bluuebunny/crossref_metadata_2025 huggingface dataset:
Pressure Derivatives of the Sound Velocities of Polycrystalline Alumina
Authors: SCHREIBER EDWARD , ANDERSON ORSON L.
Published: June 2006

The sound velocities and the pressure derivatives of the sound velocities were measured on a small specimen of polycrystalline alumina by the method of “pulse superposition”. The pressure derivatives found from experiments up to 4 kbars at 25°C are:
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These values lead to the variation of Poisson's ratio with pressure of dσ/dP = 1.02 × 10−4/ kbar and to the variation of (isothermal) bulk modulus with pressure of dBT/dP= 3.99. Using the above values the compression is computed up to 400 kbars and compares well with shock wave measurements. Consequently, the measured pressure derivatives may hold up to several hundred kilobars.
Formation of NiAl2O4 by Solid State Reaction
Authors: PETTIT F. S. , RANDKLEV E. H. , FELTEN E. J.
Published: June 2006

The growth of nickel‐aluminum spinel, NiAl2O4, in diffusion couples of polycrystalline Al2O3 and NiO was investigated between 1200° and 1500°C. The growth kinetics for the spinel layer obeyed a parabolic rate law in this temperature range. Marker experiments showed that the spinel layer formed by counterdiffusion of nickel and aluminum ions. Comparison of experimental and theoretical values of the parabolic rate constants suggests that the diffusion of aluminum ions through the spinel layer is rate controlling.
Observation and Control of Deviations in Molar Composition in Single‐Crystal Growth of Mixed Oxides
Authors: COCKAYNE B.
Published: June 2006

A technique is described for the preparation of optically transparent crystals of CaO.2Al2O3, 12CaO.7Al2O3, and 3Y2O3.5Al2O3. The main difficulties in obtaining optically transparent crystals of these materials by direct Czochralski growth from the component oxides arise from deviations in molar composition.
Devitrified Barium Titanate Dielectrics
Authors: ULRICH DONALD R. , SMOKE EDWARD J.
Published: June 2006

Pure barium titanate was made into a glass by flame‐spraying and after sufficient comminution was processed into specimens and fired. During this firing the glass devitrified to tetragonal barium titanate and contained crystals of sizes from 0.5 to below 0.2μ. The small crystals exhibit Curie temperatures from 120° to above 185°C. The dielectric Curie temperature of the devitrified ceramic is 150° to 155°C.
Thermal Expansion and Elastic Properties of Two‐Phase Ceramic Bodies
Authors: HUNTER ORVILLE , BROWNELL W. E.
Published: June 2006

The elastic properties and thermal expansion coefficients of two‐phase ceramic bodies were determined in order to study the effect of the difference in thermal expansions of the two phases. Room‐temperature elasticity was determined by a dynamic method. These values were extrapolated to theoretical density to obtain values for the fully dense bodies. Thermal expansion, measured on a precision dilatometer at 25° to 350°C, was independent of porosity. Experimental values of elastic moduli and expansion coefficients were compared with values given by several theories. Where the difference in expansion coefficients was small the experimental and theoretical values of elastic moduli and expansion coefficients were in agreement. Microscopic examination of these bodies did not reveal any internal cracking. When the difference in expansion coefficients became large enough, the experimental data were scattered and not in agreement with theory for either the elastic properties or expansion coefficients. Microscopic observations of these specimens revealed microcracks.
Chemical Strengthening of Glass‐Ceramics in the System Li2O‐Al2O3‐SiO2
Authors: KARSTETTER B. R. , VOSS R. O.
Published: June 2006

Fine‐grained glass‐ceramics containing a large proportion of β‐spodumene solid‐solution crystals were strengthened by immersion in molten sodium and potassium salt baths. An ion‐exchange reaction placed sodium or potassium ions in lithium ion sites in the β‐spodumene structure. The resultant “crowding” of the structure produced a surface compressive layer. In this system, strengths (modulus of rupture on abraded specimens) in excess of 100,000 psi were realized. In a similar manner, stuffed β‐quartz solid‐solution glass‐ceramics derived from the crystallization of Li2O‐Al2O3‐SiO2 glasses containing an appropriate amount of nucleating agent were strengthened by K+‐for‐Li+ exchange. Stable β‐quartz solid‐solution glass‐ceramics were strengthened by Na+‐for‐Li+ exchange, but no significant increase in strength was obtained in the metastable β‐quartz materials.
Disproportionation and Vaporization of Solid Silicon Monoxide
Authors: HERTL W. , PULTZ W. W.
Published: June 2006

The vaporization rate of solid SiO was studied in the temperature range 1005° to 1475°C. It was concluded that (a) in an argon atmosphere the vaporization rate is external gas diffusion controlled; (b) only the upper layers of the charge contribute to the vaporization, so that a zero‐order process is observed; (c) the heat of vaporization of SiO is 72.5 kcal/mole. Solid SiO disproportionates when heated in the temperature range 1000° to 1440°C, but the reaction does not go to completion. The reaction in the solid state is irreversible. The product silicon inhibits the reaction.
Structural Similarities Between a Glass and Its Melt
Authors: RIEBLING E. F.
Published: June 2006

It is suggested that the large expansion coefficient increase that occurs near Tg, for mixed oxide glasses is related to cooperative thermal displacements involving polyanionic clusters in the liquid state. This is illustrated by the striking relation between melt isoexpansion coefficient contours and structure for these ternary oxide systems. It is also shown that the molar volume dependence on composition for a series of oxide glasses can be quite similar to that observed for their liquid state analogs. The adjusted melt partial molar volume models can be used to develop realistic glass models, suggesting structural similarities between an oxide glass and its corresponding high‐temperature melt. Recently acquired evidence for alkali borogermanate compositions indicates a shift toward the right for the GeO6⇄GeO4 equilibrium in GeO2−rich melts at relatively high temperatures. Thus, an exact structural correlation between an oxide melt and its corresponding glass may, in some cases, be limited to temperatures below Tg+ΔT (where ΔT ~300° to 400°C).
Thermal Conductivity and Heat Capacity of the Monophosphide and Monosulfide of Plutonium
Authors: MOSER J. B. , KRUGER O. L.
Published: June 2006

The thermal properties of PUP and PUS were measured from room temperature to 650° C by a heat‐pulse technique. Disk‐shaped specimens of 90% theoretical density were made by isostatic cold‐pressing and sintering. The thermal conductivity of PUP corrected to theoretical density ranged from 0.014 cal sec‐cm‐1°C‐1 at room temperature to 0.019 at 650° C. Over this temperature range the heat capacity increased from 0.055 to 0.056 cal g‐l°C‐1. The thermal conductivity of PUS decreased approximately 16% from its room temperature value of 0.023 cal sec‐cm‐1°C‐1 and then rose to 0.037 at 650°C. The temperature dependence of the thermal conductivity of PUP is apparently related to the quasimetallic electrical properties of this compound. PUS is a semiconductor and the rise in its thermal conductivity (after passing through a minimum) may be partly attributed to a bipolar thermal diffusion mechanism.
Effect of Synthesis Parameters on the Magnetic Properties of Manganese Zinc Ferrites
Authors: NATANSOHN S. , BAIRD D. H.
Published: June 2006

The magnetic properties which make high permeability manganese zinc ferrites useful in telecommunications applications are strongly affected by both the composition and the synthesis method. Some of the effects discussed are: (a) variation of the magnitude and temperature dependence of the permeability as a function of the composition, (b) effect of the type of ferric oxide used in the synthesis on these two magnetic parameters, (c) effect of the sintering atmosphere on the disaccommodation and the temperature dependence of the permeability, and (d) the relation between the ferrous ion concentration and the disaccommodation characteristics of the ferrite materials.
Mechanical Damping Spectrum for Mixed‐Alkali R2 O·Al2 O3·6SiO2 Glasses
Authors: DAY DELBERT E. , STEINKAMP W. E.
Published: June 2006

The internal friction of R2O·Al2O3·6SiO2 glasses was measured from‐180° to 700°C at 0.4 Hz. Glasses containing Li2O or Na2O exhibited only the one internal friction peak characteristic of the stress‐induced movement of the alkali ions. Substitution of a second alkali resulted in two significant changes in the internal friction: (1) a rapid reduction in the magnitude of the original alkali peak and (2) the appearance of a new internal friction peak whose magnitude was especially sensitive to the concentration of the second alkali. Each combination of two alkali ions resulted in a new peak, with peaks being observed for the combinations Li‐Na, Na‐K, and Li‐K. A mechanical damping spectrum is predicted for aluminosilicate glasses containing more than two alkali ions.
Zircon‐Vanadium Blue Pigment
Authors: DEMIRAY TEMEL , NATH D. K. , HUMMEL F. A.
Published: June 2006

Vanadium was incorporated into zircon by heating in air and in controlled atmospheres of oxygen. It was found that V2+ could not be incorporated into zircon by firing in a hydrogen atmosphere. Comparison of the absorption spectrum of V3+ in YPO4 with that of blue zircons prepared in air and oxygen atmospheres, with and without fluoride additives, showed that it is highly probable that V4+ is solely responsible for the color of the pigment. Crystal field analysis confirmed the existence of V in the ZrO8 position in the zircon structure.
Preparation of Beryllium Fluoride Glasses Containing Xenon(VI) and/or Thallium (I)
Authors: RIEBLING E. F. , BLASZYK P. E. , SMITH D. W.
Published: June 2006

The dissolution of CsXeF7 in molten alkali fluoroberyllate glasses between 250° and 500°C is described. The apparent small solubility of Xe(VI) in these ionic glass‐forming melts (about 1 to 2 wt% or less) may be related to retention of a molecular configuration by XeF6 that is caused by its strong fluoride ion donor properties and/or to the nonmelting behavior of numerous MF‐XeF6 salts when they are heated. Rather low‐softening (about 100°C) glasses were also prepared in the TIHF2‐NaHF2‐BeF2 system, whereas TlHF2 has a relatively low melting point (about 85°C). Contrary to expectations, Xe(VI) appears to oxidize TI+ in these molten glass environments at 250°C.
Phase Separation by Spinodal Decomposition in the Tetragonal System
Authors: STUBICAN V. S. , SCHULTZ A. H.
Published: June 2006

Coherent spinodal curves for the [001] and [100] directions were calculated for the system TiO2‐SnO2. Inside the [001] spinodal curve, the crystalline solutions decomposed by a modulated phase composed of TiO2‐rich and SnO2‐rich plates perpendicular to the [001] direction. No modulation of structure was observed at compositions and temperatures between the [001] coherent spinodal and the equilibrium curve. The kinetics of the decomposition showed that the wavelength of the modulation decreased in the early stages of the separation, reaching minimum observable values of approximately 110 Å at 925°C, 170 Å at 1000°C, and 240 Å at 1150°C. In the second stage when the coherency was lost, the wavelength increased. Theoretical calculations to find the elastic free energy/unit volume to cause fluctuation of composition in the spinodal process were worked out for the tetragonal system. The calculations were done for an arbitrary direction and involved elastic constants. The theoretical prediction and the experimental results for the system TiO2‐SnO2 agreed well.
Subsolidus Studies in the System PbO‐SiO2
Authors: OTT W. RICHARD , McLAREN MALCOLM G.
Published: June 2006

The subsolidus region of the PbO‐SiO2 system was studied by DTA and X‐ray diffraction. X‐ray diffraction analysis showed the presence of five compounds: 4PbO.SiO2, 3PbO·SiO2, 2PbO·SiO2, 3PbO·2SiO2, and PbO·SiO2. The compound 4PbO·SiO2 has previously been reported to have three polymorphic forms; there are two polymorphs of 2PbO·SiO2 with the inversion at 460°±15°C. The compounds 3PbO·SiO2 and 3PbO·2SiO2 were unstable above 430°±10° and 585°±15°C, respectively; PbO·SiO2 was unstable below 525°±15°C. DTA patterns were determined for glasses of the composition of each of these compounds.
Studies in the System BaO‐Al2O3−SiO2: V. The Ternary System Sanbornite‐Celsian‐Silica *
Authors: LIN H. C. , FOSTER W. R.
Published: June 2006

Phase relations in the BaSi2O5−BaAl2Si2O8−SiO2 portion of the system BaO‐Al2O3−SiO2 were reinvestigated by the standard quenching method. In contrast to the results of earlier studies, this portion is revealed as a simple ternary system; its features include a ternary eutectic at 1122°±7°C and a composition of BaO 35.2, Al2O3 9.5, and SiO2 55.3 wt%, involving the phases sanbornite, celsian, and silica. These results are compared with those of earlier quenching studies, with relations in analogous ternary systems, with data from hydrothermal experiments, and with observations of natural mineral assemblages.
Influence of Hydrogen and Alkali Impurities on the High‐Temperature Indentation Hardness of Natural Quartz Crystals
Authors: NADEAU JOHN S.
Published: June 2006

The indentation hardness of a natural quartz crystal was measured from 25° to 1000°C. The concentrations of alkali ions and hydrogen were varied by annealing and electrolysis; hydrogen content was determined from infrared absorption. The untreated crystal was soft from 500° to 850°C; there was evidence of transformation beneath the indenter to a phase of silica denser than quartz. When the crystal was annealed to remove alkali ions and hydrogen, it remained hard throughout the temperature range of the tests. Injection of hydrogen by electrolysis into previously annealed specimens reduced the strength slightly; injection of lithium by electrolysis produced a greater reduction in hardness. Only the untreated samples and those doped with lithium appeared to have transformed to a denser phase. Thus, trace impurities can influence the hardness of quartz by acting as “mineralizers” to promote densification and by facilitating normal deformation mechanisms involving dislocations.
Influence of Milled Powder Particle Size Distribution on the Microstructure and Electrical Properties of Sintered Mn‐Zn Ferrites
Authors: CHOL GÉRARD R.
Published: June 2006

The grain growth and densification rates of Mn‐Zn ferrites during sintering are closely linked to the characteristics of the calcined and milled powders used. Long milling times enlarge powder particle size distributions and tend to promote discontinuous grain growth during sintering. For fixed sintering conditions, an optimum milling time, which corresponds to minimal eddy current and hysteresis losses, exists. The electrical properties of overmilled powders deteriorate greatly because duplex structure occurs. Theoretical analysis of the probability of discontinuous grain growth occurring during sintering in relation to powder particle size distribution agrees with the experimental results.
Influence of Porosity on Deformation and Fracture of UO2
Authors: ROBERTS J. T. A. , UEDA Y.
Published: June 2006

The effects of porosity on the deformation characteristics of sintered polycrystalline UO2 were determined at 500°, 1250°, and 1600°C at a strain rate of ∼0.1 h−1. At 500°C, fracture was brittle and transgranular and initiated from the large pores present after fabrication. An increase in porosity from 5 to 16 vol% caused a 79% reduction in strength. At 1250° and 1600°C, plastic deformation preceded fracture, and the effect of porosity was much more complex. At 1250°C, an increase in porosity increased the strength but lowered the ductility, and the fracture mode changed from intergranular to transgranular. In contrast, at 1600°C porosity had little effect on strength. This behavior was associated with the relative magnitudes of the stress necessary to extend a preexisting flaw and the yield stress and their influence on the brittle‐to‐ductile transition temperature, Tc.
Diffusion in the System K2O‐SrO‐SiO2: III, Interdiffusion Coefficients*
Authors: VARSHNEYA A. K. , COOPER A. R.
Published: June 2006

The matrix of interdiffusion coefficients, [D], was determined by measuring spatial composition distribution in couples with compositions (in wt fractions) near 0.21K2O‐0.17SrO‐0.62SiO2 after they were heat‐treated for various times at 630° to 810°C. The results are consistent with the Onsager hypothesis in that [D] at a given temperature is independent of diffusion time and the direction (in composition space) of the diffusion couple. The eigenvectors and eigenvalues of the [D] matrix were determined; the diffusion paths in composition space are thus easily understood. As is consistent with intuition, the “fast” eigenvector nearly parallels the direction of constant SiO2 concentration.
Kinetics of Solid‐State Reactions of Particulate Ensembles with Size Distributions
Authors: KAPUR P. C.
Published: June 2006

Rate equations for solid‐state reactions of monosized spheres cannot be applied directly to particulate ensembles with a distribution of sizes, such as are frequently encountered in practice. A method using experimental data for the overall extent of reaction as a function of time is proposed for identification of the reaction mechanism and computation of the rate constant and activation energy when the particle‐size spectrum of the starting material is known. The method, which is based on comparison of the characteristic paths of the assumed reaction mechanisms with experimental data, may be applied to a wide range of solid‐state kinetic models.
Equilibrium Compressibilities and Density Fluctuations in K2O–SiO2 Glasses
Authors: LABERGE N. L. , VASILESCU V. V. , MONTROSE C. J. , MACEDO P. B.
Published: June 2006

The density fluctuations contributing to light scattering in a glass are governed by the flctive temperature of the glass and the equilibrium compressibility of the melt. Using ultrasonic velocity data for K2O–SiO2 melts, these compressibilities were evaluated, and the magnitude of the density fluctuations were calculated. In this system, the mean–square amplitude of the fluctuations reaches a minimum value (about half that of pure SiO2) for a composition of ∼20 mol% K2O. By extrapolating the equilibrium compressibilities to zero K2O content, the density fluctuations can be calculated for pure SiO2 glass; this calculation agrees well with the result obtained from light–scattering measurements.
Rayleigh and Brillouin Scattering in K2O–SiO2 Glasses
Authors: SCHROEDER J. , MOHR R. , MACEDO P. B. , MONTROSE C. J.
Published: June 2006

The intensity and spectral distribution of light scattered by K2O‐SiO2 glasses (K2O content up to 40 mol%) were measured. The transverse and longitudinal sound‐wave velocities and the photoelastic constants were evaluated from the results. The total intensity of the scattering (and therefore the attenuation caused by it) exhibited a minimum at a concentration of ∼25 mol% K2O. For this composition the attenuation is ∼2/2 of that in pure SiO2. This behavior results from the existence of anomalously small concentration fluctuations in the melt of K2O·3SiO2 glass. A qualitative explanation of this result, involving low‐temperature immiscibility regions, is presented.
Oxidation of Tetragonal PbO in Air
Authors: SORRELL CHARLES A.
Published: June 2006

Isothermal oxidation of tetragonal PbO in air produced multiphase assemblages with apparent equilibrium compositions which varied linearly with temperature from PbO1.548 at 286°C to PbO1.333 at 351°C. Oxidation at each temperature was relatively rapid to PbO1.40 and very slow from PbO1.40 to apparent equilibrium values. Pseudocubic PbO1+x, with compositions between PbO1.41 and PbO1.57, was indexed on a cubic unit cell at the lower O/Pb ratios and on a tetragonal unit cell at the higher ratios. Linear changes in lattice parameters and deviation from cubic symmetry accompanied reversible oxidation and reduction of the phase. Pseudocubic PbO1+x was reduced irreversibly to Pb3O4 below the composition PbO1.41. Hexagonal PbO1+x, with compositions between PbO1.333 and PbO1.41, developed to a maximum of 60% at intermediate temperatures. The hexagonal phase oxidized irreversibly to pseudocubic PbO1+x at lower temperatures and reduced irreversibly to Pb3O4 at higher temperatures. The extent of oxidation at a given temperature was greater in PbO with a mean diameter of 0.52 μm than in PbO with a mean diameter of 2.89 μm, indicating a metastable assemblage. Linear variation of oxidation limits with temperature across the composition boundary between the PbO1+x phases suggests that the free energies are equal at PbO1.41, with the lower limit of pseudocubic PbO1+x determined by tolerance of the structure for oxygen vacancies.
Phase Relations in (Pb,La)Zr0.65Ti0.35O3
Authors: O'BRYAN H. M.
Published: June 2006

Low‐temperature phase relations in (Pb,La)Zr0.65Ti0.35O3 ceramics were determined as a function of La content and temperature. Dielectric and piezoelectric measurements and X‐ray data were used to locate and identify phase transitions. The FE1‐FE2 transition between rhombohedral ferroelectric phases occurs at higher temperatures as the La eontent is increased. For x>4, where x is the atom % La substituted for Pb, a phase region exists between the paraelectric and ferroelectric states. Dielectric data suggest that this region is antiferroelectric. For 6<x<9 a field‐induced phase transition accompanies poling. Poled material with x∼8 exhibits unusual mechanical properties.
Yield Point of Sapphire
Authors: FIRESTONE R. F. , HEUER A. H.
Published: June 2006

Yielding in sapphire undergoing basal slip appears to occur by a dislocation‐multiplication mechanism and thus depends on the initial density of dislocation sources. In verneuil and Czochralski sapphire, these sources appear to be associated with surface damage, and yield drops can be enhanced by mechanical or thermal treatments that improve the surface perfection. Annealing and flame polishing also increased the lower yield stress. This hardening appears to be caused by formation of gaseous or solid precipitates. In addition, a yield drop can be induced in sapphire by strain aging; this phenomenon does not appear to be associated with impurities.
Studies on Nonmetals During Irradiation: V, Growth and Decay of Color Centers in Barium Aluminoborate Glasses Containing Cerium
Authors: LEVY P. W. , MATTERN P. L. , LENGWEILER K. , BISHAY A. M.
Published: June 2006

The radiation‐induced absorption of a group of barium aluminoborate glasses was studied in a new facility for measuring optical absorption during irradiation with γ‐rays. The results demonstrate that this technique provides significant new information on the kinetics of the radiation‐induced coloring of glasses and suggest that most previous measurements are, at best, suspect. Barium aluminoborate glasses, both with and without Ce, were prepared under normal and reducing conditions. The coloring during irradiation and the decay after irradiation can be characterized by the absorption at 3.0 e V and at 2.25 or 1.90 e V. The Ce‐free base glass continued to color as long as irradiated and, at a given dose, the absorption was at least 2 or 3 times that of the other glasses. The totally reduced 1% Ce glass colored to a constant level in the uv, but in the visible the coloring increased to a maximum and then decreased to a constant value. The partially reduced 1% Ce glass also colored to a constant value in the uv, but in the visible the original absorption decreased slightly. All the coloring curves recorded during irradiation are described accurately by expressions that include one or more increasing saturating exponential terms and may contain one linear or one decreasing saturating exponential term. After irradiation the coloring curves decrease and can be resolved accurately into one or more decreasing exponential components. Futhermore, all the observed coloring‐curve features were derived from relatively simple kinetics.
Effect of Oxygen on the Reaction Between Copper and Sapphire
Authors: O'BRIEN T. E. , CHAKLADER A. C. D.
Published: June 2006

The effect of oxygen potential on the wetting behavior and interfacial energy between Cu and sapphire was studied using the sessile drop technique in a CO‐CO2 atmosphere. A linear relation was found between γSL and logpO2 (atm) from 10−16 to 10−5. Beyond 10−5 atm γSL approached a constant value asymptotically. A barrier surface layer was proposed to explain this change. The Gibbs adsorption equation was used to evaluate the characteristics of the interfaces. Formation of a Cu2O film at the liquid‐vapor interface and a CuAlO2 film at the solid‐liquid interface is suggested. The work of adhesion reached a maximum at ∼ 0.01 at.% oxygen, corresponding to pO2∼ 10−9atm. Measurements of the basal radius as a function of oxygen content were used to evaluate the role of oxygen in promoting spreading. Spreading on sapphire is directly proportional to the logarithm of oxygen present in the molten Cu drops.
Equilibrium in the System CaSO4.2H2O‐CaSO4.½H2O‐H2O
Authors: ŠATAVA VLADIMIR
Published: June 2006

Using a simple geometric model, the conditions of equilibrium for topotactical dehydration of gypsum to the hemihydrate in liquid H2O were determined. The calculated equilibrium temperature agrees with the experimentally determined temperature at which the rate of topotactical dehydration of gypsum single crystals approaches zero.
Failure Probability at the Predicted Minimum Lifetime After Proof Testing
Authors: RITTER J. E. , COYNE D. C. , JAKUS KARL
Published: June 2006

Experimental variation in crack growth parameters introduces an uncertainty in the predicted minimum lifetime after proof testing that results in a possibility of failure at times less than the “minimum” lifetime. This failure probability is estimated with a Monte carlo simulation technique. A A example is given of how this failure probability can be made vanishingly small by increasing the proof stress or by decreasing the allowable stress or permissible lifetime in service.
Fractographic Analysis of Delayed Failure in Soda‐Lime Glass
Authors: MECHOLSKY J. J. , GONZALEZ A. C. , FREIMAN S. W.
Published: June 2006

Fractographic analysis of soda‐lime bars which failed under dead weight loading shows that the fracture mirror to initial flaw size ratio is a function of time under load, but that the mirror to critical flaw size ratio is a constant. The mirror constants are the same in delayed and rapid failure. The experimental results correlate with fracture mechanics predictions of time‐to‐failure based on subcritical crack growth. Scatter of the data about the prediction is discussed in terms of variations in flaw geometry.
Heats and Free Energies of Formation of Two Sialons by Mass Spectrometry
Authors: MOON KENNETH A. , KANT ARTHUR , CROFT WILLIAM J.
Published: June 2006

The heats of formation at 298 K of SiAl2O2N2(c) (β'‐sialon) and SiAl4O2N4(c) (15R‐sialon) were determined as −413±6 and −592±8 kcal/mol by the third‐law method. Second‐law values were −414±4 and −595±5 kcal/mol. A tentative method of predicting the heats is given. The major vapor species observed were SiO and N2. It was found that the normal valences of the elements in these two sialons are not rigorously maintained during decomposition in vacuum.
The Dependence of Strength‐Controlling Fracture Energy on the Flaw‐Size to Grain‐Size Ratio
Authors: RICE R. W. , FREIMAN S. W. , MECHOLSKY J. J.
Published: June 2006

The transition from single‐crystal to polycrystalline fracture energies was studied as a function of the flaw‐size to grain‐size ratio by two methods. The primary method was calculating fracture energies from observed flaw sizes found at fracture origins in strength‐test specimens. Some measurements were also made by varying the number of grains across the web in the applied‐moment DCB test. Both methods agreed and generally snowed the transition to polycrystalline fracture energies being completed at flaw‐size to grain‐size ratios of ∼1 to ∼ 6 for the cubic materials studied. It is estimated that cracks less than ∼½ to ¼ of the grain size cannot be arrested at grain boundaries and that single‐crystal fracture energies can be applied below this limit. The grain‐size range over which this fracture‐energy transition occurs was shown to be a function of extrinsic factors, such as texture, as well as intrinsic factors, such as the number and multiplicity of low‐energy single‐crystal fracture planes.
Morphological Development of Hydrating Tricalcium Silicate as Examined by Electron Microscopy Techniques
Authors: JENNINGS H. M. , DALGLEISH B. J. , PRATT P. L.
Published: June 2006

This study of C3S hydrates used a high‐voltage electron microscope equipped with a gas reaction cell that allows the specimen to be kept moist, and high‐resolution scanning and scanning transmission microscopes. Mechanical thinning and ion‐beam thinning coupled with fractography allowed this study of microstructural development with time, enabling both the morphologies and the spatial relations of the morphologies to be observed. The combination of several microscopic techniques allowed the hydration products of C3S to be classified and compared with those of Diamond for portland cement hydrates.
Reversible Weight Change of Acceptor‐Doped BaTiO3
Authors: HAGEMANN H.‐J. , HENNINGS D.
Published: June 2006

The oxygen vacancy concentration of BaTiO3 doped with acceptors (Cr to Ni) is determined gravimetrically as a function of the O2 partial pressure during and after annealing at 700° to 1300°C. The oxygen vacancy concentration of these materials is larger than that of undoped and donor‐doped BaTiO3. The oxygen vacancies are doubly ionized and they compensate the acceptors of lower valence. Both the vacancy concentration and the valence of the acceptor dopants depend on the annealing conditions. The electronic energy levels of the acceptors within the BaTiO3 band gap are derived from the gravimetric measurements. The electrical properties of the acceptor‐doped ceramics are favorable for base‐metal‐electrode multilayer capacitors, which require sintering in reducing atmospheres.
Electrical Conductivity of MgAl2O4 and Y3A15O12
Authors: Bates J. Lambert , Gamier John E.
Published: June 2006

The electrical conductivities of single crystal and polycrystalline MgAl2O4 and Y3Al5O12 were measured to 1260 K using a three‐contact, guard‐ring technique. The electrical conduction mechanisms change with temperature, with anomalous oxygen pressure and time‐dependent inflections in log σ versus T−1 curves between 900 to 1000 K. The conduction processes of Y3Al5O12 and MgAl2O4 appear to be similar and possibly related to A13+ ion diffusion.
Thermodynamic Properties of Fe3O4‐FeAl2O4 Spinel Solid Solutions
Authors: PETRIC A. , JACOB K.T. , ALCOCK C.B.
Published: June 2006

The Gibbs energy of mixing for the system Fe3O4‐FeAl2O4 was determined at 1573 K using a gas‐metal‐oxide equilibration technique. Oxide solid solution samples were equilibrated with Pt foils under controlled CO+CO2 gas streams. The equilibrium iron concentration in the foil was determined by chemical analysis. The cation distribution between tetrahedral and octahedral sites in the spinel crystal can be calculated from site‐preference energies and used as an alternate method of determining some thermodynamic properties, including the Gibbs energy of mixing. The solvus occurring at low temperatures in the system Fe3C4‐FeAl2C4 was used to derive the effect of lattice distortion due to cation size difference on the enthalpy of mixing and to obtain a better approximation to the measured thermodynamic quantities.
Small‐Angle X‐Ray Scattering Analysis of Nucleation in Glass: II, Selenium Ruby Glasses
Authors: WILLIAMS JOHN A. , RINDONE GUY E. , McKINSTRY HERBERT A.
Published: June 2006

Nucleation studies were conducted on several selenium ruby glasses, of different colorant concentrations, using the technique of small‐angle X‐ray scattering. The glass rnicrostructure increased from homogeneous to 6‐nm (60‐Å) precipitating particles as the colors changed from colorless through yellow and orange to red. The glasses showed little difference in particle morphology despite differences in color, supporting the explanation of ruby color formation as due to energy band‐gap phenomena. Matrix intensities, particle volume concentrations, and interfacial surface areas were also determined.
Effects of AIN Additions and Atmosphere on the Synthesis of Cubic Boron Nitride
Authors: HIRANO SHIN‐ICHI , YAMAGUCHI TAKAYUKI , NAKA SHIGEHARU
Published: June 2006

Aluminum nitride was found to act as the catalyst for the synthesis of cubic BN by sealing the mixture of hexagonal BN and AIN in a pressure cell under the inert or reducing atmosphere. No conversion of hexagonal BN to cubic BN was observed under pressures below 7×109 Pa (7 GPa, 70 kbar) without AIN addition. All hexagonal BN could be completely converted to cubic BN under 6.5 GPa at 1600°C by the addition of 20 mol% AIN. The cubic BN thus synthesized was a typical tetrahedron (grain size ≅2 μm). The pressure‐temperature diagram for the synthesis of cubic BN was determined at >7 GPa and T<1700°C.
The contribution of Bruce Glick to the definition of the role played by the bursa of Fabricius in the development of the B cell lineage
Authors: Ribatti D , Crivellato E , Vacca A
Published: June 2006

In 1956, Bruce Glick and Timothy Chang reported that the bursa of Fabricius plays an important role in antibody production. Their demonstration that antibody responses are suppressed in the majority of bursectomized chickens became the cornerstone of modern immunology. Bursa research increased considerably during the 1960s and early 1970s.
Role of the pro‐inflammatory cytokines TNF‐α and IL‐1β in HIV‐associated dementia
Authors: Brabers N. A. C. H. , Nottet H. S. L. M.
Published: June 2006

Human immunodeficiency virus‐1 (HIV‐1)‐infected and immune‐activated macrophages and microglia secrete neurotoxins. Two of these neurotoxins are the pro‐inflammatory cytokines tumour necrosis factor‐α (TNF‐α) and interleukin‐1β (IL‐1β), which are thought to play a major role in inducing neuronal death. Both TNF‐α and IL‐1β increase the permeability of the blood–brain barrier, through which subsequently HIV‐infected monocytes can enter the brain. They both induce over‐stimulation of the NMDA‐receptor via several pathways, resulting in a lethal neuronal increase in Ca2+levels. Additionally, TNF‐α co‐operates with several other proinflammatory mediators to enhance their toxic effects. Although most research has focused on the neurotoxic effects of TNF‐α and IL‐1β in HAD, there is also evidence that these cytokines can be neuroprotective. In this paper the effect of TNF‐α and IL‐1β on neuronal life and death in HAD is discussed.
Innovation in anti‐herbivore defense systems during neopolypoloidy – the functional consequences of instantaneous speciation
Authors: Pearse Ian S. , Krügel Tamara , Baldwin Ian T.
Published: June 2006

Allopolyploid hybridization instantly merges two differentially adapted genomes into one individual. Allopolyploids are often evolutionarily successful, undergoing adaptive radiations despite the genetic and physiological challenges of merging genomes. We examine a suite of induced herbivore resistance traits in three independent lines of the synthetic allopolyploidNicotiana×mierata(Nma) and its parent species,N. miersii(Nmi) andN. attenuata(Na), to determine how a complex polygenetic adaptation fares during the early stages of neoallopolyploid formation. All species responded toManduca sextaoral secretions (OS) with a temporally prolonged jasmonate (JA) burst. In one parent (Na), the JA burst was additionally amplified and associated with the elicitation of direct and indirect defenses. In the other parent (Nmi), OS neither amplified the JA burst nor elicited defense responses, although applied MeJA confirmed the inducibility of the defense responses. All lines ofNmaretained enough aspects ofNa’s JA signaling to recognize OS and to accumulate sufficient direct defenses to impair the growth ofManducalarvae. Most defense‐related metabolites were retained inNmaeven if inherited from only one parent; however, OS‐elicited volatiles, trypsin protease inhibitors (TPIs) and chlorogenic acid were lost in some lines, even though MeJA treatment elicited similar responses in all lines. Herbivore defense systems are flexibly inherited in allopolyploids, causing individuals to diverge over only a few generations; for example, line 1 ofNmacould not produce TPIs after OS elicitation, whereas lines 2 and 3 could. This flexible integration of defense signaling systems with a diversity of elicited responses may explain why adaptive radiations are commonly found in allopolyploid lineages.
Maize mutants affected at distinct stages of the arbuscular mycorrhizal symbiosis
Authors: Paszkowski Uta , Jakovleva Ludmila , Boller Thomas
Published: June 2006

Maize mutants affected in the symbiotic interaction with the arbuscular mycorrhizal fungus Glomus mosseae have been found by a visual, macroscopic screen in a Mutator‐tagged population of maize. Seven mutants have been identified, falling into three phenotypic classes. For each class one mutant has been characterized in more detail. The nope1 (noperception 1) mutant does not support appressoria formation of G. mosseae, suggesting the absence of a plant‐encoded function necessary for early recognition prior to contact. The phenotype segregated as a monogenic recessive trait, indicating that a mutation in a single locus abolished compatibility of maize to G. mosseae. On a second mutant termed taci1 (taciturn 1), appressoria form at reduced frequency but their morphology is normal and leads to penetration of the rhizodermis. However, intraradically, the majority of hyphae are septate, resulting in terminated fungal spreading. This phenotype suggests that the mutation of taci1 has an effect on recognition and on cortex invasion. Segregation analysis indicates taci1 to carry a recessive mutation. In contrast, wild‐type fungal morphology has been recorded in the Pram1 (Precocious arbuscular mycorrhiza 1) mutant, which displays enhanced and earlier fungal invasion. This trait segregates in a dominant fashion indicative of a gain‐of‐function mutation affecting the plant's control over restricting fungal colonization.
Risk factors for chickenpox incidence in Taiwan from a large‐scale computerized database
Authors: Wu Po‐yuan , Li Yu‐Chuan , Wu Hong‐Dar Isaac
Published: June 2006

Objective  We analyzed data from the National Health Insurance Research (NHIR) database in the year 2000 to estimate the seasonal variation in the chickenpox rate in Taiwan.

Patients and Methods  All chickenpox cases listed in the NHIR database were included (n = 165,719). A Lorenz curve was plotted and a chi‐square test for equal proportions calculated for seasonal variation. To determine the effects of temperature and season on outcome values, generalized estimating equation methods were utilized to adjust the effects of other possible influencing factors and take into account the within‐subject dependence over repeated assessments.

Results  All four regions of the country had highest incidence rates in January, and three of them had lowest rates in September. Incidence was significantly higher in females aged 15–24 years than in males. An increment of 1 °C resulted in an incidence ratio of approximately 0.98 or, equivalently, a 10 °C increment gives an incidence ratio of approximately 0.78.

Conclusion  The results suggest that season and temperature are significantly related to the incidence of chickenpox. Infectious diseases can be monitored. Prevention procedures can be taken by understanding its pattern and activity in order to decide the best policy for vaccination. Further studies are warranted, particularly for long‐term trends, and in other nations with different seasonal temperatures from Taiwan.
Predominance of nocturnal hypertension in pediatric renal allograft recipients*
Authors: McGlothan Kim R. , Wyatt Robert J. , Ault Bettina H. , Hastings Margaret C. , Rogers Taurus , DiSessa Thomas , Jones Deborah P.
Published: June 2006

Abstract:  Hypertension is common in children with end‐stage renal disease who have undergone renal transplantation. We performed ambulatory blood pressure monitoring (ABPM) in renal allograft recipients who were on stable maintenance immunosuppressive medications and were more than six months post‐transplant. Echocardiographic measurement of left ventricular mass index (LVMI) was obtained at the time of ABPM. Twenty‐nine children with a mean age of 14.8 yr (8–18 yr) were evaluated 4.3 yr (0.6–12.8 yr) after deceased donor (n = 13) or living donor (n = 16) transplantation. BP levels were higher during sleep compared with when awake using the 95th percentile to standardize mean BP for each period: mean BP was expressed as a standard deviation score (SDS) for each time period, awake vs. sleep: systolic (s) BP SDS were 0.43 ± 1.3 vs. 1.29 ± 1.2 (p < 0.001) and diastolic (d) BP SDS were 0.04 ± 1.3 vs. 1.34 ± 1.2 (p < 0.001). Significant differences between awake and sleep BP were also confirmed using the mean BP for each period expressed as a BPI. Hypertension (HTN) during sleep was more common than awake HTN. Based upon BPI, 21% had sHTN when awake compared with 48% during sleep and 7% had dHTN when awake compared with 41% during sleep (p < 0.05). Based upon mean BP load, 38% had sHTN when awake compared with 55% during sleep and 21% demonstrated dHTN when awake compared with 52% during sleep (p < 0.05). Left ventricular mass (LVM) was abnormally increased in six of 17 children (35%); LVM was not correlated with BP. Children prescribed angiotensin converting enzyme inhibitors or angiotensin II receptor blockers (ACEi/ARB) had significantly lower systolic BP compared with those on calcium channel blocking agents (CCB). Mean sSDS was −0.11 ± 1.1 in those children on ACEi/ARB compared with 1.6 ± 1.2 in those on CCB (p = 0.02): sSDS during sleep was significantly lower in the ACEi/ARB group compared with CCB (0.70 ± 1.1 vs. 2.0 ± 1.1, p = 0.04). Isolated nocturnal HTN is more common than daytime HTN among clinically stable pediatric renal allograft recipients. Detection and treatment of nocturnal HTN in pediatric allograft recipients could potentially affect graft survival.
Calcium × phosphate product
Authors: Hawley Carmel
Published: June 2006

Date written: August 2005

Final submission: October 2005
Effects of arachidonic acid on the spatial cognition of aged rats
Authors: OKAICHI YOKO , OKAICHI HIROSHIGE , AKIMOTO KENGO , KAWASHIMA HIROSHI , TOYODA‐ONO YOSHIKO , KISO YOSHINOBU , TOKIMOTO NAOKO
Published: June 2006

Abstract:  To examine the effects of arachidonic acid (AA) on age‐related cognitive deficits, Fischer 344 rats were given an AA‐supplemented powder diet for 12 weeks from 18.6 months old as part of the old AA (OA) group. Other age‐matched rats were fed a non‐AA‐supplemented powder diet as part of the old control (OC) group, and young rats were fed lab pellets as part of the young control (YC) group. When the aged rats reached 20.0 months old, all animals were tested for spontaneous activity in an open field, followed by the Morris water maze place and cue tasks. Escape latencies for the place task showed that the YC rats were fastest, and there was no difference between the OA and OC groups. However, the probe test and the first block of the cue task indicated that the OA rats remembered the location of an invisible platform better than the OC rats. Although the amount of hippocampal AA was larger in the OA rats than in the OC rats, the difference was not significant. The results showed that AA administration to aged animals may alleviate age‐related deficits in spatial cognition.
Decreased IH in Hippocampal Area CA1 Pyramidal Neurons after Perinatal Seizure‐inducing Hypoxia
Authors: Zhang Kun , Peng Bi‐wen , Sanchez Russell M.
Published: June 2006

Summary:  Purpose: The hyperpolarization‐activated cation current (IH) has been proposed to play a role in some forms of epileptogenesis, as it critically regulates synaptic integration and intrinsic excitability of principal limbic neurons and can be pathologically altered after experimentally induced seizures. In hippocampal CA1 pyramidal neurons, IH is functionally decreased after kainate‐induced status epilepticus in adult rats but is increased after hyperthermia‐induced seizures in immature rat pups. This study aimed to determine whether and how IH may be altered in CA1 pyramidal neurons after seizure‐inducing global hypoxia in the neonatal brain.

Methods: Seizures were induced in rat pups on postnatal day 10 by 14‐ to 16‐min exposure to 5–7% O2. Whole‐cell patch‐clamp recordings were obtained from hippocampal CA1 pyramidal neurons in slices 30 min to 3 days after hypoxia treatment, and from control age‐matched littermates. IH was isolated under voltage‐clamp by subtracting current responses to hyperpolarizing voltage steps before and during application of the IH blocker ZD 7288 (100 μM).

Results: IH was significantly decreased in pyramidal neurons from the hypoxia‐treated group compared with controls (p < 0.001; 19 controls; 15 hypoxia). Analyses of tail currents and activation kinetics indicated no statistically significant differences between groups in the voltage dependence or time constants of activation.

Conclusions: These data indicate that a single episode of neonatal hypoxia that induces seizures can persistently decrease IH in CA1 pyramidal neurons, raising this as a potential contributing mechanism to epileptogenesis in this setting. Our findings further indicate that the consequences of seizures for IH may depend more on seizure etiology than on maturational stage.
Risk factors for oral hairy leukoplakia in HIV‐infected adults of Brazil
Authors: Moura Mariela Dutra Gontijo , Grossmann Soraya de Mattos Camargo , Fonseca Linaena Méricy da Silva , Senna Maria Inês Barreiros , Mesquita Ricardo Alves
Published: June 2006

Background:  Oral hairy leukoplakia (OHL) may be an indicator of the progression of Human Immunodeficiency Virus (HIV)‐induced immuno‐depression, and the evaluation of risk factors leading to OHL is important in the management of these HIV‐infected patients. However, there are few studies that analyze risk factors leading to OHL in the Brazilian population. The aim of this case–control study is to present data about prevalence rates and risk factors leading to OHL in a sample of HIV‐infected adults in Brazil.

Methods:  This case–control study included 111 HIV‐infected patients treated at a clinic for sexually transmitted diseases and HIV. In the initial examinations with dentists, variables were collected from all patients. Diagnosis of OHL was performed in accordance with the International Classification System and cytological features. The Fisher and the chi‐squared tests were used for statistical analysis. The proportional prevalence and odds ratio were estimated.

Results:  Outcome presented a positive, statistically significant association among the presence of OHL and viral load of 3000 copies/μl or greater (P = 0.0001; odds ratio (OR) = 5.8), presence of oral candidiasis (P = 0.0000; OR = 11.1), previous use of fluconazole (P = 0.0000; OR = 24.6), and use of systemic acyclovir (P = 0.032; OR = 4.3). Antiretroviral medication presented a negative, statistically significant association with the presence of OHL (P = 0.002; OR = 8.4).

Conclusions:  Prevalence of OHL was 28.8%. Viral load, oral candidiasis, previous use of fluconazole, and systemic acyclovir were determined to be risk factors for OHL. Antiretroviral medication proved to be protective against the development of OHL.