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  • 1
    Electronic Resource
    Electronic Resource
    Optoelectronic properties of ZnSe/ZnMgSSe multiple quantum wells (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 3725-3729 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Optoelectronic properties of undoped ZnSe/ZnMgSSe multiple quantum wells (MQWs) grown by molecular beam epitaxy on (001) GaAs substrates have been investigated by photoluminescence, photoconductivity, and persistent photoconductivity (PPC) measurements. The features related to the band-to-band excitonic and impurity-related transitions of ZnSe/ZnMgSSe MQWs are observed and discussed. In addition, the parameters that describe the temperature dependence of the interband transition energy and broadening function of the excitonic feature are evaluated. PPC has been observed in undoped ZnSe/ZnMgSSe MQWs. The decay kinetics of the PPC effect can be described by a stretched-exponential function, Ippc(t)=Ippc(0)exp[−(t/τ)β], (0〈β〈1). Through the study of the PPC effect under various conditions, such as different temperature, different photon energy of photoexcitation, and different ZnSe well width, we identify that the carrier excitation from the defect level in ZnMgSSe barrier layer into the ZnSe well layer is the origin of the PPC effect in ZnSe/ZnMgSSe MQWs. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1350416
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  • 2
    Electronic Resource
    Electronic Resource
    Strong visible photoluminescence from SiO2 nanotubes at room temperature (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 78 (2001), S. 3791-3793 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The optical studies of SiO2 mesoporous materials with hierarchical tubules-within-tubule structure have been investigated by photoluminescence and Fourier-transform infrared transmittance (FTIR). Our results suggest that the radiative intensity can be strongly enhanced by annealing the samples in N2 environment. From the FTIR spectra, we have pointed out that the origin responsible for the strong emission is Si–OH complexes located on nanotube surface. It has been observed that after turning off the pumping laser, the photoluminescence signal of SiO2 nanotubes can persist for several seconds, which is much longer than that of most materials performed under similar conditions. We have found that the decay of the photoluminescence signal is due to the quantum tunneling process. These are triplet and singlet states of Si–OH complexes that are responsible for the observed persistent photoluminescence. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1370991
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  • 3
    Electronic Resource
    Electronic Resource
    Mechanism of photoluminescence in GaN/Al0.2Ga0.8N superlattices (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 3806-3808 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present photoluminescence (PL) and time-resolved photoluminescence measurements in GaN/Al0.2Ga0.8N superlattices grown by metalorganic chemical vapor deposition under the optimal GaN-like growth conditions. We found that the carrier confinement of our samples is better than most of the previous reports. The dependence of the PL emission energy and intensity on temperature, in the low temperature regime, is consistent with recombination mechanisms involving localized states attributed to a small degree of interface fluctuations. Picosecond time-resolved photoluminescence spectroscopy has been employed to probe the well-width dependence of the lifetime of these superlattices. We see that the recombination lifetime increases with the decrease of well width. This behavior can be interpreted by the fact that the effect of localization keeping carriers away from nonradiative pathways can be enhanced by a decrease in the well width. This explanation is consistent with the temperature-dependent PL data. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1420495
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  • 4
    Electronic Resource
    Electronic Resource
    Prediction of local cooling rates and cell survival during the freezing of a cylindrical specimen
    Amsterdam : Elsevier
    Cryobiology 25 (1988), S. 67-82 
    Details
    ISSN: 0011-2240
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/0011-2240(88)90022-3
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  • 5
    Electronic Resource
    Electronic Resource
    State, institutions and structural change
    Amsterdam : Elsevier
    Structural Change and Economic Dynamics 5 (1994), S. 293-313 
    Details
    ISSN: 0954-349X
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Economics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0954-349X(94)90006-X
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  • 6
    Electronic Resource
    Electronic Resource
    Regular copolyamides. II. Preparation and characterization of regular aliphatic copolyoxamidesFor Part I, see Chang and Vogl.1 (1977)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 15 (1977), S. 1043-1060 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Regular copolyoxamides were prepared from diamine-oxamides and aliphatic diacid chlorides by interfacial and solution polymerization. Interfacial polymerization is preferred with diamineoxamides where the diamine portion has two to six methylene groups and the diamine-oxamides are readily soluble in water. Regular aliphatic polyoxamides from diamine-oxamides are readily soluble in water. Regular aliphatic polyoxamides from diamine-oxamides with more than six methylene groups in the diamine portion of the molecule are better prepared by solution polymerization in dimethyl acetamide. Regular aliphatic oxamides are soluble in trifluoroacetic acid and hexafluoroisopropanol and show a considerable alternation of the melting point behavior in the diamine portion of the polyamides with up to five methylene groups. Copolyoxamides with two and four methylene groups melt higher than the copolyoxamides with three and five methylene groups. Aliphatic copolyoxamides/adipamides melt at approximately 260°C and show a steady decrease in melting points to about 220°C for polyoxamides with twelve methylene groups.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1977.170150503
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  • 7
    Electronic Resource
    Electronic Resource
    Regular copolyamides. I. A facile method for the preparation of diamine-oxamides (1977)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 15 (1977), S. 311-322 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: α,ω-Diamine-oxamides with 2-12 CH2 groups between the two amino groups were obtained by the reaction of the diamines and diethyl or dimethyl oxalate. Diethyl oxalate is added slowly to a substantial excess of diamine in the proper solvent over a period of time under controlled temperature conditions. All variables are very important for each individual diamine in order to obtain optimal conversions to the diamine-oxamides under the most favorable conditions. Diamine-oxamides were obtained in approximately 80% yield with only small amounts (5-10%) of the corresponding polyoxamides as the side product. Diamine-oxamides from diamines with less than six methylene groups are water-soluble. All diamine-oxamides show an alternation of their melting points and are useful intermediates for the preparation of regular copolyoxamides.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1977.170150205
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