Future teachers’ competence to plan a lesson: first results of a six-country study on the efficiency of teacher education

The study "Mathematics Teaching in the 21st Century (MT21)" focuses beyond others on the measurement of teachers’ general pedagogical knowledge (GPK). GPK is regarded as a latent construct embedded in a larger theory of teachers’ professional competence. It is laid out how GPK was defined and operationalized. As part of an international comparison GPK was measured with several complex vignettes. In the present paper, the results of future mathematics teachers’ knowledge from four countries (Germany, South Korea, Taiwan, and the US) with very different teacher-education systems are presented. Significant and relevant differences between the four countries as well as between future teachers at the beginning and at the end of teacher education were found. The results are discussed with reference to cultural discourses about teacher education.     

Dividing a complex reaction involving a hypervalent iodine reagent into three limiting mechanisms by ab initio molecular dynamics

The electrophilic N‐trifluoromethylation of MeCN with a hypervalent iodine reagent to form a nitrilium ion, that is rapidly trapped by an azole nucleophile, is thought to occur via reductive elimination (RE). A recent study showed that, depending on the solvent representation, the S_N2 is favoured to a different extent over the RE. However, there is a discriminative solvent effect present, which calls for a statistical mechanics approach to fully account for the entropic contributions. In this study, we perform metadynamic simulations for two trifluoromethylation reactions (with N‐ and S‐nucleophiles), showing that the RE mechanism is always favoured in MeCN solution. These computations also indicate that a radical mechanism (single electron transfer) may play an important role. The computational protocol based on accelerated molecular dynamics for the exploration of the free energy surface is transferable and will be applied to similar reactions to investigate other electrophiles on the reagent. Based on the activation parameters determined, this approach also gives insight into the mechanistic details of the trifluoromethylation and shows that these commonly known mechanisms mark the limits within which the reaction proceeds. © 2015 Wiley Periodicals, Inc.     

High-order finite elements in numerical electromagnetism: degrees of freedom and generators in duality

Explicit generators for high-order (r>1) scalar and vector finite element spaces generally used in numerical electromagnetism are presented and classical degrees of freedom, the so-called moments, revisited. Properties of these generators on simplicial meshes are investigated, and a general technique to restore duality between moments and generators is proposed. Algebraic and exponential optimal h- and r-error rates are numerically validated for high-order edge elements on the problem of Maxwell’s eigenvalues in a square domain.     

Synthesis, characterisation and cytotoxicity of polyoxometalate/carboxymethyl chitosan nanocomposites

Chitosan and its derivates continue to attract considerable research interest as effective drug carriers with good biocompatibility and high cellular uptake rates. We used these versatile features to tap the considerable biomedical potential of polyoxometalates (POMs) through their encapsulation into a carboxymethyl chitosan (CMC) matrix. The nanocapsules were prepared by ionic gelification with Ca(2+); their size distribution ranges from 60 to 150 nm. Because [Co(4)(H(2)O)(2)(PW(9)O(34))(2)](10-) is well known for its manifold properties, such as antiviral activity, it was selected as a model POM. The resulting composites were characterised with a wide range of analytical methods, which pointed to quantitative encapsulation of intact POMs within the CMC matrix. We studied the biocompatibility of the POM/CMC nanocomposites on HeLa cells through MTT and proliferation assays. Even after prolonged incubation times at high concentrations, the composites did not display cytotoxicity, thereby drastically reducing the side effects of the pristine POMs. This opens up new avenues for designing novel inorganic drug prototypes from bioactive POMs.     

Efficient organic monoliths prepared by γ-radiation induced polymerization in the evaluation of histone deacetylase inhibitors by capillary(nano)-high performance liquid chromatography and ion trap mass spectrometry

New monolithic HPLC columns were prepared by γ-radiation-triggered polymerization of hexyl methacrylate and ethylene glycol dimethacrylate monomers in the presence of porogenic solvents. Polymerization was carried out directly within capillary (250-200 μm I.D.) and nano (100-75 μm I.D.) fused-silica tubes yielding highly efficient columns for cap(nano)-LC applications. The columns were applied in the complete separation of core (H2A, H2B, H3, and H4) and linker (H1) histones under gradient elution with UV and/or electrospray ionization (ESI) ion trap mass spectrometry (MS) detections. Large selectivity towards H1, H2A-1, H2A-2, H2B, H3-1, H3-2 and H4 histones and complete separation were obtained within 8 min time windows, using fast gradients and very high linear flow velocities, up to 11 mm/s for high throughput applications. The method developed was the basis of a simple and efficient protocol for the evaluation of post-translational modifications (PTMs) of histones from NCI-H460 human non-small-cell lung cancer (NSCLC) and HCT-116 human colorectal carcinoma cells. The study was extended to monitoring the level of histone acetylation after inhibition of Histone DeACetylase (HDAC) enzymes with suberoylanilide hydroxamic acid (SAHA), the first HDAC inhibitor approved by the FDA for cancer therapy. Attractive features of our cap(nano)-LC/MS approach are the short analysis time, the minute amount of sample required to complete the whole procedure and the stability of the polymethacrylate-based columns. A lab-made software package ClustMass was ad hoc developed and used to elaborate deconvoluted mass spectral data (aligning, averaging, clustering) and calculate the potency of HDAC inhibitors, expressed through a Relative half maximal Inhibitory Concentration parameter, namely R_IC(50) and an averaged acetylation degree.     

Solvent effects on the complexation of 1-alkanols by parent and modified cyclodextrins. Calorimetric studies at 298 K

The formation of complexes of parent and alkylated cyclodextrins (CDs) with 1-heptanol and 1-octanol has been studied calorimetrically at 298 K in water and in concentrated aqueous solutions of urea. The forces involved in the association process are discussed in the light of the signs and values of the thermodynamic parameters obtained: association enthalpy, binding constant, Gibbs free energy, and entropy. It was inferred that: (i) in water, the formation of complexes for parent and substituted α-cyclodextrins (αCDs) is determined by enthalpy. For parent and substituted β-cyclodextrins (βCDs), instead, hydrophobic interactions are the prevailing forces determining complexation, as indicated by the small and negative or positive enthalpies and by the high and positive entropies. (ii) In urea, hydrophilic interactions are attenuated. The formation of complexes with alkylated CDs does not occur. (iii) The analysis of the thermodynamic properties confirms that inclusion is a process dominated by hydration phenomena. Modifications experienced by the solvent water in the hydration shells of the interacting substances upon association determine the formation of the complexes.     

Kinetic and equilibrium studies on the polyazamacrocycle neotetren: metal-complex formation and DNA interaction

The macrocyclic polyamine 2,5,8,11,14-pentaaza[15]-[15](2,9)[1,10]phenanthrolinophane (neotetren) is studied in its ability to coordinate Cu(ii) even at very low pH values and to interact, as a metal complex, with DNA. The kinetics and equilibria for 1 : 1 and 2 : 1 metal-ligand complexes formation are studied by the stopped-flow method and UV spectrophotometry. Differently protonated complexes are formed, with rate constants much lower than that of water exchange at copper(II) and other Cu(II)/amine systems, this behaviour being ascribed to ring effects and intra-molecular hydrogen bonds. Concerning the DNA/copper(II)-neotetren complexes interaction, analysis of data suggests an intercalative mode of binding. The kinetic results for both DNA/CuL and DNA/Cu(2)L systems agree with the sequence D + S <-->D,S <-->DS where the metal complexes (D) react with the DNA sites (S) leading to fast formation of an externally bound form (D,S) which is converted into an intercalated complex (DS). A very slow process is also detected and ascribed to a conformational change in the polynucleotide secondary structure where the metal centre plays a crucial role. Chromatographic experiments demonstrate that both the investigated Cu(II)/L complexes are able to cleave DNA, but only in the presence of hydrogen peroxide.     

The Vatican museum and the organic natural products. The Raphael’s frescoes and the “Last Judgment” by Nicolò and Giovanni

Abstract

In the second half of the 90s, alongside the restoration works of the Quattrocentisti (fifteenth century painters) in the Sistine Chapel, it also carried out the restoration of the frescoes of the Stanze di Raffaello. The results of scientific investigations conducted by the Scientific Research Laboratory of the Vatican Museums, previously presented in some assays of study, are summarised and presented in this letter to the Editor for the special issue of Natural Product Research: Natural Products in Cultural Heritage.