Property investigation and sputter deposition of dispersion-hardened copper for fatigue specimen fabrication

Sputter-deposited alloys of dispersion-hardenable Cu-0.25 vol% SiC and Cu-0.50 vol% SiC and precipitation-hardenable Cu-0.15 wt% Zr and Cu-0.05 wt% Mg-0.15 wt% Zr-0.40 wt% Cr were investigated for selection to evaluate fatigue specimen performance with potential application in fabricating regeneratively cooled rocket thrust chambers. Yield strengths in the 700 to 1000-MN/sq m range were observed with uniform elongation ranging from 0.5 to 1.5% and necking indicative of greater ductility. Electrical conductivity measured as an analog to thermal conductivity gave values 90% IACS for Cu-0.15 wt% Zr and Cu-0.05 wt% Mg-0.15 wt% Zr-0.40 wt% Cr. A 5500-g sputtered deposit of Cu-0.15 wt% Zr alloy, 12.29 mm (0.484 in.) average thickness in the fatigue specimen gage length, was provided to NASA on one of their substrates

Fabrication of thick structures by sputtering

Deposit, 5500-gram of Cu-0.15 wt % Zr alloy, sputtered onto copper cylinder to average thickness of 12.29 mm. Structure was achieved with high-rate sputter deposition for about 100 hours total sputtering time. Material had twice the strength of unsputtered material at temperatures to 723 K and equivalent strength at nearly 873 K

The importance of habitat quality for marine reserve fishery linkages

We model marine reserve - fishery linkages to evaluate the potential contribution of habitat-quality improvements inside a marine reserve to fish productivity and fishery catches. Data from Mombasa Marine National Park, Kenya, and the adjacent fishery are used. Marine reserves increase total fish biomass directly by providing refuge from exploitation and indirectly by improving fish habitat in the reserve. As natural mortality of the fish stock decreases in response to habitat enhancement in the reserve, catches increase by up to 2.6 tonnes (t).km(-2).year(-1) and total fish biomass by up to 36 t.km(-2). However, if habitat-quality improvement reduces the propensity of fish to move out of the reserve, catches may fall by up to 0.9 t.km(-2).year(-1). Our results indicate that habitat protection in reserves can underpin fish productivity and, depending on its effects on fish movements, augment catches

The Structure of Na_xPt_3O_4

In the preceding note Galloni and Busch report the results of a spectroscopic analysis of a platinum oxide similar to the compound recently investigated by us. While their compound apparently did not contain significant amounts of sodium, we had assigned the formula NaPt_3O_4 to our preparation

The Crystal Structure of NaPt_3O_4

The structure of a microcrystalline platinum compound is derived from x‐ray data. Space group O h 3—Pm3n, a_0 = 5.69A, with 6 Pt at ±(¼ 0 ½, ↺), 8 O at ±(¼ ¼ ¼, ¼ ¾ ¾, ↺), and 2 Na at (000, ½ ½ ½), corresponding to the formula NaPt_3O_4. The coordinations are as follows: platinum 4 O and 2 Pt, oxygen: 3 O and 2 Na,sodium: 8 O. The substance is an ionic conductor

Fast Ray Tracing of Lunar Digital Elevation Models

Ray-tracing (RT) of Lunar Digital Elevation Models (DEM)'s is performed to virtually derive the degree of radiation incident to terrain as a function of time, orbital and ephemeris constraints [I- 4]. This process is an integral modeling process in lunar polar research and exploration due to the present paucity of terrain information at the poles and mission planning activities for the anticipated spring 2009 launch of the Lunar Reconnaissance Orbiter (LRO). As part of the Lunar Exploration Neutron Detector (LEND) and Lunar Crater Observation and Sensing Satellite (LCROSS) preparations RI methods are used to estimate the critical conditions presented by the combined effects of high latitude, terrain and the moons low obliquity [5-7]. These factors yield low incident solar illumination and subsequently extreme thermal, and radiation conditions. The presented research uses RT methods both for radiation transport modeling in space and regolith related research as well as to derive permanently shadowed regions (PSR)'s in high latitude topographic minima, e.g craters. These regions are of scientific and human exploration interest due to the near constant low temperatures in PSRs, inferred to be < 100 K. Hydrogen is thought to have accumulated in PSR's through the combined effects of periodic cometary bombardment and/or solar wind processes, and the extreme cold which minimizes hydrogen sublimation [8-9]. RT methods are also of use in surface position optimization for future illumination dependent on surface resources e.g. power and communications equipment

Climate warming, marine protected areas and the ocean-scale integrity of coral reef ecosystems

Coral reefs have emerged as one of the ecosystems most vulnerable to climate variation and change. While the contribution of a warming climate to the loss of live coral cover has been well documented across large spatial and temporal scales, the associated effects on fish have not. Here, we respond to recent and repeated calls to assess the importance of local management in conserving coral reefs in the context of global climate change. Such information is important, as coral reef fish assemblages are the most species dense vertebrate communities on earth, contributing critical ecosystem functions and providing crucial ecosystem services to human societies in tropical countries. Our assessment of the impacts of the 1998 mass bleaching event on coral cover, reef structural complexity, and reef associated fishes spans 7 countries, 66 sites and 26 degrees of latitude in the Indian Ocean. Using Bayesian meta-analysis we show that changes in the size structure, diversity and trophic composition of the reef fish community have followed coral declines. Although the ocean scale integrity of these coral reef ecosystems has been lost, it is positive to see the effects are spatially variable at multiple scales, with impacts and vulnerability affected by geography but not management regime. Existing no-take marine protected areas still support high biomass of fish, however they had no positive affect on the ecosystem response to large-scale disturbance. This suggests a need for future conservation and management efforts to identify and protect regional refugia, which should be integrated into existing management frameworks and combined with policies to improve system-wide resilience to climate variation and change

The Structure of Na_xPt_3O_4

In the preceding note Galloni and Busch report the results of a spectroscopic analysis of a platinum oxide similar to the compound recently investigated by us. While their compound apparently did not contain significant amounts of sodium, we had assigned the formula NaPt_3O_4 to our preparation

The Crystal Structure of NaPt_3O_4

The structure of a microcrystalline platinum compound is derived from x‐ray data. Space group O h 3—Pm3n, a_0 = 5.69A, with 6 Pt at ±(¼ 0 ½, ↺), 8 O at ±(¼ ¼ ¼, ¼ ¾ ¾, ↺), and 2 Na at (000, ½ ½ ½), corresponding to the formula NaPt_3O_4. The coordinations are as follows: platinum 4 O and 2 Pt, oxygen: 3 O and 2 Na,sodium: 8 O. The substance is an ionic conductor

Ion implantation of krypton in sputter-deposited metal matrices

Krypton 85 has been successfully stored in a metal matrix by bombarding the metal surface with krypton ions while the metal is being deposited by sputtering. The krypton is thus incorporated into the metal in concentrations approaching 200 cm/sup 3/ of Kr(STP)cm/sup 3/ of deposit. Cost estimates of a facility to perform this work are given. (GHT