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  • 1
    Electronic Resource
    Electronic Resource
    Direct tunneling hole currents through ultrathin gate oxides in metal-oxide-semiconductor devices (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 258-264 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present a physical model to calculate the direct tunneling hole current through ultrathin gate oxides from the inversion layer of metal–oxide–semiconductor field-effect transistors. A parametric self-consistency method utilizing the triangular well approximation is used for the electrostatics of the inversion layer. For hole quantization in the inversion layer, an improved one-band effective mass approximation, which is a good approximation to the rigorous six-band effective mass theory, is used to account for the band-mixing effect. The tunneling probability is calculated by a modified Wentzel–Kramers–Brilliouin (WKB) approximation, which takes the reflections near the Si/SiO2 interfaces into account. It is found that the parabolic dispersion in the SiO2 band gap used in the WKB approximation is only applicable for hole tunneling in oxides thinner than about 2 nm and for low gate voltage. A more reasonable Freeman–Dahlke hole dispersion form with significantly improved fitting to all experimental data for different oxide thickness and gate voltage range is adopted and discussed. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1416861
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  • 2
    Electronic Resource
    Electronic Resource
    Interlayer segregation of Cu atoms in Ta/NiFe/Cu/NiFe/FeMn/Ta spin-valve multilayers and its influence on magnetic properties (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 3759-3763 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Experimental results show that the exchange coupling field (Hex) of NiFe/FeMn for Ta/NiFe/FeMn/Ta multilayers is higher than that for spin-valve multilayers Ta/NiFe/Cu/NiFe/FeMn/Ta. In order to find out the reason, the composition and chemical states at the surface of Ta(12 nm)/NiFe(7 nm), Ta(12 nm)/NiFe(7 nm)/Cu(4 nm), and Ta(12 nm)/NiFe(7 nm)/Cu(3 nm)/NiFe(5 nm) were studied using x-ray photoelectron spectroscopy. The results show that no elements from lower layers float out or segregate to the surface in the first and second samples. However, Cu atoms segregate to the surface of Ta(12 nm)/NiFe(7 nm)/Cu(3 nm)/NiFe(5 nm) multilayers, i.e., Cu atoms segregate to the NiFe/FeMn interface for Ta/NiFe/Cu/NiFe/FeMn/Ta multilayers. We believe that the presence of Cu atoms at the interface of NiFe/FeMn is one of the important factors which causes the exchange coupling field (Hex) of Ta/NiFe/Cu/NiFe/FeMn/Ta to be weaker than that of Ta/NiFe/FeMn/Ta. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1450033
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  • 3
    Electronic Resource
    Electronic Resource
    Interface reaction of Ta/Ni81Fe19 or Ni81Fe19/Ta and its suppression (2002)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 80 (2002), S. 455-457 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ta/Ni81Fe19 and Ni81Fe19/Ta structures are commonly used in the magnetic multilayers with giant magnetoresistance. For a Ta/Ni81Fe19/Ta fundamental structure, Ta seed and Ta cap layers resulted in a loss of moment equivalent to a magnetically dead layer of thickness 1.6±0.2 nm. In order to find out the reason, the composition and chemical states at the interface regions of Ta/Ni81Fe19 and Ni81Fe19/Ta were studied using the x-ray photoelectron spectroscopy and peak decomposition technique. The results show that there are thermodynamically favorable reactions at the Ta/Ni81Fe19 and Ni81Fe19/Ta interfaces: 2Ta+Ni=NiTa2. However, the thickness of a magnetically dead layer was significantly reduced by the insertion of a small amount of Bi in the Ta/Ni81Fe19/Ta structure. This result indicates that a surfactant Bi can suppress the interface reaction in multilayers. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1433913
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  • 4
    Electronic Resource
    Electronic Resource
    An analysis of temperature dependent piezoelectric Franz–Keldysh effect in AlGaN (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 1033-1035 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Strong Franz–Keldysh oscillations near the band gap of AlGaN are observed in the contactless electroreflectance (CER) studies of a GaN/InGaN/AlGaN multilayer structure. The line shape analysis of the CER spectra at different temperatures provides an accurate determination of the AlGaN band gap energies and the built-in electric fields. Using the existing data of the thermal expansion coefficients of GaN and sapphire, and the piezoelectric constants of AlGaN, the temperature dependence of the electric field is estimated and is in good agreement with the experimental results between 15 and 300 K. We attribute such electric field to the piezoelectric strain effect. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.125929
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  • 5
    Electronic Resource
    Electronic Resource
    Modeling and characterization of direct tunneling hole current through ultrathin gate oxide in p-metal–oxide–semiconductor field-effect transistors (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 78 (2001), S. 4034-4036 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the calculation of hole direct tunneling (DT) current from the inversion layer in a p-metal–oxide–semiconductor field-effect transistor based on a solid physical background. Our results are in good agreement with those obtained from carrier separation measurements over a wide range of oxide thicknesses in the ultrathin regime. The effect of valence band mixing on hole quantization in an inversion layer in a Si substrate is properly accounted for by an improved one-band effective mass approximation. A modified Wentzel–Kramers–Brillouin approximation to calculate the hole transmission probability is used by adopting a more accurate dispersion equation in the oxide gap. Our method is general, simple, and computationally efficient. It may even be used to calculate the hole DT current in other gate dielectric materials. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1379786
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  • 6
    Electronic Resource
    Electronic Resource
    Energy gap and band alignment for (HfO2)x(Al2O3)1−x on (100) Si (2002)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 81 (2002), S. 376-378 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: High-resolution x-ray photoelectron spectroscopy (XPS) was applied to characterize the electronic structures for a series of high-k materials (HfO2)x(Al2O3)1−x grown on (100) Si substrate with different HfO2 mole fraction x. Al 2p, Hf 4f, O 1s core levels spectra, valence band spectra, and O 1s energy loss all show continuous changes with x in (HfO2)x(Al2O3)1−x. These data are used to estimate the energy gap (Eg) for (HfO2)x(Al2O3)1−x, the valence band offset (ΔEν) and the conduction band offset (ΔEc) between (HfO2)x(Al2O3)1−x and the (100) Si substrate. Our XPS results demonstrate that the values of Eg, ΔEν, and ΔEc for (HfO2)x(Al2O3)1−x change linearly with x. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1492024
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  • 7
    Electronic Resource
    Electronic Resource
    Macrophage colony stimulatory factor and interferon-γ trigger distinct mechanisms for augmentation of β-amyloid-induced microglia-mediated neurotoxicity (2004)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 91 (2004), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Dysregulated stimulation of microglia, the resident macrophages in the brain, can lead to excessive induction of inflammatory agents and subsequently damage to neurons. Fibrillar β-amyloid peptide (fAβ), a major component of senile plaques in Alzheimer's disease (AD) brain, is known to induce microglial-mediated neurotoxicity under certain conditions. Microglial ‘priming’ by macrophage colony stimulatory factor (MCSF) or interferon-gamma (IFNγ) appears to be required for this fAβ-induced microglia mediated neurotoxicity in vitro. We report here that while both MCSF and IFNγ induce microglial-mediated fAβ neurotoxicity, their mechanisms of toxicity differ. The enhancement of neurotoxicity by IFNγ or MCSF is not due to enhanced Aβ ingestion by microglia or to the direct effect of proinflammatory cytokine production. The neurotoxicity resulting from IFNγ/fAβ treatment was blocked by pretreatment with nitric oxide synthase inhibitor l-N-5-(1-iminoethyl) ornithine hydrochloride (l-NIO), consistent with a role for nitric oxide in the IFNγ-mediated toxicity mechanism. In contrast, no induction of nitric oxide production was detected for microglia treated with MCSF/fAβ. Furthermore, inhibiting the generation of reactive oxygen species (ROS) using the specific NADPH oxidase inhibitor apocynin reversed fAβ/MCSF-induced neurotoxicity while l-NIO had little effect. As MCSF is endogenously expressed within the brain, and both its level and that of the MCSF receptor are dramatically increased in the AD brain, the neurotoxicity resulting from ROS release by fAβ/MCSF coactivated microglia may be a more appropriate model for assessing fAβ-induced microglial-mediated neuropathology in AD.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.2004.02765.x
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  • 8
    Electronic Resource
    Electronic Resource
    Co-localization of histamine and dopamine-β-hydroxylase in sympathetic ganglion and release of histamine from cardiac sympathetic terminals of guinea-pig (2003)
    Oxford, UK : Blackwell Science Ltd
    Autonomic & autacoid pharmacology 23 (2003), S. 0 
    Details
    ISSN: 1474-8673
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Chemistry and Pharmacology , Medicine
    Notes: 1 The aim of this study was to investigate the co-localization of histamine and dopamine-β-hydroxylase in the superior cervical ganglion of guinea-pig and release of histamine from cardiac sympathetic terminals in guinea-pig isolated atrium. 2 Histidine decarboxylase (a histamine-synthesizing enzyme) mRNA signals were detected in the neurones of superior cervical ganglion of guinea-pig by in situ hybridization. The results of double-labelled immunofluorescence further confirmed the co-localization of histamine and dopamine-β-hydroxylase in the large principle neurons and small intensely fluorescent cells in the superior cervical ganglion. The immunoreactivities of both histamine and dopamine-β-hydroxylase were significantly attenuated after 6-hydroxydopamine-induced lesion of sympathetic nerves. 3 The refractory electrical field stimulation caused the release of histamine from cardiac sympathetic terminals of guinea-pig isolated atria (112.14 ± 40.34 ng ml−1), which was significantly attenuated to 35 ± 15.57 ng ml−1 by reserpine pretreatment. Following administering compound 48/80, a mast cell degranulator, electrical field stimulation induced a dramatic increase of endogenous histamine release from isolated atria (303.57 ±72.93 ng ml−1). When compound 48/80 was added to the reserpine-treated atria, the release of histamine induced by field stimulation was decreased to 207.14 ± 76.39 ng ml−1. 4 These results provide novel evidence that histamine co-exists with noradrenaline in sympathetic nerves and might act as a neurotransmitter to modulate sympathetic neurotransmission.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1474-8673.2004.00305.x
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  • 9
    Electronic Resource
    Electronic Resource
    The effect of thermocycling and dentine pre-treatment on the durability of the bond between composite resin and dentine (2004)
    Oxford, UK : Blackwell Science Ltd
    Journal of oral rehabilitation 31 (2004), S. 0 
    Details
    ISSN: 1365-2842
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Summary  The high bond strength between restorative resin and dentine plays an important role in long-term performance of restorations in the oral environment. A variety of treatment techniques have been described to enhance the bond strength of composite resin to dentine. Unfortunately, few studies have reported available bond durability of adhesive resins to dentine. The purpose of this research was to study the shear bond strength of composite resin to dentine pre-treated with phosphoric acid, self-etching agent or Nd:YAP laser irradiation. The durability of bond strength between resin and dentine stored in the artificial saliva thermocycling between 5 and 55 °C was also evaluated. The scanning electron microscope was used to assess the treated-dentine surfaces. The mean value of the shear bond strength in the acid-etching group (18·2 ± 4·9 MPa) was the highest among the three dentine treatments (self-etching system: 12·6 ±3·0 MPa, Nd:YAP laser: 13·4 ± 3·3 MPa) prior to thermocycling. After thermocycling, shear strength values of all treated dentines decreased with increasing number of the cycles. When subjected to 3000 thermocycles, the mean bond strengths of these pre-treated samples to composite resin became 9·1 ± 1·4, 7·8 ± 1·8, and 8·1 ± 1·7 MPa for acid-etching, self-etching and laser-irradiation, respectively, with a significant reduction of 38–50%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2842.2004.01272.x
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  • 10
    Electronic Resource
    Electronic Resource
    Acidic motif responsible for plasma membrane association of the voltage-dependent calcium channel β1b subunit (2000)
    Oxford, UK : Blackwell Science Ltd
    European journal of neuroscience 12 (2000), S. 0 
    Details
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Voltage-dependent calcium channels consist of a pore-forming transmembrane α1-subunit, which is known to associate with a number of accessory subunits, including α2-δ- and β-subunits. The β-subunits, of which four have been identified (β1–4), are intracellular proteins that have marked effects on calcium channel trafficking and function. In a previous study, we observed that the β1b-subunit showed selective plasma membrane association when expressed alone in COS7 cells, whereas β3 and β4 did not. In this study, we have examined the basis for this, and have identified, by making chimeric β-subunits, that the C-terminal region, which shows most diversity between β-subunits, of β1b is responsible for its plasma membrane association. Furthermore we have identified, by deletion mutations, an 11-amino acid motif present in the C terminus of β1b but not in β3 (amino acids 547–556 of β1b, WEEEEDYEEE), which when deleted, reduces membrane association of β1b. Future research aims to identify what is binding to this sequence in β1b to promote membrane association of this calcium channel subunit. It is possible that such membrane association is important for the selective localization or clustering of particular calcium channels with which β1b is associated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-9568.2000.00981.x
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