The Genetics and Genomics of Virus Resistance in Maize

Viruses cause significant diseases on maize worldwide. Intensive agronomic practices, changes in vector distribution, and the introduction of vectors and viruses into new areas can result in emerging disease problems. Because deployment of resistant hybrids and cultivars is considered to be both economically viable and environmentally sustainable, genes and quantitative trait loci for most economically important virus diseases have been identified. Examination of multiple studies indicates the importance of regions of maize chromosomes 2, 3, 6, and 10 in virus resistance. An understanding of the molecular basis of virus resistance in maize is beginning to emerge, and two genes conferring resistance to sugarcane mosaic virus, Scmv1 and Scmv2, have been cloned and characterized. Recent studies provide hints of other pathways and genes critical to virus resistance in maize, but further work is required to determine the roles of these in virus susceptibility and resistance. This research will be facilitated by rapidly advancing technologies for functional analysis of genes in maize

Negative thermal expansion in the siliceous zeolites chabazite and ITQ-4: a powder neutron diffraction study

We present the results of quantitative variable-temperature neutron powder diffraction experiments performed on the OSIRIS instrument at the ISIS facility on the pure silica zeolites chabazite and ITQ-4. Chabazite has been found to be one of the most strongly contracting materials known, with a linear expansion coefficient alpha(v)/3 varying from -0.5 x 10(-6) to -16.7 x 10(-6) K-1 over the temperature range 293-873 K. Full Rietveld refinement has been carried out using three different refinement strategies: free isotropic refinements, refinement using geometrical restraints,and a rigid body refinement. The free isotropic refinement was found to be the most successful. In agreement with previous studies on ZrW3O8 and Sc-2(WO4)(3) type materials, we suggest that changes in Si-O-Si interpolyhedral bond angles are the driving force for the contraction mechanism. ITQ-4 has also been found to contract over the temperature range 95-510 K, with alpha(v)/3 varying from -2.2 x 10(-6) to -3.7 x 10(-6) K-1 over this range.</p

Negative thermal expansion in the siliceous zeolites chabazite and ITQ-4: a powder neutron diffraction study

We present the results of quantitative variable-temperature neutron powder diffraction experiments performed on the OSIRIS instrument at the ISIS facility on the pure silica zeolites chabazite and ITQ-4. Chabazite has been found to be one of the most strongly contracting materials known, with a linear expansion coefficient alpha(v)/3 varying from -0.5 x 10(-6) to -16.7 x 10(-6) K-1 over the temperature range 293-873 K. Full Rietveld refinement has been carried out using three different refinement strategies: free isotropic refinements, refinement using geometrical restraints,and a rigid body refinement. The free isotropic refinement was found to be the most successful. In agreement with previous studies on ZrW3O8 and Sc-2(WO4)(3) type materials, we suggest that changes in Si-O-Si interpolyhedral bond angles are the driving force for the contraction mechanism. ITQ-4 has also been found to contract over the temperature range 95-510 K, with alpha(v)/3 varying from -2.2 x 10(-6) to -3.7 x 10(-6) K-1 over this range.</p

Strong negative thermal expansion in the siliceous zeolites ITQ-1, ITQ-3 and SSZ-23

Strong negative thermal expansion has been found for the pure SiO2 zeolites ITQ-1 (alpha(v) = -12.1 X 10(-6) K-1), SSZ-23 (alpha(v) = -10.3 x 10(-6) K-1) and ITQ-3 (alpha(v) = -11.4 x 10(-6) K-1) from 50 to 500 degrees C and above.</p

Strong negative thermal expansion in the siliceous zeolites ITQ-1, ITQ-3 and SSZ-23

Strong negative thermal expansion has been found for the pure SiO2 zeolites ITQ-1 (alpha(v) = -12.1 X 10(-6) K-1), SSZ-23 (alpha(v) = -10.3 x 10(-6) K-1) and ITQ-3 (alpha(v) = -11.4 x 10(-6) K-1) from 50 to 500 degrees C and above.</p