Sol-Gel Template Synthesis, Structural Characterization and Growth Mechanism of Barium Zirconate Nanotubes

In this paper, we report the synthesis of barium zirconate, BaZrO3, (BZ) nanotubes fabricated by the modified sol-gel method within the nanochannels of anodic aluminum oxide (AAO) templates. The morphology, structure, and composition of as prepared nanotubes were characterized by means of X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), transmission electron microscope (TEM), selected-area electron diffraction ( SAED), high resolution TEM (HRTEM) and energy-dispersive X-ray spectroscopy (EDX). The results of XRD and SAED indicated that postannealed (at 650 degrees C for 1 h) BZ nanotubes (BZNTs) exhibited a polycrystalline cubic perovskite crystal structure. SEM and TEM analysis revealed that BZNTs possessed a uniform length and diameter (similar to 200 nm) and the thickness of the wall of the BZNTs was about 20 nm. Y-junctions, multiple branching and typical T-junctions were also observed in some BZNTs. EDX analysis demonstrated that stoichiometric BaZrO3 was formed. HRTEM image confirmed that the obtained BZNTs were composed of nanoparticles in the range of 5-10 nm. The possible formation mechanism of BZNTs was discussed.

Vocalizations of wild Asian elephants (Elephas maximus): Structural classification and social context

Elephants use vocalizations for both long and short distance communication. Whereas the acoustic repertoire of the African elephant (Loxodonta africana) has been extensively studied in its savannah habitat, very little is known about the structure and social context of the vocalizations of the Asian elephant (Elephas maximus), which is mostly found in forests. In this study, the vocal repertoire of wild Asian elephants in southern India was examined. The calls could be classified into four mutually exclusive categories, namely, trumpets, chirps, roars, and rumbles, based on quantitative analyses of their spectral and temporal features. One of the call types, the rumble, exhibited high structural diversity, particularly in the direction and extent of frequency modulation of calls. Juveniles produced three of the four call types, including trumpets, roars, and rumbles, in the context of play and distress. Adults produced trumpets and roars in the context of disturbance, aggression, and play. Chirps were typically produced in situations of confusion and alarm. Rumbles were used for contact calling within and among herds, by matriarchs to assemble the herd, in close-range social interactions, and during disturbance and aggression. Spectral and temporal features of the four call types were similar between Asian and African elephants.

Structural-stratigraphic reconstruction of the lower Whakataki formation, north island, New Zealand

This thesis details a Miocene aged sedimentary rock formation located in north island New Zealand. Mapping, stratigraphic logging and petrographic analysis of the rock formation ascertained that it was deposited in a deep-marine, tectonically active region. The work details the make-up of the sedimentary rocks using geochemistry and microscopy to define their origin. This definition was used to interpret the depositional model of the sediments detailing how they were transported and how they were emplaced.

Pseudo-time marching schemes for inverse problems in structural health assessment and medical imaging

We propose a self-regularized pseudo-time marching strategy for ill-posed, nonlinear inverse problems involving recovery of system parameters given partial and noisy measurements of system response. While various regularized Newton methods are popularly employed to solve these problems, resulting solutions are known to sensitively depend upon the noise intensity in the data and on regularization parameters, an optimal choice for which remains a tricky issue. Through limited numerical experiments on a couple of parameter re-construction problems, one involving the identification of a truss bridge and the other related to imaging soft-tissue organs for early detection of cancer, we demonstrate the superior features of the pseudo-time marching schemes.

Mutations in known monogenic high bone mass loci only explain a small proportion of high bone mass cases

High bone mass (HBM) can be an incidental clinical finding; however, monogenic HBM disorders (eg, LRP5 or SOST mutations) are rare. We aimed to determine to what extent HBM is explained by mutations in known HBM genes. A total of 258 unrelated HBM cases were identified from a review of 335,115 DXA scans from 13 UK centers. Cases were assessed clinically and underwent sequencing of known anabolic HBM loci: LRP5 (exons 2, 3, 4), LRP4 (exons 25, 26), SOST (exons 1, 2, and the van Buchem's disease [VBD] 52-kb intronic deletion 3'). Family members were assessed for HBM segregation with identified variants. Three-dimensional protein models were constructed for identified variants. Two novel missense LRP5 HBM mutations ([c.518C>T; p.Thr173Met], [c.796C>T; p.Arg266Cys]) were identified, plus three previously reported missense LRP5 mutations ([c.593A>G; p.Asn198Ser], [c.724G>A; p.Ala242Thr], [c.266A>G; p.Gln89Arg]), associated with HBM in 11 adults from seven families. Individuals with LRP5 HBM ( approximately prevalence 5/100,000) displayed a variable phenotype of skeletal dysplasia with increased trabecular BMD and cortical thickness on HRpQCT, and gynoid fat mass accumulation on DXA, compared with both non-LRP5 HBM and controls. One mostly asymptomatic woman carried a novel heterozygous nonsense SOST mutation (c.530C>A; p.Ser177X) predicted to prematurely truncate sclerostin. Protein modeling suggests the severity of the LRP5-HBM phenotype corresponds to the degree of protein disruption and the consequent effect on SOST-LRP5 binding. We predict p.Asn198Ser and p.Ala242Thr directly disrupt SOST binding; both correspond to severe HBM phenotypes (BMD Z-scores +3.1 to +12.2, inability to float). Less disruptive structural alterations predicted from p.Arg266Cys, p.Thr173Met, and p.Gln89Arg were associated with less severe phenotypes (Z-scores +2.4 to +6.2, ability to float). In conclusion, although mutations in known HBM loci may be asymptomatic, they only account for a very small proportion ( approximately 3%) of HBM individuals, suggesting the great majority are explained by either unknown monogenic causes or polygenic inheritance.

Next-generation sequencing: A frameshift in skeletal dysplasia gene discovery

In the last decade, huge breakthroughs in genetics - driven by new technology and different statistical approaches - have resulted in a plethora of new disease genes identified for both common and rare diseases. Massive parallel sequencing, commonly known as next-generation sequencing, is the latest advance in genetics, and has already facilitated the discovery of the molecular cause of many monogenic disorders. This article describes this new technology and reviews how this approach has been used successfully in patients with skeletal dysplasias. Moreover, this article illustrates how the study of rare diseases can inform understanding and therapeutic developments for common diseases such as osteoporosis. © International Osteoporosis Foundation and National Osteoporosis Foundation 2013.

Whole-exome re-sequencing in a family quartet identifies POP1 mutations as the cause of a novel skeletal dysplasia

Recent advances in DNA sequencing have enabled mapping of genes for monogenic traits in families with small pedigrees and even in unrelated cases. We report the identification of disease-causing mutations in a rare, severe, skeletal dysplasia, studying a family of two healthy unrelated parents and two affected children using whole-exome sequencing. The two affected daughters have clinical and radiographic features suggestive of anauxetic dysplasia (OMIM 607095), a rare form of dwarfism caused by mutations of RMRP. However, mutations of RMRP were excluded in this family by direct sequencing. Our studies identified two novel compound heterozygous loss-of-function mutations in POP1, which encodes a core component of the RNase mitochondrial RNA processing (RNase MRP) complex that directly interacts with the RMRP RNA domains that are affected in anauxetic dysplasia. We demonstrate that these mutations impair the integrity and activity of this complex and that they impair cell proliferation, providing likely molecular and cellular mechanisms by which POP1 mutations cause this severe skeletal dysplasia. © 2011 Glazov et al.

Transcriptional activation of the Escherichia coli bgl operon: negative regulation by DNA structural elements near the promoter

The bgl operon of Escherichia coil is transcriptionally inactive in wild-type cells. DNA insertion sequences (IS) constitute a major class of spontaneous mutations that activate the cryptic bgl promoter. In an attempt to study the molecular mechanism of activation mediated by insertion sequences, transcription of the bgl promoter was carried out in vitro. Stimulation of transcription is observed when a plasmid containing an insertionally activated bgl promoter is used as a template in the absence of proteins other than RNA polymerase. Deletions that remove sequences upstream of the bgl promoter, and insertion of a 1.2 kb DNA fragment encoding resistance to kanamycin, activate the promoter. Point mutations within a region of dyad symmetry upstream of the promoter, which has the potential to extrude into a cruciform structure under torsional stress, also lead to activation, Introduction of a sequence with dyad symmetry, upstream of an activated bgl promoter carrying a deletion of upstream sequences, results in a fourfold reduction in transcription, These results suggest that the cryptic nature of the bgl promoter is because of the presence of DNA structural elements near the promoter that negatively affect transcription.

Two highly unsymmetrical tetradentate (N3O) Schiff base copper(II) complexes: Template synthesis, structural characterization, magnetic and computational studies

Two new copper(II) complexes, [Cu-2(L-1)(2)](ClO4)(2) (1) and [Cu(L-2)(ClO4)] (2), of the highly unsymmetrical tetradentate (N3O) Schiff base ligands HL1 and HL2 (where HL1 = N-(2-hydroxyacetophenone)-bis-3-aminopropylamine and HL2 = N-(salicyldehydine)-bis-3-aminopropylamine) have been synthesised using a template method. Their single crystal X-ray structures show that in complex 1 two independent copper(II) centers are doubly bridged through sphenoxo-O atoms (O1A and O1B) of the two ligands and each copper atom is five-coordinated with a distorted square pyramidal geometry. The asymmetric unit of complex 2 consists of two crystallographically independe N-(salicylidene) bis(aminopropyl)amine-copper(II) molecules, A and B, with similar square pyramidal geometries. Cryomagnetic susceptibility measurements (5-300 K) on complex 1 reveal a distinct antiferromagnetic interaction with J=-23.6 cm(-1), which is substantiated by a DFT calculation (J=-27.6 cm(-1)) using the B3LYP functional. Complex 1, immobilized over highly ordered hexagonal mesoporous silica, shows moderate catalytic activity for the epoxidation of cyclohexene and styrene in the presence of TBHP as an oxidant.

Structural Investigation of Activated Lattice Oxygen in Ce1-xSnxO2 and Ce1-x-ySnxPdyO2-delta by EXAFS and DFT calculation

Substitution of Sn4+ ion in CeO2 creates activated oxygen in Ce0.8Sn0.2O2 leading to higher oxygen storage capacity compared to Ce0.8Zr0.2O2. With Pd ion substitution in Ce0.8Sn0.2O2,activation of oxygen is further enhanced as observed from the H-2/TPR study. Both EXAFS analysis and DFT calculation reveal that in the solid solution Ceexhibits 4 + 4 coordination, Sri exhibits 4 + 2 + 2 coordination and Pd has 4 + 3 coordination. While the oxygen in the First four coordination with short M-O bonds are strongly held in the lattice, the oxygens in the second and higher coordinations with long M-O bonds are weakly bound, and they are the activated oxygen ill the lattice. Bond valence analysis shows that oxygen with valencies as low its 1.65 are created by the Sn and Pd ion Substitution. Another interesting observation is that H-2/TPR experiment of Ce1-xSnxO2 shows a broad peak starting from 200 to 500 degrees C, while the same reduction is achieved in a single step at similar to 110 degrees C in presence Pd2+ on. Substitution of Pd2+ ion thus facilitates synergistic reduction of the catalyst at lower temperature. We have shown that simultaneous reduction of the Ce4+ and Sr4+ ions by Pd-0 is the synergistic interaction leading to high oxygen storage capacity at low temperature.

Bi4Ti3O12-5BiFeO(3) Aurivillius intergrowth: Structural and ferroelectric properties

Aurivillus intergrowth Bi4Ti3O12-5BiFeO(3) was demonstrated to be ferroelectric that evoked the possibility of achieving high temperature magnetoelectric property in this family of compounds. X-ray diffraction studies confirmed its structure to be orthorhombic [Fmm2; a=5.5061(11) A degrees, b=5.4857(7) A degrees, c=65.742(12) A degrees]. However, transmission electron microscopy established the random incidence of intergrowth at nanoscale corresponding to n=6 and n=7 members of the Aurivillius family. Diffuse ferroelectric orthorhombic to paraelectric tetragonal phase transition around 857 K was confirmed by dielectric and high temperature x-ray diffraction studies. Polarization versus electric field hysteresis loops associated with 2P(r) of 5.2 mu C/cm(2) and coercive field of 42 kV/cm were obtained at 300 K.

Temperature dependent structural properties of nanocrystalline SnS structures

This letter explores the structural behavior of nanocrystalline tin mono sulfide (SnS) structures with respect to temperature (100-600 K). These studies emphasize that the structural properties of SnS nanocrystalline structures depend on the surrounding temperature. The lattice parameters of SnS nanocrystals slightly varied like their microstructures with the increase of temperature. These changes strongly influence the optical properties of SnS nanostructures. On the other hand, the structures exhibited higher strain (similar to 0.44%) than that of microstructured (0.3%) and bulk (0.12%) counterparts. The observed results are discussed under the light of existing concepts and reported.

Structural and functional characteristics of homing endonucleases

Mobile genetic elements constitute a remarkably diverse group of nonessential selfish genes that provide no apparent function to the host. These selfish genes have been implicated in host extinction, speciation and architecture of genetic systems. Homing endonucleases, encoded by the open reading frames embedded in introns or inteins of mobile genetic elements, possess double-stranded DNA-specific endonuclease activity. They inflict sequence-specific double-strand breaks at or near the homing site in intron- or intein-less allele. Subsequently, through nonreciprocal exchange the insertion sequence (intron or intein) is transferred from an intein- or intron-containing allele to an intein- or intron-less allele. The components of host double-strand break repair pathway are thought to finish the "homing" process. Several lines of evidence suggest that homing endonucleases are capable of promoting transposition into ectopic sites within or across genomes for their survival as well as dispersal in natural populations. The occurrence of inteins at high frequencies serves as instructive models for understanding the mechanistic aspects of the process of homing and its evolution. This review focuses on genetic, biochemical, structural, and phylogenetic aspects of homing endonucleases, and their comparison with restriction endonucleases.

DNA-induced conformational changes in RecA protein. Evidence for structural heterogeneity among nucleoprotein filaments and implications for homologous pairing

We have used circular dichroism as a probe to characterize the solution conformational changes in RecA protein upon binding to DNA. This approach revealed that RecA protein acquires significant amounts of alpha-helix upon interaction with DNA. These observations, consistent with the data from crystal structure (Story, R. M., Weber, I., and Steitz, T. (1992) Nature 355, 318-325), support the notion that some basic domains including the DNA binding motifs of RecA protein are unstructured and might contribute to the formation of alpha-helix. A comparison of nucleoprotein filaments comprised of RecA protein and a variety of DNA substrates revealed important structural heterogeneity. The most significant difference was observed with poly(dG). poly(dC) and related polymers, rich in GC sequences, which induced minimal amounts of alpha-helix in RecA protein. The magnitude of induction of alpha-helix in RecA protein, which occurred concomitant with the production of ternary complexes, was 2-fold higher with homologous than heterologous duplex DNA. Most importantly, the stimulation of ATP hydrolysis by high salt coincided with that of the induction of alpha-helix in RecA protein. These conformational differences provide a basis for thinking about the biochemical and structural transitions that RecA protein experiences during the formal steps of presynapsis, recognition, and alignment of homologous sequences.