scholarly journals Vitesse de croissance et renouvellement des dents chez les Amphibiens

Development ◽  
1977 ◽  
Vol 42 (1) ◽  
pp. 43-63
Author(s):  
Par Pierre Chibon
Keyword(s):  
Growth Rate ◽  
Golgi Apparatus ◽  
Life Time ◽  
Young Larva ◽  
Tooth Replacement ◽  
Hatching Time ◽  
Functional Tooth ◽  
Organic Matrices ◽  
Pulp Cells

Growth rate and replacement of teeth in Amphibians The growth rate of teeth depends on age: it varies from 5 days for the first teeth, functional at hatching time, to 2 months for 2-year-old animals. The life time of a functional tooth is 20 days in the young larva and in the young post-metamorphic individual; it is not precisely known in adults. The proteins of organic matrices are elaborated in ergastoplasm, transported through the Golgi apparatus and Golgian vesicles, and deposited outside the cells within 1 h. Destruction of old teeth begins before metamorphosis; it is performed by pulp cells necrosis, and intervention of macrophages and osteoclasts; teeth are completely destroyed in situ, allowing growth of the replacement teeth. Thyroxine hastens tooth replacement.

The Growth Of High-Quality MCT Films by MBE Using in Situ Ellipsometry

1994 ◽  
Vol 299 ◽  
Author(s):  
K.K. Svitashev ◽  
S.A. Dvorwetsky ◽  
V.A. Shvets ◽  
A.S. Mardezhov ◽  
YU.G. Sidoroy ◽  
...  
Keyword(s):  
Growth Rate ◽  
Initial Temperature ◽  
Film Surface ◽  
Life Time ◽  
Optimal Growth ◽  
Ellipsometric Parameter ◽  
High Quality ◽  
Initial Stage ◽  
Optimal Growth Condition

AbstractThe ellipsometry and RHEED study of MCT grown on (112) CdTe and GaAs by MBE was carried out. The dependence of ellipsometric parameter on composition is evaluated. As shown we can measure the growth rate, the roughness changing, initial temperature and composition by ellipsometry in situ. We investigated the evolution of roughness of film surface. We observed the appearance of surface roughness at initial stage of MCT growth under various composition (XcdTe0÷0.4). The following growth in optimal growth condition (including constancy of substrate temperature) gives us the smoothing of the surface and supplies us the high-quality MCT films. It is found that under constant temperature of substrate heater we can not grow the thick, perfect film of MCT. The concentration, mobility and life time of carriers in MCT films were respectively: n=1.8*1014 ÷8.2*1015cm−3, μn=44000÷370000cm2 V−1 s−1, τ=40÷220ns;p=1.8*1015÷8.4*1015 cm−3, μp=215÷284 cm2V−1 s−1 τ=12÷20ns.

The threshold energy for atom displacement in fcc metals

1990 ◽  
Vol 48 (4) ◽  
pp. 530-531
Author(s):  
Wilfried Sigle ◽  
Matthias Hohenstein ◽  
Alfred Seeger
Keyword(s):  
Growth Rate ◽  
Elevated Temperatures ◽  
Threshold Energy ◽  
Dislocation Loops ◽  
Absolute Minimum ◽  
Voltage Electron ◽  
Atom Displacement ◽  
Electron Microscopes ◽  
Fcc Metal

Prolonged electron irradiation of metals at elevated temperatures usually leads to the formation of large interstitial-type dislocation loops. The growth rate of the loops is proportional to the total cross-section for atom displacement,which is implicitly connected with the threshold energy for atom displacement, Ed . Thus, by measuring the growth rate as a function of the electron energy and the orientation of the specimen with respect to the electron beam, the anisotropy of Ed can be determined rather precisely. We have performed such experiments in situ in high-voltage electron microscopes on Ag and Au at 473K as a function of the orientation and on Au as a function of temperature at several fixed orientations.Whereas in Ag minima of Ed are found close to <100>,<110>, and <210> (13-18eV), (Fig.1) atom displacement in Au requires least energy along <100>(15-19eV) (Fig.2). Au is thus the first fcc metal in which the absolute minimum of the threshold energy has been established not to lie in or close to the <110> direction.

In-Situ Dual-Wavelength Ellipsometry and Light Scattering Monitoring of Si/Si1−xGex Heterostructures and Multiuantum Wells

1993 ◽  
Vol 324 ◽  
Author(s):  
C. Pickering ◽  
D.A.O. Hope ◽  
W.Y. Leong ◽  
D.J. Robbins ◽  
R. Greef
Keyword(s):  
Growth Rate ◽  
Light Scattering ◽  
Laser Light ◽  
Growth Period ◽  
Laser Light Scattering ◽  
Heterojunction Bipolar Transistor ◽  
Dual Wavelength ◽  
Multi Quantum Well ◽  
Refractive Index Data

AbstractIn-situ dual-wavelength ellipsometry and laser light scattering have been used to monitor growth of Si/Si1−x,Gex heterojunction bipolar transistor and multi-quantum well (MQW) structures. The growth rate of B-doped Si0 8Ge0.2 has been shown to be linear, but that of As-doped Si is non-linear, decreasing with time. Refractive index data have been obtained at the growth temperature for x = 0.15, 0.20, 0.25. Interface regions ∼ 6-20Å thickness have been detected at hetero-interfaces and during interrupted alloy growth. Period-to-period repeatability of MQW structures has been shown to be ±lML.

Deposition and Crystallisation Behaviour of Amorphous Silicon Thin Films Obtained by Pyrolysis of Disilane Gas at Very Low Pressure

1994 ◽  
Vol 345 ◽  
Author(s):  
T. Kretz ◽  
D. Pribat ◽  
P. Legagneux ◽  
F. Plais ◽  
O. Huet ◽  
...  
Keyword(s):  
Activation Energy ◽  
Growth Rate ◽  
Amorphous Silicon ◽  
Vapor Deposition ◽  
Electrical Conductance ◽  
Chemical Vapor ◽  
Crystalline Fraction ◽  
Silicon Thin Films ◽  
Crystallisation Behaviour

AbstractHigh purity amorphous silicon layers were obtained by ultrahigh vacuum (millitorr range) chemical vapor deposition (UHVCVD) from disilane gas. The crystalline fraction of the films was monitored by in situ electrical conductance measurements performed during isothermal annealings. The experimental conductance curves were fitted with an analytical expression, from which the characteristic crystallisation time, tc, was extracted. Using the activation energy for the growth rate extracted from our previous work, we were able to determine the activation energy for the nucleation rate for the analysed-films. For the films including small crystallites we have obtained En ∼ 2.8 eV, compared to En ∼ 3.7 eV for the completely amorphous ones.

In situ growth rate measurements for plasma processing of opaque materials

2002 ◽  
Vol 418 (2) ◽  
pp. 151-155
Author(s):  
A Salifu ◽  
G Zhang ◽  
Edward A Evans
Keyword(s):  
Growth Rate ◽  
Plasma Processing ◽  
In Situ Growth

scholarly journals In-situ SEM and optical microscopy testing for investigation of fatigue crack growth mechanism under overload

2018 ◽  
Vol 165 ◽  
pp. 13013
Author(s):  
Wei Zhang ◽  
Liang Cai
Keyword(s):  
Growth Rate ◽  
Crack Growth Rate ◽  
Optical Microscopy ◽  
Crack Growth ◽  
Load Condition ◽  
Crack Tip ◽  
Initial Crack ◽  
Crack Growth Behavior ◽  
Single Overload

In this paper, the in-situ scanning electron microscope (SEM) and optical microscopy experiments are performed to investigate the crack growth behavior under the single tensile overload. The objectives are to (i) examine the overload-induced crack growth micromechanisms, including the initial crack growth acceleration and the subsequent retardation period; (ii) investigate the effective region of single overload on crack growth rate. The specimen is a small thin Al2024-T3 plate with an edge-crack, which is loaded and observed in the SEM chamber. The very high resolution images of the crack tip are taken under the simple variable amplitude loading. Imaging analysis is performed to quantify the crack tip deformation at any time instant. Moreover, an identical specimen subjected to the same load condition is observed under optical microscope. In this testing, fine speckling is performed to promote the accuracy of digital imaging correlation (DIC). The images around the crack tip are taken at the peak loads before, during and after the single overload. After that, the evolution of local strain distribution is obtained through DIC technique. The results show that the rapid connection between the main crack and microcracks accounts for the initial crack growth acceleration. The crack closure level can be responsible for the crack growth rate during the steady growth period. Besides that, the size of retardation area is larger than the classical solution.

Relationship between the gas production profiles of mixtures of hay and maize and the patterns of rumen fermentation observed in sheep fed those mixtures

1998 ◽  
Vol 1998 ◽  
pp. 63-63
Author(s):  
C. Rymer ◽  
D.I. Givens
Keyword(s):  
Growth Rate ◽  
Feed Intake ◽  
Rumen Fermentation ◽  
Gas Production ◽  
Post Feeding ◽  
Molar Proportion ◽  
Rumen Ph ◽  
The Mean

The gas production (GP) technique has been developed to assess dynamics of ruminant digestion. Relationships have been observed between a feed's GP profile and in vivo parameters such as digestibility (Khazaal et al., 1993), feed intake and growth rate (Blümmel and Ørskov, 1993), and in situ degradability (Sileshi et al., 1997). However, there are few studies which relate GP data to the in vivo pattern of rumen fermentation (in terms of the rate of pH decline 2 h post-feeding and the mean rumen pH, concentration of total VFA and molar proportion of individual VFA). The object of this experiment was to determine whether such a relationship existed between a feed's GP profile and the pattern of rumen fermentation observed in animals fed that feed.

scholarly journals Microstructure of Anaerobic Granules Bioaugmented with Desulfitobacterium frappieri PCP-1

2002 ◽  
Vol 68 (8) ◽  
pp. 4035-4043 ◽  
Author(s):  
M. Lanthier ◽  
B. Tartakovsky ◽  
R. Villemur ◽  
G. DeLuca ◽  
S. R. Guiot
Keyword(s):  
Growth Rate ◽  
In Situ Hybridization ◽  
Outer Layer ◽  
Specific Growth ◽  
Anaerobic Sludge ◽  
Oligonucleotide Probes ◽  
Reactor Operation ◽  
Mathematical Simulations ◽  
Successful Colonization

ABSTRACT Oligonucleotide probes were used to study the structure of anaerobic granular biofilm originating from a pentachlorophenol-fed upflow anaerobic sludge bed reactor augmented with Desulfitobacterium frappieri PCP-1. Fluorescence in situ hybridization demonstrated successful colonization of anaerobic granules by strain PCP-1. Scattered microcolonies of strain PCP-1 were detected on the biofilm surface after 3 weeks of reactor operation, and a dense outer layer of strain PCP-1 was observed after 9 weeks. Hybridization with probes specific for Eubacteria and Archaea probes showed that Eubacteria predominantly colonized the outer layer, while Archaea were observed in the granule interior. Mathematical simulations showed a distribution similar to that observed experimentally when using a specific growth rate of 2.2 day−1 and a low bacterial diffusion of 10−7 dm2 day−1. Also, the simulations showed that strain PCP-1 proliferation in the outer biofilm layer provided excellent protection of the biofilm from pentachlorophenol toxicity.

Single Crystal Silicon Carbide On Silicon Using A Supersonic Gas Jet Of Methylsilane

1997 ◽  
Vol 483 ◽  
Author(s):  
S. A. Ustin ◽  
C. Long ◽  
L. Lauhon ◽  
W. Ho
Keyword(s):  
Growth Rate ◽  
Growth Rates ◽  
Single Crystal Silicon ◽  
Maximum Growth ◽  
X Ray Diffraction ◽  
Crystal Silicon ◽  
Cross Sectional ◽  
Supersonic Molecular Beam ◽  
Transmission Electron

AbstractCubic SiC films have been grown on Si(001) and Si(111) substrates at temperatures between 600 °C and 900 °C with a single supersonic molecular beam source. Methylsilane (H3SiCH3) was used as the sole precursor with hydrogen and nitrogen as seeding gases. Optical reflectance was used to monitor in situ growth rate and macroscopic roughness. The growth rate of SiC was found to depend strongly on substrate orientation, methylsilane kinetic energy, and growth temperature. Growth rates were 1.5 to 2 times greater on Si(111) than on Si(001). The maximum growth rates achieved were 0.63 μm/hr on Si(111) and 0.375μm/hr on Si(001). Transmission electron diffraction (TED) and x-ray diffraction (XRD) were used for structural characterization. In-plane azimuthal (ø-) scans show that films on Si(001) have the correct 4-fold symmetry and that films on Si(111) have a 6-fold symmetry. The 6-fold symmetry indicates that stacking has occurred in two different sequences and double positioning boundaries have been formed. The minimum rocking curve width for SiC on Si(001) and Si(111) is 1.2°. Fourier Transform Infrared (FTIR) absorption was performed to discern the chemical bonding. Cross Sectional Transmission Electron Microscopy (XTEM) was used to image the SiC/Si interface.

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