Optimal Aero-Elastic Design of a Rotor with Bend-Twist Coupling

Passive Bend-Twist Coupling (BTC) can be used in blades to alleviate loads and generate more Annual Energy Production (AEP). However, BTC is inherently aero-elastic, thus difficult to incorporate into the design with sequential design process. Multi-disciplinary Design Optimization (MDO) is an attractive approach for overcoming these challenges. This paper presents the re-design of a 100kW BTC rotor using the MDO rotor design package HAWTOpt2. In the preliminary design phase, MDO was used to assess the differences between elastic BTC (i.e. off-axis fibers) and geometric BTC (i.e. sweep). This work found that aero-elastic design optimization without BTC was able to achieve a 16% improvement, then with sweep a 18% improvement and with material coupling a 17% improvement. Due to the reduced stiffness of off-axis fibers, material coupled designs had more difficulty satisfying the tip deflection constraint. The geometric BTC concept was chosen for the final design. The design optimization was repeated with additional manufacturing constraints. The final design achieved a 12% improvement

Studying functions on coral reefs : past perspectives, current conundrums, and future potential

This work was funded by the Australian Research Council (DRB; grant number FL190100062).Function-based studies have opened a new chapter in our understanding of coral reefs. Unfortunately, we are opening this chapter as the world’s reefs rapidly transform. In this context, one of the most important roles of function-based studies is to inform coral reef conservation. At this critical juncture, we have a chance to reflect on where we have come from, and where we are going, in coral reef functional ecology, with specific consideration of what this means for our approaches to conserving reefs. As focal examples, we examine the role of corals on reefs, and the practice of culling crown-of-thorns starfish, from a functional perspective. We also consider how the papers in this special issue build on our current understanding. Ultimately, we highlight how robust scientific investigation, based on an understanding of ecosystem functions, will be key in helping us navigate reefs through the current coral reef crisis.Peer reviewe

Extremely Metal-Poor Stars: The Local High Redshift Universe

Extremely metal-poor (EMP) stars can only have formed early in the history of the Galaxy, and represent the local equivalent of the high redshift universe. With them, we can study the early supernovae, the early chemical evolution of the Galaxy, and the history of star formation in the Milky Way. By analogy we can learn about those epochs of galaxy formation in the distant past that are currently at such high redshifts that they are beyond the reach of even the largest existing telescopes, a technique some call “near-field cosmology”. While H, He, and some Li came out of the Big Bang, all other elements were formed in stars, and were dispersed by supernovae and stellar winds into the gas from which subsequent stellar generations formed. The ejecta from supernovae played the most important role in the early Universe. SN models have many parameters, including the history of the progenitor star (initial mass, mass loss history, internal nucleosynthesis history prior to the explosion, etc), the details of the explosion (energy, ejected mass, mixing) etc. There are vigorous groups pursuing the details of these models both theoretically and computationally in the US and abroad. But there are so many free or poorly known parameters that these efforts are best guided by observations of metal-poor stars

MIR137 is an androgen regulated repressor of an extended network of transcriptional coregulators

Androgens and the androgen receptor (AR) play crucial roles in male development and the pathogenesis and progression of prostate cancer (PCa). The AR functions as a ligand dependent transcription factor which recruits multiple enzymatically distinct epigenetic coregulators to facilitate transcriptional regulation in response to androgens. Over-expression of AR coregulators is implicated in cancer. We have shown that over-expression of KDM1A, an AR coregulator, contributes to PCa recurrence by promoting VEGFA expression. However the mechanism(s) whereby AR coregulators are increased in PCa remain poorly understood. In this study we show that the microRNA hsa-miR-137 (miR137) tumor suppressor regulates expression of an extended network of transcriptional coregulators including KDM1A/LSD1/AOF1, KDM2A/JHDM1A/FBXL11, KDM4A/JMJD2A, KDM5B JARID1B/PLU1, KDM7A/JHDM1D/PHF8, MED1/TRAP220/DRIP205 and NCoA2/SRC2/TIF2. We show that expression of miR137 is increased by androgen in LnCaP androgen PCa responsive cells and that the miR137 locus is epigenetically silenced in androgen LnCaP:C4-2 and PC3 independent PCa cells. In addition, we found that restoration of miR137 expression down-regulates expression of VEGFA, an AR target gene, which suggests a role of miR137 loss also in cancer angiogenesis. Finally we show functional inhibition of mIR137 function enhanced androgen induction of PSA/KLK3 expression. Our data indicate that miR137 functions as an androgen regulated suppressor of androgen signaling by modulating expression of an extended network of transcriptional coregulators. Therefore, we propose that epigenetic silencing of miR137 is an important event in promoting androgen signaling during prostate carcinogenesis and progression

Spectroscopic Observations of Convective Patterns in the Atmospheres of Metal-Poor Stars

Convective line asymmetries in the optical spectrum of two metal-poor stars, Gmb1830 and HD140283, are compared to those observed for solar metallicity stars. The line bisectors of the most metal-poor star, the subgiant HD140283, show a significantly larger velocity span that the expectations for a solar-metallicity star of the same spectral type and luminosity class. The enhanced line asymmetries are interpreted as the signature of the lower metal content, and therefore opacity, in the convective photospheric patterns. These findings point out the importance of three-dimensional convective velocity fields in the interpretation of the observed line asymmetries in metal-poor stars, and in particular, urge for caution when deriving isotopic ratios from observed line shapes and shifts using one-dimensional model atmospheres. The mean line bisector of the photospheric atomic lines is compared with those measured for the strong Mg I b1 and b2 features. The upper part of the bisectors are similar, and assuming they overlap, the bottom end of the stronger lines, which are formed higher in the atmosphere, goes much further to the red. This is in agreement with the expected decreasing of the convective blue-shifts in upper atmospheric layers, and compatible with the high velocity redshifts observed in the chromosphere, transition region, and corona of late-type stars.Comment: 27 pages, LaTeX; 10 Figures (14 PostScript files); to be published in The Astrophysical Journa

The Isotopic Mixture of Barium in the Metal-poor Subgiant HD 140283

Analyses of the abundances of neutron-capture elements have led to the belief that these elements in metal-poor stars are r-process products with relative abundances closely resembling those found in the solar system. This picture was challenged by Magain (1995), who found that a pure r-process mix of the barium isotopes was inconsistent with the mix of odd to even barium isotopes derived from analysis of the Ba II line at 4554 A in the spectrum of the metal-poor subgiant HD 140283. In this paper, we address Magain's challenge using new high resolution high signal-to-noise spectra of HD 140283, and find, in contrast to his result, that a solar-like r-process isotopic mixture provides a fair fit to the observed 4554 A profile.Comment: 11 pages, 6 figures; uses mn.sty, included; accepted for publication in MNRA

Renal neuroendocrine control of desiccation and cold tolerance by Drosophila suzukii

Background: Neuropeptides are central to the regulation of physiological, and behavioural processes in insects, directly impacting cold and desiccation survival. However, little is known about the control mechanisms governing these responses in D. suzukii. The close phylogenetic relationship of D. suzukii with D. melanogaster allows, through genomic and functional studies, an insight into the mechanisms directing stress tolerance in D. suzukii. Results: Capa, Leucokinin, DH44 and DH31 neuropeptides demonstrate a high level of conservation between D. suzukii and D. melanogaster with respect to peptide sequences, neuronal expression, receptor localisation, and diuretic function in the Malpighian tubules. Despite D. suzukii’s ability to populate cold environments, they proved sensitive to both cold and desiccation. Furthermore, in D. suzukii, Capa acts as a desiccation-and cold stress-responsive gene, while DH44 gene expression is increased only after desiccation exposure, and the LK gene after nonlethal cold stress recovery. Conclusion: This study provides a comparative investigation into stress tolerance mediation by neuroendocrine signalling in two Drosophila species, providing evidence that similar signalling pathways control fluid secretion in the Malpighian tubules. Identifying processes governing specific environmental stresses affecting D. suzukii could lead to the development of targeted integrated management strategies to control insect pest populations

High Resolution Optical Spectroscopy of the F Supergiant Proto-Planetary Nebula V887 Her=IRAS 18095+2704

An abundance analysis is presented for IRAS 18095+2704 (V887 Her), a post-AGB star and proto-planetary nebula. The analysis is based on high-resolution optical spectra from the McDonald Observatory and the Special Astrophysical Observatory. Standard analysis using a classical Kurucz model atmosphere and the line analysis program MOOG provides the atmospheric parameters: Teff = 6500 K, log g = +0.5, and a microturbulent velocity Vt = 4.7 km/s and [Fe/H] = -0.9. Extraction of these parameters is based on excitation of FeI lines, ionization equilibrium between neutral and ions of Mg, Ca, Ti, Cr, and Fe, and the wings of hydrogen Paschen lines. Elemental abundances are obtained for 22 elements and upper limits for an additional four elements. These results show that the star's atmosphere has not experienced a significant number of C- and s-process enriching thermal pulses. Abundance anomalies as judged relative to the compositions of unevolved and less-evolved normal stars of a similar metallicity include Al, Y, and Zr deficiencies with respect to Fe of about 0.5 dex. Judged by composition, the star resembles a RV Tauri variable that has been mildly affected by dust-gas separation reducing the abundances of the elements of highest condensation temperature. This separation may occur in the stellar wind. There are indications that the standard 1D LTE analysis is not entirely appropriate for IRAS 18095+2704. These include a supersonic macroturbulent velocity of 23 km/s, emission in H-alpha and the failure of predicted profiles to fit observed profiles of H-beta and H-gamma.Comment: Accepted for publication in MNRA

Manganese Abundances in the Globular Cluster Omega Centauri

We present manganese abundances in 10 red-giant members of the globular cluster Omega Centauri; 8 stars are from the most metal-poor population (RGB MP and RGB MInt1) while two targets are members of the more metal rich groups (RGB MInt2 and MInt3). This is the first time Mn abundances have been studied in this peculiar stellar system. The LTE values of [Mn/Fe] in Omega Cen overlap those of Milky Way stars in the metal poor Omega Cen populations ([Fe/H] ~ -1.5 to -1.8), however unlike what is observed in Milky Way halo and disk stars, [Mn/Fe] declines in the two more metal-rich RGB MInt2 and MInt3 targets. Non-LTE calculations were carried out in order to derive corrections to the LTE Mn abundances. The non-LTE results for Omega Cen in comparison with the non-LTE [Mn/Fe] versus [Fe/H] trend obtained for the Milky Way confirm and strengthen the conclusion that the manganese behavior in Omega Cen is distinct. These results suggest that low-metallicity supernovae (with metallicities < -2) of either Type II or Type Ia dominated the enrichment of the more metal-rich stars in Omega Cen. The dominance of low-metallicity stars in the chemical evolution of Omega Cen has been noted previously in the s-process elements where enrichment from metal-poor AGB stars is indicated. In addition, copper, which also has metallicity dependent yields, exhibits lower values of [Cu/Fe] in the RGB MInt2 and MInt3 Omega Cen populations.Comment: Accepted for publication in the Ap