An exploration of secondary students' mental states when learning about acids and bases

This study explored factors of students’ mental states, including emotion, intention, internal mental representation, and external mental representation, which can affect their learning performance. In evaluating students’ mental states during the science learning process and the relationship between mental states and learning achievement, valid, reliable, and scalable measures of students’ mental states and learning achievement are needed. This paper presents the development of the Mental State Conceptual Learning Inventory (MSCLI) to identify students’ mental states before and after learning about acids and bases. This instrument is time efficient and convenient and can be administered to large student samples so that teachers and researchers can gain profound insights into their students’ learning of acids and bases in science class. The results of this study indicate that students’ mental states are highly correlated with their achievement. As a whole, low-achieving students tended to have negative emotions and low intentions, were not good at internal visualization, and were unable to interpret graphics and draw pictures. In contrast, high-achieving students had positive emotions and intentions when learning life-related topics about acids and bases, and were good at internal visualization and drawing and interpreting graphics

Space Charge at Nanoscale: Probing Injection and Dynamic Phenomena Under Dark/Light Configurations by Using KPFM and C-AFM

International audienc

Highly efficient dicyano-phenylenevinylene fluorophore as polymer dopant or zinc-driven self-assembling building block

From a diamino dicyano-phenylenevinylene skeleton a symmetrically di-salen dye was obtained and employed both as a dopant in non-emissive polymer matrixes and as building blocks in the preparation of a zinc self-assembly polymer. The new fluorophore C1 belongs to the class of the luminescent liquid crystals (LLCs). The molecule produces red emission in the crystalline phase and yellow luminescence in the nematic phase, which dramatically decreases in on-off switch mode after LC order was lost. Both C1 and its self-assembly zinc-based coordination polymer suffers a lot aggregation caused quench effect (ACQ). Conversely, thin films obtained by dispersion in polystyrene (PS) and poly(9-vinylcarbazole) (PVK) show remarkably enhanced fluorescence, reaching the noteworthy value of 77% Photoluminescence Quantum Yield (PLQY) for the PVK doped sample

A symmetrical azo-based fluorophore and the derived salen multipurpose framework for emissive layers

The development of new organic simple and low-cost fluorophores is a current topic. To date innovative solutions include azo dyes because of the unique absorption behavior, but the azo group gives poor luminophores in the solid state. In order to produce a luminescent azo dye, we synthesized compound A2, 4,4′-((1,1′)-(2,5-dimethoxy-1,4-phenylene)bis(diazene-2,1-diyl))dianiline, and its symmetrical Schiff-base derivative C2. The new compound C2 is a weakly luminescent fluorophore in the crystalline phase and when employed as building blocks in self-assembly of zinc (II) coordination polymer. Nevertheless, if used as a dopant in PS and PVK, C2 shows enhanced fluorescence and represents a good on-off naked-eye switch when dispersed in a room-temperature nematic polymer

Organic solar cells defects classification by using a new feature extraction algorithm and an EBNN with an innovative pruning algorithm

Physical defects reduce the organic solar cells (OSC) functioning. Throughout the OSC fabrication process, the defects can occur, for instance, by scratches or uneven morphologies. In general, bulk defects, interface defects, and interconnect defects can promote shunt and series resistance of the cell. It is crucial to properly detect and classify such defects and their amount in the structure. Correlating such defects with the performance of the cell is important both during the R&D stages to optimize processes, and for mass production stages where defects detection is an integral part of the production line. For the recognition of texture variations in the scanning electron microscope images caused by these defects is crucial the definition of a set of features for texture representation. Because the low-order Zernike moments can represent the whole shape of the image and the high-order Zernike moments can describe the detail. Then, in our case, the feature of the image can be represented by a small number of Zernike moments. In fact, the feature set extracted and described by the Zernike moments are not sensitive to the noises and are hardly redundant. So it possible concentrate the signal energy over a set of few vectors. Finally, for classification, an elliptical basis function neural networks was used. The results show effectiveness of the proposed methodology. In fact, we obtained correct classification of 89.3% over testing data set

Spectroscopic behaviour of two novel azobenzene fluorescent dyes and their polymeric blends

Two novel symmetrical bis-azobenzene red dyes ending with electron-withdrawing or donor groups were synthesized. Both chromophores display good solubility, excellent chemical, and thermal stability. The two dyes are fluorescent in solution and in the solid-state. The spectroscopic properties of the neat crystalline solids were compared with those of doped blends of different amorphous matrixes. Blends of non-conductive and of emissive and conductive host polymers were formed to evaluate the potential of the azo dyes as pigments and as fluorophores. Both in absorbance and emission, the doped thin layers have CIE coordinates in the spectral region from yellow to red. The fluorescence quantum yield measured for the brightest emissive blend reaches 57%, a remarkable performance for a steadily fluorescent azo dye. A DFT approach was employed to examine the frontier orbitals of the two dyes

The effect of bulky substituents on two π-conjugated mesogenic fluorophores. Their organic polymers and zinc-bridged luminescent networks

From a dicyano-phenylenevinylene (PV) and an azobenzene (AB) skeleton, two new symmetrical salen dyes were obtained. Terminal bulky substituents able to reduce intermolecular interactions and flexible tails to guarantee solubility were added to the fluorogenic cores. Photochemical performances were investigated on the small molecules in solution, as neat crystals and as dopants in polymeric matrixes. High fluorescence quantum yield in the orange-red region was observed for the brightest emissive films (88% yield). The spectra of absorption and fluorescence were predicted by Density Functional Theory (DFT) calculations. The predicted energy levels of the frontier orbitals are in good agreement with voltammetry and molecular spectroscopy measures. Employing the two dyes as dopants of a nematic polymer led to remarkable orange or yellow luminescence, which dramatically decreases in on-off switch mode after liquid crystal (LC) order was lost. The fluorogenic cores were also embedded in organic polymers and self-assembly zinc coordination networks to transfer the emission properties to a macro-system. The final polymers emit from red to yellow both in solution and in the solid state and their photoluminescence (PL) performance are, in some cases, enhanced when compared to the fluorogenic cores