Substitutional reaction in Si–O network of molecular dynamics-modeled liquid Na2SiO3: Microscopic and statistical study

The study of the bond breaking and formation processes, that is, the chemical reaction, in the Si–O network structure in liquid alkali silicates at temperatures around or higher than the glass-transition temperature is important for understanding kinetic processes such as the structural relaxation of the network, viscous flow, and diffusion of the network former ions. Herein, novel methods for analyzing the reactions in a molecular-dynamics-modeled liquid Na₂SiO₃ were used to confirm the following results: (a) the substitutional reactions (in which a nonbridging O ion of a Si–O chain or a SiO₄ tetrahedron attacks the Si ion of another chain from backside of a bridging O ion, which acts as the leaving group, and the bridging O leaves the Si ion) primarily occur in the Si–O network of liquid Na₂SiO₃; and (b) The abundance ratio of Q_n species can be quantitatively reproduced by the reaction rate.     

Pyrolysis of Poly(isopropyliminoalane) to Aluminum Nitride

The pyrolysis processes of poly(isopropyliminoalane) ((HAlN ⁱ Pr) _n ) were investigated, using mass spectrometry to analyze the gases and infrared spectroscopy to analyze the residual solids. The major mass loss (in the temperature range of 240°–540°C) consisted of two different pyrolysis stages. At the first stage (240°–320°C), (HAlN ⁱ Pr)₆ was detected continuously as a gas, and the precursor was converted to a cross-linked structure. A polymerization mechanism without a release of organic compounds has been proposed, and the formation of (HAlN ⁱ Pr)₆ during polymerization (besides its evaporation) has been suggested. The second stage (320°–560°C) involved the formation of various organic compounds, and radical processes for their formation were proposed.     

Low‐temperature and highly efficient conversion of saccharides into formic acid under hydrothermal conditions

Production of formic acid, which has been regarded as an important H₂ carrier, from biomass can be a highly potential way to provide human societies with renewable energy source. To attain economically viable production of formic acid from biomass on an industrial scale, the system operation at low reaction temperature is crucially important. In this work, a low‐temperature hydrothermal conversion of carbohydrates such as monosaccharides and disaccharides into formic acid is reported. A good formic acid yield of 80–85% was obtained at a lower temperature of 423 K for only 15–20 min in the presence of NaOH without any other catalyst. The alkali was found to act as two roles in enhancing the production of formic acid. One was inhibition of the formic acid decomposition; another was favorable for the oxidation selectively at C‐1 for aldoses, which leads to the formation of formic acid via the rupture of the C1–C2 bond. © 2016 American Institute of Chemical Engineers AIChE J, 62: 3657–3663, 2016     

Partial hydrothermal oxidation of unsaturated high molecular weight carboxylic acids for enhancing the cold flow properties of biodiesel fuel

Biodiesel fuel has become more attractive recently because of its environmental benefits and the fact that it is a product made from renewable resources. However the less favorable cold flow properties or the low temperature operability of biodiesel fuel compared to conventional diesel is a major drawback limiting its use. The poor flow properties of biodiesel at cold temperatures are mainly due to biodiesel fuel being composed of long-chain fatty acids with an alcohol molecule attached. If the double bond of unsaturated fatty acids in these long-chain fatty acids could be ruptured selectively, then the cold flow properties of biodiesel fuel would be enhanced by reducing its viscosity.In this study, the selective hydrothermal oxidation of oleic acid, as a model compound of unsaturated high molecular weight carboxylic acids, was studied experimentally. The objective was to use this as a model to investigate whether the double bond of unsaturated fatty acids can be ruptured selectively by partial hydrothermal oxidation. Demonstration of this method could then be used to show the potential to improve the cold flow properties of biodiesel. Results showed that the amount of mono-carboxylic acids, aldehyde, di-carboxylic acids, and aldehyde-acids with a carbon number of 9 was significantly higher than other oxidative products. This suggests that the oxidative cleavage may principally occur at the double bond in hydrothermal conditions. The cloud and pour points for biodiesel fuel (B100) and B100 blend with a mixture of methyl esters or acetals were measured. These are the most important indicators for the cold flow properties of biodiesel fuel. The methyl esters or acetals used were made from the esterification of carboxylic acids or aldehydes by simulating the major oxidation products. These were obtained from the hydrothermal oxidation of oleic acid at different oxygen supply rates. Results showed that the cloud and pour points of the blend were significantly enhanced compared to those of B100.     

Effect of timing and duration of midseason aeration on CH<Subscript>4</Subscript> and N<Subscript>2</Subscript>O emissions from irrigated lowland rice paddies in China

Midseason aeration (MSA) of rice paddy fields functions to mitigate CH₄ emission by a large margin, while simultaneously promoting N₂O emission. Alternation of timing and duration of MSA would affect CH₄ and N₂O emissions from intermittently irrigated rice paddies. A pot trial and a field experiment were conducted to study the effect of timing and duration of MSA on CH₄ and N₂O emissions from irrigated lowland rice paddy soils in China. Four different water regimes, i.e., early aeration, normal aeration (the same as the local practice in timing and duration of aeration), delayed aeration, and prolonged aeration, were adopted separately and compared with respect to global warming potential (GWP) of CH₄ and N₂O emissions and rice yields as well. Total emission of CH₄ from the rice fields ranged from 28.6 to 64.1 kg CH₄ ha⁻¹, while that of N₂O did from 1.71 to 6.30 kg N₂O–N ha⁻¹ during the study periods. Compared with the local practice, early aeration reduced CH₄ emission by 13.3–16.2% and increased N₂O emission by 19.1–68.8%, while delayed aeration reduced N₂O emission by 6.8–26.0% and increased CH₄ emission by 22.1–47.3%. The lowest GWP of CH₄ and N₂O emissions occurred in prolonged aeration treatment, however, rice grain yield was reduced by 15.3% in this condition when compared with normal practice. It was found in the experiments that midseason aeration starting around D 30 after rice transplanting, just like the local practice, would optimize rice yields while simultaneously limiting GWPs of CH₄ and N₂O emissions from irrigated lowland rice fields in China.     

Greenhouse gas emissions from tropical peatlands of Kalimantan,Indonesia

Greenhouse gas emissions were measured from tropical peatlands of Kalimantan, Indonesia. The effect of hydrological zone and land-use on the emission of N₂O, CH₄ and CO₂ were examined. Temporal and annual N₂O, CH₄ and CO₂ were then measured. The results showed that the emissions of these gases were strongly affected by land-use and hydrological zone. The emissions exhibited seasonal changes. Annual emission of N₂O was the highest (nearly 1.4 g N m^–2y^–1) from site A-1 (secondary forest), while there was no signi.cant difference in annual N₂O emission from site A-2 (paddy field) and site A-3 (rice-soybean rotation field). Multiplying the areas of forest and non-forest in Kalimantan with the emission of N₂O from corresponding land-uses, the annual N₂O emissions from peat forest and peat non-forest of Kalimantan were estimated as 0.046 and 0.004 Tg N y^–1, respectively. The emissions of CH₄ from paddy field and non-paddy field were estimated similarly as 0.14 and 0.21 Tg C y^–1, respectively. Total annual CO₂ emission was estimated to be 182 Tg C y^–1. Peatlands of Kalimantan, Indonesia, contributed less than 0.3 of the total global N₂O, CO₂ or CH₄ emission, indicating that the gaseous losses of soil N and C from the study area to the atmosphere were small.     

Soft manipulator inspired by octopi: object grasping in all anatomical planes using a tendon-driven continuum arm

Artificial Life and Robotics - In this paper, we focus on the development of a soft continuum arm manipulator inspired by the morphology of octopi and their intelligent behavior. The proposed arm...     

Six-legged crawling soft robot: NOBIYAKA

Artificial Life and Robotics - In recent years, soft robotics composed of soft silicone rubber have attracted significant attention, as they can adapt to various unknown environments owing to their...