90 research outputs found

    Dynamic contrast enhanced (DCE) MRI estimation of vascular parameters using knowledge-based adaptive models

    Get PDF
    We introduce and validate four adaptive models (AMs) to perform a physiologically based Nested-Model-Selection (NMS) estimation of such microvascular parameters as forward volumetric transfer constant, K(trans), plasma volume fraction, v(p), and extravascular, extracellular space, v(e), directly from Dynamic Contrast-Enhanced (DCE) MRI raw information without the need for an Arterial-Input Function (AIF). In sixty-six immune-compromised-RNU rats implanted with human U-251 cancer cells, DCE-MRI studies estimated pharmacokinetic (PK) parameters using a group-averaged radiological AIF and an extended Patlak-based NMS paradigm. One-hundred-ninety features extracted from raw DCE-MRI information were used to construct and validate (nested-cross-validation, NCV) four AMs for estimation of model-based regions and their three PK parameters. An NMS-based a priori knowledge was used to fine-tune the AMs to improve their performance. Compared to the conventional analysis, AMs produced stable maps of vascular parameters and nested-model regions less impacted by AIF-dispersion. The performance (Correlation coefficient and Adjusted R-squared for NCV test cohorts) of the AMs were: 0.914/0.834, 0.825/0.720, 0.938/0.880, and 0.890/0.792 for predictions of nested model regions, v(p), K(trans), and v(e), respectively. This study demonstrates an application of AMs that quickens and improves DCE-MRI based quantification of microvasculature properties of tumors and normal tissues relative to conventional approaches

    An Objective Method to Assess and Recommend Exertion and Exercise Targets for Return to Play Post concussion

    Get PDF
    Introduction. Concussions are of significant concern for athletic trainers, and there is a critical need to objectively and safely allow an athlete to return to play. In sports the objective is return as safely and soon as possible. Exertion is a consideration regarding progressing an athlete back to play. The ability to exert in cardiovascular and strength and conditioning contexts are two critical steps in most return to play protocols. Being able to make objective recommendations is urgently needed, as trial and error leads to unnecessary risk of eliciting symptoms and/or causing setbacks. Objective. The object of this paper is to present the athletic trainer with data associated with a methodology that can be used to aid in designing a cardiovascular and strength training program post concussion. This objective measure does not rely on subjective patient reports of symptoms and utilizes a reflex based assessment method. Description. The transient exertion related carotid (TERC) murmur is a murmur that is heard at the carotid arteries during exercise. It normally is heard at around a heart rate of 150, but is heard at lower heart rates in patients who have sustained a concussion. Listening for the TERC murmur during a cardiovascular and strength training assessment can be used to provide information to the athletic trainer about safer target heart rates or safer lifting strategies post-concussion. We present data concerning 71 athletes (mean age 20.8 years) who were assessed for cardiovascular conditioning and body weight assessment. With 73% of the cardio assessment subjects, a TERC murmur was detected at a heart rate of 127.2 bpm (± 16 SD). For the strength assessment 42.1% had a TERC murmur. Clinical advantages. The clinical advantage of the TERC murmur is that it can be utilized by any athletic trainer trained to take a blood pressure. It provides objective information concerning safe target heart rates that will allow an athletic trainer to recommend appropriate exercise prescriptions. The TERC murmur assessment can also be used to help guide strength training protocols to facilitate safe return. Being able to safely recommend a means by which an athlete can recommence their training (cardiovascular and/or strength training) may accelerate return to play as well as aid in keeping the athlete happy, healthy and engaged

    Protest Cycles and Political Process: American Peace Movements in the Nuclear Age

    Full text link
    Since the dawn of the nuclear age small groups of activists have consistently protested both the content of United States national security policy, and the process by which it is made. Only occasionally, however, has concern about nuclear weapons spread beyond these relatively marginal groups, generated substantial public support, and reached mainstream political institutions. In this paper, I use histories of peace protest and analyses of the inside of these social movements and theoretical work on protest cycles to explain cycles of movement engagement and quiescence in terms of their relation to external political context, or the "structure of political opportunity." I begin with a brief review of the relevant literature on the origins of movements, noting parallels in the study of interest groups. Building on recent literature on political opportunity structure, I suggest a theoretical framework for understanding the lifecycle of a social movement that emphasizes the interaction between activist choices and political context, proposing a six-stage process through which challenging movements develop. Using this theoretical framework I examine the four cases of relatively broad antinuclear weapons mobilization in postwar America. I conclude with a discussion of movement cycles and their relation to political alignment, public policy, and institutional politics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68552/2/10.1177_106591299304600302.pd

    The Iso2k database: a global compilation of paleo-δ18O and δ2H records to aid understanding of common era climate

    Get PDF
    Reconstructions of global hydroclimate during the Common Era (CE; the past ~2,000 years) are important for providing context for current and future global environmental change. Stable isotope ratios in water are quantitative indicators of hydroclimate on regional to global scales, and these signals are encoded in a wide range of natural geologic archives. Here we present the Iso2k database, a global compilation of previously published datasets from a variety of natural archives that record the stable oxygen (δ18O) or hydrogen (δ²H) isotopic composition of environmental waters, which reflect hydroclimate changes over the CE. The Iso2k database contains 756 isotope records from the terrestrial and marine realms, including: glacier and ground ice (205); speleothems (68); corals, sclerosponges, and mollusks (145); wood (81); lake sediments and other terrestrial sediments (e.g., loess) (158); and marine sediments (99). Individual datasets have temporal resolutions ranging from sub-annual to centennial, and include chronological data where available. A fundamental feature of the database is its comprehensive metadata, which will assist both experts and non-experts in the interpretation of each record and in data synthesis. Key metadata fields have standardized vocabularies to facilitate comparisons across diverse archives and with climate model simulated fields. This is the first global-scale collection of water isotope proxy records from multiple types of geological and biological archives. It is suitable for evaluating hydroclimate processes through time and space using large-scale synthesis, model-data intercomparison and (paleo)data assimilation. The Iso2k database is available for download at: https://doi.org/10.25921/57j8-vs18 (Konecky and McKay, 2020) and is also accessible via through the NOAA/WDS Paleo Data landing page: https://www.ncdc.noaa.gov/paleo/study/29593

    The Arctic

    Full text link
    peer reviewe

    The Johnson Years, Volume Two: Vietnam, the Environment, and Science

    Get PDF
    Stretching from November 1963 to January 1969, the administration of Lyndon Baines Johnson was marked both by division and tumult and by significant accomplishments. In this volume, Robert Divine has brought together seven senior scholars who, in new essays, explore aspects of domestic and foreign policy during the Johnson years. This collection is a sequel to Divines earlier volume (originally published as Exploring the Johnson Years). The seven essays that compose Volume Two, together with Divine’s incisive and perceptive historiographical overview, offer new insights into Johnson’s complex character and leadership style. The LBJ that emerges from these pages is a very human figure who understands the corrosive, pervasive impact of the Vietnam War on his administration and who struggles to try to preserve the domestic programs he fought so long and hard to achieve. In exploring the antiwar movement, tax and foreign economic policies, environmental and health care questions, and the space program, these essays demonstrate how domestic issues were critically affected by the Vietnam War and provide a fuller understanding of Johnsons vital but flawed legacy to the nation. Description Robert A. Divine is the George W. Littlefield Professor Emeritus in American History at the University of Texas at Austin. He is a past president of the Society of Historians of American Foreign Relations, and his publications include Blowing on the Wind: The Nuclear Test Ban Debate, 1954–1960 and Eisenhower and the Cold War. This Kansas Open Books title is funded by a grant from the National Endowment for the Humanities and the Andrew W. Mellon Foundation Humanities Open Book Program.https://digitalcommons.pittstate.edu/kansas_open_books/1018/thumbnail.jp

    NASA and the Space Industry. By

    No full text

    American foreign policy

    No full text
    318 p.; 20 cm
    corecore