bluuebunny/crossref_metadata_2025 huggingface dataset:
High‐Temperature Immittance Response in Anatase‐Based Sensor Materials
Authors: Azad Abdul M. , Akbar Sheikh A. , Younkman Lora B. , Alim Mohammad A.
Published: March 2005

The ac small‐signal electrical response of anatase‐based sensors is examined at elevated temperatures (400°C T 900°C) via lumped parameter/complex plane analysis (LP/CPA). The ac data, monitored in the frequency range 5 Hz f 13 MHz, are used to establish the role of microstructures on the resulting electrical behavior in these polycrystalline materials. Two semicircular relaxations, observed in the impedance plane, are attributed to the low‐frequency related grain boundary and high‐frequency related grain response. The grain‐boundary response is difficult to quantify at elevated temperatures via LP/CPA and dc measurements. The electrical path homogeneity is examined via the presence of the depression angle which remained nearly invariant in the range of measurement temperatures. These features are discussed and compared with the results obtained at room temperature.
Effect of Particle Size on the Room‐Temperature Crystal Structure of Barium Titanate
Authors: Begg Bruce D. , Vance Eric R. , Nowotny Janusz
Published: March 2005

The room‐temperature tetragonal‐to‐cubic transformation in BaTiO3 powders with decreasing particle size has been carefully studied, using materials prepared mainly by hydrothermal methods. Hydrothermal BaTiO3 powders exhibited a more uniform particle size distribution than oxalate‐route powders, with X‐ray diffraction and electron microscopy indicating that powders 0.19 μm in size were fully cubic while powders 0.27 μ were completely tetragonal (within a 5% detection limit for cubic material) at room temperature. The tetragonal‐to‐cubic transformation temperature was also found to lie in the range of 121°± 3°C for BaTiO3 powders with room‐temperature (c/a) values > 1.008. No transformation could be detected using differential scanning calorimetry for BaTiO3 particles with a (c/a) > 1.008 at room temperature. BaTiO3 powder with a particle size just too small (0.19 μm) to be tetragonal at room temperature remained cubic down to 80 K. Different models for the cubic‐to‐tetragonal room‐temperature transformation are discussed. Hydroxyl ions do not appear to greatly affect the cubic‐to‐tetragonal transformation, which appears to be essentially dependent on particle size. It is concluded that a model based on surface free energy, as previously discussed for the monoclinic‐to‐tetragonal transformation at room temperature of fine ZrO2 particles, is consistent with the experimental data.
Thermodynamics and Kinetics of Surface Area Changes of Faceted Particles
Authors: Searcy Alan W. , Bullard Jeffrey W.
Published: March 2005

An equation is derived that describes the influence of particle size and shape on the free energies of particles of anisotropic specific surface free energies. When the specific surface free energy is isotropic, the general equation reduces directly to the Gibbs–Thomson equation for the chemical potential of spherical drops and predicts the accepted driving force for neck growth between two spherical particles. The general equation is also used to obtain equations for the chemical potentials of particles of non‐equilibrium shapes and to derive alternate rate equations for different possible rate‐controlling steps of mass transport when faceted {100} ridge/channel arrays etched into a {100} single‐crystal surface decrease in depth to reduce the surface free energy. Edge free energies are suggested to sometimes play important roles in determining the sequence of shape changes that occur when particles of non‐equilibrium shapes are annealed.
Electron Channeling Pattern of Ceramic Platelets
Authors: Pezzotti Giuseppe , Aoyagi Eiji , Suzuki Toshiko , Sakai Mototsugu
Published: March 2005

Electron channeling patterns (ECPs) have been generated in the scanning electron microscope from hexagonal‐close‐packed ceramic (tungsten carbide and silicon carbide) single crystals extracted from commercially available powders. The crystals, commonly employed as reinforcing phases in ceramic composites, were typically platelet‐shaped with smooth surfaces. Their average diameter was 25 μm with a thickness ranging between 3 and 7 μm. After theoretical maps for the selected crystallographic poles were constructed with a procedure similar to that used for convergent beam electron diffraction, the experimental patterns were indexed and the crystallographic orientation of the crystals was determined. Specific applications for ceramic materials are discussed in comparison with previous work dealing with metals and, as an example of the application of the ECP method, the cleavage plane of fracture has been determined for the SiC platelet embedded in a Si3N4 matrix.
Effect of Processing Parameters on Phase and Microstructure Evolution in RBAO Ceramics
Authors: Holz Dietmar , Wu Suxing , Scheppokat Sven , Claussen Nils
Published: March 2005

Important parameters controlling the reaction‐bonding of Al2O3 (RBAO) process are Al content, particle size, and green density. Successful fabrication of high‐strength bodies requires fine and homogeneous powders. Low milling intensity does not lead to the required particle fineness, whereas overmilling causes extensive oxidation and hydrolyzation of Al. Oxidation of Al during milling is enhanced by ZrO2 additions. As much of the Al should be oxidized by solid/gas reaction as possible. Milled RBAO precursor powder contains physically‐adsorbed and chemically‐bonded (aluminum hydroxide) water. Decomposition of chemically‐bonded water promotes cracking in the temperature range 450–550°C. Bloating of RBAO occurs when the surface region becomes dense before complete decomposition of aluminum hydroxide in the interior of the body.
Ultrasonic Characterization of Oxidation Mechanisms in Nicalon/C/SiC Composites
Authors: Huger Marc , Fargeot Dominique , Gault Christian
Published: March 2005

The nonbrittle fracture of composites consisting of ex polycarbosilane SiC (Nicalon) fibers in a SiC matrix prepared by chemical vapor infiltration is strongly dependent on the presence of a pyrocarbon layer at the fiber/matrix interface (Nicalon/C/SiC composites). The mechanical properties of such materials are known to be influenced by oxidation reactions. Elastic modulus measurements, using ultrasonic wave propagation in the “long bar” mode, have been used to show the influence of the environmental parameters temperature, atmosphere, and pressure on the mechanical behavior of bidirectional Nicalon/C/SiC. In situ, measurements of elastic modulus performed in parallel with thermogravimetric analysis allow examination of oxidation mechanisms which affect interfacial properties. Results showed the modulus to be affected by two interfacial oxidation mechanisms: (1) oxidation of pyrocarbon coating and (2) closure of the resulting interphase gap by silica formation.
Fracture Strength–Fracture Resistance Response and Damage Resistance of Sintered Al2O3–ZrO2 (12 mol% CeO2) Composites
Authors: Becher Paul F. , Warwick Wilbur H.
Published: March 2005

The fracture strengths of sintered Al2O3 containing 20 and 40 vol% ZrO2(12 mol% CeO2)—zirconia‐toughened alumina (ZTA)—composites along with the fracture resistance can be increased (e.g., to ∼900 MPa and >12 Mpa·m1/2, respectively), by increasing the mean grain size of the t‐ZrO2 (and the Al2O3) from ∼0.5 μm to ∼3 μm. At these lower t‐ZrO2 contents, the fracture strength‐fracture resistance curves show a continuous rise as opposed to the strength maxima observed in polycrystalline t‐ZrO2(12 mol% CeO2), CeTZP, and ZrO2(12 mol% CeO2) ceramics containing ≤20 vol% Al2O3. The toughened composites also exhibit excellent damage resistance with fracture strengths of 500 MPa retained with surfaces containing ∼150‐N Vickers indentations which produce cracks of ∼160‐μm radius. Greater damage resistance correlates with an increase in the apparent R‐curve response of these composites.
Electronic and Ionic Trapping at Domain Walls in BaTiO3
Authors: Warren William L , Dimos Duane , Tuttle Bruce A. , Smyth Donald M.
Published: March 2005

We have coupled electron paramagnetic resonance (EPR) and polarization–voltage measurements to understand the effects of reducing ambients on the remanent polarization and density of paramagnetic centers in BaTiO3, single crystals. Two types of reducing ambients were explored; one was done under vacuum (slightly reducing) and the second was performed in forming gas (very reducing). It is found that the vacuum anneal caused a reduction in the remanent polarization and a concomitant decrease in the isolated Fe3+ EPR resonance. The Fe3+–Vo complex EPR signal was relatively unaffected by this vacuum anneal. By injecting charge using an ultraviolet (UV) light and an applied bias combination, the polarization and the isolated Fe3+ signal intensity were restored, thereby suggesting that the suppression of the remanent polarization is due to trapping of electronic charge at the domain walls. For the forming gas anneal, we observe a much larger decrease in remanent polarization with an accompanying decrease in both the isolated Fe3+ and Fe3+–Vo complex EPR signals. For this anneal, charge injection by the UV light/bias combination did not restore the polarization nor the EPR densities. The remanent polarization, the isolated Fe3+, and the Fe3+–VoVo complex could be restored only by a reoxidizing anneal, suggesting that ionic defects {oxygen vacancies) are now responsible for pinning the domain walls. Collectively, these results suggest reducing anneals can suppress the amount of switchable polarization in BaTiO3 by either electronic or ionic trapping mechanisms.
Properties of BaO–R2O3– Ga2O3–GeO2 (R = Y, Al, La, and Gd) Glasses
Authors: Jewell John M. , Higby Paige L. , Aggarwal Ishwar D.
Published: March 2005

Barium gallogermanate glasses were prepared with substitutions of Al2O3, Y2O3, La2O3, and Gd2O3 for Ga2O3. The effects of these substitutions on the glass transformation temperature, viscosity, thermal expansion, and molar volume have been determined. The changes in properties associated with each substitutional ion are consistent with structural roles reported for these ions in other glasses. Aluminum acts as an intermediate with [AlO4–] tetrahedra substituting directly for [GaO4–] tetrahedra. Yttrium and gadolinium act as “atypical” modifier ions because of their large field strengths. Finally, the properties of the La2O3‐substituted glasses indicate a possible dual structural role for La3+ ions in these glasses.
A Novel Reaction Path to BaTiO3 by the Oxidation of a Solid Metallic Precursor
Authors: Schmutzler Hans J. , Antony Michael M. , Sandhage Kenneth H.
Published: March 2005

Multilayer capacitors with thin, dielectric BaTiO3 layers can possess a relatively high capacitance per unit volume. A solid metallic precursor method has recently been developed for preparing thin BaTiO3/noble metal laminates. In the present paper, the phase and microstructural evolution of Ba‐Ti metallic precursors were examined after oxidation at 300° to 900°C in pure oxygen at 1 atm pressure. Barium peroxide, BaO2, formed rapidly during oxidation at 300°C, with titanium largely remaining as unoxidized particles in the peroxide matrix. Between 375° and 500°C, the solidstate reaction of barium peroxide with metallic titanium yielded barium orthotitanate, Ba2TiO4. Further exposure to temperatures between 500° and 900°C resulted in the oxidation of residual metallic titanium. The oxidized titanium then reacted with the orthotitanate matrix to form barium metatitanate, BaTiO3. The rate of formation of BaTiO3 was found to be strongly dependent on the degree of milling of the Ba‐Ti precursors and on the heating rate between 300° and 500°C.
29Si NMR Spectroscopy of Silicate Anions in Hydrothermally Formed C‐S‐H
Authors: Okada Yoshihiko , Ishida Hideki , Mitsuda Takeshi
Published: March 2005

Hydrothermal treatment of lime–silica mixtures under saturated steam pressures below 200°C usually gives C‐S‐H as an initial product, which reacts further to give crystalline calcium silicate hydrates. In this paper, C‐S‐H was hydro–thermally prepared using CaO and silicic acid at Ca/Si ratios of 0.3 to 2.0 and 120° to 180°C for 2 h. The C‐S‐H was examined mainly using 29Si NMR by the magic angle spinning gate proton decoupling and cross polarization magic angle spinning methods. XRD for all of the C‐S‐H showed bands at 0.304, 0.280, 0.183, and 0.166 nm. NMR results showed that all of the C‐S‐H contained single chains of silicate anion, which became progressively longer as the Ca/Si ratio decreased, i.e., as the system became richer in silica. This was independent of the preparation temperature. The 0.8 ratio preparations at 180°C contained small amounts of double‐chain structure of 1.1‐nm tobermorite. The reaction processing in the lime‐ silicic acid mixtures is also discussed.
Lead Oxide Coatings on Sol–Gel‐Derived Lead Lanthanum Zirconium Titanate Thin Layers for Enhanced Crystallization into the Perovskite Structure
Authors: Tani Toshihiko , Payne David A.
Published: March 2005

An improved method is described for the sol–gel preparation of PLZT thin layers in the perovskite structure. The method uses a PbO cover coat. Details are reported for the sol‐gel processing route and heat‐treatment conditions. Through use of this method it is possible to prepare singlephase perovskite material with improved properties. The deleterious effect of additional phases—which are not present when a PbO cover coat is used—is attributed to Pb loss from the surface during thermal processing. Examples are given for PLZT thin layers integrated on Si with and without a PbO cover coat. The dielectric and ferroelectric properties were always found to be superior for coated structures.
Evolution of Microstructure and V‐Shaped Positive Temperature Coefficient of Resistivity of (Pb0.6Sr0.4)TiO3 Materials
Authors: Lee Chengkuo , Lin I‐Nan , Hu Chen‐Ti
Published: March 2005

The effects of various liquid‐phase sintering aids on (Pb0.6SrO0.4)TiO3 ceramics have been investigated. The relationships between electrical properties and microstructures have been scrutinized. It has been found that, among the sintering aids studied, only SiO2 exhibits a significant effect on the grain growth of (Pb0.6SrO4)TiO3. The optimum firing profiles for sound microstructure and good electrical properties of (Pb0.6SrO0.4)TiO3+ 5.0 mol% SiO2 have been established. The V‐shaped electrical behavior is prominent, and a PTCR jump of about 102.9 is observed. The formation of cation vacancies may increase the resistivity of the over‐fired specimens. Various milling methods to pulverize the calcined powder and the optimum amount of packing protection powder during sintering are also discussed.
Analytical Modeling of the Propagation of a Thermal Reaction Front in Condensed Systems
Authors: Lakshmikantha Medamaranahally , Sekhar Jainagesh Akkaraju
Published: March 2005

An improved analytical model for combustion synthesis has been developed. The features of the model include consideration of the thermophysical and chemical properties of both the reactants and products, as well as considerations of porosity for both reactants and products. An analysis of the variation of the dimensionless velocity with the variation of dimensionless thermal conductivity, density, and heat capacity is carried out. The equations for the combustion temperature and combustion velocity with the inclusion of nonreacting diluents and different thermophysical and chemical properties of the reactants and products is also developed. An equation for the velocity as a function of the nonmelting reactant radius and the different thermophysical and chemical properties of the reactants and products is derived using a diffusion kinetic equation. Master plots for general solid–solid reaction systems, which relate dimensionless velocity, thermal conductivity, density, and heat capacity, are presented. Application of this model to the combustion synthesis of TiC has been carried out to study the variation of combustion front motion with the radius of carbon particles. A comparison of velocities for NiAl predicted by the model as a function of the reactant porosity is presented and compared with the experimentally determined value. The comparison is noted to be close except when the thin zone approximation is no longer valid.
High‐Resolution Transmission Electron Microscopy Studies of a Near Σ11 Grain Boundary in α‐Alumina
Authors: Höche Thomas , Kenway Philip R. , Kleebe Hans‐Joachim , Rühle Manfred , Morris Patricia A.
Published: March 2005

The atomistic structure of a near Σ11 (N211) grain boundary in ultrapure α‐AI2O3 bicrystals was determined by quantitative high‐resolution transmission electron microscopy (HRTEM). High‐resolution imaging revealed an atomically sharp interface with a characteristic periodic pattern at (0111) ‖ (0111) facets. The pattern was analyzed by comparing the HRTEM micrographs with simulated images of different structures that had been relaxed by static‐lattice calculations. The best agreement with experiment was reached for the grain boundary structure with the lowest energy (1.7 J·m−2). Although this structure reproduces the relative translation state of the adjacent crystals to within 0.02 nm, the calculated structure was not in complete agreement with the periodic pattern at the grain boundary. The origin of this difference is probably due to a slight misalignment of the two crystals adjacent to the boundary.
Effect of Notch‐Root Radius on the Fracture Toughness of a Fine‐Grained Alumina
Authors: Nishida Toshihiko , Hanaki Yoshikazu , Pezzotti Giuseppe
Published: March 2005

The dependence of KIc on the notch‐root radius has been examined for a notch radius as small as a few micrometers in a dense, fine‐grained, polycrystalline alumina ceramic. The notch radius can be systematically varied by using a semimanual procedure in a special jig which polishes out rather than cuts the specimen. KIc is independent of the notch sharpness for notch‐root radii < 10 μm. The results are critically compared with those obtained by other standard techniques and discussed in terms of residual compressive stresses introduced during the notching procedure.
Plasma‐Sprayed Lead Zirconate Titanate‐Glass Composites
Authors: Sherrit Stewart , Savin Chris R. , Wiederick Harvey D. , Mukherjee Binu K. , Prasad S. Eswar
Published: March 2005

A plasma‐spray process was used to produce piezoelectric lead zirconate titanate (PZT)‐glass composite thick films. The films were found to have the same crystal structure as the PZT (Navy‐type V) and lead‐based glass starting powder mixture. The films showed good adhesion to stainless steel and silver‐coated glass slides and poor adhesion to aluminum substrates. The dielectric constant of the films varied between 58 and 20 with dissipations between 0.019 and 0.032. The films were poled, and their piezoelectric charge coefficient, d33, was 1.1 pC/N.
Processing and Microstructure Development in Alumina–Silicon Carbide Intragranular Particulate Composites
Authors: Piciacchio Alan , Lee Sang‐Ho , Messing Gary L.
Published: March 2005

Al2O3–SiC particulate composites were fabricated by hot‐pressing mixtures of 5–30 vol% SiC with either α‐Al2O3, γ‐Al2O3, or boehmite (γ‐AlOOH) to determine whether grain growth or the α‐alumina phase transformation could be used to fabricate intragranular particulate composites. Samples starting with α‐alumina resulted in primarily intergranular SiC of 0.3 μ and an alumina grain size of 1.5–4.1 μm. Heat treatments resulted in SiC coarsening but no entrapment of SiC by grain boundary breakaway. The α‐alumina transformation in the samples starting with γ‐alumina resulted in the entrapment of ∼48% of the 5 vol% of SiC added whereas 79% of the SiC was entrapped in the α‐alumina grains in samples starting with boehmite. Only SiC particles ≤0.2 SmUm were entrapped in the α‐alumina grains during the phase transformation. With increasing SiC content, the relative volume of intragranular SiC decreased, but the amount of intragranular SiC was constant and independent of the amount of SiC added before transformation. The formation of intragranular composites from γ‐alumina and boehmite samples was explained with a model that attributes particle entrapment to the vermicular growth of α‐alumina into the transition alumina matrix during the α‐alumina phase transformation. Seeding the boehmite‐based samples did not affect the concentration of entrapped SiC, but did lower the hot‐pressing densification temperature by as much as 150°C.
Electrochemical Liquid Deposition of Ceria
Authors: Tanner Cameron W. , Virkar Anil V.
Published: March 2005

Electrochemical liquid deposition (ELD) has been used to grow fully dense films of ceria on impervious gadolinia‐doped ceria substrates of variable thickness. The process is similar to electrochemical vapor deposition (EVD) except that a liquid is used instead of a vapor to provide precursor material to the growing film. ELD film growth data have been analyzed in a manner similar to that for EVD demonstrated previously. Experimental results verify that the pertinent rate equation is obeyed phenomenologically. Rate constants for the film (CeO2) and the substrate (l‐l‐mol%‐Gd2O3‐doped CeO2) at 1200°C have been determined as Kf= 33.1 × 10−12 m2/s and Ks= 51.6 × 10−12 m2/s, respectively.
Effects of Melt Composition on the Growth Behavior of 211 Particles in the Y‐Ba‐Cu‐O Systein
Authors: Lee Hee‐Gyoun , Lim Dae‐Ho , Song Myoung‐Youp , Park Jong‐Hyun , Won Dong‐Yeon , Hong Gye‐Won
Published: March 2005

Growth behavior of 211 particles in the Y‐Ba‐Cu‐O system was investigated using CuO and CuO + BaCuO melts. The inhibiting effect of Sn on the growth of 211 particles was not as great for the specimen heat‐treated using CuO + BaCuO melts. Fast growth of 211 particles was observed in the CuO melt at high temperature (1100°C), whereas the growth of 211 particles was extraordinally suppressed by the addition of Sn to the CuO melt. It is believed that Sn Is an effective element for the refinement of 211 particles in the Y‐Ba‐Cu‐O system but that additional Ba nullifies the refinement effect of the Sn.
Effect of Antimony Addition on Electrical and Optical Properties of Tin Oxide Film
Authors: Kim Kwang Ho , Lee Soo Won , Shin Dong Won , Park Chan Gyung
Published: March 2005

Antimony‐doped tin oxide films were prepared on Corning glass substrate by chemical vapor deposition from a gas mixture of SnCl4–SbCl5–H2O. The electrical conductivity and optical transmission of tin oxide films were studied with antimony doping. The film conductivity increased largely without losing optical transparency with a small addition of antimony. The increase of the conductivity was attributed mainly to more electrons donated by pentavalent Sb ions in the SnO2 lattice. Large additions of antimony, however, diminished the conductivity, optical transparency, and crystallinity of the film. The diminution was found to be caused by fine Sb2O5 phases codeposited with SnO2.
Novel Equipment for the Study of the Compaction of Fine Powders
Authors: Chen Wei , Pechenik Alexander , Dapkunas Stanley J. , Piermarini Gasper J. , Malghan Subhas G.
Published: March 2005

This paper describes a highly specialized system for studies of time‐dependent compaction of nano‐size and other fine‐size powders under a variety of atmospheres and at temperatures ranging from 77 to 1000 K. The system incorporates a 10 000 kg screw‐driven press with a piston–cylinder type of die and can produce cylindrical powder compacts, 3mm in diameter and of various thicknesses, utilizing pressures up to 3 GPa. The system is computer‐controlled and permits measurements of the sample volume with an uncertainty of 0.07 mm3 and, after appropriate calibration, can determine the rate and degree of densification of the compacting powder as pressure is applied. To illustrate its capabilities, the system was used to study the densification of several powders, including nano‐size γ‐Al2O3, submicrometer 95%α‐Si3N4, RbBr, and KC1. The results obtained on RbBr and KC1, used for calibration and testing of the equipment, are in good agreement with previously published data for these materials.
Strength versus Gauge Length in Ceramic‐Matrix Composites
Authors: Curtin William A.
Published: March 2005

The strength of ceramic‐matrix composites as a function of sample gauge length is derived as a function of the composite constituent material properties. Within the context of a global load‐sharing assumption for how load is transferred from broken to unbroken fibers, the analysis shows that, for samples shorter than 0.8δc (where δc is the characteristic‐slip length determining composite pullout), the composite ultimate strength increases with decreasing gauge length. For samples longer than 0.8δc, the strength is independent of gauge length. Implications of these results on the performance of composites with small‐scale stress concentrators is briefly discussed.
In Situ Fiber Strengths in Ceramic‐Matrix Composites from Fracture Mirrors
Authors: Curtin William A.
Published: March 2005

The in situ breaking stresses of pulled‐out fibers on the fracture surface of a fiber‐reinforced composite can be determined ex post facto from a measurement of the fracture mirrors on the surfaces of the fibers. Here, the relationship between the resultant distribution of breaking stresses and the true in situ fiber strength distribution, as characterized by a Weibull modulus m and characteristic strength óc, is derived for composites that fail after the first matrix crack has propagated. Specifically, it is demonstrated thai, if the true in situ parameters are m and σc >, then the distribution of breaking stresses is well approximated by a Weibull form with apparent Weibull modulus m* and apparent characteristic strength S*. The relationships between m* and m, and S* and σc, are presented, and these results allow for the conversion of fracture mirror data, or any fracto‐graphic determination of fiber strength, to the true strength parameters necessary for predicting/interpreting composite performance.
Preparation and Optical Nonlinear Property of Sol–Gel‐Derived Cu─SiO2 Thin Films
Authors: Kundu Debtosh , Honma Itaru , Osawa Toshio , Komiyama Hiroshi
Published: March 2005

Cu‐metal‐doped glass films having a Cu:Si atomic ratio of 0.05 ± 0.002 were successfully prepared by a sol‐gel method using a dipping technique. The appearance of surface plasmon of Cu metal at about 570 nm was observed after heat treatment at or above 700°C. The third‐order nonlinear susceptibility (x3) was as high as 5.0 × 10–8 esu at 570 nm.
Analysis of internal deletions within the BCL6 gene in B‐cell non‐Hodgkin's lymphoma
Authors: Nakamura Yuichi , Saito Kenji , Furusawa Shinpei
Published: March 2005

The BCL6 gene is frequently altered by chromosomal translocations and/or point mutations at its 5′ non‐coding portion in B‐cell non‐Hodgkin's lymphoma (B‐NHL). We analysed submicroscopic structural alterations of the BCL6 gene which had arisen from internal deletion in four cases with B‐NHL and found that these deletions overlapped at the 280 bp region in the first intron. In electrophoretic mobility shift assay, nuclear extracts prepared from various cell lines were shown to bind to a fragment from this commonly deleted region. Our results suggest that deregulation of BCL6 expression would be caused by loss of this putative protein‐binding sequence in some B‐NHL cases.
Acquired APC resistance and oral contraceptives: differences between two functional tests
Authors: Curvers Joyce , Thomassen M. Christella L. G. D. , Nicolaes Gerry A. F. , Van Oerle Rene , Hamulyak Karly , Coenraad HEMKER H. , Tans Guido , Rosing Jan
Published: March 2005

Resistance to activated protein C (APC) is often associated with a mutation in factor V (factor VLeiden). Individuals without factor VLeiden who exhibit a response in functional APC‐resistance tests similar to that of carriers of factor VLeiden are considered to be acquired APC resistant. This phenomenon is particularly observed in women using oral contraceptives (OC).

In the present study we compared the response to APC in plasma from normal individuals, carriers of factor VLeiden and women who use OC using functional tests that either quantify the effect of APC on the endogenous thrombin potential (ETP) or on the activated partial thromboplastin time (aPTT).

Both tests discriminated equally well between individuals with and without factor VLeiden who were not using OC. In contrast to the aPTT‐based test, the ETP‐based assay yielded significant differences in sensitivity to APC between non‐OC users and OC users and between users of second and third generation OC. Since there was no correlation between APC‐sensitivity determined with both assays in non‐carriers of factor VLeiden and in women who use OC and a poor correlation in carriers of factor VLeiden, we propose that other plasma components differentially modulate the response to APC in the aPTT‐ and ETP‐based APC‐resistance tests and that OC change the level of plasma protein(s) that modulate the effect of APC on thrombin formation initiated via the extrinsic coagulation pathway.
Activated T‐lymphocytes with myelosuppressive properties in patients with chronic idiopathic neutropenia
Authors: Papadaki H. A. , Stamatopoulos K. , Damianaki A. , Gemetzi C. , Anagnostopoulos A. , Papadaki T. , Eliopoulos A. G. , Eliopoulos G. D.
Published: March 2005

To characterize the cellular components responsible for the impaired granulopoiesis in chronic idiopathic neutropenia (CIN), we investigated the origin of the proapoptotic cytokine producing cells in the bone marrow (BM) microenvironment of CIN patients. We found that the interferon gamma (IFNγ) and/or Fas‐ligand expressing cells in patient BM mononuclear cells and long‐term BM culture stroma cells were the CD3+ T‐lymphocytes but not the CD14+ monocytes/macrophages. The percentage of activated T‐lymphocytes was increased in patients’ BM as indicated by the proportions of human leucocyte antigen (HLA)‐DR+, CD25+, CD38+, CD69+ and Fas+ cells within the CD3+ fraction. Intracellular IFNγ expression was higher in the BM than peripheral blood of the patients and was associated with increased BM T‐lymphocyte numbers. In crossover experiments, patient CD3+ T‐lymphocytes conferred autologous and allogeneic haemopoietic progenitor cell colony inhibition. Patients’ T‐cell receptor repertoire and polymerase chain reaction analysis did not reveal any clonal T‐lymphocyte expansion, suggesting the absence of a direct, antigen‐driven recognition of CD34+ myeloid progenitor cells by patient T‐lymphocytes. We conclude that CIN patients have increased number of activated T‐lymphocytes in the BM, probably in the setting of a localized polyclonal immune reaction and that these cells confer an inhibitory effect on myelopoiesis through myelosuppressive cytokines including Fas‐ligand and IFNγ.
Overexpression of the Doppel protein in acute myeloid leukaemias and myelodysplastic syndromes
Authors: Travaglino Erica , Comincini Sergio , Benatti Chiara , Azzalin Alberto , Nano Rosanna , Rosti Vittorio , Ferretti Luca , Invernizzi Rosangela
Published: March 2005

We investigated the expression patterns and distribution of Doppel (Dpl), the product of the prion‐like gene PRND, in the leukaemic cell lines HL‐60 and K562 and in bone marrow cells from 44 patients with acute myeloid leukaemia (AML) and 63 patients with myelodysplastic syndrome (MDS). Whereas normal samples were negative or showed very weak expression that was restricted to CD34+ cells, Dpl was detected in both cell lines and in most AML and MDS cases by immunocytochemistry and Western blotting. Quantitative reverse transcription polymerase chain reaction revealed variable mRNA levels in almost all AML and MDS cases, but barely detectable levels in normal bone marrow. These differences were confirmed by in situ hybridization. PRND expression was higher in advanced compared with early MDS (P = 0·01), but Dpl levels did not predict disease progression. In AML there was no correlation between Dpl levels and clinical or laboratory findings. In conclusion, this is the first time that the expression of PRND has been demonstrated in human bone marrow. The molecular mechanism of the observed overexpression is unknown; however, the differential Dpl distribution in AML and MDS versus healthy subjects makes it a possible leukaemia‐associated antigen that could be useful for diagnostic and therapeutic purposes.
Importance of the River Teviot to Atlantic salmon, Salmo salar, rod catches in the River Tweed, Scotland
Authors: HEDDELL‐COWIE M.
Published: March 2005

Abstract  The body mass distributions and variations in abundance of the spring and autumn catches of Atlantic salmon, Salmo salar L., were compared between fisheries above and below the confluence of the rivers Tweed and Teviot, Scotland. Significant differences between the distributions were found over three periods, one in spring and two in autumn, when salmon catches were high. Correlations were found between abundance trends for periods when distributions were similar or dissimilar. Abundance of salmon returning to the River Teviot was proportional to the main river. However, its population structure differed when abundances were high, suggesting different survival strategies. It appears that changes in the numbers returning to the river were resultant of changes in the marine rather than freshwater environment.
Prevalence and impact of oral pain in 8‐year‐old children in Sri Lanka
Authors: RATNAYAKE N. , EKANAYAKE L.
Published: March 2005

Objective.  The present study aimed to determine the prevalence and impact of oral pain in 8‐year‐old Sri Lankan children and their parents.

Design.  A cross‐sectional study using a multistage cluster sampling technique was carried out in a sample of 614 children attending schools in the Education Division of Badulla, Uva province, Sri Lanka. Data were collected by means of a pre‐tested questionnaire that was sent to each of the children and their parents. The children were also given an oral examination. Of the 614 questionnaires which were sent to parents, 30 were not returned and eight had to be excluded from the analysis because the respondents had answered only two questions. Therefore, the present analysis is limited to data from 576 children and their parents.

Results.  The lifetime prevalences of oral pain, as reported by the children and parents, were 49% and 53%, respectively. According to the children's report, 25% had experienced oral pain in the past 2 months while 31% of the parents reported that their child had experienced oral pain within the same period. Of those children who reported that they had experienced oral pain in the past 2 months, nearly 45% stated that the pain was severe. In 48%, the pain was triggered when biting. ‘Presence of cavity/decayed tooth’ was cited as the most common cause of oral pain (67%). Overall, 74% of children had experienced a negative impact as a result of the pain whilst 66% of the parents said that the child's pain had had an impact on them. Ethnic group, parental income and level of education, and the caries experience of the child were significantly associated with the reporting of oral pain in the past 2 months.

Conclusions.  The prevalence of oral pain was high among these children, and had a considerable impact on both the children and their parents.
Molluscum contagiosum in Greek children: a case series
Authors: Kakourou Talia , Zachariades Asimina , Anastasiou Tasos , Architectonidou Eleni , Georgala Sofia , Theodoridou Maria
Published: March 2005

Background  Epidemiological studies of molluscum contagiosum (MC) in children are limited.

Patients and method  Between 1997 and 1999, 110 children with MC (60 boys, 50 girls, mean age: 4.8 years) were studied. Treatment consisted of removal of all MC lesions in a single session by sterilized tweezers.

Results  In children aged ≤ 2 years, the MC lesions were located mainly on the face, whereas in older children they were located on the trunk. Twenty children had atopic dermatitis (18.2% vs. 5% of Greek children aged 1–6 years; P < 0.001). Four children had numerous and recurrent MC lesions without any other systemic manifestations. In these children, humoral and cellular immunities were found to be normal. Seventy‐seven children (70%) were cured after one treatment session, 22 children (20%) after a second session and 11 (10%) after ≥ three sessions. No patients experienced secondary bacterial infection or scarring.

Conclusions  In contrast to cool climates where the age of peak incidence of MC in children is 10–12 years, in a warm country such as Greece, it is at the younger age of 4.8 years. In young children aged 2 years, the MC lesions are located mainly on the face, whereas in older children they are located on the trunk. Atopic dermatitis is a predisposing factor for MC. In cases where MC lesions are numerous and/or persist but there are no other signs of systemic infections, the possibility of immunodeficiency is minimal. Removal of MC lesions by tweezers is an efficient, simple and inexpensive method of treatment without sequelae.
De novo design of a pentameric coiled‐coil: decoding the motif for tetramer versus pentamer formation in water‐soluble phospholamban*
Authors: Slovic A.M. , Lear J.D. , DeGrado W.F.
Published: March 2005

Abstract:  Water‐soluble phospholamban (WSPLB) is a designed, water‐soluble analogue of the pentameric membrane protein phospholamban (PLB), which contains the same core and interhelical residues as PLB, with only the solvent‐exposed positions mutated. WSPLB contains the same secondary and quaternary structure as PLB. The hydrophobic cores of PLB and WSPLB contain Leu and Ile at the a‐ and d‐positions of a heptad repeat (abcdefg) from residues 31–52, while residues 21–30 are rich in polar amino acids at these positions. While the full‐length WSPLB forms pentamers in solution, truncated peptides lacking residues 21–30 are largely tetrameric. Thus, truncation of residues 1–20 promotes a switch from pentamer to tetramer formation. Here, the motifs for WSPLB pentamerization were elucidated by characterizing a series of peptides, which were progressively truncated in this polar ‘switch’ region. When fully present, the ‘switch’ region promotes pentamer formation in WSPLB, by destabilizing a more stable tetrameric species which exists in its absence. We find that the burial of hydrogen bonding residues from 21 to 30 drives WSPLB from a tetramer to a pentamer, with direct implications for coiled‐coil design.
Improve Board Effectiveness: the Need for Incentives
Authors: Shen Wei
Published: March 2005

Roberts, McNulty and Stiles (2005) focus on the attitudes and behaviours of non‐executive directors in their recommendations for improving board effectiveness. This paper addresses the importance of providing incentives for non‐executives in order to improve board effectiveness. It first points out that the current norms and practices in corporate governance suggest that, without strong incentives, non‐executive directors are unlikely to become engaged in corporate governance, to challenge executive decision, and to remain independent of executive influences. It then proposes that, for non‐executive directors to develop the attitudes and behaviors recommended by Roberts, McNulty and Stiles, it is important to require them own a significant amount of company stocks over a long period of time. It also addresses some concerns regarding the use of stock ownership to improve the effectiveness of non‐executive directors in corporate governance.
The Political Significance of the George W. Bush Administration
Authors: Aberbach Joel D.
Published: March 2005

This article argues that the George W. Bush administration is an important milestone in evolving notions about governance and policy that are increasingly identified with the Republican Party in the United States. Joining ideas about the power of the president that received their major impetus in the Nixon administration (especially the “administrative presidency”) and policy ideas developed by neoconservatives, the Bush administration has implemented an agenda with important consequences for social policy and for the role of government in general. A series of policy examples, including Medicare drug prescription benefits, education, and what is known as the “faith‐based initiative,” demonstrate the active role government has played under Bush and the techniques his administration has used to get what it wants.
Making It Happen: The Case for Compromise in the Federal Cocaine Law Debate
Authors: Sabet Kevin A.
Published: March 2005

The US has taken an active role in formulating drugs policy for over a century, and thus much debate on how best to control drug use occurs in that country. Though most Americans support keeping drugs illegal, voices for changing the specifics of how prohibition is administered have grown louder and more effective in the past ten years—witness the recent success on the state and local level for rolling back restrictions on medical cannabis or punitive state mandatory minimum penalties (i.e. Rockefeller drug laws). Expectedly, these successful reforms have happened with the support of voters in those particular states and localities where reforms have been introduced. On the federal level, the accusation of racism has become a familiar cry among anti‐prohibitionists, who argue that cocaine laws, in particular, disproportionately affect African‐Americans and contribute to racial division. The federal government makes a great distinction in sentencing between powder cocaine, usually snorted, and crack cocaine, which is smoked. A person caught in possession of five grams of crack gets an automatic mandatory minimum sentence of five years in prison. Possessing cocaine in its powder form does not carry a mandatory minimum. Additionally, these laws are the target of much debate because, for trafficking in the drug, it takes 100 times more powder cocaine than crack to trigger the same mandatory minimum penalty (the so‐called “100 to 1 quantity ratio”). I will argue that repealing the mandatory minimum sentence for crack is both justified based on the evidence and politically viable. Although the number of people affected by this law every year is minuscule, African‐Americans are undoubtedly disproportionately affected by the penalty. Eliminating the provision should not be expected to have a deleterious effect on crime or drug control efforts, and would instead have a positive effect in reinvigorating faith in the criminal justice system and in promoting positive race relations. Very importantly, it is a politically realistic reform for making prohibition work better. Erasing or dramatically changing the more controversial 100 to 1 quantity ratio—though affecting far more people than the mandatory minimum for crack possession—may or may not justify itself based on the evidence. Nonetheless, it is certainly not a politically realistic option for lawmakers.
Fluctuation Tests for a Change in Persistence*
Authors: Taylor A. M. Robert
Published: March 2005

In this paper, we develop a set of new persistence change tests which are similar in spirit to those of Kim [Journal of Econometrics (2000) Vol. 95, pp. 97–116], Kim et al. [Journal of Econometrics (2002) Vol. 109, pp. 389–392] and Busetti and Taylor [Journal of Econometrics (2004) Vol. 123, pp. 33–66]. While the exisiting tests are based on ratios of sub‐sample Kwiatkowski et al. [Journal of Econometrics (1992) Vol. 54, pp. 158–179]‐type statistics, our proposed tests are based on the corresponding functions of sub‐sample implementations of the well‐known maximal recursive‐estimates and re‐scaled range fluctuation statistics. Our statistics are used to test the null hypothesis that a time series displays constant trend stationarity [I(0)] behaviour against the alternative of a change in persistence either from trend stationarity to difference stationarity [I(1)], or vice versa. Representations for the limiting null distributions of the new statistics are derived and both finite‐sample and asymptotic critical values are provided. The consistency of the tests against persistence change processes is also demonstrated. Numerical evidence suggests that our proposed tests provide a useful complement to the extant persistence change tests. An application of the tests to US inflation rate data is provided.
OFFICIAL FOREIGN EXCHANGE INTERVENTION AS A COORDINATING SIGNAL IN THE DOLLAR–YEN MARKET
Authors: Taylor Mark P.
Published: March 2005

Abstract.  I examine the effectiveness of exchange rate intervention within the context of a Markov‐switching model for the real dollar–yen exchange rate over the period April 1991–December 2003. The probability of switching between stable and unstable regimes depends nonlinearly upon the amount of intervention, the degree of misalignment and the duration of the regime. I find that intervention increases the probability of stability when the rate is misaligned, and that its influence grows with the degree of misalignment. However, intervention within a small neighbourhood of equilibrium will result in a greater probability of instability.
Mitochondrial DNA depletion in liver tissue of patients infected with hepatitis C virus: contributing effect of HIV infection?
Authors: Bäuerle J , Laguno M , Mauss S , Mallolas J , Murillas J , Miquel R , Schmutz G , Setzer B , Gatell JM , Walker UA
Published: March 2005

Objectives

It has been suggested that chronic hepatitis C virus (HCV) infection depletes mitochondrial DNA (mtDNA) in the liver. Because decreased mtDNA levels were also found in humans infected with HIV, we investigated whether HIV may have aggravated hepatic mtDNA depletion in individuals with HCV infection.

Methods

In this cross‐sectional study, liver biopsies were performed in a total of 40 individuals prior to any antiviral therapy. The individuals were recruited from the Hospital Cliníc, Barcelona and the HIV Centre, Düsseldorf. Seventeen patients were negative for HIV and HCV and were biopsied for liver enzyme elevation of unknown cause (controls), 14 individuals had chronic HCV but no HIV infection, and nine subjects were coinfected with both viruses. mtDNA and liver histology were centrally assessed.

Results

The groups did not differ with respect to age, gender, liver function tests and HCV viral load, where applicable. mtDNA levels were decreased by 19% in the HCV‐monoinfected group (P=0.03) and by 27% in the HIV/HCV‐coinfected subjects (P=0.02) compared to controls. The mtDNA content, however, did not differ between individuals with HCV monoinfection and HCV/HIV coinfection (P=0.75). The degrees of liver fibrosis, inflammatory activity or steatosis did not correlate with mtDNA content.

Conclusions

Liver mtDNA content is reduced in both HCV‐monoinfected and HIV/HCV‐coinfected patients. Under the limitations of our study, we could demonstrate only a slight trend towards more pronounced mtDNA depletion in HIV/HCV‐coinfected subjects.