7,412 research outputs found

    Isoprene Emission and Carbon Dioxide Protect Aspen Leaves from Heat Stress

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    High temperature, especially above 35oC, is known to reduce leaf photosynthetic rate in many tree species. This study investigated the effect of high temperature on isoprene-emitting (aspen) and non- emitting (birch) trees under ambient and elevated CO2 under open field conditions. Aspen trees tolerate heat better than birch trees and elevated CO2 protects both species against moderate heat stress. The increased thermotolerance in aspen trees compared to the birch trees may result from the aspen's ability to produce isoprene. Elevated CO2 increased carboxylation capacity, photosynthetic electron transport capacity and triose phosphate use in both birch and aspen trees. High temperature decreased all of these parameters in birch regardless of CO2 treatment but only photosynthetic electron transport and triose phosphate use at ambient CO2 were reduced in aspen. As temperature rises, non-isoprene-emitting trees will be at a disadvantage and biological diversity and species richness might be lost in some ecosystems. Our results indicate that isoprene emitting tree species will have an advantage over non-isoprene emitting ones under high temperatures

    Geology of the Early Arikareean Sharps Formation on the Pine Ridge Indian Reservation and Surrounding Areas of South Dakota and Nebraska

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    Based on geologic mapping, measured sections, and lithologic correlations, the local features of the upper and lower type areas of the Early Arikareean (30.8–20.6 million years ago) Sharps Formation are revised and correlated. The Sharps Formation above the basal Rockyford Member is divided into two members of distinct lithotypes. The upper 233 feet of massive siltstones and sandy siltstones is named the Gooseneck Road Member. The middle member, 161 feet of eolian volcaniclastic siltstones with fluvially reworked volcaniclastic lenses and sandy siltstone sheets, is named the Wolff Camp Member. An ashey zone at the base of the Sharps Formation is described and defined as the Rockyford Ash Zone (RAZ) in the same stratigraphic position as the Nonpareil Ash Zone (NPAZ) in Nebraska. Widespread marker beds of fresh water limestones at 130 feet above the base of the Sharps Formation and a widespread reddish-brown clayey siltstone at 165 feet above the base of the Sharps Formation are described. The Brown Siltstone Beds of Nebraska are shown to be a southern correlative of the Wolff Camp Member and the Rockyford Member of the Sharps Formation. Early attempts to correlate strata in the Great Plains were slow in developing. Recognition of the implications of the paleomagnetic and lithologic correlations of this paper will provide an added datum assisting researchers in future biostratigraphic studies. Based on similar lithologies, the Sharps Formation, currently assigned to the Arikaree Group, should be reassigned to the White River Group

    Geology of the Early Arikareean Sharps Formation on the Pine Ridge Indian Reservation and Surrounding Areas of South Dakota and Nebraska

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    Based on geologic mapping, measured sections, and lithologic correlations, the local features of the upper and lower type areas of the Early Arikareean (30.8–20.6 million years ago) Sharps Formation are revised and correlated. The Sharps Formation above the basal Rockyford Member is divided into two members of distinct lithotypes. The upper 233 feet of massive siltstones and sandy siltstones is named the Gooseneck Road Member. The middle member, 161 feet of eolian volcaniclastic siltstones with fluvially reworked volcaniclastic lenses and sandy siltstone sheets, is named the Wolff Camp Member. An ashey zone at the base of the Sharps Formation is described and defined as the Rockyford Ash Zone (RAZ) in the same stratigraphic position as the Nonpareil Ash Zone (NPAZ) in Nebraska. Widespread marker beds of fresh water limestones at 130 feet above the base of the Sharps Formation and a widespread reddish-brown clayey siltstone at 165 feet above the base of the Sharps Formation are described. The Brown Siltstone Beds of Nebraska are shown to be a southern correlative of the Wolff Camp Member and the Rockyford Member of the Sharps Formation. Early attempts to correlate strata in the Great Plains were slow in developing. Recognition of the implications of the paleomagnetic and lithologic correlations of this paper will provide an added datum assisting researchers in future biostratigraphic studies. Based on similar lithologies, the Sharps Formation, currently assigned to the Arikaree Group, should be reassigned to the White River Group

    Mechanism Design and Testing of a Self-Deploying Structure Using Flexible Composite Tape Springs

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    The detailed mechanical design of a novel deployable support structure that positions and tensions a membrane optic for space imagining applications is presented. This is a complex three-dimensional deployment using freely deploying rollable composite tape spring booms that become load bearing structural members at full deployment. The deployment tests successfully demonstrate a new architecture based on rolled and freely deployed composite tape spring members that achieve simultaneous deployment without mechanical synchronization. Proper design of the flexible component mounting interface and constraint systems, which were critical in achieving a functioning unit, are described. These flexible composite components have much potential for advancing the state of the art in deployable structures, but have yet to be widely adopted. This paper demonstrates the feasibility and advantages of implementing flexible composite components, including the design details on how to integrate with required traditional mechanisms

    E-Payment Acceptance Among German Millennials: Perception and Demographic Background

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    During the last twenty years, the growth of the internet and its ability to facilitate e-commerce transactions has had a profound impact on the way business is done by both corporations and individuals (Herhausen et al., 2015; Jeffus et al., 2017). The unprecedented growth of e-commerce has driven the creation of new payment systems to transfer funds electronically from person-to-person or person-to-business (Teoh et al., 2013; Sumanjeet, 2009). The intent of this research is to explore the factors surrounding e-payment use in specific geographical regions to provide a better understanding of that regions e-payment behaviors. This research centers on German millennials, how they value e-payment, and what factors influence their acceptance of electronic funds transfer technology. To reach this goal, a survey was conducted with German millennials exploring what behavior affects their usage of e-payment systems. The results of this survey can provide insights to understand attitudes and behaviors of young generations in their e-payment. The results of this exploratory study center on the descriptive statistics of the respondents

    Gender Imbalance Improvements in Academia, Business, and Physical Education

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    Traditionally, men have disproportionally held leadership positions in academia, business, and physical education. Fortunately, graduate programs in each field are providing women opportunities that were not apparent a few decades ago. We examine Business and Physical Education for transgressions of discrimination and provide evidence from personal interviews which indicate progress has been made for women in these fields. We provide several cross-disciplinary themes that transcend gender barriers to promote an equitable workforce in addition to field specific recommendations

    The decontamination of radioactive ion exchange resins using neutral salts as elutriants

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    Includes bibliographical references (leaves 124-126
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