5,652 research outputs found

    A regional perspective on the palynofloral response to K-T boundary event(s) with emphasis on variations imposed by the effects of sedimentary facies and latitude

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    Palynological studies deal with fossil reproductive bodies that were produced by fully functioning plants, whereas most faunal studies are based on death assemblages. Therefore, changes in pollen and spore assemblages cannot be used directly as evidence of catastrophic mass killings but only to indicate changes in ecological conditions. The impact of the Cretaceous-Tertiary boundary event on terrestrial plant communities is illustrated by the degree, rate and selectivity of change. As in most classical palynological studies, the degree of change is expressed in terms of relative abundance and changes in species diversity. It is recognized that sampling interval and continuity of the rock record within individual sections can affect the percieved rate of change. Even taking these factors into account, a gradual change in relative abundance and multiple levels of apparent extinctions, associated with the interval bounding the K-T boundary, can be demonstrated. Climatic change, which locally exceeds the tolerance of individual species, and the possible loss of a group of pollinating agents are examined as possible explanations for the selectivity of apparent extinctions and/or locally truncated occurrences. The aspects of change are demonstrated with data from four different K-T boundary localities in Western Canada between paleolatitudes 60 and 75 deg north. Together, the four localities discussed allow changes imposed by latitude and differences in the depositional environment be isolated from the boundary event itself which is reflected by the truncated ranges of several species throughout the region of study. What must be recognized is that variations in the response of vegetation to the K-T boundary event(s) occurred throughout the Western Interior basin

    Specifications for and preliminary design of a plant growth chamber for orbital experimental experiments

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    It was proposed that plant experiments be performed on board the space shuttle. To permit the proper execution of most tests, the craft must contain a plant growth chamber which is adequately designed to control those environmental factors which can induce changes in a plant's physiology and morphology. The various needs of, and environmental factors affecting, plants are identified. The permissilbe design, construction and performance limits for a plant-growth chamber are set, and tentative designs were prepared for units which are compatible with both the botanical requirements and the constraints imposed by the space shuttle

    Re-thinking the Legacy 2012: The Olympics as commodity and gift

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    This paper opens discussion about the nature of Olympic ‘legacy’ and articulates a contradiction in the way ‘legacy’ is conceived - between ’gift’ and ’commodity’ (Mauss 1954).The The paper argues that establishing working definitions and parameters for ‘legacy’ is a difficult task. Defining ‘legacy’ is problematic especially if conceived as an entirely predictable or measurable set of objectives. Indeed, the definition of ‘legacy’ is partly constitutive of the legacy itself, a component of achievements that the city might make. Such a ‘legacy definition’ will become a functional term in the complex planning and evolving conceptions underpinning urban change for some time—if successfully negotiated and if governable. As such, ‘legacy’, and the activities and values entailed to it, can come to provide a catalytic ‘vocabulary of motives’ and a legitimating discourse enabling politicians, communities and their individual representatives to justify investments, evolving strategies and activities connected to and connecting developmental gains in a more or less healthy fashion. It is because of this that legacy and its various meanings come to matter

    Gynecologic conditions and bacterial vaginosis: implications for the non-pregnant patient.

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    Bacterial vaginosis is characterized by a shift from the predominant lactobacillus vaginal flora to an overgrowth of anaerobic bacteria. Bacterial vaginosis is associated with an increased risk of gynecologic complications, including pelvic inflammatory disease, postoperative infection, cervicitis, human immunodeficiency virus (HIV), and possibly cervical intraepithelial neoplasia (CIN). The obstetrical risks associated with bacterial vaginosis include premature rupture of membranes, preterm labor and delivery, chorioamnionitis and postpartum endometritis. Despite the health risks associated with bacterial vaginosis and its high prevalence in women of childbearing age, bacterial vaginosis continues to be largely ignored by clinicians, particularly in asymptomatic women

    Synthesizing Cyber Intrusion Alerts using Generative Adversarial Networks

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    Cyber attacks infiltrating enterprise computer networks continue to grow in number, severity, and complexity as our reliance on such networks grows. Despite this, proactive cyber security remains an open challenge as cyber alert data is often not available for study. Furthermore, the data that is available is stochastically distributed, imbalanced, lacks homogeneity, and relies on complex interactions with latent aspects of the network structure. Currently, there is no commonly accepted way to model and generate synthetic alert data for further study; there are also no metrics to quantify the fidelity of synthetically generated alerts or identify critical attributes within the data. This work proposes solutions to both the modeling of cyber alerts and how to score the fidelity of such models. Generative Adversarial Networks are employed to generate cyber alert data taken from two collegiate penetration testing competitions. A list of criteria defining desirable attributes for cyber alert data metrics is provided. Several statistical and information-theoretic metrics, such as histogram intersection and conditional entropy, meet these criteria and are used for analysis. Using these metrics, critical relationships of synthetically generated alerts may be identified and compared to data from the ground truth distribution. Finally, through these metrics, we show that adding a mutual information constraint to the model’s generation increases the quality of outputs and successfully captures alerts that occur with low probability

    Civil tiltrotor missions and applications. Phase 2: The commercial passenger market

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    The commercial passenger market for the civil tiltrotor was examined in phase 2. A market responsive commercial tiltrotor was found to be technically feasible, and a significant worldwide market potential was found to exist for such an aircraft, especially for relieving congestion in urban area-to-urban area service and for providing cost effective hub airport feeder service. Potential technical obstacles of community noise, vertiport area navigation, surveillance, and control, and the pilot/aircraft interface were determined to be surmountable. Nontechnical obstacles relating to national commitment and leadership and development of ground and air infrastructure were determined to be more difficult to resolve; an innovative public/private partnership is suggested to allow coordinated development of an initial commercial tiltrotor network to relieve congestion in the crowded US Northeast corridor by the year 2000

    Professionials\u27 perceived qualities for collaborative parent and professional partnerships

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    To truly appreciate and address the strengths and needs of children with disabilities, parents and professionals must be able to work collaboratively within longterm partnerships. Challenging the creation of parent and professional partnerships is a lack of common understanding or agreement upon what relationship qualities facilitate or deter from their development and preservation. This study investigated what relationship qualities are considered necessary according to a select group of professionals to foster collaborative partnerships between professionals and parents as well as to improve their handling of conflict. The study found that relationship qualities such as communication, respect, honesty, trust, flexibility, and confidence were believed essential by professionals for collaborative partnerships to exist. In addition, the professionals attributed these qualities as being critical for conflict prevention. This study also explored expectations professionals held for parents, relationship-building strategies, conflict prevention strategies, and conflict-resolution strategies. The study found that the relationship qualities identified as important for collaborative partnerships and conflict prevention were reflected within the strategies for relationship-building and addressing conflict. However, the relationship qualities for conflict resolution were less apparent within the strategies identified for conflict resolution. This study provides a beginning for parents and professionals to explore the values they bring to partnerships and whether they are demonstrating congruency between their values and actions. The professionals in this study believed that in collaborative partnerships, parents and professionals engage in open and honest communication, take responsibility to work together as a team across home and school environments, share common goals, and engage in mutual childcentered decision-making in order to move children forward and create positive student outcomes. Additional research is still needed to support the findings of this study and to gain the perspectives of parents and professionals representing different cultures and regions and other local systems of special education. Future research should continue to strive for a balance between the perspectives of parents and professionals and to focus on creating additional clarity regarding the meanings of mutually agreed upon relationship qualities as well as factors that indicate the presence of these factors
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