Cognitive opportunities in textbooks: the cases of grade four and eight textbooks in Israel

The cognitive domain in mathematics, defined as thinking and understanding in the process of learning mathematics, is a main focus of curricula in many countries. This study explores breadth and depth of understanding as addressed in mathematics textbooks certified as aligned to Israeli national mathematics curricula. We compare opportunities for students to engage with mathematics requiring different types and levels of understanding provided by the tasks in mathematics textbooks. Comparison of two fourth grade and two eighth grade mathematics textbooks showed significant differences in the opportunities to learn in the cognitive domain that each provides. These differences can be quantified; the quantification defines the cognitive demand of the textbook. The cognitive demand of the four textbooks varies. This reveals a potential source of inequity in students’ opportunities to learn mathematics. Results should prompt discussion around standardization and alignment of textbooks to the cognitive goals of the curriculum.     

Synthesizing a new dielectric elastomer exhibiting large actuation strain and suppressed electromechanical instability without prestretching

Prestrain provides high actuation performance in dielectric elastomers (DEs) but increases the bulk, mass, and fatigue of the resulting actuators. Based on our experiments on prestrain‐locked interpenetrating polymer films and the model developed by Zhao and Suo, materials with a certain stress–strain relationship should be capable of high strain without prestrain by suppressing electromechanical instability (EMI). Here, we report the synthesis of an acrylic elastomer capable of achieving high actuation performance without prestrain. DE films were directly fabricated by ultraviolet curing of precursors comprising a mixture of acrylate comonomers. Varying the amount of crosslinker comonomer in the precursor allowed us to tune the stress–strain relationship and completely suppress EMI while maintaining high strain performance. Addition of plasticizing agents increased strain sensitivity. The result is a new DE, synthesized from scratch, capable of high actuation strain (>100%), high energy density (>1 J g^?1), and good temperature and frequency response without requiring prestretching. The material can be fabricated using conventional coating techniques and the process can allow for high volume throughput of stacked DE actuators. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013     

Fougerite FeII − III oxyhydroxycarbonate in environmental chemistry and nitrate reduction

The identification of the fougerite mineral responsible for the bluish-green shade of gleysols in aquifers as being the Fe^II???III oxyhydroxycarbonate $\text{GR}(\text{CO}_{3}^{2-})^*$ of formula, $[\text{Fe}^{\rm II}_{6x}\text{Fe}^{\rm III}_{6(1 - x)}\text{O}_{12}\text{H}_{2(7-3x)}]^{2+}\bullet[\text{CO}_{3}^{2-}\bullet3\text{H}_{2}\text{O}]^{2-}$ where the ferric molar ratio x = [Fe^III/Fe_total] is restricted to the domain [1/3–2/3] induces to study the reactivity of the synthetic green rust for reducing some major pollutants. The oxidation within the solid compound $\text{GR}(\text{CO}_{3}^{2-})^*$ in the presence of nitrates is followed by miniaturized Mössbauer spectrometer (MIMOS). Ratio x = [Fe^III/Fe_total] increases up to 0.67 where $\text{GR}(\text{CO}_{3}^{2-})^*$ transforms gradually into magnetite. This could well explain the composition variability of fougerite occurrences.     

Theoretical studies on the electronic and optoelectronic properties of [A.2AP(w)/A*.2AP(WC)/C.2AP(w)/C*.2AP(WC)/C.A(w)/C*.A(WC)]–Au8 mismatch nucleobase complexes

The electronic and optoelectronic properties of [A.2AP(w)/A^*.2AP(WC)/C.2AP(w)/C^*.2AP(WC)/C.A(w)/ C^*.A(WC)]–Au₈ metal-mismatch nucleobase complexes are investigated by means of density functional theory and time-dependent methods. We selected these mispairs as 2-aminopurine (2AP) produces incorporation errors when binding with cytosine (C) into the wobble (w) C·2AP(w) mispair, and is tautomerised into Watson–Crick (WC)-like base mispair C^*·2AP(WC) and less effectively produces A.2AP(w)/A^*.2AP(WC) mispairs. The vertical ionisation potential, vertical electron affinity, hardness and electrophilicity index of these complexes have also been discussed. The modifications of energy levels and charge density distributions of the frontier orbitals are also analysed. The absorption spectra of these complexes lie in the visible region, which suggests their application in fluorescent-bio imaging. The mechanism of cooperativity effect is studied by molecular orbital potential (MEP), atoms-in-molecules (AIM) and natural bond orbital analyses. Most metalated pairs have smaller HOMO–LUMO band gaps than the isolated mismatch nucleobases which suggest interesting consequences for electron transfer through DNA duplexes.     

An inclusive SUSY approach to position dependent mass systems

The supersymmetry (SUSY) formalism for a position dependent mass problem with a more general ordering is yet to be formulated. In this paper, we present an unified SUSY approach for PDM problems of any ordering. Highlighting all non-Hermitian Hamiltonians of PDM problems are of quasi-Hermitian nature, the SUSY operators of these problems are constructed using similarity transformation. The methodology that we propose here is applicable for even more general cases where the kinetic energy term is represented by linear combination of infinite number of possible orderings. We illustrate the method with an example, namely Mathews-Lakshmanan (ML) oscillator. Our results show that the latter system is shape invariant for all possible orderings. We derive eigenvalues and eigenvectors of this nonlinear oscillator for all possible orderings including Hermitian and non-Hermitian ones.     

Titanium Nanorods Loaded PCL Meshes with Enhanced Blood Vessel Formation and Cell Migration for Wound Dressing Applications

Proper management of nonhealing wounds is an imperative clinical challenge. For the effective healing of chronic wounds, suitable wound coverage materials with the capability to accelerate cell migration, cell proliferation, angiogenesis, and wound healing are required to protect the healing wound bed. Biodegradable polymeric meshes are utilized as effective wound coverage materials to protect the wounds from the external environment and prevent infections. Among them, electrospun biopolymeric meshes have got much attention due to their extracellular matrix mimicking morphology, ability to support cell adhesion, and cell proliferation. Herein, electrospun nanocomposite meshes based on polycaprolactone (PCL) and titanium dioxide nanorods (TNR) are developed. TNR incorporated PCL meshes are fabricated by electrospinning technique and characterized by scanning electron microscopy, energy dispersive X‐ray spectroscopy, Fourier transform infrared spectroscopy (FTIR) analysis, and X‐Ray diffraction (XRD) analysis. In vitro cell culture studies, in ovo angiogenesis assay, in vivo implantation study, and in vivo wound healing study are performed. Interestingly, obtained in vitro and in vivo results demonstrated that the presence of TNR in the PCL meshes greatly improved the cell migration, proliferation, angiogenesis, and wound healing. Owing to the above superior properties, they can be used as excellent biomaterials in wound healing and tissue regeneration applications.     

Generation of Electromagnetic Wave in Two-Electron-Temperature Plasmas

It is shown that in a two-electron-temperature plasma a finite amplitude upper-hybrid wave can parametrically decay into an electrostatic electron acoustic wave (EAW) and a left handed circularly polarized (LHCP) electromagnetic wave propagating along the magnetic field. The electromagnetic oscillating two stream instability is also discussed in the same system. The role of second electron component is discussed with its application in lab plasma as well as in space plasma.