bluuebunny/crossref_metadata_2025 huggingface dataset:
Emergency Treatment of Migraine
Authors: Ducros A
Published: July 2008

During the past few years, several surveys have highlighted the high prevalence of migraine amongst the general French population and the large healthcare burden associated with suboptimal treatment. Since it opened, the Centre d'Urgences Céphalées (EHC) has treated more than 55 000 patients, the majority of whom were suffering from migraine. Expert diagnosis of the type and causes of the headache, followed by immediate medication, allows patient stabilization. Detailed assessments can then determine the most appropriate treatment for each patient to improve outcomes and reduce the necessity for further emergency admissions. Triptans are generally recommended, and for those patients who currently have ineffective migraine control with one triptan, individual evaluation allows prescription of an alternative triptan which will better suit their needs. Follow-up is crucial to ensure that treatment remains optimal and that patient expectations are being met. Although a minority of patients with severe headache will continue to require repeated emergency treatment, more than 90% of patients seen at the EHC can be successfully managed with this combination of accurate diagnosis, effective treatment and individualized follow-up care.
Almotriptan in Triptan-Naïve Patients: New Evidence of Benefits
Authors: Pascual J
Published: July 2008

Although triptans represent the standard of care for migraine that is severe, disabling and/or suboptimally responsive to migraine non-specific analgesia, they are often underused in clinical practice. Simple analgesics and non-steroidal anti-inflammatory drugs (NSAIDs) may provide effective treatment in some patients, but it is an inadequate response to these drugs that drives the therapeutic progression to triptans at the end of the traditional ‘step-care’ approach. However, there are several disadvantages to this approach. It may cause patients to lose confidence in their physician during this hierarchical ‘trial-and-error’ search for optimal treatment when prescribed medications are ineffective, leading them to cease consulting before triptans are tried. It may also result in a protracted time interval of suboptimal treatment, with unnecessary suffering in patients who are triptan candidates. The alternative approach of ‘stratified care’, in which medication is prescribed according to the severity of symptoms, enables triptans to be used earlier in the treatment plan, especially when triptan candidates are given a choice between simple analgesic/NSAID and triptan medication from the start. This raises the question about the efficacy of triptans in triptan-naïve (TN) patients. A recent exploratory post-hoc analysis compared the effect of almotriptan 12.5 mg in TN patients ( n = 342) with that in triptan-experienced patients ( n = 237). Almotriptan was effective in both cohorts with a consistent trend in favour of the efficacy of almotriptan in TN patients, notably for sustained pain freedom (SPF) and SPF plus no adverse events. Moreover, both headache recurrence at 24 h and the use of rescue medication was lower in the TN patients, whereas tolerability was equally good in both cohorts. These findings indicate that TN patients can expect excellent symptom control when they progress from non-specific analgesia to treatment with almotriptan and support the earlier use of triptans in line with the stratified care paradigm.
Pathways to the Best Fit of Triptans for Migraine Patients
Authors: Buzzi MG
Published: July 2008

Variability in drug response is a major barrier to the successful treatment of migraine, and most treatments are only optimal in a subset of patients. Although triptans provide the best therapeutic option for the treatment of acute migraine, it has not previously been possible to predict how well patients will respond to a specific triptan or whether they will experience unpleasant adverse events. Hence, it has been difficult for physicians to match individual patients with the most suitable agent to treat their migraine pain. Intrapatient variability has been associated with polymorphisms in genes encoding drug-metabolizing enzymes, drug transporters and drug targets. Pharmacogenetics provides the possibility of tailoring the therapeutic approach to individual patients, in order to maximize treatment efficacy while minimizing the potential for unwanted side-effects. This review demonstrates how almotriptan may overcome genetically determined responses by utilizing diverse metabolic pathways to provide therapeutic benefit to many migraineurs.
Early Treatment in Migraine: How Strong is the Current Evidence?
Authors: Gendolla A
Published: July 2008

Over the last 10 years, triptans (serotonin 5-HT1B/1D receptor agonists) have proved to be efficacious in treating migraine pain. However, recent evidence suggests that patients are still not receiving optimal pain management, particularly in clinical trials, where triptan treatment is generally not initiated until pain has reached moderate intensity. Pathophysiological evidence indicates that if treatment is initiated at an early stage, while pain is still mild and before the onset of central sensitization, outcomes for patients may be improved. In addition, a small number of clinical trials have been reported in which triptans were taken early (within 1 h of pain onset) or while pain was still mild; although constraints of trial design and data analysis limit definite conclusions, overall the results suggest that this early/mild approach results in more rapid and sustained pain relief. New studies are therefore needed to clarify the clinical benefits of early treatment, whilst taking into account potential risks, such as medication overuse. Ultimately, migraine treatment strategies require optimization in order to meet patient expectations and to reduce the current burden of migraine-associated disability.
Applying the benefits of the AwM Study in the clinic
Authors: Dodick DW
Published: July 2008

The Act when Mild (AwM) Study has illustrated the benefits to migraineurs of taking triptan medication when their migraine pain is still mild and within 1 h of the onset of symptoms. Yet many patients wait until the attack has fully developed before taking their medication, with potentially inferior outcomes. In order to reproduce the benefits of early intervention using the AwM paradigm in daily practice, a number of key barriers need to be addressed at both the physician and patient level. Notable physician-related barriers to be overcome, particularly at the primary care level, include accuracy of an early diagnosis of migraine in newly presenting patients, communication skills that generate a therapeutic engagement with migraine patients and enhance patient confidence, the application of knowledge about up-to-date strategies to optimize treatment outcomes, and the setting of achievable goals to avoid unrealistic expectations. Patient-related obstacles that need to be identified and overcome encompass patient attitude, expectations, and behaviour. Migraine patients may be reluctant to consult their physician, and, of those who do, many stop consulting because they perceive that physicians can do little to improve their situation. For this reason, migraine patients need to be counselled about the most appropriate medication for their level of symptoms. Moreover, patients need to be confident before they will adhere routinely to the advice they receive, and high in the priority of advice is the use of medication, particularly triptans, at the first sign of a migraine attack, rather than waiting until their attack has progressed to moderate or severe intensity. Patients who adhere to this advice are likely to experience a notable reduction in the pain, disability and time lost that they would otherwise suffer. The beneficial effects of early triptan intervention illustrated in the AwM Study can therefore be best reproduced in the clinic if the correct advice given to patients is not only accepted and applied by them, but also followed up by their physician.
STRATOCLADISTICS AND EVALUATION OF EVOLUTIONARY MODES IN THE FOSSIL RECORD: AN EXAMPLE FROM THE AMMONITE GENUS SEMIFORMICERAS
Authors: PARDO JASON D. , HUTTENLOCKER ADAM K. , MARCOT JONATHAN D.
Published: July 2008

Abstract:  At least two predominating modes of evolution have been proposed for the Early Tithonian oppeliid ammonite genus Semiformiceras, including phyletic transformation of a single lineage (S. darwini–S. semiforme–S. fallauxi) and, most recently, a bifurcating or cladogenetic model of speciation. We discuss methodological obstacles in past studies that have focused on specific modes of evolution, and offer a reanalysis of the morphological data first presented by Cecca and Rouget [Palaeontology, 49, 1069–1080] using the stratocladistic software StrataPhy. The present analysis utilizes 11 ammonite taxa and 15 characters (14 morphological and one stratigraphic) and assesses all previous phylogenetic hypotheses, including those that recruit OTUs in ancestral or ‘nodal’ positions, without excluding evolutionary modes. The results cast doubt on the monophyly of S. darwini, S. semiforme and S. fallauxi, but do not follow completely the direct anagenetic progression proposed by stratophenetic hypotheses. We conclude that stratocladistics is a helpful tool for elucidating the extent of anagenesis and cladogenesis in extinct lineages owing to its capacity to reconstruct phylograms in their temporal framework, and to assess the distinctness and monophyly, not just of clades but of the OTUs themselves. Ultimately, this study addresses the novel utility of computer‐assisted stratocladistic analysis in assessing evolutionary modes beyond the reach of traditional cladistic‐based methodologies.
Conservation Goals and the Relative Importance of Costs and Benefits in Reserve Selection
Authors: PERHANS KARIN , KINDSTRAND CLAES , BOMAN MATTIAS , DJUPSTRÖM LINE BOBERG , GUSTAFSSON LENA , MATTSSON LEIF , SCHROEDER LEIF MARTIN , WESLIEN JAN , WIKBERG SOFIE
Published: July 2008

Abstract: Including both economic costs and biological benefits of sites in systematic reserve selection greatly increases cost‐efficiency. Nevertheless, limited funding generally forces conservation planners to choose which data to focus the most resources on; therefore, the relative importance of different types of data must be carefully assessed. We investigated the relative importance of including information about costs and benefits for 3 different commonly used conservation goals: 2 in which biological benefits were measured per site (species number and conservation value scores) and 1 in which benefits were measured on the basis of site complementarity (total species number in the reserve network). For each goal, we used site‐selection models with data on benefits only, costs only, and benefits and costs together, and we compared the efficiency of each model. Costs were more important to include than benefits for the goals in which benefits were measured per site. By contrast, for the complementarity‐based goal, benefits were more important to include. To understand this pattern, we compared the variability in benefits and in costs for each goal. By comparing the best and the worst possible selection of sites with regard to costs alone and benefits alone for each conservation goal, we introduced a simple and consistent variability measure that is applicable to all kinds of reserve‐selection situations. In our study, benefit variability depended strongly on how the conservation goal was formulated and was largest for the complementarity‐based conservation goal. We argue that from a cost‐efficiency point of view, most resources should be spent on collecting the most variable type of data for the conservation goal at hand.
Efficiency and Concordance of Alternative Methods for Minimizing Opportunity Costs in Conservation Planning
Authors: CAMERON SUSAN E. , WILLIAMS KRISTEN J. , MITCHELL DAVID K.
Published: July 2008

Abstract:  Scarce resources and competing land‐use goals necessitate efficient biodiversity conservation. Combining multicriteria analysis with conservation decision‐support tools improves efficiency of conservation planning by maximizing outcomes for biodiversity while minimizing opportunity costs to society. An opportunity cost is the benefit that could have been received by taking an alternative course of action (i.e., costs to society of protecting an area for biodiversity rather than developing it for some other use). Although different ways of integrating multiple opportunity costs into conservation planning have been suggested, there have been no tests as to which method is most efficient. We compared the relative efficiency of 3 such procedures
(Faith & Walker [1996], Sarkar et al. [2004], and a procedure of our own design) in a systematic conservation‐planning framework for the Milne Bay Province of Papua New Guinea. We devised 14 opportunity costs and assigned these to 3 scenarios representing different conservation planning concerns: food security, macro‐economic development, and biodiversity persistence. For each scenario, we compared the efficiency of the 3 methods in terms of amount of biodiversity protected relative to total expenditure for each opportunity cost. All 3 methods captured similar amounts of biodiversity, but differed in total cost. Our method had the least overall cost and was therefore most efficient. Nevertheless, there was a high correlation and geographical concordance among all 3 methods, indicating a high degree of spatial overlap. This suggests that choosing an appropriate approach may often depend on contextual factors related to the design of the planning question, rather than efficiency alone.
Densification of Si3N4 with LiYO2 Additive
Authors: Matovic Branko , Rixecker Georg , Aldinger Fritz
Published: July 2008

This paper deals with the densification and phase transformation during pressureless sintering of Si3N4 with LiYO2 as the sintering additive. The dilatometric shrinkage data show that the first Li2O‐ rich liquid forms as low as 1250°C, resulting in a significant reduction of sintering temperature. On sintering at 1500°C the bulk density increases to more than 90% of the theoretical density with only minor phase transformation from α‐Si3N4 to β‐Si3N4 taking place. At 1600°C the secondary phase has been completely converted into a glassy phase and total conversion of α‐Si3N4 to β‐Si3N4 takes place. The grain growth is anisotropic, leading to a microstructure which has potential for enhanced fracture toughness. Li2O evaporates during sintering. Thus, the liquid phase is transient and the final material might have promising mechanical properties as well as promising high‐temperature properties despite the low sintering temperature. The results show that the Li2O−Y2O3 system can provide very effective low‐temperature sintering additives for silicon nitride.
Tape Casting, Pressureless Sintering, and Grain Growth in Ti3SiC2 Compacts
Authors: Murugaiah A. , Souchet A. , El‐Raghy T. , Radovic M. , Sundberg Mats , Barsoum M. W.
Published: July 2008

In this work we demonstrate that fine Ti3SiC2 powders can be tape‐cast and/or cold‐pressed and pressureless‐sintered in Ar‐ or Si‐rich atmospheres to produce fully dense, oriented microstructures in which the basal planes are parallel to the surfaces. Carbon‐ and/or Si‐rich environments suppress grain growth. In the case of the tape casting, the C‐residue from binder burnout results in small core grains relative to the surface grains that can grow significantly. When sintering in high Si activities, titanium silicide phases form at the grain boundaries that slow grain growth. Annealing the latter in Ar at 1600°C, for extended periods (30 h), rids the samples of these grain‐boundary phases, which in turn results in grain growth. The advantage of the latter process is that the final grain size distribution is more uniform from surface to bulk.
Sintering of (Cu0.25Ni0.25Zn0.50)Fe2O4 Ferrite
Authors: Barba Antonio , Clausell Carolina , Felíu Carlos , Monzó María
Published: July 2008

A study has been conducted on the sintering of a ceramic ferrite having the composition (Cu0.25Ni0.25Zn0.50)Fe2O4. The study analyzes the evolution of ferrite relative to density and microstructure with peak sintering temperature and dwell time at peak temperature. The densification and grain‐growth rates are correlated with average grain size, relative density, and temperature. Corresponding rate‐controlling diffusion mechanisms are proposed.
Electric‐Field‐Controlled Permittivity Ferroelectric Composition for Microwave LTCC Modules
Authors: Hu Tao , Jantunen Heli , Deleniv Anatoli , Leppävuori Seppo , Gevorgian Spartak
Published: July 2008

A low‐temperature cofired ferroelectric ceramic composition for electrically tunable radio frequency devices is introduced. A sintering temperature of 950°C for BaSrTiO3–MgO was obtained following the combined addition of B2O3 and Li2CO3. The effects of these sintering aids on densification, microstructure, and ferroelectric properties were investigated. The permittivity and dissipation factor values were 234 and 0.0010, respectively, measured at 286.3 K, 1 kHz. The electrically tunable ferroelectric structure for microwave measurement was fabricated throughout the tape‐casting process. Measured permittivity was 130 at 26 GHz and tunability >15% (4 V/μm).
Phase Formation and Dielectric Characterization of the Bi2O3–TeO2 System Prepared in an Oxygen Atmosphere
Authors: Udovic Marko , Valant Matjaz , Suvorov Danilo
Published: July 2008

Solid‐state synthesis of compositions from the Bi2O3–TeO2 system show that, under an oxygen atmosphere, Te4+ oxidizes to Te6+ and yields four room‐temperature stable compounds: Bi2Te2O8, Bi2TeO6, Bi6Te2O15, and new a compound with the nominal composition 7Bi2O3·2TeO2. Dense ceramics can be prepared from all these compounds by sintering between 650° and 800°C under an oxygen atmosphere. The permittivity of these compounds varies from ∼30 to ∼54, the Q×f value from 1.100 to 41.000 GHz (∼5 GHz), and the temperature coefficient of resonant frequency from −43 to −144 ppm/K. Bi6Te2O15 and 7Bi2O3·2TeO2 do not react with silver, and, therefore, they have the potential to be used for applications in low‐temperature cofired ceramic (LTCC) technology.
Fabrication of Ceramic Photonic Crystals with Diamond Structure for Microwave Applications
Authors: Yin Haiqing , Kirihara Soshu , Miyamoto Yoshinari
Published: July 2008

A process for fabricating three‐dimensional photonic crystals composed of SiO2–TiO2‐based ceramics with a diamond structure was investigated. An epoxy structure having an inverse diamond configuration was fabricated by stereolithography, a rapid prototyping method. The epoxy structure was infiltrated with a ceramic slurry and then cold isostatically pressed. After sintering at 670°C for 5 h in air, the epoxy was burned off, leaving behind the desired structure of a ceramic photonic crystal. The calculated band diagram indicated that an absolute photonic band gap for all wave vectors existed. The measurement of transmission in the 〈100〉 direction from 10 to 20 GHz showed that a complete band gap formed at about 14.7–18.5 GHz. The magnitude of the maximum attenuation was as large as 30 dB at 17 GHz, which indicated that the fabricated structure worked well as a photonic crystal.
Grain Orientation Effects on the Properties of a Bismuth Layer‐Structured Ferroelectric (BLSF) Bi3NbTiO9 Solid Solution
Authors: Zhang Zhen , Yan Haixue , Xiang Pinghua , Dong Xianlin , Wang Yongling
Published: July 2008

Bi3NbTiO9 ceramics were prepared by ordinary firing and by hot‐press sintering. The crystal structures of the ceramics were investigated by X‐ray diffractometry. Scanning electron microscopy observation showed that the platelike grains were oriented after hot pressing. Dielectric, piezoelectric, and ferroelectric characterizations, as well as the electrical resistivities, showed remarkable anisotropy in the hot‐pressed samples. Because of grain orientation in the hot‐pressed samples, the remanent polarization and piezoelectric constant in the direction perpendicular to the pressing axis were much higher than in the unoriented, ordinary fired samples.
Preparation and Properties of Lead Zirconate Stannate Titanate Sintered by Spark Plasma Sintering
Authors: Zhou Longjie , Zhao Zhe , Zimmermann André , Aldinger Fritz , Nygren Mats
Published: July 2008

Lanthanum‐doped lead zirconate stannate titanate ceramics were successfully compacted to full density by spark plasma sintering (SPS). SPS samples densified at 900° or 950°C exhibit nearly full density and fine grain size (about 300 nm). Compared with samples from conventional sintering (CS), SPS samples show larger permittivity accompanied by a deterioration in dielectric loss and special strain hysteresis loops similar to those of ferroelectric relaxors, with a diffuse AFE–FE phase transition and less field‐induced longitudinal strain. The differences in the properties of SPS and CS materials are attributed to the variations of the resultant microstructures, especially the grain size, of the ceramics.
Solid‐Solution Formation in the Synthesis of Fe‐Zircon
Authors: Cortés Enrique Carreto , de la Fuente J. Ascención Montoya , Moreno Jorge Morgado , Pérez Cira Piña , Cordoncillo Eloisa Cordoncillo , Castelló Juan B. Carda
Published: July 2008

To investigate solid‐solution formation in the iron‐doped silicate (zircon) system, different samples were prepared by the ceramic method with addition of LiF as a mineralizer. The results of X‐ray powder diffraction (XRD), 57Fe Mössbauer, and UV–visible spectroscopy showed that in the as‐prepared samples, only a small fraction of iron, i.e., about 2.5 mol%, is hosted in the zircon structure as paramagnetic Fe3+ species, while the remaining Fe3+ cations form magnetic α‐Fe2O3 particles that are trapped in the zircon matrix.
Reduction of Thermal‐Gradient‐Induced Stresses in Composites Using Mixed Fibers
Authors: Parthasarathy Triplicane A. , Keller Kristen A. , Mah Tai‐Il , Kerans Ronald J. , Butner Steve
Published: July 2008

The possibility of using fibers of varying thermal expansivities to reduce stresses generated from thermal gradients in service was explored. Laminates of aluminosilicate‐ and alumina‐matrix composites were fabricated using a combination of Nextel 610™ and Nextel 720™ fibers. The composites were tested for mechanical behavior and thermomechanical behavior in comparison to control composite specimens which contained a single type of fiber. Mixed‐fiber composites show strength and fracture behavior similar to those of single‐fiber‐type composites. Their thermomechanical behavior is consistent with 2D laminate models, making it possible to design composites using such models. Interlaminar shear stress is a key, but sole limitation and the use of gradation in fiber mixture is suggested.
Influence of the Y2O3 Content and Temperature on the Mechanical Properties of Melt‐Grown Al2O3–ZrO2 Eutectics
Authors: LLorca J. , Pastor José Y. , Poza Pedro , Peña José I. , de Francisco Isabel , Larrea Angel , Orera Victor M.
Published: July 2008

The effect of Y2O3 content on the flexure strength of melt‐grown Al2O3–ZrO2 eutectics was studied in a temperature range of 25°–1427°C. The processing conditions were carefully controlled to obtain a constant microstructure independent of Y2O3 content. The rod microstructure was made up of alternating bands of fine and coarse dispersions of irregular ZrO2 platelets oriented along the growth axis and embedded in the continuous Al2O3 matrix. The highest flexure strength at ambient temperature was found in the material with 3 mol% Y2O3 in relation to ZrO2(Y2O3). Higher Y2O3 content did not substantially modify the mechanical response; however, materials with 0.5 mol% presented a significant degradation in the flexure strength because of the presence of large defects. They were nucleated at the Al2O3–ZrO2 interface during the martensitic transformation of ZrO2 on cooling and propagated into the Al2O3 matrix driven by the tensile residual stresses generated by the transformation. The material with 3 mol% Y2O3 retained 80% of the flexure strength at 1427°C, whereas the mechanical properties of the eutectic with 0.5 mol% Y2O3 dropped rapidly with temperature as a result of extensive microcracking.
Effect of Strong Anisotropy in Grain‐Boundary Energy on Boundary Mobility in Abnormally Grown Grains
Authors: Brosh Eli , Shneck Roni Z.
Published: July 2008

The growth of a large crystal into a fine‐grained polycrystal of the same phase is considered through a two‐dimensional model. The macroscopic driving force for growth depends only on the average energy of the grain boundaries of the polycrystalline matrix. The analysis reveals a dependence of the local driving force and effective mobility on the orientation of the interface between the large crystal and the matrix. The orientations with very low energy relative to the neighboring orientations also have low effective mobility. Applications are found in modeling of abnormal grain growth in ceramics and in experiments designed to measure the mobility of grain boundaries.
Metastable Crystal Structure of Strontium‐ and Magnesium‐Substituted LaGaO3
Authors: Rozumek Michael , Majewski Peter , Aldinger Fritz
Published: July 2008

The metastable crystal structure of strontium‐ and magnesium‐substituted LaGaO3 (LSGM) was studied at room and intermediate temperatures using powder X‐ray diffractometry and Rietveld refinement analysis. With increased strontium and magnesium content, phase transitions were found to occur from orthorhombic (space group Pbnm) to rhombohedral (space group R[Threemacr]c) at the composition La0.825Sr0.175Ga0.825Mg0.175O2.825 and, eventually, to cubic (space group Pm[Threemacr]m) at the composition La0.8Sr0.2Ga0.8Mg0.2O2.8. At 500°C in air and at constant strontium and magnesium content, a phase transformation from orthorhombic (space group Pbnm) to cubic (space group Pm[Threemacr]m) was observed. For the orthorhombic modification, thermal expansion coefficients were determined to be αa,ortho = 10.81 × 10−6 K−1, αb,ortho = 9.77 × 10−6 K−1, and αc,ortho = 9.83 × 10−6 K−1 (25°–400°C), and for the cubic modification to be αcubic= 13.67 × 10−6 K−1 (500°–1000°C).
La1+xSr1–xGa3O7–δ Melilite‐Type Ceramics ‐ Preparation, Composition, and Structure
Authors: Rozumek Michael , Majewski Peter , Sauter Linda , Aldinger Fritz
Published: July 2008

Ceramic samples of the melilite‐type La1+xSr1–xGa3O7–δ (x=−0.15 to 0.60) compound were prepared by conventional ceramic processing. Sintering characteristics and microstructural evolution were studied. A phase diagram study was performed to establish the solid solubility limits as a function of the La:Sr ratio. Structural investigations of the Dalton composition as well as strontium‐ and lanthanum‐rich samples entailed X‐ray, neutron, and electron diffraction techniques at ambient and elevated temperatures. The homogeneity region was remarkably broad (x=−0.15 to 0.60) with no changes in space group observed. A small shrinkage of the unit cell was found with increased lanthanum content. Phase transitions at ambient and intermediate temperatures did not occur.
Effect of Yttria and Yttrium‐Aluminum Garnet on Densification and Grain Growth of Alumina At 1200°–1300°C
Authors: Cinibulk Michael K.
Published: July 2008

Densification and grain growth of alumina were studied with yttria or yttrium‐aluminum garnet (YAG) additives at the relatively low temperatures of 1200°–1300°C. Yttria doping was found to inhibit densification and grain growth of alumina at 1200°C and, depending on dopant level, had a lesser effect at 1300°C. At 1200°C, yttria inhibits densification more than it hinders grain growth. The rate of grain growth increases faster with temperature than the rate of densification. Alumina‐YAG particulate composites were difficult to sinter, yielding relative densities of only 65% and 72% after 100 h at 1200° and 1300°C, respectively. Pure YAG compacts exhibited essentially no densification for times up to 100 h at 1300°C.
SiC/ZTM Nanocomposite with Needlelike Mullite Grains and Enhanced Mechanical Properties
Authors: Jin Xihai , Gao Lian
Published: July 2008

Zirconia‐toughened mullite (SiC/ZTM) nanocomposites were prepared by a chemical precipitation method. The samples showed good sinterability and could be densified to >98.7% of the theoretical density at 1350°–1550°C. Because of the addition of mullite seeds in the starting powder and the pinning effects of ZrO2 and SiC particles on mullite grain growth, a fine‐grained microstructure formed. Mullite grains were generally equiaxed for the sample sintered at 1400°C; whereas, for the sample sintered at 1550°C, most mullite grains took a needlelike morphology, and SiC particles were primarily located within mullite grains. The strength and toughness increased with the increasing sintering temperature, and reached their respective maximum of 780 MPa and 3.7 MPa·m1/2 for the sample sintered at 1550°C.
Processing and Properties of in Situ‐Reinforced α‐SiAlONs Stabilized with Y2O3 and Lu2O3
Authors: Jones Mark I. , Hyuga Hideki , Hirao Kiyoshi , Yamauchi Yukihiko
Published: July 2008

α‐SiAlONs with equiaxed and elongated microstructures stabilized with Y2O3 and Lu2O3 were produced by hot pressing, and the phase structure and room‐ and high‐temperature mechanical properties were assessed. Additional liquid added to the starting composition in the form of 5 wt% rare‐earth monosilicate resulted in the formation of elongated microstructures and improvements in room‐temperature strength and fracture toughness. The elongated grain growth was promoted by the additional liquid phase, which crystallized to form a secondary grain‐boundary phase thought to be J′ (Re4Si2–xAlxO7+xN2–x). For the equiaxed and the elongated samples, those sintered with Lu2O3 showed higher hardness than the comparable Y2O3‐sintered materials, and, at elevated temperature, the strength retention of the elongated Lu2O3 SiAlON was much higher than that of the Y2O3 sample, which was attributed to properties of the residual grain‐boundary phase associated with the difference in the cationic radius of the stabilizing cation.
Highly Transparent Lu‐α‐SiAlON
Authors: Jones Mark I. , Hyuga Hideki , Hirao Kiyoshi , Yamauchi Yukihiko
Published: July 2008

Novel Lu‐α‐SiAlON ceramics were produced by hot pressing mixtures of Si3N4, Lu2O3, AlN, and Al2O3 at 1950°C for 2 h in a nitrogen atmosphere. The resultant SiAlON was fully dense and possessed a uniform, equiaxed microstructure with a grain size of ∼1 μm, which resulted in a high hardness of >19 GPa. In addition to high hardness, the sample showed very high optical transparency in the visible light region, with >70% transmission at higher wavelengths. This high transparency was attributed to the uniform, dense microstructure and lack of residual grain‐boundary phase.
Effect of Low‐Energy Accelerated Ion Bombardment on the Properties of Metal‐Organic Decomposition Derived SrBi2(Ta,Nb)2O9 Thin Films Processed at Low Temperature
Authors: Lee Jang‐Sik , Jia Q. X. , Park Jung‐Ho , Joo Seung‐Ki , Yang Woo Seok , Kim Nam Kyeong , Yeom Seung Jin , Roh Jae Sung
Published: July 2008

Ferroelectric SrBi2(Ta,Nb)2O9 (SBTN) thin films were deposited on Pt (200 nm)/TiOx(40 nm)/SiO2 (100 nm)/Si substrates by metal‐organic decomposition. The effects of bombardment from accelerated argon and oxygen ions on the properties of SBTN thin films were investigated. It was found that the argon ion bombardment could decrease the crystallization temperature owing to the increase of internal energy of the films. Also, the oxygen vacancies at the interface between the SBTN film and platinum bottom electrode or at grain boundaries in the film were passivated through the oxygen ion treatment, resulting in the improved electrical properties. By optimizing the process parameters and using bombardment of accelerated argon and oxygen ions, SBTN films with good ferroelectric and electrical properties could be obtained, at a temperature as low as 650°C.
Rapid Densification and Deformation of Li‐Doped Sialon Ceramics
Authors: Shen Zhijian , Peng Hong , Nygren Mats
Published: July 2008

Two lithium‐doped sialon ceramics were densified and superplastically deformed by spark plasma sintering (SPS). Rapid densification with linear shrinkage rates of approximately 5 × 10−3 s−1 were observed for samples heated at a rate of 100°C/min up to ∼1400°C under a uniaxial pressure of 40 MPa. Isothermal deformation by SPS‐preprepared, fully densified ceramics performed at T≥ 1450°C yielded strain rates in the order of 10−2 s−2. It is suggested that a high heating rate promotes material transport via formation of a nonequilibrated oxygen‐rich liquid of low viscosity. This finding most likely holds true for other liquid‐phase sintered ceramics as well and has implications for cost‐effective manufacturing of ceramic components.
Translucent α‐Sialon Ceramics by Hot Pressing
Authors: Su Xinlu , Wang Peiling , Chen Weiwu , Zhu Bo , Cheng Yibing , Yan Dongsheng
Published: July 2008

The single‐phase α‐sialon ceramics with high optical transmittance have been prepared by hot pressing. The maximum transmittance reached 65.2% and 52.2% in the infrared wavelength region, 58.5% and 40% in the visible region for the samples 1.0 and 1.5 mm thickness, respectively. The material also exhibited good mechanical properties of high hardness (20 GPa) and better fracture toughness (5.1 MPa·m1/2). Both high optical transmittance and improved toughness of α‐sialon ceramics were attributed to the less‐grain‐boundary glassy phase and the homogeneous microstructure, which was obtained by a proper process and confirmed by SEM and TEM observation, compared to that prepared by ordinary sintering. It is, therefore, expected that the translucent α‐sialon ceramics could be a promising optical window material.
Growing SiC Nanowires on Tyranno‐SA SiC Fibers
Authors: Yang Wen , Araki Hiroshi , Kohyama Akira , Hu Quanli , Suzuki Hiroshi , Noda Tetsuji
Published: July 2008

A new in situ process for growing SiC nanowires on Tyranno‐SA SiC fibers (2‐D, plain‐woven) was developed using the thermal decomposition of methyltrichlorosilane in hydrogen. The process was performed using a chemical vapor infiltration system. β‐SiC nanowires ∼100‐nm thick and several tens of micrometers long were successfully synthesized on the fibers. The growing of the SiC nanowires suggests a conditions‐dependent process.
Microstructure of Varistors Prepared with Zinc Oxide Nanoparticles Coated with Bi2O3
Authors: Yuan Fangli , Ryu Hojin
Published: July 2008

Zinc oxide (ZnO) nanoparticles coated with 1–5 wt% Bi2O3 were prepared by precipitating a Bi(NO3)3 solution onto a ZnO precursor. Transmission electron microscopy showed that a homogeneous Bi2O3 layer coated the surface of the ZnO nanoparticles and that the ZnO particle size was ∼30–50 nm. Scanning electron microscopy showed that ZnO grains sintered at 1150°C were homogeneous in size and surrounded by a uniform Bi2O3 layer. When the ZnO grains were surrounded fully by Bi2O3 liquid phases, further increases in the ZnO grain size were not affected by the Bi2O3 content. This predesigned ZnO nanoparticle structure was shown to promote homogeneous ZnO grains with perfect crystal growth.
Dielectric Behavior of Na0.5Bi0.5TiO3‐Based Composites Incorporating Silver Particles
Authors: Lin Yuanhua , Nan Ce‐Wen , Wang Jianfei , Liu Gang , Wu Junbo , Cai Ning
Published: July 2008

The dielectric properties of Na0.5Bi0.5TiO3 (NBT) ‐based composites incorporating silver particles prepared by sintering at a low temperature of ∼900°C are reported. The dielectric constant increases with the amount of metal silver particles in the measured frequency range (150 Hz to 1 MHz), and could be enhanced up to ∼20 times higher than that of pure NBT ceramics, which was ascribed to the effective electric fields developed between the dispersed particles in the matrix and the percolation effect. Further investigation revealed that the dielectric constant of the composites has weak frequency and temperature dependence (−50°C to +50°C).
HIP‐Sintered Composites of C (Diamond)/SiC
Authors: Shimono Masaru , Kume Shoichi
Published: July 2008

Diamond (carbon) and silicon powders were mixed and HIPed under temperatures of 1300°–1500°C and pressure at 50 MPa for 30 min. When heated at >1300°C, the products were >90% sintered compacts. Density and bending strength were measured. The highest values of 3.3 g/cm3 and 750 MPa were obtained when the starting material was a mixture of fine and coarse‐grained diamond and silicon powder. The photomicrograph of polished surface of the product revealed that it consisted primarily of two types of substances with few pores. XRD showed the coexistence of diamond and SiC. No trace of conversion reaction from diamond to graphite was seen, although the sample was treated under conditions in which diamond was thermodynamically metastable. The summarized results suggest that the HIP process can be a useful way to synthesize diamond/SiC composites.
Positive Temperature Coefficient of Electrical Resistivity below 150 K in Barium Strontium Titanate
Authors: Viviani Massimo , Leoni Marcello , Buscaglia Maria Teresa , Buscaglia Vincenzo , Nanni Paolo
Published: July 2008

The resistivity of Ba(1–y)(1–x)Sry(1–x)LaxTiO3ceramics with x= 0.0025 and y= 0.25, 0.5, 0.75, and 0.9 was measured between 50 and 400 K. A resistivity anomaly corresponding to the positive temperature coefficient of electrical resistivity (PTCR) effect was observed for all compositions. The onset temperature decreased from 320 K (y= 0.25) to 70 K (y= 0.9). The extent of the PTCR effect was significantly enhanced for the strontium‐rich composition and reached ∼8 orders of magnitude for y= 0.9. These results strongly suggested the possibility to fabricate PTCR devices based on (Sr,Ba)TiO3 ceramics for application at cryogenic temperatures.
Deposition of Silicon Carbide/Titanium Carbide Laminar Ceramics by Electrophoresis and Densification by Spark Plasma Sintering
Authors: You Chang , Jiang Dongliang , Tan Shouhong
Published: July 2008

SiC/TiC laminar ceramic composites were fabricated using electrophoretic deposition (EPD) from acetone‐based suspensions. The growth rate of the SiC was almost twice that of the TiC at the same deposition voltage and solids loading. Pressureless sintering and spark plasma sintering (SPS) of the composites were investigated. SiC in the composites without sintering additives could not be densified using pressureless sintering, even at 2000°C. SPS, however, could densify the SiC/TiC composites at 1800°C and 35 MPa. The relative density of the SPS sample was 98.9%.
Coating Fine Nickel Particles with Al2O3 Utilizing an Atomic Layer Deposition‐Fluidized Bed Reactor (ALD–FBR)
Authors: Wank Jeffrey R. , George Steven M. , Weimer Alan W.
Published: July 2008

An atomic layer deposition–fluidized bed reactor (ALD–FBR) method has been developed to deposit ultrathin and conformal coatings on fine particles. Experiments of Al2O3 deposition on 150‐μm‐diameter nickel particles were conducted. The fluidized bed was constructed to operate under vacuum, and the fluidizing gas used was nitrogen. Trimethylaluminum and water were used as dosing reagents. The reactions were conducted at 450 K. Successful deposition of alumina films, with thickness controllable at the nanometer level, was observed based on transmission electron microscopy imaging, inductively coupled plasma atomic emission spectrometry, X‐ray photoemission spectroscopy, particle‐size distributions, and wavelength‐dispersive spectrometry imaging.
Cutaneous bioengineering instrumentation standardization: the Tissue Viability Imager
Authors: Nilsson Gert E. , Zhai Hongbo , Chan Heidi P. , Farahmand Sara , Maibach Howard I.
Published: July 2008

Background: Tissue Viability Imaging (TiVi) is a new bioengineering technology intended for remote two‐dimensional mapping of skin red blood cell concentration (RBCconc). Before use in the laboratory, work‐site and dermatology clinic, critical performance parameters of this emerging technology require careful evaluation.

Objective: To assess short‐ and long‐term stability, image uniformity, distance and image size dependence, ambient light and curvature influence in a production batch of Tissue Viability Imagers.

Methods: Four Tissue Viability Imagers from the same production batch were evaluated at two laboratories (one industrial and one dermatological) with respect to critical parameter performance.

Results: The average systematic drift in sensitivity over time was 0.27% and <1.02% for all four units tested. Difference in sensitivity between units was limited to 4.1% and was due to offset rather than gain deviation. Spatial variation in image uniformity was below 3.08% and 1.93% in the corners and centre of an individual image, respectively. This spatial variation could be further reduced to 0.25% and 0.13%, respectively by image normalization. Ambient light from a 40 W bulb or a 11 W fluorescent light source at a distance of 50–60 cm above the object, reduced the recorded values by about 10%, while the camera to object distance and image size had no detectable influence on sensitivity. Curved objects, such as human forearm, demonstrated an edge effect limited to below 10%.

Conclusion: The critical TiVi performance parameters evaluated proved stable in relation to expected variations in skin RBCconc over time. Calibration by way of a two‐point method may reduce differences in sensitivity between instruments to further facilitate inter‐laboratory comparison of results.
Comparative Analysis of JmjC Domain‐containing Proteins Reveals the Potential Histone Demethylases in Arabidopsis and Rice
Authors: Lu Falong , Li Guanglin , Cui Xia , Liu Chunyan , Wang Xiu‐Jie , Cao Xiaofeng
Published: July 2008

Histone methylation homeostasis is achieved by controlling the balance between methylation and demethylation to maintain chromatin function and developmental regulation. In animals, a conserved Jumonji C (JmjC) domain was found in a large group of histone demethylases. However, it is still unclear whether plants also contain the JmjC domain‐containing active histone demethylases. Here we performed genome‐wide screen and phylogenetic analysis of JmjC domain‐containing proteins in the dicot plant, Arabidopsis, and monocot plant rice, and found 21 and 20 JmjC domain‐containing, respectively. We also examined the expression of JmjC domain‐containing proteins and compared them to human JmjC counterparts for potential enzymatic activity. The spatial expression patterns of the Arabidopsis JmjC domain‐containing genes revealed that they are all actively transcribed genes. These active plant JmjC domain‐containing genes could possibly function in epigenetic regulation to antagonize the activity of the large number of putative SET domain‐containing histone methyltransferase activity to dynamically regulate histone methylation homeostasis.
Subcellular Localizations of AS1 and AS2 Suggest Their Common and Distinct Roles in Plant Development
Authors: Zhu Yan , Li Ziyu , Xu Ben , Li Hongda , Wang Lingjian , Dong Aiwu , Huang Hai
Published: July 2008

During leaf organogenesis, a critical step for normal leaf primordium initiation is the repression of the class 1 KNOTTED1‐like homeobox (KNOX) genes. After leaf primordia are formed, they must establish polarity for normal leaf morphogenesis. Recent studies have led to the identification of a number of genes that participate in the class 1 KNOX gene repression and/or the leaf polarity establishment. ASTMMETRIC LEAVES1 and 2 (AS1 and AS2) are two of these genes, which are critical for both of these two processes. As a first step towards understanding the molecular genetic basis of the AS1–AS2 action, we determined the subcellular localizations of the two proteins in both tobacco BY2 cells and Arabidopsis plants, by fusing them to yellow/cyan fluorescent protein (YFP/CFP). Our data showed that AS1 and AS2 alone were predominantly localized in the nucleolus and the nucleoplasm, respectively. The presence of both AS1 and AS2 proteins in the same interphase cell demonstrated their co‐localization in both nucleolus and nucleoplasm. In addition, AS1 alone was able to associate with the condensed chromosome in the metaphase cell. Our data suggest that AS1, AS2 and the AS1‐AS2 protein complex may have distinct functions, which are all required for normal plant development.
Gamete Recognition in Higher Plants: An Abstruse but Charming Mystery
Authors: Peng Xiong‐Bo , Sun Meng‐Xiang
Published: July 2008

Although much effort has been made to uncover the mechanism underlying double fertilization, little knowledge has been acquired for understanding the molecular base of gamete recognition, mainly because of technical limitations. Still, progress has been made in terms of the mechanism, including the identification of candidate molecules that are involved in gamete recognition in angiosperms. New cues for gamete recognition have been found by the successful separation of the gametes and construction of gamete‐specific cDNA libraries in several species, and the application of molecular approaches for studying this process by mutations. Thus, the topic is considered an abstruse but charming mystery.
Membrane Transporters for Nitrogen, Phosphate and Potassium Uptake in Plants
Authors: Chen Yi‐Fang , Wang Yi , Wu Wei‐Hua
Published: July 2008

Nitrogen, phosphorous and potassium are essential nutrients for plant growth and development. However, their contents in soils are limited so that crop production needs to invest a lot for fertilizer supply. To explore the genetic potentialities of crops (or plants) for their nutrient utilization efficiency has been an important research task for many years. In fact, a number of evidences have revealed that plants, during their evolution, have developed many morphological, physiological, biochemical and molecular adaptation mechanisms for acquiring nitrate, phosphate and potassium under stress conditions. Recent discoveries of many transporters and channels for nitrate, phosphate and potassium uptake have opened up opportunities to study the molecular regulatory mechanisms for acquisition of these nutrients. This review aims to briefly discuss the genes and gene families for these transporters and channels. In addition, the functions and regulation of some important transporters and channels are particularly emphasized.
Rising jet-inflated bubbles in clusters of galaxies
Authors: Sternberg Assaf , Soker Noam
Published: July 2008

We conduct two-dimensional axisymmetric (referred to as 2.5D) hydrodynamical numerical simulations of bubble evolution in clusters of galaxies. We inflate bubbles using slow, massive jets with a wide opening angle, and follow their evolution as they rise through the intracluster medium. We find that these jet-inflated bubbles are quite stable, and can reach large distances in the cluster while maintaining their basic structure. The stability of the jet-inflated bubble comes mainly from the dense shell that forms around it during its inflation stage, and from the outward momentum of the bubble and shell. On the contrary, bubbles that are inserted by hand on to the grid and not inflated by a jet, i.e. an artificial bubble, lack these stabilizing factors; therefore, they are rapidly destroyed. The stability of the jet-inflated bubble removes the demand for stabilizing magnetic fields in the bubble.