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

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

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

SANS From Tetradecylpyridinium Bromide Based Microemulsions

Small-angle neutron scattering is used to investigate tetradecyl pyridinium bromide/pentanol/heptane/heavy water microemulsions in the water-in-oil (W/O) microemulsion phase diagram region. The heavy water content is increased while the other components (surfactant, cosurfactant, hydrocarbon) are kept constant. With use of a simple model assuming spherical micelles interacting with a hard-sphere potential (Percus-Yevick model), aggregate sizes and packing fractions have been extracted and found to agree with values determined from the mixing conditions. These experiments clearly show the transition from the single-particle (heavy water + Stern layer droplet) scattering regime at low water concentration to the mixed single/interdroplet scattering regime when the intermicellar distance becomes comparable to the size of the micelles. © 1990 American Chemical Society

Preferential selection of viral escape mutants by CD8+ T cell 'sieving' of SIV reactivation from latency

HIV rapidly rebounds after interruption of antiretroviral therapy (ART). HIV-specific CD8+ T cells may act to prevent early events in viral reactivation. However, the presence of viral immune escape mutations may limit the effect of CD8+ T cells on viral rebound. Here, we studied the impact of CD8 immune pressure on post-treatment rebound of barcoded SIVmac293M in 14 Mamu-A*01 positive rhesus macaques that initiated ART on day 14, and subsequently underwent two analytic treatment interruptions (ATIs). Rebound following the first ATI (seven months after ART initiation) was dominated by virus that retained the wildtype sequence at the Mamu-A*01 restricted Tat-SL8 epitope. By the end of the two-month treatment interruption, the replicating virus was predominantly escaped at the Tat-SL8 epitope. Animals reinitiated ART for 3 months prior to a second treatment interruption. Time-torebound and viral reactivation rate were significantly slower during the second treatment interruption compared to the first. Tat-SL8 escape mutants dominated early rebound during the second treatment interruption, despite the dominance of wild-type virus in the proviral reservoir. Furthermore, the escape mutations detected early in the second treatment interruption were well predicted by those replicating at the end of the first, indicating that escape mutant virus in the second interruption originated from the latent reservoir as opposed to evolving de novo post rebound. SL8-specific CD8+ T cell levels in blood prior to the second interruption were marginally, but significantly, higher (median 0.73% vs 0.60%, p = 0.016). CD8+ T cell depletion approximately 95 days after the second treatment interruption led to the reappearance of wild-type virus. This work suggests that CD8+ T cells can actively suppress the rebound of wild-type virus, leading to the dominance of escape mutant virus after treatment interruption

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

The Branched GDGT Isomer Ratio Refines Lacustrine Paleotemperature Estimates

Branched glycerol dialkyl glycerol tetraethers (brGDGTs) are membrane-spanning lipids synthesized by bacteria in numerous substrates. The degree of methylation of the five methyl brGDGTs in both soils and lake sediments, described by the MBT′5Me index, is empirically related to surface atmospheric temperature. This relationship in lakes is generally assumed to reflect lake surface temperatures captured by brGDGT production in the water column and exported to lake sediments, and the MBT′5Me index has been applied to brGDGTs in lake sediment successions to reconstruct changes in temperature through time. We analyzed the relationship between MBT′5Me and the isomerization of brGDGTs (IR6Me) in globally distributed surficial lake sediments and demonstrated that the relationship, and calibrations, of MBT′5Me and temperature in middle and high latitude lakes are sensitive to incompletely understood factors related to IR6Me. IR6Me does not appear to track a non-thermal influence of brGDGT methylation in tropical lakes, but this could change as the data set is expanded. We address ongoing challenges in the application of the MBT′5Me paleothermometer in middle and high latitude lakes with new MBT′5Me-temperature calibrations based on grouping lakes by IR6Me. We demonstrate how IR6Me can distinguish samples with a significant non-thermal influence on MBT′5Me by targeting anomalously warm temperatures during the Last Glacial Maximum from newly analyzed piston and gravity core samples from Lake Baikal, Russia

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