Breakdown of disordered media by surface loads

We model an interface layer connecting two parts of a solid body by N parallel elastic springs connecting two rigid blocks. We load the system by a shear force acting on the top side. The springs have equal stiffness but are ruptured randomly when the load reaches a critical value. For the considered system, we calculate the shear modulus, G, as a function of the order parameter, \phi, describing the state of damage, and also the ``spalled'' material (burst) size distribution. In particular, we evaluate the relation between the damage parameter and the applied force and explore the behaviour in the vicinity of material breakdown. Using this simple model for material breakdown, we show that damage, caused by applied shear forces, is analogous to a first-order phase transition. The scaling behaviour of G with \phi is explored analytically and numerically, close to \phi=0 and \phi=1 and in the vicinity of \phi_c, when the shear load is close but below the threshold force that causes material breakdown. Our model calculation represents a first approximation of a system subject to wear induced loads.Comment: 15 pages, 7 figure

Ark or park: the need to predict relative effectiveness of ex situ and in situ conservation before attempting captive breeding

1. When species face extinction, captive breeding may be appropriate. However, captive breeding may be unsuccessful, while reducing motivation and resources for in situ conservation and impacting wild source populations. Despite such risks, decisions are generally taken without rigorous evaluation. We develop an individual-based, stochastic population model to evaluate the potential effectiveness of captive-breeding and release programmes, illustrated by the Critically Endangered Ardeotis nigriceps Vigors great Indian bustard. 2. The model was parameterized from a comprehensive review of captive breeding and wild demography of large bustards. To handle uncertainty in the standards of captive-breeding performance that may be achieved we explored four scenarios of programme quality: ‘full-range’ (parameters sampled across the observed range), ‘below-average’, ‘above-average’ and ‘best possible’ (performance observed in exemplary breeding programmes). Results are evaluated examining i) the probability of captive population extirpation within 50 years and ii) numbers of adult females subsequently established in the wild following release, compared to an alternative strategy of in situ conservation without attempting captive breeding. 3. Successful implementation of captive breeding, involving permanent retention of 20 breeding females and release of surplus juveniles, required collection of many wild eggs and consistent ‘best possible’ performance across all aspects of the programme. Under ‘full-range’ and ‘above-average’ scenarios captive population extirpation probabilities were 73–88% % and 23‒51%% respectively, depending on egg collection rates. 4. Although most (73‒92%) ‘best possible’ programmes supported releases, re-establishment of free-living adults also required effective in situ conservation. Incremental implementation of effective conservation measures over the initial 10 years resulted in more free-living adults within 35 years if eggs were left in the wild without attempting captive breeding. 5. Synthesis and applications. For the great Indian bustard Ardeotis nigriceps, rapid implementation of in situ conservation offers a better chance to avoid extinction than captive breeding. Demographic modelling should be used to examine whether captive breeding is likely to bring net benefits to conservation programmes

Finite-element analysis of contact between elastic self-affine surfaces

Finite element methods are used to study non-adhesive, frictionless contact between elastic solids with self-affine surfaces. We find that the total contact area rises linearly with load at small loads. The mean pressure in the contact regions is independent of load and proportional to the rms slope of the surface. The constant of proportionality is nearly independent of Poisson ratio and roughness exponent and lies between previous analytic predictions. The contact morphology is also analyzed. Connected contact regions have a fractal area and perimeter. The probability of finding a cluster of area $a_c$ drops as $a_c^{-\tau}$ where $\tau$ increases with decreasing roughness exponent. The distribution of pressures shows an exponential tail that is also found in many jammed systems. These results are contrasted to simpler models and experiment.Comment: 13 pages, 15 figures. Replaced after changed in response to referee comments. Final two figures change

An integrated study of earth resources in the State of California based on ERTS-1 and supporting aircraft data

There are no author-identified significant results in this report

Spiked GBS: a unified, open platform for single marker genotyping and whole-genome profiling

Citation: Rife, T. W., Wu, S. Y., Bowden, R. L., & Poland, J. A. (2015). Spiked GBS: a unified, open platform for single marker genotyping and whole-genome profiling. Bmc Genomics, 16, 7. https://doi.org/10.1186/s12864-015-1404-9Background: In plant breeding, there are two primary applications for DNA markers in selection: 1) selection of known genes using a single marker assay (marker-assisted selection; MAS); and 2) whole-genome profiling and prediction (genomic selection; GS). Typically, marker platforms have addressed only one of these objectives. Results: We have developed spiked genotyping-by-sequencing (sGBS), which combines targeted amplicon sequencing with reduced representation genotyping-by-sequencing. To minimize the cost of targeted assays, we utilize a small percent of sequencing capacity available in runs of GBS libraries to "spike" amplified targets of a priori alleles tagged with a different set of unique barcodes. This open platform allows multiple, single-target loci to be assayed while simultaneously generating a whole-genome profile. This dual-genotyping approach allows different sets of samples to be evaluated for single markers or whole genome-profiling. Here, we report the application of sGBS on a winter wheat panel that was screened for converted KASP markers and newly-designed markers targeting known polymorphisms in the leaf rust resistance gene Lr34. Conclusions: The flexibility and low-cost of sGBS will enable a range of applications across genetics research. Specifically in breeding applications, the sGBS approach will allow breeders to obtain a whole-genome profile of important individuals while simultaneously targeting specific genes for a range of selection strategies across the breeding program

Evaluation of advanced lift concepts and fuel conservative short-haul aircraft, volume 2

For abstract, see N75-20291

Evaluation of advanced lift concepts and fuel conservative short-haul aircraft, volume 1

The performance and economics of a twin-engine augmentor wing airplane were evaluated in two phases. Design aspects of the over-the-wing/internally blown flap hybrid, augmentor wing, and mechanical flap aircraft were investigated for 910 m. field length with parametric extension to other field lengths. Fuel savings achievable by application of advanced lift concepts to short-haul aircraft were evaluated and the effect of different field lengths, cruise requirements, and noise levels on fuel consumption and airplane economics at higher fuel prices were determined. Conclusions and recommendations are presented

The Identification of Infrared Synchrotron Radiation from Cassiopeia A

We report the discovery of polarized flux at 2.2 micron from the bright shell of the approximately 320 year old supernova remnant Cas A. The fractional polarizations are comparable at 6 cm and 2.2 micron, and the polarization angles are similar, demonstrating that synchrotron radiation from the same relativistic plasma is being observed at these widely separated wavebands. The relativistic electrons radiating at 2.2 micron have an energy of ~ 150 GeV, (gamma ~ 3e5), assuming an ~500 microGauss magnetic field. The total intensity at 2.2 micron lies close to the power law extrapolation from radio frequencies, showing that relativistic particle acceleration is likely an ongoing process; the infrared emitting electrons were accelerated no longer than ~80 years ago. There is a small but significant concave curvature to the spectrum, as expected if the accelerating shocks have been modified by the back pressure of the cosmic rays; given calibration uncertainties, this conclusion must be considered tentative at present. The 2.2 micron polarization angles and the emission-line filaments observed by HST are both offset from the local radial direction by 10 - 20 degrees, providing evidence that the magnetic fields in Cas A are generated by Rayleigh-Taylor instabilities in the decelerating ejecta.Comment: 11 pages, 3 figures, accepted for publication Ap