bluuebunny/crossref_metadata_2025 huggingface dataset:
Relationship between the Bond Valence and the Temperature Coefficient of the Resonant Frequency in the Complex Perovskite (Pb1−xCax)[Fe0.5(Nb1−yTay)0.5]O3
Authors: Park Heung Soo , Yoon Ki Hyun , Kim Eung Soo
Published: January 2009

The temperature coefficient of the resonant frequency (TCF) of complex perovskite (Pb1−xCax)[Fe0.5(Nb1−yTay)0.5]O3 ceramics (x= 0.5, 0.55; 0.0 ≤y≤ 1.0) was investigated, relative to the bond valence of the A‐ and B‐site ions in the ABO3 perovskite structure (such as the barium‐, strontium‐, and calcium‐based complex perovskites). The TCF of these complex perovskite compounds varied with the bond valence of the A‐ and B‐sites and the tolerance factor (t) in the perovskite structure. In the tilted region (t < 1.0), the tilting of the oxygen octahedra increased and the TCF decreased, because of the increased bond valence of the B‐site. Also, the dependence of TCF on the bond valence of the A‐site was similar to its dependence on t.
Thermal Shock of Layered Ceramic Structures with Crack‐Deflecting Interfaces
Authors: Vandeperre Luc J. , Kristofferson Annika , Carlström Elis , Clegg William J.
Published: January 2009

In this paper the influence of crack‐deflecting interlayers on the thermal shock behavior of a ceramic body has been studied. It is observed that the presence of such interlayers inhibits the penetration of cracks into the body and that the magnitude of this effect is much greater than that of internal stresses or of possible increases in fracture energy of the layers, because cracking occurs in a manner different from that expected. A finite difference model has been used to estimate the temperature distribution in the body, from which the crack driving force and its variation with time and penetration into the body have been calculated. It is shown that these observations are consistent with quantitative predictions, if continued crack growth in the laminate requires that the stress in the outermost intact layer is equal to the failure strength of that layer, rather than the crack driving force for the overall penetrating crack being equal to the fracture energy of the material.
Morphology and Phase Stability of Nitrogen–Partially Stabilized Zirconia (N‐PSZ)
Authors: Chung Tai‐Joo , Lee Jong‐Sook , Kim Doh‐Yeon , Kim Gyeung‐Ho , Song Huesup
Published: January 2009

The surface layer of yttria‐doped tetragonal zirconia materials that have been heat‐treated with zirconium nitride was observed to consist of a nitrogen‐rich cubic matrix with nitrogen‐poor tetragonal precipitates. The precipitates had a thin, oblate‐lens shape, similar to those observed in magnesia–partially stabilized zirconia. Because of the fast diffusion of N4− ions, the precipitates grew rather large, up to ∼5 μm in length, and remained stabilized in the tetragonal form at room temperature. Because the nitrided layer grew in the two‐phase field, the size and distribution of the precipitates each was very irregular. The nitrogen content was observed to determine the proportion of cubic and tetragonal phases in the same way as in conventional cation‐stabilized partially stabilized zirconia. A ternary phase diagram for the zirconium(yttrium)–nitrogen–oxygen system was suggested to explain the concentration gradient in the cubic matrix and the phase distribution of the nitrided layer.
Synthesis of CoO/Ni Composite Powders for Molten Carbonate Fuel Cells
Authors: Fukui Takehisa , Okawa Hajime , Hotta Tadashi , Naito Makio , Yokoyama Toyokazu
Published: January 2009

CoO/Ni composite particles were prepared by the advanced mechanical‐coating method called Mechanofusion™. These composite particles were composed of nickel particles uniformly covered with fine CoO particles. A new cathode structure for molten carbonate fuel cells (MCFCs), where the NiO core was coated with an outer layer of lithiated cobalt and nickel solid‐solution oxide (Li(Co,Ni) oxide), was formed by oxidation and lithiation using these CoO/Ni composite particles. The solubility of nickel in this Li(Co,Ni) oxide layer into carbonate melt decreased to two‐thirds of that of NiO when used as a cathode for MCFCs.
Microcontact Impedance Spectroscopy at Single Grain Boundaries in Fe‐Doped SrTiO3 Polycrystals
Authors: Rodewald Stefan , Fleig Jürgen , Maier Joachim
Published: January 2009

Microcontacts on adjacent grains of polycrystalline Fe‐doped SrTiO3 samples have been used to locally investigate the properties of individual grain boundaries. Impedance spectroscopy was employed to separate bulk and grain boundary impedances. Experiments at about 30 different grain boundaries permit far‐reaching conclusions on the distribution of grain boundary resistances, capacitances, and peak frequencies measured between adjacent grains. The rather narrow distribution of the grain boundary peak frequencies indicates a narrow distribution of grain boundary resistivities. All features (e.g., nonlinear current–voltage characteristics, grain boundary thickness, temperature dependence) are in accordance with the assumption of space charge depletion layers (double Schottky barriers) as the origin of the enhanced grain boundary resistivity. The average barrier height measured was about 630 mV. For comparison conventional (macroscopic) impedance measurements on a polycrystal were also performed and a brick layer model was used to extract effective properties. The reasonable agreement between these effective parameters and the average of the locally obtained parameters demonstrates that, in this case, a brick layer analysis of conventional impedance experiments yields satisfying estimates of the grain boundary properties.
Cyclic Fatigue–Crack Propagation Behavior in Silicon Carbide: Long‐ and Small‐Crack Behavior
Authors: Han Yoon Soo , Kim Do Kyung , Gilbert Christopher J. , Ritchie Robert O.
Published: January 2009

Cyclic fatigue properties of high‐toughness SiC with additives of Al2O3 and Y2O3 were examined, with a focus on differences between long‐ (>3 mm) and small‐crack (<200 μm) behavior. Small cracks were initiated with Vickers indents placed on the tensile surfaces of beams, and crack extension was monitored optically under cyclic load. For small cracks, high growth rates which exhibited a negative dependence on the far‐field driving force were observed. Such behavior was explained by both indent‐induced residual stresses and the relative size of cracks compared with bridging zone lengths.
Brittle Fracture versus Quasi Plasticity in Ceramics: A Simple Predictive Index
Authors: Rhee Young‐Woo , Kim Hae‐Won , Deng Yan , Lawn Brian R.
Published: January 2009

Simple relations for the onset of competing brittle and quasi‐plastic damage modes in Hertzian contact are presented. The formulations are expressed in terms of well‐documented material parameters, elastic modulus, toughness, and hardness, enablinga prioripredictions for given ceramics and indenter radii. Data from a range of selected ceramic (and other) materials are used to demonstrate the applicability of the critical load relations, and to evaluate coefficients in these relations. The results confirm that quasi plasticity is highly competitive with fracture in ceramics, over a sphere radius range 1–10 mm. Implications concerning the brittleness of ceramics in the context of indentation size effects are discussed.
Design and Fracture of Layered Al2O3/TZ3Y Composites Produced by Electrophoretic Deposition
Authors: Hatton Benjamin , Nicholson Patrick S.
Published: January 2009

Alumina/yttria‐stablized tetragonal zirconia (Al2O3/TZ3Y) multilayer composites with strong interfaces and containing residual stresses were produced by electrophoretic deposition. As‐synthesized and Vickers‐indented samples with different layering designs have been tested in bending (up to 1300°C) to experimentally define conditions for crack deflection and flaw tolerance. The compressive residual stress in the Al2O3 layers (ςr) is a function of layer thickness (t). It was found that the parameter ςr2t is an effective indicator of the fracture behavior, as predicted by strain energy release calculations. With decreasing ςr2t, the fracture followed a sequence from spontaneous delamination, multistage fracture with extensive crack deflection, to catastrophic failure with, and finally without, deflection steps. Decrease of ςr with increasing test temperature causes changes in fracture behavior which correspond to the room‐temperature transitions of ςr2t.
Boron Carbide–Zirconium Boride In Situ Composites by the Reactive Pressureless Sintering of Boron Carbide–Zirconia Mixtures
Authors: Goldstein Adrian , Geffen Ygal , Goldenberg Ayala
Published: January 2009

The heating of B4C–YTZP (where YTZP denotes yttria‐stabilized zirconia polycrystals) mixtures, under an argon atmosphere, generates B4C–ZrB2 composites, because of a low‐temperature (<1500°C) carbide–oxide reaction. Composites derived from mixtures that include ≥15% YTZP are better sintered than monolithic B4C that has been fired under the same conditions. Firing to ∼2160°C (1 h dwell) generates specimens with a bulk density of ≥91% of the theoretical density (TD) for cases where the initial mixture includes ≥15% YTZP. Mixtures that include 30% YTZP allow a fired density of ≥97.5% TD to be attained. The behavior of the B4C–YTZP system is similar to that of the B4C–TiO2 system. Dense B4C–ZrB2 composites attain a hardness (Vickers) of 30–33 GPa.
Low‐Temperature Reactive Sintering of 0.65PMN·0.35PT
Authors: Kwon Seongtae , Sabolsky Edward M. , Messing Gary L.
Published: January 2009

Dense, fine‐grained 0.65PMN·0.35PT ceramics were fabricated by reactive sintering of a mixture of metal oxides at 1000°C. The fine nature of the precursor powder resulted in rapid, direct transformation to perovskite PMN–PT at 600°C. Because of the fine structure of the perovskite, no excess PbO was required for sintering.
Influence of Washing on Zirconia Powder for Electrophoretic Deposition
Authors: Hatton Benjamin D. , Sakka Yoshio
Published: January 2009

The effects of powder washing on the colloidal stability and electrophoretic deposition rate of 3‐mol%‐Y2O3‐doped tetragonal‐ZrO2 powder from ethanol suspensions are shown experimentally. Simultaneous acoustic and electroacoustic measurements make it possible to determine independently particle size and zeta‐potential in concentrated ethanol suspension. It is suggested that ionic (Na+) surface contamination, which is reduced by laundering cycles, is the cause of the low zeta‐potential and deposition rate of the as‐received powder.
Structural Evolution of Thermal‐Sprayed Yttria‐Stabilized ZrO2 Thermal Barrier Coatings with Annealing—A Neutron Diffraction Study
Authors: Vogt Tom , Hunter Brett A. , Thornton John
Published: January 2009

We studied the influence of the annealing temperature on the atomic structure of yttria‐stabilized tetragonal zirconia (YSZ) which was deposited as a 300 μm thick thermal barrier coating (TBC) on nickel superalloy substrates by plasma spraying. To obtain neutron powder diffraction patterns of the barrier coatings we used an experimental technique where the sample is randomly rotated in the neutron beam. The time‐averaged neutron diffraction pattern was then analyzed using the Rietveld refinement technique without any need for corrections. This allowed the comparison of the average crystals structures from bulk tetragonal samples obtained via common ceramic routes and those of micrometer thick films deposited on substrates using plasma spray or other nonequilibrium techniques.
Catalytically Assisted Self‐Propagating High‐Temperature Synthesis of Tantalum Carbide Powders
Authors: Kim Troy , Wooldridge Margaret S.
Published: January 2009

The use of gas‐phase iodine and carbon dioxide as transport agents in the tantalum/carbon/tantalum carbide combustion synthesis system has been examined to determine the effects of transport agents on product composition and microstructure. Two tantalum reactant particle sizes, a range of transport agent concentrations, and total pressures were studied. The effects of the combustion conditions on product morphology and composition were evaluated using scanning electron microscopy, nitrogen adsorption (specific surface area), and X‐ray diffraction analyses. The results of the investigation indicate that the presence of the iodine vapor and carbon dioxide significantly enhances the combustion synthesis process, leading to higher conversion efficiencies and influencing product microstructure. The results are discussed in the context of gas‐phase and solid‐phase transport models.
Electric‐Field Effects on Sintering and Reaction to Form Aluminum Titanate from Binary Alumina–Titania Sol–Gel Powders
Authors: Stanciu Lia A. , Groza Joanna R. , Kodash Vladimir Y. , Crisan Maria , Zaharescu Maria
Published: January 2009

The field‐activated sintering technique (FAST) was applied to simultaneously sinter and react sol–gel amorphous powders to form Al2TiO5. Densities close to theoretical and conversion to Al2TiO5 (to 92.5%) have been achieved using FAST at 1050°–1200°C for 10 min. Conventional sintering of the same powders at 1300°C for 2 h resulted in 88.9% Al2TiO5 and ∼75% of theoretical density. The enhanced sintering and compound formation using FAST have been explained by the synergistic effects of precursor reactivity, nanosized powders, and electric‐field effects.
Influence of Dopant Concentration on Creep Properties of Nd2O3‐Doped Alumina
Authors: Wang Chong‐Min , Cho Junghyun , Chan Helen M. , Harmer Martin P. , Rickman Jeffrey M.
Published: January 2009

The microstructural features and tensile creep behavior of Al2O3 doped with Nd2O3 at levels ranging from 100 to 1000 ppm (Nd:Al atomic ratio) were systematically investigated. Compositional mapping, using both high‐resolution scanning transmission electron microscopy and secondary ion mass spectroscopy revealed that, for all of the compositions studied, the Nd3+ ions were strongly segregated to the Al2O3 grain boundaries. Microstructural observations revealed that the solubility of Nd2O3 was between 100 and 350 ppm. Tensile creep tests were conducted over a range of temperatures (1200°–1350°C) and stresses (20–75 MPa). Both the stress and grain‐size exponents were analyzed. In selected experiments, controlled grain‐growth anneals were used to enable creep testing of samples of the same average grain size but different neodymium concentrations. Independent of dopant level, the neodymium additions decreased the creep rate by 2–3 orders of magnitude, compared with that of undoped Al2O3. The value of the apparent creep activation energy increased with increased dopant concentration and then saturated at dopant levels exceeding the solubility limit. Overall, the results of the present study were consistent with a creep‐inhibition mechanism whereby oversized segregant ions reduce grain‐boundary diffusivity by a site‐blocking mechanism.
Phase Separation in an SiCO Glass Studied by Transmission Electron Microscopy and Electron Energy‐Loss Spectroscopy
Authors: Kleebe Hans‐Joachim , Turquat Christian , Sorarù Gian Domenico
Published: January 2009

SiCO glasses prepared from sol–gel precursors via pyrolysis in argon at temperatures ranging from 1000° to 1400°C were studied by transmission electron microscopy (TEM), in conjunction with electron energy‐loss spectroscopy (EELS). EELS analysis showed that stoichiometric SiCO glass underwent phase separation, forming SiO2‐ and SiC‐based environments. This process started at ∼1200°C. However, at temperatures >1300°C, precipitation of nanometer‐sized SiC particles embedded in vitreous SiO2 was monitored by high‐resolution TEM.
Crystallization of Sol–Gel‐Derived Barium Strontium Titanate Thin Films
Authors: Gust Maria C. , Momoda Leslie A. , Evans Neal D. , Mecartney Martha L.
Published: January 2009

Microstructural development of thin‐film barium strontium titanate (BaxSr1–xTiO3) as a function of strontium concentration and thermal treatment were studied, using transmission electron microscopy (TEM) and X‐ray diffractometry (XRD). Thin films, ∼250 nm thick, were spin‐coated onto Pt/Ti/SiO2/Si substrates, using methoxypropoxide alkoxide precursors, and crystallized by heat‐treating at 700°C. All films had the cubic perovskite structure, and their lattice parameters varied linearly with strontium content. Films with higher strontium concentrations had a larger average grain size. In situ TEM heating experiments, combined with differential thermal analysis/thermogravimetric analysis results, suggest that the gel films crystallize as an intermediate carbonate phase, BaxSr1–xTiO2CO3 (with a solid solution range from x= 1 to x= 0). Before decomposition at 600°C, this carbonate phase inhibits the formation of the desired perovskite phase.
Hydration Characteristics of Portland Cement after Heat Curing: II, Evolution of Crystalline Aluminate‐Bearing Hydrates
Authors: Yang Renhe , Sharp John H.
Published: January 2009

The development of crystalline aluminate‐bearing hydrates in portland cement mortars during water storage at room temperature for periods of up to 1 year after an initial heat cure for 12 h has been observed by quantitative X‐ray diffraction analysis and backscattered electron imaging. Ettringite was present in the mortars immediately after a short‐term cure at 20° and 60°C, calcium carboaluminate (C4AC̄H11) at 60°C, monosulfate at 85°C, and hydrogarnet at 85°C and above. Ettringite started to form after an induction period ranging from several days to several months after the initial heat cure at 85/100°C, and developed substantially during the period of expansion of the mortar associated with delayed ettringite formation (DEF). Ettringite growth was also observed in the nonexpansive cement mortars. Development of the ettringite bands occurred exclusively in the expansive mortars. Although monosulfate observed in the mortars that had been heat cured at 85°C sometimes increased in amount on initial storage at room temperature, it appeared to vary little in amount for up to 1 year. The amount of hydrogarnet in the heat‐cured cement product did not change significantly during storage at room temperature for more than 1 year. DEF expansion of the heat‐cured mortars was attributed to ettringite band formation, which started to form at the surface of the cement product and gradually developed inwards.
Raman Study of Hi‐Nicalon‐Fiber‐Reinforced Celsian Composites: I, Distribution and Nanostructure of Different Phases
Authors: Gouadec Gwénaël , Colomban Philippe , Bansal Narottam P.
Published: January 2009

Hi‐Nicalon‐fiber‐reinforced celsian‐matrix composites were characterized by Raman spectroscopy and imaging, using several laser wavelengths. Composite 1 was reinforced by as‐received fibers while coatings of p‐BN and SiC protected the fibers in composite 2. The matrix contained traces of the hexagonal phase of celsian, which was concentrated in the neighborhood of fibers in composite 1. Some free silicon was evident in the coating of composite 2 which might have involved a {BN + SiC → BNC + Si}“reaction” at the p‐BN/SiC interface. Careful analysis of C–C peaks revealed no abnormal degradation of the fiber core in the composites.
Defect Structure and Electrical Properties of La1−ySryFe1−xAlxO3−δ
Authors: Kus̆c̆er Danjela , Hanz̆el Darko , Holc Janez , Hrovat Marko , Kolar Drago
Published: January 2009

La1−ySryFe1−xAlxO3−δ perovskites were studied as potential materials for solid‐oxide fuel cell (SOFC) cathodes. The phase relations in the LaFeO3–SrFeO3−δ–LaAlO3 system were investigated by X‐ray powder diffraction analysis. The defect structure of the La1−ySryFe1−xAlxO3−δ perovskites was investigated by Mössbauer spectroscopy and weight‐loss analysis. Relations between the nonstoichiometry and the conductivity of the La1−ySryFe1−xAlxO3−δ perovskites were investigated. The incorporation of aluminum (x) into LaFe1−xAlxO3 was found to have no influence on the defect structure but to decrease the conductivity. The incorporation of strontium (y) into La1−ySryFe1−xAlxO3−δ promotes the formation of anion vacancies and Fe4+ that lead to higher conductivity.
Direct‐Write Fabrication of Pb(Nb,Zr,Ti)O3 Devices: Influence of Paste Rheology on Print Morphology and Component Properties
Authors: Morissette Sherry L. , Lewis Jennifer A. , Clem Paul G. , Cesarano Joseph , Dimos Duane B.
Published: January 2009

Lead niobium zirconate titanate (PNZT) pastes with tailored rheological properties have been developed for direct‐write fabrication of thick‐film capacitor elements in highly integrated, multifunctional electroceramic devices. Such pastes exhibited pseudoplastic behavior with a low shear apparent viscosity of roughly 1 × 106 cP. On aging, the degree of shear thinning and the low shear apparent viscosity decreased. Pastes prepared from as‐received powders attained printable, steady‐state viscosities of ∼2 × 105 cP after 50 days of aging. In contrast, pastes prepared from dispersant‐coated powders showed no measurable rheological changes after 1 day of aging. Square elements were patterned on dense alumina substrates or Teflon sheets. Leveling behavior as a function of time for single line prints, and the resulting surface topographies of dried PNZT films were measured by laser profilometry. PNZT layers sintered at varying temperatures between 950° and 1050°C for 5 h in either air or a lead‐rich atmosphere yielded porous microstructures as revealed by scanning electron microscopy (SEM). Such layers exhibited dielectric constants (K) of 1400–1570 at 1 kHz with dissipation factors (D) of less than 4.1%.
Synthesis and Colloidal Processing of Zirconia Nanopowder
Authors: Vasylkiv Oleg , Sakka Yoshio
Published: January 2009

Nanosized tetragonal 3 mol% Y2O3‐doped ZrO2 powder was produced by hydrothermal precipitation from metal chlorides and urea sol followed by a washing–drying treatment and calcination. The effects on powder properties of powder washing by water and ethanol with subsequent centrifuging, with possible deagglomeration using microtip ultrasonication, were experimentally shown. Ultrasonic irradiation induced pressure waves, which generated cavities that could violently collapse, producing intense stress. This induced stress was effective in minimizing secondary particle size, deagglomerating the powder, redispersing the ZrO2 after all the washing–centrifuging cycles, and minimizing mean aggregate size after final calcination. A uniformly aggregated tetragonal ZrO2 nanopowder with a mean secondary particle size of ∼45 nm and without hard agglomerates was prepared. The properties of the nanopowders produced by colloidal processing and CIP were studied. Determination of the best suspension parameters allowed for low‐temperature sinterability, which resulted in a nanograined ∼95 nm ceramic.
Structural and Property Evolution of Aqueous‐Based Lead Zirconate Titanate Tape‐Cast Layers
Authors: Smay James E. , Lewis Jennifer A.
Published: January 2009

We have developed aqueous suspensions of lead zirconate titanate (PZT) and an acrylic latex emulsion binder for tape casting. Rheological measurements were conducted to optimize their flow behavior at high solids volume fraction (φsolids). Concentrated suspensions (φsolids> 0.45) were tape cast onto a silicone‐coated mylar carrier film, and the effect of cellulose (a viscosifier) and surfactant additions on wetting behavior was studied. Drying stress measurements were performed on tape‐cast layers using a substrate deflection technique. The initial period of stress rise was analogous to that observed for binder‐free ceramic films, whereas the stress decay was influenced by latex coalescence. Tape‐cast layers exhibited a constant PZT volume fraction of 0.49 and uniform binder distribution independent of the PZT/latex volume ratio. The dielectric and piezoelectric properties of sintered multilayer samples were comparable to those obtained for bulk, isopressed samples. Our work provides guidelines for developing aqueous formulations for tape casting complex electroceramic oxide layers.
Microwave Dielectric Properties of (1 –x)(Al1/2Ta1/2)O2–x(Mg1/3Ta2/3)O2 Ceramics
Authors: Choi Ji‐Won , Kucheiko Sergey , Yoon Seok‐Jin , Kim Hyun‐Jai , Yoon Ki Hyun
Published: January 2009

The microwave dielectric properties of (1 –x)(Al1/2Ta1/2)O2–x(Mg1/3Ta2/3)O2 (0 ≤x≤ 1.0) ceramics were investigated. (Al1/2Ta1/2)O2 and (Mg1/3Ta2/3)O2 had orthorhombic and tetragonal structure, respectively. As (Mg1/3Ta2/3)O2 concentration increased, (1 – x)(Al1/2Ta1/2)O2–x(Mg1/3Ta2/3)O2 transformed to tetragonal structure. Specimens having a tetragonal single phase could be obtained for x > 0.6. As (Mg1/3Ta2/3)O2 concentration increased, the grain size, dielectric constant (ɛr) and quality factor (Q) significantly increased, and the temperature coefficient of resonant frequency (τf) changed from a negative to a positive value. A τf of 0 ppm/°C was realized at x= 0.65 and the Qfo value and ɛr for this composition were 112 470 GHz and 26.1, respectively. The relationship between microstructures and dielectric properties was also investigated.
Role of Internal Friction in Indentation Damage in a Mica‐Containing Glass‐Ceramic
Authors: Fischer‐Cripps Anthony C.
Published: January 2009

The indentation response of a mica‐containing glass‐ceramic that exhibits shear‐driven yield in an indentation test is interpreted in terms of events occurring on the microstructural scale. It is proposed that shear‐driven damage within the specimen occurs via internal sliding along cleavage planes within the mica platelets. The sliding surfaces in this case are considered to be atomically smooth so the real and apparent areas of contact coincide. The frictional shear stress is thus independent of the normal forces arising from thermal mismatch stresses and only depends on the work of adhesion of the interface and the scale of the contacts. The scale of contacts for these materials lies within an intermediate zone in which the frictional shear stress arises from the stress required to nucleate dislocation‐like discontinuities within the material. This leads to a size effect similar to that experienced by a crack in Mode II loading and is in accordance with previous work in which a connection between such a size effect and the macroscopic response of the material was identified. This work has particular relevance to the design and manufacturing of ceramics in machining, wear, bearings, and coatings applications.
Effect of NiO‐to‐Ni Transformation on Conductivity and Structure of Yttria‐Stabilized ZrO2
Authors: Linderoth Søren , Bonanos Nikolaos , Jensen Karin V. , Bilde‐Sørensen Jørgen B.
Published: January 2009

The conductivity and structure of 8‐mol%‐yttria‐stabilized zirconia with additions of nickel oxide has been investigated, both in the as‐prepared state and after reduction of NiO in hydrogen. During reduction at 1000°C, the conductivity decreases by 40%–50% and most of the NiO dissolved in the zirconia is exsolved in the form of nickel particles. This is accompanied by the formation of tetragonal zirconia precipitates of size 10–40 nm and by an increase in the lattice parameter. On reoxidation in air at 1000°C, the change in lattice parameter is partly reversed, but the conductivity shows no further changes.
Structure and Chemistry of Basal‐Plane Inversion Boundaries in Antimony Oxide‐Doped Zinc Oxide
Authors: Rečnik Aleksander , Daneu Nina , Walther Thomas , Mader Werner
Published: January 2009

The atomic structure and the chemistry of basal‐plane inversion boundaries in Sb2O3‐doped ZnO were investigated using quantitative transmission electron microscopy techniques. Electron microdiffraction and high‐resolution transmission electron microscopy were used to determine the orientation of the polar c‐axis on both sides of the inversion boundary and the translation state between the inverted ZnO domains. Quantitative energy‐dispersive X‐ray spectroscopy combined with high‐resolution transmission electron microscopy allowed us to determine the exact amount and the arrangement of antimony in the boundary layer. Inversion boundaries are head‐to‐head oriented with a displacement vector of the oxygen sublattice of RIB=⅓[01[Onemacr]0] – 0.102[0001]. The boundary plane consists of a highly ordered SbZn2 monolayer in which the cations occupy the octahedral interstices of the structure. In the octahedral boundary layer, zinc and antimony atoms constitute a honeycomb superstructure with a threefold (3m) in‐plane symmetry.
Synthesis of Calcium Hexaboride Powder via the Reaction of Calcium Carbonate with Boron Carbide and Carbon
Authors: Zheng Shuqi , Min Guanghui , Zou Zengda , Yu Huashun , Han Jiande
Published: January 2009

The synthesis of calcium hexaboride (CaB6) powder via the reaction of calcium carbonate (CaCO3) with boron carbide (B4C) and carbon has been investigated systematically in the present study. The influences of heating temperature and holding time on the reaction products have been studied using X‐ray diffractometry, and the morphologies of CaB6 obtained at various temperatures and holding times have been investigated via scanning electron microscopy. The interaction in the CaCO3–B4C–carbon system by which CaB6 is formed is a solid‐phase process that passes through the transition phases Ca3B2O6 and CaB2C2. The optimal conditions for CaB6 synthesis are a holding time of 2.5 h at a temperature of 1673 K, under vacuum (a pressure of 10−2 Pa). CaB6 powder has the same morphology as B4C, and the properties and the shape of CaB6 powders can be improved by choosing good‐quality raw materials.
Increased production of cysteinyl leukotrienes and prostaglandin D2 during human anaphylaxis
Authors: Ono E. , Taniguchi M. , Mita H. , Fukutomi Y. , Higashi N. , Miyazaki E. , Kumamoto T. , Akiyama K.
Published: January 2009

Background
Anaphylaxis is a life‐threatening syndrome resulting from the sudden release of mast cell‐ and basophil‐derived mediators into the circulation. However, pathological evidence of the association between inflammatory mediators and human anaphylaxis is insufficient.

Objective
The aim of this study was to better understand the relationship between in vivo production of inflammatory mediators and the pathogenesis of anaphylaxis. We also sought to evaluate mast cell activation in anaphylaxis.

Methods
We measured the concentrations of various inflammatory mediators in urine samples, which were collected from 32 anaphylactic patients during the onset of anaphlaxis and during clinical remission, 21 patients with asthma on acute exacerbation and 15 healthy control subjects. Blood and urine specimens were collected from the patients after provocation test. Urinary leukotriene E4 (LTE4), 9α, 11β‐prostaglandin F2 (9α, 11β‐PGF2), eosinophil‐derived neurotoxin (EDN) and leukotriene B4 glucuronide (LTBG) concentrations were determined by enzyme immunoassay, and the activity of plasma platelet‐activating factor acetylhydrolase and serum tryptase concentration were measured using commercially available kits.

Results
Significantly higher concentrations of urinary LTE4 and 9α, 11β‐PGF2, which immediately decreased during clinical remission, were observed in the anaphylactic patients than in asthmatic patients on acute exacerbation and healthy control subjects. Concentrations of EDN and LTBG were not significantly different among the anaphylactic patients, asthmatic patients on acute exacerbation and healthy subjects. There was a significant correlation between urinary LTE4 and 9α, 11β‐PGF2 concentrations in the anaphylactic patients (r=0.672, P=0.005, n=32). In addition, LTE4 concentration in patients with anaphylactic shock is significantly elevated compared with that in patients without anaphylactic shock.

Conclusions
This is a report on the significant increase in urinary LTE4 and 9α, 11β‐PGF2 concentrations during anaphylaxis. Urinary LTE4 and 9α, 11β‐PGF2 concentrations may be a reliable marker of endogenous production of inflammatory mediators associated with anaphylaxis.
Aquaculture, non‐native salmonid invasions and associated declines of native fishes in Northern Patagonian lakes
Authors: ARISMENDI IVÁN , SOTO DORIS , PENALUNA BROOKE , JARA CARLOS , LEAL CARLOS , LEÓN‐MUÑOZ JORGE
Published: January 2009

1. Even though intensive aquaculture production of salmonids in lakes occurs in many locations around the world published studies on the survival and reproductive success of escaped cultured salmonids in freshwater ecosystems are not common. A recent expansion of aquaculture in Chile has led it to become the world’s second largest producer of cultured salmonids.

2. We document the recent history of escaped and self‐sustaining salmonid populations over a wide spatial scale and a long temporal scale in Chilean Patagonian lakes. Our hypotheses are that salmonid density in lakes will be higher where there is intensive aquaculture, due to greater numbers of potential escapees. Secondly, if non‐native salmonids have adverse impacts on native fishes, increases in the abundance of non‐native species should be associated with decreases in relative abundance of native species. Finally, if the first two hypotheses are correct we anticipate that diets of salmonids may show evidence of predation on native fishes, diet overlap with native species, and evidence of the influence of feed from aquaculture operations in the diets of salmonids and native fishes.

3. We sampled six lakes with gill nets from 1992 to 2001. Our results show that the relative abundance of free‐living salmonids is closely related to the level of fish farming production. Salmonids are the top predators and in lakes with fish farming the main prey item is native fishes. The relative abundance of native fishes has decreased, most likely due to predation by salmonids.

4. Our study contributes to the understanding of the effects of non‐native salmonids in oligotrophic lakes, and it provides a starting point to judge the establishment of new fish farming sites in lakes around the world.
Root canal morphology of the mesiobuccal root of maxillary first molars: a micro‐computed tomographic analysis
Authors: Somma F. , Leoni D. , Plotino G. , Grande N. M. , Plasschaert A.
Published: January 2009

Aim  To investigate ex vivo, the root canal morphology of the MB root of maxillary first molar teeth by means of micro‐computed tomography.

Methodology  Thirty extracted intact human maxillary first molar teeth were selected for micro‐tomographic analysis (SkyScan 1072, Aartselaar, Belgium) with a slice thickness of 38.0 μm. The following data regarding the MB root were analysed and recorded: number and type of root canals, prevalence of isthmuses, prevalence of intercanal connections, presence of accessory canals, presence of loops and number of apical foramina.

Results  The MB2 canal was present in 80% of specimens and was independent in 42% of these cases. When present, the MB2 canal merged with the MB1 canal in 58% of cases. Communications between the two canals were found in all specimens, with isthmuses in 71% of the cases. These communications and isthmuses were respectively in 42% and 54% of the cases in the coronal third, in 59% and 79% of the cases in the middle third and in 24% and 50% of the cases in the apical third. A single apical foramen was found in 37% of specimens, two apical foramina were present in 23% of the cases, with three or more separate apical foramina occurring in 40% of the specimens.

Conclusions  The MB root canal anatomy was complex: a high incidence of MB2 root canals, isthmuses, accessory canals, apical delta and loops was found.
Evaluation of two mineral trioxide aggregate compounds as pulp‐capping agents in human teeth
Authors: Accorinte M. L. R. , Loguercio A. D. , Reis A. , Bauer J. R. O. , Grande R. H. M. , Murata S. S. , Souza V. , Holland R.
Published: January 2009

Aim  The present randomized, controlled prospective study evaluated the histomorphological response of human dental pulps capped with two grey mineral trioxide aggregate (MTA) compounds.

Methodology  Pulp exposures were performed on the occlusal floor of 40 human permanent pre‐molars. The pulp was capped either with ProRoot (Dentsply) or MTA‐Angelus (Angelus) and restored with zinc oxide eugenol cement. After 30 and 60 days, teeth were extracted and processed for histological examination and the effects on the pulp were scored. The data were subjected to Kruskal–Wallis and Conover tests (α = 0.05).

Results  In five out of the 40 teeth bacteria were present in pulp tissue. No significant difference was observed between the two materials (P > 0.05) in terms of overall histological features (hard tissue bridge, inflammatory response, giant cells and particles of capping materials). Overall, 94% and 88% of the specimens capped with MTA‐Angelus and ProRoot, respectively, showed either total or partial hard tissue bridge formation (P > 0.05).

Conclusions  Both commercial materials ProRoot (Dentsply) and MTA‐Angelus (Angelus) produced similar responses in the pulp when used for pulp capping in intact, caries‐free teeth.
Accidental injection with sodium hypochlorite: report of a case
Authors: Motta M. V. , Chaves‐Mendonca M. A. L. , Stirton C. G. , Cardozo H. F.
Published: January 2009

Aim  A case is reported in which sodium hypochlorite (NaOCl) was mistaken for anaesthetic solution and infiltrated into the buccal mucosa during routine root canal treatment.

Summary  A 1.5% sodium hypochlorite solution, kept in an anaesthetic cartridge, was inadvertently injected in the buccal mucosa of a 56‐year‐old female during routine root canal treatment. Soft tissue necrosis, labial ptosis and paraesthesia occurred shortly after the injection. Tissues healed with scarring and lip paraesthesia persisted for 3 years.

Key learning points  • NaOCl is highly irritant when introduced into oral tissues.

• NaOCl solutions should not be kept in anaesthetic cartridges.

• Accidents with NaOCl should be carefully assessed and when appropriate active  hospital treatment should be sought.

• Early recognition of NaOCl accidents may avert potentially more serious outcomes.
Which function describes the species–area relationship best? A review and empirical evaluation
Authors: Dengler Jürgen
Published: January 2009

Aim  The aims of this study are to resolve terminological confusion around different types of species–area relationships (SARs) and their delimitation from species sampling relationships (SSRs), to provide a comprehensive overview of models and analytical methods for SARs, to evaluate these theoretically and empirically, and to suggest a more consistent approach for the treatment of species–area data.

Location  Curonian Spit in north‐west Russia and archipelagos world‐wide.

Methods  First, I review various typologies for SARs and SSRs as well as mathematical models, fitting procedures and goodness‐of‐fit measures applied to SARs. This results in a list of 23 function types, which are applicable both for untransformed (S) and for log‐transformed (log S) species richness. Then, example data sets for nested plots in continuous vegetation (n = 14) and islands (n = 6) are fitted to a selection of 12 function types (linear, power, logarithmic, saturation, sigmoid) both for S and for log S. The suitability of these models is assessed with Akaike’s information criterion for S and log S, and with a newly proposed metric that addresses extrapolation capability.

Results  SARs, which provide species numbers for different areas and have no upper asymptote, must be distinguished from SSRs, which approach the species richness of one single area asymptotically. Among SARs, nested plots in continuous ecosystems, non‐nested plots in continuous ecosystems, and isolates can be distinguished. For the SARs of the empirical data sets, the normal and quadratic power functions as well as two of the sigmoid functions (Lomolino, cumulative beta‐P) generally performed well. The normal power function (fitted for S) was particularly suitable for predicting richness values over ten‐fold increases in area. Linear, logarithmic, convex saturation and logistic functions generally were inappropriate. However, the two sigmoid models produced unstable results with arbitrary parameter estimates, and the quadratic power function resulted in decreasing richness values for large areas.

Main conclusions  Based on theoretical considerations and empirical results, I suggest that the power law should be used to describe and compare any type of SAR while at the same time testing whether the exponent z changes with spatial scale. In addition, one should be aware that power‐law parameters are significantly influenced by methodology.
Antioxidant responses of chickpea plants subjected to boron toxicity
Authors: Ardıc M. , Sekmen A. H. , Tokur S. , Ozdemir F. , Turkan I.
Published: January 2009

This study investigated oxidative stress and the antioxidant response to boron (B) of chickpea cultivars differing in their tolerance to drought. Three‐week‐old chickpea seedlings were subjected to 0.05 (control), 1.6 or 6.4 mmB in the form of boric acid (H3BO3) for 7 days. At the end of the treatment period, shoot length, dry weight, chlorophyll fluorescence, B concentration, malondialdehyte content and the antioxidant enzymes superoxide dismutase (SOD), peroxidase (POX), catalase (CAT), ascorbate peroxidase (APX) and glutathione reductase (GR) were measured. The 1.6 mmB treatment did not cause significant changes in shoot length of cultivars, although shoot length increased in the drought‐tolerant Gökce and decreased in the drought‐sensitive Küsmen after 6.4 mmB treatment. Dry weights of both cultivars decreased with 6.4 mmB treatment. Chlorophyll fluorescence (Fv/Fm) did not change in Gökce at either B level. Nor did it change in Küsmen with 1.6 mmB but Fv/Fm decreased with 6.4 mmB. Boron concentration in the shoots of both cultivars increased significantly with increasing levels of applied B. Significant increases in total SOD activity were observed in shoots of both cultivars given 1.6 and 6.4 mmB. Shoot extracts exhibited five activity bands, two of which were identified as MnSOD and Cu/ZnSOD. In comparison to the control group, all enzyme activities (except APX and SOD) decreased with 1.6 mmB stress. GR activity decreased, while activities of CAT, POX and APX did not change with 6.4 mmB in Küsmen. On the other hand, activities of CAT, APX and SOD increased in Gökce at both B levels. In addition, lipid peroxidation was higher in Küsmen than in Gökce, indicating more damage by B to membrane lipids in the former cultivar. These results suggest that (i) Gökce is tolerant and Küsmen is sensitive to B, and (ii) B tolerance of Gökce might be closely related to increased capacity of the antioxidative system (total SOD, CAT and APX) to scavenge reactive oxygen species and thus suppress lipid peroxidation under B stress. To the best of our knowledge, this is the first report on the antioxidant response of chickpea seedlings to B toxicity.
Advocacy for mothers with psychiatric illness: A clinical perspective
Authors: Lagan Maureen , Knights Kathryn , Barton Jodi , Boyce Philip M.
Published: January 2009

Motherhood is a challenging role and a life‐changing experience. For women living with psychiatric illness, the challenge of motherhood is amplified. Psychiatric illness (including schizophrenia, affective and personality disorders) is associated with multiple adversities that can impair the capacity to parent. Social adversity, fluctuating symptoms, and medications and their related side‐effects, can create difficulties for the new mother as she adjusts to her role. The risk for relapse among women who are unwell is heightened during the post‐partum period. For many other women, the post‐partum period is when psychiatric symptoms emerge for the first time. Equally important are the continuing concerns pertaining to infant well‐being where maternal psychiatric illness is present. For mothers who exhibit symptoms at this time, a very real threat of protective removal exists. In the mother–infant setting, child protection legislation is biased towards the rights of the child. While there are cases for which this bias is clearly appropriate, there are less clear situations from which the infant is removed with little regard for the mother. Often mothers with psychiatric illness struggle to meet the cognitive, emotional, and financial demands of drawn‐out custody proceedings. For these mothers, there is a paucity of appropriate support available, as will be evidenced throughout the present paper. There is an urgent need for professional advocacy to support women who are unwell in their transition to motherhood. The mental health nurse is able to fill a key advocating role in the perinatal psychiatric setting. Nurses in this role hold a unique position whereby social and community supports can be activated, while guidance is imparted from a ground‐level standpoint. The nurse in this role has the capacity to liaise with authorities, negotiate service provision, and ensure that key parenting skills are acquired by the mother as she works to secure her role. Through the provision of proactive advocacy during this time, the nurse has the potential to ameliorate the outcomes of mothers who are unable to cope alone and the well‐being of their infants.
What Is Benford's Law?
Authors: Bradley Jonathan R. , Farnsworth David L.
Published: January 2009

The surprising property of many data sets that their first significant digits follow Benford's Law provides examples that can pique and hold students’ interest. Several ideas for student activities are presented.
Creating Realistic Data Sets with Specified Properties via Simulation
Authors: Goldman Robert N. , McKenzie Jr. John D.
Published: January 2009

We explain how to simulate both univariate and bivariate raw data sets having specified values for common summary statistics. The first example illustrates how to ‘construct’ a data set having prescribed values for the mean and the standard deviation – for a one‐sample t test with a specified outcome. The second shows how to create a bivariate data set with a specified correlation coefficient.
ICTS AND THE DECOUPLING OF EVERYDAY ACTIVITIES, SPACE AND TIME: INTRODUCTION
Authors: SCHWANEN TIM , DIJST MARTIN , KWAN MEI‐PO
Published: January 2009

This article is an introduction to and reflection on the papers about ICTs and everyday life in this issue. It outlines the motivations for the focus on the decoupling of activities, physical space and chronological time and characterises this process and three of its modalities: activity fragmentation; multi‐tasking; and personalised networking. The piece concludes by singling out some common elements that run through the set of papers and by identifying four avenues for future research.
ICT AND TEMPORAL FRAGMENTATION OF ACTIVITIES: AN ANALYTICAL FRAMEWORK AND INITIAL EMPIRICAL FINDINGS
Authors: HUBERS CHRISTA , SCHWANEN TIM , DIJST MARTIN
Published: January 2009

It is commonly believed that the widespread use of Information and Communication Technologies (ICTs) facilitates the fragmentation of daily activities across times and spaces. However, a clear conceptualisation of what fragmentation is and how it can be measured empirically has been lacking. As a consequence, hardly any empirical evidence has been provided for these notions. The goal of this paper is twofold: (1) to propose a theoretical and methodological framework for identifying and measuring activity fragmentation; and (2) to assess temporal fragmentation empirically and consider its associations with ICT usage while controlling for sociodemographic variables, residential context, day of the week, activity pattern characteristics and some attitudinal variables. Activity fragmentation is defined as a process whereby a certain activity is divided into several smaller pieces, which are performed at different times and/or locations. The proposed theoretical and methodological framework covers three main dimensions of fragmentation: the number of fragments; the distribution of the sizes of fragments; and the temporal configuration of fragments. Based on travel diary data from the Netherlands the analytical results are insightful and promising. The framework is not only capable of detecting temporal activity fragmentation for various trip purposes, but there are also indications of a positive relation between ICT usage and temporal fragmentation.