Hydrogen Activation by Benzene-Ruthenium Complexes in Aqueous Solution: Synthesis, Molecular Structure, and Intercalation of the Cluster Cation [{C₆H₆)₄Ru₄H₄]²⁺

The hydrogenation of the aqua complex [(C6H6)Ru(H2O)3]2+, prepared in situ by hydrolysis of (C6H6)2Ru2Cl4 in water, was found to lead to the tetranuclear cluster dication [(C6H6)4Ru4H4]2+ (1) which crystallizes as the dichloride from the aqueous solution. In the presence of acetate ions, however, the reaction yields the dinuclear cations [(C6H6)2Ru2H(OOCCH3)X]+ (X=OH: 2, X=Cl: 3) which crystallize as the hexafluorophosphate salts. The X-ray crystal-structure analysis of [(C6H6)4Ru4H4]Cl2 reveals the cluster dication 1 to consist of a tetrahedral ruthenium framework; the four hydrido ligands are presumably coordinated to three faces and to one edge of the Ru4 tetrahedron. The cationic complexes 1 and 2 have been found to intercalate in sodium hectorite

Ruthenium Nanoparticles Intercalated in Hectorite: A Reusable Hydrogenation Catalyst for Benzene and Toluene

The cationic organometallic aqua complexes formed by hydrolysis of [(C6H6)RuCl2]2 in water, mainly [(C6H6)Ru(H2O)3]2+, intercalate into sodium hectorite by ion exchange, replacing the sodium cations between the anionic silicate layers. The yellow hectorite thus obtained reacts in ethanol with molecular hydrogen (50 bar, 100°C) with decomposition of the organometallic aqua complexes to give a black material, in which ruthenium(0) nanoparticles (9-18nm) are intercalated between the anionic silicate layers, the charges of which being balanced by hydronium cations. The black ruthenium-modified hectorite efficiently catalyses the hydrogenation of benzene and toluene in ethanol (50 bar H2, 50°C), the turnover frequencies attaining 7000 catalytic cycles per hou

Pre-service Biology Teachers’ Responses to First-Hand Anomalous Data During Modelling Processes

In this research project we investigate the role of responses to anomalous data during modelling processes. Modelling is seen as a comprehensive practice that encompasses various aspects of scientific thinking; hence, it is an important style of scientific thinking, especially if analysed from a process-based perspective. Therefore, it provides the opportunity to understand the role of anomalous data on scientific thinking from a broader perspective. We analysed how pre-service biology teachers (N = 11) reacted to self-generated anomalous data during modelling processes induced by investigating a water black box. The videotaped and transcribed modelling processes were analysed using qualitative content analysis. If anomalous data were recognised, a majority of explanations were based on methodical issues. This finding supports results from previous studies investigating responses to first-hand anomalous data. Furthermore, we found four response patterns to anomalous data during modelling processes: no recognition, no explanation, methodical explanation, and model-related explanation. Besides, our study indicates by trend a systematic relation between response patterns to anomalous data and modelling strategies. Consequently, the improvement of responses to anomalous data could be a promising way to foster modelling competencies. We are convinced that an integrated approach to anomalous data and modelling could lead to deeper insights into the role of data in scientific thinking processes

The Headgroup (A)Symmetry Strongly Determines the Aggregation Behavior of Single-Chain Phenylene-Modified Bolalipids and Their Miscibility with Classical Phospholipids

In the present work, we describe the synthesis of two single-chain phenylene-modified bolalipids, namely PC-C17pPhC17-PC and PC-C17pPhC17-OH, with either symmetrical (phosphocholine) or asymmetrical (phosphocholine and hydroxyl) headgroups using a Sonogashira cross-coupling reaction as key step. The temperature-dependent aggregation behavior of both bolalipids in aqueous suspension was studied using transmission electron microscopy (TEM), differential scanning calorimetry (DSC), Fourier-transform infrared (FTIR) spectroscopy, small angle neutron scattering (SANS), and X-ray scattering. We show that different headgroup symmetries lead to a change in the aggregation behavior: Whereas PC-C17pPhC17-PC forms nanofibers with a diameter of 5.7 nm that transform into small ellipsoidal micelles at 23 °C, the PC-C17pPhC17-OH self-assembles into lamellae with bolalipid molecules in an antiparallel orientation up to high temperatures. Furthermore, the mixing behavior of both bolalipids with bilayer-forming phospholipids (DPPC and DSPC) was studied by means of DSC and TEM. The aim was to stabilize bilayer membranes formed of phospholipids in order to improve these mixed lipid vesicles for drug delivery purposes. We show that the symmetrical PC-C17pPhC17-PC is miscible with DPPC and DSPC; however, closed lipid vesicles are not observed, and elongated micelles and bilayer fragments are found instead. In contrast, the asymmetrical PC-C17pPhC17-OH shows no miscibility with phospholipids at all

Investigating students’ modelling styles in the process of scientific-mathematical modelling

Modelling plays an important role for inquiry in science and mathematics education; therefore, a lot of research has been done in this field from both perspectives. However, an integrated view combining previous findings is rather limited. For the specific case of line graphs as a common representation that models relations between different variables in science, an integrated model of scientific-mathematical modelling was developed. The model integrates a scientific and mathematical perspective that describes line graphs as graphical representations of functional relationships. This model is used as a theoretical framework a) to describe cognitive processes that are necessary for modelling scientific phenomena with mathematical functions represented as line graphs and b) to analyse these processes empirically. In the presented study two modelling tasks were developed in which 10th grade students (N = 15) are asked to model biological phenomena graphically as line graphs. Modelling processes are recorded using a SmartPen and concurrent think aloud. Results show that participants’ modelling processes can be divided into sub-processes, related to the model of scientific-mathematical modelling. Furthermore, different individual modelling processes are reconstructed and graphically represented as graphical representations of individual modelling processes (GRIMPs). Based on a clustering process using GRIMPs, eight modelling styles are defined.Peer Reviewe

(Cryo)Transmission Electron Microscopy of Phospholipid Model Membranes Interacting with Amphiphilic and Polyphilic Molecules

Lipid membranes can incorporate amphiphilic or polyphilic molecules leading to specific functionalities and to adaptable properties of the lipid bilayer host. The insertion of guest molecules into membranes frequently induces changes in the shape of the lipid matrix that can be visualized by transmission electron microscopy (TEM) techniques. Here, we review the use of stained and vitrified specimens in (cryo)TEM to characterize the morphology of amphiphilic and polyphilic molecules upon insertion into phospholipid model membranes. Special emphasis is placed on the impact of novel synthetic amphiphilic and polyphilic bolalipids and polymers on membrane integrity and shape stability

Visualizing pre-service biology teachers´ conceptions about population dynamics in ecosystems

The Balance of Nature (BoN) metaphor leads to various naïve conceptions about ecosystem dynamics that do not address current scientific theories adequately. An appropriate alternative is the Flux of Nature (FoN) metaphor. Approaches to conceptual development in science education aim for learners to develop scientifically adequate conceptions rather than maintain naïve conceptions. Our goal was to investigate naïve BoN conceptions and their sources with the method of visualization. Therefore, we examined pre-service biology teachers’ (n = 26) conceptions about ecosystem dynamics by asking them to draw and explain line graphs to predict the development of a population. Graphs and explanations were analyzed with qualitative content analysis and assigned into categories related to either the BoN or the FoN metaphor. The majority of the graphical predictions were found to be in line with the BoN metaphor, which replicates the findings of previous studies. Additionally, the method of visualization shows that a common model used in ecology that is often presented in biological textbooks influenced the predictions made by our participants. When used uncritically, this model can support naïve BoN conceptions. Thus, our results suggest that the use of scientific models and pedagogical materials may influence conceptual development in this context.Peer Reviewe