2,772 research outputs found
Orbital-assisted metal-insulator transition in VO
We found direct experimental evidence for an orbital switching in the V 3d
states across the metal-insulator transition in VO. We have used
soft-x-ray absorption spectroscopy at the V edges as a sensitive
local probe, and have determined quantitatively the orbital polarizations.
These results strongly suggest that, in going from the metallic to the
insulating state, the orbital occupation changes in a manner that charge
fluctuations and effective band widths are reduced, that the system becomes
more 1-dimensional and more susceptible to a Peierls-like transition, and that
the required massive orbital switching can only be made if the system is close
to a Mott insulating regime
Proof of anthocyanins in the carnivorous plant genus Nepenthes
Yellow to red colored betalains are a chemotaxonomic feature of Caryophyllales, while in most other plant taxa, anthocyanins are responsible for these colors. The carnivorous plant family Nepenthaceae belongs to Caryophyllales; here, redâpigmented tissues seem to attract insect prey. Strikingly, the chemical nature of red color in Nepenthes has never been elucidated. Although belonging to Caryophyllales, in Nepenthes, some molecular evidence supports the presence of anthocyanins rather than betalains. However, there was previously no direct chemical proof of this. Using ultraâhighâperformance liquid chromatographyâelectrospray ionizationâhighâresolution mass spectrometry, we identified cyanidin glycosides in Nepenthes species and tissues. Further, we reveal the existence of a complete set of constitutively expressed anthocyanin biosynthetic genes in Nepenthes. Thus, here we finally conclude the longâterm open question regarding red pigmentation in Nepenthaceae
A construction of Frobenius manifolds with logarithmic poles and applications
A construction theorem for Frobenius manifolds with logarithmic poles is
established. This is a generalization of a theorem of Hertling and Manin. As an
application we prove a generalization of the reconstruction theorem of
Kontsevich and Manin for projective smooth varieties with convergent
Gromov-Witten potential. A second application is a construction of Frobenius
manifolds out of a variation of polarized Hodge structures which degenerates
along a normal crossing divisor when certain generation conditions are
fulfilled.Comment: 46 page
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