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Ion channeling and x-ray diffraction studies of epitaxial Fe on GaAs(001) (1999)

Lallaizon, C. ; Lépine, B. ; Ababou, S. ; [et al.]

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 86 (1999), S. 5515-5519

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ISSN: 1089-7550

Source: AIP Digital Archive

Topics: Physics

Notes: Epitaxial 80-nm-thick films of Fe were grown at room temperature by molecular beam epitaxy on GaAs(001) and on a reacted layer composed of a mixture of (Fe2As+Fe3Ga1.8As0.2) resulting from the solid-state interdiffusions in a (20 nm Fe)/GaAs(001) structure annealed at 450 °C. The partially relaxed strains induced by the lattice mismatch were studied using ion channeling, Rutherford backscattering, and x-ray diffraction. Both channeled angular scans and x-ray diagrams showed that the 80 nm Fe films are not fully relaxed. The average crystalline quality of the Fe films is better on GaAs(001) (χmin=3%) than on the reacted layer (χmin=7%) mainly because of the mosaic structure of the reacted layer. The strains parallel to the surface in the Fe films were found to be compressive in the Fe/GaAs(001) heterostructure and tensile in the Fe/(Fe2As+Fe3Ga1.8As0.2)/GaAs(001) one. Therefore, our work shows that the presence of a reacted layer at the interface in a Fe/GaAs structure does not impede the epitaxial growth of Fe but can invert the kind of strain appearing in the Fe film. © 1999 American Institute of Physics.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.371553

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Solid state interdiffusions in epitaxial Fe/GaAs(001) heterostructures during ultrahigh vacuum annealings up to 450 °C (1998)

Lépine, B. ; Ababou, S. ; Guivarc'h, A. ; [et al.]

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 83 (1998), S. 3077-3080

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ISSN: 1089-7550

Source: AIP Digital Archive

Topics: Physics

Notes: We have used a set of complementary experimental techniques to characterize an epitaxial structure (25 nm Fe)/GaAs(001) annealed at 450 °C under ultrahigh vacuum conditions. The solid state interdiffusion leads to the formation of an epitaxial reaction layer made of Fe2As patches embedded in a Ga rich Fe3Ga2−XAsX ternary phase. The epitaxial character of this layer explains how the usually reported epitaxial growth of Fe on GaAs performed in the temperature range of 175 to 225 °C is possible in spite of the species intermixing occurring at the interface. Moreover, the observed grains of Fe2As explain the decrease of magnetization at the interface in such contact, since Fe2As is an antiferromagnetic alloy. © 1998 American Institute of Physics.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.367063

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Instability of phenotype and gene expression in long-term culture of carrot hairy root clones (1999)

Guivarc'h, A. ; Boccara, M. ; Prouteau, M. ; [et al.]

Springer

Plant cell reports 19 (1999), S. 43-50

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ISSN: 1432-203X

Keywords: Key words Agrobacterium rhizogenes ; β-Glucuronidase ; Daucus carota ; gus gene ; Root culture ; NAM test ; Opines ; Gene expression

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract Hairy root clones were established from carrot root discs inoculated with an agropine-type strain of Agrobacterium rhizogenes A4 harbouring the gus reporter gene on the TL-DNA. The clones were periodically examined for their phenotypic characteristics and for their ability to express the gus gene, to produce opines and to grow in the presence of NAM. The presence of the gus gene in the roots was confirmed by Southern blot hybridisation. The clones displayed various morphologies which were generally not correlated with the transformation events, and they were highly unstable throughout the successive subcultures, both for their phenotype and for their ability to express the transgenes. Reversible inactivation of the gus gene expression was associated with a high gus copy number. This could have some consequences for fundamental studies and practical uses of hairy roots.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s002990050708

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The pleiotropic effects induced by therolC gene in transgenic plants are caused by expression restricted to protophloem and companion cells (1996)

Guivarc'H, A. ; Spena, A. ; Noin, M. ; [et al.]

Springer

Transgenic research 5 (1996), S. 3-11

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ISSN: 1573-9368

Keywords: Agrobacterium rhizogenes ; gene expression ; GUS staining ; immunolocalization ; Nicotiana tabacum ; rolC gene

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract Expression of therolC gene fromAgrobacterium rhizogenes causes morphological and developmental alterations in transgenic plants. The histological alterations underlying the macroscopic changes and the cellular localization of the site of expression of therolC gene have shown that: (i) the expression of therolC gene is developmentally regulated, (ii) in vegetative transgenic plants, the expression of therolC gene under the control of its own promoter is restricted to companion and protophloem cells, (iii) the site of action of the product(s) of the activity of the rolC enzyme is distinct from its site of expression, (iv) precise localization of the rolC peptide has been achieved by immunocytochemistry but not by the histochemical GUS assay. These results imply that the sites of action and expression of therolC gene in trangenic plants are physically separated. Thus the product(s) of the activity of the rolC enzyme must be a factor capable of being transported. Current models forrolC gene action are discussed taking into account the reported results.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF01979917

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In situ detection of expression of thegus reporter gene in transgenic plants: ten years of blue genes (1996)

Guivarc'h, A. ; Caissard, J. C. ; Azmi, A. ; [et al.]

Springer

Transgenic research 5 (1996), S. 281-288

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ISSN: 1573-9368

Keywords: reporter genes ; β-glucuronidase ; transgenic plants ; immunocytochemistry ; in situ hybridization

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract Among the methods now available to localize the sites of gene expression in plant materials, reporter genes based on thegus (uidA) gene ofEscherichia coli, which encodes a β-glucuronidase (E.C. 3.2.1.31; GUS), have been the most widely used during the last ten years. The apparent simplicity of the histochemical GUS assay has been a major factor in the increase in articles usinggus genes. However, over the last four years, there have been occasional reports expressing doubts concerning the specificity of the observed localizations based on discrepancies between results obtained with GUS histochemistry and immunocytochemistry and/orin situ hybridization. This brief review compares the results obtained with immunocytochemistry with those obtained with various GUS substrates for histochemical studies. Certain sources of artefact are discussed, as are the limits that should be imposed on interpretation of GUS histochemistry results at the organ, tissue and cell levels.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF01968938

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