ALBERT

Notes: Abstract Further support for the view that mineralization at Mount Isa comprises two separate events is provided by 34S/32S measurement. Isotopic exchange between sulphides in lead-zinc-silver ores appears to have been promoted locally during metamorphism, whereas isotopic disequilibrium persists in the copper ores. These isotopic data are explained by a model in which sedimentary deposition of lead, zinc and silver was succeeded by the post-metamorphic emplacement of copper. Past biological activity is inferred from the occurrence of low concentrations of organic carbon with δ13C values ranging from −21 to −26‰ PDB. Carbonate contents, expressed as carbon, vary from 〈0.1% to 10.9%. The δ13C and δ18O values for the carbonates are relatively constant at −4.4±1.1‰ and −17.6±1.1‰ PDB respectively. These values are interpreted as reflecting isotopic changes induced in original marine carbonates by isotopic exchange during lower greenschist metamorphism.

Notes: Live oysters were inoculated with 01 V. cholerae or non-01 V. cholerae and the liquor from the oysters was spread onto thiosulfate citrate bile salts agar plates. After incubation the colonies with yellow centers were picked and streaked onto sheep blood agar plates. Biochemical tests were performed on all colonies. Isolates exhibiting characteristic V. cholerae reactions were checked for serological identity and inoculated into a vibrio medium. After incubation, the isolates were further analyzed for lactic and succinic acids by gas-liquid chromatography. Peak height ratios of lactic/succinic acid provided a testing parameter to distinguish all isolates of 01 V. cholerae from non-01 V. cholerae isolates recovered from the oysters.

Notes: We describe the design and construction of a new search for supernovae, based on the use of current computer and detector technology. This search uses a computer-controlled telescope and charge coupled device (CCD) detector to collect images of hundreds of galaxies per night of observation, and a dedicated minicomputer to process these images in real time. The search system has a detection threshold of 17th visual magnitude, discovered its first supernova on 18 May 1986, and at this writing has found three additional supernovae. The system currently is being upgraded with an improved detector and a more powerful computer. At full speed and sensitivity, the system will be able to search 2500 galaxies per night with a limiting magnitude of 19 or fainter.

Notes: In the past several years, research in each of the wide-band-gap semiconductors, SiC, GaN, and ZnSe, has led to major advances which now make them viable for device applications. The merits of each contender for high-temperature electronics and short-wavelength optical applications are compared. The outstanding thermal and chemical stability of SiC and GaN should enable them to operate at high temperatures and in hostile environments, and also make them attractive for high-power operation. The present advanced stage of development of SiC substrates and metal-oxide-semiconductor technology makes SiC the leading contender for high-temperature and high-power applications if ohmic contacts and interface-state densities can be further improved. GaN, despite fundamentally superior electronic properties and better ohmic contact resistances, must overcome the lack of an ideal substrate material and a relatively advanced SiC infrastructure in order to compete in electronics applications. Prototype transistors have been fabricated from both SiC and GaN, and the microwave characteristics and high-temperature performance of SiC transistors have been studied. For optical emitters and detectors, ZnSe, SiC, and GaN all have demonstrated operation in the green, blue, or ultraviolet (UV) spectra.Blue SiC light-emitting diodes (LEDs) have been on the market for several years, joined recently by UV and blue GaN-based LEDs. These products should find wide use in full color display and other technologies. Promising prototype UV photodetectors have been fabricated from both SiC and GaN. In laser development, ZnSe leads the way with more sophisticated designs having further improved performance being rapidly demonstrated. If the low damage threshold of ZnSe continues to limit practical laser applications, GaN appears poised to become the semiconductor of choice for short-wavelength lasers in optical memory and other applications. For further development of these materials to be realized, doping densities (especially p type) and ohmic contact technologies have to be improved. Economies of scale need to be realized through the development of larger SiC substrates. Improved substrate materials, ideally GaN itself, need to be aggressively pursued to further develop the GaN-based material system and enable the fabrication of lasers. ZnSe material quality is already outstanding and now researchers must focus their attention on addressing the short lifetimes of ZnSe-based lasers to determine whether the material is sufficiently durable for practical laser applications. The problems related to these three wide-band-gap semiconductor systems have moved away from materials science toward the device arena, where their technological development can rapidly be brought to maturity.

Notes: We have designed, calibrated, and deployed an electron spectrograph to measure the effect of the free-electron laser interaction on the relativistic electron beam in an FEL. The spectrograph spans a wide energy range (ΔE/E∼1) and is designed for electron energies from 2 to 4 MeV. Calibration was achieved using a 2–6-keV proton beam, and the measured dispersion is in good agreement with the value predicted from ray tracing. The spectrograph has been used to estimate the extraction efficiency, and the results agree within 25% with the observed microwave power levels.

Notes: We report the first use of high temperature superconductors for multilayer interconnection of bare semiconductor die to form multichip modules. Ten die with a total of 160 pads were interconnected on a 3.4 cm2 substrate. The interconnections were a combination of YBa2Cu3O7−δ lines and vias on two wiring levels separated by an epitaxial insulating layer. Connection between the two YBa2Cu3O7−δ wiring layers was accomplished by the use of superconducting vias through the insulator. Two similar multilayer multichip module designs, with 30- and 10-μm-wide YBa2Cu3Oδ−7 lines, were constructed.

Notes: We report the first fabrication of active semiconductor and high-temperature superconducting devices on the same substrate. Test structures of complementary metal-oxide-semiconductor transistors were fabricated on the same sapphire substrate as test structures of Y1Ba2Cu3O7−δ flux-flow transistors, and separately, Y1Ba2Cu3O7−δ superconducting quantum interference devices utilizing both biepitaxial and step-edge Josephson junctions. Both semiconductor and superconductor devices were operated at 77 K. The cofabrication of devices using these disparate yet complementary electronic technologies on the same substrate opens the door for the fabrication of true semiconductive/superconductive hybrid integrated circuits capable of exploiting the best features of each of these technologies.

Notes: We describe the fabrication of a free-standing YBa2Cu3C7−δ air bridge for useful applications of microstructures and microcircuits integration. We have used a sacrificial dielectric layer, which was subsequently etched, to produce the air gap between top and bottom layers. We have used conventional photolithographic processing, ion-beam dry etching, and selective wet etching with HF to create the novel microstructures. Step coverage of epitaxial bridge layers have been achieved without significant degradation of the superconducting properties of YBa2Cu3O7−δ layers.