Surface forces generated by the action of electric fields across liquid films

We explore the force generation and surface interactions arising when electric fields are applied across fluid films. Using a surface force balance (SFB) we measure directly the force between two electrodes in crossed-cylinder geometry across dielectric and electrolytic fluids. In the case of dielectric films the field between the electrodes exerts a force which can be well explained using classic expressions and with no fitting parameters. However when the electrodes are separated by a film of electrolyte, an alternating electric field induces a force which diverges substantially from the calculated static response of the electrolyte. The magnitude of the force is larger than predicted, and the interaction can switch from attractive to repulsive. Furthermore, the approach to steady state in electrolyte takes place over $10^2$ -- $10^3$~s which is very slow compared to both the charging and viscous timescales of the system. The non-trivial electrolyte response in AC electric fields, measured here directly, is likely to underlie several recent reports of unexpected and bifurcating forces driving colloids in AC fields. Our measurements suggest ways to control colloidal and soft matter using electric fields, as well as providing a direct measure of the length- and time-scales relevant in AC electrochemical and electrokinetic systems

The Three Rs: Reclaim, Reuse . . . Really

The Three Rs: Reclaim, Reuse . . . Really Concept. Reusing textiles has practiced because of their value and/or scarcity. Today the motivation is for waste reduction. This project reclaimed/reused textile products that would have been discarded. Thread and muslin reclaimed from flour sacks were repurposed into a jacket. Aesthetic Properties and Visual Impact. Contrasting-color labels were harvested and treated like patches. Visual repetition of shape and colors achieved unity. Process, Techniques, and Execution. Sacks were deconstructed; these rectangles were topstitched into bands. The jacket was connected using topstitching. The jacket’s canvas base was adorned with the vertical flour-sack bands emulating suspenders. The convertible collar, comprised of two sacks, is faced with muslin. Cohesion. New textiles commensurate in colors and textures were combined with the reclaimed. Together they were redefined. Design Contribution. This design illustrate true recycling by reclaiming then reusing textile entities that would otherwise have been discarded

I Heart Africa

It was the intent of this designer to contribute to the field by delving into a unique, hands-on encounter with artisan yardage. The textile was acquired in Accra, Ghana, by the client who requested an ensemble appropriate for international business occasions. She described her experiences in Ghana as inspirational. The designer purposed to create an ensemble appropriate for business events reflecting the client\u27s experiences in Africa

Scaling analysis of the screening length in concentrated electrolytes

The interaction between charged objects in an electrolyte solution is a fundamental question in soft matter physics. It is well-known that the electrostatic contribution to the interaction energy decays exponentially with object separation. Recent measurements reveal that, contrary to the conventional wisdom given by classic Poisson-Boltzmann theory, the decay length increases with ion concentration for concentrated electrolytes and can be an order of magnitude larger than the ion diameter in ionic liquids. We derive a simple scaling theory that explains this anomalous dependence of the decay length on ion concentration. Our theory successfully collapses the decay lengths of a wide class of salts onto a single curve. A novel prediction of our theory is that the decay length increases linearly with the Bjerrum length, which we experimentally verify by surface force measurements. Moreover, we quantitatively relate the measured decay length to classic measurements of the activity coefficient in concentrated electrolytes, thus showing that the measured decay length is indeed a bulk property of the concentrated electrolyte as well as contributing a mechanistic insight into empirical activity coefficients.Comment: To appear in Physical Review Letter

Modified glass ionomer and orthodontic band: An interim alternative for the treatment of molar incisor hypomineralization. A case report

Introduction: Molar incisor hypomineralization (MIH) is a developmental condition resulting in defects in the enamel characterized by demarcated opacities mainly affecting first permanent molars and occasionally permanent incisors in 1 of every 6 children worldwide. Affected molars have greater susceptibility to post eruptive breakdown, extensive caries and, in severe cases, are difficult to restore. When the MIH-affected molar presents severe crown destruction, it is necessary to perform an intermediate restoration to preserve the remaining dental structure in order to maintain occlusion, proper hygiene and periodontal health. The case of an 11-year-old patient with severe MIH is reported. The patient had extensive crown destruction by caries in tooth 1.6 without clinical or radiographic signs of pulp pathology. After an initial preventive intervention, enamel without dentin support and carious dentin were removed from tooth 1.6. Subsequently, crown restoration was performed with resin modified glass ionomer, followed by the cementation of an orthodontic band. After 18 months of follow-up, the patient reported no pain or discomfort. The restoration was preserved intact, maintaining occlusal functionality, pulp and gingival health. Conclusion: The interim treatment, cementing an orthodontic band over a tooth restored with glass ionomer seems to favor retention and compressive strength, keeping the MIH-affected molar asymptomatic for at least 18 months. Further studies evaluating this treatment option in similar clinical situations are recommended

The role of emotions and conflicting online reviews on consumers' purchase intentions

Drawing on dual-process theories, this paper explains how the systematic and heuristic information processing of online reviews with conflicting information can influence consumers' purchase decision making. The study adopts major assumptions of complexity and configuration theory in employing fuzzy-set qualitative comparative analysis on 680 TripAdvisor users to test the complex interrelationships between emotions and the systematic and heuristic cues used in processing reviews. The results show that the systematic and heuristic processing of online reviews can produce independent impacts on consumer decision making. Both processing routes can interact with each other to affect the domination of one route over the other. In the case of a positive–negative sequence, consumers mainly follow a heuristic processing route. In the reverse sequence, consumers' concerns about the credibility of the reviews leads them to think more deeply (systematic processing) and actively evaluate both the argumentation quality and the helpfulness of the online reviews

Do the unemployed hit the bottle during economic downturns? An empirical approach for Spain

Background: This paper analyses the 2008 economic collapse in Spain with its long-lasting effects. Precisely, the ones associated with lifestyles. Thus, the aim of this paper is to examine to what extent economic downturns affect individual’s drinking behavior when focusing on unemployed people. Methods: We use discrete-choice models and matching techniques. Data from the National Health Survey for 2006 and 2011–2012 provides a clear picture before and after the 2008 breakdown in Spain. Results: We find that drinking over the business cycle is a function of individual socio-demographic status. Besides, our empirical findings are consistent with the idea that following the crisis differences between unemployed and non-unemployed fell to at least in accordance with a lower overall consumption of alcoholic beverages. Conclusions: Public policy design for drinkers would require both prevention and recovery from alcohol use strategies to be met towards health and labour pillars.Ministerio de Educación | Ref. FPU AP-2012- 0415

Characterization of ionic liquid ion sources for focused ion beam applications

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2013.This thesis was scanned as part of an electronic thesis pilot project.Cataloged from PDF version of thesis.Includes bibliographical references (p. 79-82).In the Focused Ion Beam (FIB) technique, a beam of ions is reduced to nanometer dimensions using dedicated optics and directed to a substrate for patterning. This technique is widely used in micro- and nanofabrication for etching, material deposition, microscopy, and chemical surface analysis. Traditionally, ions from metals or noble gases have been used for FIB, but it may be possible to diversify FIB applications by using ionic liquids. In this work, we characterize properties of an ionic liquid ion source (ILIS) relevant for FIB and recommend strategies for FIB implementation. To install ILIS in FIB, it is necessary to demonstrate single beam emission, free of neutral particles. Beams from ILIS contain a fraction of neutral particles, which could be detrimental for FIB as they are not manipulated by ion optics and could lead to undesired sample modification. We estimate the neutral particle fraction in the beam via retarding potential analysis, and use a beam visualization tool to determine that most of the neutral population is located at the center of the beam; the neutral population might then be eliminated using filtering. The same instrument is used to determine the transition of the source from single to multiple beam emission as the extraction voltage is increased. These studies should guide in the design of the optical columns for an ILIS-based FIB.by Carla S. Perez Martinez.S.M

Aprendizagem baseada em equipes em aulas de Química orgânica no ensino superior.

Acreditando na eficiência de métodos de ensino que tornam os alunos ativos e protagonistas de seu próprio aprendizado, o principal objetivo desse trabalho foi avaliar, pela perspectiva do estudante, como uma associação entre métodos tradicionais de ensino e a metodologia ativa “Aprendizagem Baseada em Equipes” (ABE) impacta nesse estágio. Essa metodologia é previamente dependente do preparo individual de cada aluno e, após a constatação desse preparo por um primeiro teste, ocorreu formação de equipes, que deveriam aplicar os conceitos aprendidos na resolução de problemas. Após discussões e resoluções, esses receberam respostas imediatas através de gabaritos do tipo raspadinha. Quando os estudantes (Cursos de bacharelado e licenciatura em Química da Universidade Estadual de Londrina, turmas  das disciplinas de Química Orgânica II (2o ano), III e Análise Orgânica (4o ano) foram convidados a responder a um questionário de avaliação do método, observou-se impressões positivas dos alunos quanto à extensão do aprendizado e conteúdo abordado, sendo que a maioria (97,2%) concordou com a afirmação de que “a atividade ABE é uma boa ferramenta didática para auxiliar o aprendizado”. Ainda, 79,4% dos alunos acreditaram que o método ajudou na preparação para a prova, constituindo-se ferramenta importante para o preparo individual. Ao responderem de forma aberta sobre o que mais gostaram no método, muitos deles reafirmaram essa melhora na aprendizagem e no preparo para a prova.  De maneira divertida, portanto, buscou-se expandir o conhecimento adquirido nas aulas expositivas dialogadas, com a metodologia, além de aprimorar as habilidades de trabalho e tomadas de decisões em equipe