1,720,979 research outputs found
Microcapillary flow method to investigate emulsion droplet deformability
No full textEmulsions are complex systems widely used in many relevant industrial applications, such as in the food, biomedical and petrochemical fields. They are metastable systems composed of oil, water and surfactants, and show complex structures at rest spanning different spatial scales and depending on composition and temperature. Although the phase behavior of emulsions at rest has been thoroughly investigated, the behavior of emulsions under flow still remains an open question. In particular, emulsion droplet deformation in microconfined conditions is a topic of relevant importance because of its applications in a wide range of processes, such as flow in porous media and transdermal drug delivery. In this work, a microfluidic device to investigate the effect of different oils as emulsion continuous phase on droplet deformability is presented by measuring in situ the interfacial tension of water in oil emulsions flowing in a microcapillary
Semen rheology and its relation to male infertility
No full textInfertility affects 15% of couples of reproductive age worldwide. In spite of many advances in understanding and treating male infertility, there is still a number of issues that need further investigation and translation to the clinic. Here, we review the current knowledge and practice concerning semen rheology and its relation with pathological states affecting male infertility. Although it is well recognized that altered rheological properties of semen can impair normal sperm movement in the female reproductive tract, routine semen analysis is mostly focused on number, motility and morphology of spermatozoa, and includes only an approximate, operator-dependent measure of semen viscosity. The latter is based on the possible formation of a liquid thread from a pipette where a semen sample has been aspirated, a method that is sensitive not only to viscosity but also to elongational properties and surface tension of semen. The formation of a liquid thread is usually associated with a gel-like consistency of the sample and changes in spermatozoa motility in such a complex medium are still to be fully elucidated. The aim of this review is to point out that a more quantitative and reliable characterization of semen rheology is in order to improve the current methods of semen analysis and to develop additional tools for the diagnosis and treatment of male infertility
Experimental investigation on foam formation through deformable porous media
No full textFoam formation in porous media is a topic of growing scientific and industrial interest due to its range of applications, from daily life consumer products to oil recovery. Despite the work done on foams flowing through complex structures, this field still needs to be fully elucidated. An additional complexity to the problem arises when the porous medium is deformable, a situation which has only been faced from a modeling point of view. To address this, the investigation of foam formation in deformable porous media was conducted using commercial sponges as a deformable porous media system, with special emphasis on the effect of confinement on foam bubble size distribution. Foam was formed by wetting the sponge with an aqueous surfactant solution and then squeezing the sponge either between two glass cover slides or between a plastic net and a cover slide. Results revealed that the latter system allowed the formation of drier foams (i.e., with lower liquid fraction, fL < 0.3), more similar to the ones obtained in dish-washing applications. Also, the effect of sponge type, in terms of material and microstructure, on final foam was considered
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
Microstructure evolution during nano-emulsification by NMR and microscopy
No full textHypothesis: Microstructure evolution in emulsions as a function of composition is of great interest but fundamentals have not yet been fully elucidated. Here, pulsed-field gradient (PFG)NMR diffusion measurements have been combined with confocal laser scanning microscopy (CLSM)to assess evolution of dynamics and microstructure during nano-emulsification. Experiments: Diffusion coefficients of emulsions made of water, mineral oil and surfactants (Span 20 and Tween 80)were measured as a function of water composition and compared with the morphological features of the emulsions obtained by CLSM. Findings: In the absence of water, two phases are visible from CLSM, and two diffusion components are observed with PFG NMR, a major fast component attributed to a continuous oil phase containing the more hydrophobic surfactant Span 20 with traces of Tween 80, and a minor slow component attributed to a dispersed phase of the more hydrophilic surfactant Tween 80 with traces of mineral oil and Span 20. At the inversion point (25 wt% water)the two-component diffusion behavior of the oil-rich phase is drastically reversed in terms of populations, with the slow diffusion process becoming dominant. This suggests a significant structuring of the oil-rich phase in the presence of surfactants enhanced by water, which can be explained by the formation of aggregates in the oil phase as reverse micelles or of a lamellar structure, and ties in well with the rheological measurements
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
Appropriate 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
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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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