bluuebunny/crossref_metadata_2025 huggingface dataset:
Soil Heterogeneity Effects on Tallgrass Prairie Community Heterogeneity: An Application of Ecological Theory to Restoration Ecology
Authors: Baer Sara G. , Collins Scott L , Blair John M. , Knapp Alan K. , Fiedler Anna K.
Published: May 2005

Spatial heterogeneity of resources can influence plant community composition and diversity in natural communities. We manipulated soil depth (two levels) and nutrient availability (three levels) to create four heterogeneity treatments (no heterogeneity, depth heterogeneity, nutrient heterogeneity, and depth + nutrient heterogeneity) replicated in an agricultural field seeded to native prairie species. Our objective was to determine whether resource heterogeneity influences species diversity and the trajectory of community development during grassland restoration. The treatments significantly increased heterogeneity of available inorganic nitrogen (N), soil water content, and light penetration. Plant diversity was indirectly related to resource heterogeneity through positive relationships with variability in productivity and cover established by the belowground manipulations. Diversity was inversely correlated with the average cover of the dominant grass, Switchgrass (Panicum virgatum), which increased over time in all heterogeneity treatments and resulted in community convergence among the heterogeneity treatments over time. The success of this cultivar across the wide range of resource availability was attributed to net photosynthesis rates equivalent to or higher than those of the native prairie plants in the presence of lower foliar N content. Our results suggest that resource heterogeneity alone may not increase diversity in restorations where a dominant species can successfully establish across the range of resource availability. This is consistent with theory regarding the role of ecological filters on community assembly in that the establishment of one species best adapted for the physical and biological conditions can play an inordinately important role in determining community structure.
Securitization of Mortality Risks in Life Annuities
Authors: Lin Yijia , Cox Samuel H.
Published: May 2005

Abstract

The purpose of this article is to study mortality‐based securities, such as mortality bonds and swaps, and to price the proposed mortality securities. We focus on individual annuity data, although some of the modeling techniques could be applied to other lines of annuity or life insurance.
Cash‐Balance Plan Conversions: Evidence on Excise Taxes and Implicit Contracts
Authors: Niehaus Greg , Yu Tong
Published: May 2005

Abstract

Firms that wish to switch from a traditional defined‐benefit pension plan to a defined‐contribution‐type plan have a choice between converting to a cash‐balance plan or replacing the defined‐benefit plan with a full‐fledged defined‐contribution plan. According to Ippolito and Thompson's (1999; Industrial Relations, 39: 228‐245) excise tax avoidance hypothesis, a number of firms have switched to cash‐balance plans because conversion allows the firm to avoid excise taxes on its excess pension assets. In contrast to existing studies, our evidence supports the excise tax avoidance hypothesis. Cash‐balance plan conversions also have been criticized for imposing pension losses on older employees. The implicit contract theory of pensions predicts that poorly performing firms would be the ones that would impose losses on employees. However, our evidence indicates that firms converting to cash‐balance plans typically are not poor performers.
Hyperfine Characterization of the Metastable t″‐Form of the Tetragonal Phase in ZrO2–10 mol% Y2O3 Powders Synthesized by Gel Combustion
Authors: Caracoche M. C. , Martínez J. A. , Rivas P. C. , Rodríguez A. M. , Lamas D. G. , Lascalea G. E. , Walsöe de Reca N. E.
Published: May 2005

A nanocrystalline ZrO2–10 mol% Y2O3 powder synthesized by a nitrate–citrate gel‐combustion process and stabilized in the metastable t′′‐form of the tetragonal phase has been characterized using mainly the Perturbed Angular Correlations technique. The determined hyperfine interaction allows a clear distinction between the zirconium surroundings in the t′′‐form and those already known of the other forms of the tetragonal phase. Oxygen vacancies movement is revealed as a slow diffusion involving a very small activation energy. As the powder is heated, a transformation is observed to occur around 560°C, which is consistent with a t′′‐to‐cubic transition.
Comparative Studies on Sintering Behavior of Self‐Propagating High‐Temperature Synthesized Ultra‐Fine Titanium Diboride Powder
Authors: Khanra Asit Kumar , Godkhindi Mahadev Malhar , Pathak Lokesh Chandra
Published: May 2005

Sintering behavior of nano‐sized titanium diboride (TiB2) powder prepared by a self‐propagating high‐temperature synthesis (SHS) technique was compared with that of the commercially available powder. The SHS‐made powder showed excellent sinterability at low temperatures and a maximum of 97% densification was achieved at 2223 K, whereas the identically sintered commercial powder could only be densified to ∼86% at 2223 K. The estimated activation energies for sintering of 35±0.07 kJ/mole and 46±0.7 kJ/mole for the SHS and commercial powder, respectively, indicated the possibility of a different mechanism during sintering.
Spark Plasma Sintering of Bismuth Titanate Ceramics
Authors: Kan Yanmei , Wang Peiling , Xu Tao , Zhang Guojun , Yan Dongsheng , Shen Zhijian , Cheng Yi‐Bing
Published: May 2005

Spark plasma sintering (SPS) was used to fabricate bismuth titanate (Bi4Ti3O12) ceramics. The densification, microstructure development and dielectric properties were investigated. It was found that the densification process was greatly enhanced during SPS. The sintering temperature was 200°C lower and the microstructure was much finer than that of the pressureless sintered ceramics, and dense compacts with a high density of over 99% were obtained at a wide temperature range of 800°–1100°C. Dielectric property measurement indicated that the volatilization of Bi3+ was greatly restrained during SPS, resulting in an unprecedented low dielectric loss for pure Bi4Ti3O12 ceramics.
In Situ Measurement of Capacitance: A Method for Fabricating Nanoglass
Authors: Ohta Y. , Kitayama M. , Kaneko K. , Toh S. , Shimizu F. , Morinaga K.
Published: May 2005

The capacitance of the Na2O–SiO2 glass was measured in situ during heat treatment at various frequencies, 20, 100, 1, 3, 10, and 30 kHz. It was found that the capacitance of the glass abruptly decreases after a certain duration. The glass was quenched at this stage. It was confirmed by the X‐ray diffraction and transmission electron microscopy that this decrease of capacitance was associated with the formation of crystallites in the glass matrix. The size of crystallites was observed to be in the range of about 10 nm.
Mechanical Properties of Melt‐Grown Alumina–Yttrium Aluminum Garnet Eutectics up to 1900 K
Authors: Pastor José Y. , LLorca Javier , Salazar Alicia , Oliete Patricia B. , De Francisco Isabel , Peña José I.
Published: May 2005

Alumina/yttrium aluminum garnet (YAG) eutectic rods of 1 mm in diameter were grown by the laser‐heated floating zone method at different rates to obtain microstructures with the same morphology but of very different domain size. The mechanical properties of the rods (hardness, toughness, strength) were measured at ambient temperature in the longitudinal and transverse directions and, in addition, the longitudinal flexure strength was determined up to 1900 K. The fracture resistance and the hardness of the eutectics at ambient temperature were isotropic and independent of the domain size. On the contrary, the longitudinal strength was significantly higher than the transverse one and increased linearly with the growth rate, reaching almost 2 GPa in the rods grown at 750 mm/h, which presented a submicrometer homogeneous microstructure. The critical defect size was equivalent to that of Al2O3 and YAG domains in the microstructure, and the strength was proportional to the inverse of the square root of the domain size. In addition, the strength retention of the eutectics was remarkable, and the rods with the finest microstructure withstood 1.53 GPa at 1900 K. The moderate reduction in strength at very high temperature was induced by the homogeneous coarsening of the microstructure.
Synthesis and Characterization of Cadmium Selenide Nanorods Via Surfactant‐Assisted Hydrothermal Method
Authors: Chen Minghai , Gao Lian
Published: May 2005

Single‐crystal CdSe nanorods ([001] orientation) with diameters in the range of 40–60 nm and aspect ratios of 5–8 were successfully synthesized at 180°C for 10 h through a facile surfactant‐assisted hydrothermal method, using Na2SeO3 as a high‐quality soluble selenium source. The products were characterized by X‐ray diffraction, transmission electron microscopy, energy‐dispersive X‐ray spectroscopy, high‐resolution transmission electron microscopy, and ultraviolet–vis spectra analysis. It was found that the surfactant (cetyltrimethyl ammonium bromide) played a vital role in the process. Through varying the concentrations of surfactant, the morphologies changed from dendrite‐like nanostructure to nanorods, short nanorods, and nanoparticles. The possible mechanism for the growth of CdSe nanocrystals was also discussed.
Ultra‐Long Single‐Crystalline α‐Si3N4Nanowires: Derived from a Polymeric Precursor
Authors: Yang Weiyou , Xie Zhipeng , Li Jingjing , Miao Hezhuo , Zhang Ligong , An Linan
Published: May 2005

Single‐crystalline α‐Si3N4nanowires were synthesized by thermal decomposition of a polysilazane preceramic polymer using FeCl2powders as catalyst. The nanowires, which are 20–40 nm in diameter and up to several mm in length, possess smooth surfaces and uniform diameters along the entire length and contain no detectable structural defects such as dislocation or stacking faults. The study also revealed that all nanowires grow along [100] direction. The growth of the nanowires is attributed to a novel solid–liquid–gas–solid reaction/crystallization process. The mechanism that governs the formation of nanowires rather than nanobelts is discussed.
Comparison of Tribological Behavior Between α‐Sialon/Si3N4 and Si3N4/Si3N4 Sliding Pairs in Water Lubrication
Authors: Amutha Rani D. , Yoshizawa Y. , Jones M. I. , Hyuga H. , Hirao K. , Yamauchi Y.
Published: May 2005

We report here the study on tribological behavior of α‐Sialon in aqueous medium. The results derived from a wide range of test conditions are briefly discussed. A reduction in friction coefficient from 0.7 to 0.03 and a decrease in wear rate by two orders of magnitude were achieved under low load (9.8 N) and high speed (>0.54 m/s) conditions. The tribological behavior of α‐Sialon/Si3N4 ceramics was then compared with Si3N4/Si3N4 tribopairs.
Thermophysical Properties of Perovskite‐Type Strontium Cerate and Zirconate
Authors: Yamanaka Shinsuke , Kurosaki Ken , Oyama Taku , Muta Hiroaki , Uno Masayoshi , Matsuda Tetsushi , Kobayashi Shin‐Ichi
Published: May 2005

Polycrystalline samples of strontium series perovskite‐type oxides, SrCeO3 and SrZrO3, were prepared and the thermophysical properties were measured. The chemical compositions of the samples do not deviate from the stoichiometric composition. The oxygen‐to‐metal (O/M) ratios of SrCeO3 and SrZrO3 are 3.00±0.03 and 2.98±0.01, respectively. The average linear thermal expansion coefficients are 1.11 × 10−5 K−1 for SrCeO3 and 9.69 × 10−6 K−1 for SrZrO3 in the temperature range between 300 and 1000 K. The melting temperatures Tm of SrCeO3 and SrZrO3 are 2266 and 2883 K, respectively. The longitudinal and shear sound velocities were measured by an ultrasonic pulse–echo method at room temperature in air, which enables to evaluate the elastic moduli and Debye temperature. The heat capacity was measured by using a differential scanning calorimeter in high‐purity argon atmosphere. The thermal diffusivity was measured by a laser flash method in vacuum. The thermal conductivities of SrCeO3 and SrZrO3 at room temperature are 2.95 and 4.06 W·m−1·K−1, respectively.
Enhanced Creep Resistant Silicon‐Nitride‐Based Nanocomposite
Authors: Dusza J. , Kovalčík J. , Hvizdoš P. , Šajgalík P. , Hnatko M. , Reece M. J.
Published: May 2005

Silicon nitride–silicon carbide nanocomposite has been prepared by an in situ method that utilizes C+SiO2 carbo‐thermal reduction during the sintering process. The developed material is nearly defect free and consists of a silicon nitride matrix with an average grain size of approximately 200 nm with inter‐ and intra‐granular SiC particles with sizes of approximately 150 and 40 nm, respectively. The creep behavior was investigated in bending at temperatures from 1200° to 1450°C, under stresses ranking from 50 to 150 MPa in air. The stress exponents are in the interval from 0.8 to 1.28 and the apparent activation energy is 480 kJ/mol. A significantly enhanced creep resistance was achieved by the incorporation of SiC nanoparticles into the matrix. This is because of a change of the microstructure and grain boundary chemistry leading to a change of creep mechanism and creep rate.
Grain Growth of Microtubes During Sintering in Semiconducting Ba3Ce3−xBixTi5Nb5O30 (x=0.5, 1.0, 2.0, and 3.0) Ceramics
Authors: Prabhakar Rao P. , Ravindran Nair K. , Chandran M. R. , Koshy Peter , Vaidyan V. K.
Published: May 2005

Well grown microtubes of Ba3Ce3−xBixTi5Nb5O30 (x=0.5, 1.0, 2.0, and 3.0) have been observed in the sintered ceramics. The microtubes have octagonal shapes at the cylindrical ends, hollow cores with diameters of 2–3 μm, lengths over a few tens of micrometers and wall thickness of 0.5–1.0 μm. In morphology, the tubes are very straight and are apparently welded to each other on the sides. The tubular growth as well as increase of wall thickness is observed to be more with greater Bi content, but when Ce is fully substituted by Bi, the tubes have grown into solid rods without hollowness. The growth spirals at the ends of tubes as seen by scanning electron microscope indicate that growth takes place in the longitudinal direction of the tubes. Observation of growth spirals on grains of a sintered ceramic is unusual. In fact, such features are usually seen in liquid phase growth and, therefore, we propose here grain growth in partially fluid conditions. The phase identification by X‐ray diffraction shows that the compound has a tetragonal tungsten bronze type structure. The resistivity measurements above room temperature indicate that these compounds are semiconductors and both resistivity and activation energy increase with Bi content.
Increasing Wet Green Strength of Alumina Body During Microfabrication by Colloidal Isopressing
Authors: Zhang Zhuo , Liu Biao , Lange Frederick F.
Published: May 2005

Colloidal Isopressing involves formulating a slurry with a weakly attractive particle network that can be pre‐consolidated to a high relative density by pressure filtration and still retain fluid‐like characteristics. The pre‐consolidated slurry is injected into an elastomeric mold and isopressed. Isopressing rapidly converts the slurry into an elastic body that can be removed from the mold without shape distortion. Not only is this process rapid, but since the water saturated compact produced by this method does not shrink during drying, it can also be converted into a green body without a long drying period. It is demonstrated that micron‐size surface features, such as 5 μm wide channels with a depth/width ratio of 2, can be rapidly produced on the surface of alumina powder compacts. The fracturing of thin vertical portions of a micro‐patterned surface during pressure release and demolding has been an obstacle to obtaining micron‐sized features with high aspect ratios. A method is shown here that enables the fabrication of such features by strengthening the saturated isopressed body. It is shown that concentration controlled gelation of a poly(vinyl alcohol)–Tyzor® Triethanolamine Tritanate (TE) additive effectively increases the strength of the elastic, isopressed body, saturated with water, while maintaining the low viscosity of the pre‐consolidated slurry, which is required for transferring the pre‐consolidated slurry into a rubber mold prior to isopressing.
Structural Study on PbO–SiO2 Glasses by X‐Ray and Neutron Diffraction and 29Si MAS NMR Measurements
Authors: Takaishi Taigo , Takahashi Masahide , Jin Jisun , Uchino Takashi , Yoko Toshinobu , Takahashi Masahide
Published: May 2005

Structure of xPbO–(100−x)SiO2 (x=25–89) glasses has been investigated by means of the X‐ray and neutron diffraction and 29Si MAS NMR measurements. In the radial distribution functions of all the glasses, the Pb–O correlation was observed at 0.23 nm, indicating that the PbO3 trigonal pyramids units do exist in the whole glass forming composition range. Furthermore the existence of the first Pb–Pb correlation at ∼0.385 nm in the whole composition range suggests that the basic structural unit is considered to be a Pb2O4 unit, which consists of the edge‐shared PbO3 trigonal pyramids. These results strongly imply that the Pb2O4 units participate in the glass network constructed by SiO4 tetrahedra even at low PbO content. Differing from other lead‐containing glass systems, these structural characteristics of Pb ions in the PbO–SiO2 glass system are responsible for the extremely wide glass‐forming region.
Structure and Hydration Kinetics of Silica Particles in Rice Husk Ash Studied by 29Si High‐Resolution Nuclear Magnetic Resonance
Authors: Abreu R. F. , Schneider J. , Cincotto M. A.
Published: May 2005

The structure, surface fractal dimension, and global hydration kinetics of silica particles obtained from rice husk ashes (RHAs) were studied with 29Si‐NMR spectroscopy and spin–lattice relaxation techniques. Silica particles presented an amorphous fraction higher than 93%, with traces of silica‐organic bonding and crystal‐like domains. Fe‐impurities are located preferentially on the surface of the particles. From the effect of these paramagnetic ions on the spin–lattice relaxation of Q3 and Q4 silicate groups, the surface of the particles was characterized as being effectively two‐dimensional (D=1.9±0.1). The hydration kinetics of the particles during the reaction with lime and water was monitored from 8 to 706 days. The process can be described by a power law, with the characteristic exponent higher than those measured for other cements. Also, Johnson–Mehl–Avrami expressions reproduce equally well the experimental data, with parameters compatible with growth habits and morphology known for C–S–H. Two types of Q2 tetrahedra were identified in C–S–H, which can be attributed to the bridging and nonbridging silicate groups predicted by the “dreier‐kette” structural model of C–S–H.
Toughening of Mullite/Cordierite Laminated Composites by Transformation Weakening of β‐Cristobalite Interphases
Authors: Kriven Waltraud M. , Lee Sang‐Jin
Published: May 2005

An interesting concept for achieving graceful failure in oxide composites is discussed. It is based on crack deflection in a weak interphase between a matrix and reinforcement (e.g. fiber), around a fibrous core in a fibrous monolith, or in an interphase in a laminated composite. The interphase can be phase transformation weakened by a crystallographic unit cell, volume contraction, and/or shape change. Mullite/cordierite laminates with a β→α‐cristobalite, transformation‐weakened interphase were investigated for interphase debonding behavior. The laminates were fabricated by stacking alternate, tape‐cast, green sheets of chemically doped β‐cristobalite, which was synthesized by an organic steric entrapment method, and a mullite/cordierite matrix mixture. The laminate showed fracture behavior depending on a critical particle size effect. The grain size of polycrystalline β‐cristobalite was controlled by annealing time at 1300°C. A hot‐pressed laminated composite, annealed for 10 h at 1300°C, had an average grain size of ∼4 μm and a 3‐point flexure strength of 131 MPa. Its work of fracture was 2.4 kJ/m2 but non‐catastrophic fracture behavior was demonstrated. The indentation response indicated crack deflection along the cristobalite debonding interphase. With increasing annealing time, the strength decreased due to the formation of internal macrocracks in the cristobalite layer, which occurred spontaneously during thermally induced transformation.
Lowering of Preparation Temperatures of Anatase Nanocrystals‐Dispersed Coatings via Sol–Gel Process with Hot Water Treatment
Authors: Matsuda Atsunori , Matoda Tatsuo , Tadanaga Kiyoharu , Minami Tsutomu , Tatsumisago Masahiro , Kogure Toshihiro
Published: May 2005

A longer period of time was necessary to form anatase nanocrystals on silica–titania gel coatings at lower hot water treatment temperature, whereas considerable amounts of anatase nanocrystals were observed even at 38°C after a treatment of 65 h. The coatings pre‐heated at 60°C for 1 h and treated with hot water at 55°C for 15 h showed higher photocatalytic activity for methylene blue bleaching than the coatings prepared under the conditions with higher processing temperature close to 100°C. Such a high photocatalytic activity of the coatings obtained through low processing temperatures can be ascribed to a large specific surface area of the coatings and a smaller crystal size of the precipitated anatase.
Geometry of {001} Surfaces of Spinel (MgAl2O4): First‐Principles Simulations and Experimental Measurements
Authors: Van Der Laag N. J. , Fang C. M. , De With G. , De Wijs G. A. , Brongersma H. H.
Published: May 2005

The geometry of {001} surfaces of spinel (MgAl2O4) was investigated by first‐principles simulations within density‐functional theory (DFT). The calculations show that the structure relaxation or reconstruction occurs for a depth of about 0.5 nm. The (001)‐Mg surface shows moderate relaxations and the (001)‐Al surface shows reconstruction: a new surface was formed with half of the subsurface oxygen atoms moved to the top. The surface energy was calculated to be about 1.7 J/m2 for the relaxed (001)‐Mg surface and about 3.0 J/m2 for the relaxed (001)‐Al surface.

The chemical composition of a freshly fractured (001) surface of a spinel single crystal was measured using Low Energy Ion Scattering. The measured Al/Mg ratio indicates that the (001)‐Mg surface is more stable, in good agreement with the calculations.
Micro‐Indentation Fracture Toughness Evaluation with a Novel Microscopy
Authors: Cheng Ming , Chen Weinong , Jiang Jianping
Published: May 2005

A novel microscopy is developed for evaluating the fracture toughness of thin ceramic sheets using the micro‐indentation method. This microscopy overcomes the theoretical limit of measurement resolution associated with optical microscopes. Using a modified optical microscope, the crack lengths produced by micro‐indentation on the surface of an as‐fired ceramic sheet can now be measured. Experimental results on an 8 mol% yttria‐stabilized zirconia ceramic substrate show that the accuracy of the fracture toughness evaluation is satisfactory. This micro‐indentation fracture toughness evaluation method is efficient and economical for thin ceramic substrate surfaces, either polished or as‐fired.
Oxidation of SiC/Porous Al2O3 Laminated Ceramic Composites
Authors: Krishnamurthy R. , Sheldon B. W.
Published: May 2005

The oxidation behavior of SiC/porous Al2O3 interphase laminated composites was studied using oxidation experiments and mathematical modeling of the reaction/porous diffusion kinetics in this system. Oxidation at 800°C produced both closure of the interlayer porosity at the lateral ends of the laminate and a limited penetration of the oxidation product layer front from the laminate edges to its interior. Oxidation at 800°C resulted in a persistent product layer of nearly uniform thickness that is more suited to test the effects of oxidation on laminate properties. The modeling approach, which explicitly considers the porous microstructure of the interphase and its evolution upon oxidation, reproduces these experimental observations successfully. The model was extended to study the effect that the mixing of SiC grains with Al2O3 grains to form a two‐phase porous interphase has on pore closure at the interface and oxide product front penetration into the interior of the laminate. Pore closure was found to be accelerated considerably with increasing SiC content, and was not accompanied by any significant decrease in the distance from the laminate edges upto which an oxidation product layer was formed.
Model for Sintering Devitrifying Glass Particles with Embedded Rigid Fibers
Authors: Pascual M. J. , Durán A. , Prado M. O. , Zanotto E. D.
Published: May 2005

We extend the Clusters model to account for the presence of rigid inclusions and use it to analyze the experimental sintering kinetics of composites of 60SiO2·24B2O3·16Na2O glass particles and zirconia fibers. We followed the densification kinetics of such composites as a function of the particle size, volume fraction of fibers, fiber to pore size ratio, temperature, and time of thermal treatment. The parameters of the extended Clusters model are the glass particle size distribution and shape factor, the fiber volume fraction and radii, the glass viscosity and surface tension, the number of nucleating sites per unit surface, and the crystal growth rate in the parent glass. Hydrostatic tensions caused by the fibers were also included in the calculations. The modified Clusters model with only one adjustable parameter, which is largely dominated by viscosity but also includes particle shape, allowed us to account for the effect of surface crystallization and fiber content as inhibitors of densification and successfully describe the sintering kinetics of the studied composites.
Fabrication of Fine AlN Particles by Pulverizing with Very Small ZrO2 Beads
Authors: Qiu Jin‐Yu , Hotta Yuji , Sato Kimiyasu , Watari Koji , Mitsuishi Kenshi
Published: May 2005

Nano‐sized aluminum nitride (AlN) powders can enhance the sinterability of AlN ceramics. The present work examined the pulverization and dispersion of AlN powder using ZrO2 beads of 0.1 mm in diameter as grinding medium in order to obtain nano‐sized powder for low‐temperature sintering. An attracting feature of the bead grinding is that the rotor creates centrifugal and shearing forces, which lead to efficient pulverization that exceeds the conventional grinding limit. The AlN powder with agglomerates and average particle size of 0.38 μm was broken up into more homogeneous particles with a narrow particle size distribution after 90 min of grinding. Qualitative examinations of the powder by transmission electron microscopy and BET indicated that the particle size was 50–100 nm and specific surface area was 70 m2/g.
The Densification and Microstructure of Y‐TZP Ceramics Formed Using the Hydrolysis‐Assisted Solidification Process
Authors: Kosmač Tomaž
Published: May 2005

Hydrolysis‐assisted solidification (HAS) was used in the slurry forming of yttria‐stabilized tetragonal zirconia (Y‐TZP) green bodies. AlN powder, a total of 1–5 wt% with respect to the solids, was added to a highly loaded aqueous zirconia (Y‐TZP) slurry containing 48.5 vol% of solids prior to shaping by aqueous injection molding. Aluminum hydroxide was formed during the hydrolysis of the AlN, which resulted in the production of dried green bodies with strength values ranging from 1.2 to 2.7 MPa. In the presence of alumina, formed by the thermal decomposition of the aluminum hydroxide in the green body, the densification and grain growth of the HAS‐formed material were enhanced. The fractional density, in the range 98.0–99.3%, and the bending strength, in the range 876–890 MPa, of a sintered Y‐TZP ceramic containing lower amounts (1 and 2.5 wt%) of AlN in the starting powder mixture did not differ significantly from the values obtained with conventionally formed reference material. The indentation toughness and Vickers hardness were both observed to increase, although this approximately 10% increase fell within a single standard deviation. The resistance to low‐temperature degradation of the HAS‐formed material, in terms of the thickness of the transformed monoclinic layer after aging for 24 h at 140°C in water, was found to be about four times lower and was statistically significant.
Fracture Toughness of Dental Porcelains Evaluated by IF, SCF, and SEPB Methods
Authors: Yoshimura Humberto N. , Cesar Paulo F. , Miranda Walter G. , Gonzaga Carla C. , Okada Cristina Y. , Goldenstein Hélio
Published: May 2005

Fracture toughness of six dental porcelains with leucite content ranging from 0 to 22 vol% was evaluated by indentation fracture (IF), surface crack in flexure (SCF), and single edge pre‐cracked beam (SEPB) methods. The results of the IF method were similar to those of the SCF method for all the porcelains investigated. The results of the SEPB were similar to those of the other two methods only for the glassy porcelains, but for leucite‐based porcelains this method resulted in higher values of KIc. Based on microstructure, fractographic analysis, and an additional single edge V‐notched beam test, it was concluded that the pre‐crack size influences the value of KIc for porcelains reinforced by leucite. For design and failure analysis purposes, the KIc determined by SCF method should be preferred, since fracture of dental restorations usually starts from small surface cracks.
Role of Bound Water on the Viscosity of Nanometric Alumina Suspensions
Authors: Li Chuanping , Akinc Mufit
Published: May 2005

Rheological properties of aqueous nanometric alumina suspensions with fructose as dispersant were investigated. Differential scanning calorimetry and thermogravimetry indicated that a significant fraction of the water is immobilized by the nanometric particles in the suspension. This in turn increased the viscosity of the suspensions. It was also shown that the addition of monosaccharides, fructose in particular, reduced the viscosity of the suspensions dramatically. Nuclear magnetic resonance experiments indicated that a monolayer of fructose was adsorbed on the particle surfaces. The reduction in viscosity could be attributed to release of water imposed by fructose adsorption on the alumina particles present.
USE OF COMPUTED TOMOGRAPHY AND COMPUTED TOMOGRAPHIC MYELOGRAPHY FOR ASSESSMENT OF SPINAL TUMORAL CALCINOSIS IN A DOG
Authors: Ham Luc M. Van , Bree Henri J. van , Tshamala Mulenda , Thoonen Hendrik
Published: May 2005

Spinal tumoral calcinosis is reported in a Berner sennenhund puppy. The condition was manifested clinically as a non‐ambulatory tetraparesis associated with neck pain. On survey radiographs there was a focal calcified mass at the atlantoaxial articulation. Computed tomography and computed tomographic myelography gave additional information on the extent of the mass and on the degree of spinal cord compression. The mass was removed surgically and the dog made a complete recovery.
THE NON‐CARDIAC DISTRIBUTION OF 99mTC‐METHOXY‐ISOBUTYL‐ISONITRILE (SESTAMIBI) IN NORMAL BEAGLES
Authors: Steyn Phillip F. , Ogilvie Gregory
Published: May 2005

Technetium‐99m methoxy‐isobutyl‐isonitrile (sestamibi) is a radiophartnaceutical used for the evaluation of myocardial perfusion. Increased uptake of sestamibi has also been documented in tumors. The objective of this study was to document the extracardiac biodistribution of 99mTc sestamibi in the normal dog. Nine normal beagles were given 0.35 mCi/kg 99mTc sestamibi intravenously, and 60 second images were made of the entire body at 1 hour post injection. A defined distribution pattern was recognized, with good visualization of the heart, liver, gallbladder, small intestine, kidneys, urinary bladder, popliteal lymph nodes, parotid salivary glands and zygomatic salivary glands. Splenic uptake was not seen.

Target to background ratios were calculated for all the regions listed, using background regions‐of‐interest with the smallest coefficient of variance for the denominator. The mean, range and standard deviation of these ratios are given.
POSITIVE CONTRAST SHOULDER ARTHROGRAPHY WITH IOPROMIDE* AND DIATRIZOATE†IN DOGS WITH OSTEOCHONDROSIS
Authors: Bree Henri van , Ryssen Bernadette van
Published: May 2005

Forty‐one dogs (60 joints) with clinical and radiographic signs of shoulder osteochondrosis were randomized in a study to compare the diagnostic quality of iopromide (Ultravist, Schering AG) (n = 29) and meglumine‐sodium diatrizoate (Urografin, Schering AG) (n = 31) in arthrography. The studies were performed using 1.5 to 4 ml of a solution of each contrast media at a concentration of 140 mg I/ml. Exposures were made within 5 minutes after intra‐articular injection. Iopromide gave a significantly better arthrographic quality (P < 10−6).
IMAGING ARTIFACTS IN DIAGNOSTIC ULTRASOUND—A REVIEW
Authors: Kirberger Robert M.
Published: May 2005

Imaging artifacts commonly occur during routine ultrasonographic evaluation of patients and contribute to image inaccuracies. These artifacts are classified into artifacts arising from factors controllable prior to imaging or from sound beam interactions within the patient which may result in clinically useful or confusing artifacts. Artifact formation, and how this influences the anatomical image location, echogenicity, size and shape, is described. The clinical interpretation of artifacts is explained in order to gain maximum diagnostic information from an ultrasonographic image.
THE SCINTIGRAPHIC EVALUATION OF SOLID PHASE GASTRIC EMPTYING IN NORMAL CATS
Authors: Steyn Phillip F. , Twedt David , Toombs Wanda
Published: May 2005

The gastric emptying half‐time of solid food in normal cats was determined using a scintigraphic technique. 99mTc‐sulfur colloid was applied to dry food. Sequential images were acquired post prandial, and the gastric emptying half‐time was determined for several different acquisition and processing parameters. Good correlation was found between different acquisition and processing methods, some of which made use of edge detection applications, while others used different views, or number of views from which the gastric emptying half‐time was calculated. The mean ± standard deviation, (range) and median of the gastric emptying half‐time determined using the geometric mean of total counts in hand‐drawn regions of interest from the lateral and ventral images were 2.47 × 0.71, (1.42–3.61) and 2.37 hours respectably.
LESIONS OF THE RENAL PELVIS AND PROXIMAL URETER IN VARIOUS NEPHRO‐UROLOGICAL CONDITIONS: AN ULTRASONOGRAPHIC STUDY
Authors: Felkai Cs. , Vörös K. , Fenyves B.
Published: May 2005

The applicability of ultrasonography was studied in the diagnosis of lesions of the renal pelvis and ureter in 10 dogs. Ultrasonographic findings of processes associated with dilatation and concretion formation in the renal pelvis were described and the differential diagnosis of the lesions was discussed. The authors propose a new classification system for judging processes characterized by dilatation of the renal pelvis. Experience suggests that ultrasonography is an effective procedure in the diagnosis of certain diseases of the upper urinary tract in dogs.
EVALUATION OF SUPERFICIAL DIGITAL FLEXOR TENDINITIS IN RACING HORSES THROUGH GRAY SCALE HISTOGRAM ANALYSIS OF TENDON ULTRASONOGRAMS
Authors: Tsukiyama Katsuji , Acorda Jezie A. , Yamada Haruo
Published: May 2005

Normal and diseased superficial digital flexor tendons at different stages of healing from seven Thoroughbred horses, aged 3–6 years, were evaluated by correlation of gray scale histogram analysis of tendon cross‐sectional ultrasonograms with histopathologic examination. Normal tendon and tendons at different stages of healing, excluding acute tear stage, were characterized by normally distributed histogram patterns. The histogram mean value of normal tendons was higher than the corresponding values in diseased tendons at different stages of healing (p < 0.01). In addition, the histogram mean of acute lesions was lower than for early fibrosis or healed lesions (p < 0.01). The histogram mean increased as healing progressed. The results show that gray scale histogram analysis of tendon ultrasonogram can be used to distinguish between normal and abnormal superficial digital flexor tendon in racing horses.
PRESUMPTIVE TENOSYNOVIAL OSTEOCHONDROMATOSIS IN A HORSE
Authors: Newell Susan M. , ROBERTS Royce E. , Baskett Anne
Published: May 2005

A 5 year old Arabian mare was evaluated for a non‐painful swelling located dorsal to the right carpus which had been present for 2 years. Radiographically, multiple mineralized bodies were identified dorsal to the distal radius and carpus in the region of the tendon sheath of the extensor carpi radialis muscle. The radiographic appearance of the carpal bones was within normal limits. On ultrasound examination, multiple hyperechoic foci with posterior shadowing were seen adjacent to the extensor carpi radialis tendon. There was minimal distension of the tendon sheath and no abnormalities within the substance of the extensor carpi tendon were identified. Considering the radiographic and sonographic findings, a presumptive diagnosis of tenosynovial osteochondromatosis was made. Histological confirmation of this diagnosis was not obtained as the owner declined further diagnostic evaluation.
EFFECTS OF EXPERIMENTAL NERVE ROOT COMPRESSION ON ARTERIAL BLOOD FLOW VELOCITY IN THE SEVENTH LUMBAR SPINAL GANGLION OF THE DOG: MEASUREMENT USING INTRAOPERATIVE DOPPLER ULTRASONOGRAPHY
Authors: Jones Jeryl C. , Hudson Judith A. , Sorjonen Donald C. , Hoffman Charles E. , Braund Kyle G. , Wright James C. , Garrett Phillip D. , Bartels Jan E.
Published: May 2005

Intraoperative Doppler ultrasonography was used to measure the effects of four experimental nerve root compression treatments (central compression, central‐plus‐lateral compression, lateral compression, and compression release) on arterial blood flow velocities in the seventh lumbar spinal ganglion of three dogs. Graphed blood flow velocity changes (change = treatment value − pretreatment value) were below baseline during the first three compression treatments and above baseline following compression release. Mean blood flow velocity changes for both central‐plus‐lateral compression and lateral compression differed (p ≤ 0.05) from changes for central compression. Changes for central‐plus‐lateral compression did not differ (p > 0.05) from changes for lateral compression. Changes among the first three compression treatments differed (p ≤ 0.05) from changes for compression release. No histologic abnormalities were identified in compressed nerve tissues, compared to contralateral controls. These findings indicate that stenosis within the L7‐S1 intervertebral foramen may cause ischemia of the L7 spinal ganglion in dogs.
SCINTIGRAPHIC DETECTION OF SUBCUTANEOUS METASTASIS IN A DOG WITH APPENDICULAR OSTEOSARCOMA
Authors: DANIEL Gregory B. , Avenell James S. , Young Karen , Mason Gary L. , Hahn Kevin A.
Published: May 2005

This report describes the detection of subclinical soft tissue metastasis of an appendicular osteosarcoma in a dog using bone scintigraphy. A 7‐year‐old spayed female Rottweiler was presented with a biopsy confirmed diagnosis of osteosarcoma. Initial radiographs revealed an aggressive bone lesion of the left distal radius. At presentation, there was no clinical or radiographic evidence of metastasis; however, a nuclear bone scan showed the primary bone lesion of the distal left radius and numerous soft tissue lesions consistent with diffuse soft tissue metastases. A left foreleg amputation was performed and cisplatin chemotherapy was given post‐operatively. A second bone scan performed one month following initial presentation showed progression in size and number of soft tissue masses. Many of the lesions had become apparent on physical exam and survey radiographs. Excisional biopsy was performed on one of the soft tissue masses and a diagnosis of metastatic osteosarcoma was made. The dog was euthanized 2 months after initial presentation at the owners request due to deterioration of the animals physical condition.
POSTOPERATIVE IRRADIATION OF SPINAL CORD TUMORS IN 9 DOGS
Authors: Siegel Sheri , Kornegay Joe N. , Thrall Donald E.
Published: May 2005

Between 1985 and 1993, nine dogs with spinal cord tumors were treated postoperatively with cobaltradiation at North Carolina State University‐Veterinary Teaching Hospital. Total doses ranged between 33.3–48.0 Gy given in 10–12 fractions of 3–4 Gy over a four week period. Five dogs were euthanized due to recurrence of the tumor or neurologic signs and two dogs were euthanized due tounrelated problems. Two dogs were alive but lost to follow‐up at 12 and 25 months. Survival time ranged from 6.5–70.0 months. Median survival time (95% confidence interval) was 17 (12–70) months. Results of this study suggest decompressive surgery followed by irradiation can be an effective treatment for dogs with spinal cord tumors.
ULTRASONOGRAPHIC IDENTIFICATION AND CHARACTERIZATION OF SPLENIC NODULAR LIPOMATOSIS OR MYELOLIPOMAS IN CHEETAHS (ACINONYX JUBATUS)
Authors: Walzer Christian , Hittmair Katharina , Walzer‐Wagner Christa
Published: May 2005

A total of 44 live cheetahs were examined sonographically between 1989 and 1994. Seventeen of these animals originated from 4 European facilities, the other 27 cheetahs were examined in 3 facilities in Namibia. Evaluation of the cheetahs included a clinical examination, abdominal ultrasound, and complete blood work. Splenic myelolipomas were diagnosed sonographically in 11 cheetahs. In 7 cheetahs the diagnosis was confirmed at necropsy. Nine of the 14 cheetahs in Europe had myelolipomas in the spleen, while in the African cheetahs there were only 2 animals with myelolipomas. Histologically these lesions were characterized by fatty nodules. A more fitting term of Nodular Lipomatosis of the spleen is therefore suggested. All cheetahs with nodular lipomatosis of the spleen, had concurrent chronic diseases at necropsy. An indicator function of splenic nodular lipomatosis for chronic disease and/or stress is possible.
AZYGOS CONTINUATION OF THE CAUDAL VENA CAVA IN A DOG: RADIOGRAPHIC AND ULTRASONOGRAPHIC DIAGNOSIS
Authors: Barthez Paul Y. , Siemens Lori M. , Koblik Philip D.
Published: May 2005

Azygos continuation of the caudal vena cava was identified via ultrasonography and angiography in a 7 month old female boxer. Azygos continuation of the caudal vena cava is a rare vascular anomaly that results from failure of anastomosis between the caudal cardinal system and the right vitelline vein during embryogenesis. This anomaly has also been described in association with portoazygos shunt.
CEREBRAL SINUS VENOGRAPHY IN THE DOG: A NEW TECHNIQUE
Authors: Pluhar G. Elizabeth , Tucker Russell L. , Gavin Patrick R. , Bagley Rodney S. , Takeuchi Mitsuhiko
Published: May 2005

A new of performing cerebral sinus venography was developed that opacivies both the ventral and most of the dorsal venous sinus systems. A pediatric angiographic catheter was introduced into the external jugular vein and advanced to the level of the temporal sinus. Iodinated contrast medium was injected manually and radiographs were made. Subtraction radiography was used to visualize vessels field wit contast medium. Venography was simple and relatively non‐invasive and was considered safe. The technique was used to confirm occlusion of the transverse venous sinus in healthy dogs that had undergone radical craniectomies.
ULTRASONOGRAPHIC ADRENAL GLAND MEASUREMENTS IN DOGS WITHOUT EVIDENCE OF ADRENAL DISEASE
Authors: Douglass James P. , Berry Clifford R. , James Stephanie
Published: May 2005

The purpose of this retrospective study was to determine measurements of adrenal glands from longitudinal sonograms, in a large population of dogs and to correlate these measurements to age, sex and descriptors of body size. Dogs were selected from the clinic population presented for routine abdominal ultrasonography between September, 1991 and March, 1994. Dogs with elevated serum cholesterol or alkaline phosphatase levels, polyuria/polydipsia, and/ or clinical diagnoses of adrenal pathology were excluded. Dogs with ultrasound‐documented abnormalities (mass lesions, abnormal architecture) of either adrenal were not considered. Age, sex, weight and breed were recorded, and the body surface area of each dog was calculated. Adrenal length and caudal polar width were determined from longitudinal, two‐dimensional ultrasounhd images. Adrenal measurements were compared with body size measurements and age using least squares linear regression analysis and the correlation coefficient (r) and coefficient of determination (r2)calculated. One hundred and ninety three dogs were included in the study, with a weight and body surface area range of 1.8–72kg and 0.2–1.8m2m respectively. The left adrenal gland (n=182) length range was from 10.7 to 50.2mm, and the range of the caudal polar widths was 1.9 to 12.4mm. Right adrenal gland (n=85) length range was from 10 to 39.3 mm, and the range of the caudal polar widths was from 3.1 to 12mm. In dogs where both adrenal gland lengths were measured (n = 74), the right adrenal gland length was less than that of the left in 46dogs, equal to the left in one dog, and greater than the length of the left in 27 dogs. The strongest linear association was noted between the left adrenal gland length of the left in 27 dogs. The strongest linear association wasw noted between the left adrenal gland length and body weight (kg, r = 0.71, p<0.0001) or body surface area (m2, r = 0.0001).significant association was noted between the right adrenal gland length and body weight kg, r = 0.69, p<0.0001). A significant positive association was also noted between age and left adrenal gland length, (r = 0.25, p = 0.009). The summation of all four adrenal measurement values (left length and width, right length and width) did slightly improve the correlation (r = <0.74, p<0.0001) when compared with body weight (kg). There was not a significant difference in the adrenal measurements with regard to sex. With regard to the correlation coefficient values, there was no advantage noted to calculating the body surface area from body weight. The causes for the low degrees of the correlation between adrenal size and the variables investigated in this study are unknown; measurement error, effects of nonadrenal illness on adrenal size, and a non‐linear or complex linear relationship between adrenal gland size (as measured by longitudinal parameters and descriptors of body size are among possible exphanations.
THE USE OF RADIONUCLIDE ANGIOGRAPHY TO STUDY BLOOD FLOW THROUGH ENDOTHELIAL CELL SEEDED EXTRATHORACIC BYPASS GRAFTS IN THE DOG
Authors: Sackman Jill E. , Daniel Gregory B. , Freeman Michael B. , Lothrop Clinton D.
Published: May 2005

Endothelial seeding of vascular grafts has been shown to decrease graft thrombogenicity and prolong longevity when implanted in vivo. Previous studies have utilized anatomic grafts to study endothelialization and healing. Anatomic thoracoabdominal grafts do not allow for sequential biopsy for evaluation of individual grafts nor do they approximate the environment for long bypass grafts used in limb salvage. This study evaluated the use of an extra‐anatomic aortic bypass graft to assess the healing of endothelial cell seeded expanded polytetrafluoroethylene (ePTFE). Radionuclide angiography was used to evaluate graft patency and quantify blood flow through the graft. Dogs underwent placement of an extra‐anatomic 60 cm long, 8 mm internal diameter, graft seeded with autologous endothelium. Grafts were biopsied from 2 weeks up to 1 year. Radionuclide studies were performed postimplantation and following each graft biopsy. Graft placement and biopsies were well tolerated in all dogs. Biopsied segments of graft allowed for sequential studies of the healing of implanted grafts by scanning electron and light microscopy. Flow through the implanted graft was close to 50% of the total caudal abdominal aortic flow. No significant difference in graft flow was noted either between animals or overtime.