Chemical characterisation of marine aerosol at Amsterdam Island during the austral summer of 2006–2007

Atmospheric aerosols were collected in separate fine (<2.5 μm) and coarse (>2.5 μm) size fractions in the period December 2006–March 2007 at Amsterdam Island in the southern Indian Ocean. A major objective of the study was to assess biogenic impact on the marine aerosol. The samples were analysed for organic carbon, water-soluble organic carbon, major inorganic ionic species, and organic species, including methanesulphonate (MSA), dicarboxylic acids, and organosulphates. The concentrations of sea salt, non-sea-salt sulphate, and water-soluble and water-insoluble organic matter (WSOM and WIOM) were estimated. Sea salt dominated the composition of the aerosol and accounted for 83% and 91% of the sum of the mass of the four aerosol types in the fine and coarse size fractions, respectively. WSOM, which can serve as a proxy for biogenic secondary organic aerosol (SOA), accounted for only 2.8% of the sum of the mass of the four aerosol types in the fine size fraction. MSA was the dominating organic compound with a median concentration of 47 ng m^?3. The organosulphates were characterised as sulphate esters of hydroxyl acids and a dihydroxylaldehyde, which may originate from the oxidation of algal/bacterial unsaturated fatty acid residues. No evidence was found for isoprene SOA.     

Mechanical and fracture properties of cement-based bi-materials after thermal cycling

This study investigates the effect of thermal cycles on the fracture properties of the cement-based bi-materials. Sixty eight cubes were exposed to a varied number of 24-hour thermal cycles ranging from 0 to 90 and subsequently were tested in a wedge splitting configuration. The mechanical and fracture properties of normal strength and high strength concretes are substantially improved after 30 thermal cycles, but less so after 90 thermal cycles both in isolation and when bonded to an ultra high-performance fibre-reinforced cement-based composite.     

Nutrient digestibility in food waste ingredients for Pekin and Muscovy ducks

Food wastes are valuable resources to be recycled into new added-value products through animal production. The determination of energy and digestibility values of these wastes is essential for feed formulation. Corn, soybean meal (SBM), and a total of nine industrial food waste ingredients were tested in a comparative metabolic study in Pekin and Muscovy ducklings at two different ages during growth. The "precision-feeding" technique was employed to establish DM, fat, and fiber digestibility as well as retention of N and energy (AME, AMEn in Pekins; and AME, AMEn, TME, TMEn in Muscovies) for the 11 ingredients. For Pekin at 3 wk of age, the AMEn of peanuts, tofu, pogo, granola, waste diet, bread, corn, SBM, okara, and brewers grains were 5,141, 4,019, 3,971, 3,908, 3,141, 2,279, 1,572, and 1,442 kcal/kg, respectively. For Pekin at 6 wk of age, the AMEn of peanuts, pogo, tofu, granola, waste diet, bread, corn, SBM, and okara were 5,340, 4,327, 4,254, 4,079, 3,567, 3,302, 3,201, 2,416, and 1,562 kcal/kg, respectively. For Muscovy at 7 wk of age, the TMEn of peanuts, pogo, granola, waste diet, corn, tofu, bread, SBM, okara, and peanut skin were 5,207, 4,321, 4,057, 3,733, 3,233, 3,180, 3,084, 2,236, 1,575, and 904 kcal/kg, respectively. For Muscovy at 11 wk of age, the TMEn of peanuts, pogo, granola, tofu, waste diet, corn, bread, SBM, okara, and brewers grains were 5,077, 4,137, 4,025, 3,921, 3,586, 3,254, 3,123, 2,245, 2,007, and 1,392 kcal/kg, respectively. Nitrogen retention was significantly (P < 0.05) higher for SBM, tofu, okara, pogo, peanuts, and the food waste diet and lower for bread, corn, granola, brewers grains, and peanut skin. Dry matter digestibility was high for granola, pogo, corn, bread, and the food waste diet. Fat digestibility was generally the same for all the ingredients and was consistently over 97%. Bread neutral detergent fiber (NDF) was significantly (P < 0.05) the most digestible (88.92% NDF digestibility), as it consisted of 96.29% hemicellulose, whereas okara NDF was significantly (P < 0.05) the least digestible (26.94% NDF digestibility) and contained only 14.38% hemicellulose. Peanut skins and SBM with 30% hemicellulose showed only slightly higher digestibilities of NDF. The results of this study establish reliable data for formulation of duck diets using the tested industrial food waste ingredients as well as corn and SBM in both Pekin and Muscovy ducklings at two different ages during growth to market weight.     

Beneficial Effects of Silicon (Si) on Sea Barley (Hordeum marinum Huds.) under Salt Stress

Silicon - Silicon (Si) plays an important role in providing beneficial effects on plant growth and yield, especially under stressful environments such as salinity. The objective of this work is to...     

Lipid oxidation in glassy and rubbery-state starch extrudates

This work describes the principle of protecting polyunsaturated fatty acids by holding them in the low moisture/solid/glassy-state starch matrix. One strategy already employed commercially is to encapsulate oil droplets within a solid wall that is highly impermeable to oxygen. These microencapsulated powders can then be added to foods. A shorter route would be to add PUFA-rich oils directly into a food formulation during the processing of a low moisture product. This should effectively encapsulate the valuable oils and protect them from oxidation. ω-6 Linoleic acid was incorporated into a waxy maize starch matrix via extrusion cooking. Linoleic acid oxidation occurred when this model food system was held in both the glassy and rubbery states (0.3 and 0.95 Aw, respectively) at 50 °C. The initial oxidation, not surprisingly, occurs near the surface, but interestingly the highest initial rate of lipid oxidation occurred, not in the rubbery samples, but in glassy state starch extrudates with surface micro-cracks.     

A coarse/fine preconditioner for very ill-conditioned finite element problems

We consider the problem of applying the conjugate gradient method to solve-ill-conditioned large algebraic systems of equations resulting from the finite element discretization of some three-dimensional boundary value problems. We present an effective preconditioner for such systems based on a multigrid technique. We assess its performance with examples borrowed from large flexible aerospace structures.     

Lactone monomers obtained by enzyme catalysis and their use in reversible thermoresponsive networks

Enzyme-catalyzed transformations have a great potential in both the pharmaceutical and chemical industry to achieve complex and (stereo)selective synthesis under mild reaction conditions. Still, the implementation of biocatalysis in the prerequisite upgrading of inert synthons into activated monomers for polymer applications has not yet been fully realized. In this contribution, we show that scaled-up synthesis of bicyclic norcamphor lactone using an engineered Baeyer–Villiger monooxygenase (BVMO) is feasible to reach complete conversion of the corresponding ketone in 24 h in shake-flask. The lactone monomer obtained by enzyme catalysis was copolymerized with ε-caprolactone via ring-opening polymerization to study the impact of the additional ring on material properties. Moreover, four-arm star-like, homo and block copolymers were designed from ε-caprolactone, ε-decalactone, and norcamphor lactone and characterized for their structural and thermal properties. These newly explored macromolecules were functionalized with furan rings using the enzyme Candida antarctica lipase B which allowed the formation of thermolabile networks via the pericyclic reaction with bismaleimide by means of Diels–Alder chemistry. The bonding/debonding state of these star-like based materials can be tuned by a suitable selection of thermal treatment. The temperature-dependent reversibility was assessed by thermal analysis and solubility test. Our results presented here shed light on the high potential of the use of chemoenzymatic approaches in the synthesis of new functional materials with tuned physiochemical properties. © 2020 The Authors. Journal of Applied Polymer Science published by Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48949.     

Fast frequency sweep computations using a multi‐point Padé‐based reconstruction method and an efficient iterative solver

Problems of the form Z (σ) u (σ)= f (σ), where Z is a given matrix, f is a given vector, and σ is a circular frequency or circular frequency‐related parameter arise in many applications including computational structural and fluid dynamics, and computational acoustics and electromagnetics. The straightforward solution of such problems for fine increments of σ is computationally prohibitive, particularly when Z is a large‐scale matrix. This paper discusses an alternative solution approach based on the efficient computation of u and its successive derivatives with respect to σ at a few sample values of this parameter, and the reconstruction of the solution u (σ) in the frequency band of interest using multi‐point Padé approximants. This computational methodology is illustrated with applications from structural dynamics and underwater acoustic scattering. In each case, it is shown to reduce the CPU time required by the straightforward approach to frequency sweep computations by two orders of magnitude. Copyright © 2006 John Wiley & Sons, Ltd.     

Fabrication of a “Soft” Membrane Electrode Assembly Using Layer‐by‐Layer Technology

A new type of thin‐film electrode that does not utilize conducting polymers or traditional metal or chemical vapor deposition methods has been developed to create ultrathin flexible electrodes for fuel cells. Using the layer‐by‐layer (LbL) technique, carbon–polymer electrodes have been assembled from polyelectrolytes and stable carbon colloidal dispersions. Thin‐film LbL polyelectrolyte–carbon electrodes (LPCEs) have been successfully assembled atop both metallic and non‐metallic, porous and non‐porous substrates. These electrodes exhibit high electronic conductivities of 2–4 S cm^–1, and their porous structure provides ionic conductivities in the range of 10^–4 to 10^–3 S cm^–1. The electrodes show remarkable stability towards oxidizing, acidic, or delaminating basic solutions. In particular, an LPCE consisting of poly(diallyldimethyl ammonium chloride)/poly(2‐acrylamido‐2‐methyl‐1‐propane sulfonic acid)/carbon–platinum assembled on a porous stainless steel support yields an open‐circuit potential similar to that of a pure platinum electrode. With LbL carbon–polymer electrodes, the membrane‐electrode assembly (MEA) in a fuel cell can be made several times thinner, assume multiple geometries, and hence be more compact. The mechanism for LPCE deposition, electrode structure, and miniaturization will be presented and discussed, and demonstrations of the LbL electrodes in a traditional Nafion‐based proton fuel cell and the first demonstration of a thin‐film hydrogen–air “soft” fuel cell fully constructed using multilayer assembly are described.     

FETI‐DP: a dual–primal unified FETI method—part I: A faster alternative to the two‐level FETI method

The FETI method and its two‐level extension (FETI‐2) are two numerically scalable domain decomposition methods with Lagrange multipliers for the iterative solution of second‐order solid mechanics and fourth‐order beam, plate and shell structural problems, respectively.The FETI‐2 method distinguishes itself from the basic or one‐level FETI method by a second set of Lagrange multipliers that are introduced at the subdomain cross‐points to enforce at each iteration the exact continuity of a subset of the displacement field at these specific locations. In this paper, we present a dual–primal formulation of the FETI‐2 concept that eliminates the need for that second set of Lagrange multipliers, and unifies all previously developed one‐level and two‐level FETI algorithms into a single dual–primal FETI‐DP method. We show that this new FETI‐DP method is numerically scalable for both second‐order and fourth‐order problems. We also show that it is more robust and more computationally efficient than existing FETI solvers, particularly when the number of subdomains and/or processors is very large. Copyright © 2001 John Wiley & Sons, Ltd.