parameters, one component completely repels from the trap center giving rise a donut shape density profile. Further, we find that the in-phase dipole oscillation frequency is consistent with Kohn's theorem and other two dipole mode frequencies are strongly effected by the interactions and the number of atoms in the harmonic trap.Comment: Total seven pages with five figures. Published versio

Site-specific conjugation of 8-ethynyl-BODIPY to a protein by [2+3] cycloaddition

We report a straightforward synthesis of 8-ethynyl-BODIPY derivatives and their potential as fluorescent labeling compounds using an alkyne-azide click chemistry approach. The ethynyl substituted BODIPY dyes at the meso-position were reacted under Cu+ catalysis and mild physiological conditions in organic and biological model systems using benzyl azide and a Barstar protein which was selectively modified by a single amino acid substituted methionine at the N-terminus (Met1). azidohomoalanine (Aha). Conjugation with the protein and the model azide was indicated by a significant blue shift upon formation of the triazole moiety system, which allowed easy distinction between free and coupled dyes. This blue shift was rationalized by the perpendicular orientation of the triazole relative to the chromophore using time dependent density functional theory (TDDFT) calculations. A full spectroscopic and thermodynamic characterization of the protein revealed that a fluorophore was incorporated without the cross influence of protein stability and functional integrity. Furthermore, model reactions of 8-ethynyl-BODIPY derivatives with benzyl azide under copper-free conditions indicate second order kinetics with high rate constants comparable with those found for the strain-promoted azide-alkyne cycloaddition (SPAAC). In this way, we establish a unique and highly efficient method to introduce alkyne-BODIPY into a protein scaffold potentially useful for diverse applications in areas ranging from fundamental protein dynamics studies to biotechnology or cell biology

Observation of an Efimov resonance in an ultracold mixture of atoms and weakly bound dimers

We discuss our recent observation of an atom-dimer Efimov resonance in an ultracold mixture of Cs atoms and Cs_2 Feshbach molecules [Nature Phys. 5, 227 (2009)]. We review our experimental procedure and present additional data involving a non-universal g-wave dimer state, to contrast our previous results on the universal s-wave dimer. We resolve a seeming discrepancy when quantitatively comparing our experimental findings with theoretical results from effective field theory.Comment: Conference Proceeding ICPEAC 2009 Kalamazoo, to appear in Journal of Physics: Conference Serie