bluuebunny/crossref_metadata_2025 huggingface dataset:
Language identities, ideologies, and policy relevance
Authors: Davis Kathryn A.
Published: July 2009

By examining specific articles on the subject, this commentary explores how language policies and use in Luxembourg individually and collectively inform the complex intersections of multilingualism/ecology, identities/agency and nationalism/ideology. These studies suggest theoretical and policy implications by investigating the topics of agency, ideology and ecology as these unfold in everyday situated practices. The papers specifically offer contributions to our understanding of multilingualism, transnational identities, and nationalism. The commentary concludes by suggesting the need for policies relevant to diverse linguistic and ethnic identities which, thus, foster educational and social equity.
Vancomycin Therapeutic Guidelines: A Summary of Consensus Recommendations from the Infectious Diseases Society of America, the American Society of Health-System Pharmacists, and the Society of Infectious Diseases Pharmacists
Authors: Rybak Michael J. , Lomaestro Ben M. , Rotscahfer John C. , Moellering Robert C. , Craig Willam A. , Billeter Marianne , Dalovisio Joseph R. , Levine Donald P.
Published: July 2009

Practice guidelines for therapeutic monitoring of vancomycin treatment for Staphylococcus aureus infection in adult patients were reviewed by an expert panel of the Infectious Diseases Society of America, the American Society of Health-System Pharmacists, and the Society of Infectious Diseases Pharmacists. A literature review of existing evidence regarding vancomycin dosing and monitoring of serum concentrations, in addition to patient outcomes combined with expert opinion regarding the drug's pharmacokinetic, pharmacodynamic, and safety record, resulted in new recommendations for targeting and adjustment of vancomycin therapy.
IMG ER: a system for microbial genome annotation expert review and curation
Authors: Markowitz Victor M. , Mavromatis Konstantinos , Ivanova Natalia N. , Chen I-Min A. , Chu Ken , Kyrpides Nikos C.
Published: June 2009

Motivation: A rapidly increasing number of microbial genomes are sequenced by organizations worldwide and are eventually included into various public genome data resources. The quality of the annotations depends largely on the original dataset providers, with erroneous or incomplete annotations often carried over into the public resources and difficult to correct.

Results: We have developed an Expert Review (ER) version of the Integrated Microbial Genomes (IMG) system, with the goal of supporting systematic and efficient revision of microbial genome annotations. IMG ER provides tools for the review and curation of annotations of both new and publicly available microbial genomes within IMG's rich integrated genome framework. New genome datasets are included into IMG ER prior to their public release either with their native annotations or with annotations generated by IMG ER's annotation pipeline. IMG ER tools allow addressing annotation problems detected with IMG's comparative analysis tools, such as genes missed by gene prediction pipelines or genes without an associated function. Over the past year, IMG ER was used for improving the annotations of about 150 microbial genomes.

Contact:  vmmarkowitz@lbl.gov

Supplementary information:  Supplementary data are available at Bioinformatics online.
ITM Probe: analyzing information flow in protein networks
Authors: Stojmirović Aleksandar , Yu Yi-Kuo
Published: June 2009

Summary: Founded upon diffusion with damping, ITM Probe is an application for modeling information flow in protein interaction networks without prior restriction to the sub-network of interest. Given a context consisting of desired origins and destinations of information, ITM Probe returns the set of most relevant proteins with weights and a graphical representation of the corresponding sub-network. With a click, the user may send the resulting protein list for enrichment analysis to facilitate hypothesis formation or confirmation.

Availability:  ITM Probe web service and documentation can be found at www.ncbi.nlm.nih.gov/CBBresearch/qmbp/mn/itm_probe

Contact:  yyu@ncbi.nlm.nih.gov
HAPLOWSER: a whole-genome haplotype browser for personal genome and metagenome
Authors: Kim Jong Hyun , Kim Woo-Cheol , Waterman Michael S. , Park Sanghyun , Li Lei M.
Published: June 2009

Summary: Haplotype assembly is becoming a very important tool in genome sequencing of human and other organisms. Although haplotypes were previously inferred from genome assemblies, there has never been a comparative haplotype browser that depicts a global picture of whole-genome alignments among haplotypes of different organisms. We introduce a whole-genome HAPLotype brOWSER (HAPLOWSER), providing evolutionary perspectives from multiple aligned haplotypes and functional annotations. Haplowser enables the comparison of haplotypes from metagenomes, and associates conserved regions or the bases at the conserved regions with functional annotations and custom tracks. The associations are quantified for further analysis and presented as pie charts. Functional annotations and custom tracks that are projected onto haplotypes are saved as multiple files in FASTA format. Haplowser provides a user-friendly interface, and can display alignments of haplotypes with functional annotations at any resolution.

Availability: Haplowser, written in Java, supports multiple platforms including Windows and Linux. Haplowser is publicly available at http://embio.yonsei.ac.kr/haplowser

Contact:  sanghyun@cs.yonsei.ac.kr; lilei@usc.edu

Supplementary information:  Supplementary data are available at http://embio.yonsei.ac.kr/haplowser
Analyzing the U.S. Senate in 2003: Similarities, Clusters, and Blocs
Authors: Jakulin Aleks , Buntine Wray , Pira Timothy M. La , Brasher Holly
Published: July 2009

In this paper, we apply information theoretic measures to voting in the U.S. Senate in 2003. We assess the associations between pairs of senators and groups of senators based on the votes they cast. For pairs, we use similarity-based methods, including hierarchical clustering and multidimensional scaling. To identify groups of senators, we use principal component analysis. We also apply a discrete multinomial latent variable model that we have developed. In doing so, we identify blocs of cohesive voters within the Senate and contrast it with continuous ideal point methods. We find more nuanced blocs than simply the two-party division. Under the bloc-voting model, the Senate can be interpreted as a weighted vote system, and we are able to estimate the empirical voting power of individual blocs through what-if analysis.
Horizontal gene transfer from extinct and extant lineages: biological innovation and the coral of life
Authors: Fournier Gregory P. , Huang Jinling , Gogarten J. Peter
Published: July 2009

Horizontal gene transfer (HGT) is often considered to be a source of error in phylogenetic reconstruction, causing individual gene trees within an organismal lineage to be incongruent, obfuscating the ‘true’ evolutionary history. However, when identified as such, HGTs between divergent organismal lineages are useful, phylogenetically informative characters that can provide insight into evolutionary history. Here, we discuss several distinct HGT events involving all three domains of life, illustrating the selective advantages that can be conveyed via HGT, and the utility of HGT in aiding phylogenetic reconstruction and in dating the relative sequence of speciation events. We also discuss the role of HGT from extinct lineages, and its impact on our understanding of the evolution of life on Earth. Organismal phylogeny needs to incorporate reticulations; a simple tree does not provide an accurate depiction of the processes that have shaped life's history.
Early origin of the bilaterian developmental toolkit
Authors: Erwin Douglas H.
Published: July 2009

Whole-genome sequences from the choanoflagellateMonosiga brevicollis, the placozoanTrichoplax adhaerensand the cnidarianNematostella vectensishave confirmed results from comparative evolutionary developmental studies that much of the developmental toolkit once thought to be characteristic of bilaterians appeared much earlier in the evolution of animals. The diversity of transcription factors and signalling pathway genes in animals with a limited number of cell types and a restricted developmental repertoire is puzzling, particularly in light of claims that such highly conserved elements among bilaterians provide evidence of a morphologically complex protostome–deuterostome ancestor. Here, I explore the early origination of elements of what became the bilaterian toolkit, and suggest that placozoans and cnidarians represent a depauperate residue of a once more diverse assemblage of early animals, some of which may be represented in the Ediacaran fauna (c. 585–542 Myr ago).
Getting a better picture of microbial evolution en route to a network of genomes
Authors: Dagan Tal , Martin William
Published: July 2009

Most current thinking about evolution is couched in the concept of trees. The notion of a tree with recursively bifurcating branches representing recurrent divergence events is a plausible metaphor to describe the evolution of multicellular organisms like vertebrates or land plants. But if we try to force the tree metaphor onto the whole of the evolutionary process, things go badly awry, because the more closely we inspect microbial genomes through the looking glass of gene and genome sequence comparisons, the smaller the amount of the data that fits the concept of a bifurcating tree becomes. That is mainly because among microbes, endosymbiosis and lateral gene transfer are important, two mechanisms of natural variation that differ from the kind of natural variation that Darwin had in mind. For such reasons, when it comes to discussing the relationships among all living things, that is, including the microbes and all of their genes rather than just one or a select few, many biologists are now beginning to talk about networks rather than trees in the context of evolutionary relationships among microbial chromosomes. But talk is not enough. If we were to actually construct networks instead of trees to describe the evolutionary process, what would they look like? Here we consider endosymbiosis and an example of a network of genomes involving 181 sequenced prokaryotes and how that squares off with some ideas about early cell evolution.
Modulating myelination: knowing when to say Wnt: Figure 1.
Authors: Rosenberg Sheila S. , Chan Jonah R.
Published: July 2009

Balancing extrinsic and intrinsic cues plays an integral part in shaping the complex architecture of the nervous system. During development, oligodendrocyte precursor cells integrate environmental signals and coordinate the activation of the transcriptional machinery necessary for differentiation and myelination. In this issue of Genes & Development, Fancy and colleagues (pp. 1571–1585) demonstrate that canonical Wnt signaling contributes to the decision of an oligodendrocyte precursor cell to differentiate—both during development and after demyelination. These findings provide new insight into the precise spatiotemporal coordination required for oligodendrocyte development.
The SESA network links duplication of the yeast centrosome with the protein translation machinery
Authors: Sezen Bengü , Seedorf Matthias , Schiebel Elmar
Published: July 2009

The yeast spindle pole body (SPB), the functional equivalent of mammalian centrosome, duplicates in G1/S phase of the cell cycle and then becomes inserted into the nuclear envelope. Here we describe a link between SPB duplication and targeted translation control. When insertion of the newly formed SPB into the nuclear envelope fails, the SESA network comprising the GYF domain protein Smy2, the translation inhibitor Eap1, the mRNA-binding protein Scp160 and the Asc1 protein, specifically inhibits initiation of translation of POM34 mRNA that encodes an integral membrane protein of the nuclear pore complex, while having no impact on other mRNAs. In response to SESA, POM34 mRNA accumulates in the cytoplasm and is not targeted to the ER for cotranslational translocation of the protein. Reduced level of Pom34 is sufficient to restore viability of mutants with defects in SPB duplication. We suggest that the SESA network provides a mechanism by which cells can regulate the translation of specific mRNAs. This regulation is used to coordinate competing events in the nuclear envelope.
DNA Isolation from Ants
Authors: Gadau Jürgen
Published: July 2009

INTRODUCTION

Many different DNA isolation methods have been employed successfully in ants. Parameters such as the size and developmental stage of the specimen (egg, larvae, or adult) and the subsequent use of the DNA will mostly determine which method should be used. Ant body sizes range from minute (1-2 mm in length) to large (30 mm), and the volume of the initial digestion should be adjusted accordingly. Whereas workers usually have low concentrations of storage proteins and fat, queens and larvae can contain considerable amounts of these substances that can interfere with the subsequent use of the isolated DNA. Ants also have many glands in the head and abdomen, and the contents of these glands can also interfere with the successful application of polymerase chain reaction (PCR) or restriction digests of the isolated DNA. This protocol presents two DNA isolation methods that have worked reliably for a wide range of ant species: a “quick and dirty” technique using Chelex isolation, and a more elaborate, classical phenol:chloroform procedure.
Radiochemical Assay of Juvenile Hormone Biosynthesis Rate in Ants
Authors: Brent Colin , Dolezal Adam
Published: July 2009

INTRODUCTION

Juvenile hormone (JH) is an important insect hormone known to have many effects on development, reproduction, and behavior in both solitary and social insects. This protocol describes how to quantify in vitro biosynthesis rates from excised corpora allata (CA), the glands responsible for JH production. Excised glands are incubated with radiolabeled methionine, resulting in the production of radiolabeled JH III, which can then be quantified. This protocol is most useful when quantification of the activity of the glands, rather than circulating JH levels, is desired. Its difficulties lie primarily in the ability to remove and handle the glands correctly.
In Situ Hybridization on Ant Ovaries and Embryos
Authors: Khila Abderrahman , Abouheif Ehab
Published: July 2009

INTRODUCTION

The detection of transcript distribution throughout a fixed tissue is a major step in studying the transcriptional activity of target genes and their function. In situ hybridization specifically detects the spatial distribution of RNA transcripts using an antisense RNA probe. This protocol describes the preparation of digoxigenin-labeled antisense RNA probes and their hybridization to complementary mRNA sequences; expression can then be localized using an antibody against digoxigenin conjugated to a chromogenic enzyme. In ants, this method can be applied to visualize cell populations of interest among other populations in a tissue, such as insect ovaries, or in the whole organism, such as insect embryos. Specific markers (e.g., genes known to be expressed in particular clusters of cells) can be cloned and used as probes to study the distribution and development of germline cells (e.g., nanos, vasa), neurons (repo), or limb structures (e.g., distal-less). Various markers might also allow the study of oogenesis (nanos, par-1, oskar), segmentation in the embryo (e.g., engrailed, wingless), or other developmental processes.
Establishment of the Winter-Annual Growth Habit viaFRIGIDA-Mediated Histone Methylation atFLOWERING LOCUS CinArabidopsis
Authors: Jiang Danhua , Gu Xiaofeng , He Yuehui
Published: July 2009

In Arabidopsis thaliana, flowering-time variation exists among accessions, and the winter-annual (late-flowering without vernalization) versus rapid-cycling (early flowering) growth habit is typically determined by allelic variation at FRIGIDA (FRI) and FLOWERING LOCUS C (FLC). FRI upregulates the expression of FLC, a central floral repressor, to levels that inhibit flowering, resulting in the winter-annual habit. Here, we show that FRI promotes histone H3 lysine-4 trimethylation (H3K4me3) in FLC to upregulate its expression. We identified an Arabidopsis homolog of the human WDR5, namely, WDR5a, which is a conserved core component of the human H3K4 methyltransferase complexes called COMPASS-like. We found that recombinant WDR5a binds H3K4-methylated peptides and that WDR5a also directly interacts with an H3K4 methyltransferase, ARABIDOPSIS TRITHORAX1. FRI mediates WDR5a enrichment at the FLC locus, leading to increased H3K4me3 and FLC upregulation. WDR5a enrichment is not required for elevated H3K4me3 in FLC upon loss of function of an FLC repressor, suggesting that two distinct mechanisms underlie elevated H3K4me3 in FLC. Our findings suggest that FRI is involved in the enrichment of a WDR5a-containing COMPASS-like complex at FLC chromatin that methylates H3K4, leading to FLC upregulation and thus the establishment of the winter-annual growth habit.
Novel Method for Coating Magnetic Iron Oxide Particles with Carbon Black
Authors: Hayashi Kazuyuki , Kamigaki Mamoru , Morii Hiroko , Okuyama Kikuo
Published: July 2009

Magnetic particles with finer size, higher coercive force, higher blackness, and lower electrical resistance are required to produce better magnetic tape materials. A new method to coat iron oxide particles with carbon black using an adhesive agent is reported in this paper. Magnetic tapes prepared using the coated particles in the recording layer exhibit improvements in both light transparency and electrical resistance. A decrease in transparency of ∼20% and a reduction in electrical resistance of ∼1 order of magnitude relative to conventionally prepared tapes are achieved when ∼5% of the particle weight is carbon black. Surface smoothness and the orientation ratio are also improved because the dispersibility of these particles in magnetic lacquer is better than that of uncoated magnetic iron oxide particles. Higher electromagnetic performance relative to the conventionally prepared layers is also obtained. TEM photographs indicate that all the carbon black is firmly bound to the surface of the magnetic iron oxide particles in a distinct layer.
Joining Si3N4‐Based Ceramics with Oxidation‐Formed Surface Layers
Authors: Plucknett Kevin P.
Published: July 2009

A simple processing technique has been developed for joining Si3N4‐based ceramics. Thin (<5 μm thick), amorphous, or partially crystalline SiO2‐based surface layers were formed, via low‐temperature oxidation (at 1200°C), on the faces to be joined. Joining of the surface‐coated pieces could then be performed in an inert environment at typical sintering/joining temperatures (i.e., 1700°C), with or without applied gas pressure, via a transient viscous/liquid phase. This method was most effective for Si3N4 ceramics with single oxide sintering additives when a thin (∼1 μm thick), highly smooth (RMS roughness <60 nm) SiO2 layer was formed, and essentially ‘pore‐free’ joints could be formed. However, the method was less suitable for a multi‐additive SiAlON material under current experimental conditions, as relatively high roughness (RMS roughness >400 nm) oxide scales formed, leaving residual porosity at the joint interface.
Processing and Properties of Blackglas™–Nextel™ 312 (BN) Composites Incorporating Fillers
Authors: Allahverdi Mehdi , Cannon W. Roger , Danforth Stephen C.
Published: July 2009

Blackglas™–Nextel™ 312 (BN) composites with and without filler materials have been processed and characterized. SiC as inactive filler, and Ti and TiB2 as active fillers, were incorporated into the Blackglas resin, and the resulting slurries were painted on Nextel fabrics. The painted fabrics were laminated at 150°C and then pyrolyzed at 1000°C under nitrogen to fabricate ceramic–ceramic composites. The pyrolyzed composites were infiltrated with the resin up to five times to minimize the porosity and microcracks formed upon pyrolysis. Dimensional changes, open porosity, and densities of the composites were monitored throughout the process. The flexural strengths of the unfilled and filled composites after 2, 3, 4, and 5 infiltration cycles were measured by four‐point bending. It was found that the addition of filler materials eliminated the delamination problem at a low number of infiltration cycles; however, the strengths of the filled composites did not reach the level of the unfilled composite. Much higher moduli were obtained for the filled composites because of the higher modulus of the filler materials relative to Blackglas.
Effect of Silver on the Sintering and Grain‐Growth Behavior of Barium Titanate
Authors: Chen Chin‐Yi , Tuan Wei‐Hsing
Published: July 2009

Silver and its alloys frequently are used as electrode material for BaTiO3‐based dielectrics. In the present study, a small amount of fine silver particles have been intimately mixed with BaTiO3 powder. The sintering and grain‐growth behavior of the silver‐doped BaTiO3 in air are investigated. The solubility of silver in BaTiO3, as revealed by lattice‐parameter measurement, electrical measurement, and electron probe microanalysis, is <300 ppm. The densification of BaTiO3 is slowed slightly by the addition of silver inclusions. However, the presence of a small amount (<0.3 wt%) of silver increases the amount and size of abnormal grains. When the silver content is >0.3 wt%, the grain growth of BaTiO3 then is prohibited by the silver inclusions.
Fabrication and Properties of Tape‐Cast Laminated and Functionally Gradient Alumina–Titanium Carbide Materials
Authors: Zeng Yu‐Ping , Jiang Dong‐Liang , Watanabe Tadahiko
Published: July 2009

A tape‐casting process was used to prepare various Al2O3–TiC green tapes, from which laminated and functionally gradient Al2O3–TiC materials (FGM Al2O3–TiC) were produced by cutting, stacking, and laminating the material, removing the binder, and hot‐pressing the green bodies. The bending strength of the FGM Al2O3–TiC composites was not much less than that of the laminated Al2O3–TiC composites. However, the fracture toughness was >50% higher; the fracture toughness of the FGM composite sintered at 1700°C was 9.43 MPa·m1/2. This increased toughness was attributed to the stress distribution that was caused by variations in the composition of the FGM composite layers. The present results demonstrate that the FGM design is a useful method for modifying the mechanical properties of ceramic composites.
Effects of Heating Rate on the Sintering Behavior and the Dielectric Properties of Ba0.7Sr0.3TiO3 Ceramics Prepared by Boron‐Containing Liquid‐Phase Sintering
Authors: Rhim Sung Min , Bak Heungjin , Hong Seokmin , Kim Ok Kyung
Published: July 2009

The effects of heating rate on the sintering behavior and the dielectric properties of Ba0.7Sr0.3TiO3 ceramics prepared by boron‐containing liquid‐phase sintering were investigated. When 0.5 wt% B2O3 was added to Ba0.7Sr0.3TiO3, sintering was achieved at ∼1150°C, and the overdoped B2O3 did not form an adequate amount of liquid phase or volatilize; it remained in the samples and formed a secondary phase. A transition broadening was observed as the heating rate increased. As the heating rate increased, the Curie temperature increased and the maximum dielectric constant (kmax) at the Curie temperature decreased. This result is attributable to a decrease in the diffuseness parameter (δ) and the tetragonality (c/a).
Effect of Microstructure on High‐Temperature Compressive Creep of Self‐Reinforced Hot‐Pressed Silicon Nitride
Authors: Boling‐Risser Martha A. , Goretta K. C. , Routbort J. L. , Faber K. T.
Published: July 2009

An experimental self‐reinforced hot‐pressed silicon nitride was used to examine the effects of microstructure on high‐temperature deformation mechanisms during compression testing. At 1575–1625°C, the as‐received material exhibited a stress exponent of 1 and appeared to deform by steady‐state grain‐boundary sliding accommodated by solution‐reprecipitation of silicon nitride through the grain‐boundary phase. The activation energy was 610 ± 110 kJ/mol. At 1450–1525°C for the as‐received material, and at 1525–1600°C for the larger‐grained heat‐treated samples, the stress exponent was >1. Damage, primarily in the form of pockets of intergranular material at two‐grain junctions, was observed in these samples.
Humidity Dependence of the Fatigue of High‐Strength Fused Silica Optical Fibers
Authors: Armstrong Janet L. , Matthewson M. John , Kurkjian Charles R.
Published: July 2009

Strength and dynamic fatigue behavior of silica fibers has been measured as a function of ambient humidity. Bare and polymer‐coated fibers were compared to determine the influence of the coating. The results verify earlier work that suggests the degradation reaction is approximately second order with respect to humidity. However, we verify this result using rigorous data analysis techniques and, unlike the earlier work, the result is shown to be independent of the form of the kinetic model for crack growth. Trends in the calculated fatigue parameters illustrate that a simple exponential crack growth law best describes the humidity data. No significant differences were found between coated and bare fibers, provided the coated fibers were properly equilibrated. A data analysis methodology is given for obtaining valid reaction orders independently of the crack growth law form.
Texture Development and Microstructure Evolution in Liquid‐Phase‐Sintered α‐Alumina Ceramics Prepared by Templated Grain Growth
Authors: Seabaugh Matthew M. , Messing Gary L. , Vaudin Mark D.
Published: July 2009

Texture development in alumina that contains calcia and silica and has been templated with platelet‐shaped α‐Al2O3particles has been evaluated. The texture fraction is shown to be related directly to template growth. Texture quality is controlled by the template concentration, decreasing at template concentrations of >10%, as a result of template–template interactions during tape casting. Almost fully textured alumina has been obtained at template concentrations of ≥20%. The growth of template grains is much more rapid in the radial direction and is shown to be inversely related to the thickness of the grain‐boundary liquid. The activation energy for growth (376 kJ/mol) and the inverse relation with the grain‐boundary thickness indicate that template growth in the radial direction is controlled by Al3+diffusion.
Microstructural Evolution in Triaxial Porcelain
Authors: Iqbal Yaseen , Lee William Edward
Published: July 2009

Microstructural evolution in a model triaxial porcelain was studied by X‐ray diffractometry and electron microscopy of quenched samples after firing for 3 h at 600°–1500°C. The clay component dehydroxylated to metakaolin at ∼550°C. Metastable sanidine formed from decomposition of the feldspar at >600°C and dissolved at >900°C. Liquid formation at ∼1000°C was associated with melting of feldspar and silica discarded from metakaolin formation via the K2O–Al2O3–SiO2 eutectic. Liquid content increased at 1000°–1200°C with further feldspar melting and additionally at >1200°C because of quartz dissolution. Small (≤7 nm) mullite and γ‐alumina crystals precipitated in pure clay relicts and larger (≤30 nm) mullite crystals in mixed clay‐feldspar relicts at 1000°C. In the evolving microstructures, three regions were observed. These regions were derived from pure clay relicts containing primary (type‐I) mullite; feldspar‐penetrated clay relicts, also containing secondary (granular type‐II) mullite; and the matrix of fine clay, feldspar, and quartz, containing secondary (granular type‐II and elongated type‐III) mullite. In addition to shape, the mullite size changed, increasing from regions containing type‐I to type‐III mullite, because the increasingly fluid liquid enhanced crystal growth. Below 1300°C, primary mullite was richer in Al2O3 than the secondary mullite, and the glass composition was inhomogeneous, with the K2O and Al2O3 contents varying throughout the microstructure. Above 1400°C, mullite began to dissolve.
Crystallization and Dielectric Properties of SrO–BaO–Nb2O5–SiO2 Tungsten‐Bronze Glass‐Ceramics
Authors: Shyu Jiin‐Jyh , Wang Jenn‐Rong
Published: July 2009

The crystallization and dielectric properties of SrO–BaO–Nb2O5–SiO2 glass‐ceramics have been investigated. Glass‐ceramics that contain strontium barium niobate (SBN) as a primary crystalline phase, which has a tungsten bronze structure, are produced. The formation of crystalline secondary phases also has been studied. The SBN phase shows evidence of both surface nucleation and bulk nucleation, and the crystals have an average composition of Sr0.47Ba0.53Nb2O6. The dendritic morphology of the SBN crystals has been examined. The SBN content and composite dielectric constant each has been studied as a function of heating temperature/time. The highest SBN content and dielectric constant obtained in the present study are 42 vol% and 180, respectively. The dielectric constant of the glass‐ceramics is determined primarily by the SBN content and the residual glass phase. The dielectric constant of the randomly oriented SBN crystal in the glass‐ceramics is calculated, using dielectric mixture rules, to be ∼400.
Crystallization of Electrostatically Seeded Lanthanum Hexaluminate Films on Polycrystalline Oxide Fibers
Authors: Saruhan Bilge , Abothu Isaac Robin , Komarneni Sridhar , Loong Chun‐Keung
Published: July 2009

Lanthanum hexaluminate (LaAl11O18), which features easily cleavable atomic planes in the magnetoplumbite (MP) structure, is a good candidate material for the fiber/matrix interface in oxide/oxide‐fiber‐reinforced composites. Difficulties that are encountered when using sol–gel synthesis to produce this material include the high crystallization temperature and the occurrence of an intermediate phase. This paper presents a method to overcome these difficulties by introducing crystalline seeds into the LaAl11O18 sol during the fiber coating. Seed particles are deposited initially on the fibers via electrostatic forces. Then, the sol is dip‐coated on the preseeded fibers, and the final LaAl11O18 coating is achieved via the use of heat treatments. The crystallization temperature can be reduced by at least 50°C, in comparison with that for the unseeded case, according to differential scanning calorimetry measurements, and no intermediate LaAlO3 phase is formed. The estimated seed numbers are on the order of 109 seeds/cm3 in the preseeded sol‐coated fiber surfaces and 1011 seeds/cm3 in the 4‐wt%‐seeded gels. The crystallization and structure of the La1−xAl12−yO19−z MP phase in the 4‐wt%‐seeded gels that have been heated at 400° and 1200°C have been studied using powder neutron diffraction.
Effects of Microstructure on Superplastic Behavior and Deformation Mechanisms in β‐Silicon Nitride Ceramics
Authors: Zhan Guo‐Dong , Mitomo Mamoru , Ikuhara Yuichi , Sakuma Taketo
Published: July 2009

The influence of grain shape and size on superplastic behavior and deformation mechanisms was investigated in annealed β‐silicon nitride materials and compared with the results for hot‐pressed material. The microstructure of the annealed materials consisted of fine equiaxed β‐grains together with some elongated ones. Similar to the deformation behavior in the hot‐pressed material, strain hardening did not occur in these annealed materials. Moreover, in contrast to the deformation behavior under tension, grain alignment under compression resulting from the development of a mild texture did not give rise to strain hardening. An annealed material with small elongated grains had a flow‐stress dependency of n= 1, whereas other annealed materials with large elongated grains exhibited a flow‐stress dependency of n= 1.6. In terms of texture development and the effect of grain shape on the creep rate when diffusion was the rate‐controlling mechanism, a single curve with a stress exponent of ∼1 and a grain‐size exponent of 3 were obtained for all materials. This suggests that the deformation mechanism in these annealed materials was the same as that of fine equiaxed β‐silicon nitride.
R‐Curve for a Lead Zirconate Titanate Ceramic Obtained from Tensile Strength Tests with Knoop‐Damaged Specimens
Authors: Fett Theo , Munz Dietrich
Published: July 2009

A procedure was used that made it possible to determine the R‐curve for piezoelectric ceramics from tensile strength tests conducted with Knoop‐damaged specimens. The resulting crack‐tip toughness KI0 was 0.6 MPa·m1/2, and the R‐curve starting from this value increased to 1.4 MPa·m1/2 within a 0.7 mm crack extension.
Synthesis of Phase‐Pure Pb(ZnxMg1–x)1/3Nb2/3O3 up to x= 0.7 from a Single Mixture via a Soft‐Mechanochemical Route
Authors: Shinohara Seiji , Baek Jong‐Gab , Isobe Tetsuhiko , Senna Mamoru
Published: July 2009

Phase‐pure perovskite Pb(ZnxMg1–x)1/3Nb2/3O3 solid solution (PZxM1–xN) is obtained for x≦ 0.7 by heating a milled stoichiometric mixture of PbO, Mg(OH)2, Nb2O5, and 2ZnCO3·3Zn(OH)2·H2O at 1100°C for 1 h. Percent perovskite (fP) with respect to total crystalline phase decreases with increasing temperature of subsequent heating then increases to 900°C for the mixtures where x≦ 0.8 and milled for 3 h. For mixtures with x= 0.9 and x= 1, fP decreases monotonically. Curie temperature increases almost linearly with increasing x up to x= 0.7. The maximum dielectric constant at 1 kHz is 2×104 and 1.7×104 for the mixture with x= 0.4 and x= 0.7, respectively. The stabilization mechanism of strained perovskite is discussed.
Micropatterning on Methylsilsesquioxane– Phenylsilsesquioxane Thick Films by the Sol–Gel Method
Authors: Matsuda Atsunori , Sasaki Teruyuki , Tatsumisago Masahiro , Minami Tsutomu
Published: July 2009

Prismatic patterns with a pitch of 30 μm and a slant height of 30 μm were embossed successfully in 70:30 (in mol%) methylsilsesequioxane:phenylsilsesqeioxane (MeSiO3/2–PhSiO3/2) thick films on glass substrates by laminating an organic polymer sheet as a stamper with the patterns against the films. The embossed shape of the prismatic patterns precisely agreed with the negative shape of those of the stamper that was used. The resultant MeSiO3/2–PhSiO3/2 films were transparent, and the refractive index of the films was adjusted to 1.51, to match that of the glass substrate.
Enhanced Phase Stability for Tetragonal Zirconia in Precipitation Synthesis
Authors: Wu Nae‐Lih , Wu Ton‐Fon
Published: July 2009

Tetragonal ZrO2 nanocrystallites—with or without yttria (3 mol%) doping—have been synthesized via a precipitation process in which the hydrous oxide precipitate reacts with hexamethyldisilazane (HMDS) vapor before calcination. The nanocrystallites are formed and retain a tetragonal structure for hours after calcination at temperatures of 300°–1100°C. The enhanced structural metastability has been attributed to the combined effect of suppressed grain growth and reduced surface energy that results from the HMDS treatment.
Preparation of Strontium‐ and Zinc‐Doped LaGaO3 Powders via Precipitation in the Presence of Urea and/or Enzyme Urease
Authors: Taş A. Cüneyt , Majewski Peter J. , Aldinger Fritz
Published: July 2009

Solid oxide fuel cell powders having a composition of La0.8Sr0.2Ga0.8Zn0.2O2.8 (LSGZ) were prepared by aqueous chemical precipitation in the presence of decomposing urea, followed by single‐step calcination in air. In some synthesis experiments the decomposition of urea was catalyzed by the enzyme urease. The calcination behavior of the precursor powders was studied over the temperature range of 90–1300°C, in an air atmosphere. Characterization of the samples was performed by XRD, TG/DTA, FTIR, FESEM, EDS, and carbon analyses. Two tentative XRD patterns have been created for the hydroxycarbonate precursors and the product LSGZ ceramics, respectively.
Interactions of Organic Additives with Boric Oxide in Aqueous Barium Titanate Suspensions
Authors: Li Chia‐Chen , Jean Jau‐Ho
Published: July 2009

The interactions between added boric oxide (B2O3) and organic additives, and their effects on the colloidal stability of aqueous BaTiO3 suspensions have been investigated. The initially Newtonian or pseudoplastic aqueous BaTiO3 suspension with poly(vinyl alcohol) (PVA) becomes dilatant, and its viscosity also increases dramatically when a critical amount of B2O3, 0.4 wt%, is added. This has been attributed to a chemical reaction between the dissociated borate ion (B(OH)4−) and PVA, which form a gel‐type structure in the aqueous BaTiO3 suspension. The dilatancy and viscosity of the aqueous BaTiO3 suspension with PVA and B2O3 increase significantly when a dispersant of ammonium salt of poly(acrylic acid) (PAA‐NH4) is present. The ionization of B2O3 is enhanced by the basicity of dissociated PAA−, promoting the formation of PVA‐B(OH)4− gel‐type structure in the aqueous BaTiO3 suspensions. With added plasticizer of 1,2‐ (e.g., ethylene glycol (EG)) or 1,3‐diol (e.g., 1,3‐propanediol (PPDL)) molecular structure, both the dilatancy and viscosity of aqueous BaTiO3 suspensions with PVA, B2O3, and PAA‐NH4 decrease dramatically. Stable compounds of diol‐B(OH)4− are formed before the dissociated B(OH)4− reacts with PVA, reducing the degree of gelation of aqueous BaTiO3 suspensions. A stability map is constructed to describe the amount of EG required to obtain colloidally stable aqueous BaTiO3 powder suspensions with PVA, PAA‐NH4, and B2O3.
Interaction between Dissolved Ba2+ and PAA‐NH4 Dispersant in Aqueous Barium Titanate Suspensions
Authors: Li Chia‐Chen , Jean Jau‐Ho
Published: July 2009

The interaction between dissolved Ba2+ and dissociated ammonium salt of poly(acrylic acid) (PAA‐NH4) in aqueous suspension has been studied. The dissolved Ba2+ causes flocculation of dissociated PAA‐NH4, thus degrading its dispersing effectiveness in aqueous BaTiO3 suspensions. The concentration of PAA‐NH4 required to stabilize aqueous BaTiO3 suspension increases with increasing Ba2+ concentration at a given pH. A stability map, which is determined by a rheological study, is constructed to describe the amount of PAA‐NH4 required to have well‐dispersed aqueous BaTiO3 suspensions as a function of Ba2+ concentrations at different pH values.
Compact Formation during Colloidal Isopressing
Authors: Yu Benjamin C. , Biesheuvel P. Maarten , Lange F. F.
Published: July 2009

In colloidal isopressing, a preconsolidated slurry with a high relative density (∼0.58) is converted into an elastic body (compact) under the influence of an isostatic pressure. Experiments suggest that during isopressing, the preconsolidated slurry is separated from the elastic body by a transition plane that rapidly moves into the preconsolidated slurry, leaving behind the elastic body which is formed against a piece of porous material present within the rubber mold. The porous material will accommodate the liquid phase squeezed out of the preconsolidated slurry, allowing for the conversion to the denser elastic body (∼0.63). The results of experiments with varied isopressure are compared with simulations based on a filtration model. The good agreement indicates that colloidal isopressing can be considered a special case of consolidation via pressure filtration. Compared with conventional pressure filtration, the extremely rapid consolidation is due to the high relative density of the preconsolidated slurry used to fill the mold as well as the high applied isopressure. The simulation used here is a useful tool in the design and understanding of shape forming by colloidal isopressing and shows how process variables such as particle size, relative density, and applied pressure influence compact formation time.
Effect of Potassium Concentration on the Grain Orientation in Bismuth Sodium Potassium Titanate
Authors: Fukuchi Eiichiro , Kimura Toshio , Tani Toshihiko , Takeuch Tsuguto , Saito Yasuyoshi
Published: July 2009

Bi0.5(Na1‐xKx)0.5TiO3 (BNKT) bulk ceramics with a preferred <100> orientation were prepared using the reactive templated grain‐growth method with platelike Bi4Ti3O12 particles as templates for BNKT. The potassium concentration (x value) had a large effect on the degree of orientation, and highly oriented ceramics were obtained for the specimens with x= 0.10 and x= 0.15, whereas the specimen with x= 0.00 had a small degree of orientation. Increased potassium concentration from x= 0.00 to x= 0.15 decreased the grain‐growth rate and changed the grain shape from irregular to cubic. These factors were responsible for the increased degree of orientation.
Hydroxylation and Dehydroxylation Behavior of Silica Glass Fracture Surfaces
Authors: D'Souza Andrew S. , Pantano Carlo G.
Published: July 2009

The hydroxylation and dehydroxylation behavior of amorphous silica fracture surfaces was studied using temperature‐programmed static SIMS. The results show that vacuum heat treatments result in more extensive condensation of silanol groups on the silica glass fracture surface as compared to fumed silica (Cabosil). This is attributed to differences in the distribution of silanol groups on the two silica surfaces. The rehydration kinetics of the dehydroxylated silica fracture surfaces showed two distinct reaction rates—an initial rapid increase in the silanol concentration, followed by a slower rehydration for longer dosing times. The slower rehydration reaction was shown to follow first‐order reaction kinetics with the reaction rate constant, suggesting hydrolysis of strained siloxane bonds on three‐membered silicate ring structures. The much faster initial rehydration is attributed to the hydrolysis of extremely strained siloxane bonds in two‐membered, edge‐shared tetrahedral rings. The effect of the dehydration time and temperature (i.e., thermal history of the surface) on the rehydration kinetics is also discussed.
Strength Retention in Hot‐Pressed Si3N4 Ceramics with Lu2O3 Additives after Oxidation Exposure in Air at 1500°C
Authors: Guo Shuqi , Hirosaki Naoto , Yamamoto Yoshinobu , Nishimura Toshiyuki , Mitomo Mamoru
Published: July 2009

The effect of oxidation exposure on room‐temperature flexural strength was examined in 3.33‐ and 12.51‐wt%‐Lu2O3‐containing hot‐pressed Si3N4 ceramics exposed to air at 1500°C for up to 1000 h. After oxidation exposure, the room‐temperature strength of the ceramics was degraded, and strength retention decreased with time at temperature, dependent on the amount of additive. The retention in room‐temperature strength displayed by the two compositions after 1000 h of oxidation exposure was 75%–80%. The degradation in strength was attributed to the formation of new defects at and/or near the interface between the oxide layer and the Si3N4 bulk during oxidation exposure.
Sodium‐Accelerated Diffusion of Magnesium in Silica and Its Retardation by Aluminum
Authors: Mukundhan Priya , Du Henry H. , Withrow Stephen P.
Published: July 2009

Fused silica platelets were implanted or coimplanted with sodium, magnesium, and aluminum and annealed in 1 atm flowing oxygen at 900°C. Concentration depth profiles of these elements in the implanted samples were obtained using secondary ion mass spectrometry before and after the annealing treatment. The presence of fast‐moving sodium markedly accelerated the diffusion of magnesium in silica. Incorporation of aluminum in silica significantly retarded the diffusion of sodium and magnesium. This study yielded valuable information for the understanding of the roles of various grain‐boundary cations in oxidation of silica‐forming ceramics.
Water‐Induced Degradation in Zinc Oxide‐Based Ceramic Varistors
Authors: Chen Wan‐Ping , Chan Helen L. W.
Published: July 2009

Water‐induced degradation in ZnO‐based ceramic varistors is reported. A comparison experiment was conducted in which some varistors were immersed in a 0.05M NaOH solution for some time while other varistors were placed in a 0.05M NaOH solution to evolve hydrogen on their silver electrode by electrolysis of water. No degradation occurred to those samples that were immersed in the NaOH solution; the leakage currents increased by orders of magnitude and the switch voltage remained unchanged in the samples treated by electrolysis of water. These results indicate that the degradation resulted from the reduction reaction of hydrogen atoms generated by electrolysis of water rather than the permeation of water into the ceramics. Because water can be formed on varistors by condensation of aqueous vapor in air and varistors are usually operated under electric fields, it is proposed that the reduction reaction of hydrogen atoms generated by electrolysis of water may be an important origin for the degradation in ZnO varistors.
Effect of Nitrogen Atmosphere on the Densification of a 3‐mol%‐Yttria‐Doped Zirconia
Authors: Paek Yeong‐Kyeun , Ahn Jung‐Ho , Kim Gyeung‐Ho , Kang Suk‐Joong L.
Published: July 2009

The densification behavior of a 3‐mol%‐Y2O3‐doped ZrO2 (3Y‐ZrO2) has been investigated under N2 and O2 atmospheres. Powder compacts have been sintered at 1550° and 1400°C for various times. The density of the specimen sintered at 1550°C is higher in N2 than in O2, while the contrary result is obtained in the case of the specimen sintered at 1400°C. Such results can be explained in terms of nitrogen solubility and oxygen vacancy in a ZrO2 matrix. Because nitrogen solubility into the ZrO2 increases with an increase in heat‐treatment temperature, leading to the formation of oxygen vacancy, the densification rate becomes higher. The present study thus shows evidence of nitrogen solubility into the ZrO2 and its role on the densification behavior of 3Y‐ZrO2.
Synthesis and Structural Characterization by X‐ray Absorption Spectroscopy of Tin‐Doped Mullite Solid Solutions
Authors: Caballero Alfonso , Ocaña Manuel
Published: July 2009

The formation of solid solutions between tin cations and mullite by calcination at 1400°C of amorphous precursors prepared by pyrolysis of aerosols is reported. The oxidation state of the tin cations and the position that they occupy in the mullite structure have been analyzed using XAS (XANES and EXAFS) spectroscopy, which shows that the tetravalent tin cations are located at the octahedral positions of the Al3+ ions, which induces cell expansion. The limit of tin incorporation under the experimental conditions reported here correspond to a tin/mullite mole ratio of ∼5%, which is within the range previously reported for other tetravalent cations (4%–6%).
Direct Synthesis of New Zircon‐Type ZrGeO4 and Zr(Ge,Si)O4 Solid Solutions
Authors: Hirano Masanori , Morikawa Hiroshi , Inagaki Michio , Toyoda Masahiro
Published: July 2009

A new phase of ZrGeO4 was hydrothermally synthesized from a mixture of ZrOCl2 solution and GeO2 powder at 240°C. X‐ray diffractometry patterns of synthesized ZrGeO4 particles, which had better crystallinity than ZrSiO4 particles prepared by the same process from ZrOCl2 and tetraethoxysilane, could be indexed for a zircon‐type tetragonal structure, having a0= 0.6694(0) and c0= 0.6265(7) nm. The c/a ratio of synthesized ZrGeO4 (0.9360) was larger than that of ZrSiO4 (0.9054). Solid solutions with zircon‐type structure over the whole composition range in the ZrGeO4‐ZiSiO4 system were also directly synthesized through the same solution route. The secondary particle size of zircon‐type Zr(Ge,Si)O4 solid solutions decreased, and its morphology gradually changed from octahedron‐like to blood‐red cell‐like with decreased GeO2 content.
X‐ray Photoelectron Spectroscopy Study on the Process of Apatite Formation on a Sodium Silicate Glass in Simulated Body Fluid
Authors: Takadama Hiroaki , Kim Hyun‐Min , Kokubo Tadashi , Nakamura Takashi
Published: July 2009

The process of apatite formation on the surface of Na2O–SiO2 glass in a body environment was investigated, mainly by X‐ray photoelectron spectroscopy, as a function of soaking time in a simulated body fluid (SBF). The glass was found to release Na+ ions via exchange with H3O+ ions in the SBF to form Si—OH groups on its surface. These Si—OH groups induced apatite formation indirectly, by forming calcium silicate and amorphous calcium phosphate. The formation of the calcium silicate and amorphous calcium phosphate is attributed to electrostatic interactions between the Si—OH groups on the glass surface and the calcium and phosphate ions in the SBF.