Exposure to Sublethal Doses of Fipronil and Thiacloprid Highly Increases Mortality of Honeybees Previously Infected by Nosema ceranae

International audienceBACKGROUND: The honeybee, Apis mellifera, is undergoing a worldwide decline whose origin is still in debate. Studies performed for twenty years suggest that this decline may involve both infectious diseases and exposure to pesticides. Joint action of pathogens and chemicals are known to threaten several organisms but the combined effects of these stressors were poorly investigated in honeybees. Our study was designed to explore the effect of Nosema ceranae infection on honeybee sensitivity to sublethal doses of the insecticides fipronil and thiacloprid. METHODOLOGY/FINDING: Five days after their emergence, honeybees were divided in 6 experimental groups: (i) uninfected controls, (ii) infected with N. ceranae, (iii) uninfected and exposed to fipronil, (iv) uninfected and exposed to thiacloprid, (v) infected with N. ceranae and exposed 10 days post-infection (p.i.) to fipronil, and (vi) infected with N. ceranae and exposed 10 days p.i. to thiacloprid. Honeybee mortality and insecticide consumption were analyzed daily and the intestinal spore content was evaluated 20 days after infection. A significant increase in honeybee mortality was observed when N. ceranae-infected honeybees were exposed to sublethal doses of insecticides. Surprisingly, exposures to fipronil and thiacloprid had opposite effects on microsporidian spore production. Analysis of the honeybee detoxification system 10 days p.i. showed that N. ceranae infection induced an increase in glutathione-S-transferase activity in midgut and fat body but not in 7-ethoxycoumarin-O-deethylase activity. CONCLUSIONS/SIGNIFICANCE: After exposure to sublethal doses of fipronil or thiacloprid a higher mortality was observed in N. ceranae-infected honeybees than in uninfected ones. The synergistic effect of N. ceranae and insecticide on honeybee mortality, however, did not appear strongly linked to a decrease of the insect detoxification system. These data support the hypothesis that the combination of the increasing prevalence of N. ceranae with high pesticide content in beehives may contribute to colony depopulation

Rotationally resolved infrared spectrum of the Li+_D2 cation complex

The infrared spectrum of mass selected Li +-D 2 cations is recorded in the D-D stretch region (2860-2950 cm -1) in a tandem mass spectrometer by monitoring Li + photofragments. The D-D stretch vibration of Li +-D 2 is shifted by -79 cm -1 from that of the free D 2 molecule indicating that the vibrational excitation of the D 2 subunit strengthens the effective Li +-D 2 intermolecular interaction. Around 100 rovibrational transitions, belonging to parallel K a=0-0, 1-1, and 2-2 subbands, are fitted to a Watson A-reduced Hamiltonian to yield effective molecular parameters. The infrared spectrum shows that the complex consists of a Li + ion attached to a slightly perturbed D 2 molecule with a T-shaped equilibrium configuration and a 2.035 A vibrationally averaged intermolecular separation. Comparisons are made between the spectroscopic data and data obtained from rovibrational calculations using a recent three dimensional Li +-D 2 potential energy surface [R. Martinazzo, G. Tantardini, E. Bodo, and F. Gianturco, J. Chem. Phys. 119, 11241 (2003)]

Infrared spectra of the Li +_(H 2)n(n=1-3) cation complexes

The Li+–(H2)n n = 1–3 complexes are investigated through infrared spectra recorded in the H–H stretch region (3980–4120 cm−1) and through ab initio calculations at the MP2∕aug-cc-pVQZ level. The rotationally resolved H–H stretch band of Li+–H2 is centered at 4053.4 cm−1 [a −108 cm−1 shift from the Q1(0) transition of H2]. The spectrum exhibits rotational substructure consistent with the complex possessing a T-shaped equilibrium geometry, with the Li+ ion attached to a slightly perturbed H2 molecule. Around 100 rovibrational transitions belonging to parallel Ka = 0‐0, 1-1, 2-2, and 3-3 subbands are observed. The Ka = 0‐0 and 1-1 transitions are fitted by a Watson A-reduced Hamiltonian yielding effective molecular parameters. The vibrationally averaged intermolecular separation in the ground vibrational state is estimated as 2.056 Å increasing by 0.004 Å when the H2 subunit is vibrationally excited. The spectroscopic data are compared to results from rovibrational calculations using recent three dimensional Li+–H2 potential energy surfaces [ Martinazzo et al., J. Chem. Phys. 119, 11241 (2003); Kraemer and Špirko, Chem. Phys. 330, 190 (2006) ]. The H–H stretch band of Li+–(H2)2, which is centered at 4055.5 cm−1 also exhibits resolved rovibrational structure. The spectroscopic data along with ab initio calculations support a H2–Li+–H2 geometry, in which the two H2 molecules are disposed on opposite sides of the central Li+ ion. The two equivalent Li+⋯H2 bonds have approximately the same length as the intermolecular bond in Li+–H2. The Li+–(H2)3 cluster is predicted to possess a trigonal structure in which a central Li+ ion is surrounded by three equivalent H2 molecules. Its infrared spectrum features a broad unresolved band centered at 4060 cm−1

Power and temperature dependent model for High Q superconductors

Measuring the internal quality factor of coplanar waveguide superconducting resonators is an established method of determining small losses in superconducting devices. Traditionally, the resonator losses are only attributed to two-level system (TLS) defects using a power dependent model for the quality factor. However, excess non-equilibrium quasiparticles can also limit the quality factor of the planar superconducting resonators used in circuit quantum electrodynamics. At millikelvin temperatures, quasiparticles can be generated by breaking Cooper pairs via a single high-energy or multiple sub-gap photons. Here a two-temperature, power and temperature dependent model is proposed to evaluate resonator losses for isolating TLS and quasiparticle loss simultaneously. The model combines the conventional TLS power and temperature dependence with an effective temperature non-equilibrium quasiparticle description of the superconducting loss. The quasiparticle description is based on the quasiparticle number density calculated using rate equations for an external quasiparticle generation source, recombination, and trapping. The number density is translated to an effective temperature using a thermal distribution that may be different from the bath. Experimental measurements of high-quality factor resonators fabricated from single crystal aluminum and titanium nitride thin films on silicon are interpreted with the presented model. This approach enables identification of quasiparticle and TLS loss, resulting in the determination that the TiN resonator has comparable TLS and quasiparticle loss at low power and low-temperature, while the low-temperature Al resonator behavior is dominated by non-equilibrium quasiparticle loss