High-temperature ''hydrostatic'' extrusion

Quasi-fluids permit hydrostatic extrusion of solid materials. The use of sodium chloride, calcium fluoride, or glasses as quasi-fluids reduces handling, corrosion, and sealing problems, these materials successfully extrude steel, molybdenum, ceramics, calcium carbonate, and calcium oxide. This technique also permits fluid-to-fluid extrusion

Identifying optimum parameters of hot extrusions Interim report no. II

Techniques and effects of hot extruding magnesium oxid

System for the measurement of ultra-low stray light levels

An apparatus is described for measuring the effectiveness of stray light suppression light shields and baffle arrangements used in optical space experiments and large space telescopes. The light shield and baffle arrangement and a telescope model are contained in a vacuum chamber. A source of short, high-powered light energy illuminates portions of the light shield and baffle arrangement and reflects a portion of same to a photomultiplier tube by virtue of multipath scattering. The resulting signal is transferred to time-channel electronics timed by the firing of the high energy light source allowing time discrimination of the signal thereby enabling the light scattered and suppressed by the model to be distinguished from the walls and holders around the apparatus

Shoot growth of woody trees and shrubs is predicted by maximum plant height and associated traits

1. The rate of elongation and thickening of individual branches (shoots) varies across plant species. This variation is important for the outcome of competition and other plant-plant interactions. Here we compared rates of shoot growth across 44 species from tropical, warm temperate, and cool temperate forests of eastern Australia.2. Shoot growth rate was found to correlate with a suite of traits including the potential height of the species, xylem-specific conductivity, leaf size, leaf area per xylem cross-section, twig diameter (at 40 cm length), wood density and modulus of elasticity.3. Within this suite of traits, maximum plant height was the clearest correlate of growth rates, explaining 50 to 67% of the variation in growth overall (p p 4. Growth rates were not strongly correlated with leaf nitrogen or leaf mass per unit leaf area.5. Correlations between growth and maximum height arose both across latitude (47%, p p p p < 0.0001), reflecting intrinsic differences across species and sites

Design definition study of a NASA/Navy lift/cruise fan technology V/STOL airplane: Risk assessment addendum to the final report

An assessment of risk, in terms of delivery delays, cost overrun, and performance achievement, associated with the V/STOL technology airplane is presented. The risk is discussed in terms of weight, structure, aerodynamics, propulsion, mechanical drive, and flight controls. The analysis ensures that risks associated with the design and development of the airplane will be eliminated in the course of the program and a useful technology airplane that meets the predicted cost, schedule, and performance can be produced

Oak forest carbon and water simulations:Model intercomparisons and evaluations against independent data

Models represent our primary method for integration of small-scale, process-level phenomena into a comprehensive description of forest-stand or ecosystem function. They also represent a key method for testing hypotheses about the response of forest ecosystems to multiple changing environmental conditions. This paper describes the evaluation of 13 stand-level models varying in their spatial, mechanistic, and temporal complexity for their ability to capture intra- and interannual components of the water and carbon cycle for an upland, oak-dominated forest of eastern Tennessee. Comparisons between model simulations and observations were conducted for hourly, daily, and annual time steps. Data for the comparisons were obtained from a wide range of methods including: eddy covariance, sapflow, chamber-based soil respiration, biometric estimates of stand-level net primary production and growth, and soil water content by time or frequency domain reflectometry. Response surfaces of carbon and water flux as a function of environmental drivers, and a variety of goodness-of-fit statistics (bias, absolute bias, and model efficiency) were used to judge model performance. A single model did not consistently perform the best at all time steps or for all variables considered. Intermodel comparisons showed good agreement for water cycle fluxes, but considerable disagreement among models for predicted carbon fluxes. The mean of all model outputs, however, was nearly always the best fit to the observations. Not surprisingly, models missing key forest components or processes, such as roots or modeled soil water content, were unable to provide accurate predictions of ecosystem responses to short-term drought phenomenon. Nevertheless, an inability to correctly capture short-term physiological processes under drought was not necessarily an indicator of poor annual water and carbon budget simulations. This is possible because droughts in the subject ecosystem were of short duration and therefore had a small cumulative impact. Models using hourly time steps and detailed mechanistic processes, and having a realistic spatial representation of the forest ecosystem provided the best predictions of observed data. Predictive ability of all models deteriorated under drought conditions, suggesting that further work is needed to evaluate and improve ecosystem model performance under unusual conditions, such as drought, that are a common focus of environmental change discussions

The Principle of Valence Bond Amplitude Maximization in Cuprates: How it breeds Superconductivity, Spin and Charge Orders

A simple microscopic principle of `Valence bond (nearest neighbor singlet) amplitude maximization '(VBAM) is shown to be present in undoped and optimally doped cuprates and unify the very different orderings such as antiferromagnetism in the Mott insulator and the robust superconductivity accompanied by an enhanced charge and stripe correlations in the optimally doped cuprates. VBAM is nearly synonymous with the energy minimization principle. It is implicit in the RVB theory and thereby makes the predictions of RVB mean field theory of superconductivity qualitatively correct.Comment: 4 pages, RevTe

Anatomy and origin of authochthonous late Pleistocene forced regression deposits, east Coromandel inner shelf, New Zealand: implications for the development and definition of the regressive systems tract

High-resolution seismic reflection data from the east Coromandel coast, New Zealand, provide details of the sequence stratigraphy beneath an autochthonous, wave dominated inner shelf margin during the late Quaternary (0-140 ka). Since c. 1 Ma, the shelf has experienced limited subsidence and fluvial sediment input, producing a depositional regime characterised by extensive reworking of coastal and shelf sediments during glacio-eustatic sea-level fluctuations. It appears that only one complete fifth-order (c. 100 000 yr) depositional sequence is preserved beneath the inner shelf, the late Pleistocene Waihi Sequence, suggesting any earlier Quaternary sequences were mainly cannibalised into successively younger sequences. The predominantly Holocene-age Whangamata Sequence is also evident in seismic data and modern coastal deposits, and represents an incomplete depositional sequence in its early stages of formation. A prominent aspect of the sequence stratigraphy off parts of the east Coromandel coast is the presence of forced regressive deposits (FRDs) within the regressive systems tract (RST) of the late Pleistocene Waihi Sequence. The FRDs are interpreted to represent regressive barrier-shoreface sands that were sourced from erosion and onshore reworking of underlying Pleistocene sediments during the period of slow falling sea level from isotope stages 5 to 2 (c. 112-18 ka). The RST is volumetrically the most significant depositional component of the Waihi Sequence; the regressive deposits form a 15-20 m thick, sharp-based, tabular seismic unit that downsteps and progrades continuously across the inner shelf. The sequence boundary for the Waihi Sequence is placed at the most prominent, regionally correlative, and chronostratigraphically significant surface, namely an erosional unconformity characterised in many areas by large incised valleys that was generated above the RST. This unconformity is interpreted as a surface of maximum subaerial erosion generated during the last glacial lowstand (c. 18 ka). Although the base of the RST is associated with a prominent regressive surface of erosion, this is not used as the sequence boundary as it is highly diachronous and difficult to identify and correlate where FRDs are not developed. The previous highstand deposits are limited to subaerial barrier deposits preserved behind several modern Holocene barriers along the coast, while the transgressive systems tract is preserved locally as incised-valley fill deposits beneath the regressive surface of erosion at the base of the RST. Many documented late Pleistocene RSTs have been actively sourced from fluvial systems feeding the shelf and building basinward-thickening, often stacked wedges of FRDs, for which the name allochthonous FRDs is suggested. The Waihi Sequence RST is unusual in that it appears to have been sourced predominantly from reworking of underlying shelf sediments, and thus represents an autochthonous FRD. Autochthonous FRDs are also present on the Forster-Tuncurry shelf in southeast Australia, and may be a common feature in other shelf settings with low subsidence and low sediment supply rates, provided shelf gradients are not too steep, and an underlying source of unconsolidated shelf sediments is available to source FRDs. The preservation potential of such autochthonous FRDs in ancient deposits is probably low given that they are likely to be cannibalised during subsequent sea-level falls