bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanical Behavior of a Continuous‐SiC‐Fiber‐Reinforced RBSN‐Matrix Composite
Authors: Nair Shanti V. , Gwo Tsung‐Ju , Narbut Nancy M. , Kohl James G. , Sundberg Glenn J.
Published: March 2005

The results of a detailed study are presented on the toughening of reaction‐bonded silicon nitride reinforced with large‐diameter SiC monofilaments at ambient and elevated temperatures. Composite stiffness, strength, toughness, and R‐curve behavior were investigated at ambient temperature, with strengths measured up to 1400°C. At elevated temperature, toughening mechanisms were explored by investigating crack initiation and growth under creep conditions. The results show that, at ambient temperature, the composite exhibited noncatastrophic failure with substantial toughening associated with contributions of both fiber pullout and elastic bridging of fibers in the crack wake, consistent with predictions using available models. Limited R‐curve measurements suggest that large‐scale bridging effects may be present. At elevated temperature, crack initiation occurred in the matrix at about 1000°C, but in the fiber at higher temperatures. Growth of cracks is governed by time‐dependent bridging of unbroken fibers in the crack wake, consistent with a model based on fiber pullout by viscous sliding of fibers out of the matrix along amorphous interfacial layers.
Phase Composition, Oxygen Content, and Thermal Conductivity of AIN(Y2O3) Ceramics
Authors: Buhr Hendrik , Müller Gerd , Wiggers Hartmut , Aldinger Fritz , Foley Paul , Roosen Andreas
Published: March 2005

An indirect method to determine the oxygen dissolved in AIN is devised for AIN(Y2O3) ceramics and then related to thermal conductivity. Dissolved oxygen is determined by first constructing the AIN‐rich corner of the AIN—Y2O3—Al2O3 phase diagram (isothermal section). This is achieved by (1) measuring the total oxygen content and subtracting from it the oxygen in the Y2O3, resulting in a virtual alumina content; (2) placing the sample composition on the diagram; (3) determining the phases present by XRD for each sample; and (4) drawing phase boundaries which best agree with the phases present. The intersection of these tie lines through the sample location with the AIN—Al2O3 axis then gives the particular Al2O3 oxygen content dissolved in the AIN lattice. For the system AIN—Y2O3—Al2O3, it is shown that it is indeed this fraction of the total oxygen content that has a decisive limiting influence on thermal conductivity of dense, polyphase AIN ceramics.
Influence of Stress Ratio on the Elevated‐Temperature Fatigue of a Silicon Carbide Fiber‐Reinforced Silicon Nitride Composite
Authors: Holmes John W.
Published: March 2005

The influence of stress ratio on the tensile fatigue behavior of a unidirectional SiC‐fiber/Si3N4‐matrix composite was investigated at 1200°C. Tensile stress ratios of 0.1, 0.3, and 0.5 were examined. Fatigue testing was conducted in air, at a sinusoidal loading frequency of 10 Hz. For peak fatigue stresses below the proportional limit of the composite (approximately 195 MPa at 1200°C) specimens survived 5 × 106 cycles, independent of stress ratio. At peak stresses above the proportional limit, fatigue failures were observed; fatigue life decreased significantly as the stress ratio was lowered from 0.5 to 0.1. Creep appears to be the predominant damage mechanism which occurs during fatigue below the proportional limit. Both mechanical cycle‐by‐cycle fatigue damage and creep contribute to specimen failure at peak stresses above the proportional limit.
Mode I Fracture Resistance of a Laminated Fiber‐Reinforced Ceramic
Authors: Zok Frank , Sbaizero Orfeo , Hom Craig L. , Evans Anthony G.
Published: March 2005

The mode I fracture resistance of a ceramic matrix composite has been measured. Simultaneous observations have revealed that the resistance is dominated by frictional dissipation upon the pullout of fibers that fracture in the crack wake off the crack plane. Numerical and analytical crack growth simulations have been compared with the experimental results. One important feature in this comparison concerns the occurrence of large‐scale bridging. With these effects taken into account, the simulations and the experiments are found to be in good correspondence for acceptable magnitudes of the interface sliding stress.
Optimization of the Mechanical Properties of Silicon Carbide‐Fiber‐Reinforced Zirconia Titanate Matrix Composites through Controlled Processing
Authors: Bender Barry A. , Jessen Todd L. , Lewis David
Published: March 2005

The effects of processing parameters on the microstructure and mechanical behavior of a SiC‐fiber‐reinforced ZrTiO4 matrix composite were evaluated through a controlled study. The microstructure was analyzed using X‐ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Mechanical behavior was characterized by strength and toughness measurements, which were correlated with the microstructure of the composite. The optimized processing schedule developed included incorporation of CO‐heat‐treated BN‐coated fibers, composite calcination at 530°C, and consolidation via hot‐pressing at 1270°C and 17.25 MPa applied pressure in an atmosphere of CO at an overpressure of 111.5 kPa (1.1 atm). Use of this processing schedule improved in situ fiber strength and modified the fiber/matrix interfacial microstructure to ameliorate its sliding and debonding resistance, leading to a composite with average strength over 1 GPa and a toughness of 26 MPa.m1/2.
Glass‐Forming Ability and Crystallization Tendency Evaluated by the DTA Method in the Na2O–B2O3–Al2O3 System
Authors: Wakasugi Takashi , Ota Rikuo , Fukunaga Jiro
Published: March 2005

In order to evaluate the crystallization tendency of glasses, the ratio of the crystallization temperature to the liquidus temperature (Tc/TL) was obtained by DTA measurement for the Na2O–B2O3 and Na2O–B2O3–Al2O3 systems. The critical cooling rate for glass formation (Q*) was also measured. The measurements were performed in the composition range of (100 −x)Na2O–(x)B2O3, (x= 25–35 and 60–100 mol%), and (100 −y)0.5Na2O·0.5B2O3−(y)Al2O3, (y= 6–34 mol%). The relationship between Tc/TL and Q* was discussed. A linear relationship between Tc/TL and log Q* for these systems was found. Furthermore, the relationship between Tc/TL and Q* was verified by computer simulation based on the crystallization kinetics of glass or supercooled liquid.
Determination of Fracture Toughness at High Temperatures after Subcritical Crack Extension
Authors: Fett Theo , Munz Dietrich
Published: March 2005

As a consequence of R‐curve behavior, ceramic materials may exhibit increased fracture toughness (KIc) following slow crack extention. In this investigation, the effect of crack propagation on fracture toughness is studied in static bending tests. For the calculation of stress intensity factors (KI) the stress distribution must be known at the moment of fracture. As a consequence of creep, this stress distribution must deviate from the linear distribution. The corresponding stress intensity factors are computed using the fracture mechanical weight function. Experimental results for fracture toughness are communicated for a 2.5%‐MgO‐doped hot‐pressed Si3N4 at 1300°.
Effect of Reinforcement Particle Size on the Thermal Conductivity of a Particulate‐Silicon Carbide‐Reinforced Aluminum Matrix Composite
Authors: Hasselman D. P. H. , Donaldson Kimberly Y. , Geiger Alan L.
Published: March 2005

The thermal conductivity of a 40 vol% silicon carbide‐particulate‐reinforced aluminum matrix composite was determined as a function of silicon carbide mean particle size ranging from 0.7 to 28 μm. A size dependence was found consisting of a decrease in thermal conductivity with decreasing SiC particle size. This effect is in accordance with theoretical expectations for composites with an interfacial thermal barrier at the dispersion–matrix interface. At the finest particle size of the silicon carbide, the composite thermal conductivity approached the value for the matrix with pores, as expected from theory. Only at the largest SiC particle size did the composite thermal conductivity exceed the value for the matrix. These results suggest that in maximizing the thermal conductivity of composites with an interfacial thermal barrier, the reinforcement particle size should be as large as practically possible.
Low‐Temperature Formation of Fluorapatite in Aqueous Solution
Authors: Fulmer Mark , Brown Paul W.
Published: March 2005

The low‐temperature formation of Fluorapatite by the reaction of particulate calcium phosphate precursors in aqueous solution was investigated:
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Variations in the aqueous phase were measured and these corelated with the consumption of reations and the formation of apatitic phases. The variations in solution pH and fluoide are in accord with a mechanism by which CaF2 precipitates relatively early in the reaction. After this, minimal fluoride is consumed until the formation of an apatitic phase reaches substantial for hydroxl and the pH increase. The extent of aptite formation exhibits a storong dependence on the concetration of the NaF solution in which reation is occuring. Analysis of reaction is saturated CaF2 solution indicates that apatite formation precedes the uptake of fluoride from solution. For reaction in dilute suspension, a low concentration of NaF retards apatite formation whereas a higher one accelerates it. Alternatively, when reaction is carried outa low liquid‐to‐solids rario, apatite formation is accelerated in NaF solution regardless of concetration.
Strength and Creep Behavior of Rare‐Earth Disilicate–Silicon Nitride Ceramics
Authors: Cinibulk Michael K. , Thomas Gareth , Johnson Sylvia M.
Published: March 2005

The flexural strength and creep behavior of RE2Si2O7–Si3N4 materials were examined. The retention in room‐temperature strengths displayed by these ceramics at 1300°C was 80–91%, with no evidence of inelastic deformation preceding failure. The steady‐state creep rates, at 1400°C in flexural mode, displayed by the most refractory materials are among the lowest reported for sintered Si3N4. The creep behavior was found to be strongly dependent on residual amorphous phase viscosity as well as on the oxidation behavior of these materials. All of the rare‐earth oxide sintered materials, with the exception of Sm2Si2O7–Si3N4, had lower creep strains than the Y2Si2O7–Si3N4 material.
Microstructure of Platelet‐Reinforced Ceramics Prepared by the Directed Reaction of Zirconium with Boron Carbide
Authors: Breval Else , Johnson William B.
Published: March 2005

The microstructure of a ZrB2‐platelet‐reinforced ZrCx composite was examined using transmission electron microscopy and X‐ray diffraction. The composites, which are formed by the reaction of molten Zr with B4C, contain a small amount of residual Zr, the amount of which can be varied by altering the processing conditions. Results on two different materials are reported, one with a low Zr content, ∼2.5 vol%, and the other with a very low Zr content, ∼0.5 vol%. In the former, metallic Zr was found at triple points and as a grain boundary phase between the boride and carbide, and to a lesser degree between the boride grains. In the latter, it was only found as a ternary Zr–ZrB2–ZrCx eutectic at the triple points. Both materials showed a nearly random distribution of the boride and carbide constituents, though specific crystallographic relationships were found between the various constituents.
Phase Transformations in Dicalcium Silicate: II, TEM Studies of Crystallography, Microstructure, and Mechanisms
Authors: Kim Young Joong , Nettleship Ian , Kriven Waltraud M.
Published: March 2005

The crystallography, microstructures, and phase transformation mechanisms in dicalcium silicate (Ca2SiO4) were studied by TEM. Three types of superlattice structures were observed in the α′L and β phases. Almost all β grains were twinned and strained. Symmetry‐related domain structures inherited from previous high‐temperature transformations were observed in β grains. Both the α→α′H and α′L→β transformations were considered to be ferroelastic, and spontaneous strains were calculated. In terms of the crystal structures, the major driving force for the β→γ transformation is proposed to be strains and cation charge repulsions in the β structure. This mechanism can be displacive, but it needs to overcome a comparatively high energy barrier.
Mullite‐Type Structures in the Systems Al2O3–Me2O (Me = Na, K) and Al2O3–B2O3
Authors: Mazza Daniele , Vallino Mario , Busca Guido
Published: March 2005

A morphous solids belonging to the systems Al2O3–Me2O (Me = Na, K) and Al2O3–B2O3 were prepared by nitrate decomposition, introducing boron in the form of boric acid. Crystalline metastable solids with pseudotetragonal symmetry were obtained from thermal treatment at 850° to 900°C for the compositions Al6MexO(9+0.5x) (x≅ 1; Me = Na, K) and Al6‐xBxO9 (1 x 3). The resultant solids were stable only within a difinite temperature range and transformed, with further treatment increases, into stable equilibrium phases. The structures of the metastable phases were examined by X‐ray diffraction and Fourier transform infrared spectroscopy, and both analyses showed a mullite type of framework, inside of which the atomic coordinates were refined in the Pbam (no. 55) space group. The present results indicate that these silica‐free mullite structures are stabilized by two different mechanisms: (1) interstitial occupation of bulky cations (Na+, K+) or (2) substitution of B for Al in some of the tetrahedral positions.
Effect of Loading Mode and Coating on Dynamic Fatigue of Optical Fiber in Two‐Point Bending
Authors: Rondinella Vincenzo V. , Matthewson M. John
Published: March 2005

Two‐point bending is a useful method for investigating the mechanical properties of optical fiber and has several advantages when compared to the traditional tensile test. However, the strength of the fiber is usually determined at constant faceplate velocity rather than at constant strain rate as in the uniaxial tensile test, and previous work casts doubt on the comparability of fatigue results obtained using different loading modes and hence on the reliability of the bending technique. This paper presents dynamic fatigue results using a two‐point bend apparatus that can be programmed to operate in constant velocity, constant strain rate, and constant stress rate loading modes. These results, obtained for both bare and polymer‐coated fused silica optical fiber, show no significant differences in the calculated fatigue parameters for the three loading modes and clearly indicate the reliability of the two‐point bend method at constant faceplate velocity. The results, however, show that the obtained value of the stress corrosion susceptibility parameter, n, is dependent on the quantity used to define it, i.e., stress or strain to failure, because of the nonlinear elastic behavior of silica.
Tensile Creep and Creep‐Recovery Behavior of a SiC‐Fiber─Si3N4‐Matrix Composite
Authors: Holmes John W. , Park Yong H. , Jones J. Wayne
Published: March 2005

The tensile creep and creep‐recovery behavior of a unidirectional SiC‐fiber/Si3N4‐matrix composite was investigated at 1200°C in air. A primary objective of the study was to determine how various sustained and cyclic creep loading histories would influence the creep rate, accumulated creep strain, and the amount of strain recovered upon specimen unloading. The key results obtained from the investigation can be summarized as follows: (1) A threshold stress of 60 MPa was identified, below which the creep rate of the composite was exceedingly low (∼10−12 s−1). (2) Periodic fiber fracture was identified as a fundamental damage mode for sustained tensile creep at stresses of 200 and 250 MPa. (3) Because of transient stress redistribution between the fibers and matrix, the creep life and failure mode at 250 MPa. were strongly influenced by the rate at which the initial creep stress was applied. (4) Very dramatic creep‐strain recovery occurred during cyclic creep; for cyclic loading between stress limits of 200 and 2 MPa, 80% of the prior creep strain was recovered during 50‐h‐creep/ 50‐h‐unloading cycles and over 90% during 300‐s‐creep/ 300‐s‐unloading cycles. (5) Cyclic loading significantly lowered the duration of primary creep and overall creep‐strain accumulation. The implications of the results for microstructural and component design are discussed.
Liquid Precursor Route for Hetero‐epitaxy of Zr(Y)O2 Thin Films on (001) Cubic Zirconia
Authors: Seifert Andreas , Lange Fred F. , Speck J. S.
Published: March 2005

ZrO2–3 mol% Y2O3„single‐crystal” thin films with multiple variants were epitaxially formed on (100) cubic zirconia substrates. The films were prepared by spin‐coating an aqueous zirconium acetate/yttrium nitrate solution onto the cubic zirconia substrates and subsequently heat‐treated at temperatures between 1100° and 1400°C. Electron diffraction and dark‐field TEM observations showed that the film has tetragonal symmetry and consists of 50–100 nm variants with their c‐axes aligned with one of the three substrate cube axes. Unrelaxed strain energy estimates indicate that the two variants with their c1‐axis parallel to the substrate/thin film interface are energetically favorable.
Effect of Rare‐Earth Additives on Electromechanical Properties of Modified Lead Titanate Ceramics
Authors: Suwannasiri Thitima , Safari Ahmad
Published: March 2005

The influence of rare‐earth additives, such as La, Nd, Sm, and Gd, and poling conditions on the electromechanical properties of (Pb1−3x/2Lnx)(Ti0.98Mn0.02)O3 compositions, x= 0.04–0.12, were investigated. The type and amount of additive were found to affect the lattice anisotropy, dielectric constant, and electromechanical properties. A large electromechanical anisotropy (kt/kp) could be obtained in 10 mol% Sm‐modified and 8 mol% Gd‐modified lead titanate ceramics, and seemed to correlate to a low Poisson's ratio.
Effect of Heating Rate on Pore Shrinkage in Yttria‐doped Zirconia
Authors: Kim Do‐Hyeong , Kim Chong Hee
Published: March 2005

The advantage of fast firing depends not only on the finer grain‐size effect at the sintering temperature, but also on the smaller pore‐size effect which results from the restricted pore growth. Pore growth due to the differential sintering during heating was observed to occur at relatively low temperature regions, and rapid passing through the region restricted the pore growth and enhanced the densification.
Quantum Chemical Determination of the Al‐Substituted Site in Tobermorite
Authors: Kashihara Seiichi , Yamanaka Shozo , Inoue Takayuki , Komatsu Takahiro , Toyoshima Hideo
Published: March 2005

Ab initio and semiempirical molecular orbital (MO) calculations have been performed to determine the position of the substitution of Al for Si in tobermorite. Replacement energies were calculated for the cluster models of tobermorite framework. Al was found to be substituted mainly in chain middle groups (Q2 sites). Correlation has been recognized between the site occupancy order in the unit cell and structural parameters such as bond lengths and bond angles. It was also found that the variation among energies required for double replacements at the different sites can be explained in terms of the Löewenstein rule.
Vibrational Technique for Stress Measurement in Films: II, Extensions and Complicating Effects
Authors: Tong Quinn K. , Maden Michele A. , Jagota Anand , Farris Richard J.
Published: March 2005

Several extensions and complicating effects in the vibrational technique for the measurement of stress in films are discussed in this, the second part of the study. The principles of the technique, based on ideal membrane behavior, and some applications were presented in the companion paper. Several complicating effects can be important due to deviation from ideal behavior. For lowdensity polymer membranes, air loading can shift the natural frequencies considerably. This effect is studied by measuring stress at different air pressures and compared to a theoretical model for the correction of air loading effects. The effect of bending stiffness can be important for thick and stiff films. This effect has been studied systematically and it is shown that it can be used to measure the stress and stiffness of the film simultaneously. A powerful extension of the technique to the measurement of anisotropic biaxial stresses is also demonstrated.
Effect of Dopants on Zirconia Stabilization—An X‐ray Absorption Study: III, Charge‐Compensating Dopants
Authors: Li Ping , Chen I‐Wei , Penner‐Hahn James E.
Published: March 2005

X‐ray absorption spectra at the Zr‐, Y‐, and Nb‐K edges of ZrO2‐YNBO4 solid solutions have been measured at 10 K to determine the local atomic structures. Both Y and Nb cations substitute for Zr in the cation network but maintain rather different local oxygen coordination from Zr. In tetragonal zirconia solid solutions, Y adopts a YO8 structure with a bond length of 2.32 Å. This is the same as the structure found in ZrO2–Y2O3, solid solutions, confirming our previous conclusion that Y is not associated with oxygen vacancies. Nb has an NbO4 structure with a bond length of 1.90 Å. This is shorter than the Zr–O, distance of 2.10 Å. The strong Nb–O coordination increases the bonding disparity between Zr–O layers, thus increasing tetragonality. This is similar to the trend previously established for ZrO2‐GeO2 solid solutions. Severe distortion of neighboring cations around the undersized Nb, similar to that previously found for undersized Fe3+ and Ga3+, is also observed. At higher temperatures, local Y–Nb cation ordering occurs at a concentration below the solubility limit, similar to the Zr–Ge ordering reported previously. This cation ordering mechanism allows the charge‐compensating Y‐Nb pair to stabilize the tetragonal structure but increase tetragonality.
Experimental Study of Stress‐Induced Localized Transformation Plastic Zones in Tetragonal Zirconia Polycrystalline Ceramics
Authors: Sun Qingping , Zhao Zhijun , Chen Weizhe , Qing Xinglin , Xu Xiaojian , Dai Fuloon
Published: March 2005

Stress‐induced martensitic transformation plastic zones in ceria‐stabilized tetragonal zirconia polycrystalline ceramics (Ce‐TZP), under loading conditions of uniaxial tension, compression, and three‐point bending, are studied by experiments. The transformed monoclinic phase volume fraction distribution and the corresponding plastic strain distribution and the surface morphology (surface uplift) are measured by means of moire interferometry, Raman microprobe spectroscopy, and the surface measurement system. The experimental results from the above three kinds of specimens and methods consistently show that the stress‐induced transformation at room temperature of the above specimen is not uniform within the transformation zone and that the plastic deformation is concentrated in some narrow band; i.e., macroscopic plastic flow localization proceeds during the initial stage of plastic deformation. Flow localization phenomena are all observed in uniaxial tension, compression, and three‐point bending specimens. Some implications of the flow localization to the constitutive modeling and toughening of transforming thermoelastic polycrystalline ceramics are explored.
Saccharomyces boulardii in the prevention of antibiotic‐associated diarrhoea in children: a randomized double‐blind placebo‐controlled trial
Authors: Kotowska M. , Albrecht P. , Szajewska H.
Published: March 2005

Background : Co‐treatment with Saccharomyces boulardii appears to lower the risk of antibiotic‐associated diarrhoea in adults receiving broad‐spectrum antibiotics.

Aim : To determine whether S. boulardii prevents antibiotic‐associated diarrhoea in children.

Methods : A total of 269 children (aged 6 months to 14 years) with otitis media and/or respiratory tract infections were enrolled in a double‐blind, randomized placebo‐controlled trial in which they received standard antibiotic treatment plus 250 mg of S. boulardii (experimental group, n = 132) or a placebo (control group, n = 137) orally twice daily for the duration of antibiotic treatment. Analyses were based on allocated treatment and included data from 246 children.

Results : Patients receiving S. boulardii had a lower prevalence of diarrhoea (≥3 loose or watery stools/day for ≥48 h occurring during or up to 2 weeks after the antibiotic therapy) than those receiving placebo [nine of 119 (8%) vs. 29 of 127 (23%), relative risk: 0.3, 95% confidence interval: 0.2–0.7]. S. boulardii also reduced the risk of antibiotic‐associated diarrhoea (diarrhoea caused by Clostridium difficile or otherwise unexplained diarrhoea) compared with placebo [four of 119 (3.4%) vs. 22 of 127 (17.3%), relative risk: 0.2; 95% confidence interval: 0.07–0.5]. No adverse events were observed.

Conclusion : This is the first randomized‐controlled trial evidence that S. boulardii effectively reduces the risk of antibiotic‐associated diarrhoea in children.
Systematic review: the liver in coeliac disease
Authors: Duggan J. M. , Duggan A. E.
Published: March 2005

Background : For over a decade isolated reports have noted liver histology and biochemistry changes in patients with coeliac disease. The prevalence and response to treatment is clinically important.

Aim : To outline the frequency and significance of liver abnormalities in coeliac disease.

Methods : A Medline search using Ovid–Coeliac/Coeliac (exp) and liver disease (exp) was completed of English references published during 1966–June 2003. Bibliographic references and other appropriate sources were also searched.

Results : Six studies reported liver biochemistry in 591 patients; 248 patients had abnormal results. Elevated transaminases were the most frequently reported abnormality. A gluten‐free diet produced resolution of elevated transaminases in 115 of 130 patients. There was a greater than expected association with primary biliary cirrhosis and advanced liver disease.

Conclusions : Mildly abnormal liver biochemistry is frequent in untreated coeliac disease and may provide a key to the diagnosis. Routine investigations for undiagnosed liver disease should include tissue transglutaminase testing. Left untreated, coeliac‐induced hepatitis may rarely progress to end‐stage liver disease. Primary biliary cirrhosis is clearly linked to coeliac disease. The full story of these linkages is yet to be written.
Hospital health care resource utilization and costs of colorectal cancer during the first 3‐year period following diagnosis in Switzerland
Authors: Delcò F. , Egger R. , Bauerfeind P. , Beglinger C.
Published: March 2005

Background: In industrialized countries, colorectal cancer is a leading cause of morbidity and mortality. Decisions on colorectal cancer screening are based on cost‐effectiveness analyses that rely on colorectal cancer cost studies. Additionally, the study of the resource utilization pattern may lead to cost‐saving strategies in the care of colorectal cancer.

Aim: To estimate hospital resource utilization, the use of various therapy modalities and costs of colorectal cancer cases undergoing surgery during the first 3 years following the diagnosis at a Swiss university hospital.

Methods: Consecutive colorectal cancer patients from 1997 to 1998 were identified using the surgery database of the University Hospital of Basel and followed for a period of 3 years. In‐hospital resource utilization and costs were retrieved from the computerized administrative records. Treatment outside of the hospital during the study period constituted an exclusion criterion.

Results: Eighty‐three (94%) of 89 patients undergoing surgery for colorectal cancer were included in the study, 58 with colon cancer and 25 with rectal cancer. The average ages were 70.3 and 63.6 years, respectively. Overall, 59% of the patients were treated with surgery alone, 27% also had chemotherapy and 15% received additional chemoradiotherapy. These percentages and resource utilization varied broadly between the two colorectal cancer groups. On average, patients were admitted to the hospital 2.7 times and the hospital length of stay amounted to 35 days. They were visited by doctors 69 times, and examined with colonoscopy, ultrasonography and computerized tomography 2.7, 3.2 and 2.4 times, respectively. Mean costs incurred for rectal cancer ($40 230) were about 22% higher than for colon cancer patients ($33 079). Hospitalization and surgical therapy generated the greatest costs. Expenses were highest for the first year and with more severe disease stages at diagnosis.

Conclusions: Colorectal cancer is an expensive disease. Economic analyses on screening should take into account the large resource utilization and cost variability by performing sensitivity analysis on broad cost ranges. Furthermore, they should consider stage shifting at diagnosis and include stage‐specific costs.
Dynamic decision analysis to determine optimal treatment duration in chronic hepatitis C
Authors: Veldt B. J. , Hansen B. E. , Eijkemans M. J. C. , de Knegt R. J. , Stijnen T. , Habbema J. D. F. , Schalm S. W.
Published: March 2005

Background : Current guidelines for stopping treatment of chronic hepatitis C are based on hepatitis C ribonucleic acid measurements at 12 and 24 weeks.

Aim : To explore an alternative approach for making individualized recommendations about treatment duration, based on simple alanine aminotransferase tests and on cost‐per‐cure.

Methods : We analysed individual patient data from 13 randomized, controlled trials with interferon alone or combined with ribavirin. Using multiple logistic regression, we built a model that estimated the probability of sustained virological response for treatment durations of 24 and 48 weeks. Decisions to prolong treatment were based on an increase in probability of sustained virological response. If the increase was 10%, the cost‐per‐cure became decisive with a limit of 50 000 €.

Results : Noncirrhotics with genotype 2 or 3 did not benefit when treatment was continued beyond 24 weeks. Sustained virological response rates in cirrhotic patients increased by 14–47% if treatment was continued up to 48 weeks. In noncirrhotic genotype 1 or 4 patients who had elevated alanine aminotransferase levels at week 4, the probability of sustained virological response increased by <10% if treatment was continued up to 48 weeks; the cost‐per‐cure for these patients would exceed 50 000 €.

Conclusion : The dynamics of alanine aminotransferase levels and cost‐per‐cure provides a useful alternative to determine the duration of therapy in chronic hepatitis C.
A comparative study of the early effects of tenatoprazole 40 mg and esomeprazole 40 mg on intragastric pH in healthy volunteers
Authors: Galmiche J. P. , Sacher‐Huvelin S. , Bruley des Varannes S. , Vavasseur F. , Taccoen A. , Fiorentini P. , Homerin M.
Published: March 2005

Background : Tenatoprazole is a novel proton pump inhibitor with a seven‐hour plasma half‐life.

Aim : To compare the effects of tenatoprazole 40 mg and esomeprazole 40 mg on intragastric acidity during the first 48 h in healthy volunteers.

Methods : This randomized two‐period crossover study included 24 Helicobacter Pylori‐negative subjects; tenatoprazole 40 mg or esomeprazole 40 mg daily were given before breakfast for two consecutive days, with a 2‐week wash‐out between the administration periods. Intragastric pH was monitored for 48 h.

Results : Over 48 h, tenatoprazole 40 mg exerted a more potent acid inhibition than esomeprazole 40 mg (median pH: 4.3 vs. 3.9, P < 0.08; per cent of time above pH 4: 57% vs. 49%, P < 0.03; proportion of subjects with at least half of the time above pH 4: 71% vs. 46%). These differences resulted from better night‐time acid control with tenatoprazole 40 mg than esomeprazole 40 mg (first night median pH: 4.2 vs. 2.9, P < 0.0001; second night: 4.5 vs. 3.2, P < 0.0001). The duration of nocturnal acid breakthroughs was significantly reduced during both nights. In contrast, no significant difference was detected during the daytime periods between both regimens.

Conclusion : Over the first 48 h, tenatoprazole 40 mg achieves a better overall and night‐time control of gastric pH than esomeprazole 40 mg. The translation of better early control of acidity into clinical benefits deserves further studies.
Relationship between serum ferritin, hepatic iron staining, diabetes mellitus and fibrosis progression in patients with chronic hepatitis C
Authors: D'Souza R. F. C. , Feakins R. , Mears L. , Sabin C. A. , Foster G. R.
Published: March 2005

Background : Chronic infection with the hepatitis C virus affects over 170 million individuals worldwide and 20% of patients develop cirrhosis after 20 years. Increased iron stores and hepatic iron content have been suggested to be important in fibrosis progression. The increased prevalence of diabetes mellitus has been associated with increased iron deposits in patients with chronic hepatitis C.

Aim : To assess the potential relationship between serum ferritin and hepatic iron staining and liver fibrosis in patients with chronic hepatitis C virus infection and whether these factors are increased in diabetic patients with hepatitis C virus.

Methods : This was a cross‐sectional, multi‐centre study involving hospitals in the north‐east of London between 1992 and 2003. Chronic hepatitis C patients with a liver biopsy and data concerning age, sex, basal metabolic index, diabetes mellitus or impaired glucose tolerance, alcohol intake, serum ferritin level and ethnicity were enrolled. Each biopsy was scored for fibrosis and stained for hepatic iron.

Results : Three hundred and thirty nine patients (200 Caucasian; 139 Asian) were enrolled. Fifty three patients had no fibrosis, 131 had mild fibrosis (stage one to two Modified Ishak), 68 moderate fibrosis (stage three to four) and 87 cirrhosis (stage five to six). 4.4% of patients had elevations in serum ferritin, whilst 11% had increased hepatic iron staining. The serum ferritin and hepatic iron staining were unrelated to the degree of fibrosis. Serum ferritin was significantly higher in patients with diabetes or impaired glucose tolerance compared to non‐diabetics. No association was seen between diabetes and hepatic iron staining.

Conclusions : Many patients with chronic hepatitis C virus infection may have elevated serum ferritin and/or iron deposition within the liver. However, both played no significant role in the progression of hepatitis C virus related liver injury. The association between chronic hepatitis C virus infection and type II diabetes mellitus exists, however the biological mechanism of this association still remains to be elucidated.
Occurrence and risk factors for benign epithelial gastric polyps in atrophic body gastritis on diagnosis and follow‐up
Authors: Di Giulio E. , Lahner E. , Micheletti A. , Milione M. , D'Ambra G. , Bordi C. , Delle Fave G. , Annibale B.
Published: March 2005

Background : Benign epithelial gastric polyps have been reported to be more common in atrophic body gastritis. The role of Helicobacter pylori infection in the induction of gastric atrophy is well‐known. The development of hyperplastic polyps may be in relation to H. pylori infection.

Aim : To investigate occurrence of benign epithelial gastric polyps in atrophic body gastritis patients at diagnosis and follow‐up, and the role of H. pylori and other risk factors for the development of benign epithelial gastric polyps.

Methods : A total of 259 consecutive atrophic body gastritis patients included in a follow‐up programme, of whom 202 were followed up for median period of 4 years (range: 2–11). At baseline and follow‐up gastroscopies, the presence of benign epithelial gastric polyps was evaluated. Biopsies for histology were obtained from all detected benign epithelial gastric polyps.

Results : Frequency of benign epithelial gastric polyps in atrophic body gastritis patients were 4.6% at baseline and 5.9% at follow‐up. About 91.7% were hyperplastic polyps. H. pylori infection was detected in 79.2% atrophic body gastritis patients with benign epithelial gastric polyps, and in 70.8% without benign epithelial gastric polyps. Smoking was more frequent among patients with benign epithelial gastric polyps [42% vs. 20%, OR 2.8 (95% CI: 1.2–6.9)].

Conclusions : Benign epithelial gastric polyps occur in about 5% of atrophic body gastritis patients, and the vast majority are hyperplastic polyps. Smoking habit, but not H. pylori infection, increases the risk for benign epithelial gastric polyps in atrophic body gastritis patients.
Dental pulp capping: effect of Emdogain Gel on experimentally exposed human pulps
Authors: Olsson H. , Davies J. R. , Holst K. E. , Schröder U. , Petersson K.
Published: March 2005

Aim  To investigate the effect of Emdogain Gel (Biora AB, Malmö, Sweden), consisting of a enamel matrix derivative (EMD) in a propylene glycol alginate (PGA) vehicle, on experimentally exposed human pulps and to register postoperative symptoms.

Methodology  Nine pairs of contralateral premolars scheduled for extraction on orthodontic indications were included. Following a superficial pulp amputation performed with a small (016) diamond bur, either EMDgel or a mix of calcium hydroxide and sterile saline was placed at random in contact with the pulp wound. The subjects made records of symptoms and were also interviewed about pain/discomfort by a blinded examiner. After 12 weeks the teeth were extracted, prepared and subjected to light microscopic examination in which the inflammation and newly formed hard tissue in the pulp were analysed. Immunohistochemistry was performed using affinity‐purified rabbit anti‐EMD polyclonal antibodies.

Results  Postoperative symptoms were less frequent in the EMDgel‐treated than in the calcium hydroxide‐treated teeth, especially during the first six weeks. In the EMDgel‐treated teeth, new tissue partly filled the space initially occupied by the gel and hard tissue was formed alongside the exposed dentine surfaces and in patches in the adjacent pulp tissue. EMD was detected in the areas where new hard tissue had been formed. The wound area of the EMDgel‐treated teeth exhibited inflammation in the majority of the teeth whereas less inflammation was seen in the calcium hydroxide‐treated teeth where the hard tissue was formed as a bridge.

Conclusions  In the EMDgel‐treated teeth, postoperative symptoms were less frequent and the amount and pattern of hard tissue formation were markedly different than in the teeth treated with calcium hydroxide. However, the operative procedure and the formulation with EMD in a PGA vehicle do not seem to be effective for the formation of a hard tissue barrier.
Copper–zinc superoxide dismutase activity in healthy and inflamed human dental pulp
Authors: Varvara G. , Traini T. , Esposito P. , Caputi S. , Perinetti G.
Published: March 2005

Aim  To examine copper–zinc superoxide dismutase (Cu, Zn‐SOD) activity in clinically healthy and symptomatic human dental pulps.

Methodology  Twenty‐five systemically healthy patients, 14 females and 11 males (age: 13.1–34.6 years; mean: 21.7 ± 6.3), were the source of the pulp tissue. The condition of the pulps was assessed using clinical and radiographic evaluation. The pulp tissue was collected by longitudinally grooving and splitting the teeth (if extracted) or during endodontic treatment, and were age‐ and sex‐matched between the healthy and the irreversible symptomatic pulpitis tissue groups. Cu, Zn‐SOD activity was determined through spectrophotometric methods and a Mann–Whitney test assessed the significance of differences between the groups.

Results  The enzyme activities were 144.8 ± 42.2 and 68.1 ± 25.0 U mg−1 in the healthy and irreversible symptomatic pulp tissue, respectively. The difference between the groups was statistically significant (P < 0.001).

Conclusions  These results demonstrate a potential role for Cu, Zn‐SOD during dental pulp inflammation in humans.
Dental arch morphological and dimensional characteristics in Jordanian children and young adults with β‐thalassaemia major
Authors: AL‐WAHADNI A. , QUDEIMAT M. A. , AL‐OMARI M.
Published: March 2005

Objective.   The aim of this study was to examine the arch dimensions of Jordanian patients with β‐thalassaemia major in comparison with an unaffected control group.

Methods.   The sample consisted of 24 patients who suffered from β‐thalassaemia major (mean age = 13·9 ± 3·1 years) and an unaffected control group (mean age = 13·5 ± 2·9 years) matched for dental age, sex, and incisor and molar relationships. The unaffected control group was randomly selected from four public schools in the Governate of Irbid‐Jordan. Alginate impressions were taken of the maxillary and mandibular dental arches of all participants. All measurements of the arch dimensions were made on the casts using an electronic digital sliding calliper.

Results.   In the mandibular arch, when compared with the patients with thalassaemia, the unaffected control group subjects showed a (statistically) significantly larger incisor width, larger arch depth, and larger left and right anterior arch lengths (1·18, 2·58, and 1·85 and 1·12 mm, respectively). In the maxillary arch, there was a statistically significant difference in the mean incisor width (± 2·16 mm), arch depth (± 3·14 mm), inter‐molar width (± 1·21 mm) and in the left anterior arch length (± 1·97 mm). The canine widths, premolar widths, left and right posterior arch length, and curve of Spee of both arches showed no statistically significant differences between the two groups.

Conclusion.   When compared to unaffected subjects, patients with β‐thalassaemia major exhibited: a narrower maxilla; a shorter maxilla and mandible; and smaller incisor widths for the maxillary and mandibular arches.
Effect of the diurnal rhythm and 24 h of sleep deprivation on dichotic temporal order judgment
Authors: BABKOFF HARVEY , ZUKERMAN GIL , FOSTICK LEAH , BEN‐ARTZI ELISHEVA
Published: March 2005

The present study examined the impact of mild (24 h) sleep deprivation and of the circadian rhythm on auditory temporal resolution, measured by dichotic temporal order judgment (TOJ). The rationale for the present study was based on several areas of research. First, the ‘sleep‐based neuropsychological perspective’ hypothesis posits that sleep reduction initially impacts the functions associated with intact prefrontal cortical activity, e.g. language tasks. Secondly, recent studies indicate the importance of the role of auditory temporal resolution in speech comprehension. Thirdly, there is accumulating evidence of the involvement of prefrontal cortical structures in auditory temporal resolution. We hypothesized that mild to moderate sleep deprivation would affect dichotic TOJ negatively. The results showed that: (1) 24 h of sleep deprivation significantly reduced the overall level of accuracy in dichotic TOJ and increased dichotic TOJ threshold from 57.61 ms to 73.93 ms, a reduction in temporal resolution of 28.3%; (2) dichotic TOJ was subject to a small, but significant diurnal rhythm having a nadir in early to mid afternoon. As auditory temporal resolution of speech and non‐speech sounds seems to be dependent on intact functioning of the left inferior and left dorso‐lateral prefrontal cortex (PFC), these data strengthen the argument that even mild to moderate sleep deprivation can impact negatively on PFC‐dependent functions. Furthermore, based on these findings, we suggest that the deficit in auditory temporal resolution in individuals suffering from sleep loss may also affect language comprehension.
The ontogeny of mammalian sleep: a response to Frank and Heller (2003)
Authors: BLUMBERG MARK S. , KARLSSON KARL Æ. , SEELKE ADELE M. H. , MOHNS ETHAN J.
Published: March 2005

In a recent review, Frank and Heller (2003) provided support for their ‘presleep theory’ of sleep development. According to this theory, rapid eye movement (REM) and non‐rapid eye movement (Non‐REM) sleep in rats emerge from a common ‘dissociated’ state only when the neocortical EEG differentiates at 12 days of age (P12). Among the assumptions and inferences associated with this theory is that sleep before EEG differentiation is only ‘sleep‐like’ and can only be characterized using behavioral measures; that the neural mechanisms governing presleep are distinct from those governing REM and Non‐REM sleep; and that the presleep theory is the only theory that can account for developmental periods when REM and Non‐REM sleep components appear to overlap. Evidence from our laboratory and others, however, refutes or casts doubt on these and other assertions. For example, infant sleep in rats is not ‘sleep‐like’ in that it satisfies nearly every criterion used to characterize sleep across species. In addition, beginning as early as P2 in rats, myoclonic twitching occurs only against a background of muscle atonia, indicating that infant sleep is not dissociated and that electrographic measures are available for sleep characterization. Finally, improved techniques are leading to new insights concerning the neural substrates of sleep during early infancy. Thus, while many important developmental questions remain, the presleep theory, at least in its present form, does not accurately reflect the phenomenology of infant sleep.
Sleep disturbance and daytime symptoms in wheezing school‐aged children
Authors: DESAGER KRISTINE N. , NELEN VERA , WEYLER JOOST J. J. , DE BACKER WILFRIED A.
Published: March 2005

The aim of the study was to investigate whether wheezing is associated with disturbed sleep and increased daytime symptoms in school‐aged children. A random sample of 1234 children, aged 6–14 years, participated in a respiratory health study in the region of Antwerp. The International Study of Asthma and Allergies in Childhood questionnaire and a separate sleep questionnaire were completed. In the children who wheezed in the last 12 months, sleep quality was more frequently disturbed due to nocturnal awakenings and restless sleep compared with children who did not wheeze. Daytime sleepiness and tiredness were more common in wheezing than in non‐wheezing children. After adjusting for possible confounders a positive association was found between wheeze and: difficulties falling asleep [odds ratio (OR) = 2.0], restless sleep (OR = 5.0), daytime sleepiness (OR = 3.8) and daytime tiredness (OR = 5.1). Chronic cough (OR = 2.4), snoring (OR = 2.0), chronic rhinitis (OR = 2.6) and eczema (OR = 3.3) were associated with disturbed sleep. Chronic cough (OR = 2.5) and rhinitis (OR = 4.1) were related to daytime tiredness. Chronic rhinitis was an important risk factor for snoring (OR = 1.9). In wheezing school‐aged children, decreased quality of sleep and increased daytime tiredness and sleepiness were more often reported. Upper airway symptoms were related to the sleep disturbances.