RESUMEN
This study investigates the relations between the shape of hydrologic responses and the dynamic transport properties of channel networks within the framework of random walks on fractal networks, focusing on the shape parameter of Nash model. To this end, we evaluate the static fractal structures and the dynamic transport properties of various channel networks and, then, validate Liu's conjecture (1992) for the shape of hydrologic responses. In the context of random walks on fractal networks, the fractal dimensions of channel networks can directly connect the static structure to the dynamic transport properties of channel networks through Horton's law of drainage composition. It is observed that the peak coordinates of hydrologic responses would have a more intimate relation to the connectivity of channel networks than the conductivity of those. The characteristic times of hydrologic responses also tend to be related to the connectivity of channel networks. Thereby, the shape of hydrologic responses would be expected directly affected by the fractal dimension of channel networks in terms of their static structure, while interpreted a combined result of the conductivity and the connectivity of channel networks in terms of their dynamic transport properties. So, the runoff hydrographs of a river basin could be considered shaped by the fractal dimensions of its channel networks following the linear hydrologic system theory.
RESUMEN
This study presents a theoretical framework based on power law distribution to identify the vulnerable regions to soil loss in Susu river basin at Cameron Highlands, Malaysia by using the geomorphologic factors from Digital Elevation Model (DEM). Drainage area is used to describe the runoff aggregation structure of the watershed which represents the magnitude of discharge. Stream power is also used to describe the energy expenditure pattern of the watershed. They are fitted to power law distribution by means of the maximum likelihood to estimate the threshold for soil loss. The landscape stability condition is assessed through the mechanism of channel initiation. Two regions in the slope area plot are recognized as the regimes susceptible to soil loss, in that discharge, local slope and energy are sufficient for the initiation of soil movement. The result is further improved by incorporating the Topographic Wetness Index (TWI) aiming to locate vulnerable regions to soil loss under the dynamic saturation process. The final result indicates that the vulnerable regions expand from perennial reaches to ephemeral reaches as saturation process develops. It implies the transition of runoff generation from groundwater in perennial reaches to surface runoff in ephemeral reaches. Identification of soil loss vulnerable regions under the dynamic saturation process helps in planning of the mitigation measures for soil erosion.
RESUMEN
PURPOSE: To compare the efficacy of single vitrified-warmed blastocyst embryo transfer (SVBT) versus double vitrified-warmed blastocyst embryo transfer (DVBT) according to the day of vitrification. METHODS: This retrospective study included a total of 1,051 cycles in women less than 37 years of age with their autologous SVBT cryopreserved on day 5 (5d-SVBT, n = 737) or day 6 (6d-SVBT, n = 154) and DVBT on day 5 (5d-DVBT, n = 129) or day 6 (6d-DVBT, n = 31) from January 2009 to December 2011. RESULTS: The clinical pregnancy rate (41.8 % vs. 48.1 %, p = 0.184) and ongoing pregnancy rate (36.6 % vs. 45.0 %, p = 0.072) were not significantly different between the 5d-SVBT group and the 5d-DVBT group. However, the clinical pregnancy (29.9 % vs. 58.1 %, p = 0.003) and ongoing pregnancy rates (23.4 % vs. 51.6 %, p = 0.001) were significantly lower in the 6d-SVBT group compared with those in the 6d-DVBT group. The implantation rate (42.2 % vs. 34.5 %, p = 0.03) of the 5d-SVBT group was significantly higher than that of the 5d-DVBT group, while the implantation rate (29.9 % vs. 37.1 %, p = 0.303) of the 6d-SVBT group was not statistically different compared with that in the 6d-DVBT group. The multiple pregnancy rates (1.0 % in the 5d-SVBT group vs. 38.7 % in the 5d-DVBT group, p < 0.001 and 0 % in the 6d-SVBT group vs. 22.2 % in the 6d-DVBT group, p = 0.001) were statistically significantly lower in the SVBT group compared with those in the DVBT group regardless of the day of vitrification. CONCLUSIONS: This study showed that the 5d-SVBT resulted in comparable clinical outcomes compared to the 5d-DVBT while the 6d-SVBT yielded significantly lower clinical outcomes compared to the 6d-DVBT.