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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 59 (1993), S. 445-450 
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Small deviations from the standard model may exist in the hadronic and leptonic cross sections at KEK. We explore the possibility that these may be accounted for by the extra gauge bosonsZ′ andW′ in theSP(6) L ⊗U(1) Y model, with its parameters constrained by the LEP data.
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  • 2
    ISSN: 1439-0973
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Ein 24jähriger Mann klagte seit drei Monaten über unklares abdominelles Völlegefühl und einen dumpfen, leicht epigastrischen Schmerz. Zwei Monate vor Aufnahme war in einem klinischen Zentrum ein Pankreaskopftumor festgestellt worden. Sonographisch, durch endoskopische retrograde Cholangiopankreatographie und Computertomographie des Abdomens wurde der Pankreaskopftumor bestätigt. Wegen des hochgradigen Verdachtes auf Pankreaskopfkarzinom wurde eine Laparotomie vorgenommen. Dabei fand sich im Pankreaskopf eine indurierte Masse, vergrößerte Lymphknoten und weiße Tuberkel auf dem Darm. Die histologische Untersuchung bestätigte das Vorliegen tuberkulöser Granulome. Säurefeste Stäbchen konnten histologisch ebenfalls nachgewiesen werden. Der Patient wurde mit Tuberkulostatika behandelt und ist jetzt in guter Verfassung. Um unnötige Laparotomien zu vermeiden, sollte bei Patienten mit Pankreastumor eine computertomographisch oder sonographisch kontrollierte Aspirationsbiopsie mit zytologischer oder histologischer Untersuchung durchgeführt und auch kulturell der Nachweis von Mykobakterien versucht werden. Dies gilt vor allem für Regionen, in denen die Lungentuberkulose und abdominelle Tuberkulosen keine Seltenheit darstellen.
    Notes: Summary A 24-year-old man presented with vague abdominal fullness and a mild epigastric dull pain for about 3 months was found to have a pancreatic head tumor at a medical center 2 months ago. He came to our hospital for further treatment. Ultrasonography, endoscopic retrograde cholangiopancreatography (ERCP) and abdominal computed tomography (CT) all revealede a pancreatic head tumor. Laparotomy was performed because pancreatic head carcinoma was highly suspected. Indurated mass in the pancreatic head, enlarged lymph nodes and white tubercles on the intestine proved to be tuberculosis on histological examination of a frozen section. Acid fast bacilli were also found. The patient was given antituberculous therapy and is now doing well. To avoid unnecessary laparotomy, CT, echo-guided percutaneous aspiration cytology or biopsy and culture of the tissue for mycobacteria should be done in a patient with pancreatic mass, especially in a region where pulmonary and abdominal tuberculosis are common.
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  • 3
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We calculate the ground-state energy of normal and spin-polarized3He within a model-space ring diagram framework where the particle-particle hole-hole (pphh) ring diagrams of the ground-state energy shift are summed up to all orders. The Aziz HFDHE2 and HFD-B(HE) interactions are employed. We first calculate a model space reaction matrix(G M ) whose intermediate states are required to be outside the chosen model space. The pphh ring diagrams withG M -matrix vertices are then summed within the model space by way of a PRA-type secular equation. The continuous single-particle spectrum of Mahaux is chosen in the present work. It is found that the inclusion of the pphh ring diagrams gives a significant increase in the binding energy per particle(BE/A) as compared with Brueckner-Hartree-Fock calculations. For normal and spin-polarized3He our calculated values forBE/A and saturation densities are respectively (1.86 K, 0.72 Å−1) and (1.59 K, 0.91 Å−1), while the corresponding experimental values for normal3He are (2.47 K, 0.785 Å−1).
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  • 4
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 3399-3401 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The successful growth of ultrathin CoGa on GaAs by MBE is demonstrated. The crystalline quality of the films is verified by in situ RHEED, RBS, and x-ray rocking curve. Transport studies are performed in the temperature range of 4 to 300 K for layer thickness from 10 to 730 A(ring), and all the films are found to be electrically continuous. The Markowitz's model [Phys. Rev. B 15, 3617 (1977)] of the electrical resistivity is applied to analyze the measured data. Finally, the specularly scattering probability of these thin films is studied using Fuchs' theory [Proc. Cambridge Philos. Soc. 34, 100 (1938)].
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  • 5
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 1062-1064 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A scanning tunneling microscope (STM) was used for the first time to investigate the (100)CoGa/GaAs interfaces grown by molecular beam epitaxy. The surface image indicates a vertical variation of about 7.5 A(ring) with some domains of dimensions of about 170 A(ring). Furthermore, ballistic-electron-emission-microscopy spectra of this metal/semiconductor interface show two turn-on voltages, which account for the change of transmission probabilities for electrons with energies above the L minima and X minima of GaAs, respectively. The transmission into the X valleys of GaAs is found to be relatively stronger than that into the L valleys. This is explained by the CoGa band structure and the conservation of energy and transverse momentum for ballistically injected electrons. So far no ballistic electron current flowing into the Γ valley has been observed. For this reason, Schottky barrier height and its spatial variation measured by STM were not directly from the anticipated turn-on voltage at the Γ minimum, but instead, from the thresholds corresponding to transmission into higher valleys.
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  • 6
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Heterojunction bipolar transistors (HBTs) with bases composed of a single monolayer of dopant are found to have exponentially increasing current gain as the temperature is lowered, in contrast to the gains of homogeneously doped HBTs, which have little dependence on temperature. We present GaAs-AlGaAs HBTs with base doping as high as 3×1014 cm−2 with a room-temperature current gain of 14. The sheet resistance of such a layer is 270 Ω/square at room temperature, and the carriers are restricted to a 15 A(ring) layer, implying an extremely short base transit time. AT 77 K the gain increases to 220, while the base resistance decreases to 190 Ω/square. Therefore by operating this HBT at low temperature we have achieved for the first time high gain and low base resistance in a HBT with an infinitesimally thin base.
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  • 7
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 61 (1992), S. 2869-2871 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The Schottky barrier formation of CoGa on (100)n-GaAs is investigated. CoGa is grown by molecular beam epitaxy and the epitaxial orientation is controlled by the initial growth conditions of the GaAs substrate. Schottky diodes with three different phases of CoGa: (100)CoGa, (110)CoGa, and mixed (100) and (110)CoGa, are fabricated and Schottky barrier heights are measured by I-V, C-V, and internal photoemission. The fact that these three types of diodes have different values of barrier height indicates that the mechanisms of the barrier formation for these three phases are different. Finally, the temperature dependence of the Schottky barrier height is also examined and the barrier height is found to be constant from 150 to 300 K for each of the phases.
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  • 8
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 1452-1454 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We examine atomic diffusion of Si, when initially δ doped into very pure GaAs layers grown by gas source molecular beam epitaxy. A nonlinear Si diffusion coefficient versus inverse temperature is observed as a two-component Arrhenius dependence in which the activation energies change by 1.5 eV. Furthermore, when Si diffusion is thermally activated with the lower energy kinetics, the corresponding impurity profile grows in width linearly with the anneal time. We explain the above departures of measured Si diffusivity from classical impurity diffusion via a nonequilibrated concentration of vacancies generated at the δ position during the anneal.
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  • 9
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 1191-1193 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Schottky barrier heights in the epitaxial (100) CoGa/n-(100) GaAs diodes were studied by the I-V and internal photoemission methods. Diodes of these epitaxial contacts were shown to exhibit good rectifying behaviors and the forward current was found to follow the thermionic emission theory. Using the temperature dependence of the barrier heights, we show that the Schottky barrier heights are about 0.67 eV by I-V and 0.68 eV by internal photoemission measurements. The Schottky barrier height was found to be constant for contacting to n-type GaAs in the temperature range between 150 and 300 K. From this fact, we conclude that the metal Fermi level is pinned relatively to the GaAs conduction band minimum in this case. This finding is similar to other epitaxial contacting cases, CoSi2/Si and ErSi2/Si, where the Fermi level pins to the nearest semiconductor band [J. Y. Duboz, P. A. Badoz, F. Arnaud d'Avitaya, and E. Rosenche, Phys. Rev. B 40, 10 607 (1989)].
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  • 10
    ISSN: 1617-4623
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Ten nitrate reductase (NR)-deficient mutants have been characterized for their cross-reactivity against specific barley (Hordeum vulgare L.) nitrate reductase antibodies. The rabbit antibodies raised against the purified barley wild type (cv. Steptoe) enzyme quantitatively inactivate nitrate reductase in crude extracts. All nitrate-grown (induced) mutants show positive precipitin reaction against the antiserum by Ouchterlony double diffusion test and all have the ability to neutralize antisera in a NR protection assay. Under induced growth conditions, mutants Az 12, Az 23, Az 29 and Az 30 which have low NR associated catalytic activities also have the lowest level of antigenicity; mutants Az 13, Az 31, Az 33 and Az 34 have intermediate level of both NR associated catalytic activities and antigenicity, while mutants Az 28 and Az 32 have the highest level of both NR associated catalytic activities and antigenicity. Under noninduced growth conditions, all mutants except Az 12 contain detectable but very low levels of NR antigenicity. These results support the concept that these NR-deficient mutants with various levels of NR associated catalytic activities represent different mutation events at the loci coding the NR structural components.
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