A VERSATILE FOOD RHEOMETER

A new texture test instrument is described that applies linear or rotary deformations, singly or in combination, to food samples. A range of texture test cells and mixing, consistometer or viscometer attachments are adaptable to this apparatus so that many test methods presently used to measure the properties of foods can be performed with the instrument. Different transducers can be installed to detect force, torque, deformation and deformation rate, which are precisely recorded electronically. Environmental and sample temperature controls are built into the equipment. Application of the apparatus is illustrated with measurements of consistency during the formation of wiener emulsions and the rupture property of the wieners.     

Mechanical Behavior of Polycrystalline Magnesium Oxide at High Temperatures

High-temperature tensile deformation of paolycrystalline magnesia prepared by ( a ) single-crystal recrystallization and ( b ) hot-pressing, is described. Recrystallized polycrystalline magnesia goes through a brittle-ductile transition at 1700°C (strain rate 10⁻⁴ sec⁻¹). The brittleness below 1700°C is due to a lack of slip systems and grain boundary sliding. At 1700°C grain boundary migration produces corrugations in the interface which interfere with sliding. Above 1700°C the matrix becomes sufficiently plastic through multiple slip and polygonization to accommodate any distortion. Polycrystalline specimens then neck down for completely ductile fracture. Hot-pressed magnesia starts through a transition at 2200°C, i.e. 500°C higher. The increase is attributed to pores and impurity. Porosity is considered to promote grain boundary sliding by ( a ) providing the source for intergranular sliding, ( b ) decreasing the interfacial contact area, and ( c ) preventing grain boundary migration and corrugation. These observations confirm that high-temperature deformation occurs by dislocation glide and climb and by grain boundary sliding and migration.     

Mesenchymal stem cell-derived exosomes as new remedy for the treatment of inflammatory eye diseases

Detrimental immune response has a crucially important role in the development and progression of inflammatory eye diseases. Inflammatory mediators and proteolytic enzymes released by activated immune cells induce serious injury of corneal epithelial cells and retinal ganglion cell which may result in the vision loss. Mesenchymal stem cells (MSCs) are regulatory cells which produce various immunosuppressive factors that modulate phenotype and function of inflammatory immune cells. However, several safety issues, including undesired differentiation and emboli formation, limit clinical use of MSCs. MSC-derived exosomes (MSC-Exos) are nano-sized extracellular vesicles which contain all MSC-derived immunoregulatory factors. Intraocular administration of MSC-Exos efficiently attenuated eye inflammation and significantly improved visual acuity in experimental animals without causing any severe side effects. As cell-free product, MSC-Exos addressed all safety issues related to the transplantation of MSCs. Therefore, MSC-Exos could be considered as potentially new remedy for the treatment of inflammatory eye diseases which efficacy should be explored in up-coming clinical trials.     

The system generator concept for FMS research and analysis

In the research area of FMS, much past work has concentrated upon unique systems analysing production control strategies. In some cases, no physical system was available as reference, necessitating a variety of system assumptions by researchers. It has been very difficult to compare control strategy effectiveness among applications or among researchers due to many different system assumptions and a general lack of standardization among system definitions.

This paper discusses development of a system generator procedure, which would greatly enhance generic control strategy research by allowing rapid generation of test system environments. The basic issues and considerations involved in development of a system generator are discussed. Considering these issues, an implementation of a system generator procedure is presented along with an example of output system representations for given inputs to the generator procedure.     

Partial Purification and Thermal Characterization of Pectinmethylesterase from Red Grapefruit Finisher Pulp

Four forms of pectinmethylesterase have been partially purified from red grapefruit finisher pulp by chromatography on Heparin-Sepharose CL-6B. Three forms bound to the heparin-sepharose and could be eluted with a sodium chloride gradient. One form (RGPME3) exhibited high thermal stability retaining 66.7% relative activity after 2 min incubation in an 80°C water bath, and 45.2% of its relative activity after 60 set incubation in a 95°C water bath. RGPME3 had a K_m of 0.106 mg * mL^?1 citrus pectin and a pH optimum between 6 and 7. The most abundant form (RGPMEZ) had a K_m of 0.079 mg * mL^?1 citrus pectin. Denaturing electrophoresis and gel filtration chromatography suggested molecular weights between 20 and 40 kDa for the various forms.     

Three‐dimensional bright‐field scanning transmission electron microscopy elucidate novel nanostructure in microbial biofilms

Bacterial biofilms play key roles in environmental and biomedical processes, and understanding their activities requires comprehension of their nanoarchitectural characteristics. Electron microscopy (EM) is an essential tool for nanostructural analysis, but conventional EM methods are limited in that they either provide topographical information alone, or are suitable for imaging only relatively thin (<300 nm) sample volumes. For biofilm investigations, these are significant restrictions. Understanding structural relations between cells requires imaging of a sample volume sufficiently large to encompass multiple cells and the capture of both external and internal details of cell structure. An emerging EM technique with such capabilities is bright‐field scanning transmission electron microscopy (BF‐STEM) and in the present report BF‐STEM was coupled with tomography to elucidate nanostructure in biofilms formed by the polycyclic aromatic hydrocarbon‐degrading soil bacterium, Delftia acidovorans Cs1‐4. Dual‐axis BF‐STEM enabled high‐resolution 3‐D tomographic recontructions (6–10 nm) visualization of thick (1250 and 1500 nm) sections. The 3‐D data revealed that novel extracellular structures, termed nanopods, were polymorphic and formed complex networks within cell clusters. BF‐STEM tomography enabled visualization of conduits formed by nanopods that could enable intercellular movement of outer membrane vesicles, and thereby enable direct communication between cells. This report is the first to document application of dual‐axis BF‐STEM tomography to obtain high‐resolution 3‐D images of novel nanostructures in bacterial biofilms. Future work with dual‐axis BF‐STEM tomography combined with correlative light electron microscopy may provide deeper insights into physiological functions associated with nanopods as well as other nanostructures.     

Mechanical Behavior of Magnesium Oxide at High Temperatures

Magnesium oxide crystals show a wide variety of deformation and fracture modes under tension. These modes are determined by the number of slip systems operating concurrently in a given volume. (1) At low temperatures, slip is confined to a single (110) (110) system and plasticity is limited by stress concentrations which develop where slip switches from one plane to another. (2) At intermediate temperatures, (110) (110) slip systems at 90° can interpenetrate but those at 60° cannot. Mechanical properties then depend on the initial slip distribution. When slip is confined to 90° systems there is little work hardening and crystals neck down to a knife-edge ductile fracture. When slip is confined to 60° systems, crystals work harden and fracture by cleavage. (3) At high temperatures, dislocations can interpenetrate on all systems and polygonization can occur. After easy glide the crystals work harden and elongate over 100% before fracturing in a completely ductile manner. The transition temperature from one mode to another depends on strain rate.     

Thermal-Mechanical History and the Strength of Magnesium Oxide Single Crystals: I, Mechanical Tests

Various dislocation impurity interactions in magnesium oxide and their effect on mechanical properties between room temperature and 1000°C are discussed. (1) Impurity precipitate particles in single crystals can be redistributed by heat treatment. Their size and density affect the lattice resistance to the motion of fresh dislocations and thus affect the yield strength at room temperature. Above 1200°C impurities go into solid solution and the strength decreases to 0.7 times the as-received fully-precipitated value. (2) Fresh dislocations can be locked by heating above 600°C to produce yield phenomena at room temperature. The upper yield strength increases with time and temperature particularly when the aging temperature exceeds 1000°C. Locking is attributed to the diffusion of impurities and point defects to dislocations. (3) The basic temperature dependence of yield strength contains two regions: (a) Up to approximately 500°C the strength decreases rapidly, suggesting a dislocation cutting mechanism during flow. Material preheated above 1200°C shows a stronger dependence than as-received material. (b) Above 500° C strength decreases linearly at a rate equal to the decline in elastic modulus. Superimposed on this basic temperature dependence curve there is, for material preannealed above 1200° C, a hump due to reprecipitation between 500° and 1000°c.