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  • 1
    Electronic Resource
    Electronic Resource
    Determination of nanometer structures and surface roughness of polished Si wafers by scanning tunneling microscopy (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 4273-4281 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Roughness and general surface topography of polished Si wafers were systematically studied on an angstrom to nanometer scale by scanning tunneling microscopy (STM). Evaluation of a large number of STM images by using a simple classification scheme assures statistically relevant results without the disadvantages and loss of information connected with averaging the rms roughness or similar methods. For the flat parts of the surface, a rms roughness of 1.2–1.8 A(ring) is found, comparable to that derived from light scattering and diffraction measurements on similar surfaces. Significant amounts of the surfaces were found to exhibit more pronounced structures, contrasting results of other techniques. The reliability and applicability of STM measurements on technical surfaces, on an angstrom to nanometer scale, is discussed in the light of these results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348399
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  • 2
    Electronic Resource
    Electronic Resource
    Writing electronic nanometer structures into porous Si films by scanning tunneling microscopy (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 2253-2255 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Under conditions of increased tunnel current and voltage, with the electron flow directed towards the sample, nanometer-scale structures have been written into ultrathin (∼20 nm) light-emitting porous silicon (PS) films using scanning tunneling microscopy in a high-vacuum environment. For the writing process, a threshold voltage of ∼4.5 V is observed and the resulting dimensions range between 20 and 50 nm. Depending on the writing parameters, the modified regions relax or remain stable during the observation time of several days at room temperature. These results can be assigned, in the first case, to a disruption of a small number of bonds, followed by reconfiguration, and a charging of dangling bond sites, followed by carrier release, in near surface regions. In the latter case, the creation of time-stable defect states within the PS layer is proposed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.111635
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  • 3
    Electronic Resource
    Electronic Resource
    Writing electronically active nanometer-scale structures with a scanning tunneling microscope (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 2136-2138 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A scanning tunneling microscope (STM) is used to locally modify p-n junctions on a scale of a few tens of nanometers. The p-n junction is composed of a phosphorus-doped, hydrogenated amorphous Si [a-Si:H(P)] layer deposited on heavily doped p-type crystalline Si(111). Under conditions of high current densities, with the p-n junction biased in forward direction, the a-Si:H layer is structurally changed leading to a decrease of the junction barrier height. The resulting exponential increase of hole injection into the modified amorphous layer leads to electronically active structures. They are detected by STM owing to their differing electronic properties.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.106104
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  • 4
    Electronic Resource
    Electronic Resource
    Correlation of surface morphology with luminescence of porous Si films by scanning tunneling microscopy (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 1365-1367 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The evolution of visible photoluminescence is demonstrated by measuring the surface morphology of thin (∼20 nm) electrochemically etched porous silicon (PS) films with scanning tunneling microscopy (STM). Using low current densities, three sorts of samples were prepared under different conditions: In the dark (A), under illumination with ultraviolet (UV) light (B), and in the dark followed by a postphotochemical treatment (C). Upon UV light excitation, type A samples do not emit visible light, while samples of type B and C show weak and efficient photoluminescence in the visible range, respectively. STM imaging of these PS layers reveals a considerable decrease in the lateral dimensions of the surface features from approximately 10 nm (type A) to roughly 2 nm (type C), in accordance with the quantum confinement approach in describing the luminescence properties.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.111936
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  • 5
    Electronic Resource
    Electronic Resource
    Spin correlations of inhomogeneous valence bond solid chains (1992)
    Springer
    The European physical journal 88 (1992), S. 279-282 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We consider a spacially inhomogeneous generalization of the valence bond solid (VBS) chain by permitting an arbitrary distribution of the numbers of valence bonds. We evaluate all two point correlation functions of these VBS states. The correlation functions turn out to factorize completely into a product of local factors. This leads to very simple rules for their evaluation and implies the breaking of correlations of higher rank by a single weak link.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01470914
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  • 6
    Electronic Resource
    Electronic Resource
    Anisotropy of optical activity and Faraday effect in TeO2 (1993)
    Springer
    The European physical journal 90 (1993), S. 47-50 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The tensor of optical activity of TeO2 was derived with the aid of measurements of the Faraday effect. This technique allows the separation of gyrative effects in crystals having a large birefringence. The natural activity of TeO2 perpendicular to the fourfold axis is by about a factor two larger than along this axis. The sign of the tensorial components is related to structural details.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01321031
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  • 7
    Electronic Resource
    Electronic Resource
    Comparison of the biosynthesis of the methanobacterial pseudomurein and the eubacterial murein (1990)
    Springer
    Naturwissenschaften 77 (1990), S. 472-475 
    Details
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01135923
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  • 8
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    Pynsent, R. B. (ed.). "Decadence and Innovation. Austro-Hungarian Life and Art at the Turn of the Century" (Book Review) (1991)
    London, etc. : Periodicals Archive Online (PAO)
    Slavonic and East European review. 69:3 (1991:July) 559 
    Details
    ISSN: 0037-6795
    Topics: History , Slavonic Studies
    Notes: REVIEWS
    URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pao:&rft_dat=xri:pao:article:0072-1991-069-03-000053
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  • 9
    Electronic Resource
    Electronic Resource
    A novel pathway of peptide biosynthesis found in methanogenic Archaea (1994)
    Springer
    Archives of microbiology 162 (1994), S. 430-432 
    Details
    ISSN: 1432-072X
    Keywords: Key words     Methanogens ; Archaea ; Methanobacterium thermoautotrophicum ; Cell walls ; Peptide biosynthesis ; Pseudomurein
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract      The peptide subunits of the pseudomurein, the cell-wall peptidoglycan of some methanogens, are usually composed of glutamic acid, alanine and lysine. In order to get a more detailed picture of the biosynthetic pathway of the peptide subunit, we performed in vitro assays. Starting from glutamic acid a pentapeptide was obtained in seven steps: Nα-UDP-Gluγ→Ala→εLys→Ala ↑γ Glu The pentapeptide structure was identical to that of the peptide subunit of the intact pseudomurein except one additional alanine residue, which is split off during further processing. The pentapeptide synthesis starts with glutamic acid, which is phosphorylated at the Nα-amino group. Nα-phosphoryl-glutamic acid is transferred to a nucleotide-carrier, forming Nα-UDP-glutamic acid. The further pentapeptide biosynthesis is achieved via a di-, tri- and tetrapeptide by stepwise addition of the corresponding amino acids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002030050161
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  • 10
    Electronic Resource
    Electronic Resource
    Microtubule distribution in gravitropic protonemata of the mossCeratodon (1990)
    Springer
    Protoplasma 159 (1990), S. 60-69 
    Details
    ISSN: 1615-6102
    Keywords: Gravity ; Microtubules ; Protonema ; Ceratodon ; Gravitropism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Tip cells of dark-grown protonemata of the mossCeratodon purpureus are negatively gravitropic (grow upward). They possess a unique longitudinal zonation: (1) a tip group of amylochloroplasts in the apical dome, (2) a plastid-free zone, (3) a zone of significant plastid sedimentation, and (4) a zone of mostly non-sedimenting plastids. Immunofluorescence of vertical cells showed microtubules distributed throughout the cytoplasm in a mostly axial orientation extending through all zones. Optical sectioning revealed a close spatial association between microtubules and plastids. A majority (two thirds) of protonemata gravistimulated for 〉20 min had a higher density of microtubules near the lower flank compared to the upper flank in the plastid-free zone. This apparent enrichment of microtubules occurred just proximal to sedimented plastids and near the part of the tip that presumably elongates more to produce curvature. Fewer than 5% of gravistimulated protonemata had an enrichment in microtubules near the upper flank, whereas 14% of vertical protonemata were enriched near one of the side walls. Oryzalin and amiprophos-methyl (APM) disrupted microtubules, gravitropism, and normal tip growth and zonation, but did not prevent plastid sedimentation. We hypothesize that a microtubule redistribution plays a role in gravitropism in this protonema. This appears to be the first report of an effect of gravity on microtubule distribution in plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01326635
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