scholarly journals Endothelium-derived hyperpolarizing factor in preeclampsia: heterogeneous contribution, mechanisms, and morphological prerequisites

2008 ◽  
Vol 294 (2) ◽  
pp. R510-R519 ◽  
Author(s):  
Leanid Luksha ◽  
Henry Nisell ◽  
Natallia Luksha ◽  
Marius Kublickas ◽  
Kjell Hultenby ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Subcutaneous Fat ◽  
Normal Pregnancy ◽  
Transmission Electron ◽  
Main Pathway ◽  
Before And After ◽  
Group 2 ◽  
Cytochrome P 450 ◽  
Group 1

We hypothesized that in preeclampsia (PE), contribution of endothelium-derived hyperpolarizing factor (EDHF) and the mechanism/s of its action differ from that in normal pregnancy (NP). We aimed to assess endothelial function and morphology in arteries from NP and PE with particular focus on EDHF. Arteries (≈200 μm) were dissected from subcutaneous fat biopsies obtained from women undergoing cesarean section. With the use of wire myography, responses to the endothelium-dependent agonist bradykinin (BK) were determined before and after inhibition of pathways relevant to EDHF activity. The overall responses to BK in arteries from PE ( n = 13) and NP ( n = 17) were similar. However, in PE, EDHF-mediated relaxation was reduced ( P < 0.05). All women within the PE group were divided into two subgroups: with more ( group 1) or less ( group 2) than 50% reduction of EDHF-typed responses after 18-α-glycyrrhetinic acid (an inhibitor of myoendothelial gap junctions, MEGJs). The division showed that 1) MEGJs are principally involved when the EDHF contribution is reduced; and 2) when the EDHF contribution is similar to that in NP, the H2O2 and/or cytochrome P-450 epoxygenase products of arachidonic acid (AA), along with MEGJs, confer EDHF-mediated relaxation. In contrast, MEGJs were the main pathway for EDHF in NP. The abundant presence of MEGJs in arteries from NP but deficiency of them in PE was observed using transmission electron microscopy. We conclude that PE is associated with heterogeneous contribution of EDHF, and the mechanism behind EDHF-typed responses is mediated either by MEGJs alone or in combination with H2O2 or cytochrome P-450 epoxygenase metabolites of AA.

Microstructure Origin for Thermal Fatigue of TiNi Films

2001 ◽  
Vol 672 ◽  
Author(s):  
Shulin Wen ◽  
Jibao He
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Thermal Fatigue ◽  
Microstructure Change ◽  
Fatigue Specimen ◽  
Niti Sma ◽  
Transmission Electron ◽  
Alloy Material ◽  
Before And After ◽  
20 Nm

ABSTRACTIn order to improve the performance and prolong the life of shape memory alloy material (SMA), it is very important to trace and study the microstructure change on the fatigue of SMA. The microstructure features between the samples before and after thermal fatigue (about 100,000 thermal cycles) of the NiTi-SMA films were examined and compared with each other by transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS). It was found that there is no difference of microstructures between the two kinds of samples except some precipitates appeared in the fatigue specimen. These precipitates which may be identified as TiNi3 phase with a grain size of 10-20 nm may impede transformation from martensite to austenite which works as mechanism of SMA during thermal fatigue. Therefore, these precipitates result in the serious decay on SMA performance and further fracture of the SMA material.

The Relationship Between Pit Membrane Ultrastructure and Chemical Impregnability of Wood

Holzforschung ◽  
1999 ◽  
Vol 53 (4) ◽  
pp. 341-346 ◽  
Author(s):  
Adya Singh ◽  
Bernard Dawson ◽  
Robert Franich ◽  
Faye Cowan ◽  
Jeremy Warnes
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Light Microscopy ◽  
Cell Types ◽  
Transmission Electron ◽  
Pit Membrane ◽  
Before And After ◽  
Ray Cells ◽  
Membrane Ultrastructure ◽  
The Relationship

Summary The woods of Alder and Eucalypt were examined by light microscopy before and after a chemical treatment by the Indurite process to increase the hardness of the wood. The pattern of wood cell impregnation for Alder differed significantly from Eucalypt in some respects. In Alder wood all cell types eg. vessels, fibres and rays, were impregnated in similar proportions. In comparison, in Eucalypt wood the impregnation material was largely confined to ray cells and the lumina of vessels; other cell types were either not impregnated or impregnated in very small numbers. Transmission electron microscopy of Alder and Eucalypt woods suggests that ultrastructural differences in the texture and porosity of pit membranes may be the main reason for the observed differences between these wood species with regard to their impregnability by the impregnation material used.

Structure of Al-Hf Films

1976 ◽  
Vol 34 ◽  
pp. 634-635
Author(s):  
P. J. Smith ◽  
J. K. Howard ◽  
W. K. Chu ◽  
R. F. Lever
Keyword(s):  
Electron Microscopy ◽  
Thin Films ◽  
Transmission Electron Microscopy ◽  
Silicon Wafer ◽  
Layer Structure ◽  
Nitrogen Atmosphere ◽  
Aluminum Layer ◽  
Transmission Electron ◽  
Before And After

The structure of Al-Hf thin films, before and after annealing, has been studied by transmission electron microscopy. A 7000-Å layer of aluminum was evaporated, at a pressure of 5 x 10-7 Torr, onto a silicon wafer that had 5000 Å of thermal SiO2 on top. Onto the aluminum layer, with no break in the vacuum, a 1700-Å. layer of hafnium and then a 1000-Å layer of aluminum were deposited. The resulting three-layer structure was used to determine how different atomic ratios of Al and Hf influence the phases formed.After 4 hr of annealing at 400 C in a dry nitrogen atmosphere, the upper part of the film was found to be composed of grains of Al3Hf (ZrAl3-type), about 700 Å in diameter (Fig. 1). The reaction appeared to be complete in the upper layer; none of the relatively large Al grains, 2000 Å in diameter, that had been present in the as-deposited sample were found.

scholarly journals Correlation between Taylor Model Prediction and Transmission Electron Microscopy-Based Microstructural Investigations of Quasi-In Situ Tensile Deformation of Additively Manufactured FeCo Alloy

2021 ◽  
Author(s):  
Sudipta Pramanik ◽  
Lennart Tasche ◽  
Kay-Peter Hoyer ◽  
Mirko Schaper
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Tensile Test ◽  
Deformation Behavior ◽  
Dislocation Cell ◽  
Taylor Model ◽  
Feco Alloy ◽  
Transmission Electron ◽  
Before And After ◽  
Active Slip

AbstractWithin this research, the multiscale microstructural evolution before and after the tensile test of a FeCo alloy is addressed. X-ray µ-computer tomography (CT), electron backscattered diffraction (EBSD), and transmission electron microscopy (TEM) are employed to determine the microstructure on different length scales. Microstructural evolution is studied by performing EBSD of the same area before and after the tensile test. As a result, $$\langle$$ ⟨ 001$$\rangle$$ ⟩ ||TD, $$\langle$$ ⟨ 011$$\rangle$$ ⟩ ||TD are hard orientations and $$\langle$$ ⟨ 111$$\rangle$$ ⟩ ||TD is soft orientations for deformation accommodation. It is not possible to predict the deformation of a single grain with the Taylor model. However, the Taylor model accurately predicts the orientation of all grains after deformation. {123}$$\langle$$ ⟨ 111$$\rangle$$ ⟩ is the most active slip system, and {112}$$\langle$$ ⟨ 111$$\rangle$$ ⟩ is the least active slip system. Both EBSD micrographs show grain subdivision after tensile testing. TEM images show the formation of dislocation cells. Correlative HRTEM images show unresolved lattice fringes at dislocation cell boundaries, whereas resolved lattice fringes are observed at dislocation cell interior. Since Schmid’s law is unable to predict the deformation behavior of grains, the boundary slip transmission accurately predicts the grain deformation behavior.

Transmission Electron Microscopy (TEM) Studies of Ge Nanocrystals

2004 ◽  
Vol 818 ◽  
Author(s):  
Q. Xu ◽  
I.D. Sharp ◽  
C.Y. Liao ◽  
D. O. Yi ◽  
J.W. Ager ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Ion Beam ◽  
Carbon Films ◽  
Ultrasonic Dispersion ◽  
Transmission Electron ◽  
Before And After ◽  
The Matrix ◽  
A Charge ◽  
Ge Nanocrystals

Abstract74Ge nanocrystals were formed by ion beam synthesis in SiO2. Transmission Electron Microscopy was used to characterize the structure and properties of these Ge nanocrystals before and after liberation from the matrix. The liberation from the SiO2matrix was achieved through selective etching in a HF bath. High-resolution micrographs and selective area diffraction confirm that the crystallinity is retained in this process. Transfer of released nanocrystals is achieved through ultrasonic dispersion in methanol and deposition onto lacey carbon films via evaporation of methanol. In an effort to determine the melting point of Ge nanocrystals and observe the growth and evolution of nanocrystals embedded in the amorphous SiO2during heat treatment, as-grown nanocrystals were heatedin-situup to 1192°C±60°C in a JEOL 200CX analytical electron microscope. Electron diffraction patterns are recorded using a Charge-Coupled Device. A large melting hysteresis was observed around the melting temperature of bulk Ge.

Enhanced Strength and Ductility at a Cryogenic Temperature in a Nanostructured Ni-Fe Alloy

2007 ◽  
Vol 539-543 ◽  
pp. 2828-2833
Author(s):  
Hong Qi Li ◽  
Kai Xiang Tao ◽  
Hahn Choo ◽  
Peter K. Liaw
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Cryogenic Temperature ◽  
Room Temperature ◽  
Liquid Nitrogen Temperature ◽  
Compressive Behavior ◽  
Grain Sizes ◽  
Transmission Electron ◽  
Before And After ◽  
Strength And Ductility

The compressive behavior was investigated on an electrodeposited nanocrystalline Ni-20%Fe alloy with a grain size of about 22 nm at room temperature (RT), 298 K, and the liquid nitrogen temperature (LN2T), 77 K. The sensitivity of the yield strength and plastic strain to the test temperature at different grain sizes was discussed. Moreover, through the Transmission Electron Microscopy (TEM) examination and microhardness measurement, the microstructures before and after the compression test at RT and LN2T were studied.

Microstructural Characterization of Epitaxial Cubic Silicon Carbide Using Transmission Electron Microscopy

2010 ◽  
Vol 645-648 ◽  
pp. 379-382
Author(s):  
Bralee Chayasombat ◽  
Y. Kimata ◽  
T. Kato ◽  
Tomoharu Tokunaga ◽  
Katsuhiro Sasaki ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Silicon Carbide ◽  
Ion Implantation ◽  
Microstructural Characterization ◽  
Transmission Electron ◽  
Before And After ◽  
Bulge Region ◽  
Cubic Silicon Carbide

Microstructures of switch-back epitaxy cubic silicon carbide (3C-SiC) before and after Al ion implantation were investigated by transmission electron microscopy (TEM). Stacking faults aligned along the {111} were observed in 3C-SiC. A surface bulge was observed in some regions and planar defects were observed under the bulge region. After ion implantation of 3C-SiC, defects were observed to be distributed up to a depth approximately 500 nm from the surface.

scholarly journals Synthesis of Chromium Carbide Nanopowders by Microwave Heating and Their Composition and Microstructure Change under Gamma Ray Irradiation

Molecules ◽  
2018 ◽  
Vol 24 (1) ◽  
pp. 16 ◽  
Author(s):  
Kai Jin ◽  
Yuanbo Jia ◽  
Zhiwei Zhao ◽  
Weiqiang Song ◽  
Shun Wang ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Microwave Heating ◽  
Chromium Carbide ◽  
Photoelectron Spectroscopy ◽  
Gamma Ray ◽  
X Ray ◽  
Transmission Electron ◽  
Before And After ◽  
Gamma Ray Irradiation

Chromium carbide nanopowders were synthesized by mechanical alloying-assisted microwave heating. The effect of gamma irradiation on phase composition and microstructure of chromium carbide nanopowders synthesized by the microwave heating method was analyzed. The samples were characterized by X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM) techniques. The results showed that well-dispersed chromium carbide nanopowders can be synthesized by maintaining the temperature at 1000 °C for 1 h. Gamma ray irradiation had an important effect on the microstructure of chromium carbide nanopowders. The interplanar spacings of chromium carbide (110) crystal faces before and after gamma ray irradiation were 0.3725 nm and 0.3824 nm, respectively. The crystal structure of chromium carbide was changed by gamma ray irradiation. Gamma ray irradiation can also increase the binding energy of chromium carbide, which is beneficial to improve the thermal stability and mechanical properties of chromium carbide at high temperature.

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