The role of metacognitive monitoring in explaining differences in mathematics achievement

The relationship between practised monitoring activities and performance, especially in mathematics was examined within three nested studies. The first study deals with problems of faulty term rewritings submitted to three groups of subjects—10th to 13th graders, differing in their mathematical performance—whose task was to find the mistakes. Moreover, a questionnaire on the practice and appreciation of monitoring activities was developed. The third study, first, repeats the first study with a similar population and secondly adds interviews with some of the subjects while solving additional items concerning faulty term rewritings. Studies 1 and 3 show similar success in finding mistakes and in the replies to the questionnaire within the various groups. Furthermore, the third study points up that the subject’s answers do neither predict the practised monitoring nor the success in the test. However, the success correlates significantly with the practised monitoring. For a deeper understanding concerning the role of metacognition in explaining performance, the second study examined two of the groups who had already been involved in the first study. These were assigned some problems of a matrices test as used in cognitive psychology. While trying to solve the problem, their eye movements were recorded by means of an eye-tracker. Afterwards they had to justify their solutions in an interview. The eye movements were analysed, the verbal comments classified. Again, the groups differ in their problem solving success, dependant on the quality of the monitoring practised. Altogether, the results of the three studies elucidate the importance of practised metacognitive monitoring activities not only for success in school algebra, but furthermore the ability and the willingness to do it is deeper anchored in a person than just a trained behaviour for school algebra.     

Edge-reinforced random walk on one-dimensional periodic graphs

In the present paper, linearly edge-reinforced random walk is studied on a large class of one-dimensional periodic graphs satisfying a certain reflection symmetry. It is shown that the edge-reinforced random walk is recurrent. Estimates for the position of the random walker are given. The edge-reinforced random walk has a unique representation as a random walk in a random environment, where the random environment is given by random weights on the edges. It is shown that these weights decay exponentially in space. The distribution of the random weights equals the distribution of the asymptotic proportion of time spent by the edge-reinforced random walker on the edges of the graph. The results generalize work of the authors in Merkl and Rolles (Ann Probab 33(6):2051–2093, 2005; 35(1):115–140, 2007) and Rolles (Probab Theory Related Fields 135(2):216–264, 2006) to a large class of graphs and to periodic initial weights with a reflection symmetry.     

Myxobacterial natural product assembly lines: fascinating examples of curious biochemistry

Over the last 20 years myxobacteria have made their way from highly exotic organisms to one of the major sources of microbial natural products with interesting biological activities. Recent progress towards achieving a better understanding of the genetics and the biochemistry of myxobacterial secondary metabolism, revealed the involvement of numerous exceptional combinations of polyketide synthases and nonribosomal peptide synthetases operating far from textbook biosynthetic logic. In this Highlight, selected examples of recently described systems are discussed in comparison to all myxobacterial natural product assembly lines known to date.     

The Fundamental Solution of the Linearized Navier–Stokes Equations for Spinning Bodies in Three Spatial Dimensions – Time Dependent Case

Explicit formulae for the fundamental solution of the linearized time dependent Navier–Stokes equations in three spatial dimensions are obtained. The linear equations considered in this paper include those used to model rigid bodies that are translating and rotating at a constant velocity. Estimates extending those obtained by Solonnikov in [23] for the fundamental solution of the time dependent Stokes equations, corresponding to zero translational and angular velocity, are established. Existence and uniqueness of solutions of these linearized problems is obtained for a class of functions that includes the classical Lebesgue spaces L^p(R³), 1 < p < ∞. Finally, the asymptotic behavior and semigroup properties of the fundamental solution are established.     

Anti-malarial, anti-algal, anti-tubercular, anti-bacterial, anti-photosynthetic, and anti-fouling activity of diterpene and diterpene isonitriles from the tropical marine sponge Cymbastela hooperi

In an investigation into their potential ecological role(s), a group of mainly diterpene isonitriles, nine in total, isolated from the tropical marine sponge Cymbastela hooperi, and the sesquiterpene axisonitrile-3, isolated from the tropical marine sponge Acanthella kletra, were evaluated in a series of bioassays including anti-fouling, anti-algal, anti-photosynthetic, anti-bacterial (Gram +ve and -ve), anti-fungal, and anti-tubercular. The results of these assays showed that all of the tested compounds, with the exception of diterpene 9, were active in at least two of the applied test systems, with axisonitrile-3 (10) and diterpene isonitrile 1 being the two most active compounds overall, closely followed by diterpene isonitrile 3. Based on the results of the photosynthetic study a molecular modelling investigation was undertaken with all of the compounds used in that study. The results showed a positive correlation between reduction in photosynthetic activity and the interaction of the modelled compounds with a potential enzyme active site.     

Rapid identification and semi-quantitative determination of polymer additives by desorption electrospray ionization/time-of-flight mass spectrometry

A fast and simple method for the direct qualitative and semi-quantitative determination of a set of four polymer additives in plastic samples by desorption electrospray ionization time-of-flight mass spectrometry (DESI-TOF-MS) is presented. After evaluation of crucial DESI parameters such as composition of spray solutions and spray voltages, a series of lab-made polypropylene samples containing Chimassorb 81 (2-hydroxy-4-n-octoxybenzophenone), Tinuvin 328 (2-(2-hydroxy-3, 5-ditert-pentylphenyl)-benzotriazole), Tinuvin 326 (2-(2-hydroxy-3-tert-butyl-5-methylphenyl)-5-chloro benzotriazole), and Tinuvin 770 (bis(2,2,6,6,-tetramethyl-4-piperidyl)sebaceate) in concentrations between 0.02% and 0.2% were analyzed, resulting in calibration graphs with R ² better than 0.994. To demonstrate the applicability of the developed method for the investigation of real samples, liners for in-ground swimming pools and polypropylene granules were analyzed with respect to their content in the selected polymer additives. Two alternative methods, both well established in the fields of polymer additive analysis, namely HPLC with UV detection (after previous extraction) and thermodesorption gas chromatography/mass spectrometry have been employed for evaluation of the results from the DESI experiments.     

Preparation of polymer based sorbents for solid phase extraction of polyphenolic compounds

This article discusses the preparation of different polymeric sorbents for solid phase extraction. Various monomers like acrylamide, methacrylic acid and 4-vinylpyridine (VP), cross-linkers such as divinylbenzene (DVB) and ethyleneglycoldimethacrylate (EDMA), porogens like tetrahydrofuran (THF) and dimethylsulphoxide (DMSO) / acetonitrile (ACN) with different ratios were investigated in order to optimize recoveries. Resulting polymers were characterized through scanning electron microscope (SEM) and compared with Oasis HLB (Waters, MA, USA) and Strata-X (Phenomenex, Torrance, USA) on the basis of extraction performance, recovery efficiency and loading capacity. Sample applied was a mixture of flavonoid standards (rutin, myricetin, luteolin, quercetin, apigenin and kaempferol). HPLC hyphenated with PDA was used for the analysis of samples. Results showed that among the prepared SPE materials, 4-VP-co-EDMA produced best results. Comparison of the produced polymers with of Oasis HLB and Strata-X resulted in comparable efficiencies; especially the polymer 4-VP-co-EDMA gave almost similar results for all analytes to those of commercially available SPE materials. A general trend of decrease in retention efficiency with increase in polarity has been observed in both synthesized and already available SPE materials. The newly synthesized polymeric materials can be employed as SPE sorbents for efficient extraction of polyphenolic compounds especially for flavonoid aglycons.