3,036 research outputs found
Adhesive coating eliminated in new honeycomb-core fabrication process
Technique eliminates use of silicone-based adhesive material as bonding medium. Adhesive requires precise time-temperature cure. Prepreg resin is used as bonding medium, and each layer is laminated together to form honeycomb billet. Process can be used in any application where nonmetallic honeycomb core is being fabricated
The Lennard-Jones-Devonshire cell model revisited
We reanalyse the cell theory of Lennard-Jones and Devonshire and find that in
addition to the critical point originally reported for the 12-6 potential (and
widely quoted in standard textbooks), the model exhibits a further critical
point. We show that the latter is actually a more appropriate candidate for
liquid-gas criticality than the original critical point.Comment: 5 pages, 3 figures, submitted to Mol. Phy
Detecting human impacts on the flora, fauna, and summer monsoon of Pleistocene Australia
International audienceAll of Australia's largest mammalian vertebrates became extinct 50 to 45 ka (thousand years ago), shortly after human colonization. Between 60 and 40 ka Australian climate was similar to present and not changing rapidly. Consequently, attention has turned toward plausible human mechanisms for the extinction, with proponents for over-hunting, ecosystem change, and introduced disease. To differentiate between these options we utilize isotopic tracers of diet preserved in eggshells of two large, flightless birds to track the status of ecosystems before and after human colonization. ?13C preserved in their eggshells monitor a bird's dietary intake in the weeks to months before egg-laying. More than 500 dated eggshells from central Australia of the Australian emu (Dromaius novaehollandiae), an opportunistic, dominantly herbivorous feeder, provide a continuous 140 kyr dietary ? 13C reconstruction. More than 350 dated eggshells from the same region of the heavier, extinct, giant bird Genyornis newtoni define its dietary intake from 140 ka until its extinction about 50 ka. Additional dietary records for both species were developed from two distant regions. Dromaius eggshell dietary ?13C reveals an unprecedented reduction in the bird's food resources about 50 ka, coeval in all three regions, suggesting conversion at that time of a tree/shrub savannah with occasionally rich grasslands to the modern desert scrub. We speculate that ecosystem collapse across the arid and semi-arid zones is a consequence of systematic burning by early humans. Genyornis diet everywhere is more restricted than in co-existing Dromaius, implying a more specialized feeding strategy. These data suggest that generalist feeders, such as Dromaius, were able to adapt to a changed vegetation regime, whereas more specialized feeders, such as Genyornis, became extinct. The altered vegetation may have also impacted Australian climate. Changes in the strength of climate feedbacks linked to vegetation and soil type (moisture recycling, surface roughness, albedo) may have weakened the penetration of monsoon moisture into the continental interior under the new ecosystem. Climate modeling suggests such a shift may have reduced monsoon rain in the interior by as much as 50%
Democratization in a passive dendritic tree : an analytical investigation
One way to achieve amplification of distal synaptic inputs on a dendritic tree is to scale the amplitude and/or duration of the synaptic conductance with its distance from the soma. This is an example of what is often referred to as “dendritic democracy”. Although well studied experimentally, to date this phenomenon has not been thoroughly explored from a mathematical perspective. In this paper we adopt a passive model of a dendritic tree with distributed excitatory synaptic conductances and analyze a number of key measures of democracy. In particular, via moment methods we derive laws for the transport, from synapse to soma, of strength, characteristic time, and dispersion. These laws lead immediately to synaptic scalings that overcome attenuation with distance. We follow this with a Neumann approximation of Green’s representation that readily produces the synaptic scaling that democratizes the peak somatic voltage response. Results are obtained for both idealized geometries and for the more realistic geometry of a rat CA1 pyramidal cell. For each measure of democratization we produce and contrast the synaptic scaling associated with treating the synapse as either a conductance change or a current injection. We find that our respective scalings agree up to a critical distance from the soma and we reveal how this critical distance decreases with decreasing branch radius
Recovery and Utilization of Deceased Donor Kidneys from Small Pediatric Donors
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72146/1/j.1600-6143.2006.01353.x.pd
The role, function and identity of music therapists in the 21st century, including new research and thinking from a UK perspective
This article examines the identity of music therapy and music therapists, focussing upon the United Kingdom as a case study, but also considering international trends. Milestones in the history of music therapy in postwar United Kingdom and professional development in the 21st century are discussed, drawing upon research and clinical practice. Research outcomes across different specialities indicate that music therapy should be widely available to many populations, such as for people with dementia, autism, stroke and mental health problems and so on. These advancements mean that music therapists need to be clear about their role and identity in both doing the work and communicating about it. The article celebrates advances in research, thinking and provision and emphasis collaboration across multidisciplinary groups through an overview of different identities
Combined BIMA and OVRO observations of comet C/1999 S4 (LINEAR)
We present results from an observing campaign of the molecular content of the
coma of comet C/1999 S4 (LINEAR) carried out jointly with the millimeter-arrays
of the Berkeley-Illinois-Maryland Association (BIMA) and the Owens Valley Radio
Observatory (OVRO). Using the BIMA array in autocorrelation (`single-dish')
mode, we detected weak HCN J=1-0 emission from comet C/1999 S4 (LINEAR) at 14
+- 4 mK km/s averaged over the 143" beam. The three days over which emission
was detected, 2000 July 21.9-24.2, immediately precede the reported full
breakup of the nucleus of this comet. During this same period, we find an upper
limit for HCN 1-0 of 144 mJy/beam km/s (203 mK km/s) in the 9"x12" synthesized
beam of combined observations of BIMA and OVRO in cross-correlation (`imaging')
mode. Together with reported values of HCN 1-0 emission in the 28" IRAM
30-meter beam, our data probe the spatial distribution of the HCN emission from
radii of 1300 to 19,000 km. Using literature results of HCN excitation in
cometary comae, we find that the relative line fluxes in the 12"x9", 28" and
143" beams are consistent with expectations for a nuclear source of HCN and
expansion of the volatile gases and evaporating icy grains following a Haser
model.Comment: 18 pages, 3 figures. Uses aastex. AJ in pres
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