The impact of neogene grassland expansion and aridification on the isotopic composition of continental precipitation

The late Cenozoic was a time of global cooling, increased aridity, and expansion of grasslands. In the last two decades numerous records of oxygen isotopes have been collected to assess plant ecological changes, understand terrestrial paleoclimate, and to determine the surface history of mountain belts. The δ¹⁸(O) values of these records, in general, increase from the mid-Miocene to the Recent. We suggest that these records record an increase in aridity and expansion of grasslands in midlatitude continental regions. We use a nondimensional isotopic vapor transport model coupled with a soil water isotope model to evaluate the role of vapor recycling and transpiration by different plant functional types. This analysis shows that increased vapor recycling associated with grassland expansion along with biomechanistic changes in transpiration by grasses themselves conspires to lower the horizontal gradient in the δ¹⁸(O) of atmospheric vapor as an air mass moves into continental interiors. The resulting signal at a given inland site is an increase in δ¹⁸(O) of precipitation with the expansion of grasslands and increasing aridity, matching the general observed trend in terrestrial Cenozoic δ¹⁸(O) records. There are limits to the isotopic effect that are induced by vapor recycling, which we refer to here as a “hydrostat.” In the modern climate, this hydrostatic limit occurs at approximately the boundary between forest and grassland ecosystems

Mental Health and School Functioning for Girls in the Child Welfare System : the Mediating Role of Future Orientation and School Engagement

This study investigated the association between mental health problems and academic and behavioral school functioning for adolescent girls in the child welfare system and determined whether school engagement and future orientation meditated the relationship. Participants were 231 girls aged between 12 and 19 who had been involved with the child welfare system. Results indicated that 39% of girls reported depressive symptoms in the clinical range and 54% reported posttraumatic symptoms in the clinical range. The most common school functioning problems reported were failing a class (41%) and physical fights with other students (35%). Participants reported a mean number of 1.7 school functioning problems. Higher levels of depression and PTSD were significantly associated with more school functioning problems. School engagement fully mediated the relationship between depression and school functioning and between PTSD and school functioning, both models controlling for age, race, and placement stability. Future orientation was not significantly associated with school functioning problems at the bivariate level. Findings suggest that school engagement is a potentially modifiable target for interventions aiming to ameliorate the negative influence of mental health problems on school functioning for adolescent girls with histories of abuse or neglect

Inertial currents in the Caribbean Sea

Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to [email protected], referencing the URI of the item.Not availabl

Currents at Little Lake Harbor, Lake Superior /

Cover title."January 1966."Includes bibliographical references (p. 18).Mode of access: Internet

Customer-Driven Project Management : Building Quality into Project Processes

xxxv, 609 p. : il.; 21 c

Customer-driven project management : a new paradigm in total quality implementation

xxiii, 508 p. : il.; 21 cm

Redesign of a Quadrotor Capable of Autonomous Flight and Collaboration with a UGV

The goal of this project was to analyze, design and implement an autonomous quadrotor aerial vehicle for collaborative operations with autonomous ground vehicles. The main design constraints were to maximize payload and flight time. The quadrotor consists of a delrin hub with four aluminum arms, and is infused with an IMU and multiple range finder sensors. The quadrotor is capable of formation control, docking with the ground robot for power conservation during transit and rapid deploy