Understanding Global Positioning System Limitations: A Case Study of Mapping and Survey Grade GPS

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The long-term development of a watershed: spatial patterns, streamflow, and sustainability

This study examines the relationship between the developing landscape and the water flowing through it. The study area was an 86 sq. mi. watershed located in the coastal plains in Harris County, Texas. Daily streamflow data for 52 years was obtained from USGS and coincident precipitation data was obtained from NOAA. Georeferenced parcel-level data was obtained from the Harris County Appraisal District with sufficient detail to determine year of development, parcel area, and impervious cover. Watershed boundaries were obtained from the Harris County Flood Control District. After controlling for daily precipitation, streamflow exhibited significant increases at all levels over time. Increasing streamflow was not associated with climate change. FRAGSTATS was used to quantify spatial patterns in the developed landscape on an annual basis. Regression analysis was used to determine the relationship between spatial and non-spatial measures of development and streamflow. It was found that models based on the spatial configuration of the developed landscape predict streamflow better than non-spatial measures such as total impervious cover. Several metrics were identified for their potential use as guidelines for urban planning

Alcohol Consumption Inhibits Bone Growth and Development in Young Actively Growing Rats

Adolescence is an age of widespread alcohol abuse, but the effect of alcohol consumption on bone formation has not been studied in the young population. This study addresses the effect of alcohol on the early phases of bone growth and development in an animal model. Four‐week‐old, female Sprague‐Dawley rats were divided into three groups. Alcohol‐treated animals were fed a modified Lieber‐DeCarli diet ad libitum containing 35% ethanol‐derived calories, whereas the pair‐fed animals (weight‐matched to ethanol rats) received an iso‐caloric liquid diet in which maltose‐dextrin substituted calories supplied by ethanol. Chow animals were fed a standard rat chow ad libitum. Proximal tibiae (primarily cancellous bone) and femora (primarily cortical bone) were removed for analysis after 2, 4, 6, or 8 weeks on the diets. Serum was collected for analysis of calcium levels, osteocalcin, corticosterone, growth hormone, parathyroid hormone, and 25‐hydroxyvitamin D. The most rapid weight gain occurred between 6 and 8 weeks of age, and it was significantly delayed in alcohol and pair‐fed animals. Almost all morphological parameters of bone were lower in the alcohol groups. No significant difference in serum calcium levels, osteocalcin, or growth hormone levels were found, and small difference in calciotropic hormone levels was found between groups. The results indicate that chronic alcohol consumption during the age of bone development reduces bone density and peak bone mass in both cortical and cancellous bone. The mechanism whereby this effect occurs is not fully understood, but, our results suggest that the negative impact of alcohol on growing bone is not due to the secondary effects of altered bone mineral regulating hormones