bluuebunny/crossref_metadata_2025 huggingface dataset:
Sinterability of β‐Calcium Orthophosphate Powder Prepared by Spray‐Pyrolysis
Authors: Itatani Kiyoshi , Nishioka Toshio , Seike Satoru , Howell F. Scott , Kishioka Akira , Kinoshita Makio
Published: March 2005

Mixed solutions of Ca(NO3)2 and (NH4)2HPO4 with Ca/P = 1.50 were spray‐pyrolyzed at 600°C to produce β‐calcium orthophosphate (β‐Ca3(PO4)2) powder; the spray‐pyrolyzed powder was ground and then calcined at 600°C for 1 h. The best crystalline β‐Ca3(PO4)2 powder was obtained from the solution with 1.80 mol.L–1 Ca(NO3)2, 1.20 mol.L–1 (NH4)2HPO4. The resulting powder was composed of primary particles with sizes of <0.5 μm. Dense β‐Ca3(PO4)2 ceramics with a relative density of 96.1% could be fabricated by firing this compressed powder at 1070°C for 5 h.
Evolution of Interfacial Microstructure between Barium Titanate and Binary Glasses
Authors: Kuromitsu Yoshirou , Wang Sea Fue , Yoshikawa Shoko , Newnham Robert E.
Published: March 2005

Evolution of interfacial microstructure between BaTiO3 and the binary glasses used as frits in thick‐film technology has been studied. Possible reaction mechanisms for the interfacial compounds have been determined by comparing the results of the sintering study with the reaction of BaTiO3, powder with glass powders. The interfacial microstructure can be divided into two types. The first type of interfacial microstructure is observed for glasses rich in PbO or Bi2O3 network modifiers and is characterized by the penetration of glass into the BaTiO3 grain boundaries, accompanied by incorporation of Pb into the perovskite lattice. The second type of interfacial microstructure is observed for glasses rich in B2O3 or SiO2 network formers and is characterized by the formation of interfacial compounds.
Interfacial Microstructure and Chemistry of SiC/BN Dual‐Coated Nicalon‐Fiber‐Reinforced Glass‐Ceramic Matrix Composites
Authors: Sun Ellen Y. , Nutt Steven R. , Brennan John J.
Published: March 2005

Glass‐ceramic composites with improved high‐temperature mechanical properties have been produced by incorporating continuous SiC fibers into a barium magnesium aluminosilicate matrix. Control of the fiber/matrix interface was achieved by a dual‐layer coating of SiC/BN(C) applied to the fibers by CVD. The weakly bonded interface resulted in composites with high fracture toughness and strength up to 1100°C, and the composite system was oxidatively stable during long‐term exposure to air at high temperatures. Composites with different thermal and mechanical histories were studied, and interfaces were characterized using transmission electron microscopy (TEM), Auger electron spectroscopy, and fiber pushout tests. Observations of interfacial microstructure were correlated with the mechanical properties of the composite and with interface properties determined from fiber push‐out tests.
Rapid Process for Manufacturing Aluminum Nitride Powder
Authors: Weimer Alan W. , Cochran Gene A. , Eisman Glenn A. , Henley John P. , Hook Bruce D. , Mills Lynne K. , Guiton Theresa A. , Knudsen Arne K. , Nicholas Nicholas R. , Volmering James E. , Moore William G.
Published: March 2005

A rapid, direct nitridation process for the manufacture of sinterable aluminum nitride (A1N) powder was developed at the pilot scale. Atomized aluminum metal and nitrogen gas were heated and reacted rapidly to synthesize A1N while they passed through the reaction zone of a transport flow reactor. The heated walls of the reactor simultaneously initiated the reaction and removed the generated heat to control the exotherm. Several variations of the process were required to achieve high conversion and reduce wall deposition of the product. The fine A1N powder produced did not require a postreaction grinding step to reduce particle size. However, a secondary heat treatment, following a mild milling step to expose fresh surface, was necessary to ensure complete conversion of the aluminum. In some instances, a final air classification step to remove large particles was necessary to promote densification by pressureless sintering. The A1N powder produced was pressureless sintered with 3 wt% yttria to fabricate fully dense parts which exhibited high thermal conductivity. The powder was shown to be less sinterable than commercially available car‐bothermally produced powders.
Crack Shielding in Ce‐TZP/Al2O3 Composites: Comparison of Fatigue and Sustained Load Crack Growth Specimens
Authors: Tsai Jing‐Fong , Belnap J. Daniel , Shetty Dinesh K.
Published: March 2005

Crack shielding stress intensities in in situ loaded compact tension specimens of two types of ceria‐partially‐stabilized zirconia/alumina (Ce‐TZP/Al2O3) composites with prior histories of subcritical crack growth in sustained and tension‐tension fatigue loading were directly assessed using laser Raman spectroscopy. Crack‐tip stress fields within the transformation zones were measured by measuring a stress‐induced frequency shift of a peak corresponding to the tetragonal phase. The peak shift as a function of the applied stress was separately calibrated using a ball‐on‐ring flexure test. Total crack shielding stress intensity was estimated from the far‐field applied stress intensity and the local crack‐tip stress intensity assessed from the measured near‐crack‐tip stresses. The shielding stress intensities were consistently lower in the fatigue specimens than in the sustained load crack growth specimens. The reduced crack shielding developed in the fatigue specimens was independently confirmed by measurements of larger crack‐opening displacement under far‐field applied load as compared to the sustained load crack growth specimens. Thus, diminished crack shielding was a major factor contributing to the higher subcritical crack growth rates exhibited by the Ce‐TZP/Al2O3 composites in tension–tension cyclic fatigue. Calculations of zone shielding considering only the dilatational strains in the transformation zones accounted for 81% and 86% of the measured values in the sustained load crack growth specimens, but significantly overestimated the shielding in the fatigue specimens. Possible reasons for the diminished crack shielding in the fatigue specimens are discussed.
Bend Strength versus Tensile Strength of Fiber‐Reinforced Ceramics
Authors: Steif Paul S. , Trojnacki Andrzej
Published: March 2005

The bending strength of fiber‐reinforced glasses and ceramics is often observed to be higher than their tensile strength; the difference varies, however, from one material to another. To gain an understanding of the relationship between these two measure of strength, we have carried out an analysis of bending which accounts for the deviations from linearity that occur on the tensile side of the beam. The results of this analysis indicate that the strength ratio (bending strength/tensile strength) depends most sensitively on the rate at which the stress drops after the ultimate tensile strength. In particular, composites failing gracefully (with a gradual decay in stress) tend to have comparatively higher strengths in bending. A method of inferring the: tensile strength from simply the load‐deflection curve in bending is proposed. In addition, by accounting for the weakness in interlaminar shear, we can predict the variation in bend strength with beam aspect ratio. The various theories are compared with experimental data.
Critical Appraisal of Limiting Strain Rates for Compression Testing of Ceramics in a Split Hopkinson Pressure Bar
Authors: Ravichandran Guruswami , Subhash Ghatuparthi
Published: March 2005

The split Hopkinson pressure bar (SHPB) is being widely used to determine the dynamic compressive strength of ceramics and ceramic composites. However, extreme caution needs to be exercised while testing these highstrength ceramics at high strain rates. The highest strain rate at which ceramics can be tested using an SHPB without violating the underlying assumptions is found to be in the range of 2500–3000/s. It is also shown that at very high loading rates, dispersion in the transmitted pulse can lead to discrepancies in measuring the dynamic failure strength of ceramics.
Wetting and Joining of Mullite Ceramics by Active‐Metal Braze Alloys
Authors: Loehman Ronald E. , Tomsia Antoni P.
Published: March 2005

Mullite and ZrO2‐toughened mullite (ZTM) were joined with Ag─Cu eutectic braze alloys that contain Ti or Zr as active elements. Although neither the alloy compositions nor the processing conditions were optimized, four‐point bend strengths of joined bars were as high as 108 MPa. Joining reactions were studied by conducting separate sessile drop experiments with molten Ti─Ag─Cu and Zr─Ag─Cu alloys on mullite for times and temperatures that were similar those used for joining. Detailed compositional and microstructural analyses of those metal–ceramic interfaces revealed a complex reaction zone in which the oxide of the active element was a principal reaction product. Compared with the Ti‐containing alloys, those with Zr were more refractory, they were less reactive with the mullite, and the Zr did not segregate as completely to the interface during heating.
Piezospectroscopic Determination of Residual Stresses in Polycrystalline Alumina
Authors: Ma Qing , Clarke David R.
Published: March 2005

The residual stresses created in polycrystalline aluminum oxide as a result of its constrained anisotropic thermal contraction are measured with the technique of piezospectroscopy using the fluorescence from trace Cr3+impurities. The average residual stresses in the crystallographic a and c directions are determined as a function of grain size for a high‐purity alumina, as is the width of the stress distribution (assuming it to be Gaussian). Over the range of grain sizes investigated, from 2 to 16 μm, the residual stresses exhibit a dependence on grain size consistent with the prediction of the Evans‐Clarke model of thermal stress relaxation by grain boundary diffusion.
α‐Al2O3 (0001) Surfaces: Atomic and Electronic Structure
Authors: Gautier Martine , Fenaud Gilles , Pham Van Laurent , Villette Bruno , Pollak Maud , Thromat Nathalie , Jollet François , Duraud Jean‐Paul
Published: March 2005

New results on the R± 9° reconstructed α‐Al2O3 (0001) surface, which can be obtained after heating at high temperature (1400°C) under vacuum, are presented. The atomic structure has been studied by combining low‐energy electron diffractometry and grazing incidence X‐ray scattering. The surface structure is found to be perfectly commensurable with the underlying bulk lattice. The surface consists of hexagonal zones of two, nearly perfect, close‐packed Al (111) planes separated by a defect of hexagonal periodicity with a parameter of 26.44 Å. This model is consistent with previous surface studies of this reconstruction. The electronic structure has been investigated using valence band photoemission spectroscopy, X‐ray absorption spectroscopy at the O K edge, electron energy loss spectroscopy, and X‐ray‐induced Auger electron spectroscopy. Interpretation of these experimental data in the frame of a self‐consistent, tight‐binding calculation leads to the conclusion that the
R± 9° reconstructed surface is more covalent than the (1 × 1) surface. Significant changes in the; Al‐O hybridizations are observed; these are likely due to a difference in the interatomic distances along the [0001] axis (relaxations). The increase of covalent character is mainly due to a strong decrease of the Madelung field on the reconstructed surface.
Structure and Energetics of Alumina Surfaces Calculated from First Principles
Authors: Manassidis Ioannis , Gillan Michael J.
Published: March 2005

First‐principles calculations based on density–functional theory and pseudopotentials are used to calculate the energies and relaxed structures of five low‐index surfaces of α‐alumina. Evidence for the reliability of the theoretical methods is provided by calculations of the lattice parameters and internal coordinates of the perfect crystal, which agree very closely with experimental data. It is shown that, for some of the surfaces, relaxation effects reduce the surface energy by over a factor of two and lead to major changes of surface structure, with particularly large effects being found for the (0001) and (1010) surfaces. Results are also presented for the distribution of valence electron charge in the surface region. These results suggest that α‐alumina is highly ionic even for ions at the surface.
In Situ‐Toughened Silicon Carbide
Authors: Padture Nitin P.
Published: March 2005

A new processing strategy based on atmospheric pressure sintering is presented for obtaining dense SiC‐based materials with microstructures consisting of (i) uniformly distributed elongate‐shaped α‐SiC grains and (ii) relatively high amounts (20 vol%) of second‐phase yttrium aluminum garnet (YAG). This strategy entails the sintering of β‐SiC powder doped with α‐SiC, Al2O3, and Y2O3. The Al2O3 and Y2O3 aid in the liquid‐phase sintering of SiC and form in situ YAG, which has a significant thermal expansion mismatch with SiC. During a subsequent grain‐growth heat treatment, it is postulated that the α‐SiC “seeds” assist in controlling in situ growth of the elongated α‐SiC grains. The fracture pattern in the in situ‐toughened SiC is intergranular with evidence of copious crack‐wake bridging, akin to toughened Si3N4 ceramics. The elongate nature of the α‐SiC grains, together with the high thermal‐residual stresses in the microstructure, enhance the observed crack‐wake bridging. This bridging accounts for a measured twofold increase in the indentation toughness of this new class of in situ‐toughened SiC relative to a commercial SiC.
Equilibrium‐State Density Profiles of Centrifuged Cakes
Authors: Shih Wei‐Heng , Shih Wan Y. , Kim Seong‐Il , Aksay Ilhan A.
Published: March 2005

We have examined the equilibrium‐state density profiles of centrifuged cakes both theoretically and experimentally. The theoretical density profiles were obtained by implementing the experimental pressure‐density relationship into the general differential equation for centrifugation with appropriate boundary conditions. With a power‐law pressure‐density relationship, P =βφn, we show that

where φmax is the density at the bottom of the cake, z the distance measured from the bottom of the cake, and zm the distance at which the cake density vanishes. Experimentally, the density profiles were examined with γ‐ray densitometry. The predicted density profiles are in good agreement with the experimental ones. We also show that the form
applies to sedimentation cakes as well, provided the pressure‐density relationship of sedimentation cakes is also a power‐law one.
Relationship between Fracture. Toughness and Phase Assemblage in Mg‐PSZ
Authors: Hannink Richard H. J. , Howard Christopher J. , Kisi Erich H. , Swain Michael V.
Published: March 2005

The phase content, size, and distribution have a marked effect on the thermomechanical properties of a 9 mol% MgO‐ZrO2(Mg‐PSZ) alloy. The work undertaken in this study is the first investigation to simultaneously measure and characterize the quantitative bulk phase contents and correlate these parameters to the fracture toughness andR‐curve behavior of a variously aged Mg‐PSZ alloy. Quantitative bulk phase characterization entailed a systematic evaluation using neutron diffraction. In addition, microscopy techniques were used to determine the phase distribution and assemblage. The results indicate that the maximum toughness is attained, for a constant tetragonal precipitate size, when the anion‐ordered δ‐phase (Mg2Zr5O12) replaces a major portion of the cubic matrix phase after and 1100°C aging treatment. The shape of theR‐curve and the stress required to transform the tetragonal precipitates are also significantly influenced by the δ‐pnase content.
Thermal Conductivity of a Particulate‐Diamond‐Reinforced Cordierite Matrix Composite
Authors: Hasselman D. P. H. , Donaldson Kimberly Y. , Liu Jeng , Gauckler Ludwig J. , Ownby P. Darrell
Published: March 2005

The effect of 15 vol% particulate diamond reinforcement on the thermal conductivity of a cordierite matrix was studied as a function of diamond particle size from room temperature to 700°C. The thermal conductivity was found to increase with increasing particle size to a maximum increase of about 75% for a mean particle size of 50 μ. The particle size effect was found to be more pronounced at the lower temperatures than at the higher temperatures. The observed effect of particle size and temperature was attributed to the existence of an interfacial thermal barrier, possibly resulting from interfacial phonon scattering, with a positive temperature dependence of the interfacial thermal conductance. The magnitude of this conductance suggested strong adhesion between the diamond and cordierite.
Effect of Carboxylic Acid Adsorption on the Hydrolysis and Sintered Properties of Aluminum Nitride Powder
Authors: Egashira Makoto , ShImizu Yasuhiro , Takao Yuji , Yamaguchi Ryoji , Ishikawa Yasuhiro
Published: March 2005

To suppress the reactivity of ALN powder with water, chemical surface modification with carboxylic acids has been investigated. It was found that the chemical stability of ALN powder increased as the number of carbon atoms in carboxylic acids used for the surface treatment increased. Among the carboxylic acids tested, stearic acid was the most promising from the viewpoint of the chemical stability of the treated powder and the thermal conductivity of the sintered ceramics prepared by cold isostatic pressing and pres‐sureless sintering.
Direct Observation of Preceramic and Organic Binder Decomposition in 2‐D Model Microstructures
Authors: Lewis Jennifer A. , Cima Michael J. , Rhine Wendell E.
Published: March 2005

Preceramic and organic binder decomposition processes were studied during thermolysis to determine how the physico‐chemical properties of the binder affected the microstructural development of the ceramic component. Specifically, the behavior of two organic polymers, poly(methyl methacrylate) (PMMA) and a cross‐linked poly(methyl methacrylate) (x‐PMMA), and two preceramic polymers, polycarbosilane (PCS) and vinylic polysilane (VPS) was observed as a function of temperature. Binder‐filled two‐dimensional (2‐D) model microstructures were fabricated to simulate ceramic green bodies whose pores were completely filled with binder. Examination of these 2‐D samples by hot‐stage optical microscopy enabled direct observations of pore development and changes in polymer morphology during binder thermolysis. These observations revealed that the mass transport processes involved during thermolysis as well as the developing microstructural features, depend on the properties of the binder system during thermal decomposition. The organic polymers were investigated because of their chemical similarity and markedly different physical behavior upon heating. It was shown that thermoplastic polymers (e.g., PMMA) are influenced by capillary forces during thermolysis, while thermosetting polymers (e.g., x‐PMMA) do not flow within these porous microstructures. Both of the preceramic polymers displayed a range of physical behavior over the temperatures Studied. The decomposition chemistry and weight loss at a given temperature combined with the associated physical behavior had a dramatic effect on the final distribution of the pyrolyzed product (amorphous silicon carbide and glassy carbon) formed during thermolysis. The pyrolysis product formed from PCS was observed to segregate to the smaller pore channels in the 2‐D microstructures, while the pyrolysis product formed from VPS was observed to be homogeneously distributed in these model microstructures. This work offers guidelines to improve the microstructural homogeneity of ceramic–ceramic composites derived from particulate–preceramic polymer green bodies.
Fatigue of Thick Thermal Barrier Coatings
Authors: Wesling Kevin F. , Socie Darrell F. , Beardsley Brad
Published: March 2005

Thick thermal barrier coatings (TTBCs) of plasma‐sprayed 8% Y2O3–ZrO2 were fatigued in compression as part of a reliability and durability study to evaluate their potential use in high‐performance diesel engines. Test specimens were designed to test the bulk ceramic uniaxialiy, independent of the substrate. A test machine was designed to alleviate the mechanical gripping and alignment difficulties associated with cyclically stressing brittle ceramics in compression. Higher fatigue limits, 375 vs 200 MPa, were observed at 800°C than at room temperature. Specimens tested at room temperature after high‐temperature com‐pressive cycling also had higher fatigue limits, indicating that the strengthening was permanent. At temperatures of 800°C, the coatings showed evidence of low‐temperature, pressure‐induced sintering. The extent to which sintering occurred was determined by studying the change in the elastic modulus as a result of the application of varying temperatures and static stresses.
Electrophoretic Deposition Forming of SiC‐TZP Composites in a Nonaqueous Sol Media
Authors: Zhang Zongtao , Huang Yong , Jiang Zuozhao
Published: March 2005

Electrophoretic deposition (ED) was used to form uniform–structure green bodies with a thickness of about 3 mm of SiC whisker–tetragonal zirconia polycrystals (TZP) mixtures. A kinetic model for ED is presented. The model predicts the decrease of the forming rate as an exponential function of time. Diagrams of colloidal groups and electrochemical reactions of charged solid particles on the deposited electrode are proposed. The effects of applied electric field, viscosity, dielectric constant, amount of suspending agent, and zeta potential of the solid particles in Al(OC3H7)3–C3H7OH–CH3OH sol on ED processing are discussed.
Effects of Transition‐Metal Additions on the Properties of AlN
Authors: Kasori Mitsuo , Ueno Fumio , Tsuge Akihiko
Published: March 2005

Transition‐metal oxide additions to AlN ceramics produced no significant deterioration in thermal conductivity. In the present study, TiN, ZrN, TaC, NbC, W, and unidentified Hf phases, found as fine particles located inter‐ and intragranularly, were distributed randomly in the AlN. Phases containing Fe, Co, and Cr, on the contrary, always were located at the three grain points. Most of the added transition‐metal compounds turned the ceramics black or gray. The shading mechanism was attributed to optical absorption by the surfaces of the electrically conductive fine particles and to multiple reflections among these particles.
Nucleation and Growth of Diamond Films on Ni‐Cemented Tungsten Carbide: Effects of Substrate Pretreatments
Authors: Polini Riccardo , Marcheselli Giancarlo , Traversa Enrico
Published: March 2005

The nucleation and growth of diamond films on Nicemented carbide is investigated. Substrates made of WC with 6 wt% of Ni were submitted to grinding, and then to different pretreatments (scratching, etching, and/or decarburization) before diamond deposition. Diamond synthesis was carried out by hot‐filament chemical vapor deposition (HFCVD) using a mixture of CH4 (1% v/v) and H2. Depositions were performed for different lengths of time with the substrates at various temperatures. The specimens were analyzed before and after deposition by scanning electron microscopy (SEM), energy‐dispersive spectroscopy (EDS), and X‐ray diffractometry (XRD). Raman spectra showed that the phase purity of the diamond films was not affected by the presence of nickel on the substrate surface. After wet etching pretreatments, the nucleation of diamond was enhanced, mainly at the WC grain boundaries. Continuous films were obtained on scratched and etched substrates. The decarburizing treatment led to the formation of metallic tungsten and of brittle nicke–tungsten carbide phases. These phases reacted in the early stages of diamond film formation with gaseous carbon species with a parallel process which competes with stable diamond nucleus formation. The diamond film formed after long‐term deposition on these samples was not continuous.
Kinetics and Mechanisms of Oxidation of 2D Woven C/SiC Composites: II, Theoretical Approach
Authors: Lamouroux Franck , Naslain Roger , Jouin Jean‐Marie
Published: March 2005

A model for the oxidation kinetics of SiC‐coated 2D C/SiC composites is developed on the basis of mechanisms derived from TGA data (between 700° and 1500°C in dry oxygen or air, P= 100 kPa). Carbon/oxygen reaction, gas phase diffusion through microcracks present in the external SiC coating, and silica growth are the main phenomena taken into account in the modeling. A morphological characterization of the microcracks network based on a compression test and SEM observations has been developed. The differential equations of the model are solved according to an iterative procedure. The mass variations of the composite during an oxidation test, as derived from the model, are in good agreement with the experimental data. The model is then used to predict the oxidation rate variations when (i) the oxygen partial pressure is decreased, and (ii) the state of damage of the external SiC coating is increased by mechanical loading.
Groove Angles and Surface Mass Transport in Polycrystalline Alumina
Authors: Tsoga Anna , Nikolopoulos Panagiotis
Published: March 2005

Grain‐boundary grooving was studied on polished surfaces of polycrystalline alumina, after annealing, in air, under vacuum, and in argon atmospheres in the temperature range 1273 to 1736 K. The groove angles, measured by optical interferometry, showed no significant change with experimental conditions, giving a mean value of 138.57°± 0.08° and a ratio of the grain‐boundary energy to surface energy of 0.707 ± 0.001. From the experiments it was determined that surface diffusion was the dominant mechanism for the mass transport. The surface diffusion coefficient, Ds(cm2/s) = 0.48 exp(−256(kJ/mol)/RT), was practically independent of the furnace atmosphere, and, in the low‐temperature region examined, depended on the structural damage in the near‐surface region which occurred during mechanical polishing.
Development of Short‐Range Repulsive Potentials in Aqueous, Silicon Nitride Slurries
Authors: Luther Erik P. , Kramer Thomas M. , Lange Fred F. , Pearson Dale S.
Published: March 2005

The properties of aqueous, dispersed, silicon nitride slurries, with an isoelectric point of pH 5.5, can be changed with additions of NH4CI. At pH 10 the effect of adding NH4Cl is similar to that suggested by DLVO theory; namely, for concentrations .0.5M, the viscosity vs shear rate behavior, the elastic modulus, and the relative packing density are identical to those for slurries prepared at the isoelectric point. On the other hand, the effect of salt on dispersed slurries prepared at pH 2 differs from the behavior implied by classic DLVO theory; i.e., measurement of the same properties showed that the attractive interparticle potential was much weaker relative to that produced at the isoelectric point. As previously reported for alumina slurries, the results suggest that a short‐range, repulsive interparticle potential is developed in salt‐added slurries prepared at pH 2 which prevents attractive particles in the slurry from touching and aids particle packing. The same short‐range potential apparently is not developed with salt additions at pH 10. The difference between silicon nitride and alumina slurries is apparent when the slurries are consolidated. Bodies consolidated from any silicon nitride slurry are elastic (i.e., they fracture before they flow) unlike salt‐added alumina slur‐ries, which are plastic.
Transendothelial migration of lymphocytes in chronic lymphocytic leukaemia is impaired and involved down‐regulation of both L‐selectin and CD23
Authors: Chen Joan , Gu Ben , Dao Lan‐Phuong , Bradley Christopher , Mulligan Stephen , Wiley James
Published: March 2005

Chronic lymphocytic leukaemia (B‐CLL) is characterized by a progressive accumulation of B lymphocytes in blood and bone marrow and high concentrations of soluble CD23 and L‐selectin are found in the serum of these patients. In this study lymphocytes from normal subjects and patients with B‐CLL were allowed to undergo transendothelial migration across confluent layers of human umbilical vein endothelial cells. Lymphocytes in B‐CLL samples showed an impaired capacity to migrate while the minor proportion of normal T cells was enriched by a mean of 2.5‐fold in the transmigrated lymphocytes. In contrast, the ratio of B to T lymphocytes in normal preparations was unchanged in the transmigrated population. The expression of adhesion molecules on B‐CLL lymphocytes before and after transendothelial migration was studied by flow cytometry which showed that 71 ± 5% of L‐selectin was lost from the surface of transmigrated lymphocytes. T and B cells from normal subjects also showed a major loss of L‐selectin after transmigration. B‐CLL lymphocytes and normal B cells expressed CD23 but this molecule was down‐regulated following transendothelial migration, whereas the expression of VLA‐4, ICAM‐1, LFA‐1 and CD44 was unchanged. Lymphocytes incubated with oxidized ATP, an irreversible inhibitor of P2Z/P2X7 purinoceptors, retained their capacity for transendothelial migration and showed the same loss of L‐selectin as control leukaemic lymphocytes. Our results show that B‐CLL lymphocytes have impaired ability for transendothelial migration compared to normal peripheral blood lymphocytes. Moreover, transendothelial migration involves a universal loss of L‐selectin and CD23 from lymphocytes which suggests that the high serum levels of soluble L‐selectin and CD23 observed in B‐CLL may be generated by shedding during the process of transendothelial migration.
Use of 18F‐FDG positron emission tomography following allogeneic transplantation to guide adoptive immunotherapy with donor lymphocyte infusions
Authors: Hart D. P. , Avivi I. , Thomson K. J. , Peggs K. S. , Morris E. C. , Goldstone A. H. , Linch D. C. , Ell P. J. , Bomanji J. B. , Mackinnon S.
Published: March 2005

Fluorine‐18 fluorodeoxyglucose positron emission tomography (18F‐FDG PET) provides valuable prognostic information in the management of lymphoma patients. However, the utility of 18F‐FDG PET following allografting is unclear. We analysed the use of 18F‐FDG PET after allogeneic reduced‐intensity transplantation (RIT) performed in our institution. Between June 1998 and January 2002, 55 patients underwent RIT for either Hodgkin or non‐Hodgkin lymphoma. At least one 18F‐FDG PET scan was performed during the post‐transplant period (median five studies) in 15 (27·2%) of these 55 patients. PET scans were performed after re‐staging computed tomography (CT) and were categorised depending on 18F‐FDG uptake. The first PET scan was informative in 11 of 15 patients (73%) and influenced the administration of donor lymphocyte infusions (DLI) in nine: leading to earlier DLI administration in two patients, earlier dose escalation in one, withholding of DLI administration in five and dose reduction in one. In addition, subsequent monitoring with 18F‐FDG PET scans documented a graft‐versus‐lymphoma effect in five patients (median post‐DLI follow‐up 33 months, range 13–36 months). These preliminary data suggest that 18F‐FDG PET has a role in guiding DLI administration and monitoring the immunotherapeutic effect in patients after allogeneic transplantation. This retrospective pilot study forms the basis for a prospective study to clarify the utility of 18F‐FDG PET/CT in these patients.
Methylation status of the p15 and p16 genes in paediatric myelodysplastic syndrome and juvenile myelomonocytic leukaemia
Authors: Hasegawa Daisuke , Manabe Atsushi , Kubota Takeo , Kawasaki Hirohide , Hirose Imiko , Ohtsuka Yoshitoshi , Tsuruta Toshihisa , Ebihara Yasuhiro , Goto Yu‐ichi , Zhao Xiao Yan , Sakashita Kazuo , Koike Kenichi , Isomura Mariko , Kojima Seiji , Hoshika Akinori , Tsuji Kohichiro , Nakahata Tatsutoshi
Published: March 2005

Aberrant DNA methylation is frequently observed in adults with myelodysplastic syndrome (MDS), and is recognized as a critical event in the disease's pathogenesis and progression. This is the first report to investigate the methylation status of p15 and p16, cell cycle regulatory genes, in children with MDS (n = 9) and juvenile myelomonocytic leukaemia (JMML; n = 18) by using a methylation‐specific polymerase chain reaction. The frequency of p15 hypermethylation in paediatric MDS was 78% (7/9), which was comparable to that in adult MDS. In contrast, p15 hypermethylation in JMML was a rare event (17%; 3/18). In JMML, clinical and laboratory characteristics including PTPN11 mutations and aberrant colony formation were not different between the three patients with hypermethylated p15 and the others. Aberrant methylation of p16 was not detected in children with either MDS or JMML. Since p15 and p16 genes were unmethylated in two children with JMML, in whom the disease had progressed with an increased number of blasts, a condition referred to as blastic crisis, we infer that the aberrant methylation of these genes is not responsible for the progression of JMML. The results suggest that demethylating agents may be effective in most children with MDS and a few patients with JMML.
Prediction of individual response to chemotherapy in patients with acute myeloid leukaemia using the chemosensitivity index Ci
Authors: Staib Peter , Staltmeier Elke , Neurohr Katja , Cornely Oliver , Reiser Marcel , Schinköthe Timo
Published: March 2005

As the response to chemotherapy in patients with acute myeloid leukaemia (AML) may still not be accurately determined by known prognostic factors, such as karyotype, the ex vivo chemosensitivity profile may help to predict the individual response. The predictive accuracy of an ex vivo assay should be assessed by correlation of assay results with both response rate and survival. We prospectively investigated the prognostic relevance of pre‐therapeutic ex vivo chemosensitivity testing in primary cell cultures from adult AML patients by applying a new evaluation methodology, designated the chemosensitivity index, Ci. This Ci was designed as a prognostic index by taking the area under the curve as an exact measure of the total dose–response relationship. We found an overall predictive accuracy of 98·2% concerning treatment response, which compares favourably with previously published data ranging from 75% to 92%. Moreover, the Ci proved to be the strongest prognostic factor for overall survival in a multivariate Cox regression analysis including karyotype grouping and age (P < 0·001), and enabled the evaluation of response to combination therapies and selection of possible treatment alternatives. Our data suggest that ex vivo chemosensitivity testing evaluated by the Ci could serve as a powerful tool for assay‐directed therapy strategies in AML.
Effects of fish stocking on the zooplankton community structure in a shallow lake in China
Authors: YANG Y. F. , HUANG X. F. , LIU J. K. , JIAO N. Z.
Published: March 2005

Abstract Changes in the zooplankton community structure in relation to fishery practices in Lake Donghu, Wuhan, China were examined. The number of Protozoa species increased slightly, whereas the number of rotifers and crustaceans decreased from the 1960s to the 1990s. The total annual average densities of zooplankton increased 15–20 times in the 1990s compared with the 1960s. This increase was largely attributed to Protozoa, which contributed 93.4% by number of the total zooplankton density in 1991. Cladoceran densities decreased markedly from 1987. Changes in densities of rotifers and copepods were not evident. Trends in zooplankton biomass were similar to density. Large changes in zooplankton community structure coincided with markedly changes in concentration of chlorophyllaand transparency in Lake Donghu in 1987. The year 1987 seems to be the threshold year when the zooplankton community structure changed considerably. These changes were related to continuously increasing fish stock biomass in the lake. It was suggested that fish stocking and fish biomass should be a better managed for improvement of the quality of the lake's environment.
Nutrient digestibility of angling baits for carp, Cyprinus carpio, with implications for groundbait formulation and eutrophication control
Authors: ARLINGHAUS R. , NIESAR M.
Published: March 2005

Abstract  To evaluate the suitability of angling groundbaits as a fish feed and the potential for nutrient loss, the macronutrient digestibility of four groundbaits was investigated in carp, Cyprinus carpio L., using a sieving method of faeces collection and chromic oxide. Apparent digestibility coefficients (ADCs) of protein and lipids were >80% for all angling baits. ADCs of nitrogen‐free extracts and phosphorus (P) differed significantly between the test diets, probably because of divergent feed compositions and ingredient treatments. The generally high digestibility estimates indicated that fish feeding on angling groundbait will benefit from this food source. The differences in nutrient digestibility suggested that type of groundbait and ingredient used will have a major effect on potential eutrophication and fish production caused by groundbaiting. The principle of groundbaits to protect the environment should be to minimise the P‐content of the groundaits and maximising P‐digestibility and P‐retention efficiency.
Noonan syndrome with giant cell lesions
Authors: LEE S. M. G. , COOPER J. C.
Published: March 2005

Noonan syndrome is characterised by short stature, unusual facies, congenital heart disease, chest deformity and mild mental retardation. It may be sporadic or inherited as an autosomal dominant trait and occurs between one in 1000–2500. Cherubism is a giant cell lesion of the jaws thought to be transmitted as an autosomal dominant trait. It is usually recognised by age two to four years, follows a variable course, and is not known to be related to other genetic disorders. The purpose of this article is to report a case of multiple giant cell lesions of the mandible that occurred in a patient with phenotypic features of Noonan syndrome. The emerging relationship between these cherubism‐like findings and Noonan syndrome will be discussed.
Anaphylactic shock as the only clinical manifestation of hepatic hydatid disease
Authors: Georgiou Sophia , Maroulis John , Monastirli Alexandra , Pasmatzi Efi , Pavlidou Despina , Karavias Dionysios , Tsambaos Dionysios
Published: March 2005

The case of a 35‐year‐old man is reported who developed a spontaneous anaphylactic shock as the only clinical manifestation of hepatic hydatidosis. Dermatologists should consider asymptomatic hydatid disease in the differential diagnosis of anaphylactic reactions, particularly in patients from regions in which echinococcosis is endemic.
Alginate as an auxiliary bacterial membrane: binding of membrane‐active peptides by polysaccharides*
Authors: Chan C. , Burrows L.L. , Deber C.M.
Published: March 2005

Abstract:  The chronicity of Pseudomonas aeruginosa infections in cystic fibrosis (CF) patients is characterized by overproduction of the exopolysaccharide alginate, in which biofilm bacteria are embedded. Alginate apparently contributes to the antibiotic resistance of bacteria in this form by acting as a diffusion barrier to positively charged antimicrobial agents. We have been investigating cationic antimicrobial peptides (CAPs) (prototypic sequence: KKAAAXAAAAAXAAWAAXAAAKKKK‐NH2, where X is any of the 20 commonly occurring amino acids) that were originally designed as transmembrane mimetic peptides. Peptides of this group above a specific hydrophobicity threshold insert spontaneously into membranes and have antibacterial activity at micromolar concentrations. While investigating the molecular basis of biofilm resistance to peptides, we found that the anionic alginate polysaccharide induces conformational changes in the most hydrophobic of these peptides typically associated with insertion of such peptides into membrane environments [Chan et al., J. Biol. Chem. (2004) vol. 279, pp. 38749–38754]. Through a combination of experiments measuring release of the fluorescent dye calcein from phospholipid vesicles, peptide interactions with vesicles in the presence and absence of alginate, and affinity of peptides for alginate as a function of net peptide core hydrophobicity, we show here that alginate offers a microenvironment that provides a protective mechanism for the encased bacteria by both binding and promoting the self‐association of the CAPs. The overall results indicate that hydrophilic alginate polymers contain a significant hydrophobic compartment, and behave as an ‘auxiliary membrane’ for bacteria, thus identifying a unique protective role for biofilm exopolysaccharide matrices.
Liposomal cargo unloading induced by pH‐sensitive peptides
Authors: Lee H.‐M. , Chmielewski J.
Published: March 2005

Abstract:  Amphiphilic peptides designed to have a pH‐dependent conformational change and membrane activity are described. At physiologic pH, the peptides would exist in a random coil conformation, but at endosomal pH values they would switch to amphiphilic α‐helices, disrupt membranes, and release liposomal contents. A series of peptides have been investigated that contain a high percentage of Glu residues for the pH‐induced conformational switch, and Leu residues for optimal lipid binding. Circular dichroism (CD) results in aqueous and liposomal environments were performed and demonstrate a pH‐dependent shift to helicity upon acidification. Liposomal release data at neutral and acidic pH, also document the success of this design strategy.
Water‐soluble prodrugs of cyclosporine A with tailored conversion rates
Authors: Hamel A.R. , Hubler F. , Mutter M.
Published: March 2005

Abstract:  A novel type of water‐soluble prodrugs of cyclosporine A (CsA) is described, featuring a modular system of an enzyme‐cleavable group, a solubilizing moiety and a chemodegradable spacer attached to the hydroxyl function of (4R)‐4‐[(E)‐2‐butenyl]‐4‐,N‐dimethyl‐l‐threonine (MeBmt)‐1 of CsA. The chemical synthesis of these double prodrugs proceeds in high yield and purity and allows for a systematic study of the influence of the structural parameters upon physicochemical and pharmacological properties. The evaluation of the chemical and enzymatic stability results in differential values of the conversion rates (minutes to several hours) in support of an enzyme‐triggered release of the parent drug as the rate‐limiting step. In vitro studies show that the designed prodrug systems can be regarded as soft prodrugs in being devoid of cyclophiline A (CypA) binding and that complete conversion to the parent drug occurs in whole rat blood, setting the stage for therapeutic use.
Characterization of interactions of Na+/H+ exchanger regulatory factor‐1 with the parathyroid hormone receptor and phospholipase C*
Authors: Sun C. , Mierke D.F.
Published: March 2005

Abstract:  The Na+/H+ exchanger regulatory factor‐1 (NHERF1) is a molecular scaffold important for the signaling of the G‐protein coupled receptor for the parathyroid hormone (PTH1R). The two PDZ (PSD‐95, Discs‐large, ZO1) domains of NHERF1 through association with the C‐termini of PTH1R and phospholipase C enhance the signaling pathway associated with PTH. To examine these interactions, we have produced the individual PDZ1 and PDZ2 domains as well as the tandem PDZ1–PDZ2 domains (PDZ12) of NHERF1 and have characterized the binding affinities of the C‐terminal motifs of PTH1R and PLCβ using fluorescence anisotropy. Circular dichroism indicates that the PDZ1 and PDZ2 are properly folded. Based on fluorescence anisotropy we find that the C‐terminus of PTH1R, containing ETVM, has similar affinities (approximately 10 μm) for both PDZ1 and PDZ2. The PTH1R displayed reduced binding affinity for the tandem PDZ12 (16 μm) compared with the individual domains or a solution of equal molar concentrations of PDZ1 and PDZ2 (5.8 μm), suggesting negative cooperativity between the PDZ domains or intervening region. The C‐termini of PLCβ (both β1 and β2 isozymes were examined, containing DTPL and ESRL, respectively) displayed a diminished affinity for PDZ2 (approximately 30 μm) over that of PDZ1 (approximately 8 μm). Finally, we demonstrate trans PDZ1–PDZ2 association that is enhanced in the presence of the C‐terminus of PTH1R or PLCβ, suggesting oligomerization of NHERF as a mode for enhancing the signaling associated with PTH.
Corporate Governance and Director Accountability: an Institutional Comparative Perspective*
Authors: Aguilera Ruth V.
Published: March 2005

This paper examines the role of boards of directors in light of institutional contingencies and recent best practice governance guidelines and regulation such as the United Kingdom Higgs Review and the United States Sarbanes‐Oxley Act 2002. Particular attention is paid to discussing the role of independent directors across countries, and the implications for corporate governance innovation. It concludes by posing questions about recent corporate governance transformations and providing suggestions for future research.
Facing the Future: America's Post‐multiculturalist Trajectory
Authors: King Desmond
Published: March 2005

America's multicultural struggles are now relatively dated. The policies about which multicultural‐type struggles now occur are quite modest (compared, for instance, with the much more extensive measures implemented in Canada and Australia). The reforms of the 1960s not only heralded unexpected consequences (such as the growth of the Asian and Latino populations) but were unavoidable if the US polity was to satisfy the basic criteria of democracy. These civil rights reforms and connected public policy measures, such as affirmative action or multicultural educational curricula, shape US politics—but in a way which interacts more genuinely with the country's vast diversity of peoples. Group‐based divisions are deep and enduring but they are expressed in an individualist political culture whose political institutions are responsive to individualist‐based demands, even when these demands are expressed through group loyalties.
THE SOCIAL ACCOUNTS FROM A CONSUMER'S POINT OF VIEW
Authors: Stone Richard
Published: March 2005

After a short introduction, the first part of this paper (section 3 through 9) provides an outline of the revisions proposed to the System of National Accounts (SNA) of the United Nations which are now under discussion. These proposals were considered by an expert group at the end of 1964 and were accepted by the Statistical Commission of the United Nations in 1965 as the basis for further work on the extension and revision of the SNA. The aim of the revision is to provide a fully integrated system of accounts and balance sheets in which input‐output, flows‐of‐funds and sector balance sheets are incorporated in a generalised accounting framework. Whereas the real side of the economy has been studied analytically in many countries (input‐output analysis, demand analysis and so on) much less experience is available on modelling the financial side of the economy, apart from econometric work on saving behaviour, which is fairly widespread. Accordingly, the second part of the paper (sections 10 through 14) contains a discussion of financial model‐building in which a number of possibilities are explored. The final topic discussed (section 15) is demographic accounting, by which is meant a framework for recording and analysing human, as opposed to economic, flows and stocks. The development of such a system arose out of the emphasis placed by the expert group on the integration of demographic and economic information.
THE NATIONAL BALANCE SHEET OF THE UNITED KINGDOM
Authors: Revell Jack
Published: March 2005

The paper discusses national balance sheets in the light of the proposals for their inclusion in the revised SNA. The author uses his own estimated national balance sheet of the United Kingdom as a basis for discussing the problems encountered in the compilation of national balance sheets, and the greater part of the paper is concerned with questions of valuation, classification and statistical source material. The concluding section deals briefly with the structure of the national balance sheet of the United Kingdom and compares its structure with that of the national balance sheet of the United States. Provisional national balance sheets of the United Kingdom for each of the five years 1957 to 1961 are presented.