Turkish high school students’ definitions for parallelograms: appropriate or inappropriate?

The aim of this study was to investigate the appropriateness of high school students' definitions. The participants in this study were 269 high school students from a public school in Ordu city, which is on the Black Sea coast of Turkey. The participants were asked to write their definitions with no time constraints. In the analysis of the definitions, students' ability to distinguish necessary and sufficient conditions and their ability to use appropriate mathematical terminology were taken into account. The task used in this study enabled us to mirror students' difficulties and inadequacies about their definitions of a parallelogram. The findings indicated that most of the students defined parallelogram inappropriately because they had used incomplete or incorrect statements. On the other hand, for the appropriate definitions, it was found that the number of uneconomical definitions was almost the same as the number of economical ones. At the end of the study, it was suggested that defining activities should be integrated into curriculums explicitly and should be given importance in our mathematic lessons.     

Polarimetric interferometer for measuring nonlinearity error of heterodyne interferometric displacement system

This letter presents a polarimetric interferometer(PI) that can measure the ellipsometric parameter θ with an accuracy of 0.01 leading to a potential accuracy of 17 pm.The PI is constructed and compared with a commercial heterodyne interferometer(HI).Given its low nonlinearity,the PI is used to measure the residual nonlinearity of a heterodyne interferometric displacement system.A rotating half-wave plate is used to compensate for a part of the nonlinearity error caused by the misalignment of the axis between input polarizing states and beamsplitter.     

Quantitative mineralogical properties (morphology-chemistry-structure) of pharmaceutical grade kaolinites and recommendations to regulatory agencies

The physical and chemical characteristics of kaolinite (kaolin) may be variable, and minor amounts of other clay minerals, nonclay minerals, and other impurities may affect the properties of kaolinites. Thus specific technical properties of pharmaceutical grade kaolinites become very important because these clays are used in medical applications, e.g., as pharmaceutical excipients, and will be consumed by humans. Seven pharmaceutical grade kaolinite specimens were used in this study: K1004, KA105, 2242-01, K2-500, Acros, Acros-mono, and KX0007-1. In addition, two kaolinites from the Clay Minerals Society Source Clays, KGa-1b and KGa-2, were used for comparison purposes. The Acros-mono and 2242-01 kaolinites contained minor amounts of illite, which was demonstrated both compositionally and structurally by using inductively coupled plasma spectroscopy and powder X-ray diffraction. The KX0007-1 kaolinite powder was found to be heavily contaminated with quartz, cristobalite, and alunite. Crystal structure computations also showed excess Si in its tetrahedral site, and the mineral no longer has the typical kaolinite crystal structure. These widely-used industrial standards should be quantitatively characterized morphologically, compositionally, and structurally. Results of the mineralogical characteristics should be clearly labeled on the pharmaceutical grade kaolinites and reported to the relevant regulatory agencies.     

Optimising a nonlinear utility function in multi-objective integer programming

In this paper we develop an algorithm to optimise a nonlinear utility function of multiple objectives over the integer efficient set. Our approach is based on identifying and updating bounds on the individual objectives as well as the optimal utility value. This is done using already known solutions, linear programming relaxations, utility function inversion, and integer programming. We develop a general optimisation algorithm for use with k objectives, and we illustrate our approach using a tri-objective integer programming problem.     

Detection of melamine in milk by surface-enhanced Raman spectroscopy coupled with magnetic and Raman-labeled nanoparticles

A new method based on surface-enhanced Raman spectroscopy (SERS) has been developed for sensitive and rapid detection of melamine. Spherical magnetic-core gold-shell nanoparticles (AuNPs) and rod-shaped gold nanoparticles (nanorods) labeled with a Raman-active compound were used to form a complex with the melamine molecules. 5,5'-Dithiobis(2-nitrobenzoic acid) was used as Raman-active compound because it is readily adsorbed by a gold nanoparticle surface forming a self-assembled monolayer (SAM) and has strong Raman scattering at 1330 cm(-1), because of the symmetric NO(2) stretch. The calibration curve was obtained by plotting Raman band area at 1330 cm(-1) against melamine concentration. A linear relationship was obtained with a high determination coefficient (R(2)=0.997). The method was validated for linearity, sensitivity, precision (intra-day and inter-day repeatability), and recovery. In the model system, the limits of detection (LOD) and quantification (LOQ) were 0.38 and 1.27 mg L(-1), respectively. For melamine-spiked milk samples, LOD and LOQ values were 0.39 mg L(-1) and 1.30 mg L(-1), respectively. Intra and inter-day precision were 3.73 and 4.94 %, respectively. This method was applied to samples of skimmed milk that had been spiked with melamine at different concentrations. The recovery of the method was 95-109 % in the concentration range 2-15 mg L(-1), and average RSD was 1.71 %. Total analysis time was less than 15 min.     

Using the anisotropy of magnetic susceptibility to infer flow-induced orientation of anisotropic particles: feasibility and sensitivity

In this paper, the use of anisotropy of magnetic susceptibility (AMS) measurements has been investigated in order to check the sensitivity of this technique versus the flow conditions. The orientation of anisotropic magnetic particles during the flow of a polystyrene $/$ magnetite blend through a capillary rheometer has been studied. Thanks to the magnetic properties of the magnetite, AMS measurements are possible. Different values of the filler concentration, viscosity, and shear rate were used. It is shown that the AMS technique is able to detect accurately particle orientation and that sensitivity decreases when increasing the concentration of magnetite grains. In addition, the rectangular-shaped sample imposed by the rheological device does not affect measures of AMS significantly. The results give reasons to consider that the measure of AMS is an accurate and sensitive method to access the mean local rheological behavior in filled or non-filled systems containing anisotropic tracers.     

Numerical investigation of a water flow in a rib-roughened channel by using Reynolds stress model

In this paper, water flow in a rib-roughened channel is investigated numerically by using Reynolds stress turbulence models (RSM) on a three-dimensional (3-D) domain. Computational results for mean streamwise velocity component and turbulent kinetic energy show good agreements with available experimental data. Five rib pitch-to-height ratios (p/h) of 1, 5, 10, 15 and 20 are analysed for six different Reynolds numbers (Re) of 3000, 7000, 12,000, 20,000, 40,000 and 65,000. Velocity vectors, streamlines and Reynolds stresses are showed for these ratios and Re numbers. Streamlines revealed that Reynolds numbers do not affect flowfield but play an important role in the Reynolds stresses.     

Radioactivity levels in surface water of lakes around Izmir/Turkey

The aim of this study is to determine the radioactivity levels as a baseline for further studies and to obtain the distribution patterns of radioactivity in lake surface water around Izmir/Turkey. In this study, surface water samples were collected from three lakes around Izmir–Turkey. Surface water samples were analyzed for pH, mV conductivity and alkalinity content. The gross alpha/beta and uranium concentrations were investigated in the collected lake water samples. Mean gross alpha and gross beta activity concentrations in the surface water were found to be between (0.03 and 2.62) Bq l⁻¹ for Karagol Lake, (0.75 and 2.35) Bq l⁻¹ for Golcuk Lake, (0.03 and 1.77) Bq l⁻¹ for Cakalbogaz Lake, respectively. Uranium concentration varied between (0.05 and 900) μg l⁻¹ for Karagol Lake, (0.05 and 0.95) μg l⁻¹ for Golcuk Lake and (3.33 and 10) μg l⁻¹ for Cakalbogaz Lake. Radioactivity contour maps were produced and their data were evaluated statistically.     

From Dark to Light to Fluorescence Resonance Energy Transfer (FRET): Polarity‐Sensitive Aggregation‐Induced Emission (AIE)‐Active Tetraphenylethene‐Fused BODIPY Dyes with a Very Large Pseudo‐Stokes Shift

The work presented herein is devoted to the fabrication of large Stokes shift dyes in both organic and aqueous media by combining dark resonance energy transfer (DRET) and fluorescence resonance energy transfer (FRET) in one donor–acceptor system. In this respect, a series of donor–acceptor architectures of 4,4‐difluoro‐4‐bora‐3a,4a‐diaza‐s‐indacene (BODIPY) dyes substituted by one, two, or three tetraphenylethene (TPE) luminogens were designed and synthesised. The photophysical properties of these three chromophore systems were studied to provide insight into the nature of donor–acceptor interactions in both THF and aqueous media. Because the generation of emissive TPE donor(s) is strongly polarity dependent, due to its aggregation‐induced emission (AIE) feature, one might expect the formation of appreciable fluorescence emission intensity with a very large pseudo‐Stokes shift in aqueous media when considering FRET process. Interestingly, similar results were also recorded in THF for the chromophore systems, although the TPE fragment(s) of the dyes are non‐emissive. The explanation for this photophysical behaviour lies in the DRET. This is the first report on combining two energy‐transfer processes, namely, FRET and DRET, in one polarity‐sensitive donor–acceptor pair system. The accuracy of the dark‐emissive donor property of the TPE luminogen is also presented for the first time as a new feature for AIE phenomena.