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.     

Updated Correlation Between Aircraft Smoke Number and Black Carbon Concentration

Aircraft emissions of black carbon (BC) contribute to anthropogenic climate forcing and degrade air quality. The smoke number (SN) is the current regulatory measure of aircraft particulate matter emissions and quantifies exhaust plume visibility. Several correlations between SN and the exhaust mass concentration of BC (C _BC) have been developed, based on measurements relevant to older aircraft engines. These form the basis of the current standard method used to estimate aircraft BC emissions (First Order Approximation version 3 [FOA3]) for the purposes of environmental impact analyses. In this study, BC with a geometric mean diameter (GMD) of 20, 30, and 60 nm and filter diameters of 19 and 35 mm are used to investigate the effect of particle size and sampling variability on SN measurements. For BC with 20 and 30 nm GMD, corresponding to BC emitted by modern aircraft engines, a smaller SN results from a given C _BC than is the case for BC with 60 nm GMD, which is more typical of older engines. An updated correlation between C _BC and SN that accounts for typical size of BC emitted by modern aircraft is proposed. An uncertainty of ±25% accounts for variation in GMD in the range 20–30 nm and for the range of filter diameters. The SN–C _BC correlation currently used in FOA3 underestimates by a factor of 2.5–3 for SN ≤15, implying that current estimates of aircraft BC emissions derived from SN are underestimated by the same factor.

Copyright 2013 American Association for Aerosol Research     

Layered double hydroxide platelets exfoliation into a water‐based polyester

Nitrate layered double hydroxide (LDH) phase Zn₂Al(OH)₆(NO₃)·2H₂O is successfully exfoliated in the presence of polyester under mild conditions using water as essential solvent and at room temperature under air. From small angle X‐ray scattering spectroscopy a total exfoliation is found to be achieved using up to 10 wt % LDH, while intercalated polymer nanocomposite structures largely extended up to 14 nm are observed for loading ranging from 10 to 20 wt %. The process is found to be explained by the diffusion of the polymer chain into the interlayer host structure. Starting from an initial value of 0.89 nm, ≈3, 7, 10, 14, and 20 nm transient interleaved nanostructures are formed without any carbonate uptake. The collective gap distance is certainly due to a defined number of polymer chains diffusing into the LDH interstices. Similarly, starting from an aqueous polyester solution highly concentrated in LDH nitrate phase up to 50% w.w, successive dilutions yield platelet exfoliation, thus rendering a smooth chemistry process attractive for potential applications. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

High hydrostatic pressure modification of whey protein concentrate for improved functional properties

Whey protein concentrate (WPC) has many applications in the food industry. Previous research demonstrated that treatment of whey proteins with high hydrostatic pressure (HHP) can enhance solubility and foaming properties of whey proteins. The objective of this study was to use HHP to improve functional properties of fresh WPC, compared with functional properties of reconstituted commercial whey protein concentrate 35 (WPC 35) powder. Fluid whey was ultrafiltered to concentrate proteins and reconstituted to equivalent total solids (8.23%) as reconstituted commercial WPC 35 powder. Solutions of WPC were treated with 300 and 400 MPa (0- and 15-min holding time) and 600 MPa (0-min holding time) pressure. After HHP, the solubility of the WPC was determined at both pH 4.6 and 7.0 using UDY and BioRad protein assay methods. Overrun and foam stability were determined after protein dispersions were whipped for 15 min. The protein solubility was greater at pH 7.0 than at pH 4.6, but there were no significant differences at different HHP treatment conditions. The maintenance of protein solubility after HHP indicates that HHP-treated WPC might be appropriate for applications to food systems. Untreated WPC exhibited the smallest overrun percentage, whereas the largest percentage for overrun and foam stability was obtained for WPC treated at 300 MPa for 15 min. Additionally, HHP-WPC treated at 300 MPa for 15 min acquired larger overrun than commercial WPC 35. The HHP treatment of 300 MPa for 0 min did not improve foam stability of WPC. However, WPC treated at 300 or 400 MPa for 15 min and 600 MPa for 0 min exhibited significantly greater foam stability than commercial WPC 35. The HHP treatment was beneficial to enhance overrun and foam stability of WPC, showing promise for ice cream and whipping cream applications.     

Altering iodine metabolism in the calf by feeding iodine-binding agents.

Effects of feeding cottonseed meal and anion-exchange resin on iodine absorption and excretion by calves were investigated. Each additional amount of resin fed from .3 to 3.5 g/kg body weight further increased fecal excretion from single oral iodine-131 and intravenous iodine-125 doses. By feeding 3 to 10 g cottonseed meal/kg body weight, excretion of oral iodine-131 given daily was increased 7 to 94% in feces and reduced as much as 35% in urine, but plasma iodine-131 was not changed. Introducing 1 g resin/kg body weight daily into the diet increased fecal iodine-131 excretion three to five times that with cottonseed meal alone and reduced both plasma and urinary iodine-131. The same amount of resin fed daily had similar effects on excretion of iodine-131 injected subcutaneously each day. Although iodine depletion by a highly efficient iodine binder (resin) in the gastrointestinal tract is probable, iodine binding by a natural feed constituent (cottonseed meal) was relatively inefficient.     

Use of mini-computers for large scale structural analysis programs

One of the major new developments in computing technology is the mini-computer. This paper presents the results of the implementation of the ANSYS computer program (a large-scale structural analysis system) on a mini-computer.The implementation of ANSYS started with an evaluation of the existing and proposed mini-computer hardware and software systems, relative to a set of criteria derived from the structural software requirements.After benchmarking several systems to compare the claimed performances with the actual performance, the system which most nearly met the requirements for the ANSYS program was selected and ordered.The configuration chosen for this development machine is illustrated and variations from the development configuration which would be desirable for a production environment are discussed.The results of the implementation of ANSYS on the selected mini-computer system are presented. Included in the presentation are run times, run costs, accuracy of results and computer storage requirements.Finally, this paper discusses the future directions which will be pursued in this development effort. Included are discussions of the interface between the mini-computer and a larger central computer, the limits on problem size imposed by core memory and solution time and suggestions for the improvement of the performance of structural problems in a mini-computer environment.     

The optical (free-carrier) absorption of a hole-electron plasma in silicon

The near-IR absorption of a heavily injected silicon p-i-n diode has been measured. This is thought to be the first comprehensive measurement of the free-carrier absorption of a hole-electron plasma, and it behaves as expected with temperature, injection level and wavelength.

However, the absolute value of the absorption is higher than can be accounted for by ionized impurity scattering mechanisms by a factor of about 2.     

THE ORIGIN, DISTRIBUTION AND COMPOSITION OF LATERITE

The term laterite means a red rock or red earth deposit. Laterites are formed by the decomposition of different kind of rocks, under conditions yielding aluminum and iron hydroxides. The different theories of origin are discussed, as well as the chemical process of laterization, and the geographic distribution of this peculiar type of clay.     

SETTING INTERNAL AUDIT’S LONG-TERM PRIORITIES

As I have discussed in past articles, internal audit efforts must be risk-based and contribute to the long-term assurance needs of the organization and its board. A formal risk-assessment audit must be completed at least annually and the results of that assessment should direct audit priorities. Periodic updates throughout the year are also highly recommended. Over time, a focus on short-term results (quarterly financial results, meeting current regulatory requirements, etc.) has driven the priorities of management and consequently the organization toward a short-term perspective. Similarly, internal auditing’s efforts has commonly moved toward this short-term focus, boiling down priorities to whichever audits the company needs to complete in the immediate quarter or two. During the challenging business environment period some would say it is not a good time to refocus sights on the long-term horizon. I disagree. For example, knowing what the organization want to achieve in the next two to five years, and what does it need to do to get there, is critical to success! Certainly, each organization will have different goals, objectives, issues, and challenges, and no single “standard” long-term internal audit plan will work; but I took a shot at it anyway, and present the results in this article.