1,721,153 research outputs found
Experimental study and computer modeling of hydration-related behavior of L-tyrosine-derived polyarylates
No full textWater uptake influences many properties of polymers and has been widely studied. In the context of polymeric biomaterials, several recent publications reported an unusual high variability of analytical results of water uptake. In the current investigation, two possible causes for the high variability of water uptake data are studied: (1) variations in the initial molecular weight of the polymer samples and (2) variations in the processing conditions used during sample preparation. Using model polymers from the combinatorial library of L-tyrosine-derived polyarylates, it was shown that the water uptake variability could be reduced significantly by annealing the film specimens after pressing. With the introduction of an annealing step, accurate and reproducible results (relative SD < 11 %) could be obtained using a 3H-radiolabeled water method that enables parallel measurements required for the efficient screening of multiple polymer samples.
Water uptake from a subset of 23 polymers from this library could not be predicted using a single parameter such as glass transition temperature or hydrophobicity. Thus, a semi-empirical model using artificial neural networks was developed to predict with high accuracy (Pearson coefficient > 0.6) the water uptake, represented by the Weibull equation. Accurate predictions (within experimental error) of water uptake were obtained for 10 of the 18 polymers used in this study, with only one polymer for which predictions were very inaccurate. The model was evaluated in an external polymer set and showed high accuracy. A semi-empirical model was also obtained for degradation kinetic parameters, with accurate predictions (Pearson coefficient = 0.7) for the kinetic coefficient of the first order model, suggesting a first order mechanism.
Predictions of water uptake and degradation kinetics were obtained for the rest of the library. These predictions may be used to select a group of polymers that satisfy certain design criteria, and eventually find a lead polymer for a specific medical application. However, modeling does not eliminate the need to run experiments, it only reduces the space of polymers that should be tested to find that lead polymer.Ph.D.Includes bibliographical references (p. 139-158)by Loreto M. Valenzuel
Valori e stili d’insegnamento nelle scuole primarie. Uno studio sulle auto-percezioni degli insegnanti
No full textIl contributo vuole essere una proposta concettuale che si inserisce nel dibattito sulla valutazione dei docenti e vuole fornire un contributo alla spiegazione delle variabili che incidono e caratterizzano l’insegnamento dei docenti della scuola primaria. L’apporto dello studio contribuisce al dibattito internazionale legato al tema e agli strumenti utilizzati, riporta l’interesse sui Valori come dimensione psicologica che caratterizza gli stili di insegnamento e le competenze auto-valutate dagli insegnanti. L’utilizzo della scala spagnola, Escala de Evaluación de la Competencia Autopercibida del Docente de Educación Primaria (ECAD-EP), congiuntamente alla Scala di Schwartz PVQ (Portrait Values Questionnaire) ha coinvolto un campione 203 docenti di scuola elementare. Da quanto è emerso, si può dire che i valori che principalmente incidono sullo sviluppo di tali capacità e comportamenti professionali, sono: tradizione, universalismo, autodirezione e benevolenza. I primi due influiscono in modo maggiormente significativo e su un più elevato numero di competenze, mentre gli ultimi due possiedono delle influenze più specifiche e mirate. Studi futuri mostreranno il ruolo delle variabili socio-demografiche influenti negli stili di insegnamento, contribuendo alla letteratura internazionale sul tema.This contribution is aimed to be a conceptual proposal within the discussion on the teachers’ assessment and also intends to make a contribution in the explanation of the variables affecting and characterizing the primary school teachers’ teaching styles. The study fits within the international debate on this topic and more in specific on the tools used for the assessment, and returns the interest on Values as psychological dimension characterizing the teaching styles and the teachers’ self-assessed skills. The use of the spanish scale ‘Escala de Evaluación de la Competencia Autopercibida del Docente de Educación Primaria’ (ECAD-EP), together with the Schwartz PVQ scale (Portrait Values Questionnaire) involved a sample of 203 primary school teachers. According to the results, the values whom primarily affect the development of these skills and professional behaviors are: tradition, universalism, benevolence and self-direction. The first two affect more significantly and on a higher number skills, while the rest have more specific and targeted influences. Further studies will show in depth the socio-demographic variables impact on the teaching styles, contributing to the international literature about these issues
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
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
Predictors of female business conduct
No full textLa capacidad empresarial, se refiere al reconocimiento de oportunidades de realizar algo nuevo de parte de quien, trabajando en una organización, individua y organiza los recursos humanos y económicos con la finalidad de alcanzar los objetivos de la organización misma.
La investigación intenta analizar la opinión que la población básica sobre algunos constructos Importantes onstructos de predicción de conductas empresariales; locus de control interno, la autoeficacia, la proactividad, (el employability), (el engagement).
El instrumento de investigación es un cuestionario de auto-evaluación (COEM J. C. Sánchez, 2006) caracterizado por 14 secciones, que investigan sectores específicos de la conducta empresarial.
La población básica está formada por 100 trabajadoras en varias empresas de sexo femenino (Roma - Italia), entre 29 y 62 años.
La ultima fase de la investigación ha sido la construcción de una población básica de control y a partir de los resultados no emergen diferencias significativas entre los dos grupos.The entrepreneurial capability is the acknowledgement of the opportunities to do something new from someone who, while working in an organization, individuates and organizes the economic and human resources in order to reach the organization’s goals The research intends to analyze the opinion that the basic population has regarding some constructs referred to the entrepreneurial capability, which are important entrepreneurial conduct prediction constructs (The internal control locus, the auto efficiency, the proactivity, the employability and the engagement). The investigation instrument is a questionnaire of self-evaluation (COEM J. C. Sanchez, 2006). Which is composed by 14 sections that investigate on specific sectors, of business conduct. The basic population consists of 100 female workers on diverse feminine companies (Rome - Italy) between 29 and 62 years old.
The last stage of the research has consisted in the construction of a basic control population.
According with the results, there are no significant differences between both groups
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