Changes in Preservice Elementary Teachers' Sense of Efficacy in Teaching Science

This paper reports progress to date on a longitudinal study of changes in preservice teachers' sense of efficacy in teaching science. The study involved procedures designed to validate, in an Australian context, the Science Teaching Efficacy Beliefs Instrument (STEBI-B) comprised of two scales: Personal Science Teaching Efficacy Belief Scale (STE) and Science Teaching Outcome Expectancy Scale (STO). Concomitantly, the instrument was used to monitor changes in teachers' sense of science teaching efficacy employing a pretest and repeated posttest, one group research design. The subjects were students enrolled in a three-year Bachelor of Teaching (Primary) program. Correlations between pretest scores on STEBI-B and other measures of personal beliefs and behaviors, namely academic self concept and academic locus of control, supported the validity of STEBI-B. The results indicate that, over three semesters of the program, there was significant difference between the pretest and posttest scores on the STE scale. Possible explanations of the results obtained are discussed and evaluated and a justification for further long term research into teachers' sense of efficacy in teaching science is provided. Implications of the results for the teaching of elementary school science are discussed.     

Interfacial friction and adhesion of polymer brushes

A bead-probe lateral force microscopy (LFM) technique is used to characterize the interfacial friction and adhesion properties of polymer brushes. Our measurements attempt to relate the physical structure and chemical characteristics of the brush to their properties as thin-film, tethered lubricants. Brushes are synthesized at several chain lengths and surface coverages from polymer chains of polydimethylsiloxane (PDMS), polystyrene (PS), and a poly(propylene glycol)-poly(ethylene glycol) block copolymer (PPG/PEG). At high surface coverage, PDMS brushes manifest friction coefficients (COFs) that are among the lowest recorded for a dry lubricant film (μ ≈ 0.0024) and close to 1 order of magnitude lower than the COF of a bare silicon surface. Brushes synthesized from higher molar mass chains exhibit higher friction forces than those created using lower molar mass polymers. Increased grafting density of chains in the brush significantly reduces the COF by creating a uniform surface of stretched chains with a decreased surface viscosity. Brushes with lower surface tension and interfacial shear stresses manifest the lowest COF. In particular, PDMS chains exhibit COFs lower than PS by a factor of 3.7 and lower than PPG/PEG by a factor of 4.7. A scaling analysis conducted on the surface coverage (σ) in relation to the fraction (ε) of the friction force developing from adhesion predicts a universal relation ε ~ σ(4/3), which is supported by our experimental data.     

Determination of CO2 capture during accelerated carbonation of engineered cementitious composite pastes by thermogravimetry

Journal of Thermal Analysis and Calorimetry - The present study has evaluated the rheological behavior of an oil-based (5W50) hybrid nanofluid [magnesium oxide (65%)–multi-walled carbon...     

Voltammetric determination of chlorothalonil and its respective reduction mechanism studied by density functional theory

Journal of Solid State Electrochemistry - A simple, fast, and direct electroanalytical method has been developed for the pesticide chlorothalonil determination using a boron-doped diamond electrode...     

Chemically‐reduced Graphene Oxide Sensor for Dipyrone Quantification in Pharmaceutical Samples Using Amperometric Detection

Dipyrone (metamizole sodium) is one of the most consumed drugs in the world. In this work a novel analytical method was developed for dipyrone sensing. This method involves the amperometric detection on a chemically‐reduced graphene‐oxide (CRGO)‐modified glassy carbon electrode. Raman spectroscopy and scanning electron microscopy revealed the presence of multilayer graphene layers that contributed to the electrocatalytic oxidation of dipyrone and increase in the electroactive area. Advantages of this sensor include elimination of previous separations, solvent extraction, or sample filtration, low detection limit (0.13 μmol L^?1) with a linear range from 48 to 246 μmol L^?1 and adequate recovery values (97–103 %). Applied to commercial pharmaceutical samples, this method showed results ranging from 451 to 541 mg of dipyrone per tablet, which agreed with the expected values. The results obtained by amperometry were compared statistically with the official method recommended by the Brazilian Pharmacopoeia (iodometric method), with no significant differences between them at 95 % confidence level. The proposed method is accurate for the monitoring of sodium dipyrone in pharmaceutical formulations, highlighting the lower reagent consumption and interferences in the analytical process.     

Acyclic Stereocontrol in the Additions of Nucleophilic Alkenes to α-Chiral N-Sulfonyl Imines

Diastereoselective Lewis acid-mediated additions of nucleophilic alkenes to N-sulfonyl imines are reported. The canonical polar Felkin–Anh model describing additions to carbonyls does not adequately describe analogous additions to N-sulfonyl imines. Herein, we describe the development of conditions to produce both syn and anti products with high diastereoselectivity and good yields. A stereoelectronic model consistent with experimental outcomes is also proposed.     

Significant Associations Between Sun Exposure and Adiposity Were Not Observed in Breast and Prostate Cancer Patients in a Cross‐sectional Analysis

Obesity is a significant health problem worldwide. Exposure to low‐dose ultraviolet radiation (like that in sunlight) suppresses the development of obesity in mice; however, the nature of the associations between sun exposure and adiposity is not well understood in humans. The present study characterized cross‐sectional relationships between sun exposure and adiposity in a convenience cohort of breast (n = 269; mean age = 58 years) and prostate (n = 78; mean age = 69 years) cancer patients. Participants were enrolled in a 3‐month exercise program in Perth, Australia. Self‐reported questionnaires measured time spent outdoors (previous week, winter and summer), sex, age, treatment received and physical activity levels. Adiposity measures included body mass index, waist‐hip ratio and body fat percentage (measured via DXA). In unadjusted models, greater time spent outdoors across all times was significantly associated with lower waist‐hip ratio, while greater time spent outdoors in the last winter was associated with lower body fat percentage, but not when stratified by sex. There were no statistically significant associations between time spent outdoors and adiposity after adjusting for sex, age, treatments received and physical activity. Longitudinal studies in larger populations may elucidate significant associations not found in our study due to the cross‐sectional design and power limitations.     

Spin–Spin Coupling Between Two meta-Benzyne Moieties In a Quinolinium Tetraradical Cation Increases Their Reactivities

The reactivity of a carbon-centered σ,σ,σ,σ-type singlet-ground-state tetraradical containing two meta-benzyne moieties was examined in the gas phase. Surprisingly, the tetraradical showed higher reactivity than its individual meta-benzyne counterparts. The reactivity of meta-benzynes is controlled by their (calculated) distortion energy ΔE_2.3, singlet–triplet spitting ΔE_S–T, and electron affinity (EA_2.3) of the meta-benzyne moiety at the transition state geometry for hydrogen-atom abstraction reactions. The addition of a second meta-benzyne moiety to a meta-benzyne does not significantly change EA_2.3. However, ΔE_2.3 is substantially decreased for both meta-benzyne moieties in the tetraradical, and this explains their higher reactivities. The decrease in ΔE_2.3 for each meta-benzyne moiety in the tetraradical is rationalized by stabilizing spin–spin coupling between one radical site in each meta-benzyne moiety. Therefore, spin–spin coupling between the meta-benzyne moieties in this tetraradical increases its reactivity, whereas spin–spin coupling within each meta-benzyne moiety decreases its reactivity.     

Metal-Free Electrochemical Reduction of Carbon Dioxide Mediated by Cyclic(Alkyl)(Amino) Carbenes

Carbenes are known to activate carbon dioxide to form zwitterionic adducts. Their inherent metal-free redox activity remains understudied. Herein, we demonstrate that zwitterionic adducts of carbon dioxide formed with cyclic(alkyl)(amino) carbenes are not only redox active, but they can mediate the stoichiometric reductive disproportionation of carbon dioxide to carbon monoxide and carbonate. Infrared spectroelectrochemical experiments show that the reaction proceeds through an intermediate radical anion formed by one-electron reduction, ultimately generating a ketene product and carbonate in the absence of additional organic or inorganic reagents.