Feshbach Molecules in a One-dimensional Optical Lattice

We present the theory of a pair of atoms in a one-dimensional optical lattice interacting via a narrow Feshbach resonance. Using a two-channel description of the resonance, we derive analytic results for the scattering states inside the continuum band and the discrete bound states outside the band. We identify a Fano resonance profile, and the survival probability of a molecule when swept through the Bloch band of scattering states by varying an applied magnetic field. We discuss how these results may be used to investigate the importance of the structured nature of the continuum in experiments.Comment: 4 pages, 3 figure

Two-channel Feshbach physics in a structured continuum

We analyze the scattering and bound state physics of a pair of atoms in a one-dimensional optical lattice interacting via a narrow Feshbach resonance. The lattice provides a structured continuum allowing for the existence of bound dimer states both below and above the continuum bands, with pairs above the continuum stabilized by either repulsive interactions or their center of mass motion. Inside the band the Feshbach coupling to a closed channel bound state leads to a Fano resonance profile for the transmission, which may be mapped out by RF- or photodissociative spectroscopy. We generalize the scattering length concept to the one-dimensional lattice, where a scattering length may be defined at both the lower and the upper continuum thresholds. As a function of the applied magnetic field the scattering length at either band edge exhibits the usual Feshbach divergence when a bound state enters or exits the continuum. Near the scattering length divergences the binding energy and wavefunction of the weakly bound dimer state acquires a universal form reminiscent of those of free-space Feshbach molecules. We give numerical examples of our analytic results for a specific Feshbach resonance, which has been studied experimentally.Comment: 18 pages, 9 embedded figure

Scattering and binding of different atomic species in a one-dimensional optical lattice

The theory of scattering of atom pairs in a periodic potential is presented for the case of different atoms. When the scattering dynamics is restricted to the lowest Bloch band of the periodic potential, a separation in relative and average discrete coordinates applies and makes the problem analytically tractable, and we present a number of new results and features compared to the case of identical atoms.Comment: 5 pages, 4 figure

Theory of Feshbach molecule formation in a dilute gas during a magnetic field ramp

Starting with coupled atom-molecule Boltzmann equations, we develop a simplified model to understand molecule formation observed in recent experiments. Our theory predicts several key features: (1) the effective adiabatic rate constant is proportional to density; (2) in an adiabatic ramp, the dependence of molecular fraction on magnetic field resembles an error function whose width and centroid are related to the temperature; (3) the molecular production efficiency is a universal function of the initial phase space density, the specific form of which we derive for a classical gas. Our predictions show qualitative agreement with the data from [Hodby et al, Phys. Rev. Lett. {\bf{94}}, 120402 (2005)] without the use of adjustable parameters

Ultra-high temperature measuring techniques Final report

Real time technique for measurement of high temperature gases and spectroscopic techniques for temperature measurement of hot cesium seeded hydroge

Angular momentum exchange between coherent light and matter fields

Full, three dimensional, time-dependent simulations are presented demonstrating the quantized transfer of angular momentum to a Bose-Einstein condensate from a laser carrying orbital angular momentum in a Laguerre-Gaussian mode. The process is described in terms of coherent Bragg scattering of atoms from a chiral optical lattice. The transfer efficiency and the angular momentum content of the output coupled vortex state are analyzed and compared with a recent experiment.Comment: 4 pages, 4 figure

Large-angle Electron-photon Coincidence Experiment In Atomic Hydrogen

1s-2p excitation in hydrogen has been studied by observing the angular correlation of Lyman photons detected in coincidence with inelastically scattered electrons at 54.4 eV incident energy. The electron scattering angles ranged from 10°to 133°; the results at scattering angles larger than 20°cannot be explained by currently available theories. © 1980 The American Physical Society

Identification and characterization of the heme-binding proteins SeShp and SeHtsA of Streptococcus equi subspecies equi

BACKGROUND: Heme is a preferred iron source of bacterial pathogens. Streptococcus equi subspecies equi is a bacterial pathogen that causes strangles in horses. Whether S. equi has a heme acquisition transporter is unknown. RESULTS: An S. equi genome database was blasted with the heme binding proteins Shp and HtsA of Streptococcus pyogenes, and found that S. equi has the homologue of Shp (designated SeShp) and HtsA (designated SeHtsA). Tag-free recombinant SeShp and SeHtsA and 6xHis-tagged SeHtsA (SeHtsA(His)) were prepared and characterized. Purified holoSeShp and holoSeHtsA bind Fe(II)-protoporphyrin IX (heme) and Fe(III)-protoporphyrin IX (hemin) in a 1:1 stoichiometry, respectively, and are designated hemoSeShp and hemiSeHtsA. HemiSeShp and hemiSeHtsA(His )can be reconstituted from apoSeShp and apoSeHtsA(His )and hemin. HemoSeShp is stable in air and can be oxidized to hemiSeShp by ferricyanide. HemiSeHtsA can be reduced into hemoSeHtsA, which autoxidizes readily. HemoSeShp rapidly transfers its heme to apoSeHtsA(His). In addition, hemoSeShp can also transfer its heme to apoHtsA, and hemoShp is able to donate heme to apoSeHtsA(His). CONCLUSION: The primary structures, optical properties, oxidative stability, and in vitro heme transfer reaction of SeShp and SeHtsA are very similar to those of S. pyogenes Shp and HtsA. The data suggest that the putative cell surface protein SeShp and lipoprotein SeHtsA are part of the machinery to acquire heme in S. equi. The results also imply that the structure, function, and functional mechanism of the heme acquisition machinery are conserved in S. equi and S. pyogenes

Maternal allergen immunisation to prevent sensitisation in offspring: Th2-polarising adjuvants are more efficient than a Th1-polarising adjuvant in mice

<p>Abstract</p> <p>Background</p> <p>Allergy has been an increasing problem in several parts of the world. Prenatal exposure to allergen and microbial components may affect the development of allergies in childhood, as indicated by epidemiological and experimental studies. We investigated the capacity for allergic sensitisation in offspring after induction of a Th1- or a Th2-polarised immune response to the same allergen in mothers during pregnancy.</p> <p>Results</p> <p>During pregnancy, mice were immunised with ovalbumin (OVA) given with either one of the Th2-adjuvants pertussis toxin (PT) or Al(OH)₃(aluminium hydroxide), or with the Th1 adjuvant CpG. Offspring were immunised with OVA in Al(OH)₃as young adults. Serum and supernatants from <it>ex vivo </it>stimulated or non-stimulated spleen cells from mothers and offspring were analysed for OVA-specific antibodies and cytokines, respectively. Mothers immunised with OVA together with either Al(OH)₃or PT had increased levels of OVA-specific IgE and IgG1 compared to naive mothers, whereas mothers immunised with OVA together with CpG had increased levels of OVA-specific IgG2a compared to naive mothers. In general the highest levels of IL-5, IL-10, and IFNγ were observed in spleen cells from mothers immunised with PT and OVA. Upon immunisation, offspring from mothers immunised with OVA and either PT or Al(OH)₃showed reduced levels of OVA-specific IgE and IgG1 and increased levels of OVA-specific IgG2a antibodies compared to offspring from naive mothers. Maternal immunisation with CpG and OVA did not affect antibody responses in offspring.</p> <p>Conclusion</p> <p>Allergic sensitisation in the offspring was affected by the type of adjuvant used for immunisation of the mothers with the same allergen. Th2 polarisation of the immune response in the mothers was found to give reduced IgE levels upon sensitisation of the offspring, whereas no reduction was achieved with Th1 polarisation in the mothers.</p