The influence of unsteady streaks on the stability of flat plate boundary layers

The natural mechanism for transition to turbulence in flat-plate boundary layers is the growth and breakdown of Tollmien-Schlichting (TS) waves. In the presence of significant free-stream turbulence (FST) however, streamwise velocity perturbations, known as Klebanoff modes or streaks, amplify inside the boundary layer. These distortions alter the stability characteristics of the boundary layer, and the natural mechanism is bypassed, leading to earlier transition. Herein, a model is employed to describe the Klebanoff distortions: one Fourier component of the FST is used along with its signature inside the shear region to force the boundary layer and stimulate streaks. Varying the parameters of the forcing mode causes streaks with different frequencies and amplitudes. A base flow which is periodic in two dimensions is formed, and its linear stability is investigated using Floquet theory. Two modes emerge as the most unstable, and their eigenvalues are tracked whilst varying streak frequency and amplitude. The ‘inner’ mode, is related to the TS wave, but its growth rate is enhanced by unsteady streaks. The ‘outer’ mode is a high-frequency instability of the streaks at the edge of the boundary layer. It has no counterpart in the undisturbed boundary-layer. The critical streak amplitude for the outer mode is calculated for different streak frequencies and it agrees more closely with experiments than previous analyses which assumed the streaks to be steady. The current analysis indicates that increasing the frequency of the streaks can enhance their instability. In fact an optimum frequency exists for free-stream disturbances to penetrate the shear and stimulate unstable streaks. Direct numerical simulations with streaks and secondary-instability eigenmodes are conducted. The simulations show that both the inner and outer mode can grow to nonlinear amplitudes and cause boundary-layer transition to turbulence

Les médianes classificatoires en innu : analyse morphosyntaxique et sémantique

La présente étude porte sur une hiérarchisation des arguments de verbes innus qui détermine quels arguments sont marqués dans les flexions du verbe et quel argument est incorporé en position médiane. Le corpus est constitué de 1 275 verbes innus comportant chacun au moins une parmi cinq médianes dites « classificatoires ». Faisant suite aux travaux de Drapeau (2008) qui traite de verbes comportant des médianes génériques (non-classificatoires), chaque argument sémantique se voit attribué un rôle sémantique (thématique) selon la position qu'il occupe dans la décomposition lexicale du verbe. L'objectif de l'étude est de vérifier les conclusions de Drapeau (2008), soit que, d'une part, la hiérarchisation des arguments résulte d'une interaction entre la hiérarchie des rôles sémantiques, la \ud « animacy hierarchy », et la « possessor constraint» et que, d'autre part, l'argument auquel renvoie la médiane est toujours le plus bas dans l'hiérarchie des arguments. Les résultats démontrent que la hiérarchisation proposée par Drapeau explique les données avec les médianes classificatoires. Ainsi, ils démontrent un parallélisme entre les deux types de médianes. Toutefois, ils mettent en valeur une faiblesse dans le système d'attribution de rôles sémantiques utilisé en relevant la nécessité de mieux définir le rôle de thème et celui d'instrument. Finalement, l'analyse des verbes comportant des médianes doubles remet en question la définition que donne Goddard (1990) des processus de dérivation primaire et secondaire dans les langues algonquiennes. ______________________________________________________________________________ MOTS-CLÉS DE L’AUTEUR : Innu, Médiane, Classificateur, Incorporation, Hiérarchie, Rôle sémantique

Did She Mention My Name?: Citation of Academic Authority by the Supreme Court of Canada, 1985-1990

Readers of court judgments will have observed that in the course of expressing reasons for the decisions they reach, judges commonly refer to books and articles written by academics. This is not surprising. Many scholarly publications contain information, arguments and opinions pertinent to the choices that judges must make, and lawyers commonly refer to such works in the written and oral arguments they present to courts. We would therefore expect the judges who must assess and respond to such arguments to make mention of that scholarly material. Moreover a certain portion of academic writing-in particular, a preponderance of law review articles-is written as more or less direct exhortation tojudges about how to decide cases expected to come before them.1 Possibly this is no more than a rhetorical stance, for it may be that law professors are really writing to other law professors (or to no one), and that the practice of pretending to talk to appellate courts is simply a stylistic device which they ritualistically, perhaps unthinkingly, adopt. But presumably some portion of the writing that legal scholars ostensibly direct at judges is actually intended to be read by them and to influence the decisions they make. In any event, given the amount of writing couched as advice to judges, the amount of writing on legal matters generally, and lawyers\u27 practice of citing such material in argument, it comes as no shock to see that judges make reference to academic publications in their judgments

Water quality improvements offset the climatic debt for stream macroinvertebrates over twenty years

Many species are accumulating climatic debt as they fail to keep pace with increasing global temperatures. In theory, concomitant decreases in other stressors (e.g. pollution, fragmentation) could offset some warming effects, paying climatic debt with accrued environmental credit. This process may be occurring in many western European rivers. We fit a Markov chain model to ~20,000 macroinvertebrate samples from England and Wales, and demonstrate that despite large temperature increases 1991–2011, macroinvertebrate communities remained close to their predicted equilibrium with environmental conditions. Using a novel analysis of multiple stressors, an accumulated climatic debt of 0.64 (±0.13 standard error) °C of warming was paid by a water-quality credit equivalent to 0.89 (±0.04)°C of cooling. Although there is finite scope for mitigating additional climate warming in this way, water quality improvements appear to have offset recent temperature increases, and the concept of environmental credit may be a useful tool for communicating climate offsetting

Nutritional and Phytochemical Content of High-Protein Crops

The authors acknowledge support from the Scottish Government’s Rural and Environment Science and Analytical Services Division (RESAS) via their strategic research and partnership programs.Peer reviewedPostprin

Effects of wheat and oat-based whole grain foods on serum lipoprotein size and distribution in overweight middle aged people : a randomised controlled trial

Peer reviewedPublisher PD

Evaluating Network Performance of Containerized Test Framework for Distributed Space Systems

Distributed space systems are a mission architecture consisting of multiple spacecraft as a cohesive system which provide multipoint sampling, increased mission coverage, or improved sample resolution, while reducing mission risk through redundancy. To fully realize the potential of these systems, eventually scaling to hundreds or thousands of spacecraft, distributed space systems need to be operated as a single entity, which will enable a variety of novel scientific space missions. The Distributed Spacecraft Autonomy (DSA) project is a software project which aims to mature the technology needed for those systems, namely autonomous decision-making and swarm networking. The DSA project leverages a containerized swarm test framework to simulate spacecraft software, which can identify emergent behavior early in development. Container virtualization allows distributed spacecraft systems to be simulated entirely in software on a single computer, avoiding the overhead associated with conventional approaches like hardware facsimiles and virtual machines. For this approach to be effective, the simulated system behavior must not be artificially influenced by the swarm test framework itself. To address this, we present a series of benchmarks to quantify virtual network bandwidth available on a single-host computer and contextualize this against the network and application behavior of the DSA swarm test framework

Auxin and tryptophan homeostasis are facilitated by the ISS1/VAS1 aromatic aminotransferase in arabidopsis

Indole-3-acetic acid (IAA) plays a critical role in regulating numerous aspects of plant growth and development. While there is much genetic support for tryptophan-dependent (Trp-D) IAA synthesis pathways, there is little genetic evidence for tryptophan-independent (Trp-I) IAA synthesis pathways. Using Arabidopsis, we identified two mutant alleles of ISS1 ( I: ndole S: evere S: ensitive) that display indole-dependent IAA overproduction phenotypes including leaf epinasty and adventitious rooting. Stable isotope labeling showed that iss1, but not WT, uses primarily Trp-I IAA synthesis when grown on indole-supplemented medium. In contrast, both iss1 and WT use primarily Trp-D IAA synthesis when grown on unsupplemented medium. iss1 seedlings produce 8-fold higher levels of IAA when grown on indole and surprisingly have a 174-fold increase in Trp. These findings indicate that the iss1 mutant's increase in Trp-I IAA synthesis is due to a loss of Trp catabolism. ISS1 was identified as At1g80360, a predicted aromatic aminotransferase, and in vitro and in vivo analysis confirmed this activity. At1g80360 was previously shown to primarily carry out the conversion of indole-3-pyruvic acid to Trp as an IAA homeostatic mechanism in young seedlings. Our results suggest that in addition to this activity, in more mature plants ISS1 has a role in Trp catabolism and possibly in the metabolism of other aromatic amino acids. We postulate that this loss of Trp catabolism impacts the use of Trp-D and/or Trp-I IAA synthesis pathways.T32 AR059033 - NIAMS NIH HH

Turnover in floral composition explains species diversity and temporal stability in the nectar supply of urban residential gardens

Residential gardens are a valuable habitat for insect pollinators worldwide, but differences in individual gardening practices substantially affect their floral composition. It is important to understand how the floral resource supply of gardens varies in both space and time so we can develop evidence‐based management recommendations to support pollinator conservation in towns and cities. We surveyed 59 residential gardens in the city of Bristol, UK, at monthly intervals from March to October. For each of 472 garden surveys, we combined floral abundances with nectar sugar data to quantify the nectar production of each garden, investigating the magnitude, temporal stability, and diversity and composition of garden nectar supplies. We found that individual gardens differ markedly in the quantity of nectar sugar they supply (from 2 to 1,662 g), and nectar production is higher in more affluent neighbourhoods, but not in larger gardens. Nectar supply peaks in July (mid‐summer), when more plant taxa are in flower, but temporal patterns vary among individual gardens. At larger spatial scales, temporal variability averages out through the portfolio effect, meaning insect pollinators foraging across many gardens in urban landscapes have access to a relatively stable and continuous supply of nectar through the year. Turnover in species composition among gardens leads to an extremely high overall plant richness, with 636 taxa recorded flowering. The nectar supply is dominated by non‐natives, which provide 91% of all nectar sugar, while shrubs are the main plant life form contributing to nectar production (58%). Two‐thirds of nectar sugar is only available to relatively specialised pollinators, leaving just one‐third that is accessible to all. Synthesis and applications. By measuring nectar supply in residential gardens, our study demonstrates that pollinator‐friendly management, affecting garden quality, is more important than the size of a garden, giving every gardener an opportunity to contribute to pollinator conservation in urban areas. For gardeners interested in increasing the value of their land to foraging pollinators, we recommend planting nectar‐rich shrubs with complementary flowering periods and prioritising flowers with an open structure in late summer and autumn

Buckwheat, Fava Bean and Hemp Flours Fortified with Anthocyanins and Other Bioactive Phytochemicals as Sustainable Ingredients for Functional Food Development

Funding: This research was funded by the Scottish government’s Rural and Environment Science and Analytical Services Division (RESAS). Acknowledgments: The authors acknowledge Viv Buchan from the Analytical Department, The Rowett Institute, University of Aberdeen, for her help with the sugar content determinations.Peer reviewedPublisher PD