bluuebunny/crossref_metadata_2025 huggingface dataset:
Kinetics of Tricalcium Aluminate and Tetracalcium Aluminoferrite Hydration in the Presence of Calcium Sulfate
Authors: Brown Paul Wencil
Published: March 2005

Hydration reactions of C3A and C4AF with calcium sulfate hemihydrate and gypsum were investigated and the kinetics of the reactions compared. The rates of C3A and C4AF hydration, as determined by heat evolution, vary depending on whether the sulfate‐containing reactant is gypsum or calcium sulfate hemihydrate. The following sequence of reactions involving C4AF occurs when hemihydrate is the reactant: gypsum formation during the first hour, ettringite formation between 20 and 36 hours, and the conversion of ettringite to monosulfate over a period of about 12 hours. Monosulfate formation initiates prior to the complete consumption of gypsum. The onset of this conversion occurs at a shorter hydration time when hemihydrate is a reactant and the total amount of heat evolved is lower. The hydration reactions in saturated calcium hydroxide solution occur more slowly than those in water. Based on heat liberation, C4AF reacts at a much higher rate than C3A. Ettringite formation occurs during the first 8 to 9 days of C3A hydration. Once the gypsum is consumed, ettringite converts to monosulfate during two additional days. Compared to gypsum, hemihydrate decreases the rates of hydration of both C3A and C4AF. The effects on the hydration characteristics of C4AF are significant. The hydration of C3A with gypsum in water, in saturated Ca(OH)2 solution, and in 0.3M NaOH solution were compared. Heat evolution is the lowest for hydration in 0.3M NaOH. The onset of monosulfate formation occurs prior to the complete reaction between gypsum and C3A in the NaOH solution.
A New Technique for Monitoring Aging in Yttria–Tetragonal Zirconia Polycrystals
Authors: Lawson Simon , Smith Paul A.
Published: March 2005

Conventional techniques used to monitor aging‐induced phase relationships in zirconia ceramics are shown to be limited as to the amount of information that can be obtained without sectioning the sample. Measurement of the microwave dielectric loss tangent of progressively aged Y‐TZP samples is shown to be a suitable technique to monitor the growth of the transformed monoclinic layer with time.
Chemically Corroded Pristine Silica Fibers: Blunt or Sharp Flaws?
Authors: Inniss Daryl , Zhong Qian , Kurkjian Charles R.
Published: March 2005

Bare silica fiber is aged in the vapor of a hydrofluoric acid solution, the inert strength is determined, and the resulting surface topography is characterized with an atomic force microscope. This chemical treatment results in well‐defined, spatially resolved etched holes whose dimensions can be readily characterized. The aspect ratios range from 10−3 to 1, with c≤a, where c is the flaw length and a is its half width, and the inert strength ranges from 5.4 to 12.5 GPa. Better agreement is observed for the measured and calculated strength when the flaws are defined as blunt rather than sharp (i.e., c/a rather than c1/2). This model agrees with results in the literature for chemically corroded pristine fiber. The geometry of the maximum stress concentrator is characterized as a partially embedded hemispherical pit and, therefore, suggests a lower limit for the inert strength of a chemically corroded pristine fiber when c/a= 1. In addition, these results suggest reevaluation of the long‐term mechanical reliability assessment of optical fibers, because a sharp flaw model (i.e., c≫a) is currently used.
Synthesis, Properties, and Ternary Phase Stability of M6X Compounds in the Ti─Cu─O System
Authors: Kelkar Girish P. , Carim Altaf H.
Published: March 2005

A section of the Ti─Cu─O ternary phase diagram was investigated at 925°C. The system contains two M6X‐type compounds, Ti4Cu2O and Ti3Cu3O, which are isostructural with the η‐carbides and are stabilized by O. The presence of two of these compounds and the size of their single‐phase fields contradict earlier predictions in the literature based on the valence and location of the elements in the periodic table. It is proposed that the atomic radii of the elements may also be a factor, especially for compounds containing Ti. The two observed M6X‐type compounds occur as products of reaction at the Ag─Cu─Ti/Al2O3 interface. The compounds were synthesized in bulk for characterization of their properties which influence the performance of the brazed joints. The compounds are stable in inert atmospheres up to their melting points, but are easily oxidized in ambients containing even trace amounts of O and form a coherent layer of reaction products. The values of elastic coefficients, thermal expansion, and resistivity of these compounds are intermediate between those of Al2O3 and Cu and would therefore provide a gradual transition across the interface.
Reaction Bonding and Mechanical Properties of Mullite/Silicon Carbide Composites
Authors: Wu Suxing , Claussen Nils
Published: March 2005

Based on the RBAO technology, low‐shrinkage mullite/SiC/ Al2O3/ZrO2 composites were fabricated. A powder mixture of 40 vol% Al, 30 vol% A12O3 and 30 vol% SiC was attrition milled in acetone with TZP balls which introduced a substantial ZrO2 wear debris into the mixture. The precursor powder was isopressed at 300–900 MPa and heattreated in air by two different cycles resulting in various phase ratios in the final products. During heating, Al oxidizes to Al2O3 completely, while SiC oxidizes to SiO2 only on its surface. Fast densification (at >1300°C) and mullite formation (at 1400°C) prevent further oxidation of the SiC particles. Because of the volume expansion associated with the oxidation of Al (28%), SiC (108%), and the mullitization (4.2%), sintering shrinkage is effectively compensated. The reaction‐bonded composites exhibit low linear shrinkages and high strengths: shrinkages of 7.2%, 4.8%, and 3%, and strengths of 610, 580, and 490 MPa, corresponding to compaction pressure of 300, 600, and 900 MPa, respectively, were achieved in samples containing 49–55 vol% mullite. HIPing improved significantly the mechanical properties: a fracture strength of 490 MPa and a toughness of 4.1 MPa.m1/2 increased to 890 MPa and 6 MPa.m1/2, respectively.
Model for the Developing Microstructure in Portland Cement Pastes
Authors: Jennings Hamlin M. , Tennis Paul D.
Published: March 2005

A method is proposed for quantitatively predicting the volume of the major phases in hydrated cement pastes as a function of (1) the composition of the cement, (2) the degree of reaction, and (3) the initial water:cement ratio. This procedure is then used to develop a quantitative model for the surface area and volume of porosity that is accessible to nitrogen in C‐S‐H. Published values for surface areas and volume of pores are compared with the predictions made by the model. An implication of the model is that there are two types of C‐S‐H, or perhaps regions within the C‐S‐H: one that nitrogen can penetrate and one that it cannot.
Tensile Creep Behavior of Alumina/Silicon Carbide Nanocomposite
Authors: Ohji Tatsuki , Nakahira Atsushi , Hirano Takeshi , Niihara Koichi
Published: March 2005

Tensile creep and creep rupture behaviors of alumina/17 vol% silicon carbide nanocomposite and monolithic alumina Were investigated at 1200° to 1300°C and at 50 to 150 MPa. Compared to the monolithic alumina, the nanocomposite exhibited excellent creep resistance. The minimum creep rate of the nanocomposite was about three orders of magnitude lower and the creep life was 10 times longer than those of the monolith. The nanocomposite demonstrated transient creep until failure, while accelerated creep was observed in the monolith. It was revealed that rotating and plunging of intergranular silicon carbide nanoparticles into the alumina matrix increased the creep resistance with grain boundary sliding.
Thermogravimetric Determination of Carbon, Nitrogen, and Oxygen in Aluminum Nitride
Authors: Nicolaescu Ion V. , Tardos Gabriel , Riman Richard E.
Published: March 2005

A thermogravimetric method for the measurement of carbon, nitrogen, and oxygen in aluminum nitride is described. Since carbon oxidation occurs at lower temperatures than the oxidation of the aluminum compounds, thermogravimetric analyses in the respective temperature regimes can yield measurement of the oxygen, nitrogen, and carbon content. Thermogravimetric analyses were performed on mixtures of aluminum nitride and carbon with various concentrations in order to evaluate the accuracy of this method. The results were compared with those obtained by the hot gas extraction method. Errors produced by overlapping of the temperature ranges of the reactions were evaluated and experimental conditions were optimized to minimize error. This method can produce reliable results at elemental concentrations higher than a few percent. The absolute errors of the C/AI, N/Al, and O/Al atomic ratios were less then 0.02. The detection limit was evaluated to 0.2 wt% of each element. The applicability of the method to the study of the kinetics of the nitridation reaction was demonstrated.
Role of Defect Interaction in Boundary Mobility and Cation Diffusivity of CeO2
Authors: Chen Pei‐Lin , Chen I‐Wei
Published: March 2005

Grain boundary mobility of CeO2 containing 0.1% and 1.0% trivalent dopant cations (Sc, Yb, Y, Gd, and La, in order of increasing ionic radius) has been measured. At the lower dopant concentration (intrinsic regime), mobility is controlled by grain boundary diffusion of host cations, whereas at the higher dopant concentration (extrinsic regime), mobility is controlled by solute drag through the lattice. The effect of trivalent dopants is closely associated with their ability to provide and to interact with oxygen vacancies. Evidence consistent with an interstitial mechanism for cation diffusion has been found which is remarkably affected by the presence of oxygen vacancies. Ce diffusion is enhanced by free oxygen vacancies in the system, while dopant diffusion is suppressed if a dopantassociated oxygen vacancy is not present. A bare Sc cation, however, appears to be a fast‐diffusing species, due to its highly distorted local environment, while Y at 1.0% emerges as the most effective grain growth suppressant.
Effect of Crystal‐Axis Orientation on Dielectric Properties of Ceramics Prepared from Fibrous Barium Titanate
Authors: Ohara Yoshinobu , Koumoto Kunihito , Yanagida Hiroaki
Published: March 2005

Barium titanate (BaTiO3) ceramics with high degrees of a‐ and c‐axis orientation were fabricated by combining hydrothermal synthesis of fibrous particles, formation of green compacts with aligned extruded rods in the mold, and normal sintering. The orientation of crystal axes in such ceramics gives rise to high dielectric permittivity. Ceramics with an orientation degree f=76% showed values of ε/ε0 which are 1.5 times (ε/ε0= 2700) as large as those of a randomly oriented (commercial) ceramic (ε/ε0= 1800).
Hardness–Grain‐Size Relations in Ceramics
Authors: Rice Roy W. , Wu Carl Cm. , Boichelt Fred
Published: March 2005

Both Vickers and Knoop hardness (H), measured at two or more loads in the range of 100–2000 g (most commonly 100 and 500 g) for a variety of dense oxide and non‐oxide materials, covering a range of grain sizes (G), including single crystals where possible, were shown to generally be consistent with (often more limited) literature data. Apparently, conflicting trends of H (1) showing either no G dependence, (2) decreasing from single‐crystal or large G values with decreasing G, or (3) having the generally accepted increase with decreasing G are shown to be due to the combination of the limited extent of data and H generally heing determined by two basic trends. These two trends are (a) the normal inverse G (i.e., H–G−1/2) dependence at finer G, (b) a variable G minimum at intermediate G, and (c) H increasing with increasing G at larger G (to. single‐crystal values). The H minimum is due to local cracking around the indent (mostly along grain boundaries), generally reaching a maximum effect, e.g., minimum in H, when the indent and grain sizes are similar, and tends to be greater for Vickers vs Knoop indents, higher loads and probably greater grain boundary Impurity, additive contents, and stresses.
Devitrification of the Grain Boundary Glassy Phase in a High‐Alumina Ceramic Substrate
Authors: Powell‐Dogan Cynthia A. , Heuer Arthur H. , O'Bryan Henry M.
Published: March 2005

Devitrification of the (Na, Mg, Ca) aluminosilicate glass phase in a high‐alumina (>99%) ceramic substrate has been studied by TEM. MgAl2O4 (spinel) and a Ca‐rich plagio‐clase (a solid solution between CaAl2Si208 (anorthite) and NaAlSi3O8 (albite)) are the dominant crystalline phases. Significant spatial variability exists both in the extent of crystallization and in the glass composition.
Dielectric Properties of (Pb1–xXx) (Zr0.7Ti0.3)O3(X = Ca, Sr, Ba) Ceramics
Authors: Kanai Hideyuki , Furukawa Osamu , Abe Hidekazu , Yamashita Yohachi
Published: March 2005

The dielectric properties of (Pb1–xXx) (Zr0.7Ti0.3)O3(X = Ca, Sr, Ba) ceramics (abbreviated PXZT) were investigated for applications to multilayer ceramic capacitors (MLCs) with dielectric layers thinner than 10 μm. The dissipation factors for MLCs with 5‐μm‐thick dielectric layers were estimated from those for 100‐μm‐thick disk specimens measured at an oscillation voltage of 20 Vrms. Those for PCZT and PSZT were less than 1.0% when the oscillation voltage was 20 Vrms, while those for conventional BaTiO3‐based dielectric ceramics were greater than 2.5% at 20 Vrms. According to polarization–electric field hysteresis measurements, PCZT and PSZT revealed linear and double hysteresis loops, respectively, while PBZT and BaTiO3indicated typical ferroelectric hysteresis loops. The differences in the dissipation factors for the dielectric compositions are attributed to hysteresis in the polarization–electric field loops. These results suggest that PCZT and PSZT are promising dielectric ceramics for MLCs with dielectric layers thinner than 10 μm.
Thermogravimetric Analysis and Defect Models of the Oxygen Nonstoichiometry in La2–xSrxCuO4–y
Authors: Opila Elizabeth J. , Tuller Harry L.
Published: March 2005

The oxygen nonstoichiometry, y, of La2–xSrxCuO4–y (0 ≤x≤ 1) was determined as a function of temperature (800–1050°C) and oxygen partial pressure (10–4 to 1 atm) by a thermogravimetric technique. The results were interpreted in terms of a number of defect models. It was found that a model based on the defect reaction 4Cu×Cu+ 2V¨o+ O2(g)= 4Cu.Cu+ 2O×o described the results well when the x and y dependences of the partial molar enthalpy of oxygen in the solid were considered. The large defect concentrations observed in this system lead to defect interactions, possibly ordering on the oxygen sublattice.
Effect of Relative Humidity on Repetitive Impact Behavior of Machined Silicon Nitride
Authors: Srinivasan Sreeram R. , Blau Peter J.
Published: March 2005

Silicon nitride is a promising candidate material to replace metallic valves in internal combustion engines. Its attractive mechanical properties relative to conventional alloys are expected to lead to reduced valve wear. As valves operate under combined conditions of impact and sliding contact, the durability of Si3N4 under a repetitive 45° impact was studied to assess the performance of these materials as valves. A significant effect of relative humidity on the impact behavior of Si3N4 was noticed. Humid conditions resulted in a significant increase in impact wear resistance. This increase appears to be related to the differences in fracture modes under humid versus dry conditions. A possible mechanism for the observed humidity effects in Si3N4 is advanced to explain the change in fracture modes. Increased impact resistance is expected to be a useful property for valve materials, as engine atmospheres contain significant amounts of water vapor resulting from the combustion reactions.
Thin Glass Film between Ultrafine Conductor Particles in Thick‐Film Resistors
Authors: Chiang Yet‐Ming , Silverman Lee A. , French Roger H. , Cannon Rowland M.
Published: March 2005

Thick‐film resistors arc electrical composites containing ultrafine particles of ruthenate conductor (Pb2Ru2O7 in the present materials) distributed in a highly modified silicate glass. We show that conductor particles remain flocced in the absence of any applied or capillary pressures, but are separated at equilibrium by a nanometer‐thick film of glass. Microstructures show evidence for liquid‐phase sintering, i.e., contact flattening of particles, under van der Waals attraction alone. Titania addition, which in dilute concentrations markedly increases the resistivity, decreases the temperature coefficient of resistance, and improves voltage stability and noise, is found to increase the equilibrium film thickness between particles by a few angstroms. STEM analyses show that the added titania preferentially concentrates in the silicate‐rich grain boundary film, as well as at particle–glass interfaces. The roles of interparticle forces and adsorption on the glass film thickness with and without titania are discussed. The large increase in resistivity caused by titania additions is attributed to the increase in Film thickness as well as to local chemical changes of two possible types. Titania enrichment within the glass film itself is expected to decrease the local ruthenium ion solubility, and this along with the possible formation of a more insulating titania‐substituted surface layer on ruthenate grains will decrease the tunneling conductivity between conductor grains.
Bonelike Hydroxyapatite Induction by a Gel‐Derived Titania on a Titanium Substrate
Authors: Li Panjian , Kangasniemi Ilkka , de Groot Klaas , Kokubo Tadashi
Published: March 2005

Gel‐derived titania coating on commercial pure (c.p.) titanium induces hydroxyapatite formation onto its surface from a simulated body fluid (SBF, a metastable calcium phosphate solution). The induced apatite is similar to bone apatite in that it is poorly crystallized, calcium‐deficient, and carbonate‐containing. Furthermore, the carbonate (CO2–3) groups go into the apatite lattice and lie at the positions of PO3–4 and OH– to replace these ionic groups, resembling the (CO2–3) groups of bone apatite. Therefore, the apatite induced by the gel‐derived titania is said to be bonelike. A chemical stimulation, stemming from abundant hydroxyl groups and negative charges at the surface of the titania gel, is believed to be responsible for the bonelike apatite induction. The potential of bone‐bonding is predicted for the gel‐derived titania, for it is an efficient bonelike apatite inducer in the SBF.
An Unusual Twin Structure in Transformed Precipitates in Y‐PSZ Single Crystals
Authors: Fernández Julian Martínez , Melendo Manuel Jiménez , Rodríguez Arturo Domínguez , Heuer Arthur H. , Hayakawa Motozo
Published: March 2005

Mosaic‐like monoclinic ZrO2 particles form in TEM thin foils in 3.4‐mol%‐Y2O3‐partially‐stabiIized ZrO2 (Y‐PSZ) single crystals aged for 150 h at 1600°C. These particles transformed martensitically during TEM foil preparation; the parent phase existed as internally twinned tetragonal ZrO2 precipitates which had formed during aging. These monoclinic particles contain (100)m and {110}m transformation twins, and the twin variants have uniform thickness. The origin of this transformation microstructure, the lattice correspondences, and the applicability of the invariant plane strain model of martensitic transformations are discussed.
Effects of Hydrogen and Temperature on the Kinetics of the Fluidized‐Bed Nitridation of Silicon
Authors: Jovanovic Zoran , Kimura Shoichi , Levenspiel Octave
Published: March 2005

Silicon nitride was produced via direct nitridation of silicon powder, using nitrogen with 10–40 vol% hydrogen, in a fluidized‐bed reactor, 55 mm in diameter, operated at temperatures in the range of 1200–1390°C. Hydrogen enhanced the nitridation of silicon toward its completion. The overall conversion of silicon as well as the yield of α‐silicon nitride increased with an increase in reaction temperature, while the yield of β‐silicon nitride decreased. In nitridation at 1300°C with 40 vol% hydrogen in nitrogen, 99% of silicon was nitrided in 24 h with a yield of α‐silicon nitride of about 90% in the product. When the reactor temperature was raised stepwise from 1300° to 1390°C along with the progress of nitridation, 99% of silicon was nitrided in 2.5 h and 85% of the product was α‐form.
Calcium Hydroxide Deposition in the Near Interfacial Zone in Plain Concrete
Authors: Bonen David
Published: March 2005

The near interfacial zone in plain concrete, as seen by back‐scatter electron microscopy, is characterized by calcium I hydroxide (CH) deposition and large pores. CH was deposited around many of the aggregate particles, irrespective of rock type as irregular but conspicuous coatings. The common thickness of the CH coating was about 2–3 μm, but occasionally it thinned or thickened to form lenslike deposits up to 8 μm wide. A greater amount of CH was encountered in zones confined between close‐packed aggregates where the precipitated CH bridged the spaces between aggregates. It is suggested that the formation of the CH coating combined with the presence of large pores makes this region vulnerable to solution ingress and chemical attack.
Proposed Phenomenological PTCR Model and Accompanying Phenomenological PTCR Chart
Authors: Huybrechts Ben , Ishizaiki Kozo , Takata Masasuke
Published: March 2005

The positive temperature coefficient of resistivity (PTCR) behavior of semiconductive BaTiO3 is well explained by the Heywang model, which predicts the resistivity behavior above the Curie point based on the acceptor state density at the grain boundaries, the charge carrier density, and the energy gap, Es, between the conduction band and the acceptor levels. However, the relationship between these parameters and the production parameters (sintering time, composition, and cooling rate) is not well understood. Recently, the present authors have found that Es can be increased by thorough oxidation. This increase is attributed to a change in the oxidation state of the acceptor. Based on this finding and results from the literature, a phenomenological PTCR model and an accompanying PTCR chart for acceptor–donor‐codoped BaTiO3 are proposed to clarify this relationship. The PTCR chart clarifies that acceptor dopant concentrations, oxidation time, and oxygen partial pressure during oxidation or cooling can be optimized simultaneously to obtain optical PTCR properties.
Citrate‐Gel Syntheses in the Y(O)–Ba(O)–Cu(O) System
Authors: Karen Pavel , Kjekshus Arne
Published: March 2005

A synthetic procedure has been developed for the yttrium‐barium‐copper oxides, in terms of a liquid‐mixed citrate precursor and the use of yttrium oxide, barium carbonate, and basic copper carbonate as starting materials. The stability of the citrate gels against phase separation is investigated as a function of the content of metal oxides in the gels, and critical concentrations for the individual metals are derived in terms of the maximum metal‐to‐citric acid ratio across the Y(O)–Ba(O)–Cu(O) phase diagram. Sintering properties and compositions of the products are investigated as functions of the thermal treatment of the citrate precursor. The present citrate‐gel procedure does not make use of internal oxidants like nitrates and polymerization agents like glycol. This approach decreases the incineration temperature and leads to a nanodispersed precursor (except submicrometer Cu), which, e.g., yields virtually phase‐pure (< 1% of impurities) YBa2Cu3O7 already after the first firing at 900°C in pure O2.
Effect of Yttria on the Thermal Conductivity of Aluminum Nitride
Authors: de Baranda Pedro Sainz , Knudsen Arne K. , Ruh Edwin
Published: March 2005

The effect of yttria additions up to 10 wt% on the thermal conductivity of pressureless‐sintered aluminum nitride was investigated. Additions of up to 3 wt% increased the thermal conductivity to values around 160 W/(m·K). Additions higher than 5 wt% slowly decreased the thermal conductivity because of the increasing volume fraction of the low‐conductivity yttrium aluminate phases. In all cases samples containing the same yttria content with the binder burned out in nitrogen had higher thermal conductivity than those with the binder burned out in air. Comparisons are made to previous studies containing additives of silica and calcia to aluminum nitride.
Interpretation of Compositional Patterns Found by Quantitative Energy Dispersive X‐ray Analysis for Cement Paste Constituents.
Authors: Bonen David , Diamond Sidney
Published: March 2005

More than 200 individual particles within a portland scement paste were morphologically categorized by backscatter SEM and analyzed systematically by EDXA. Nearly all of the analyses fall either in a dense cluster around a mean C‐S‐H gel composition or along tie lines connecting this composition to theoretical compositions for calcium hydroxide, monosulfate, ettringite, and ferrite. “Phenograin” C‐S‐H gel (formed as a direct replacement product within large cement grains) contains small amounts of Al, Fe, and S, but otherwise shows almost negligible compositional variation. In contrast, smaller groundmass particles and shells of gapped phenograins show a slightly differentc S‐H gel composition. Some of these, despite being morphologically homogeneous, show compositions falling along tie lines to the other recognized phases. This is attributed to extensive occurrence of intimate mixtures of C‐S‐H gel with the other components below the scale of SEM observation. Ionic substitutions appear to be minor except for the monosulfate and ettringite components in such mixtures. These show a variable but usually high deficiency in the sulfate content.
Flexural Properties of Brittle Multilayer Materials: II, Experiments
Authors: Folsom Craig A. , Zok Frank W. , Lange Fred F.
Published: March 2005

An experimental investigation of the flexural properties of a variety of brittle multilayer materials has been conducted. The results have been compared with the predictions of a model presented in a companion paper. Three types of systems have been studied. The first consisted of glass sheets bonded together with a thermoplastic adhesive. The glass sheets had been precracked by indentation prior to bonding such that their strengths were essentially deterministic. The flexural response of this system is characterized by an initial linear elastic regime, followed by a stepwise reduction in the stress–strain curve during cracking. The second system consisted of thin glass sheets (without indents), also bonded with a thermoplastic adhesive. This system exhibited flexural characteristics similar to those found in the system with indented glass plates. In both systems, the measured stress–strain behavior was in good agreement with the model predictions, incorporating the strength characteristics of the constituent layers. The third type of system was a hybrid composite comprised of alternating layers of a brittle phase (either glass or Al2O3) and a carbon‐fiber‐reinforced epoxy composite. These systems exhibited an initial linear elastic response, followed by a regime in which multiple cracks formed in each of the brittle layers, with the exception of the one on the compressive face. This process generally occurred subject to a progressively increasing stress. None of the fiber‐reinforced layers failed during this stage. The peak stress coincided with the onset of failure of the fiber‐reinforced layers. The progressive failure of these layers was accompanied by steplike load drops, similar to those observed in the single‐phase glass multilayer specimens. The measured response of these systems was qualitatively consistent with the model predictions, though some discrepancies have been noted and their origins briefly discussed.
Model of the Nonlinear Mechanical Behavior of 2D SiC–SiC Chemical Vapor Infiltration Composites
Authors: Aubard Xavier , Lamon Jacques , Allix Olivier
Published: March 2005

An approach to the nonlinear stress–strain behavior of ceramic matrix composites was proposed, based upon damage mechanics. Damage–loading relations taking into account effects of anisotropy and coupling were established. These relations allowed prediction of the stress–strain behavior, and ultimate failure. The theory was then applied to a 2D SiC/SiC composite subject to tensile loading under 0°, 20°, and 45° off‐axis angles. A two‐stage damage mechanism was identified by optical microscopy on specimens under load. Predictions of the stress–strain behavior were in excellent agreement with experimental data.
Grain‐Boundary‐Phase Identification of a Lead‐Based Relaxor by X‐ray Photoelectron Spectroscopy
Authors: Kanai Hideyuki , Yoshiki Masahiko , Hayashi Masaru , Kuwae Ryosho , Yamashita Yohachi
Published: March 2005

X‐ray photoelectron spectroscopy was used to study a lead‐based relaxor dielectric ceramic to identify the grain‐boundary phase most likely to be responsible for the insulation degradation of relaxor dielectric ceramics under humid loading conditions. The grain‐boundary phase consisted mainly of lead and oxygen. The binding energies of Pb4f7/2 and O1s in the grain‐boundary phase were found to be 137.3 eV and 528.8 eV, respectively, and these values agreed well with those for Pb3O4 and PbO2. In addition, the broadness of the Pb4f7/2 peak suggested the presence of PbO. Measurements were made of lead dissolution from dielectric ceramics in hot water; specimens with a grain‐boundary phase gave a 30 to 50 times greater lead concentration in the hot water than specimens without a grain‐boundary phase. This demonstrated that the grain‐boundary phase easily dissolved in hot water. Thus, it was concluded that the grain‐boundary phase contained water‐soluble PbO2 and PbO. The results strongly supported the resistance degradation mechanism of relaxor dielectric ceramics under humid loading conditions as previously proposed by the authors.
Porosity Effects on Machining Direction—Strength Anisotropy and Failure Mechanisms
Authors: Rice Roy W.
Published: March 2005

The anisotropy in room‐temperature flexural strength of ceramics as a result of machining test bar tensile surfaces parallel vs perpendicular to the bar axis was studied for various porous bodies. This shows that fine, relatively homogeneous porosity has no significant effect on such Strength anisotropy, implying that such porosity has no significant effect on flaw sizes or shapes, which was also shown by fractography. However, as the size of pores or pore clusters (due to pore heterogeneity) increases, the strength anisotropy diminishes, becoming zero when the pores or pore clusters dominate failure. Logarithm of strength vs porosity (P) plots for the two machining directions followed nearly parallel lines for fine, homogeneous porosity, but have less separation and intersect at lower porosity as pore size or heterogeneity increases. Fracture toughnesses calculated from fractography data for A12O3 and B of varying porosity levels could be normalized to values at P ∼ 0. Thus, extrapolation of strengths to P= 0 is clearly justified for bodies with fine, homogeneous porosity, but may be uncertain in bodies with coarser, or heterogeneous porosity.
Modified Envelope Method for Obtaining Optical Properties of Weakly Absorbing Thin Films and Its Application to Thin Films of Pb(Zr,Ti)O3 Solid Solutions
Authors: Peng Chien H. , Desu Seshu B.
Published: March 2005

A modified envelope method, which includes the consideration of the light intensity loss from the back surface of the substrate, was developed and shown to be a simple and convenient tool for obtaining the optical properties and the thickness of the film by using the transmission spectra alone in the medium and weak absorption regions. In the near‐optical band gap region, both the transmission and the reflection spectra were used to calculate the optical constants of the films. This technique was applied to the thin films of PZT solid solutions across the entire composition range. The film thickness derived from the envelope method was cross‐checked by a computer simulation method and was found to have an accuracy better than 2%. In addition, the refractive indices were fitted to a simple Sellmeier‐type equation for determining the dispersion constants for PZT films. The valid wavelength range of these dispersion relations was from 350 to 2000 nm. The refractive index of the PZT films decreased linearly with increasing zirconium content. On the other hand, the optical band gap energy of the PZT films increased with increasing zirconium content.
Active‐to‐Passive Transition and Bubble Formation for High‐Temperature Oxidation of Chemically Vapor‐Deposited Silicon Carbide in CO–CO2 Atmosphere
Authors: Narushima Takayuki , Goto Takashi , Yokoyama Yoshio , Takeuchi Masahito , Iguchi Yasutaka , Hirai Toshio
Published: March 2005

Oxidation behavior of chemically vapor‐deposited SiC in CO─CO2 atmospheres (0.1 MPa) was investigated using a thermogravimetric technique at temperatures from 1823 to 1923 K. Active or passive oxidation was observed depending on temperature and CO2/CO partial pressure ratio (Pco2/Pco). The critical Pco2/Pco value for the transition was 1O2 times as large as a theoretical value calculated from the Wagner model. In the passive oxidation above 1873 K, SiO2 bubbles were grown. The expansion and rupture of bubbles caused cyclic rapid mass gain and mass loss.
Fabrication of Barium Titanate Single Crystals by Solid‐State Grain Growth
Authors: Yamamoto Takahisa , Sakuma Taketo
Published: March 2005

BaTiO3 single crystals were prepared by solid‐state grain growth. The single crystals were obtained by seeding a poly‐crystalline, TiO2‐excess BaTiO3, which exhibited abnormal grain growth. The condition for single‐crystal growth was essentially dependent on the grain growth behavior of the polycrystalline, sintered bodies. The annealing temperature suitable for the single‐crystal growth was just below the critical temperature of abnormal grain growth in TiO2‐excess BaTiO3, which is about 1300°C.
Inadequacies in the postnatal management of fetomaternal alloimmune thrombocytopenia (FMAIT)
Authors: Murphy M. F. , Verjee S. , Greaves M.
Published: March 2005

93 (31%) of the 301 Haematology Departments in the U.K. responded to a questionnaire about the postnatal management of fetomaternal alloimmune thrombocytopenia (FMAIT). The number of reported cases of FMAIT was less than half than that estimated from its known incidence, suggesting that the condition is under‐recognized. There was a consensus that the optimal approach to postnatal management is to transfuse compatible platelets promptly. However, a number of problems in the delivery of treatment were identified, including an apparent lack of awareness of the potential seriousness of the condition amongst clinical staff, and the availability of HPA‐1a negative platelets.
Myelodysplastic syndrome with monosomy 5 and/or 7 following therapy with 2‐chloro‐2′‐deoxyadenosine
Authors: Van Den Neste E. , Louviaux I. , Michaux J.‐L. , Delannoy A. , Michaux L. , Hagemeijer A. , Scheiff J.‐M. , Bosly A. , Straetmans N. , Ferrant A.
Published: March 2005

A few cases of secondary neoplasms occurring after treatment with 2‐chloro‐2′‐deoxyadenosine (2CdA) have been reported, mostly in patients previously exposed to other anti‐cancer drugs including alkylating agents (AA). Here we report on the occurrence of a myelodysplastic syndrome (MDS) with monosomy 5 and/or 7 in two patients after 2CdA treatment, without or prior to other toxic exposure. In light of a literature review and given the involvement of chromosomes frequently abnormal in secondary leukaemias, we suggest that 2CdA may induce therapy‐related MDS (t‐MDS).
Peripheral blood stem cell versus autologous bone marrow transplantation for Hodgkin's disease: equivalent survival outcome in a single‐centre matched‐pair analysis
Authors: Perry A. R. , Peniket A. J. , Watts M. J. , Leverett D. , Goldstone A. H. , Linch D. C.
Published: March 2005

A matched‐pair retrospective analysis was used to compare 70 patients who had undergone peripheral blood stem cell transplantation (PBSCT) with 70 who had undergone autologous bone marrow transplantation (ABMT) for Hodgkin's disease. All transplants took place at a single centre using the same conditioning regimen (BEAM). Patients were matched for sex, previous chemotherapy and relapse status: factors which have previously been shown to have prognostic significance for transplant outcome in Hodgkin's disease at this centre. The two groups were also generally comparable for unmatched patient and disease characteristics. Toxic deaths and 90 d outcome were not different between the two groups. Three‐year overall survival was 68.6% for the ABMT group and 78.2% for the PBSCT group (P = 0.078); progression‐free survival was 59.4% for the ABMT group and 58.1% for the PBSCT group (P = 0.255), and relapse rates were 36.9% and 42.6% respectively (P = 0.30). Within the limitations of retrospective analysis, we conclude that there is no major overall or progression‐free survival advantage for PBSCT compared to ABMT in Hodgkin's disease.
Analysis of the region of the 5′ end of the MLL gene involved in genomic duplication events
Authors: Wiedemann Leanne M. , MacGregor Angus , Caldas Carlos
Published: March 2005

Rearrangements of the MLL gene are associated with both myeloid and lymphoid acute leukaemia. The gene is commonly involved in reciprocal translocations leading to the creation of chimaeric genes encoding novel protein products. An alternative mechanism of MLL gene rearrangement is due to intragenic duplication, leading to partial duplication of the amino‐terminal portion of the protein. This occurs in leukaemia, but it has recently been shown that partial duplications of the MLL gene are detectable in peripheral blood and bone marrow of healthy donors and in normal non‐haemopoietic tissues. Sequence analysis of the 45 kb of the 5′ end of the MLL locus encompassing the breakpoints of these genomic duplications has failed to show a definitive reason as to why this region is such a frequent target of rearrangement. Indeed, although the majority of the breakpoint joins are the result of apparent Alu‐mediated homologous recombination, several joins do not involve Alu elements in the region, despite a high density of these repetitive elements in the sequence.
Paraproteins and monoclonal expansion of CD3+CD8+ CD56−CD57+ T lymphocytes in a patient with HIV infection
Authors: Smith Penelope , Helbert Matthew , Raftery Martin , Forster Greta , Cavenagh Jamie
Published: March 2005

An expansion of CD8+ lymphocytes associated with a monoclonal rearrangement of the T‐cell receptor γ locus was found in a woman with HIV‐1 infection. A subpopulation of HIV‐positive patients display an unusual response to HIV infection characterized by a persistent marked CD8+ lymphocytosis, the presence of which appears to be associated with an improved long‐term prognosis. This condition is thought to represent a florid immune response to an ongoing viral infection which may be HIV itself, and suggests that monoclonal proliferation of CD8+ lymphocytes does not imply the presence of an underlying malignant process.
Leucocyte alkaline phosphatase identifies terminally differentiated normal neutrophils and its lack in chronic myelogenous leukaemia is not dependent on p210 tyrosine kinase activity
Authors: Dotti Gianpietro , Garattini Enrico , Borleri Gianmaria , Masuhara Kensaku , Spinelli Orietta , Barbui Tiziano , Rambaldi Alessandro
Published: March 2005

Leucocyte alkaline phosphatase (LAP) is a marker of post‐mitotic granulocytes and its activity is reduced or absent in chronic myelogenous leukaemia (CML) granulocytes as a consequence of LAP messenger RNA (mRNA) deficiency. We provide evidence that along the granulocytic maturation in normal marrow, the acquisition of LAP surface expression, identified by the monoclonal antibody 1B12.1, was restricted to CD11bbright/CD16bright positive cells. Moreover, in normal granulocytes, exposure to granulocyte colony‐stimulating factor (G‐CSF) in vitro and in vivo increased the cell surface expression of LAP. Although G‐CSF was able to induce the LAP surface expression in CML granulocytes, the inhibition of p210 tyrosine kinase activity by genistein or CGP75148B failed to restore LAP mRNA expression and LAP protein synthesis. In conclusion, the acquisition of LAP protein on the cell surface of granulocytes follows CD16 antigen expression and can be considered as the last marker of terminally differentiated neutrophils. G‐CSF is a potent regulator of the LAP mRNA expression and protein synthesis in normal and CML‐derived neutrophils. The lack of direct activity of p210 tyrosine kinase on LAP mRNA expression in CML neutrophils supports the notion that the LAP defect in this disease could be related to a precocious and uncontrolled release of white blood cells from the bone marrow into the blood stream.
An association between mitochondrial function and all‐trans retinoic acid‐induced apoptosis in acute myeloblastic leukaemia cells
Authors: Zheng Aiping , Mäntymaa Pentti , Säily Marjaana , Siitonen Timo , Savolainen Eeva‐Riitta , Koistinen Pirjo
Published: March 2005

The present study investigated whether all‐trans retinoic acid (ATRA)‐induced apoptosis in acute myeloblastic leukaemia (AML) is related to changes in mitochondrial function. Two human AML cell lines, OU‐AML‐3 and OU‐AML‐7, known to be inducible to time‐dependent apoptosis of varying degrees by ATRA, were used. Apoptosis induced by ATRA was shown to be a slow event. It was detected by the DNA electrophoretic method and cytofluorimetrical annexin V assay after 48 h exposure, and by morphology and polyADPribose polymerase (PARP) cleavage after 72 h exposure of AML cells to ATRA. The efflux of mitochondrial cytochrome c to cytosol was notable in Western blotting after 48 h exposure of the cells to ATRA and was observed before the drop in the mitochondrial membrane potential, which only took place after 72 h exposure, when measured by flow cytometry and a JC‐1 probe. The apoptotic events in mitochondria were more evident in the OU‐AML‐3 than the OU‐AML‐7 cell line. This might relate to the different bcl‐2 contents of the cell lines: the basic bcl‐2 levels of the OU‐AML‐7 cell line were almost twofold compared to that of the OU‐AML‐3 cell line, as analysed by the ELISA method. However, both of the cell lines showed progressive down‐regulation of bcl‐2, which began after 12–24 h exposure of the cells to ATRA as determined by ELISA, Western blotting and flow cytometry. The present results show that mitochondria have a role in ATRA‐induced apoptosis in AML cells and down‐regulation of bcl‐2 is related to it. In view of the previously published studies, the present results underline the fact that the timing of apoptotic events, such as fragmentation of DNA, externalization of phosphatidylserine, cytochrome c efflux, change in mitochondrial membrane potential and cleavage of PARP, are, to a notable extent, cell type and inducer‐dependent.
Paroxysmal cold haemoglobinuria caused by non‐Hodgkin's lymphoma
Authors: Sivakumaran M. , Murphy P. T. , Booker D. J. , Wood J. K. , Stamps R. , Sokol R. J.
Published: March 2005

Paroxysmal cold haemoglobinuria is an autoimmune haemolytic anaemia characterized by a biphasic polyclonal IgG autoantibody, the Donath‐Landsteiner (D‐L) antibody. Although classically described in association with chronic syphilis, it is most commonly seen after acute viral infections in children. We describe a case of high‐grade B‐cell non‐Hodgkin's lymphoma which presented with paroxysmal cold haemoglobinuria. The lymphoma responded promptly to combination chemotherapy whilst, at the same time, the haemolytic process rapidly resolved. Subsequent investigations showed that the D‐L antibody originated from the lymphoma cells.
Perforin and lymphohistiocytic proliferative disorders
Authors: Katano Harutaka , Cohen Jeffrey I.
Published: March 2005

Perforin is critical for cytotoxicity mediated by granules present in natural killer (NK) cells and cytotoxic T lymphocytes (CTLs). Perforin‐deficient mice have impaired cytotoxicity by NK cells and CTLs, resulting in failure to control infections with certain viruses or bacteria. Infection of perforin‐deficient mice with lymphocytic choriomeningitis virus results in haemophagocytic lymphohistiocytosis and elevated levels of pro‐inflammatory cytokines. Mutations throughout the perforin gene have been identified in patients with familial haemophagocytic lymphohistiocytosis (FHL) type 2. These patients present with fever, hepatosplenomegaly, pancytopenia, have marked elevations of T‐helper type 1 and type 2 cytokines, and have impaired NK cell and CTL cytotoxicity. A number of infectious pathogens have been implicated as triggering the onset of disease. Identification of mutations in perforin as the cause of FHL should allow prenatal diagnosis of the disorder. While stem cell transplantation is curative, gene therapy might be effective in the future.
Defining stroke risk in children with sickle cell anaemia
Authors: Hoppe Carolyn
Published: March 2005

Sickle cell anaemia (SCA) is the most common cause of childhood stroke, occurring with the highest frequency before the age of 6 years. Despite the relative frequency of stroke in SCA, few predictors of risk exist. Anaemia, leucocytosis, hypertension, silent infarction, and history of acute chest syndrome are well‐documented risk factors for ischaemic stroke in SCA. Recent data suggest that other environmental and genetic factors, many unrelated to SCA, influence the development of cerebrovascular disease. Non‐invasive assessment of individual stroke risk using transcranial Doppler ultrasonography has provided a means of selecting and prophylactically treating SCA children at highest risk. With the ultimate goal of preventing stroke, the information gained from the studies reviewed here may lead to improved prediction of stroke so that clinical trials to assess risk‐based therapy may be carried out on selected children with SCA.
Concurrent detection of minimal residual disease (MRD) in childhood acute lymphoblastic leukaemia by flow cytometry and real‐time PCR
Authors: Kerst Gunter , Kreyenberg Hermann , Roth Carmen , Well Catrin , Dietz Klaus , Coustan‐Smith Elaine , Campana Dario , Koscielniak Ewa , Niemeyer Charlotte , Schlegel Paul G. , Müller Ingo , Niethammer Dietrich , Bader Peter
Published: March 2005

Minimal (i.e. submicroscopic) residual disease (MRD) predicts outcome in childhood acute lymphoblastic leukaemia (ALL). To be used clinically, MRD assays must be reliable and accurate. Two well‐established techniques, flow cytometry (FC) and polymerase chain reaction (PCR), can detect leukaemic cells with a sensitivity of 0·01% (10−4). We analysed diagnostic samples of 45 ALL‐patients (37 B‐lineage ALL, eight T‐lineage ALL) by four‐colour FC and real‐time PCR. Leukaemia‐associated immunophenotypes, at a sensitivity of MRD detection by FC at the 0·01% level, were identified in 41 cases (91%); antigen‐receptor gene rearrangements suitable for MRD detection with a sensitivity of 0·01% or better by PCR were identified in 38 cases (84%). The combined use of FC and PCR allowed MRD monitoring in all 45 patients. In 105 follow‐up samples, MRD estimates by both methods were highly concordant, with a deviation factor of <5 by Bland–Altman analysis. Importantly, the concordance between FC and PCR was also observed in regenerating bone marrow samples containing high proportions of CD19+ cells, and in samples studied 24 h after collection. We conclude that both MRD assays yield generally concordant results. Their combined use should enable MRD monitoring in virtually all patients and prevent false‐negative results due to clonal evolution or phenotypic shifts.