97 research outputs found
Deuterium-deuterium nuclear cross-sections in insulator and metallic environments
The three-dimensional Thomas-Fermi (TF) model is used to simulate the
variation of the d+d to t + p cross-section at low impact energies, when the
target deuterium nucleus is embedded in metallic or insulator environments.
Comparison of the computational results to recent experiments demonstrates that
even though the TF model can explain some increase in the low energy cross
section for metallic host, a full explanation of the experimental results is
still lacking. Possible reasons for the disagreement are discussed.Comment: 6 pages;6 figures. Accepted for publication in Eur. Phys. Jour.
Sex Pheromone Evolution Is Associated with Differential Regulation of the Same Desaturase Gene in Two Genera of Leafroller Moths
Chemical signals are prevalent in sexual communication systems. Mate recognition has been extensively studied within the Lepidoptera, where the production and recognition of species-specific sex pheromone signals are typically the defining character. While the specific blend of compounds that makes up the sex pheromones of many species has been characterized, the molecular mechanisms underpinning the evolution of pheromone-based mate recognition systems remain largely unknown. We have focused on two sets of sibling species within the leafroller moth genera Ctenopseustis and Planotortrix that have rapidly evolved the use of distinct sex pheromone blends. The compounds within these blends differ almost exclusively in the relative position of double bonds that are introduced by desaturase enzymes. Of the six desaturase orthologs isolated from all four species, functional analyses in yeast and gene expression in pheromone glands implicate three in pheromone biosynthesis, two Δ9-desaturases, and a Δ10-desaturase, while the remaining three desaturases include a Δ6-desaturase, a terminal desaturase, and a non-functional desaturase. Comparative quantitative real-time PCR reveals that the Δ10-desaturase is differentially expressed in the pheromone glands of the two sets of sibling species, consistent with differences in the pheromone blend in both species pairs. In the pheromone glands of species that utilize (Z)-8-tetradecenyl acetate as sex pheromone component (Ctenopseustis obliquana and Planotortrix octo), the expression levels of the Δ10-desaturase are significantly higher than in the pheromone glands of their respective sibling species (C. herana and P. excessana). Our results demonstrate that interspecific sex pheromone differences are associated with differential regulation of the same desaturase gene in two genera of moths. We suggest that differential gene regulation among members of a multigene family may be an important mechanism of molecular innovation in sex pheromone evolution and speciation
Longitudinal spin fluctuations and superconductivity in ferromagnetic ZrZn<sub>2</sub> from <i>ab initio</i> calculations
The recent discovery of superconductivity coexisting with weak itinerant
ferromagnetism in the -electron intermetallic compound ZrZn strongly
suggests spin-fluctuation mediated superconductivity. {\it Ab initio}
electronic structure calculations of the Fermi surface and generalized
susceptibilities are performed to investigate the viability of longitudinal
spin-fluctuation-induced spin-triplet superconductivity in the ferromagnetic
state. The critical temperature is estimated to be of the order of 1 K.
Additionally, it is shown that in spite of a strong electron-phonon coupling
(), conventional s-wave superconductivity is inhibited by the
presence of strong spin-fluctuations.Comment: 5 pages, 1 figur
Electronic topological transitions, magnetic ordering and the Fermi surfaces of Y and the heavy rare earths
Fermi surface reconstruction from 2D-ACAR data using maximum-likelihood fitting of wavelet-like functions
Fermi surface as the driving mechanism for helical antiferromagnetic ordering in Gd-Y alloys
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