bluuebunny/crossref_metadata_2025 huggingface dataset:
Replication of simian virus 40 (SV40) DNA in virus-infected CV1 cells selectively permeabilized for small molecules by Staphylococcus aureus α-toxin: involvement of mitochondria in the fast O2-dependent regulation of SV40 DNA replication
Authors: RIEDINGER Hans-Jörg , EGER Frank , TRUMMLER Klaus , PROBST Hans
Published: March 2005

SV40 (simian virus 40)-infected CV1 cells were permeabilized with Staphylococcus aureus α-toxin for small molecules (<2 kDa) in a medium that supports DNA replication. Incorporation of [α-32P]dATP was shown to proceed at an essentially constant rate for at least 1 h. 32P-labelled DNA replication intermediates and products were analysed by alkaline sucrose density centrifugation. The results suggested that SV40 DNA replication in α-toxin-permeabilized CV1 cells occurred essentially as in vivo. After bromodeoxyuridine 5′-triphosphate-labelling and isopycnic banding, significant amounts of DNA density-labelled in both strands were detected from 110 min of permeabilization onwards, indicating repeated rounds of viral DNA replication in the permeabilized cells. Incubation of permeabilized SV40-infected cells under hypoxic culture conditions caused inhibition of SV40 DNA replication. As seen in unpermeabilized cells, SV40 DNA replication was inhibited at the stage of initiation. The inhibition of DNA replication induced by hypoxia was mimicked by AA (antimycin A), an inhibitor of mitochondrial respiration, and also by the replacement of glutamate, a substrate of mitochondrial respiration, by Hepes in the permeabilization medium. Inhibition of DNA replication was not mediated by intracellular ATP depletion. AA also inhibited SV40 DNA replication in unpermeabilized, normoxically incubated cells. Moreover, as in hypoxically incubated cells, the addition of glucose to SV40-infected cells incubated for several hours with AA induced a burst of new initiations followed by a nearly synchronous round of viral DNA replication. Taken together, these results indicate that mitochondria are involved in the oxygen-dependent regulation of SV40 DNA replication.
Contact mechanisms and design principles for Schottky contacts to group-III nitrides
Authors: Mohammad S. Noor
Published: March 2005

Contact mechanisms and design principles for Schottky contacts to group-III nitrides have been studied. These contacts, made generally by using simple principles and past experiences, suffer from serious drawbacks. The importance of various parameters such as surface morphology, surface treatment, metal/semiconductor interactions at the interface, thermal stability, minimization of doping by metal deposition and etching, elimination of edge electric field, etc., for them has been thoroughly investigated. Several design principles have been proposed. Both theoretical and experimental data have been presented to justify the validity of the proposed contact mechanisms and design principles. While theoretical calculations provide fundamental physics underlying heavy doping, leakage, etc., the experimental data provide verification of the contact mechanisms and design principles. The proposed principles are general enough to be applicable to most, if not all, Schottky contacts.
Water-driven programmable polyurethane shape memory polymer: Demonstration and mechanism
Authors: Huang W. M. , Yang B. , An L. , Li C. , Chan Y. S.
Published: March 2005

We demonstrate the new features of a polyurethane shape memory polymer: water-driven actuation and recovery in sequence (i.e., programmable). Hydrogen bonding is identified as the reason behind these features. In addition, the absorbed water is quantitatively separated into two parts, namely, the free water and bound water. Their individual contribution on the glass transition temperature is identified.
Evolution of elongated (In,Ga)As–GaAs(100) islands with low indium content
Authors: Cho S. O. , Wang Zh. M. , Salamo G. J.
Published: March 2005

Nucleation and growth of (In,Ga)As–GaAs(100) islands with low In content by molecular-beam epitaxy is investigated by scanning tunneling microscopy. The islands tend to nucleate at upper convex edges of surface steps due to elastic strain relaxation. They are elongated along [01-1] with a flat top (100) facet. The growth of the islands, mainly through uphill transport of the (In,Ga)As material, is characterized by shrinking of the top (100) facet but the ratio of island elongation keeps constant.
De novogeneration of antigen-specific CD4+CD25+regulatory T cells from human CD4+CD25–cells
Authors: Walker Mindi R. , Carson Bryan D. , Nepom Gerald T. , Ziegler Steven F. , Buckner Jane H.
Published: March 2005

Antigen-specificity is a hallmark of adaptive T cell-mediated immune responses. CD4+CD25+FOXP3+regulatory T cells (TR) also require activation through the T cell receptor for function. Although these cells require antigen-specific activation, they are generally able to suppress bystander T cell responses once activated. This raises the possibility that antigen-specific TRmay be useful therapeutically by localizing generalized suppressive activity to tissues expressing select target antigens. Here, we demonstrate that TRspecific for particular peptide-MHC complexes can be generated from human CD4+CD25–T cellsin vitroand isolated by using HLA class II tetramers. Influenza hemagglutinin epitopes were used to generate hemagglutinin-specific TR, which required cognate antigen for activation but which subsequently suppressed noncognate bystander T cell responses as well. These findings have implications for the generation of therapeutic regulatory T cells in disease, and also suggest an important mechanism by which T cells may be regulated at the site of inflammation.
Risk preference instability across institutions: A dilemma
Authors: Berg Joyce , Dickhaut John , McCabe Kevin
Published: March 2005

In this article we use laboratory experiments to ask a fundamental question: Do individuals behave as if their risk preferences are stable across institutions? In particular, we study the decisions of cash-motivated subjects in the repeated play of three different institutions: a value elicitation procedure for the sale of a risky asset, an English clock auction for the sale of a risky asset, and a first-price auction for the purchase of a riskless asset. We first do a simple categorical comparison of each subject's risk preferences across tasks by comparing the individual's decisions with an expected value maximizer. All subjects acted as if they were risk-loving in the English clock auctions and risk-averse in the first-price auctions. In the Becker, Degroot, and Marschack procedure, behavior was split between risk-loving and risk-averse bidding. For each institution we also estimate an individual's risk coefficient. We test the hypotheses that for the same individuals the estimated risk coefficient across institutions is the same. We find that these estimates are statistically different.
Enhanced cocaine responsiveness and impaired motor coordination in metabotropic glutamate receptor subtype 2 knockout mice
Authors: Morishima Yosuke , Miyakawa Tsuyoshi , Furuyashiki Tomoyuki , Tanaka Yasuhiro , Mizuma Hiroshi , Nakanishi Shigetada
Published: March 2005

Extensive pharmacological studies have recently emerged indicating that group 2 metabotropic glutamate receptors (mGluRs) comprising mGluR2 and mGluR3 subtypes are associated with several neurological and psychiatric disorders. mGluR2 is widely distributed both presynaptically and postsynaptically in a variety of neuronal cells, but the physiological role of mGluR2 in brain function is poorly understood. This investigation involves a comprehensive behavioral analysis of mGluR2
–/–
knockout (KO) mice to explore the physiological role of mGluR2 in brain function. Although, under general observation, mGluR2
–/–
KO mice appeared to have no behavioral abnormalities, they exhibited several lines of behavioral alterations in the enforcing and defined behavioral tests. They showed a significant increase in locomotor sensitization and conditioned place preference in association with repeated cocaine administration, indicating that mGluR2 contributes to behavioral responses implicated in reinforcement and addiction of cocaine. Upon
in vivo
microdialysis analysis after cocaine administration, not only did extracellular levels of dopamine increase but also the response pattern of glutamate release markedly changed in the nucleus accumbens of mGluR2
–/–
KO mice. The mGluR2
–/–
KO mice also showed significant impairment in motor coordination in the accelerating rota-rod test and exhibited hyperlocomotion in novel environmental and stressful conditions, when assessed by the open-field and forced-swim tests. These results indicate that the inhibitory mGluR2 plays a pivotal role in synaptic regulation of glutamatergic transmission in the neural network.
Engineering of vault nanocapsules with enzymatic and fluorescent properties
Authors: Kickhoefer Valerie A. , Garcia Yvette , Mikyas Yeshi , Johansson Erik , Zhou Jing C. , Raval-Fernandes Sujna , Minoofar Payam , Zink Jeffrey I. , Dunn Bruce , Stewart Phoebe L. , Rome Leonard H.
Published: March 2005

One of the central issues facing the emerging field of nanotechnology is cellular compatibility. Nanoparticles have been proposed for diagnostic and therapeutic applications, including drug delivery, gene therapy, biological sensors, and controlled catalysis. Viruses, liposomes, peptides, and synthetic and natural polymers have been engineered for these applications, yet significant limitations continue to prevent their use. Avoidance of the body's natural immune system, lack of targeting specificity, and the inability to control packaging and release are remaining obstacles. We have explored the use of a naturally occurring cellular nanoparticle known as the vault, which is named for its morphology with multiple arches reminiscent of cathedral ceilings. Vaults are 13-MDa ribonucleoprotein particles with an internal cavity large enough to sequester hundreds of proteins. Here, we report a strategy to target and sequester biologically active materials within the vault cavity. Attachment of a vault-targeting peptide to two proteins, luciferase and a variant of GFP, resulted in their sequestration within the vault cavity. The targeted proteins confer enzymatic and fluorescent properties on the recombinant vaults, both of which can be detected by their emission of light. The modified vaults are compatible with living cells. The ability to engineer vault particles with designed properties and functionalities represents an important step toward development of a biocompatible nanocapsule.
TRPV4 channel is involved in the coupling of fluid viscosity changes to epithelial ciliary activity
Authors: Andrade Yaniré N. , Fernandes Jacqueline , Vázquez Esther , Fernández-Fernández José M. , Arniges Maite , Sánchez Trinidad M. , Villalón Manuel , Valverde Miguel A.
Published: March 2005

Autoregulation of the ciliary beat frequency (CBF) has been proposed as the mechanism used by epithelial ciliated cells to maintain the CBF and prevent the collapse of mucociliary transport under conditions of varying mucus viscosity. Despite the relevance of this regulatory response to the pathophysiology of airways and reproductive tract, the underlying cellular and molecular aspects remain unknown. Hamster oviductal ciliated cells express the transient receptor potential vanilloid 4 (TRPV4) channel, which is activated by increased viscous load involving a phospholipase A2–dependent pathway. TRPV4-transfected HeLa cells also increased their cationic currents in response to high viscous load. This mechanical activation is prevented in native ciliated cells loaded with a TRPV4 antibody. Application of the TRPV4 synthetic ligand 4α-phorbol 12,13-didecanoate increased cationic currents, intracellular Ca2+, and the CBF in the absence of a viscous load. Therefore, TRPV4 emerges as a candidate to participate in the coupling of fluid viscosity changes to the generation of the Ca2+ signal required for the autoregulation of CBF.
Nuclear markers confirm taxonomic status and relationships among highly endangered and closely related right whale species
Authors: Gaines C.A , Hare M.P , Beck S.E , Rosenbaum H.C
Published: March 2005

Right whales (genus:Eubalaena) are among the most endangered mammals, yet their taxonomy and phylogeny have been questioned. A phylogenetic hypothesis based on mitochondrial DNA (mtDNA) variation recently prompted a taxonomic revision, increasing the number of right whale species to three. We critically evaluated this hypothesis using sequence data from 13 nuclear DNA (nuDNA) loci as well as the mtDNA control region. Fixed diagnostic characters among the nuclear markers strongly support the hypothesis of three genetically distinct species, despite the lack of any diagnostic morphological characters. A phylogenetic analysis of all data produced a strict consensus cladogram with strong support at nodes that define each right whale species as well as relationships among species. Results showed very little conflict among the individual partitions as well as congruence between the mtDNA and nuDNA datasets. These data clearly demonstrate the strength of using numerous independent genetic markers during a phylogenetic analysis of closely related species. In evaluating phylogenetic support contributed by individual loci, 11 of the 14 loci provided support for at least one of the nodes of interest to this study. Only a single marker (mtDNA control region) provided support at all four nodes. A study using any single nuclear marker would have failed to support the proposed phylogeny, and a strong phylogenetic hypothesis was only revealed by the simultaneous analysis of many nuclear loci. In addition, nuDNA and mtDNA data provided complementary levels of support at nodes of different evolutionary depth indicating that the combined use of mtDNA and nuDNA data is both practical and desirable.
Phenotypic plasticity in the developmental integration of morphological trade-offs and secondary sexual trait compensation
Authors: Tomkins Joseph L , Kotiaho Janne S , LeBas Natasha R
Published: March 2005

Trait exaggeration through sexual selection will take place alongside other changes in phenotype. Exaggerated morphology might be compensated by parallel changes in traits that support, enhance or facilitate exaggeration: ‘secondary sexual trait compensation’ (SSTC). Alternatively, exaggeration might be realized at the expense of other traits through morphological trade-offs. For the most part, SSTC has only been examined interspecifically. For these phenomena to be important intraspecifically, the sexual trait must be developmentally integrated with the compensatory or competing trait. We studied developmental integration in two species with different development: the holometabolous beetleOnthophagus taurusand the hemimetabolous earwigForficula auricularia. Male-dimorphic variation in trait exaggeration was exploited to expose both trade-offs and SSTC. We found evidence for morphological trade-offs inO. taurus, but notF. auricularia, supporting the notion that trade-offs are more likely in closed developmental systems. However, we found these trade-offs were not limited solely to traits growing close together. Developmental integration of structures involved in SSTC were detected in both species. The developmental integration of SSTC was phenotypically plastic, such that the compensation for relatively larger sexual traits was greater in the exaggerated male morphs. Evidence of intraspecific SSTC demands studies of the selective, genetic and developmental architecture of phenotypic integration.
Large‐Time Asymptotics for Periodic Solutions of the Modified Burgers Equation
Authors: Sachdev P. L. , Rao Ch. Srinivasa , Enflo B. O.
Published: March 2005

In this paper, we construct large‐time asymptotic solution of the modified Burgers equation with sinusoidal initial conditions by using a balancing argument. These asymptotics are validated by a careful numerical study.
Clinicopathologic features of epidermal cysts of the sole: comparison with traditional epidermal cysts and trichilemmal cysts*
Authors: Shimizu Yoshihiko , Sakita Kenichi , Arai Eiichi , Tsuchida Tetsuya , Ogawa Fumihiro , Ban Shinichi , Mitsuhashi Tomoko , Hirose Takanori , Shimizu Michio
Published: March 2005

Background:  It has been described that the etiology of epidermal cysts on acral skin is different from that on non‐acral skin; however, no papers have been published regarding the detailed histological differences between acral and non‐acral epidermal cysts. In this study, we compared the clinicopathologic findings of epidermal cysts of the sole with those of traditional epidermal cysts and trichilemmal cysts.

Methods:  The cases studied were 12 epidermal cysts of the sole, 35 traditional (non‐acral) epidermal cysts, and 12 trichilemmal cysts. The age and sex of the patients and the site, size, and microscopic findings of the lesions were evaluated.The pattern of keratinization was specifically focused on the evaluation of microscopic findings.

Results:  Microscopically, most of the epidermal cysts of the sole showed the presence of parakeratosis and focal lack of a granular layer at least at the upper portion of the cyst wall. The cyst content of the epidermal cysts of the sole was predominantly compact orthokeratotic material. These pathological findings could be explained by the pathogenesis of epidermal cysts of the sole, namely invagination of the surface epidermis.

Conclusion:  Our study indicates that most cases of the epidermal cyst of the sole are considered to be a true traumatic epidermal inclusion cyst.
Thermodynamic Analysis of the Chemical Vapor Deposition of Composite 〈Si3N4〉‐〈BN〉 Coatings
Authors: BESMANN T.M.
Published: March 2005

A thermodynamic analysis of the chemical vapor deposition of the composite ceramic (Si3N4(BN)⋆ was performed using a general computer program for the calculation of heterogeneous equilibria. Reactants assumed were (H2SiCl2), (BCI3), and (NH3). The equilibrium conditions for the deposition of condensed phases in the B‐Si‐N system wire determined as a function of the variables temperature, total system pressure, and gram‐atomic reactant gas fractions B/(Si + B) and N/(CI + N). The phase assemblage (Si3N4)‐〈BN〉 was found to be stable over a large region. Predominant gaseous species at equilibrium were (HCI), (N2), (H2), and the silicon chlorides. Deposition efficiencies at equilibrium for (Si3N4) and (BN) were high, particularly in the presence of excess (NH3) and at temperatures below 1600 K.
Phase Formation in the System Na2O · Al2O3‐CaO · A12O3‐Al2O3 at 1200°C in Air
Authors: VERWEIJ H. , SARIS C.M.P.M.
Published: March 2005

Phase relations in the system Na2O· Al2O3‐CaO· Al2O3‐Al2O3 at 1200°C in air were determined using the quenching method and high‐temperature X‐ray diffraction. The compound 2Na2O · 3CaO · 5Al2O3, known from the literature, was reformulated as Na2O · CaO · 2Al2O3. A new compound with the probable composition Na2O · 3CaO · 8Al2O3 was found. Cell parameters of both compounds were determined. The compound Na2O · CaO‐2Al2O3 is tetragonal with a = 1.04348(24) and c= 0.72539(31) nm; it forms solid solutions with Na2O · Al2O3 up to 38 mol% Na2O at 1200°C. The compound Na2O · 3CaO · 8Al2O3 is hexagonal with) a= 0.98436(4) and c= 0.69415(4) nm. The compound CaO · 6Al2O3 is not initially formed from oxide components at 1200°C but behaves as an equilibrium phase when it is formed separately at higher temperatures. The very slow transformation kinetics between β and β”‐Al2O3 make it very difficult to determine equilibrium phase relations in the high‐Al2O3 part of the diagram. Conclusions as to lifetime processes in high‐pressure sodium discharge lamps can be drawn from the phase diagram.
Effect of MgO Solute on Microstructure Development in Al2O3
Authors: BERRY K. A. , HARMER M. P.
Published: March 2005

The effect of MgO as a solid‐solution additive in the sintering of Al2O3 was studied. The separate effects of the additive on densification and grain growth were assessed. Magnesia was found to increase the densification rate during sintering by a factor of 3 through a raising of the diffusion rate. The grain‐size dependence of the densification rate indicated control primarily by grain‐boundary diffusion. Magnesia also increased the grain growth rate during sintering by a factor of 2.5. The dependence of the grain growth rate on density and grain size suggested a mechanism of surface‐diffusion‐controlled pore drag. It was argued, therefore, that MgO enhanced grain growth by raising the surface diffusion coefficient. The effect of MgO on the densification rate/grain growth rate ratio was, therefore, found to be minimal and, consequently, MgO did not have a significant effect on the grain size/density trajectory during sintering. The role of MgO in the sintering of alumina was attributed mainly to its ability to lower the grain‐boundary mobility.
Preparation and Sintering of Monosized Al2O3‐TiO2 Composite Powder
Authors: Okamura Heromichi , Barringer Eric A. , Bowen H. Kent
Published: March 2005

An unagglomerated, monosized Al2O3TiO2 composite powder was prepared by the stepwise hydrolysis of titanium alkoxide in an Al2O3 dispersion. Particle size was controlled by selecting the particle size of the starting Al2O3 powder; TiO2 content was determined by the amount of alkoxide hydrolyzed. A composite‐powder compact containing 50 mol% TiO2, when fired at 1350°C for 30 min, showed nearly theoretical density with aluminum titanate phase formation.
A Model for Silicon Self‐Diffusion in Silicon Carbide: Anti‐Site Defect Motion
Authors: Birnie Dunbar P.
Published: March 2005

A simple defect interaction model was developed that explains the identical activation energies observed for carbon and silicon diffusion in single‐crystal silicon carbide. In accord with experimental measurement of nonstoichiometry, the model requires a substantial concentration of silicon anti‐site defects. The diffusion of silicon is limited by the motion of these defects; this is suggested to occur by their interaction with carbon vacancies. The model predicts that boron doping will increase both carbon and silicon diffusion coefficients.
Reaction of Strontium Carbonate with Anatase and Rutile
Authors: TAGAWA HIROAKI , IGARASHI KAORU
Published: March 2005

The kinetics of the solid‐state reaction of strontium carbonate with anatase and rutile in air and carbon dioxide were studied by use of a thermobalance. The product was single‐phase SrTiO3 in all cases. The relation between fraction reacted and time was fitted to the Jander equation and to the Carter equation for both anatase and rutile. For anatase the rate constant in carbon dioxide did not differ from that in air. The reaction rates for rutile in air and in carbon dioxide were ⅓ and ⅛ that for anatase, respectively. The In k vs 1/T relation for anatase gave two straight lines with different slopes having a break point at ∼820°C in both air and carbon dioxide. The Jander activation energies for anatase in the higher and lower temperature regions were ∼340 and ∼290 kj · mol−1, respectively, and those for rutile in air and carbon dioxide were 340 and 390 KJ · mol−1, respectively.
Lattice Parameters and Density for Y2O3‐Stabilized ZrO2
Authors: INGEL R. P. , III D. LEWIS
Published: March 2005

Lattice parameter and density data were compiled for Y2O3‐Stabilized ZrO2, both from the literature and from experimental measurements. The data are described very well over a wide range of composition by the model of Aleksandrov et al., which assumes Y substitution for Zr in the unit cell with compensating anion vacancies. Effects are noted in two‐phase cubic‐tetragonal materials which indicate significant lattice strains in the two‐phase materials.
Ceramic Composite Pipes Produced by a Centrifugal‐Exothermic Process
Authors: Odawara Osamu , Ikeuchi Jun
Published: March 2005

Ceramic composite pipes were produced by a centrifugal‐exothermic process in a short time without the use of a high‐temperature furnace. The process is characterized by an exothermic reaction following a thermite reaction. The reactions occur under the influence of centrifugal force. Two‐layer ceramic pipes composed of molybdenum carbide or boride combined with aluminum oxide were produced using mixtures of MoO3, Al, and C or B powders.
Knoop and Vickers Indentation in Ceramics Analyzed as a Three‐Dimensional Fracture
Authors: KEER LEON M. , FARRIS THOMAS N. , LEE JUNG‐CHUAN
Published: March 2005

A three‐dimensional fracture analysis is applied to the Knoop and Vickers indentation fracture of ceramics. A brief discussion of the accuracy of the analysis applied to model the step load on the crack face caused by the residual stresses is given. A study is made of the effect of the elongated plastic zone in Knoop indentation on the unloaded radial fracture. It is shown that for small indentation loads the published experimental data can be verified by varying the depth reached by the semielliptical plastic zone with given surface length. An analysis and interpretation of the interaction between the two halfpenny‐shaped radial cracks induced by Vickers indentation is also given.
Effects of Bismuth Sesquioxide on the Characteristics of ZnO Varistors
Authors: TAKEMURA TAKETOSHI , KOBAYASHI MASAHIRO , TAKADA YOSHIO , SATO KEN
Published: March 2005

The nonlinearity of ZnO varistors is significantly influenced by the Bi2O3 and Sb2O3 contents, as well as by the phase composition of the Bi2O3. Degradation of the current‐voltage characteristics due to the applied voltage is not always lowered by the β—γ transition of the Bi2O3 phase. Lattice parameter determinations and stress analyses suggest that the Bi2O3‐rich phase in multigrain junctions causes mechanical strain at the grain boundary which may play an important role in the current‐voltage characteristics of ZnO varistors.
Strength Limitations of Transformation‐Toughened Zirconia Alloys
Authors: SWAIN M. V. , ROSE L. R. F.
Published: March 2005

Two mechanisms are proposed for the limitation of strength in transformation‐toughened zirconia ceramics: that the strength is limited by the critical stress to induce the tetragonal‐to‐monoclinic zirconia phase transformation and that the inherent R‐curve behavior of these materials limits the strength. Experimental evidence to support both mechanisms is presented which agrees tolerably well with theoretical predictions. However, for materials with larger initial flaws and higher toughness the experimental results favor the R‐curve argument.
Significance of Internal Stresses for the Martensitic Transformation in Yttria‐Stabilized Tetragonal Zirconia Polycrystals During Degradation
Authors: SCHMAUDER S. , SCHUBERT H.
Published: March 2005

Various aspects of the tetragonal (t) to monoclinic (m) transformation during degradation have been studied experimentally and theoretically in yttria‐stabilized tetragonal zirconia polycrystals (Y‐TZP), i.e., polycrystalline t‐ZrO2 containing Y2O3 in solution. Transmission electron microscopy (TEM) revealed that protruding grains at the surface of Y‐TZP specimens do not transform under corrosive conditions (250°C, humid atmosphere) even after an annealing time of 168 h. Eigenstresses due to anistropic thermal expansion In and around protruding and bulk grains have been calculated for Y‐TZP containing 2 and 3 mol% Y2O3. The prominent role of these stresses on subsequent transformation nucleation during degradation is shown to agree qualitatively with an established free energy concept. The lack of complete transformation of m‐ZrO2 is attributed to characteristics of the nucleation‐ and growth‐controlled transformation process.
Aqueous Solubility Relationships for Two Types of Calcium Silicate Hydrate
Authors: JENNINGS HAMLIN M.
Published: March 2005

There are many published values for the concentrations of lime and silica in the aqueous phase which is in contact with calcium silicate hydrate. These have been collected, carefully analyzed, and found often to be apparently inconsistent. When, however, they are interpreted as having come from an aqueous phase which is in near equilibrium with one or another of two possible modifications of calcium silicate hydrate, almost all the data are rationalized. Some important insights emerge for the understanding of the complex processes which occur during the hydration of tricalcium silicate.
Comparison of the Liquid‐Nitrogen Strength and the High‐Stressing‐Rate Strength of Soda‐Lime Glass
Authors: Roach D. H.
Published: March 2005

Indentation strength testing is used to compare two methods of avoiding slow crack growth: a high‐stressing‐rate test under ambient conditions vs testing under liquid nitrogen. The liquid‐nitrogen strength of soda‐lime glass is found to be 9% greater than the high‐stressing‐rate strength. This is consistent with previous measurements of an increase in Kc of 9.3% at liquid‐nitrogen temperature. The implication of this finding regarding time‐to‐failure calculations is discussed.
Preparation of Fine Alumina Powder in Alcohol
Authors: Fanelli Anthony J. , Burlew Joan V.
Published: March 2005

The preparation of fine alumina powder from alcoholic solutions of the metal alkoxide is described. The water for the hydrolysis reaction is generated in situ as a result of dehydration of the solvent at elevated temperature in an autoclave. The amount of water generated can be controlled according to the time temperature schedule employed. Control over the amount of water formed provides a means of controlling certain physical properties of the products, e. g., crystal structure and surface area.
Tape Casting of Al2O3/ZrO2 Laminated Composites
Authors: Boch Philippe , Chartier Thierry , Huttepain Muriel
Published: March 2005

Fracture toughness of ZrO2‐toughened alumina could he increased by macroscopic interfaces, such as those existing in laminated composites. In this work, tape casting was used to produce A/A or A/B laminates, where A and B can be Al2O3, Al2O3/5 vol% ZrO2, and Al2O3/l0 vol% ZrO2. An increase of toughness is observed, even in the Al2O3/Al2O3 laminates.
Influence of Iron Solute on the Structure of Small‐Angle [001] Twist Boundaries in Magnesium Oxide
Authors: EASTMAN JEFFREY A. , SASS STEPHEN L.
Published: March 2005

The structure of small‐angle [001] twist boundaries in pure and Fe‐doped MgO was examined by electron imaging techniques in order to study the influence of solute on grain‐boundary structure. In addition, the effect of the oxidation state of the Fe on the boundary structure was also examined. The [001] twist boundaries were produced in the form of bicrystals, by the hot‐pressing of cleaved single crystals of pure MgO and MgO containing Fe. In pure MgO the [001] twist boundaries produced with small plastic strains are planar and contain a square array of screw dislocations with Burgers vectors of the type a/2<110>. In the presence of solute the original interface becomes wavy and dissociates into subboundaries. Distorted hexagonal dislocation networks as well as square arrays of screw dislocations are often observed in Fe‐doped MgO. These observations are evidence that [001] twist boundaries in MgO whose production was accompanied by small amounts of plastic deformation undergo a structural transformation induced by the presence of Fe solute. The influence of the Fe oxidation state on boundary structure is less well understood. It appears that when the [001] twist boundaries are produced using crystals containing a substantial amount of Fe3+ ions, the resulting boundary structure is more likely to contain distorted hexagonal dislocation networks than when the boundary is produced from crystals containing predominantly Fe2+ ions.
Development of Aluminum Titanate‐Mullite Composite Having High Thermal Shock Resistance
Authors: Morishima Hiroyuki , Kato Zenji , Uematsu Keizo , Saito Katsukazu , Yano Toyohiko , Ootsuka Noboru
Published: March 2005

Thermomechanical properties of aluminum titanate‐mullite composites were studied for a wide composition range to develop material having high thermal shock resistance. The thermal shock resistance tended to increase with increasing aluminum titanate content. Composite having 82 vol% aluminum titanate can withstand water quench from above 1200°C and has a room‐temperature strength of 60 MPa. Composite with less aluminum titanate has lower thermal shock resistance but has higher strength. The relation between thermal shock resistance and strength, Young's modulus, and thermal expansion coefficient is discussed.
Bonding of Dental Glass to Nickel‐Chromium Alloys
Authors: Tomsia Antoni P. , Pask Joseph A.
Published: March 2005

Two 80Ni · 20Cr‐type alloys, one 99.99% pure and one with 98% purity, formed a multilayer oxide scale with an outer layer of NiO and a single‐layer scale with outer portion richer in Cr2O3, respectively. An applied K‐aluminosilicate glass at 1020°C penetrated the latter oxide scale. Adherence was present at all interfaces due to the existence of chemical equilibrium. Fracture occurred in the multilayer oxide scale and in the glass close to the oxide glass interface, respectively.
Immiscibility in the CoO‐NiO System
Authors: Bergman Bill , Agren John
Published: March 2005

The thermodynamic properties of the solid CoO‐NiO solution have been assessed in terms of a thermodynamic model including a contribution from the magnetic transition. The parameters in the model have been adjusted to fit emf measurements in the literature. The miscibility gap at low temperatures is calculated and compared to the gap proposed by Kinoshita, Kingery, and Bowen from their TEM studies. A very severe discrepancy between experimental maximum temperature (760°C) and the calculated one (185°C) is found. Various reasons for the descrepancy are discussed.
Electrical Conductivity Measurements to Detect Suspected Liquid Phase in the Al2O3‐I mol% TiO2‐0.5 mol% NaO1/2 and Other Systems
Authors: Morgan Peter E. D. , Koutsoutis Michael S.
Published: March 2005

A liquid phase in the Al2O3‐1 mol% TiO2‐0.5 mol% NaO1/2 composition is confirmed at ±1300°C by an electrical conductivity measurement. The ease of the method led to a study of the Al2O3‐2 mol% CuO‐2 mol% TiO2 system and to the geologically important detection of eutectics (peritectics) in rock materials.
Investigations of NiO‐CuO Solid Solutions Using Transmission Electron Microscopy: II, Evidence for Long‐Range Cation Order
Authors: DAVIES P.K.
Published: March 2005

Further studies of rock salt solid solutions in the (NixCu1‐x)O system have given direct structural evidence of long‐range cation order. Using transmission electron microscopy a structural modulation has been observed at high NiO concentration, x < 0.85, and superlattice reflections and fringes confirmed the formation of an ordered compound Ni2CuO3. The cationic arrangement in Ni2CuO3 is analogous to the atomic arrangement in the alloy Ni2V The proposed structure is orthorhombic with a=acubic/√2, b= 3acubic/√2, and c=acubic, and it shows considerable microtwinning. The arrangement of cations is compared to that in Cu2MgO3 and these two compounds are found to be closely related. The structural models are discussed in terms of the energetics of the (Nix, Cu1‐x)O system. The behavior of CuO‐MO systems, containing Ni2+, is compared and contrasted to that in the Co and Mg systems.
Kinetic Processes Involved in the Sintering and Crystallization of Glass Powders
Authors: CLARK TERENCE J. , REED JAMES S.
Published: March 2005

Viscometry, crystal growth kinetics, and glass powder sintering were used to determine the activation energies of viscous flow, crystal growth, and sintering behavior of a standard NBS 710 glass and two crystallizable glass powders in the calciaaluminosilicate system. In a system which sintered successfully to zero porosity, the activation energy for sintering was comparable to the activation energy of viscous flow. When the apparent activation energy for the sintering process was lower than that of viscous flow, sintering was found to proceed at a slower rate because the precipitated crystalline phase retarded viscous flow and the shrinkage of the pores. Initial crystallization appeared to occur on the surfaces of coalesced particles. A chemical treatment was partially successful in suppressing the onset of surface nucleation of the precursor powder.
Germanium‐Modified Cordierite Ceramics with Low Thermal Expansion
Authors: AGRAWAL D. K. , STUBICAN V. S. , MEHROTRA Y.
Published: March 2005

Magnesium cordierite ceramics modified by ionic substitution of Ge for Si were synthesized, fabricated, and characterized. The effect of the amount of ionic substitution on thermal expansion was investigated. Ionic substitution of ∼20% germanium for silicon reduces thermal expansion to zero at room temperature. A processing schedule to achieve nearly theoretical densities in germanium cordierite specimens was developed, and the microstructures of sintered samples were examined by scanning electron microscopy. Other thermal properties such as specific heat and thermal conductivity were also measured for the germanium‐modified cordierites.
Electrical Conductivity of A12O3: Fe + Y
Authors: KORIPELLA CHOWDARI R. , KRÖGER FERDINAND A.
Published: March 2005

High‐temperature dc electrical conductivity and emf of oxygen concentration cells with A12O3 as the electrolyte were studied. The defect structure of α‐Al2O3 doped with Fe and Y was investigated to test an explanation proposed for the favorable effect of Y addition to super alloys (Fe, Cr, Ni, Al) which leads to well‐adherent and nonconvoluted A12O3 oxide scales. Results indicate that Y is a singly ionizable donor in Al2O3 and Y additions are effective in compensating Fe acceptors in A12O3 at iron concentrations up to the solubility limit of Y. At higher acceptor concentrations leading to a decrease in [V“‘Al] and an increase in [Al…i], incorporation of Y leads to a small increase in the concentration of V’”Al. This suggests that the mechanism proposed for the prevention of oxide scale spallation based on the Y donor action to suppress the bulk diffusion of aluminum interstitials created by the Fe acceptors cannot explain the effect. Energy level positions of Fe and Y in A12O3 are estimated, and values for electron and hole mobility at 1500°C are derived.
Formation and Crystallization in the Yttrium Aluminosilicate Glasses Containing Zinc Oxide
Authors: Makishima Akio , Kubo Hajime , Kotani Kazuo , Tsutsumi Masayuki , Asami Mitsuaki
Published: March 2005

Formation of yttrium aluminosilicate glasses containing zinc oxide from batches melted at 1550°C was investigated. Densities, thermal expansion coefficients, and Vickers hardnesses were measured for some glasses. In a specific compositional region, crystals with a convex and pyramidal habit were observed on the glass surface. The crystal was identified as ZnAl2O4 (gahnite) which has a Moh's hardness number of ∼8.
Kinetics of Phase Transformation in the TiO2‐SnO2 System Outside the Coherent Spinodal: Role of Aliovalent Dopants
Authors: Yuan Thomas C. , Virkar Anil V.
Published: March 2005

The kinetics of phase transformation in the TiO2‐SnO2 system above the coherent spinodal is examined with small additions of Al and Ta as dopants. Al increased the rate of phase separation while Ta suppressed it. Precipitation in the undoped sample occurred by cellular mechanism while in the Al‐doped sample it seems to have occurred by heterogeneous nucleation and growth mechanism at the grain boundaries of the original solid solution.
Kinematical Model for Stress‐Induced Transformation around Cracks
Authors: ROSE L. R. F.
Published: March 2005

In materials susceptible to transformation toughening, the two experimental measures of fracture toughness, namely the specific work of fracture, R, and the nominal stress intensity factor, K are not equivalent during the transient stage of cracking, before steady‐state conditions are reached. The reason for the difference is discussed theoretically, using a model in which the transformation zone is represented by a set of strain nuclei such that crack growth can be regarded as the translation of a composite elastic singularity, and consequently the crack extension force can be determined analytically by using the Eshelby‐Rice J integral. The difference between the two measures of toughness for this model is associated with the strain nuclei representing the trailing end of the transformation zone. With increasing crack extension, the influence of these trailing strain nuclei decreases and eventually becomes negligible as cracking proceeds to steady‐state conditions.
Fracture Toughness of MgO‐Partially‐Stabilized ZrO2 Specimens with KR‐Curve Behavior from Transformation Toughening
Authors: BURNS S. J. , SWAIN M. V.
Published: March 2005

Transformation‐toughened MgO‐partially‐stabilized ZrO2 exhibits a crack‐wake‐induced load‐point displacement in fracture samples. The equations of linear elastic fracture mechanics were self‐consistently reformulated to include the residual displacement from the transformation wake. Application of these equations to double‐cantilever‐beam specimens of transformation‐toughened ZrO2, with the martensitic start transformation temperature close to the testing temperature, gives a decreasing KR curve and initial toughness values near 30Mpa·ml/2.
Anisotropic Thermal Expansion Coefficients of Y2O3‐Stabilized Tetragonal Zirconia
Authors: SCHUBERT H.
Published: March 2005

The transformability of the grains in tetragonal zirconia polycrystals is determined by thermal stresses (eigenstresses) which develop because of anisotropic expansion behavior of the tetragonal grains on cooling. Anisotropic thermal expansion coefficients based on lattice parameter determinations at room temperature and 600° and 800°C are presented for tetragonal zirconia containing 2 and 3 mol% Y2O3. The sources of errors in these data are discussed.
Crystallization of MgO‐Al2O3‐SiO2‐ZrO2 Glasses
Authors: McCOY M. , LEE W. E. , HEUER A. H.
Published: March 2005

The crystallization of MgO‐Al2O3‐SiO2‐ZrO2 glasses at 1000°C was studied. Isothermal heat treatments of a cordierite‐based glass (2MgO.2Al2O3.5SiO2= Mg2Al4Si5O18) with 7 wt% ZrO2 produced surface crystallization of α‐cordierite and tetragonal ZrO2 (t‐ZrO2). These phases advanced into the glass by cocrystallization of t‐ZrO2 rods in an α‐cordierite matrix with a well‐defined orientation relation. The t‐ZrO2 rods were unstable with respect to diffusional breakup (a Rayleigh instability) and decomposed into rows of aligned ellipsoidal and spheroidal particles. The t‐ZrO2 was very resistant to transformation to monoclinic symmetry. With a similar glass containing 15 wt% ZrO2, surface crystallization of α‐cordierite and t‐ZrO2 was accompanied by internal crystallization of t‐ZrO2 dendrites. Transformation of the dendrites to mono‐clinic symmetry was observed under some conditions.
Yellow Coatings Produced on Glasses and Aluminum by the Sol‐Gel Process
Authors: Makishima Akio , Kubo Hajime , Wada Kenji , Kitami Yoshizo , Shimohira Takajiro
Published: March 2005

The preparation of CeO2‐TiO2 coatings by the sol‐gel dip‐coating process, with curing at 500°C, was studied. The films were brilliant yellow and adherent to soda‐lime glass, a PbO‐containing glass, and aluminum foil. The transmittance, chromaticity, thickness, phase content, and surface microstructure of the films were determined.
Kinetics of BaTiO3and PbTiO3Formation from Metallo‐organic Precursors
Authors: SHAIKH AZIZ S. , VEST GERALDINE M.
Published: March 2005

Kinetics of BaTiO3and PbTiO3formation from metalloorganic precursors were studied. The fine grain size of the decomposed product and the greater degree of mixing led to very rapid kinetics of compound formation. The kinetics data were fitted to the Carter model for a diffusion‐controlled process. Formation of PbTiO3was modeled as a two‐stage process with a single activation energy, and the formation of BaTiO3as a single‐stage process.
Unstable Spreading of a Fluid Inclusion in a Grrain Boundary under Normal Stress
Authors: RAJ RISHI
Published: March 2005

A fluid inclusion trapped in a stress‐free grain boundary will assume an equilibrium lenslike shape. The dihedral angle at apex will be determined by the ratio of the (isotropic) solid‐solid and solid‐liquid interface energies. The radius of curvature of the lens surface will depend on the volume of the inclusion. If a normal stress is now applied across the interface, then the mechanical energy (equal to the sum of the external work and (he strain energy) and the interface energy will together determine the shape of the inclusion. In this paper it is shown that the inclusion can spread catastrophically if the applied stress is greater than a critical value. The magnitude of the critical stress depends on the equilibrium dihedral angle and the volume of the inclusion. A smaller angle and a larger volume lead to a smaller value of the critical stress. As an example a fluid inclusion which is ∼1 μm in size and forms a dihedral angle of 15° is unstable under an applied stress of 100 MPa. The results have slgniflciincc in the phenomenon of liquid‐phase‐enlianccd sintering and diffuslonal creep.
Optical and Thermal Bleaching of X‐Irradiated Barium Aluminoborate Glasses
Authors: PONTUSCHKA WALTER MAIGON , ISOTANI SADAO , PICCINI ANGELO
Published: March 2005

Photoproduction of interstitial atomic hydrogen centers (H0i), apparently at the expense of boron electron centers (BEC) in barium aluminoborate glasses X‐irradiated at 77 K, is reported. Electron paramagnetic resonance studies of isothermal and isochronal annealing of BEC and correlated decay of BEC with corresponding growth of H0i under exposure of light were carried out. Some possible interactions between chemical states induced by irradiation are discussed.
Preparation of Crystalline Aluminum Phosphate by the Reaction Using Boron Phosphate
Authors: Vasović Dušanka , Stojaković Djordje , Stanković Slavica
Published: March 2005

The use of BPO4 in the synthesis of crystalline AlPO4 has been investigated. The best results are obtained if BPO4 and hydrated alumina are heated in molten KCl: at 1050°C the conversion degree of BPO4 into AlPO4 is >90% (in 4 h). The product consists of the tridymite AlPO4 form.
Thermodynamics of Calcium Silicate Hydrates and Their Solutions
Authors: GARTNER ELLIS M. , JENNINGS HAMLIN M.
Published: March 2005

The solution that surrounds hydrating cement particles contains dissolved species which are important in the overall process. A method, based on the Gibbs‐Duhem equation for a three‐component system, has been developed for computing the composition of one phase from values for its equilibrium solubility in a second phase. The method has been used to compute the CaO:SiO2 ratio for two types of calcium silicate hydrate (C‐S‐H) gel, one of which is thought to form from hydrating tricalcium silicate (Ca3SiO5), and the other by precipitation from appropriate solutions. The results agree well with measured values reported in the literature. They have also been used to help define the probable composition of the C‐S‐H layer which forms on tricalcium silicate surfaces during the early stages of hydration when the reaction is slow. A chemical potential phase diagram is constructed from which thermodynamic quantities can be computed directly. The free energies of formation have been estimated for two types of C‐S‐H formed from CaO, SiO2, and H2O, These results provide insight into the structure and composition of C‐S‐H, which is the most abundant product in portland cement systems.
Alumina‐Silica Phase Diagram in the Mollite Region
Authors: KLUG FREDERIC J. , PROCHAZKA SVANTE , DOREMUS ROBERT H.
Published: March 2005

The alumina‐silica phase relations of samples annealed in oxygen and quenched were studied by optical microscopy, image analysis, X‐ray diffraction, and the electron microprobe. The solid solution boundaries of mullite changed with increasing temperature and joined at 1890°C and a composition of 77.15 wt% alumina. The melting point of mullite was 189°C with a peritectic between 76.5 and 77.0 wi% alumina.