Selection Among and Within S1 Lines of Maize on S2 Line and Testcross Performance

Most maize (Zea mays L.) breeders practice visual selection among lines during inbreeding, but may not be certain of the effectiveness of such selection. Visual selection among and within 1,636 S1 lines of maize derived from \u27Lancaster Composite\u27 was used to select 200 S2 lines, and a random set of 200 S2 lines also was developed. Yield trials of the 400 S2 lines in three environments and their testcrosses to (B73 x B84) in four environments were conducted to determine whether visual selection was effective in choosing high-yielding and agronomically desirable lines with superior combining ability. Grain yield of the visually selected S1 lines (3.11 Mg ha-1) was significantly (P\u3c0.05) greater than that of the unselected lines (2.94 Mg ha-1), but there was no difference in testcross means. Visually selected S1 lines had slightly greater mean grain moisture and slightly less mean stalk lodging than unselected lines in individual environments. Testcrosses of visually selected lines had greater grain moisture and less stalk lodging than testcrosses of unselected lines in individual environments. Estimates of genetic variance, heritability, and gain from selection were not consistently affected by visual selection. Many superior S2 lines and testcrosses were unselected lines, showing that visual selection failed to identify many desirable genotypes. Our results suggest that visual selection should not be used to attempt to select the most superior genotypes, but should emphasize discarding of undesirable genotypes before yield testing

Post-harvest fisheries development: A guide to handling, preservation, processing, and quality

In the early 1980s, the Tropical Products Institute (a forerunner of NRI) published a two volume report entitled Fish Handling, Preservation and Processing in the Tropics. It was written to provide a basis for middle management training courses in government and industry in tropical developing countries. Over the years, the publication has been one of the most popular of NRI's series of technical and scientific reports; it has been reprinted on a number of occasions and distributed to thousands of people worldwide. The present book is an updated version of the original. It is designed to bring to a lay audience the basic concepts behind post-harvest fisheries science and technology, and to assist the non-specialist with decision making. Readers familiar with the previous publication will find that parts of this book have been extensively revised. Where possible, a list of suggested further reading has been included at the end of each chapter so that more details can be obtained if required. If readers have difficulty in obtaining these publications, or need further information, the fisheries group of NRI can be contacted for assistance

Marked differences in foraging area use and susceptibility to predation between two closely-related tropical seabirds

Ecological theory predicts that closely-related species must occupy diferent niches to coexist. How marine top predators achieve this during breeding, when they often gather in large multi-species colonies and are constrained to central-place foraging, has been mostly studied in productive temperate and polar oceans with abundant resources, but less so in poorer, tropical waters. Here, we track the foraging movements of two closely-related sympatric seabirds—the white-tailed and red-tailed tropicbirds Phaethon lepturus and P. rubricauda—breeding on Aldabra Atoll, Seychelles, to investigate potential mechanisms of niche segregation and shed light on their contrasting population trends. Combining data from GPS, immersion, depth and accelerometry loggers, we show that the two species have similar behaviour at sea, but are completely segregated spatially, with red-tailed tropicbirds fying further to feed and using diferent feeding areas than white-tailed tropicbirds. Using nest-based camera traps, we show that low breeding success of both species—which likely drives observed population declines—is caused by high nest predation. However, the two species are targeted by diferent predators, with native avian predators mainly targeting red-tailed tropicbird nests, and invasive rats raiding white-tailed tropicbird nests when they leave their eggs unattended. Our fndings provide new insight into the foraging ecology of tropicbirds and have important conservation implications. The extensive range and spatial segregation highlight the importance of considering large-scale protection of waters around tropical seabird colonies, while the high level of nest predation provides evidence in support of rat eradication and investigating potential nest protection from native avian predators. Invasive species · Niche partitioning · Spatial segregation · Seychelles · SympatrypublishedVersio

Internal Flow Behaviour and Microstructural Evolution of the Bobbin-FSW Welds: Thermomechanical Comparison between 1xxx and 3xxx Aluminium Grades

The influences of processing parameters and tool feature on the microstructure of AA1100 and AA3003 aluminium alloys were investigated using bobbin friction stir welding (BFSW). The research includes flow visualization and microstructural evolution of the weld texture using the metallographic measurement method. Results indicated that the operational parameters of the welding (e.g. feed rate, rotating speed) and the geometry of the tool can directly affect the flow patterns of the weld structure. The microscopic details revealed by the optical and electron microscope imply the dynamic recrystallization including grain refinement and precipitation mechanisms within the stirring zone of the weld region. The microscopic observations for the weld samples show a better performance of the fully-featured tool (tri-flat threaded pin and scrolled shoulders) compared to the simple tool without inscribed surface features. The fully-featured tool resulted in a more uniform thermomechanical plastic deformation within the weld structure along with the precipitation hardening and the homogeneity of the microstructure.</jats:p

The Effects of Cooling and Shrinkage on the Life of Polymer 3D Printed Injection Moulds

3D Printed Injection Moulds (3DIM), commonly used for low volume production and prototyping purposes, are known to fail abruptly and have a comparatively shorter life than conventional moulds. Investigating the underlying critical factors affecting failure may help in reducing the risk of abrupt failures and possibly prolong the 3DIM tool life. A hypothesis that the cooling time of the Injection Moulding (IM) process is a critical factor for 3DIM tool failure has been pro-posed. The failure hypothesis has been validated by theoretical calculations, FEA simulations and experimental investigations. Experiments were performed using two different materials for the 3DIM tool (Visijet M3-X and Digital ABS) and an engineering thermoplastic (Lexan 943-A) as the moulding material. Results showed that cooling time was a critical factor on tool life and managing the thermal loading on a 3DIM tool could lead to increased tool life. The paper identifies cooling time as the critical factor affecting 3DIM tool life and presents a cooling regime that could possibly lead to prolonged tool life

Internal Material Flow Layers in AA6082-T6 Butt-Joints during Bobbin Friction Stir Welding

Bobbin friction stir welding with a double-sided tool configuration produces a symmetrical solid-state joint. However, control of the process parameters to achieve defect-free welds is difficult. The internal flow features of the AA6082-T6 butt-joints in bobbin friction stir welding were evaluated using a set of developed reagents and optical microscopy. The key findings are that the dark curved patterns (conventionally called 'flow-arms'), are actually oxidation layers at the advancing side, and at the retreating side are elongated grains with a high-density of accumulation of sub-grain boundaries due to dynamic recrystallization. A model of discontinuous flow within the weld is proposed, based on the microscopic observations. It is inferred that the internal flow is characterized by packets of material ('flow patches') being transported around the pin. At the retreating side they experience high localized shearing at their mutual boundaries, as evidenced in high density of sub-grain boundaries. Flow patches at the advancing side are stacked on each other and exposed to oxidization

The politics of one Oregon: the causes, consequences and prospects of overcoming the rural-urban divide

Presentation and paper from 2008 "Toward One Oregon" Conference

Fate specification and tissue-specific cell cycle control of the <i>Caenorhabditis elegans</i> intestine

Coordination between cell fate specification and cell cycle control in multicellular organisms is essential to regulate cell numbers in tissues and organs during development, and its failure may lead to oncogenesis. In mammalian cells, as part of a general cell cycle checkpoint mechanism, the F-box protein β-transducin repeat-containing protein (β-TrCP) and the Skp1/Cul1/F-box complex control the periodic cell cycle fluctuations in abundance of the CDC25A and B phosphatases. Here, we find that the Caenorhabditis elegans β-TrCP orthologue LIN-23 regulates a progressive decline of CDC-25.1 abundance over several embryonic cell cycles and specifies cell number of one tissue, the embryonic intestine. The negative regulation of CDC-25.1 abundance by LIN-23 may be developmentally controlled because CDC-25.1 accumulates over time within the developing germline, where LIN-23 is also present. Concurrent with the destabilization of CDC-25.1, LIN-23 displays a spatially dynamic behavior in the embryo, periodically entering a nuclear compartment where CDC-25.1 is abundant

Trypanosoma brucei aquaglyceroporin 2 is a high-affinity transporter for pentamidine and melaminophenyl arsenic drugs and the main genetic determinant of resistance to these drugs.

OBJECTIVES: Trypanosoma brucei drug transporters include the TbAT1/P2 aminopurine transporter and the high-affinity pentamidine transporter (HAPT1), but the genetic identity of HAPT1 is unknown. We recently reported that loss of T. brucei aquaglyceroporin 2 (TbAQP2) caused melarsoprol/pentamidine cross-resistance (MPXR) in these parasites and the current study aims to delineate the mechanism by which this occurs. METHODS: The TbAQP2 loci of isogenic pairs of drug-susceptible and MPXR strains of T. brucei subspecies were sequenced. Drug susceptibility profiles of trypanosome strains were correlated with expression of mutated TbAQP2 alleles. Pentamidine transport was studied in T. brucei subspecies expressing TbAQP2 variants. RESULTS: All MPXR strains examined contained TbAQP2 deletions or rearrangements, regardless of whether the strains were originally adapted in vitro or in vivo to arsenicals or to pentamidine. The MPXR strains and AQP2 knockout strains had lost HAPT1 activity. Reintroduction of TbAQP2 in MPXR trypanosomes restored susceptibility to the drugs and reinstated HAPT1 activity, but did not change the activity of TbAT1/P2. Expression of TbAQP2 sensitized Leishmania mexicana promastigotes 40-fold to pentamidine and >1000-fold to melaminophenyl arsenicals and induced a high-affinity pentamidine transport activity indistinguishable from HAPT1 by Km and inhibitor profile. Grafting the TbAQP2 selectivity filter amino acid residues onto a chimeric allele of AQP2 and AQP3 partly restored susceptibility to pentamidine and an arsenical. CONCLUSIONS: TbAQP2 mediates high-affinity uptake of pentamidine and melaminophenyl arsenicals in trypanosomes and TbAQP2 encodes the previously reported HAPT1 activity. This finding establishes TbAQP2 as an important drug transporter