Kazunari Ohgaki

Bio: Kazunari Ohgaki is an academic researcher from Osaka University. The author has contributed to research in topics: Hydrate & Clathrate hydrate. The author has an hindex of 33, co-authored 141 publications receiving 4344 citations. Previous affiliations of Kazunari Ohgaki include University of Ottawa & National Institute of Advanced Industrial Science and Technology.

Methane exploitation by carbon dioxide from gas hydrates - Phase equilibria for CO2-CH4 mixed hydrate system

Abstract: Natural-gas hydrate fields having a large amount of methane deposits have become the object of public attention as a potential natural-gas resource. An idea of methane exploitation in linkage with CO2 isolation has been presented elsewhere. In the present study, the isothermal phase equilibrium relations of pressure and compositions in the gas, liquid, and hydrate phases for the CO2-CH4 mixed hydrate system at 280 K are obtained in company with the apparent Henry constants for the methane-water system and the three-phase coexisting lines for the methane hydrate system. The averaged distribution coefficient of methane between gas phase and hydrate phase is about 2.5, that is, methane in the hydrate phase is replaced selectively by CO2. This is the first experimental evidence for the possibility of methane exploitation combined with CO2 isolation.

Isothermal Vapor-Liquid Equilibrium Data for Binary Systems Containing Carbon Dioxide at High Pressures: Methanol-Carbon Dioxide, n-Hexane-Carbon Dioxide, and Benzene-Carbon Dioxide Systems

Abstract: Isothermal vapor-liquid equilibrium data for the systems methanol-carbon dioxide, n-hexane-carbon dioxide, and benzene-carbon dioxide were measured by a static method at 25' and 4OoC. By use of the Lewis rule and the RedlichKwong equation of state for carbon dioxide in the vapor phase, the activity coefficients in the liquid phase and the fugacity coefficients in the vapor phase were evaluated from thermodynamic relationships. The isothermal vapor-liquid equilibria at high pressures for binary systems containing carbon dioxide were reported in previous papers, in which methanol-carbon dioxide and acetone-carbon dioxide systems were measured by a vapor recirculation method (3), and ethyl ether-carbon dioxide and methyl acetate-carbon dioxide systems by a static method In this study the vapor-liquid equilibria for three binary systems of methanol-carbon dioxide, n-hexane-carbon dioxide, and benzene-carbon dioxide were measured at 25' and 4OoC by the static method. The activity coefficients in the liquid phase and fugacity coefficients in the vapor phase were determined by using the Lewis rule and the Redlich-Kwong equation of state for carbon dioxide in the vapor phase. The liquid activity coefficients in the methanol-carbon dioxide system are the largest of the three systems, though those in n-hexane-carbon dioxide and benzene-carbon dioxide are also considerably large. Experimental

High-Pressure Phase Equilibrium and Raman Microprobe Spectroscopic Studies on the Methane Hydrate System

Abstract: The three-phase coexistence curve of methane hydrate + saturated water + saturated fluid CH4 was investigated in the temperature range from 305 to 321 K and pressure range from 98 to 500 MPa. The equilibrium curve increases monotonically on a T−p diagram at these experimental conditions. The Raman spectra of the C−H symmetric vibration mode in the methane hydrate split into two peaks, while a single peak is detected in the fluid CH4 and water phases. The split of the Raman peak indicates that two kinds of hydrate cages are occupied by the CH4 molecules. The peak intensity ratio of two types of CH4 molecules is almost independent of pressure in the range up to 500 MPa; that is, the cage occupancy ratio is constant. The Raman spectrum for the intermolecular vibration mode (O−O stretching) of the water molecules changes linearly with pressure from 207 to 228 cm-1, and the Raman shifts of the C−H vibration mode in the S-cage and in the water phase vary linearly with pressure from 2915 to 2919 cm-1 and from 29...

Strategies to Address Low Drug Solubility in Discovery and Development

Abstract: Drugs with low water solubility are predisposed to low and variable oral bioavailability and, therefore, to variability in clinical response. Despite significant efforts to "design in" acceptable developability properties (including aqueous solubility) during lead optimization, approximately 40% of currently marketed compounds and most current drug development candidates remain poorly water-soluble. The fact that so many drug candidates of this type are advanced into development and clinical assessment is testament to an increasingly sophisticated understanding of the approaches that can be taken to promote apparent solubility in the gastrointestinal tract and to support drug exposure after oral administration. Here we provide a detailed commentary on the major challenges to the progression of a poorly water-soluble lead or development candidate and review the approaches and strategies that can be taken to facilitate compound progression. In particular, we address the fundamental principles that underpin the use of strategies, including pH adjustment and salt-form selection, polymorphs, cocrystals, cosolvents, surfactants, cyclodextrins, particle size reduction, amorphous solid dispersions, and lipid-based formulations. In each case, the theoretical basis for utility is described along with a detailed review of recent advances in the field. The article provides an integrated and contemporary discussion of current approaches to solubility and dissolution enhancement but has been deliberately structured as a series of stand-alone sections to allow also directed access to a specific technology (e.g., solid dispersions, lipid-based formulations, or salt forms) where required.

Global Energy Assessment: Toward a Sustainable Future

Abstract: The Global Energy Assessment (GEA) brings together over 300 international researchers to provide an independent, scientifically based, integrated and policy-relevant analysis of current and emerging energy issues and options. It has been peer-reviewed anonymously by an additional 200 international experts. The GEA assesses the major global challenges for sustainable development and their linkages to energy; the technologies and resources available for providing energy services; future energy systems that address the major challenges; and the policies and other measures that are needed to realize transformational change toward sustainable energy futures. The GEA goes beyond existing studies on energy issues by presenting a comprehensive and integrated analysis of energy chalenges, opportunities and strategies, for developing, industrialized and emerging economies. This volume is a invaluable resource for energy specialists and technologists in all sectors (academia, industry and government) as well as policymakers, development economists and practitioners in international organizations and national governments.