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  • 1995-1999  (5)
  • 1985-1989  (2)
  • 1935-1939  (1)
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  • 1
    Electronic Resource
    Electronic Resource
    Diels–Alder reactions of butadienes with the Si(100)-2×1 surface as a dienophile: Vibrational spectroscopy, thermal desorption and near edge x-ray absorption fine structure studies (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 108 (1998), S. 4599-4606 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The mechanism and intermediates of a Diels–Alder-type cycloaddition reaction between dienes and the silicon dimers of a Si(100)-2×1 surface, which was theoretically predicted by Doren and Konecny, have been investigated. The reactions of 1,3-butadiene and 2,3-dimethyl-1,3-butadiene were studied using multiple internal reflection infrared spectroscopy, thermal desorption spectrometry, and near edge x-ray absorption fine structure (NEXAFS) measurements. The results show that the compounds physisorb on Si(100)-2×1 at cryogenic temperature. Infrared studies of the room temperature adsorption of both dienes indicate that reaction leads to the formation of stable, chemisorbed Diels–Alder adducts. By NEXAFS measurements on 2,3-dimethyl-1,3-butadiene, we determine that the angle between the π orbitals of the reaction product and the Si(100)-2×1 surface is near 40°. Upon heating, the chemisorbed butadienes primarily decompose to form adsorbed carbon and hydrogen at the surface. Hydrogenation of chemisorbed butadienes by atomic hydrogen was also investigated, and conversion from the Diels–Alder geometry to [2+2] bonding is observed. This effect is attributed to cleavage of the Si–Si dimer bond upon atomic hydrogen exposure. Temperature dependent studies suggest the presence of an activation barrier for chemisorption at low temperature. The parallels between our experimental results and the theoretical studies of these reactions are discussed. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.475870
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Adsorption of ethylene on the Ge(100)-2×1 surface: Coverage and time-dependent behavior (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 10545-10553 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Studies of the adsorption and thermal chemistry of ethylene on the Ge(100)-2×1 surface have been performed. The results of multiple internal reflection Fourier transform infrared (MIR-FTIR) spectroscopy and temperature programmed desorption (TPD) show that ethylene chemisorbs molecularly on the Ge(100)-(2×1) surface at room temperature. Infrared spectroscopy gives evidence for only one adsorbate configuration on this surface at room temperature, consistent with a structure in which ethylene bridges across a germanium dimer. However, TPD measurements show two molecular desorption features at almost all coverages, indicating that at least two adsorption states can be formed. Further shifts in one of the peaks with both coverage and time, paralleled by changes in the vibrational spectrum, suggest the presence of attractive intermolecular interactions or cooperative effects. The complex time- and coverage dependence of ethylene adsorption on Ge(100)-2×1 is analyzed using a two-state kinetic model. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.478986
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Elastic constants and crystal anisotropy of titanium diboride (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 70 (1997), S. 1959-1961 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this study, the elastic constants of a titanium diboride (TiB2) single crystal were measured using resonant ultrasound spectroscopy. In contrast to previous work, the current results are consistent with the measured elastic constants of TiB2 polycrystals. In addition, the crystal anisotropy of TiB2 was examined. The current data show that the elastic properties of TiB2 are much more isotropic than previously considered. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.118791
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  • 4
    Electronic Resource
    Electronic Resource
    Determination of Gold in Dental Gold Alloys (1936)
    s.l. : American Chemical Society
    Industrial and engineering chemistry 8 (1936), S. 368-369 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ac50103a026
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Effects of sedimentary sorting on neodymium isotopes in deep-sea turbidites (1989)
    [s.l.] : Nature Publishing Group
    Nature 337 (1989), S. 547-549 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The neodymium model age of a sediment or sedimentary rock is generally interpreted as the average age of extraction from the mantle of the various provenance components1. Complications involving uncertainties in mantle evolution models and possible changes in the Sm/Nd ratio during crustal ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/337547a0
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Gross deletions of the neurofibromatosis type 1 (NF1) gene are predominantly of maternal origin and commonly associated with a learning disability, dysmorphic features and developmental delay (1998)
    Springer
    Human genetics 〈Berlin〉 102 (1998), S. 591-597 
    Details
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Mutation screening in neurofibromatosis type 1 (NF1) families has long been hampered by the complexity of the NF1 gene. By using a novel multi-track screening strategy, 67 NF1 families (54 two-generation, 13 three-generation) with a de novo mutation in the germline of the first generation were studied with two extragenic and 11 intragenic markers. The pathological lesion was identified in 31 cases. Loss of heterozygosity (LOH) in the affected individual revealed a gross gene deletion in 15 of the two-generation families; in 12 (80%) of them, the deletion was maternally derived. Eleven patients with a gross deletion exhibited developmental delay, ten had dysmorphic features and six manifested a learning disability. No gross deletion was apparent in any of the 13 three-generation families, suggesting that such lesions are subject to more intense selection. In these families, the new mutation was of paternal origin in 11 kindreds and the underlying mutational event could be characterised in three of them.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004390050746
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    The Role of Convection During the Self-Focusing of Nonlinear Second Sound Pulses Near the Lambda Point (1998)
    Springer
    Journal of low temperature physics 110 (1998), S. 949-962 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Second sound in superfluid helium is made up of scalar temperature and vector convective velocity fields. The local sound velocity is altered by these fields, leading to finite amplitude effects. The vector convective field and the direction of propagation are colinear for infinite plane waves and the amplitude dependent velocity is described by the Khalatnikov nonlinear coefficient. For finite sources of second sound, the convective velocity and the local sound velocity may not be colinear, leading to unusual nonlinear effects. We present a vector representation of the finite amplitude velocity of sound emitted from arbitrary sources of second sound, and apply it to a model of two point sources. This simple model is used to show how the linear superposition of signals delayed by the scalar temperature and vector convective fields of second sound may describe a finite amplitude phenomenon: The distortion, due to self-focusing, of pulsed nonplanar second sound near the lambda point.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022304014347
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  • 8
    Electronic Resource
    Electronic Resource
    Morphological and biochemical effects of sodium morrhuate on tendons (1985)
    Hoboken, NJ [u.a.] : Wiley-Blackwell
    Journal of Orthopaedic Research 3 (1985), S. 236-248 
    Details
    ISSN: 0736-0266
    Keywords: Sclerotherapy ; Sodium morrhuate ; Tendons ; Collagen ; Ligaments ; Life and Medical Sciences
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The purpose of this study was to determine some of the morphological and biochemical effects of sodium morrhuate injections into intact rabbit patellar tendons and Achilles tendons. The effects of one, three, and five 100 μ1 injections of sodium morrhuate on tendon circumference, cell content, collagen fibril diameter, collagen-proteoglycan relationships, water content, amino sugar content, and hydroxyproline content were investigated over periods of 1, 4, and 9 weeks. In general, sodium morrhuate injected tendons were larger in diameter and contained more cells, smaller collagen fibrils, increased water and amino sugar content, and reduced hydroxyproline content compared with their contralateral controls. As a sclerosing agent, sodium morrhuate appears to mimic the early stages of an injury-repair sequence when injected directly into intact tendons. Whether sodium morrhuate may hasten repair responses or improve joint laxity remains to be determined.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jor.1100030214
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