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Mandelik Asit ve Propan-1,2,3-Trikarboksilik Asitin Kalsiyum Oksalat Monohidrat Kristalizasyonuna Etkisi
No full textThe effects of mandelic and propane-1,2,3-tricarboxylic acids as additives on calcium oxalate monohydrate (COM) crystals were investi-gated in this study. The physicochemical properties of the COM crystals prepared with and without these additives were characterized us-ing X-ray powder diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and zeta po-tential analysis. The XRD and SEM results showed that the crystals prepared in pure medium were monohydrates and consisted primarily of hexagonal crystals, respectively. The additives mandelic acid and propane-1,2,3-tricarboxylic acid in the crystallization media signifi-cantly changed the size and morphology of the COM crystals, the effects of which were more pronounced with higher concentrations of the additives. The results of FTIR suggested that both carboxylic acids were adsorbed onto the surface of the COM crystals. The zeta po-tential analysis showed a negative charge on the surface of the COM crystals in the mandelic acid medium, while the surface became more positive in the medium containing increasing concentrations of propane-1,2,3-tricarboxylic acid. In addition, an analysis was conducted to evaluate the thermal characteristics of the COM crystals prepared with and without the additives. The data obtained were used to calculate the kinetic parameters, such as the activation energy and pre-exponential factor, using the Coats-Redfern method. The calculated activation energies for stages I, II, and III in pure medium were 98.76, 270.69, 258.55 kJ/mol, respectively, which were lower than that of COM crys-tals prepared in the two media containing the additives
Box–Behnken experimental design for zinc borate Zn2_x000D_ B6_x000D_ O11·7H2_x000D_ O
No full textThe present study investigated the effect of the operating conditions on thecrystallization of zinc borate. For zinc borate crystallization, sodium tetraboratedecahydrate and zinc sulfate heptahydrate were used as reactants. In thefirst part of the study, the crystals were characterized by X-ray diffractionspectroscopy (XRD), Fourier-transform infrared spectroscopy (FTIR), lightmicroscopy, and particle size and thermogravimetric analysis. The resultsshow that the obtained crystals were in the form of Zn2B6O11·7H2O, and theoperating conditions had a significant effect on the size, morphology, andfiltration characteristics of the zinc borate crystals. In the second part ofthe study, Box–Behnken design (BBD) with response surface methodology(RSM) was employed to determine the optimal operating conditions for zincborate crystallization. The effects of stirring rate, temperature, and reactantfeed rate on the average particle size were investigated. The results show thatthe data sufficiently fit the second-order polynomial model. The crystallizationconditions, including stirring rate, temperature, and reactant feed rate, werestudied at 400–500 rpm, 45–85 ºC, and 300–900 mL/h, respectively. Theminimum particle size (3.3 µm) was obtained at a stirring rate of 450 rpm, atemperature of 85 ºC, and a reactant feed rate of 300 mL/h
Effects of polyelectrolytes on the hardness of borax decahydrate crystals
No full textThe hardness of borax decahydrate crystals was measured using cationicpolyelectrolytes of FO4115, FO4400 and FO4990 with anionic polyelectrolytesof AN923, AN930 and AN999 as an additive. The measurements were carriedout in the indentation load range of 10 g to 30 g. It was determined that theVickers hardness (HV) decreased with increasing applied load, showing thatthe borax decahydrate crystals exhibited an indentation size effect. Vickersmicrohardness measurements revealed that pure borax decahydrate crystals hada brittle structure, yet the crystals obtained in additive media were categorizedas a soft material. The proportional specimen resistance model was applied todetermine the load-independent microhardness. The crystal hardness of boraxdecahydrate was found to change depending on the type and concentration ofpolyelectrolyte used. In addition to the mechanical properties, the thermal andphysical characteristics of borax decahydrate crystals were investigated bythermogravimetric and Fourier transform infrared spectroscopy analysis. Thecharacterization results confirmed that the polyelectrolytes were adsorbed on thecrystal’s surface
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Ultrasonic Irradiation during the Calcium Sulfate Hemihydrate to Dihydrate Transformation Process
No full textIn Vitro Study on the Influence of Proline on Struvite Crystals
Get PDFThis study investigated the effect of amino acid proline, as crystal modifier, on the struvite crystallization in vitro conditions. The struvite crystals were evaluated experimentally through XRD, SEM, and FTIR to determine the structure, morphology, and chemical composition, respectively. XRD analysis pointed out that struvite crystals belonged to the orthorhombic Pmn21 space group. SEM analysis depicted that proline had a significant influence on the morphology as well as the particle size of the struvite. Moreover, the length and width of struvite crystals varied with different concentrations of proline. The length of struvite crystals decreased, and their width thickened in the presence of the crystal modifier. The negativity of the zeta potential value became less negative in the presence of proline and the values were determined to be –6.10 mV and -4.00 mV for 25 and 100 ppm, respectively. According to BET analysis results, the surface area of the struvite decreased in the proline media when compared with the crystals formed without the crystal modifier. In addition, the thermal degradation of the formed crystals was examined. Regarding the results of the thermodynamic analysis, the average ∆H , ∆G , and ∆S were 92.17 kJ/mol, 197.85 kJ/mol, and −254.63 J/mol K, respectively. As a result, this study could provide a potential crystal modifier for the inhibition of struvite stones
Variations on the Author
Get PDF“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
Effects of tricarballylic acid on phase transformation of calcium sulfate hemihydrate to the dihydrate form
No full textAppropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe 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
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