Environmentally persistent free radicals induce airway hyperresponsiveness in neonatal rat lungs

Background  

Increased asthma risk/exacerbation in children and infants is associated with exposure to elevated levels of ultrafine particulate matter (PM). The presence of a newly realized class of pollutants, environmentally persistent free radicals (EPFRs), in PM from combustion sources suggests a potentially unrecognized risk factor for the development and/or exacerbation of asthma.     

Anodic behaviour of oxidised Ni–Fe alloys in cryolite–alumina melts

Nickel-iron alloys have been identified as promising inert anode candidates for the Hall–Héroult process. In this study, binary Ni–Fe alloys of various compositions were subjected to short-term galvanostatic electrolysis in a cryolite–alumina bath at 960 °C. Prior to electrolysis, the anodes were oxidised at 800 °C for 48 h, forming a protective scale. Fe₂O₃, Ni_xFe_3−xO₄ and Ni_xFe_{1 − x}O were identified as the major scale components using a combination of X-ray diffraction (XRD) analysis and energy dispersive X-ray spectroscopy (EDX). Anodes having Ni content of 50–65 wt% performed adequately during short-term electrolysis, operating at a steady potential of 3–3.5 V vs. AlF₃/Al. Overall, it was found that the pre-formed oxide scale was effective in reducing anode wear and fluoridation. In the absence of a pre-formed scale, anodes were shown to undergo appreciable internal corrosion and/or passivation due to metal fluoride formation. Analysis of the anodes following electrolysis was performed using XRD and electron microprobe analysis (EPMA).     

Modelling the surface adsorption of methane on carbon nanostructures

Methane (CH₄) adsorption is investigated on both graphite and in the region between two aligned single-walled carbon nanotubes, which we refer to as the groove site. We exploit the Lennard–Jones potential function and the continuous approximation to determine surface binding energies between a single CH₄ molecule and graphite and between a single CH₄ and two aligned single-walled carbon nanotubes. Our modelling indicates that for a CH₄ molecule interacting with graphite, the binding energy of the system is minimized when the CH₄ carbon is 3.83 Å above the surface of the graphitic carbon, while the binding energy of the CH₄–groove site system is minimized when the CH₄ carbon is 5.17 Å away from the common axis shared by the two aligned single-walled carbon nanotubes. Our results confirm the current view that for larger groove sites, CH₄ molecules in grooves are likely to move towards the outer surfaces of one of the single-walled carbon nanotubes. Our results are computationally efficient and are in good agreement with experiments and molecular dynamics simulations, and show that CH₄ adsorption on graphite and groove surfaces is more favourable at lower temperatures and higher pressures.     

Extrusion of highly filled flexible polymer sheet

Highly-filled polymer systems include color masterbatches, feedstocks for powder injection molding, and rigid sheets with high levels of flame retardants, but they have not been explored for flexible sheet. This work investigated the (a) selecting a polymer matrix with enough melt strength and flexibility to form a stable sheet with high filler loading, (b) the maximum achievable filler loading for the sheet, and (c) optimizing the process of extruding a highly-filled flexible polymer system. Extrusion grade low-density polyethylene (LDPE) provided sufficient flexibility and permitted a maximum filler loading of 36 vol% (~78 wt%). Good dispersion of the nanoparticle filler, however, required two passes through multiple screw extruders and a small reduction in the viscosity of the LDPE. Sheet with thickness of 415 μm, surface roughness of <1 μm, and sufficient flexibility was extruded continuously at a rate of 10 m/min., but it required a more traditional coat hanger manifold to prevent filler hang up in the sheet die. The filler particles were distributed uniformly through the core and skin of the sheet, giving the sheet good mechanical properties.     

Low Loss,High NA Chalcogenide Glass Fibers for Broadband Mid‐Infrared Supercontinuum Generation

High‐purity Ge–As–Se and Ge–As–S chalcogenide glasses were prepared by modified physical and chemical purification techniques. Using the purified glasses, step‐index fibers with a small core (~5.5 μm) and large numerical aperture (~1.3) were fabricated. When a 13.5‐cm‐long fiber was pumped with 320 fs pulses at a repetition rate of 10.5 MHz at 4.1 μm, supercontinuum spanning from ~1.8 to ~9.8 μm with a dynamic range of ±10 dB and an average power of ~3 mW was generated.     

Imaging and Diffraction Study of Continuous α-Fe2O3 Films on (0001)Al2O3

Continuous α-Fe₂O₃ films grown on bulk (0001)Al₂O₂ substrates by low-pressure chemical vapor deposition have been studied by transmission electron microscopy and the observations compared to those obtained from discontinuous films at an earlier stage of the growth process. Plan-view specimens revealed significant thermal stress in the continuous films, while cross-sectional specimens showed that cracking occurs in thicker films. The free surface of the film and the film/substrate interface appeared sharp and flat, apart from growth ledges and steps. Weak-beam imaging revealed a hexagonal misfit dislocation network consisting of perfect edge dislocations. Fine structure in the selected-area diffraction patterns which corroborates these observations is also discussed. The misfit network of partial dislocations previously observed in the discontinuous films was not observed for the continuous films, indicating an effect of film thickness, growth rate, or surface preparation on the Fe₂O₃/(0001)Al₂O₃ interface structure.     

Nanograin magnetoresistive manganite coatings for EMI shielding against directed energy pulses

Two magnetoresistive manganites, La_0.83Sr_0.17MnO₃ and La_0.7Sr_0.3MnO₃, are synthesized by the environmentally friendly “deposition by aqueous acetate solution (DAAS)” technique. The manganite film has a grain size of 100 nm, and can be processed as thinly as 0.03 μm per layer, while the powder form has a crystallite size of 40 nm. These magnetoresistive materials are shown to be effective and inexpensive electromagnetic interference (EMI) shield for the extremely low frequency (ELF) EM fields. The electrical resistance of manganites is very sensitive to external influences, such as temperature and electromagnetic fields. Both permeability (μ) and conductivity (σ) of manganites tend to increase with increasing applied magnetic field. The manganites have been shown to “react” to field increases in a way that is particularly useful for shielding EMI field fluctuations (e.g., due to current or voltage spikes).

The manganite properties, e.g., crystal structure, film morphology, radiation absorption and reflection, electrical resistivity, and magnetization, etc., have been measured. The ceramic manganites have a metal–insulator transition at 300 K or higher, and are suitable for a room temperature operation. A thin film (approx. 0.1 μm) of La_0.83Sr_0.17MnO₃ was fabricated on a quartz tube or refractory ceramic fiber blanket. Using this thin manganite film, the EMI shielding effectiveness for the measured E-field attenuation is similar to that of a 25 μm thickness of copper tube, aluminum foil, and silver–nickel particle-dispersed paper. The silver–nickel impregnated paper has an EMI shielding effectiveness of 35 dB at 10 kHz, and 15 dB at 60 Hz (or frequency above 1 MHz). The ceramic manganites are chemically inert, thermally stable, and mechanically flexible. They provide low cost EMI shielding against directed energy pulses and may serve as a “signature reduction” barrier.     

Simulated weather variables effects on millet fertilized with phosphate rock in the Sahel

The Sudano–Sahelian agroecological zone is characterized by low and variable rainfall regimes and P deficiency. The present study complements previous research efforts and the objective was (i) to use the Newhall Simulation Model (NSM) to characterize three ICRISAT research sites, and (ii) to use output of NSM to develop an empirical model to guide efficient use of rainfall and fertilizers. The results show that length of the periods that rainfall exceeded evapotranspiration was larger in Bengou than in Gobery and Sadoré. Total positive moisture balance during the three growing seasons was 85.7 mm at Bengou and 19.7 mm at Sadoré. The model explained 52% of the variability in millet yields based on curvilinear response to P fertilizer, standardized May–June (R_mj) rainfall, and the number of wet days in the year (BW₃). Yields appear more sensitive to BW₃ than to R_mj. Their respective elasticity coefficients (E _c ) were 0.62 and 0.09. Assessment of the model using R²=0.76 and the D-index = 0.85 showed reasonable agreement between model estimation and actual field yields. The study demonstrates the application of simulation models as a cost-effective means in terms of time and funds to agronomic research.     

Polyurethane‐infiltrated carbon foams: A coupling of thermal and mechanical properties

The thermal and mechanical properties of polyurethane‐infiltrated carbon foam of various densities were investigated. By combining the high thermal conductivity of the carbon foam with the mechanical toughness of the pure polyurethane, a mechanically tough composite (relative to the unfilled foam) that could be used at higher temperatures than the polyurethane's degradation was formed. Both the tensile strength and the modulus increased by an order of magnitude for the composites compared to unfilled foam, while the compressive and shear strengths and moduli of the composites approached values exhibited by pure polyurethane. At both 300 and 400°C, the rectangular blocks of pure polyurethane lost their mechanical integrity due to decomposition in air. Thermogravimetric analysis confirms substantial initial weight loss above 290°C. Filled carbon foam blocks, however, maintain their mechanical integrity at both 300 and 400°C indefinitely, although the bulk of the rectangular block mass is polyurethane. Three different carbon foam densities are examined. As expected, the higher density foams show greater heat transfer. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2348–2355, 2003     

High Brightness 2.2–12 μm Mid‐Infrared Supercontinuum Generation in a Nontoxic Chalcogenide Step‐Index Fiber

An environment friendly nonlinear chalcogenide glass fiber with a Ge‐Sb‐Se core and a Ge‐Se cladding is fabricated for bright broadband mid‐infrared (MIR) supercontinuum (SC) generation. The fabricated Ge‐Sb‐Se/Ge‐Se fiber with a core diameter of 6 μm shows zero group velocity dispersion at ~4.2 μm and ~7.3 μm. By pumping the fiber with a length of 11 cm at 4.485 μm with 330 fs pulses, we achieve a SC covering the 2.2–12 μm spectral range and with an output average power of ~17 mW. This bright broadband SC source is promising for high‐resolution MIR spectroscopy.