Statistical Model Explaining the Fine Structure and Interface Reference of Localized Excitons in Type-II GaAs/AlAs Superlattices

1998 ◽  
Vol 07 (01) ◽  
pp. 13-35 ◽  
Author(s):  
M. V. Belousov ◽  
A. Yu. Chernyshov ◽  
I. V. Ignatev ◽  
I. E. Kozin ◽  
A. V. Kavokin ◽  
...  
Keyword(s):  
Statistical Model ◽  
Energy State ◽  
Integer Number ◽  
Type Ii ◽  
Interface Quality ◽  
Alas Layer ◽  
Densities Of States ◽  
Fine Structures ◽  
Localized Excitons

Raman scattering experiments have allowed the determination of the spatial distribution of the thicknesses of GaAs and AlAs layers in a gradient GaAs/AlAs superlattice. A statistical model is developed which is consistent with all the data and ways to improve interface quality are suggested. The fine structures of XΓ and ΓΓ excitons observed in photoluminescence and differential reflection are found to be governed by the fractional parts of the average thickness of the layer (in monolayers). We conclude that each structure has two scales of fluctuations which form the relief of the AlAs surface. The largest fluctuations repeat the relief of the GaAs surface. The second scale has the size of a typical XΓ exciton Bohr radius. The smaller fluctuations disappear when the thickness of the AlAs layer is equal to an integer number of monolayers, which provide interfaces of the quality. The correlation of macro-rough fluctuations on the surface of AlAs and GaAs causes an asymmetry in the densities of states of type II excitons located at either AlAs-on-GaAs or GaAs-on-AlAs interfaces. Hence the lowest PL line is formed by excitons localized across the AlAs-on-GaAs interface. On the other hand, in structures with micro-rough but uncorrelated AlAs surfaces, the lowest energy state is expected to be occupied by excitons localized across the GaAs-on-AlAs interface.

STATISTICAL MODEL FOR DETERMINATION OF PROBABILITY OF LIGHTNING STROKES TO GROUND OBJECTS

2016 ◽  
Vol 2016 (2) ◽  
pp. 11-18 ◽  
Author(s):  
E.I. Sokol ◽  
◽  
М.М. Rezinkina ◽  
О.L. Rezinkin ◽  
O.G. Gryb ◽  
...  
Keyword(s):  
Statistical Model

Preparation of graft copolymers by the reaction of polymeric acyl chlorides with monohydroxy-terminated polymers: An introductory study

1988 ◽  
Vol 53 (8) ◽  
pp. 1735-1744 ◽  
Author(s):  
Jitka Horská ◽  
Jaroslav Stejskal ◽  
Pavel Kratochvíl ◽  
Aubrey D. Jenkins ◽  
Eugenia Tsartolia ◽  
...  
Keyword(s):  
Light Scattering ◽  
Chemical Composition ◽  
Statistical Model ◽  
Graft Copolymers ◽  
Coupling Reaction ◽  
Molecular Characteristics ◽  
Gel Formation ◽  
Acyl Chlorides ◽  
Molecular Weights

An attempt was made to prepare well-defined graft copolymers by the coupling reaction between acyl chloride groups located along the backbone chain and monohydroxy-terminated grafts prepared separately. The molecular weights and the parameters of heterogeneity in chemical composition of the products were determined by light scattering and osmometry. The determination of molecular characteristics revealed that the degree of grafting was low. The results therefore could not be confronted with a statistical model at this stage. The problems encountered in the synthesis, e.g., gel formation, and the data relating to the soluble products are discussed.

Human Umbilical Cord Mesenchymal Stem Cells Induce into Chondrocytes in 3D Cultured System

2013 ◽  
Vol 749 ◽  
pp. 198-205
Author(s):  
Li Yu ◽  
Jing Liu ◽  
Chao Xu ◽  
Er Mei Luo ◽  
Ming Qiao Tang
Keyword(s):  
Real Time ◽  
Alcian Blue ◽  
Culture System ◽  
Type Ii Collagen ◽  
Human Umbilical Cord ◽  
Type Ii ◽  
Pellet Culture ◽  
Hla Dr

Objective: To investigate a better method of inducing hUC-MSCs into chondrocytes in different culture system in vitro. Method: hUC-MSCs were isolated and cultured by tissue block culture, and the cells surface antigens were identified by flow cytometry, hUC-MSCs were cultured with chondrogenic media and stained with Alcian Blue. The production of matrix was estimated from the determination of hydroxyproline content and Alcian Blue method. Expressions of glycosaminoglycan (GAG), type II collagen and Sox-9 were assayed by real-time fluorescence quantitative PCR. Results: The cultured hUC-MSCs phenotype was CD105+/CD29+/CD44+/ CD31-/CD34-/ CD40-/CD45-/HLA-DR-. hUC-MSCs weakly expressed chondrocyte marker, which strongly expressed GAG and type II collagen after chondrogenic induction, and the cells were incubated in pellet culture with higher expression. Real-time PCR results demonstrated that chondrogenic induction cells were expressed GAG, type II collagen and Sox-9, and the cells were incubated in pellet culture with higher expression. Conclusion: hUC-MSCs incubated in pellet culture is more conducive to differentiate into chondrocytes than those cultured in monolayer culture system.

scholarly journals Determination of free L-carnitine levels in type II diabetic women with and without complications

2007 ◽  
Vol 61 (7) ◽  
pp. 892-895 ◽  
Author(s):  
A Poorabbas ◽  
F Fallah ◽  
J Bagdadchi ◽  
R Mahdavi ◽  
A Aliasgarzadeh ◽  
...  
Keyword(s):  
Type Ii

Administration of a Mixture of Fungal Glucosidases to a Patient with Type II Glycogenosis (Pompe's Disease)

PEDIATRICS ◽  
1968 ◽  
Vol 42 (4) ◽  
pp. 672-676
Author(s):  
Ronald M. Lauer ◽  
Thelma Mascarinas ◽  
Antonio S. Racela ◽  
Antoni M. Diehl ◽  
Barbara Illingworth Brown
Keyword(s):  
Skeletal Muscle ◽  
Enzyme Assay ◽  
Glycogen Content ◽  
Hydrolytic Enzymes ◽  
Type Ii ◽  
Electron Microscopic ◽  
Pompe’S Disease ◽  
Pompe's Disease ◽  
Type Ii Glycogenosis

A case of Type II glycogenosis (Pompe's disease) has been studied by histochemical, electron microscopic, and biochemical techniques. These studies have been made prior to and after the intramuscular administration for 1 week of a mixture of hydrolytic enzymes containing both α-1,4- and α-1,6-glucosidase activities. Electron photomicrographs of the liver before enzyme administration showed glycogen to be located both within and outside of membrane-limited vacuoles. No change in this distribution could be detected in tissue removed by biopsy after enzyme administration. This impression was confirmed by the determination of glycogen content which was shown to be unchanged. Nevertheless, the liver was found by enzyme assay to contain the administered enzyme. Leucocytes isolated from blood taken 4 hours after the last enzyme injection were also shown to contain the parenterally administered glucosidases. In skeletal muscle glycogen was present chiefly as extrasaccular deposits which were unchanged in appearance by enzyme administration. No glucosidase activity was demonstrable in the skeletal muscle after such a treatment. Myocardium sectioned after autopsy had major deposits of glycogen in extrasaccular areas.

Introduction to light absorption: visible and ultraviolet spectra

2000 ◽  
Author(s):  
Robert K. Poole ◽  
Uldis Kalnenieks
Keyword(s):  
Electromagnetic Radiation ◽  
Light Absorption ◽  
Energy State ◽  
Monochromatic Light ◽  
Heat Radiation ◽  
Infrared Light ◽  
Visible Radiation ◽  
Absorption Of Light ◽  
The Difference

Light is a form of electromagnetic radiation, usually a mixture of waves having different wavelengths. The wavelength of light, expressed by the symbol λ, is defined as the distance between two crests (or troughs) of a wave, measured in the direction of its progression. The unit used is the nanometre (nm, 10-9 m). Light that the human eye can sense is called visible light. Each colour that we perceive corresponds to a certain wavelength band in the 400-700 nm region. Spectrophotometry in its biochemical applications is generally concerned with the ultraviolet (UV, 185-400 nm), visible (400-700 nm) and infrared (700-15 000 nm) regions of the electromagnetic radiation spectrum, the former two being most common in laboratory practice. The wavelength of light is inversely related to its energy (E), according to the equation: . . . E = ch/ λ . . . where c denotes the speed of light, and h is Planck’s constant. UV radiation, therefore, has greater energy than the visible, and visible radiation has greater energy than the infrared. Light of certain wavelengths can be selectively absorbed by a substance according to its molecular structure. Absorption of light energy occurs when the incident photon carries energy equal to the difference in energy between two allowed states of the valency electrons, the photon promoting the transition of an electron from the lower to the higher energy state. Thus biochemical spectrophotometry may be referred to as electronic absorption spectroscopy. The excited electrons afterwards lose energy by the process of heat radiation, and return to the initial ground state. An absorption spectrum is obtained by successively changing the wavelength of monochromatic light falling on the substance, and recording the change of light absorption. Spectra are presented by plotting the wavelengths (generally nm or μm) on the abscissa and the degree of absorption (transmittance or absorbance) on the ordinate. For more information on the theory of light absorption, see Brown (1) and Chapters 2, 3 and 4. The most widespread use of UV and visible spectroscopy in biochemistry is in the quantitative determination of absorbing species (chromophores), known as spectrophotometry.

scholarly journals DETERMINATION OF CROSS SECTIONS FOR GRAVITY TYPE QUAY WALLS

2017 ◽  
pp. 5
Author(s):  
Tugce Yuksel ◽  
Yalcin Yuksel ◽  
Busra Basaran ◽  
Esin Cevik
Keyword(s):  
Cross Sections ◽  
Vertical Wall ◽  
Block Size ◽  
Seismic Loading ◽  
Block Type ◽  
Type I ◽  
Type Ii ◽  
Seismic Loadings ◽  
Port Structures

Block type quay walls are widely used as port structures in the world. In this study three types of vertical block type quay walls with different block size exposed to seismic loading were investigated experimentally. The block ratios of Type I, Type II and III vertical wall models are B/h=2, 1.5 and 1.5 & H/h=6, 6 and 3, respectively. The tests were conducted in the shaking tank with different harmonic seismic loadings and the behaviors of these walls were investigated comparatively.

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