| 1. |
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| 2. |
- Carolipio, E. M., et al.
(författare)
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The toroidicity-induced Alfven eigenmode structure in DIII-D : Implications of soft x-ray and beam-ion loss data
- 2001
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Ingår i: Physics of Plasmas. - : AIP Publishing. - 1070-664X .- 1089-7674. ; 8:7, s. 3391-3401
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Tidskriftsartikel (refereegranskat)abstract
- The internal structure of the toroidicity-induced Alfven eigenmode (TAE) is studied by comparing soft x-ray profile and beam ion loss data taken during TAE activity in the DIII-D tokamak [W. W. Heidbrink , Nucl. Fusion 37, 1411 (1997)] with predictions from theories based on ideal magnetohydrodynamic (MHD), gyrofluid, and gyrokinetic models. The soft x-ray measurements indicate a centrally peaked eigenfunction, a feature which is closest to the gyrokinetic model's prediction. The beam ion losses are simulated using a guiding center code. In the simulations, the TAE eigenfunction calculated using the ideal MHD model acts as a perturbation to the equilibrium field. The predicted beam ion losses are an order of magnitude less than the observed similar to6%-8% losses at the peak experimental amplitude of deltaB(r)/B(0)similar or equal to2-5x10(-4).
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| 3. |
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| 4. |
- Fu, Q. X., et al.
(författare)
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Doped ceria-chloride composite electrolyte for intermediate temperature ceramic membrane fuel cells
- 2002
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Ingår i: Materials letters (General ed.). - 0167-577X .- 1873-4979. ; 53:3, s. 186-192
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Tidskriftsartikel (refereegranskat)abstract
- A kind of oxide-salt composite electrolyte, gadolinium-doped ceria (GDC)-LiCl-SrCl2, prepared with hot-press technique, shows superior ionic conductivity, which is 2-10 times higher than that of GDC itself at the temperature range of 400-600 degreesC. More interestingly, not like the GDC electrolyte, which has some extent of electronic conduction under reducing atmosphere, the composite electrolyte is almost a pure ionic conductor, evidenced by the fuel cell's (FC) open circuit voltage (OCV) close to the theoretical one. The fuel cells based on this composite electrolyte show excellent power density output even at temperature as low as 500 degreesC (240 mW cm(-2)) in spite of the relatively thick electrolyte (0.4 mm). Such high performance, in combination with its low cost in both raw materials and fabrication process, make this kind of composite electrolyte a good candidate electrolyte material for future ultra-low-cost intermediate temperature ceramic membrane fuel cells (IT-CMFCs).
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| 5. |
- Fu, Q. X., et al.
(författare)
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Intermediate temperature fuel cells based on doped ceria-LiCl-SrCl2 composite electrolyte
- 2002
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Ingår i: Journal of Power Sources. - 0378-7753 .- 1873-2755. ; 104:1, s. 73-78
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Tidskriftsartikel (refereegranskat)abstract
- A new type of oxide-salt composite electrolyte, gadolinium-doped ceria (GDC)-LiCl-SrCl2, was developed and demonstrated its promising use for intermediate temperature (400-700 degreesC) fuel cells (ITFCs). The dc electrical conductivity of this composite electrolyte (0.09-0.13 S cm(-1) at 500-650 degreesC) was 3-10 times higher than that of the pure GDC electrolyte, indicating remarkable proton or oxygen ion conduction existing in the LiCl-SrCl2 chloride salts or at the interface between GDC and the chloride salts. Using this composite electrolyte, peak power densities of 260 and 510 mW cm(-2), with current densities of 650 and 1250 mA cm(-2) were achieved at 550 and 625 degreesC, respectively. This makes the new material a good candidate electrolyte for future low-cost ITFCs.
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| 6. |
- Fu, X, et al.
(författare)
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Oxytocin-induced oscillations of cytoplasmic Ca2+ in human myometrial cells.
- 2000
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Ingår i: Acta Obstetricia et Gynecologica Scandinavica. - 0001-6349 .- 1600-0412. ; 79:3
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: To investigate the mechanisms of oxytocin (OT) induced oscillations of the cytoplasmic Ca2+ concentration ([Ca2+]i) in cultured human myometrial cells.METHODS: [Ca2+]i was measured in individual myometrial cells by dual wavelength spectrophotofluorometry using the fluorescent indicator fura-2. Myometrium was obtained at abdominal hysterectomy (n=8) and during cesarean section (n=7).RESULTS: OT (10-300 nM) typically induced [Ca2+]i oscillations with frequencies in the 0.6-0.8/min range. There were no obvious differences in the responses of cells taken from non-pregnant and term pregnant women. The frequency and amplitude of the oscillations were not significantly affected by OT concentrations up to 300 nM. The amplitude of the oscillations decreased in the presence of the voltage-dependent Ca2+ channel antagonist verapamil and gradually disappeared in Ca2+-free medium. The oscillations were further blocked by the inorganic Ca2+ antagonist La3+ and by the intracellular Ca2+-ATPase inhibitor 2.5-di-tert-butylhydroquinone (DTBHQ). Caffeine inhibited the OT-induced oscillations in a concentration-dependent manner. DTBHQ and high concentrations of OT made [Ca2+]i remarkably sensitive to changes in the external Ca2+ concentration.CONCLUSIONS: The results indicate that OT-induced [Ca2+]i oscillations in human myometrial cells are due to inositol 1,4,5-trisphosphate-mediated release of intracellular Ca2+ combined with capacitative as well as voltage-dependent influx of the ion.
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| 7. |
- Fu, Y, et al.
(författare)
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Capacitance analysis for a metal-insulator-semiconductor structure with an ultra-thin oxide layer
- 2003
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Ingår i: Applied Physics A. - : Springer Science Business Media. - 0947-8396 .- 1432-0630. ; 76:1, s. 27-31
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Tidskriftsartikel (refereegranskat)abstract
- We have studied theoretically the capacitance characteristics of a metal-insulator-semiconductor structure with an ultra-thin oxide layer by self-consistently solving Schrodinger and Poisson equations. It is demonstrated that a diffused interface between Si and SiO2 results in a better agreement between the theoretical prediction of conduction current and experimental I-V data. The calculated steady-state capacitance, obtained both analytically and numerically, increases following the increase of the gate bias when the gate bias is small; it reaches a saturation value at intermediate gate bias. The capacitance decreases with increasing gate bias when the gate bias is rather large due to the depletion of the gate material. Simple analytical expressions for the gate capacitance are derived, based on quantum-mechanical considerations, for future device design. The steady-state capacitance of a metal-insulator-semiconductor structure with an oxide layer of 1.5-2.0 nm by state-of-the-art technology is 20 mF/m(2), while it is 40 mF/m(2) when the practical limit of SiO2 layer thickness, i.e. 10-12 Angstrom, is reached.
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| 8. |
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| 9. |
- Fu, Y, et al.
(författare)
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Electron mobilities, Hall factors, and scattering processes of n-type GaN epilayers studied by infrared reflection and Hall measurements
- 2003
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - : American Physical Society. - 1098-0121 .- 1550-235X. ; 67:11
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Tidskriftsartikel (refereegranskat)abstract
- We have studied the drift and Hall mobilities of electrons in metal-organic chemical-vapor-deposited wurtzite GaN thin films on sapphire substrate by infrared (IR) reflection and Hall measurements. By analyzing the Hall factor (the ratio between the drift mobility obtained from IR reflection spectra and the Hall mobility from the Hall measurements), it has been concluded that the electron mobility in GaN epilayer is determined by the ionized impurity when the electron concentration is low. At a high carrier concentration of 3.2x10(18) cm(-3), electronic states of more than 70 meV become populated taking into account the thermal excitation, so that the optical-phonon-scattering process becomes activated (the optical-phonon energy is 69.43 meV obtained from IR reflection measurements). Thus, in highly doped wurtzite GaN epilayers, ionized-impurity- and optical-phonon-scattering processes jointly determine the carrier transport properties.
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| 10. |
- Fu, Y, et al.
(författare)
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Formation and charge control of a quantum dot by etched trenches and multiple gates
- 2002
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Ingår i: Applied Physics A. - : Springer Science Business Media. - 0947-8396 .- 1432-0630. ; 74:6, s. 741-745
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Tidskriftsartikel (refereegranskat)abstract
- We have fabricated a GaAs/InGaAs/AlGaAs-based single-electron transistor (SET) formed by etched trenches and multiple gates. Clear Coulomb-blockade oscillations have been observed when the gate biases are scanned. By self-consistently solving three-dimensional Schrodinger and Poisson equations, we have studied the energy-band structure and the carrier distribution of our SET. General agreement between numerical simulation results and measurement data has been obtained, thus indicating the effectiveness of our SET-device design as well as the necessity of a complete three-dimensional quantum-mechanical simulation.
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| 11. |
- Fu, Y, et al.
(författare)
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Hole conduction characteristics of strained Si1-xGex/Si resonant tunneling diode
- 2002
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Ingår i: Physica. E, Low-Dimensional systems and nanostructures. - : Elsevier Science B.V., Amsterdam.. - 1386-9477 .- 1873-1759. ; 13:1, s. 72-79
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Tidskriftsartikel (refereegranskat)abstract
- We study the hole conduction characteristics of p-type strained Si1-xGex/Si double-barrier resonant tunneling diodes (RTD). By extensive theoretical calculation of the 6 x 6 k (.) p model together with the deformation potential to account to the strain in Si1-xGex layer, we have obtained the hole conduction characteristics which explains the recent experimental results of Han et al. (J. Cryst. Growth 209 (2000) 315), where it was reported that the low-bias resonance peak becomes dissolved by increasing the device temperature. The calculated I-V characteristics exhibits several resonance peaks, and the current density varies drastically (the second-resonance peak current density is higher than the first one by a factor of 10(3)). Since only resonance peak having high-enough current density is measurable, low-temperature I-V characterization can only dissolve high-bias resonance. Increasing the device temperature, low-bias resonance becomes significant due to thermal excitation.
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| 12. |
- Fu, Y, et al.
(författare)
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Optical spectra of low-dimensional semiconductors
- 2003
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Ingår i: Hongwai yu haomibo xuebao. - : Science Press. - 1001-9014. ; 22:6, s. 401-405
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Tidskriftsartikel (refereegranskat)abstract
- We have studied the optical spectra of low-dimensional semiconductor systems by calculating all possible optical transitions between electronic states. Optical absorption and emission have been obtained under different carrier population conditions and in different photon wavelengths. The line-shapes of the peaks in the optical spectrum are determined by the density of electronic states of the system, and the symmetries and intensities of these peaks can be improved by reducing the dimensionality of the system. Optical gain requires in general a population inversion, whereas for a quantum-dot system, there exists a threshold value of the population inversion.
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| 13. |
- Fu, Y, et al.
(författare)
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Photocurrents of 14 mu m quantum-well infrared photodetectors
- 2003
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Ingår i: Journal of Applied Physics. - : American Institute of Physics. - 0021-8979 .- 1089-7550. ; 93:12, s. 9432-9436
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Tidskriftsartikel (refereegranskat)abstract
- We study the factors that determine photogenerated carriers and response wavelengths of photocurrents of long wavelength (similar to14 mum) quantum well (QW) infrared photodetectors (QWIPs). The material structures of QWIPs are first characterized by the photoluminescence measurements (PL). By calculating the density of photogenerated carriers in the continuum above the energy barriers using the PL calibrated QWIP structures, we have demonstrated that due to the sample quality, the photocarriers can be either in miniband states (Bloch states in the multiple quantum wells), or they transport from one quantum well to the next in the form of running waves. By including possible scattering processes at the QWIP working temperature to link the theoretically calculated photocarrier density with the experimentally measured photocurrent, it is shown that the width of the photocurrent peaks of 14 mum GaAs/AlGaAs QWIPs under investigation is determined by the optical phonon emissions of photocarriers. We have further calculated the densities of photocarriers in the QWIPs reported in the literature. It is shown that the Bloch wave boundary conditions are appropriate for QWIPs with narrow QWs, whereas running wave boundary conditions are appropriate for wide QWs.
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| 14. |
- Fu, Ying, 1964, et al.
(författare)
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Photoluminescence spectra of doped GaAs films
- 2004
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Ingår i: Applied Physics A. - : Springer Science Business Media. - 0947-8396 .- 1432-0630. ; 79:3, s. 619-623
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Tidskriftsartikel (refereegranskat)abstract
- We have studied the dependence of the photoluminescence (PL) spectrum on the doping level and the film thickness of n-GaAs thin films, both experimentally and theoretically. It has been shown theoretically that modification of the PL spectrum of p-type material by p-type doping is very small due to the large valence-band hole effective mass. The PL spectrum of n-type material is affected by two factors: (1) the electron concentration which determines the Fermi level in the material; (2) the thickness of the film due to re-absorption of the PL signal. For the n-type GaAs thin films under current investigation, the doping level as well as the film thickness can be very well calibrated by the PL spectrum when the doping level is less than 2 x 10(18) cm(-3) and the film thickness is in the range of the penetration length of the PL excitation laser.
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| 15. |
- Fu, Y, et al.
(författare)
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Quantum mechanical model and simulation of GaAs/AlGaAs quantum well infrared photodetector-I optical aspects
- 2002
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Ingår i: Hongwai yu haomibo xuebao. - : Science Press. - 1001-9014. ; 21:5, s. 321-326
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Tidskriftsartikel (refereegranskat)abstract
- A complete quantum mechanical model for GaAs/AlGaAs quantum well infrared photodetectors(QWIPs) is presented here. The model consisted of four parts: (1) Starting with the description of the electromagnetic field of the infrared radiation in the QWIP, effective component of the vector potential [\A(z)\] along the QWIP growth direction (z-axis) due to the optical diffraction grating was calculated. (2) From the wave transmissions and the occupations of the electronic states, it was discussed that the dark current in the QWIP is determined by the drift-diffusion current of carriers thermally excited from the ground sublevel in the quantum well to extended states above the barrier. (3) The photocurrent was investigated by the optical transition (absorption coefficient between the ground state to excited states due to the nonzero-[\A(z)\]). (4) By studying the inter-diffusion of the At atoms across the GaAs/AlGaAs heterointerfaces, the mobility of the drift-diffusion carriers in the excited states was calculated, so the measurement results of the dark current and photocurrent spectra can be explained theoretically. With the complete quantum mechanical descriptions of (1-4), QWIP device design and optimization are possible.
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| 16. |
- Fu, Y, et al.
(författare)
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Quantum mechanical model and simulation of GaAs/AlGaAs quantum well infrared photodetector-II electrical aspects
- 2002
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Ingår i: Hongwai yu haomibo xuebao. - : Science Press. - 1001-9014. ; 21:6, s. 401-407
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Tidskriftsartikel (refereegranskat)abstract
- A complete quantum mechanical model for GaAs/AlGaAs quantum well infrared photodetectors (QWIPs) was presented. The photocurrent was investigated by the optical transition( absorption coefficient) between the ground state and the excited states due to the nonzero component of the radiation field along the sample growth direction. By studying the inter-diffusion of the Al atoms across the GaAs/AlGaAs heterointer faces, the mobility of the drift-diffusion carriers in the excited states was calculated. As a result, the measurement results of the dark current and the photocurrent spectra are explained theoretically.
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| 17. |
- Fu, Y., et al.
(författare)
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Reduced effective temperature of hot electrons in nano-sized metal-oxide-semiconductor field-effect transistors
- 2003
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Ingår i: Applied Physics A. - Berlin / Heidelberg : Springer Berlin/Heidelberg. - 0947-8396 .- 1432-0630. ; 77:6, s. 799-803
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Tidskriftsartikel (refereegranskat)abstract
- Hot electron effects have been extensively studied in metal-oxide-semiconductor field-effect transistors (MOSFETs). The importance of these effects when the dimensions are drastically reduced has so far not been thoroughly investigated. The scope of this paper is therefore to present a detailed study of the effective temperature of excess electrons in nanoscale MOSFETs by solving coupled Schrödinger and Poisson equations. It is found that the increased doping levels and reduced junction depths lead to substantially higher local Fermi levels in the source and drain regions. As a result, the temperature difference between electrons injected into the drain and local electrons is reduced. The scaling of the gate oxide thickness, as well as the drain voltage furthermore reduces the electron temperature in the drain. The detrimental effects of hot electron injection are therefore expected to be decreased by scaling the MOSFET.
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| 18. |
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| 19. |
- Li, Z-F, et al.
(författare)
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Determination of carrier-transfer length from side-wall quantum well to quantum wire by micro-photoluminescence scanning
- 2003
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Ingår i: Journal of Electronic Materials. - : Springer Science Business Media. - 0361-5235 .- 1543-186X. ; 32:8, s. 913-916
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Tidskriftsartikel (refereegranskat)abstract
- Micro-photoluminescence (mu-PL) line scanning across a single V-groove, GaAs/AlGaAs quantum wire (QWR) has been performed at room temperature, revealing a clear spatial-dependence of the PL. After fitting each PL spectrum by multi-Gaussian line shapes, intensity profiles of each PL component from confined structures have been obtained as functions of the scanning position. The PL quenching of a side-wall quantum well (SQWL) has been recognized in a certain area in the vicinity of the QWR and is interpreted by carrier transfer into the QWR within effective transfer length. By simulating the carrier-transfer process from SQWL to QWR as a convolution of a step function for carrier distribution and a Gaussian function for exciting laser irradiance, the effective transfer length of about 1.8+/-0.3 mum has, therefore, been concluded.
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| 20. |
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| 21. |
- Liu, Jing-fu, et al.
(författare)
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Ionic liquids/water distribution ratios of some polycyclic aromatic hydrocarbons
- 2004
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Ingår i: Journal of Chemical and Engineering Data. - : American Chemical Society (ACS). - 1520-5134 .- 0021-9568. ; 49:5, s. 1422-1424
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Tidskriftsartikel (refereegranskat)abstract
- By using the shake-flask procedure, the distribution ratios (D) at infinite dilution and 298.1 K of 15 polycyclic aromatic hydrocarbons (PAHs) between room-temperature ionic liquids, 1-alkyl-3-methylimiazolium hexafluorophosphates ([CnMIM] [PF6], n = 4 and 8), and water were determined. The log D values are in the range of 3.34-4.36, which increased very slowly with the molar mass of PAHs.
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| 22. |
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| 23. |
- Ouacha, H., et al.
(författare)
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Comparison between the noise properties of PtSi/p-Si1-xGex and Pt/p-Si1-xGex Schottky contacts prepared by co-sputtering and thermal reaction
- 2001
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Ingår i: Semiconductor Science and Technology. - : IOP Publishing. - 0268-1242 .- 1361-6641. ; 16:4, s. 255-259
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Tidskriftsartikel (refereegranskat)abstract
- The noise properties of Pt/p-Si1-xGex and PtSi/p-Si1-xGex (x = 0.14) Schottky contacts have been studied. The silicide layer PtSi was formed by thermal reaction (TR) of Pt with a silicon substrate and by co-sputtering (CS) of Pt and Si onto the strained Si1-xGex layer. The noise measurements were performed at temperature T = 77 K over the frequency range 10-104 Hz. Higher noise level was observed in the annealed diode Pt/p-Si1-xGex. In both diodes, the noise was found to exhibit 1/f behaviour and was attributed to fluctuations of the generation-recombination current at the interface states. The results reveal significant reductions in the total noise by 70%, and the interface state density Nit by three orders of magnitude when the silicide is formed by the CS process.
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| 24. |
- Staudt, A, et al.
(författare)
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beta(1)-Adrenoceptor antibodies induce positive inotropic response in isolated cardiomyocytes.
- 2001
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Ingår i: European journal of pharmacology. - 0014-2999. ; 423:2-3, s. 115-9
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Tidskriftsartikel (refereegranskat)abstract
- beta(1)-Adrenoceptor autoantibodies are present in approximately 30% of patients suffering from dilated cardiomyopathy. The inotropic effects mediated by these antibodies remain to be studied. Monoclonal antibodies were raised against a peptide corresponding to the second extracellular loop of the human beta(1)-adrenoceptor in balb/C mouse (n=6), and were characterized by enzyme immunoassay after purification by protein A. Purified immunoglobulin G from non-immunized animals (controls) did not influence Ca(2+) transient and cell shortening of rat cardiomyocytes measured by confocal-laser-scanning-microscopy. beta(1)-adrenoceptor antibodies caused a dose-related increase in Ca(2+) transient (dilution 1:2: +35.3+/-5.1%), and in cell shortening (dilution 1:2: +40.5+/-6.3%) (P<0.01 vs. controls). The effect of the beta(1)-adrenoceptor antibodies was blocked by the antigenic peptide and by the antagonist metoprolol. In addition, beta(1)-adrenoceptor antibodies induced a dose-dependent increase of the cyclic adenosine monophosphate. The inotropic response induced by isoproterenol was attenuated by the beta(1)-adrenoceptor antibody. beta(1)-adrenoceptor antibodies as partial agonists induce a specific positive inotropic effect via the protein-kinase-A-cascade.
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| 25. |
- Testa, D., et al.
(författare)
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Experimental test of damping models for n=1 toroidal Alfven eigenmodes in JET
- 2003
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 0029-5515 .- 1741-4326. ; 43:6, s. 479-482
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Tidskriftsartikel (refereegranskat)abstract
- The damping rate of the n = 1 toroidal Alfven eigenmodes (TAE) mode in Ohmic-heated JET plasmas has been measured and compared with the prediction of the kinetic NOVA-K code, which includes electron and ion Landau damping of the global shear-Alfven wave field, collisional damping, and radiative damping. It was found that the calculated damping rate is too small to account for the measured value under these experimental conditions. A relatively weak dependence of the damping rate on the normalized Larmor radius is observed experimentally.
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