Search results for "Electron microscope"
showing 10 items of 784 documents
Ergastoplasmic paracrystalline inclusion bodies in the adipose gonadal envelope and fat body of the glow worm, Lampyris noctiluca (Insecta, Coleopter…
2001
Abstract The gonads of glow worm larvae are enveloped by adipose tissue which represents a specialized fat body. The adipose gonadal envelope, and also to a lesser extent the fat body cells, contain tubular paracrystalline inclusion bodies (PIBs). Cells of other tissues are devoid of such inclusions. The PIBs form in the cisternae of rough ER. In young larvae PIB formation is sparse, but at advanced larval stages PIBs often occur as bundles in stacks of ergastoplasm. Typically, a PIB within a cisterna consists of four to seven parallel tubules. The outer diameter of a tubule is ca 28.8 nm and the width of the tubule lumen ca 12.2 nm. The “wall” of a tubule contains globular protein subunits…
Vapor phase epitaxy of Hg1−xCdxI2 on sapphire
1998
Abstract We demonstrate the possibility of growing Hg 1− x Cd x I 2 layers on sapphire substrates by vapor-phase epitaxy (VPE). The successful growth has been carried out using an α-HgI 2 polycrystalline source and a CdTe buffer layer grown on sapphire by metalorganic vapor phase epitaxy (MOVPE) before the Hg 1− x Cd x I 2 VPE growth. The Hg 1− x Cd x I 2 /sapphire 20–40 μm thick layers with a uniform composition in the range of x =0.2–0.6 were grown at 220–250°C for 70–300 h. The layers were studied by scanning electron microscopy, energy disperse X-ray analysis and X-ray diffractometry. Results on the layer characterization are reported and the effect of VPE conditions on the layer proper…
Structural characterization of CdTe layers grown on (0001) sapphire by MOCVD
2004
Abstract We report on the growth of CdTe layers directly onto (0 0 0 1) sapphire substrates by MOCVD. The structure and morphology of the layers have been investigated as a function of growth temperature and II/VI precursor molar ratio by X-ray diffraction and scanning electron microscopy. The texture of the samples has revealed the existence of a temperature threshold, with higher growth temperatures resulting on completely (1 1 1) oriented layers. Some of these layers contained microtwins, as indicated by the extra peaks in the {4 2 2} Φ scans, leading to the existence of two different domains. The structural quality of each domain, as well as of the sample as a whole, has been determined…
From nitrides to carbides: topotactic synthesis of the η-carbides Fe3Mo3C and Co3Mo3C
2004
The molybdenum bimetallic interstitial carbides Fe(3)Mo(3)C and Co(3)Mo(3)C have been synthesized by temperature-programmed reaction (TPR) between the molybdenum bimetallic interstitial nitrides Fe(3)Mo(3)N and Co(3)Mo(3)N and a flowing mixture of CH(4) and H(2) diluted in Ar. These compounds have been characterized by X-ray diffraction, laser Raman spectroscopy, elemental analysis, energy dispersive analysis of X rays, thermal analysis (in air) and scanning electron microscopy (field emission). Their structures have been refined from X-ray powder diffraction data. These carbides crystallize in the cubic system, space group Fd3m[a= 11.11376(6) and 11.0697(3)[Angstrom] for Fe and Co compound…
Selective area vapor-phase epitaxy and structural properties of Hg1 − xCdxTe on sapphire
1997
Selective area (SA) Hg1 − xCdxTesapphire layers have been grown using the recently developed technique of the vapor-phase epitaxy (VPE) of Hg1 − xCdxTe layers on CdTesapphire heteroepitaxial substrates (HS), which we have called “VPE on HS technique” (Sochinskii et al., J. Crystal Growth 149 (1995) 35; 161 (1996) 195). First, planar CdTe (1 1 1) 5–7 μm thick layers were grown on sapphire (0 0 0 1) wafers by metalorganic vapor-phase epitaxy (MOVPE) at 340°C for 1–2.5 h using dimethylcadmium and di-isopropyltellurium as precursors. Second, CdTe/sapphire mesas were formed using standard photolithography in the form of alternating parallel linear arrays consisting of 500 × 70 μm2 elements. Thir…
Monitoring the carburization of molybdenum bimetallic nitrides and oxynitrides with CH4/H2/Ar mixtures: identification of a new carbonitride.
2008
A new carbonitride Ni2Mo3(CxNy) has been synthesized by temperature-programmed carburization of the Ni2Mo3N precursor with a CH4/H2/Ar gas mixture at 923 K. This compound has been characterized by X-ray diffraction, elemental analysis, Auger electron spectroscopy, laser Raman spectroscopy, thermogravimetric analysis and field-emission scanning electron microscopy. Ni2Mo3(CxNy) crystallizes in the cubic space group P4(1)32, with a lattice parameter of a=6.64575(3) A, corresponding to the unusual filled beta-Mn structure. Its formation occurs by partial substitution of N by C via a topotactic and pseudomorphic reaction and its stability in air is higher that of Ni2Mo3N. A two-phase mixture wi…
Morphology evolution in mesoporous titania block copolymer composite films with increasing Sol-Gel reaction time
2013
A morphology evolution of thin films of titania from spherical mesopores to worm-shaped mesopores was realized by simply varying the sol–gel reaction time from 46 min to 25 h in the quadruple system consisting of polystyrene–block-poly(ethylene oxide) (PS–b-PEO), 1,4-dioxane, concentrated HCl, and titanium tetraisopropoxide (TTIP). Imaging techniques including scanning electron microscopy (SEM) and atomic force microscopy (AFM) were applied to investigate the local structure change of the as-prepared, calcined, and UV-degraded composite films. Grazing incidence small angle X-ray scattering (GISAXS) experiments prove that the structure change in local areas is representative of that over the…
Wear rates and wear mechanisms of alumina-based tools cutting steel at a low cutting speed
1997
Abstract Three ceramic insert materials, zirconia-toughened alumina (Al 2 O 3 –7vol%ZrO 2 ), mixed-based alumina (Al 2 O 3 –TiN–TiC–ZrO 2 ) and alumina reinforced with SiC whiskers (Al 2 O 3 –SiC w ), were used to cut AISI 1040 steel at 3.9 m s −1 . In addition, a traditional grade P10 insert (WC–TiC–Co) was tested. The lifetimes, according to KT/KM and VB B criteria, were determined using a profilometer and by image processing. The worn zones were observed with scanning electron microscopy techniques. Adhesion and plastic deformation were dominant wear mechanisms in zirconia-toughened alumina, mixed-based alumina and sintered carbide P10, both in the craters and in the cutting edges. As we…
Design characteristics, primary stability and risk of fracture of orthodontic mini-implants: Pilot scan electron microscope and mechanical studies
2013
Objectives: Orthodontic mini-implants (OMIs) are increasingly used in orthodontics but can fail for various reasons. This study investigates the effects of OMI design characteristics on the mechanical properties in artificial bone. Material and Methods: Twelve self-drilling OMIs (2 small, 6 medium, 4 large) from 8 manufacturers were tested for their primary stability in simulated medium-high cancellous bone and the risk to fracture in high-density methacrylate blocks. For the assessments of the maximum insertion torque (IT) and torsional fracture (TF) 5 of each OMI were used and for the pull-out strength (POS) 10. The OMIs were inserted with a torque screwdriver (12 sec/360°) until the bott…
A novel magnetic Preyssler acid grafted chitosan nano adsorbent: synthesis, characterization and adsorption activity
2015
BACKGROUND This study concerns the application of magnetic heteropolyacids composite for the adsorption of organic compounds from aqueous solutions. A novel magnetic Preyssler/chitosan/Fe3O4 nanoparticles composite (PCNF) adsorbent was designed using a one-pot synthesis method and characterized by multiple techniques including X-ray powder diffraction (XRD), infrared spectroscopy (FT-IR), N2 adsorption–desorption isotherms and scanning electron microscopy (SEM). RESULTS The adsorption activity of PCNF was evaluated by the removal of methyl orange (as an anionic azo dye model, MO) from aqueous solution and all the factors influencing the removal efficiency, such as adsorbent dosage, initial …