Enhancement of the thermal stability and mechanical properties of a PMMA/aluminum trihydroxide composite synthesized via bead milling

The use of aluminum trihydroxide (ATH) fillers as non-halogen flame retardants for polymethylmethacrylates (PMMA) creates a conflict between the mechanical properties and heat resistance of the composites. Therefore, to ensure that the PMMA mechanical properties remain satisfactory, improvements in both the filler–polymer interactions and the ability to control the size and size distribution, morphology and dispersion of the fillers are required. Thus, in the present study, bead milling was used to control both the size distribution and dispersion of ATH fillers in MMA, which had an initial average size of 0.75 μm. The dispersion was obtained by alteration of the surface characteristics of ATH fillers using a silane-based dispersing agent, (3-acryloxypropyl) trimethoxysilane (APTMS). Bead milling successfully comminuted the ATH particles and prevented the formation of ATH agglomerates. The smallest average size of the ATH particles after bead milling was 300 nm. Highly dispersed ATH filler particles were observed in the TEM images of the PMMA/ATH composites. The filler–polymer interaction, i.e. the interaction parameter (B), was calculated. The effects of volume fraction, particle size distribution, and surface modification of the fillers on the results of dynamic mechanical analysis (DMA) are discussed. The thermal stability of the PMMA/ATH composites was also investigated using thermal gravimetric analysis (TGA).     

Very high temperature annealing effect on amorphous carbon films grown on refractory oxide substrates by pulsed laser deposition

We have carried out very high temperature heat treatment at 1400–2700 °C of about 10 nm-thick amorphous carbon thin films deposited on refractory substrates MgO, Al₂O₃, and yttria-stabilized zirconia (YSZ) using pulsed laser deposition techniques. After the annealing, a few nanometer scale sp² crystallization of the films and a large corrugation with a height of more than 1 μm were observed by Raman spectroscopy analysis and optical/atomic force microscopes, respectively. The corrugation is probably caused by the formation of gases at the film/substrate interface during the heat treatment.     

Re-evaluation of Radiation-Energy Transfer to an Extraction Solvent in a Minor-Actinide-Separation Process Based on Consideration of Radiation Permeability

ABSTRACT

Absorbed-dose estimation is essential for evaluation of the radiation tolerance of minor-actinide-separation processes. We propose a dose-evaluation method based on radiation permeability, with comparisons of heterogeneous structures seen in the solvent-extraction process, such as emulsions forming in the mixture of the organic and aqueous phases. A demonstration of radiation-energy-transfer simulation is performed with a focus on the minor-actinide-recovery process from high-level liquid waste with the aid of the Monte Carlo radiation-transport code PHITS. The simulation results indicate that the dose absorbed by the extraction solvent from alpha radiation depends upon the emulsion structure, and that from beta and gamma radiation depends upon the mixer-settler-apparatus size. Non-negligible contributions of well-permeable gamma rays were indicated in terms of the plant operation of the minor-actinide-separation process.     

Revealing microbial community structures in large- and small-scale activated sludge systems by barcoded pyrosequencing of 16S rRNA gene

The diversity of bacterial groups in activated sludge from large- and small-scale wastewater treatment plants was explored by barcoded pyrosequencing of 16S rRNA gene. Activated sludge samples (three small and 17 large scale) were collected from 12 wastewater treatment plants to clarify precise taxonomy and relative abundances. DNA was extracted, and amplified by 4 base barcoded 27f/519r primer set. The 454 Titanium (Roche) pyrosequences were obtained and analyses performed by Quantitative Insight Into Microbial Ecology (QIIME) with around 100,000 reads. Sequence statistics were computed, while constructing a phylogenetic tree and heatmap. Computed results explained total microbial diversity at phylum and class level and resolution was further extended to Operational Taxonomic Unit (OTU) based taxonomic assignment for investigating community distribution based on individual sample. Composition of sequence reads were compared and microbial community structures for large- and small-scale treatment plants were identified as major phyla (Proteobacteria and Bacteroidetes) and classes (Betaproteobacteria and Bacteroidetes). Also, family level breakdowns were explained and differences in family Nitrospiraceae and phylum Actinobacteria found at their species level were also illustrated. Thus, the pyrosequencing method provides high resolution insight into microbial community structures in activated sludge that might have been unnoticed with conventional approaches.     

A novel ATP regeneration system using polyphosphate-AMP phosphotransferase and polyphosphate kinase

Polyphosphate-AMP phosphotransferase (PAP) and polyphosphate kinase (PPK) were used for designing a novel ATP regeneration system, named the PAP-PPK ATP regeneration system. PAP is an enzyme that catalyzes the phospho-conversion of AMP to ADP, and PPK catalyzes ATP formation from ADP. Both enzymes use inorganic polyphosphate [poly(P)] as a phosphate donor. In the PAP-PPK ATP regeneration system, ATP was continuously synthesized from AMP by the coupling reaction of PAP and PPK using poly(P). Poly(P) is a cheap material compared to acetyl phosphate, phosphoenol pyruvate and creatine phosphate, which are phosphate donors used for conventional ATP regeneration systems. To achieve efficient synthesis of ATP from AMP, an excessive amount of poly(P) should be added to the reaction solution because both PAP and PPK consume poly(P) as a phosphate donor. Using this ATP generation reaction, we constructed the PAP-PPK ATP regeneration system with acetyl-CoA synthase and succeeded in synthesizing acetyl-CoA from CoA, acetate and AMP. Since too much poly(P) may chelate MG2+ and inhibit enzyme activity, the Mg2+ concentration was optimized to 24 mM in the presence of 30 mM poly(P) in the reaction. In this reaction, ATP was regenerated 39.8 times from AMP, and 99.5% of CoA was converted to acetyl-CoA. In addition, since the PAP-PPK ATP regeneration system can regenerate GTP from GMP, it could also be used as a GTP regeneration system.     

Anti-aging effects of caloric restriction: Involvement of neuroendocrine adaptation by peripheral signaling

Many hormonal signals from peripheral tissues contribute to the regulation of energy homeostasis and food intake. These regulators including leptin, insulin, and ghrelin, modulate the orexigenic and anorexigenic neuropeptide expression in hypothalamic nuclei. The anti-aging effects of caloric restriction have been explained from an evolutional viewpoint of the adaptive response of the neuroendocrine and metabolic response systems to maximize survival during periods of food shortage. In organisms, excess energy is stored in adipose tissues as a triglyceride preparation for such survival situations. Adipose tissue has recently been recognized as an endocrine organ, and leptin, as secreted by adipocyte, seems to be an especially important factor for the adaptive response to fasting and neuroendocrine alterations under caloric restriction. In this review, we discuss the potential involvement of neuroendocrine modulators in longevity and the anti-aging effects of caloric restriction.     

Coexisting phenomena of surge and rotating stall in an axial flow compressor

The unsteady inner flow structure of a single-stage axial flow compressor under the coexisting conditions of surge and rotating stall was experimentally investigated via detailed measurements of the unsteady characteristics and the internal flow velocity fluctuations. The main relevant feature of the tested compressor is a shock tube with a capacity tank connected in series to the compressor outlet through slits and a concentric duplex pipe： surge and rotating stall can both be generated by connecting the shock tube. Research attention is focused on the unsteady behavior of a rotating stall during the surge cycle. The size of the rotating stall cell during the recovery process of an irregular surge cycle was experimentally determined by the circumferential flow velocity fluctuations ahead of the rotor blade. The results suggested that the size of the rotating stall cell at the switching point of the performance curve between large and small cycles is considered to be the key parameter in determining the following surge cycle. In addition, the surge cycle is largely influenced by the unsteady behavior of the rotating stall cell.     

Experimental and numerical study on hydrodynamics of riparian vegetation

Recently, many channelized rivers tend to be heavily vegetated due to regime shifts in hydrological, fluvial and ecological processes. Dense vegetation in a river frequently obstructs a flood flow and reduces conveyance capacity of channels. On the other hand, river vegetation provides various ecological services such as habitats for various species and life, natural cycle of organic and inorganic substances, etc.. It is of engineering importance to understand vegetation hydrodynamics in order to preserve vegetation nature and keep a certain level of flow conveyance capacity. In view that willows tend to be densely vegetated along the shoreline of floodplains or sandbars, a field measurement, a physical model experiment and a numerical analysis were carried out for investigating hydrodynamics in an open channel with riparian vegetation. Discussion was made focusing on flow and shear layer structures developed around the vegetation canopy.