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  • 1
    Electronic Resource
    Electronic Resource
    Hindered rotation of H2 adsorbed interstitially in nanotube bundles (2002)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 116 (2002), S. 1720-1724 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A theoretical study of the rotational dynamics of H2 molecules trapped in the interstitial channels of a carbon nanotube bundle is presented. The potential used in this study is modeled as a sum of atom–atom (C–H) van der Waals interactions and electrostatic interactions of the molecule with the surrounding nanotubes. The rotational energy spectra is calculated using a product wave function, where the coupling between translational and rotational modes is treated in a mean-field manner. A molecular dynamics simulation study was performed for estimating the hydrogen rotational barrier. Both theoretical calculations and simulation results reveal the existence of a large rotational barrier (∼40 meV). The consequences of this rotational barrier for the rotational energy levels are worked out in detail. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1424290
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  • 2
    Electronic Resource
    Electronic Resource
    Essential role of the mitochondrial apoptosis-inducing factor in programmed cell death (2001)
    [s.l.] : Macmillian Magazines Ltd.
    Nature 410 (2001), S. 549-554 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Programmed cell death is a fundamental requirement for embryogenesis, organ metamorphosis and tissue homeostasis. In mammals, release of mitochondrial cytochrome c leads to the cytosolic assembly of the apoptosome—a caspase activation complex involving Apaf1 and caspase-9 that induces ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/35069004
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  • 3
    Electronic Resource
    Electronic Resource
    Induction of integrin-associated protein (IAP) mRNA expression during memory consolidation in rat hippocampus (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: We have previously demonstrated that hippocampal integrin-associated protein (IAP) gene expression is associated with memory formation in a one-way inhibitory avoidance learning in rats. In the present study, we further investigated the role and mechanism of IAP involved in memory consolidation in rats. Because of the minute amount of IAP present in the brain, we have adopted the quantitative reverse transcription-polymerase chain reaction (RT-PCR) method. Our results revealed that hippocampal IAP mRNA expression is approximately fourfold higher in rats showing good memory retention (GM, retention score of 600 s) at 3 h, but not at other time points, after training when compared with the poor memory rats (retention score 〈 80 s). On the other hand, integrin αv mRNA level was markedly increased (∼ twofold), while integrin β3 mRNA level was decreased (∼ 50%) at 1 h post-training. Further, separate sets of RT-PCR analysis revealed that IAP5 and IAP6 mRNA expressions, but not that of IAP7, were markedly increased in GM rats 3 h post-training. Moreover, regional distribution studies revealed that different isoforms of the IAP gene are similarly distributed in different brain areas, while IAP7 has been the predominant form present in astrocyte cells. These results together suggest that IAP mRNA expression is indeed induced upon training, rather than that the GM rats have constitutively higher levels of IAP. The unparallel change of IAP and integrin mRNA expressions as far as time-course is concerned suggests that they are possibly involved in different forms and stages of memory processing. Further, IAP5 and IAP6 are more closely associated with memory consolidation, while IAP7 may constitute the major isotype for signal transduction in astrocyte cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-9568.2000.00985.x
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  • 4
    Electronic Resource
    Electronic Resource
    Determination of the direction of the "easy" axis at a twisted nematic liquid crystal-wall using half-leaky guided modes (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 4553-4557 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Theoretical analysis and numerical modeling indicate that, under high fields, the director of a thin region of liquid crystal close to the wall of a twisted nematic cell returns to the "easy" axis on the interface. Polarization conversion reflectivity signals are recorded for half-leaky guided modes from a twisted nematic cell subject to high ac fields. By fitting model theory to reflectivities recorded for a particular region of incidence angles, the director twist at the cell walls is deduced. In the high-field limit, this then gives the original director alignment axis, the easy axis, at the wall of a twisted nematic cell. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1311812
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  • 5
    Electronic Resource
    Electronic Resource
    Properties of Mg activation in thermally treated GaN:Mg films (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 6515-6518 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The Mg acceptors of GaN films are activated as p-type GaN with rapid thermal annealing (RTA) and furnace treatments. The GaN:Mg films are activated successfully by using the RTA system below 1000 °C for 1 min. After the RTA treatment, we observed a sharper linewidth and stronger emission intensities from donor to acceptor peaks in the photoluminescence spectra. By comparing the electrical properties of GaN:Mg films at optimum conditions made with RTA (800 °C) and furnace (700 °C) treatments, we find similar activated hole concentration and a higher hole mobility for GaN:Mg films with RTA treatment at 800 °C. A higher bulk resistivity caused by increasing nitrogen vacancies is found at higher temperature and longer time RTA treatments. Faster treatment times and lower temperatures for the GaN:Mg films were achieved with the RTA activation process. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1308097
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  • 6
    Electronic Resource
    Electronic Resource
    Ballistic magnetoresistance in a nanocontact between a Ni cluster and a magnetic thin film (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 2946-2948 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present measurements of ballistic magnetoresistance in nanocontacts grown by electrodeposition of Ni microclusters on magnetic thin films covered by aluminum oxide layers, using a technique proposed by Schad et al. [D. Allen, R. Schad, G. Zangari, I. Zana, D. Yang, M. C. Tondra, and D. Wang, J. Vac. Sci. Technol. A. 18, 1830 (2000); Appl. Phys. Lett. 76, 407 (2000); D. Allen, R. Schad, G. Zangari, I. Zana, D. Yang, M. C. Tondra, D. Wang, and D. Reed, J. Appl. Phys. 89, 6662 (2001)]. The measurements are made on single Ni clusters in contact with a Ni and Co thin film. We measure the magnetoresistance and observe the relaxation of the magnetization and electrical resistance as a function of time. The clusters are electrodeposited under several different experimental conditions. Some are deposited randomly on an unpatterned film and some through various patterned photoresists that control the location at which the cluster is grown. The typical contact size is estimated from the electrical resistance to be 10–30 nm. Ballistic magnetoresistance values up to 14% are obtained in these first experiments. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1413734
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  • 7
    Electronic Resource
    Electronic Resource
    Tensile strength of single-walled carbon nanotubes directly measured from their macroscopic ropes (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 3161-3163 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: 20 mm long ropes consisting of soundly aligned single-walled carbon nanotube (SWNT) ropes, synthesized by the catalytic decomposition of hydrocarbons, were employed for direct tensile strength measurements. The average tensile strength of SWNT rope composites is as high as 3.6±0.4 GPa, similar to that of carbon fibers. The tensile strength of SWNT bundles was extrapolated from the strength of the composites to be 2.3±0.2 to 14.2±1.4 GPa after simply taking into account the volume fraction of SWNT bundles in the minicomposite, and the tensile strength of single SWNTs was estimated to be as high as 22.2±2.2 GPa. The excellent mechanical properties of SWNTs will make them an ideal reinforcement agent for high performance composite materials. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1324984
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  • 8
    Electronic Resource
    Electronic Resource
    Volumetric hydrogen storage in single-walled carbon nanotubes (2002)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 80 (2002), S. 2389-2391 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Macroscopically long ropes of aligned single-walled carbon nanotubes (SWNTs), synthesized by a hydrogen and argon arc discharge method, were cold pressed into tablets without any binder for measurements of their volumetric hydrogen storage capacity. The typical apparent density of the tablets was measured to be around 1.7 g/cm3 with respect to a molding pressure of 0.75 Gpa. A volumetric and mass hydrogen storage capacity of 68 kg H2/m3 and 4.0 wt %, respectively, was achieved at room temperature under a pressure of 11 MPa for suitably pretreated SWNT tablets, and more than 70% of the hydrogen adsorbed can be released under ambient pressure at room temperature. Pore structure analysis indicated that the molding process diminished the mesopore volume of the SWNT ropes, but exerts little influence on their intrinsic pore textures. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1466517
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  • 9
    Electronic Resource
    Electronic Resource
    Improved contact performance of GaN film using Si diffusion (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 1878-1880 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this letter, we investigate a metalization process for reducing the contact resistance on undoped GaN layers. The Si metal source was diffused successfully into the GaN films by using SiOx/Si/GaN/Al2O3 structures. By using a high-temperature annealing process, we diffused and activated the Si atoms into the GaN film. This caused a heavy doped n-type GaN layer to be formed near the GaN surface. Under high temperatures, such as a diffusion process at 1000 °C, the as-deposited Ni/Al/Ti contact had good ohmic properties and a low specific contact resistivity (ρc) of 1.6×10−3 Ω cm2. Rapid thermal annealing the contact at 800 °C for 30 s caused the ρc to decrease rapidly to 5.6×10−7 Ω cm2. The Ni/Al/Ti contact characteristics on the GaN films diffused at various temperatures are also discussed. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.126198
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  • 10
    Electronic Resource
    Electronic Resource
    X-ray absorption studies of carbon-related materials (2001)
    Chester : International Union of Crystallography (IUCr)
    Journal of synchrotron radiation 8 (2001), S. 145-149 
    Details
    ISSN: 1600-5775
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: X-ray absorption near-edge structure (XANES) measurements have been performed on nitrogen-doped diamond films with three different dopant concentrations and iron-layer-stabilized carbon nanotube (CNT) structures with various diameters at the C K-absorption edge using the sample drain current mode. The C K-edge XANES spectra of these N-doped diamond films resemble that of the undoped diamond regardless of the dopant concentration, which suggest that the overall bonding configuration of the C atom is unaltered. N dopants are found to reduce the intensities of both the sp2- and sp3-bond-derived resonance features in the XANES spectra. On the other hand, the C K-edge XANES spectra of CNTs indicate that the intensities of the π* and σ* bands and the interlayer-state features vary with the diameter of the CNT. This phenomenon may be caused by the Fe-layer-catalysed bending of the graphite sheet and the interaction between C and Fe atoms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0909049500019750
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