N-Nitrosodimethylamine Formation from Hydrazine Compounds on Ozonation

N-Nitrosodimethylamine formation from six hydrazine compounds on ozonation was investigated. N-Nitrosodimethylamine formation yields in groundwater (pH 7) were 7.5%–89%. Results in the presence of tert-butyl alcohol indicated that N-nitrosodimethylamine was formed by reaction with molecular ozone, except for tetramethyltetrazene. From the results of effects of pH, tert-butyl alcohol and water matrix (groundwater and river water), it was suggested that reactions of tetramethyltetrazene with ozone, hydroxyl radicals, etc., were associated with N-nitrosodimethylamine formation. Some reactions restricted N-nitrosodimethylamine formation. Because N-nitrosodimethylamine formation of hydraxine compounds on chloramination was low, they are more important N-nitrosodimethylamine precursors on ozonation in actual water treatment.     

Synthesis of a novel vitamin E derivative, 2-(α-d-glucopyranosyl)methyl-2,5,7,8-tetramethylchroman-6-ol, by α-glucosidase-catalyzed transglycosylation

A novel derivative of vitamin E, vitamin E glucoside, was synthesized from 2-hydroxymethyl-2,5,7,8-tetramethylchroman-6-ol and maltose in a solution containing DMSO by transglycosylation with α-glucosidase from Saccharomyces species. The glycosylated product was identified as 2-(α-d-glucopyranosyl)methyl-2,5,7,8,-tetramethylchroman-6-ol (TMG) by mass spectrometry and nuclear magnetic resonance spectroscopy. The optimal pH of transglycosylation was 5.5, and the yield of TMG increased as the concentration of maltose increased. IMG has high solubility in water (>1×10³ mg/mL). The 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity of TMG was found to be nearly the same as those of α-tocopherol, Trolox (2-carboxy-2,5,7,8-tetramethylchroman-6-ol), and ascorbic acid.     

Local Controlled Release of Polyphenol Conjugated with Gelatin Facilitates Bone Formation

Catechins are extensively used in health care treatments. Nevertheless, there is scarce information about the feasibility of local administration with polyphenols for bone regeneration therapy, possibly due to lack of effective delivery systems. Here we demonstrated that the epigallocatechin-3-gallate-conjugated gelatin (EGCG/Gel) prepared by an aqueous chemical synthesis using 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-morpholinium chloride (DMT-MM) gradually disintegrated with time and facilitated bone formation in a critical size defect of a mouse calvaria. Conjugation of EGCG with the Gel generated cross-linking between the two molecules, thereby leading to a retardation of the degradation of the EGCG/Gel and to a delayed release of EGCG. The prepared EGCG/Gels represented significant osteogenic capability compared with that of the uncross-linked Gel and the cross-linked Gel with uncombined-EGCG. In vitro experiments disclosed that the EGCG/Gel induced osteoblastogenesis of a mouse mesenchymal stem cell line (D1 cells) within 14 days. Using fluorescently-labeled EGCG/Gel, we found that the fraction of EGCG/Gel adsorbed onto the cell membrane of the D1 cells possibly via a Gel-cell interaction. The interaction might confer the long-term effects of EGCG on the cells, resulting in a potent osteogenic capability of the EGCG/Gel in vivo. These results should provide insight into local controlled release of polyphenols for bone therapy.     

Influence of Spark Plasma Sintering (SPS) Conditions on Transmission of MgAl2O4 Spinel

The effects of the spark plasma sintering (SPS) parameters, such as heating rate α, temperature T and soak time t_s, and impurities on in‐line transmission T_in were examined in MgAl₂O₄ spinel. The SPS processing at T = 1300°C for t_s = 20 min with a low heating rate of α = 10°C/min is a preferable condition for attaining higher T_in. For the higher T or the longer t_s, grain coarsening enhanced the coalescence of residual pores and second phase precipitation, resulting to the limited T_in even at the slow α. Although the lower T and longer t_s attained fine and dense microstructure simultaneously, the maximum T_in was limited to about 50%. The limited transmission, particularly in the visible range, can be ascribed to the discoloration caused by the carbon contamination. The carbon contamination arose from the preexisting trace CO₃ impurities, irrespective of the SPS conditions. For the higher α, which is the primary advantage of the SPS technique, the additional carbon contamination occurred from the paper/die and remained as glassy carbon in the matrix. To attain higher T_in by the SPS technique, the lower α and T, and the shorter t_s should be utilized after removing the impurities.     

Preparation and characterization of a nanofiber mat consisting of Tetra‐PEG prepolymers

Tetra‐PEG gel, which has been known as a mechanically tough and biocompatible gel, was processed into a nanofiber mat by electro‐spinning (ES) and 2‐step treatment process using w/o type emulsion consisted of the Tetra‐PEG prepolymer 1‐octanol/water solution. The 2‐step treatment was carried out in order to increase the cross‐linking points to the as‐spun nanofibers. From this study, we succeeded in insolubilizing poly(ethylene glycol) (PEG) nanofiber, and it was found that the Tetra‐PEG gel nanofiber mat showed high tensile property even at swollen state. The elastic modulus at equilibrium swollen state was 4.5 kPa. In addition, we compared the differences of the structure and tensile property between the Tetra‐PEG nanofiber mat and porous Tetra‐PEG gel prepared by freeze‐dry method. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41353.     

Acid-, base-, and heat-induced degradation behavior of Chinese sepiolite

The stability of Chinese sepiolite with respect to acid, base, and heat treatments was examined based on changes that occur in its crystal structure, its morphology, its surface area, and the ions that leach into solution. Treatment in HCl for 3 h caused predominantly Mg²⁺ to leach and increased the surface area of the sepiolite. Increased temperature accelerated the leaching, resulting in the disappearance of the sepiolite phase above 100 °C. Treatment in NaOH caused Si⁴⁺ to be leached and this was accompanied by a minor change in the crystal structure of the sepiolite. Thermal treatment in air caused the manifestation of several types of dehydration behavior and the sepiolite was decomposed completely at above ～800 °C. Composite sheets of sepiolite and nitrile butadiene rubber were made from sepiolite after it had undergone various treatments. The tensile stress of each composite was measured and this is discussed with respect to its degradation features.     

High-Temperature Fatigue Strength of Crack-Healed Al2O3 Toughened by SiC Whiskers

Al₂O₃ reinforced by SiC whiskers (Al₂O₃/SiC-W) was hot-pressed to investigate the fatigue strength of crack-healed specimens at high temperature. Semielliptical surface cracks of 100 μm surface length were introduced on each specimen surface. These specimens were crack-healed at 1300°C for 1 h in air, and static and cyclic fatigue strengths were systematically investigated at room temperature, 900° and 1100°C by three-point bending. The static and cyclic fatigue limits of the crack-healed specimens were more than 70% of the average bending strength at each testing temperature. Crack-healed specimens of Al₂O₃/SiC-W were not sensitive to static and cyclic fatigue at room temperature and high temperatures. Therefore, the combination of crack-healing and whisker reinforcement can play an important role in increasing static and cyclic fatigue strengths at high temperature.     

One second growth of carbon nanotube arrays on a glass substrate by pulsed-current heating

We report the very rapid growth of carbon nanotubes (CNTs) at high temperatures that can be tolerated by glass substrates. Glass substrates with metal microelectrodes and sputtered catalysts are heated by a pulsed current in a chemical vapour deposition gas environment for 0.5–1 s to synthesize CNTs of several micrometres in height without damaging the glass substrate. CNTs with structures from single-walled to multi-walled and morphologies from entangled networks to vertically aligned forests are grown simply by changing the nominal thickness of the catalyst, and such CNTs grown selectively on the microelectrodes worked as field emitters for cathodoluminescence. Rapid, easy growth of patterned CNT arrays on glass substrates without using furnaces/heaters or vacuum pumps will be useful for various applications of CNTs.     

Inhibition of GTRAP3-18 May Increase Neuroprotective Glutathione (GSH) Synthesis

Glutathione (GSH) is a tripeptide consisting of glutamate, cysteine, and glycine; it has a variety of functions in the central nervous system. Brain GSH depletion is considered a preclinical sign in age-related neurodegenerative diseases, and it promotes the subsequent processes toward neurotoxicity. A neuroprotective mechanism accomplished by increasing GSH synthesis could be a promising approach in the treatment of neurodegenerative diseases. In neurons, cysteine is the rate-limiting substrate for GSH synthesis. Excitatory amino acid carrier 1 (EAAC1) is a neuronal cysteine/glutamate transporter in the brain. EAAC1 translocation to the plasma membrane promotes cysteine uptake, leading to GSH synthesis, while being negatively regulated by glutamate transport associated protein 3-18 (GTRAP3-18). Our recent studies have suggested GTRAP3-18 as an inhibitory factor for neuronal GSH synthesis. Inhibiting GTRAP3-18 function is an endogenous mechanism to increase neuron-specific GSH synthesis in the brain. This review gives an overview of EAAC1-mediated GSH synthesis, and its regulatory mechanisms by GTRAP3-18 in the brain, and a potential approach against neurodegeneration.