464 research outputs found
δ Orionis: Further temporal variability and evidence for small-scale structure in the interstellar medium
No full textWe report here the detection of both spatial and temporal variations in interstellar absorption in the line of sight to δ Orionis. First, we present new high-resolution (R≈110 000) observations of the interstellar D lines of Na i towards both δ Ori A and C. Comparison of these spectra highlights variations in absorption between the two stars, indicative of small-scale spatial structure in the interstellar medium in this direction over distances of less than ≈15 000 au (the projected separation of the two stars). Components with the largest Na i column densities and lowest velocity dispersions are, in general, found to be subject to the greatest differences; in fact the narrowest component detected is only observed in one of the sightlines. This effect has also been reported by Meyer & Blades. Secondly, we present new ultra-high-resolution (R≈900 000) Na i D1 observations and high-resolution (R≈110 000) Ca ii H & K observations of δ Ori A which, through ultra-high-resolution work conducted between 1994 and 2000, has been shown to exhibit a time-variable interstellar Na i absorption component. These new observations, while revealing the further reduction in intensity of the time-variable Na i absorption, indicate constant Ca ii absorption over the same period. This results in a dramatic reduction in the Na°/Ca+ abundance ratio, perhaps indicating the line of sight to be gradually probing a less-dense outer region of an absorbing filament
Ten eclipsing binaries in the Small Magellanic Cloud: fundamental parameters and Cloud distance
No full textWe present the first results of an observational programme to measure the fundamental parameters of over 100 eclipsing binaries in the Small Magellanic Cloud (SMC). The spectroscopic data have been obtained by using the two degree field (2dF) multi-object spectrograph on the 3.9-m Anglo-Australian Telescope, and have been used in conjunction with photometry from the Optical Gravitational Lensing Experiment (OGLE) data base of SMC eclipsing binaries. In this first paper, we discuss 10 systems: three are detached early-B binaries, six are in a semi-detached configuration, and one is in a marginal contact state. We conclude that the semi-detached systems are undergoing the slow mass-transfer phase of case-A binary evolution, in which the mass donor has reached its Roche lobe while still on the main sequence. Each system provides a primary distance indicator. By constructing a new calibration between spectral type and temperature for O and early B stars, we find a mean distance modulus to the SMC of 18.89 ′ 0.04 (statistical) ′0.10 (systematic). This value represents one of the most precise determinations to date of the distance to the SMC
κ Velorum: Another variable interstellar sightline?
No full textWe present ultra-high-resolution (R = 900 000) observations of interstellar Na i and K i absorption lines towards κ Vel (HD 81188) which show clear evidence for temporal variation between 1994 and 2000. Specifically, the column densities of K0 and Na0 in the main velocity component have increased by 40 and 16 per cent, respectively, over this period. Earlier work had suggested that this component actually consists of two unresolved sub-components; this result is confirmed here, and the overall line profile is found to be consistent with only one of these sub-components having increased in strength since 1994. We argue that this variation is consistent with the line of sight gradually probing a cold, dense interstellar filament of the kind recently proposed by Heiles to explain other observations of small-scale structure in the interstellar medium
DNS of inertial wave attractors in a librating annulus with height-dependent gap width
No full textDirect numerical simulations (DNS) of inertial wave attractors have been carried out in a librating Taylor-Couette system with broken mirror symmetry in the radial-axial cross-section. The inertial wave excitation mechanism and its localisation at the edges was clarified by applying boundary layer theory. Additional resonance peaks in the simulated response spectra were found to agree with low-order wave attractors obtained by geometric ray tracing. Numerics and theory are in qualitative agreement with recent lab experiments
Intradermal immunization with a bovine herpesvirus-1 DNA vaccine induces protective immunity in cattle
No full textAlthough intramuscular (i.m.) injection of DNA encoding glycoprotein D (gD) of bovine herpesvirus-1 (BHV-1) induces immune responses in cattle, this route of delivery is inefficient. Here we assessed three parameters that may enhance the efficacy of a gD DNA vaccine in cattle. First, the immune response generated by i.m. injected plasmid expressing a secreted form of gD (tgD) was determined and found to be very similar in magnitude to the response induced by gD-expressing plasmid. Secondly, gD- and tgD-expressing plasmids were administered by intradermal (i.d.) immunization, which resulted in a superior immune response to the secreted form, but no improvement in the response to the membrane-associated form. However, the form of gD used for immunization did not influence the immunoglobulin subtype, the ratio of antigen-specific IgG1 to IgG2 being approximately 4:1. Finally, the effect of promoter strength was assessed by replacing the Rous sarcoma virus (RSV) promoter, which was used in the original experiments, with the human cytomegalovirus immediate early promoter and first intron A (HCMV/IA). Although upon transfection in vitro the HCMV/IA promoter appeared to be stronger than the RSV promoter, there was only a 2-fold higher antibody response in vivo upon i.d. injection of cattle. Protection against virus challenge was obtained in the calves immunized i.d. with tgD-encoding plasmid, as shown by a significant reduction in weight loss, virus excretion, temperature response and clinical disease. No significant protection was observed in the animals vaccinated i.d. with the gD-expressing plasmid, which correlates with the lower level of immunity pre-challenge.ID: 3643; LR: 20081121; JID: 0077340; 0 (Antibodies, Viral); 0 (Immunoglobulin G); 0 (Vaccines, DNA); 0 (Viral Proteins); 0 (Viral Vaccines); 0 (bovine herpesvirus type-1 glycoproteins); 82115-62-6 (Interferon-gamma); ppublishSource type: Electronic(1
Gas path analysis for the MTT micro turbine
No full textGas turbine diagnostics is as old as the gas turbine itself. Over the years, performance based diagnostics allowed for a shift from time-based maintenance to more economical condition based maintenance playing a fundamental role in enhancing the availability and reliability of gas turbines. By monitoring the condition of the engine over time, maintenance actions can be taken based on information collected from the field. MTT (Micro Turbine Technology) is currently developing a low cost 3kWe micro-turbine CHP (Combined Heat and Power)-system by using off-the-shelf technologies. Once the system will be launched on the market an organized, cost-effective maintenance procedure will be required. The objective of this M. Sc. thesis project was to develop and demonstrate a Gas Path Analysis diagnostic concept for the micro-turbine. Gas Path Analysis (GPA) is a method to assess the condition of the gas turbine by using performance measurements from the gas path. The feasibility of the diagnostic concept was demonstrated by some case studies using data from the first generation field test units. After reviewing a number of gas turbine diagnostic techniques, a non-linear model based gas path analysis approach was chosen. For the development of the diagnostic concept, a non-linear model of a healthy reference engine was used to simulate the off-design behaviour of the engine and derive healthy performance parameter baselines. These baselines are used to compare the performance of field engines against. A component based modelling environment called GSP or the Gas turbine Simulation Program was used to simulate the effect of ambient conditions and deterioration on performance. The diagnostic concept relies on the principle that deterioration causes corrected measurement parameters to shift from the healthy reference baselines. Measurement performance parameters are first corrected to standard ISA conditions before being compared against the healthy baselines. By modelling specific types of deterioration in GSP, signature parameter shifts could be recorded for each of the deterioration modes. These signature parameter shifts are used to compare shifts in performance parameters against and determine the closest pattern-match which can be used to identify the most probable cause of deterioration. The proposed concept is capable of performing engine level diagnostics and partially component level diagnostics. Multiple fault diagnostics and quantifying the level of deterioration are more difficult due to the limited number of sensors and the relatively large impact of second-order effects such as heat-loss, auxiliary power take-off, mechanical losses, etc. The performance parameter baselines together with the derived rulesets can easily be implemented in a maintenance tool making the concept flexible and easy to use.MastersFlight performance and propulsionAerospace Engineerin
Parallel implementation of interior-point methods for semidefinite optimization
No full textElectrical Engineering, Mathematics and Computer Scienc
Ruth Kundrats Identification Card
No full textRuth KundratsImmigration I.D. Card juaranteeing passge aboard the passenger ship the 'Samaria"4.0 Latvian Immigration Into Canad
Des données numériques aux connaissances pluridisciplinaires : enjeux de documentation et de formalisation
No full textContributeurs : Violette Abergel, Pierre Arese, Florent Comte, Iwona Dudek, Anaïs Guillem, Antoine Gros, Kévin Réby, Livio De Luca, Aurore Pfitzmann, Pascal Bénistant //Author contributions : Conceptualization: V.A., P.A., F.C., I.D., A.Gu., A.Gr., K.R.; Data curation: V.A., P.A., F.C., I.D., A.Gu., A.Gr., K.R.; Formal analysis: ; Funding acquisition: L.D.L.; Investigation: ; Methodology: V.A., P.A., F.C., I.D., A.Gu., A.Gr., K.R.; Project administration: L.D.L., A.P.; Resources: P.B.; Software: ; Supervision: L.D.L.; Validation: L.D.L.; Visualization: V.A., P.A., F.C., I.D., A.Gu., A.Gr., K.R.; Writing – original draft: V.A., P.A., F.C., I.D., A.Gu., A.Gr., K.R.; Writing – review & editing: V.A., P.A., F.C., I.D., A.Gu., A.Gr., K.R.International audiencePrésentation des procédés de gestion et de structuration des données acquises lors du Chantier Scientifique de Notre-Dame de Pari
Des données numériques aux connaissances pluridisciplinaires : enjeux de documentation et de formalisation
No full textContributeurs : Violette Abergel, Pierre Arese, Florent Comte, Iwona Dudek, Anaïs Guillem, Antoine Gros, Kévin Réby, Livio De Luca, Aurore Pfitzmann, Pascal Bénistant //Author contributions : Conceptualization: V.A., P.A., F.C., I.D., A.Gu., A.Gr., K.R.; Data curation: V.A., P.A., F.C., I.D., A.Gu., A.Gr., K.R.; Formal analysis: ; Funding acquisition: L.D.L.; Investigation: ; Methodology: V.A., P.A., F.C., I.D., A.Gu., A.Gr., K.R.; Project administration: L.D.L., A.P.; Resources: P.B.; Software: ; Supervision: L.D.L.; Validation: L.D.L.; Visualization: V.A., P.A., F.C., I.D., A.Gu., A.Gr., K.R.; Writing – original draft: V.A., P.A., F.C., I.D., A.Gu., A.Gr., K.R.; Writing – review & editing: V.A., P.A., F.C., I.D., A.Gu., A.Gr., K.R.International audiencePrésentation des procédés de gestion et de structuration des données acquises lors du Chantier Scientifique de Notre-Dame de Pari
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