We investigate the energy dependence and the internal-state dependence of the charge-exchange collision cross sections in a mixture of 6 Li atoms and 40 Ca + ions. Deliberately excited ion micromotion is used to control the collision energy of atoms and ions. The energy dependence of the charge-exchange collision cross section obeys the Langevin model in the temperature range of the current experiment, and the measured magnitude of the cross section is correlated to the internal state of the 40 Ca + ions. Revealing the relationship between the charge-exchange collision cross sections and the interaction potentials is an important step toward the realization of the full quantum control of the chemical reactions at an ultralow temperature regime.

We demonstrated sympathetic cooling of a single ion in a buffer gas of ultracold atoms with small mass. Efficient collisional cooling was realized by suppressing collision-induced heating. We attempt to explain the experimental results with a simple rate equation model and provide a quantitative discussion of the cooling efficiency per collision. The knowledge we obtained in this work is an important ingredient for advancing the technique of sympathetic cooling of ions with neutral atoms.PACS numbers: 37.10. Ty,03.67.Lx Sympathetic cooling, where we thermally contact two distinct systems at different temperatures, is an effective method for cooling an object to a desired energy regime. Nowadays, this is commonly used in the field of low-temperature physics for producing a cold sample for a molecular beam or degenerate atomic gases. The elemental mechanism of this technique extracts energy from a target object through interaction (normally by collisions) with a coolant system. In cooling of translational motion, for example, an exchange of moment between the two systems can remove kinetic energy from the thermal system, and eventually they reach thermal equilibrium, resulting in cooling of the target object.To introduce an ultracold atomic gas as a coolant for trapped ions is attractive, since collisions with ultracold atoms enable efficient cooling of a number of vibrational modes simultaneously. It is beneficial for many applications, for example, continuous cooling of ion qubits in quantum information processing. In addition, this method has been proven to be effective for the cooling of atomic or molecular systems, especially when no conventional laser cooling transition is accessible, as demonstrated in rotational-vibrational cooling of molecular ions [1,2].In buffer-gas cooling of a charged particle, however, the situation is not as simple as in the usual schemes, e.g., evaporation or sympathetic cooling in a mixture of neutral gases. This is simply attributed to the dynamics of trapping it in a radiofrequency (RF) trap, where slow (secular) and rapid (micro) motion are superimposed on the motion of the ion. The main point is that an abrupt interception of coherent ion motion by an atom-ion collision complicates the kinetics of the ion. Importantly, an ion can be either cooled or even heated, depending on the instantaneous phase of micromotion at the moment of a collision, which prevents efficient collisional cooling [3]. In addition, this peculiar feature modifies the energy distribution of an ion by inducing a deviation from a normal (Maxwell-Boltzmann) distribution to * haze@ils.uec.ac.jp a super-statistical (so-called Tsallis) distribution accompanied with a power-law tail in a high-energy region [4][5][6]. These subjects have been pointed out since the early stages of ion trapping experiments [7], and they were recently revisited again in conjunction with the rapidly growing field of ultracold atom-ion hybrid systems [8].A key parameter for characterizing the kinetics of the ion in a buffer gas is t...

Abstract. Hole propagator of spin 1/2 Calogero-Sutherland model is derived using Uglov's method, which maps the exact eigenfunctions of the model, called Yangian Gelfand-Zetlin basis, to a limit of Macdonald polynomials (gl 2 -Jack polynomials). To apply this mapping method to the calculation of 1-particle Green's function, we confirm that the sum of the field annihilation operatorψ ↑ +ψ ↓ on Yangian Gelfand-Zetlin basis is transformed to the field annihilation operatorψ on gl 2 -Jack polynomials by the mapping. The resultant expression for hole propagator for finite-size system is written in terms of renormalized momenta and spin of quasi-holes and the expression in the thermodynamic limit coincides with the earlier result derived by another method. We also discuss the singularity of the spectral function for a specific coupling parameter where the hole propagator of spin Calogero-Sutherland model becomes equivalent to dynamical colour correlation function of SU(3) Haldane-Shastry model.

Stressful exercise results in temporary immune depression. However, the impact of exercise on the immune responses via toll-like receptor (TLR) 7, which recognizes the common viral genomic feature, single-stranded RNA, remains unclear. To clarify the effect of stressful exercise on immune function in response to viral infection, we measured the changes in the plasma concentration of tumor necrosis factor (TNF)-α and interferon (IFN)-α, which are induced downstream from the TLR-ligand interaction, in exhaustive-exercised mice immediately after treatment with the imidazoquinoline R-848, which can bind to and activate TLR7. Both exhaustive-exercised (EX) and non-exercised (N-EX) male C3H/HeN mice were injected with R-848 (5 mg kg(-1)), and blood samples were collected. In addition, RAW264 cells, which are mouse macrophage cells, were cultured 30 min after epinephrine (10 μM) or norepinephrine (10 μM) treatments, and were then stimulated with R-848 (10 μg ml(-1)). In addition, the effect of propranolol (10 mg kg(-1)) as blockade of β-adrenergic receptors on R-848-induced TNF-α and IFN-α production in the exercised mice was examined. Both the TNF-α and IFN-α concentrations in the plasma of EX were significantly lower than those in the plasma of N-EX after R-848 injection (P < 0.05 and P < 0.01, respectively), although the R-848 treatment increased the plasma TNF-α and IFN-α concentrations in both groups (P < 0.01, respectively). The R-848-induced TNF-α production in RAW264 cells was significantly inhibited by epinephrine and norepinephrine pre-treatment, although IFN-α was not detected. The propranolol treatment completely inhibited exercise-induced TNF-α and IFN-α suppression in response to R-848 in the mice. These data suggest that EX induces a reduction in TNF-α and IFN-α production in response to R-848, and that these phenomena might be regulated by an exercise-induced elevation of the systemic catecholamines.

A time-reversal invariant Kitaev-type model is introduced in which spins (Dirac matrices) on the square lattice interact via anisotropic nearest-neighbor and next-nearest-neighbor exchange interactions. The model is exactly solved by mapping it onto a tight-binding model of free Majorana fermions coupled with static Z2 gauge fields. The Majorana fermion model can be viewed as a model of time-reversal invariant superconductor and is classified as a member of symmetry class DIII in the Altland-Zirnbauer classification. The ground-state phase diagram has two topologically distinct gapped phases which are distinguished by a Z2 topological invariant. The topologically nontrivial phase supports both a Kramers' pair of gapless Majorana edge modes at the boundary and a Kramers' pair of zero-energy Majorana states bound to a 0-flux vortex in the π-flux background. Power-law decaying correlation functions of spins along the edge are obtained by taking the gapless Majorana edge modes into account. The model is also defined on the one-dimension ladder, in which case again the ground-state phase diagram has Z2 trivial and non-trivial phases.