Objectives: To investigate the effect of different self-etch adhesive systems application techniques: active or passive in a single or double layer on adhesive–dentin microshear bond strength.
Methods: Occlusal surfaces of 48 extracted human molars were ground to expose flat superficial dentin surfaces. Specimens were randomly divided into two main groups according to the tested self-etch adhesive system either: One-step self-etch (AdperTM easy-one) or two-step self-etch (AdperTM SE Plus). Each adhesive system was applied on the prepared dentin surfaces followed one of these techniques: (1) Passive application of a single layer, (2) Active application of single layer, (3) Passive application of double adhesive layer (with light curing in between), and (4) Active application of double adhesive layers. Resin composite was packed inside micro-tubes fixed on the bonded dentin surfaces and light cured for 40 s. All specimens were stored in artificial saliva either for 24 h or 3 months before testing. Microshear bond strength test was employed using a universal testing machine at a crosshead speed of 0.5 mm/min.
Results: AdperTM SE Plus showed higher significant microshear bond strength in compared with AdperTM easy-one. For both adhesive systems active application showed higher significant microshear bond strength to dentin than passive application. Double application of adhesive systems showed lower microshear bond strength than single application.
Conclusion: Active application of self-etch adhesives could improve the dentin microshear bond strength. Double application with curing in between the layers did not improve the bond strength to the tested adhesive. 相似文献
Three amidosulfobetaine surfactants were synthesized namely: 3-(N-pentadecanamidopropyl-N,N-dimethyl ammonium) propanesulfonate (2a); 3-(N-heptadecanamidopropyl-N,N-dimethyl ammonium) propanesulfonate (2b), and 3-(N-nonadecanamidopropyl-N,N-dimethyl ammonium) propanesulfonate (2c). These surfactants were prepared by direct amidation of commercially available fatty acids with 3-(dimethylamino)-1-propylamine and subsequent reaction with 1,3-propanesultone to obtain quaternary ammonium salts. The synthesized surfactants were characterized by IR, NMR and mass spectrometry. Thermogravimetric analysis (TGA) results showed that the synthesized surfactants have excellent thermal stability with no major thermal degradation below 300 °C. The critical micelle concentration (CMC) values of the surfactants 2a and 2b were found to be 2.2 × 10?4 and 1.04 × 10?4 mol/L, and the corresponding surface tension (γCMC) values were 33.14 and 34.89 mN m?1, respectively. The surfactants exhibit excellent surface properties, which are comparable with conventional surfactants. The intrinsic viscosity of surfactant (2b) was studied at various temperatures and concentrations of multi-component brine solution. The plot of natural logarithm of relative viscosity versus surfactant concentration obtained from Higiro et al. model best fit the surfactant behavior. Due to good salt resistance, excellent surface properties and thermal stability, the synthesized surfactant has potential to be used in various oil field applications such as enhanced oil recovery, fracturing, acid diversion, and well stimulation. 相似文献
Zwitterionic surfactants based on 3-(1-alkyl-3-imidazolio) propane-sulfonate ([ImS3-R] where R is octyl or dodecyl) is an emerging and important class of amphiphile due to their relevance as nano reactors for the synthesis of metallic nanoparticles and accelerated acid hydrolysis. The physicochemical properties of such synthesized imidazolium ring-containing zwitterionic surfactants have been characterized by surface tension and small-angle neutron scattering (SANS) techniques. Surface tension measurements were used to calculate several thermodynamic parameters over a range of concentrations and temperatures (298–313 K). The results obtained showed a weak signature representing the critical micelle concentration (CMC) for ImS3-8, however, by increasing the alkyl length of the hydrophobic group to dodecyl, that is, ImS3-8 to ImS3-12, the signature of the CMC was much more evident. As expected, the CMC for ImS3-12 shifted to a lower concentration. An increase in temperature increased the surface activity and decreased the CMC of both zwitterionic surfactants, although the changes were small. Compared to classical surfactants, that is, sodium dodecyl sulfate and dodecyl trimethylammonium bromide, the CMC of ImS3-12 is much lower. Modeling of SANS data demonstrated that the morphology of the micelles formed by these amphiphiles may be described by the “classical” model, a central hydrophobic core, with a shell of hydrated headgroups. Due to their widespread applications in colloidal and interfacial science, the present study adds new insight to the fundamental understanding of these interesting imidazolium-based surface-active ionic liquids (ImS3-R). 相似文献
Silicon - The present study evaluated the effect of silicon (Si) seed priming and sulfur (S) foliar spray on drought tolerance of two contrasting maize hybrids viz. drought tolerant Hi-Corn 11 and... 相似文献
The performances of three advanced non-linear controllers are analyzed for the optimal set point tracking of styrene free radical polymerization (FRP) in batch reactors. The three controllers are the artificial neural network-based MPC (NN-MPC), the artificial fuzzy logic controller (FLC) as well as the generic model controller (GMC). A recently developed hybrid model (Hosen et al., 2011a. Asia-Pac. J. Chem. Eng. 6(2), 274) is utilized in the control study to design and tune the proposed controllers. The optimal minimum temperature profiles are determined using the Hamiltonian maximum principle. Different types of disturbances are introduced and applied to examine the stability of controller performance. The experimental studies revealed that the performance of the NN-MPC is superior to that of FLC and GMC. 相似文献
For precise and accurate patient dose delivery,the dosimetry system must be calibrated properly according to the recommendations of standard dosimetry protocols such as TG-51 and TRS-398. However, the dosimetry protocol followed by a calibration laboratory is usually different from the protocols that are followed by different clinics, which may result in variations in the patient dose.Our prime objective in this study was to investigate the effect of the two protocols on dosimetry measurements.Dose measurements were performed for a Co-60 teletherapy unit and a high-energy Varian linear accelerator with 6 and 15 MV photon and 6, 9, 12, and 15 MeV electron beams, following the recommendations and procedures of the AAPM TG-51 and IAEA TRS-398 dosimetry protocols. The dosimetry systems used for this study were calibrated in a Co-60 radiation beam at the Secondary Standard Dosimetry Laboratory(SSDL) PINSTECH,Pakistan, following the IAEA TRS-398 protocol. The ratio of the measured absorbed doses to water in clinical setting,D_w(TG-51/TRS-398), was 0.999 and 0.997 for 6 and15 MV photon beams,whereas these ratios were 1.013,1.009, 1.003, and 1.000 for 6, 9, 12, and 15 MeV electron beams, respectively. This difference in the absorbed dosesto-water D_w ratio may be attributed mainly due to beam quality(K_Q) and ion recombination correction factor. 相似文献