Rate-dependent hydroelastic response of self-adaptive composite propellers in fully wetted and cavitating flows

The objectives of this work are to investigate the fully wetted and cavitating performance of a self-adaptive composite propeller and its dependence on the propeller rotational frequency (RPM or revolution per minute) in addition to the advance coefficient and ambient pressure. Self-adaptive composite propellers are designed to take advantage of the intrinsic deformation coupling behavior of anisotropic composites to improve propeller performance via automatic, passive blade pitch adjustment in spatially or temporally varying flow. The design methodology, numerical and experimental studies of selfadaptive composite propellers in fully wetted flow can be found in [1-7]. In past studies, the primary focus was the fully wetted performance of the composite propellers operating at the design RPM. However, since the deformations of adaptive composite propellers depend on the hydrodynamic load, which in turn depends on the propeller RPM, the response of adaptive composite propellers depend on both the advance coefficient and RPM. Moreover, at high RPMs, composite propellers may be subject to resonant vibration failure due to the inherent flexibility needed to achieve the desired self-adaptive behavior, and due to the decrease in natural frequency caused by added mass effects. Hence, it is important to evaluate the ratedependent behavior of self-adaptive composite propellers. It is also important to evaluate the cavitating performance of self-adaptive composite propellers since cavitation can lead to thrust breakdown, decrease in efficiency, as well as erosion and localized impact damage to the composite blades. In this work, a previously validated coupled boundary element method finite element method (BEMFEM) is used to analyze the rate-dependent response of self-adaptive composite propellers in fully wetted and cavitating flows. Implications of the rate-dependent behavior on the design and interpretation of experimental studies, particularly cavitation tunnel studies, are discussed.http://deepblue.lib.umich.edu/bitstream/2027.42/84256/1/CAV2009-final60.pd

Yeast peroxisomes multiply by growth and division

Peroxisomes can arise de novo from the endoplasmic reticulum (ER) via a maturation process. Peroxisomes can also multiply by fission. We have investigated how these modes of multiplication contribute to peroxisome numbers in Saccharomyces cerevisiae and the role of the dynamin-related proteins (Drps) in these processes. We have developed pulse-chase and mating assays to follow the fate of existing peroxisomes, de novo–formed peroxisomes, and ER-derived preperoxisomal structures. We find that in wild-type (WT) cells, peroxisomes multiply by fission and do not form de novo. A marker for the maturation pathway, Pex3-GFP, is delivered from the ER to existing peroxisomes. Strikingly, cells lacking peroxisomes as a result of a segregation defect do form peroxisomes de novo. This process is slower than peroxisome multiplication in WT cells and is Drp independent. In contrast, peroxisome fission is Drp dependent. Our results show that peroxisomes multiply by growth and division under our assay conditions. We conclude that the ER to peroxisome pathway functions to supply existing peroxisomes with essential membrane constituents

A dual function for Pex3p in peroxisome formation and inheritance

Saccharomyces cerevisiae Pex3p has been shown to act at the ER during de novo peroxisome formation. However, its steady state is at the peroxisomal membrane, where its role is debated. Here we show that Pex3p has a dual function: one in peroxisome formation and one in peroxisome segregation. We show that the peroxisome retention factor Inp1p interacts physically with Pex3p in vitro and in vivo, and split-GFP analysis shows that the site of interaction is the peroxisomal membrane. Furthermore, we have generated PEX3 alleles that support peroxisome formation but fail to support recruitment of Inp1p to peroxisomes, and as a consequence are affected in peroxisome segregation. We conclude that Pex3p functions as an anchor for Inp1p at the peroxisomal membrane, and that this function is independent of its role at the ER in peroxisome biogenesis

A ground-based experimental test program to duplicate and study the spacecraft glow phenomenon

The use of a plasma device, the Advanced Concepts Torus-I, for producing atoms and molecules to study spacecraft glow mechanisms is discussed. A biased metal plate, located in the plasma edge, is used to accelerate and neutralize plasma ions, thus generating a neutral beam with a flux approx. 5 x 10 to the 14th power/sq cm/sec at the end of a drift tube. Our initial experiments are to produce a 10 eV molecular and atomic nitrogen beam directed onto material targets. Photon emission in the spectral range 2000 to 9000 A from excited species formed on the target surface will be investigated

Characterization of a 5-eV neutral atomic oxygen beam facility

An experimental effort to characterize an existing 5-eV neutral atomic oxygen beam facility being developed at Princeton Plasma Physics Laboratory is described. This characterization effort includes atomic oxygen flux and flux distribution measurements using a catalytic probe, energy determination using a commercially designed quadrupole mass spectrometer (QMS), and the exposure of oxygen-sensitive materials in this beam facility. Also, comparisons were drawn between the reaction efficiencies of materials exposed in plasma ashers, and the reaction efficiencies previously estimated from space flight experiments. The results of this study show that the beam facility is capable of producing a directional beam of neutral atomic oxygen atoms with the needed flux and energy to simulate low Earth orbit (LEO) conditions for real time accelerated testing. The flux distribution in this facility is uniform to +/- 6 percent of the peak flux over a beam diameter of 6 cm

Survey of research approaches utilised in the scholarship of teaching and learning publications

The Scholarship of Teaching and Learning (SoTL) has been described as the fastest growing academic development movement in higher education. As this field of inquiry matures, there is a need to understand how SoTL research is conducted. The purpose of our study was to inform this debate by investigating research approaches used in SoTL publications. We analysed 223 empirical research studies published from 2012 to 2014 in three explicitly focused SoTL journals. We classified the studies as either qualitative, quantitative, or mixed methods using an analytical framework devised from existing literature on research methods. We found that the use of the three research designs was fairly evenly distributed across the papers examined: qualitative (37.2%), quantitative (29.6%), and mixed methods (33.2%). However, there was an over-reliance on data collection from a single source in 83.9% of papers analysed, and this source was primarily students. There was some, but limited, evidence of the use of triangulation through the use of multiple data collection instruments (e.g. survey, assessment tasks, grade databases). Similarly, only one-third of publications classified as mixed methods integrated the analysis and interpretation of the qualitative and quantitative data equally within the study. We conclude that current SoTL research is characterised by methodological pluralism but could be advanced through inclusion of more diverse approaches, such as close reading, and adoption of strategies known to enhance the quality of research, for example, triangulation and visual representation

Phosphatidylinositol-(4,5)-bisphosphate regulates sorting signal recognition by the clathrin-associated adaptor complex AP2

The alpha,beta2,mu2,sigma2 heterotetrameric AP2 complex is recruited exclusively to the phosphatidylinositol-4,5-bisphosphate (PtdIns4,5P(2))-rich plasma membrane where, amongst other roles, it selects motif-containing cargo proteins for incorporation into clathrin-coated vesicles. Unphosphorylated and mu2Thr156-monophosphorylated AP2 mutated in their alphaPtdIns4,5P(2), mu2PtdIns4,5P(2), and mu2Yxxvarphi binding sites were produced, and their interactions with membranes of different phospholipid and cargo composition were measured by surface plasmon resonance. We demonstrate that recognition of Yxxvarphi and acidic dileucine motifs is dependent on corecognition with PtdIns4,5P(2), explaining the selective recruitment of AP2 to the plasma membrane. The interaction of AP2 with PtdIns4,5P(2)/Yxxvarphi-containing membranes is two step: initial recruitment via the alphaPtdIns4,5P(2) site and then stabilization through the binding of mu2Yxxvarphi and mu2PtdIns4,5P(2) sites to their ligands. The second step is facilitated by a conformational change favored by mu2Thr156 phosphorylation. The binding of AP2 to acidic-dileucine motifs occurs at a different site from Yxxvarphi binding and is not enhanced by mu2Thr156 phosphorylation

Safety issues in fabricating mixed oxide fuel using surplus weapons plutonium

This paper presents an assessment of the safety issues and implications of fabricating mixed oxide (MOX) fuel using surplus weapons plutonium. The basis for this assessment is the research done at Los Alamos National Laboratory (LANL) in identifying and resolving the technical issues surrounding the production of PuO{sub 2} feed, removal of gallium from the PuO{sub 2} feed, the fabrication of test fuel, and the work done at the LANL plutonium processing facility. The use of plutonium in MOX fuel has been successfully demonstrated in Europe, where the experience has been almost exclusively with plutonium separated from commercial spent nuclear fuel. This experience in safely operating MOX fuel fabrication facilities directly applies to the fabrication and irradiation of MOX fuel made from surplus weapons plutonium. Consequently, this paper focuses on the technical difference between plutonium from surplus weapons, and light-water reactor recycled plutonium. Preliminary assessments and research lead to the conclusion that no new process or product safety concerns will arise from using surplus weapons plutonium in MOX fuel