Valence state of titanium in the Wark-Lovering rim of a Leoville CAI as a record of progressive oxidation in the early Solar Nebula

Simon et al. (2005) reported low Ti³⁺/Ti⁴⁺ values in Ti-rich pyroxenes in the Wark-Lovering rim (WL) of a Leoville CAI (144A) as compared to the interior of the inclusion. These electron microprobe analyses were interpreted as evidence that the growth of the WL rim is the manifestation of an evolution to a more oxidizing environment. Further work by Simon et al. (2007) used XANES analyses to argue for higher Ti³⁺ abundances and interpreted the data of Simon et al. (2005) as the result of X-ray contamination by neighboring phases, specifically spinel. Late-stage alteration was also included as a possible explanation.To investigate further the oxidation state of Ti in WL rims, we re-analyzed Leoville 144A to obtain a more complete data set of Ti³⁺/Ti⁴⁺ values in the Wark-Lovering rims. We conducted experiments on spinel-mixing to determine whether this was a plausible explanation for the observed paucity of Ti³⁺ in WL rims. While we found a wider range of Ti³⁺/Ti⁴⁺ in these WL rim data than in our original study, our new data show that the original conclusion that rims are lower in Ti³⁺/Ti⁴⁺ than interiors remains valid. We conclusively rule out spinel-mixing as an explanation for our data, and we see no clear inconsistency between our electron microprobe data and the XANES data. The WL rim of CAI Ef3 was also analyzed by EMPA and compared to the results of Leoville 144A.To predict compositional consequences of this hypothesis, we constructed a reaction space between Ti-rich pyroxene in the WL rim, perovskite, Mg_(g), Ca_(g), O_2(g), and SiO_(g). We find the oxidation of Ti³⁺, coupled with Ti loss via perovskite formation, explains many features of WL rim EMPA analyses. We maintain that the WL rim pyroxenes are compositionally distinct from those in the interior, and are evidence of a more oxidizing environment during WL rim formation.     

Source parameters of mining-induced seismic events: An evaluation of homogeneous and inhomogeneous faulting models for assessing damage potential

Source parameter estimates based on the homogeneous and inhomogeneous source models have been examined for an anomalous sequence of seven mine-induced events located between 640 and 825 m depth at Strathcona mine, Ontario, and having magnitudes ranging betweenm _N 0.8 and 2.7. The derived Brune static stress drops were found to be similar to those observed for natural earthquakes (30 bars), whereas dynamic stress drops were found to range up to 250–300 bars. Source radii derived from Madariaga's model better fit documented evidence of underground damage. These values of source radii were similar to those observed for the inhomogeneous model. The displacement at the source, based on the observed attenuation relationship, was about 60 mm for three magnitude 2.7 events. This is in agreement with slip values calculated using peak velocities and assuming the asperity as a Brune source within itself (72 mm). By using Madariaga's model for the asperity, the slip was over 3 times larger than observed. Peak velocity and acceleration scaling relations with magnitude were investigated by incorporating available South African data, appropriately reduced to Canadian geophysical conditions. The dynamic stress drop scaled as the square root of the seismic moment, similar to reported results in the literature for crustal earthquakes. This behavior suggests that the size of the asperities responsible for the peak ground motion, with respect to the overall source size, follow distributions that may be similar over a wide range of magnitudes. Measurements of source rupture complexity (ranging from 2 to 4) were found to agree with estimates of overall source to asperity radii, suggesting, together with the observed low rupture velocities (0.3 to 0.6 ), that the sources were somewhat complex. Validation of source model appropriateness was achieved by direct comparison of the predicted ground motion level to observed underground damage in Creighton mine, located within the same regional stress and geological regime as Strathcona mine. Close to the source (<100 m), corresponding to relatively higher damage levels, a good agreement was found between the predicted peak particle velocities for the inhomogeneous model and velocities derived based on established geomechanical relationships. The similarity between asperity radii and the regions of the highest observed damage provided additional support for the use of the inhomogeneous source model in the assessment of damage potential.     

Association of iron oligomeric species with natural organic matter: a combined EELS and M?ssbauer investigation

The nature of the interaction between iron oxyhydroxide compounds and natural organic matter (NOM) may take various forms and is still a matter of debate. It is an important field to understand, especially for water treatment applications and for the knowledge of iron transport in the environment. The nature of association reached between iron oligomeric species and NOM is here investigated using M?ssbauer spectroscopy and electron energy-loss spectroscopy (EELS) at the Fe-L3 edge. Raw water NOM taken from Moselle River (France), natural humic substances extracted from the riverine suspended matter, and a synthesized humic-like substance, are coagulated with iron nitrate according to a jar-test procedure. The results from M?ssbauer spectroscopy indicate that Fe is present in an octahedral coordination environment, which is consistent with prior X-ray absorption spectroscopy reported in the literature. The areas beneath the peaks (Fe L3 edge) and the peak shapes of EELS spectra differ according to the origin of the organic matter, suggesting that various types of Fe populations can be distinguished using the EELS technique. Combining the selectivity of both M?ssbauer spectroscopy for identifying trace, poorly crystalline Fe solids, oxidation state and of EELS for being able to characterize the population of Fe based on L-edge spectra, appears promising for characterizing Fe in systems containing NOM.     

Numerical simulation of impact loads using a particle method

The violent free-surface motions interacting with structures are investigated using the moving particle semi-implicit (MPS) method, which was originally proposed by Koshizuka and Oka (1996) for incompressible flow simulation. In the present numerical method, a more efficient algorithm for Lagrangian moving particles is used for solving various highly nonlinear free-surface problems without using the Eulerian approach or the grid system. Therefore, the convection terms and time derivatives in the Navier–Stokes equation can be calculated more directly without any numerical diffusion, instabilities, or topological failure. In particular, the MPS method is applied to the simulation of liquid-entry and slamming problems, such as wet-drop (liquid–liquid collision) tests in an LNG tank and slamming loads (solid–liquid collision) on rigid plates with various incident angles. The numerical results are in good agreement with available experimental data.     

Approximated solution on the properties of the scavenging gap during precipitation using harmonic mean method

Wet deposition refers to both natural and artificial processes where particles are scavenged by atmospheric hydrometeors. Below-cloud atmospheric particles are removed by raindrops via Brownian diffusion, interception, and impaction. The overall scavenging coefficient has a broad and distinctive minimum for aerosol penetration between 0.1 and several micrometers in diameter. In this study, the approximated analytical solution for most penetrating particle size during precipitation was obtained. Brownian diffusion and interception were considered under the assumption of the inertial impaction can be neglected in this study conditions. Both the minimum collection efficiency and minimum scavenging coefficient particle size were estimated using the harmonic mean type approximation, with the solution compared to the numerically calculated results. The approximated results were comparable with the numerical solutions. The results showed that collection efficiency diameter is a function of terminal velocity and the collection mechanisms included. When considering Brownian diffusion and interception, most penetrating particle size increases as drop diameter increases, which shows a contrary to the study of Wang (1978) and this shows that most penetrating particle size depends on collection efficiency mechanism, flow velocity and collector diameter. Consequently, this study analytically approximated general type-solutions for scavenging gap particle size and minimum collection efficiency during precipitation.     

Understanding the impact of droughts in the Yarmouk Basin,Jordan: monitoring droughts through meteorological and hydrological drought indices

This article assesses drought status in the Yarmouk Basin (YB), in northern Jordan, using the Standardized Precipitation Index (SPI), the Standardized Water-Level Index (SWI), and the Percent Departure from Normal rainfall (PDNimd) during the years 1993–2014. The results showed that the YB suffers from frequent and irregular periods of drought as variations in drought intensity and frequency have been observed. The SPI results revealed that the highest drought magnitude of ??2.34 appeared at Nuaimeh rainfall station in 1991. This station has also experienced severe drought particularly in years 1995, 1999, 2005, and 2012 with SPI values ranging from ??1.51 to ??1.59. Some other rainfall stations such as Baqura, Ibbin, Khanasiri, Kharja, Mafraq police, Ramtha, Turra, and Umm Qais have also suffered several periods of drought mostly in 1993. The SWI results show the highest extreme drought events in 2001 in Souf well while other extreme drought periods were observed at Wadi Elyabis well in 1994 and at Mafraq well in 1995. As compared to SPI maps, our SWI maps reflect severe and extreme drought events in most years, negatively impacting the groundwater levels in the study area.     

Relations among net-transfer reaction progress, 18O−13C depletion,and fluid infiltration in a clinohumite-bearing marble

A siliceous dolomitic marble xenolith within a mid-crustal Jurassic diorite exhibits mineralogical and stable isotopic evidence for infiltration of water-rich fluid. Adjacent to endoskarn which bounds the xenolith, forsterite has been replaced by clinohumite as a result of a devolatilization reaction driven by addition of aqueous fluid and extraction of heat. Isotopic compositions of calcite also record infiltration of aqueous fluid concentrated near contacts with endoskarn. Marble calcite ¹⁸O_SMOW values range from +19.5 at the center of the xenolith to +12.6 adjacent to endoskarn. Calcite ¹³C_PDB decreases sympathetically from +3.0 to +1.4. The calculated equilibrium composition of coexisting C–O–H–F fluid and a quantitative characterization of the whole-rock reaction which produced clinohumite and consumed graphite are used to place inequality contraints on the composition of the infiltrated fluid. Continnum mechanical transport models based on the resulting fluid compositions suggest that a small time-integrated Darey flux of 44 cm³/cm² coupled with diffusive transport in the fluid was sufficient to produce both the isotopic shifts and the net-transfer reactions evidenced in the xenolith. The calculations demonstrate the importance of graphite as an indicator of time-integrated flux. The maximum possible CH₄ content of the infiltrated fluid is sufficiently high to impart a 2.0 uncertainty in the ¹³C of the fluid. The isotopic composition of the fluid is consistent with a magmatic origin when this uncertainty is taken into account.     

Identifying factors influencing flood mitigation at the local level in Texas and Florida: the role of organizational capacity

In the United States, mitigating the adverse impacts of flooding has increasingly become the responsibility of local decision makers. Despite the importance of understanding why flood mitigation techniques are implemented at the local level, few empirical studies have been conducted over the last decade. Our study addresses this lack of research by examining the factors influencing local communities to adopt both structural and non-structural flood mitigation strategies. We use statistical models to predict multiple flood mitigation techniques implemented by cities and counties based on a survey of floodplain administrators and planning officials across Texas and Florida. Particular attention is paid to the role of organizational capacity to address floods in addition to various local geophysical and socioeconomic characteristics. Results indicate that organizational capacity is a significant factor contributing to the implementation of both structural and non-structural flood mitigation techniques, even when controlling for contextual characteristics.