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  • 1
    Electronic Resource
    Electronic Resource
    Particle- and photoinduced conductivity in type-IIa diamonds (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 1086-1095 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electrical characteristics associated with radiation detection were measured on single-crystal natural type-IIa diamond using two techniques: charged particle-induced conductivity and time-resolved transient photoinduced conductivity. The two techniques complement each other: The charged particle-induced conductivity technique measures the product of the carrier mobility μ and lifetime τ throughout the bulk of the material while the transient photoconductivity technique measures the carrier mobility and lifetime independently at the first few micrometers of the material surface. For each technique, the μτ product was determined by integration of the respective signals. The collection distance that a free carrier drifts in an electric field was extracted by each technique. As a result, a direct comparison of bulk and surface electrical properties was performed. The data from these two techniques are in agreement, indicating no difference in the electrical properties between the bulk and the surface of the material. The collection distance continues to increase with field up to 25 kV/cm without saturation. Using the transient photoconductivity technique the carrier mobility was measured separately and compared with a simple electron-phonon scattering model. The general characteristics of carrier mobility, lifetime, and collection distance at low electric field appear to be adequately described by the model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354957
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  • 2
    Electronic Resource
    Electronic Resource
    Thickness dependence of the electrical characteristics of chemical vapor deposited diamond films (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 193-195 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The electrical characteristics of chemically vapor deposited (CVD) diamond films were measured as a function of film thickness. The samples studied were polycrystalline with the average grain size increasing from approximately 1 μm on the substrate side to approximately 30 μm on the growth surface for the thickest sample. Using time-resolved transient photoconductivity and charged-particle induced conductivity, the collection distance (d) that a free carrier drifts under the influence of an applied electric field was measured. Our data indicate that there is a gradient in the collection distance through the material. This gradient in electrical properties has implications for electronic uses of CVD diamond.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.111501
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  • 3
    Electronic Resource
    Electronic Resource
    A general route to enantiomerically pure sulfoxides from a chiral sulfite (1991)
    s.l. : American Chemical Society
    The @journal of organic chemistry 56 (1991), S. 5991-5999 
    Details
    ISSN: 1520-6904
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/jo00021a008
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  • 4
    Electronic Resource
    Electronic Resource
    Solid angle as steric parameter of acyclic saturated groups (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 3 (1991), S. 242-253 
    Details
    ISSN: 0899-0042
    Keywords: steric effects ; geometric model ; ester hydrolysis ; ester conformation ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: With the early aim of quantifying steric consequences of chirality, efforts to define a nonempirical steric parameter of chemical groups are reported. Steric hindrance of a reacting center by any acyclic saturated R group has been characterized by a geometric “axial steric parameter”: the solid angle of R. When the group is a “symmetric top substituent” (i.e., when all the terminal atoms are equivalent), the solid angle matches the solid angle of a cone envelope of R. The definition of this cone is compared with Tolman's definition of a ligand cone in organometallic complexes. The chemical significance of this parameter is shown by an excellent correlation with the Dubois' experimental steric parameter E′s. Modeling steric repulsion by the cone of R, and correcting solid angles for conformational effects, only 3 empirical coefficients are needed to calculate 33 values of E′s with less than 10% error. The cone model is suggested to be relevant within the limits of random and independent free rotations about all the bonds in the C-R group. A separation between “axial cone steric hindrance” and other steric effects is proposed. The basic model and the corrections proposed allow the conformational features of esters to be discussed.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530030406
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  • 5
    Electronic Resource
    Electronic Resource
    Role of EP2 receptors and cAMP in prostaglandin E2 regulated expression of type I collagen α1, lysyl oxidase, and cyclooxygenase-1 genes in human embryo lung fibroblasts (1998)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 71 (1998), S. 254-263 
    Details
    ISSN: 0730-2312
    Keywords: lysyl oxidase ; cyclooxygenase-1 ; type I collagen α1 ; prostaglandin E2 ; prostaglandin E2 receptors ; cyclic AMP ; interleukin-1β ; transforming growth factor-β ; forskolin ; 11-deoxy PGE1 ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: In a recent communication, we demonstrated that prostaglandin E2 (PGE2) lowers basal while it ablates interleukin-1β( (IL-1β) and transforming growth factor-β (TGFβ) upregulated lysyl oxidase (LO) mRNA levels. Correspondingly, PGE2 increases cyclooxygenase-1 (COX1) mRNA in diploid, human embryo lung fibroblasts (IMR90) [Roy et al., 1996]. We now report that these actions by PGE2 are routed through cAMP via the PGE2, EP2 receptor. Among the PGE2 receptor types, the IMR90 predominantly express the EP2 mRNA. These cells also express EP3 and EP4 mRNA at comparatively low levels. Northern blot analyses show that 11-deoxy PGE1, an EP2/EP4 agonist, emulates the action of PGE2. In a similar manner to PGE2, 11-deoxy PGE1 decreases basal and TGF-β induced type I collagen α1 (COL) mRNA, basal and IL-1β induced LO mRNA while it increases COX1 mRNA. Sulprostone, an EP3/EP1 agonist, has no effect on the expression of these three genes. Forskolin, an adenylate cyclase activator, acts in a very similar manner to PGE2or 11-deoxy PGE1. It suppresses both basal and TGF-β induced COL mRNA levels. Both PGE2 and 11-deoxy PGE1 increase cAMP to a level comparable with forskolin. The role of the EP2 receptor in controlling collagen production is further underscored in the immortalized Rat-1 fibroblasts, derived from Fischer rat embryos, which do not express detectable EP2 mRNA. In these cells, PGE2 has little effect on COL mRNA level, whereas forskolin increases it. Furthermore, forskolin increases cAMP level in Rat-1 cells, whereas PGE2 does not. Overall, these results illustrate that much of the PGE2 action on the expression of COL, LO, and COX1 genes is mediated through the EP2 receptor and a subsequent increase in intracellular cAMP. J. Cell. Biochem. 71:254-263, 1998. © 1998 Wiley-Liss, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Synthesis of tertiary phosphine oxides mediated by SmCp2 or Sml2 (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 9 (1995), S. 431-435 
    Details
    ISSN: 0268-2605
    Keywords: samarium di-iodide ; divalent samarium ; samarium dicyclopentadienide ; phosphine oxide ; Michael additions ; diphenyl alkyl phosphine oxide ; phenyl dialkyl phosphine oxide ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Tertiary phosphine oxides are prepared under mild conditions by sequential addition of diphenylphosphinoyl chloride to divalent samarium compounds (SmCp2 and SmI2) followed by reaction with various electrophiles such as organic halides, tosylates, epoxides or α,β-unsaturated ketones. Biscyclopentadienylsamarium (SmCp2) gives better yields than SmI2. Similar reactions, using phenylphosphonoyl dichloride, SmI2 and subsequent addition of two equivalents of activated halides, yield the corresponding tertiary phosphine oxides.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aoc.590090510
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