21 research outputs found

    Sisters, Visiting

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    The Housekeeper

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    The Third World

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    Motherland

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    The Horologist

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    Visiting Hours

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    Study of Charge-Dependent Transport and Toxicity of Peptide-Functionalized Silver Nanoparticles Using Zebrafish Embryos and Single Nanoparticle Plasmonic Spectroscopy

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    Nanomaterials possess unusually high surface area-to-volume ratios and surface-determined physicochemical properties. It is essential to understand their surface-dependent toxicity in order to rationally design biocompatible nanomaterials for a wide variety of applications. In this study, we have functionalized the surfaces of silver nanoparticles (Ag NPs, 11.7 ±+2.7 nm in diameter) with three biocompatible peptides (CALNNK, CALNNS, CALNNE) to prepare positively (Ag-CALNNK NPs+ζ), negatively (Ag-CALNNS NPs−2ζ), and more negatively charged NPs (Ag-CALNNE NPs−4ζ), respectively. Each peptide differs in a single amino acid at its C-terminus, which minimizes the effects of peptide sequences and serves as a model molecule to create positive, neutral, and negative charges on the surface of the NPs at pH 4-10. We have studied their charge-dependent transport into early developing (cleavage-stage) zebrafish embryos and their effects on embryonic development using dark-field optical microscopy and spectroscopy (DFOMS). We found that all three Ag-peptide NPs passively diffused into the embryos via their chorionic pore canals, and stayed inside the embryos throughout their entire development (120 h), showing charge-independent diffusion modes and charge-dependent diffusion coefficients. Notably, the NPs create chargedependent toxic effects on embryonic development, showing that the Ag-CALNNK NPs+ζ (positively charged) are the most biocompatible while the Ag-CALNNE NPs−4ζ (more negatively charged) are the most toxic. By comparing with our previous studies of the same sized citrated Ag and Au NPs, the Ag-peptide NPs are much more biocompatible than the citrated Ag NPs, and nearly as biocompatible as the Au NPs, showing the dependence of nanotoxicity upon the surface charges, surface functional groups, and chemical compositions of the NPs. This study also demonstrates powerful applications of single NP plasmonic spectroscopy for quantitative analysis of single NPs in vivo and in tissues, and reveals the possibility of rational design of biocompatible NPs

    The Dissolution of the Marriage, Ship's Garbage and Inside the Wooden Horse

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    White House publicity operations during the Korean War, June 1950 – June 1951

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    Truman was the first modern president to face the challenge of selling a limited war. Based on a wide range of primary sources, this article explores the impact that the Korean War had on Truman’s publicity operations. Whereas all wars place important new demands on presidents to speak out more frequently and forcefully, limited wars place significant constraints on what presidents can say and do. During the Korean War, Truman refused to go public at key moments, often employed rhetoric that was more restrained than at earlier moments of the Cold War, and shied away from creating new structures to coordinate the official message. Such actions also had important consequences. In 1950-51, they hampered the task of effective presidential communication, and contributed to the war’s growing unpopularity. For the longer term, they demonstrated the difficulties of selling a limited war, and hence place into sharper context the problems that beset Truman’s successors during the subsequent conflict in Vietnam
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