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  1. Smith-Renner, A. ; Taele, P. (Ed.)
    Many retired people engage in volunteer opportunities as a means to give back to their communities, stay physically and intellectually active, and build and expand their social networks. However, our semi-structured interviews of six retirees found that they typically avoid searching for volunteer opportunities through websites and social media due to a lack of trust in those tools and a concern for privacy. Instead, they rely on word-of-mouth communication facilitated through emails with individuals and organizations they trust. To support this type of communication, we designed an adaptive interaction mechanism in the form of a newsletter with volunteer opportunities that are personalized using recommender system technology. The newsletter mechanism leverages personal connections through user-defined preference-based communities that allow users to share volunteer opportunities with their peers. 
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  2. null (Ed.)
    Generative models for 3D shapes represented by hierar- chies of parts can generate realistic and diverse sets of out- puts. However, existing models suffer from the key practi- cal limitation of modelling shapes holistically and thus can- not perform conditional sampling, i.e. they are not able to generate variants on individual parts of generated shapes without modifying the rest of the shape. This is limiting for applications such as 3D CAD design that involve adjust- ing created shapes at multiple levels of detail. To address this, we introduce LSD-StructureNet, an augmentation to the StructureNet architecture that enables re-generation of parts situated at arbitrary positions in the hierarchies of its outputs. We achieve this by learning individual, probabilis- tic conditional decoders for each hierarchy depth. We eval- uate LSD-StructureNet on the PartNet dataset, the largest dataset of 3D shapes represented by hierarchies of parts. Our results show that contrarily to existing methods, LSD- StructureNet can perform conditional sampling without im- pacting inference speed or the realism and diversity of its outputs. 
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  3. null (Ed.)
    Let $G$ be one of the two multigraphs obtained from $K_4-e$ by replacing two edges with a double-edge while maintaining a minimum degree of~2. We find necessary and sufficient conditions on $n$ and $\lambda$ for the existence of a $G$-decomposition of $^{\lambda}K_n$. 
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  4. null (Ed.)
    Consider the multigraph obtained by adding a double edge to $K_4-e$. Now, let $D$ be a directed graph obtained by orientating the edges of that multigraph. We establish necessary and sufficient conditions on $n$ for the existence of a $(K^{*}_{n},D)$-design for four such orientations. 
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  5. Abstract

    The Mid‐Pliocene Warm Period (MPWP, 2.9 to 3.3 Ma), along with older Pliocene (3.2 to 5.3 Ma) records, offers potential past analogues for our 400‐ppmv world. The coastal geology of western and southern coasts of the Republic of South Africa exposes an abundance of marine deposits of Pliocene and Pleistocene age. In this study, we report differential GPS elevations, detailed stratigraphic descriptions, standardized interpretations, and dating of relative sea‐level indicators measured across ~700 km from the western and southern coasts of the Cape Provinces. Wave abrasion surfaces on bedrock, intertidal sedimentary structures, and in situ marine invertebrates including oysters and barnacles provide precise indicators of past sea levels. Multiple sea‐level highstands imprinted at different elevations along South African coastlines were identified. Zone I sites average +32 ± 5 m (six sites). A lower topographic Zone II of sea stands were measured at several sites around +17 ± 5 m. Middle and late Pleistocene sites are included in Zone III. Shoreline chronologies using87Sr/86Sr ages on shells from these zones yield ages from Zone I at 4.6 and 3.0 Ma and Zone II at 1.04 Ma. Our results show that polar ice sheets during the Plio‐Pleistocene were dynamic and subject to significant melting under modestly warmer global temperatures. These processes occurred during a period when CO2concentrations were comparable to our current and rapidly rising values above 400 ppmv.

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  6. Abstract

    A steady‐state spectral wave model, STWAVE, is evaluated as a tool for predicting wave‐induced sediment resuspension in lake littoral zones. Steady‐state wave height and bed‐shear stress estimates are tested against 2 years of high‐frequency wave height and turbidity data from six littoral measurement stations in Lake Tahoe. Average wave and sediment resuspension response to a broad range of wind conditions are well captured by the model. Despite steady‐state assumptions, the model reproduces patterns in wave height and sediment resuspension under time‐varying wind conditions at sites with different wave exposure. Model results are insensitive to the measurement location of wind data input among six offshore meteorological buoys. Uniform and variable wind field assumptions yield similar resuspension predictions. Results representing the steady‐state response to spatially uniform wind speed‐direction combinations enable output from a single set of model runs to serve as a reasonable static reference for hindcasting and predicting wave resuspension patterns. This obviates the need for repeated model runs, making STWAVE output an efficient tool for exploring long‐term spatio‐temporal patterns in nearshore wave forcing. Application of this tool is limited by wave height overprediction for short fetches and presumably by the validity of uniform wind field assumptions over very long fetches. Applied successfully at Lake Tahoe, we find that the north and east shores, exposed to the prevailing southwesterly winds, see resuspension conditions upward of 3,000 hr/year, while the south and west shores typically see less than 500. Location‐specific resuspension hours can vary by upward of ±200 hr/year due to shifting interannual wind patterns.

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