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Microstructural Features (microstructural + feature)
Selected AbstractsMicrostructural features of albite porphyroblasts as indicators of sequential Barrovian metamorphic mineral growth in the Caledonides of the SW Scottish HighlandsJOURNAL OF METAMORPHIC GEOLOGY, Issue 7 2004V. Mathavan Abstract Inclusion , porphyroblast and porphyroblast , porphyroblast relationships show that abundant albite in mica schists in the Caledonides of the SW Scottish Highlands are part of the Barrovian metamorphic assemblage. Growth early in the D2 deformational phase of porphyroblast cores followed the growth of Mn-rich garnet but preceded the growth of porphyroblasts of the index mineral almandine. Two sets of inclusion trails in the albite correspond to the regionally expressed S1 and S2. Straight trails of muscovite, chlorite, quartz, epidote and the earliest growth of biotite make up S1. Crenulated trails express deformation of S1 early in D2 with muscovite, chlorite, biotite, quartz, epidote and the Mn-rich garnet associated with the development of S2 crenulation cleavage. The geometries of these trails uniquely record early stages of D2 deformational history. An 0,3 growth is related to the temporal coincidence of the formation of S1,S2 crenulation cleavage hinges as favourable sites for nucleation and the release of large amounts of water from prograde reactions during tectonothermal reconstitution of first cycle immature sediments with a volcanic component. The main characteristics of the regionally expressed D2 schistosity were developed during the major grain coarsening that followed both albite and almandine porphyroblast growth. Essentially inclusion-free An 4,19 rims grew on the inclusion-containing cores in the almandine zone in the later stages of schistosity growth and unoriented porphyroblasts of muscovite, biotite and chlorite indicate that mineral growth extended from the later stages of D2 to post-D2. Previous interpretations of the albite porphyroblast growth having been during D4 to post-D4 contemporaneous with retrogression are inconsistent with the microstructural evidence. [source] Apparent diffusion coefficient of the superior cerebellar peduncle differentiates progressive supranuclear palsy from Parkinson's disease,MOVEMENT DISORDERS, Issue 16 2008Giuseppe Nicoletti MD Abstract The early diagnosis of progressive supranuclear palsy (PSP) may be challenging, because of clinical overlapping features with Parkinson's disease (PD) and other parkinsonian syndromes such as the Parkinsonian variant of multiple system atrophy (MSA-P). Conventional MRI can help in differentiating parkinsonian disorders but its diagnostic accuracy is still unsatisfactory. On the basis of the pathological demonstration of superior cerebellar peduncle (SCP) atrophy in patients with PSP, we assessed the SCP apparent diffusion coefficient (ADC) values in patients with PSP, PD, and MSA-P in order to evaluate its differential diagnostic value in vivo. Twenty-eight patients with PSP (14 with possible-PSP and 14 with probable-PSP), 15 PD, 15 MSA-P, and 16 healthy subjects were studied by using diffusion weighted imaging (DWI). ADC was calculated in regions of interest defined in the left and right SCP by two clinically blinded operators. Intrarater (r = 0.98, P < 0.001) and interrater reliability (r = 0.97; P < 0.001) for SCP measurements were high. Patients with PSP had higher SCP rADC values (median 0.98 × 10,3mm2/s) than patients with PD (median 0.79 × 10,3 mm2/s, P < 0.001), MSA-P (median 0.79 × 10,3 mm2/s, P < 0.001), and healthy controls (median 0.80 × 10,3 mm2/s, P < 0.001). DWI discriminated patients with PSP from PD and healthy subjects on the basis of SCP rADC individual values (100% sensitivity and specificity) and from patients with MSA-P (96.4% sensitivity and 93.3% specificity). The higher values of rADC in SCP of patients with PSP correspond with the in vivo microstructural feature of atrophy detected postmortem and provide an additional support for early discrimination between PSP and other neurodegenerative parkinsonisms. © 2008 Movement Disorder Society [source] The Art and Science of Tailoring Materials by Nanostructuring for Advanced Properties Using SPD Techniques,ADVANCED ENGINEERING MATERIALS, Issue 8 2010Ruslan Z. Valiev In recent years a breakthrough has developed in the studies of nanostructured metals and alloys as advanced structural and functional materials associated both with the development of new routes for the fabrication of bulk nanostructured materials using severe plastic deformation (SPD) and with investigations of the fundamental mechanisms that lead to the new properties of these materials. This review paper discusses new concepts and principles in using SPD processing to fabricate bulk nanostructured metals with advanced properties. Special emphasis is placed on the relationship between microstructural features and properties, as well as the innovation potential of SPD-produced nanomaterials. [source] Influence of Interface Characteristics on the Mechanical Properties of Hi-Nicalon type-S or Tyranno-SA3 Fiber-Reinforced SiC/SiC MinicompositesINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 3 2010C. Sauder The tensile behavior of CVI SiC/SiC composites with Hi-Nicalon type-S (Hi-NicalonS) or Tyranno-SA3 (SA3) fibers was investigated using minicomposite test specimens. Minicomposites contain a single tow. The mechanical behavior was correlated with microstructural features including tow failure strength and interface characteristics. The Hi-NicalonS fiber-reinforced minicomposites exhibited a conventional damage-tolerant response, comparable to that observed on composites reinforced by untreated Nicalon or Hi-Nicalon fibers and possessing weak fiber/matrix interfaces. The SA3 fiber-reinforced minicomposites exhibited larger interfacial shear stresses and erratic behavior depending on the fiber PyC coating thickness. Differences in the mechanical behavior were related to differences in the fiber surface roughness. [source] Progress in Nanoengineered Microstructures for Tunable High-Current, High-Temperature Superconducting Wires,ADVANCED MATERIALS, Issue 3 2008G. Holesinger Abstract High critical current densities (Jc) in thick films of the Y1Ba2Cu3O7,, (YBCO, Tc , 92 K) superconductor directly depend upon the types of nanoscale defects and their densities within the films. A major challenge for developing a viable wire technology is to introduce nanoscale defect structures into the YBCO grains of the thick film suitable for flux pinning and the tailoring of the superconducting properties to specific, application-dependent, temperature and magnetic field conditions. Concurrently, the YBCO film needs to be integrated into a macroscopically defect-free conductor in which the grain-to-grain connectivity maintains levels of inter-grain Jc that are comparable to the intra-grain Jc. That is, high critical current (Ic) YBCO coated conductors must contain engineered inhomogeneities on the nanoscale, while being homogeneous on the macroscale. An analysis is presented of the advances in high-performance YBCO coated-conductors using chemical solution deposition (CSD) based on metal trifluoroacetates and the subsequent processing to nano-engineer the microstructure for tuneable superconducting wires. Multi-scale structural, chemical, and electrical investigations of the CSD film processes, thick film development, key microstructural features, and wire properties are presented. Prospects for further development of much higher Ic wires for large-scale, commercial application are discussed within the context of these recent advances. [source] First identification of an ancient Egyptian mummified human placentaINTERNATIONAL JOURNAL OF OSTEOARCHAEOLOGY, Issue 1 2005A.-M. Mekota Abstract In the course of excavations at Thebes-West, Upper Egypt, a human organ was recovered from the poorly preserved torso of a female mummy, which was archaeologically dated to the New Kingdom. In the field, the organ was tentatively identified as a liver, but without much certainty. After rehydration and fixation, histological observations led to a rejection of this diagnosis and resulted in the hypothesis that this organ could be a placenta. Comparative histology, performed on an experimentally mummified modern human placenta, revealed a close similarity of microstructural features, which strongly supports the diagnosis of the organ as a placenta. In this paper, we can therefore present the first report of an ancient Egyptian mummified human placenta and provide new insight into Egyptian funeral practices in general, and the fate of the excavated female in particular. Copyright © 2004 John Wiley & Sons, Ltd. [source] Water-Insoluble, Whey Protein- based Microspheres Prepared by an All-aqueous ProcessJOURNAL OF FOOD SCIENCE, Issue 1 2004M. ROSENBERG ABSTRACT: Calcium-alginate coated microspheres consisting of whey proteins and a model sensitive core, paprika oleoresin, were prepared using an all-aqueous process. Core-in-wall emulsions containing 20% or 25% whey protein isolate and 15% to 50% (wt/wt) core were investigated. Retention of proteins and core during the process ranged from 84.9% to 95.6% and from 91.4% to 95.7%, respectively. Results indicated that microspheres were water-insoluble and the encapsulated sensitive core was effectively protected against oxidative deterioration. This protection could be attributed to the protein-based layer adsorbed at the oil/water interface. The matrix of the microspheres exhibited microstructural features of an interactive composite-type material. Results suggested the potential suitability of the microspheres as delivery systems for controlled core release in food applications. [source] Optical microscopy of isothermally decomposed , copper based SM alloysJOURNAL OF MICROSCOPY, Issue 1 2004M. L. CASTRO Summary The usefulness of two etching procedures for revealing the microstructural features in thermal treated beta copper-based SM alloys is shown. Colour etching is used to improve the detection of the phases and achieve a higher accuracy in their identification. [source] Biaxial Flexural Strength and Microstructure Changes of Two Recycled Pressable Glass CeramicsJOURNAL OF PROSTHODONTICS, Issue 3 2004Mohammad Albakry BSc Purpose: This study evaluated the biaxial flexural strength and identified the crystalline phases and the microstructural features of pressed and repressed materials of the glass ceramics, Empress 1 and Empress 2. Materials and Methods: Twenty pressed and 20 repressed disc specimens measuring 14 mm × 1 mm per material were prepared following the manufacturers' recommendations. Biaxial flexure (piston on 3-ball method) was used to assess strength. X-ray diffraction was performed to identify the crystalline phases, and a scanning electron microscope was used to disclose microstructural features. Results: Biaxial flexural strength, for the pressed and repressed specimens, respectively, were E1 [148 (SD 18) and 149 (SD 35)] and E2 [340 (SD 40), 325 (SD 60)] MPa. There was no significant difference in strength between the pressed and the repressed groups of either material, Empress 1 and Empress 2 (p > 0.05). Weibull modulus values results were E1: (8, 4.7) and E2: (9, 5.8) for the same groups, respectively. X-ray diffraction revealed that leucite was the main crystalline phase for Empress 1 groups, and lithium disilicate for Empress 2 groups. No further peaks were observed in the X-ray diffraction patterns of either material after repressing. Dispersed leucite crystals and cracks within the leucite crystals and glass matrix were features observed in Empress 1 for pressed and repressed samples. Similar microstructure features,dense lithium disilicate crystals within a glass matrix,were observed in Empress 2 pressed and repressed materials. However, the repressed material showed larger lithium disilicate crystals than the singly pressed material. Conclusions: Second pressing had no significant effect on the biaxial flexural strength of Empress 1 or Empress 2; however, higher strength variations among the repressed samples of the materials may indicate less reliability of these materials after second pressing. [source] Polymer-Derived Ceramics: 40 Years of Research and Innovation in Advanced CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2010Paolo Colombo Preceramic polymers were proposed over 30 years ago as precursors for the fabrication of mainly Si-based advanced ceramics, generally denoted as polymer-derived ceramics (PDCs). The polymer to ceramic transformation process enabled significant technological breakthroughs in ceramic science and technology, such as the development of ceramic fibers, coatings, or ceramics stable at ultrahigh temperatures (up to 2000°C) with respect to decomposition, crystallization, phase separation, and creep. In recent years, several important advances have been achieved such as the discovery of a variety of functional properties associated with PDCs. Moreover, novel insights into their structure at the nanoscale level have contributed to the fundamental understanding of the various useful and unique features of PDCs related to their high chemical durability or high creep resistance or semiconducting behavior. From the processing point of view, preceramic polymers have been used as reactive binders to produce technical ceramics, they have been manipulated to allow for the formation of ordered pores in the meso-range, they have been tested for joining advanced ceramic components, and have been processed into bulk or macroporous components. Consequently, possible fields of applications of PDCs have been extended significantly by the recent research and development activities. Several key engineering fields suitable for application of PDCs include high-temperature-resistant materials (energy materials, automotive, aerospace, etc.), hard materials, chemical engineering (catalyst support, food- and biotechnology, etc.), or functional materials in electrical engineering as well as in micro/nanoelectronics. The science and technological development of PDCs are highly interdisciplinary, at the forefront of micro- and nanoscience and technology, with expertise provided by chemists, physicists, mineralogists, and materials scientists, and engineers. Moreover, several specialized industries have already commercialized components based on PDCs, and the production and availability of the precursors used has dramatically increased over the past few years. In this feature article, we highlight the following scientific issues related to advanced PDCs research: (1) General synthesis procedures to produce silicon-based preceramic polymers. (2) Special microstructural features of PDCs. (3) Unusual materials properties of PDCs, that are related to their unique nanosized microstructure that makes preceramic polymers of great and topical interest to researchers across a wide spectrum of disciplines. (4) Processing strategies to fabricate ceramic components from preceramic polymers. (5) Discussion and presentation of several examples of possible real-life applications that take advantage of the special characteristics of preceramic polymers. Note: In the past, a wide range of specialized international symposia have been devoted to PDCs, in particular organized by the American Ceramic Society, the European Materials Society, and the Materials Research Society. Most of the reviews available on PDCs are either not up to date or deal with only a subset of preceramic polymers and ceramics (e.g., silazanes to produce SiCN-based ceramics). Thus, this review is focused on a large number of novel data and developments, and contains materials from the literature but also from sources that are not widely available. [source] Processing Routes to Macroporous Ceramics: A ReviewJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 6 2006André R. Studart Macroporous ceramics with pore sizes from 400 nm to 4 mm and porosity within the range 20%,97% have been produced for a number of well-established and emerging applications, such as molten metal filtration, catalysis, refractory insulation, and hot gas filtration. These applications take advantage of the unique properties achieved through the incorporation of macropores into solid ceramics. In this article, we review the main processing routes that can be used for the fabrication of macroporous ceramics with tailored microstructure and chemical composition. Emphasis is given to versatile and simple approaches that allow one to control the microstructural features that ultimately determine the properties of the macroporous material. Replica, sacrificial template, and direct foaming techniques are described and compared in terms of microstructures and mechanical properties that can be achieved. Finally, directions to future investigations on the processing of macroporous ceramics are proposed. [source] Microstructure,Property Correlations in Industrial Thermal Barrier CoatingsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2004Anand A. Kulkarni This paper describes the results from multidisciplinary characterization/scattering techniques used for the quantitative characterization of industrial thermal barrier coating (TBC) systems used in advanced gas turbines. While past requirements for TBCs primarily addressed the function of insulation/life extension of the metallic components, new demands necessitate a requirement for spallation resistance/strain tolerance, i.e., prime reliance, on the part of the TBC. In an extensive effort to incorporate these TBCs, a design-of-experiment approach was undertaken to develop tailored coating properties by processing under varied conditions. Efforts focusing on achieving durable/high-performance coatings led to dense vertically cracked (DVC) TBCs, exhibiting quasi-columnar microstructures approximating electron-beam physical-vapor-deposited (EB-PVD) coatings. Quantitative representation of the microstructural features in these vastly different coatings is obtained, in terms of porosity, opening dimensions, orientation, morphologies, and pore size distribution, by means of small-angle neutron scattering (SANS) and ultra-small-angle X-ray scattering (USAXS) studies. Such comprehensive characterization, coupled with elastic modulus and thermal conductivity measurements of the coatings, help establish relationships between microstructure and properties in a systematic manner. [source] Microstructure and Mechanical Properties of Silicon Nitride Ceramics with Controlled PorosityJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 6 2002Jian-Feng Yang Porous silicon nitride ceramic with a porosity from 0,0.3 was fabricated by partial hot-pressing of a powder mixture of ,-Si3N4 and 5 wt% Yb2O3 as sintering additive. Irrespective of the porosity, the samples exhibited almost the same microstructural features including grain size, grain aspect ratio, and pore size. Porosity dependences of Young's modulus, flexural strength, and fracture toughness (KIC) were investigated. All these properties decreased with increasing porosity. However, because of the fibrous microstructure, the decreases of flexural strength and fracture toughness were moderate compared with the much greater decrease of Young's modulus. Thus, the strain tolerance (fracture strength/Young's modulus) increased with increasing porosity. The critical energy release rate also increased slightly with an increasing volume fraction of porosity to 0.166 and remained at the same level with that of the dense sample when the porosity was 0.233. They decreased as porosity increased further. [source] Enigmatic polychaete jaws from the Silurian of Gotland, SwedenLETHAIA, Issue 3 2000Mats Eriksson The jaws of the new polychaetaspid polychaete, Oenonites? honki, from the Silurian of Gotland, Sweden, differ from most Palaeozoic polychaete jaws. They exhibit enigmatic microstructural features in that they appear rough and give a corroded, or weathered impression. The altered microstructure of the jaws suggests a jaw chemistry and/or composition differing in some way from that of the co-occurring polychaete taxa. The jaws appear to have limited preservational potential and/or were particularly susceptible to secondary processes, resulting in microstructural alteration. Commonly, a row of distinct pits occurs on the outer face, especially of the first right maxillae (MIr). Because these pits are interpreted as associated with the dentary, the term ,denticle marks' is suggested. The pits may be the result of primary or secondary physical wear, or, more probably, secondary chemical alteration of localized mineral deposits. The primary function of such mineral deposits was to harden those parts of the surface that were exposed to great stress. The restricted occurrence of O.? honki, coupled with occasional increases in abundance (especially in the Halla Formation, unit b), indicates a preference for shallow marine, high-energy environments, particularly in reefal pockets with calcilutitic sediments. Highest frequency coincides with faunas characteristically containing a few labidognath species also displaying high frequencies. [source] Wear and microstructural characteristics of spray atomized zircon sand reinforced LM13 alloy.MATERIALWISSENSCHAFT UND WERKSTOFFTECHNIK, Issue 7 2010Verschleiß- und Gefügecharakteristik von sprühkompaktierter mit Zirkoniumsand verstärkter LM13 Legierung Verbundwerkstoff; Aluminiummatrix; Sprühkompaktieren; Verschleißverhalten Abstract The requirement of the high performance light weight materials demands the development of varieties of materials within the economical range to get it commercialized. Light weight aluminium alloys are used in several structural applications like automotive, aerospace, defense industry and other fields of engineering. The ceramic particle reinforced aluminium metal matrix composites (AMCs) have emerged as a suitable candidate for commercial applications. A variety of processing routes have been adopted to manufacture AMCs. In the present work LM13 alloy reinforced with zircon sand is formed via spray forming. During experimentation a self prepared convergent-divergent nozzle is used for inert gas atomization of the melt which is subsequently deposited on copper substrate placed vertically below the atomizer. The zircon sand particles are injected in the atomization zone by external injectors aligned perpendicular to the gas atomization axis. Zircon sand has been found to have new promising economical commercial candidate due to its easy availability and good mechanical properties like high hardness, high modulus of elasticity and good thermal stability. The microhardness of cast alloy and spray formed composite shows that the spray formed zircon sand reinforced composite has higher hardness. Also the lower wear rate has been observed in case of the zircon sand reinforced AMC as compared to LM13 alloy. This behaviour is further analyzed in light of microstructural features of the spray deposited composite using optical and scanning electron microscope (SEM). A comparative study of this material (LM13/Zircon sand) with the parent alloy (LM13) is presented in this work. [source] Melt processed microporous films from compatibilized immiscible blends with potential as membranesPOLYMER ENGINEERING & SCIENCE, Issue 4 2002M. Xanthos Microporous flat films with potential as membranes were produced via melt processing and post-extrusion drawing from immiscible polypropylene/polystyrene blends containing a compatibilizing copolymer. The blends were first compounded in a co-rotating twin-screw extruder and subsequently extruded through a sheet die to obtain the precursor films. These were uniaxially drawn (100%,500%) with respect to the original dimensions to induce porosity and then post-treated at elevated temperatures to stabilize the resultant structure, which consisted of uniform microcracks in the order of a few nanometers in width. The effects of blend composition and extrusion process parameters on surface and cross-sectional porosity and solvent permeability of the prepared films are presented and related to specific microstructural features of the films before and after drawing. Finite element modeling of the stretching operation in the solid state yielded a successful interpretation of the blend response to uniaxial tension that resulted in microcrack formation. Comparison of some of the novel microporous structures of this work with commercial membranes prepared by solvent-based phase inversion processes suggests comparable pore size and porosity ranges, with narrower pore size distribution. [source] | ||||||||||||||||||||||||||||