98 research outputs found
Insoluble Coatings for Stirling Engine Heat Pipe Condenser Surfaces
The principal objective of this Phase 2 SBIR program was to develop and demonstrate a practically insoluble coating for nickel-based superalloys for Stirling engine heat pipe applications. Specific technical objectives of the program were: (1) Determine the solubility corrosion rates for Nickel 200, Inconel 718, and Udimet 72OLI in a simulated Stirling engine heat pipe environment, (2) Develop coating processes and techniques for capillary groove and screen wick structures, (3) Evaluate the durability and solubility corrosion rates for capillary groove and screen wick structures coated with an insoluble coating in cylindrical heat pipes operating under Stirling engine conditions, and (4) Design and fabricate a coated full-scale, partial segment of the current Stirling engine heat pipe for the Stirling Space Power Convertor program. The work effort successfully demonstrated a two-step nickel aluminide coating process for groove wick structures and interior wall surfaces in contact with liquid metals; demonstrated a one-step nickel aluminide coating process for nickel screen wick structures; and developed and demonstrated a two-step aluminum-to-nickel aluminide coating process for nickel screen wick structures. In addition, the full-scale, partial segment was fabricated and the interior surfaces and wick structures were coated. The heat pipe was charged with sodium, processed, and scheduled to be life tested for up to ten years as a Phase 3 effort
Anisotropic Small-Polaron Hopping In W:Bivo4 Single Crystals
DC electrical conductivity, Seebeck and Hall coefficients are measured between 300 and 450 K on single crystals of monoclinic bismuth vanadate that are doped n-type with 0.3% tungsten donors (W:BiVO4). Strongly activated small-polaron hopping is implied by the activation energies of the Arrhenius conductivities (about 300 meV) greatly exceeding the energies characterizing the falls of the Seebeck coefficients' magnitudes with increasing temperature (about 50 meV). Small-polaron hopping is further evidenced by the measured Hall mobility in the ab-plane (10(-1) cm(2) V-1 s(-1) at 300 K) being larger and much less strongly activated than the deduced drift mobility (about 5 x 10(-5) cm(2) V-1 s(-1) at 300 K). The conductivity and n-type Seebeck coefficient is found to be anisotropic with the conductivity larger and the Seebeck coefficient's magnitude smaller and less temperature dependent for motion within the ab-plane than that in the c-direction. These anisotropies are addressed by considering highly anisotropic next-nearest-neighbor (approximate to 5 angstrom) transfers in addition to the somewhat shorter (approximate to 4 angstrom), nearly isotropic nearest-neighbor transfers. (C) 2015 AIP Publishing LLC.U.S. Department of Energy (DOE), DE-FG02-09ER16119Welch Foundation Grant F-1436Hemphill-Gilmore Endowed FellowshipNSF MIRT DMR 1122603Chemical EngineeringTexas Materials InstituteChemistr
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The plasma formation stage in magnetic compression/magnetized target fusion (MAGO/MTF)
In early 1992, emerging governmental policy in the US and Russia began to encourage ``lab-to-lab`` interactions between the All- Russian Scientific Research Institute of Experimental Physics (VNIIEF) and the Los Alamos National Laboratory (LANL). As nuclear weapons stockpiles and design activities were being reduced, highly qualified scientists become for fundamental scientific research of interest to both nations. VNIIEF and LANL found a common interest in the technology and applications of magnetic flux compression, the technique for converting the chemical energy released by high-explosives into intense electrical pulses and intensely concentrated magnetic energy. Motivated originally to evaluate any possible defense applications of flux compression technology, the two teams worked independently for many years, essentially unaware of the others` accomplishments. But, an early US publication stimulated Soviet work, and the Soviets followed with a report of the achievement of 25 MG. During the cold war, a series of conferences on Megagauss Magnetic Field Generation and Related Topics became a forum for scientific exchange of ideas and accomplishments. Because of relationships established at the Megagauss conferences, VNIIEF and LANL were able to respond quickly to the initiatives of their respective governments. In late 1992, following the Megagauss VI conference, the two institutions agreed to combine resources to perform a series of experiments that essentially could not be performed by each institution independently. Beginning in September, 1993, the two institutions have performed eleven joint experimental campaigns, either at VNIIEF or at LANL. Megagauss- VII has become the first of the series to include papers with joint US and Russian authorship. In this paper, we review the joint LANL/VNIIEF experimental work that has relevance to a relatively unexplored approach to controlled thermonuclear fusion
Gravitational intraction on quantum level and consequences thereof
The notion of gravitational emission as an emission of the same level with
electromagnetic emission is based on the proven fact of existence of electrons
stationary states in its own gravitational field, characterized by
gravitational constantComment: 22 pages, 9 figure
An Overview of Long Duration Sodium Heat Pipe Tests
High temperature heat pipes are being evaluated for use in energy conversion applications such as fuel cells, gas turbine re-combustors, and Stirling cycle heat sources; with the resurgence of space nuclear power, additional applications include reactor heat removal elements and radiator elements. Long operating life and reliable performance are critical requirements for these applications. Accordingly long-term materials compatibility is being evaluated through the use of high temperature life test heat pipes. Thermacore International, Inc., has carried out several sodium heat pipe life tests to establish long term operating reliability. Four sodium heat pipes have recently demonstrated favorable materials compatibility and heat transport characteristics at high operating temperatures in air over long time periods. A 3l6L stainless steel heat pipe with a sintered porous nickel wick structure and an integral brazed cartridge heater has successfully operated at 650 to 700 C for over 115,000 hours without signs of failure. A second 3l6L stainless steel heat pipe with a specially-designed Inconel 60 I rupture disk and a sintered nickel powder wick has demonstrated over 83,000 hours at 600 to 650 C with similar success. A representative one-tenth segment Stirling Space Power Converter heat pipe with an Inconel 718 envelope and a stainless steel screen wick has operated for over 41 ,000 hours at nearly 700 0c. A hybrid (i.e. gas-fired and solar) heat pipe with a Haynes 230 envelope and a sintered porous nickel wick structure was operated for about 20,000 hours at nearly 700 C without signs of degradation. These life test results collectively have demonstrated the potential for high temperature heat pipes to serve as reliable energy conversion system components for power applications that require long operating lifetime with high reliability, Detailed design specifications, operating hi story, and test results are described for each of these sodium heat pipes. Lessons learned and future life test plans are also discussed
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The VNIIEF/LANL collaboration : ten years of scientific benefit to the Russian Federation and the United States
Since 1992, the All-Russian Scientific Research Institute of Experimental Physics (VNIIEF) and the Los Alamos National Laboratory (LANL), the institutes that designed the first nuclear weapons of the Soviet Union and the United States, respectively, have been working together in fundamental research related to pulsed power technology and high energy density science. Experimental and theoretical work has been performed at Sarov and Los Alamos in areas as diverse as imploding liner physics and applications, fusion plasma formation, isentropic compression of noble gases, and explosively driven high current generation technology, all traditional areas of the Megagauss series of conferences. Recent joint work has focused on the Atlas capacitor bank (23 MJ, 30 MA, 6 ps) now operational at LANL. Even before Atlas became operational, VNIIEF's DEMG capability was used to provide the US with the first available data at ATLAS! upper performance limit (31 MA, 4 ps, 12 km/s velocity for 50 g liner mass). VNIIEF has recently designed and fielded imploding liner experiments on Atlas, with the goal of studying material strength properties by observing unstable perturbation growth. This paper traces the origins of this collaboration and reviews the scientific accomplishments
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Computational modeling of ``MAGO`` and other magnetized target fusion concepts
One possible way to obtain a preheated and magnetized plasma suitable for subsequent implosion is the ``MAGO`` concept. The unique MAGO discharge consists of a two chambers, with electrical current flowing in one chamber accelerating plasma flow into an implosion chamber. Up to 4 {times} 10{sup 13} D-T neutrons have been produced in the MAGO discharge. In this paper, we discuss our computational modeling of MAGO. Our objectives are to characterize the plasma, compare with the limited diagnostics available, and to understand the neutron production. We also discuss, briefly, some other possible means for creating a magnetized plasma
Unravelling the phylogenetic relationships of lichenised fungi in Dothideomyceta
We present a revised phylogeny of lichenised Dothideomyceta
(Arthoniomycetes and Dothideomycetes) based on a combined
data set of nuclear large subunit (nuLSU) and mitochondrial small subunit
(mtSSU) rDNA data. Dothideomyceta is supported as monophyletic with
monophyletic classes Arthoniomycetes and Dothideomycetes;
the latter, however, lacking support in this study. The phylogeny of
lichenised Arthoniomycetes supports the current division into three
families: Chrysothrichaceae (Chrysothrix),
Arthoniaceae (Arthonia s. l., Cryptothecia,
Herpothallon), and Roccellaceae (Chiodecton, Combea,
Dendrographa, Dichosporidium, Enterographa, Erythrodecton, Lecanactis,
Opegrapha, Roccella, Roccellographa, Schismatomma, Simonyella). The
widespread and common Arthonia caesia is strongly supported as a
(non-pigmented) member of Chrysothrix. Monoblastiaceae, Strigulaceae,
and Trypetheliaceae are recovered as unrelated, monophyletic clades
within Dothideomycetes. Also, the genera Arthopyrenia
(Arthopyreniaceae) and Cystocoleus and Racodium
(Capnodiales) are confirmed as Dothideomycetes but unrelated
to each other. Mycomicrothelia is shown to be unrelated to
Arthopyrenia s.str., but is supported as a monophyletic clade sister
to Trypetheliaceae, which is supported by hamathecium characters. The
generic concept in several groups is in need of revision, as indicated by
non-monophyly of genera, such as Arthonia, Astrothelium, Cryptothecia,
Cryptothelium, Enterographa, Opegrapha, and Trypethelium in our
analyses
CTLA-4 and PD-1 dual blockade induces SIV reactivation without control of rebound after antiretroviral therapy interruption
The primary human immunodeficiency virus (HIV) reservoir is composed of resting memory CD4+ T cells, which often express the immune checkpoint receptors programmed cell death protein 1 (PD-1) and cytotoxic T lymphocyte-associated protein 4 (CTLA-4), which limit T cell activation via synergistic mechanisms. Using simian immunodeficiency virus (SIV)-infected, long-term antiretroviral therapy (ART)-treated rhesus macaques, we demonstrate that PD-1, CTLA-4 and dual CTLA-4/PD-1 immune checkpoint blockade using monoclonal antibodies is well tolerated, with evidence of bioactivity in blood and lymph nodes. Dual blockade was remarkably more effective than PD-1 blockade alone in enhancing T cell cycling and differentiation, expanding effector-memory T cells and inducing robust viral reactivation in plasma and peripheral blood mononuclear cells. In lymph nodes, dual CTLA-4/PD-1 blockade, but not PD-1 alone, decreased the total and intact SIV-DNA in CD4+ T cells, and SIV-DNA and SIV-RNA in B cell follicles, a major site of viral persistence during ART. None of the tested interventions enhanced SIV-specific CD8+ T cell responses during ART or viral control after ART interruption. Thus, despite CTLA-4/PD-1 blockade inducing robust latency reversal and reducing total levels of integrated virus, the degree of reservoir clearance was still insufficient to achieve viral control. These results suggest that immune checkpoint blockade regimens targeting PD-1 and/or CTLA-4, if performed in people living with HIV with sustained aviremia, are unlikely to induce HIV remission in the absence of additional interventions
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