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Carbon-14 is an important radionuclide in the inventory of radioactive waste and is considered to be a key radionuclide in performance assessment. In Switzerland, the 14C inventory in a cement-based repository for low- and intermediate-level radioactive waste is mainly associated with activated steel (∼85%). Anaerobic corrosion of the activated steel will determine the time-dependent release of 14C-bearing compounds from the cementitious near field into the host rock. The present study was carried out to provide an overview on the current state of the art knowledge regarding the carbon speciation during the anaerobic corrosion of activated and non-activated iron/steel and to critically assess the capability of thermodynamic modelling to predict 14C speciation in anoxic alkaline conditions. Previous experimental work showed the presence of oxidized and reduced hydrocarbons during corrosion in iron-water systems in anoxic (near neutral to alkaline) conditions which appears to be inconsistent with the negative redox potential of the system. The capability of thermodynamic modelling to predict the carbon speciation in these conditions was found to be limited due to uncertainties associated with the concept of metastability in the C–H–O system.
Particle size reduction is a primary means of improving efficiency in herbivores. The mode of food particle size reduction is one of the main differences between herbivorous birds (gizzard) and mammals (teeth). For a quantitative comparison of the efficiency of food comminution, we investigated mean fecal particle sizes (MPS) in 14 herbivorous bird species and compared these with a data set of 111 non-ruminant herbivorous mammal species. In general MPS increased with body mass, but there was no significant difference between birds and mammals, suggesting a comparable efficiency of food processing by gizzards and chewing teeth. The results lead to the intriguing question of why gizzard systems have evolved comparatively rarely among amniote herbivores. Advantages linked to one of the two food comminution systems must, however, be sought in different effects other than size reduction itself. In paleoecological scenarios, the evolution of “dental batteries,” for example in ornithopod dinosaurs, should be considered an advantage compared to absence of mastication, but not compared to gizzard-based herbivory.
We are big fans of propositions. But we are not big fans of the “propositional approach” proposed by Mitchell et al. The authors ignore the critical role played by implicit, non-inferential processes in biological cognition, overestimate the work that propositions alone can do, and gloss over substantial differences in how different kinds of animals and different kinds of cognitive processes approximate propositional representations.
We present phase resolved spectra of the Be binary ϕ Per. It is shown that orbital phase variations of the He I line profiles are due to a sector emission region in the circumprimary disk facing the secondary. The increasing asymmetry of Fe II emission lines indicates a density inhomogeneity in the circumprimary disk that developed after 1996.
In this talk I give a short overview of models for spectral lines in Be stars disks which I think are quite instructive. I then examine the arguments for my own model assumptions and discuss selected topics concerning radiative line transfer calculations in three dimensions. We show that symmetric Hα emission lines of Be stars can be understood in terms of Keplerian disks. It is also demonstrated that one-armed global disk oscillations provide the best available solution to understand the long-term V/R variations in Be star emission lines.
Low dielectric constant F-doped silicon oxide films (SiO:F) can be prepared by adding fluorine source, like as CF4 to the conventional PECVD processes. We could obtain SiO:F films with dielectric constant as low as 2.6 from the reaction mixture of SiH4/N2 O/CF4. The structural changes of the oxides were sensitively detected by Raman spectroscopy. The three-fold ring and network structure of the silicon oxides were selectively decreased by adding fluorine into the film. These structural changes contribute to the decrease ionic polarization of the film, but it was not the major factor for the low dielectric constant. The addition of fluorine was very effective to eliminate the Si-OH in the film and the disappearance of the Si-OH was the key factor to obtain low dielectric constant. A kinetic analysis of the process was also performed to investigate the reaction mechanism. We focused on the effect of gas flow rate, i.e. the residence time of the precursors in the reactor, on growth rate and step coverage of SiO:F films. It revealed that there exists two species to form SiO:F films. One is the reactive species which contributes to increase the growth rate and the other one is the less reactive species which contributes to have uniform step coverage. The same approach was made on the PECVD process to produce low-k C:F films from C2F4, and we found ionic species is the main precursor to form C:F films.
The recent introduction of dual inlaid Cu and oxide based interconnects within sub-0.25μm CMOS technology has delivered higher performance and lower power devices. Further speed improvements and power reduction may be achieved by reducing the interconnect parasitic capacitance through integration of low-k interlevel dielectric (ILD) materials with Cu. This paper demonstrates successful multi-level dual inlaid Cu/low-k interconnects with ILD permittivities ranging from 2.0 to 2.5. Integration challenges specific to inorganic low-k and Cu based structures are discussed. Through advanced CMP process development, multi-level integration of porous oxide materials with moduli less than 0.5 GPa is demonstrated. Parametric data and isothermal annealing of these Cu/ low-k structures show results with yield comparable to Cu/oxide based interconnects.
The thermal and chemical stability of low k fluorinated amorphous carbon (a-C:F) material, deposited by a novel co-sputtering process using both polytetrafluoroethylene (PTFE) and graphite targets was investigated. Thin films of a-C:F with fluorine concentration of 2–55% were deposited, and carbon is observed by XPS in four distinct chemical states, C-C, C-F, C-F2, C-F 3. The relative intensity of C-Fx to C-C increased in intensity with increasing fluorine content and decreasing deposition temperature. Formation of tantalum fluoride was observed upon deposition of tantalum nitride, and the defluorination of the film could lead to reliability and delamination problems.
Porous organosilicates useful for on-chip insulator applications can be prepared by templating the vitrification of low molecular weight silsesquioxanes (SSQs) using highly branched, thermally labile macromolecules which are subsequently removed in a thermal process to generate porosity. The process involves spin coating a mixture of the matrix material and the porogen (pore generator) followed by thermal curing to initiate vitrification and decomposition of the porogen. The morphology is fixed during the formation of the nanoscopic inorganicorganic hybrid and is maintained during foaming. This process generates controllable and stable morphologies where the void volume is determined by the porogen loading level. The porous materials are thermally robust and intrinsically hydrophobic without subsequent chemical treatment. Dielectric constants of < 2.2 are easily achieved for pore volumes of only 20%, and this porosity appears to be predominately closed cell in nature. These materials display a number of thermal mechanical and electric properties consistent with the requirements for on-chip insulator applications.
We derive the temperature and density structure of the accretion disk of the dwarf nova U Gem in quiescence from 3D radiative line and continuum transport calculations of a differentially rotating disk.
Magnetic properties of photoluminescing spark-processed silicon (sp-Si) have been investigated for the first time. Contrary to the diamagnetic signal known for bulk silicon, sp-Si displays a paramagnetic resonance as well as a ferromagnetic hysterisis loop. The paramagnetic resonance was studied using an EPR system and showed a high concentration of at least two distinct paramagnetic centers. One center can be eliminated by annealing in Ultra-High Purity nitrogen for 30 minutes at 600 °C. Measurements utilizing a SQUID magnetometer revealed that sp-Si displays ferromagnetic ordering with a saturization magnetization occuring at low fields. This is attributed to the high density of paramagnetic centers. Temperature dependent measurements were performed to establish possible links between magnetic properties and the luminescence of sp-Si.
We present 3-D LTE radiative transfer calculations  for H, He and Ca in accretion disks (AD) of dwarf novae in quiescence. The model disk is assumed to be in hydrostatic equilibrium vertically, and to rotate with Keplerian velocities. Calculated emission lines are fitted to phase-averaged, continuum-subtracted spectra of U Gem (Fig. 1) and T Leo (Fig. 2). Up to four parameters of the AD have been fitted: distance D, baryonic number density N, isotropic turbulence Vtu and disk temperature T; the latter two are assumed to be constant throughout the disk. Geometrical parameters are from  and .
Transparent, nanophase-separated, inorganic-organic hybrid polymers with dielectric constants below 3.0 have been prepared from reactively functionalized poly(amic ester) derivatives and substituted, oligomeric silsesquioxanes. These hybrid materials are stable to 400 °C and above and form tough, crack-free films. Induced cracking and crack propagation studies performed with the application of external stress suggest a maximum critical film thickness of at least 2.0 μm under severe stress conditions. These hybrid materials appear to be significantly toughened by the chemical incorporation of the polyimides relative to organically modified silicates and spin-on-glasses without significantly effecting other important polymer properties of the silicates.
Electrical resistance data were gathered from AI(Cu) VLSI metallization test structures during pulsed DC current stressing (15 mA peak) at elevated temperature (200 °C). Duty cycles of 50%, 67%, and 80% were applied at a frequency (repetition rate) of 133 MHz. Also, a duty cycle of 50% was applied at frequencies of 100 KHz, I MHz, and 133 MHz. The resistance-to-starting resistance ratio, R/Ro, was logged over time, and the data were used to extract the median time dependence of the resistance change. This, in effect, reveals the dependence of the median “failure” time on the R/Ro (or ΔR/Ro) criterion. An “enhancement factor” was defined as the ratio of the median “failure” time from a given pulsed test to that from a DC test with the same peak current. A weak dependence of this enhancement factor on R/Ro was found in the range examined. The degree of enhancement corresponds more closely to the average current density prediction than to the on-time prediction, although there is some small variation according to duty cycle and frequency.