bluuebunny/crossref_metadata_2025 huggingface dataset:
Structural Investigations of Alkali Silicate Gels
Authors: Hou Xiaoqiang , Kirkpatrick R. James , Struble Leslie J. , Monteiro Paulo J. M.
Published: April 2005

Investigation of a series of synthetic alkali silicate gels and gels produced by the alkali silica reaction (ASR) in field concrete using 29Si NMR spectroscopy, X‐ray diffraction, and bulk chemical analysis shows that local structures of the synthetic and field gels are quite similar. The most abundant Si sites for the field and synthetic gels with similar compositions have Q3 polymerization, and the number of non‐bridging oxygens per Si is similar for these samples. These samples also yield a basal X‐ray diffraction peak near 8–12 Å, suggesting that the structure is dominated by sheet‐like units, consistent with the dominant Q3 polymerization. Calculations based on the relative site abundances of the sites observed by 29Si NMR and the bulk chemical compositions indicate that there is insufficient alkali to charge‐balance all the non‐bridging oxygens and that there is a significant concentration of Si–OH linkages. The results provide strong support for the basic structural concepts of the so‐called kanemite model for ASR gel proposed by Wieker and coworkers, although the overall gel structure is likely to be more complex.
Structure–Property Correlations in Y–Ca–Mg–Sialon Glasses: Physical and Mechanical Properties
Authors: Rouxel T. , Dély N. , Sangleboeuf J. C. , Dériano S. , LeFloch M. , Beuneu B. , Hampshire S.
Published: April 2005

The physical and mechanical properties of 12 glasses from the Y–(Mg,Ca)–Si–Al–O–N and (Mg,Ca)–Si–Al–O–N systems were investigated. The effect of the substitution of magnesium for calcium through two series of glasses, one consisting of oxides glasses and the other of glasses containing 6 at.% of nitrogen (15 e/o N), was considered. The change of the glass transition temperature through the glass series provides evidence for a mixed‐alkaline‐earth effect between magnesium and calcium species. The indentation hardness (H), Young's modulus (E), and indentation fracture toughness (KC) were found to increase significantly with either the magnesium or the nitrogen content, and nitrogen also seems to enhance the effect of magnesium on the properties. The network structure was analyzed both by29Si and27Al Magic Angle Spinning Nuclear Magnetic Resonance and by neutron scattering experiment, which allows for the estimation of some atomic bond lengths in such complex glasses. Nitrogen was found to have a significant structural effect on the magnesium environment and on the glass polymerization degree, and hence on the glass properties.
Phase Assemblages of Pr α‐sialon Derived from SHS‐ed Powders and TEM Study on the Nucleation of Pr α‐sialon
Authors: Jiang Jiuxin , Zhu Bo , Wang Peiling , Chen Weiwu , Yan Dongsheng , Zhuang Hanrui , Cheng Yibing
Published: April 2005

The Pr α‐sialon powders prepared by self‐propagating high‐temperature synthesis (SHS), consisting of 55 wt% Pr α‐sialon and 45 wt% of β‐sialon (abbreviated as α′ and β′), were hot‐pressed at 1800°C for 1 h. The results showed that Pr α′ phase would transfer to β′ with the appearance of JEM phase (Pr(Si6−zAlz)(N10−zOz)) after sintering, thus resulting in the increase of β′ phase to 86 wt%. The addition of Y2O3 into SHS‐ed Pr α′ powders as the starting materials restrains the transformation of α′ to β′ and prevents the formation of JEM phase as well. The nucleation mechanism of Pr α′ grain during hot‐pressing was investigated in terms of transmission electron microscope and energy‐dispersive spectrometer analysis. Two nucleation modes of Pr α′ grains were found, i.e., nucleating on the undissolved Pr α′ grains and on the nuclei of (Pr, Y) α′ grains precipitated from liquid phase.
Preparation of Titanium Dioxide Nanocrystallite with High Photocatalytic Activities
Authors: Yang Songwang , Gao Lian
Published: April 2005

Anatase nanocrystalline titanium dioxide (TiO2) with high photocatalytic activities was prepared by hydrothermal crystallization with the addition of acetic acid. The presence of acetic acid could arrest the growth of the nanocrystallites during the hydrothermal processes and be propitious to form nanocrystallites with round edges and corners. This morphology of (TiO2) had more active sites in the photocatalytic process and showed high photocatalytic activity in the degradation of the methylene blue in the aqueous solution.
A Novel Spray‐Pyrolysis Technique to Produce Nanocrystalline Lanthanum Strontium Manganite Powder
Authors: Kumar Abhoy , Devi Parukuttyamma Sujatha , Sharma Abhijit Das , Maiti Himadri Sekhar
Published: April 2005

Nanocrystalline, single phase, and highly homogeneous La0.84Sr0.16MnO3 (LSM) powder was prepared by a unique spray‐pyrolysis process for solid oxide fuel cell applications. Atomization of a citrate–nitrate precursor solution consisting of La3+, Sr2+, and Mn2+ ions in the molar ratio 0.84:0.16:1.0, which can initiate a controlled exothermic anionic oxidation‐reduction reaction leading to a self‐propagating auto‐ignition (self‐ignition) reaction within individual droplets led to the conversion of the precursor to their corresponding single‐phase LSM powder. Characterization of the as‐sprayed and calcined products by X‐ray powder diffraction, thermal analysis, and microstructural analysis confirmed the formation of nanocrystalline single‐phase LSM powder by this process.
Direct Synthesis of Tungsten Carbide Nanoparticles by Mechanically Assisted Carbothermic Reduction of Natural Wolframite
Authors: Temuujin Jadambaa , Senna Mamoru , Jadambaa Tsedev , Byambasuren Dondog
Published: April 2005

Carbothermic reduction of natural wolframite (FeWO4) to nano‐sized tungsten carbide (WC) particles was achieved by calcining mechanically activated mixtures of FeWO4 and active carbon at 1100°C under flowing Ar gas. The average particle size ranged between 20 and 25 nm. Intermediates, Fe6W6C and Fe3W3C, were observed between 900° and 1100°C, which decomposed to give the final product, WC. Homogeneity increase and associated decrease in the diffusion path by milling are mainly responsible for the successful production of WC. The process paves the way to rational utilization of natural FeWO4 directly to fine advanced materials.
Preparation of Monodispersed Tin‐Doped Indium Oxide Powders by Hydrothermal Method
Authors: Xu Huarui , Zhu Guisheng , Zhou Huaiying , Yu Aibing
Published: April 2005

This paper presents a hydrothermal method for synthesizing tin‐doped indium oxide (ITO) powder. It shows that monodispersed ITO powders of diameter 70±10 nm can be readily prepared by a process using NaOH as a basic source and involving hydrothermal synthesis at 240°C in 12 h and post‐calcination at 500°C. The powder size is decreased by increasing the initial indium and tin concentration ([In+Sn]precursor) and the excess NaOH concentration ([NaOH]excess) in the solution. The proposed technique has a significant potential for the commercial production of ITO nanopowders.
Mesoporous AlPO4 Glass from a Simple Aqueous Sol–Gel Route
Authors: Zhang Long , Bögershausen Ansgar , Eckert Hellmut
Published: April 2005

Transparent and colorless AlPO4 gel and glass are prepared via a simple aqueous sol–gel route using aluminum lactate and phosphoric acid as precursors. The stoichiometric AlPO4 glass derived from this sol–gel route has a mesoporous structure with a surface area of 504 m2/g after calcination to 600°C. With increasing gel‐to‐glass processing temperature, the average degree of P/Al connectivity increases. After sample calcination at 600°C for 4 h, 27Al MAS NMR spectra indicate that aluminum is almost completely converted into AlO4 units. 27Al{31P} rotational echo double resonance and 31P{27Al} rotational echo adiabatic passage double resonance NMR experiments as well as 27Al and 31P MAS NMR results further confirm that the prepared AlPO4 glass has a three‐dimensional network based on alternating Al(OP)4 and P(OAl)4 tetrahedral units in analogy to the local structure of crystalline AlPO4.
Solvothermal Synthesis and Processing of Yttria‐Stabilized Zirconia Nanopowder
Authors: Wang Xin M. , Lorimer Gordon , Xiao Ping
Published: April 2005

A solvothermal method has been used to produce nanoparticles of cubic/tetragonal yttria‐stabilized zirconia (YSZ) with uniform particle size, homogenous composition, and high crystallinity. The effects of reaction time, reactant concentration, processing temperature, and solvent composition on prime particle size and YSZ phase proportion have been investigated. The effect of solvent, a mixture of ethanol/2‐propanol, on crystallite size and agglomerate size was studied and discussed according to Derjaguin‐Landau‐Verwey‐Overbeek (DLVO) theory and surface chemistry. The prime particle diameter was 2–4 nm and secondary particle size was 140–180 nm. After compaction and sintering at 1000°C, YSZ with a grain size of approximately 50 nm in diameter was obtained with a typical relative density of 94%.
Fabrication of Transparent, Sintered Sc2O3Ceramics
Authors: Li Ji‐Guang , Ikegami Takayasu , Mori Toshiyuki
Published: April 2005

We report here the fabrication of transparent Sc2O3ceramics via vacuum sintering. The starting Sc2O3powders are pyrolyzed from a basic sulfate precursor (Sc(OH)2.6(SO4)0.2·H2O) precipitated from scandium sulfate solution with hexamethylenetetramine as the precipitant. Thermal decomposition behavior of the precursor is studied via differential thermal analysis/thermogravimetry, Fourier transform infrared spectroscopy, X‐ray diffractometry, and elemental analysis. Sinterability of the Sc2O3powders is studied via dilatometry. Microstructure evolution of the ceramic during sintering is investigated via field emission scanning electron microscopy. The best calcination temperature for the precursor is 1100°C, at which the resultant Sc2O3powder is ultrafine (∼85 nm), well dispersed, and almost free from residual sulfur contamination. With this reactive powder, transparent Sc2O3ceramics having an average grain size of ∼9 μm and showing a visible wavelength transmittance of ∼60–62% (∼76% of that of Sc2O3single crystal) have been fabricated via vacuum sintering at a relatively low temperature of 1700°C for 4 h.
Yield Strength of α‐Silicon Nitride at High Pressure and High Temperature
Authors: Qian J. , Pantea C. , Zhang J. , Daemen L. L. , Zhao Y. , Tang M. , Uchida T. , Wang Y.
Published: April 2005

Through the analysis of peak broadening of energy‐dispersive diffraction lines from a powdered sample, the yield strength of α‐Si3N4 was investigated at a pressure of 9 GPa and temperatures up to 1234°C. During compression at room temperature, the lattice strain deduced from peak broadening increased linearly with pressure up to 9.2 GPa, with no clear indication of strain saturation. While heating at 9 GPa, diffraction peaks narrowed and significant stress relaxation was observed at temperatures above 400°C, indicating the onset of yielding. The yield strength of α‐Si3N4 decreases rapidly with increasing temperature: from 8.7 GPa at 400°C to 4.0 GPa at 1234°C. The low temperature for the onset of yielding and decrease of yield strength upon further heating bring up concern regarding the performance of α‐Si3N4 as an engineering material. Finally, the grain size variation is also outlined together with the dependence of differential strain on pressure and on temperature. This provides crucial information for clarifying the “fine structure” of the evolution of the differential strain.
Oxygen Vacancy Relaxation and Domain Wall Hysteresis Motion in Cobalt‐Doped Barium Titanate Ceramics
Authors: Cheng Bo Lin , Button Tim W. , Gabbay Maurice , Fantozzi Gilbert , Maglione Mario
Published: April 2005

Mechanical and dielectric loss measurements were carried out in the BaTiO3 ceramics doped with Co at frequencies between 0.01 Hz and 1 MHz as a function of temperature from −150° to 150°C. The relaxation peak observed in the ferroelectric phase with an activation energy of 0.27 eV is assumed to be related to the motion of oxygen vacancies. This peak could be because of the reorientation of an electrical dipole made of oxygen vacancies and Co3+ ions in the lattice. Furthermore, another loss peak located just below the Curie temperature Tc could be interpreted as hysteretic motion of the domain walls in a regime where the domain wall density is changing.
Fabrication Routes for Yttria‐Stabilized Zirconia Suitable for the Production of Minor Actinide Transmutation Targets
Authors: Somers Joseph , Fernández Asunción
Published: April 2005

The actual fabrication processes of targets for the transmutation of actinides in nuclear reactors will need to be dust‐free and compatible with automation and remote operation. The developments reported here mark an important technical breakthrough in the fabrication of highly active materials. The sol–gel external gelation, modified by the addition of carbon, and infiltration methods have been used here to produce high‐quality, dust‐free yttria‐stabilized zirconia beads, with excellent compaction and sintering properties. Furthermore, the beads produced in this way have higher porosity, which permits the infiltration of hitherto unattainable quantities of the actinide.
A New Scratch Resistance Measure for Structural Ceramics
Authors: Subhash Ghatu , Bandyo Raka
Published: April 2005

Scratch resistance of several structural ceramics was investigated using a conical diamond tool in an instrumented rotating scratch facility. The normal (thrust) and the tangential (cutting) forces induced during the scratch process were recorded using high‐speed force transducers. The volume of material removed and the complete scratch groove characteristics were analyzed using laser profilometry and scanning electron microscopy. Based on the volume of material removed in a given scratch groove, material properties, and the measured forces, a “scratch resistance measure” that reflects the susceptibility of a ceramic to scratching‐induced damage was developed. This measure is expected to assist in the ranking of ceramics for their resistance to scratching.
Melt Differentiation Induced by Zonal Structure Formation of Calcium Aluminoferrite in a CaO–SiO2–Al2O3–Fe2O3 Pseudoquaternary System
Authors: Fukuda Koichiro , Matsunaga Ken‐ichi , Bessho Takahiro , Yoshida Hideto
Published: April 2005

The phase stability in part of the P2O5‐bearing pseudoquaternary system CaO–SiO2–Al2O3–Fe2O3 has been studied by electron probe microanalysis, optical microscopy, and powder X‐ray diffractometry. At 1973–1653 K, the α‐Ca2SiO4 solid solution [α‐C2S(ss)] and melt coexisted in equilibrium, both chemical variations of which were determined as a function of temperature. The three phases of melt, calcium aluminoferrite solid solution (ferrite), and C2S(ss) coexisted at 1673–1598 K. On the basis of the chemical compositions of these phases, a melt‐differentiation mechanism has been, for the first time, suggested to account for the crystallization behavior of Ca3Al2O6 solid solution [C3A(ss)]. When the α‐C2S(ss) and melt were cooled from high temperatures, the melt would be induced to differentiate by the crystallization of ferrite. Because the local equilibrium would be continually attained between the rims of the precipitating ferrite and coexisting melt during further cooling, the melt would progressively become enriched in Al2O3 with respect to Fe2O3. The resulting ferrite crystals would show the zonal structure, with the Al/(Al+Fe) value steadily increasing up to 0.7 from the cores toward the rims. The C3A(ss) would eventually crystallize out of the differentiated melt between the zoned ferrite crystals in contact with their rims.
Shape Evolution of SrTiO3 Crystals During Coarsening in a Titania‐Rich Liquid
Authors: Sano Tomoko , Kim Chang‐Soo , Rohrer Gregory S.
Published: April 2005

To identify factors that might affect capillary driving forces and interface structure‐dependent mechanisms for coarsening, we have used a stereological analysis to determine the changes in the morphology of SrTiO3 crystals in contact with a titania‐rich liquid at 1500°C. A combination of flat and curved surfaces is observed in contact with the liquid. The (100) surface is the most common, followed by (110). A range of surfaces in the 〈100〉 zone are also found, but with a lower frequency. The areas of the {100} and {110} surfaces are approximately equal at the initial stage, but after 24 h of growth, the {100} surface area is more than twice as great as the {110} surface area. At this point, {100} surfaces make up more than 25% of the surface area in contact with the liquid. The results suggest that morphological changes during growth continuously reduce the average surface energy and interface mobility. This provides a plausible explanation for coarsening rates that decrease faster than predicted by the classical theory.
Al2O3–ZrO2–SiO2 Ternary Glasses for Molybdenum Oxidation Barriers
Authors: Espino Ana M. , Díaz Luis A. , Fernández Adolfo , Torrecillas Ramón , Moya José S.
Published: April 2005

The wettability of binary and ternary glasses belonging to SiO2–Al2O3–ZrO2 diagram has been studied using the sessile drop technique at 1750° and 1800°C. The ternary SiO2–Al2O3–ZrO2 (90–5–5 wt%) glass has proved to be well appropriated as a molybdenum oxidation barrier coating. The addition of 5 wt% of MoO2 slightly improves its wettablity at higher temperatures without affecting its oxidation barrier properties. The Mo comes into the glass network as a mixture of Mo5+, Mo4+, and Mo6+. After oxidation at 1000°C in oxygen atmosphere, the molybdenum remains in the glass network as Mo6+.
A High‐Strain‐Rate Alumina‐Based Ceramic Composite
Authors: Chen Tiandan , Mecartney Martha L.
Published: April 2005

An alumina‐based ceramic codispersed with zirconia and mullite was synthesized with a submicron grain size. At high temperatures, steady‐state creep with very limited grain growth was achieved for samples with 40 vol% alumina, 30 vol% zirconia, and 30 vol% mullite (AZ30M30). Constant stress compressive creep behavior of AZ30M30 showed a stress exponent of 2 and an activation energy of 880 kJ/mol. A strain rate of 0.01 s−1 was obtained for AZ30M30 at 60 MPa and 1500°C, indicating the potential for high‐strain‐rate superplasticity.
Preparation and Upconversion Properties of Yb3+, Ho3+: Lu2O3 Nanocrystalline Powders
Authors: An Liqiong , Zhang Jian , Liu Min , Wang Shiwei
Published: April 2005

Yb3+, Ho3+: Lu2O3 nanocrystalline powders were synthesized by a reverse‐strike co‐precipitation method using NH4HCO3 and NH3·H2O as precipitators. X‐ray diffraction analysis and field emission scanning electron microscopy observation showed that the phase composition of the powders was cubic and the particle size was 30–50 nm. Under the excitation of a 980 nm continuous wave diode laser, green and red emissions centered around 548 and 667 nm, respectively, were observed and the green emission dominated the upconversion spectrum. Power studies revealed that a two‐photon process was involved in the upconversion emissions and the possible upconversion mechanisms were discussed.
Dispersion of SiC in Aqueous Media with Al2O3 and Y2O3 as Sintering Additives
Authors: Zhang Jingxian , Iwasa Mikio , Jiang Dongliang
Published: April 2005

It has been well accepted that polyethylene imine (PEI) is an effective dispersant for silicon carbide (SiC) in aqueous media. However, after the addition of sintering additives (Al2O3 and Y2O3), this dispersing effect is reduced significantly. In this work, a second dispersant, citric acid, was used to resolve this problem. It was found that citric acid could decrease the slurry viscosity (without sintering additives) and enhance the PEI adsorption on SiC particle surface. The optimal amount of citric acid required to achieve a minimum viscosity for 55 vol% SiC suspensions was equal to ∼0.87 wt% (at pH ∼6.8). With the aid of citric acid, well‐stabilized SiC suspensions (containing sintering additives) were realized, which exhibited slight shear thinning rheologies. After tape casting and SPS sintering, dense SiC samples were obtained with a homogeneous fine‐crystalline microstructure. Results showed that citric acid was an effective dispersant for improving the dispersion of SiC particles containing sintering additives.
The Influence of Random Defect Density on the Thermal Stability of Kaolinites
Authors: He Hongping , Yuan Peng , Guo Jiugao , Zhu Jianxi , Hu Cheng
Published: April 2005

The thermal stability of kaolinite and the microstructure of its thermal products strongly depend on random defects (R2) rather than crystalline defects (HI). Kaolinite with a lower random defect density is more stable than that with higher defect density during dehydroxylation and the derived metakaolinite can be directly transformed into orthorhombic mullite (3/2‐mullite). However, for kaolinite with higher random defect density, there is a cubic phase occurring in the transformation from metakaolinite to primary mullite. Primary mullite will be transformed into orthorhombic mullite as temperature increases. AlV is universally present in the metakaolinite and the relative amounts of AlVI, AlV, and AlIV vary with the random defect density of the parent kaolinite.
Formation of Lithium Niobate from Peroxide Aqueous Solution
Authors: Cheng Zhenxiang , Ozawa Kiyoshi , Miyazaki Akimitsu , Kimura Hideo
Published: April 2005

A novel aqueous chemical solution was developed as a precursor both for LiNbO3 powder and thin film. In this method, hydrogen peroxide aqueous solution (H2O2) reacts with niobium and lithium alkoxide ethanol solution to form metal peroxide aqueous solution. From this solution, crystalline LiNbO3 were synthesized at a temperature as low as 350°C. LiNbO3 thin films with well‐developed grains were fabricated by spin‐coating on silicon and sapphire substrates. In comparison with the alkoxide solution method, this peroxide solution method provides significant advantages, such as low weight loss in the sintering process and easy handling.
Fabrication of Patterned Inorganic–Organic Hybrid Film for the Optical Waveguide by Microfluidic Lithography
Authors: Jeong Sunho , Ahn Sung‐Jin , Moon Jooho
Published: April 2005

Inorganic–organic hybrid materials for the optical waveguide were synthesized by the sol–gel process starting from the acid‐catalyzed solutions of phenyltrimethoxysilane, methyltriethoxysilane, and tetraethylorthosilicate. The control of the refractive index in the organically modified silicate films was achieved by varying the content of phenyltrimethoxysilane incorporated as a refractive index modifier. A single spin‐coating with the precursor solution produced a crack‐free buffer layer of 22‐μm thickness with a dense microstructure. For the fabrication of the patterned guiding layer on top of the buffer layer, the microfluidic lithography method was used. The patterned microlines of the linewidth of 20–35 μm with a sharp edge definition could form by filling the precursor solutions into the microchannels associated with the polydimethylsiloxane microfluidic device. The patterned guiding layer was optically transparent as similar as the bare quartz glass at the wavelength above 500 nm and had a low propagation loss of 0.77 dB/cm at 1310 nm.
High‐Temperature Oxidation at 1500° and 1600°C of SiC/Graphite Coated with Sol–Gel‐Derived HfO2
Authors: Shimada Shiro , Aketo Takeshi
Published: April 2005

Oxidation of SiC compositionally graded (SCGed) graphite coated with HfO2 derived from HfCl4 by a sol–gel process was performed at 1500° and 1600°C in a flowing gas mixture of Ar and O2 (80/20 kPa). SCGed graphite was produced by reaction of graphite with either molten Si or SiO gas at 1450°C. The sol–gel‐derived HfO2 precursor was deposited on SCGed graphite by a dip‐coating method. Isothermal and cyclic oxidation of uncoated‐ and HfO2‐coated SCGed graphite was studied by monitoring overall weight change using an electro‐microbalance. Scanning electron microscopy with energy‐dispersive X‐ray analysis was used to observe the surfaces and cross‐sections of the oxidized HfO2‐coated SCGed graphite. The formation of HfSiO4 was confirmed on the outer layer of the oxidized sample, beneath which a thin silica layer was formed. The improved oxidation resistance of SCGed graphite by coating with HfO2 is discussed on the basis of the formation of these two layers.
Effective Viscosity of Suspensions of Spheres
Authors: Hsueh Chun‐Hway , Becher Paul F.
Published: April 2005

Modeling the effective viscosity of suspensions of spheres beyond the dilute limit is a difficult problem that has challenged researchers for nearly a century since Einstein derived an equation for dilute suspensions. Hydrodynamics modeling requires complex mathematical treatments of integral equations describing interactions between spheres, and its solutions have been limited to semidilute dispersion of monosized hard spheres. Mechanics modeling treats suspensions in a statistical sense and generally provides upper and lower bounds solutions for polydispersed suspensions. A closed‐form solution for the effective viscosity of concentrated suspensions of monosized spheres using both the elastic‐viscous analogy and the analogy between the effective dielectric constant of a polarizable medium and the effective viscosity of two‐phase flow is derived in the present study. Existing measurements and numerical simulations support present analytical results. A closed‐form solution for polydispersed suspensions using a differential model is also derived, and the results are within existing bounds solutions.
Electrical Conductivity of the Manganese Chromite Spinel Solid Solution
Authors: Lu Zigui , Zhu Jiahong , Andrew Payzant E. , Paranthaman Mariappan P.
Published: April 2005

Spinel phase based on Mn1+xCr2−xO4 (0≤x≤1) was synthesized and characterized. The lattice parameter of the spinel was found to increase with increasing Mn content up to x=0.7. At x>0.7, the cubic spinel changed to tetragonal because of Jahn–Teller distortion. The electrical conductivity of the spinel also increased with increasing Mn content. Electrical conduction in this phase was likely through a small polaron hopping mechanism. The spinel phase showed similar electrical conductivity in both oxidizing and reducing environments expected in a solid oxide fuel cell operation.
A Practical Model for the Interactions Between Hydrating Portland Cements and Poly‐β‐Naphthalene Sulfonate Condensate Superplasticizers
Authors: Nakajima Yutaka , Goto Takaharu , Yamada Kazuo
Published: April 2005

The performance of poly‐β‐naphthalene sulfonate condensate superplasticizer (BNS) as a dispersant for cement in concrete is affected severely by slight differences in the characteristics of the cement. In order to be able to predict these effects, a model for estimating the fluidity of cement paste containing BNS is proposed. This model is based on an assumption that the fluidity of cement paste is proportional to the BNS adsorption amount per surface area of hydrated cement (Ad/Hy). BNS is known to show two types of sorption on hydrated cement: one is the bulk absorption into initial hydrates and the other one is the superficial adsorption onto hydrates. Only the superficially adsorbed BNS is expected to work as a dispersant. By assuming a competitive Langmuir‐type adsorption on hydrates between BNS and SO42−, a simple method to estimate Ad/Hy is developed, with the concentrations of BNS and SO42− as the only two independent parameters. The resulting estimates of Ad/Hy show a good correlation with paste flow and its change with elapsed time for a broad range of cements. The SO42− concentration in the aqueous phase of the cement paste just after the beginning of the mixing is known to affect the performance of BNS as a dispersant. By using the proposed model to discriminate between the superficial adsorption and bulk absorption of BNS, this phenomenon is explained quantitatively.
Poly(Vinyl Pyrrolidone), a Dispersant for Non‐Aqueous Processing of Silicon Carbide
Authors: Zhang Jingxian , Jiang Dongliang , Lin Qingling
Published: April 2005

In this paper, poly(vinyl pyrrolidone) (PVP) was selected as a dispersant for preparation of high concentrated silicon carbide (SiC) slurries in an ethanol (EtOH)/methyl ethylene ketone (MEK) solvent system. The interactions between (1) solvent and powders, (2) the solvent and dispersant, and (3) dispersant and powder were characterized in terms of adsorption and viscosity measurement. It was evidenced that the dispersion of SiC slurries was highly dependent on the solvent composition. Well‐stabilized SiC slurries could be obtained using PVP as a dispersant in EtOH/MEK media with the content of EtOH in the 40–50 wt% range. The optimal dosage of PVP as a dispersant was at a PVP/SiC mass ratio of 17 mg/g. Results showed that PVP was an effective dispersant for SiC in EtOH/MEK media.
Thermoplastic Green Machining for the Fabrication of a Piezoelectric Ceramic/Polymer Composite with 2‐2 Connectivity
Authors: Koh Young‐Hag , Yoon Chang‐Bun , Lee Sung‐Mi , Kim Hyoun‐Ee
Published: April 2005

A piezoelectric ceramic/polymer composite with 2‐2 connectivity was fabricated by thermoplastic green machining. A thermoplastic body, consisting of 60 vol% lead zirconate titanate ceramic particles (PZT) and 40 vol% thermoplastic binders, was computer numeric controlled‐machined, creating periodic channels in the green PZT body. Following thermal treatment (binder burnout and sintering), a 25 vol% array of 147 μm thin PZT slabs with an aspect ratio of seven separated by 442 μm channels was fabricated. The channels were infiltrated with epoxy resin, in order to fabricate the PZT/epoxy composite with 2‐2 connectivity. This novel process was evaluated in terms of the machinability and sinterability of the thermoplastic PZT compound. Also, the electromechanical properties of the PZT/epoxy composite were measured.
Cubic Aluminum Nitride Transformed Under Reduced Pressure Using Aerosol Deposition Method
Authors: Iwata Atsushi , Akedo Jun , Lebedev Maxim
Published: April 2005

Higher thermal conductivity is expected for cubic aluminum nitride that is very difficult to make. Thick aluminum nitride films that have mixed crystal structures of rock salt (cubic) and wurtzite are made at room temperature by aerosol deposition method. The maximum micro‐Vickers hardness number is 1200. The primary powder has wurtzite structure, which indicates part of the original crystals is transformed. Only very small crystallites are transformed. The transformation is supposed to occur by shock of the particle impact on the film. The pressure at the impact is estimated to be only 7 GPa.
New Glass–Ceramic Inclusion Pigment
Authors: Bondioli Federica , Manfredini Tiziano , Siligardi Cristina , Ferrari Anna Maria
Published: April 2005

Recently, the traditional ceramic industry has demonstrated increased interest in obtaining inclusion pigments to stabilize unstable chromophores, such as hematite or cadmium sulfoselenide, at firing temperature and in studying the actions of molten glasses. This present work focuses on a new method for synthesizing hematite–zircon inclusion pigments from an unconventional mixture of precursors. For this purpose, a glassy composition that belongs to the LiO2–ZrO2–SiO2 system and that crystallizes into zircon during the calcination step has been chosen.
Superconducting Characteristics of Polycrystalline Magnesium Diboride Ceramics Fabricated by a Spark Plasma Sintering Technique
Authors: Shim Seung Hwan , Shim Kwang Bo , Yoon Jong‐Won
Published: April 2005

Highly densified MgB2 superconductors were successfully fabricated using a spark plasma sintering (SPS) technique, and their superconductivity with respect to microstructural evolution was evaluated. Full densification with final density close to the theoretical density was achieved at a temperature of 1000°C within a total SPS processing time of 40 min. Both an MgB2 specimen sintered at 1000°C for 30 min and one sintered at 1050°C for 10 min exhibited a high critical transition temperature (Tc) similar to that of an MgB2 single crystal (39 K), and a very sharp superconducting transition width (ΔT) less than 0.5 K. In addition, high critical current densities (Jc) of 7.7 × 105 A/cm2 in a field of 0.6 T at 5 K and of 8.3 × 104 A/cm2 in a field of 0.09 T at 35 K were obtained. These excellent superconducting characteristics of the SPS‐processed MgB2 are attributed to uniformly distributed secondary MgO phase nanoparticles and well‐developed dislocations in the microstructure that may act effectively as extrinsic flux pinning sites, resulting in the strong pinning force showing a high Jc of 8.7 × 104 A/cm2 even in the condition of a field of 4 T at 5 K.
High Temperature Nanocomposite Through Engineered Synthesis of Hafnia Nano‐Dispersoids in Hexagonal Mesoporous Silica
Authors: Loureiro Sergio M. , Ramos Michael L. , Manoharan Mohan
Published: April 2005

In this communication, we show a solution‐based synthetic route that yields a dual‐phase SiO2‐based ceramic–ceramic composite capable of retaining nano‐structural features up to very high temperatures. The nanocomposite was produced by self‐assembly of mesoporous silica using a non‐ionic surfactant, and subsequent infiltration of the mesoporosity with a solution containing a high‐temperature metal‐oxide‐based composition (HfO2). The nanocomposite was consolidated and processed up to 1500°C.
Successful treatment of disseminated aspergillosis with the combination of voriconazole, caspofungin, granulocyte transfusions, and surgery followed by allogeneic blood stem cell transplantation in a patient with primary failure of an autologous stem cell graft
Authors: Dinser Robert , Grgic Aleksandar , Kim Yoo‐Jin , Pfreundschuh Michael , Schubert Jörg
Published: April 2005

Abstract:  The treatment of disseminated aspergillus infections in neutropenic patients remains a major challenge in spite of several new antifungal drugs. We report the case of a patient with multiple myeloma in prolonged neutropenia after primary failure of an autologous stem cell graft who developed invasive aspergillosis despite voriconazole monotherapy. He responded to a combination of voriconazole and caspofungin, supported by granulocyte transfusions and surgery. A subsequent allogeneic peripheral blood stem cell transplantation did not lead to recurring aspergillus infection. The patient is well and free of clinical disease with respect to the fungal infection and myeloma more than 18 months after the allogeneic transplantation.
Prenatal diagnosis of recessive congenital methaemoglobinaemia type II: novel mutation in the NADH‐cytochrome b5 reductase gene leading to stop codon read‐through
Authors: Leroux Alena , Leturcq France , Deburgrave Nathalie , Szajnert Marie‐France
Published: April 2005

Abstract:  A case of type II recessive congenital methaemoglobinaemia (RCM) observed in a Lebanese subject with a novel mutation in NADH‐cytochrome b5 reductase gene is described. A homozygous mutation CAC to AA identified at Thr 295 with an out‐of‐frame 1‐bp deletion leads to a frameshift with translational read‐through of the natural stop codon. The molecular mechanism is demonstrated by an in vitro translation study. The model of mutated cytochrome b5 reductase protein possessing 46 additional amino acids was obtained by homology modelling. The mutation causes an alteration of hydrophobicity in the carboxyl‐terminal portion, resulting in the conformation being drastically disturbed by the presence of 46 supplementary amino acids. The identical mutation was found in the heterozygous state in the patient's parents and sister. Identification of this new mutation enabled us to perform the molecular prenatal diagnosis of type II RCM at the DNA level.
Band 3Tambaú: a de novo mutation in the AE1 gene associated with hereditary spherocytosis. Implications for anion exchange and insertion into the red blood cell membrane
Authors: Lima Paulo Roberto Moura , Baratti Mariana Ozello , Lúcia Chiattone Maria , Costa Fernando Ferreira , Saad Sara Teresinha Olalla
Published: April 2005

Abstract:  Hereditary spherocytosis (HS) is attributed to red blood cell membrane protein defects, caused by mutations in ankyrin, spectrin, band 3 and protein 4.2. In this study, the presence of band 3 mutations was investigated in a patient presenting mild HS and band 3 deficiency. Using single strand conformation polymorphism analysis, a shift in exon 16 of the band 3 gene was found. DNA sequencing revealed a point mutation 2102 T>C, changing methionine at position 663 to lysine. The M663K substitution was not found in either the parents or in the siblings, and the restriction fragment length polymorphism analysis of 100 alleles from a random Brazilian population did not reveal this mutation, suggesting that this gene defect is more likely to be a de novo mutation, causing HS. Flow cytometry of eosin‐5‐isothiocyanate (EITC)‐labelled erythrocytes showed, in the patient, 54% of band 3 protein content vs. 78% based on the sodium dodecyl sulphate‐polyacrylamide gel electrophoresis (SDS‐PAGE) analysis, suggesting that flow cytometry is a more sensitive method and may be used as a diagnostic tool in membrane disorders related to band 3 deficiency. The characterisation of novel AE1 mutations is helpful to improve the understanding of the role of band 3 protein in cell physiology.
Comparison of DXA, QCT and trabecular structure in β‐thalassaemia
Authors: Mylona Maria , Leotsinides Michalis , Alexandrides Theodoros , Zoumbos Nikolaos , Dimopoulos Panagiotis A.
Published: April 2005

Abstract:  Osteopathy, as a major feature of homozygous β‐thalassaemia, is a multifactorial disorder, not fully understood. We studied the lumbar vertebrae of 48 patients using Dual‐Energy X‐ray Absorptiometry (DXA) and Quantitative Computed Tomography (QCT), and we focused on structural properties, assessed by High Resolution Computed Tomography (HRCT). Bone Mineral Density (BMD) values were expressed as Z‐scores and the results were correlated. The effect of age, sex, and type of thalassaemia and hormonal factors on BMD was assessed. We estimated, with HRCT, the cortex integrity and the number and thickness of trabeculae; the latter were classified to a three‐grade scale. Our results showed the overall prevalence of osteoporosis to be 44% with DXA and 6% with QCT. Both techniques revealed an inverse correlation between age and BMD, whereas hormonal factors demonstrated associations with QCT and DXA measurements. The correlation coefficient between DXA's BMD and QCT's trabecular BMD was 0.545 (P < 0.001) whereas the corresponding value for Z‐scores was r = 0.491 (P < 0.001). The classification of the patients into normal, osteopenic and osteoporotic categories, using QCT's Z, was in better agreement with the assignment based on trabecular number (K = 0.209, P = 0.053) than the classification using DXA's Z (K = 0.145, P = 0.120). Cortex evaluation by HRCT showed discontinuity in 15 patients. Both methods indicate a progression of osteoporosis with age. Hormonal deficiency is associated with thalassaemic osteoporosis whereas the visual estimation of cortex indicates that Thalassaemia Intermedia (TI) patients could be more affected than Thalassaemia Major (TM). Using the trabecular number as an indicator of osteoporosis, it seems that QCT may evaluate osteopathy better than DXA. Since the former has the ability to measure trabecular and cortical BMD separately, it could give early indication of which changes more rapidly and to what degree.
Methylation status analysis of cell cycle regulatory genes (p16INK4A, p15INK4B, p21Waf1/Cip1, p27Kip1 and p73) in natural killer cell disorders
Authors: Kawamata Norihiko , Inagaki Naoko , Mizumura Sachiko , Sugimoto Kei‐ji , Sakajiri Sakura , Ohyanagi‐Hara Mutsuko , Oshimi Kazuo
Published: April 2005

Abstract:  Natural killer (NK) cell disorders are rare diseases. Genetic abnormalities of the several tumor suppressor genes, including p15INK4B, p16INK4A/p14ARF, p53, p73, and Rb genes have been reported. Deletions and point mutations of these genes are frequently detected in these diseases. It has been reported that tumor suppressor genes are inactivated by DNA methylation of the promoter region and/or first exon of the genes in a variety of human cancers. In this study we analyze the methylation status of the genes associated with cell cycle regulation, including p16INK4A, p15INK4B, p21/Waf1/Cip1, p27/Kip1, p73, and p14ARF, by methylation specific (MS) PCR and/or bisulfite sequencing. We examined 29 cases of NK cell disorders (five aggressive NK cell leukemia/lymphoma, three blastic NK cell lymphoma/leukemia, five nasal NK cell lymphoma, three myeloid/NK cell precursor acute leukemia, 13 chronic NK lymphocytosis). We found methylation of the first exon of the p16INK4A gene in two cases (one aggressive, one blastic), and methylation of the p14ARF gene in one aggressive NK cell leukemia. Bisulfite sequencing revealed that methylation of the p15 and p27 genes was rare in these disorders. MS‐PCR suggested that the p73 and p21 genes were methylated in seven cases, respectively (p73: one blastic, one nasal, five chronic; p21: one myeloid/NK, one aggressive, one nasal, and four chronic); bisulfite sequencing confirmed that methylated alleles of these genes were dominant in the samples except three cases (one myeloid/NK, one aggressive, and one chronic) in which methylated alleles of the p21 genes were less than 34% of all alleles. These results suggested that inactivation of the cell cycle regulatory genes by DNA methylation could be associated with tumorigenesis in NK cell disorders, not only aggressive subtypes but also chronic subtype.
Requirement for Microtubules and Dynein Motors in the Earliest Stages of Peroxisome Biogenesis
Authors: Brocard Cécile B. , Boucher Krissy K. , Jedeszko Christopher , Kim Peter K. , Walton Paul A.
Published: April 2005

Our aim was to determine the role of microtubules in the biogenesis of peroxisomes. Fusion experiments between human PEX16‐ and PEX1‐mutant cells in the presence of nocodazol implied that microtubules were not required for import of proteins into the peroxisomal matrix after cell fusion complementation. We further studied the importance of microtubules in the early stages of peroxisome biogenesis following the microinjection complementation of PEX16‐mutant cells. In the absence of nocodazol, nuclear microinjection of plasmids expressing EGFP‐SKL and Pex16p in PEX16‐mutant cells resulted in the accumulation of EGFP‐SKL into newly formed peroxisomes. However, pretreatment of the cells with nocodazol, prior to microinjection, resulted in the inhibition of complementation of the PEX16 mutant and the cytosolic location of the EGFP‐SKL. In addition, coexpression of a dominant‐negative CC1 subunit of the dynein/dynactin motor complex resulted in the inability to complement PEX16‐mutant cells. Both of these treatments resulted in the cytosolic localization of expressed Pex16p. Our results demonstrate that the formation of peroxisomes via the preperoxisomal compartment is dependent upon microtubules and minus‐end‐directed motor proteins and that the inhibition described above occurs at a step that precedes the association of Pex16p with the vesicles that would otherwise become the peroxisomes.
Direct Observation of Rapid Internalization and Intracellular Transport of Sterol by Macrophage Foam Cells
Authors: Wüstner Daniel , Mondal Mousumi , Tabas Ira , Maxfield Frederick R.
Published: April 2005

Transport of the fluorescent cholesterol analog dehydroergosterol (DHE) from the plasma membrane was studied in J774 macrophages (Mφs) with normal and elevated cholesterol content. Cells were labeled with DHE bound to methyl‐β‐cyclodextrin. In J774, Mφs with normal cholesterol, intracellular DHE became enriched in recycling endosomes, but was not highly concentrated in the trans‐Golgi network or late endosomes and lysosomes. After raising cellular cholesterol by incubation with acetylated low‐density lipoprotein (AcLDL), DHE was transported to lipid droplets, and less sterol was found in recycling endosomes. Transport of DHE to droplets was very rapid (t1/2 = 1.5 min after photobleaching) and did not require metabolic energy. In cholesterol‐loaded J774 Mφs, the initial fraction of DHE in the plasma membrane was reduced, and rapid DHE efflux from the plasma membrane to intracellular organelles was observed. This rapid sterol transport was not related to plasma membrane vesiculation, as DHE did not become enriched in endocytic vesicles formed after sphingomyelinase C treatment of cells. When cells were incubated with DHE ester incorporated into AcLDL, fluorescence of the sterol was first found in punctate endosomes. After a chase, this DHE colocalized with transferrin in a distribution similar to cells labeled with DHE delivered by methyl‐β‐cyclodextrin. Our results indicate that elevation of sterol levels in Mφs enhances transport of sterol from the plasma membrane by a non‐vesicular pathway.
Intermediate Filaments and Vesicular Membrane Traffic: The Odd Couple's First Dance?
Authors: Styers Melanie L. , Kowalczyk Andrew P. , Faundez Victor
Published: April 2005

During the last two decades, much attention has been focused on the regulation of membrane traffic by the actin and microtubule cytoskeletal networks. Their dynamic and polarized behavior and associated motors provide a logical framework from which architectural and movement cues can be communicated to organelles. The study of these cytoskeletal systems has been greatly aided by pharmacological agents. In contrast, intermediate filaments (IFs) have largely been neglected as a potential player in membrane traffic, both because a comprehensive pharmacology to perturb them does not exist and because they lack the intrinsic polarity and specific motors that make the other cytoskeletal systems attractive. In this review, we will discuss evidence suggesting that IFs may play roles in controlling organelle positioning and in membrane protein targeting. Furthermore, we will discuss potential mechanisms by which IFs may regulate the localization and function of organelles.
Translocation Through the Nuclear Pore Complex: Selectivity and Speed by Reduction‐of‐Dimensionality
Authors: Peters Reiner
Published: April 2005

Translocation through the nuclear pore complex (NPC), a large transporter spanning the nuclear envelope, is a passive, diffusion‐driven process, paradoxically enhanced by binding. To account for this mystery, several models have been suggested. However, recent experiments with modified NPCs make reconsideration necessary. Here, we suggest that nuclear transport receptors (NTRs) such as the karyopherins, in accordance with their peculiar boat‐like structure, act as nanoscopic ferries transporting cargos through the NPC by sliding on a surface of phenylalanine glycine (FG) motifs. The dense array of FG motifs that covers the cytoplasmic filaments of the NPC is thought to continue on the wall of the large channel permeating the central framework of the NPC and on parts of the nuclear filaments to yield a coherent FG surface. Nuclear transport receptors are assumed to bind to the FG surface at filaments or at the channel entrance and then to rapidly search the FG surface by a two‐dimensional random walk for the channel exit where they are released. The passage of neutral molecules is restricted to a narrow tube in the center of the central channel by a loose network of peptide chains. The model features virtual gating, is compatible with but not dependent on FG affinity gradients and tolerates deletions and transpositions of FG motifs. Implications of the model are discussed and tests are suggested.