ICT integration in mathematics initial teacher training and its impact on visualization: the case of GeoGebra

This case study investigates the impact of the integration of information and communications technology (ICT) in mathematics visualization skills and initial teacher education programmes. It reports on the influence GeoGebra dynamic software use has on promoting mathematical learning at secondary school and on its impact on teachers’ conceptions about teaching and learning mathematics. This paper describes how GeoGebra-based dynamic applets – designed and used in an exploratory manner – promote mathematical processes such as conjectures. It also refers to the changes prospective teachers experience regarding the relevance visual dynamic representations acquire in teaching mathematics. This study observes a shift in school routines when incorporating technology into the mathematics classroom. Visualization appears as a basic competence associated to key mathematical processes. Implications of an early integration of ICT in mathematics initial teacher training and its impact on developing technological pedagogical content knowledge (TPCK) are drawn.     

Hilbert inequality on grand function spaces

In this paper, we study the Hilbert inequality with conjugate exponents in the framework of fully measurable grand Lebesgue spaces and grand Bochner Lebesgue spaces.     

Space-time discontinuous Galerkin method for the solution of fluid-structure interaction

The paper is concerned with the application of the space-time discontinuous Galerkin method (STDGM) to the numerical solution of the interaction of a compressible flow and an elastic structure. The flow is described by the system of compressible Navier-Stokes equations written in the conservative form. They are coupled with the dynamic elasticity system of equations describing the deformation of the elastic body, induced by the aerodynamical force on the interface between the gas and the elastic structure. The domain occupied by the fluid depends on time. It is taken into account in the Navier-Stokes equations rewritten with the aid of the arbitrary Lagrangian-Eulerian (ALE) method. The resulting coupled system is discretized by the STDGM using piecewise polynomial approximations of the sought solution both in space and time. The developed method can be applied to the solution of the compressible flow for a wide range of Mach numbers and Reynolds numbers. For the simulation of elastic deformations two models are used: the linear elasticity model and the nonlinear neo-Hookean model. The main goal is to show the robustness and applicability of the method to the simulation of the air flow in a simplified model of human vocal tract and the flow induced vocal folds vibrations. It will also be shown that in this case the linear elasticity model is not adequate and it is necessary to apply the nonlinear model.     

Loss of collectivity in 79Rb

High-spin states in ⁷⁹Rb were populated in the reaction at E(beam) = 60 MeV. The lifetimes of the excited states of the positive-parity yrast band and of the negative-parity band in ⁷⁹Rb were measured by the Doppler Shift Attenuation Method. The deduced transition quadrupole moments Q_t are found to have a decreasing trend with rotational frequency for both the bands, consistent with those found experimentally in neighbouring nuclei. An erratum to this article is available at .     

The evaluation of variance component estimation software: generating benchmark problems by exact and approximate methods

The prediction of breeding values depends on the reliable estimation of variance components. This complex task leads to nonlinear minimization problems that have to be solved by numerical algorithms. In order to evaluate the reliability of these algorithms benchmark problems have to be constructed where the exact solution is a priori known. We develop techniques to construct such benchmark problems for mixed models including fixed and random effects, ANOVA, ML and REML predictors, balanced and unbalanced data for 1-way classification. Besides the construction of artificial data that produce the desired variance components we describe a projection method to construct benchmark data from simulated data. We discuss the cases where exact expressions for the projection can be given and where a numerical approximation procedure has to be used.     

Smectic polymorphism of 4-decyloxybenzylidene- 4′-alkyloxyanilines and their mixtures with polar standards of mesophases

This article describes liquid crystalline properties of the homologous series of 4-decyloxybenzylidene-4′-alkyloxyanilines. Based on the polarization microscopy (POM and TOA methods) and the calorimetric (DSC) measurements a rich polymorphism has been detected. Investigated compounds exhibit nematic, smectic A, smectic C, smectic B, smectic I and G (smectic G) mesophases with their characteristic configurations. The presence of these mesophases was confirmed by the miscibility method, using 4-heptyloxybenxylidene-4′-pentylaniline as a mesophase reference. Nine other smectic standards with different polarity have been applied in order to investigate their influence on the mesophase stability.     

Structure and stability of online chat networks built on emotion-carrying links

High-resolution data of online chats are studied as a physical system in the laboratory in order to quantify collective behavior of users. Our analysis reveals strong regularities characteristic of natural systems with additional features. In particular, we find self-organized dynamics with long-range correlations in user actions and persistent associations among users that have the properties of a social network. Furthermore, the evolution of the graph and its architecture with specific k$k$-core structure are shown to be related with the type and the emotion arousal of exchanged messages. Partitioning of the graph by deletion of the links which carry high arousal messages exhibits critical fluctuations at the percolation threshold.     

CyClick Chemistry for the Synthesis of Cyclic Peptides

Here, we report a novel “CyClick” strategy for the macrocyclization of peptides that works in an exclusively intramolecular fashion thereby precluding the formation of dimers and oligomers via intermolecular reactions. The CyClick chemistry is highly chemoselective for the N‐terminus of the peptide with a C‐terminal aldehyde. In this protocol, the peptide conformation internally directs activation of the backbone amide bond and thereby facilitates formation of a stable 4‐imidazolidinone‐fused cyclic peptide with high diastereoselectivity (>99 %). This method is tolerant to a variety of peptide aldehydes and has been applied for the synthesis of 12‐ to 23‐membered rings with varying amino acid compositions in one pot under mild reaction conditions. The reaction generated peptide macrocycles featuring a 4‐imidazolidinone in their scaffolds, which acts as an endocyclic control element that promotes intramolecular hydrogen bonding and leads to macrocycles with conformationally rigid turn structures.     

DNA Interaction with 17α‐Ethinylestradiol Studied Using Electrochemical Biosensors and Biosensing in Solution

The synthetic estrogen 17α‐ethinylestradiol (EE2) is an active component of oral contraceptives. It is considered as an endocrine disrupting compound that, once incorporated into an organism, affects the hormonal balance of animals and humans. In this study we characterized the DNA‐EE2 interaction using an electrochemical biosensor and biosensing in solution phase with the double stranded DNA from salmon sperm and deoxyguanosine monophosphate (dGMP). Differential pulse voltammetry method has been applied based on voltammetric anodic responses of the deoxyguanine (dGuo) and deoxyadenine (dAdo) as well as EE2 in the medium of phosphate buffer solution pH 7.0. Binding of EE2 to the nucleobases leads to a decrease of their anodic signals. Association constant for DNA‐EE2 interaction has been estimated to be about 1.1 ? 10³ L mol^?1 and 1.4 ? 10³ L mol^?1 for dGuo and dAdo responses, respectively. The association is reversible as indicated by decrease of the EE2 response in pure buffer solution due to leaching of EE2 from the surface attached DNA. The DNA‐EE2 association has been confirmed also by UV‐vis spectrometric experiments.     

Isosorbide‐based polysebacates as polymeric components for development of in situ forming implants

In situ forming implants (ISFIs) appear to be a convenient drug delivery system, alternative to conventional preformed implants and microparticles for parenteral drug delivery applications. It has been shown that they offer several advantages including easy and minimally invasive application, potential for local/site‐specific drug delivery that allows reduction of side effects associated with systemic administration of drug. A few ISFI formulations based on poly(α‐hydroxy acids), solidifying by solid phase separation, are currently commercially available. In this work, polyesters based on sebacic acid, isosorbide, and optionally 1,2‐propanediol were synthesized and characterized. Poly(isosorbide sebacate‐co‐1,2‐propylene sebacate) (PISEBPG) was chosen as an essential constituent of new ISFI formulations dedicated to controlled release of doxycycline hyclate (DOXY). Basic characteristics of new ISFI formulations were investigated. In particular, the influence of addition of a relatively hydrophobic cosolvent (triacetin, TA) to a more hydrophilic 1‐methyl‐2‐pyrrolidone (NMP) as well as the presence of calcium carbonate (CAC) on the morphology of resulted depots and DOXY release profile was evaluated. Scanning electron microscopy (SEM) analysis revealed that the presence of TA resulted in more porous morphology of the depots. DOXY has been releasing continuously from depots in vitro within 12 weeks depending on the composition. The release profile of the PISEBPG‐based formulation containing CAC indicates that it could be useful where short‐term (up to 14 d), rapid release of the antibiotic is required, while formulation without CAC, where after 21 days about 50% of the drug loaded may still be available for release, may be better for the long‐term delivery of DOXY.