Foam processing and cellular structure of polypropylene/clay nanocomposites

Polypropylene (PP)/clay nanocomposites (PPCNs) were autoclave‐foamed in a batch process. Foaming was performed using supercritical CO₂ at 10 MPa, within the temperature range from 130.6°C to 143.4°C, i.e., below the melting temperature of either PPCNs or maleic anhydride‐modified PP (PP‐MA) matrix without clay. The foamed PP‐MA and PPCN2 (prepared at 130.6°C and containing 2 wt% clay) show closed cell structures with pentagonal and/or hexagonal faces, while foams of PPCN4 and PPCN7.5 (prepared at 143.4°C, 4 and 7.5 wt% clay) had spherical cells. Scanning electron microscopy confirmed that foamed PPCNs had high cell density of 10⁷–10⁸ cells/mL, cell sizes in the range of 30–120 μm, cell wall thicknesses of 5–15 μm, and low densities of 0.05–0.3 g/mL. Interestingly, transmission electron microscopic observations of the PPCNs' cell structure showed biaxial flow‐induced alignment of clay particles along the cell boundary. In this paper, the correlation between foam structure and rheological properties of the PPCNs is also discussed.     

A Simple Model to Predict Formation of Bromate Ion and Hypobromous Acid/Hypobromite Ion through Hydroxyl Radical Pathway during Ozonation

A simple model is developed to predict the formation of bromate ion as well as hypobromous acid/hypobromite ion through the hydroxyl radical pathway. For simplicity of the model, hydroxyl radical concentrations are represented by the concentration ratio of hydroxyl radical to dissolved ozone under the different pH conditions. A kinetic analysis is conducted to evaluate the ratio under the different pH conditions based on the experimental data. The different extent of the ratio by one pH unit is found to be 3–4 times. This model can favorably simulate the formations of bromate ion as well as hypobromous acid/hypobromite ion in spite of the simplicity of the model. So it is likely that this model will be applicable to the prediction of bromate ion formation in water purification process such as drinking water treatment by introducing the concentration ratio of hydroxyl radical to dissolved ozone.     

Formation of a thiamine disulfide complex with fatty acid: Mechanism of formation of the complex

The formation of complexes between thiamine disulfide (TDS) orO-acetyl thiamine disulfide (O-acetyl TDS) and fatty acid or fatty acid methyl ester in methanol has been studied by fluorescence quenching and¹³C NMR relaxation (T₁) measurements. The association constants (K-values) of TDS andO-acetyl TDS with fatty acids (from 11∶0 to 18∶0, and 18∶1, 18∶2, 18∶3 and 20∶4) and fatty acid methyl esters have been determined. These values do not depend on either the number of carbon atoms or the degree of unsaturation of the fatty acid. The K-values of TDS andO-acetyl TDS with fatty acid were 7.8 M⁻¹ and 5.1 M⁻¹, respectively. The K-values of TDS andO-acetyl TDS with fatty acid methyl ester were very small. These results show that the-OH moiety in TDS and the-COOH moiety in the fatty acid are necessary for formation of the complex     

Microfiltration and stabilization of egg yolk phospholipid emulsions by a microporous glass membrane

A microporous glass membrane with a narrow-range pore size was applied for the microfiltration of egg yolk phospholipid emulsions. The oil-in-water and water-in-oil emulsions were successfully filtered using the membrane without any coalescence of oil droplets or the breakdown of the emulsions. The filtrated oil-in-water emulsion was stable for at least 6 wk when stored at 5°C. The results obtained suggest that the technique would be valuable for the precise filtration of emulsions for food uses as well as intravenous fat and/or drug carrier emulsions, and offer the stabilization of the emulsions.     

Point mutation of alanine (31) to valine prohibits the folding of reduced lysozyme by sulfhydryl--disulfide interchange

In the preceding paper in this issue, we described the overproduction of one mutant chicken lysozyme in Escherichia coil.Since this lysozyme contained two amino acid substitutions (Ala³¹ValandAsn¹⁰⁶Ser)in addition to an extra methionine residue at theNH₂-terminus the substituted amino acid residues were convertedback to the original ones by means of oligonucleotide-directedsite-specific mutagenesis and in vitro recombination. Thus fourkinds of chicken lysozyme [Met^–1 Val³¹Ser¹⁰⁶-, Met^–1Ser¹⁰⁶-,Met^–1 Val³¹-and Met^–1 (wild type)] wereexpressed in E. coli. From the results of folding experimentsof the reduced lysozymes by sulfhydryl-disulfide interchangeat pH 8.0 and 38°C, follow ed by the specific activity measurementsof the folded en zymes, the following conclusions can be drawn:(i) an extra methionine residue at the NH₂-terminus reducesthe folding rate but does not affect the lysozyme activity ofthe folded enzyme; (ii) the substitution of Asn¹⁰⁶ by Ser decreasesthe activity to 58% of that of intact native lysozyme withoutchanging the folding rate; and (iii) the substitution of Ala³¹Val prohibits the correct folding of lysozyme. Since the wildtype enzyme (Met^–1-lysozyme) was activated in vitro withoutloss of specific activity, the systems described in this study(mutagenesis, overproduction, purification and folding of inactivemutant lysozymes) may be useful in the study of folding pathways,expression of biological activity and stability of lysozyme.     

Grain boundary engineering: historical perspective and future prospects

A brief introduction of the historical background of grain boundary engineering for structural and functional polycrystalline materials is presented herewith. It has been emphasized that the accumulation of fundamental knowledge about the structure and properties of grain boundaries and interfaces has been extensively done by many researchers during the past one century. A new approach in terms of the concept of grain boundary and interface engineering is discussed for the design and development of high performance materials with desirable bulk properties. Recent advancements based on these concepts clearly demonstrate the high potential and general applicability of grain boundary engineering for various kinds of structural and functional materials. Future prospects of the grain boundary and interface engineering have been outlined, hoping that a new dimension will emerge pertaining to the discovery of new materials and the generation of a new property originating from the presence of grain boundaries and interfaces in advanced polycrystalline materials.     

Estimation of Δf of nitro derivatives of benzene and toluene using AM1 and DSC

Abstract

The AM1 molecular orbital method and reduced pressure differential scanning calorimetry(RP-DSC) were applied to nitro derivatives of benzene and toluene for estimating Δ_f(1) and Δ_f(c). The heats of phase change were determined by RP-DSC with moderate accuracy and the combination of the heats and Δ_f(g) estimated by AM1 gave Δ_f in condensed phases which are similar to those found in literatures.     

Evaluation of Injured Axons Using Two-Photon Excited Fluorescence Microscopy after Spinal Cord Contusion Injury in YFP-H Line Mice

Elucidation of the process of degeneration of injured axons is important for the development of therapeutic modules for the treatment of spinal cord injuries. The aim of this study was to establish a method for time-lapse observation of injured axons in living animals after spinal cord contusion injury. YFP (yellow fluorescent protein)-H transgenic mice, which we used in this study, express fluorescence in their nerve fibers. Contusion damage to the spinal cord at the 11th vertebra was performed by IH (Infinite Horizon) impactor, which applied a pressure of 50 kdyn. The damaged spinal cords were re-exposed during the observation period under anesthesia, and then observed by two-photon excited fluorescence microscopy, which can observe deep regions of tissues including spinal cord axons. No significant morphological change of injured axons was observed immediately after injury. Three days after injury, the number of axons decreased, and residual axons were fragmented. Seven days after injury, only fragments were present in the damaged tissue. No hind-limb movement was observed during the observation period after injury. Despite the immediate paresis of hind-limbs following the contusion injury, the morphological degeneration of injured axons was delayed. This method may help clarification of pathophysiology of axon degeneration and development of therapeutic modules for the treatment of spinal cord injury.