9,9‐Diaryl‐4,5‐diazafluorene‐based Cardo polymer; Synthesis and characteristic properties

To open out new aspects of 9,9‐diarylfluorene (DAF)‐based polymers with high performances, 9,9‐(4‐hydroxyphenyl)‐4,5‐diazafluorene ( N‐BPF ) was designed as a new cardo structure and the properties of poly(ether ketone)s ( N‐PEKs ) containing N‐BPF skeletons were examined in detail. N‐PEKs were synthesized in high yields via polycondensation of N‐BPF with difluoroarenes. N‐PEKs showed cardo polymer‐specific properties such as high thermal stability and high solubility in organic solvents. The addition of p‐toluenesulfonic acid (TsOH) to N‐PEK resulted in the formation of network polymer based on interchain hydrogen bonds. It turned out that the films of network polymer are flexible and transparent and exhibit high refractive index and low birefringence. The effects of feed ratio of TsOH to N‐PEK were also evaluated on the mechanical properties of network polymer. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4541–4549     

Online tool for calculating null points in various inversion recovery sequences

Accurate equations for calculating the inversion time of the null point (TI_null) in inversion recovery (IR) sequences are required for adequate suppression of fat or cerebrospinal fluid (CSF) but are not widely known. The purpose of this study is to elucidate the process of deriving accurate TI_null equations using schematic diagrams that allow the equations to be easily understood, and to devise a convenient online tool for instant calculation of TI_null.     

Evaluation of thermodynamic consistency of isobaric and isothermal binary vapor–liquid equilibrium data using the PAI test II,alcohol + n-alkane, +aromatic, +cycloalkane systems

The thermodynamic consistency of binary vapor–liquid equilibrium data has been examined for 46 binary alcohol + hydrocarbon systems with 310 data sets in total (145 isobaric and 165 isothermal sets) using the PAI test proposed in our previous study. The PAI test permits an overall check of the data by combining three tests: a point test, an area test, and an infinite dilution test. In this work, the PAI test was incorporated with the NRTL equation for fitting data. The results of the PAI test for the vapor–liquid equilibrium data showed that the PAI test was able to strictly select reliable data.     

Dynamic Enumeration of All Mixed Cells

The polyhedral homotopy method, which has been known as a powerful numerical method for computing all isolated zeros of a polynomial system, requires all mixed cells of the support of the system to construct a family of homotopy functions. The mixed cells are reformulated in terms of a linear inequality system with an additional combinatorial condition. An enumeration tree is constructed among a family of linear inequality systems induced from it such that every mixed cell corresponds to a unique feasible leaf node, and the depth-first search is applied to the enumeration tree for finding all the feasible leaf nodes. How to construct such an enumeration tree is crucial in computational efficiency. This paper proposes a dynamic construction of an enumeration tree, which branches each parent node into its child nodes so that the number of feasible child nodes is expected to be small; hence we can prune many subtrees which do not contain any mixed cell. Numerical results exhibit that the proposed dynamic construction of an enumeration tree works very efficiently for large scale polynomial systems; for example, it generated all mixed cells of the cyclic-15 problem for the first time in less than 16 hours.     

Preconcentration of atrazine and simazine with multiwalled carbon nanotubes as solid-phase extraction disk

A sensitive and selective preconcentration method using solid-phase extraction (SPE) disk, namely multiwalled carbon nanotubes (MWCNTs) disk, is proposed for the determination of atrazine and simazine in water samples. Atrazine and simazine were extracted on MWCNTs disk and then determined by gas chromatography–mass spectrometry (GC/MS). Several parameters on the enrichment factor of the analytes were investigated. The experimental results showed that it was possible to obtain quantitative analysis when the solution pH was 5 using 200 mL of validation solution containing 0.1 μg of triazines and 5 mL of acetone as an eluent. The maximum enrichment factors for atrazine and simazine were 3900 ± 250 and 4000 ± 110, respectively when 200 mL of sample solution volume was used. Relative standard deviations for seven determinations were 6.9% (atrazine) and 3.0% (simazine) under optimum conditions. The linear range of calibration curves were 0.1 to 1 ng mL^{− 1} for each analyte with good correlation coefficients. The detection limits (3S/N) were 2.5 and 5.0 pg mL^{− 1} for atrazine and simazine, respectively. The proposed method was successfully applied to the determination of atrazine and simazine in environmental water samples with high precision and accuracy.