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  • 11
    Electronic Resource
    Electronic Resource
    Role of Endothelium/Nitric Oxide and Cyclic AMP in Isoproterenol Potentiation of 17ß-Estradiol-Mediated Vasorelaxation (2002)
    350 Main Street , Malden , MA 02148 , USA. , and 9600 Garsington Road , Oxford OX4 2DQ , England . : Blackwell Science Inc
    Journal of cardiac surgery 17 (2002), S. 0 
    Details
    ISSN: 1540-8191
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Estrogen exerts vasorelaxation and cardiac protection via multiple cellular mechanisms. Estrogen modifies vasodilatation induced by certain relaxants such as ß-adrenoceptor agonists. However, little is known whether low concentrations of ß-adrenoceptor agonists would also influence the acute relaxant response to estrogen. The present study was designed to investigate the synergistic interaction between isoproterenol and 17ß-estradiol, and to study the role of endothelium and cyclic AMP-dependent pathway in this interaction. Changes in vessel tone of the isolated rat mesenteric artery rings were measured by force-displacement Grass transducer. In 9,11-dideoxy-11α, 9α-epoxy-methanoprostaglandin F2α- preconstricted endothelium-intact rings, 17ß-estradiol induced concentration-dependent relaxation with pD2 of 5.074 ± 0.043. Pretreatment of endothelium-intact rings with isoproterenol (1-3 × 10-9 M, 1-h incubation time) significantly enhanced 17β-estradiol-induced relaxation. Longer incubation (2.5 h) did not produce further amplifying effect. This effect was inhibited by Rp-cGMPS triethylamine (3 × 10-6 M), and disappeared in the presence of 3 × 10-5 M NG-nitro-L-arginine methyl ester or in the endothelium-denuded rings. The effect of isoproterenol was partially antagonized by propranolol (3 × 10-6 M), ICI 118,551 (3 × 10-6 M) but not by atenolol (10-5 M). None of three β-adrenoceptor antagonists affected 17ß-estradiol-induced relaxation in the absence of isoproterenol. Rp-cAMPS triethylamine (3 × 10-6 M) abolished the effect of isoproterenol. Besides, exposure to 3 × 10-9 M forskolin for 1 h also potentiated the relaxant response to 17β-estradiol. In summary, this isoproterenol enhancement was dependent on the presence of endothelium and abolished by L-NAME via a β2-adrenoceptor-mediated cyclic AMP-dependent mechanism. These data also indicate the possible existence of cyclic AMP-dependent nitric oxide-producing pathway in the regulation of the vascular response to vasodilators. (supported by UPGC Direct Grant)
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1540-8191.2002.10149.x
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  • 12
    Electronic Resource
    Electronic Resource
    Effects of planting Eulaliopsis binata on soil quality in the red soil region of southern China (2004)
    Oxford, UK : Blackwell Publishing Ltd
    Soil use and management 20 (2004), S. 0 
    Details
    ISSN: 1475-2743
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract. Eulaliopsis binata is a perennial fibre-producing plant, which has a growing market in southern China and also has favourable effects on soil and water conservation. In the present study, three land use treatments, Eulaliopsis binata (EB), undisturbed natural grassland (NG) and orange grove (OG) were compared with respect to their effects upon a red soil after 20 years. Of these treatments, EB had the most favourable effects on soil physicochemical and biological properties and on soil microclimate. These properties were combined in a relative soil quality index (RSQI), which gave values in the order EB 〉 OG 〉 NG. Soil microbial numbers and enzyme activities were shown to be sensitive indicators of overall changes in soil properties.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1475-2743.2004.tb00350.x
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  • 13
    Electronic Resource
    Electronic Resource
    Changes in soil quality due to introduction of broad-leaf trees into clear-felled Chinese fir forest in the mid-subtropics of China (2004)
    Oxford, UK : Blackwell Publishing Ltd
    Soil use and management 20 (2004), S. 0 
    Details
    ISSN: 1475-2743
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract. After clear-felling of a first generation Chinese fir (Cunninghamia lanceolata) forest, mixed stands of Chinese fir and Michelia macclurei (a broadleaf tree) (MCM), pure M. macclurei stands (PMS) and pure Chinese fir stands (PCS) were established in 1983. The effects on soil were evaluated 20 years after planting by measuring physicochemical, microbiological and biochemical parameters. Both broadleaf monoculture and mixtures of broadleaf and conifer exerted a favourable effect on soil fertility. A soil quality index (SQI) decreased in the order: PMS (0.62) 〉 MCM (0.57) 〉 PCS (0.41). Improvement in soil quality, enhanced biological activity and forest productivity demonstrated that mixed stands are an effective measure to maintain sustainable forest productivity, as well as to control soil degradation under successive stands of Chinese fir. In addition, since the microbiological and biochemical parameters measured were sensitive to the forest management, they may be potential indicators for assessing the sustainability of different management systems. The results also showed that total organic carbon, cation exchange capacity and microbial biomass carbon are effective indicators of the improvement or deterioration of soil quality under forest.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1475-2743.2004.tb00391.x
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  • 14
    Electronic Resource
    Electronic Resource
    Polarized edge-incident photovoltage spectroscopy and reflectance characterization of a GaAs/GaAlAs vertical-cavity surface-emitting laser structure (2002)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 80 (2002), S. 752-754 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Polarized edge-incident photovoltage spectroscopy (EPVS) and normal-incident reflectance (NIR) studies are performed at room temperature on a bare as-grown wafer of GaAs/GaAlAs-based vertical-cavity surface-emitting laser (VCSEL) structure, designed for emitting at a wavelength near 850 nm. In addition to the interference features related to the properties of the mirrors stacks, in the NIR spectrum only the Fabry–Pérot cavity mode is clearly visible, while the polarized EPV spectra are used to identify the wavelength of fundamental and higher-order transitions from the quantum wells (QWs) in the active region. By comparing the experimental results with theoretical calculations, we are able to ascertain the Al composition, structure parameters, and material quality of the QWs in the VCSEL active regions. We demonstrate the potential of polarized EPVS for the contactless and nondestructive characterization of VCSELs at room temperature. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1445463
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  • 15
    Electronic Resource
    Electronic Resource
    Surface photovoltage spectroscopy characterization of a GaAlAs/InGaAs/GaAs pseudomorphic high electron mobility transistor structure (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 949-951 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Using room-temperature surface photovoltage spectroscopy (SPS), we have characterized a GaAlAs/InGaAs/GaAs pseudomorphic high electron mobility transistor (pHEMT) structure. Signals have been observed from every region of the sample. From a line shape fit to the normalized first derivative of the surface photovoltage signal with respect to photon energy, the two-dimensional electron gas density (Ns) was obtained and found to be in good agreement with Hall measurement. The Al composition and the properties of the GaAs/GaAlAs superlattice buffer layer also were obtained from the SPS spectrum. The results demonstrate the considerable potential of SPS for the contactless and nondestructive characterization of pHEMT structures at room temperature. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1392974
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  • 16
    Electronic Resource
    Electronic Resource
    Surface photovoltage spectroscopy, photoreflectance, and reflectivity characterization of an InGaAs/GaAs/GaAlAs vertical-cavity surface-emitting laser including temperature dependence (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 37-39 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have investigated an InGaAs/GaAs/GaAlAs vertical-cavity surface-emitting laser using surface photovoltage spectroscopy (SPS) in the temperature range of 15 K〈T〈400 K. For comparison purposes, we have also (a) measured temperature-dependent photoreflectance (PR) and normal-incidence reflectivity (NIR); and (b) calculated the number of photoexcited carriers (PEC), which is related to the SPS signal. The SPS spectra exhibit both the fundamental conduction to heavy-hole (1C–1H) excitonic transition and cavity mode plus a rich interference pattern related to the properties of the mirror stack. The PR data show only the 1C–1H excitonic transition (plus Franz–Keldysh oscillations) while the cavity mode is detected by NIR. The temperature variation of 1C–1H/cavity mode is the same for SPS and PR/SPS and NIR. The SPS interference pattern from the DBRs is in good agreement with the PEC calculation. This experiment demonstrates the considerable potential of SPS for the characterization of these devices. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.126869
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  • 17
    Electronic Resource
    Electronic Resource
    Self-field ac losses of a twisted multifilamentary (Bi, Pb)2Sr2Ca2Cu3O10/AgAu tape (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 3983-3985 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Self-field loss measurements at 77 K on a superconducting (Bi, Pb)2Sr2Ca2Cu3O10/AgAu tape with twisted filaments are presented. Using the first- and third-harmonic components of the electric field, the hysteretic losses are separated from the total loss. At peak transport currents less than half the critical current, the hysteretic losses are considerably reduced. However, sizable nonhysteretic losses are also observed. At higher currents, the hysteretic loss increases, dominating the total loss, and is similar to that for an untwisted tape. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.126842
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  • 18
    Electronic Resource
    Electronic Resource
    Piezoreflectance study of silicon carbon nitride nanorods (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 2044-2046 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Detailed piezoreflectance (PzR) measurements of quasialigned silicon carbon nitride nanorods in the temperature range between 15 and 400 K were performed. The direct band-to-band transition energies Egd at various temperatures were determined accurately through line shape fit of the experimental PzR spectra. The temperature dependence of Egd is analyzed by the Varshni equation [Y. P. Varshni, Physica, (Amsterdam) 34, 149 (1967)] and an expression containing the Bose–Einstein occupation factor for phonons proposed by L. Viña, S. Logothetidis, and M. Cardona [Phys. Rev. B 30, 1979 (1984)]. The parameters that describe the temperature dependence of Egd are evaluated and discussed. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.126249
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  • 19
    Electronic Resource
    Electronic Resource
    Surface photovoltage spectroscopy characterization of a GaAs/GaAlAs vertical-cavity-surface-emitting-laser structure: Angle dependence (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 3227-3229 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An angle-dependent surface photovoltage spectroscopy (SPS) study has been performed at room temperature on a GaAs/GaAlAs-based vertical-cavity-surface-emitting-laser (VCSEL) structure emitting at a wavelength near 850 nm. For comparison purposes, we have also measured the angle-dependent reflectance (R). The surface photovoltage spectra exhibit both the fundamental conduction to heavy-hole (1C–1H) excitonic transition and cavity mode plus additional interference features related to the properties of the mirror stacks, whereas in the R spectra only the cavity mode and interference features are clearly visible. The energy position of the excitonic feature is not dependent on the angle of incidence, in contrast to that of the cavity mode, whose angular dependence can be fitted with a simple model. This study demonstrates the considerable potential of angle-dependent SPS for the contactless and nondestructive characterization of VCSEL structures at room temperature. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1418027
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  • 20
    Electronic Resource
    Electronic Resource
    Automatic feature selection for unsupervised image segmentation (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 1230-1232 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A computational bottleneck is often imposed by the volume of image data generated in disciplines such as remote sensing and medical imaging, especially in situations where automatic analysis or interpretation is required. Segmentation and classification tasks that utilize multivariate data can be impeded by this dimensionality. A general-purpose unsupervised image segmentation system is presented here for the automatic detection of image regions exhibiting different visual texture properties. A suboptimal feature selection procedure is proposed to automatically select the set of texture features best suited for the particular application. Results are presented for the segmentation of ground-penetrating radar images for generating automatic subsurface reports. The reduction in the size of the feature set both reduces the computation time and improves the accuracy. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1289267
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