PIV-LIF determination of mean velocity field and Reynolds stress tensor in a cavitating mixing layer

The purpose of this experimental study was to analyze a 2D cavitating shear layer. The global aim of this work was a better understanding and modeling of cavitation phenomena from a 2D turbulent shear flow to rocket engine turbopomp inducers. This 2D mixing layer flow provided us a well documented test case to be used for comparison between the behavior with and without cavitation. Similarities and differences led to characterize effects of the cavitation on the flow dynamic. The run fluid was liquid water. The experimental facility allowed us to set two distinct configurations with different cavitation levels: - CDM: a mixing layer flow (U1 = 15.8 m/s for the high speed side and U2= 3.5 m/s for the low speed side) - MD: a downward facing step flow (U1 = 13.5 m/s and U2 = 0 m/s). The development of Kelvin-Helmholtz instabilities was observed at the interface. Vaporizations and implosions of cavitating structures inside the vortices were also observed. PIV-LIF(Particle Image Velocimetry Laser Induced Fluorescence) system was used to measure the velocity of the liquid phase. Instantaneous velocity fields were measured in the whole flow. The self similarity of the flow was characterized by the dimensionless analysis of the mean and fluctuating velocity fields. Parameters that characterized the flow dynamic were studied and quantified: Vorticity thickness, growth rate and Reynolds tensor components. Turbulent kinetic energy and the anisotropy tensor components were also analyzed and estimated. General behaviors of the two configurations have been observed: - In the CDM case the mixing area developed along the x-axis a turbulent shear area, growing linearly, showing a constant growth rate over the studied cavitation parameter range. - The MD case was more complex, presenting a flow separation with a large recirculating area and a quite large positive pressure gradient. The reattachment point moved depending on the cavitation level. The recirculating area seemed to have an unsteady behavior and was certainly pulsing and shedding vortices downstream. Successive vaporizations and condensations of the fluid particles inside the turbulent area have generated additional velocity fluctuations due to the strong density changes associated with the vaporization and condensation processes. However, the mean spatial development of the mixing area was only barely affected over the studied cavitation number range. The main results of this study clearly showed that the turbulence-cavitation relationship inside a mixing layer is not only driven by a simple change of compressibility properties of the fluid in the turbulent field due to the presence of a twophase flow.http://deepblue.lib.umich.edu/bitstream/2027.42/84239/1/CAV2009-final38.pd

Glittering in the dark: Memory, culture, and critique in light of the history of information

An ethical and human-centered approach to Information Science requires rigorous, historically-informed analysis of both the resources that inform this discipline and the cultural role it inhabits. This session will present and discuss significant recent developments in the history and foundations of the field. ASIST has formally established a new volunteer administrative position of ASIST Curator. Kathryn La Barre, the newly-appointed Curator, will describe the role and responsibilities of this position and assess the state of Information Science history in relation to the conference themes. In two complementary reports: Michael Buckland will examine theoretical accounts of the materials made use of in Information Science; and Sachi Arafat will explain why Information Retrieval and Information Science should be integrated and rethought as a science of technology-mediated experience, and how this new kind of science relates to the pre-modern memory arts tradition

Structuration de la diversité génétique chez la luzerne cultivée, conséquence pour l'identification de gènes liés à des caractères agronomiques

La luzerne, espèce allogame et autotétraploïde, est une légumineuse fourragère dont l’intérêt connaît un renouveau certain grâce à ses atouts pour le développement durable de l’agriculture. L’amélioration des variétés nécessite de mieux connaître les ressources génétiques, pour les exploiter, que ce soit en sélection classique ou en utilisant les outils moléculaires pour implémenter la sélection assistée par marqueurs. En étudiant 10 variétés européennes, nous avons montré que la diversité à l’intérieur des variétés est grande (hétérozygotie attendue de 0.75, déviation standard de 0.80, pour des caractères phénotypiques et des marqueurs moléculaires neutres, respectivement). La différenciation entre variétés est notable pour les caractères phénotypiques. Cette structuration de la diversité est favorable à l’utilisation de la génétique d’association basée sur des gènes candidats pour identifier des gènes liés à des caractères agronomiques. Une telle étude a permis de montrer que le gène Constans-like contribue à expliquer les différences de longueur de tiges chez la luzerne, une composante du rendement fourrager. Alfalfa, an allogamous and autotetraploid species, is a forage legume for which a renewed interest has raised because of its advantages for a sustainable agriculture. Variety improvement requires a better knowledge of the genetic resources in order to exploit them, with classical breeding methods or with molecular tools to implement marker assisted selection. We have described 10 European varieties and found a large within-variety diversity (expected heterozygozity of 0.75, standard deviation of 0.80, with phenotypic traits and neutral molecular markers, respectively). Differentiation between varieties was noticeable for phenotypic traits. This genetic structure of diversity is favourable to the use of association genetics based on candidate genes to identify genes related to agronomic traits. Such a study showed that Constans-like gene contributes to explain differences in alfalfa stem length, a component of forage yield

Rapid Development of Medical Imaging Tools with Open-Source Libraries

Rapid prototyping is an important element in researching new imaging analysis techniques and developing custom medical applications. In the last ten years, the open source community and the number of open source libraries and freely available frameworks for biomedical research have grown significantly. What they offer are now considered standards in medical image analysis, computer-aided diagnosis, and medical visualization. A cursory review of the peer-reviewed literature in imaging informatics (indeed, in almost any information technology-dependent scientific discipline) indicates the current reliance on open source libraries to accelerate development and validation of processes and techniques. In this survey paper, we review and compare a few of the most successful open source libraries and frameworks for medical application development. Our dual intentions are to provide evidence that these approaches already constitute a vital and essential part of medical image analysis, diagnosis, and visualization and to motivate the reader to use open source libraries and software for rapid prototyping of medical applications and tools

Synthesis by the polyol process and ionic conductivity of nanostructured La2Mo2O9 powders

International audienceLa2Mo2O9 nanostructured powders were synthesized by the polyol process. The effects of the nature of the polyol, the refluxing time, the hydrolysis ratio, the metal concentration and the addition of hydroxide ions, on the purity and morphology of the powders are determined. Two main morphologies are observed, the particles being in the shape of platelets or spheres, with respectively diethylene glycol or ethylene glycol as solvent. A specific surface area of 24 m2/g was reached by varying the metal concentration. The conductivity measurements were recorded on pellets that present in some cases a closed porosity, the relative density reaching 95% without any milling step. According to the synthesis parameters, the grain conductivity can be slightly increased, the total conductivity remaining only slightly lower than that of pellets made of powders synthesized by solid state reaction

Genetic Diversity Among Alfalfa Cultivars Using SSR Markers

Alfalfa (Medicago sativa) is an autotetraploid, allogamous and heterozygous species. Cultivated varieties are synthetic cultivars, usually obtained through 3 or 4 generations of panmictic reproduction of a set of various numbers of parents. The parents can be clones, half-sib or full-sib families. The breeders apply selection pressure for some agronomic traits, to induce changes in the genetic background. The objective of this study was to investigate the differentiation level among seven cultivars originating from one breeding program, and between these cultivars and the breeding pool, with eight SSR markers

Conserved presence of G-quadruplex forming sequences in the Long Terminal Repeat Promoter of Lentiviruses

G-quadruplexes (G4s) are secondary structures of nucleic acids that epigenetically regulate cellular processes. In the human immunodeficiency lentivirus 1 (HIV-1), dynamic G4s are located in the unique viral LTR promoter. Folding of HIV-1 LTR G4s inhibits viral transcription; stabilization by G4 ligands intensifies this effect. Cellular proteins modulate viral transcription by inducing/unfolding LTR G4s. We here expanded our investigation on the presence of LTR G4s to all lentiviruses. G4s in the 5'-LTR U3 region were completely conserved in primate lentiviruses. A G4 was also present in a cattle-infecting lentivirus. All other non-primate lentiviruses displayed hints of less stable G4s. In primate lentiviruses, the possibility to fold into G4s was highly conserved among strains. LTR G4 sequences were very similar among phylogenetically related primate viruses, while they increasingly differed in viruses that diverged early from a common ancestor. A strong correlation between primate lentivirus LTR G4s and Sp1/NF\u3baB binding sites was found. All LTR G4s folded: their complexity was assessed by polymerase stop assay. Our data support a role of the lentiviruses 5'-LTR G4 region as control centre of viral transcription, where folding/unfolding of G4s and multiple recruitment of factors based on both sequence and structure may take place