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  • 1
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Trisomy 8, in mosaic or non-mosaic form is an extremely rare chromosomal condition in man. Liveborn subjects usually present with mental retardation, bone and joint anomalies and a variety of other physical anomalies. The mental retardation associated with the condition is, however, usually moderate compared to that found in other viable human autosomal trisomic conditions. The present report describes a trisomy 8 mosaic male subject with normal IQ and near-normal phenotype, ascertained through infertility. Chromosome studies on peripheral blood lymphocytes reveal a pure trisomy 8 constitution; cultured skin fibroblasts show 46,XY/47,XY+8 mosaicism. At meiosis, the extra No. 8 chromosome is missing from the germ line. The testicular histology indicates a germ cell maturation arrest in many spermatocytes and the patient is severely oligospermic. Biochemical studies to assay levels of glutathione reductase, a red cell enzyme, the gene for which resides in chromosome 8, show increased levels in the trisomy 8 patient compared with controls.
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  • 2
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] XLRP is one of the most severe clinical forms of RP, with onset in males in the first decade, progressing to blindness by the third or fourth decade6. Female carriers show a variable but generally mild degree of visual loss, which occurs much later than in males and is associated with ...
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  • 3
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A new thermally stable, low-resistance In-based ohmic contact to n-type GaAs has been developed. The contacts consist of ion-beam sputtered Ni (5 nm)/In (5 nm)/Ni (5 nm) layers with a magnetron sputtered WNx overlayer. A low-contact resistance of ∼0.3 Ω mm was obtained by rapid thermal annealing at 750 °C for ∼5 s. The contact resistance and the excellent contact morphology remained unchanged after annealing at 400 °C for more than 100 h. The present deposition technique provides several advantages over previously reported electron-beam evaporated In-based contacts. In particular, the ability to deposit a thick WNx overlayer simplifies GaAs integrated circuit (IC) fabrication by (a) eliminating the need for separate diffusion barrier deposition and patterning steps, and (b) providing for low-sheet resistance (∼2 Ω/(D'Alembertian)) IC interconnect capabilities. In addition, sputter deposition allows for the controlled incorporation of n-type dopants into the metallization if further reduction of the contact resistance is required.
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  • 4
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 51 (1987), S. 664-666 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A new thermally stable, low-resistance NiInW contact metal to n-type GaAs has been developed by depositing a thin In layer with Ni and W layers and annealing at elevated temperatures for a short time. Low resistances of ∼0.3 Ω mm were obtained at annealing temperatures in the range of 800 to 1000 °C. The contact resistances were stable during subsequent annealings at 400 °C for 100 h and 500 °C for 10 h. The thermal stability of the contact resistance and the surface morphology of this contact are superior to those of the conventionally used AuNiGe contacts and this new contact is suitable for various device applications. Further reduction of the contact resistance can be achieved simply by reducing the sheet resistance of the contact metals.
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  • 5
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 213 (1967), S. 815-815 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] All the patients admitted to this hospital have severely disordered personalities and they have been classified according to whether the cause is known or not. For example, some have brain damage which followed infections, others are epileptics, and others suffer from a psychosis. The largest group ...
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  • 6
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 222 (1969), S. 1294-1295 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The recent isolation of an attenuated strain (Langat E5) of Langat virus3 and the limited increase of the severity of infection in mice treated with cyclophosphamide ('Cytoxan')4'5 led us to develop an experimental model to compare the role of neutralizing antibody in protection by live and ...
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  • 7
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effects of Si or Ge addition to NiInW ohmic contacts on their electrical behavior were studied, where the samples were prepared by evaporating Ni(Si) or Ni(Ge) pellets with In and W and annealed by a rapid thermal annealing method. An addition of Si affected the contact resistances of NiInW contacts: the resistances decreased with increasing the Si concentrations in the Ni(Si) pellets and the lowest value of ∼0.1 Ω mm was obtained in the contact prepared with the Ni-5 at. % Si pellets after annealing at temperatures around 800 °C. The contact resistances did not deteriorate during isothermal annealing at 400 °C for more than 100 h, far exceeding process requirements for self-aligned GaAs metal-semiconductor field-effect-transistor devices. In addition, the contacts were compatible with TiAlCu interconnects which have been widely used in the current Si process. Furthermore, the addition of Si to the NiInW contacts eliminated an annealing step for activation of implanted dopants and low resistance (∼0.2 Ω mm) contacts were fabricated for the first time by a "one-step'' anneal. In contrast, an addition of Ge to the NiInW contacts did not significantly reduce the contact resistances.
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  • 8
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thermally stable, low-resistance ohmic contacts on n-type GaAs are required to fabricate high-speed GaAs integrated circuits. MoGeW contacts prepared by annealing at high temperature around 800 °C in an InAs overpressure are attractive, because the contact is expected to be thermally stable during subsequent annealing at 400 °C, which is required by several process steps following ohmic contact formation. In the present experiment, the contact resistance measurements and microstructural analysis of MoGeW contacts were carried out to establish a fabrication process which forms ohmic contacts with low contact resistance. The contact metals were prepared by sequentiallydepositing Ge, Mo, Ge, and W, with various Mo/Ge layer thickness ratios, onto (100)-oriented GaAs wafers. The conducting channels were formed by doping GaAs with about 1×1018 cm−3 Si. Contact resistances were determined by the transmission line method, and microstructural analysis was carried out by x-ray diffraction, Auger electron spectroscopy, secondary ion mass spectroscopy (SIMS), and transmission electron microscopy. Contact resistance (Rc) was found to be strongly influenced by the Mo/Ge layer thickness ratio and annealing temperature. Rc values lower than 0.5 Ω mm were obtained for samples with a Mo/Ge thickness ratio in the range 0.6–1.3 and annealed at around 800 °C. The lowest mean Rc value obtained in the present experiment was 0.3 Ω mm. The major compound formed in this contact was identified to be Mo5As4, which has a high melting point. No changes in the microstructure and the Rc values were observed after annealing the contacts at 400 °C for more than 100 h. Finally, an attempt to understand the carrier transport mechanism was carried out by correlating the electrical behavior with the film microstructure. For this purpose the samples were annealed in an InAs overpressure with or without a Si3N4 cap, by flash annealing, and in an arsine atmosphere. The ohmic behavior was observed only in the samples annealed in an InAs overpressure. The SIMS analysis indicated that a small amount of In, less than 1 at. %, was segregated at the metal/GaAs interfaces in this sample. The In could form compounds with GaAs and reduce the barrier height, resulting in reduction of the contact resistances.
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  • 9
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: It was previously found that a small amount of In impurity was able to convert MoGeW contacts from Schottky to ohmic behavior yielding thermally stable, low-resistance ohmic contacts n-type GaAs. In the present experiment transport measurements and materials studies were carried out for MoGeInW contacts in which a thin layer of In was directly added to the MoGeW contacts during deposition. The transition from Schottky to ohmic behavior was observed by adding an In layer as thin as ∼1 nm to the MoGeW. Contact resistances were found to be very sensitive to the deposition sequence, the annealing method, the annealing temperature, and the In layer thickness. Low resistances of ∼0.5 Ω mm were obtained in the MoGeInW contacts with 2-nm-thick In layers, annealed by the heat-pulse method at temperatures in the range of 880–960 °C for 2 s. Contact resistances were stable during subsequent annealing at 400 °C for 100 h. Evidence of formation of the parallel diode areas with various barrier heights was obtained for these contacts after annealing at elevated temperatures. These low-barrier-height areas are believed to be the interfaces between the contact metals and InGaAs phases. The composition within the ternary phases was uniform, and no composition gradient was observed. The composition was determined by small-probe x-ray energy dispersive spectrum to be close to In0.2Ga0.8As. The distribution of these ternary phases, influenced by the contact fabrication process parameters, strongly affected the contact resistance.
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  • 10
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Analytical chemistry 35 (1963), S. 595-596 
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
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