The gelatinization and retrogradation of cornstarch gels in the presence of citric acid

The effects of citric acid on the gelatinization and retrogradation for 20 wt% cornstarch gels were studied by differential scanning calorimetry (DSC) measurements, uniaxial compression tests and dynamic viscoelastic measurements. The pH value of cornstarch dispersion was adjusted to between 5.0 and 3.0 by adding citric acid. The pH of gels without citric acid (control) was 6.3. The cornstarch gels with pH value adjusted to 3.0 were brittle, while the values of Young’s modulus and dynamic viscoelasticity were higher than those of other samples. It is thought that hydrolysis of amylose and amylopectin chains by adding citric acid occurred and the length of elastically active chains decreased, also leading to the formation of new networks. It was found that when cornstarch gels with added citric acid were stored, they became brittle, but became hard to deform against small deformation. However, when cornstarch gels with or without citric acid were stored for longer time at 5 °C, the retrogradation ratio estimated by thermal analysis was not affected by the presence of citric acid.     

New insight in characterization of red wine astringency using soft tribology method

The variation of friction coefficient (μ) of model wine and model saliva mixtures with entrainment speed (V_R) on simulated oral surfaces was evaluated by oral tribology. Combined with techniques of dynamic light scattering (DLS), atomic force microscopy (AFM), rheometer, and quartz crystal microbalance with dissipation monitoring (QCM-D), the correlation between characteristics of the model wine and model saliva mixtures (particle size and morphology, suspension viscosity, adsorption film thickness, and viscoelasticity) and the oral lubrication loss was established. The results showed that the higher the concentration of tannin in the model wine, the larger the size of the complexes with the model saliva, and the higher the thickness, viscoelasticity, and roughness of the adsorption film formed, which resulted in the increase of friction coefficient in the boundary lubrication regime. Different from previous results, it is found that the maximum value of the friction coefficient (μ_max) in the boundary regime has the best positive correlation with the astringency perception intensity of the model wine accordingly.     

Thermal and rheological properties of tapioca starch gels with and without xanthan gum under cold storage

Changes in the thermal and rheological properties of tapioca starch (TS) with and without xanthan gum (Xan) (total polysaccharide concentration = 25% w/w) were investigated using a differential scanning calorimeter, Rheolograph Gel and Texture Analyser. The gelatinization temperatures of TS shifted to higher values with the Xan concentration. Xan enhanced the retrogradation of TS during the initial stage of storage but retarded the process for a further storage time at 5 °C. The onset temperature of all reheated TS/Xan gels decreased with increasing storage time indicating thermally unstable structure formation after a longer storage time. Storage Young’s moduli (E′) of the TS and TS/Xan gels stored at 5 °C increased with increasing storage time. The E′ values became more temperature dependent with storage time due to the weak cross-linkage of amylopectin molecules in the gels but became less dependent in the system containing Xan. TS/Xan gels kept for 14 days showed lower Young’s moduli than TS gels from the compression test confirming retardation of the retrogradation process by Xan. The results suggested that Xan could retard the retrogradation of TS gels for longer storage times.     

Design of a complex system based on the maximum entropy principle

A complex system is a system composed of many dynamic elements with mutual interactions. This paper proposes a unified approach for the design of an information processing system using a complex system. The method of design is based on the maximum entropy principle. After a detailed explanation, the proposed method is applied to the design of a spatial filter using a complex system. This work was presented, in part, at the International Symposium on Artificial Life and Robotics, Oita, Japan, February 18–20, 1996.     

Hierarchical VLSI Fault Tracing by Successive Circuit Extraction from CAD Layout Data in the CAD-Linked EB Test System

A hierarchical VLSI fault tracing method is proposed which isapplicable to the case where only CAD layout data is available in theCAD-linked electron beam test system. The CAD layout data is assumedto be hierarchically structured. The method uses the expansion of apreviously proposed integrated algorithm which combines atransistor-level fault tracing algorithm and a successive circuitextraction from a non-hierarchically or a flat structured CAD layoutdata. The method allows us to trace a fault hierarchically from thetop level cell to the lowest primitive cell and from the primitivecell to the transistor-level circuit in a consistent mannerindependent of circuit functions even when the cell data and thetransistor-level circuit data exist in a level as a mixture. Anapplication of the method to a hierarchically structured CMOS modellayout with about 600 transistors shows its validity.     

An exploratory study on the efficacy of rat dedifferentiated fat cells (rDFATs) with a poly lactic-co-glycolic acid/hydroxylapatite (PLGA/HA) composite for bone formation in a rat calvarial defect model

In the last two decades, tissue-engineering approaches using scaffolds, growth factors, and cells, or their combination, have been developed for the regeneration of periodontal tissue and bone. The aim of this study was to examine the effects of rat dedifferentiated fat cells (rDFATs) with a poly lactic-co-glycolic acid/hydroxylapatite (PLGA/HA) composite on bone formation in rat calvarial defects. Twenty animals surgically received two calvarial defects (diameter, 5 mm) bilaterally in each parietal bone. The defects were treated by one of the following procedures: PLGA/HA+osteo-differentiated rDFATs implantation (PLGA/HA+rDFATs (OD)); PLGA/HA+rDFATs implantation (PLGA/HA+rDFATs); PLGA/HA implantation (PLGA/HA); no implantation as a control. The animals were euthanized at 8 weeks after the surgery for histological evaluation. The PLGA/HA composite was remarkably resorbed and the amounts of residual PLGA/HA were very slight at 8 weeks after the surgery. The PLGA/HA-implanted groups (PLGA/HA+rDFATs (OD), PLGA/HA+rDFATs and PLGA/HA) showed recovery of the original volume and contour of the defects. The newly formed bone area was significantly larger in the PLGA/HA group (42.10 ± 9.16 %) compared with the PLGA/HA+rDFATs (21.35 ± 13.49 %) and control (22.17 ± 13.08 %) groups (P < 0.05). The percentage of defect closure (DC) by new bone in the PLGA/HA+rDFATs (OD) group (83.16 ± 13.87 %) was significantly greater than that in the control group (40.61 ± 29.62 %) (P < 0.05). Furthermore, the PLGA/HA+rDFATs (OD) group showed the highest level of DC among all the groups. The present results suggest that the PLGA/HA composite is a promising scaffold and that PLGA/HA+DFATs (OD) may be effective for bone formation.     

Rheological properties of gum arabic solution: From Newtonianism to thixotropy

The influence of molecular association on the rheological behavior of gum arabic solution was studied. Using time-dependence of transient shear stress a reversible molecular association could be arrested and the thixotropy of gum arabic solution was interpreted. The structural breakdown, buildup and the effect of shear history due to molecular association could be related using the Casson’s equation. Stress jump measurements distinguished the effect of molecular association on the elastic and viscous contributions of shear stress. An elastic-like contribution dominated at low shear rates whereas the viscous component became important at high shear rates. The elastic contribution was strongly affected by the molecular association of gum arabic, with increased molecular association contributing to a larger elastic contribution. The elastic and viscous contributions were also investigated in transient flow. Both of the contributions increased with rest time, indicating a buildup of molecular association. With increasing the rest time the elastic contribution increased much faster than the viscous contribution to the total stress.     

Physicochemical aspects of hydrocolloid extract from the seeds of Lepidium sativum

Acid equivalent weight, intrinsic viscosity and FT‐IR measurements have demonstrated a polyelectrolyte nature to Lepidium sativum seed extract. The polyelectrolyte nature relates to the carboxyl groups carried by galacturonic acid and glucuronic acid unit. The seed extract exhibited pronounced shear thinning in steady shear rheology and a weak gel type behaviour in dynamic rheology when the concentration is high i.e. > 1%. Such behaviour suggests the ability of L. sativum seed extract to structure a liquid, thus showing the possibility of applying it as a novel thickener and stabiliser in aqueous systems. The characteristic could be due to a strong tendency of molecular association of L. sativum seed extract as found for high M/G ratio galactomannans, and possibly also the enhanced macromolecular entanglement due to relatively rigid chain conformation. Temperature dependence study showed that the rheological properties of L. sativum structured solution is stable against temperature variation.     

Sheet forming process of carbon fiber reinforced plastics for lightweight parts

The use of carbon fiber reinforced plastics is increasing markedly, particularly in aircraft bodies, but the time required to manufacture CFRP parts should be shortened to realize mass production. The stamping of solidified CFRP sheets can reduce the production time and may increase the flexibility of the manufacturing process. A new sheet forming process for solidified CFRP, in which a CFRP sheet is sandwiched by dummy metallic sheets during stamping, is proposed. The dummy metallic sheets act as protective materials as well as media for heating the CFRP sheet. The results of applying the proposed process are presented.