The properties of macerals in Czechoslovak coals rich in inertinite

Czechoslovak bituminous coals rich in inertinite contain a considerable amount of inertinite with a reflectance range displaced towards and partly overlapping that of the vitrinite reflectance. Together with the existence of the transitional maceral group of semivitrinite, this causes difficulties in maceral analysis as well as in the technological evaluation of these coals. The relationship between the volatile matter of vitrinite and its reflectance is very close for both vitrinite- and inertinite-rich coals. The analogous relationship between the vitrinite reflectance and the volatile matter of inertinite displays a considerable scatter due to the effects of some higher values of the volatile matter of inertinite — related to the presence of inertinite with relatively low reflectance. The results of investigations into the coking properties of coals rich in inertinite, however, do not supply any proof of a higher fusibility of these coals.     

A micro-investigation of unsaturated sand in mini-triaxial compression based on micro-CT image analysis

Acta Geotechnica - The mechanical behaviours of unsaturated soils are highly related to the water content and pore water and air distributions. Under the context of climate change, geo-disasters...     

The structure of metamict zircon: A temperature-dependent EXAFS study

The thermal annealing (300–1700 K) of two metamict zircons (Ampagabe, Madagascar and Näegy, Japan) has been studied using X-Ray Diffraction (XRD) and Extended X-ray Absorption Fine Structure spectroscopy (EXAFS) at Zr K-edge. Two stages of thermal annealing within the aperiodic zircon are evidenced between 293 and 1700 K. The first stage (up to 600° C) shows a decrease of the a ₀-cell parameter from 6.674 (at 300° C) to 6.610 (at 600° C)± 0.005 Å. In that temperature range, the average local environment around Zr (presence of ^VIIZr and d(Zr-Zr) 3.3–3.6 Å) shows a weak, but significant increase of the Zr-Zr correlations located at 3.3–3.4 Å, undetectable by XRD. At temperatures up to 700° C (stage 2), the XRD-Bragg component arising from crystalline zircon increases in magnitude, whereas, Zr-K EXAFS analysis indicates a progressive ^VIIZr^VIIIZr transition, associated with a recovery of the crystalline zircon medium-range environment. For both techniques, the zircon structure is fully recovered at annealing temperatures up to 900° C.Electrostatic modelings suggest that the ^VIIIZr^VIIZr transition observed in zircon with increasing alpha-decay damage creates significantly overbonded oxygen atoms around Zr. With increasing temperature, those oxygen atoms are better bonded to ^VIIZr, due to the thermal expansion of the Zr-O bond. The congruent recovery of the zircon structure should therefore be favoured with increasing temperature. On the other hand, the metamict network can be also partially reorganized around 400–500° C, with the creation of Zr-rich domains, as measured by EXAFS. However, the growth of these domains after 3 hours annealing affects only minor portions of the aperiodic network. This model is corroborated by a similar thermal behaviour observed for a synthetic sol-gel of ZrO₂ · SiO₂ composition.     

Early Pre-Main Sequence Evolution of Low Mass Stars

Evolution of the gravitational contraction phase of stars having masses 0.3 < M/M⊙ < 1.5 were studied along with deuterium burning. The equation of state developed by Mihalas et al. (1988) and OPAL opacity tables were used in our investigation. The theoretical time lines were compared with observations. This revised version was published online in July 2006 with corrections to the Cover Date.     

Applications of innovative polygonal trend analyses to precipitation series of Eastern Black Sea Basin,Turkey

Theoretical and Applied Climatology - Examining historical variations of hydroclimatic variables can provide crucial information about changes of water resources in a water cycle. In this study,...     

Modeling flood dynamics in a temporary river draining to an eutrophic reservoir in southeast Portugal

Enxoé is a small temporary river with a flushy regime, which flash floods carry significant loads to the reservoir. As a result, the reservoir, which supplies 25,000 inhabitants, exhibits a high trophic state and cyanobacteria blooms since its construction in 1998, with water abstractions requiring extensive treatment. This study aimed to understand the contribution of flash floods to the Enxoé’s reservoir high trophic state using a modeling approach. This was the first time the river was monitored and that a modeling study was carried out. The MOHID-Land model was implemented to assess the water path in the catchment, and was integrated with field data to compute river loads. Results confirmed the importance of flash events. During flash floods, water properties were determined by soil surface and river bottom wash out, and depended mostly on the flush sequence and intensity. Model simulations showed that soil surface permeability reduction was an important factor regulating surface runoff while soil moisture was low. The first flood after the dry period contributed to 2% of the yearly discharge, 3% of yearly N load, and 7% of the yearly P loads. Winter floods contribution differed, producing 10% of both yearly discharge and loads. However, concentration of particulate matter and organic compounds in the first flood were one order of magnitude higher than in winter floods. This was due to river bottom resuspension and erosion of riparian areas, representative dynamics of a flushy regime. During subsequent winter floods, nutrient concentrations tended to remain constant as the watershed surface and respective soils were washed. Further work should link a watershed model to a reservoir model to depict the flood impact in the reservoir, and test management strategies to reduce the reservoir trophic state.     

Contrasting oxygen fugacity of I- and S-type granites from the Araçuaí orogen,SE Brazil: an approach based on opaque mineral assemblages

Mineralogy and Petrology - This study presents mineralogical characterization of opaque assemblages from I- and S-type granites from the Araçuaí orogen, southeastern Brazil that belong...