Using 2-(N-Methyl-N-Phenylamino) acetonaphthone as photoinitiator for the polymerization of methyl methacrylate

Summary 2-(N-Methyl-N-phenylamino) acetonaphthone (MPA) was synthesized as a cleavable photoinitiator and the structure of the photoinitiator was confirmed by spectral and elemental analysis. MPA shows a much higher molar absorptivity than the commercially used acetophenone derivative. The photoinitiation capability of MPA was demonstrated by using methyl methacrylate and a formulation containing multifunctional monomers. Incorporation of the naphthoyl moiety into the polymer was demonstrated by spectroscopic methods.     

Hydroxyl‐terminated poly(urethane acrylate) as a soft liner in dental applications: Synthesis and characterization

Hydroxyl‐terminated poly(urethane acrylate)s were synthesized for use in biomedical applications. Acrylate end capping via an interesterification reaction was successfully achieved with methacryloyl chloride addition to the hydroxyl ends of the polyurethane at low temperatures. 2,4‐Toluene diisocyanate, 1,6‐hexane diisocyanate, and methylene diphenyl diisocyanate were used as diisocyanates for urethane synthesis, and they were end‐capped with methyl methacrylate and hydroxyethyl methacrylate. The nature of the monomers that we used had an effect on the thermal and morphological properties that were interpreted in terms of the level of hydrogen bonding and the degree of phase separation. The synthesized polymers were characterized by NMR, Fourier transform infrared/attenuated total reflectance spectroscopy, differential scanning calorimetry, thermogravimetric analysis, and gel permeation chromatography. The number‐average molecular weights of the poly(urethane acrylate)s were 2500–6000 g/mol. To use the polymer as a soft‐liner material in denture applications, the residual isocyanate should not exist. In this study, we showed that a prepolymer without residual isocyanate could be synthesized. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Study on physiochemical structure and in vitro release behaviors of doxycycline‐loaded PCL microspheres

This study aimed to develop drug delivery system of doxycycline‐loaded polycaprolactone (PCL) microspheres. The investigated microsphere formulation can be considered for local application in bone infections and degenerative joint diseases, which generally require long‐term treatments via systemic drugs. PCL‐14 kDa and 65 kDa were used in microsphere preparation. Before release, the microspheres were characterized by scanning electron microscopy, differential scanning calorimetry, and X‐ray photoelectron spectroscopy. The mean particle size of microspheres was in the range of 74–122 µm and their drug loadings ranged between 10 and 30%. In vitro release profiles were described using the Higuchi and the Korsmeyer–Peppas equations. Diffusion model was applied to experimental data for estimating diffusion coefficients of microspheres; calculated as between 4.5 × 10^?10 and 9.5 × 10^?10 cm²/s. Although long‐term release from microspheres of PCL‐14 kDa obeyed diffusion model, PCL‐65 kDa microspheres showed this tendency only for some period. Modeling studies showed that the drug release mechanism was mainly dependent on loading and molecular weight differences. Release behavior of PCL‐65 kDa microspheres, however, might be better represented by derivation of a different equation to model for the total release period. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41768     

Dynamic Magnetic Hysteresis Behaviors in a Mixed Spin (3/2, 2) Bilayer System with Different Crystal-Field Interactions

Dynamic magnetic hysteresis (DMH) behaviors of the mixed spin-3/2 and spin-2 Ising bilayer system with different crystal-field interactions on a two-layer square lattice is studied by the use of dynamic mean field calculations based on the Glauber-type stochastic. The hysteresis loops are obtained for different reduced temperatures (T), magnetic field amplitudes (h), frequencies (w) and interlayer coupling constants (J ₃). Influences of the T, h, w and J ₃ on the DMH properties are investigated. We also study the temperature, frequency and interlayer coupling interaction dependence of the coercive field and remanent magnetization. We compare our results with some theoretical and experimental works and observe a quantitatively good agreement with some theoretical and experimental results.     

Direct-Charge-Transfer Pseudo-N-Path SC Circuit Insensitive to the Element Mismatch and Opamp Nonidealities

A novel pseudo-N-path switched-capacitor circuit is described. Its center frequency is insensitive to element mismatch as well as to the finite gain and bandwidth of the opamps used. In this new architecture, the charges from the input source to the output are not transferred by an opamp; rather the opamp is used only as a buffer. The performance of the circuit is superior to that of a regular pseudo-N-path structure.     

A 1-V 10-MHz clock-rate 13-bit CMOS ΔΣ modulator usingunity-gain-reset op amps

The problem of low-voltage operation of switched-capacitor circuits is discussed, and several solutions based on using unity-gain-reset of the opamps are proposed. Due to the feedback structure, the opamps do not need to be switched off during the reset phase of the operation, and hence can be clocked at a high rate. A low-voltage ΔΣ modulator, incorporating pseudodifferential unity-gain-reset opamps, is described. A test chip, realized in a 0.35-μm CMOS process and clocked at 10.24 MHz, provided a dynamic range of 80 dB and a signal-to-noise+distortion (SNDR) ratio of 78 dB for a 20-kHz signal bandwidth, and a dynamic range of 74 dB and SNDR of 70 dB for a 50-kHz bandwidth, with a 1-V supply voltage     

Voltage-mode high-Q band-pass filters and oscillators employing single CDBA and minimum number of components

In this paper, voltage-mode second order high-Q band pass filters and oscillators which employ only single current differencing buffered amplifier (CDBA) as the active component are proposed. One of the four filter circuits and two of the four oscillators described have minimum passive component count properties, without using the internal pole of the active element. These BP filters can be easily cascaded without any recourse to impedance matching circuitry. The circuits have been analysed theoretically, simulated and experimentally tested in a laboratory. It is shown that the results of simulations and experimental work are in agreement with theoretical predictions.     

Hydrogen applications in selective catalytic reduction of NOx emissions from diesel engines

Diesel engines have been considered as a major source in nitrogen oxide (NO_x) formation worldwide. The widespread use of diesel engines in consequence of their low fuel consumption, high durability and efficiency increases NO_x emissions day by day. NO_x emissions from diesel engines cause unavoidable damage on environment and people health. Although so many technologies such as exhaust gas recirculation (EGR), lean burn combustion, electronic controlling fuel injection systems, etc. have been developed to control NO_x emissions from diesel engines, they couldn't meet the desired reduction in NO_x emissions. In any case, Selective Catalytic Reduction (SCR) as one of the most promising aftertreatment-emission control technologies is an effective solution in restriction of NO_x emissions. The use of SCR systems especially in heavy-duty diesel powered vehicles has been increasing nowadays. In these systems, to use of hydrogen (H₂) as a reductant or promoter have been improved the conversion efficiency especially at low exhaust temperatures. Many researchers have been focused on the use of H₂ in SCR systems for controlling NO_x emissions.In this study, the applications of H₂ in SCR of NO_x have been discussed. The studies on use of H₂ in SCR of NO_x emissions were examined and the effects on NO_x conversions were determined. Consequently, it is confirmed that H₂ is a promising and alternative reductant in SCR of NO_x and it has been kept as an attracting subject for many researchers.     

Microtensile Bond Strength of Self-Adhesive Resin-Based Dental Cement to Bleached Enamel

This study investigated the effectiveness of bleaching agents on the micro tensile bond strength (µTBS) of self-adhesive luting cement and enamel. A total of 126 samples were prepared from the labial surfaces of permanent human maxillary central incisors and assigned into three groups with 42 samples each as: control, enamel bleached with 10% hydrogen peroxide (HP), and enamel bleached with 10% carbamide peroxide (CP). Rely X Unicem® (3 M, ESPE) was used as self-adhesive resin cement. The total testing period for bleaching was selected as 14 days and the bleaching agents were applied 8 hours a day. The statistical one-way ANOVA model and Tukey HSD multiple comparison test (α = .01) were used to assess the differences. The control group demonstrated the highest value (18.245 MPa) while HP and CP showed the much lower values of 11.150 and 14.222 MPa, respectively. Bleaching agents affect the µTBS negatively. Failure analysis of the fracture surfaces demonstrated that almost all samples showed adhesive failures at the cement-enamel interface.