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  • 1
    Digitale Medien
    Digitale Medien
    Superconducting resonator circuits at frequencies above the gap frequency (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 1795-1804 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The frequency response of three superconductive niobium resonating circuits, formed by a Nb microstrip and a Nb tunnel junction, is measured and analyzed at frequencies above the superconducting gap frequency. The circuits are placed in a waveguide system and the frequency response is determined with a Fourier transform spectrometer. The calculated and measured resonance frequencies and bandwidths are in good agreement with the extreme anomalous limit of the Mattis–Bardeen theory on the anomalous skin effect in superconductors [D.C. Mattis and J. Bardeen, Phys. Rev. 111, 412 (1958)]. The observed loss is higher than predicted by this theory, in agreement with previous observations on Nb films. The use of other materials for striplines as tuning circuits for heterodyne superconducting tunnel junction mixers is analyzed. © 1995 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.358876
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  • 2
    Digitale Medien
    Digitale Medien
    The ac-Josephson effect above the gap frequency (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 8016-8021 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The rf-power dependence of the ac-Josephson steps is measured at 720 GHz, using small area Nb tunnel junctions. This frequency is well above the gap frequency of Nb. The junction is placed in a waveguide, and connected to a superconducting stripline, which effectively tunes out the junction capacitance and facilitates the coupling of the radiation to the junction. We observe three Josephson steps, and the first step crosses the zero current axis over a considerable range of rf-power. This indicates the possible application of THz Josephson steps in voltage standards. The data are compared to the theory and we find clear evidence for the predicted intrinsic roll-off of the Josephson current amplitude above the gap frequency. © 1994 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.357919
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  • 3
    Digitale Medien
    Digitale Medien
    Low-energy vibrational modes of the monolayer adsorbate CO2/NaCl(001) (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 98 (1993), S. 10096-10099 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Dispersion curves of surface vibrational modes of monolayer CO2/NaCl(001) have been measured by inelastic He atom scattering along the ΓX azimuth. Eight phonon modes could be followed across almost the entire Brillouin zone. The identification of the modes is discussed based on previously calculated normal mode energies at the zone origin.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.464399
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  • 4
    Digitale Medien
    Digitale Medien
    Extensive test of the three-port quantum mixer theory on 345 GHz superconductor-insulator-superconductor mixers (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 4762-4773 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Predictions of the three-port model of the quantum theory of mixing are compared with measured results on 345 GHz superconductor-insulator-superconductor waveguide mixers. Single Nb-Al2O3-Nb tunnel junctions or two or four identical junctions in series are used as mixing elements. Two different waveguide mixerblocks, one with two tuners and another with one tuner, are used. In addition a single junction with integrated tuning stub is analyzed. Embedding impedances are obtained from fits to the pumped I-V curves for all three types of mixing elements. In all cases the dependence of mixer conversion and mixer noise on bias voltage, pump power, and embedding impedance is well described by the three-port model. The measured mixer gain is lower than the calculated gain by a factor of 0.35–0.65, independent of the type of mixer. The use of an additional integrated tuning element does not change this factor. It is concluded that an excess noise power equivalent with a blackbody source of 40–65 K must be added to the mixer noise to account for the absolute value of the observed noise power.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.354347
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  • 5
    Digitale Medien
    Digitale Medien
    Physical model of photostimulated luminescence of x-ray irradiated BaFBr:Eu2+ (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 1405-1412 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A dynamical model of the temporal dependence of photostimulated luminescence of the storage phosphor BaFBr:Eu2+ as a result of preceeding x-ray irradiation is presented. The model is based on a monomolecular recombination mechanism. The commonly used bimolecular mechanism leads to contradictions with experimental observations. The monomolecular recombination is explained by the existence of a photostimulable luminescence complex with a recombination center and an electron trap in close proximity. Charge transfer after optical excitation occurs through tunneling. The simulation of the transient charge carrier dynamics is performed through rate equations. Good agreement wih experimentally determined temporal responses for different x-ray doses applied and stimulating light intensities is obtained.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.341838
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  • 6
    Digitale Medien
    Digitale Medien
    Low-noise 1 THz superconductor–insulator–superconductor mixer incorporating a NbTiN/SiO2/Al tuning circuit (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 436-438 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Low-noise heterodyne mixing at 1 THz is demonstrated in a quasioptical mixer incorporating Nb superconductor–insulator–superconductor tunnel junctions and a NbTiN/SiO2/Al tuning circuit. Receiver noise temperatures as low as 250 K at 850 GHz, 315 K at 980 GHz, and 405 K at 1015 GHz are measured—a factor of 2 improvement in sensitivity versus state-of-the-art 1 THz receivers, which incorporate normal metal tuning circuits. An analysis of the receiver sensitivity at 980 GHz demonstrates that NbTiN is low loss up to ∼1 THz. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1384005
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  • 7
    Digitale Medien
    Digitale Medien
    Heterodyne mixing with Nb tunnel junctions above the gap frequency (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 3039-3041 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The noise and gain of a heterodyne waveguide mixer employing Nb/Al2O3/Nb superconducting tunnel junctions with an on-chip integrated tuning element are measured and analyzed at 680–750 GHz and at 840 GHz. The lowest receiver noise temperatures are 400 K (double side band) at 720 GHz and 1500 K (3000 K including the beam splitter loss) at 840 GHz. We compare data of the pumped I–V curves with the quantum theory of mixing and demonstrate good agreement at frequencies well above the gap frequency.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.111399
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  • 8
    Digitale Medien
    Digitale Medien
    The structure and dynamics of CO2 on NaCl(001) studied by helium atom scattering (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 103 (1995), S. 2308-2319 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The structure and dynamics of physisorbed carbon dioxide on in situ cleaved single crystal sodium chloride surfaces was studied by means of elastic as well as inelastic helium atom scattering. At Tsurface=80–83.5 K the diffraction patterns indicate a commensurate (2×1) monolayer superstructure on the (001) plane of the substrate, the unit cell containing a glide plane. This is in agreement with results obtained from low energy electron diffraction and infrared spectroscopy. In time-of-flight experiments single phonon low-energy loss and gain features were observed which can be attributed to acoustic and optical modes. Two higher-energy features are probably due to the first combination modes observed by helium atom scattering so far. The growth of solid CO2 adsorbed on NaCl(001) was also studied. © 1995 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.469706
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  • 9
    Digitale Medien
    Digitale Medien
    Optic nerve responses to visual stimuli in squid (1974)
    Springer
    Journal of comparative physiology 93 (1974), S. 37-54 
    Details
    ISSN: 1432-1351
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Single unit optic nerve responses were studied in isolated eye-optic lobe preparations ofLoligo opalescens. Units could be classified as fast or slow. Fast units were invariably receptor cell axons; slow units might be either receptor cell axons or centrifugal axons.On, on-off, andoff units could be found within these classes. A given unit was not stable with respect to these latter attributes which depended greatly on the history and level of illumination. The curve which relates quantal content of a brief flash to number of spikes in the response has a logarithmic phase, but it saturates as brightness is increased further. An inhibitory component has been demonstrated following the response to a flash. It is probably responsible for the non-monotonic relationship between frequency and light intensity which is observed for sustained stimuli. Background light or previous illumination can lead to a facilitation of the response to a flash.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00608758
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  • 10
    Digitale Medien
    Digitale Medien
    Retinal responses in squid and octopus (1974)
    Springer
    Journal of comparative physiology 93 (1974), S. 19-36 
    Details
    ISSN: 1432-1351
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Electroretinogram and optic nerve impulse recordings from an isolated eye-optic lobe preparation of squid and octopus show: 1) linear and nonlinear responses to modulated light; 2) facilitation of retinal and optic nerve responses to pairs and trains of suitably spaced brief flashes; 3) bothon andoff responses in optic nerve fibers; 4) centrifugally conducted impulses in the optic nerve which may be excited or inhibited by light; and 5) oscillatory behavior which has a stable, temperature dependent frequency. All of these phenomena other than the centrifugal activity can be gotten with isolated eyes. The non-impulse behavior can also be gotten from small pieces of retina. There is therefore evidence for highly complex activity within local areas of the anatomically simple retina.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00608757
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