The Influence of Mind Mapping on Eighth Graders’ Science Achievement

This study assessed the influence of using mind maps as a learning tool on eighth graders’ science achievement, whether such influence was mediated by students’ prior scholastic achievement, and the relationship between students’ mind maps and their conceptual understandings. Sixty‐two students enrolled in four intact sections of a grade 8 science classroom were randomly assigned to experimental and comparison conditions. Participants in the experimental group received training in, and constructed, mind maps throughout a science unit. Engagement with mind mapping was counterbalanced with involving the comparison group participants with note summarization to control for time on task as a confounding variable. Otherwise, the intervention was similar for both groups in all respects. A multiple choice test was used to measure student gains across two categories and three levels of achievement. Data analyses indicated that the experimental group participants achieved statistically significant and substantially higher gains than students in the comparison group. The gains were not mediated by participants’ prior scholastic achievement. Analyses also indicated that iconography was not as central to participants’ mind maps as often theorized. Depicting accurate links between central themes and major and minor concepts, and using colors to represent concepts were the major aspects that differentiated the mind maps built by students who achieved higher levels of conceptual understanding.     

On algebraic surfaces with an infinite set of planes of skew symmetry

We consider (m-1)-dimensional noncylindrical algebraic surfaces in a real spaceR ^m with infinite symmetry groupsG generated by skew reflections with respect to planes, along with the relative locations of linear hulls of fourG-orbits of the directions of symmetry. Translated fromDinamicheskie Sistemy. Vol. 12. pp. 69–74. 1993.     

Calix(aza)crowns: synthesis, recognition, and coordination. A mini review

Attaching azacrown bridges on calixarene platform generates calix(aza)crown family. This article reviews synthetic routes for their design and discusses their ion-binding properties by means of coordination and stability constants.     

A new thermostable peroxidase from garlic Allium sativum

Analysis of peroxidase activity by native polyacrylamide gel electrophoresis (PAGE) from a garlic bulb (Allium sativum L) extract showed two major activities (designated POX1 and POX2). The POX2 isoenzyme was purified to homogeneity by ammonium sulfate precipitation, gel filtration, and cation-exchange chromatography. The purified enzyme was found to be monomeric with a molecular mass of 36.5 kDa, as determined by sodium dodecyl sulfate-PAGE. The optimum temperature ranged from 25 to 40 degrees C and optimum pH was about 5.0. The apparent Km values for guaiacol and H2O2 were 9.5 and 2 mM, respectively. POX2 appeared highly stable since 50% of its activity was conserved at 50 degrees C for 5 h. Moreover POX2 was stable over a pH range of 3.5-11.0. Immobilization of POX2 was achieved by covalent binding of the enzyme to an epoxy-Sepharose matrix. The immobilized enzyme showed great stability toward heat and storage when compared with soluble enzyme. These properties permit the use of this enzyme as a biosensor to detect H2O2 in some food components such as milk or its derivatives.     

Synthesis of new azo compounds based on N-(4-hydroxypheneyl)maleimide and N-(4-methylpheneyl)maleimide

Maleic anhydride was reacted with p-aminophenol and p-toluidine in the presence of di-phosphorus pentoxide (P?O?) as a catalyst to produce two compounds: N-(4-hydroxy-phenyl)maleimide (I) and N-(4-methylphenyl)maleimide (II). The new azo compounds I(a-c) and II(a-c) were prepared by the reaction of I and II with three different aromatic amines, namely aniline, p-aminophenol and p-toluidine. The structures of these compounds were confirmed by CHN, FT-IR, 1H-NMR, 13C-NMR, mass spectrum and UV/Vis spectroscopy.     

Ni(0)-CMC-Na - nickel colloids in sodium carboxymethyl-cellulose: catalytic evaluation in hydrogenation reactions

A recyclable catalyst, Ni(0)-CMC-Na, composed of nickel colloids dispersed in a water soluble bioorganic polymer, sodium carboxymethylcellulose (CMC-Na), was synthesized by a simple procedure from readily available reagents. The catalyst thus obtained is stable and highly active in alkene hydrogenations.     

A Fluorescent and Phosphorescent Nanoporous Solid: Crystalline Calix[4]arene

Calix[4]arene forms elongated nanoporous microcrystals. The pores are linear nano-channels (1.7 nm diameter) arranged in a honeycomb network. The crystals luminesce at room temperature according to a variety of processes that include monomer fluorescence (lifetime of ca. 1.1 ns), dimer fluorescence (lifetime of ca. 5.4 ns), and monomer phosphorescence (lifetime of ca. 2 s). The dimers result from pi-orbital overlap of adjacent phenol groups from neighboring nano-channels, with C-C distances of ca. 4 A.     

Multigrid solvers in reconfigurable hardware

The problem of finding the solution of partial differential equations (PDEs) plays a central role in modeling real world problems. Over the past years, Multigrid solvers have showed their robustness over other techniques, due to its high convergence rate which is independent of the problem size. For this reason, many attempts for exploiting the inherent parallelism of Multigrid have been made to achieve the desired efficiency and scalability of the method. Yet, most efforts fail in this respect due to many factors (time, resources) governed by software implementations. In this paper, we present a hardware implementation of the V-cycle Multigrid method for finding the solution of a 2D-Poisson equation. We use Handel-C to implement our hardware design, which we map onto available field programmable gate arrays (FPGAs). We analyze the implementation performance using the FPGA vendor's tools. We demonstrate the robustness of Multigrid over other similar iterative solvers, such as Jacobi and successive over relaxation (SOR  ), in both hardware and software. We compare our findings with a C++$\mathrm{C}++$ version of each algorithm. The obtained results show better performance when compared to existing software versions.     

Finite Rank Commutators and Semicommutators of Quasihomogeneous Toeplitz Operators

We study finite rank semicommutators and commutators of Toeplitz operators on the Bergman space with quasihomogeneous symbols. We show that in this context, the situation is different from the case of harmonic Toeplitz operators. Submitted: July 23, 2007. Accepted: December 4, 2007.