Role of carbene complexes in chain initiation and propagation of double-boot redistribution reactions

1976 ◽  
Vol 25 (5) ◽  
pp. 1053-1057 ◽  
Author(s):  
B. A. Dolgoplosk ◽  
K. L. Makovetskii ◽  
E. I. Tinyakova ◽  
T. G. Golenko ◽  
I. A. Oreshkin
Keyword(s):  
Carbene Complexes ◽  
Chain Initiation ◽  
Initiation And Propagation ◽  
Redistribution Reactions

An Study of Influence of Imperfections on the Delamination of Diamond-Like Carbon Films

2002 ◽  
Vol 719 ◽  
Author(s):  
Myoung-Woon Moon ◽  
Kyang-Ryel Lee ◽  
Jin-Won Chung ◽  
Kyu Hwan Oh
Keyword(s):  
Cross Sections ◽  
Focused Ion Beam ◽  
Imaging System ◽  
Ion Beam ◽  
Carbon Films ◽  
Diamond Like Carbon ◽  
Glass Substrates ◽  
Atomic Force ◽  
Initiation And Propagation

AbstractThe role of imperfections on the initiation and propagation of interface delaminations in compressed thin films has been analyzed using experiments with diamond-like carbon (DLC) films deposited onto glass substrates. The surface topologies and interface separations have been characterized by using the Atomic Force Microscope (AFM) and the Focused Ion Beam (FIB) imaging system. The lengths and amplitudes of numerous imperfections have been measured by AFM and the interface separations characterized on cross sections made with the FIB. Chemical analysis of several sites, performed using Auger Electron Spectroscopy (AES), has revealed the origin of the imperfections. The incidence of buckles has been correlated with the imperfection length.

Effects of diabetes on protein synthesis in fast- and slow-twitch rat skeletal muscle

1980 ◽  
Vol 239 (1) ◽  
pp. E88-E95 ◽  
Author(s):  
K. E. Flaim ◽  
M. E. Copenhaver ◽  
L. S. Jefferson
Keyword(s):  
Skeletal Muscle ◽  
Protein Synthesis ◽  
Peptide Chain ◽  
Fiber Types ◽  
Chain Initiation ◽  
Rapid Reversal ◽  
Slow Twitch ◽  
Fast Twitch

The effects of acute (2-day) and long-term (7-day) diabetes on rates of protein synthesis, peptide-chain initiation, and levels of RNA were examined in rat skeletal muscles that are known to have differing proportions of the three fiber types: fast-twitch white, fast-twitch red, and slow-twitch red. Short-term diabetes resulted in a 15% reduction in the level of RNA in all the muscles studied and an impairment in peptide-chain initiation in muscles with mixed fast-twitch fibers. In contrast, the soleus, a skeletal muscle with high proportions of slow-twitch red fibers, showed little impairment in initiation. When the muscles were perfused as a part of the hemicorpus preparation, addition of insulin to the medium caused a rapid reversal of the block in initiation in mixed fast-twitch muscles but had no effect in the soleus. The possible role of fatty acids in accounting for these differences is discussed. Long-term diabetes caused no further reduction in RNA, but resulted in the development of an additional impairment to protein synthesis that also affected the soleus and that was not corrected by perfusion with insulin. The defect resulting from long-term diabetes may involve elongation or termination reactions.

scholarly journals Di-tungsten Bis-carbene Complexes Linked by Condensed Heteroaromatic Spacers

2007 ◽  
Vol 62 (3) ◽  
pp. 419-426 ◽  
Author(s):  
Marilé Landmana ◽  
Helmar Görls ◽  
Chantelle Crause ◽  
Hubert Nienaber ◽  
Andrew Olivier ◽  
...  
Keyword(s):  
Structural Features ◽  
Crystallographic Data ◽  
Reaction Conditions ◽  
Carbene Complexes

The 2,7-dilithiated substrates of 3,6-dimethylthieno[3,2-b]thiophene, N,N′-dimethylpyrrolo[3,2- b]pyrrole and N-methylthieno[3,2-b]pyrrole were reacted with W(CO)6 to give, after subsequent alkylation with Et3OBF4, the ditungsten biscarbene complexes [(CO)5W{C(OEt)XXC(OEt)} W(CO)5] (XX = condensed heteroaromatic spacers). Sites of attack during the dilithiation of the condensed rings were studied and compared, and the yields of the desired ditungsten biscarbene complexes optimized by changing the reaction conditions according to the role of the heteroatoms in the rings. The crystallographic data of the three ditungsten biscarbene complexes are reported and their structural features compared. The methyl substituents on the condensed heteroaromatic rings play an important role in determining the molecular configurations.

scholarly journals Processes and mechanisms governing the initiation and propagation of CMEs

2008 ◽  
Vol 26 (10) ◽  
pp. 3089-3101 ◽  
Author(s):  
B. Vršnak
Keyword(s):  
Magnetic Flux ◽  
External Disturbance ◽  
Source Region ◽  
Flux Rope ◽  
Impulsive Phase ◽  
3 Dimensional ◽  
Initiation And Propagation ◽  
Region Size ◽  
The Magnetic Field

Abstract. The most important observational characteristics of coronal mass ejections (CMEs) are summarized, emphasizing those aspects which are relevant for testing physical concepts employed to explain the CME take-off and propagation. In particular, the kinematics, scalings, and the CME-flare relationship are stressed. Special attention is paid to 3-dimensional (3-D) topology of the magnetic field structures, particularly to aspects related to the concept of semi-toroidal flux-rope anchored at both ends in the dense photosphere and embedded in the coronal magnetic arcade. Observations are compared with physical principles and concepts employed in explaining the CME phenomenon, and implications are discussed. A simple flux-rope model is used to explain various stages of the eruption. The model is able to reproduce all basic observational requirements: stable equilibrium and possible oscillations around equilibrium, metastable state and possible destabilization by an external disturbance, pre-eruptive gradual-rise until loss of equilibrium, possibility of fallback events and failed eruptions, relationship between impulsiveness of the CME acceleration and the source-region size, etc. However, it is shown that the purely ideal MHD process cannot account for highest observed accelerations which can attain values up to 10 km s−2. Such accelerations can be achieved if the process of reconnection beneath the erupting flux-rope is included into the model. Essentially, the role of reconnection is in changing the magnetic flux associated with the flux-rope current and supplying "fresh" poloidal magnetic flux to the rope. These effects help sustain the electric current flowing along the flux-rope, and consequently, reinforce and prolong the CME acceleration. The model straightforwardly explains the observed synchronization of the flare impulsive phase and the CME main-acceleration stage, as well as the correlations between various CME and flare parameters.

Mechanical Behavior and Failure Mechanisms of SCS-6/Ti3Al Composites

1990 ◽  
Vol 194 ◽  
Author(s):  
S. M. Jeng ◽  
C. J. Yang ◽  
J.-M. Yang ◽  
D. G. Rosenthal ◽  
J. Goebel
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Room Temperature ◽  
Failure Mechanisms ◽  
Crack Initiation And Propagation ◽  
Al Composite ◽  
Initiation And Propagation ◽  
Bend Tests ◽  
Scanning Electron

AbstractThe mechanical properties and failure mechanisms of the SCS-6/Ti3Al composite have been studied. Both tensile and notched bend tests were conducted at room temperature on the monolithic and fiber-reinforced Ti-25Al-10Nb-3V-1Mo. Optical and scanning electron microscopy were used to study the crack initiation and propagation mechanisms. The role of the fiber, matrix and interfacial properties on the composite behavior was also assessed.

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