Radiological characterization of neutron-activated metal wastes from nuclear power stations

Three different methods for determining the long-lived radionuclide contents of highly neutron activated metal wastes are being compared and assessed using samples of pressurized-water reactor (PWR) and boiling-water reactor (BWR) spent fuel disassembly hardware and control rods. These methods include: 1) empirical analyses involving sampling and laboratory measurements; 2) direct assay techniques; 3) calculation methods. These techniques are discussed and the results of the comparisons made to date are presented. The agreement between empirical versus calculational methods for the disassembly hardware was generally within 10% to 50%, and rarely exceeded a factor of 2.5, especially near the fueled region of the reactor core. However, large discrepancies between the measured versus calculated concentrations were observed for⁵⁹Ni and⁶³Ni at the end fittings of the fuel assembly hardware, where the calculations underestimated the concentrations by factors varying from about 8 to 28. The calculation errors are believed to be due to inadequate cross section data for the nickel isotopes.Pacific Northwest Laboratory is operated for the U. S. Department of Energy by Battelle Memorial Institute under Contract DE-AC06-76RLO 1830.     

Measurement of the charging of individual dust grains in a plasma

An experiment is described for investigating the charging of dust grains in a plasma. The apparatus is a double plasma device into which single dust grains are dropped from the top. The dust charge is detected and measured by a sensitive electrometer attached to a Faraday cup on the bottom. Experiments with electrons from the emissive filaments but without plasma indicate that the grains charge to approximately the filament potential for filament bias voltages smaller in absolute value than -70 V. The charge is of order 10⁶ electrons for SiC grains 30-150 μm in diameter. At higher bias voltage the charge is reduced due to secondary emission. The charge on grains increases with grain size and is nearly independent of the filament emission current. With plasma in the device, the grains charge both positively and negatively     

Torsion in Boundary Coinvariants and K -Theory for Affine Buildings

Let (G, I, N, S) be an affine topological Tits system, and let Γ be a torsion-free cocompact lattice in G. This article studies the coinvariants H ₀(Γ; C(Ω,Z)), where Ω is the Furstenberg boundary of G. It is shown that the class [1] of the identity function in H ₀(Γ; C(Ω, Z)) has finite order, with explicit bounds for the order. A similar statement applies to the K ₀ group of the boundary crossed product C ^*-algebra C(Ω)Γ. If the Tits system has type ? ₂, exact computations are given, both for the crossed product algebra and for the reduced group C ^*-algebra.     

Kohlenstoffbestimmung auf nassem Wege

Ohne Zusammenfassung     

Control of Schottky barrier heights on high-K gate dielectrics for future complementary metal-oxide semiconductor devices

The calculated Schottky barrier heights of polar and nonpolar interfaces of many metals on HfO2 high dielectric constant gate oxide have been found to vary strongly with the metal work function and also with oxide termination, with relatively little Fermi level pinning. This indicates that the choice of metal gate materials will not limit the continued scaling of metal-oxide semiconductor devices.     

Scalable silicon nanowire photodetectors

This paper presents photodetectors having vertically stacked electrodes with sub-micron (300 nm) separation based on silicon nanowire (SiNW) nanocomposites. The thin-film-like devices are made using standard photolithography instead of electron beam lithography and thus are amenable to scalable low-cost manufacturing. The processing technique is not limited to SiNWs and can be extended to different nanowires (NWs) (e.g., ZnO, CdSe) and substrates. The current–voltage characteristics show Schottky behaviour that is dependent on the properties of the contact metal and that of the pristine SiNWs. This makes these devices suitable for examination of electronic transport in SiNWs. Preliminary results for light sensitivity show promising photoresponse that is a function of effective NW density.     

Gold‐Catalyzed Intermolecular Anti‐Markovnikov Hydroamination of Alkylidenecyclopropanes

The cationic gold phosphine complex [{PCy₂(o‐biphenyl)}Au(NCMe)]⁺SbF₆^? (Cy=cyclohexyl) catalyzes the intermolecular, anti‐Markovnikov hydroamination reaction of monosubstituted and cis‐ and trans‐disubstituted alkylidenecyclopropanes (ACPs) with imidazolidin‐2‐ones and other nucleophiles. This reaction forms 1‐cyclopropyl alkylamine derivatives in high yield and with high regio‐ and diastereoselectivity. NMR spectroscopic analysis of gold π‐ACP complexes and control experiments point to the sp hybridization of the ACP internal alkene carbon atom as controlling the regiochemistry of the ACP hydroamination reaction.