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  • 2000-2004  (13)
  • 2001  (13)
  • 1
    Electronic Resource
    Electronic Resource
    Superconductivity and flux pinning in Y and heavily Pb codoped Bi-2212 single crystals (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 7669-7671 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Studies of superconductivity and flux pinning were carried out on (Bi1.64Pb0.36)Sr2Ca1−xYxCu2O8+y (x=0, 0.05, 0.11, 0.33) single crystals grown by the self-flux method. X-ray diffraction, transport, and magnetic measurements were performed for purposes of characterization. X-ray analysis revealed that the c lattice parameter systemically decreases as the Y doping level increases. The superconducting transition temperature Tc decreases from 80 to 30 K as x increases. A strong annealing effect on Tc and superconducting volume has been observed. Resistance measurements show that x=0.33 samples are semiconductive over a wide temperature range between 4.2 and 300 K for the as-grown state, but become metallic with Tc of 65–70 K after air or oxygen annealing. Flux pinning was studied by measuring the hysteresis loop at different temperatures and different fields. A peak effect was observed in all the codoped samples. Results show that at low temperatures, the peak field is smaller than in solely Pb doped crystals and decreases as x increases (x〉0.1). However, the peak field at high temperature for the x=0.05 sample is higher than in heavily Pb doped Bi2212 crystals, indicative of a strong pinning due to the codoping. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1356055
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  • 2
    Electronic Resource
    Electronic Resource
    Dead space effect in space-charge region of collector of AlGaAs/InGaAs p-n-p heterojunction bipolar transistors (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 5351-5356 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Hole-initiated avalanche multiplication is investigated using an AlGaAs/InGaAs p-n-p heterojunction bipolar transistor (HBT). Both experimental measurements and theoretical calculation are used to determine the avalanche multiplication factor. A large departure is observed at low electric field when comparison is made between the measured data and theoretical results obtained from the standard ionization model. The comparison shows that the conventional impact ionization model, based on local electric field, substantially overestimates the hole avalanche multiplication factor Mp−1 in the AlGaAs/InGaAs p-n-p HBT, where a significant dead space effect occurs in the collector space-charge region. A simple correction model for the dead space is proposed, that allows the multiplication to be accurately predicted, even in a heavily doped structure. Based on this model, multiplication characteristics for different threshold energy of the hole are calculated. A threshold energy of 2.5 eV was determined to be suitable for describing the hole-initiated impact ionization process. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1412836
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  • 3
    Electronic Resource
    Electronic Resource
    Fabrication and temperature dependence of the resistance of single-crystalline Bi nanowires (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 3847-3851 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Single-crystalline Bi nanowires with diameters ranging from 20 to 70 nm were prepared by electrodeposition using nanoporous aluminum oxide membranes rather than the more usual track-etched polycarbonate membranes. X-ray diffraction and selected area electron diffraction investigations revealed that the nanowires are essentially single crystalline and highly oriented. The temperature dependence of zero-field resistance of different diameter nanowires indicated that these Bi nanowires undergo a semimetal–semiconductor transition due to two-dimensional quantum confinement effects. The resistance maximum was observed at 50 K in zero magnetic field for 20 nm Bi nanowires, while the resistance minimum at 258 K for 50 nm Bi nanowires, due to the quantum size effect. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1352562
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  • 4
    Electronic Resource
    Electronic Resource
    Enhanced performance of pulse driven small area polyfluorene light emitting diodes (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 171-173 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have investigated the performance of conjugated polymer light emitting diodes (LEDs) as their active areas are reduced to dimensions typical for pixellated displays. We find that by reducing the active diameter of the device from our standard size (1.5×3 mm) to 50 μm, the current density that can be sustained before LED failure increases by a factor of 9. This increase in current density is mirrored by similar increases in maximum LED brightness. We propose that such effects occur due to improved thermal management in small area devices. Using pulsed driving schemes, devices with a diameter of 50 μm sustained current densities of 5.1 MA m−2, and have emitted electroluminescence with a brightness of 6.5 Mcd m−2. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1383799
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  • 5
    Electronic Resource
    Electronic Resource
    Determination of oscillator strength of C–F vibrations in fluorinated amorphous-carbon films by infrared spectroscopy (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 78 (2001), S. 3079-3081 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Fluorinated amorphous-carbon (a-CFx) films deposited by plasma-enhanced chemical-vapor deposition were investigated by Fourier transform infrared transmission spectroscopy and Rutherford backscattering. The proportionality constant between the fluorine concentration and the integrated absorption of C–F vibration modes is 3.52±0.3×1019 cm−2, and is constant within experimental uncertainty over a wide range of processing conditions. It is shown that the fluorine content can be accurately determined from the infrared absorption spectrum of a-CFx films. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1371970
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  • 6
    Electronic Resource
    Electronic Resource
    Ordered indium-oxide nanowire arrays and their photoluminescence properties (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 839-841 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ordered semiconductor In2O3 nanowire arrays are uniformly assembled into hexagonally ordered nanochannels of anodic alumina membranes (AAMs) by electrodeposition and oxidizing methods. Their microstructures were characterized by x-ray diffraction, scanning electron microscopy, and transmission electron microscopy. A blue-green photoluminescence (PL) band in the wavelength range of 300–650 nm was observed in the In2O3/AAM assembly system. The PL intensity and peak position depend on the annealing temperature, which is mainly attributed to the singly ionized oxygen vacancy in the In2O3 nanowire array system. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1389071
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  • 7
    Electronic Resource
    Electronic Resource
    Standardization of the Ammonia Electrode Method for Evaluating Seafood Quality by Correlation to Sensory Analysis (2001)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 66 (2001), S. 0 
    Details
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: : Ammonia ion-selective electrode (ISE) measurements, reported as apparent ammonia, were correlated to expert sensory assessments of 6 different fish species stored on ice and at room temperature. Total volatile base nitrogen (TVB-N), trimethylamine nitrogen (TMA-N), and apparent ammonia showed the same development trend during storage. ISE measurements and TVB concentrations had a correlation of r2= 0.92. Sensory assessment, using a 1- to 100-mm line scale with values 〉 50 considered unacceptable, resulted in an r2between sensory scores and ISE measurements of 0.78. Regression analysis predicted 19.6 mg/100 g of apparent ammonia in fish tissue at the sensory limit of 50, regardless of storage conditions. ISE measurements could be used in predicting borderline quality and decomposition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2621.2001.tb08217.x
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  • 8
    Electronic Resource
    Electronic Resource
    Rapid introduction of disease resistance from rye into common wheat by anther culture of a 6x triticale × nulli-tetrasomic wheat (2001)
    Oxford, UK : Blackwell Publishing Ltd
    Plant breeding 120 (2001), S. 0 
    Details
    ISSN: 1439-0523
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Powdery mildew (caused by Erysiphe graminis) and yellow rust (caused by Puccinia striiformis) are the two most serious wheat diseases found in China. Rye chromosomes, carrying genes for resistance to these diseases, were introduced into common wheat in two generations using chromosome engineering and anther culture. The F1 hybrids from a cross involving a hexaploid triticale (×Triticosecale Wittmack) בChinese Spring’ nulli-tetrasomic N6DT6A wheat aneuploid line were anther cultured and doubled-haploid plants were regenerated. Using genomic in situ hybridization, C-banding and biochemical marker analyses, one of the anther-cultured lines (ZH-1)studied in detail, proved to be a doubled-haploid with one rye chromosome pair added (1R) and a homozygous 6R/6D substitution (2n= 44). The line was tested for expression of disease resistance and found to be highly resistant to powdery mildew and moderately resistant to yellow rust.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1439-0523.2001.00550.x
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  • 9
    Electronic Resource
    Electronic Resource
    Investigation of orbital momentum profiles of methylpropane (isobutane) by binary (e,2e) spectroscopy (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 114 (2001), S. 882-888 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Momentum profiles of the valence orbitals of methylpropane, also known as isobutane (CH3CH(CH3)CH3), have been studied by using a high resolution binary (e,2e) electron momentum spectrometer (EMS), at an impact energy of 1200 eV plus the binding energy, and using symmetric noncoplanar kinematics. The coincidence energy resolution of the EMS spectrometer is 0.95 eV full width at half-maximum. The experimental momentum profiles of the valence orbitals are compared with the theoretical momentum distributions calculated using Hartree–Fock (HF) and density functional theory (DFT) methods with the two basis sets of 6-31G and 6-311++G**. The B3LYP functionals are used for the DFT calculations. In general, the experimental momentum distributions are well described by the HF and DFT calculations. The pole strengths of the main ionization peaks from the orbitals in the inner valence are estimated. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1321313
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  • 10
    Electronic Resource
    Electronic Resource
    Regulation of Surface and Intracellular Expression of CTLA-4 on Human Peripheral T Cells (2001)
    Oxford, UK : Blackwell Science Ltd
    Scandinavian journal of immunology 54 (2001), S. 0 
    Details
    ISSN: 1365-3083
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Cytotoxic T-lymphocyte-associated antigen (CTLA-4) is an important downregulator of T-cell activation. In order to analyze the expression and regulation of CTLA-4 on human peripheral T cells, CTLA-4 mRNA and protein expression were determined using analysis by reverse transcription–polymerase chain reaction (RT–PCR) and FACs, respectively. Intracellular CTLA-4 was constitutively expressed in unstimulated CD4+ and CD8+ T cells. Interleukin (IL)-2 induced a dose-dependent increase of both intracellular and surface expression of CTLA-4 (CD152). Most of the CD4+ and CD8+ cells expressing CTLA-4 also expressed CD25. Interferon (IFN)-γ induced the upregulation of CTLA-4 expression via antigen-presenting cells (APC) activation. The CTLA-4delTM mRNA (550 bp) had a shorter half-life than the full length CTLA-4 mRNA and the expression was downregulated upon activation of the cells by treatment with IL-2. Given an inhibitory role of CTLA-4 and CD4+ CD25+ T cells in immune responses, the present findings suggest that IL-2-induced immunosuppression may result from its stimulatory effect of the CTLA-4 expression.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3083.2001.00985.x
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