Forces between Colloidal Particles in Aqueous Solutions Containing Monovalent and Multivalent Ions

The present article provides an overview of the recent progress in the direct force measurements between individual pairs of colloidal particles in aqueous salt solutions. Results obtained by two different techniques are being highlighted, namely with the atomic force microscope (AFM) and optical tweezers. One finds that the classical theory of Derjaguin, Landau, Verwey, and Overbeek (DLVO) represents an accurate description of the force profiles even in the presence of multivalent ions, typically down to distances of few nanometers. However, the corresponding Hamaker constants and diffuse layer potentials must be extracted from the force profiles. At low salt concentrations, double layer forces remain repulsive and may become long ranged. At short distances, additional short range non-DLVO interactions may become important. Such an interaction is particularly relevant in the presence of multivalent counterions.Comment: Submitted on 30th of May 2016 as invited article to Curr. Opinion Colloid Interf. Sci. Edited by W. Ducker and P. Claesson. 15 Pages, 7 Figures 82 reference

The Journey from Data to Qualitative Inductive Paper: Who Helps and How?

How do qualitative inductive researchers move from raw data to publishable paper? Existing scholarly resources focus on how to analyze data more deeply and write it up to make a compelling contribution. Much less discussed but also critical is how researchers enlist others in the journey from data to paper – even when they are single authors of their work. Our chapter uncovers qualitative researchers’ helpers and the types of help they provide. Drawing on data from detailed accounts of single authored qualitative, inductive studies, we explain the role of qualitative and quantitative scholars, peers and hired professionals, field informants and journal editors. We talk about help with theorizing, paper structure, emotional support, efficiency enhancement, and process guidance, and we offer practical tips for seeking these different forms of help throughout the research journey

Interactions between Silica Particles in the Presence of Multivalent Coions

Forces between charged silica particles in solutions of multivalent coions are measured with colloidal probe technique based on atomic force microscopy. The concentration of 1:z electrolytes is systematically varied to understand the behavior of electrostatic interactions and double-layer properties in these systems. Although the coions are multivalent the Derjaguin, Landau, Verwey, and Overbeek (DLVO) theory perfectly describes the measured force profiles. The diffuse-layer potentials and regulation properties are extracted from the forces profiles by using the DLVO theory. The dependencies of the diffuse-layer potential and regulation parameter shift to lower concentration with increasing coion valence when plotted as a function of concentration of 1:z salt. Interestingly, these profiles collapse to a master curve if plotted as a function of monovalent counterion concentration

Formation and relaxation kinetics of starch-particle complexes

© The Royal Society of Chemistry.The formation and relaxation kinetics of starch-particle complexes were investigated in this study. The combination of cationic nanoparticles in suspension and anionic starch in solution gave rise to aggregate formation which was studied by dynamic light scattering, revealing the initial adsorption of the starch molecules on the particle surface. By examining the stability ratio, W, it was found that even in the most destabilized state, i.e. at charge neutralization, the starch chains had induced steric stabilization to the system. At higher particle and starch concentrations relaxation of the aggregates could be seen, as monitored by a decrease in turbidity with time. This relaxation was evaluated by fitting the data to the Kohlrausch-Williams-Watts function. It was found that irrespective of the starch to particle charge ratio the relaxation time was similar. Moreover, a molecular weight dependence on the relaxation time was found, as well as a more pronounced initial aggregated state for the higher molecular weight starch. This initial aggregate state could be due to bridging flocculation. With time, as the starch chains have relaxed into a final conformation on the particle surface, bridging will be less important and is gradually replaced by patches that will cause patchwise flocculation. After an equilibration time no molecular weight dependence on aggregation could be seen, which confirms the patchwise flocculation mechanism

Introduction: Prisoners of the Asia-Pacific War – Forgotten Locales, Transimperial Links, and Selective Memorialisation

This introduction explores the major contributions of the special issue in broadening understanding of captivity in the Asian and Pacific theatres during the Second World War. First, it decentralises national narratives, highlighting the transnational and diasporic identities of both military and civilian prisoners and the colonial and decolonialising contexts that shaped their experiences. Second, it foregrounds specific memories of wartime captivity that have been marginalised by dominant war narratives and post-war decolonial struggles. Lastly, it underscores the diverse experiences, institutions, and memory practices of captivity, contributing to a more nuanced understanding of wartime captivity and its memorialization

Forces between Silica Particles in Isopropanol Solutions of 1:1 Electrolytes

Interactions between silica surfaces across isopropanol solutions are measured with colloidal probe technique based on atomic force microscope. In particular, the influence of 1:1 electrolytes on the interactions between silica particles is investigated. A plethora of different forces are found in these systems. Namely, van der Waals, double-layer, attractive non-DLVO, repulsive solvation, and damped oscillatory interactions are observed. The measured decay length of the double-layer repulsion is substantially larger than Debye lengths calculated from nominal salt concentrations. These deviations are caused by pronounced ion pairing in alcohol solutions. At separation below 10 nm, additional attractive and repulsive non-DLVO forces are observed. The former are possibly caused by charge heterogeneities induced by strong ion adsorption, whereas the latter originate from structuring of isopropanol molecules close to the surface. Finally, at increased concentrations the transition from monotonic to damped oscillatory interactions is uncovered

Remnants of Empire in the Cold War : How Post-War Repatriation to Japan Occasionally Kept Open the ‘Bamboo Curtain’

Globalization, Localization, and Japanese Studies in the Asia-Pacific Region : Past, Present, Future, シドニー大学, 2003年11月10日-13

Other "Hamlet" in Puppet Theatre: A Contribution to Central European Theatre Diversity of the 1980s-1990s

This study aims to address the stigmatization and reductionism of Central European culture by many scholars and to decentralize it. At the Crossing Borders with Shakespeare Since 1945 conference, the roundtable discussion raised questions about naming and defining “Central Europe” and revealed several discrepancies. However, the discussion lacked cultural, political, and historical context. To address this, the author examines a lesser-known artistic genre, puppet theatre, for answers and comparisons. Zlatko Bourek, a Croatian artist and director, offers a unique perspective on the theatre of the 1980s and serves as an example of the diversity and heterogeneity of Central European cultural expression. Bourek’s work draws from the tradition of Central European puppetry and explores connections between the Iron Curtain and Yugoslavia. His artistic style is exemplified in his adaptation of Tom Stoppard’s play Fifteen-Minute Hamlet, which masterfully condenses the entire plot of William Shakespeare’s Hamlet into a fifteen-minute performance. Bourek’s concept of combining Shakespearean tragedy with farce, presented through Japanese traditional Bunraku theatre, represents an important experiment of the 1980s. The use of syncretism and the aesthetics of ugliness are notable features of this experiment. It is a breakthrough in the perceived history of puppet theatre for adults and an aesthetic experiment in the era of Central European totalitarianism

A Simple Method to Determine Critical Coagulation Concentration from Electrophoretic Mobility

Critical coagulation concentration (CCC) is a key parameter of particle dispersions, since it provides the threshold limit of electrolyte concentrations, above which the dispersions are destabilized due to rapid particle aggregation. A computational method is proposed to predict CCC values using solely electrophoretic mobility data without the need to measure aggregation rates of the particles. The model relies on the DLVO theory; contributions from repulsive double-layer forces and attractive van der Waals forces are included. Comparison between the calculated and previously reported experimental CCC data for the same particles shows that the method performs well in the presence of mono and multivalent electrolytes provided DLVO interparticle forces are dominant. The method is validated for particles of various compositions, shapes, and sizes