Hexaazatriphenylene-Based Two-Dimensional Conductive Covalent Organic Framework with Anisotropic Charge Transfer

The development of covalent organic frameworks (COFs) with efficient charge transport is of immense interest for applications in optoelectronic devices. To enhance COF charge transport properties, electroactive building blocks and dopants can be used to induce extended conduction channels. However, understanding their intricate interplay remains challenging. We designed and synthesized a tailor-made COF structure with electroactive hexaazatriphenylene (HAT) core units and planar dioxin (D) linkages, denoted as HD-COF. With the support of theoretical calculations, we found that the HAT units in the HD-COF induce strong, eclipsed π–π stacking. The unique stacking of HAT units and the weak in-plane conjugation of dioxin linkages leads to efficient anisotropic charge transport. We fabricated HD-COF films to minimize the grain boundary effect of bulk COFs, which resulted in enhanced conductivity. As a result, the HD-COF films showed an electrical conductivity as high as 1.25 S cm⁻¹ after doping with tris(4-bromophenyl)ammoniumyl hexachloroantimonate.     

Pre-service Teachers’ Developing Conceptions about the Nature and Pedagogy of Mathematical Modeling in the Context of a Mathematical Modeling Course

Adopting a multitiered design-based research perspective, this study examines pre-service secondary mathematics teachers’ developing conceptions about (a) the nature of mathematical modeling in simulations of “real life” problem solving, and (b) pedagogical principles and strategies needed to teach mathematics through modeling. Unlike other studies that have focused on single-topic and lesson-sized research sites, a course-sized research site was used in this study. Having been through several iterations over three teaching semesters, the 15-week long course was implemented with 25 pre-service secondary mathematics teachers. Findings revealed that pre-service teachers developed ideas about the nature of mathematical modeling involving what mathematical modeling is, the relationship between mathematical modeling and meaningful understanding, and the nature of mathematical modeling tasks. They also realized the changing roles of teachers during modeling implementations and diversity in students’ ways of thinking. The researchers’ conceptual development, on the other hand, involved realizing the critical aspect of the “teacher role” played by the instructor during modeling implementations, and the need for more experience of modeling implementations for pre-service teachers.     

Nonthermal Atomization Using Atom Traps in Flame AAS

The most sensitive atomic spectrometric technique has been ETA-AAS for many years. Recently, ICP-MS has emerged as an approach which provides even lower detection limits, but at considerably higher instrument and running costs. Flame AAS, on the other hand, is still being used widely in many laboratories in world. Therefore, alternative approaches for better sensitivity using flame AAS should be relevant and important.     

Bertrand curves of AW(k)-type in Lorentzian space

In this study, firstly, we give curvature conditions of AW(k)-type (1≤k≤3$1\le k\le 3$) curves. Then considering AW(k)-type curves, we investigate Bertrand curves γ:I→L³$\gamma :I\to L^3$ with _κ1(s)≠0${\kappa }_1\left(s\right)\ne 0$ and _κ2(s)≠0${\kappa }_2\left(s\right)\ne 0$. We show that there are Bertrand curves of AW(1)-type and AW(3)-type. Moreover, we study weak AW(2)-type and AW(3)-type conical geodesic curves in L³$L^3$.     

Study of the stability of the fermionic instanton solutions by the scale index method

In the last years, there has been great interest to the formulation and application of wavelet transformation in variety of fields to investigate the characteristics of dynamical systems. Recently, a method based on the scalogram analysis of the continuous wavelet transform, the scale index has been proposed to measure aperiodicity and determine the transitions from aperiodic behaviour to periodic behaviour in nonlinear dynamical systems. In this work we test the scale index method by performing the analysis of the deterministic behaviour of the fermion-like two-dimensional Akdeniz–Smailagic instanton solution in Thirring Model. We show that the scale index method can also be considered to detect the periodic behaviours of the fermion-like instanton solutions.     

Antioxidant secondary metabolites from Geranium lasiopus Boiss. & Heldr

Chromatographic studies on the EtOAc soluble portion of the MeOH extract of Geranium lasiopus led to the isolation of eight flavonoids (kaempferol (1), quercetin (2), quercetin 3-O-β-glucopyranoside (3), quercetin 3-O-β-galactopyranoside (4), kaempferol 3-O-α-rhamnopyranosyl-(1?→?6)-β-glucopyranoside (5), quercetin 3-O-α-rhamnopyranosyl-(1?→?6)-β-glucopyranoside (6), kaempferol 3-O-α-rhamnopyranosyl-(1?→?2)-β-glucopyranoside (7) and quercetin 3-O-α-rhamnopyranosyl-(1?→?2)-β-glucopyranoside (8)), two simple phenolic compounds (gallic acid (9) and its methyl ester (10)) and a hydrolysable tannin (pusilagin (11)). The structures of the compounds were elucidated by 1- and 2-dimensional NMR techniques ((1)H, (13)C, COSY, HMBC, HMQC) and ESI-TOF-MS spectrometry. Inhibitory effects on H(2)O(2)-induced lipid peroxidation in human red blood cells of the different extracts of G. lasiopus, as well as isolated compounds, were investigated. All tested compounds showed comparable or higher activity than that of ascorbic acid and trolox.     

In Vitro Inhibition Effect of Some Dihydroxy Coumarin Compounds on Purified Human Serum Paraoxonase 1 (PON1)

Human serum paraoxonase 1 (PON1; EC 3.1.8.1) is a high-density lipoprotein associated, calcium-dependent enzyme that hydrolyses aromatic esters, organophosphates and lactones and can protect the low-density lipoprotein against oxidation. In this study, in vitro inhibition effect of some dihydroxy coumarin compounds namely 6,7-dihydroxy-3-(2-methylphenyl)-2H-chromen-2-one (A), 6,7-dihydroxy-3-(3-methylphenyl)-2H-chromen-2-one (B) and 6,7-dihydroxy-3-(4-methylphenyl)-2H-chromen-2-one (C) on purified PON1 were investigated by using paraoxon as a substrate. PON1 was purified using two-step procedures, namely ammonium sulphate precipitation and Sepharose-4B-l-tyrosine-1-naphthylamine hydrophobic interaction chromatography. The purified enzyme had a specific activity of 11.76?U/mg. The dihydroxy coumarin derivatives of A and B compounds inhibited PON1 enzyme activity in a noncompetitive inhibition manner with K _i of 0.0080?±?0.256 and 0.0003?±?0.018?mM values, respectively. C compound exerted an uncompetitive inhibition of PON1 enzyme activity with K _i of 0.0010?±?0.173?mM. Moreover, dihydroxy coumarin derivatives of A, B and C compounds were effective inhibitors on purified human serum PON1 activity with IC₅₀ of 0.012, 0.022 and 0.003?mM values, respectively. IC₅₀ value of unsubstituted 6,7 dihydroxy coumarin was found as 0.178?mM. The present study has demonstrated that PON1 activity is very highly sensitive to studied coumarin derivatives.     

Preparation of bow tie–type methacrylated poly(caprolactone‐co‐lactic acid) scaffolds: effect of collagen modification on cell growth

A branched methacrylated poly(caprolactone‐co‐lactic acid) and methacrylated poly(tetramethylene ether glycol) (PTMG‐IEM) resins were synthesized. ¹H‐NMR spectroscopy, attenuated total reflectance Fourier transform infrared spectroscopy (ATR‐FTIR) spectroscopy, and gel permeation chromatography confirmed the chemical structures of copolymers. The photoinitiated polymerization of formulation composed of various amounts of methacrylated poly(caprolactone‐co‐lactic acid), PTMG‐IEM, poly(ethylene glycol) diacrylate, water, and photoinitiator were performed. The curing reactions were followed by photo‐DSC (Differential scanning calorimetry). Gel fraction was calculated from the insoluble part and found as ≥93%. Swelling and contact angles were measured, and all increased with the increasing amount of PTMG‐IEM in network formulations. In vitro degradation studies were performed at 37 °C in phosphate‐buffered saline (pH 7.4). Collagen‐modified polymers were also prepared and introduced as a bioactive moiety to modify the polymer to enhance cell affinity. To compare the cell adhesion affinity to the polymer with and without collagen, cell growth experiments were performed. The results showed that collagen improves the cell adhesion onto the polymer surface. With the increasing amount of collagen, cell viability increases 86% (ECV304, p < 0.05) and 83% (3 T3, p < 0.05). Copyright © 2011 John Wiley & Sons, Ltd.     

One Pot Synthesis of Graphene through Microwave Assisted Liquid Exfoliation of Graphite in Different Solvents

This study presents an easy and quick method for the synthesis of graphene from graphite in a set of solvents, including n-Hexadecane (n-Hexa), dimethylsulfoxide (DMSO), sodium hydroxide (NaOH), 1-octanol (OCTA), perchloric acid (PA), N,N-Dimethylformamide (DMF), ethylene glycol (EG), and ethylene diamine (ED), via microwave (MW) energy. The properties of final products were determined by X-ray diffraction spectroscopy (XRD), Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible (UV-Vis) spectroscopy, and the four-point probe technique. The XRD spectra of most of the MW-assisted graphene products showed peaks at 2θ = 26.5° and 54°. Layer numbers extend from 2 and 25, and the leading comes about were gotten by having two-layered products, named as graphene synthesized in dimethylsulfoxide (G-DMSO), graphene synthesized in ethylene glycol (G-EG), and graphene synthesized in 1-octanol (G-OCTA). G-DMF has the highest electrical conductivity with 22 S/m. The electrical conductivity is higher when the dipole moment of the used solvent is between 2 and 4 Debye (D). The FTIR spectra of most of the MW-assisted graphene products are in line with commercial graphene (CG). The UV-Vis spectra of all MW-assisted graphene products showed a peak at 223 nm referring to characteristic sp2 C=C bonds and 273 nm relating to the n → π * transition of C-O bonds.