Mechanically responding nanovalves based on polyelectrolyte multilayers

The alternate deposition of exponentially and linearly growing polyelectrolyte multilayers leads to the formation of multicompartment films. In this study, a new system consisting in nanometer-sized multilayer barriers deposited on or between multilayer compartments was designed to respond to mechanical stimuli and to act as nanovalves. The diffusion of polyelectrolytes through the barrier from one compartment to another can be switched on/off by tuning the mechanical stretching and thereby opening or closing nanopores in the barrier. This work represents a first step toward the design of chemically or biologically active films responding to mechanical stresses.     

Ex Situ Electroreclamation of Heavy Metals Contaminated Sludge: Pilot Scale Study

The ex situ remediation of heavy metals-contaminated industrial sludge (pH = 10.35, Zn = 3,500 mg∕kg) by electroreclamation (I = 2.5 A) was studied at pilot scale (42.5 kg of sludge). This research focused on acidification of sludge and electrochemically induced migration of metals, emphasizing their partitioning prior to electroreclamation. The sludge was preacidified to an initial pH of 4.5. After treatment, a very low anode reservoir pH (near 0) was reached, and the average sludge pH was 2. Addition of 1 M HNO3 to the cathode reservoir prevented basic conditions in the sludge. In accordance with selective sequential extraction results, a low migration of Zn and Cu was obtained. In the anode region, Zn and Cu concentrations decreased by 33 and 39%, respectively, and increased in the cathode region by 33 and 26%, respectively. These metals were concentrated in the cathode area but were not effectively transported onto the cathode. Mn appeared to be more mobile than other metals. After 10 days of current application, a layer mainly composed of Ca, Fe, and Mn appeared on the cathode surface.     

Correlation between activity and acidity on zeolites: a high temperature infrared study of adsorbed acetonitrile

The influence of the temperature on the protonation of acetonitrile by acidic zeolites was studied by infrared spectroscopy. Acidity at room or low temperature was not correlated with the protonation temperature, but the zeolitic structure played an important role. A new technique is presented for the study of the acidity of solids under reaction conditions. A good correlation was obtained in a series of various zeolites between the catalytic activity in the cracking of n-hexane and the protonation temperature of acetonitrile. This revised version was published online in June 2006 with corrections to the Cover Date.     

New cold-rolled deep-drawing grades

An unstabilised ultra low carbon steel (12 ppm of C) offers an attractive combination of formability properties like yield strength, elongation, mean r-value and BH-index. The major drawback is its large planar anisotropy. This is attributed to the large grain-size of the hot-rolled product. An increase in the cooling rate (using ultra fast cooling technology) or a decrease in the coiling temperature do not refine the hot-band grain size. However, an optimisation of the cold-rolling and the annealing sequences result in a better balance of the drawing properties. Alloying elements like Cr, B, V, Al. Si or reduction of Mn content exert only a minor influence on the final properties. An addition of Nb (mass contents of 0.01 %) improves the drawability but decreases the BH-index when conventional continuous annealing temperatures are applied.     

Immunohistochemical Evaluation of Periodontal Regeneration Using a Porous Collagen Scaffold

(1) Aim: To immunohistochemically evaluate the effect of a volume-stable collagen scaffold (VCMX) on periodontal regeneration. (2) Methods: In eight beagle dogs, acute two-wall intrabony defects were treated with open flap debridement either with VCMX (test) or without (control). After 12 weeks, eight defects out of four animals were processed for paraffin histology and immunohistochemistry. (3) Results: All defects (four test + four control) revealed periodontal regeneration with cementum and bone formation. VCMX remnants were integrated in bone, periodontal ligament (PDL), and cementum. No differences in immunohistochemical labeling patterns were observed between test and control sites. New bone and cementum were labeled for bone sialoprotein, while the regenerated PDL was labeled for periostin and collagen type 1. Cytokeratin-positive epithelial cell rests of Malassez were detected in 50% of the defects. The regenerated PDL demonstrated a larger blood vessel area at the test (14.48% ± 3.52%) than at control sites (8.04% ± 1.85%, p = 0.0007). The number of blood vessels was higher in the regenerated PDL (test + control) compared to the pristine one (p = 0.012). The cell proliferative index was not statistically significantly different in pristine and regenerated PDL. (4) Conclusions: The data suggest a positive effect of VCMX on angiogenesis and an equally high cell turnover in the regenerated and pristine PDL. This VCMX supported periodontal regeneration in intrabony defects.     

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.     

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.