2,526 research outputs found

    Transport and degradation of phytoplankton in permeable sediment

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    In flume and field experiments we demonstrate that interfacial water flows, generated when bottom currents interact with sea bed topography, provide a fast and efficient pathway for the transport of suspended phytoplankton into subsurface layers of permeable sandy sediments. The advective transport, associated with small mounds and ripples as commonly found on shelf sediments, increased penetration depth of unicellular algae (Dunaliella spec.) into sandy sediment (permeability k = 4 × 10−11 m2) up to a factor of 7 and flux up to a factor of 9 relative to a smooth control sediment. The pore water flow field produced a distinct distribution pattern of particulate organic matter in the sediment with subsurface concentration maxima and zones depleted of algae. Flux chamber simulations of advective transport of algae into sands of different grain sizes revealed increasing fluxes, algal penetration depths, and degradation rates with increasing permeability of the sediment. Two experiments conducted in intertidal sand flats confirmed the importance of the advective interfacial transport of phytoplankton for natural settings, showing permeability‐dependent penetration of planktonic algae into embedded sand cores of different grain sizes. The significance of our results is discussed with respect to particulate organic matter flux and mineralization in shelf sands, and we suggest the concept of a decomposition layer

    An Alternative Narrative of Integration In Germany through an Ethnographic Exploration of Cuban Immigration

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    This ethnographic study on Cuban immigrants conducted in Germany explored the dynamics of integration through an understudied immigrant population. Most of the research conducted on integration in Germany has overwhelmingly been on Turkish immigrants, which is Germany’s majority immigrant group. To contribute to Integration Studies, this research focused on a minority and lesser studied immigrant group, Cuban immigrants. Cuban immigrants in Germany not only have a different historical and geopolitical relationship with Germany than its majority group but they also subscribe to different cultural and ethnoreligious categories. Because of these varying circumstances, Cubans act as a counter example to the majority immigrant group, creating an alternative narrative to integration in Germany. This dissertation addressed the methodology used in this study, explored the complexity of identity, examined German immigration and integration policies, reviewed the Cuban diaspora in the United States and globally, and presented an ethnography of Cuban integration in Germany. Effectively contributing to not only Integration Studies but also to Cuban Diaspora Studies, and Identity Studies

    A Review of Indigenous Food Crops in Africa and the Implications for more Sustainable and Healthy Food Systems

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    Indigenous and traditional foods crops (ITFCs) have multiple uses within society, and most notably have an important role to play in the attempt to diversify the food in order to enhance food and nutrition security. However, research suggests that the benefits and value of indigenous foods within the South African and the African context have not been fully understood and synthesized. Their potential value to the African food system could be enhanced if their benefits were explored more comprehensively. This synthesis presents a literature review relating to underutilized indigenous crop species and foods in Africa. It organizes the findings into four main contributions, nutritional, environmental, economic, and social-cultural, in line with key themes of a sustainable food system framework. It also goes on to unpack the benefits and challenges associated with ITFCs under these themes. A major obstacle is that people are not valuing indigenous foods and the potential benefit that can be derived from using them is thus neglected. Furthermore, knowledge is being lost from one generation to the next, with potentially dire implications for long-term sustainable food security. The results show the need to recognize and enable indigenous foods as a key resource in ensuring healthy food systems in the African continent

    Determinants of grassland primary production in seasonally-dry silvopastoral systems in Central America

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    Grassland primary productivity is the function that underpins the majority of the fodder production in cattle-rearing silvopastoral farms. Hence, understanding the factors that determine grassland productivity is critical for the design and management of silvpastoral systems. We studied the effect of two factors with documented impact on grassland productivity in seasonally dry silvopastures of Nicaragua, rainfall and trees. We assessed the effects of three species that differed in crown size and phenology, one evergreen, Cassia grandis, and two deciduous species, Guazuma ulmifolia and Tabebuia rosea. Overall, grassland ANPP had a quadratic response to rainfall, with a decline at high rainfall that coincided with peak standing biomass and grassland cover. Trees had a predominately negative effect on grassland productivity, and the effect was concentrated in the rainy season at peak productivity. The effect of the trees corresponded with the tree crown area, but not with crown density. Trees reduced the standing biomass of graminoids and increased forb biomass; thus, the effect of trees on grassland ANPP appears in part to respond to changes in grassland composition. We also found higher levels of soil moisture content below the tree canopy, particularly at the peak of the rainy season when soils tend to become waterlogged. The evergreen species, C. grandis, affected grassland ANPP more strongly than the deciduous specie

    Linking cause assessment, corporate philanthropy, and corporate reputation

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    This study analyzes the link between cause assessment, corporate philanthropy, and dimensions of corporate reputation from different stakeholders' perspectives, using balance theory as a conceptual framework and the telecommunications industry in Austria and Egypt as the empirical setting. Findings show that corporate philanthropy can improve perceptions of the corporate reputation dimensions, but the results vary between customers and non-customers and depend on the country setting

    Higher-order Quasi-Monte Carlo Training of Deep Neural Networks

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    We present a novel algorithmic approach and an error analysis leveraging Quasi-Monte Carlo points for training deep neural network (DNN) surrogates of Data-to-Observable (DtO) maps in engineering design. Our analysis reveals higher-order consistent, deterministic choices of training points in the input data space for deep and shallow Neural Networks with holomorphic activation functions such as tanh. These novel training points are proved to facilitate higher-order decay (in terms of the number of training samples) of the underlying generalization error, with consistency error bounds that are free from the curse of dimensionality in the input data space, provided that DNN weights in hidden layers satisfy certain summability conditions. We present numerical experiments for DtO maps from elliptic and parabolic PDEs with uncertain inputs that confirm the theoretical analysis

    Telling Our Story with Data: From Numbers to a Narrative

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    In this session we will share our story about moving from quantitative reference statistics to qualitative data. Our journey involved both in-person and online reference transactions prior to the pandemic and moved to 100% virtual reference service during the pandemic. We will describe how our approaches evolved due to changes in software options and how we have continued to tell our story during the pandemic. We will identify opportunities to use qualitative reference statistics to demonstrate library value and we will articulate how qualitative and quantitative reference statistics can be used for internal library planning. We will offer library professionals the opportunity to consider how they can use qualitative and quantitative data collection practices to increase internal and external communication, demonstrate how librarians impact student success, allow for better follow through when problems arise, and increase opportunities to analyze reference transactions and improve resource management
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