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  • 1
    Electronic Resource
    Electronic Resource
    Polarization induced modification of thermal radiative properties of solid density plasmas produced by subpicosecond laser (2001)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 8 (2001), S. 5239-5243 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Near solid density plasmas have been obtained by the interaction of ultraintense (2×1018 W cm−2) clean laser pulses with targets composed of different thickness of Al on a Si substrate. The depth of the x-ray emission and spectral shapes were measured using x-ray spectroscopy, which simultaneously characterized the emitting plasma and the suprathermal electron distribution. Strong modifications of the plasmas thermal radiative properties have been observed, for the first time, by changing the laser polarization from S to P. This correlates with an increase of suprathermal electrons production. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1415749
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  • 2
    Electronic Resource
    Electronic Resource
    Ge/Si interdiffusion in the GeSi dots and wetting layers (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 4290-4292 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The Ge/Si interdiffusion in GeSi dots grown on Si (001) substrate by gas-source molecular beam epitaxy is investigated. Transmission electron microscopy images show that, after annealing, the aspect ratio of the height to base diameter increases. Raman spectra show that the Si–Ge mode redshifts and the intensity of the local Si–Si mode increases with the increase of annealing temperature, which suggests the Ge/Si interdiffusion during annealing. The photoluminescence peaks from the dots and the wetting layers show blueshift due to the atomic intermixing during annealing. The interdiffusion thermal activation energies of GeSi dots and the wetting layers are 2.16 and 2.28 eV, respectively. The interdiffusion coefficient of the dots is about 40 times higher than that of wetting layers and the reasons were discussed. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1403667
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  • 3
    Electronic Resource
    Electronic Resource
    Characterization of a subpicosecond x-ray streak camera for ultrashort laser-produced plasmas experiments (2000)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 71 (2000), S. 3627-3633 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We present results of the characterization of an ultrafast x-ray streak camera, based on Photonis (formerly Philips Photonics) P860 tube, developed for use in ultrashort laser-produced plasma research. The streak camera presented here (called PX1) has been extensively characterized with continuous and pulsed x-ray sources. Time resolution of 350 fs in the keV x-ray range has been achieved, while maintaining a high spatial resolution of 40 μm along a direction perpendicular to the time dispersion axis. It is shown that the streak camera response is lower when the photocathode is illuminated by a pulsed source than when used with a continuous one. This effect seems to be related to a change in the phosphor response. The camera has been used to achieve high-resolution subpicosecond time-resolved spectroscopy of ultrashort laser plasmas allowing the measurements of K-shell line emission durations of 700 fs. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1310347
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  • 4
    Electronic Resource
    Electronic Resource
    Effects of interdiffusion on the band alignment of GeSi dots (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 1980-1982 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The interdiffusion effects on the band alignment of the GeSi dots embedded in Si matrix were studied by temperature- and excitation-power-dependent photoluminescence measurements. A different power-dependent behavior of the photoluminescence for the as-grown and the annealed samples was observed. It was suggested that the band alignments of the dots changed from type II to type I after annealing due to the Ge/Si interdiffusion. The decrease of the valence band offset, which was also induced by the Ge/Si interdiffusion, was observed from the temperature-dependent photoluminescence measurements. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1405152
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  • 5
    Electronic Resource
    Electronic Resource
    Lattice strains and composition of self-organized Ge dots grown on Si(001) (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 3397-3399 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: X-ray diffraction measurements at different grazing angles for self-organized Ge dots grown on Si(001) are carried out by using synchrotron radiation as a light source. The lattice parameters parallel and perpendicular to the surface are determined from the grazing angle and ordinary x-ray diffraction spectra. A 1.2% lattice constant expansion parallel to the interface and a 3.1% lattice expansion along the growth direction, as compared with the Si lattice, are found within the Ge dots. Based on the Poisson equation and the Vegard law, the Ge dot should be a partially strain relaxed SiGe alloy with the Ge content of 55%. The composition change in Ge dots is suggested to be caused by the atomic intermixing during the islanding growth. In the small grazing angle x-ray diffraction spectrum, a peak located at the higher angle side of Si(220) is observed. The origin of this peak is attributed to the near surface compressive strain in the peripheral substrate regions surrounding the Ge dots. This compressive strain is induced by the formation of Ge dots and leads to a −0.8% lattice constant change parallel to the interface. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.126658
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  • 6
    Electronic Resource
    Electronic Resource
    Silicon-based photonic crystal heterostructure (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 3395-3397 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A silicon-based one-dimensional photonic crystal heterostructure is proposed, and its applications to an omnidirectional reflector and a transverse electric/transverse magnetic (TE/TM) splitter are illustrated. The photonic crystal heterostructure consists of two sets of multilayers, each has six periods of bilayers of poly-silicon and silicon dioxide. When the incident light comes from a medium with refractive index lower than 1.16, there is a frequency range over which of both TE and TM polarizations will be totally reflected at any incident angle. In such a case, the photonic crystal heterostructure can be used as a low loss omnidirectional dielectric reflector. However, when the refractive index of the medium is higher than 1.16, the heterostructure will serve as a good TE/TM splitter of very low crosstalk within certain ranges of light frequency and incident angle. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1421093
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  • 7
    Electronic Resource
    Electronic Resource
    Band alignments and photon-induced carrier transfer from wetting layers to Ge islands grown on Si(001) (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 78 (2001), S. 1763-1765 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Temperature- and excitation-power-dependent photoluminescence measurements were carried out for the multilayer structure of Ge islands grown on a Si(001) substrate by gas-source molecular-beam epitaxy. When the excitation power increases from 10 to 400 mW, the photoluminescence peak from the Ge islands showed a large linear blueshift of 34 meV while that of the wetting layers did not change much. These two different power dependences are explained in terms of type-II and type-I band alignments for the islands and the wetting layers, respectively. When the sample temperature increased from 8 to 20 K, an anomalous increase of photoluminescence intensity for islands was accompanied by a rapid decrease of that from the wetting layers, implying that a large portion of photon-induced carriers in the wetting layer was transfered to the neighboring islands and the Si layer, respectively, thus resulting in an increase of photoluminescence intensity of the islands. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1356454
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  • 8
    Electronic Resource
    Electronic Resource
    Ceramides induce apoptosis in HeLa cells and enhance cytochrome c-induced apoptosis in Xenopus egg extracts (2000)
    Springer
    Cellular and molecular life sciences 57 (2000), S. 1117-1125 
    Details
    ISSN: 1420-9071
    Keywords: Key words. Ceramide; HeLa cell; apoptosis; egg extract; cytochrome c; nuclei.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. Ceramide has been reported to induce typical apoptotic changes in nuclei incubated in a cell-free system, and that the addition of ceramide bypasses the requirement for mitochondria. Here, we explore the possible pathways by which ceramide induces apoptosis either in intact cells or in a cell-free system which we have developed. We found that in the cell-free system, C2-ceramide is not able to induce apoptosis in nuclei whereas cytochrome c does, but it is able to induce HeLa cells to undergo apoptosis. Ceramide is also not able to induce apoptosis when added into the cell-free system together with purified mitochondria. Further investigation showed that C2-ceramide at certain concentrations greatly increases nuclear apoptosis caused by cytochrome c in the cell-free system. From these results we conclude that the induction of apoptosis by ceramide may require intact cells in which some unknown signal transduction pathways are involved.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00000748
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  • 9
    Electronic Resource
    Electronic Resource
    Analysis of non-conducting powders by direct current glow discharge atomic emission spectrometry and application to the determination of rare earth elements (2000)
    Springer
    Fresenius' journal of analytical chemistry 366 (2000), S. 36-40 
    Details
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Some characteristics for the analysis of non-conducting powders by direct current glow discharge atomic emission spectroscopy (dc-GD-AES) were investigated. Copper powder was chosen as a suitable host conducting material for the analysis of mixtures of rare earth oxides. The influences of sample preparation and discharge parameters on the sputtering rate, discharge stability and emission intensity of the analyte were investigated systematically. The sample-to-sample reproducibility was discussed, and the average RSDs were in the range from 4% to 5%. The proposed method was applied to the analysis of a mixture of rare earth oxides and the results obtained were in good agreement with those obtained by ICP-AES.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002160050008
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  • 10
    Electronic Resource
    Electronic Resource
    Direct determination of trace rare earth elements in high purity Y2O3 using fluorination assisted electrothermal vaporization inductively coupled plasma atomic emission spectrometry with slurry sampling (2000)
    Springer
    Fresenius' journal of analytical chemistry 367 (2000), S. 259-263 
    Details
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A new method for the determination of trace amounts of 14 rare earth elements in high purity Y2O3 using fluorination assisted electrothermal vaporization inductively coupled plasma atomic emission spectrometry with slurry sampling was developed. A polytetrafluoroethylene (PTFE) emulsion was used as a fluorinating reagent to promote the vaporization of the analytes from graphite furnace. The main factors affecting analytical signals were investigated systematically. The interference of matrix could be minimized in the presence of PTFE. Under optimum conditions, the detection limits for rare earth elements were 0.032 ng∼2.52 ng and the relative standard deviations were in the range of 1.4% to 4.3%. The proposed method was applied to the direct analysis of high purity Y2O3 powder with satisfactory results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002160000329
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