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PubMed2005

Exploring the relationship between hydrologic parameters and nutrient loads using digital elevation model and GIS - a case study from Sugarcreek headwaters, Ohio, U.S.A.

Ohio is typical among the Midwestern and Eastern United States with high levels of water pollutants, the main sources being from agriculture. In this study, we used a digital elevation model in conjunction with hydrological indices to determine the role of landscape complexity affecting the spatial and temporal variation in pollutant levels, in one of the most impaired headwater streams in Ohio. More than eighty five percent of the study area is dominated by agriculture. Spatial distribution of slope (S), altitude and wetness index along with other watershed parameters such as flow direction, flow accumulation, stream networks, flow stream orders and erosion index were used within a Geographic Information Systems framework to quantify variation in nitrate and phosphate loads to headwater streams. Stream monitoring data for nutrient loads were used to correlate the observed spatial and temporal patterns with hydrological parameters using multiple linear regressions. Results from the wetness index calculated from a digital elevation model suggested a range of 0.10-16.39, with more than 35% having values less than 4.0. A Revised Universal Soil Loss Equation (RUSLE) predicted soil loss in the range of 0.01-4.0 t/ha/yr. Nitrate nitrogen levels in the study area paralleled precipitation patterns over time, with higher nitrate levels corresponding to high precipitation. Atmospheric deposition through precipitation could explain approximately 35% of total nitrate levels observed in streams. Among the different topographic variables and hydrological indices, results from the step-wise multiple regression suggested the following best predictors, (1) elevation range and upstream flow length for nitrate, (2) flow direction and upstream flow length for ammonia-nitrogen and slope, and (3) elevation range for phosphate levels. Differences in the landscape models observed for nitrate, phosphate and ammonia-nitrogen in the surface waters were attributed partly to differences in the chemical activity and source strengths of the different forms of these nutrients through agricultural management practices. The results identify geomorphologic and landscape characteristics that influence pollutant levels in the study area.

Ammonia↗

PubMed2005

Egocentrism over e-mail: can we communicate as well as we think?

Without the benefit of paralinguistic cues such as gesture, emphasis, and intonation, it can be difficult to convey emotion and tone over electronic mail (e-mail). Five experiments suggest that this limitation is often underappreciated, such that people tend to believe that they can communicate over e-mail more effectively than they actually can. Studies 4 and 5 further suggest that this overconfidence is born of egocentrism, the inherent difficulty of detaching oneself from one's own perspective when evaluating the perspective of someone else. Because e-mail communicators "hear" a statement differently depending on whether they intend to be, say, sarcastic or funny, it can be difficult to appreciate that their electronic audience may not.

Affect↗

PubMed2004

Chronic stress accelerates ultraviolet-induced cutaneous carcinogenesis.

BACKGROUND: Physical and emotional stressors have been found to mediate a wide variety of biological changes including the facilitation of tumor progression; however most of these paradigms utilized artificial sources of neoplasms and stress. METHODS: Skh mice were exposed to carcinogenic doses of ultraviolet light (UV). The stressed group was subjected to the close proximity of fox urine as a source of stress from the presence of the odor of their natural predator, while the control group remained stress free. RESULTS: A significant acceleration in the development of cutaneous neoplasms was observed in mice that had been exposed to the stressor. The first tumor appeared in the group after 8 weeks, whereas nonstressed mice began to develop these by week 21. CONCLUSION: These results suggest that stress plays a role in potentiating cutaneous carcinogenesis.

Animals↗