We report the detection of absorption lines by the reactive ions OH + , H 2 O + and H 3 O + along the line of sight to the submillimeter continuum source G10.6−0.4 (W31C). We used the Herschel HIFI instrument in dual beam switch mode to observe the ground state rotational transitions of OH + at 971 GHz, H 2 O + at 1115 and 607 GHz, and H 3 O + at 984 GHz. The resultant spectra show deep absorption over a broad velocity range that originates in the interstellar matter along the line of sight to G10.6−0.4 as well as in the molecular gas directly associated with that source. The OH + spectrum reaches saturation over most velocities corresponding to the foreground gas, while the opacity of the H 2 O + lines remains lower than 1 in the same velocity range, and the H 3 O + line shows only weak absorption. For LSR velocities between 7 and 50 km s −1 we estimate total column densities of N(OH + ) ≥ 2.5 × 10 14 cm −2 , N(H 2 O + ) ∼6 × 10 13 cm −2 and N(H 3 O + ) ∼4.0 × 10 13 cm −2 . These detections confirm the role of O + and OH + in initiating the oxygen chemistry in diffuse molecular gas and strengthen our understanding of the gas phase production of water. The high ratio of the OH + by the H 2 O + column density implies that these species predominantly trace low-density gas with a small fraction of hydrogen in molecular form.

We report the detection of absorption by interstellar hydroxyl cations and water cations, along the sight-line to the bright continuum source W49N. We have used Herschel's HIFI instrument, in dual beam switch mode, to observe the 972 GHz N = 1-0 transition of OH + and the 1115 GHz 1 11 −0 00 transition of ortho-H 2 O + . The resultant spectra show absorption by ortho-H 2 O + , and strong absorption by OH + , in foreground material at velocities in the range 0 to 70 km s −1 with respect to the local standard of rest. The inferred OH + /H 2 O + abundance ratio ranges from ∼3 to ∼15, implying that the observed OH + arises in clouds of small molecular fraction, in the 2−8% range. This conclusion is confirmed by the distribution of OH + and H 2 O + in Doppler velocity space, which is similar to that of atomic hydrogen, as observed by means of 21 cm absorption measurements, and dissimilar from that typical of other molecular tracers. The observed OH + /H abundance ratio of a few ×10 −8 suggests a cosmic ray ionization rate for atomic hydrogen of 0.6−2.4 × 10 −16 s −1 , in good agreement with estimates inferred previously for diffuse clouds in the Galactic disk from observations of interstellar H + 3 and other species.

This paper focuses on monitoring setting and strength development in cemented paste backfill (CPB). The composition of the paste is altered to study the effects of binder type and content, selected chemical admixtures (superplasticizers), mineral additives (e.g., fly ash), and pore fluid chemistry (e.g., ionic concentration and pH) on these properties. The three main techniques utilized are shear wave velocity measurements, penetration tests (e.g., Vicat needle tests), and unconfined compressive strength tests. All of these tests are sensitive to changes in the paste composition. The effect of the pore fluid chemistry and the chemical additives on the CPB properties depends on the ion type and concentration and the chemical composition of the superplasticizers. The shear wave velocity in both uncemented and cemented pastes increases with time as a result of self-weight consolidation, capillary forces, and cementation (the precipitation of ions in uncemented tailings pastes or cement hydration in cemented tailings pastes).Résumé : Cet article se concentre sur le montage d'instrumentation et sur le développement de la résistance dans un remblai de pâte-ciment (CPB). La composition de la pâte est modifiée pour étudier les effets sur ses propriétés du type et de la teneur du liant, des mélanges chimiques sélectionnés (superplastifiants), des additifs minéraux (e.g., cendres volantes), et de la chimie du fluide interstitiel (e.g., concentration ionique et pH). Les trois principales techniques utilisées sont les ondes de cisaillement, les essais de pénétration (e.g., essais à l'aiguille Vicat) et les essais de résistance en compression simple. Tous ces essais sont sensibles aux changements dans la composition de la pâte. L'effet de la chimie du fluide interstitiel et des additifs chimiques sur les propriétés du CPB dépend du type et de la concentration d'ions, et de la composition chimique des superplastifiants. La vitesse des ondes de cisaillement tant dans les pâtes cimentées que non cimentées augmente avec le temps à cause de la consolidation sous son propre poids, des forces capillaires et de la cimentation (la précipitation des ions dans les pâtes de stériles non cimentées ou l'hydratation du ciment dans les pâtes de stériles cimentées).Mots clés : remblai de pâte-ciment, vitesse des ondes de cisaillement, montage, résistance en compression simple.[Traduit par la Rédaction] Klein and Simon 324

Electrical conductivity can be accurately and readily measured in the laboratory and in the field, with minimal electrode effects even in high specific surface soils and∕or high ionic concentration pore fluids. Electrical conductivity combines the contributions of particle conduction, surface conduction and pore fluid conduction, and the effects of particle shape and fabric. The interplay between participating soil parameters is often obscured in typical empirical equations, such as Archie’s law. New experimental results show that surface conduction is an important contributor to global soil conduction in high specific surface soils that are saturated with low-ionic concentration pore fluids; the relevance of surface conduction increases with decreasing porosity. On the other hand, pore fluid conduction prevails as the conductivity of the electrolyte and the porosity of the soil increase. Furthermore, low frequency conductivity anisotropy increases with increasing ionic concentration. Simple yet robust microscale analytical models properly capture the observed interplay between the most relevant soil parameters.