Synthesis and cytotoxic activities of transition-metal complexes of a binaphthyl-linked bipyridine ligand

A binaphthyl-linked bipyridyl compound, 1,1′-bis(6-methyl-6′-oxymethylenyl-2,2′-bipyridine)binaphthyl, (L) has been synthesised and used as a ligand for the formation of Cu(II), Ni(II), and Co(II) complexes. The ligand and its transition-metal complexes were characterized by physico-chemical and spectroscopic methods. The complexes were also investigated for cytotoxic activity. The cytotoxicity of complexes, CuL(ClO₄)₂, NiL(ClO₄)₂(H₂O), CoL(ClO₄)₂, were tested in vitro applying seven well-characterized human tumor cell lines, MCF7, EVSA-T, WIDR, IGROV, M19 MEL, A498, H226, and the microculture sulforhodamine B (SRB) test. All complexes show a very high cytotoxicity (ID₅₀ < 250 ng/ml) in these cell lines.     

Factors Associated With Mathematics Achievement and Participation in Advanced Mathematics Courses: An Examination of Gender Differences From an International Perspective

This paper reports results of an exploratory study examining factors that might be associated with achievement in mathematics and participation in advanced mathematics courses in Canada, Norway, and the United States of America (USA). These factors, which were not directly related to schooling accounted for large degrees of variability, 24% to 39%, in mathematics achievement scores. Confidence in mathematics was the strongest predictor of achievement for students from Canada and Norway, whereas for the students from the USA, parents' highest education level was the highest predictor of achievement. Student home environment related variables were stronger predictors of achievement for females than for males in all three countries. The participation in advanced mathematics courses could be predicted with 72% to 76% accuracy by the same variables. In all of the three countries, the strongest predictors of participation in advanced mathematics courses were students' attitudes toward mathematics. Parents' education level, a socioeconomic related variable, was one of the strongest predictors of participation for Canadian female students and all students from the USA.     

Optical CO<Subscript>2</Subscript> Sensing with Ionic Liquid Doped Electrospun Nanofibers

The first use of electrospun nanofibrous materials as highly responsive fluorescence quenching-based optical CO₂ sensors is reported. Poly(methyl methacrylate) and ethyl cellulose were used as polymeric materials. Sensing slides were fabricated by electrospinning technique. A fiber-optic bundle was used for the gas detection. CO₂ sensors based on the change in the fluorescence signal intensity of ion pair form of 8-hydroxypyrene-1,3,6-trisulfonic acid (HPTS). The sensor slides showed high sensitivities due to the high surface area-to-volume ratio of the nanofibrous membrane structures. The preliminary results of Stern-Volmer analysis show that the sensitivities of electrospun nanofibrous membranes to detect CO₂ are 24 to 120 fold higher than those of the thin film based sensors. The response times of the sensing reagents were short and the signal changes were fully reversible. The stability of ion pair form of HPTS in the employed matrix materials was excellent and when stored in the ambient air of the laboratory there was no significant drift in signal intensity after 7 months. Our stability tests are still in progress.     

The effects of formalism on teacher trainees’ algebraic and geometric interpretation of the notions of linear dependency/independency

The aim of this study is to identify the effects of formalism in teaching on primary and secondary school mathematics teacher trainees’ algebraic and geometric interpretations of the notions of linear dependency/independency. Quantitative research methods are drawn in order to determine differences in success levels between algebraic and geometric interpretations of the linear dependency/independency of vectors presented in two- and three-dimensional space. On the other hand, qualitative research methods were utilized in order to investigate thinking modes involved in the geometric interpretation of the same notion. The participants were a total of 144 teacher trainees registered at the Selçuk University, Education Faculty in 2007–2008 academic year. 33 participants were first year students at Secondary Mathematics Education Department, while 111 were second year students at Primary Mathematics Education Department. The results indicated that correlations between the formal definition of the notions of linear dependency/independency and the items of the test which required algebraic and geometric interpretation were both low. Yet, the correlation for the algebraic dimension of the test was higher than the geometric dimension. Likewise, algebraic mean success score was significantly higher than the geometric mean score.     

Minimization principle and generalized Fourier series for discontinuous Sturm-Liouville systems in direct sum spaces

By modifing the Green''s function method we study certain spectral aspects of discontinuous Sturm-Liouville problems with interior singularities. Firstly, we define four eigen-solutions and construct the Green''s function in terms of them. Based on the Green''s function we establish the uniform convergeness of generalized Fourier series as eigenfunction expansion in the direct sum of Lebesgue spaces $L_2$ where the usual inner product replaced by new inner product. Finally, we extend and generalize such important spectral properties as Parseval equation, Rayleigh quotient and Rayleigh-Ritz formula (minimization principle) for the considered problem.     

Fiber optic pH sensing with long wavelength excitable Schiff bases in the pH range of 7.0-12.0

Most of the fluorescent pH probes work near neutral or acidic regions of the pH scale. In this work, two different fluorescent Schiff bases, chloro phenyl imino propenyl aniline (CPIPA) and nitro phenyl imino propenyl aniline (NPIPA), have been investigated for pH sensing in the alkaline region. Absorption and emission based spectral data, quantum yield, fluorescence lifetime, photostability and acidity constant (pK(a)) of the Schiff bases were determined in conventional solvents and in PVC. The long wavelength excitable immobilized Schiff bases CPIPA (lambda(ex)=556 nm) and NPIPA (lambda(ex)=570 nm) exhibited absorption and emission based optical response to proton in the pH range of 8.0-12.0 and 7.0-12.0, respectively. Response of the CPIPA was fully reversible within the dynamic working range. The response times were between 3-13 min. A relative signal change of 95% and 96% have been achieved for sensor dyes of CPIPA and NPIPA, respectively. The CPIPA displayed better fluorescence quantum yield (varphi(F)=3.7 x 10(-1)) and higher matrix compatibility compared to NPIPA (varphi(F)=1.6 x 10(-1)) in immobilized PVC. The CPIPA and NPIPA exhibited a slight cross sensitivity to the ions of Hg(+) and Fe(3+), respectively.     

On the steady solitary-wave solution of the Green–Naghdi equations of different levels

The steady-state solitary wave solution of high-level Green–Naghdi (GN) equations is obtained by use of the Newton–Raphson method. Four aspects of solitary waves are studied: the wave speed, wave profile, velocity field and particle trajectory. A convergence study is performed for each individual case. Results of the converged model are compared with the existing laboratory experiments and other theoretical solutions for an inviscid and incompressible fluid, including the solutions of the Euler equations. Particle trajectories, predicted by the GN model, show close agreement with the laboratory measurements and provide a new approach to understanding the movement of the particles under a solitary wave. It is further shown that high-level GN equations can predict the solitary wave of the highest height.     

Energy Crops and Methane: Process Optimization of Ca(OH)2 Assisted Thermal Pretreatment and Modeling of Methane Production

Switchgrass earned its place globally as a significant energy crop by possessing essential properties such as being able to control erosion, low cost of production, biomass richness, and appeal for biofuel production. In this study, the impact of a Ca(OH)₂-assisted thermal pretreatment process on the switchgrass variety Shawnee for methane fuel production was investigated. The Ca(OH)₂-assisted thermal pretreatment process was optimized to enhance the methane production potential of switchgrass. Solid loading (3–7%), Ca(OH)₂ concentration (0–2%), reaction temperature (50–100 °C), and reaction time (6–16 h) were selected as independent variables for the optimization. Methane production was obtained as 248.7 mL CH₄ gVS⁻¹ under the optimized pretreatment conditions. Specifically, a reaction temperature of 100 °C, a reaction time of 6 h, 0% Ca(OH)₂, and 3% solid loading. Compared to raw switchgrass, methane production was enhanced by 14.5%. Additionally, the changes in surface properties and bond structure, along with the kinetic parameters from first order, cone, reaction curve, and modified Gompertz modeling revealed the importance of optimization.     

Microstructural and superconducting properties of C6H6 added bulk MgB2 superconductor

The effect of aromatic hydrocarbon (benzene, C₆H₆) addition on lattice parameters, microstructure, critical temperature (T_c), critical current density (J_c) of bulk MgB₂ has been studied. In this work only 2 mol% C₆H₆ addition was found to be very effective in increasing the J_c values, while resulting in slight reduction of the T_c. J_c values of 2 mol% C₆H₆ added MgB₂ bulks reached to 1.83×10⁶ A/cm² at 15 K and 0 T. Microstructural analyses suggest that J_c enhancement is associated with the substitution of carbon with boron and which also results in the smaller MgB₂ grain size. The change in the lattice parameters or the lattice disorder is claimed as a cause of the slight reduction in the T_c by carbon addition. We note that our results show the advantages of C₆H₆ addition include homogeneous mixing of precursor powders, avoidance of expansive nanoadditives, production of highly reactive C, and significant enhancement in J_c of MgB₂, compared to un-doped samples.