Chemical Durability Of Simulated Nuclear Waste Glasses And Their Natural Analogues In Submarine Conditions

Glass corrosion in MCC-1 tests at 90{dollar}\sp\circ{dollar}C and 30{dollar}\sp\circ{dollar}C was characterized by dissolution of glass and formation of surface layers. All three glasses studied showed greater durability in seawater (SW) than in distilled and deionized water (DDW). Among three types of glass, PNL 76-68 was least stable in both DDW and SW. ABS-118 glass and basaltic glass showed comparable dissolution rates.;A reaction zone was found between surface layer and unaltered glass. This was usually less than 1000 A and depleted in soluble elements such as B, Na, and Mo. For PNL 76-68 glass, Si was also depleted in this zone. When SW was used as leachant, Mg was found to diffuse through the reaction zone.;Glass corrosion consists of three successive stages: (1) ion-exchange between alkalis in glass and H{dollar}\rm\sb3O\sp+{dollar} (and/or Mg{dollar}\sp{lcub}2+{rcub}{dollar}) in leachant; (2) formation of a reaction zone depleted in B, Na, Li, Mo, and Si; and (3) slow dissolution of the reaction zone at solid/solution interface accompanied by diffusion of ions from the fresh glass boundary, and subsequent precipitation of hydroxides and silicates. The dissolution reaction slows down when silicate phases attain saturation. Mg diffusion through the reaction zone and rapid saturation of Mg layer silicate contribute to the enhanced stability of the glasses in SW.;Palagonitization of basaltic glass from DSDP Site 335 bears remarkable similarities to the corrosion processes in the laboratory conditions. The laboratory determined dissolution rate was found to be the same order as those of basaltic glass from Site 335. At 90{dollar}\sp\circ{dollar}C, the glasses studied would dissolved at a rate of a few to a few tens of micrometers per year

Approximations and Bounds for (n, k) Fork-Join Queues: A Linear Transformation Approach

Compared to basic fork-join queues, a job in (n, k) fork-join queues only needs its k out of all n sub-tasks to be finished. Since (n, k) fork-join queues are prevalent in popular distributed systems, erasure coding based cloud storages, and modern network protocols like multipath routing, estimating the sojourn time of such queues is thus critical for the performance measurement and resource plan of computer clusters. However, the estimating keeps to be a well-known open challenge for years, and only rough bounds for a limited range of load factors have been given. In this paper, we developed a closed-form linear transformation technique for jointly-identical random variables: An order statistic can be represented by a linear combination of maxima. This brand-new technique is then used to transform the sojourn time of non-purging (n, k) fork-join queues into a linear combination of the sojourn times of basic (k, k), (k+1, k+1), ..., (n, n) fork-join queues. Consequently, existing approximations for basic fork-join queues can be bridged to the approximations for non-purging (n, k) fork-join queues. The uncovered approximations are then used to improve the upper bounds for purging (n, k) fork-join queues. Simulation experiments show that this linear transformation approach is practiced well for moderate n and relatively large k.Comment: 10 page

Cyclization reactions induced by Samarium(II) iodide

Describes studies on Samarium(II) iodide mediated cyclizations to prepare cyclopentane analogs

Calibration of the angular momenta of the minor planets in the solar system

We aim to determine the relative angle between the total angular momentum of the minor planets and that of the Sun-planets system, and to improve the orientation of the invariable plane of the solar system. By utilizing physical parameters available in public domain archives, we assigned reasonable masses to 718041 minor planets throughout the solar system, including near-Earth objects, main belt asteroids, Jupiter trojans, trans-Neptunian objects, scattered-disk objects, and centaurs. Then we combined the orbital data to calibrate the angular momenta of these small bodies, and evaluated the specific contribution of the massive dwarf planets. The effects of uncertainties on the mass determination and the observational incompleteness were also estimated. We determine the total angular momentum of the known minor planets to be $1.7817\times10^{46}$ g $\cdot$ cm$^2$ $\cdot$ s$^{-1}$. The relative angle $\alpha$ between this vector and the total angular momentum of the Sun-planets system is calculated to be 14.74 deg.. By excluding the dwarf planets Eris, Pluto, and Haumea, which have peculiar angular momentum directions, $\alpha$ drops sharply to 1.76 deg.; a similar result applies to each individual minor planet group. This suggests that, without these three most massive bodies, the plane perpendicular to the total angular momentum of the minor planets would be close to the invariable plane of the solar system. On the other hand, the inclusion of Eris, Haumea, and Makemake can produce a difference of 1254 mas in the inclination of the invariable plane, which is much larger than the difference of 9 mas induced by Ceres, Vesta, and Pallas as found previously. By taking into account the angular momentum contributions from all minor planets, including unseen ones, the orientation improvement of the invariable plane is larger than 1000 mas in inclination with a $1\sigma$ error of 50-140 mas.Comment: 10 pages, 3 figures, published in A&

Stable Isotopes of Clay Minerals from Autoclave Tests of Oil Sands: Implications for Clay Formation during Steaming of Alberta Clearwater Oil Sands

In an effort to evaluate mineral-water isotopic exchange during cyclic steam stimulation (CSS), solutions and\u3c2 μm berthierine-dominated solids from the Clearwater Formation oil sands of Alberta, Canada were analyzed for stable isotope compositions before and after reaction in autoclaves for 1008 h at 250 °C. There was no significant change in solution δ18O and δ2H, which is consistent with the high water/mineral ratio used in the experiments. The solids showed a marked decrease in both δ18O and δ2H following the experiments. Pre-run solids have δ18O of +9.5 to +12.9‰and δ2H of −114 to −113‰, whereas post-run solids have δ18O of −4.7 to +2.1‰ and δ2H of −147 to −128‰. Neither oxygen- nor hydrogen-isotope equilibrium was established between the solids and the solutions. Calculation suggests that oxygen-isotope exchange (44–58%) was greater between the solids and the solutions than was the case for hydrogen isotopes (23–50%). We propose that this behaviour resulted from partial inheritance of the pre-run berthierine structure during formation of the post-run smectite, chlorite-smectite and chlorite. This process confounds the use of clay mineral stable isotope compositions as a temperature indicator of in situ steam/steam condensate interaction with oil-sands reservoirs. The results also suggest an additional mechanism by which new clay minerals can be formed during CSS-related, artificial diagenesis