Isolation and identification of a ferulic acid dehydrotrimer from saponified maize bran insoluble fiber

Following saponification of maize bran insoluble fiber a ferulic acid dehydrotrimer was isolated using Sephadex LH-20 chromatography. Structural identification was carried out using UV-spectroscopy, mass spectrometry and 1D and 2D NMR experiments ( ¹H, ¹³C, DEPT, COSY, TOCSY, ¹³C- ¹H HSQC, HMBC). UV-spectroscopy indicated characteristics of ferulate structures, mass spectrometry showed a trimeric ferulate structure, and the NMR spectra provided diagnostic evidence for its being a 5-5/8-O-4-coupled dehydrotrimer. Ferulic acid dehydrodimers are mainly derived from diferulates which cross-link polysaccharides. Because of the involvement of a 5-5-dehydrodiferulic acid unit in the identified trimer, this novel dehydrotriferulic acid from cereal grain fiber need not imply the cross-linking of three polysaccharide chains; molecular modeling of the ferulate dehydrodimerization in earlier studies showed that the 5-5-diferulate, uniquely, can form intramolecularly. This first identified ferulic acid dehydrotrimer nevertheless reveals that polysaccharide chains can be more extensively cross-linked than previously recognized.     

Book Review Corner

A thermal circuit model has been used to examine the heat transfer characteristics of an idealized station-keeping near-space platform. Forced convection, natural convection, and thermal radiation heat transfer mechanisms have been included in the model. The contributions of forced and natural convection were incorporated using previously published correlations. Thermal radiation heat transfer was assumed to be the result of direct solar flux, planetary infrared, and planetary albedo thermal radiation contributions. Model closure was obtained by using data from the 1976 standard atmosphere model, an empirical model for wind speed and models for variable thermophysical properties. The results of the scaling analysis indicate that, as expected, natural convection may be neglected above certain altitudes. The results also show the relative importance of thermal radiation and forced convection as the dominant heat transfer mechanisms with respect to altitude. Results from parametric studies of albedo and surface material effects are also included.     

Comparison of approximate solution methods for the solid phase diffusion equation in a porous electrode model

Approximation methods are often used in porous electrode models to eliminate the need to solve the local solid phase diffusion equation. These methods include Duhamel's superposition method, a diffusion length method and a polynomial approximation method which have long been used in the literature. The pseudo steady state (PSS) method is a method that has been used recently to develop a solution to the diffusion equation in a spherical particle with time dependent boundary conditions, but the PSS method has not been used in a porous electrode model. These methods are compared to each other in a dimensionless analysis study, and they are used in a porous electrode model to predict the discharge curves for a LiCoO₂ electrode. Simulation results presented here indicate that the PSS method or the high order polynomial method should be used in a porous electrode model to obtain accuracy and save computation time.     

A comparison of pyrrolidide and picolinyl ester derivatives for the identification of fatty acids in natural samples by gas chromatography-mass spectrometry

The pyrrolidide and picolinyl ester derivatives of the fatty acids in two natural lipid samples rich in unsaturated fatty acids, pig testis lipids and cod liver oil were satisfactorily resolved on capillary columns of fused silica coated with stationary phases of varying polarity. The picolinyl esters, in particular, when subjected to gas chromatography-mass spectrometry on a column containing a cross-linked methyl silicone, gave distinctive mass spectra, which could be interpreted in terms of both the numbers and positions of the double bonds.     

Synchrotron X-ray microdiffraction reveals rotational plastic deformation mechanisms in polycrystalline thin films

Understanding the mechanical response of polycrystalline materials on the mesoscopic scale remains a challenge as it is largely determined by grain-to-grain interactions and the discrete underlying microstructure. We conducted in situ synchrotron Laue microdiffraction experiments to map local strain tensors and orientations over polycrystalline thin gold films for different applied biaxial strain states. The experimental results demonstrate stress relaxation to be accompanied by cooperative transport of dislocation density leading to rotational plastic deformation heterogeneities. We propose a disclination model of closed dislocation walls and consider the geometry of transformations corresponding to a Burgers circuit enclosing the multipole disclination configuration. The observed stress-driven rotational deformation of the grain is shown to be described by the change in rotational closure failure associated with a Burgers circuit around the multipole disclination configuration. This concept is further advanced in a non-Euclidian geometry to demonstrate that the observed microrotation is captured by higher-order gradients in a micropolar continuum theory.     

Low-Temperature Densification of Lanthanum Strontium Manganite (La1−xSrxMnO3+δ), x=0.0–0.20

Intermediate-stage sintering of lanthanum strontium manganite (LSM, where Sr=0.00, 0.05, 0.10, 0.15, and 0.20) was shown in dilatometry studies to be accelerated when subjected to alternating flows of air and nitrogen. The extent of rate enhancement decreased with increased Sr content, and decreased with increased temperature, which coincides with diminished oxygen nonstoichiometry. Shrinkage rates were further shown to be sensitive to the difference in oxygen content in the alternating gas flows. Baseline air sintering rates were measured using stepwise isothermal dilatometry, from which kinetic parameters were calculated using the Makipirtti–Meng model. Activation energies for sintering in air were determined to be 255 ± 26, 258 ± 28, 308 ± 32, 373 ± 37, and 417 ± 41 kJ/mol for Sr=0.0, 0.05, 0.10, 0.15, and 0.20, respectively. A diffusion-based model is proposed that is consistent with trends in accelerated shrinkage versus temperature. Transient cation vacancy gradients, which lead to higher cation mobility, were calculated from established oxygen diffusivities and oxygen nonstoichiometry as a function of temperature and time. A potential application of this approach is the processing of LSM-based cathode-side contact pastes in solid oxide fuel cells.     

Warm homes: Drivers of the demand for heating in the residential sector in New Zealand

New Zealand houses are large, often poorly constructed and heated, by OECD standards, and consequently are colder and damper indoors than recommended by the World Health Organisation. This affects both the energy consumption and the health of households. The traditional New Zealand household pattern of only heating one room of the house has been unchanged for decades, although there has been substantial market penetration of unflued gas heaters and more recently heat pumps. This paper describes the residential sector and the results of two community-based trials of housing and heating interventions that have been designed to measure the impact of (1) retrofitting insulation and (2) replacing unflued gas heaters and electric resistance heaters with heat pumps, wood pellet burners and flued gas heaters. The paper describes findings on the rebound effect or ‘take-back’—the extent to which households take the gains from insulation and heating improvements as comfort (higher temperatures) rather than energy savings, and compares energy-saving patterns with those suggested by an earlier study. Findings on these aspects of household space heating are discussed in the context of the New Zealand government's policy drive for a more sustainable energy system, and the implications for climate change policy.