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  • 1
    Electronic Resource
    Electronic Resource
    Preparation and characterization of organic superlattice thin films grown on hydrogenated silicon single-crystal substratesPaper presented at ECASIA 93, Catania, Sicily. 4-8 October 1993. (1994)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 21 (1994), S. 356-364 
    Details
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: We have succeeded in preparing very thin (nanometre order) alternating layers that can be called ‘organic superlattices’ by using a special combination of materials, substrates and deposition conditions with good verification by various characterization techniques.Specially surface-treated single-crystal silicon substrates with hydrogen-terminated dangling bonds on the surface were used to induce van der Waals heteroepitaxial growth. Choice of materials with the appropriate molecular shapes and aggregation force is also important for preparing flat molecular films. Tetraphenylporphyrins (H2TPP and ZnTPP) and phthalocyanines were used for this purpose. A molecular beam epitaxy chamber with specially designed cells was used with the cooled substrates.Direct proof of the alternating composition was given by transmission electron microscopy observation, avoiding decomposition by the electron beam, and also by SIMS depth profiling under special conditions to ensure good depth resolution. X-ray diffraction in the small-angle region gives the periodicity of the alternating layers, as well as their crystal quality. Atomic force microscopy confirms the atomic flatness and also gives the molecular orientation in the films. Fourier transform infrared spectroscopy examines the chemical stability of the compounds during deposition and also gives the axial orientation of the molecules in the films.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/sia.740210606
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  • 2
    Electronic Resource
    Electronic Resource
    Quantitative investigation of the O2+-induced topography of GaAs and other III-V semiconductors: An STM study of the ripple formation and suppression of the secondary ion yield change by sample rotation (1995)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 23 (1995), S. 506-513 
    Details
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Roughening procedures including the early stage of the O2+-induced ripple formation of GaAs were studied quantitatively by scanning tunnelling microscopy (STM). Detailed examinations of the beginning of topography development using fast Fourier transform of the STM images revealed that the ripple formation was not caused by any accidental defects, particles or original irregularity on the substrate, but solely by the conditions of the ion beam. A systematic investigation of the rippled GaAs surface produced under various O2+ bombardment conditions was conducted. The ripple wavelength and the transition depth were almost exactly proportional to EPcos θ, where EP and θ are the energy of the ion beam and the incident angle, respectively. For GaAs, the secondary ion yield transition occurs when the slope of ripples facing the incident O2+ beam reaches a saturation angle of 20-30° from the macroscopic surface plane. Topography change on other III-V semiconductors was also examined for comparison. There was no ripple generation observed for GaP; InP gave a ripple-like structure without secondary ion yield change. A relatively rough surface resulted on GaSb and InAs at a much shallower depth than for GaAs. Rippling and ion yield changes during depth profiling have been suppressed successfully by sample rotation even in a magnetic sector-based instrument.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/sia.740230710
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  • 3
    Electronic Resource
    Electronic Resource
    Effects of surface cleaning and X-ray irradiation in XPS study of polymers (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 41 (1990), S. 1451-1458 
    Details
    ISSN: 0021-8995
    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
    Notes: We have examined effects of surface cleaning and X-ray irradiation in XPS study of polymers. Contamination-free surfaces of polymer samples for XPS study were successfully prepared by ultrasonic washing in organic solvents. Polymers were revealed to have lower surface chemical activity than metal and semiconductor crystals. The degradation behavior of polymers induced by X-ray irradiation was found to be different from thermal degradation processes. Polymers like PET, polyimide, and PAN have high stability against X-ray irradiation in XPS measurement. On the other hand, we must take degradation into consideration in XPS measurement for polymers such as PTFE and nylon because of their low stability against X-ray irradiation. For an extremely X-ray-sensitive polymer like nitrocellulose, a quantitative XPS study cannot be carried out.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1990.070410708
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  • 4
    Electronic Resource
    Electronic Resource
    FT-IR study of the stabilization reaction of polyacrylonitrile in the production of carbon fibers (1986)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 24 (1986), S. 1989-1995 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The stabilized fibers prepared by heating PAN and a PAN copolymer in air and under reduced pressure have been examined by FT-IR spectroscopy in order to determine their chemical structures. Three kinds of reactions, cyclization, dehydrogenation, and oxygen uptake are found to occur almost simultaneously in the stabilization process in air by digital difference spectrum method. The effect of the comonomer is confirmed to accelate the dehydrogenation reaction and also the formation of acridone ring in the thermal stabilization in air by kinetic study.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1986.080240819
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  • 5
    Electronic Resource
    Electronic Resource
    XPS studies on the chemical structure of the stabilized polyacrylonitrile fiber in the carbon fiber production process (1986)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 24 (1986), S. 3101-3107 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In the carbon fiber production process from polyacrylonitrile (PAN), PAN precursor is heated first in air to secure stabilization in the succeeding carbonization process at higher temperature. The mechanism of the stabilization reaction and chemical structure of the stabilized PAN have been examined by x-ray photoelectron spectroscopy and elemental analysis. The stabilized PAN was determined to have a ladderlike structure consisting of 40% acridone ring, 30% naphtyridine ring, 20% hydronaphtyridine ring, and others. This structure well explains the stability of the polymer in the succeeding carbonization process on carbon fiber production with conjugated π-electron systems over the whole polymer chain and intermolecular hydrogen bonds. A comonomer addition to the precursor was found to accelerate the dehydrogenation reaction in the stabilization process.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1986.080241134
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  • 6
    Electronic Resource
    Electronic Resource
    XPS analysis of NH3 plasma-treated polystyrene films utilizing gas phase chemical modification (1988)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 26 (1988), S. 559-572 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Gas phase chemical modification (GCM) is found to be more preferable as a pretreatment for the XPS surface analysis of polymer materials than the conventional liquid phase treatment because it can circumvent problems such as solvent contamination and swelling. We have tried the quantification of the surface composition successfully by estimating the yield of the reaction from model samples. GCM was then applied to correlate the surface composition of NH3 plasma-treated polystyrene films with their cell-affinity. The amount of primary-amine and that of carboxylic acid were directly determined by GCM. Although the amount of primary-amine, 15-20% of total nitrogen, did not depend on the treatment intensity, the total amine content for the treated samples increased with the plasma treatment intensity. The quantity of carboxylic acid generated was found to be very small. All treated samples had better cell-affinity than the control. The sample N2 (of medium treatment) showed the best cell-affinity. The most strongly treated sample N3, with larger amine content than N2, showed worse cell-affinity because of the interference by the sputtered SiO2 on the surface.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1988.080260219
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  • 7
    Electronic Resource
    Electronic Resource
    A study of XPS O1s spectrum of poly(ethylene terephthalate) (1990)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 28 (1990), S. 1813-1821 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The XPS (x-ray photoelectron spectroscopy) O1s spectrum of PET [poly(ethylene terephthalate)] was examined in detail. Spectra of related compounds were also studied for comparison. The O1s peak profile of asymmetric doublet with π-π* satellites characteristic of PET was successfully explained both from comparison with the observed O1s spectra of the related compounds and from ab initio δSCF calculation.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1990.080280713
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  • 8
    Electronic Resource
    Electronic Resource
    Small-angle x-ray scattering of distorted lamellar structures (1993)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 31 (1993), S. 1179-1186 
    Details
    ISSN: 0887-6266
    Keywords: small angle x-ray scattering (SAXS) of distorted lamellar structures ; polypropylene, hard elastic, SAXS of, electron micrograph of, density of ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Small-angle x-ray scattering (SAXS) intensity for the lamellar structure of polymeric materials has been formulated with consideration of structural defects such as the finiteness of the lamellar stack, the lamellar bend, and the paracrystalline distortions. In particular, the effects of the lamellar bend on the SAXS profile have been elucidated on the basis of Vonk'xss formula γ1(x) - γ01(x)exp(-2x/d). Here, the scattering profile due to the lamellar bend is shown to be expressed by a Cauchy function. The integral breadth is equal to 2π/d, being independent of the order of scattering. As an example of the SAXS analysis based on the theory, the characterization of the lamellar structure in the “hard” elastic polypropylene films is reported. The long period and the lamellar thickness are evaluated from the correlation function, and the distortion length and Hosemann's g factor are estimated according to the procedure presented here. On the basis of these structural parameters, the relationship between the manufacturing process and the lamellar structure of the polypropylene films is discussed. © 1993 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1993.090310912
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  • 9
    Electronic Resource
    Electronic Resource
    An experimental study on saturation swelling of styrene-acryronitrile copolymer particles with styrene and acrylonitrile monomers (1994)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 32 (1994), S. 2491-2498 
    Details
    ISSN: 0887-6266
    Keywords: emulsion copolymerization ; swelling of polymer particles ; monomer partitioning ; styrene ; acrylonitrile ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The saturation swelling behavior of styrene and acrylonitrile (SAN) copolymer particles with a styrene (St) and acrylonitrile (AN) comonomer mixture was investigated experimentally. The effects of the copolymer composition and the compositional inhomogeneity in SAN Copolymer particles on their swelling behavior were examined. The experimental results show that both the copolymer composition and the compositional inhomogeneity in SAN copolymer particles have little or no influence on the swellability of SAN copolymer particles with a St and AN comonomer mixture, as long as the weight fraction of AN monomer units in SAN copolymer particles is less than a certain value between 0.6 and 0.8. With increasing AN content in the copolymer particles beyond this value, however, the swellability of SAN copolymer particles gradually decreases. Semiempirical equations are proposed, which correlate the saturation concentration of each monomer in SAN copolymer particles as a function of the comonomer composition in the monomer droplets and the overall copolymer composition in SAN copolymer particles. © 1994 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1994.090321506
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  • 10
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    Structural basis for translational fidelity ensured by transfer RNA lysidine synthetase (2009)
    Nature Publishing Group (NPG)
    Details
    Publication Date: 2009-10-23
    Description: Maturation of precursor transfer RNA (pre-tRNA) includes excision of the 5' leader and 3' trailer sequences, removal of introns and addition of the CCA terminus. Nucleotide modifications are incorporated at different stages of tRNA processing, after the RNA molecule adopts the proper conformation. In bacteria, tRNA(Ile2) lysidine synthetase (TilS) modifies cytidine into lysidine (L; 2-lysyl-cytidine) at the first anticodon of tRNA(Ile2) (refs 4-9). This modification switches tRNA(Ile2) from a methionine-specific to an isoleucine-specific tRNA. However, the aminoacylation of tRNA(Ile2) by methionyl-tRNA synthetase (MetRS), before the modification by TilS, might lead to the misincorporation of methionine in response to isoleucine codons. The mechanism used by bacteria to avoid this pitfall is unknown. Here we show that the TilS enzyme specifically recognizes and modifies tRNA(Ile2) in its precursor form, thereby avoiding translation errors. We identified the lysidine modification in pre-tRNA(Ile2) isolated from RNase-E-deficient Escherichia coli and did not detect mature tRNA(Ile2) lacking this modification. Our kinetic analyses revealed that TilS can modify both types of RNA molecule with comparable efficiencies. X-ray crystallography and mutational analyses revealed that TilS specifically recognizes the entire L-shape structure in pre-tRNA(Ile2) through extensive interactions coupled with sequential domain movements. Our results demonstrate how TilS prevents the recognition of tRNA(Ile2) by MetRS and achieves high specificity for its substrate. These two key points form the basis for maintaining the fidelity of isoleucine codon translation in bacteria. Our findings also provide a rationale for the necessity of incorporating specific modifications at the precursor level during tRNA biogenesis.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Nakanishi, Kotaro -- Bonnefond, Luc -- Kimura, Satoshi -- Suzuki, Tsutomu -- Ishitani, Ryuichiro -- Nureki, Osamu -- England -- Nature. 2009 Oct 22;461(7267):1144-8. doi: 10.1038/nature08474.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Biological Information, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Yokohama, Kanagawa 225-8501, Japan.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/19847269" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acyl-tRNA Synthetases/*chemistry/genetics/*metabolism ; Apoproteins/genetics/metabolism ; Bacillus subtilis ; Bacterial Proteins/*chemistry/genetics/*metabolism ; Base Sequence ; Catalytic Domain ; Crystallography, X-Ray ; Escherichia coli ; Geobacillus ; Kinetics ; Lysine/analogs & derivatives/metabolism ; Mass Spectrometry ; Models, Molecular ; Molecular Sequence Data ; *Protein Biosynthesis ; Pyrimidine Nucleosides/metabolism ; RNA, Transfer, Ile/genetics/metabolism ; Substrate Specificity
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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