scholarly journals Asymptotics for Rayleigh--Bloch Waves along Lattice Line Defects

2013 ◽  
Vol 11 (3) ◽  
pp. 871-889 ◽  
Author(s):  
L. M. Joseph ◽  
R. V. Craster
Keyword(s):  
Lattice Line ◽  
Bloch Waves ◽  
Line Defects

Application of Modified Bloch Waves to Image Analysis of Extended Linear Defects

1974 ◽  
Vol 32 ◽  
pp. 402-403
Author(s):  
S. Nakahara ◽  
D. M. Maher
Keyword(s):  
Image Analysis ◽  
Computational Approach ◽  
Dislocation Loops ◽  
Plane Wave Expansion ◽  
Dynamical Equations ◽  
Bloch Waves ◽  
Linear Defects ◽  
Imperfect Crystal ◽  
Localized Defects ◽  
Defective Crystals

Since Head first demonstrated the advantages of computer displayed theoretical intensities from defective crystals, computer display techniques have become important in image analysis. However the computational methods employed resort largely to numerical integration of the dynamical equations of electron diffraction. As a consequence, the interpretation of the results in terms of the defect displacement field and diffracting variables is difficult to follow in detail. In contrast to this type of computational approach which is based on a plane-wave expansion of the excited waves within the crystal (i.e. Darwin representation ), Wilkens assumed scattering of modified Bloch waves by an imperfect crystal. For localized defects, the wave amplitudes can be described analytically and this formulation has been used successfully to predict the black-white symmetry of images arising from small dislocation loops.

Defects in Crystals

1968 ◽  
Vol 26 ◽  
pp. 244-245
Author(s):  
Kenneth R. Lawless
Keyword(s):  
Electron Microscope ◽  
Point Defects ◽  
Surface Defects ◽  
Chemical Properties ◽  
Material Point ◽  
Crystal Defects ◽  
Defects In Crystals ◽  
Irradiation Effects ◽  
Normal Lattice ◽  
Line Defects

One of the most important applications of the electron microscope in recent years has been to the observation of defects in crystals. Replica techniques have been widely utilized for many years for the observation of surface defects, but more recently the most striking use of the electron microscope has been for the direct observation of internal defects in crystals, utilizing the transmission of electrons through thin samples.Defects in crystals may be classified basically as point defects, line defects, and planar defects, all of which play an important role in determining the physical or chemical properties of a material. Point defects are of two types, either vacancies where individual atoms are missing from lattice sites, or interstitials where an atom is situated in between normal lattice sites. The so-called point defects most commonly observed are actually aggregates of either vacancies or interstitials. Details of crystal defects of this type are considered in the special session on “Irradiation Effects in Materials” and will not be considered in detail in this session.

Guided and standing Bloch waves in periodic elastic strips

2009 ◽  
Vol 19 (2) ◽  
pp. 321-346 ◽  
Author(s):  
Samuel D.M. Adams ◽  
Richard V. Craster ◽  
Sebastien Guenneau
Keyword(s):  
Bloch Waves

scholarly journals Line defects in the 3d Ising model

2013 ◽  
Vol 2013 (7) ◽  
Author(s):  
M. Billó ◽  
M. Caselle ◽  
D. Gaiotto ◽  
F. Gliozzi ◽  
M. Meineri ◽  
...  
Keyword(s):  
Ising Model ◽  
Line Defects ◽  
3D Ising Model

scholarly journals Friction Stir Welding of AA2024-T3 plate – the influence of different pin types

2015 ◽  
Vol 6 (1) ◽  
pp. 51-55 ◽  
Author(s):  
D. Trimble ◽  
H. Mitrogiannopoulos ◽  
G. E. O'Donnell ◽  
S. McFadden
Keyword(s):  
Friction Stir Welding ◽  
Parent Material ◽  
Micro Hardness ◽  
Workpiece Material ◽  
Friction Stir ◽  
Hardness Tests ◽  
Weld Profile ◽  
Unaffected Parent ◽  
Line Defects ◽  
Tool Pin

Abstract. Some aluminium alloys are difficult to join using traditional fusion (melting and solidification) welding techniques. Friction Stir Welding (FSW) is a solid-state welding technique that can join two plates of material without melting the workpiece material. This proecess uses a rotating tool to create the joint and it can be applied to alumium alloys in particular. Macrostructure, microstructure and micro hardness of friction stir welded AA2024-T3 joints were studied. The influence of tool pin profile on the microstructure and hardness of these joints was examined. Square, triflute and tapered cylinder pins were used and results from each weldment are reported. Vickers micro hardness tests and grain size measurements were taken from the transverse plane of welded samples. Distinct zones in the macrostructure were evident. The zones were identified by transitions in the microstructure and hardness of weld samples. The zones identified across the sample were the the unaffected parent metal, the Heat Affected Zone (HAZ), the Thermo-Mechanicaly Affected Zone (TMAZ), and the Nugget Zone (NZ). Measured hardness values varied through each FSW zone. The hardness in each zone was below that of the parent material. The HAZ had the lowest hardness across the weld profile for each pin type tested. The cylindrical pin consistently produced tunnel and joint-line defects. Pin profiles with flat surface features and/or flutes produced consolidated joints with no defects.

Line defects guided molecular patterning on graphene

2014 ◽  
Vol 104 (9) ◽  
pp. 093102 ◽  
Author(s):  
Yinjun Huang ◽  
Shuze Zhu ◽  
Teng Li
Keyword(s):  
Molecular Patterning ◽  
Line Defects

Traps in Si-doped AlxGa1-xN Grown by Molecular Beam Epitaxy on Sapphire Characterized by Deep Level Transient Spectroscopy

2006 ◽  
Vol 955 ◽  
Author(s):  
Mo Ahoujja ◽  
S Elhamri ◽  
M Hogsed ◽  
Y. K. Yeo ◽  
R. L. Hengehold
Keyword(s):  
Molecular Beam Epitaxy ◽  
Deep Level Transient Spectroscopy ◽  
Molecular Beam ◽  
Deep Level ◽  
Unknown Origin ◽  
Shallow Donor ◽  
Related Point ◽  
Line Defects ◽  
Si Doped ◽  
Transient Spectroscopy

ABSTRACTDeep levels in Si doped AlxGa1−xN samples, with Al mole fraction in the range of x = 0 to 0.30, grown by radio-frequency plasma activated molecular beam epitaxy on sapphire substrates were characterized by deep level transient spectroscopy (DLTS). DLTS measurements show two significant electron traps, P1 and P2, in AlGaN at all aluminum mole fractions. The electron trap, P2, appears to be a superposition of traps A and B , both of which are observed in GaN grown by various growth techniques and are thought to be related to VGa-shallow donor complexes. Trap P1 is related to line defects and N-related point defects. Both of these traps are distributed throughout the bulk of the epitaxial layer. An additional trap P0 which was observed in Al0.20Ga0.80N and Al0.30Ga0.70N is of unknown origin, but like P1 and P2, it exhibits dislocation-related capture kinetics. The activation energy measured from the conduction band of the defects is found to increase with Al mole content, a behavior consistent with other III-V semiconductors.

scholarly journals RecQ helicases: suppressors of tumorigenesis and premature aging

2003 ◽  
Vol 374 (3) ◽  
pp. 577-606 ◽  
Author(s):  
Csanád Z. BACHRATI ◽  
Ian D. HICKSON
Keyword(s):  
Replication Fork ◽  
Germ Line ◽  
Genetic Disorders ◽  
Premature Aging ◽  
Recq Helicase ◽  
Dna Helicases ◽  
Recq Helicases ◽  
Protein Partners ◽  
Line Defects ◽  
Rothmund Thomson Syndrome

The RecQ helicases represent a subfamily of DNA helicases that are highly conserved in evolution. Loss of RecQ helicase function leads to a breakdown in the maintenance of genome integrity, in particular hyper-recombination. Germ-line defects in three of the five known human RecQ helicases give rise to defined genetic disorders associated with cancer predisposition and/or premature aging. These are Bloom's syndrome, Werner's syndrome and Rothmund–Thomson syndrome, which are caused by defects in the genes BLM, WRN and RECQ4 respectively. Here we review the properties of RecQ helicases in organisms from bacteria to humans, with an emphasis on the biochemical functions of these enzymes and the range of protein partners that they operate with. We will discuss models in which RecQ helicases are required to protect against replication fork demise, either through prevention of fork breakdown or restoration of productive DNA synthesis.

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