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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 469-475 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A model describing the current-voltage characteristics of organic thin-film transistors (TFTs) is presented. The model is based on the trap distribution deduced from temperature-dependent current-voltage measurements on Au/alpha-sexithienyl (α6T)/Au symmetrical structures, which comprises a dominant single shallow trap level located near the valence-band edge. Numerical and approximate analytical derivations of the saturation current density as a function of the gate voltage have been made. From these calculations, the dependence of the threshold voltage on the parameters of the trap level (density and energy) is deduced. It appears that the threshold voltage corresponds to the filling of traps, and is a surface equivalent of the trap-filled limit voltage in bulk space-charge-limited current. The model is in good agreement with experimental data on α6T TFTs. The energy of the trap level compares well with that obtained from the temperature-dependent conductivity. However, the mobility is much lower in the TFT than in a bulk structure. This is tentatively explained by the strong influence of the state of the insulator-semiconductor interface on the characteristics of a TFT.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0935-9648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-4986
    Keywords: HT-29 cells ; mucins ; aryl-glycosides ; O-glycosylation ; sialyltransferases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract We have analysed the mucins synthesized by the HT-29 MTX cell subpopulation, derived from the HT-29 human colon carcinoma cells through a selective pressure with methotrexate (Lesuffleuret al., 1990,Cancer Res 50: 6334–43), in the presence of benzyl-N-acetyl-α-galactosaminide (GalNAcα-O-benzyl), which is a potential competitive inhibitor of the β1,3-galactosyltransferase that synthesizes the T-antigen. The main observation was a 13-fold decrease in the sialic acid content of mucins after 24 h of exposure to 5mm GalNAcα-O-benzyl. This effect was accompanied by an increased reactivity of these mucins to peanut lectin, testifying to the higher amount of T-antigen. The second observation was a decrease in the secretion of the mucins by GalNAcα-O-benzyl treated cells. The decrease in mucin sialyation was achieved through thein situ β-galactosylation of GalNAcα-O-benzyl into Galβ1–3GalNAcα-O-benzyl, which acts as a competitive substrate of Galβ1–3GalNAc α2,3-sialyltransferase, as shown by the intracellular accumulation of NeuAcα2–3Galβ1–3GalNAcα-O-benzyl in treated cells.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1573-4986
    Keywords: sialyltransferases ; breast cancer cells ; multiplex RT-PCR ; glycosyltransferases ; bp, base pair ; GAPDH, glyceraldehyde-3-phosphate dehydrogenase ; kb, kilobase ; PNA, Peanut (Arachis hypogaea) agglutinin ; RT-PCR, reverse transcription-polymerase chain reaction ; TBE, Tris base 0.13 M, boric acid 45 mM ; Na2EDTA 2.55 mM, pH 8.8 buffer ; Tm, melting temperature ; the nomenclature of sialyltransferases is based on that of Tsuji et al. [36]: ST3Gal I: CMP-NeuAc, Gal beta 1-3GalNAc alpha 2,3-sialyltransferase, EC 2.4.99.4 ; ST3Gal III: CMP-NeuAc, Gal beta 1-3/4GlcNAc alpha 2,3-sialyltransferase, EC 2.4.99.6 ; ST3Gal IV: CMP-NeuAc, Gal beta 1-4GlcNAc or Gal beta 1-3GalNAc alpha 2,3-sialyltransferase, EC 2.4.99. ; ST6Gal I: CMP-NeuAc, Gal beta 1-4GlcNAc alpha 2,6-sialyltransferase, EC 2.4.99.1.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In many cases of human cancer, the appearance of hypersialylated glycan structures is related to a precise stage of the disease; this may depend on altered regulation of one or more sialyltransferases genes. Since several distinct sialyltransferase enzymes arising from different unique genes transfer sialic acid residues in the same linkage onto the same acceptor, it is impossible to precisely determine which enzyme is involved in the observed phenotype based on enzymatic assays. We have developed a very sensitive and highly reproducible multiplex reverse transcriptase-polymerase chain reaction technique in order to monitor the expression of four human sialyltransferases genes ST6Gal I, ST3Gal I, ST3Gal III and ST3Gal IV in small cell samples. Multiplex PCR amplification using specific primers for each sialyltransferase and detection of amplification products by polyacrylamide gel electrophoresis is a method that is fast and easy to handle and has proven to be useful for establishing sialyltransferase patterns of expression in breast immortalized cell line HBL100 as well as in breast cancer cell lines MCF-7/6, MCF-7/AZ and MDA.
    Type of Medium: Electronic Resource
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