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  • 1
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 47 (1986), S. 0 
    ISSN: 1471-4159
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Abstract Using chicken brain mRNAs, α and γ enolase precursors were synthesized in the rabbit reticulocyte cell-free translation system. The product proteins showed molecular weights almost identical to those of the mature subunits. The levels of translatable mRNAs for α and γ subunits were determined by the cell-free translation system and immuno-precipitation with specific antisera, during development of chicken brain. The level of α mRNA was high at any developmental stage of the brain. On the other hand, the γ mRNA level was very low at the early embryonic stage, and increased rapidly during development of the brain. These changes were closely correlated with those of the corresponding enzyme activities, indicating that the levels of enolase activities in developing brain were controlled primarily by the level of the translatable α and γ mRNAs.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 7281-7283 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We have fabricated semiconductor-based magnetic superlattices (SLs) containing GaAs:MnAs granular material in which MnAs nanoclusters are embedded in GaAs, and have characterized their structural, optical, and magneto-optical properties. SLs consisting of GaAs:MnAs and AlAs are shown to have good crystalline quality and excellent compatibility with nonmagnetic GaAs/AlAs heterostructures. The optical transmission properties were improved in the SLs, while keeping the strong magneto-optical properties of GaAs:MnAs. We used these magnetic SLs in a semiconductor-based magnetic microcavity as the central magnetic layer, and its optical transmission was found to have improved compared with our previous multilayer structures. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 4673-4675 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Introduction of a ferromagnetic quantum well in a ferromagnetic tunnel junction is shown to greatly enhance the tunneling magnetoresistance (TMR) effect, due to spin filtering as well as energy filtering. We have theoretically analyzed resonant transmission probability of a magnetic double barrier heterostructure consisting of III–V based ferromagnetic semiconductor GaMnAs, and nonmagnetic semiconductor AlAs. Experimentally, we have observed very large TMR effect of such a system grown by low-temperature molecular-beam epitaxy, and have shown that some of the measured tunneling features are attributed to spin-dependent resonant tunneling. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 6695-6697 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We have succeeded in growing MnAs/GaAs/MnAs ferromagnet/semiconductor trilayer heterostructures on GaAs(111)B substrates by molecular-beam epitaxy. Double-step features were observed in magnetization characteristics due to the difference in coercive force between the top and bottom MnAs layers. Magnetoresistance (MR) curves in current-in-plane geometry showed the spin-valve effect, which was caused by the change of the magnetic alignment of the two ferromagnetic MnAs layers from parallel to antiparallel orientation. Temperature dependence of the MR was also investigated. We infer that the positive temperature coefficient of the MR by the spin-valve effect suggests the heat (carrier) induced interlayer exchange coupling. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 71 (2000), S. 1125-1127 
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Filamentless negative ion beam production was investigated with a compact microwave ion source (2.45 GHz). One of the key points for negative ion production is the magnetic configuration. A magnetic filter field to lower electron temperature was generated in a negative ion production cell, which was shielded magnetically from a discharge cell with a magnetic field to couple microwave to plasma. Production of H− beam was studied with this source. H− was extracted through a grid slit (2×16 mm2) from plasma and accelerated to 20–40 keV. H− beam current was measured with a Faraday cup after magnetic mass separation. Continuous H− beam current of 73 μA (0.23 mA/cm2) was obtained with a magnetron power of 700 W. H− beam current was increased around 1.4 times by adding Xe gas to the H2 gas. Other negative ion species, which have a potential for applications to industrial ion beam processing with little charge-up problem, were also investigated. Carbon and hydrocarbon negative ion beams were produced using boron alkoxide (B(OCH3)3) and methane. C2H2− beams (22 μA) were obtained with the alkoxide. C2−(1.6 μA), C2H−(2.3 μA), C2H2−(0.6 μA), and H−(6.9 μA) beams were produced with methane. SiF4 and BF3 were used to generate F−, Si−, SiF3− and B− beams. Beam currents of these ion species were 17, 0.25, 1.5, and 0.03 μA, respectively. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
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  • 6
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Transconductance oscillations were observed for silicon-on-insulator metal–oxide–semiconductor field-effect transistors with 50 nm channel length and 6 nm Si-layer thickness in the temperature range of 39–50 K. By investigating the temperature dependence of the oscillations it was found that the oscillations were caused by two reasons. One reason is the roughness at the Si/insulator interface responsible for the low-gate-voltage oscillations. The roughness results in different thicknesses of the Si layer along the channel, causing different quantized energy levels, which act as barriers for carriers moving in the channel. The other reason is the tunneling through the potential barrier at the p/n junctions between the contacts and the channel, which is responsible for the high-gate-voltage oscillations. © 2002 American Institute of Physics.
    Materialart: Digitale Medien
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  • 7
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 6745-6747 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We have observed very large tunneling magnetoresistance (TMR) in Ga1−xMnxAs/AlAs/Ga1−xMnxAs ferromagnetic semiconductor tunnel junctions. A TMR ratio as high as 75% was obtained in a junction with a thin (1.5 nm) AlAs tunnel barrier when the magnetic field was applied along the [100] axis in the film plane. The TMR ratio decreased when the applied magnetic field direction was along the [11¯0] and [110]. This anisotropic TMR was found to be explained by the single-domain theory assuming cubic magnetic anisotropy with the easy axis of 〈100〉, which is induced by the zincblende-type Ga1−xMnxAs crystal structure. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
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  • 8
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 7395-7397 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The temperature dependence of magneto-optical property in the visible wavelength region has been studied on four-element semimagnetic semiconductor CdMnCoTe films deposited on quartz glass substrates by using MBE equipment. A large dispersion of Faraday rotation was observed, and the peak of the Faraday rotation was shifted to the higher photon energies with increasing Mn concentration at low temperatures. At 180 K, the value of the Faraday rotation observed for the Cd0.647Mn0.34Co0.013Te film on quartz glass was −0.36 deg/cmG at 630 nm. It is equivalent to the value of −0.36 deg/cmG observed at 77 K for the Cd0.52Mn0.48Te film on quartz glass. At 77 K, the Faraday rotation observed for the Cd0.647Mn0.34Co0.013Te film on quartz glass was −0.49 deg/cmG at 610 nm. The value is approximately two times larger than that of the Cd0.52Mn0.48Te film deposited on the same quartz glass substrate. The origin of the enhancement of Faraday rotation in CdMnCoTe films has been discussed in terms of the magnetic susceptibility χ. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
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  • 9
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 5914-5914 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Recently, high-Tc oxide superconductors have been extensively studied because these materials can be applied to various electronic devices, especially highly sensitive magnetic sensors or high-speed switching elements. For such the applications, thin films with superior superconductivity and very smooth surfaces are needed. The purpose of this work is to develop an as-grown technique of Y-Ba-Sr-Cu-O films on comparatively low-temperature substrates by adopting a newly devised alternative sputtering. The sputtering apparatus was constructed by three targets and a substrate holder which was intermittently rotated and stopped facing the desired target. The targets were Y2O, BaO+SrO, and Cu or CuO. The thickness of the oxide layer alternately deposited was adjusted to the thickness of the each metal-oxide monolayer. The substrate used was a (100) plane of a single-crystal MgO. The substrate temperature Ts was changed from 450 to 600 °C. The deposition rate of the each layer was affected by Ts. Especially, the deposition of the CuO layer was very sensitive to conditions of the film growing surface: Ts and/or degree of oxidation. The film composition was adjusted by changing the deposition time of the each layer. The crystal with an oxygen-defective perovskite nucleated even at a Ts of about 500 °C. In the case of sintered bulks, a tetragonal phase was obtained when the content of Sr was comparatively large. In contrast, an orthorhombic phase was stabilized in the sputtered films. As-grown films showed a poor superconductivity. After a post-annealing in 1-atom O2 at a low temperature of about 450 °C, a sharp superconducting transition was observed above 77 K. As we increase the content of Sr, the resistivity of the film became large and semiconductive.
    Materialart: Digitale Medien
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  • 10
    Digitale Medien
    Digitale Medien
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 1214-1216 
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Transport properties of electrons in a novel in-plane superlattice structure are studied and the field-effect transistor action has been demonstrated. The structure consists of an n-AlGaAs/GaAs modulation-doped heterojunction in which an array of monolayer-thick AlAs grid is embedded with an average period of 162 A(ring) in the channel region of the heterojunction. This grid has been prepared with molecular beam epitaxy by depositing a half monolayer of AlAs on a GaAs (001) vicinal plane, where periodically spaced atomic terraces are formed. The electron mobilities μ(parallel),μ⊥ parallel and normal to the grid are measured as functions of electron concentration NS. While the mobility ratio (μ(parallel)/μ⊥) is nearly unity at low NS, the ratio is found to get as large as 2.2 as NS increases. This anisotropic behavior of μ is well accounted for by the calculated nonparabolicity in the miniband structure of in-plane superlattices.
    Materialart: Digitale Medien
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