bluuebunny/crossref_metadata_2025 huggingface dataset:
Accuracy of Physical Examination and Intra‐Access Pressure in the Detection of Stenosis in Hemodialysis Arteriovenous Fistula
Authors: Campos Rodrigo Peixoto , Chula Domingos Candiota , Perreto Sonia , Riella Miguel Carlos , Do Nascimento Marcelo Mazza
Published: February 2008

Both physical examination (PE) and intra‐access pressure (IAP) measurements have been used in the identification of stenosis in an arteriovenous access. The aim of this study was to evaluate the accuracy of PE and IAP in the diagnosis of arteriovenous fistula (AVF) stenosis. A total of 84 patients were enrolled in the study (54% men, mean age of 50.7 ± 12.7 years and mean AVF patency of 24.9 ± 7.8 months, 52% radiocephalic). Abnormalities of pulse and thrill were used as the diagnostic tools for the detection of stenosis using the physical examination. For IAP, stenosis was suspected when the ratio between IAP at the arterial puncture site and the mean blood pressure was <0.13 or >0.43. The diagnosis of stenosis was confirmed by Doppler ultrasound (DU). Sensitivity (S), specificity (SP), positive predictive value (PPV), negative predictive value (PNV), and accuracy were calculated for the two early detection tests. According to DU, 50 (59%) AVF were considered positive for the presence of stenosis. Fifty‐six (66%) AVF were considered positive for the presence of stenosis by PE and 34 (40%) by IAP. S, SP, PPV, and NPV for PE and IAP were 96%, 76%, 86%, and 93% and 60%, 88%, 88%, and 60%, respectively. The accuracy for PE and IAP was 88% and 71%, respectively. PE proved to be an accurate method for the diagnosis of stenosis and should be part of all surveillance protocols of stenosis detection in AVF.
Implementation of routine screening for Kell antibodies: does it improve perinatal survival?
Authors: Kamphuis Marije M. , Lindenburg Irene , Van Kamp Inge L. , Meerman Robertjan H. , Kanhai Humphrey H.H. , Oepkes Dick
Published: February 2008

BACKGROUND: In 1998 a national program for first‐trimester screening for red cell (RBC) antibodies in all pregnant women was implemented. The aim of our study was to assess the impact on perinatal mortality caused by Kell alloimmunization

STUDY DESIGN AND METHODS: Prospectively collected data on all pregnant women referred to our center from 1988 until 2005 for intrauterine transfusion (IUT) for fetal anemia due to Kell alloantibodies were analyzed. The cohort was divided into two groups, those treated before 1998 and those treated after 1998. The primary outcome was fetal and neonatal survival. Secondary outcome variables were gestational age, fetal hemoglobin (Hb) levels at first IUT, severity of hydrops, and total number of IUTs per pregnancy. Causes for mortality were analyzed in detail.

RESULTS: A total of 43 pregnancies were included, 18 before introduction of screening and 25 thereafter. Perinatal survival increased from 61 percent in the first period to 100 percent after introduction of screening. After 1998, fetal hydrops was generally less severe at first IUT, while gestational age and fetal Hb levels at first IUT were similar.

CONCLUSION: Implementation of routine screening for Kell antibodies in pregnancy was associated with an increased referral rate for suspected fetal anemia, more timely referrals, and a higher perinatal survival rate after intrauterine treatment.
Modeling Housing Market Fundamentals: Empirical Evidence of Extreme Market Conditions
Authors: Stevenson Simon
Published: February 2008

This article examines the issues encountered in the modeling of market fundamentals during a period of extreme price behavior. The study analyzes the price behavior of the residential property market in Ireland using a number of alternative methodological approaches in the estimation of fundamental market value. Limitations in conventional models such as an inverted demand model are highlighted, in particular, with regard to diagnostic concerns and the static nature of the model. The use of an error correction framework provides more consistent and robust findings. The analysis does appear to indicate that a substantial premium over fundamental values developed in the Irish market during the late 1990s, reaching a peak in 1999 and 2000. However, in recent years, prices have largely been in line with fundamentals.
Electrophysiological Characteristics and Catheter Ablation in Patients with Paroxysmal Supraventricular Tachycardia and Paroxysmal Atrial Fibrillation
Authors: CHANG SHIH‐LIN , TAI CHING‐TAI , LIN YENN‐JIANG , LO LI‐WEI , TUAN TA‐CHUAN , UDYAVAR AMEYA R. , TSAO HSUAN‐MING , HSIEH MING‐ HSIUNG , HU YU‐FENG , CHIANG SHUO‐JU , CHEN YI‐JEN , WONGCHAROEN WANWARANG , UENG KWO‐CHANG , CHEN SHIH‐ANN
Published: February 2008

Introduction:
Paroxysmal supraventricular tachycardia (PSVT) is often associated with paroxysmal atrial fibrillation (AF). However, the relationship between PSVT and AF is still unclear. The aim of this study was to investigate the clinical and electrophysiological characteristics in patients with PSVT and AF, and to demonstrate the origin of the AF before the radiofrequency (RF) ablation of AF.

Methods and Results:
Four hundred and two consecutive patients with paroxysmal AF (338 had a pure PV foci and 64 had a non‐PV foci) that underwent RF ablation were included. Twenty‐one patients (10 females; mean age 47 ± 18 years) with both PSVT and AF were divided into two groups. Group 1 consisted of 14 patients with inducible atrioventricular nodal reentrant tachycardia (AVNRT) and AF. Group 2 consisted of seven patients with Wolff‐Parkinson‐White (WPW) syndrome and AF. Patients with non‐PV foci of AF had a higher incidence of AVNRT than those with PV foci (11% vs. 2%, P = 0.003). Patients with AF and atypical AVNRT had a higher incidence of AF ectopy from the superior vena cava (SVC) than those with AF and typical AVNRT (86% vs. 14%, P = 0.03). Group 1 patients had smaller left atrial (LA) diameter (36 ± 3 vs. 41 ± 3 mm, P = 0.004) and higher incidence of an SVC origin of AF (50% vs. 0%, P = 0.047) than did those in Group 2.

Conclusion:
The SVC AF has a close relationship with AVNRT. The effect of atrial vulnerability and remodeling may differ between AVNRT and WPW syndrome.
Estimation of Global Ventricular Activation Sequences by Noninvasive Three‐Dimensional Electrical Imaging: Validation Studies in a Swine Model During Pacing
Authors: LIU CHENGUANG , SKADSBERG NICHOLAS D. , AHLBERG SARAH E. , SWINGEN CORY M. , IAIZZO PAUL A. , HE BIN
Published: February 2008

Background: A novel noninvasive imaging technique, the heart‐model‐based three‐dimensional cardiac electrical imaging (3DCEI) approach was previously developed and validated to estimate the initiation site (IS) of cardiac activity and the activation sequence (AS) from body surface potential maps (BSPMs) in a rabbit model. The aim of the present study was to validate the 3DCEI in an intact large mammalian model (swine) during acute ventricular pacing.

Methods and Results: The heart–torso geometries were constructed from preoperative magnetic resonance (MR) images acquired from each animal. Body surface potential mapping and intracavitary noncontact mapping (NCM) were performed simultaneously during pacing from both right ventricular (RV) (intramural) and left ventricular (LV) sites (endocardial). Subsequent 3DCEI analyses were performed from the measured BSPMs. The estimated ISs were compared with the precise pacing locations and estimated ASs were compared with those recorded by the NCM system. In total, five RV and five LV sites from control and heart failure (HF) animals were paced and sequences of 100 paced beats were analyzed (10 for each site). The averaged localization error (LE) of the RV and LV sites were 7.3 ± 1.8 mm (n = 50) and 7.0 ± 2.2 mm (n = 50), respectively. The global 3D ASs throughout the ventricular myocardium were also derived. The endocardial ASs as a subset of the estimated 3D ASs were consistent with those reconstructed from the NCM system.

Conclusion: The present experimental results demonstrate that the noninvasive 3DCEI approach can localize the IS and estimate AS with good accuracy in an in vivo setting under control, paced, and/or diseased conditions.
Dual Independent Atrial Tachycardias After Ablation of Chronic Atrial Fibrillation
Authors: MATSUO SEIICHIRO , LIM KANG‐TENG , KNECHT SÉBASTIEN , ARANTES LEONARDO , HAÏSSAGUERRE MICHEL
Published: February 2008

We report the case of a 71‐year‐old man with two atrial tachycardias evolving simultaneously and independently in two dissociated regions after extensive ablation for chronic atrial fibrillation. One tachycardia was a focal tachycardia originating from the right inferior pulmonary vein and activating the posterior left atrium with a 2:1 conduction block, while the other tachycardia was an atrial flutter circulating around the tricuspid annulus, activating the right atrium and the anterior wall of the left atrium. These two atrial tachycardias were successfully ablated prior to restoration of sinus rhythm.
Titanium Silicon Carbide Pest Induced by Nitridation
Authors: Zhang Haibin , Zhou Yanchun , Bao Yiwang , Li Meishuan
Published: February 2008

The thermal stability of bulk Ti3SiC2 in high‐purity nitrogen was investigated. It was surprising to observe that Ti3SiC2 underwent rapid and catastrophic disintegration above 1300°C, although this material was thermally stable below this temperature. This degradation was unexpected and extremely serious, and has been termed “Ti3SiC2 pest.” This phenomenon was related to the volume change associated with the formation of mixtures of TiCx, Ti(C, N)x, and TiN, which caused internal tensile stresses and cracked the resulting layers. “Ti3SiC2 pest” could be prevented by increasing oxygen partial pressure in nitrogen.
Synthesis, Characterization, and Antibacterial Action of Hollow Ceria Nanospheres with/without a Conductive Polymer Coating
Authors: Kartsonakis Ioannis A. , Liatsi Penelope , Daniilidis Ioannis , Kordas George
Published: February 2008

Hollow ceria nanospheres were synthesized using anionic polystyrene lattices which were prepared by emulsion polymerization of styrene using potassium persulfate as the initiator. These anionic colloidal particles were dispersed in water in the presence of poly(vinylpyrrolidone) and mixed with aqueous solutions of cerium (III) acetylacetonate [Ce(acac)3]. Subsequently, hollow nanospheres of cerium compounds were obtained by calcination of the coated polystyrene lattices at an elevated temperature in air. The hollow ceria nanospheres were characterized by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, X‐ray diffraction, thermogravimetric analysis, and differential thermal analysis. The hollow ceria nanospheres were coated with conductive polymers (polyaniline and polypyrrole) via an electropolymerization process. Moreover, the antibacterial action of illuminated hollow ceria nanospheres and hollow ceria nanospheres coated with conductive polymers (CPCeO2) on a pure culture of Escherichia coli was studied. A decrease of E. coli concentration was observed after illumination of bacteria in the presence of hollow ceria nanospheres and CPCeO2.
Nanoscale ZnO and Al‐Doped ZnO Coatings on ZnS:Ag Phosphors and their Cathodoluminescent Properties
Authors: Choi Sung‐Woo , Hong Seong‐Hyeon , Ko Ki‐Young , Do Young Rag
Published: February 2008

Blue‐emitting ZnS:Ag phosphors were coated with nanoscale zinc oxide (ZnO) and Al‐doped ZnO (AZO) and the cathodoluminescence (CL) performance of the coated phosphors was investigated. The nanoscale coating was obtained by controlling the hydrolysis reaction of ZnCl2 alcoholic solution using diethylamine as a gradual OH− former, and Al doping was performed to increase the electrical conductivity of ZnO. The coatings were composed of either nanosized particles or a continuous nano layer, and the AZO‐coated phosphor had a more uniformly covered surface. The coated phosphors exhibited improved aging behavior under CL excitation and the AZO coating was more effective at suppressing the degradation, possibly due to its uniformity and high conductivity.
Borate Distribution in Stabilized Stainless‐Steel Slag
Authors: Durinck Dirk , Arnout Sander , Mertens Gilles , Boydens Eddy , Jones Peter Tom , Elsen Jan , Blanpain Bart , Wollants Patrick
Published: February 2008

Disintegration of stainless‐steel slag during cooling is caused by the β→γ transformation of dicalcium silicate (2CaO·SiO2 or C2S). It is well established that disintegration can be avoided by borate additions, which are commonly believed to stabilize the high‐temperature polymorphs by forming a solid solution with C2S. In this study, the borate distributions in slowly cooled synthetic and industrial slag samples are determined. The slag microstructures are characterized using electron probe microanalysis (EPMA), quantitative X‐ray diffraction (QXRD), and wavelength dispersive spectroscopy (WDS). The results show that only a limited fraction of the added borates forms a solid solution with the C2S phase, while the main fraction is found in a calcium borosilicate phase. In combination with literature data, this suggests that slag stabilization involves more than the chemical stabilization of the high‐temperature C2S polymorphs.
Crystallization of Bismuth Borosilicate‐Based Dielectric Thick Films on a LiZn Ferrite Substrate
Authors: Kim Byeong Kon , Cho Yong Soo , Lee Jung Won , Lee Jong Won , Song Jun Kwang
Published: February 2008

The compatibility and crystallization of dielectric thick films, consisting of a bismuth borosilicate glass and crystalline cordierite, on a LiZn ferrite substrate were investigated by focusing on phase development and microstructural changes. Significant diffusion of Li and Fe from the substrate to the dielectric was confirmed as unexpected crystalline phases such as Li2Al2Si3O10 and Fe2O3 were found in the thick films fired at 850°C. The crystallization was believed to be initiated from the film interface and developed further toward the film surface as evidenced from cross‐sectional microstructures of the films with additional firings. The degree of crystallization and the relative contents of the observed phases were dependent on the ratio between the glass and cordierite and the number of refirings.
Structure and Properties of ZrO2 Ceramic Coatings on AZ91D Mg Alloy by Plasma Electrolytic Oxidation
Authors: Yao Zhongping , Gao Huihui , Jiang Zhaohua , Wang Fuping
Published: February 2008

ZrO2 ceramic coatings were prepared in situ on an AZ91D Mg alloy by plasma electrolytic oxidation in a K2ZrF6 solution. The phase composition and the surface morphology of the coatings were examined with X‐ray diffraction and scanning electron microscopy. The thermal shock resistance of the coatings was evaluated by a thermal shock test. The corrosion resistance of the coated samples was examined by the polarizing curve method in a 3.5% NaCl solution. The prepared coating was composed of t‐ZrO2 and a small amount of c‐ZrO2. There were many residual discharging channels on the coating surface. The coated samples showed excellent thermal shock resistance under 500°C, which improved with increasing frequency or decreasing current density or PEO time. Besides, the coating improved the corrosion resistance of AZ91D Mg alloy considerably. In the experiments, the corrosion current density of the coated samples prepared under 1000 Hz was the least, which also decreased with the current density during the PEO process.
The Li2O–Nb2O5–TiO2 Composite Microwave Dielectric Ceramics with Adjustable Permittivities
Authors: Zeng Qun , Li Wei , Shi Jian‐lin , Dong Xian‐lin , Guo Jing‐kun
Published: February 2008

A group of new y M‐phase/(1−y) Li2+xTi1−4xNb3xO3 composite ceramics with adjustable permittivities for low‐temperature co‐fired ceramic applications was initially investigated in the study. The 0.5 M‐phase/0.5 Li2+xTi1−4xNb3xO3 (x=0.01, 0.02, 0.04, 0.06, 0.081) composite ceramics were first investigated to find the appropriate “Li2TiO3ss” composition (x value). The best dielectric properties of ɛr=40.1, Q×f values up to 9318 GHz, τf=25 ppm/°C, were obtained for the ceramics composites at x=0.02. Based on the good dielectric properties, the suitable “Li2TiO3ss” composition with x=0.02 was mixed with the Li1.0Nb0.6Ti0.5O3 powder as the ratio of y“M‐phase”/(1−y) “Li2TiO3ss” (y=0.2, 0.4, 0.5, 0.6, 0.8). By adjusting the y values, the group of composite ceramics could exhibit largely are adjustable permittivities varying from ∼20 to ∼60, while Q×f and τf values relatively good. Nevertheless, in this study, because there are interactions between the M‐phase and Li2TiO3ss during sintering process, their microwave dielectric properties could not be predicted precisely by the empirical model.
ZnO Nanofiber Field‐Effect Transistor Assembled by Electrospinning
Authors: Wu Hui , Lin Dandan , Zhang Rui , Pan Wei
Published: February 2008

A ZnO nanofiber field‐effect transistor (FET) was assembled by electrospinning. Uniform ZnO nanofibers with a diameter of ∼70 nm and length over 100 μm were first synthesized by electrospinning. Using two paralleled electrodes as fiber collectors, we have successfully placed a single ZnO nanofiber on the electrodes, and an FET device was fabricated based on the assembled nanofiber. An electrical transport measurement was conducted on the FET device, showing that ZnO nanofibers are intrinsic n‐type semiconductors. The present findings demonstrate that electrospinning can potentially be used as a straightforward and cost‐effective means for the assembly of one‐dimensional nanostuctures for building integrated nanodevices for various applications, such as transistors, sensors, diodes, and photodetectors.
Thermodynamic Properties and Phase Diagram for the System MoO2–TiO2
Authors: Jacob K. Thomas , Shekhar Chander , Waseda Yoshio
Published: February 2008

The activity of molybdenum dioxide (MoO2) in the MoO2–TiO2 solid solutions was measured at 1600 K using a solid‐state cell incorporating yttria‐doped thoria as the electrolyte. For two compositions, the emf was also measured as a function of temperature. The cell was designed such that the emf is directly related to the activity of MoO2 in the solid solution. The results show monotonic variation of activity with composition, suggesting a complete range of solid solutions between the end members and the occurrence of MoO2 with a tetragonal structure at 1600 K. A large positive deviation from Raoult's law was found. Excess Gibbs energy of mixing is an asymmetric function of composition and can be represented by the subregular solution model of Hardy as follows

image

The temperature dependence of the emf for two compositions is reasonably consistent with ideal entropy of mixing. A miscibility gap is indicated at a lower temperature with the critical point characterized by Tc (K)=1560 and
. Recent studies indicate that MoO2 undergoes a transition from a monoclinic to tetragonal structure at 1533 K with a transition entropy of 9.91 J·(mol·K)−1. The solid solubility of TiO2 with rutile structure in MoO2 with a monoclinic structure is negligible. These features give rise to a eutectoid reaction at 1412 K. The topology of the computed phase diagram differs significantly from that suggested by Pejryd.
Theoretical Calculation and Measurement of the Hardness of Diopside
Authors: Smedskjaer Morten M. , Jensen Martin , Yue Yuan‐Zheng
Published: February 2008

In the present paper, we test the suitability of a previously proposed model by Gao et al.9 for describing the hardness of more complicated, multicomponent crystals by both calculating and measuring the hardness of a diopside crystal. We analyze the limitations of the model and suggest that factors like load and temperature should be considered in the model. The calculated value of hardness of the diopside crystal is compared with the Vickers hardness values measured at different loads. A good agreement is found between the calculated hardness and the value measured at 25°C at a load of 0.5 N. Crystal orientation and measurement temperature have an impact on the experimental value of hardness of the crystals.
B6O: A Correlation Between Mechanical Properties and Microstructure Evolution upon Al2O3 Addition During Hot Pressing
Authors: Kleebe H.‐J. , Lauterbach S. , Shabalala T. C. , Herrmann M. , Sigalas I.
Published: February 2008

B6O powders were hot pressed with and without Al2O3 as a sintering additive at temperatures up to 1900°C and a pressure of 50 MPa. The microstructure of a doped and undoped sample was studied by transmission electron microscopy techniques. This paper aims at studying the correlation between micro/nanostructure evolution and the resulting mechanical properties; i.e., hardness and fracture toughness. The addition of alumina yields the formation of a secondary aluminum borate phase in addition to promoting grain growth strongly. While the addition of Al2O3 slightly decreased the hardness of the B6O polycrystals, the corresponding fracture toughness was strongly improved, as compared with the undoped material.
Effect of Silica on the Reactive Sintering of Polycrystalline Nd:YAG Ceramics
Authors: Maître Alexandre , Sallé Christian , Boulesteix R. , Baumard Jean‐François , Rabinovitch Yoël
Published: February 2008

In the present work, the role of silica as sintering aids in the densification and the grain growth of yttrium aluminum garnet doped by neodymium (Nd:YAG) ceramics has been investigated. The samples were prepared by ball milling of pure oxides (Al2O3, Y2O3, Nd2O3, SiO2), shaped by cold uniaxial pressing, and sintered in vacuum between 1473 and 1973 K. After cooling, the specimens were annealed under air or vacuum. Their microstructure and the chemical composition of the secondary phases were examined using electron probe microanalysis, scanning electron microscopy, or transmission electron microscopy techniques. From these results, silica addition proved to be efficient on the densification kinetics between 1673 and 1873 K, especially when SiO2 content exceeds 0.05 wt%. Indeed, the solid‐state reaction between SiO2 and Nd:YAG particles in the vicinity of 1660 K leads to a liquid phase that adopts a eutectic composition in the Al2O3–Y2O3–SiO2 system. This phase enhances the densification by improving rearrangement of particles and mass transport at the grain boundaries. At a high temperature, liquid phase and silica were partially removed and some intergranular and intragranular inclusions of residual silica remained after cooling. The most promising thermal treatment consists of sintering Nd:YAG ceramics under vacuum at a high temperature (T≥1973 K) to reach fully dense pieces and to decrease the volume fraction of secondary phases (i.e., liquid phase or silica‐based phases). Finally, these conditions would allow to produce transparent YAG pieces due to their good homogeneity with regard to their microstructural properties (grain size, volume fraction of secondary phases).
Inverse Opal Structure of Nitrogen‐Doped Titanium Oxide with Enhanced Visible‐Light Photocatalytic Activity
Authors: Li Qi , Shang Jian Ku
Published: February 2008

Nitrogen‐doped titanium oxide inverse opal structure was synthesized to combine both chemical and physical modifications on n‐TiO2 by the polystyrene sphere self‐assembly followed by a sol–gel process. Enhanced visible‐light absorption and subsequently enhanced photodegradation efficiency were observed in this unique structure, which can be attributed to both nitrogen‐doping effect and inverse opal structure effect. Our work suggests that the coupling of photonic band gap structure with photocatalytic materials is a promising approach to achieve maximum enhancement for various photocatalytic materials, especially for environmental applications and solar cell devices.
Deposition of TiO2 on NiTi by Cathodic Synthesis for Improving Corrosion Resistance and Apatite‐Forming Ability
Authors: Wong Man‐Hong , Cheng Fai‐Tsun , Man Hau‐Chung
Published: February 2008

TiO2 was fabricated on nickel titanium (NiTi) shape memory alloy via a two‐step low‐temperature process for enhancing surface properties in orthopedic applications. A peroxotitanium hydrate deposit was first formed on NiTi by cathodic synthesis, and then transformed into TiO2 anatase by hydrothermal treatment in steam. The oxide coating was characterized by scanning electron microscopy, atomic‐force microscopy, thin‐film X‐ray diffractometry, and X‐ray photoelectron spectroscopy. The corrosion resistance in Hanks' solution, as evaluated by electrochemical impedance spectroscopy and potentiodynamic polarization tests, was increased by more than two orders of magnitude due to the oxide coating. A layer of hydroxyapatite of a few micrometers in thickness grew on the coated samples after immersion in Kokubo's solution for 14 days. These results indicate that the low‐temperature process reported provides a simple route for synthesizing an adherent oxide coating on NiTi with high corrosion resistance and enhanced apatite‐forming ability.
Positron Annihilation Lifetime Spectra in a Metakaolin‐Based Geopolymer
Authors: Vance Eric R. , Hadley Joseph H. , Hsu Frank H. , Drabarek Elizabeth
Published: February 2008

Significant nanoporosity as indicated by positron annihilation lifetime spectroscopy (PALS) has been observed in a metakaolin‐based geopolymer. The nanoporosity was indicated by a component of the PALS spectrum having a lifetime of 1.5–2 ns, characterizing a pore diameter size of ∼0.5 nm. Progressive heating to 600°C decreased the intensity of this spectral component from ∼10% to 2.5%. Positron annihilation in free pore water appears to be only a minor contributor to this spectral component. The Barrett–Joyner–Halenda (BJH) method pore distribution data, derived from BET nitrogen adsorption isotherms, showed the presence of considerable meso‐ and macroporosity in the samples. However, these porosities were not evident in the PALS spectrum. Heating from 150° to 600°C progressively changed the smallest detectable pore size via the BJH method from 3.3 to 7.1 nm.
Grain Growth‐Controlled Giant Permittivity in Soft Chemistry CaCu3Ti4O12 Ceramics
Authors: Marchin Loïc , Guillemet‐Fritsch Sophie , Durand Bernard , Levchenko Andrey A. , Navrotsky Alexandra , Lebey Thierry
Published: February 2008

We report a dielectric constant of up to 5.4 × 105 at room temperature and 1 kHz for CaCu3Ti4O12 (CCTO) ceramics, derived from multiphase powders (coprecipitation products), made by a “chimie douce” (coprecipitation) method, and then sintered in air. The sintered products are pure‐phase CCTO ceramics. The high dielectric constant is achieved by tuning the size of grains and the thickness of grain boundaries. The grain growth is controlled by varying the concentration of excess CuO in the initial powder (calcined coprecipitation products) between 1 and 3.1 wt%. The dielectric constant of pure CCTO ceramics increases with the initial CuO concentration, reaching its maximum at 2.4 wt% of CuO. A further increase of excess CuO in powders results in a permittivity decrease, accompanied by the formation of CuO as a separate phase in the sintered products. The unusual grain growth behavior is attributed to a eutectic reaction between CuO and TiO2 present in the initial powder.
Effects of Oxidation Curing and Sintering Additives on the Formation of Polymer‐Derived Near‐Stoichiometric Silicon Carbide Fibers
Authors: Chen Lifu , Zhang Li , Cai Zhihui , Yu Yuxi , Gu Hui , Zhang Litong
Published: February 2008

The effects of oxygen pick‐up and sintering additives on the formation of silicon carbide (SiC) fibers from polyaluminocarbosilane are studied. It has been found that the strict control of oxygen pick up during the oxidation curing is essential to produce near‐stoichiometric SiC fibers. When the molar ratio of oxygen to excess carbon in the pyrolyzed fibers (SiCxOy) is slightly over 1 (O/CExcess=y/(x−1)>1), the excess carbon is eliminated during the subsequent sintering as CO and CO2 as a result of the decomposition of SiCxOy; the remaining oxygen is removed as SiO and CO vapor, leaving near‐stoichiometric SiC as the residue. However, with still increasing oxygen pick up, the final ceramic fibers become more porous and rich in silicon. The evolution of CO, CO2, and SiO generates high porosity in the absence of a sintering additive, leading to low fiber density. The inter‐connected and open porosity favors the formation of CO. In contrast, for the fibers containing aluminum (Al) or Al/B sintering additives, the pores are much smaller and essentially closed, favoring the formation of CO2. Therefore, after sintering at 1800°C, the fibers without sintering additives contain excess silicon, while those with sintering additives are near stoichiometric. Al is beneficial to the densification but it alone cannot produce fibers of high density. When B is added in addition to Al, the fibers can be sintered to nearly full density.
Mechanical Properties of Dental Porcelain with Different Leucite Particle Sizes
Authors: Zhang Yi , Rao Pinggen , Lü Ming , Wu Jianqing
Published: February 2008

This research aims to investigate the effect of leucite particle size on the mechanical properties of dental porcelain with a similar leucite content and chemical composition. Leucite powders of different particle sizes were synthesized by a hydrothermal method and a high‐temperature fusing‐crystallization method, respectively. Dental porcelains with different average leucite particle sizes (i.e., 0.5±0.2, 1.2±0.3, and 5±2 μm) were prepared by sintering the mixture of different leucite powders and a low temperature frit. The crystalline phase, crystalline content, relative density, hardness, flexural strength, and fracture toughness of the porcelains were measured by X‐ray diffraction (XRD), quantitative XRD analysis, the Archimedes method, a Vickers microhardness tester, a universal testing machine, and a single‐edge precracked beam method, respectively. The microcrack density and the distribution of leucite particles were also quantitatively assessed from micrographs. The results showed that the leucite particle size did not have a significant effect on the average of the measured flexural strength, fracture toughness, and hardness of dental porcelains. However, because of a existence of the large number of microcracks, the relative density and the Weibull modulus of the sample groups with an average leucite particle size of 5 μm were statistically lower.
Analysis of Infrared Reflection Spectra of (Mg1−xZnx)Al2O4 Microwave Dielectric Ceramics
Authors: Zheng Chang Wei , Fan Xie Cheng , Chen Xiang Ming
Published: February 2008

Infrared reflection spectra of (Mg1−xZnx)Al2O4 ceramics were analyzed by Kramers–Kroning analysis and classical oscillator model simulation. The dielectric properties were extrapolated down to the microwave range using the classical oscillator model for fitting the dielectric function. According to structure analysis, the losses originating from bend vibration and stretch vibration of the bond between A‐site cation and oxygen anion dominated the whole dielectric losses of the spinel ceramics. The coexistence of Mg and Zn deteriorated the intrinsic dielectric properties due to the bond asymmetry thus introduced. The calculated Qf (∼105 GHz) was much higher than the measured ones (∼104 GHz), suggesting that the extrinsic loss was significant. Therefore, the microwave dielectric properties of MgAl2O4 and ZnAl2O4 could be improved much by microstructure modification, and the little superiority in their solution compared with the end‐members was due to microstructure improvement.
Spark Plasma Sintering of Nanocrystalline Niobium Nitride Powders
Authors: Ran Songlin , Gao Lian
Published: February 2008

Nanocrystalline niobium nitride (NbN) powders were sintered by spark plasma sintering under a nitrogen atmosphere at temperatures from 1040° to 1230°C. Fully dense bulk NbN ceramic with grain sizes of 0.5–1.0 μm was obtained at 1130°C. The effects of sintering temperature on the density, phase content, electrical conductivity, Vickers hardness, and microstructure of the NbN ceramic were discussed.
Low‐Temperature Sintering and Microwave Dielectric Properties of the Zn2SiO4 Ceramics
Authors: Kim Jin‐Seong , Nguyen Ngoc‐Huan , Lim Jong‐Bong , Paik Dong‐Soo , Nahm Sahn , Paik Jong‐Hoo , Kim Jong‐Hee , Lee Hwack‐Joo
Published: February 2008

B2O3 was added to nominal composition Zn1.8SiO3.8 (ZS) ceramics to decrease their sintering temperature for application to low‐temperature cofired ceramic (LTCC) devices. B2O3 reacted with SiO2 to form a liquid phase containing SiO2 and B2O3. The composition and melting temperature of the liquid phase depended on the sintering temperature and the B2O3 content. The specimen containing 20.0 mol% of B2O3 sintered at 900°C exhibited high microwave dielectric properties of Q×f=53 000 GHz, ɛr=5.7, and τf=−16 ppm/°C, confirming the promising potential of the B2O3‐added ZS ceramics as candidate materials for the LTCC devices.
On the Mechanism of Densification of Porous Alumina by Infiltration with an Aqueous Solution of Chromium Oxide
Authors: Mogilevsky Pavel , Lee HeeDong
Published: February 2008

Densification of porous alumina by CrO3 infiltration was investigated on model composites containing a sapphire interface. Gas–solid deposition of Cr2O3 from CrO3 source on sapphire and glass at 600°C was also investigated. The deposited Cr2O3 layers were characterized using X‐ray diffraction and transmission electron microscopy. It was found that similar to gas‐phase deposition on sapphire, in CrO3‐infiltrated porous alumina Cr2O3 grows epitaxially on adjacent alumina surfaces, suggesting a gas–solid condensation mechanism. The deposition rate and morphology of the Cr2O3 film deposited on alumina depend strongly on the crystallographic orientation.
Constraint of Oxygen Fugacity During Field‐Assisted Sintering: TiO2 as a Test Case
Authors: Quach Dat V. , Levchenko Andrey A. , Navrotsky Alexandra , Groza Joanna R.
Published: February 2008

Field‐assisted sintering exposes samples in a graphite die to reducing conditions. Using TiO2 as a test case, this work shows that internal redox equlibria in the sample, rather than the graphite–CO–O2 equilibrium, appear to control the oxygen fugacity. Samples sintered at 1160°C for 20 min are homogeneous in oxygen content and have an average composition of TiO1.983±0.001. The oxygen fugacity during these sintering experiments is calculated to be about 10−16 atm, which is higher than the value obtained from thermodynamic equilibrium of graphite–CO–O2 at the given temperature. The oxygen fugacity is similar to that for the quasi‐two‐phase region, or hysteresis loop, representing the coexistence of reduced rutile with random crystallographic shear (CS) planes and the first ordered CS phase.
Formation and Properties of the Novel GeSe2–In2Se3–CsI Chalcohalide Glasses
Authors: Xu Yinsheng , Yang Guang , Wang Wei , Zeng Huidan , Zhang Xianghua , Chen Guorong
Published: February 2008

The glass‐forming region of the GeSe2–In2Se3–CsI system was reported firstly. The dependence of glass properties on compositions as formulas of (1−2x)GeSe2−x(In2Se3–CsI) and (0.8−x)GeSe2−0.2In2Se3−xCsI was investigated. Properties measurements include density, DTA, Raman spectra, visible and near infrared, and infrared (IR) transmission spectra. Raman spectra show that [GeSe4/2] and [InSe4−xIx] tetrahedra are the main structural units in the network of the present glass system. Glasses show larger density (4.29–4.51 g/cm3), wider optical transmission window from 0.56 to 16 μm, and higher thermal stability characterized by the bigger ΔT (ΔT=Tx–Tg>110°C), which make them the promising candidate materials for IR optics.
Processing and Characterization of Multiphase Ceramic Composites Part III: Strong, Hard and Tough, High Temperature‐Stable Quadruplex and Quintuplex Composites
Authors: Kim Dong‐Kyu , Kriven Waltraud M.
Published: February 2008

Multiphase ceramic composites with improved mechanical properties and high‐temperature stabilities resulting from minimized grain sizes due to extended diffusion distances are introduced. Four‐phase (quadruplex) composites of 25 vol% Al2O3–25 vol% NiAl2O4–25 vol% TiC–25 vol%“ZrO2”; 30 vol% Al2O3–30 vol% NiAl2O4–10 vol% TiC–30 vol%“ZrO2”; and 50 vol% Al2O3–20 vol% NiAl2O4–10 vol% TiC–20 vol%“ZrO2” as well as a five‐phase (quintuplex) composite of 20 vol% Al2O3–20 vol% TiB2–20 vol% TiC–20 vol% ZrB2–20 vol%“ZrO2” were fabricated using hot‐pressing procedures. The 25 vol% Al2O3–25 vol% NiAl2O4–25 vol% TiC–25 vol%“ZrO2”‡composite, hot pressed at 1600°C for 1 h in an Ar atmosphere, had three‐point bend strength, hardness, and toughness values of 984 MPa, 1251 kg/mm2, and 4.74 MPa·m1/2, respectively. The chemically compatible, quintuplex composite consisting of 20 vol% Al2O3–20 vol% TiB2–20 vol% TiC–20 vol% ZrB2–20 vol%“ZrO2” was hot pressed at 1800°C in an Ar atmosphere for 5 h and it had hardness, bend strength, and toughness values of 1707 kg/mm2, 714 MPa, and 5.12 MPa·m1/2, respectively. The four‐ and five‐phase composites, heat‐treated under an Ar atmosphere at 1600°C for 100 h, each showed high‐temperature stabilities without any severe changes in the microstructural and mechanical properties.
In Situ Diffraction Study of Self‐Recovery in Aluminum Titanate
Authors: Low It‐Meng , Oo Zeya
Published: February 2008

Aluminum titanate (Al2TiO5) is an excellent refractory and thermal shock resistant material due to its relatively low‐thermal expansion coefficient and high melting point. However, Al2TiO5 is only thermodynamically stable above 1280°C and undergoes a eutectoid decomposition to α‐Al2O3 and TiO2 (rutile) in the temperature range of 900°–1280°C. In this paper, we describe the use of high‐temperature neutron diffraction to study the properties of self‐recovery in Al2TiO5 when it is annealed at ≥1300°C in air. It is shown that the process of decomposition in Al2TiO5 is reversible and that self‐recovery occurs readily when decomposed Al2TiO5 is reheated above 1300°C. It is further shown that the existence of a temperature range (900°–1280°C) in which Al2TiO5 is prone to decomposition can be explained by the competing dominance of self‐recovery at ≥1280°C and decomposition at ≤1280°C.
Transparent 8 mol% Y2O3–ZrO2 (8Y) Ceramics
Authors: Tsukuma Koji , Yamashita Isao , Kusunose Takafumi
Published: February 2008

Highly transparent 8 mol% Y2O3–ZrO2 (8Y) ceramics were fabricated by the hot isostatic pressing method. The transmission in a visible light region was comparable to that of a single crystal. In this work, the microstructural relationship between presintered and hot isostatic‐pressed material was examined. The transmission is sensitive to the microstructure of presintered material. The microstructural features of fine grains and small intergranular pores are significant to give high transparency for a resultant hot isostatic‐pressed material. A theoretical model based on Mie scattering revealed that the residual pore with submicrometer size is responsible for the transmission in the visible light region. The porosity <100 ppm is required for high transparency.
Preparation and Sintering of Macroporous Ceramic Membrane Support from Titania Sol‐Coated Alumina Powder
Authors: Wang Yong Hong , Cheng Ji Gui , Liu Xing Qin , Meng Guang Yao , Ding Yan Wei
Published: February 2008

The preparation of ceramic support at relatively low sintering temperature of 1350°–1500°C was investigated with a powder processing route, namely, titania sol coated on coarse alumina powder (median particle size d50, 27.5 μm). The sintering kinetics analysis indicates that the microstructure control of support is closely related to the sol coating and the sintering conditions. The mechanisms of sintering process were discussed in detail with the corresponding kinetics parameter, i.e., activation energy Ea and exponent n as well as the microstructure characterization. The prepared support provides practical applications with tunable pore size and desired mechanical strength.
Effect of CO32− Incorporation on the Mechanical Properties of Wet Chemically Synthesized β‐Tricalcium Phosphate (TCP) Ceramics
Authors: Dantas Alan C. S. , Greil Peter , Müller Frank A.
Published: February 2008

Calcium‐deficient hydroxyapatite (CDHA) powders were synthesized by a wet chemical precipitation method using Ca(OH)2 and H3PO4 solutions. Single‐phase β‐tricalcium phosphate (β‐TCP) powder with a molar (Ca+Mg)/P ratio of 1.5 was obtained after calcination of CDHA synthesized under vacuum. During synthesis in air, CO2 can be adsorbed and HBO42− is partly substituted by CO32−, resulting in a lower phosphorous content and consequently an increase of the molar (Ca+Mg)/P ratio to 1.53. A two‐phase β‐TCP powder containing 20 wt% hydroxyapatite (HA) was obtained after calcination. Samples prepared from β‐TCP powders synthesized under vacuum achieved a compressive strength of 301±23 MPa at 99.6% fractional density, while TCP/HA samples prepared in air achieved a maximum compressive strength of 132±29 MPa at 91.7% fractional density. This decrease in strength can be correlated to the porosity retaining due to CO2 release during sintering and residual tensile stresses in the TCP matrix caused by the thermal expansion mismatch of β‐TCP and HA.
Effects of Individual Layer Thickness on the Microstructure and Optoelectronic Properties of Sol–Gel‐Derived Zinc Oxide Thin Films
Authors: Bel Hadj Tahar Noureddine , Bel Hadj Tahar Radhouane , Ben Salah Abdelhamid , Savall André
Published: February 2008

Zinc oxide (ZnO) thin films were prepared under different conditions on glass substrates using a sol–gel process. The microstructure of ZnO films was investigated by means of diffraction analysis, and plan‐view and cross‐sectional scanning electron microscopy. It was found that the preparation conditions strongly affected the structure and the optoelectronic properties of the films. A structural evolution in morphology from spherical to columnar growth was observed. The crystallinity of the films was improved and columnar film growth became more dominant as the zinc concentration and the substrate withdrawal speed decreased. The individual layer thickness for layer‐by‐layer homoepitaxy growth that resulted in columnar grains was <20 nm. The grain columns are grown through the entire film with a nearly unchanged lateral dimension through the full film thickness. The columnar ZnO grains are c‐axis oriented perpendicular to the interface and possess a polycrystalline structure. Optical transmittance up to 90% in the visible range and electrical resistivity as low as 6.8 × 10−3·Ω·cm were obtained under optimal deposition conditions.
Magnetoelectric Laminate Composites: An Overview
Authors: Zhai Junyi , Xing Zengping , Dong Shuxiang , Li Jiefang , Viehland Dwight
Published: February 2008

Since the turn of the millennium, giant magnetoelectric (ME) effects have been found in laminated composites of piezoelectric and magnetostrictive layers. Compared with ME single phase and two‐phase particulate composites, laminated composites have much higher ME coefficients and are also readily fabricated. Here, we will overview the brief history of ME laminates, discussing some of the important advancements in material couples, laminate configurations, and operational modes that have allowed for dramatic enhancements in the ME voltage and charge coefficients.
Densification and Phase Transformation During Pressureless Sintering of Nanocrystalline ZrO2–Y2O3–CuO Ternary System
Authors: Zhang Yongsheng , Hu Litian , Li HaoKun , Chen Jianmin
Published: February 2008

ZrO2–Y2O3–CuO nanocrystalline powders have been synthesized using a chemical coprecipitation method. Nano‐powders were compacted uniaxially and densified in a muffle furnace. Densification studies show that the presence of CuO accelerates the densification process of ZrO2(3Y). A fully dense (>96%) pellet of ZrO2(3Y)/5 mol% CuO was obtained after sintering at 900°C, with a very small grain size of 44 nm calculated by X‐ray line broadening.
Efficacy of two alcohol‐free cetylpyridinium chloride mouthwashes – a randomized double‐blind crossover study
Authors: Rawlinson Andrew , Pollington Sarah , Walsh Trevor F. , Lamb David J. , Marlow Ian , Haywood Julia , Wright Philip
Published: February 2008

Aim: (1) To determine the plaque inhibition properties of two formulations of alcohol‐free mouthwash [0.1% w/w cetylpyridinium chloride (CPC) (B) and 0.05% w/w CPC (A)] versus a placebo mouthwash (C). (2) To compare the plaque‐inhibiting activity between these two new CPC mouthwashes.

Material and Methods: A double‐blind, crossover study with three 1‐week periods was used. Subjects were randomly assigned to one of the following groups. Group 1 (n=10) received the mouthwashes A, C and B in the periods 1, 2 and 3, respectively, group 2 (n=11) received the mouthwashes in the order B, A, C, while group 3 (n=11) received the mouthwashes in the order C, B, A.

Mean plaque areas and Quigley & Hein plaque index scores were analysed using anova (analysis of variance). Measurements were made at the start of each period (baseline) and at 16, 24 and 40 h.

Results: Mean plaque scores were similar across the groups at baseline. At all time points thereafter, volunteers using mouthwash A or B had significantly lower plaque areas and plaque index scores than those using mouthwash C (p<0.05), but there were no significant differences between the test formulations. At 16 h, the reduction in plaque area relative to mouthwash C was 22% for mouthwash A and 18% for mouthwash B; at 24 h, 11% for mouthwash A and 15% for mouthwash B; and at 40 h, 15% for mouthwash A and 16% for mouthwash B.

Conclusions: The use of both CPC mouthwashes resulted in less plaque accumulation compared with the control. There was no statistically significant difference in plaque accumulation between the two CPC mouthwashes.
Human leukocyte antigen polymorphism in chronic and aggressive periodontitis among Caucasians: a meta‐analysis
Authors: Stein Jamal M. , Machulla Helmut K. G. , Smeets Ralf , Lampert Friedrich , Reichert Stefan
Published: February 2008

Aim: Multiple studies have reported associations between periodontitis and particular human leukocyte antigens (HLA). Because associations are inconsistent, we conducted a systematic literature review and a meta‐analysis focusing on Caucasian case–control studies.

Material and Methods: A literature search reporting on the distribution of HLA class I and II phenotypes in Caucasian patients with chronic periodontitis (CP) and aggressive periodontitis (AP) was performed. Data sources included electronic databases and bibliographies of published articles. Screening and data abstraction were conducted independently by different reviewers.

Results: Out of 174 publications, 12 studies were considered to be suitable for meta‐analysis. In patients with CP, no significant HLA associations were found. Patients with AP showed a positive association with HLA‐A9 [odds ratio=2.59 (95% confidence interval 1.36–4.83), p=0.004] and HLA‐B15 [1.90 (1.15–3.16), p=0.01] as well as a negative association with HLA‐A2 [0.72 (0.56–0.94), p=0.01] and ‐B5 [0.49 (0.30–0.79), p=0.004]. On grouping all patients into one periodontitis group (AP+CP), the same deviations were confirmed with higher statistical significance. For HLA‐A9 and ‐B15, significant heterogeneity was found between the studies. No significant associations were found with HLA class II antigens.

Conclusions: HLA‐A9 and ‐B15 seem to represent susceptibility factors for AP whereas HLA‐A2 and ‐B5 are potential protective factors against periodontitis among Caucasians.