Weathering sequences of clay minerals in soils along a serpentinitic toposequence

There has been limited research on clay mineral transformation in serpentinitic soils under humid tropical conditions. In this study, four soil pedons were selected along a toposequence from the summit (Entisol), shoulder (Vertisol), backslope (Alfisol) to footslope (Ultisol) positions to explore the contributions and the significance of landscape and weathering status of serpentinitic rock with regard to clay mineral transformations in eastern Taiwan. Experimental results indicated that the large amount of dithionite-citrate-bicarbonate-extractable Fe (Fe) and clay in the subsurface horizon were mainly caused by the strong leaching potential from intensive rainfall and weathering of the fine-grained parent rocks. The clay mineralogy reflected the clear weathering trend of the soils along the toposequence: (1) the soils on the summit and shoulder contained smectite and serpentine, which are predominant in the young soils derived from serpentinitic rocks; and (2) vermiculite gradually increased in the relatively old soils on backslope and footstope. The mineralogical transformations observed along the toposequence indicated that chlorite and serpentine, initially present in the Entisol on the summit, weather into smectite and interstratified chlorite-vermiculite in the intermediate soil on the shoulder under strong leaching and oxidizing conditions. Furthermore, vermiculite formed as the major weathering product of chlorite and smectite in the soil developed on the backslope. In addition to vermiculite, kaolinite and quartz formed in the soils on the footslope with the greatest concentration of Fe along the toposequence

The Role of Long and Short Paths in Circuit Performance Optimization

We consider the problem of determining the smallest clock period for a combinational circuit by considering both the long and short paths. To bring in the timing of the circuit, we make use of a new class of paths called the shortest destabilizing paths as well as the longest sensitizable paths. The bounds on the clock period can alternatively be viewed as optimization objectives. At the physical level, the problem becomes applying transistor sizing and delay buffer insertion to achieve specified upper bounds on clock period and latency. We present experimental results that reflect the complexity of the optimization problem. The clock period determination can also be extended to circuits with feedbacks

Collagen grafted 3D polycaprolactone scaffolds for enhanced cartilage regeneration

10.1039/c3tb20680gJournal of Materials Chemistry B1435971-5976JMCB