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  • 1
    Electronic Resource
    Electronic Resource
    N-Alkyloxycarbonyl-3-aryloxaziridines: Their Preparation, Structure, and Utilization As Electrophilic Amination Reagents (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1691-1709 
    Details
    ISSN: 0947-6539
    Keywords: aminations ; electrophilic substitutions ; hydrazines ; oxaziridines ; pseudopeptides ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This paper reports the synthesis of a series of N-protected oxaziridines (N-Moc, Boc, Z or Fmoc) and discusses their ability to deliver their N-alkoxycar-bonyl fragment to amines, enolates, sulfur, and phosphorus nucleophiles (electrophilic amination). These oxaziridines are prepared by oxidation of the corresponding imines with oxone or anhydrous MCPBA lithium salt as the source of oxygen. They transfer their N-protected fragment to primary and secondary amines to give protected hydrazines in fair to excellent yield. The nitrogen transfer to free amino acids (in form of their R4N+ salts) is particularly fast, even at low temperature, providing L (or D) N-protected α-hydrazino acids. Enolates are C-aminated to give N-protected α-amino ketones, esters, or amides in modest yield, due to a side aldol reaction of the unreacted enolate with the released benzaldehyde. With tertiary amines (Et3N), sulfides (PhSMe), and phosphines (Ph3P), amination and oxidation proceed in a parallel way; the amount of amination product increases when the temperature is lowered (kinetic control). Some of the factors that can orient the oxaziridine reactivity towards amination or oxidation of nucleophiles are considered.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.19970031019
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  • 2
    Electronic Resource
    Electronic Resource
    Chemical sources of singlet oxygen. 3. Peroxidation of water-soluble singlet oxygen carriers with the hydrogen peroxide-molybdate system (1989)
    s.l. : American Chemical Society
    The @journal of organic chemistry 54 (1989), S. 726-728 
    Details
    ISSN: 1520-6904
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/jo00264a046
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  • 3
    Electronic Resource
    Electronic Resource
    Bis(.alpha.-lactams) derived from adamantane (1970)
    s.l. : American Chemical Society
    Journal of medicinal chemistry 13 (1970), S. 1021-1022 
    Details
    ISSN: 1520-4804
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/jm00299a070
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  • 4
    Electronic Resource
    Electronic Resource
    Fermi level position at metal Si1−x−yGexCy interfaces (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 5533-5542 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this work, we have investigated the Schottky barrier heights on n- and p-type Si1−x−yGexCy alloys with Zr, Ti, W, Ni and Pt as metals (ΦBn and ΦBp, respectively). Contacts on Si1−xGex alloys showed various behaviors depending on the metal work function Φm. For low-Φm metals (Zr, Ti), ΦBn increases with x, while ΦBp(x) decreases. For higher Φm metals (Pt), ΦBn strongly decreases with x. In the particular case of W (intermediate Φm value), ΦBp follows exactly the decrease of the SiGe band gap with x, while ΦBn remains constant. Nevertheless, whatever the metal, the reduction of the sum ΦBn+ΦBp gives the band-gap variation as a function of x, and the Fermi level is located at the same position for both n and p-type layers. A weaker effect of Φm on the Schottky barrier heights is observed compared to pure Si: the position of the Fermi level tends to remain in the range 0.60–0.65 eV below the conduction band, as soon as Ge is adding in Si. W contacts on Si1−x−yGexCy alloys evidenced the strong effect of C on ΦBn and ΦBp. The variations of ΦBn(y) or ΦBp(y) cannot be correlated to the band gap. In addition, the position of the Fermi level at the interface depends on the type of the alloy. Nevertheless, as in the case of the binary alloy SiGe, a weaker dependence on Φm compared to that observed for pure Si is shown. High values of the ideality factor with increasing the C content may evidence the presence of interfacial inhomogeneities, which could be correlated to C short range order. The present results have been compared to existing published results. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1365943
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  • 5
    Electronic Resource
    Electronic Resource
    Phase formation and strain relaxation during thermal reaction of Zr and Ti with strained Si1−x−yGexCy epilayers (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 1418-1423 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Silicides are often used in Si technology for both their ohmic and rectifying properties. In this work, we have compared Zr and Ti germanosilicides as possible metallic contacts on SiGeC alloys in terms of phase formation and stability of the unreacted SiGeC alloy. The germanosilicides are obtained after rapid thermal annealings of Zr or Ti with strained SiGeC layers. The interactions of the metal films with these alloys have been investigated by sheet resistance measurements, x-ray diffraction (XRD), cross-sectional transmission electron microscopy (TEM), and energy dispersive spectroscopy in situ in the TEM. Four crystal x-ray diffraction was performed to measure the residual strain of the unreacted SiGeC epilayer after reaction. The analyses indicate that the final compounds are the C49–Zr(SiGe)2 and C54–Ti(SiGe)2 phases, respectively: In both cases, the compound is formed by monocrystalline grains with various orientations. Nevertheless, neither XRD, nor sheet resistance measurements give any clear information about the C incorporation in the phase, when the reaction occurs with a SiGeC layer. We have observed that the use of Zr completely avoids Ge segregation with an uniform layer formed, while in the case of the reaction with Ti, the grains do not form a continuous layer and Ge-segregation is evidenced: A Ge-rich Si1−z−yGez(Cy) alloy is detected in between the metallic grains. In addition, an early strain relaxation of the unreacted SiGe layer is observed after reaction, and it is much more important after reaction with Ti. During the reaction with nearly compensated SiGeC layers, Zr totally prevents the initial state of strain, while Ti strongly affects the unreacted SiGeC alloy and destroys its initial state. All these results indicate that Zr may be an interesting candidate for realizing germanosilicide contacts on IV–IV alloys, due to its good thermal stability. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.373833
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  • 6
    Electronic Resource
    Electronic Resource
    The dynamics of spatiotemporal modulations (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Chaos 5 (1995), S. 578-588 
    Details
    ISSN: 1089-7682
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The modulational instability of traveling waves is often thought to be a crucial point in the mechanism of transition to space–time disorder and turbulence. The aim of this paper is to study the effect of spatiotemporal modulations on some dynamics u0(x,t), which may occur as an instability process when a control parameter varies, for instance. We analyze the properties of the modulated dynamics of the form g1(x)g2(t)u0(x,t) compared to those of the reference dynamics u0(x,t), using operator theory. We show that, if the reference dynamics is invariant under some space–time symmetry in the sense of Ref. [J. Nonlinear Sci. 2, 183 (1992)], the modulation has the effect of either deforming this symmetry or breaking it, depending on whether the corresponding operator remains unitary or not. We also demonstrate that the smallest Euclidean space containing the modulated dynamics has a dimension smaller than or equal to the smallest Euclidean space containing u0(x,t). The previous results are then applied to the case of modulated uniformly traveling waves. While the spatiotemporal translation invariance of the wave never persists in the presence of a modulation, the existence of a spatiotemporal symmetry depends on the resonance of the Fourier sidebands due to the modulation. In case of nonresonance, a spatiotemporal symmetry exists and is explicitly determined. In this situation, the modulated wave and the carrier wave have the same spectrum (up to a normalization factor), the same entropy, and the spatial (resp., temporal) two-point correlation is deformed only by the spatial (resp., temporal) modulation. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.166127
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  • 7
    Electronic Resource
    Electronic Resource
    Structural properties and stability of Zr and Ti germanosilicides formed by rapid thermal annealing (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 5468-5473 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Because of their good ohmic and rectifying properties, silicides are routinely used in Si technology. This approach has been recently extended to the novel devices produced using Si1−xGex alloys. Here, we study the Zr and Ti germanosilicides produced in the low thermal budget contact formation during Si/Si1−xGex heterodevice processing. Phase formation was monitored by combining a range of spectrometries with electron microscopy and x-ray diffraction techniques, while sheet resistance measurements allowed correlation of phase formation with film conductance. After completion of the reaction, the final crystalline phase was either C49–Zr(Si1−yGey)2 in the entire Ge composition (x) range, or C54–Ti(Si1−yGey)2 in the Ge composition range 0–0.47. In the Zr–Si–Ge system, the C49–Zr(Si1−yGey)2 formation temperature (Tf) decreases as x increases, and films formed at this temperature are continuous. Excess heating (above Tf) produces islanded films with embedded grains. A most significant feature of the results was that no Ge segregation was detected at any annealing temperature and that the Ge content in the C49 phase (y) remained equal to x for all x. This is in contrast to results on the C54–Ti(Si1−yGey)2 films, which were discontinuous when x〉0.10, and in which Ge segregation occurred in the form of Ge-rich SiGe decorations separating the germanosilicide grains. The Ge content in the final C54 phase (y) was always lower than the value of x in the initial SiGe alloy, and the measured sheet resistance of the corresponding contacts was large. Our results indicate that the alloys formed between Zr and Si1−xGex are good candidates as stable contacts on Si1−xGex, and hence that Zr should be preferred for contacting in Ge-rich SiGe-based applications. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1462855
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  • 8
    Electronic Resource
    Electronic Resource
    Schottky diodes with high series resistance: Limitations of forward I-V methods (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 7973-7984 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Some methods have been proposed to deduce the value of Schottky parameters from forward I-V characteristic even in the presence of a large series resistance. In this paper, some well-known methods have been applied to experimental data of a real diode and to computer calculated curves. A comparison is made between these methods and the standard procedure. Some indications are given on the validity and the main limitations of all these techniques. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357909
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  • 9
    Electronic Resource
    Electronic Resource
    INTEGRATION OF SIGNALING NETWORKS THAT REGULATE DICTYOSTELIUM DIFFERENTIATION (1999)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Cell and Developmental Biology 15 (1999), S. 469-517 
    Details
    ISSN: 1081-0706
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology , Medicine
    Notes: Abstract In Dictyostelium amoebae, cell-type differentiation, spatial patterning, and morphogenesis are controlled by a combination of cell-autonomous mechanisms and intercellular signaling. A chemotactic aggregation of ~105 cells leads to the formation of a multicellular organism. Cell-type differentiation and cell sorting result in a small number of defined cell types organized along an anteroposterior axis. Finally, a mature fruiting body is created by the terminal differentiation of stalk and spore cells. Analysis of the regulatory program demonstrates a role for several molecules, including GSK-3, signal transducers and activators of transcription (STAT) factors, and cAMP-dependent protein kinase (PKA), that control spatial patterning in metazoans. Unexpectedly, two component systems containing histidine kinases and response regulators also play essential roles in controlling Dictyostelium development. This review focuses on the role of cAMP, which functions intracellularly to mediate the activity of PKA, an essential component in aggregation, cell-type specification, and terminal differentiation. Cytoplasmic cAMP levels are controlled through both the regulated activation of adenylyl cyclases and the degradation by a phosphodiesterase containing a two-component system response regulator. Extracellular cAMP regulates G-protein-dependent and -independent pathways to control aggregation as well as the activity of GSK-3 and the transcription factors GBF and STATa during multicellular development. The integration of these pathways with others regulated by the morphogen DIF-1 to control cell fate decisions are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.cellbio.15.1.469
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  • 10
    Electronic Resource
    Electronic Resource
    Schottky barrier heights of W on Si1−xGex alloys (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 2520-2522 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The Schottky barrier height of W on p-type Si1−xGex/Si has been investigated as a function of composition (10%≤x≤33%) and Si1−xGex thickness for a given composition. The barrier height decreases with increasing Ge fraction and follows the rate of strain relaxation. These results suggest that the Fermi level at the interface is pinned relative to the conduction band.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.110468
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