Generating scenarios of addition and subtraction: A study of Japanese university students

Students are presented with problems involving three scenario types of addition and subtraction in elementary mathematics: one dynamic (Change) and two static (Combine, Compare). Previous studies have indicated that the dynamic type is easier for school children, whereas the static types are more difficult and comprehended only gradually throughout elementary grades. However, these differences in scenario difficulty have not be adequately investigated in adults to ascertain whether they persist in adults who have used the operations for a long period of time. This study examined this with Japanese university students (ages 18–23 years). In Study 1, 99 participants were provided with one numerical equation and one picture representing one of the three scenario types, and were instructed to generate a single scenario. In Study 2, 97 participants were provided with one numerical equation and were instructed to recall the various scenario types that they had encountered previously and to generate multiple scenarios of diverse types. Results indicated that participants found the dynamic scenario types easier than static ones, and they tended to understand the given information of static types by interpreting them in dynamic forms (Study 1). In addition, they strongly preferred generating scenarios of dynamic type over static types (Study 2). Implications for mathematics learning are discussed.     

Analysis of swelling process of protein by positron annihilation lifetime spectroscopy and differential scanning calorimetry

The change in the nanoscopic structure and bound state of water in the protein gel were investigated using positron annihilation lifetime spectroscopy (PALS) and differential scanning calorimetry (DSC). Gelatin was used as a protein. To examine the bound state of water in gelatin gel, the amount of freezing and nonfreezing water in gelatin gels were evaluated by fusion enthalpy of DSC curves. Below water content of 40% (w/w), the whole amount of water was nonfreezing water, whereas above water content of 40% (w/w), the amount of freezing water increased according to increase in water content. To investigate the nanoscopic spatial structure under coexistence of polymer and water, positron annihilation lifetime measurement was performed. The lifetime of o‐Ps or the pore size increased according to increase in water content, particularly below the water content of 40% (w/w). When the water penetrates into the gelatin network, the water molecules form hydrogen bonds with hydrophilic groups inside the helical structure in gelatin gel. The water molecules inside the helical structure expand the structure outward, leading to increase in pore size. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2031–2037, 2007.     

A sensitive and selective method for determination of gold(III) based on electrothermal atomic absorption spectrometry in combination with dispersive liquid-liquid microextraction using dicyclohexylamine

A combined method with dispersive liquid-liquid microextraction (DLLME) and electrothermal atomic absorption spectrometry (ETAAS) has been developed for determining gold(III). Dicyclohexylamine, a new extractant for gold(III), showed excellent performance in DLLME. Acetone was indispensable to the quantitative extraction of gold(III), contributing to decrease in hydration, decrease in the difference in the dielectric constants between the supernatant phase and the sedimented phase, and dissolution of a part of chloroform as an extraction solvent to the supernatant phase as well as improvement of dipersibility. In DLLME using a mixture of 1.0 mL of acetone and 100 μL of chloroform containing 50 mmol L⁻¹ of dicyclohexylamine, gold(III) could be extracted selectively and effectively from 8 mL of a sample solution in the presence of iron(III), cobalt(II), nickel(II), copper(II), palladium(II), and platinum(IV) at pH 1. The extracted gold(III) was determinable by ETAAS; the detection limit was 0.002 μg L⁻¹ (three times the standard deviation of the blank values, n = 8) as a gold(III) concentration in 8 mL of sample solution. The proposed method was applicable to the determination of gold in platinum metal and its alloy as well as effluent without any interference by the matrices.     

FT Raman and DFT Study on a Series of All‐anti Oligothienoacenes End‐Capped with Triisopropylsilyl Groups

Herein, we study the π‐conjugational properties of a homologous series of all‐anti oligothienoacenes containing four to eight fused thiophene rings by means of FT Raman spectroscopy and DFT calculations. The theoretical analysis of the spectroscopic data provides evidence that selective enhancement of a very limited number of Raman scatterings is related to the occurrence in these oligothienoacenes of strong vibronic coupling between collective ν(C?C) stretching modes in the 1600–1300 cm^?1 region and the HOMO/LUMO frontier orbitals (HOMO=highest occupied molecular orbital; LUMO=lowest unoccupied molecular orbital). The correlation of the Raman spectroscopic data and theoretical results for these all‐anti oligothienoacenes with those previously collected for a number of all‐syn oligothienohelicenes gives further support to the expectation that cross‐conjugation is dominant in heterohelicenes. Fully planar all‐anti oligothienoacenes display linear π conjugation which seemingly does not reach saturation with increasing number of annulated thiophene rings in the oligomeric chain at least up to the octamer.     

Thiophene-fused ladder boroles with high antiaromaticity

A series of polycyclic thiophene-fused boroles were synthesized on the basis of stepwise substitution reactions from thienylboronic ester precursors. In these ladder-type π-conjugated systems, the thiophene-fused structure enhances the antiaromaticity of the borole ring. This trend is opposite to the conventional understanding that the arene-fused structure decreases the antiaromaticity of the 4π-electron ring skeletons. The ladder boroles exhibited characteristic properties such as long-wavelength absorptions and low reduction potentials.     

Neutral and Oxidized Triisopropylsilyl End‐Capped Oligothienoacenes: A Combined Electrochemical,Spectroscopic, and Theoretical Study

This work presents an analysis of the structural, electrochemical, and optical properties of a family of triisopropylsilyl end‐capped oligothienoacenes (TIPS‐ Tn ‐TIPS, n=4–8) by combining cyclic voltammetry, spectroscopic techniques, and quantum‐chemical calculations. TIPS‐ Tn ‐TIPS compounds form stable radical cations, and dications are only obtained for the longest oligomers (n=7 and 8). Oxidation leads to the quinoidization of the conjugated backbone, from which electrons are mainly extracted. The absorption and fluorescence spectra show partially resolved vibronic structures even at room temperature, due to the rigid molecular geometry. Two well‐resolved vibronic progressions are observed at low temperatures due to the vibronic coupling, with normal modes showing wavenumbers of ≈1525 and ≈480 cm^?1. Optical absorption bands display remarkable bathochromic dispersion with the oligomer length, indicative of the extent of π conjugation. The optical properties of the oxidized compounds are characterized by in situ UV/Vis/NIR spectroelectrochemistry. The radical cation species show two intense absorption bands emerging at energies lower than in the neutral compounds. The formation of the dication is only detected for the heptamer and the octamer, and shows a new band at intermediate energies. Optical data are interpreted with the help of density functional theory calculations performed at the B3LYP/6‐31G** level, both for the neutral and the oxidized compounds.     

Suzuki–Miyaura cross-coupling reaction of aryl and heteroaryl pinacol boronates for the synthesis of 2-substituted pyrimidines

Suzuki–Miyaura cross-coupling reaction with 2-heteroarylboronic acids is generally challenging due to these acids easy decomposition. To overcome this problem, we developed a coupling method that uses 2-heteroaryl pinacol boronates in the presence of 1.0 mol % Pd(OAc)₂ and 2.0 mol % S-Phos with 4 equiv amount of LiOH in dioxane and H₂O at 80 °C for 30 min. This developed method allowed for the synthesis of a wide variety of 2-heteroaryl pyrimidines from 2-chloropyrimidyl derivatives in high yields, and is also useful in the preparation of various biaryl derivatives from heteroaryl chlorides.