The role of volatiles in aggregation and host-seeking of the haematophagous poultry red mite Dermanyssus gallinae (Acari: Dermanyssidae)

Infestations with ectoparasitic poultry red mites (Dermanyssus gallinae) pose an increasing threat to poultry health and welfare. Because of resistance to acaricides and higher scrutiny of poultry products, alternative and environmentally safe management strategies are warranted. Therefore, we investigated how volatile cues shape the behavior of D. gallinae and how this knowledge may be exploited in the development of an attractand- kill method to control mite populations. A Y-tube olfactometer bio-assay was used to evaluate choices of mites in response to cues related to conspecific mites as well as related to their chicken host. Both recently fed and starved mites showed a strong preference (84 and 85%, respectively) for volatiles from conspecific, fed mites as compared to a control stream of clean air. Mites were also significantly attracted to ‘aged feathers’ (that had remained in the litter for 3–4 days), but not to ‘fresh feathers’. Interestingly, an air stream containing 2.5% CO2, which mimics the natural concentration in air exhaled by chickens, did attract fed mites, but inhibited the attraction of unfed mites towards volatiles from aged feathers. We conclude that both mite-related cues (aggregation pheromones) and host-related cues (kairomones) mediate the behavior of the poultry mite. We discuss the options to exploit this knowledge as the ‘attract’ component of attract-and-kill strategies for the control of D. gallina

Investment behavior and yields in some West German industries

Net investment plays a crucial role for the economic development of a country. It contributes to the growth of real income and to the supply of jobs. Therefore, in view of sluggish growth and rising unemployment in Germany, the government as well as the Deutsche Bundesbank and the Council of Economic Experts have repeatedly pointed out the need to promote overall investment. Looking at the share of fixed investment in GDP in the German economy which is relatively high by international standards the complaints about the weakness of investment appear to be somewhat exaggerated. However, a closer look at the investment numbers published by the Deutsche Bundesbank (1983a, 1984) shows that the structure of domestic capital formation has changed dramatically since 1960. While investment by the non-financial business sector excluding housing accounted for 55 per cent of total investment in 1960, it has declined to some 30 per cent in the early 1980s (Figure 1) . Investment in residential construction and public investment have increased their share from about 44 per cent to more than two thirds in the early 1980s. Thus, instead of using more resources for enlarging and improving productive capacities, an increasing share of domestic savings has been channeled into projects the choice of which has not been made according to private profitability but from the point of view of social benefits. Among these projects are expenditures on infrastructure, public swimming pools, city halls, hospitals, family homes etc., which increase social consumption but hardly contribute to improve the competitiveness of the German industry in domestic and in international markets.

The presence of webbing affects the oviposition rate of two-spotted spider mites, Tetranychus urticae (Acari: Tetranychidae)

Several species of tetranychid mites including Tetranychus urticae Koch (Acari: Tetranychidae) construct complicated three-dimensional webs on plant leaves. These webs provide protection against biotic and abiotic stress. As producing web is likely to entail a cost, mites that arrive on a leaf with web are expected to refrain from producing it, because they will gain the benefit of protection from the existing web. Mites that produce less web may then allocate resources that are not spent on web construction to other fitness-enhancing activities, such as laying eggs. To test this, the oviposition rate of T. urticae adult females was examined on leaves with web. As a control, we used leaves where the web had been removed, hence both types of leaves had been exposed to conspecifics previously and were thus damaged. On leaves with web, the oviposition rate of T. urticae females was higher than on leaves where the web had been removed. Therefore, the presence of web constructed by conspecifics enhanced the oviposition rate of T. urticae females. This provides indirect evidence that mites use the web constructed by conspecifics and thereby save resources that can be allocated to other traits that enhance reproductive succes

Persistent current in a ring coupled to an external fermionic reservoir

We study the energy spectrum and the persistent current in an ideal one-dimensional mesoscopic ring coupled to a fermionic reservoir. We find that the tunnel coupling in general leads to the suppression of the persistent current. However, with increasing coupling, the effective level structure of the ring coupled to the reservoir changes and quasistates with a sharp eigenenergy develop. Depending on the number of ring states coupled to the reservoir this results in a nonzero persistent current even at very large tunneling between the ring and the reservoir.Comment: this is a short version of cond-mat/030713

The Interface between Quantum Mechanics and General Relativity

The generation, as well as the detection, of gravitational radiation by means of charged superfluids is considered. One example of such a "charged superfluid" consists of a pair of Planck-mass-scale, ultracold "Millikan oil drops," each with a single electron on its surface, in which the oil of the drop is replaced by superfluid helium. When levitated in a magnetic trap, and subjected to microwave-frequency electromagnetic radiation, a pair of such "Millikan oil drops" separated by a microwave wavelength can become an efficient quantum transducer between quadrupolar electromagnetic and gravitational radiation. This leads to the possibility of a Hertz-like experiment, in which the source of microwave-frequency gravitational radiation consists of one pair of "Millikan oil drops" driven by microwaves, and the receiver of such radiation consists of another pair of "Millikan oil drops" in the far field driven by the gravitational radiation generated by the first pair. The second pair then back-converts the gravitional radiation into detectable microwaves. The enormous enhancement of the conversion efficiency for these quantum transducers over that for electrons arises from the fact that there exists macroscopic quantum phase coherence in these charged superfluid systems.Comment: 22 pages, 7 figures; Lamb medal lecture on January 5, 2006 at the Physics of Quantum Electronics Winter Colloquium at Snowbird, Utah; accepted for publication in J. Mod. Optic