δ13C tracing of dissolved inorganic carbon sources in major world rivers

δ13C tracing of dissolved inorganic carbon sources in major world river

Controls on dissolved organic carbon quantity and chemical character in temperate rivers of North America

Understanding the processes controlling the transfer and chemical composition of dissolved organic carbon (DOC) in freshwater systems is crucial to understanding the carbon cycle and the effects of DOC on water quality. Previous studies have identified watershed‐scale controls on bulk DOC flux and concentration among small basins but fewer studies have explored controls among large basins or simultaneously considered the chemical composition of DOC. Because the chemical character of DOC drives riverine biogeochemical processes such as metabolism and photodegradation, accounting for chemical character in watershed‐scale studies will improve the way bulk DOC variability in rivers is interpreted. We analyzed DOC quantity and chemical character near the mouths of 17 large North American rivers, primarily between 2008 and 2010, and identified watershed characteristics that controlled variability. We quantified DOC chemical character using both specific ultraviolet absorbance at 254 nm (SUVA254) and XAD‐resin fractionation. Mean DOC concentration ranged from 2.1 to 47 mg C L−1 and mean SUVA254 ranged from 1.3 to 4.7 L mg C−1 m−1. We found a significant positive correlation between basin wetland cover and both bulk DOC concentration (R2 = 0.78; p \u3c 0.0001) and SUVA254 (R2 = 0.91; p \u3c 0.0001), while other land use characteristics were not correlated. The strong wetland relationship with bulk DOC concentration is similar to that found by others in small headwater catchments. However, two watersheds with extremely long surface water residence times, the Colorado and St. Lawrence, diverged from this wetland relationship. These results suggest that the role of riverine processes in altering the terrestrial DOC signal at the annual scale was minimal except in river systems with long surface water residence times. However, synoptic DOC sampling of both quantity and character throughout river networks will be needed to more rigorously test this finding. The inclusion of DOC chemical character will be vital to achieving a more complete understanding of bulk DOC dynamics in large river systems

MERLOT: a faculty-focused website of educational resources

Journal ArticleThe Multimedia Educational Resource for Learning and Online Teaching (MERLOT) is a community of academic institutions, professional discipline organizations, and individual people building a collection of Web-based teaching and learning resources where faculty can easily find peer-reviewed materials for use in their classes. The MERLOT project is currently supported by 23 systems and institutions of higher education and by the National Science Foundation. MERLOT is developing collections of learning materials from many academic disciplines, including psychology

Ecological role of hunting in population dynamics and its implications for co-management of the Porcupine caribou herd

At a present population size of 160 000 animals, the Porcupine caribou herd has been subjected to an annual harvest rate of 2% for the past couple of decades. We modeled potential sensitivity of herd population dynamics to hunting and used that relation as a basis for a herd monitoring system. Maximum number of adult cows that could be harvested without causing a subsequent decline in herd size was calculated as a function of total number of adult cows in the herd and recruitment of calves to yearling age-class. Maximum cow harvest, therefore, is a threshold above which hunting has destabilizing effects on herd dynamics. Actual harvest in relation to theoretical maximum harvest provides a basis for prediction of herd sensitivity to hunting. Maximum harvest is a linear function of recruitment. Herd dynamics are especially sensitive to low recruitment, however, when combined with low herd size. The two relations involving recruitment and herd size provide the basis for predicting herd dynamics and sensitivity to hunting. Herd size is best estimated by aerial census, while an index of recruitment can be predicted by monitoring autumn body condition of adult females. Body condition can be estimated on the basis of a few simple metrics measured by hunters in the field. The hunters' data on body composition, combined with aerial census data on herd size, provide a useful tool for managers and co-management boards to devise policies and regulations to manage the herd. The population model and monitoring system can operate on the Internet and be accessible to all users in villages within the range of the Porcupine caribou herd

Investigation of stresses in a reinforced concrete arch of seventy foot span

Thesis (B.S.)--University of Illinois, 1910.Typescript

On the morphology and pressure-filtration characteristics of filter cake formation: insight from coupled CFD–DEM simulations

The slurry filtration process at a tunnel face plays an important role in supporting pressure transmission, which is crucial to the stability of a tunnel face during shield tunneling. In this paper, a series of coupled computational fluid dynamics (CFD)–discrete element method (DEM) numerical simulations were carried out to model the slurry filtration column test. A simplified JKR (Johnson-Kendall-Roberts) model was used to simulate the cohesion between slurry particles. Four types of filter cake formation were identified under different combinations of size ratios between slurry and sand particles, and cohesion between slurry particles according to morphology and pore pressure distribution characteristics. These types were external filter cake, external & internal filter cake, internal filter cake & deep penetration and external & internal filter cake & deep penetration. The contact-based analysis of the constriction (void throat) sizes reveals that the dynamic evolution of the pore structure is closely related to the slurry infiltration process, i.e., the infiltration of slurry particles tends to seal the infiltration channel, which prevents infiltration of any more particles. The variation of Dc50 (the median constriction size) is closely related to the infiltration state of the slurry particles. The pressure drop within the filter cake becomes significant, i.e., the filter cake will become effective, only when the ratio of Dc50 to the size of slurry particles is below a threshold value. The current study provides new insight into the fundamental mechanism underlying the slurry filtration process during shield tunneling

Midwifery education and technology enhanced learning: Evaluating online story telling in preregistration midwifery education

Background A major issue regarding the implementation of blended learning for preregistration health programmes is the analysis of students' perceptions and attitudes towards their learning. It is the extent of the embedding of Technology Enhanced Learning (TEL) into the higher education curriculum that makes this analysis so vital. Objectives This paper reports on the quantitative results of a UK based study that was set up to respond to the apparent disconnect between technology enhanced education provision and reliable student evaluation of this mode of learning. Design Employing a mixed methods research design, the research described here was carried to develop a reliable and valid evaluation tool to measure acceptability of and satisfaction with a blended learning approach, specifically designed for a preregistration midwifery module offered at level 4. Methods Feasibility testing of 46 completed blended learning evaluation questionnaires - Student Midwife Evaluation of Online Learning Effectiveness (SMEOLE) - using descriptive statistics, reliability and internal consistency tests. Results Standard deviations and mean scores all followed predicted pattern. Results from the reliability and internal consistency testing confirm the feasibility of SMEOLE as an effective tool for measuring student satisfaction with a blended learning approach to preregistration learning. Conclusions The analysis presented in this paper suggests that we have been successful in our aim to produce an evaluation tool capable of assessing the quality of technology enhanced, University level learning in Midwifery. This work can provide future benchmarking against which midwifery, and other health, blended learning curriculum planning could be structured and evaluated