Quantitative Characterization of Internal Defects in RDX Crystals

Size, shape, internal defects are very important properties of explosives crystals. These parameters play a role on both the explosive formulation processing and the detonic behavior of the explosive formulations. The use of explosive crystals free of solvent inclusions leads to decrease the shock sensitivity of cast explosive formulations. Many efforts for processing such high quality explosive crystals have been done and are still in progress. Qualitative observations of internal crystal defects can be performed by optical microscopy with matching refractive index. The purpose of this paper is to provide two accurate quantitative tools for internal crystal defects measurements. The first method is based on accurate measurements of the crystal apparent density. The second method records the mass of the species entrapped in the crystal internal cavities. Experiments are performed on two RDX batches. The strong correlation recorded between the results of the two complementary methods validates the measurements. Apparent density measurements provide an accurate global characterization of the internal defects population of a crystal batch sorting the crystals in function of their apparent density. The second method is a tool to identify the species entrapped in the crystals.     

Influence of a metallic filler on polyurethane formation

The addition of metallic fillers is recognized to impart improvement of acoustic properties to polyurethane-based materials used for marine applications. The system under consideration was obtained by the reaction of a triisocyanateterminated prepolymer with 1,4-butanediol, in the presence of various concentrations of lead powder. With increasing lead content, gelation time is reduced and an Einstein-type law does not apply. The kinetics of the reaction were determined by Fourier transform infrared spectroscopy. Deviation from the classic second order is observed for the filled systems, and the higher the lead content, the more important the deviation is, showing undoubtedly the catalytic effect of the metallic powder.     

Sequencing analysis of a 40·2 kb fragment of yeast chromosome X reveals 19 open reading frames including URA2 (5′ end), TRK1, PBS2, SPT10, GCD14, RPE1, PHO86, NCA3, ASF1, CCT7, GZF3, two tRNA genes,three remnant delta elements and a Ty4 transposon

The complete sequence of a 40 247 bp DNA segment located on the left arm of chromosome X of Saccharomyces cerevisiae has been determined and analysed. The sequence encodes the 5′ coding region of the URA2 gene and 18 open reading frames of at least 100 amino acids. Ten of these correspond to known genes, whereas eight correspond to new genes. In addition, the sequence contains a tRNA-Ala gene, a tRNA-Asp gene, a Ty4 transposable element and three delta elements. The sequence has been deposited in the EMBL databank under Accession Numbers: Z49405, Z49404, Z49403, Z49402, Z49401, Z49400, Z49399, Z49398, Z49397, Z49396, Z49394, Z49392, Z49391, Z49390, Z49389, Z49387, Z49386, Z49385.     

Considerations about synchrophasors measurement in dynamic system conditions

This paper focuses on some concepts that are to be considered to ensure interoperability of phasor measurement units (PMU) during dynamic phenomena. Interoperability of devices in dynamic system conditions is needed to allow accurate analysis and, in the near future, control of phenomena like power system oscillations. The paper emphasizes the need to extend the IEEE standard to ensure the measurement latency and accuracy are known during field measurements. It also introduces a sequential logic aiming at providing the user with more robust measurements, together with more information about the measurement quality.     

Replication of liner collapse phenomenon observed in hyperbaric type IV hydrogen storage vessel by explosive decompression experiments

An experimental design based on representative sample is described in order to reproduce the detachment and deformation of the inner polymer layer (called liner) of hyperbaric hydrogen storage vessels during the emptying step. It is the first step of a better understanding of the mechanisms involved in the creation of a liner collapse. Results showed that a hydraulic testing machine fitted with a pressure hydrogen chamber enables to create a liner collapse on small samples by explosive decompression experiments. Tomographic observations have revealed that the collapse appears at the polymer liner/composite interface in areas that are not sufficiently bonded, nor consistently. Determination of liner collapse amplitudes, assessed by tomography, has underlined that, under some specific conditions, the deformation of the liner is permanent even when hydrogen has completely desorbed from the sample. In addition to liner collapses, composite cracks were also highlighted.     

Nonlinear Convective Oscillations in Two-Layer Systems under the Action of the Horizontal Component of the Temperature Gradient

The influence of the horizontal component of the temperature gradient on nonlinear oscillatory convective flows, developed under the joint action of buoyant and thermocapillary effects in the 47 v2 silicone oil - water system, is investigated. The layers of equal thicknesses are considered. Transitions between nonlinear regimes of convection, have been studied. It is shown that under the action of the horizontal component of the temperature gradient, the asymmetric oscillatory flow takes place in the system.     

Evaluation of the dielectric properties of biodiesel fuels produced from different vegetable oil feedstocks through electrochemical impedance spectroscopy

Biodiesel fuels were prepared from different vegetable oil sources (canola, soybean, sunflower, and corn) and studied through electrochemical impedance spectroscopy. The dielectric constant from these biofuels evidenced no important dependence on feedstock, suggesting basically no change in fuels' polarity from varying the raw materials. In a different way, huge variations of the electrical resistivity and relaxation frequency were found when comparing among the studied biodiesels. Our findings demonstrate that these variations are closely associated with changes in the biodiesel viscosity, which is known to modulate charge mobility and was feedstock dependent. Accordingly, the impedance spectroscopy is here revealed to be a sensitive, alternative and reliable analytical approach for distinguishing among different feedstock-related biodiesels and monitoring certain biofuels' properties, like viscosity and interrelated parameters, usually connected with fatty acid structural profiles in biodiesel fuels.     

Mass spectrometry-based metabolomics: accelerating the characterization of discriminating signals by combining statistical correlations and ultrahigh resolution

A strategy combining autocorrelation matrices and ultrahigh resolution mass spectrometry (MS) was developed to optimize the characterization of discriminating ions highlighted by metabolomics. As an example, urine samples from rats treated with phenobarbital (PB) were analyzed by ultrahigh-pressure chromatography with two different eluting conditions coupled to time-of-flight mass spectrometric detection in both the positive and negative electrospray ionization modes. Multivariate data analyses were performed to highlight discriminating variables from several thousand detected signals: a few hundred signals were found to be affected by PB, whereas a few tenths of them were linked to its metabolism. Autocorrelation matrices were then applied to eliminate adduct and fragment ions. Finally, the characterization of the ions of interest was performed with ultrahigh-resolution mass spectrometry and sequential MS(n) experiments, by using a LC-LTQ-Orbitrap system. The use of different eluting conditions was shown to drastically impact on the chromatographic retention and ionization of compounds, thus providing a way to obtain more exhaustive metabolic fingerprints, whereas autocorrelation matrices allowed one to focus the identification work on the most relevant ions. By using such an approach, 14 PB metabolites were characterized in rat urines, some of which have not been reported in the literature.