Correlation between geochemical environments and controlling factors in the metallation of porphyrins

Experimental study on metallation of tetrapyrroles in biphasic systems showed that complexation with metal cations of the first transition series is a feasible under chemical environments similar to the naturally occurring ones. The metal transport from the aqueous media to the organic, which is a novel approach using naturally occurring fatty acids hydroxy aromatic compounds and thiols, is demonstrated. Selectivity between Ni²⁺ and VO²⁺ complexation is achieved under sulfurous rich conditions. The kinetic implications are discussed in view of their geoenvironmental applicability.     

Assessment of the coupled effects of vegetation leaf and root characteristics on soil suction: an integrated numerical modeling and probabilistic approach

Acta Geotechnica - Root depth and leaf area ratio are two important features of a plant and exhibit a coupled relation. Assessing their coupled effects on induced soil suction is essential for...     

Friction on a granite to granite interface

Summary Direct shear tests were conducted on a granite to granite interface for the purpose of tracing the evolution of frictional resistance as the initially smooth and polished surface wears during continuing shearing displacement. At the moment when sliding on the freshly manufactured interface starts (first slip), the friction angle is very low, between 15° and 20°, but then it increases with displacement rapidly without reaching a peak in the first test (maximum displacement less than 25 mm). Upon repeated shearing of the same surface (without re-finishing), this process of displacement-strengthening continues until a total accumulated displacement of about one half of one meter is reached. At this point, the angle of friction would typically be between 42° and 44°.Once the residual surface was established, the effect of time-related parameters, the duration of stationary contact under constant normal and shear load and variable displacement rate, were investigated. The frictional resistance is shown to increase with decreasing displacement rate and to increase with the duration of stationary contact.At a normal load greater than about one half of one MPa, shear displacement on a residual surface proceeds in an unstable, stick-slip manner. The change from stable to unstable sliding, that can be effected by either decreasing the sliding velocity or increasing the normal load, is not instantaneous, but occurs over a finite amount of displacement.     

Assimilation of Indian radar data with ADAS and 3DVAR techniques for simulation of a small-scale tropical cyclone using ARPS model

The center for Analysis and Prediction of Storms (CAPS) has developed a radar data assimilation system. The system consists of several principal components: (1) a program that quality-controls and remaps (or super-ob) radar data to the analysis grid, (2) a Bratseth analysis method (ADAS), or a 3DVAR method for analyzing all the data except for clouds and precipitation, (3) a cloud and hydrometer analysis package that applies diabetic adjustments to the temperature field, and (4) a non-hydrostatic forecast model named ARPS. In this study, the system is applied to a small cyclone named OGNI, which formed over Bay of Bengal, India during the last week of October 2006. Three experiments are carried out to test the impact of the radar data from Chennai, India. These experiments include (1) using NCEP GFS data to initialize the ARPS model (2) using initial and boundary condition produced from the ADAS and the cloud analysis, (3) using initial and boundary condition produced from the 3DVAR and cloud analysis. The inter-comparison of results reveals that the experiment with the 3DVAR assimilation technique produces more realistic forecast to capture the genesis, structure, and northward movement of the cyclone in the short-range time scale.     

The possible source of the causal time arrow in geo-historical explanations

My argument in this article, will be that nature, in general, and human nature in particular, suggests that, in principle, it is possible to derive the causal time arrow from several physical time arrows existing in nature and appearing to be unidirectional and irreversible phenomena. A more concrete argument will be that the assumption of a causal time arrow to which geologists resort in all geo-historical explanations, apparently originates in geo-historical time arrows concealed in unidirectional and irreversible physical-geological processes. I will illustrate this claim with a few examples of geo-historical explanations in the theory of plate tectonics, most of which are based on irreversible geo-physical processes. My final argument is a broader, of an epistemological nature, according to which the causal time arrow assumption used in logical-causative explanations in everyday life and in science, apparently “derives” in a way from the geo-historical time arrow. I will base this argument on the causal relationship and mutual influence that occurs in nature between geo-historical and evolutionary processes in animals, including developmental processes of the human brain and mind. From this reductionist argument, nicely integrated in the framework of evolutionary epistemology (EEM), it is possible to derive a wider naturalistic argument according to which, on principle, the laws of geo-historical physics can be reduced to the laws of logic and causality.