Comparison of Monomethylhydrazine/Hydroxypropylcellulose and Hydrocarbon/Silica Gels

Experimental studies have been performed to investigate rheology and droplet burning with different types of gelled propellants. Monomethylhydrazine has been gelled with organic hydroxypropylcellulose. JP-8 and RP-1 hydrocarbon gels have been produced with inorganic fumed silica particles. Rheological characterization showed the differences in terms of viscosity and yield stress behavior due to different types of gelling agents. Herschel-Bulkley and Carreau-Yasuda models have been used to characterize the gels with inorganic and organic gelling agents, respectively. First experiments with the Monomethylhydrazine/hydroxypropylcellulose gels showed a typical swelling process during combustion with a flexible viscous droplet surface. Contrary to that, the hydrocarbon/silica gels burned while a rigid silica structure was built, which remained unburned. Burning drop measurements have been compared to the d^2-squared law

Influence of carbide distribution on ductility of Haynes®282® forgings

Haynes®282®, a relatively new superalloy is used in gas turbines in form of sheets, plates and forgings. Forgings undergo a series of deformation steps at high temperatures to form complex shapes of components. The deformation on forgings, changes the microstructural features and their distribution, and any change in distribution of microstructural features can affect the mechanical properties of the material. The present study is undertaken to investigate the possible causes of anisotropy in mechanical properties of a Haynes®282® forging through optical and electron microscopy. Microscopic investigations show that ductility is anisotropic and changes from 15% to 21%. The electron backscattered diffraction (EBSD) investigation reveals that the presence of carbide stringers (banding of MC and M6C carbides) is associated with fine grains, thereby giving a bimodal distribution of grain size. Carbide stringers follow the complexity of forgings and are identified as the primary cause for the anisotropic behavior in ductility. Furthermore, micromechanical simulations of carbide stringers in association with a bimodal grain structure was seen to qualitatively correspond to the experimental observation indicating improved ductility with banding along the tensile axis

The universal red-giant oscillation pattern; an automated determination with CoRoT data

The CoRoT and Kepler satellites have provided thousands of red-giant oscillation spectra. The analysis of these spectra requires efficient methods for identifying all eigenmode parameters. The assumption of new scaling laws allows us to construct a theoretical oscillation pattern. We then obtain a highly precise determination of the large separation by correlating the observed patterns with this reference. We demonstrate that this pattern is universal and are able to unambiguously assign the eigenmode radial orders and angular degrees. This solves one of the current outstanding problems of asteroseismology hence allowing precise theoretical investigation of red-giant interiors.Comment: Accepted in A&A letter

Yes, subjective norms are important, but let's not lose sight of cultural differences

The study of social norms has great potential to broaden our understanding of the ways in which cultures are created and maintained. To maximise the benefit of this perspective, it is important to sample cultures widely and to include contexts in which norms are injunctiv

Nitrate and sulphate dynamics in peat subjected to different hydrological conditions: Batch experiments and field comparison

International audienceConservation of ecosystems that depend on water management and water quality has to be considered. We combined a field monitoring and batch experiments to better understand the impact of hydrological perturbations on peatland functioning. Factors influencing the dynamics of nitrate and sulphate concentration observed in two sites with different hydrological conditions in a south Normandy peatland were determined through the comparison of field and lab experiment. The effects of nitrate input, and oxic or anoxic conditions on nitrate and sulphate concentrations were investigated in bioreactors, using peat samples from field sites influenced by different hydrologic regimes. In this experiment, peat samples were subjected to similar conditions to address the effects of NO 3 and O2 concentrations (chemical effects), and the effect of hydrologic regimes and peat soil moisture (physical effects) on nitrate and sulphate dynamics. Cl , SO2 4 and NO 3 were monitored for 215 h. Nitrate was significantly reduced in most experiments. A complete nitrate reduction after 215 h in soil under anoxic conditions was observed. A denitrification process was also found under aerobic conditions depending on the peat site sampling, i.e. depending on the hydrological conditions. This process was interpreted as a heterotrophic denitrification. Sulphate monitoring revealed that 400 mg L 1 were produced in peat from the peat site with high hydrologic fluxes under aerobic conditions. Clear differences in chloride concentration (deviance analysis, P < 0.05), sulphate concentration and nitrate consumption dynamics (deviance analysis, P < 0.0001) were observed, for similar experimental chemical conditions, between the samples from the two peat sites. These differences were related to the field chemical variations observed and they indicate that part of the field nitrate and sulphate dynamics is linked to different bacterial activity and not only to nutrient fluxes variations

Filming the Stage: Reflections on the Historical and the Aesthetic Perspectives of an Essential Archive of the Future

Since the appearance and growth of cinema, a close but sometimes ambiguous relationship has been forged between the “Seventh Art” and the performing arts. Although cinema evolved quickly to become an art form in its own right, the stage and the productions produced for this space remain an object of attention for film directors. The relationship between the audio-visual sector and the presentational arts torments historians, creators and aestheticians alike. Experimented with and made use of by some, with varying degrees of success, fully rejected by others, the filming of the stage always raises many practical questions as well as theoretical reflections. The purpose of this article is to tackle questions and the search for possible answers which illuminate the eternal dialectical tensions between performing arts and recorded performing arts

Environmental factors influencing older adults\u27 walking for transportation: a study using walk-along interviews

<p>Abstract</p> <p>Background</p> <p>Current knowledge on the relationship between the physical environment and walking for transportation among older adults (≥ 65 years) is limited. Qualitative research can provide valuable information and inform further research. However, qualitative studies are scarce and fail to include neighborhood outings necessary to study participants’ experiences and perceptions while interacting with and interpreting the local social and physical environment. The current study sought to uncover the perceived environmental influences on Flemish older adults’ walking for transportation. To get detailed and context-sensitive environmental information, it used walk-along interviews.</p> <p>Methods</p> <p>Purposeful convenience sampling was used to recruit 57 older adults residing in urban or semi-urban areas. Walk-along interviews to and from a destination (e.g. a shop) located within a 15 minutes’ walk from the participants’ home were conducted. Content analysis was performed using NVivo 9 software (QSR International). An inductive approach was used to derive categories and subcategories from the data.</p> <p>Results</p> <p>Data were categorized in the following categories and subcategories: access to facilities (shops & services, public transit, connectivity), walking facilities (sidewalk quality, crossings, legibility, benches), traffic safety (busy traffic, behavior of other road users), familiarity, safety from crime (physical factors, other persons), social contacts, aesthetics (buildings, natural elements, noise & smell, openness, decay) and weather.</p> <p>Conclusions</p> <p>The findings indicate that to promote walking for transportation a neighborhood should provide good access to shops and services, well-maintained walking facilities, aesthetically appealing places, streets with little traffic and places for social interaction. In addition, the neighborhood environment should evoke feelings of familiarity and safety from crime. Future quantitative studies should investigate if (changes in) these environmental factors relate to (changes in) older adults’ walking for transportation.</p

Micro-Hall Magnetometry Studies of Thermally Assisted and Pure Quantum Tunneling in Single Molecule Magnet Mn12-Acetate

We have studied the crossover between thermally assisted and pure quantum tunneling in single crystals of high spin (S=10) uniaxial single molecule magnet Mn12-acetate using micro-Hall effect magnetometry. Magnetic hysteresis experiments have been used toinvestigate the energy levels that determine the magnetization reversal as a function of magnetic field and temperature. These experiments demonstrate that the crossover occurs in a narrow (~0.1 K) or broad (~1 K) temperature interval depending on the magnitude and direction of the applied field. For low external fields applied parallel to the easy axis, the energy levels that dominate the tunneling shift abruptly with temperature. In the presence of a transverse field and/or large longitudinal field these energy levels change with temperature more gradually. A comparison of our experimental results with model calculations of this crossover suggest that there are additional mechanisms that enhance the tunneling rate of low lying energy levels and broaden the crossover for small transverse fields.Comment: 5 pages, 5 figure

A Comprehensive Spectroscopic Analysis of DB White Dwarfs

We present a detailed analysis of 108 helium-line (DB) white dwarfs based on model atmosphere fits to high signal-to-noise optical spectroscopy. We derive a mean mass of 0.67 Mo for our sample, with a dispersion of only 0.09 Mo. White dwarfs also showing hydrogen lines, the DBA stars, comprise 44% of our sample, and their mass distribution appears similar to that of DB stars. As in our previous investigation, we find no evidence for the existence of low-mass (M < 0.5 Mo) DB white dwarfs. We derive a luminosity function based on a subset of DB white dwarfs identified in the Palomar-Green survey. We show that 20% of all white dwarfs in the temperature range of interest are DB stars, although the fraction drops to half this value above Teff ~ 20,000 K. We also show that the persistence of DB stars with no hydrogen features at low temperatures is difficult to reconcile with a scenario involving accretion from the interstellar medium, often invoked to account for the observed hydrogen abundances in DBA stars. We present evidence for the existence of two different evolutionary channels that produce DB white dwarfs: the standard model where DA stars are transformed into DB stars through the convective dilution of a thin hydrogen layer, and a second channel where DB stars retain a helium-atmosphere throughout their evolution. We finally demonstrate that the instability strip of pulsating V777 Her white dwarfs contains no nonvariables, if the hydrogen content of these stars is properly accounted for.Comment: 74 pages including 30 figures, accepted for publication in the Astrophysical Journa