bluuebunny/crossref_metadata_2025 huggingface dataset:
Intraoperative Epidural Analgesia Combined with Ketamine Provides Effective Preventive Analgesia in Patients Undergoing Major Digestive Surgery
Authors: Lavand’homme Patricia , De Kock Marc , Waterloos Hilde
Published: September 2005

Background

As a broader definition of preemptive analgesia, preventive analgesia aims to prevent the sensitization of central nervous system, hence the development of pathologic pain after tissular injury. To demonstrate benefits from preventive treatment, objective measurement of postoperative pain such as wound hyperalgesia and persistent pain should be evaluated. The current study assessed the role and timing of epidural analgesia in this context.

Methods

In a randomized, double-blinded trial, 85 patients scheduled to undergo neoplastic colonic resection were included. All the patients received a thoracic epidural catheter, systemic ketamine at a antihyperalgesic dose, and general anesthesia. Continuous infusion of analgesics belonging to the same class was administered by either intravenous or epidural route before incision until 72 h after surgery. Patients were allocated to four groups to receive intraoperative intravenous lidocaine-sufentanil-clonidine or epidural bupivacaine-sufentanil-clonidine followed postoperatively by either intravenous (lidocaine-morphine-clonidine) or epidural (bupivacaine-sufentanil-clonidine) patient-controlled analgesia. Postoperative pain scores (visual analog scale), analgesic consumption, wound area of punctuate hyperalgesia, residual pain, and analgesics needed from 2 weeks until 12 months were recorded.

Results

Analgesic requirements, visual analog scale scores, and area of hyperalgesia were significantly higher in the intravenous treatment group (intravenous-intravenous), and more patients reported residual pain from 2 weeks until 1 yr (28%). Although postoperative pain measurements did not differ, postoperative epidural treatment (intravenous-epidural) was less effective to prevent residual pain at 1 yr (11%; P = 0.2 with intravenous-intravenous group) than intraoperative one (epidural-epidural and epidural-intravenous groups) (0%; P = 0.01 with intravenous-intravenous group).

Conclusion

Combined with an antihyperalgesic dose of ketamine, intraoperative epidural analgesia provides effective preventive analgesia after major digestive surgery.
Somatotopy in Human Primary Somatosensory Cortex in Pain System
Authors: Ogino Yuichi , Nemoto Hidenori , Goto Fumio
Published: September 2005

Background

Compared with somatotopical organization (somatotopy) in the postcentral gyrus in the tactile system, somatotopy in the pain system is not well understood. The aim of this study is to elucidate whether there is somatotopy in the human pain system.

Methods

To elucidate the somatotopy of nociceptive neurons in the postcentral gyrus, the authors recorded pain-evoked cortical responses to noxious intraepidermal electrical stimulation applied to the left hand and left foot in 11 male subjects, using magnetoencephalography.

Results

Brief painful stimuli evoked sustained cortical activity in the primary somatosensory cortex (SI) in the hemisphere contralateral to the stimulated side and in the secondary somatosensory cortex in both hemispheres. In SI, representations of the hand and foot were distinctly separated, with a more medial and posterior location for the foot, whereas no significant difference was found in the locations for the secondary somatosensory cortex dipole. The SI arrangement along the central sulcus was compatible with the homunculus revealed by Penfield using direct cortical stimulation during surgery.

Conclusions

The human pain system contains a somatotopical representation in SI but with less somatotopical organization in the secondary somatosensory cortex. The current results provide supporting evidence of SI involvement in human pain perception and suggest that human SI subserves the localization of the stimulated site in nociceptive processing.
Preoperative Clinic Visits Reduce Operating Room Cancellations and Delays
Authors: Ferschl Marla B. , Tung Avery , Sweitzer BobbieJean , Huo Dezheng , Glick David B.
Published: September 2005

Background

Anesthesiologist-directed preoperative medicine clinics are used to prepare patients for the administration of anesthesia and surgery. Studies have shown that such a clinic reduces preoperative testing and consults, but few studies have examined the impact of the clinic on the day of surgery. The authors tested whether a visit to an anesthesia preoperative medicine clinic (APMC) would reduce day-of-surgery case cancellations and/or case delays.

Methods

The authors conducted a retrospective chart review of all surgical cases during a 6-month period at the University of Chicago Hospitals. Case cancellations and rates of first-start case delay over the 6-month period were cross-referenced with a database of APMC attendees in both the general operating rooms and the same-day surgery suite. The impact of a clinic visit on case cancellation and delay in both sites were analyzed separately.

Results

A total of 6,524 eligible cases were included. In the same-day surgery suite, 98 of 1,164 (8.4%) APMC-evaluated patients were cancelled, as compared with 366 of 2,252 (16.2%) in the non-APMC group (P < 0.001). In the general operating rooms, 87 of 1,631 (5.3%) APMC-evaluated patients were cancelled, as compared with 192 of 1,477 (13.0%) patients without a clinic visit (P < 0.001). For both operating areas, APMC patients had a significantly earlier room entry time than patients not evaluated in the APMC.

Conclusions

An evaluation in the APMC can significantly impact case cancellations and delays on the day of surgery.
Potential antimicrobial effects of human lactoferrin against oral infection with Listeria monocytogenes in mice
Authors: Lee Hui-Young , Park Jong-Hwan , Seok Seung-Hyeok , Baek Min-Won , Kim Dong-Jae , Lee Byoung-Hee , Kang Pil-Don , Kim Yong-Soon , Park Jae-Hak
Published: September 2005

Listeria monocytogenesis a food-borne pathogen that causes serious listeriosis in humans. Antimicrobial effects of human lactoferrin (hLF) againstL. monocytogeneshave been clearly demonstrated inin vitrostudies. However,in vivostudies have not been reported yet. This study investigated whether the oral administration of hLF could inhibit oral infection of listeria in BALB/c mice. The MICs for several strains ofL. monocytogeneswere determined, and the most sensitive strain was used for the animal work. hLF was administered to BALB/c mice for 7 days, commencing 4 days before oral infection. The effect of hLF was determined by bacterial enumeration and histopathological analysis of the liver and spleen, which are well-known as the major targets of oral listeria infection in mice. In bacterial enumeration, hLF decreased the number ofL. monocytogenescells in the liver. Histopathologically, the size and frequency of necrotic foci in the liver samples decreased with hLF administration. However, these changes were not observed in the spleen samples. The mRNA levels of inflammatory cytokines, such as interleukin (IL)-1β, tumour necrosis factor (TNF)-α and interferon (IFN)-γ, decreased in the liver of mice receiving hLF. This study has shown that hLF decreases the hepatic colonization ofL. monocytogenes, hepatic necrosis and expression of inflammatory cytokines. It revealed that perorally given hLF could mediate antimicrobial and anti-inflammatory activities remote from the gut (i.e. in the liver) of mice challenged withL. monocytogenes.
Invasive fungal infections are associated with severe depletion of circulating RANTES
Authors: Ellis Michael , al-Ramadi Basel , Hedström Ulla , Alizadeh Hussain , Shammas Victor , Kristensen Jörgen
Published: September 2005

Serum RANTES (regulated on activation, normal T-cell expressed and secreted) concentrations were measured in 14 patients who had haematological malignancies and developed invasive fungal infections (three of them definite, eight probable and three possible). RANTES levels fell substantially from pre-chemotherapy values at the start of and throughout the fungal infection, and recovered in patients who survived the fungal infection. However, in patients who died from the invasive fungal infection, RANTES levels did not recover. For survivors the mean ±sdlevels for RANTES were 7656 ± 877 pg ml−1on the day prior to chemotherapy, 3723 ± 2443 pg ml−1on the first day of fungal infection diagnosis (significantly different from baseline;P= 0.001) and 9078 ± 2256 pg ml−1at recovery from the fungal infection (significantly different from lowest value;P< 0.0001). Platelet counts were closely correlated with the RANTES levels (r= 0.63,P< 0.001). The RANTES concentrations for the three patients who died were similar to those who survived at all equivalent timepoints, but were significantly lower at the time of death (792 ± 877) compared to the values at recovery for survivors (P= 0.005). The finding that patients who died from an invasive fungal infection had very low platelet counts and RANTES concentrations suggests that these could play a role in host response to such infections.
Identification and characterization of an immunogenic 22 kDa exported protein of Mycobacterium avium subspecies paratuberculosis
Authors: Dupont Chris , Thompson Keith , Heuer Cord , Gicquel Brigitte , Murray Alan
Published: September 2005

An exported 22 kDa putative lipoprotein was identified in an alkaline phosphatase gene fusion library ofMycobacterium aviumsubsp.paratuberculosisand expressed inMycobacterium smegmatis. The full nucleic acid sequence of the gene encoding P22 was determined and the ORF was cloned into a mycobacterial expression vector, enabling full-length P22 to be produced as a C-terminal polyhistidine-tagged protein inM. smegmatis. N-terminal sequencing of the recombinant protein confirmed cleavage of a signal sequence. Native P22 was detected in culture supernatants and cell sonicates ofM. aviumsubsp.paratuberculosisstrain 316F using rabbit antibody raised to recombinant P22. Investigation of the presence of similar genes in other mycobacterial species revealed that the gene was present inMycobacterium aviumsubsp.aviumand similar genes existed inMycobacterium intracellulareandMycobacterium scrofulaceum. Database searches showed that P22 belonged to the LppX/LprAFG family of mycobacterial lipoproteins also found inMycobacterium lepraeand in members of theMycobacterium tuberculosiscomplex. P22 shared less than 75 % identity to these proteins. Recombinant P22 was able to elicit interferon-gamma secretion in blood from eight of a group of nine sheep vaccinated with a live attenuated strain ofM. aviumsubsp.paratuberculosis(strain 316F) compared to none from a group of five unvaccinated sheep. Antibody to P22 was detected by Western blot analysis in 10 out of 11 vaccinated sheep, in two out of two clinically affected cows and in 11 out of 13 subclinically infected cows.
Prostaglandin production during growth of Candida albicans biofilms
Authors: Alem Mohammed AS , Douglas L Julia
Published: September 2005

Both biofilms and planktonic (suspended) cells of Candida albicans synthesized extracellular prostaglandin(s) during growth at 37 °C, but biofilm cells secreted significantly more prostaglandin(s) when production was determined on the basis of cell dry weight. Prostaglandin synthesis by both cell types was sensitive to the cyclooxygenase inhibitors aspirin, diclofenac and etodolac. A morphological mutant blocked in two signalling pathways (cph1/cph1 efg1/efg1) produced prostaglandin levels similar to those of the parent strain, but formed yeast-only biofilms. These results suggest that prostaglandin production could be a significant virulence factor in biofilm-associated infections, although its role in C. albicans morphogenesis remains unclear.
Multiplex PCR for identification of Campylobacter coli and Campylobacter jejuni from pure cultures and directly on stool samples
Authors: Persson Søren , Olsen Katharina EP
Published: September 2005

A multiplex-PCR method, specifically designed for application in routine diagnostic laboratories, was developed for the detection ofCampylobacter coliandCampylobacter jejuni. Primers were directed towards the following loci: the hippuricase gene (hipO) characteristic ofC. jejuni, a sequence partly covering an aspartokinase gene characteristic ofC. coli, and a universal 16S rDNA gene sequence serving as an internal positive control for the PCR. The method was tested on 47C. colistrains and 88C. jejunistrains, and found to be almost 100 % in concordance with biochemical analyses (all except for oneC. colistrain), regardless of whether the DNA was prepared from colonies by a simple boiling procedure or by DNeasy Tissue Kit. Pure cultures ofC. coliandC. jejuniwere identified at 10–100 cells per PCR. When the multiplex-PCR method was used on spiked human stool samples, both strains were identified at 105cells per ml stool. This sensitivity limit was the same whether the DNA was purified by the method of KingFisher mL or QIAamp DNA Stool Kit. When the same spiked stools were grown on modified charcoal cefoperazone deoxycholate agar (mCCDA) plates before PCR, the sensitivity was 100 cells per ml stool, indicating that culturing of campylobacters on mCCDA plates is superior to direct DNA extraction at least when fresh stool samples are analysed by PCR.
Eyeglass frame allergic contact dermatitis: does tacrolimus prevent recurrences?
Authors: Nakada Tokio , Iijima Masafumi , Maibach Howard I.
Published: September 2005

A 35‐year‐old man developed well‐demarcated, oedematous and erosive erythematous lesions on the nasal bridge and retroauricular regions bilaterally. His eyeglass frame was repaired by an optician 2 weeks prior to symptom onset. Patch testing revealed a positive reaction to scrapings of nose pads and temples of the frame in petrolatum. Because the patient did not take our exhortation to change eyeglass frames, we advised him to cover their nose pads and temples with vinyl tape to prevent direct skin contact. Although topical corticosteroid therapy produced clinical resolution temporally, recurrences were not prevented. After starting tacrolimus ointment therapy, recurrence has not occurred for 9 months. Tacrolimus may be effective for allergic contact dermatitis patients who cannot avoid repeated allergen exposure, as it may not only reduce inflammation but inhibit recurrences.
Hapten–protein binding: from theory to practical application in the in vitro prediction of skin sensitization
Authors: Divkovic Maja , Pease Camilla K. , Gerberick G. Frank , Basketter David A.
Published: September 2005

In view of the forthcoming European Union ban on in vivo testing of cosmetic and toiletry ingredients, following the publication of the 7th amendment to the Cosmetics Directive, the search for practical, alternative, non‐animal approaches is gathering pace. For the end‐point of skin sensitization, the ultimate goal, i.e. the development and validation of alternative in vitro/in silico assays by 2013, may be achieved through a better understanding of the skin sensitization process on the cellular and molecular levels. One of the key molecular events in skin sensitization is protein haptenation, i.e. the chemical modification of self‐skin protein(s) thus forming macromolecular immunogens. This concept is widely accepted and in theory can be used to explain the sensitizing capacity of many known skin sensitizers. Thus, the principle of protein or peptide haptenation could be used in in vitro assays to predict the sensitization potential of a new chemical entity. In this review, we consider some of the theoretical aspects of protein haptenation, how mechanisms of protein haptenation can be investigated experimentally and how we can use such knowledge in the development of novel, alternative approaches for predicting skin sensitization potential in the future.
Cutaneous hypersensitivity to Candida albicans in idiopathic vulvodynia
Authors: Ramirez De Knott Haydee M. , McCormick Thomas S. , Do Shaheen Oshtory , Goodman Wendy , Ghannoum Mahmoud A. , Cooper Kevin D. , Nedorost Susan T.
Published: September 2005

We have observed that the majority of our vulvodynia patients give a previous history of vaginal candidiasis that was treated but was followed by symptoms of chronic vulvodynia. 27 vulvodynia patients were patch‐tested to a standard series of contact allergens, a customized vulvar series and commensal organisms including ultraviolet‐killed Candida albicans. Comparison tests for the commensal organism were made to a group of 13 female atopic dermatitis patients and to 19 female dermatitis patients without a history of childhood flexural dermatitis who were undergoing patch test evaluation in our clinic. Patients reporting vulvodynia were significantly (P < 0.05) more likely to react to C. albicans than the dermatitis comparison group. Interestingly, lower concentrations of C. albicans caused more positive patch tests than higher concentrations. Our findings suggest that previous C. albicans infection may predispose patients to a subsequent hypersensitivity response to C. albicans that is expressed only in areas of high cutaneous peripheral fibre density. Low levels of C. albicans may also be required to elicit this response as high levels of C. albicans may actually result in decreased cutaneous inflammation and decreased intensity of C. albicans patch test responses.
Effect of Glass Additions on the Indentation‐Strength Behavior of Alumina
Authors: O'Donnell Heather L. , Readey Michael J. , Kovar Desiderio
Published: September 2005

The effect of small calcium aluminosilicate (CAS) glass additions on the microstructure and flaw tolerance of alumina ceramics is investigated, and the results compared to a high‐purity alumina. The high‐purity alumina specimens were dense with microstructures consisting of a uniform grain size distribution and equiaxed grain morphology. Additions of only 1 wt% glass phase resulted in a bimodal grain size distribution containing large, elongated grains within a fine‐grain matrix. Indentation‐strength tests indicated enhanced flaw tolerance with the bimodal microstructure, even though both materials had nominally the same average grain size. The strength of unindented specimens was also observed to decrease with glass additions. Observations of crack paths show a greater propensity for bridging in the glass‐containing alumina due to the presence of coarse, elongated grains and perhaps a lower grain boundary toughness. However, crack extension occurs transgranularly when the size of the coarsest grains becomes too large. This suggests that an optimum in flaw tolerance will be achieved with an elongated grain morphology and intermediate grain size.
Mechanism of La2CuO4 Solid‐State Powder Reaction by Quantitative XRD and Impedance Spectroscopy
Authors: Cooper Elizabeth A. , Mason Thomas O.
Published: September 2005

Reaction kinetics for CuO + La2O3→ La2CuO4 were quantified by X‐ray diffraction on quenched samples reacted in air. The rate was successfully modeled by the Valensi‐Carter equation, taking into account the particle size distribution. Kinetics followed diffusion‐limited rather than reaction‐limited behavior; the activation energy was 265 kJ/mol. Conductivity‐time behavior from in situ impedance spectra confirmed the reaction model; CuO rapidly coats the La2O3 particles and produces an La2CuO4 diffusion barrier. This is consistent with the basic assumptions of the Valensi‐Carter equation. It is believed that copper diffusion controls the rate of reaction.
Temperature Profiling of Glass by FT‐IR Emission Spectroscopy
Authors: Markham James R. , Cosgrove Joseph E. , Carangelo Martin D. , Solomon Peter R. , Best Philip E.
Published: September 2005

Fourier transform infrared (FT‐IR) spectroscopy is utilized to measure the wavelength and temperature‐dependent radiative properties of two glass formulations. The information gained is then used with FT‐IR measurements of radiance from hot glass to determine temperature gradient profiles through each glass thickness. Temperature profiling of clear Corning Pyrex and green‐tinted PPG Solex are presented. The Solex was measured on‐line, in situ during production at the industrial kiln. Since a temperature profile (not just bulk average) is obtained, the method offers a better understanding of process conditions for the glass industry.
Influence of Slurry Flocculation on the Character and Compaction of Spray‐Dried Silicon Nitride Granules
Authors: Takahashi Hideo , Shinohara Nobuhiro , Okumiya Masataro , Uematsu Keizo , JunIchiro Tsubaki , Iwamoto Yuji , Kamiya Hidehiro
Published: September 2005

The effect of slurry flocculation on the characteristics of silicon nitride granules prepared by the spray drying process is investigated. The flocculation state of an aqueous silicon nitride slurry is controlled by adding nitric acid and evaluated as a function of pH. Dense and hard silicon nitride granules result from a well‐dispersed slurry having a high pH (e.g., 10.8). These hard granules retain their shape in green compacts and form detrimental defects. Lowering the pH of the slurry to a certain value (e.g., pH 7.9) results in slurry flocculation. Granules prepared from this flocculated slurry have low density and low diametral compression strength and contribute to the elimination of large pores in green compacts.
Nature of Cation Vacancies Formed to Compensate Donors during Oxidation of Barium Titanate
Authors: Yamada Atsushi , Chiang Yet‐Ming
Published: September 2005

Oxidative cooling is a critical step in the processing of barrier layer electroceramics based on BaTiO3. While it has been proposed that barium vacancies are formed at the grain boundaries to compensate donors,1, 2 no direct evidence for this mechanism exists. On the other hand, literature data can be found to support the compensation of donors in the bulk by either barium or titanium vacancies. As a result the defect(s) formed at electrically active titanate grain boundaries during oxidation has remained uncertain. We explore this phenomenon by observing changes in the surface composition of donor‐doped BaTiO3 when cation vacancies are introduced during oxidation, using SAES (scanning Auger electron spectroscopy). Direct experimental support for the formation and in‐diffusion of barium vacancies during oxidative cooling is obtained in a composition containing 0.7% Nb. It is suggested that barium vacancy compensation constitutes a metastable defect equilibrium in BaTiO3. In a sample of lower concentration (0.3% Nb), results are inconclusive, perhaps because of slower oxidation limited by surface reaction kinetics.
Electrochemical Synthesis and Sintering of Nanocrystalline Cerium(IV) Oxide Powders
Authors: Zhou Yanchun , Phillips Richard J. , Switzer Jay A.
Published: September 2005

Nanocrystalline CeO2 powders were prepared electrochemically by the cathodic electrogeneration of base, and their sintering behavior was investigated. X‐ray diffraction and transmission electron microscopy revealed that the as‐prepared powders were crystalline cerium(IV) oxide with the cubic fluorite structure. The lattice parameter of the electrogenerated material was 0.5419 nm. The powders consisted of nonaggregated, faceted particles. The average crystallite size was a function of the solution temperature. It increased from 10 nm at 29°C to 14 nm at 80°C. Consolidated powders were sintered in air at both a constant heating rate of 10°C/min and under isothermal conditions. The temperature at which sintering started (750°C) for nanocrystalline CeO2 powders was only about 100°C lower than that of coarser‐grained powders (850°C). However, the sintering rate was enhanced. The temperature at which shrinkage stopped was 200°‐300°C lower with the nanoscale powder than with micrometer‐sized powders. A sintered specimen with 99.8% of theoretical density and a grain size of about 350 nm was obtained by sintering at 1300°C for 2 h.
Failure Mechanisms of a Zirconia‐8 wt% Yttria Thermal Barrier Coating
Authors: Bartlett Andrew H. , Maschio Roberto Dal
Published: September 2005

Isothermal and cyclic heat treatments of a plasma‐sprayed zirconia‐8 wt% yttria thermal barrier coating on a nickel superalloy substrate highlighted coating failure mechanisms. A reaction layer formed at the bond coat/ceramic interface, and failure of the coating initiated in the reaction layer due to opening thermal expansion mismatch stresses associated with a nonplanar interface. Crack propagation occurred in the ceramic in all cases, due to the high fracture energy of the interface. The relatively low fracture energy of the coating, in planes parallel to the interface, is the ultimate factor limiting coating lifetime.
Growth of a Bonelike Apatite Layer on a Substrate by a Biomimetic Process
Authors: Hata Kotaro , Kokubo Tadashi , Nakamura Takashi , Yamamuro Takao
Published: September 2005

A dense and uniform bonelike apatite layer was formed on a substrate by the following biomimetic method. The substrate was first placed on granular particles of CaO, SiO2‐based glass soaked in a simulated body fluid (SBF) with ion concentrations nearly equal to those of human blood plasma and then soaked in another fluid highly supersaturated with respect to the apatite. The thickness of the apatite layer increased in proportion to the soaking time in the second solution. The rate of increase in the thickness of the apatite layer increased from 0.5 to 7.0 μm/day with increasing temperature of the second solution from 10° to 60°C, increased from 0.15 to 1.7 μm/day with increasing ion concentrations of the second solution from 0.2 to 1.5 times those of the SBF, and doubled by shaking the second solution. These results indicate that the growth of the apatite layer is controlled by mass transport across the interface between the crystal and the fluid.
Nonlinear Optical Properties of TeO2‐Based Glasses: MOx‐TeO2 (M = Sc, Ti, V, Nb, Mo, Ta, and W) Binary Glasses
Authors: Kim Sae‐Hoon , Yoko Toshinobu
Published: September 2005

The third‐order nonlinear optical susceptibilities, X(3), of TeO2‐based glasses containing transition metal oxides (M = Sc2O3, TiO2, V2O5, Nb2O5, MoO3, Ta2O5, and WO3) glasses have been measured by the third harmonic generation (THG) method in order to investigate the effect of the empty d‐orbital contributions to the third‐order nonlinear optical susceptibilities. It is found that the addition of TiO2, Nb2O5, and WO3 to TeO2 glass increases the X(3) value as well as the refractive index, while others decrease both of them. The positive effect of the TiO2, Nb2O5, or WO3, on the X(3) of TeO2 glass was interpreted in terms of the cationic empty d‐orbital contribution. There is an almost linear relation between the X(3) and the term (n2ω+ 2)3.(n2ω ‐1).Ed/E20 containing three measurable parameters only, irrespective of the kinds of MO, which was derived based on the bond orbital theory developed by M. E. Lines. The largest X(3) value obtained is 1.69 × 10−12 esu for 30NbO2.5.70TeO2 glass, about 60 times larger than that of pure fused silica glass.
Formation of Small‐Sized CdSxSe1‐x Crystals in Sol‐Gel‐Derived SiO2 Glasses
Authors: Nogami Masayuki , Abe Yoshihiro , Kato Ayako
Published: September 2005

Silica glasses doped with small‐sized CdSx‐Se1‐x crystals were prepared by the sol‐gel method. Gels synthesized by the hydrolysis of Si(OC2H5)4, in the presence of CdSeO4 with NH4SCN dissolved in HNO3 or NH4OH, were heated in H2‐N2 atmosphere. The pH value of solutions for CdSeO4 and NH4SCN primarily determined the fraction of anions in CdSxSe1‐x crystals. The anion content in crystals was dependent on the pH value of the solvent and/or heat‐treatment temperature, and the sulfur fraction changed from 0.1 to 0.6. The optical absorption spectra were red‐shifted as the selenium content and the crystal size increased, and the emission spectra showed a sharp band near the absorption edge position and a broad tail extending into the long wavelength. The optical band gap energies increased reciprocally proportional to the square of the crystal size.
Compositional Change and Compositional Fluctuation in Pb(Zr,Ti)O3 Containing Excess PbO
Authors: Kakegawa Kazuyuki , Matsunaga Osamu , Kato Tamani , Sasaki Yoshinori
Published: September 2005

Compositional changes which take place during sintering of Pb(Zr,Ti)O3 (PZT) containing excess PbO were studied. The excess PbO forms a liquid phase during the sintering process. The solubility of the TiO2 component of PZT in liquid PbO is higher than that of ZrO2 component. Thus, if an excess PbO exists, the composition of PZT phase shifts towards the Ti‐lean side. A change in the lattice constants due to this compositional change was actually observed. Coexistence of tetragonal and rhombohedral phases, due to a compositional fluctuation caused by excess PbO, was observed near the morphotropic phase boundary. When PZT containing excess PbO was sintered at 1100°C, a compositional fluctuation occurred early in the process and then decreased with sintering time. These phenomena have agreed with a result of computer simulation of dissolution of TiO2 component in PZT phase into liquid PbO phase.
Wear and Wear Transition Mechanism in Silicon Carbide during Sliding
Authors: Cho Seong‐Jai , Um Chang‐Do , Kim Seock‐Sam
Published: September 2005

Wear mechanisms in SiC during sliding have been investigated experimentally under paraffin oil lubrication. The wear and friction data indicate that a transition in wear mechanism occurs abruptly after a defined period of sliding. The transition point is reached earlier as load increases. Examination of wear samples reveals that surface material is predominantly removed by a plastic grooving process in the initial stage, and by a grain pull‐out process after the transition. It is also observed that severe plastic deformation in the form of dislocations is produced during the sliding. The abrupt occurrence of the grain pull‐out after a definite sliding time is discussed in relation to the internal stresses associated with this plastic deformation.
Standard Gibbs Energy of Formation of β‐Silicon Nitride
Authors: Pánek Zdenĕk
Published: September 2005

Experimental thermochemical data (temperature, pressure) corresponding to the equilibrium conditions between finegrained β‐SiC and β‐Si3N4 for carbon activity a(C) = 1 are presented. Based on these data, the temperature dependence of ΔG°f(β‐Si3N4) has been expressed for standard states Si(s), C(s), and p(N2) = 0.1 MPa by the equation ΔA°f(β‐Si3N4) = (‐995.9 + 0.4547 T/K) kJ mol for T/K ε〈1650; 1968〉.
Crack Deflection in Ceramic/Ceramic Laminates with Strong Interfaces
Authors: Prakash Om , Sarkar Partho , Nicholson Patrick S.
Published: September 2005

Crack deflection in electrophoretically deposited Al2O3/ TZ‐3Y (3 mol% Y2O3‐stabilized tetragonal ZrO2) lamellar composites with strong interfaces is described. The fracture behavior of, and crack paths in, these materials were evaluated using indentation and four‐point bend tests. The effects of residual and induced stresses on crack deflection are considered.
Compositional Dependence of Judd‐Ofelt Parameters in Silicate, Borate, and Phosphate Glasses
Authors: Takebe Hiromichi , Nageno Yoshikazu , Morinaga Kenji
Published: September 2005

Judd‐Ofelt parameters Ωt with t= 2,4, 6 for the rare‐earth ions Pr3+, Nd3+, Sm3+, Tb3+, Dy3+, Ho3+, Er3+, and Tm3+ in alkali and/or alkaline‐earth silicate, borate, and phosphate glasses have been determined. The variations of Ωt with the number of 4f electrons of the rare‐earth ions are demonstrated, and factors affecting the Judd‐Ofelt parameter Ω6are discussed. The intensity parameter Ω6 depends on the ionic packing ratio of the glass host by changing modifier type in silicate and borate glasses, and it is independent of that in a series of borate glasses as a function of modifier content and phosphate glasses. The peak wavenumbers of the transitions whose intensities are determined mainly by the Ω6<|U(6)|>2 term—where <|U(6)|> is one of the reduced matrix elements—shift systematically with the values of Ω6 for all the rare‐earth ions.
Measurements of Refractive Indexes and Factors Affecting Dispersion in Oxide Glasses
Authors: Fujino Shigeru , Takebe Hiromichi , Morinaga Kenji
Published: September 2005

Accurate refractive indexes of oxide glasses—silica, silicate, borate, aluminate, tellurite, antimonate, and heavy metal gallate glasses—are presented in the wavelength range 0.265 to 1.710 μm. Factors affecting the refractive index dispersion are discussed by using the single‐oscillator Drude‐Voigt equation. The values of nd at 0.5876 μm are affected mainly by the average resonance wavelength at the ultraviolet region through all of the glass systems. The distinguishing features of borate glasses—relatively high refractive index and low dispersion—are related to the large number of molecules, N, in a unit volume, compared with those of the other glasses. The number N determined by density measurements is related to the fraction of the four‐coordinated borons estimated by Greenblatt and Bray.
Thermal Instability and Proton Conductivity of Ceramic Hydroxyapatite at High Temperatures
Authors: Yamashita Kimihiro , Kitagaki Kazuhisa , Umegaki Takao
Published: September 2005

In the study of the high‐temperature behavior of ceramic hydroxyapatite (HAp), it was found in relation to its ionic conduction properties that HAp underwent partial dehydration of its lattice hydroxide ions. Considering that HAp ceramics are sintered above 1200°C without destruction of the apatitic structure, the dehydration was interpreted as an unstable phenomenon of aging. The evolution of instability of dehydration was reflected in the time‐dependent characteristics of conductivity, which exhibited up‐and‐down change of 103 S·cm−1 above 700°C. The conduction was proved purely protonic by measurements of a hydrogen concentration cell, and it was noted that the protonic conductivity was increased to a high value of 10−3 S·cm−1 at the initial stage of the aging. The aging phenomenon was demonstrated to be reversible in the deuteration of fully aged HAp; the uptake of OD− inside the specimen was confirmed by infrared spectroscopic analysis after exposure to deuterium oxide vapor. Based on those results, a conduction model was proposed consistent with the aging phenomenon. The present study also showed the importance of the supply of H2O vapor to the ambient during sintering, for the lattice hydroxide ions of ceramic HAp were considerably dehydrated in sintering in air at high temperatures.
Evaluation of Tensile Strength and Fracture Toughness of Yttria‐Stabilized Zirconia Polycrystals with Fracture Surface Analysis
Authors: Oishi Manabu , Matsuda Yukihisa , Noguchi Kenichi , Masaki Takaki
Published: September 2005

The tensile strength of yttria‐stabilized tetragonal zirconia polycrystals (Y‐TZPs) was measured and the fracture surfaces were analyzed with the scanning electron microscope and X‐ray microanalyzer. The fracture origins of the pressureless‐sintered samples were voids or inclusions such as A12O3, A12O3 with SiO2, and cubic‐ZrO2, while the fracture origins of the hot isostatically pressed samples were inclusions; no voids were detected at fracture origins. The higher strengths of the hot isostatically pressed samples versus those of the pressureless‐sintered samples were consistent with the change in fracture origins. The fracture toughness of the samples calculated from the tensile strength and analysis of the fracture origins was 3.4 to 3.7 MPa √m. These values are lower than those measured with the SEPB method. These discrepancies might be caused by the difference in the state of the fracture origin and its neighborhood, such as the size of the fracture origin and interaction between two surfaces in the precrack.
Thermal Expansion and Athermal Phase Transition of Y4AI2O9 Ceramics
Authors: Yamane Hisanori , Ogawara Kazuhiro , Omori Mamoru , Hirai Toshio
Published: September 2005

Thermal expansion of Y4A14O9 ceramics prepared at 1600° and 1800°C was measured from room temperature to 1500°C in air. Volume changes at the phase transition of Y4A12O9, along with thermal hysteresis, were observed around 1400°C. The volume of the high‐temperature phase was about 0.5% lower than that of the low‐temperature phase. The hysteresis width for the sample prepared at 1600°C was 56°C, wider than that (14°C) for the sample prepared at 1800°C. The averages of phase transition start temperatures on heating and on cooling for these samples were, however, almost the same at 1377°C. The phase transitions did not occur at fixed temperatures, and the proportions of the high‐temperature phase and the low‐temperature phase did not change with time as long as the temperature remained constant (athermal character). The sample prepared at 1800°C also showed another thermal hysteresis behavior from room temperature to about 1000°C.
Effects of Temperature and Reagent Concentration on the Morphology of Chemically Vapor Deposited β‐Ta2O5
Authors: Bae Yong W. , Lee Woo Y. , Stinton David P.
Published: September 2005

Crystalline β‐Ta2O5 coatings were deposited on hot‐isostatically‐pressed Si3N4 by reacting TaCl5 with H2 and CO2 in the temperature range of 1000°–1300°C and at a pressure of 660 Pa. The Ta2O5 coatings generally consisted of wellcoalesced 2–3 μm grains, resulting in the formation of a nonporous coating morphology. However, the presence of microcracks on the as‐deposited surface was consistently observed. The surface morphology, texture, and growth rate of the coatings were examined as a function of deposition parameters.
Quantifying Local Microcrack Density in Ceramics: A Comparison of Instrumented Indentation and Thermal Wave Techniques
Authors: Smith Douglas T. , Wei Lanhua
Published: September 2005

Instrumented indentation and thermal wave techniques are used as local, quantitative probes of microcrack density in a silicon nitride that has been subjected to severe Hertzian contact stress. The techniques act as local probes, sampling volumes of material <10−3 mm3. Microcracked regions are created using a tungsten carbide spherical indenter, as a result of high shear stress in the compressive zone beneath the indenter. The microcracked zones, studied in cross section using a “bonded interface” technique, increased both in size and in degree of damage with increasing Hertzian load. Within the zones, Young's modulus is measured using instrumented indentation, and the thermal diffusivity using a thermal wave technique; both quantities are lower in the damaged regions than in the undamaged regions. The shifts in modulus and diffusivity are used independently to calculate microcrack densities using related models of the effect of microcracks on each property. The two techniques show the same functional relationship between Hertzian contact load and microcrack density, and yield densities that agree to within a factor of approximately 2.
Toughening by Crack Bridging in Heterogeneous Ceramics
Authors: Curtin William A.
Published: September 2005

The toughening of a ceramic by crack bridging is considered, including the heterogeneity caused simply by spatial randomness in the bridge locations. The growth of a single planar crack is investigated numerically by representing the microstructure as an array of discrete springs with heterogeneity in the mechanical properties of each spring. The stresses on each microstructural element are determined, for arbitrary configurations of spring properties and heterogeneity, using a lattice Green function technique. For toughening by (heterogeneous) crack bridging for both elastic and Dugdale bridging mechanisms, the following key physical results are found: (i) growing cracks avoid regions which are efficiently bridged, and do not propagate as self‐similar penny cracks; (ii) crack growth thus proceeds at lower applied stresses in a heterogeneous material than in an ordered material; (iii) very little toughening is evident for moderate amounts of crack growth in many cases; and (iv) a different R‐curve is found for every particular spatial distribution of bridging elements. These results show that material reliability is determined by both the flaw distribution and the “toughness” distribution, or local environment, around each flaw. These results also demonstrate that the “microstructural” parameters derived from fitting an R‐curve to a continuum model may not have an immediate relationship to the actual microstructure; the parameters are “effective” parameters that absorb the effects of the heterogeneity. The conceptual issues illuminated by these conclusions must be fully understood and appreciated to further develop microstructure‐property relationships in ceramic materials.
VibraForming and In Situ Flocculation of Consolidated, Coagulated, Alumina Slurries
Authors: Franks George V , Velamakanni Bhaskar V. , Lange Fred F.
Published: September 2005

Aqueous, alumina slurries dispersed at low pH form weakly attractive networks when excess counterions are added. These slurries can be consolidated to a high relative packing density via either pressure filtration or centrifugation without mass segregation or density gradients. These saturated, consolidated bodies can be reshaped by vibrating them into a complex‐shaped die cavity, a process termed VibraForm‐ing. The yield stress of these bodies can be increased by adding urea to the slurry before consolidation and then heating the VibraFormed body to change the pH of the water within the body to the isoelectric point for the alumina powder. The increased yield stress, characterized by stress relaxation experiments, allows the body to be removed from the die cavity without shape distortion.
Preparation and Elastic Properties of rf‐Sputtered Amorphous Films in the System SiO2‐Y2O3
Authors: Hanada Teiichi , Shinoda Takuya , Tanabe Setsuhisa , Soga Naohiro
Published: September 2005

Amorphous films in the SiO2‐Y2O3 system were prepared by the rf‐sputtering method. Transparent amorphous films were obtained in the region between 0 and 66 mol% Y2O3 content, only in an oxygen atmosphere. The densities and elastic constants of the films were determined. As the amount of Y2O3 addition increased, density and elastic constants increased up to about 45 mol% Y2O3, beyond which it held constant. From the relationship between the bulk modulus and the mean atomic volume, a structural change in the present films seems to occur at about 45 mol% Y2O3 content.
Formation of Infinite‐Layered (Ca1‐xSrx) CuO2 and NaCuO2‐type (Ca1‐yNay)0.85CuO2 in Tartrate Route
Authors: Kikkawa Shinichi , Kato Namie , Taya Noriko , Tada Masakazu , Kanamaru Fumikazu
Published: September 2005

Both NaCuO2‐type Ca0.85CuO2 and infinite‐layered (Ca1‐xSrx)CuO2 could be prepared much more easily by firing the dried solids from mixed acetate aqueous solutions titrated with tartaric acid than by normal calcination. The presence of a narrow solid‐solution composition range of 0.10 < x > 0.16 was confirmed in infinite‐layered (Ca1‐xSrx)CuO2 in the preparation using the tartrate route. The calcium could also be substituted by sodium in a range of y > 0.15 in NaCuO2‐type (Ca1‐yNay)0.85CuO2 using the same route. Further substitution of Ca2+ with Y3+ might also be possible in infinite‐layered (Ca1‐xSrx)CuO2, but resulted in the NaCuO2‐type compound in the substitution with Na+.
New Technique to Measure the Toughness of Thin‐Film Interfaces
Authors: Gupta Vijay , Pronin Alexander
Published: September 2005

A new technique to measure the toughness of metal—ceramic interfaces is presented. In this technique, a test coating of 100 to 200 Å is deposited on the substrate of interest. This layer is then overlaid by a residually stressed Nb coating (used as a loading device), and its thickness is controlled until the lower test layer buckles away from the substrate. By determining the intrinsic residual strain within the Nb layer in independent delamination experiments, the bilayer buckling morphology is quantified, and a measure of the interface fracture toughness is obtained. This technique has been successfully applied to interfaces between metallic coatings of Sb, Cr, Cu, Nb, Al, and substrates of sapphire with (0001) orientation. Interface toughness values of 0.31, 0.94, 0.93, 0.88, and 1.0 J/m2 were obtained for these systems, respectively.
Analytical Modeling for Bridging Stress Function Involving Grain Size Distribution in a Polycrystalline Alumina
Authors: Sohn Kee‐Sun , Lee Sunghak , Baik Sunggi
Published: September 2005

In order to investigate the microstructural effect on the R‐curve behavior in a polycrystalline alumina, an analytical model has been proposed based on the relationship between bridging stress and crack opening displacement. The crack opening displacement was measured using an in situ SEM fracture method, and then used for a fitting procedure to obtain the bridging stress distribution. The results indicated that the bridging stress function and the R‐curve computed by the current model were consistent with those computed by the power‐law relation, and that the grain size distribution was closely related to the bridging stress. Thus, the current model explained well the correlation between the bridging stress distribution and the local‐fracture‐controlling microstructural parameter to interpret the microfracture mechanism, including the R‐curve behavior.
Load Dependence of Hardness in Sintered Submicrometer Al2O3 and ZrO2
Authors: Krell Andreas
Published: September 2005

Monolithic alumina bodies with a grain size of 0.5 μm and submicrometer tetragonal ZrO2 (3 mol% Y2O3) polycrystals were produced and investigated. With decreasing indentation load, the hardness increases but may again decrease below about 5 N; relevant measurements require the application of fairly high loads. Decreasing grain sizes increase the hardness of alumina and zirconia ceramics even for very small grain sizes in the submicrometer range.
Characterization of Metastable Tetragonal Forms in ZrO2‐2. 8 mol% Y2O3 Ceramics
Authors: Rivas Patricia C. , Caracoche María C. , Pasquevich Alberto F. , Martinez Jorge A. , Rodríguez Agustín M. , García Alberto R. López , Mintzer Sergio R.
Published: September 2005

This paper deals with a perturbed angular correlation investigation of the microstructure and subsequent thermal evolution of a commercial ZrO2‐2. 8 mol% Y2O3 ceramic powder and of a pellet obtained upon sintering the powder at 1450°C. The perturbed angular correlation results, complemented by those of X‐ray diffraction and Raman spectrometry, indicate that the metastable tetragonal phase exhibits two hyperflne interaction forms instead of the interaction associated with the conventional t‐ZrO2 phase, both having different oxygen vacancy configurations around zirconium sites. While the powder sample exhibits mainly a very defective tetragonal form, the pellet exhibits a slightly distorted one as the major form. As temperature is increased, a reversible transformation between both forms occurs involving a redistribution of the oxygen vacancy. Once the transition is completed, the oxygen vacancy movement is described by a fast relaxation regime with an activation energy Eact= 0. 50 ± 0. 04 eV.
Chemical and Structural Evolution of Sol‐Gel‐Derived Hydroxyapatite Thin Films under Rapid Thermal Processing
Authors: Russell Stephen W. , Luptak Karen A. , Suchicital Carlos Tres A. , Alford Terry L. , Pizziconi Vincent B.
Published: September 2005

Chemical and structural evolution of hydroxyapatite thin films produced by sol‐gel synthesis is characterized by ion beam analysis, X‐ray diffraction, and Fourier transform infrared spectroscopy. Formation of the hydroxyapatite structure began at 500°C; no other phases were observed at higher temperatures. Elimination of residual organics was observed in the form of the disappearance of excess oxygen, hydrogen and carbon. Crystal size increases with increasing anneal temperature; spectroscopy indicates the formation of highly crystalline films. The analytical methods chosen provide insight into subtle chemical and structural changes which occur in films produced by this synthetic route.