Gelation and crosslinking characteristics of photopolymerized poly(ethylene glycol) hydrogels

The gelation and crosslinking features of poly(ethylene glycol) (PEG) hydrogels were scrutinized through the UV polymerization processes of poly(ethylene glycol) methacrylate (PEGMA) and poly(ethylene glycol) dimethacrylate (PEGDMA) mixtures. The real‐time evolutions of the elastic moduli of the prepolymerized mixtures with different crosslinking ratios of PEGMA and PEGDMA and the photoinitiator concentrations were measured during photopolymerization. The rheological properties were compared with other properties of the PEG hydrogels, including the relative changes in the C?C amounts in the mixtures before and after UV irradiation, water swelling ratio, gel fraction, mesh size, and mechanical hardness. As the portion of PEGDMA as a crosslinker increased, the final elastic modulus and gel fraction increased, whereas the swelling ratio and scratch penetration depth at the hydrogel film surface decreased because of the formation of compact networks inside the hydrogels. These results indicate that there was a good correlation between the rheological analysis for predicting the crosslinking transition during photopolymerization and the macroscopic properties of the crosslinked hydrogels. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41939.     

Removal of PM2.5 entering through the ventilation duct in an automobile using a carbon fiber ionizer-assisted cabin air filter

This study evaluated the charging characteristics of a carbon fiber ionizer for PM2.5 and carried out particle capture laboratory tests after an ionizer was installed upstream of the media of an electret cabin air filter. When the ion concentration per particle (N_i) of the carbon fiber charger was 10⁶ ions/cm³, the average charge numbers for each particle were 1.54, 0.88, and 0.49 at 0.6, 1.2, and 1.8 m/s of face velocity, respectively (the particle charging times, τ, were 167, 83, and 56 ms, respectively). For these face velocities, the PM2.5 removal efficiencies of the filter media were 69.3%, 65.2% and 62.2%, respectively, but increased to 80.4%, 71.2% and 65.5%, respectively, when the ionizer was turned on. The carbon fiber ionizer was then installed in front of an electret cabin filter in the air conditioning system of an automobile, after which field tests were performed at a roadside area. For the same N_iτ used in the lab-scale tests, the effects of the carbon fiber ionizer on increasing PM2.5 %Reduction were mild as 9.4%, 4.0%, and 2.8% when the flow rates were at the second, fourth, and sixth levels, respectively (the face velocities were 0.6, 1.2, and 1.8 m/s, respectively). The PM2.5 %Reduction can be substantially increased by 20–21%, for a higher value of N_iτ (=1.0×10⁸ ions s/cm³), which is realized by increasing the power consumption of the carbon fiber ionizer.     

Ionic liquid mediated synthesis of silica/polystyrene core–shell composite nanospheres by radical dispersion polymerization

This report describes the novel preparation of silica/polystyrene (SiO₂/PS) core–shell composite nanospheres by in situ radical dispersion polymerization in an ionic liquid (IL). Silica nanoparticles were first surface modified by the silane coupling agent methacryloxypropyltrimethoxysilane (MPTMS), which is capable of copolymerizing with styrene and provided a reactive CC bond. Transmission electron microscopy (TEM) revealed core–shell morphology with smooth surfaces. X-ray photoelectron spectroscopy (XPS) analysis demonstrated that almost all of the SiO₂ nanoparticles were encapsulated by the polymer. The composite particles were also analyzed by FT-IR spectroscopy and thermogravimetric analysis (TGA). In principle, this simple and environmentally-friendly synthetic procedure can be employed to prepare other inorganic oxide-containing polymer composites.     

Chromotropic ferrocenyl chalcone with two pyrenyl groups: Solvatochromism and molecular chemosensor for Fe(III)/Fe(II) ions

A chromotropic ferrocenyl chalcone with two pyrenyl groups (Fc-dPyr) is prepared and spectroscopically characterized. The X-ray structure analysis shows that the two pyrenyl groups are almost parallel to each other with a torsion angle of 5.57° and adopt a dimeric mode with a distance of 3.776 Å between them, ready to form an excimer. The solvatochromic fluorescence spectra indicate that the emission maxima observed in hydrogen-bonding donor (HBD) solvents (CHCl₃, EtOH and MeOH) exhibit a strictly linear relationship with the normalized E_T^N value, while those in a non-HBD solvent (CH₃CN) do not. The molecular chemosensor activity of Fc-dPyr is highly selective toward Fe(III) ions over Fe(II) ions. The fluorescence emission intensity of Fc-dPyr steeply decreases in the presence of Fe(III) ions as an oxidant, but not in the presence of Fe(II) ions.     

Development of a Simple,Rapid Multiplex PCR Method Using the 16S rRNA Gene to Determine the Country of Origin of Brackish Water Bivalve <Emphasis Type="Italic">Corbicula japonica</Emphasis>

In this study, a multiplex PCR detection method was developed to identify the country of origin of Corbicula japonica (clams), a commercially important bivalve in Asia. Specific primer sets that have a single nucleotide mismatch at the 3′ terminus were designed after sequencing the mitochondrial 16S rRNA gene of clams identified as C. japonica originating from Korea, China, and Japan. Using this method, each origin was clearly identified based on the PCR products: three bands for Korean C. japonica (100, 283, and 384 bp), one band for Chinese C. japonica (384 bp), and two bands for Japanese C. japonica (384 and 100 bp). These results indicate that the 16S rRNA gene, which is usually used to identify species, can distinguish the country of origin within C. japonica. Our multiplex PCR assay should be a useful tool for the fair trade of the species.     

Failure mechanism for metal cylinder under explosive loading

This paper presents the numerical study of dynamic fracture for metal cylinder under internal explosive loading. Also, the effects of fracture models and groove designs on fracture behavior are investigated. For the dynamic hardening behavior, the Lim-Huh model including the thermal softening effect is adopted [1, 2]. Also, the Lou-Huh fracture model considering the strain rate dependency is used for fracture prediction [3]. The tensile fracture occurs first at the outer surface, and the shear fracture is observed near the inner surface. In addition, finite element analyses are performed to study the effect of various groove designs on dynamic fracture; single U-groove and V-groove at the outer surface. The tensile and shear fracture lines are predicted near the groove tip and inner surface, respectively. It is concluded that the stress triaxiality parameter is one of the critical factors in the dynamic fracture prediction of the metal cylinder.

     

Deterioration behavior analysis of dysprosium and thulium co-doped barium titanate ceramics for multilayer ceramic capacitors

An accelerated testing method for barium titanate (BaTiO₃) dielectrics was proposed to elucidate deterioration behavior of dielectric constant based on the life-temperature relation. The accelerated degradation test (ADT) which was designed using various temperature ranges below and above Curie temperature (T_c) was focused on the optimized composition of dysprosium (Dy) and thulium (Tm) co-doped BaTiO₃. The statistical analysis of the failure time data was performed to determine the optimum distribution as a goodness-of-fitness test. A scale parameter (η) and activation energy (E_α) were calculated in order to predict the life time of the co-doped BaTiO₃, and there was difference between the expected life times according to the acceleration temperature rating of the ADT. The difference of deterioration mechanism around T_c could be deduced from the change of lattice parameter and polarization behavior. The drastic decrease of tetragonality and ferroelectric property caused by the phase transition of the co-doped BaTiO₃ was verified in the temperature above T_c. Accordingly, the acceleration factor over T_c should be considered as reliability study of the BaTiO₃ dielectrics for multilayer ceramic capacitors (MLCCs).     

Dielectric and piezoelectric properties of KCT added (Li0.02(Na0.56 K0.46)0.98(Nb0.81Ta0.15Sb0.04)O3 ceramics

In this study, [Li_0.02(Na_0.56 K_0.46)_0.98](Nb_0.81Ta_0.15Sb_0.04)O₃ + x mol% K_5.4Cu_1.3Ta₁₀O₂₉ ceramics were fabricated by conventional solid-state solution processes. Then, their dielectric and piezoelectric properties were investigated. Sinterability of all samples was enhanced because K_5.4Cu_1.3Ta₁₀O₂₉ (abbreviated as KCT) acted as sintering aids. As the result of XRD, phase structure showed orthorhombic symmetry when KCT ≤ 0.2 mol%. Whereas, the phase structure changed from orthorhombic symmetry to tetragonal symmetry when KCT?≥?0.4 mol%. The results suggest that the orthorhombic and tetragonal phases co-exist in the composition ceramics with 0.2 mol% < KCT < 0.4 mol% at room temperature. The effects of the addition of KCT on the dielectric and piezoelectric properties were investigated. As the result, excellent properties of density=4.81[g/cm³], electromechanical coupling factor (k_p)=0.48 and piezoelectric constant(d₃₃)=252[pC/N] were obtained in the composition ceramics with 0.4 mol%KCT.     

The synthesis of crown ether-appended dichlorofluoresceins and their selective Cu2+ chemosensing

Dichlorofluorescein derivatives with two aza-crown ether binding units were prepared by the Mannich reaction and their chemosensing behaviors toward transition metal ions were investigated. An 18-crown-6 ether derivative exhibited pronounced Cu²⁺-selective fluorescence signaling, with selectivity over other common physiologically important alkali, alkaline earth and transition metal ions. The compound also displayed 1:1 complex formation with Cu²⁺ ion, with a detection limit of 2.9 × 10^?6 M in an aqueous 50% DMSO solution at pH 7, showing that it may offer potential as a chemosensor for the detection of submillimolar Cu²⁺ ions in physiological environments. A 15-Crown-5 ether analogue also revealed selective Cu²⁺ signaling, although with somewhat diminished selectivity compared with its 18-crown-6 counterpart.     

A preliminary study on the development of an easy method for beef freshness using a cyclic voltammetric system

This study was carried out to develop an easy method for beef freshness using a cyclic voltammetric system. Prime graded (USDA) beef loin at 48 h postmortem was cut into pieces 3 cm thick, packaged into commercial plastic zipper bag, and then stored at 4 °C for 0, 3, 6 and 9 days. A commercial cyclic voltammetry and data processing software were used for this study and the interdigitated electrode was fabricated according to semiconductor manufacturing. The homogenated beef was filtered through Whatman No. 1 filter paper and 250 μL of the filtrate was applied on the interdigitated electrode sensor chip for electrochemical detection. Electrochemical signals changed as storage periods increased. The shape of the cyclic voltammogram changed from a roundish curve to a shapely curve. Redox values (V) also increased during storage. Electrochemical signals matched well with lipid oxidation values (Thiobarbituric acid reactive substances: TBARS). A linear relationship between redox value and TBARS was obtained with a correlation factor of 0.957. Thus, the electrochemical signal of a cyclic voltammetric system can be used as an indicator of beef freshness.