Informal seed systems, such as farmer-to-farmer exchanges and farmer self-saved seed, are critical components of resource poor farming systems. This local seed production and distribution facilitates ...maintenance of crop bio-diversity by preserving in situ locally adapted cultivars and by broadening the genetic base of production with multiple cultivars adapted to specific production systems and micro-climates. They also enhance seed and food security during periods of instability or natural disaster, including changing environmental conditions. A rich diversity of underutilized crop species function within these informal seed systems in Southeast Asia, yet current efforts to conserve, improve, and disseminate indigenous species are failing. A strategy was developed and tested linking an innovative seed bank, local farmers and non-commercial seed traders, with developing markets, supported by accessible information made available through a local outreach network. Impacts included identification of key seed traders and farmers functioning within targeted regions of high species diversity, inventories of important indigenous crop species, documentation of specific indigenous knowledge surrounding the culture of key crops, and expanded exchange and distribution of locally adapted underutilized species. This project paves the way for potential longer term benefits including formation of seed bank-farmer linkages that allow non-commercial seed producers to access new cultivars, hybrids and high-value seed resources not available from traditional sources, development of value chains around key indigenous species, and regional distribution of important seed resources to less developed neighbor nations.
The phylogenetic position of ascidians near the base of the chordate tree makes them ideal organisms for evolutionary developmental studies of programmed cell death (PCD). In the present study, the ...following key features of an apoptotic form of PCD are described in Boltenia villosa: fragmentation of DNA, increases in plasma membrane permeability, decreases in mitochondrial activity, production of reactive oxygen species (ROS), and caspase activation. First, evidence is presented for apoptosis of cells within the ovary. Later in development, during the early phase of larval tail resorption at the beginning of metamorphosis, some notochord nuclei showed DNA fragmentation and their cell corpses were rapidly eliminated from the larval body. In striking contrast to the rapid demise of notochord cells, larval muscle cells persisted for more than a week within developing juveniles. Rhodamine 123 and MTT experiments suggest that mitochondria within some of the resorbed larval tail muscle cells were metabolically active for more than a week. Furthermore, resorbed tail muscle cells contained a muscle-specific intermediate filament, termed p58, despite relatively high levels of ROS activity and the ubiquitination of their plasma membranes at day two. Corpses of larval tail muscle cells containing aggregated pigment granules survived within juveniles for more than a month, in contrast to the rapid elimination of notochord cells. Evidence consistent with the formation of larval muscle cell apoptotic bodies is presented. The most surprising result of the present study was that caspase-8, usually associated with apoptotic signaling, was activated in larval endoderm cells that develop into adult structures. When the present results were compared to features of PCD previously reported in other ascidians, significant species differences in PCD were revealed.
Fused filament fabrication of thermoplastic polyurethanes (TPUs) offers a capability to manufacture tailorable, flexible honeycomb structures which can be optimised for energy absorbing applications. ...This work explores the effect of a range of grading methodologies on the energy absorbing and damping behaviour of flexible TPU honeycomb structures. By applying density grading, the energy absorbing and damping profiles are significantly modified from the uniform density equivalent. A 3D-printing procedure was developed which allowed the manufacture of high-quality structures, which underwent cyclic loading to densification without failure. Graded honeycomb architectures had an average relative density of 0.375 ± 0.05. After quasi-static testing, arrays were subjected to sinusoidal compression over a range of amplitudes at 0.5 Hz. By grading the structural density in different ways, mechanical damping was modified. Cyclic compressive testing also showed how strain-softening of the TPU parent material could lead to reduced damping over the course of 50 cycles. Samples were subjected to impact loading at strain-rates of up to 51 s-1 and specific impact energies of up to 270 mJ/cm3. Lower peak loads were transferred for graded samples for the most severe impact cases. This behaviour reveals the potential of density grading of TPU structures to provide superior impact protection in extreme environmental conditions.
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•Hyperplastic honeycombs with 4 density grading methodologies were produced via fused filament fabrication 3D-printing.•All thermoplastic polyurethane honeycombs were subjected to quasi-static, cyclic and high strain-rate impact analysis.•By density grading, energy absorbing and damping profiles were significantly modified from the uniform density equivalent.•Samples absorbed specific impact energies of up to 270 mJ/cm3 at strain-rates of up to 51 s−1 before recovering elastically.•Lower peak loads were transferred for graded samples for the most severe impact cases.
Reliable scale-up of fluidized beds is essential to ensure that analysis and performance optimization at lab-scale can be applied to commercial scales. However, scaling fluidized beds for dynamic ...similarity continues to be challenging because flow hydrodynamics at lab-scale are largely influenced by bed geometry making extrapolation of conclusions to large-scales infeasible. Therefore, this study is focused on analyzing the effect of bed geometry on the fluidization hydrodynamics using large-scale CFD simulations. The two fluid model (TFM) is employed to describe the solids motion efficiently and simulations are conducted for fluidization of 1150μm LLDPE and 500μm glass beads in beds of different sizes (diameter D=15–70cm and initial bed height H0=10–75cm). The hydrodynamics are subsequently investigated qualitatively using time-resolved visualizations, bubble centroid and solids velocity maps as well as quantitatively using detailed bubble statistics and solids circulation metrics. It is shown that as the bed diameter is increased, average bubble sizes decrease although similar-sized bubbles rise faster because of lower wall resistance, both factors contributing to faster solids circulation. On the other hand, fluidization hydrodynamics in 50cm diameter bed are relatively insensitive to the choice of H0 and similarities in solids circulation patterns are observed in shallow beds as well as in the lower regions of deep beds. Finally, it is shown that the size and spatial-distribution of bubbles is crucial for maintaining dynamic similarity of bubbling beds. Specifically, the bed dimensions (D, H0) must ensure that (a) bubbles are typically much smaller than the bed diameter and (b) solids circulation patterns are similar across scales of interest. Overall, insights from this study can be used for describing the gas distribution and solids motion more accurately for better design of commercial beds.
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•Effect of bed diameter and initial height investigated through fine-grid simulations•Smaller bubbles with higher velocities, faster solids circulations as D increased•Hydrodynamics unaffected by H0; dynamics in shallow and deep beds similar•Scaling must ensure bubbles smaller than 0.2D, similar bulk solids circulation•D=50cm and H0/D=0.5 suitable for scaling up fluidization hydrodynamics
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