Bearing development program for a 25 kWe solar-powered organic Rankine-cycle engine

The bearing development program is summarized for a 25-kWe power conversion subsystem (PCS) consisting of an organic Rankine-cycle engine, and permanent magnetic alternator (PMA) and rectifier to be used in a 100-kWe point-focusing distributed receiver solar power plant. The engine and alternator were hermetically sealed and used toluene as the working fluid. The turbine, alternator, and feed pump (TAP) were mounted on a single shaft operating at speeds up to 60,000 rev/min. Net thermal-to-electric efficiencies in the range of 21 to 23% were demonstrated at the maximum working fluid temperature of 400 C (750 F). A chronological summary of the bearing development program is presented. The primary causes of bearing wear problems were traced to a combination of rotordynamic instability and electrodynamic discharge across the bearing surfaces caused by recirculating currents from the PMA. These problems were resolved by implementing an externally supplied, flooded-bearing lubrication system and by electrically insulating all bearings from the TAP housing. This program resulted in the successful development of a stable, high-speed, toluene-lubricated five-pad tilting-pad journal bearing and Rayleigh step thrust bearing system capable of operating at all inclinations between horizontal and vertical

Stable, low-growing plant communities in the western Cascade Mountains : species processes and their implications for rights-of-way management

The processes that lead to stable, low-growing plant communities and the characteristics of the species that form them are of great interest to rights-of-way (ROW) managers and others wishing to better understand plant community resistance to tree invasion on managed landscapes. The use of stable, low-growing plant communities as a mechanism to control tree invasion on ROWs has been widely acknowledged, but little is known about what plant characteristics lead to stable communities or how different treatment methods affect low-growing communities in the Pacific Northwest. The goal of this study was to assess the resistance of stable, low-growing communities to tree invasion on ROW in the Pacific Northwest and to identify common characteristics among the species in these communities that contributed to the formation of stable communities. To address this goal, we investigated 1) the abilities of different species within the low-growing component of the ROW communities to resist invasion by trees and to fill newly created gaps caused by disturbance, 2) the growth patterns and potential for vegetative reproduction of trailing blackberry (Rubus ursinus Cham and Schlecht) and creeping snowberry (Symphoricarpos mollis Nutt.) to understand how different clonal propagation patterns affect spread into unoccupied space and infilling of currently colonized areas, and 3) the effectiveness of several common vegetation control methods for reducing the density of undesirable species and promoting the development of lowgrowing plant communities on ROW. These factors are important processes that determine the stability of a low-growing plant community. This project was conducted at three sites in the western foothills of the Cascade Mountains of Oregon and Washington. Species composition and abundance was measured in roughly 330 2x2 m plots at each site prior to the application of three different treatments aimed at removing tall-growing target species. The plots were measured again two years later to assess changes in species cover. The growth pattern and architecture of trailing blackberry and creeping snowberry was also investigated through the careful excavation of both individual plants and lxi m plots centered in dense thickets of each species. The various treatments used in this study resulted in an average increase in nontarget cover of 65% from 2000 to 2002 while reducing tall target cover by an average of 53%. No difference was found in the change in average nontarget cover or tall target cover among treatments. The effectiveness of the various treatments in reducing target cover varied significantly based on the type of target species being treated. There were no strong differences in resistance among the common lowgrowing species to invasion by tall target species. The range in increase in tall target cover in plots dominated by low-growing species was highly skewed, as tall target cover increased very little in many plots and by as much as 28% in a very few. In the first two years following disturbance, shrubs capable of rapid horizontal expansion through vegetative reproduction, such as trailing blackberry and bracken fern (Pteridium aquilinum), were most successful filling gaps. Their ability to expand rapidly led to their high abundance following disturbance. The successful colonization of gaps by trailing blackberry was a result of its growth pattern, which focused on rapid spread as this species produced new canes annually that grew up to 1.9 m during their first year. This may allow it to be a successful colonizer of gaps. It was also capable of forming dense thickets and averaged 113 stems/m2. The growth pattern of creeping snowberry, which focused more on infilling, may allow it to maintain areas of dense, persistent cover, as it averaged 237 stems/m2 in dense thickets. It was also capable of horizontal spread through the initiation of new ramets along creeping stems. These stems averaged 0.6 m during their first year of growth. Both strategies of growth and spread allowed these shrubs to form thickets of dense vegetation. The use of stable low-growing plant communities as a management tool to reduce tree seedling establishment and growth can have many benefits including reduced costs due to lower tree density and longer periods of time between treatments, increased wildlife habitat, and aesthetic appeal. However, for this management approach to be most successful, one must have an understanding of the plant community where it is being applied, the plant characteristics that will lead to the formation of stable, low-growing communities, and how the different available treatment options will affect the resulting plant community. This study addressed many of these topics to produce a more comprehensive understanding of how stable, low-growing plant communities can be used as a management tool for reducing tree invasion in the Pacific Northwest. The two-year duration of this study, while allowing for many new insights, limited the scope of some of our conclusions. Continued monitoring of these research sites, as has been done in several locations in the northeast United States, would greatly increase the strength of our conclusions

Nuclear reactor power as applied to a space-based radar mission

The SP-100 Project was established to develop and demonstrate feasibility of a space reactor power system (SRPS) at power levels of 10's of kilowatts to a megawatt. To help determine systems requirements for the SRPS, a mission and spacecraft were examined which utilize this power system for a space-based radar to observe moving objects. Aspects of the mission and spacecraft bearing on the power system were the primary objectives of this study; performance of the radar itself was not within the scope. The study was carried out by the Systems Design Audit Team of the SP-100 Project

The anatomical and functional benefit of bevacizumab in the treatment of macular edema associated with Purtscher-like retinopathy

We read the article by Miguel et al1 regarding Purtscher’s and Purtscher-like retinopathies with great interest. As the authors well describe, ‘Purtscher-like retinopathy’ is diagnosed in patients with fundus findings similar to Purtscher’s retinopathy, without a history of trauma but with known systemic associations.1 Current proposed mechanisms for the underlying pathogenesis include leukocyte aggregation by activated complement factor 5 (C5a).2 As noted by the authors’ systematic review, there is currently no established treatment for Purtscher-like retinopathy, although the literature consists of several case reports of treatment with corticosteroids, without certainty as to effect on the clinical course.1 Herein, we report for the first time a case of Purtscher-like retinopathy treated successfully with intravitreal bevacizumab injection

Testing of Milliwatt Power Source Components

A milliwatt power source (MPS) has been developed to satisfy the requirements of several potential solar system exploration missions. The MPS is a small power source consisting of three major components: a space qualified heat source (RHU), a thermopile (thermoelectric converter or TEC) and a container to direct the RHU heat to the TEC. Thermopiles from Hi-Z Technology, Inc. of San Diego and the Institute of Thermoelectricity of Chernivtsi Ukraine suitable for the MPS were tested and shown to perform as expected, producing 40 mW of power with a temperature difference of about 170°C. Such thermopiles were successfully life tested for up to a year. A MPS container designed and built by Swales Aerospace was tested with both a TEC simulator and actual TEC. The Swales unit, tested under dynamic vacuum, provided less temperature difference than anticipated, such that the TEC produced 20 mW of power with heat input equivalent to a RHU

Miniaturized Radioisotope Solid State Power Sources

Abstract. Electrical power requirements for the next generation of deep space missions cover a wide range from the kilowatt to the milliwatt. Several of these missions call for the development of compact, low weight, long life, rugged power sources capable of delivering a few milliwatts up to a couple of watts while operating in harsh environments. Advanced solid state thermoelectric microdevices combined with radioisotope heat sources and energy storage devices such as capacitors are ideally suited for these applications. By making use of macroscopic film technology, microgenerators operating across relatively small temperature differences can be conceptualized for a variety of high heat flux or low heat flux heat source configurations. Moreover, by shrinking the size of the thermoelements and increasing their number to several thousands in a single structure, these devices can generate high voltages even at low power outputs that are more compatible with electronic components. Because the miniaturization of state-of-the-art thermoelectric module technology based on Bi 2 Te 3 alloys is limited due to mechanical and manufacturing constraints, we are developing novel microdevices using integrated-circuit type fabrication processes, electrochemical deposition techniques and high thermal conductivity substrate materials. One power source concept is based on several thermoelectric microgenerator modules that are tightly integrated with a 1.1W Radioisotope Heater Unit. Such a system could deliver up to 50mW of electrical power in a small lightweight package of approximately 50 to 60g and 30cm 3 . An even higher degree of miniaturization and high specific power values (mW/mm 3 ) can be obtained when considering the potential use of radioisotope materials for an alpha-voltaic or a hybrid thermoelectric/alpha-voltaic power source. Some of the technical challenges associated with these concepts are discussed in this paper

Flt-1 (VEGFR-1) coordinates discrete stages of blood vessel formation

In developing blood vessel networks, the overall level of vessel branching often correlates with angiogenic sprout initiations, but in some pathological situations, increased sprout initiations paradoxically lead to reduced vessel branching and impaired vascular function. We examine the hypothesis that defects in the discrete stages of angiogenesis can uniquely contribute to vessel branching outcomes

Digital transformations and the archival nature of surrogates

Large-scale digitization is generating extraordinary collections of visual and textual surrogates, potentially endowed with transcendent long-term cultural and research values. Understanding the nature of digital surrogacy is a substantial intellectual opportunity for archival science and the digital humanities, because of the increasing independence of surrogate collections from their archival sources. The paper presents an argument that one of the most significant requirements for the long-term access to collections of digital surrogates is to treat digital surrogates as archival records that embody traces of their fluid lifecycles and therefore are worthy of management and preservation as archives. It advances a theory of the archival nature of surrogacy founded on longstanding notions of archival quality, the traces of their source and the conditions of their creation, and the functional ‘‘work of the archive.’’ The paper presents evidence supporting a ‘‘secondary provenance’’ derived from re-digitization, re-ingestion of multiple versions, and de facto replacement of the original sources. The design of the underlying research that motivates the paper and summary findings are reported separately. The research has been supported generously by the US Institute of Museum and Library Services.Institute for Museum and Library ServicesPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/111825/1/J26 Conway Digital Transformations 2014-pers.pdfDescription of J26 Conway Digital Transformations 2014-pers.pdf : Main articl

Yield gains in extra-early maize cultivars of three breeding eras under multiple environments

Open Access JournalAvailability of extra-early maize cultivars has facilitated the expansion of maize production into savannas of West and Central Africa (WCA). Fifty-six extra-early maize cultivars of three breeding eras;1995 to 2000, 2001 to 2006, and 2007 to 2012 were evaluated for 2 yr under 24 multiple-stress and 28 non-stress environments in WCA. Objectives of the study were to determine genetic improvement in grain yield of cultivars developed during the breeding eras, and identify high-yielding and s multiple-stress and non-stress environments. Yield gains from era 1 to era 3 under multiple stresses was associated with increased days to anthesis, reduced stalk lodging, and improved husk cover. Cultivars 2004 TZEE-Y Pop STR C4, TZEE-W Pop STR QPM C0, and TZEE-W Pop STR BC2 C0 of era 2; and TZEE-W STR 107 BC1, TZEE-W Pop STR C5, and 2012 TZEE-Y DT STR C5 of era 3 were high-yielding and stable across multiple-stress environments while 98 Syn EE-W from era 1, FERKE TZEE-W STR, TZEE-W Pop STR C3, and TZEE-Y Pop STR QPM C0 from era 2, and TZEE-W Pop STR C5, 2009 TZEE-OR2 STR QPM, 2009 TZEE-W STR, TZEE-Y STR 106, and TZEE-W DT C0 STR C5 from era 3 were outstanding across non-stress environments and should be tested extensively and commercialized. Considerable improvement has been made in breeding for multiple-stress tolerant extra-early maize cultivars