Structural Transformations in Ferroelectrics Discovered by Raman Spectroscopy

Ferroelectrics systems are of great interest from the fundamental as well as applications points, such as ferroelectric random access memories, electro-optic switches and a number of electro-optic devices. Curie temperature (TC) is one of the important parameters of ferroelectrics for high-temperature applications. Particularly, the optical modes, which are associated with the ferroelectric to paraelectric phase transition, are of great interest. Structural transformations that alter the crystal symmetry often have a significant effect on the Raman spectroscopy. This chapter systematically studies the type ferroelectric oxides and rare earth element doped ferroelectric materials such as PbTiO3-Bi(Mg0.5Ti0.5)O3 (PT-BMT), Sr x Ba1−x Nb2O6 (SBN), Pb1−1.5x La x Zr0.42Sn0.4Ti0.18O3 (PLZST), Bi1−xLaxFe1−yTiyO3 (BLFT) and (K0.5Na0.5)NbO3-0.05LiNbO3 (KNN-LN) and so on synthesis of single crystal/ceramic and optical phonon vibration modes and the improvement of the Curie temperature characteristic using spectrometry measurements. The TC, distortion degree, and phase structure of the ferroelectric materials have been investigated by temperature-dependent Raman spectroscopy. Meanwhile, the important physical parameters exhibited a strong dependence on dopants resulting in structural modifications and performance promotion

Rescue of recombinant peste des petits ruminants virus: creation of a GFP-expressing virus and application in rapid virus neutralization test

Peste des petits ruminants virus (PPRV) causes high mortality in goats and sheep and the disease has shown a greatly increased geographic distribution over the last 15 years. It is responsible for serious socioeconomic problems in some of the poorest developing countries. The ability to create recombinant PPRV would provide a useful tool for investigating the biology of the virus and the pathology of disease, as well as for developing new vaccines and diagnostic methods. Here we report the first successful rescue of recombinant PPRV from a full-length cDNA clone of the virus genome. Successful recovery of PPRV was achieved by using a RNA polymerase II promoter to drive transcription of the full-length virus antigenome. We have used this technique to construct a virus expressing a tracer protein (green fluorescent protein, GFP). The recombinant virus replicated as well as the parental virus and could stably express GFP during at least 10 passages. The newly established reverse genetics system for PPRV provides a novel method for constructing a vaccine using PPRV as a vector, and will also prove valuable for fundamental research on the biology of the virus. We found that our recombinant virus allowed more rapid and higher throughput assessment of PPRV neutralization antibody titer via the virus neutralization test (VNT) compared with the traditional method

Stoichiometry patterns of plant organ N and P in coastal herbaceous wetlands along the East China Sea : implications for biogeochemical niche

Background and aims: Nitrogen (N) and phosphorus (P) are essential nutrients for plant growth, and their availability and stoichiometry play pivotal roles in trophic dynamics and community composition. The biogeochemical niche (BN) hypothesis claims that each species should have an optimal elemental composition and stoichiometry as a consequence of its optimal function in its specific ecological niche. Little attention, however, has been given to N and P stoichiometric patterns and test the BN hypothesis in coastal wetland communities from the perspective of organ and species-specific comparisons.Methods: We investigated factors responsible for changes in N and P stoichiometry patterns in different functional groups in coastal wetlands and tested the BN hypothesis by evaluating N and P composition in whole aboveground plants and organs.Results: Both plant N and P concentrations were high in coastal wetlands, indicating that N and P were not likely limiting, although the N:P ratio was slightly lower than the ratio reported in global and Chinese terrestrial flora. N and P concentrations and N:P ratios varied strongly between C₃ and C₄ species, among species, and among organs within species. N and P concentrations were not correlated with latitude, mean annual temperature and precipitation, although N:P ratio was weakly correlated with these factors. The differences in N and P concentrations and N:P ratios along the wetland gradients were mainly because of the species-specific community composition of each site.Conclusions: The results are consistent with the BN hypothesis. First, N and P composition is species-specific (homeostatic component of BN), each species tends to maintain its own composition even growing in different sites with different species composition. Second, different species, despite maintaining their own composition, have distinct degree of composition phenotypic flexibility (flexibility component of BN); this different size of "biogeochemical space" was observed when comparing different species living in the same community and the shifts in species BN space and size was observed when comparing populations of the same species living in different sites