Environmentally friendly composites made of poly­(vinyl alcohol) and carboxymethyl cellulose (PVA/CMC) hydrogels were proposed. The PVA/CMC hydrogels were prepared by freeze–thaw processes and applied to adsorb heavy metal ions including Ag+, Ni2+, Cu2+, and Zn2+. The phase separation of polymer solutions during freezing stages led to the formation of crystallites and resulted in insoluble hydrogels. The PVA/CMC hydrogels were effectively acquired, confirmed by at least 71% of insoluble gels found in the gel fraction. In addition, the gel fraction, physical properties, and swelling ratios were clearly modulated by the compositions of PVA and CMC among the samples of pure PVA, P2C1 (containing two-thirds of PVA and one-third of CMC), P1C1, and P1C2 hydrogels. For pure PVA hydrogels, the swelling ratio was 416%, while the P1C2 hydrogels exhibited a much higher swelling ratio (1437%). For the metal adsorption, the experimental results indicated that the P2C1 hydrogels presented not only the highest adsorption capacity toward Ag+ (8.4 mg per gram of hydrogel) but also the highest selectivity toward Ag+ in the mixed solutions. Interestingly, the experimental results revealed clearly that the adsorbed metal ions were further reduced on the P2C1 hydrogels. In summary, an insoluble hydrogel composed of PVA/CMC with excellent capacity of adsorbing metal ions was prepared in an economic and energy-saving manner. The prepared hydrogels showed potential applications for removal of heavy metal ions and wastewater treatment.

Novel modification of the TiO2/CH3NH3PbI3interface using glycine as a coupling agent induced higher coverage of perovskite through a two-step solution process.

The case-control study design is popular for genetic association studies of complex human diseases. However, case-control studies may suffer from bias due to population stratification. In this paper, the authors present simple formulas that can set a limit to the havoc population stratification bias can wreak (the lower and upper bounds of the confounding rate ratio and the upper bound of the type I error rate). The authors demonstrate applications of these formulas using two examples. The formulas can help researchers make more prudent interpretations of their (potentially biased) results.

Spherical silica microcapsules containing phase-change material (PCM) were prepared by the sol-gel method in O/W emulsion. This is the first time that inorganic encapsulation of PCM with core/shell structure has been studied. The results of this synthesis revealed that micron size (4 - 8 microm) silica microspheres encapsulating n-pentadecane can be successfully created from acidic solutions ([H+] > or = 1.44 N) by using cationic surfactants as the emulsifiers. The identification of the mechanisms for the formation of silica shell at the oil-water interface indicates that it should be the charge-controlled mechanism through S+X-I+ (positively charged surfactant-halide ion-positively charged silica species) electrostatic interactions or the reaction rates-controlled mechanism working on cationic emulsifiers.

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