One physiological significance of the red blood cell (RBC) structure is that NO binding of Hb is retarded by encapsulation with the cell membrane. To clarify the mechanism, we analyzed Hb-vesicles (HbVs) with different intracellular Hb concentrations, [Hb] ) and many enzymes; and (iv) modulation of entrapment of endogenous gaseous messenger molecules (NO and CO) (6, 7) because it has been clarified in pathological conditions with hemolysis (8) and in the development of some Hbbased oxygen carriers (HBOCs) (9 -16) that entrapment of endothelium-derived NO induces vasoconstriction, hypertension, reduced blood flow, and vascular damage. CO is also a vasorelaxation factor, especially in hepatic microcirculation (17). Entrapment of CO by a cell-free Hb solution induces constriction of sinusoidal capillaries (18). These side effects of molecular Hb imply the importance of the cellular structure of RBC. Despite such a background in this field, the mechanism of retardation of NO binding by Hb encapsulation in RBC remains controversial (19 -21). It remains unclear whether (i) an unstirred layer is formed as an extracellular diffusion barrier surrounding the RBC (6, 9); (ii) a protein-rich RBC cytoskeletal submembrane becomes a physical barrier against NO diffusion (22, 23); or (iii) gas diffusion is retarded because of the viscous Hb solution in RBC (2). As chemists, it seems to us that these controversies are attributable to the complex and fragile structure of RBC and chemically unstable NO, which make it difficult to analyze the binding rate constant of NO to RBC.Hemoglobin-vesicles (HbVs) or liposome-encapsulated Hbs have been developed as transfusion alternatives. Their efficacy as O 2 carriers is comparable with that of RBC (24 -28). It has been thought that liposomes as a molecular assembly are a fragile capsule. However, appropriate lipid composition and polyethylene glycol modification on the surface of vesicles stabilize the dispersion state (29) and enable stopped-flow measure- * This work was supported in part by Health and Labor Sciences ResearchGrants (Research on Regulatory Science of Pharmaceuticals and Medical Devices), Ministry of Health, Labor, and Welfare, Japan (to H. S. and E. T.) and by Grants-in-Aid for Scientific Research from the Japan Society for the Promotion of Science B16300162 (to H. S.) and 18500368 (to S. T.), and Global COE "Practical Chemical Wisdom" (to S. T.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

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The possibility of hydrothermal treatment (HTT) of brown coal at 200−350 °C was examined as a pretreatment method for improving the space time yield of a Victorian brown coal liquefaction reactor. Main reactions occurring during HTT below 350 °C were decarboxylation and dehydration, by which most of carboxylic groups were decomposed. Sodium and chlorine in the brown coal were almost completely removed below 250 and 300 °C, respectively, during HTT. Around 20−30% of Ca and Mg in the brown coal was also removed by HTT below 350 °C. The viscosity of the coal−solvent slurry prepared from a HTT coal was less than 1 / 10 of the viscosity of the coal−solvent slurry prepared from a just dewatered coal. This enabled the increase of the coal concentration of the coal−solvent slurry from 28 to 40 wt %. The significant increase of the coal concentration of the coal−solvent slurry prepared from the HTT coal was found to be realized mainly by the decrease of the pore volume of the coal particles through HTT. These results suggest that HTT will be a pretreatment method effective not only to increase the space time yield but to suppress the scale formation of the brown coal liquefaction process.

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Scale deposition is a very troublesome problem for a long-term stable operation of a direct coal liquefaction plant. The scale reduction effect of hydrothermal treatment (HTT) for a brown coal liquefaction was investigated using a 0.1 ton/day process development unit (PDU). It was found that the amount of scale formed was reduced by half compared to non-treated coal when HTT coal treated at 325 °C was liquefied. This was because most carboxyl groups were decomposed and exchangeable cations, such as Ca and Na, precursors of the scale, such as CaCO 3 and NaCl, were reduced during HTT. Furthermore, the formation of scale comprising Fe 1−x S and SiO 2 was also suppressed by HTT probably because of a decrease in the amounts of NaCl and CaCO 3 . Liquefying the HTT coal slightly decreased the oil yield compared to the non-treated coal. However, this disadvantage is compensated by the increase in the space time yield of the reactors liquefying HTT coal, because the coal concentration of the HTT coal−solvent slurry fed to the reactors can be increased from 28 to 42 wt % as a result of the reduction of viscosity, as reported in an our previous paper. The concentrations of major scale precursors in the HTT coal−solvent slurry of 42 wt % coal concentration are lower than those in the non-treated coal−solvent slurry of 28 wt % coal concentration. These results indicate that HTT is an effective pretreatment method not only to realize a long-term stable operation but also to improve the oil productivity of the liquefaction plant.

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