Zeta Potential of Nanobubbles Generated by Ultrasonication in Aqueous Alkyl Polyglycoside Solutions.
A simple and convenient method to measure microelectrophoretic mobilities was proposed to determine the zeta potential of nanobubbles generated by ultrasonication. Bubbles in pure water solutions and in aqueous solutions of alkyl polyglycoside (AG) with different alkyl chain lengths and degrees of polymerization in the head group were sonicated with a palladium-coated electrode designed specially by the manufacturer. The zeta potentials of bubbles with ordinary cationic and ionic surfactants are consistent with others' previous results. The average size of the bubbles generated by sonication is in the range of 300 to 500 nm. The zeta potentials of bubbles in both pure water and AG solutions at all pH values are negative. As the chain length of AG increases, zeta potentials significantly decrease at high pH. For nonionic AG, a possible charging mechanism based on known mechanisms is suggested to explain the negative charge, known to be unusual. Even with a very high concentration of H(+) ions in solution the bubbles are charged negatively because the interface is covered with slightly acidic alcohol groups of AGs. At high pH, the less polar the surfactant, the more negative the charge, since nonpolar surfactant molecules induce the adsorption of OH(-) ions, rather than H(+) ions that prefer hydration by water molecules. Copyright 2000 Academic Press.
High resolution imaging of ultrafine bubbles in water by Atmospheric SEM-CL.
Various analytical methods such as high-resolution observation of ultrafine bubbles in water are required to clarify the mechanisms and interrelationships of various effects brought about by ultrafine bubbles. In this study, we used atmospheric scanning electron microscopy-cathodoluminescence (ASEM-CL) method for observing ultrafine bubbles in water. ASEM can observe samples in water, and the fine electron beam provides high spatial resolution. Furthermore, the gas in the bubble can be estimated from the CL emission spectrum. We have measured characteristics such as bubble size and particle number density. Also, the CL spectra has shown that the ultrafine bubbles contained nitrogen.
Code switching in Ahdaf Soueif's The Map of Love
This article examines the phenomenon of code switching in The Map of Love (1999) by the Egyptian—British writer Ahdaf Soueif. Though she chooses English as a medium for her creative expression, Soueif deploys Arabic in her narrative to represent different aspects of the linguistic and cultural norms of Egyptian society. The article's methodology is informed by Kachru's framework on contact literature and his categorization of the occurrence of literary code switching or bilingual creativity into different strategies that encompass cultural and linguistic processes. The results indicate the predominance in The Map of Love of the discourse strategies of employing lexical borrowing, culture-bound references and translational transfer. Finally, the article analyzes the functional motivation of code switching in the postcolonial context of the novel and how the use of certain creative strategies might enhance or diminish the narrative's effectiveness and readability.