Formation of corn fiber gum-milk protein conjugates and their molecular characterization

Corn fiber arabinoxylan is hemicellulose B isolated from the fibrous portions (pericarp, tip cap, and endosperm cell wall fractions) of corn kernels and is commonly referred to as corn fiber gum (CFG). Our previous studies showed that CFG isolated from corn bran (a byproduct of corn dry milling) contains very little protein and is an inferior emulsifier for oil-in-water emulsion systems as compared to corn fiber gum isolated from corn fiber derived from the corn wet-milling process. The protein deficient CFG isolated from corn bran was covalently conjugated with byproducts of cheese processing, β-lactoglobulin (β-LG) and whey protein isolate (WPI) using an economical food-grade Maillard-type heating reaction for the purpose of increasing their commercialization potential as a food emulsifier and soluble nutritional additive in beverages. The formation of the CFG-protein conjugates has been confirmed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). It has also been demonstrated that CFG-protein conjugates are capable of producing fine emulsions with better stability than either CFG or protein alone. The molecular characterization of CFG-protein conjugates was performed by high-performance size-exclusion chromatography (HPSEC) coupled to on-line multi-angle laser light scattering and viscometric detection. The analysis by HPSEC revealed that CFG-protein conjugates had higher weight-average molar mass (M_w, 340-359 kDa) and polydispersity (M_w/M_n, 1.74) than the corresponding unconjugated CFG (M_w, 290 kDa and M_w/M_n, 1.35). The z-average root-mean-square radius of gyration (R_gz) of CFG-protein conjugates was slightly higher (30.5-33.5 nm) in comparison to CFG (29.5 nm) but their weight-average-intrinsic viscosity (η) remained unchanged (about 1.32 dL g⁻¹). The Mark-Houwink exponent “a” of conjugates (0.40) was lower than the unconjugated CFG (0.53) indicating the formation of a more compact structure after conjugation with protein. These findings should benefit the beverage industry, which can use this information to produce a high quality emulsifier from the low-value byproducts of corn dry milling and cheese processing.     

Homogenization pressures applied to citrus juice manufacturing. Functional properties and application

Homogenization is a unit operation that can be incorporated in citrus juice manufacturing to improve chemical and physical characteristics relevant for use in subsequent processing operations. The aim of this study was to evaluate the effect of different homogenization pressures on suspended solids and antiradical activity in mandarin low pulp juice (LPJ) and to understand their influence on a posterior vacuum impregnation operation. We found the pressure treatments applied to LPJ do not have negative effects on antiradical activity or functional compounds in the juice. In the vacuum impregnation study we found that more LPJ was introduced into the structural matrix of apples when homogenized at higher pressures and therefore more functional compounds may be introduced due to pulp stability and particle size reduction.     

Computational micro- and macroscopic models of contact and friction: formulation, approach and applications

This paper is dedicated to new asperity-based constitutive models of contact interfaces. These models have been obtained through a combination of finite element analysis of surface asperities and statistical homogenization techniques, to predict macroscopic, phenomenological behavior of the interface. This new approach has generalized the existing asperity-based models of contact and friction by considering realistic, complex shapes and mechanical properties of surface asperities, as opposed to previous simplified analytical solutions. This has been achieved by application, at the stage of asperity modeling, of the finite element method, which takes into account arbitrary shapes of asperities, non-linear material properties, molecular-range adhesion forces, and sliding resistance on the contact surface. The h–p adaptive mesh refinement techniques, adaptive timestepping and other adaptive methods are used to assure high accuracy of the solution. The result of this development is a new family of constitutive interface models, consistent with surface micromechanics and applicable to studies of static and dynamic friction phenomena. They are also extendible to calculation of thermal or electrical resistances, wear modeling, and other applications. This paper presents the theoretical formulation, numerical methodology and sample models of contact, adhesion and friction obtained through these homogenization techniques.     

Rapid amorphization of molecular crystals by absorption of solvent molecules in the presence of hydrophilic matrices

Two organic molecular crystalline species, ibuprophen (IB) and indomethacine (IM) were subjected to methanol absorption in the presence of hydrophilic organic matrix, hydroxypropyl methylcellulose (HPMC). While spraying of 8–10% methanol or water on the drug–matrix mixture decreased the subsequent milling time for amorphization, absorption of methanol in a closed container caused spontaneous amorphization of IB was observed to give a nanocomposites with macroscopic agglomerates up to 250 μm after methanol absorption for overnight. Gentle mechanical homogenization under saturated methanol vapor with a newly developed apparatus, a tandem rotation mill (TRM), brought about homogeneous grains of IB-HPMC nanocomposites with the average particle size, 30 μm. We observed amorphous particles of IB in 60 nm regime dispersed in HPMC matrix under a transmission electron microscope (TEM). In the case of IM, mechanical homogenization with TRM was indispensable to obtain similar nanocomposites with HPMC.     

村镇空间改善思路与策略

受限于乡村的技术与经济能力,各地村镇普遍处于一个快速低技术的建设模式之下,造成各地的新兴村镇景观风貌状况日益堪忧。本文立足于解决实际问题,探索在当前村镇建设模式下,如何通过可操作手段来改善村镇空间环境。     

Homogenization kinetics of a cast Ti48A12W0.5Si alloy

The homogenization kinetics of a cast Ti48A12W0.5Si alloy with a duplex microstructure was studied in terms of γ-phase dissolution and -grain growth. It was found that the measured volume fraction of remnant γ grains can be well simulated by a model of interface-controlled dissolution in a dislocation mechanism, instead of a diffusion-controlled one. The activation energy for the /γ interface reaction was found to be Q_int = 476 kJ mol⁻¹, which is much higher than the interdiffusion activation energy in TiAl alloy. The grain growth of phase during homogenization can be categorized into three stages. During the first stage, where the volume fraction of remnant γ grains is higher than about 10%, the growth of grains follows the parabolic law D = k₁t^0.2, and the activation energy for grain growth was calculated to be Q₁ = 442 kJ mol⁻¹, very close to the Q_int for /γ interface reaction. In the second stage, where few fine γ grains (1–10 vol.%) remained, a dramatic grain growth occurs. During the final stage, as the single phase is obtained, the coarsening of grains again satisfies the grain growth law D = k₃t^0.4, with the grain growth activation energy Q₃ of 147 kJ mol⁻¹, lower than the reported interdiffusion energy of γ phase.     

Tailoring materials with prescribed elastic properties

This paper describes a method to design the periodic microstructure of a material to obtain prescribed constitutive properties. The microstructure is modelled as a truss or thin frame structure in 2 and 3 dimensions. The problem of finding the simplest possible microstructure with the prescribed elastic properties can be called an inverse homogenization problem, and is formulated as an optimization problem of finding a microstructure with the lowest possible weight which fulfils the specified behavioral requirements. A full ground structure known from topology optimization of trusses is used as starting guess for the optimization algorithm. This implies that the optimal microstructure of a base cell is found from a truss or frame structure with 120 possible members in the 2-dimensional case and 2016 possible members in the 3-dimensional case. The material parameters are found by a numerical homogenization method, using Finite-Elements to model the representative base cell, and the optimization problem is solved by an optimality criteria method.

Numerical examples in two and three dimensions show that it is possible to design materials with many different properties using base cells modelled as truss or frame works. Hereunder is shown that it is possible to tailor extreme materials, such as isotropic materials with Poisson's ratio close to − 1, 0 and 0.5, by the proposed method. Some of the proposed materials have been tested as macro models which demonstrate the expected behaviour.     

Long-term consolidation mechanisms based on micro–macro behavior and in situ XRD measurement of basal spacing of clay minerals

An important issue in the area of geological disposal of high-level radioactive waste (HLW) is to demonstrate the long-term mechanical stability of the buffer. In particular, it has to be clarified whether a waste package would continue to sink in the buffer over a long time period, resulting in a significant decrease in the buffer thickness. The candidate buffer material in Japan is a mixture of silica sand and bentonite. Consolidation tests have revealed that the bentonite shows secondary consolidation phenomena similar to clay in general. Therefore, it is important to investigate the mechanism of secondary consolidation behavior.Bentonite is a microinhomogeneous material consisting of clay minerals, macrograins (mainly quartz) and others. The unique combination of molecular dynamics (MD) and homogenization analysis (HA) procedures, termed the unified MD/HA method, has been proposed for estimating the micro to macro behavior of such an inhomogeneous material (Ichikawa, Y., Kawamura, K., Nakano, M., Kitayama, K., Kawamura, H., 1998. Unified molecular dynamics/homogenization analysis for water flow in bentonite. Proc. 1998 Int. High-Level Radioactive Waste Management Conf., Las Vegas. American Nuclear Society, La Grange Park, IL, pp. 422–428). In this study, the unified MD/HA method is applied to bentonite in order to understand its long-term consolidation mechanism. Thus, it was found that the permeability decreases significantly with a decrease in the void ratio due to the evolution of consolidation. It was therefore assumed that secondary consolidation is governed by drainage from the interlayer pores (micropores) with very low permeability, and that this is the reason why secondary consolidation is very slow.This paper also documents the result of an X-ray diffraction (XRD) experiment on bentonite under consolidation (in situ XRD), which was performed in order to validate the assumption mentioned above. It was observed that interlayer space starts to decrease after the latter half of primary consolidation. This finding strongly supports the long-term consolidation mechanism presumed above from a microscopic point of view.One-dimensional consolidation analyses of the bentonite, into which the relationship between the void ratio and the permeability determined using the unified MD/HA method was introduced, were performed for comparison with a long-term consolidation test. The good agreement between the analytical result and the test result including secondary consolidation behavior also supports the long-term consolidation mechanism presumed above.     

Effective mechanical behavior of hyperelastic honeycombs and two-dimensional model foams at finite strain

The aim of the present study is the analytical and numerical determination of the effective stress–strain behavior of solid foams made from hyperelastic materials in the finite strain regime. For the homogenization of the microstructure, a strain energy-based concept is proposed which assumes macroscopic mechanical equivalence of a representative volume element for the given microstructure with a similar homogeneous volume element if the strain energy of both volume elements is equivalent, provided that the volume average of the deformation gradient is equal for both volume elements. The concept is applied to an analysis of hyperelastic solid foams using a two-dimensional model. The effective stress–strain behavior is analyzed under uniaxial and biaxial loading conditions in the tensile and in the compressive range as well as under simple shear deformation. It is observed that the effective mechanical behavior of cellular solids at infinitesimal and finite deformation is essentially different on both, the quantitative and the qualitative level.