2,566 research outputs found

    Mouse model of Schistosomiasis: infection with Schistosoma mansoni in CD-1 mice

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    Schistosomiasis is a parasitic disease that affects almost 240 million worldwide. CD1 mice were infected with cercariae of S. mansoni, after which infection developed for 8 weeks. Tissues were processed to immuno-histological techniques. It was performed H&E staining for overall analyses, Sirius Red for fibrosis and immunohistochemistry for inflammation biomarkers. The most infected organ was the liver, fibrosis decreased with egg development and Galectin-3 (Gal3) and Interleukin 6 (IL-6) were expressed inside granulomasThis work was also supported by FCT – Fundação para a CiĂȘncia e Tecnologia (REF UID/BIM/04293/2013) and by the project NORTE-01-0145-FEDER-000012 and by a scholarship to Carla LuĂ­s with the reference SAICT2016/FEDER/BIO4DIA/BTI under the supervision of Dr. RĂșben Fernandes.N/

    Two-Dimensional Bosonization from Variable Shifts in the Path Integral

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    A method to perform bosonization of a fermionic theory in (1+1) dimensions in a path integral framework is developed. The method relies exclusively on the path integral property of allowing variable shifts, and does not depend on the explicit form of Greens functions. Two examples, the Schwinger model and the massless Thirring model, are worked out.Comment: 4 page

    Workplace abuse and harassment: the vulnerability of informal and migrant domestic workers in Portugal

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    Policy makers and researchers are alarmed by the pervasive substandard working conditions and mistreatment in domestic work worldwide. Using an original dataset from a sample of domestic workers in Portugal (n=684), our study explores types of abuse and harassment and tries to unveil the potential factors affecting the likelihood of having been a victim. Empirical evidence pointed to three segments of domestic workers: victims of labour abuses related to contract and wages, victims of multiple abuses including mistreatment and also psychological and sexual harassment, and a segment with no occurrence of abuse. Informal workers are more often victims of labour abuses, while migrants, especially Brazilian women, are more likely to report all types of abuse and harassment. On the other hand, carers of the elderly often suffered multiple abuses. The results suggest that despite the prevalence of labour abuses in Portugal, the most severe abuses are uncommon.info:eu-repo/semantics/acceptedVersio

    Describe all or just a few? The influence of verbal descriptors on Likert-type variables on items’ and scales’ distribution

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    The aim of this study is to examine whether and how the use of verbal descriptors at all categories or just at the extremes of 5-point Likert-type items influences the results. Each participant was requested to mark his/her level of agreement with 18 items concerning beliefs on mathematics, using one of the following forms: with verbal descriptors at all categories or just at the extremes. Respondents were found to use more intensively the extreme categories when only these were verbally described. However, these differences were not significant when using summated scales, except in case of severe skewness.info:eu-repo/semantics/publishedVersio

    Performance of robust estimators: Sampling, variables and dimensions

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    The use of data collected from market research and opinion surveys is common in social and business areas. Probability samples are usually the first option for data collection though they are quite often excluded due to the non existence of a suitable sampling frame. In addition to the lack of randomness of sample data, further problems are caused by inadequate sample representativeness for some population characteristics, limitations of the measuring instrument and occurrence of measurement errors. In these situations, robust statistical techniques can be a valid option for estimation purposes as they are not sensitive to sample biases. The main aim of this study is to evaluate the performance of robust estimators, particularly Huber M-estimator, Tukey's biweight and Least Trimmed Squares (LTS) estimators, when compared to the sample mean and median, and applied to different types of variables, diverse sampling methods and dimensions. Quantitative and qualitative ordinal Likert type variables with 4, 6 and 10 point were used. Samples were generated by stratified and quota methods, both with dimensions 50, 100 and 300. Results show the best behavior of the Huber and the Tukey's biweight estimators in most situations, particularly for quantitative variables, for both sample methods. The LTS estimator performed worse than any other estimator, being better solely in the case of ordinal variables with a 4 point scale, sharp skewness and high kurtosis.info:eu-repo/semantics/publishedVersio

    PEGylated cationic liposome - DNA nanoparticle assembly in cell culture media: pathway effects and clues to enhanced control and transfection efficiency optimization

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    XII Spanish-Portuguese Conference on Controlled Drug DeliveryCationic Liposome – DNA nanoparticles constitute a promising approach for safe and efficient delivery of genes for therapeutic applications. In order to be used in vivo, these particles can be coated with an inert and hydrophilic polymer, such as polyethylene-glycol (PEG), which improves blood circulation time by providing steric stabilization against removal by the immune system. In this work we study the influence of the initial salt concentration, which controls the electrostatic atraction between cationic liposomes and anionic DNA, on the structure of PEGylated CL–DNA nanoparticles.info:eu-repo/semantics/publishedVersio

    Nanotechnology applied to medical biofilms control

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    Nanoscience and Nanotechnology (N&N) are new approaches to research phenomena at atomic, molecular and macromolecular scales, where properties differ significantly from those at a larger scale. This new approach can be applied to microbial biofilms, which are formed when bacterial and/or yeast cells adhere to abiotic and biotic surfaces. It is well known that microorganisms in biofilms have a different behaviour from their planktonic counterparts, demonstrating a general recalcitrance to medical therapy. Therefore, biofilm-associated infections on indwelling medical devices, such as catheters and prostheses, may persist even after suspension of antibiotic therapy and hence may require the removal of the device. In order to reduce patient`s morbidity and mortality, as well as high economical costs associated to medical biofilms, several attempts have been made to develop novel mechanisms of biofilm prevention and/or elimination. In this mini-review, the current knowledge on the features of biofilm formation and their relevance to medical device-associated infections are enclosed, as well as the new anti-biofilm approaches based on nanotechnology.The support by Portuguese Foundation for Science and Technology through the grants SFRH/BPD/47693/2008 and SFRH/BPD/20987/2004 is gratefully acknowledged

    Avaliação da resistĂȘncia Ă  ferrugem em progĂȘnies de cafeeiro F4 obtidas por cruzamentos de 'icatu' com catimor.

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    Com o objetivo de selecionar progĂȘnies de cafeeiro resistentes Ă  ferrugem foram instalados e conduzidos experimentos em TrĂȘs Pontas, SĂŁo SebastiĂŁo do ParaĂ­so e Machado. Foram avaliadas 17 progĂȘnies desenvolvidas pelo programa de Melhoramento GenĂ©tico do Cafeeiro em Minas Gerais, coordenado pela EPAMIG e obtidas pelo cruzamento ?Icatu? x Catimor, e a cultivar Rubi MG 1192 utilizada como testemunha. O delineamento foi o de blocos casualizados com trĂȘs repetiçÔes. Foram analisadas as caracterĂ­sticas incidĂȘncia da ferrugem no primeiro semestre de 2006.Os resultados obtidos permitem verificar que as progĂȘnies avaliadas apresentam variabilidade para a resistĂȘncia a ferrugem, isso Ă© confirmado pelas estimativas da herdabilidade que foram de boa magnitude, chegando atĂ© o valor de 92,8%. Essa condição aliada Ă  baixa incidĂȘncia da doença apresentada por algumas progĂȘnies, demonstrou que Ă© possĂ­vel selecionar progĂȘnies superiores em relação Ă  resistĂȘncia a ferrugem na população estudada

    Comparing the linear and non-linear principal component analysis over Likert-type items: An empirical study based on balanced bootstrap

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    The purpose of this study is to evaluate the similarity of results obtained with linear and nonlinear PCA over Likert-type items. As part of a wider project about students' perceptions of mathematics, this study analyses two dimensions: the usefulness of mathematics and the importance of understanding the concepts. Each dimension is theoretically structured by six items, three with a positive connotation and three with a negative connotation (adaptations of Fennema and Sherman, 1976 and Kloosterman and Stage, 1992). Each item is a statement that seeks to register the intensity of agreement on a 5-point scale. Four questionnaires were constructed: in the first two (A and B) the statements are evaluated by marking the response on a line segment (Visual Analogue Scale), labelled in the extreme and at the midpoint (A) or only at the extremes (B). In the third (C), Likert-type items with five labelled points are used (completely disagree, disagree, neither agree nor disagree, agree and totally agree), while in D only the extremes are labelled. This work concerns only questionnaires type C and D. Since the variables of this type are structurally ordinal variables (Gob et al, 2007), the use of a nonlinear principal components (e.g. CATPCA) is a possibility for its interdependency analysis. However, the use of linear techniques (PCA) has been widespread as a form of preferential treatment of such data. Do both techniques lead to similar results? If not, then the linearity of the treatment of such items can be questioned. Drawing on the data collected in the study mentioned, and using the balanced bootstrap as proposed in Linting et al (2007), several confidence intervals are built for the objects scores, either obtained through PCA or CATPCA, and for the correlation coefficient between paired dimensions. With these confidence intervals we expect to have a perception of the comparability of the linear and non-linear solutions.info:eu-repo/semantics/publishedVersio

    The effect of shape: Comparing different presentations of response

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    The aim of this field based work is to study in what measure different presentations of Likert-type items (including “continuous” options, i.e. marking the option on a straight line, with or without middle point and the use of all anchors vs extreme-only labels) induce different behaviours in items or scales distributions. In different areas of knowledge is necessary to know and explore indicators of attitude or motivation, in order to support the decision. To measure these non-measurable quantities, rating scales have been proposed, which intend to gather the “degree of affection” of an individual on a particular object or value. Several studies have evaluated and compared the behaviour of different rating scales. Some focus how to treat the items that compose the scales, others where the main goal is to analyse the scales' shape. As part of a wider project about perceptions of mathematics, four questionnaires were constructed: in the first two (A and B) the statements are evaluated by marking the response on a line segment (Visual Analogue Scale), labelled in the extreme and at the midpoint (A) or only at the extremes (B). In the third (C), Likert-type items with five labelled points are used (completely disagree, disagree, neither agree nor disagree, agree and totally agree), while in D only the extremes are labelled. We used theoretically-defined summated scales. The responses are compared at a scale level. The performance evaluation was made using location and shape measures, including robust variations.info:eu-repo/semantics/publishedVersio
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