1,720,995 research outputs found
Investigating the enthalpic properties of dicationic alkylammonium bromide gemini surfactants
No full textSurfactants reduce the surface tension of water. They appear in many places throughout our lives: in detergents, soaps, gels, creams and cosmetics we apply; in food; and in many prescriptions. Surfactants have substantial industrial applications as well. Thus, it is important to understand the chemical and physical properties of these molecules by utilizing various instrumental methods. In this study we investigate a series of Dicationic Alkylammonium Bromide Gemini Surfactants, on the order of 12-m-12 (where m = 2, 3, or 4). These Gemini surfactants contain two quaternary ammonium head groups and a dodecyl chain bonded to each head group. The linkage denoted as ‘m’ has been varied by 2, 3, or 4 methylene units. Using Isothermal Calorimetry, the thermodynamics of micelle formation and the critical micelle concentration were determined. By conducting these experiments at various temperatures, we have been able to determine the change in heat capacity for micelle formation
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Copper phenanthroline complexes in a new era: Utilizing “green” chemistry in the synthesis of cu-phen coordination complexes
No full textThe purpose of this research was to expand on the knowledge of a well know organometallic system: copper phenanthroline complexes. Copper phenanthroline complexes have been widely studied and are currently being investigated for uses in catalysis, medicine, and solar energy applications. It was the goal of this research to synthesize well known useful complexes using new solventless synthesis methodology as well as to create new materials to study for potential application in these fields. This thesis includes 134 figures, 64 tables, and is 189 pages long. Eight compound have been synthesized and characterized through techniques such as X-ray crystallography, elemental analysis, thermogravimetric analysis, melting point, 1H-NMR, Fourier transform infrared spectroscopy (FTIR), electronic absorption spectroscopy, diffuse reflectance spectroscopy, and photoluminescence spectroscopy. Analysis of the results are discussed and conclusions about potential applications are made
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Oil Remediation Using 12-n-12 Gemini Surfactant in Sand
No full textAn estimated 706 million gallons of oil are lost to the environment per year, the impacts are widespread from water pollution, loss of habitats, and shoreline erosion. While there are many oil remediation (OR) techniques, our focus lies in physical-chemical remediation. Gemini surfactants (GS) are a promising use in OR techniques due to the low toxicity to the environment and high efficiency. With the use of 12-n-12 (where n=2,3,4,5,6) GS, we are exploring its potential in OR due to its ability to form micelles at extremely low concentrations, known as the critical micelle concentration (cmc). To evaluate its efficacy as an OR technique, we contaminated sand with common motor oil and added varying concentrations of the GS solution to attempt to remove the motor oil from the silica sand. The results of our experiment will be analyzed by various spectroscopic and non-spectroscopic techniques. (Faculty Sponsor: Dr. Richard Sheardy) Supported by Robert A. Welch Foundation M-0200, NSF Award 195344
Understanding the Interaction Between DNA Quadruplex and Gemini Surfactants
No full textCreative Arts and Research SymposiumCreative Arts and Research SymposiumThe physical properties of the DNA quadruplex formed from (TTAGGG)4 in K+ solutions
as well as the micelles formed from the Gemini surfactants with the composition
RR’2N+(CH2)nN+RR’2 2Br, where R is -(CH2)11CH3, R’ is -CH3, and n=2, 3 or 4, have been
studied. The interactions between the quadruplex and surfactant at different
concentrations of surfactant was investigated through CD and UV/Vis techniques. Data
showed that at concentrations greater than the cmc, all DNA precipitated out of the
solution. At a concentration lower than cmc, some DNA precipitated out and the rest in
the solution assumed the quadruplex conformation. Evident data showed that the
formation of precipitate formed by the quadruplex and 12-4-12 surfactant is dependent
on the concentration of the DNA, the concentration of surfactant, the ratio between the
two, and the concentration of K+.Chemistry & Biochemistr
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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