نتایج جستجو برای: weak rocks
تعداد نتایج: 162522 فیلتر نتایج به سال:
Abstract Assessment of the microbial impact on mineral dissolution is crucial for a predictive understanding basic (Ca, Mg bearing) silicate weathering and associated CO 2 consumption, bioerosion, storage in basaltic rocks. However, there are controversies about mechanism effect, which ranges from inhibiting via nil to accelerating. Here we studied diopside interaction with heterotrophic bacter...
The Wadi Hodein area in the south Eastern Desert of Egypt is occupied by Neoproterozoic Pan-African (Precambrian) basement rocks including metamorphic and intrusive assemblages. The metamorphic assemblage comprises dismembered ophiolitic metamorphosed ultramafic rocks and island-arc calc-alkaline metavolcanics. On the other hand, the intrusive assemblage rocks include syn-tectonic tonalite-gran...
Theoretical and empirical studies of habitat selection suggest that reptiles should use ‘‘fixed’’ structural features (perch diameter, vegetation) or light intensity (sun and shade) to select thermally suitable microhabitats. But how do nocturnal species select thermally suitable diurnal retreat sites at night in the absence of visual cues? To investigate this question, we studied habitat selec...
The small GTPase RhoA can retract cell extensions by acting on two Rho kinases (ROCKs). Activated protein kinase A (PKA) inhibits RhoA and induces extensions. The isoquinoline H89 inhibits PKA and thus should prevent the inactivation of RhoA. In kinase assays, H89 has been recently found to inactivate a ROCK-II also. Because H89 may be able to exert opposite effects on cell extensions, we have ...
Sedimentary rocks are composed of detrital grains derived from source rocks, which are altered by chemical weathering, sorted during transport, and cemented during diagenesis. Fluvio-lacustrine sedimentary rocks of the Bradbury group, observed on the floor of Gale crater by the Curiosity rover during its first 860 sols, show trends in bulk chemistry that are consistent with sorting of mineral g...
We studied a suite of 40 oils and extracts of purported source rocks from the Tarim basin in NW China. The main group of oils comes from Tazhong and Tabei wells, which sample the largest known petroleum accumulations in the basin. These oils can be statistically correlated with extracts of Ordovician rocks based upon high relative concentrations of 24-isopropylcholestanes and low relative conce...
The central part of the Fennoscandian Shield in Finland is composed of the Palaeoproterozoic Svecofennian domain and the Archaean Karelian craton with a Palaeoproterozoic allochthonous and autochthonous cover. A cryptic suture separating these areas and another tentative suture dividing the Svecofennian into central and southern parts have been proposed. The chemical composition of sedimentary ...
Oxides are ubiquitous. The Earth’s crust and mantle are largely made up of compounds of metal cations and oxygen anions. Looking at the composition of the crust in Figure 1.1, we see that oxygen is the most abundant element and the most common metals are aluminum and silicon. Most rocks are therefore aluminosilicates. The next most abundant element, and the only transition metal other than tita...
a r t i c l e i n f o There are differences in the style of collisional orogens between the Phanerozoic and the Precambrian, most notably the appearance of blueschists and ultrahigh pressure metamorphic (UHPM) rocks in the geological record since the late Neoproterozoic, whereas these rocks are absent from older orogens. Understanding collisional orogenesis in the context of present-day values ...
The Apollo 14 rocks returned to ear th a re divisible into two broad groups: relatively hoinogeneous crystalline rocks and fragmental rocks (breccias). The crystalline rocks are, for the most par t , metaclastic, but a few, including the second largest sample returned, a re aphyric basalts. All of the crystalline rocks a re considered to be clasts dislodged from fragmental rocks. These fragment...
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