A study of the T2 defect and the emission properties of the E3 deep level in annealed melt grown ZnO single crystals

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Knotted vs. Unknotted Proteins: Evidence of Knot-Promoting Loops

Knotted proteins, because of their ability to fold reversibly in the same topologically entangled conformation, are the object of an increasing number of experimental and theoretical studies. The aim of the present investigation is to assess, on the basis of presently available structural data, the extent to which knotted proteins are isolated instances in sequence or structure space, and to use comparative schemes to understand whether specific protein segments can be associated to the occurrence of a knot in the native state. A significant sequence homology is found among a sizeable group of knotted and unknotted proteins. In this family, knotted members occupy a primary sub-branch of the phylogenetic tree and differ from unknotted ones only by additional loop segments. These "knot-promoting" loops, whose virtual bridging eliminates the knot, are found in various types of knotted proteins. Valuable insight into how knots form, or are encoded, in proteins could be obtained by targeting these regions in future computational studies or excision experiments

Electrical characterization of defects in heavy-ion implanted n-type Ge

Deep-level transient spectroscopy was used to investigate the electrically active defects introduced in n-type Ge during heavy-ion implantation of 160 keV ions. Various noble heavy-ions were used for implantation and the main defects introduced were found to be electron traps with energy levels at E-C - 0.09 eV, E-C - 0.15 eV and E-C - 0.30 eV. Another defect with a level at E-C - 0.38 eV, shown to be the E-center (V-Sb defect), is also present in a very low concentration. The main defects in heavy-ion implanted Ge are different from those introduced by MeV electron irradiation, where the main defect is the E-center. Since electron irradiation introduces mainly point defects, this indicates that heavy-ion implantation introduces defects of a more extended nature, such as vacancy and/or interstitial clusters and their combinations with impurities or foreign species in the Ge. We have also demonstrated that these defects are not species related. (C) 2007 Elsevier B.V. All rights reserved.status: publishe