The effect of object distance on pattern preferences in the walking fly,Drosophila melanogaster

Zusammenfassung Fliegen bevorzugen sehwinkelkonstante Vertikal- gegenüber Horizontalstreifen bei grossen, nicht dagegen bei kleinen Musterentfernungen. Diese entfernungsabhängige Vertikalstreifenpräferenz wird als Folge eines Mechanismus zur optischen Kurskontrolle verstanden, der von Art und Geschwindigkeit der retinalen Bildverschiebung abhängt.

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Financial support of the Deutsche Forschungsgemeinschaft and the Schweizerischer Nationalfonds is gratefully acknowledged.     

The role of crustecdysone in the moulting crayfish

Résumé La crustecdysone injectée dans l'écrevisse,Procambarus sinulans ne cause pas la mue chez l'animal intact mais l'accélère après ablation des pédoncules oculaires.     

Do female hyaenas choose mates based on tenure?

In their investigation into whether female mate-choice drives male dispersal, H?ner et al. argue that female spotted hyaenas (Crocuta crocuta) prefer mates whose tenure in the social group is less than the females' age, to avoid paternal incest, and suggest that male dispersal reflects this preference. However, we are not persuaded that females choose mates on the basis of tenure because H?ner et al. overlook the alternative hypothesis that dispersal status itself is important in female mate-choice, such that females prefer immigrants over natal males. Like mate-choice based on tenure, choice based on dispersal status reduces the risk of incest.     

束参数对离子束溅射法所淀积非晶硅电特性的影响

本文论述了用离子束溅射淀积非晶硅(a-Si)和氢化非晶硅(a-Si:H)的方法,提供了加速电压和衬底位置改变对薄膜暗电阻率的影响结果,通过有关淀积工艺条件的研究,得出了一些有用的结论。     

Odorant signal termination by olfactory UDP glucuronosyl transferase

The onset of olfactory transduction has been extensively studied, but considerably less is known about the molecular basis of olfactory signal termination. It has been suggested that the highly active cytochrome P450 monooxygenases of olfactory neuroepithelium are termination enzymes, a notion supported by the identification and molecular cloning of olfactory-specific cytochrome P450s (refs. 13-16). But as reactions catalysed by cytochrome P450 (refs 17, 18) often do not significantly alter volatility, lipophilicity or odour properties, cytochrome P450 may not be solely responsible for olfactory signal termination. In liver and other tissues, drug hydroxylation by cytochrome P450 is frequently followed by phase II biotransformation, for example by UDP glucuronosyl transferase (UGT), resulting in a major change of solubility and chemical properties. We report here the molecular cloning and expression of an olfactory-specific UGT. The olfactory enzyme, but not the one in liver microsomes, shows preference for odorants over standard UGT substrates. Furthermore, glucuronic acid conjugation abolishes the ability of odorants to stimulate olfactory adenylyl cyclase. This, together with the known broad spectrum of drug-detoxification enzymes, supports a role for olfactory UGT in terminating diverse odorant signals.     

Quasicrystalline valence bands in decagonal AlNiCo

Quasicrystals are metallic alloys that possess perfect long-range structural order, in spite of the fact that their rotational symmetries are incompatible with long-range periodicity. The exotic structural properties of this class of materials are accompanied by physical properties that are unexpected for metallic alloys. Considerable progress in resolving the geometric structures of quasicrystals has been made using X-ray and neutron diffraction, and concepts such as the quasi-unit-cell model have provided theoretical insights. But the basic properties of the valence electronic states--whether they are extended as in periodic crystals or localized as in amorphous materials--are still largely unresolved. Here we investigate the electronic bandstructure of quasicrystals through angle-resolved photoemission experiments on decagonal Al71.8Ni14.8Co13.4. We find that the s-p and d states exhibit band-like behaviour with the symmetry of the quasiperiodic lattice, and that the Fermi level is crossed by dispersing d-bands. The observation of free-electron-like bands, distributed in momentum space according to the surface diffraction pattern, suggests that the electronic states are not dominated by localization.