IMECE 2003-43377 HIGH AUTHORITY MORPHING STRUCTURES

ABSTRACT Recent advances in actuation technology and multifunctional materials have presented a unique opportunity to develop structures that have the ability to morph to a variety of shapes while under significant load constraints. One of the many applications of these "high-authority" systems is for morphing air wings for control and drag reduction. The exciting solution to this is the creation of a statically determinate structure that incorporates linear actuators to produce morphing capabilities. Statically determinate structures satisfy Maxwell's necessary condition that the number of member forces equal the number of joint equilibrium equations. By imposing this condition on the structure it is possible to actively change the shape of the overall structure without resulting in failure. In a morphing foil, the only induced strain within passive members will be due to the hydrodynamic forces present. Deformation of the truss members is stretch-dominated-they do not experience bending-and thus improve the load carrying capacity of the structure. Of primary interest are Shape Memory Alloy (SMAs) actuators. SMAs are useful for shape morphing concepts where large forces are needed. A prototypical foil has been built around a statically determinate structure that incorporates linear actuators to produce morphing capabilities. These "smart" foils have been tested in a wind tunnel to examine their drag reduction capabilities

Targeted recombination in plants using Agrobacterium coincides with additional rearrangements at the target locus

Microbial Biotechnolog

Homoeologous gene silencing in tissue cultured wheat callus

Abstract Background In contrast to diploids, most polyploid plant species, which include the hexaploid bread wheat, possess an additional layer of epigenetic complexity. Several studies have demonstrated that polyploids are affected by homoeologous gene silencing, a process in which sub-genomic genomic copies are selectively transcriptionally inactivated. This form of silencing can be tissue specific and may be linked to developmental or stress responses. Results Evidence was sought as to whether the frequency of homoeologous silencing in in vitro cultured wheat callus differ from that in differentiated organs, given that disorganized cells are associated with a globally lower level of DNA methylation. Using a reverse transcription PCR (RT-PCR) single strand conformation polymorphism (SSCP) platform to detect the pattern of expression of 20 homoeologous sets of single-copy genes known to be affected by this form of silencing in the root and/or leaf, we observed no silencing in any of the wheat callus tissue tested. Conclusion Our results suggest that much of the homoeologous silencing observed in differentiated tissues is probably under epigenetic control, rather than being linked to genomic instability arising from allopolyploidization. This study reinforces the notion of plasticity in the wheat epi-genome.</p

Expression of a rice chitinase gene in transgenic banana ('Gros Michel', AAA genome group) confers resistance to black leaf streak disease

Peer reviewe

The Arabidopsis thaliana F-box gene HAWAIIAN SKIRT is a new player in the microRNA pathway

In Arabidopsis, the F-box HAWAIIAN SKIRT (HWS) protein is important for organ growth. Loss of function of HWS exhibits pleiotropic phenotypes including sepal fusion. To dissect the HWS role, we EMS-mutagenized hws-1 seeds and screened for mutations that suppress hws-1 associated phenotypes. We identified shs-2 and shs-3 (suppressor of hws-2 and 3) mutants in which the sepal fusion phenotype of hws-1 was suppressed. shs-2 and shs-3 (renamed hst-23/hws-1 and hst-24/hws-1) carry transition mutations that result in premature terminations in the plant homolog of Exportin-5 HASTY (HST), known to be important in miRNA biogenesis, function and transport. Genetic crosses between hws-1 and mutant lines for genes in the miRNA pathway, also suppress the phenotypes associated with HWS loss of function, corroborating epistatic relations between the miRNA pathway genes and HWS. In agreement with these data, accumulation of miRNA is modified in HWS loss or gain of function mutants. Our data propose HWS as a new player in the miRNA pathway, important for plant growth

Phylogenetic Comparison of F-Box (FBX) Gene Superfamily within the Plant Kingdom Reveals Divergent Evolutionary Histories Indicative of Genomic Drift

The emergence of multigene families has been hypothesized as a major contributor to the evolution of complex traits and speciation. To help understand how such multigene families arose and diverged during plant evolution, we examined the phylogenetic relationships of F-Box (FBX) genes, one of the largest and most polymorphic superfamilies known in the plant kingdom. FBX proteins comprise the target recognition subunit of SCF-type ubiquitin-protein ligases, where they individually recruit specific substrates for ubiquitylation. Through the extensive analysis of 10,811 FBX loci from 18 plant species, ranging from the alga Chlamydomonas reinhardtii to numerous monocots and eudicots, we discovered strikingly diverse evolutionary histories. The number of FBX loci varies widely and appears independent of the growth habit and life cycle of land plants, with a little as 198 predicted for Carica papaya to as many as 1350 predicted for Arabidopsis lyrata. This number differs substantially even among closely related species, with evidence for extensive gains/losses. Despite this extraordinary inter-species variation, one subset of FBX genes was conserved among most species examined. Together with evidence of strong purifying selection and expression, the ligases synthesized from these conserved loci likely direct essential ubiquitylation events. Another subset was much more lineage specific, showed more relaxed purifying selection, and was enriched in loci with little or no evidence of expression, suggesting that they either control more limited, species-specific processes or arose from genomic drift and thus may provide reservoirs for evolutionary innovation. Numerous FBX loci were also predicted to be pseudogenes with their numbers tightly correlated with the total number of FBX genes in each species. Taken together, it appears that the FBX superfamily has independently undergone substantial birth/death in many plant lineages, with its size and rapid evolution potentially reflecting a central role for ubiquitylation in driving plant fitness

Doing Machismo: Legitimating speech acts as a selection discourse

This article explores the relationship between machismo and implicit power processes at a conceptual and empirical level. Implicit power processes are the taken-for-granted ways in which organizational members reproduce sexual divisions in their organizations. The empirical data are derived from the Argentine auto components industry. This is a male-dominated industry and machismo was used to explain and justify selection decisions that favoured men. Machismo is intrinsically linked to masculinity and power and should be defined as a set of hegemonic masculinities. Machismo represents four images of the dominant ideal of manhood in the Argentine society. These images are the authoritarian image, the breadwinner image, the virility image and the chivalry image. Machismo can then be studied as a discourse on masculinity that, when translated into particular selection discourses, implicitly leads to the exclusion of women from this industry. Machismo and implicit power processes are thus intertwined; both sexes routinely reproduce the male standard. In order to show how discourses on masculinity implicitly shape selection processes, this article presents a typology. The typology consists of four types, the power of natural differences, the power of denial, pastoral or caring power, and the power of the male standard. The typology serves as an analytical tool to reveal the intertwining of machismo and implicit power processes at the shop floors of Argentine auto components firms. © Blackwell Publishing Ltd 2005