Strongly Rickart objects in abelian categories: Applications to strongly regular and strongly Baer objects

We show how the theory of (dual) strongly relative Rickart objects may be employed in order to study strongly relative regular objects and (dual) strongly relative Baer objects in abelian categories. For each of them, we prove general properties, we analyze the behavior with respect to (co)products, and we study the transfer via functors. We also give applications to Grothendieck categories, (graded) module categories and comodule categories.     

Chemometric Assessment of the Interactions Between the Metal Contents,Antioxidant Activity,Total Phenolics,and Flavonoids in Mushrooms

The elemental composition and antioxidant activity have been obtained for regional mushrooms species, wild and cultivated, from Dambovita County, Romania. A multivariate approach and data mining techniques (principal component analysis and cluster analysis, respectively) were applied in order to evaluate the correlation matrix for these parameters for both caps and stipes of mushrooms. The associations between metallic elements (i.e., Fe, Cu, Cd, Pb, Co, Ni, Zn, Mn, Cr, Na, K, Ca and Mg) correlated with antioxidant activity, total phenolics, and total flavonoids were carried out by using a full factorial linear design. The multivariate functional analysis revealed on associated accumulation of several elements in mushrooms. In the cluster analysis, the dataset was treated to appreciate the correlation between metals group (e.g., heavy metals, such as Fe, Cu, Cd, Pb, Co, Ni, Zn, Mn, Cr, and important nutritional elements, such as Na, K, Ca, and Mg). Fungal species with similar characteristics in terms of metal accumulation formed two distinctive clusters. From a point of view of the consumer, the content of Cd and especially Pb in the fruiting bodies of the analyzed mushrooms species may be considered elevated, so that mapping the risk is compulsory. Applying the chemometric tools in the sense mentioned above, as well as in helping the scientific research by optimizing the number of data points, was shown to be extremely useful.     

Computing the Wedderburn decomposition of group algebras by the Brauer-Witt theorem

We present an alternative constructive proof of the Brauer-Witt theorem using the so-called strongly monomial characters that gives rise to an algorithm for computing the Wedderburn decomposition of semisimple group algebras of finite groups.

     

Learning study – promoting and hindering factors in mathematics teaching

This article focuses on presenting success factors for a group of teachers in carrying out a learning study in mathematics at their school. The research questions are: what are the actions of the school teaching community during development projects? What factors enable a group of teachers to carry out a learning study at their school? Activity theory provides a holistic framework to investigate relationships among the components present in a learning study. The results are based on analysis of interviews with teachers, students, principal organizers of schools and project coordinators, videotaped lessons, students’ tests and minutes taken at meetings of mathematics projects. The results show that the skills of facilitators, the time devoted to collaborative work, the link to learning theory and avoiding overly comprehensive content when teaching lessons are important promoting factors in mathematics teaching. The findings raise important questions about the way in which teacher work within universities.     

Strongly Rickart objects in abelian categories

We introduce and study (dual) strongly relative Rickart objects in abelian categories. We prove general properties, we analyze the behaviour with respect to (co)products, and we study the transfer via functors. We also give applications to Grothendieck categories, (graded) module categories and comodule categories. Our theory of (dual) strongly relative Rickart objects may be employed in order to study strongly relative regular objects and (dual) strongly relative Baer objects in abelian categories.     

Designing examples to create variation patterns in teaching

This paper uses a post-qualitative philosophical perspective to find new ways of understanding teaching and learning. The paper presents a series of examples that were used in a longitudinal study, with the aim of creating variation patterns that would make it possible for students to discern the use of the four basic arithmetic operations in different situations. The focus of this article is the potential of the examples to systematically create variation patterns that students need to perceive in order to make generalizations. The result demonstrates that well-thought-out examples help identify the correct arithmetic operation in different situations, and provide a basis from which students can discern the connection between text and the use of operation in mathematical example. The result also demonstrates that students develop rhizomatic thinking through the creation of new links between aspects of the object of learning, association and linking of different aspects to each other and the creation of a whole with unique and specific characteristics that cannot be explained by simply adding the characteristics of the individual parts.     

Stabilization of solid/liquid suspensions

The stability of colloidal graphite dispersions was investigated. A mixed stabilizer (CELAD) consisting of a non-ionic cellulose derivative and an anionic polymer was used to facilitate the grinding process and to stabilize the aqueous dispersions. Measurements of turbidity, ultramicroscopy and scanning electron microscopy were carried out to determine the size of the particles. Adherent films were obtained by spraying the dispersions onto glass plates. The 20 μm thick films had an electrical resistance within the 20–40 Ω cm range. They proved to be suitable for spray application onto the exernal glass cone of cathode ray tubes.     

Simple ranking method using reference profiles: incremental elicitation of the preference parameters

4OR - The Simple Ranking Method using Reference Profiles (or SRMP) is a Multi-Criteria Decision Aiding technique based on the outranking paradigm, which allows to rank decision alternatives...     

Effect of β-cyclodextrins based nanosponges on the solubility of lipophilic pharmacological active substances (repaglinide)

Cyclodextrin based nanosponges (CD-NS) are nanostructured cross-linked polymers, usually obtained by reacting cyclodextrin with a cross-linker such as carbonyldiimidazole, organic carbonates or (±) epichlorohydrin. They have been used to increase the solubility and stability of poorly soluble pharmacological active substances, as they combine the complex forming properties of CDs and properties of polymers (such as the high molecular weight). The affinity of CDs for certain lipophilic molecules is characteristic to the polymeric nano-structured system and allows the development of specific drug delivery systems. Knowing that cyclodextrin capacity to form inclusion complexes is maintained and enhanced when the CD molecules form aggregates, cross-link together or copolymerize with other compounds, we have synthesized cyclodextrin based nanosponges (from β-cyclodextrin and sulfobutylether-β-cyclodextrin). The complexing properties of the polymers were investigated against repaglinide (a hypoglycemic agent, practically insoluble in water). Solubility studies were performed according to the method reported by Higuchi and Connors and the phase solubility diagrams were plotted. The repaglinide-nanosponges complexes were prepared, lyophilized and the resulted inclusion complexes were characterized by FT-IR and NMR. The solubility profile and the loading capacity of the cyclodextrin based polymers were also determined.