Assessing Seasonal and Inter-Annual Variations of Lake Surface Areas in Mongolia during 2000-2011 Using Minimum Composite MODIS NDVI.

A minimum composite method was applied to produce a 15-day interval normalized difference vegetation index (NDVI) dataset from Moderate Resolution Imaging Spectroradiometer (MODIS) daily 250 m reflectance in the red and near-infrared bands. This dataset was applied to determine lake surface areas in Mongolia. A total of 73 lakes greater than 6.25 km2in area were selected, and 28 of these lakes were used to evaluate detection errors. The minimum composite NDVI showed a better detection performance on lake water pixels than did the official MODIS 16-day 250 m NDVI based on a maximum composite method. The overall lake area detection performance based on the 15-day minimum composite NDVI showed -2.5% error relative to the Landsat-derived lake area for the 28 evaluated lakes. The errors increased with increases in the perimeter-to-area ratio but decreased with lake size over 10 km(2). The lake area decreased by -9.3% at an annual rate of -53.7 km(2) yr(-1) during 2000 to 2011 for the 73 lakes. However, considerable spatial variations, such as slight-to-moderate lake area reductions in semi-arid regions and rapid lake area reductions in arid regions, were also detected. This study demonstrated applicability of MODIS 250 m reflectance data for biweekly monitoring of lake area change and diagnosed considerable lake area reduction and its spatial variability in arid and semi-arid regions of Mongolia. Future studies are required for explaining reasons of lake area changes and their spatial variability.

Hemodynamic effects of continuous intravenous injection and bolus plus continuous intravenous injection of oxytocin in cesarean section.

BACKGROUND: Oxytocin may cause adverse cardiovascular effects, including tachycardia and hypotension, whereas the optimal dose of oxytocin at elective cesarean section is unclear. To determine the lowest effective dose of oxytocin, we studied the hemodynamic effects of three doses during spinal anesthesia for elective single cesarean delivery. METHODS: Sixty women received oxytocin by continuous (0.5 IU/min) or bolus-continuous (2 or 5 IU prior to 0.25 IU/min continuous intravenous injection) intravenous injection after clamping of the umbilical cord. We compared changes in heart rate (HR), mean arterial pressure (MAP) and estimated blood loss (EBL). Uterine tone (UT) was assessed by palpation on a linear analog scale (LAS) at 5, 10, 15, 20 and 25 minutes after the oxytocin injection. In addition, oxytocin-related side-effects such as nausea and vomiting were recorded. RESULTS: Marked hemodynamic changes such as HR and MAP occurred in the bolus-continuous groups but not in the continuous groups. Although we were not able to observe a variation of EBL in each group, the UT significantly increased in the bolus-continuous groups when compared with that the continuous groups. In addition, the hemodynamic changes such as HR and MAP were lower in the two IU bolus-continuous group than those in the five IU group. CONCLUSIONS: Although bolus-continuous injection of oxytocin resulted in more hemodynamic changes than continuous injection, bolus-continuous injection had a greater effect on uterine contraction. Furthermore, two IU bolus-continuous injection showed lower hemodynamic changes than in the five IU bolus-continuous injection.

Simulating effects of fire disturbance and climate change on boreal forest productivity and evapotranspiration.

We used a terrestrial ecosystem process model, BIOME-BGC, to investigate historical climate change and fire disturbance effects on regional carbon and water budgets within a 357,500 km(2) portion of the Canadian boreal forest. Historical patterns of increasing atmospheric CO2, climate change, and regional fire activity were used as model drivers to evaluate the relative effects of these impacts to spatial patterns and temporal trends in forest net primary production (NPP) and evapotranspiration (ET). Historical trends of increasing atmospheric CO2 resulted in overall 13% and 5% increases in annual NPP and ET from 1994 to 1996, respectively. NPP was found to be relatively sensitive to changes in air temperature (T(a)), while ET was more sensitive to precipitation (P) change within the ranges of observed climate variability (e.g., +/-2 degrees C for T(a) and +/-20% for P). In addition, the potential effect of climate change related warming on NPP is exacerbated or offset depending on whether these changes are accompanied by respective decreases or increases in precipitation. Historical fire activity generally resulted in reductions of both NPP and ET, which consumed an average of approximately 6% of annual NPP from 1959 to 1996. Areas currently occupied by dry conifer forests were found to be subject to more frequent fire activity, which consumed approximately 8% of annual NPP. The results of this study show that the North American boreal ecosystem is sensitive to historical patterns of increasing atmospheric CO2, climate change and regional fire activity. The relative impacts of these disturbances on NPP and ET interact in complex ways and are spatially variable depending on regional land cover and climate gradients.