25 research outputs found

    Thermoplastic Labyrinth Seals For Centrifugal Compressors.

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    Tutorialpg. 113-126For over 15 years now, the efficiency and reliability of centrifugal compressors have been enhanced by the application of thermoplastic materials to the eye, shaft, and balance piston labyrinth seals. Traditionally these seals have been manufactured from metallic materials and have required relatively large clearance for reliability reasons. By upgrading to carefully selected engineered thermoplastics, the clearances can be reduced without sacrificing reliability. This results in increased compressor efficiency and the added benefit of easier installation. This tutorial will review the design and application of thermoplastic seals as used in centrifugal compressors. The tutorial will not cover in any detail abradable seals (such as babbitt or lead lined), reduced cross-coupling seals, or “other” seals (such as honeycomb, brush, carbon ring, dry gas, etc.)

    Beluga whale stewardship and collaborative research practices among Indigenous peoples in the Arctic

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    Beluga whales (Delphinapterus leucas) are an integral part of many Arctic Indigenous cultures and contribute to food security for communities from Greenland, across northern Canada and Alaska to Chukotka, Russia. Although the harvesting and stewardship practices of Indigenous peoples vary among regions and have shifted and adapted over time, central principles of respect for beluga and sharing of the harvest have remained steadfast. In addition to intra-community cooperation to harvest, process and use beluga whales, rapid environmental change in the Arctic has underscored the need for inter-regional communication as well as collaboration with scientists and managers to sustain beluga populations and their cultural and nutritional roles in Arctic communities. Our paper, written by the overlapping categories of researchers, hunters, and managers, first provides an overview of beluga hunting and collaborative research in seven regions of the Arctic (Greenland; Nunatsiavut, Nunavik, Nunavut, and the Inuvialuit Settlement Region, Canada; Alaska; and Chukotka). Then we present a more detailed case study of collaboration, examining a recent research and management project that utilizes co-production of knowledge to address the conservation of a depleted population of beluga in Nunavik, Canada. We conclude that sustaining traditional values, establishing collaborative management efforts, the equitable inclusion of Indigenous Knowledge, and respectful and meaningful collaborations among hunters, researchers and managers are essential to sustaining healthy beluga populations and the peoples who live with and depend upon them in a time of rapid social and environmental change

    Rescue of Pituitary Function in a Mouse Model of Isolated Growth Hormone Deficiency Type II by RNA Interference

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    Splicing mutations in the human GH (hGH) gene (GH-1) that cause skipping of exon 3 result in a form of GH deficiency termed isolated GH deficiency type II (IGHD II). The GH-1 gene contains five exons; constitutive splicing produces the wild-type 22-kDa hormone, whereas skipping of exon 3 results in transcripts encoding a 17.5-kDa isoform that acts as a dominant-negative to block secretion of the wild-type hormone. Common characteristics of IGHD II include short stature due to impaired bone elongation, growth, and, in severe cases, anterior pituitary hypoplasia. Typically, IGHD II is treated by sc delivery of hGH, which can rescue stature but, unfortunately, does not inhibit pituitary hypoplasia. Direct destruction of transcripts encoding the dominant-negative 17.5-kDa isoform should both rescue stature and prevent hypoplasia. Here, we have used delivery of short hairpin RNAs to rescue a murine model of IGHD II by specifically targeting transcripts encoding the 17.5-kDa isoform using RNA interference. To our knowledge, this is the first example where a short hairpin RNA has been expressed to specifically degrade an incorrectly spliced transcript and rescue a dominant-negative disease phenotype in vivo
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