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  • 1
    Electronic Resource
    Electronic Resource
    Influence of lateral propagating modes on laser output characteristics in selectively oxidized vertical cavity surface-emitting lasers with double oxide layers (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 3519-3524 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The influence of lateral propagating modes on the threshold current and the spontaneous emission factor in selectively oxidized vertical cavity surface-emitting lasers (VCSELs) is investigated based on the mode behaviors of lateral propagating modes and the rate equation model. The numerical results show that the lateral propagating modes may be trapped in the aperture region for the selectively oxidized VCSEL with two oxide layers, one above and one below the active region. The output characteristics of VCSELs can be affected due to the reabsorption of the quasitrapped lateral propagating modes. A lower threshold current can be expected for a VCSEL with double oxide layers than that with a single oxide layer. The numerical results of rate equations also show that a larger spontaneous emission factor can be obtained by fitting the output–input curves for the VCSEL with double oxide layers.© 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.371252
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  • 2
    Electronic Resource
    Electronic Resource
    Synthesis and Morphology of Niobium Monocarbide Whiskers (1998)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 81 (1998), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Niobium monocarbide (NbC) whiskers were successfully synthesized by heating mixtures of niobium oxide (Nb2O5) powder and carbon black in an argon atmosphere to temperatures in excess of 1100°C. The whiskers were mainly cuboid or cycloid needles with a square-pyramid-shaped tip and were 0.1-2.0 µm in width and 5-100 µm in length. The particular shape of the whiskers and the very low impurity levels detected suggest that the NbC whiskers grew via a solid-vapor growth process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1998.tb02535.x
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  • 3
    Electronic Resource
    Electronic Resource
    Analysis of the optical confinement factor in semiconductor lasers (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 3827-3830 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We derive formulas for the optical confinement factor Γ from Maxwell's equations for TE and TM modes in the slab waveguide. The numerical results show that the formulas yield correct mode gain for the modes propagating in the waveguide. We also compare the formulas with the standard definition of Γ as the ratio of power flow in the active region to the total power flow. The results show that the standard definition will underestimate the difference of optical confinement factors between TE and TM modes, and will underestimate the difference of material gains necessary for polarization insensitive semiconductor laser amplifiers. It is important to use correct optical confinement factors for designing polarization insensitive semiconductor laser amplifiers. For vertical cavity surface-emitting lasers, the numerical results show that Γ can be defined as the proportion of the product of the refractive index and the squared electric field in the active region. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361809
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  • 4
    Electronic Resource
    Electronic Resource
    Effect of reflectivity at the interface of oxide layer on transverse mode control in oxide confined vertical-cavity surface-emitting lasers (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 3769-3772 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The transverse mode control in oxide confined vertical-cavity surface-emitting lasers is discussed by modeling the dielectric aperture as a uniform waveguide and an extra reflectivity at the oxide layer. The phase of the extra reflectivity and the refractive index step can be adjusted to change the mode threshold gain. We calculate the lateral refractive index step from the mode wavelength difference between aperture and perimeter modes, and compare it with that obtained from the weighted average index. The mode reflectivity in terms of the lateral optical confinement factor at the oxide layer is considered in calculating the threshold gain for transverse modes. The numerical results show that higher transverse modes can be suppressed by adjusting the position of a thin AlAs-oxide layer inside a three-quarter-wave layer in the distributed Bragg reflector. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.366605
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  • 5
    Electronic Resource
    Electronic Resource
    Femtosecond Z-scan measurement of GaN (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 75 (1999), S. 3524-3526 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Nonlinear refractive index n2 of GaN was measured for the below-band-gap ultraviolet (UV) wavelength region using Z-scan techniques with femtosecond UV pulses. A large nonlinear refractive index of −2.9±1.2×10−12 cm2/W was obtained at a wavelength of 368 nm. The distribution of n2 versus wavelength was found to be consistent with a model described by the quadratic Stark effect, which is the dominant factor contributed to the nonlinear refractive index near the band gap. Our experiments show that GaN is an excellent nonlinear material with large negative n2 in the UV region. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.125376
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  • 6
    Electronic Resource
    Electronic Resource
    Improved Strength Recovery of a Titanium Carbide/Silicon Nitride Composite from Thermal Shock Damage via Microwave Heating (1999)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 82 (1999), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Microwave processing has been used to heat treat a TiC/Si3N4 ceramic composite. The strength degradation from thermal shock was substantially recovered. The recovery rate was much greater with microwave heating than with conventional heat treatment at equivalent average temperature. The mechanism of strength recovery was hypothesized to be microwave radiation, which caused selective heating of TiC particles, enhanced the reaction of grain boundaries, and resulted in the sintering of microcracks around TiC particles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1999.tb01959.x
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  • 7
    Electronic Resource
    Electronic Resource
    In Situ Synthesis of Yttria-Stabilized Tetragonal Zirconia Polycrystal Powder Containing Dispersed Titanium Carbide by Selective Carbonization (1999)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 82 (1999), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Reaction thermodynamics was utilized to analyze the selective carbonization conditions of ZrO2-TiO2-Y2O3 ultrafine powder and to define the temperature range of the selective carbonization. The ZrO2-TiO2-Y2O3 powder was prepared by coprecipitation from a solution containing Zr4+, Ti4+, and Y3+. The powder was selectively carbonized at 1350°, 1450°, 1550°, and 1650°C, respectively, for 2 h under argon atmosphere with sucrose as the carbon source. The resulting product was analyzed by X-ray diffraction. The experimental results indicated that the ZrO2-TiO2-Y2O3 powder could be selectively carbonized in situ at 1450°C to form a carbonized powder which was composed of TiC and t-ZrO2. It was also found that zirconium carbide could be formed at 1550°C, which is much lower than the carbonization temperature of ZrO2 defined by thermodynamics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1999.tb01970.x
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  • 8
    Electronic Resource
    Electronic Resource
    Micro-Electroporation: Improving the Efficiency and Understanding of Electrical Permeabilization of Cells (1999)
    Springer
    Biomedical microdevices 2 (1999), S. 145-150 
    Details
    ISSN: 1572-8781
    Keywords: electroporation ; micro-electroporation chip ; cell membrane electrical currents
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract Electroporation is commonly used in biotechnology to introduce macromolecules into cells. We have developed a micro-electroporation chip that incorporates a live biological cell in the electrical circuit. The chip configuration forces electrical currents to pass through the cell, thereby producing electrically measurable information about the electroporation state of the cell. The cell membrane electrical properties make the cell function as a diode in the electroporation current-voltage range. The chip is transparent in the area of the cell to allow microscope viewing. during electroporation. This chip may be used to study the fundamental biophysics of cell electroporation and in biotechnology for controlled macromolecule introduction in individual cells. We describe the chip principle and show results on the electrical current-voltage pattern during reversible and irreversible electroporation in individual cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009901821588
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  • 9
    Electronic Resource
    Electronic Resource
    COMMUNICATION: Mild reaction of ethyl cellulose and N- phenylmaleamic acid in acetic anhydride (1997)
    Springer
    Cellulose 4 (1997), S. 233-238 
    Details
    ISSN: 1572-882X
    Keywords: ethyl cellulose ; maleanilic acid ; N-phenylmaleamic acid ; Michael addition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The reaction at room temperature of ethyl cellulose (EC) and N-phenylmaleamic acid (NPMA) (maleanilic acid) in acetic anhydride with a catalytic amount of anhydrous sodium acetate resulted in a Michael type of product whereby a cellulose ether was formed. The cyclisation product N-phenylmaleimide was minor.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018487823326
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  • 10
    Electronic Resource
    Electronic Resource
    COMMUNICATION: New derivatives of ethyl cellulose (1997)
    Springer
    Cellulose 4 (1997), S. 247-253 
    Details
    ISSN: 1572-882X
    Keywords: ethyl cellulose ; hydroxyethylphthalimide ; carboxymethylation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Triethylamine-mediated carboxymethylation of ethyl cellulose using monochloroacetic acid produced a hydroxymethyl acetate derivative (I). The derivative (I) was subsequently converted to a phthalimidoethyl-ethyl cellulose ether derivative by reacting it with β-hydroxyethyl phthalimide using concentrated sulphuric acid as the catalyst. The elemental analysis agreed with the calculated values using an anhydroglucose unit formula that incorporates the degree of substitution. Mechanisms for the formation of these derivatives are proposed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018491924235
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