Topochemical Manipulation of Layered Perovskites

Topochemical strategies, techniques that allow one to effectively manipulate the structures of nonmolecular solids once a crystal lattice is established, are effective in the low temperature (\u3c 500 °C) modification of solid state structures, allowing the preparation of nonmolecular compounds not accessible by standard synthetic routes. Some of the techniques, ion exchange, intercalation/deintercalation, have proven to be excellent synthetic methods for preserving specific frameworks. The combination of these techniques can allow one to create a multistep approach that can be used to design new compounds with interesting properties. As an expansion to the field of topotactic reactions, a multistep approach was developed towards the synthesis of the new compounds (A xM0.5Cly)LaNb2O7 (where A = Rb, Cs; M = Fe, Ni; x ≈ 1.5;y ≈ 1) at temperatures below 400oC. The first reaction step involved the ion exchange of the host materials (ALaNb2O7, A = Rb, Cs) to form the products M0.5LaNb2O7 (where M = Fe, Ni), a structure open to further chemistry. The next step involved reductive intercalation with Rb or Cs metal to form the air sensitive mixed-valence products with the nominal compositions, A1.5M0.5LaNb2O7. The last step involved the oxidative intercalation of chlorine using chlorine gas to obtain the final compounds. This multistep approach is a design to form mix-metal halide layers, specifically those with divalent cations, within layered perovskites, opening the doors to compounds that can have interesting properties. This reaction series was also applied to the tantalate layered oxides, leading to the formation of the new compound Ni 0.5LaTa2O7 through ion exchange. The further multistep topochemical manipulation of this new compound was not successful and was indicative of the difference in chemical behavior of the tantalates versus the niobates. We have also investigated the oxidative intercalation of halogens into a series of Ruddlesden-Popper (R-P) ruthenate oxides with the formula Ae n+1RunO3n+1 (Ae = Ca, Sr; n = 1, 2, 3) using several sources of fluorine, chlorine, and bromine. A new method was developed to intercalate chlorine into layered systems; this new approach avoids the use of chlorine gas which is highly toxic. The new phase Sr3Ru2O7Cl0.7 was synthesized by the new method and further topotactic manipulations were explored. The chemistry was not limited to the n = 2 phase but was also applied to the n = 3 phase, Sr4Ru3O10

A NEW VARIANT OF CASSAVA MOSIAC VIRUS CAUSES MULBERRY MOSAIC DISEASE IN INDIA

ABSTRACT: Mulberry with typical symptoms characteristic to Gemini virus viz., enations, mosaic, deformed leaves, curling and stunted growth was collected from Thiruvananthapuram district, Kerala, India. The disease is transmitted through mechanical transmission from the sap of the infected plant to disease free mulberry seedlings and indicator plants, Nicotiana tabaccum and N. benthamiana, confirming the presence of a sap transmissible pathogen. The cassava biotype of Bemisia tabaci transmitted the disease with an AAP 24h and IAP 6h. Amplification for the Gemini virus specific primers was obtained from the total DNA isolated from the infected plants. Further with the primers specific for the coat protein gene (cp, AV1 gene of the A genome) and movement protein gene (mp, BC1gene of the B genome) of the ICMV the ~810bp and ~ 860bp specific amplifications were obtained from the Thiruvananthapuram isolate and the plants inoculated with the sap of Thiruvanathapuram isolate and from plants on which vector transmission done using B. tabaci cassava biotype.The amplified samples were sequenced and submitted the nucleotide sequences to NCBI data base, accession code for cp nucleotide sequence is FJ.827040.2 and that for mp nucleotide sequence is HM.138689.1. The two nucleotide sequences showed 98-99% identities and closest relationship with Indian Cassava Mosaic Virus (ICMV) and Sri Lankan Cassava Mosaic Virus (SLCMV). Bemisia tabaci is confirmed as the vector of the disease by transmission studies and obtained amplification of 810 bp with cp primer from the B. tabaci adults of cassava biotype used for transmission studies

ANALYSIS OF THE EFFECT OF GROUP COUNSELING ON THE COPPING BEHAVIOR OF PEOPLE LIVING WITH HIV/AIDS IN YAKURR LOCAL GOVERNMENT AREA, CROSS RIVER STATE

ABSTRACT HIV/AIDS epidemic has become a worrisome phenomenon and individual carrier of the infection suffers from several mental health consequences. The infection is associate

Synthesis, characterisation and crystal structure of a three-dimensional network of an h-bonded Ni (II) Hexametylenetetramine complex

A three-dimensional network of H-bonding nickel (II) hexamethylenetetramine complex has been synthesized and characterised and its structure determined by single crystal X-ray diffraction studies which show that [Ni(H2O)6](HMTA)2Cl32.4H2O crystallizes in the triclinic crystal system with space group PĪ, a = 9.2955(4), b = 9.3187(2), c = 9.3996 Ǻ, α = 119.4160(10), β = 94.4940(10), ɣ = 100.8680(10)º, V =682.47(4) Å3 and z = 1. The nickel atoms are each bonded to six aquo ligands giving an octahedral geometry. The ligand hexamethylenetetramine (HMTA) and chloride ions are bonded to water molecules through hydrogen bonding. Thermal studies show a decomposition pattern corresponding to the loss of the coordinated and uncoordinated water molecules, chloride ions and HMTA ligand in the form of a mixture of gases

Development of neutron resonance densitometry at the GELINA TOF facility

Neutrons can be used as a tool to study properties of materials and objects. An evolving activity in this field concerns the existence of resonances in neutron induced reaction cross sections. These resonance structures are the basis of two analytical methods which have been developed at the EC-JRC-IRMM: Neutron Resonance Capture Analysis (NRCA) and Neutron Resonance Transmission Analysis (NRTA). They have been applied to determine the elemental composition of archaeological objects and to characterize nuclear reference materials. A combination of NRTA and NRCA together with Prompt Gamma Neutron Analysis, referred to as Neutron Resonance Densitometry (NRD), is being studied as a non-destructive method to characterize particle-like debris of melted fuel that is formed in severe nuclear accidents such as the one which occurred at the Fukushima Daiichi nuclear power plants. This study is part of a collaboration between JAEA and EC-JRC-IRMM. In this contribution the basic principles of NRTA and NRCA are explained based on the experience in the use of these methods at the time-of-flight facility GELINA of the EC-JRC-IRMM. Specific problems related to the analysis of samples resulting from melted fuel are discussed. The programme to study and solve these problems is described and results of a first measurement campaign at GELINA are given.JRC.D.4-Standards for Nuclear Safety, Security and Safeguard

Microbial Transformations of Nitrogen, Sulfur, and Iron Dictate Vegetation Composition in Wetlands: A Review

The majority of studies on rhizospheric interactions focus on pathogens, mycorrhizal symbiosis, or carbon transformations. Although the biogeochemical transformations of N, S, and Fe have profound effects on vegetation, these effects have received far less attention. This review, meant for microbiologists, biogeochemists, and plant scientists includes a call for interdisciplinary research by providing a number of challenging topics for future ecosystem research. Firstly, all three elements are plant nutrients, and microbial activity significantly changes their availability. Secondly, microbial oxidation with oxygen supplied by radial oxygen loss from roots in wetlands causes acidification, while reduction using alternative electron acceptors leads to generation of alkalinity, affecting pH in the rhizosphere, and hence plant composition. Thirdly, reduced species of all three elements may become phytotoxic. In addition, Fe cycling is tightly linked to that of S and P. As water level fluctuations are very common in wetlands, rapid changes in the availability of oxygen and alternative terminal electron acceptors will result in strong changes in the prevalent microbial redox reactions, with significant effects on plant growth. Depending on geological and hydrological settings, these interacting microbial transformations change the conditions and resource availability for plants, which are both strong drivers of vegetation development and composition by changing relative competitive strengths. Conversely, microbial composition is strongly driven by vegetation composition. Therefore, the combination of microbiological and plant ecological knowledge is essential to understand the biogeochemical and biological key factors driving heterogeneity and total (i.e., microorganisms and vegetation) community composition at different spatial and temporal scales