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The phase diagram of the ZrO2-Nd2O3 system has been characterized showing isolated two-phase regions for a cubic fluorite-type ZrO2 solid solution and Nd2Zr2O7 with a pyrochlore-type structure. A thermodynamic analysis was carried out to elucidate the origin of this interesting phase equilibrium. A compound energy model with the formula (Zr4+,Nd3+)(0.5)(Nd3+,Zr4+)(0.5)(O2-,va)(2) was applied to describe the Gibbs energy for these phases in consideration of the ordering of the cation sites in the structure. The ordering arrangement on the anion sites was not taken into account. The Gibbs energy for the liquid was described using an ionic solution model, while the binary compounds, such as tetragonal and monoclinic ZrO2, and cubic and hexagonal Nd2O3, were treated as stoichiometric solid phases. The thermodynamic assessment was based on the experimental phase boundaries as well as the evaluated formation energy for the stoichiometric Nd,2Zr2O7 phase. The phase diagram calculations showed that the peculiar feature of this phase diagram was reproduced well in our work. The results strongly suggest that the two-phase boundaries between the cubic fluorite-type ZrO2 solid solution and the pyrochlore-type structure occur due to the ordering of the Zr4+ and Nd3+ cations., QC 20100525

© 2014 Macmillan Publishers Limited. All rights reserved. Anhydrobiosis represents an extreme example of tolerance adaptation to water loss, where an organism can survive in an ametabolic state until water returns. Here we report the first comparative analysis examining the genomic background of extreme desiccation tolerance, which is exclusively found in larvae of the only anhydrobiotic insect, Polypedilum vanderplanki. We compare the genomes of P. vanderplanki and a congeneric desiccation-sensitive midge P. nubifer. We determine that the genome of the anhydrobiotic species specifically contains clusters of multi-copy genes with products that act as molecular shields. In addition, the genome possesses several groups of genes with high similarity to known protective proteins. However, these genes are located in distinct paralogous clusters in the genome apart from the classical orthologues of the corresponding genes shared by both chironomids and other insects. The transcripts of these clustered paralogues contribute to a large majority of the mRNA pool in the desiccating larvae and most likely define successful anhydrobiosis. Comparison of expression patterns of orthologues between two chironomid species provides evidence for the existence of desiccation-specific gene expression systems in P. vanderplanki.

© 2014 Macmillan Publishers Limited. All rights reserved. Anhydrobiosis represents an extreme example of tolerance adaptation to water loss, where an organism can survive in an ametabolic state until water returns. Here we report the first comparative analysis examining the genomic background of extreme desiccation tolerance, which is exclusively found in larvae of the only anhydrobiotic insect, Polypedilum vanderplanki. We compare the genomes of P. vanderplanki and a congeneric desiccation-sensitive midge P. nubifer. We determine that the genome of the anhydrobiotic species specifically contains clusters of multi-copy genes with products that act as molecular shields. In addition, the genome possesses several groups of genes with high similarity to known protective proteins. However, these genes are located in distinct paralogous clusters in the genome apart from the classical orthologues of the corresponding genes shared by both chironomids and other insects. The transcripts of these clustered paralogues contribute to a large majority of the mRNA pool in the desiccating larvae and most likely define successful anhydrobiosis. Comparison of expression patterns of orthologues between two chironomid species provides evidence for the existence of desiccation-specific gene expression systems in P. vanderplanki.