bluuebunny/crossref_metadata_2025 huggingface dataset:
Population‐Specific Susceptibility to Crohn's Disease and Ulcerative Colitis; Dominant and Recessive Relative Risks in the Japanese Population
Authors: Nakagome Shigeki , Takeyama Yasuaki , Mano Shuhei , Sakisaka Shotaro , Matsui Toshiyuki , Kawamura Shoji , Oota Hiroki
Published: March 2010

Crohn's disease (CD), a type of chronic inflammatory bowel disease (IBD), is commonly found in European and East Asian countries. The calculated heritability of CD appears to be higher than that of ulcerative colitis (UC), another type of IBD. Recent genome‐wide association studies (GWAS) have identified more than thirty CD‐associated genes/regions in the European population. In the East Asian population, however, a clear association between CD and an associated gene has only been detected with TNFSF15. In order to determine if CD susceptibility differs geographically, nine SNPs from seven of the European CD‐associated genomic regions were selected for analysis. The genotype frequencies for these SNPs were compared among the 380 collected Japanese samples, which consisted of 212 IBD cases and 168 controls. We detected a significant association of both CD and UC with only the TNFSF15 gene. Analysis by the modified genotype relative risk test (mGRR) indicated that the risk allele of TNFSF15 is dominant for CD, but is recessive for UC. These results suggest that CD and UC susceptibility differs between the Japanese and European populations. Furthermore, it is also likely that CD and UC share a causative factor which exhibits a different dominant/recessive relative risk in the Japanese population.
Mother–child dyadic synchrony is associated with better functioning in hyperactive/inattentive preschool children
Authors: Healey Dione M. , Gopin Chaya B. , Grossman Bella R. , Campbell Susan B. , Halperin Jeffrey M.
Published: March 2010

Background:  Hyperactive/inattentive (HI) behaviors are common in preschoolers, but they result in functional impairment and attention deficit/hyperactivity disorder (ADHD) diagnoses in only some children. We examined whether the quality of mother–child interaction accounts for variance in level of functioning among preschool children with elevated ADHD symptoms.

Method:  Parent and teacher ADHD‐RS ratings were used to assess 126 HI preschoolers, and clinician Children’s Global Assessment Scale (CGAS) ratings were used to quantify level of functioning. Mother–child interactions during a 5‐minute free‐play and a 5‐minute structured task were coded for child, parent and dyadic behaviors.

Results:  Partial correlations, controlling for symptom severity and IQ, revealed child and dyad factors that were related to children’s functioning. Regression analyses revealed that low dyadic synchrony accounted for additional unique variance in children’s functioning, above and beyond the influence of symptom severity and IQ.

Conclusions:  Dyadic synchrony between mother and child plays a role in the functioning of preschool children displaying elevated symptoms of hyperactivity/inattention, and may represent a potential area for intervention that is not generally addressed in most parent management training programs.
Prospective effects of violence exposure across multiple contexts on early adolescents’ internalizing and externalizing problems
Authors: Mrug Sylvie , Windle Michael
Published: March 2010

Background:  Violence exposure within each setting of community, school, or home has been linked with internalizing and externalizing problems. Although many children experience violence in multiple contexts, the effects of such cross‐contextual exposure have not been studied. This study addresses this gap by examining independent and interactive effects of witnessing violence and victimization in the community, home, and school on subsequent internalizing and externalizing problems in early adolescence.

Methods:  A community sample of 603 boys and girls (78% African American, 20% Caucasian) participated in a longitudinal study of youth violence. During two assessments 16 months apart, adolescents reported on witnessing violence and victimization in the community, school, and home, and their internalizing and externalizing problems.

Results:  Multiple regressions tested the independent and interactive effects of witnessing violence or victimization across contexts on subsequent adjustment, after controlling for initial levels of internalizing and externalizing problems and demographic covariates. Witnessing violence at school predicted anxiety and depression; witnessing at home was related to anxiety and aggression; and witnessing community violence predicted delinquency. Victimization at home was related to subsequent anxiety, depression, and aggression; victimization at school predicted anxiety; and victimization in the community was not independently related to any outcomes. Finally, witnessing violence at home was associated with more anxiety, delinquency, and aggression only if adolescents reported no exposure to community violence.

Conclusions:  Violence exposure at home and school had the strongest independent effects on internalizing and externalizing outcomes. Witnessing community violence attenuated the effects of witnessing home violence on anxiety and externalizing problems, perhaps due to desensitization or different norms or expectations regarding violence. However, no comparable attenuation effects were observed for victimization across contexts.
Revisiting the latent structure of ADHD: is there a ‘g’ factor?
Authors: Martel Michelle M. , Von Eye Alexander , Nigg Joel T.
Published: March 2010

Background:  Attention‐deficit/hyperactivity disorder (ADHD) is presumed to be heterogeneous, but the best way to describe this heterogeneity remains unclear. Considerable evidence has accrued suggesting that inattention versus hyperactivity‐impulsivity symptom domains predict distinct clinical outcomes and may have partially distinct etiological influence. As a result, some conceptualizations emphasize two distinct inputs to the syndrome. Yet formal testing of models that would accommodate such assumptions using modern methods (e.g., second‐order factor and bifactor models) has been largely lacking.

Methods:  Participants were 548 children (321 boys) between the ages of 6 and 18 years. Of these 548 children, 302 children met DSM‐IV criteria for ADHD, 199 were typically developing controls without ADHD, and 47 were classified as having situational or subthreshold ADHD. ADHD symptoms were assessed via parent report on a diagnostic interview and via parent and teacher report on the ADHD Rating Scale.

Results:  A bifactor model with a general factor and specific factors of inattention and hyperactivity‐impulsivity fit best when compared with one‐, two‐, and three‐factor models, and a second‐order factor model.

Conclusions:  A bifactor model of ADHD latent symptom structure is superior to existing factor models of ADHD. This finding is interpreted in relation to multi‐component models of ADHD development, and clinical implications are discussed.
Down‐regulation of Na+‐coupled glutamate transporter EAAT3 and EAAT4 by AMP‐activated protein kinase
Authors: Sopjani Mentor , Alesutan Ioana , Dërmaku‐Sopjani Miribane , Fraser Scott , Kemp Bruce E. , Föller Michael , Lang Florian
Published: March 2010

J. Neurochem.(2010)113, 1426–1435.

The glutamate transporters EAAT3 and EAAT4 are expressed in neurons. They contribute to the cellular uptake of glutamate and aspartate and thus to the clearance of the excitatory transmitters from the extracellular space. During ischemia, extracellular accumulation of glutamate may trigger excitotoxicity. Energy depletion leads to activation of the AMP‐activated protein kinase (AMPK), a kinase enhancing energy production and limiting energy expenditure. The present study thus explored the possibility that AMPK regulates EAAT3 and/or EAAT4. To this end, EAAT3 or EAAT4 were expressed inXenopusoocytes with or without AMPK and electrogenic glutamate transport determined by dual electrode voltage clamp. In EAAT3‐ and in EAAT4‐expressing oocytes glutamate generated a current (Ig), which was half maximal (KM) at 74 μM (EAAT3) or at 4 μM (EAAT4) glutamate. Co‐expression of constitutively activeγR70QAMPK or of wild type AMPK did not affectKMbut significantly decreased the maximalIgin both EAAT3‐ (by 34%) and EAAT4‐ (by 49%) expressing oocytes. Co‐expression of the inactive mutantαK45RAMPK [α1(K45R)β1γ1] did not appreciably affectIg. According to confocal microscopy and chemiluminescence co‐expression ofγR70QAMPK or of wild type AMPK reduced the membrane abundance of EAAT3 and EAAT4. The observations show that AMPK down‐regulates Na+‐coupled glutamate transport.
Transcriptome profiling analysis reveals region‐distinctive changes of gene expression in the CNS in response to different moderate restraint stress
Authors: Wang Ke , Xiang Xiao‐Hui , He Fei , Lin Li‐Bo , Zhang Rong , Ping Xing‐Jie , Han Ji‐Sheng , Guo Ning , Zhang Qing‐Hua , Cui Cai‐Lian , Zhao Guo‐Ping
Published: March 2010

J. Neurochem.(2010)113, 1436–1446.

It is generally believed that temporary moderate stress to a living organism has protective and adaptive effects, but little is known about the responses of CNS to the moderate stresses at molecular level. This study aims to investigate the gene expression changes induced by moderate stress in CNS stress‐ and nociception‐related regions of rats. Moderate restraint was applied to rats for 50 min and cDNA microarrays were used to detect the differential gene expression in different CNS regions. Transcriptome profiling analysis showed that at acute stage stress‐related genes were up‐regulated in arcuate nucleus; fight‐or‐flight behavior‐related genes were up‐regulated in periaqueductal gray, while nitric oxide and GABA signal transmission‐related genes were up‐regulated in spinal dorsal horn. In addition, immune‐related genes were broadly regulated, especially at the late stage. These results suggested that specific genes of certain gene ontology categories were spatiotemporally regulated in specific CNS regions related to relevant functions under moderate external stimuli at acute stage, while immune response was broadly regulated at the late stage. The co‐regulated genes among the three different CNS regions may play general roles in CNS when exposed to moderate stress. Furthermore, these results will help to elucidate the physiological processes involved in moderate stress in CNS.
Commentary: Assessing the Health Effects of Medicare Coverage for Previously Uninsured Adults: A Matter of Life and Death?
Authors: McWilliams J. Michael , Meara Ellen , Zaslavsky Alan M. , Ayanian John Z.
Published: March 2010

In contrast to a previous study we conducted and other evidence, a recent study found no significant effects of Medicare coverage after age 65 on overall health for previously uninsured adults and significant adverse effects on survival for some of these adults. We discuss explanations for these inconsistent findings, particularly the different ways in which deaths were handled, a key methodological challenge in longitudinal analyses of health. We demonstrate that analytic approaches suitable for examining effects of coverage on health measures may not be suitable for effects on mortality. Thus, estimates may be misleading when these different outcomes are jointly modeled. We also present new survival analyses that suggest Medicare coverage significantly attenuated the rising risk of death for previously uninsured adults.
The Predictors of Patient–Physician Race and Ethnic Concordance: A Medical Facility Fixed‐Effects Approach
Authors: Traylor Ana H. , Schmittdiel Julie A. , Uratsu Connie S. , Mangione Carol M. , Subramanian Usha
Published: March 2010

Objective. To examine the predictors of patient–physician race/ethnicity concordance among diabetes patients in an integrated delivery system.

Data Source. Kaiser Permanente's Northern California Diabetes Registry of 2005.

Study Design. Logistic regression predicted concordance for each racial/ethnic group. Availability of a concordant physician, whether a patient chose their physician, and patient language were main explanatory variables.

Data Collection/Extraction Methods. The study population consisted of 109,745 patients and 1,750 physicians.

Principal Findings. Patients who chose their physicians were more likely to have a same race/ethnicity physician with OR of 2.2 (95 percent CI 1.74–2.82) for African American patients, 1.71 (95 percent CI 1.44–2.04) for Hispanic patients, 1.11 (95 percent CI 1.04–1.18) for white patients, and 1.38 (95 percent CI 1.23, 1.55) for Asian patients. Availability of a same race/ethnicity physician was also a predictor of concordance for African American patients (OR 2.7; 95 percent CI 2.45–2.98) and marginally significant for Hispanic patients (OR 1.02; 95 percent CI 1.01–1.02), white patients (OR 1.02; 95 percent CI 1.00–1.04), and Asian patients (OR 1.05; 95 percent CI 1.03, 1.07). Limited English language was a strong predictor of concordance for Hispanic patients (OR 4.81; 95 percent CI 4.2–5.51) and Asian patients (OR 9.8; 95 percent CI 7.7, 12.6).

Conclusion. Patient language, preferences, and the racial composition of the physician workforce predict race/ethnicity concordance.
The Relationship between Organizational Leadership for Safety and Learning from Patient Safety Events
Authors: Ginsburg Liane R. , Chuang You‐Ta , Blair Berta Whitney , Norton Peter G. , Ng Peggy , Tregunno Deborah , Richardson Julia
Published: March 2010

Objective.To examine the relationship between organizational leadership for patient safety and five types of learning from patient safety events (PSEs).

Study Setting.Forty‐nine general acute care hospitals in Ontario, Canada.

Study Design.A nonexperimental design using cross‐sectional surveys of hospital patient safety officers (PSOs) and patient care managers (PCMs). PSOs provided data on organization‐level learning from (a) minor events, (b) moderate events, (c) major near misses, (d) major event analysis, and (e) major event dissemination/communication. PCMs provided data on organizational leadership (formal and informal) for patient safety.

Extraction Methods.Hospitals were the unit of analysis. Seemingly unrelated regression was used to examine the influence of formal and informal leadership for safety on the five types of learning from PSEs. The interaction between leadership and hospital size was also examined.

Principal Findings.Formal organizational leadership for patient safety is an important predictor of learning from minor, moderate, and major near‐miss events, and major event dissemination. This relationship is significantly stronger for small hospitals (<100 beds).

Conclusions.We find support for the relationship between patient safety leadership and patient safety behaviors such as learning from safety events. Formal leadership support for safety is of particular importance in small organizations where the economic burden of safety programs is disproportionately large and formal leadership is closer to the front lines.
The ‘Us’ in Trust: Who Trusts Northern Ireland's Political Institutions and Actors?
Authors: Gormley-Heenan Cathy , Devine Paula
Published: March 2010

This article examines levels of interest and trust among the public in relation to Northern Ireland's newly established political institutions and actors, through an analysis of the results of the 2007 Northern Ireland Life and Times Survey (NILT). It is important to reveal the specific groups of people with the highest levels of political disenchantment, particularly in the context of the longer-term stability of the Northern Ireland Assembly and Executive, since the willingness of the electorate to have faith and trust in the workability of these political institutions and in the various political actors in whose custody they lie is considered vital.
Hunter Reporting of Catch per Unit Effort as a Monitoring Tool in a Bushmeat‐Harvesting System
Authors: RIST JANNA , MILNER‐GULLAND E.J. , COWLISHAW GUY , ROWCLIFFE MARCUS
Published: March 2010

Abstract:  Growing threats to biodiversity in the tropics mean there is an increasing need for effective monitoring that balances scientific rigor with practical feasibility. Alternatives to professional techniques are emerging that are based on the involvement of local people. Such locally based monitoring methods may be more sustainable over time, allow greater spatial coverage and quicker management decisions, lead to increased compliance, and help encourage attitude shifts toward more environmentally sustainable practices. Nevertheless, few studies have yet compared the findings or cost‐effectiveness of locally based methods with professional techniques or investigated the power of locally based methods to detect trends. We gathered data on bushmeat‐hunting catch and effort using a professional technique (accompanying hunters on hunting trips) and two locally based methods in which data were collected by hunters (hunting camp diaries and weekly hunter interviews) in a 15‐month study in Equatorial Guinea. Catch and effort results from locally based methods were strongly correlated with those of the professional technique and the spatial locations of hunting trips reported in the locally based methods accurately reflected those recorded with the professional technique. We used power simulations of catch and effort data to show that locally based methods can reliably detect meaningful levels of change (20% change with 80% power at significance level [α]= 0.05) in multispecies catch per unit effort. Locally based methods were the most cost‐effective for monitoring. Hunter interviews collected catch and effort data on 240% more hunts per person hour and 94% more hunts per unit cost, spent on monitoring, than the professional technique. Our results suggest that locally based monitoring can offer an accurate, cost‐effective, and sufficiently powerful method to monitor the status of natural resources. To establish such a system in Equatorial Guinea, the current lack of national and local capacity for monitoring and management must be addressed.
Infant Symbolic Play as an Early Indicator of Fetal Alcohol‐Related Deficit
Authors: Molteno Christopher D. , Jacobson Sandra W. , Carter R. Colin , Jacobson Joseph L.
Published: March 2010

Infant symbolic play was examined in relation to prenatal alcohol exposure and socioenvironmental background and to predict which infants met criteria for fetal alcohol syndrome (FAS) at 5 years. A total of 107 Cape‐Colored, South African infants born to heavy drinking mothers and abstainers/light drinkers were recruited prenatally. Complexity of play, sociodemographic and psychological correlates of maternal alcohol use, and quality of parenting were assessed at 13 months, and intelligence quotient and FAS diagnosis at 5 years. The effect of drinking on spontaneous play was not significant after control for social environment. In contrast, prenatal alcohol and quality of parenting related independently to elicited play. Elicited play predicted 5‐year Digit Span and was poorer in infants subsequently diagnosed with FAS/partial FAS and in nonsyndromal heavily exposed infants, compared with abstainers/light drinkers. Thus, symbolic play may provide an early indicator of risk for alcohol‐related deficits. The independent effects of prenatal alcohol and quality of parenting suggest that infants whose symbolic play is adversely affected by alcohol exposure may benefit from stimulation from a responsive caregiver.
Developmental Changes in Infants’ Ability to Cope with Dialect Variation in Word Recognition
Authors: Schmale Rachel , Cristià Alejandrina , Seidl Amanda , Johnson Elizabeth K.
Published: March 2010

Toward the end of their first year of life, infants’ overly specified word representations are thought to give way to more abstract ones, which helps them to better cope with variation not relevant to word identity (e.g., voice and affect). This developmental change may help infants process the ambient language more efficiently, thus enabling rapid gains in vocabulary growth. One particular kind of variability that infants must accommodate is that of dialectal accent, because most children will encounter speakers from different regions and backgrounds. In this study, we explored developmental changes in infants’ ability to recognize words in continuous speech by familiarizing them with words spoken by a speaker of their own region (North Midland‐American English) or a different region (Southern Ontario Canadian English), and testing them with passages spoken by a speaker of the opposite dialectal accent. Our results demonstrate that 12‐ but not 9‐month‐olds readily recognize words in the face of dialectal variation.
Testate Amoebae from a Cretaceous Forest Floor Microbiocoenosis of France
Authors: SCHMIDT ALEXANDER R. , GIRARD VINCENT , PERRICHOT VINCENT , SCHÖNBORN WILFRIED
Published: March 2010

ABSTRACT. Amber‐preserved shells of testate amoebae often provide as many diagnostic features as the tests of modern taxa. Most of these well‐preserved microfossils are morphologically assignable to modern species indicating either evolutionary stasis or convergent evolution. Here we describe two Lower Cretaceous testate amoebae that are clearly distinguishable from modern species. Centropyxis perforata n. sp. and Leptochlamys galippei n. sp. possessed perforate shells that were previously unknown in these genera. They are preserved in highly fossiliferous amber pieces from the Upper Albian (ca. 100 million years old) of Archingeay/Les Nouillers (Charente‐Maritime, southwestern France). Syninclusions of soil and litter dwelling arthropods and microorganisms indicate a limnetic‐terrestrial microhabitat at the floor of a coastal conifer forest.
A‐Site and B‐Site Order in (Na1/2La1/2)(Mg1/3Nb2/3)O3 Perovskite
Authors: Tarvin Rachel , Davies Peter K.
Published: March 2010

(Na1/2La1/2)(Mg1/3Nb2/3)O3 undergoes a series of phase transitions that involve cation order on the A‐ and B‐sites of the parent perovskite structure. At high temperatures both sites contain a random distribution of cations; below 1275°C a 〈111〉 layering of Mg and Nb leads to the formation of a 1:2 ordered structure with a monoclinic supercell. A second transition was observed at 925°C, where the Na and La cations order onto alternate A‐site positions along the 〈001〉 direction of the parent subcell. By quenching samples from above 1275°C to preserve the disorder on the B‐site, a fourth variant of this compound was obtained by inducing A‐site order through a subsequent anneal at 900°C. Although the changes in structure do not produce significant alterations in the relative permittivity (ɛr∼ 35), they do have a significant effect on the value of the temperature coefficient of the capacitance.
Effect of Aliovalent Substituents on the Ferroelectric Properties of Modified Barium Titanate Ceramics ‐ Relaxor Ferroelectric Behavior
Authors: Zhang Ruitao , Li Jie Fang , Viehland Dwight
Published: March 2010

Structure–property relationships were investigated to reveal the generic influence of various substituents on ferroelectric BaTiO3. Compositional modifications of ferroelectric BaTiO3 were systematically investigated for La3+ and Nb5+ substituents. A generic influence of charged point defects in breaking down the ferroelectric domains into polar clusters was demonstrated. In both types of modified BaTiO3, relaxor ferroelectric behavior was induced for higher concentrations of substituents.
Fabrication of Elongated α‐SiAlON via a Reaction‐Bonding Process
Authors: Kaga Youichirou , Jones Mark I. , Hirao Kiyoshi , Kanzaki Shuzo
Published: March 2010

A reaction‐bonding process, which offers low sintering shrinkage and is a low‐cost process, was applied to fabricate Y–α‐SiAlON ceramics. The green compacts composed of Si, Y2O3, Al2O3, and AlN were nitrided and subsequently postsintered. Dense single‐phase Y–α‐SiAlON with elongated grain morphology could be achieved in the specimen postsintered at 1900°C. The material exhibited high hardness (1850 HV10) and high fracture toughness (5.1 MPa·m1/2).
In Situ Observation of Crack Behavior in Compressively Loaded Plasma‐Sprayed 7‐wt%‐Yttria‐Stabilized Zirconia
Authors: Levin Jonathan P. , Dickinson Graeme R. , Trice Rodney W.
Published: March 2010

A plasma‐sprayed 7‐wt%‐yttria‐stabilized zirconia stand‐alone tube was incrementally loaded in uniaxial compression inside a scanning electron microscope. Micrographs taken at each increment showed cracks perpendicular to the applied load to have partially closed and cracks parallel to the applied load to have opened. New cracks were observed to nucleate and then propagate in a direction parallel to the applied load.
High Temperature Microhardness of Single Crystal Mullite
Authors: Kriven Waltraud M. , Siah Lay Foong , Schmücker Martin , Schneider Hartmut
Published: March 2010

The microhardness (H) of single crystal, orthorhombic mullite was measured on (010) and (001) faces from room temperature up to 1400°C. The microhardness versus temperature curves display sigmoidal shapes. The mean microhardness at room temperature is ∼16 Gpa and it decreases with temperature to H is ∼ 13 GPa at 300°C. At >300°C, the microhardness is only slightly reduced with temperature to H is ∼10 GPa at 1000°C. Above this temperature limit, it markedly decreases again, to a mean value of ≈6 GPa at 1400°C. Up to ∼1000°C the (010) and (001) microhardnesses are very similar. Above ∼1000°C, however, the hardness gradually becomes anisotropic, with H(010) being twice as high as H(001) at 1400°C (H(010)∼ 8 GPa, H(001)∼ 4 GPa).
Soft X‐ray Absorption Near Edge Structure Analysis on Lithium Manganese Oxide Prepared by Microwave Heating
Authors: Kobayashi Shota , Usui Tatsuya , Ikuta Hiromasa , Uchimoto Yoshiharu , Wakihara Masataka
Published: March 2010

Microwave heating, which is recognized as a time‐saving and an energy‐efficient process, was used to synthesize manganese oxide from various starting materials. LiOH and MnO2 (electrochemically prepared manganese dioxide, EMD) were used as starting materials; ε‐MnO2‐type lithium manganese oxide that showed excellent cycle ability was the result of 3 min of microwave heating. A change in electronic structure was investigated using manganese L‐edge and oxygen K‐edge X‐ray absorption spectroscopy (XAS). The XAS results indicated that the oxidation‐reduction reaction took place in the manganese 3d and in the oxygen 2p orbitals during the charge‐discharge process and that Jahn‐Teller distortion occurred in the reduced samples.
Sc2O3 Nanopowders via Hydroxyl Precipitation: Effects of Sulfate Ions on Powder Properties
Authors: Li Ji‐Guang , Ikegami Takayasu , Mori Toshiyuki , Yajima Yoshiyuki
Published: March 2010

Hydroxyl‐type Sc2O3 precursors have been synthesized via precipitation at 80°C with hexamethylenetetramine as the precipitant. The effects of starting salts (scandium nitrate and sulfate) on powder properties are investigated. Characterizations of the powders are achieved by elemental analysis, X‐ray diffractometry (XRD), differential thermal analysis/thermogravimetry (DTA/TG), high‐resolution scanning electron microscopy (HRSEM), and Brunauer‐Emmett‐Teller (BET) analysis. Hard‐aggregated precursors (γ‐ScOOH·0.6H2O) are formed with scandium nitrate, which convert to Sc2O3 at temperatures ≥400°C, yielding nanocrystalline oxides of low surface area. The use of sulfate leads to a loosely agglomerated basic sulfate powder having an approximate composition of Sc(OH)2.6(SO4)0.2·H2O. The powder transforms to Sc2O3 via dehydroxylization and desulfurization at temperatures up to 1000°C. Well‐dispersed Sc2O3 nanopowders (∼64.3 nm) of high purity have been obtained by calcining the basic sulfate at 1000°C for 4 h. The effects of SO42− on powder properties are discussed.
Processing and Properties of Sol–Gel‐Derived Alumina/Silicon Carbide Nanocomposites
Authors: Hareesh Unnikrishnan Nair Saraswathy , Sternitzke Martin , Janssen Rolf , Claussen Nils , Warrier Krishna Gopakumar
Published: March 2010

Dense alumina/5 vol% SiC nanocomposites were prepared by sol–gel processing using nanosized (180 nm) precoated SiC powders and a commercial boehmite sol. The SiC powder was precoated with boehmite by a controlled heterogeneous precipitation from an aluminum nitrate solution. The coated SiC powder was then dispersed in a boehmite sol, gelled, calcined, and densified by gas pressure sintering under argon atmosphere at 7–8 MPa pressure. The dependence of the calcination conditions on densification, the effect of seeding on the microstructural development, as well as the mechanical behavior of the sintered specimens, are presented and discussed.
Texture Control of Sol‐Gel Derived Pb(Mg1/3Nb2/3)O3–PbTiO3 Thin Films Using Seeding Layer
Authors: Gong Wen , Li Jing‐Feng , Chu Xiangcheng , Li Longtu
Published: March 2010

Lead magnesium niobium titanate (PMNT) thin films with a composition near the morphotropic phase boundary were prepared on conventional Pt(111)/Ti/SiO2/Si substrates using a modified sol‐gel process. A PbO seeding layer was introduced to the interface between the PMNT layer and the substrate to enhance the [001]‐preferential orientation of the PMNT film. Single‐phase perovskite PMNT films with highly [001]‐preferential orientation were obtained at reduced annealing temperatures compared with the PMNT films directly deposited on the same substrates. The dielectric and ferroelectric properties of the prepared PMNT films were evaluated as a function of annealing temperature.
Effect of V2O5 Doping on the Sintering and Dielectric Properties of M‐Phase Li1+x−yNb1−x−3yTix+4yO3 Ceramics
Authors: Borisevich Albina Y. , Davies Peter K.
Published: March 2010

The effect of the addition of V2O5 on the structure, sintering and dielectric properties of M‐phase (Li1+x−yNb1−x−3yTix+4y)O3 ceramics has been investigated. Homogeneous substitution of V5+ for Nb5+ was obtained in LiNb0.6(1−x)V0.6xTi0.5O3 for x≤ 0.02. The addition of V2O5 led to a large reduction in the sintering temperature and samples with x= 0.02 could be fully densified at 900°C. The substitution of vanadia had a relatively minor adverse effect on the microwave dielectric properties of the M‐phase system and the x= 0.02 ceramics had [alt epsilon]r= 66, Q×f= 3800 at 5.6 GHz, and τf= 11 ppm/°C. Preliminary investigations suggest that silver metallization does not diffuse into the V2O5‐doped M‐phase ceramics at 900°C, making these materials potential candidates for low‐temperature cofired ceramic (LTCC) applications.
Effects of Excess Barium Ions on Aqueous Barium Titanate Tape Properties
Authors: Yoon Dang‐Hyok , Lee Burtrand I.
Published: March 2010

The effects of excess free barium ions in aqueous barium titanate slip on the resulting BaTiO3 tape properties were investigated in terms of the slip behavior, green/sintered tape density and morphology, and dielectric properties. The excess free barium ions expressed by means of the Ba/Ti ratio adversely affected most tape properties. Increase in the slip viscosity, green porosity, and agglomeration along with a decrease in mechanical properties and green/sintered density were found with the increase in the Ba/Ti ratio. However, dielectric permittivity was increased with increase in the Ba/Ti ratio. An effort was made to correlate these phenomena with Ba2+ leaching in water for realistic multilayer ceramic capacitor applications.
Upconversion Luminescence in Er3+ Doped and Yb3+/Er3+ Codoped Yttria Nanocrystalline Powders
Authors: Zhang Jian , Wang Shiwei , Rong Tianjun , Chen Lidong
Published: March 2010

Y1.9Er0.1O3 and Y1.7Yb0.2Er0.1O3 nanocrystalline powders were prepared via a reverse‐strike coprecipitation method using nitrates and ammonia as raw materials. The obtained powders were of cubic‐phase structure of Y2O3 and the particle size was in the range of ∼60–80 nm. Strong red (4F9/2–4I15/2) and green (2H11/2/4S3/2–4I15/2) upconversion luminescence were observed in all the samples when excited with a 980‐nm continuous wave diode laser. The possible upconversion mechanisms in Y1.9Er0.1O3 and Y1.7Yb0.2Er0.1O3 were discussed. Power studies indicated that two‐photon processes are responsible for the green and red upconversion luminescence in these systems. The codoping of Yb3+ greatly enhanced the red (4F9/2–4I15/2) upconversion emission.
BaTiO3‐Based Ceramics for Tunable Microwave Applications
Authors: Feteira Antonio , Sinclair Derek C. , Reaney Ian M. , Somiya Yoshitaka , Lanagan Michael T.
Published: March 2010

The dielectric properties of BaTi0.90Ga0.05Nb0.05O3 (BTGN) and Ba0.60Sr0.40TiO3 (BST) ceramics prepared by the conventional solid‐state route have been investigated. Their relative potential for microwave (MW) tunable applications was assessed by the figure of merit (K) defined as K = [equation omitted] (where [alt epsilon]ro and [alt epsilon]rv are the relative permittivity at zero and 20 kV cm−1 at 10 kHz and tan δo is the loss at 10kHz or ∼1 GHz without DC bias). Fine‐grained (∼2–3 μm) BTGN ceramics fired at 1500°C in air exhibit dielectric behavior characteristic of relaxor‐type materials, with relative permittivity, [alt epsilon]r, decreasing from ∼3082 to ∼2116 and dielectric loss, tan δ, increasing from 0.0035 to 0.0542 at 10 kHz and ∼1GHz, respectively. In contrast, large‐grained (20–100 μm) BST ceramics exhibit a frequency independent [alt epsilon]r of ∼5000 and show little variation of tan δ with frequency (0.0012 at 10 kHz and ∼0.0048 at 0.6 GHz). At 10 kHz, KBTGN= 91 and KBST= 367, whereas at MW frequencies KBTGN= 6 and KBST= 92. The large decrease in KBTGN at MW frequencies is attributed to a substantial increase of tan δ. The applicability of another relaxor‐type BaTiO3‐based ceramic, Ba(Ti0.70Zr0.30)O3, which was recently proposed as promising material for tunable MW applications, is also discussed. It is demonstrated that BaTiO3‐based ferroelectric‐relaxors may exhibit good tunable characteristics at 10 kHz; however, they are not competitive with BST for high K‐factor MW applications.
Reaction Kinetics and Mechanisms between La0.65Sr0.3MnO3 and 8 mol% Yttria‐Stabilized Zirconia
Authors: Yang Chih‐Chung T. , Wei Wen‐Cheng J. , Roosen Andreas
Published: March 2010

The reaction kinetics and mechanisms between 8 mol% yttria‐stabilized zirconia (YSZ) and 30 mol% Sr‐doped lanthanum manganite (La0.65Sr0.30MnO3, LSM) with A‐site deficiency for the application of planar solid oxide fuel cells (SOFCs) were investigated. The LSM/YSZ green tapes were cofired from 1200° to 1400°C for 1 to 48 h and then annealed at 1000°C for up to 1000 h. The results showed that the diffusion of manganese cations first caused the amorphization of YSZ, and then the formation of small La2Zr2O7 (LZ) or SrZrO3 (SZ) crystals if treated for a longer time at 1400°C. The ambipolar diffusion of the Mn–O pair, transported through the migration of oxygen vacancy, plays an important role in the formation of secondary phases. The diffusion of LSM to YSZ and substitution of Mn for Zr both result in the enhanced concentration of oxygen vacancy, leading to the formation of a void‐free zone (VFZ). No additional reaction products in annealed LSM/YSZ specimens, treated at 1000°C for 1000 h, were detected. The interfacial reactions, detailed reaction kinetics, and mechanisms are reported.
Amorphous α‐Tricalcium Phosphate: Preparation and Aqueous Setting Reaction
Authors: Gbureck Uwe , Barralet Jake E. , Radu Lavinia , Klinger Hans G. , Thull Roger
Published: March 2010

The mechanical and setting properties of calcium phosphate cements are considerably determined by the pretreatment of the constituents. In this report we show for the first time that prolonged high‐energy ball milling of α‐tricalcium phosphate (α‐TCP) led to mechanically induced phase transformation from the crystalline to the amorphous state. The amorphous material demonstrated a high reactivity such that the time for substantially complete conversion of α‐TCP to calcium‐deficient hydroxyapatite in 2.5% Na2HPO4 solution decreased from about 20 h (1 h of grinding in ethanol, 85% relative crystallinity) to 4–6 h for a material with a crystallinity of 8% (24 h of grinding). This reactivity could be attributed to an increased thermodynamic and kinetic solubility of the ground materials. Mechanically activated α‐TCP cements were produced with compressive strengths of up to 80 MPa and setting times of 5–16 min. The effect of reactant preparation and cement mixing parameters on the physical and chemical properties of mechanically activated α‐TCP cement was investigated. By comparing cements of similar porosity and degree of conversion it was demonstrated that apatite specific surface area has a strong influence on cement mechanical performance, which highlights the importance of this previously overlooked parameter in improving strength.
Alkaline Activation of Fly Ashes: NMR Study of the Reaction Products
Authors: Palomo Ángel , Alonso Santiago , Fernandez‐Jiménez Ana , Sobrados Isabel , Sanz Jesús
Published: March 2010

Reaction products formed during alkaline activation, with 8M NaOH solutions, of fly ashes have been characterized with 29Si and 27Al magic‐angle spinning nuclear magnetic resonance (MASNMR) spectroscopy. In particular, the influence of curing conditions (time and temperature of reaction) has been analyzed. NMR results show the formation of amorphous tecto‐silicates in which the amount of aluminum decreases in the two consecutive formed phases. The Si/Al ratio of zeolite precursor obtained at 85°C changes from 0.95 to 1.86 when curing time is increased from 5 h to 1 week. The evolution of the mechanical properties of prepared cements has also been discussed in terms of the phases formed and texture and morphology of samples.
Direct Characterization of Grain‐Boundary Electrical Activity in Doped (Ba0.6Sr0.4)TiO3 by Combined Imaging of Electron‐Beam‐Induced Current and Electron‐Backscattered Diffraction
Authors: Hayashi Katsuro , Yamamoto Takahisa , Ikuhara Yuichi , Sakuma Taketo
Published: March 2010

Simultaneous measurements of remote electron beam induced current (REBIC) and orientation imaging microscopy (OIM) in a scanning electron microscope (SEM) have been applied to a polycrystalline (Ba0.6Sr0.4)TiO3 with a positive temperature coefficient of resistivity (PTCR) to elucidate a grain‐boundary character dependence of the potential barrier formation. The absence of electrical activity in a coherent Σ3 twin boundary is clearly imaged. The resistivity of individual grain boundaries estimated from a resistive contrast image is interpreted in terms of geometrical coherency, which is defined by the degree of coincidence in the reciprocal lattice points.
Criterion for the Avoidance of Edge Cracking in Layered Systems
Authors: He M. Y. , Evans A. G. , Yehle A.
Published: March 2010

When fabricating multilayers with brittle constituents, a prevalent design strategy is to choose fabrication conditions and thermal expansion coefficients that impose in‐plane compression on the brittle layers. In such designs, a small zone of out‐of‐plane tension is induced at the edges that can cause cracks to form and extend, especially along the midplane. The associated stresses and energy release rates have been analyzed, revealing a fail‐safe criterion, attributed to the existence of a maximum possible energy release rate, Gmax. Equating this maximum to the toughness defines a fail‐safe parameter expressing the influence of the layer thickness, the misfit stress, and the toughness. When fail‐safe designs cannot be realized, thin interlayers can be interposed in a manner that diminishes Gmax, broadening accessibility. The roles of misfit stress and interlayer thickness in attaining this condition are derived.
Ferroelectric and Photostrictive Properties of Fine‐Grained PLZT Ceramics Derived from Mechanical Alloying
Authors: Takagi Kenta , Kikuchi Shoko , Li Jing‐Feng , Okamura Hiroshi , Watanabe Ryuzo , Kawasaki Akira
Published: March 2010

Single‐phase lead lanthanum zirconate titanate (PLZT) solid solution powder was synthesized from the constituent oxides at ambient temperature through a mechanical alloying (MA) process and was then densified to fine‐grained ceramics by sintering and hot‐pressing. The anomalous photovoltaic effect (APV) and photoinduced strain of the resultant PLZT ceramics were investigated and analyzed in association with the influence of grain size. It was found that a photoinduced voltage up to 6000 V·cm−1 can be obtained as the grain size is reduced to 0.42 μm. This is extremely high and about three times that achievable in normal micrometer‐grained PLZT ceramics. The maximum photoinduced strain of the PLZT ceramics with an average grain diameter of 0.54 μm reached 0.01%, which is equivalent to electric‐field‐induced strain of common piezoelectric materials.
Hydrolysis of Pure and Sodium Substituted Calcium Aluminates and Cement Clinker Components Investigated byin SituSynchrotron X‐ray Powder Diffraction
Authors: Christensen Axel Nørlund , Jensen Torben R. , Scarlett Nicola V. Y. , Madsen Ian C. , Hanson Jonathan C.
Published: March 2010

The hydrolysis of pure and sodium‐substituted calcium aluminates and cement clinker phases was investigatedin situin the temperature range 25°–170°C, using the angle dispersive powder synchrotron powder X‐ray diffraction technique. The final hydrolysis product in all cases was Ca3Al2(OH)12. The intermediate phase Ca4Al2O7·19H2O was formed from the pure calcium aluminates, and the intermediate phases Ca4Al2O7·xH2O,x= 11, 13, or 19, were formed from the cement clinker phases.
Chemical Aspects of Direct Coagulation Casting of Alumina Suspensions
Authors: Tervoort Elena , Tervoort Theo A. , Gauckler Ludwig J.
Published: March 2010

This work presents a detailed description of urea decomposition during direct coagulation processing of alumina suspensions. We report on the chemical equilibria involved in the decomposition of urea in an aqueous environment with and without alumina particles. The model uses the logarithm of the concentrations as variables to ensure fast convergence and nonnegativity of the solutions, and is able to give a semiquantitative description of the experimentally observed development of pH and ionic strength (specific conductivity) during the decomposition of urea in a 30 vol% solid loading alumina suspension. Assuming local equilibrium, and a homogeneous distribution of the catalyst urease and the evolving educts, the results show an increasing solubility of CO2 with increasing pH. As a consequence the production of gaseous CO2 during the urea decomposition (direct coagulation casting (DCC) process), shifting the pH from 4 to 9 occurs only when a strong buffer is present at low and medium pH. This is advantageous for the preparation of defect‐poor ceramic green bodies using this internal gellation reaction in the DCC process.
Synthesis of Thermally Stable χ‐Alumina by Thermal Decomposition of Aluminum Isopropoxide in Toluene
Authors: Mekasuwandumrong Okorn , Kominami Hiroshi , Praserthdam Piyasan , Inoue Masashi
Published: March 2010

Thermal decomposition of aluminum isopropoxide in toluene at 315°C resulted in χ‐alumina that had high thermal stability, whereas the reaction at lower temperatures resulted in formation of an amorphous product. The χ‐alumina thus obtained directly transformed to α‐alumina at ∼1150°C, bypassing the other transition alumina phases, whereas the amorphous product transformed to γ‐alumina and then to θ‐alumina before final transformation to α‐alumina. When the χ‐alumina, solvothermally synthesized at 315°C, was recovered by the removal of the solvent at the reaction temperature, thermal stability of the product was improved further. This procedure is convenient because it avoids bothersome work‐up processes that yield large‐surface‐area and large‐pore‐volume alumina.
Fatigue of Field‐Induced Strain in Antiferroelectric Pb0.97La0.02(Zr0.77Sn0.14Ti0.09)O3 Ceramics
Authors: Zhou Longjie , Zimmermann André , Zeng Yu‐Ping , Aldinger Fritz
Published: March 2010

The fatigue of mechanical strain induced by electric fields was investigated for antiferroelectric Pb0.97La0.02(Zr0.77Sn0.14Ti0.09)O3 ceramics. The material shows a high resistance to fatigue owing to bipolar electric cycling up to 108 cycles. The strain hysteresis loop is still fairly symmetric, whereas the maximum field‐induced strain decreases by only 30% of its initial value. The fatigued samples show a damaged microstructure with dendritic macrocracks and microcrack clouds. The fatigue is attributed to a combination of electrochemical and mechanical mechanisms.
NiZnCu Ferrite Thick Film with Nano Scale Crystallites Formed by the Aerosol Deposition Method
Authors: Lebedev Maxim , Akedo Jun , Iwata Atsushi , Sugimoto Satoshi , Inomata Kouichiro
Published: March 2010

This paper describes the magnetic properties of NiZnCu ferrite film deposited at room temperature by an aerosol deposition method (ADM). The thickness of the film was 6 μm and the deposition rate was estimated as 2 μm/min. The microstructure of as‐deposited at room temperature films consists of randomly oriented nanocrystallites with a size of 20 nm. As‐deposited and annealed films exhibited the following magnetic properties: intensity of magnetization Ms= 0.147 T (117 emu/cm3), coercivity Hc= 40.58 kA/m (510 Oe); and Ms= 0.3 T (250 emu/cm3), Hc= 14.95 kA/m (188 Oe), respectively.
Tricalcium Silicate T1 and T2 Polymorphic Investigations: Rietveld Refinement at Various Temperatures Using Synchrotron Powder Diffraction
Authors: Peterson Vanessa K. , Hunter Brett A. , Ray Abhi
Published: March 2010

The lattice parameters, cell volume, and structure of a sample of phase pure triclinic tricalcium silicate were determined using in situ, high‐temperature synchrotron powder diffraction and full‐profile Rietveld refinement. The temperature range covered was from ambient to 740°C. Evidence of superstructure was found. The T2 type structure with disordered SiO4 tetrahedra was observed, and an average structure for the subcell (P, a= 11.7416(2) Å, b= 14.2785(2) Å, c= 13.7732(2) Å, α= 105.129(1)°, β= 94.415(1)°, and γ= 89.889(1)°) is presented. Differential thermal analysis and X‐ray fluorescence was also performed.
Comb Polymer Architecture Effects on the Rheological Property Evolution of Concentrated Cement Suspensions
Authors: Kirby Glen H. , Lewis Jennifer A.
Published: March 2010

We have studied the rheological behavior of concentrated cement suspensions in the absence and presence of comb polymers comprised of a polyacrylic acid (PAA) backbone and charge‐neutral, poly(ethylene oxide) (PEO) teeth. These species possessed a uniform backbone molecular weight and graft density, with varying teeth molecular weight. Both PAA, a linear polyelectrolyte, and PAA/PEO comb polymers imparted initial stability to concentrated cement suspensions above a critical weight fraction, w* of 4 mg/(g of cement). Cement–PAA suspensions, however, set prematurely. Their rapid, irreversible stiffening stemmed from deleterious interactions between PAA and multivalent counterions in solution. Interestingly, the presence of PEO teeth comprised of only a few monomer units in length mitigated such interactions. The rheological property evolution of concentrated cement–PAA/PEO suspensions exhibited complex behavior ranging from the reversible gel‐like response observed at short teeth lengths to a remarkable gel‐to‐fluid transition observed during the deceleratory period for systems comprised of longer PEO teeth. At longer hydration times, all cement–PAA/PEO suspensions exhibited initial elastic modulus values, Gi′∼ exp(t/τc) before the onset of the acceleratory period, followed by initial set. Their characteristic hydration time, τc, and set time depended strongly on the concentration of “free” carboxylic acid groups [COO−] arising from non‐adsorbed polyelectrolyte species in solution.