Molecular simulation of CH4 adsorption behavior in slit nanopores: Verification of simulation methods and models

The aim of this study is to select an appropriate method for CH₄ adsorption in organic nanopores for shale-gas development. Molecular dynamics (MD) and grand canonical Monte Carlo (GCMC) simulations were performed. Three comparison studies were included: (i) comparison of the adsorption behavior in kerogen nanopores using different schemes for dispersion correction, (ii) comparison of the adsorption behavior in graphite nanopores using MD and GCMC simulations, and (iii) comparison of the adsorption behavior in kerogen and graphite nanopores using MD simulations. The result was reliable when using a particle-mesh Ewald scheme or a cut-off ≥1.5 nm without dispersion correction. The simulation results were essentially identical for the MD and GCMC simulations. The free-gas CH₄ density inside the nanopores started to deviate from the bulk density at ~2 nm for the graphite model and at ~7–10 nm for the kerogen model, whereas the total CH₄ density deviates from the bulk density at ~20 nm.     

High Pressure Rheology of Environmentally Friendly Vegetable Oils

Environment-friendly lubricant is the key demand in twenty-first century for the issue of global climate change. Vegetable oils as base oil for lubricants and biodiesel fuel are environmentally preferable to petroleum. They are usually excellent boundary lubricants, but their high-pressure behavior is not investigated yet properly. In this research, first solidification characteristics of rapeseed oil, soybean oil, sunflower oil, palm oil, coconut oil, olive oil, camellia oil, mustard oil, castor oil, rapeseed methylester, and soybean methylester were investigated. Next, a very useful viscosity–pressure–temperature relation on the basis of phase diagram was derived for the nine vegetable oil.     

Molecular imprinting under molecular crowding conditions: an aid to the synthesis of a high-capacity polymeric sorbent for triazine herbicides

Molecular crowding, an important feature of the molecular environments in biological cells, was applied to the synthesis of antibody-mimic polymers selective for a group of biologically active compounds, the triazine herbicides. Synthesis of these polymers was conducted using molecular imprinting under molecular crowding conditions, whereby atrazine (a template molecule) was complexed with methacrylic acid (a functional monomer) in the presence of a macromolecular crowding agent (either poly(methyl methacrylate) (PMMA) or polystyrene (PS)) followed by cross-linking with ethylene glycol dimethacrylate. After removal of atrazine from the polymer matrix, the retention properties and selectivity of the resultant polymers were assessed by chromatographic tests. The addition of a crowding-inducing agent resulted in polymers with superior retention properties and excellent selectivity for triazine herbicides, as compared to polymers prepared without addition of a crowding-inducing agent. An imprinted polymer prepared in the presence of PS as a crowding agent exhibited a retention factor for atrazine an order of magnitude larger than that of an imprinted polymer prepared in the absence of a crowding agent. NMR results suggest that the crowding agent is capable of promoting hydrogen bond formation between atrazine and methacrylic acid, which could account for the effect of crowding on molecular imprinting.     

Control of Uninterrupted Switching Using a Virtual Synchronous Generator Between Stand‐Alone and Grid‐Connected Operation of a Distributed Generation System for Houses

The home applications of distributed generations facilities such as photovoltaic and gas engine cogeneration systems are growing and many distributed generations are connected to a grid by a DC/AC inverter. The DC/AC inverter is controlled by a phase‐locked loop (PLL) in order to be synchronized with the power system frequency. However, the control scheme of stand‐alone operation uses voltage control, and the PLL is unnecessary. Therefore, it is hard to realize uninterrupted change between stand‐alone and grid‐connected operation. In this paper, we propose a virtual synchronous generator control scheme in order to use the same control scheme in stand‐alone and grid‐connected operation. We carried out experiments to demonstrate the control characteristics.     

Step-Loading Characteristics of Gas Engine Cogeneration System Using Doubly-Fed Induction Generator in Stand-Alone Operation

Application of a DFIG （doubly-fed induction generator）, which is one of adjustable speed generators, to a gas engine cogeneration system has been investigated. To operate during a blackout as an emergency power supply is one of important roles for the gas engine eogeneration system. In the case of conventional constant speed of synchronous generator, the amount of the allowed step load is limited to around 30% of the rated power. On the other hand, DFIG is expected to increase the amount of step load during the stand-alone operation. In this paper, it has been demonstrated that an increase in the gas engine speed resulted in an increase in the maximum amount of step load using experimental equipment with a real gas engine. It has been concluded that the proposed system can improve the performance of an emergency power supply at step-loading.     

Effect of Dietary Partial Hydrolysate of Phospholipids,Rich in Docosahexaenoic Acid‐Bound Lysophospholipids,on Lipid and Fatty Acid Composition in Rat Serum and Liver

Lysophospholipids have been recognized as potent biologically active lipid mediators. However, attention has not been paid to the health benefits of dietary partial hydrolysate of phospholipids (PH‐PL), which is rich in docosahexaenoic acid (DHA)‐bound lysophospholipids. In this study, the effects of PH‐PL on serum and liver lipid profiles of rats upon administration of PH‐PL are demonstrated in comparison to those of fish oil (FO), which comprises eicosapentaenoic acid (EPA) and DHA‐bound triglyceride (TG). PH‐PL containing EPA and DHA was prepared via enzymatic modification of squid (Todarodes pacificus) meal that is rich in phospholipids. Male Wistar rats were fed a basal diet containing soybean oil alone (7%), FO, and PH‐PL. The FO and PH‐PL diets had similar EPA and DHA contents. After the rats had been fed their respective diets for 28 d, their serum and liver lipid contents, fecal lipid excretion, and hepatic gene expression level were measured. The results demonstrated that compared with the soybean oil diet alone, the PH‐PL diet decreased serum and liver TG contents partially because of the enhancement of liver acyl‐CoA oxidase activity and suppression of liver fatty acid synthase activity. In addition, compared with the soybean oil diet, the PH‐PL group exhibited lower serum cholesterol content at least in part because of the reduction of hepatic 3‐hydroxy‐3‐methylglutaryl‐CoA reductase mRNA expression level. We found that dietary administration of EPA and DHA containing PH‐PL has a hypolipidemic effect that may help prevent the development lifestyle‐related diseases.     

Inhibition of RuBisCO cloned from Thermosynechococcus vulcanus and expressed in Escherichia coli with compounds predicted by Molecular Operation Environment (MOE)

Ribulose 1,5-bisphosphate carboxylase/oxygenase (RuBisCO) of a thermophilic cyanobacterium, Thermosynechococcus vulcanus, was cloned and expressed in Escherichia coli. The purified enzyme had higher thermostability than RuBisCOs isolated from mesophilic cyanobacteria. Prediction of the tertiary structure was performed using the software Molecular Operating Environment (MOE). The predicted structure did not give any clue about the basis of thermostability. Then, the molecular docking of substrates and inhibitors in the catalytic site were carried out to test analogs for consistency of ribulose 1,5-bisphosphate, a RuBisCO substrate. The analogs were searched in the Kyoto Encyclopedia of Genes and Genomes (KEGG), and 99 compounds were selected for the docking. The mol files from LIGAND Database in KEGG were changed to a three dimensional (3D) structure for use in docking simulation. The docking simulation was performed on ASEDock of MOE, and the SiteFinder command suggested about 20 candidates for the docking site of the compounds. Based on the homology of these candidate sites with the xylulose 1,5-bisphosphate (XBP)-binding site of RuBisCO isolated from Synechococcus PCC 6301, one site was selected for the docking simulation. The 40 compounds with the highest docking energies included synthetic organic substances that had never been demonstrated to be inhibitors of RuBisCO. The total docking energies were -102 kcal/mol, -104 kcal/mol, -94.0 kcal/mol, and -57.7 kcal/mol for ribulose 1,5-bisphosphate (RuBP), etidronate, risedronate, and citrate respectively. Kinetic analysis of RuBisCO revealed a K(m) value of 315 microM for RuBP, and K(i) values of 1.70, 0.93, and 2.04 mM for etidronate, risedronate, and citrate respectively. From these values, the binding energies were estimated to be -4.85, -3.84, -4.20, and -3.73 kcal/mol for RuBP, etidronate, risedronate, and citrate respectively. The differences between the values estimated from experimental data and by simulation may mainly depend on the dissimilarity of the environment for the protein and ligands between the experiments and the simulation. The results obtained here suggested a few new inhibitors, which might be useful as tools for studying the relationship between the structure and the function of RuBisCO.