Combined HRTEM and EFTEM Study of Precipitates in Tungsten and Chromium-Containing TiB2

1999 ◽  
Vol 589 ◽  
Author(s):  
W. Mader ◽  
B. Freitag ◽  
K. Kelm ◽  
R. Telle ◽  
C. Schmalzried
Keyword(s):  
Chemical Composition ◽  
Structural Model ◽  
Chemical Constituents ◽  
Type I ◽  
Type Ii ◽  
Resolution Limit ◽  
Energy Filtering ◽  
The Matrix ◽  
Tungsten Concentration ◽  
Elemental Maps

AbstractThe structure and chemical composition of two types of precipitates in the system TiB2-WB2-CrB2 were studied by means of high-resolution TEM and energy filtering TEM. Type I particles (W2B5 structure) are precipitated at the basal plane of the hexagonal matrix whereas type II precipitates are thin platelets lying parallel to the {1100} prism planes. Lattice imaging yields displacements of the metal positions with respect to the matrix. Information on the chemical composition at high lateral resolution is obtained from elemental maps of all chemical constituents using electron spectroscopic imaging (ESI). The type II precipitates show a decrease in the B and Ti concentration, whereas the tungsten concentration increases and the Cr is homogeneously distributed. The HRTEM results combined with the results of the elemental maps allow to develop a structural model based on the intergrowth of the β-WB structure in the TiB2-rich matrix. The two deficient boron layers in W0.5Ti0.5B with a spacing of 0.38 nm can be used to examine the resolution limit of ESI.

scholarly journals Cellular heterogeneity in cultured human chondrocytes identified by antibodies specific for alpha 2(XI) collagen chains.

1989 ◽  
Vol 109 (3) ◽  
pp. 1363-1369 ◽  
Author(s):  
B Swoboda ◽  
R Holmdahl ◽  
H Stöss ◽  
K von der Mark
Keyword(s):  
Hyaline Cartilage ◽  
Type Ii Collagen ◽  
Cross Reactivity ◽  
Cellular Heterogeneity ◽  
Human Chondrocytes ◽  
Type I ◽  
Type Ii ◽  
Human Cartilage ◽  
The Matrix ◽  
Type Xi Collagen

Collagen type XI is a component of hyaline cartilage consisting of alpha 1(XI), alpha 2(XI), and alpha 3(XI) chains; with 5-10% of the total collagen content, it is a minor but significant component next to type II collagen, but its function and precise localization in cartilaginous tissues is still unclear. Owing to the homology of the alpha 3(XI) and alpha 1(II) collagen chains, attempts to prepare specific antibodies to native type XI collagen have been unsuccessful in the past. In this study, we report on the preparation and use for immunohistochemistry of a polyclonal antibody specific for alpha 2(XI) denatured collagen chains. The antibody was prepared by immunization with the isolated alpha 2(XI) chain and reacts neither with native type XI collagen nor type I, II, V, or IX by ELISA or immunoblotting, nor with alpha 1(XI) or alpha 3(XI), but with alpha 2(XI) chains. Using this antibody, it was possible to specifically localize alpha 2(XI) in cartilage by pretreating tissue sections with 6 M urea. In double immunofluorescence staining experiments, the distribution of alpha 2(XI) as indicative for type XI collagen in fetal bovine and human cartilage was compared with that of type II collagen, using a monoclonal antibody to alpha 1(II). Type XI collagen was found throughout the matrix of hyaline cartilage. However, owing to cross-reactivity of the monoclonal anti-alpha 1(II) with alpha 3(XI), both antibodies produced the same staining pattern. Cellular heterogeneity was, however, detected in monolayer cultures of human chondrocytes.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Clinopyroxene phenocrysts from the Księginki nephelinite (SW Poland)

2015 ◽  
Vol 1 (1-2) ◽  
pp. 1-15
Author(s):  
Marcin Goleń ◽  
Jacek Puziewicz ◽  
Magdalena Matusiak-Małek ◽  
Theodoros Ntaflos
Keyword(s):  
Chemical Composition ◽  
Source Rock ◽  
Significant Influence ◽  
Fractional Crystallisation ◽  
Type I ◽  
Type Ii ◽  
Linear Variation ◽  
Type Iv ◽  
Sw Poland ◽  
Type V

Abstract The Eocene nephelinite from Księginki quarry (SW Poland) contains five types of clinopyroxene phenocrysts varying by texture and chemical composition. Type I phenocrysts are formed of Mg-rich (mg# = 0.93–0.88) homogenous cores, patchy mantle and zoned rims. Abundant type II is less magnesian (mg# = 0.65–0.88) and consists of spongy or spongy-patchy core surrounded by zoned rims, whilst in type III (mg# = 0.69–0.84), the cores are massive but patchy. The mg# of cores of type IV phenocrysts is slightly lower than that of type I (0.79–0.89), but its cores are either massive or patchy. Type V is very scarce and consist of relatively Mg-poor (mg# = 0.75–0.77) core enveloped by nonpatchy, sometimes zoned mantle and zoned outer rim. Chemical composition of type I and type IV cores suggests that they are xenocrysts introduced into the nephelinite from disintegrated peridotite and clinopyroxenitic xenoliths, respectively. Type V is also of xenocrystic nature, but its source rock was significantly more evolved than mantlederived ones. Types II and III are possibly cognates from the host nephelinite or a melt related to the nephelinite. All the types of phenocrysts suffered from disequilibrium with the nephelinitic (or proto-nephelinitic) melt or dissolution during adiabatic uplift. Linear variation in chemical composition of phenocrysts of Księginki nephelinite suggests its evolution because of fractional crystallisation, without significant influence of other differentiation processes.

Study on the behaviour of DS-Class inclusions in advanced bearing steel

2019 ◽  
Vol 116 (2) ◽  
pp. 223
Author(s):  
Huajie Wu ◽  
Qiaoqi Li ◽  
Chongyi Wei ◽  
Zhe Wang
Keyword(s):  
Reaction Time ◽  
Bearing Steel ◽  
Refining Process ◽  
Formation Mechanisms ◽  
Type I ◽  
Type Ii ◽  
The Core ◽  
Metallic Inclusions ◽  
The Matrix ◽  
Solid Phases

The source and generated mechanisms of DS-size inclusions in bearing steel were studied by sampling systematically and using ASPEX, SEM and EDS to analyse the morphology, composition and amount of non-metallic inclusions larger than 13 µm. Two kinds of typical DS-size inclusions were found in the refining process: type I is CaO-MgO-Al2O3-SiO2 distributed evenly and wrapped by CaS; type II is composite inclusion with MgO-Al2O3 as the core, CaO-Al2O3 and CaO-SiO2 as the inner layer, covered by CaS. Based on the FactSage and thermodynamic calculations, the DS inclusions formation mechanisms were drawn. There are two formation mechanisms of the type II inclusions: one is the solid phases will precipitate from the matrix of type I inclusions as the temperature drops; another is that when the reaction time is not sufficient, the MgO∙Al2O3 spinel core will not be transformed completely, and the evolution can be summarized as: Al2O3 → MgO-Al2O3 → CaO-MgO-Al2O3 → surrounded by CaO-Al2O3(SiO2) → covered by CaS.

Fibronectin-independent adhesion of fibroblasts to extracellular matrix material: partial characterization of the matrix components

1983 ◽  
Vol 63 (1) ◽  
pp. 287-301
Author(s):  
P.A. Harper ◽  
P. Brown ◽  
R.L. Juliano
Keyword(s):  
Extracellular Matrix ◽  
Matrix Material ◽  
Block Type ◽  
Type I ◽  
Type Ii ◽  
Matrix Component ◽  
Tyrosine Residues ◽  
The Matrix ◽  
Dependent Type

Fibroblasts can adhere to extracellular matrix (ECM) material by fibronectin-dependent (type I) and fibronectin-independent (type II) mechanisms. In this report we investigate the biochemical characteristics of ECM that contribute to type II adhesion. ECM capable of mediating type II adhesions is produced primarily by normal diploid fibroblasts, but not by transformed cells or epithelial cells. Treatment of fibroblast ECM under conditions that result in the removal of most of the ECM lipid or most of the ECM glycosaminoglycan does not impair type II adhesion. Likewise, treatment of the ECM with large amounts of purified collagenase does not block type II adhesion. However, treatment of ECM with low doses of trypsin or with an agent that reacts with tyrosine residues, results in complete ablation of the ability of the ECM to support type II adhesion. On the basis of these observations we suggest that the matrix component(s) mediating type II adhesion are non-collagenous proteins or glycoproteins.

scholarly journals Sequence- and structure-selective mRNA m5C methylation by NSUN6 in animals

2020 ◽  
Author(s):  
Jianheng Liu ◽  
Tao Huang ◽  
Yusen Zhang ◽  
Tianxuan Zhao ◽  
Xueni Zhao ◽  
...  
Keyword(s):  
Structure Prediction ◽  
Structural Model ◽  
Secondary Structure Prediction ◽  
Structural Features ◽  
Rna Modification ◽  
Type I ◽  
Translation Efficiency ◽  
Type Ii ◽  
Mrna Methylation ◽  
Hairpin Structures

Abstract mRNA m5C, which has recently been implicated in the regulation of mRNA mobility, metabolism, and translation, plays important regulatory roles in various biological events. Two types of m5C sites are found in mRNAs. Type I m5C sites, which contain a downstream G-rich triplet motif and are computationally predicted to locate in the 5’ end of putative hairpin structures, are methylated by NSUN2. Type II m5C sites contain a downstream UCCA motif and are computationally predicted to locate in the loops of putative hairpin structures. However, their biogenesis remains unknown. Here we identified NSUN6, a methyltransferase that is known to methylate C72 of tRNAThr and tRNACys, as an mRNA methyltransferase that targets Type II m5C sites. Combining the RNA secondary structure prediction, miCLIP, and results from a high-throughput mutagenesis analysis, we determined the RNA sequence and structural features governing the specificity of NSUN6-mediated mRNA methylation. Integrating these features into an NSUN6-RNA structural model, we identified an NSUN6 variant that largely loses tRNA methylation but retains mRNA methylation ability. Finally, we revealed a weak negative correlation between m5C methylation and translation efficiency. Our findings uncover that mRNA m5C is tightly controlled by an elaborate two-enzyme system, and the protein-RNA structure analysis strategy established may be applied to other RNA modification writers to distinguish the functions of different RNA substrates of a writer protein.

scholarly journals Sequence- and structure-selective mRNA m5C methylation by NSUN6 in animals

2020 ◽  
Author(s):  
Jianheng Liu ◽  
Tao Huang ◽  
Yusen Zhang ◽  
Tianxuan Zhao ◽  
Xueni Zhao ◽  
...  
Keyword(s):  
Structure Prediction ◽  
Structural Model ◽  
Secondary Structure Prediction ◽  
Structural Features ◽  
Rna Modification ◽  
Type I ◽  
Translation Efficiency ◽  
Type Ii ◽  
Mrna Methylation ◽  
Hairpin Structures

AbstractmRNA m5C, which has recently been implicated in the regulation of mRNA mobility, metabolism, and translation, plays important regulatory roles in various biological events. Two types of m5C sites are found in mRNAs. Type I m5C sites, which contain a downstream G-rich triplet motif and are computationally predicted to locate in the 5’ end of putative hairpin structures, are methylated by NSUN2. Type II m5C sites contain a downstream UCCA motif and are computationally predicted to locate in the loops of putative hairpin structures. However, their biogenesis remains unknown. Here we identified NSUN6, a methyltransferase that is known to methylate C72 of tRNAThr and tRNACys, as an mRNA methyltransferase that targets Type II m5C sites. Combining the RNA secondary structure prediction, miCLIP, and results from a high-throughput mutagenesis analysis, we determined the RNA sequence and structural features governing the specificity of NSUN6-mediated mRNA methylation. Integrating these features into an NSUN6-RNA structural model, we identified an NSUN6 variant that largely loses tRNA methylation but retains mRNA methylation ability. Finally, we revealed a negative correlation between m5C methylation and translation efficiency. Our findings uncover that mRNA m5C is tightly controlled by an elaborate two-enzyme system, and the protein-RNA structure analysis strategy established may be applied to other RNA modification writers to distinguish the functions of different RNA substrates of a writer protein.

scholarly journals Tourmaline as a Recorder of Ore-Forming Processes in the Xuebaoding W-Sn-Be Deposit, Sichuan Province, China: Evidence from the Chemical Composition of Tourmaline

Minerals ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 438
Author(s):  
Xinxiang Zhu ◽  
Markus B. Raschke ◽  
Yan Liu
Keyword(s):  
Chemical Composition ◽  
Aqueous Fluid ◽  
Sichuan Province ◽  
Coarse Grained ◽  
Gangue Mineral ◽  
Type I ◽  
Type Ii ◽  
Type Iii ◽  
Wide Range ◽  
Granite Type

The Xuebaoding W-Sn-Be deposit located in the Songpan-Ganze Orogenic Belt (Sichuan Province, China) is a hydrothermal deposit with less developed pegmatite stage. The deposit is famous for the coarse-grained crystals of beryl, scheelite, cassiterite, apatite, fluorite, muscovite, and others. The orebody is spatially associated with the Pankou and Pukouling granites hosted in Triassic marbles and schists. The highly fractionated granites are peraluminous, Li-Rb-Cs-rich, and related to W-Sn-Be mineralization. The mineralization can chiefly be classified based on the wallrock and mineral assemblages as muscovite and beryl in granite (Zone I), then beryl, cassiterite and muscovite at the transition from granite to triassic strata (Zone II), and the main mineralized veins composed of an assemblage of beryl, cassiterite, scheelite, fluorite, and apatite hosted in metasedimentary rock units of marble and schist (Zone III). Due to the stability of tourmaline over a wide range of temperature and pressure conditions, its compositional variability can reflect the evolution of the ore-forming fluids. Tourmaline is an important gangue mineral in the Xuebaoding deposit and occurs in the late-magmatic to early-hydrothermal stage, and can thus be used as a proxy for the fluid evolution. Three types of tourmalines can be distinguished: tourmaline disseminations within the granite (type I), tourmaline clusters at the margin of the granite (type II), and tourmalines occurring in the mineralized veins (type III). Based on their chemical composition, both type I and II tourmalines belong to the alkali group and to the dravite-schorl solid solution. Type III tourmaline which is higher in X-site vacancy corresponds to foitite and schorl. It is proposed that the weakly zoned type I tourmalines result from an immiscible boron-rich aqueous fluid in the latest stage of granite crystallization, that the type II tourmalines showing skeletal texture directly formed from the undercooled melts, and that type III tourmalines occurring in the mineralized veins formed directly from the magmatic hydrothermal fluids. Both type I and type II tourmalines show similar compositional variations reflecting the highly fractionated Pankou and Pukouling granites. The higher Ca, Mg, and Fe contents of type III tourmaline are buffered by the composition of the metasedimentary host rocks. The decreasing Na content (<0.8 atoms per formula unit (apfu)) and increasing Fe3+/Fe2+ ratios of all tourmaline samples suggest that they precipitated from oxidized, low-salinity fluids. The decreasing trend of Al content from type I (5.60–6.36 apfu) and type II (6.01–6.43 apfu) to type III (5.58–5.87 apfu) tourmalines, and associated decrease in Na, may be caused by the crystallization of albite and muscovite. The combined petrographic, mineralogical, and chemical characteristics of the three types of tourmalines thus reflect the late-magmatic to early-hydrothermal evolution of the ore-forming fluids, and could be used as a geochemical fingerprint for prospecting W-Sn-Be mineralization in the Xuebaoding district.

scholarly journals The Helium Abundance in the Envelopes of the Bluest RR Lyrae Stars in Globular Clusters and Dependence of Globular Cluster Variable Star Properties on Chemical Composition

1973 ◽  
Vol 21 ◽  
pp. 229-234
Author(s):  
A. V. Mironov
Keyword(s):  
Chemical Composition ◽  
Globular Clusters ◽  
Variable Star ◽  
Variable Stars ◽  
Type I ◽  
Helium Abundance ◽  
Type Ii ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Lyrae Stars

AbstractThe helium abundance Y in the envelopes of RR Lyrae stars in globular clusters has been estimated. The values of Y range from 0.07 to 0.59. The properties of variable stars in globular clusters of two types distinguished by a type of dependence of the horizontal branch form on the chemical composition are compared. The clusters of type I are shown to be on the average poorer in RR Lyrae stars than those of type II. The RR Lyrae stars in type I clusters are on the average brighter by 0.1 mag. It is found that as Y increases, the cluster richness in W Virginis variables decreases.

X-ray Bragg reflexion, ‘spike’ reflexion and ultra-violet absorption topography of diamonds

1964 ◽  
Vol 281 (1386) ◽  
pp. 310-322 ◽  
Keyword(s):  
Ultra Violet ◽  
Perfect Crystal ◽  
Type I ◽  
Type Ii ◽  
High Definition ◽  
Characteristic Type ◽  
X Ray ◽  
The Matrix ◽  
Definition Of ◽  
Subsequent Diffusion

The relation between X-ray diffracting properties and ultra-violet absorption has been studied point by point on polished plates of diamond having thicknesses from 0-1 mm to more than 1 mm and edge lengths from 2 mm to more than 1 cm. Most specimens exhibit marked non-uniformity of ultra-violet absorption. The intensity of the ‘spike’ X-ray reflexions was found to be roughly proportional to ultra-violet absorption, point by point, a t least in the range of weak and moderate spike intensities. Hence it is concluded that the platelets responsible for the ‘spikes’ are also responsible for the characteristic type I absorptions. However, high values of spike intensity and ultra-violet absorption have only been observed in relatively perfect crystal regions with a low density of grown-in dislocations as determined by X-ray topography; and it is suggested that in imperfect regions containing many grown-in dislocations impurity precipitation in the form of platelets coherent with the matrix may have been inhibited or pre-empted by precipitation in some other way. Thus the absence of ‘ spikes ’ and characteristic type I absorptions may not necessarily imply absence of impurity. On the other hand, some regions of high ultra-violet transparency can be highly perfect; hence lattice imperfection is not necessarily associated with type II optical characteristics. A comparison of ‘spike’ intensity in equivalent cube directions, made on a specimen selected for the high definition of its ‘spike’ topograph features, showed that where platelet precipitation was present it had occurred equally on all cube planes. The sharpness of boundaries between regions of high and low ultra-violet absorption and the association of such boundaries with growth stratifications revealed by Bragg reflexion topographs suggest that they correspond to variations of concentration of grown-in impurity in the crystal, no detectable subsequent diffusion having taken place.

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